* system.h: Poison NO_RECURSIVE_FUNCTION_CSE.

[official-gcc.git] / gcc / fold-const.c

/* Fold a constant sub-tree into a single node for C-compiler
   Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
   2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

/*@@ This file should be rewritten to use an arbitrary precision
  @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
  @@ Perhaps the routines could also be used for bc/dc, and made a lib.
  @@ The routines that translate from the ap rep should
  @@ warn if precision et. al. is lost.
  @@ This would also make life easier when this technology is used
  @@ for cross-compilers.  */

/* The entry points in this file are fold, size_int_wide, size_binop
   and force_fit_type.

   fold takes a tree as argument and returns a simplified tree.

   size_binop takes a tree code for an arithmetic operation
   and two operands that are trees, and produces a tree for the
   result, assuming the type comes from `sizetype'.

   size_int takes an integer value, and creates a tree constant
   with type from `sizetype'.

   force_fit_type takes a constant and prior overflow indicator, and
   forces the value to fit the type.  It returns an overflow indicator.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "flags.h"
#include "tree.h"
#include "real.h"
#include "rtl.h"
#include "expr.h"
#include "tm_p.h"
#include "toplev.h"
#include "ggc.h"
#include "hashtab.h"
#include "langhooks.h"
#include "md5.h"

static void encode (HOST_WIDE_INT *, unsigned HOST_WIDE_INT, HOST_WIDE_INT);
static void decode (HOST_WIDE_INT *, unsigned HOST_WIDE_INT *, HOST_WIDE_INT *);
static bool negate_mathfn_p (enum built_in_function);
static bool negate_expr_p (tree);
static tree negate_expr (tree);
static tree split_tree (tree, enum tree_code, tree *, tree *, tree *, int);
static tree associate_trees (tree, tree, enum tree_code, tree);
static tree const_binop (enum tree_code, tree, tree, int);
static hashval_t size_htab_hash (const void *);
static int size_htab_eq (const void *, const void *);
static tree fold_convert_const (enum tree_code, tree, tree);
static enum tree_code invert_tree_comparison (enum tree_code);
static enum tree_code swap_tree_comparison (enum tree_code);
static int comparison_to_compcode (enum tree_code);
static enum tree_code compcode_to_comparison (int);
static int truth_value_p (enum tree_code);
static int operand_equal_for_comparison_p (tree, tree, tree);
static int twoval_comparison_p (tree, tree *, tree *, int *);
static tree eval_subst (tree, tree, tree, tree, tree);
static tree pedantic_omit_one_operand (tree, tree, tree);
static tree distribute_bit_expr (enum tree_code, tree, tree, tree);
static tree make_bit_field_ref (tree, tree, int, int, int);
static tree optimize_bit_field_compare (enum tree_code, tree, tree, tree);
static tree decode_field_reference (tree, HOST_WIDE_INT *, HOST_WIDE_INT *,
                                    enum machine_mode *, int *, int *,
                                    tree *, tree *);
static int all_ones_mask_p (tree, int);
static tree sign_bit_p (tree, tree);
static int simple_operand_p (tree);
static tree range_binop (enum tree_code, tree, tree, int, tree, int);
static tree make_range (tree, int *, tree *, tree *);
static tree build_range_check (tree, tree, int, tree, tree);
static int merge_ranges (int *, tree *, tree *, int, tree, tree, int, tree,
                         tree);
static tree fold_range_test (tree);
static tree unextend (tree, int, int, tree);
static tree fold_truthop (enum tree_code, tree, tree, tree);
static tree optimize_minmax_comparison (tree);
static tree extract_muldiv (tree, tree, enum tree_code, tree);
static tree extract_muldiv_1 (tree, tree, enum tree_code, tree);
static int multiple_of_p (tree, tree, tree);
static tree constant_boolean_node (int, tree);
static tree fold_binary_op_with_conditional_arg (enum tree_code, tree, tree,
                                                 tree, int);
static bool fold_real_zero_addition_p (tree, tree, int);
static tree fold_mathfn_compare (enum built_in_function, enum tree_code,
                                 tree, tree, tree);
static tree fold_inf_compare (enum tree_code, tree, tree, tree);
static tree fold_div_compare (enum tree_code, tree, tree, tree);
static bool reorder_operands_p (tree, tree);
static bool tree_swap_operands_p (tree, tree, bool);

static tree fold_negate_const (tree, tree);
static tree fold_abs_const (tree, tree);
static tree fold_relational_const (enum tree_code, tree, tree, tree);
static tree fold_relational_hi_lo (enum tree_code *, const tree, tree *, tree *);

/* The following constants represent a bit based encoding of GCC's
   comparison operators.  This encoding simplifies transformations
   on relational comparison operators, such as AND and OR.  */
#define COMPCODE_FALSE   0
#define COMPCODE_LT      1
#define COMPCODE_EQ      2
#define COMPCODE_LE      3
#define COMPCODE_GT      4
#define COMPCODE_NE      5
#define COMPCODE_GE      6
#define COMPCODE_TRUE    7

/* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
   overflow.  Suppose A, B and SUM have the same respective signs as A1, B1,
   and SUM1.  Then this yields nonzero if overflow occurred during the
   addition.

   Overflow occurs if A and B have the same sign, but A and SUM differ in
   sign.  Use `^' to test whether signs differ, and `< 0' to isolate the
   sign.  */
#define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
\f
/* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
   We do that by representing the two-word integer in 4 words, with only
   HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
   number.  The value of the word is LOWPART + HIGHPART * BASE.  */

#define LOWPART(x) \
  ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
#define HIGHPART(x) \
  ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
#define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)

/* Unpack a two-word integer into 4 words.
   LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
   WORDS points to the array of HOST_WIDE_INTs.  */

static void
encode (HOST_WIDE_INT *words, unsigned HOST_WIDE_INT low, HOST_WIDE_INT hi)
{
  words[0] = LOWPART (low);
  words[1] = HIGHPART (low);
  words[2] = LOWPART (hi);
  words[3] = HIGHPART (hi);
}

/* Pack an array of 4 words into a two-word integer.
   WORDS points to the array of words.
   The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces.  */

static void
decode (HOST_WIDE_INT *words, unsigned HOST_WIDE_INT *low,
        HOST_WIDE_INT *hi)
{
  *low = words[0] + words[1] * BASE;
  *hi = words[2] + words[3] * BASE;
}
\f
/* Make the integer constant T valid for its type by setting to 0 or 1 all
   the bits in the constant that don't belong in the type.

   Return 1 if a signed overflow occurs, 0 otherwise.  If OVERFLOW is
   nonzero, a signed overflow has already occurred in calculating T, so
   propagate it.  */

int
force_fit_type (tree t, int overflow)
{
  unsigned HOST_WIDE_INT low;
  HOST_WIDE_INT high;
  unsigned int prec;

  if (TREE_CODE (t) == REAL_CST)
    {
      /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
         Consider doing it via real_convert now.  */
      return overflow;
    }

  else if (TREE_CODE (t) != INTEGER_CST)
    return overflow;

  low = TREE_INT_CST_LOW (t);
  high = TREE_INT_CST_HIGH (t);

  if (POINTER_TYPE_P (TREE_TYPE (t))
      || TREE_CODE (TREE_TYPE (t)) == OFFSET_TYPE)
    prec = POINTER_SIZE;
  else
    prec = TYPE_PRECISION (TREE_TYPE (t));

  /* First clear all bits that are beyond the type's precision.  */

  if (prec == 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if (prec > HOST_BITS_PER_WIDE_INT)
    TREE_INT_CST_HIGH (t)
      &= ~((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
  else
    {
      TREE_INT_CST_HIGH (t) = 0;
      if (prec < HOST_BITS_PER_WIDE_INT)
        TREE_INT_CST_LOW (t) &= ~((unsigned HOST_WIDE_INT) (-1) << prec);
    }

  /* Unsigned types do not suffer sign extension or overflow unless they
     are a sizetype.  */
  if (TYPE_UNSIGNED (TREE_TYPE (t))
      && ! (TREE_CODE (TREE_TYPE (t)) == INTEGER_TYPE
            && TYPE_IS_SIZETYPE (TREE_TYPE (t))))
    return overflow;

  /* If the value's sign bit is set, extend the sign.  */
  if (prec != 2 * HOST_BITS_PER_WIDE_INT
      && (prec > HOST_BITS_PER_WIDE_INT
          ? 0 != (TREE_INT_CST_HIGH (t)
                  & ((HOST_WIDE_INT) 1
                     << (prec - HOST_BITS_PER_WIDE_INT - 1)))
          : 0 != (TREE_INT_CST_LOW (t)
                  & ((unsigned HOST_WIDE_INT) 1 << (prec - 1)))))
    {
      /* Value is negative:
         set to 1 all the bits that are outside this type's precision.  */
      if (prec > HOST_BITS_PER_WIDE_INT)
        TREE_INT_CST_HIGH (t)
          |= ((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
      else
        {
          TREE_INT_CST_HIGH (t) = -1;
          if (prec < HOST_BITS_PER_WIDE_INT)
            TREE_INT_CST_LOW (t) |= ((unsigned HOST_WIDE_INT) (-1) << prec);
        }
    }

  /* Return nonzero if signed overflow occurred.  */
  return
    ((overflow | (low ^ TREE_INT_CST_LOW (t)) | (high ^ TREE_INT_CST_HIGH (t)))
     != 0);
}
\f
/* Add two doubleword integers with doubleword result.
   Each argument is given as two `HOST_WIDE_INT' pieces.
   One argument is L1 and H1; the other, L2 and H2.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
add_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT l2, HOST_WIDE_INT h2,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT l;
  HOST_WIDE_INT h;

  l = l1 + l2;
  h = h1 + h2 + (l < l1);

  *lv = l;
  *hv = h;
  return OVERFLOW_SUM_SIGN (h1, h2, h);
}

/* Negate a doubleword integer with doubleword result.
   Return nonzero if the operation overflows, assuming it's signed.
   The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
neg_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  if (l1 == 0)
    {
      *lv = 0;
      *hv = - h1;
      return (*hv & h1) < 0;
    }
  else
    {
      *lv = -l1;
      *hv = ~h1;
      return 0;
    }
}
\f
/* Multiply two doubleword integers with doubleword result.
   Return nonzero if the operation overflows, assuming it's signed.
   Each argument is given as two `HOST_WIDE_INT' pieces.
   One argument is L1 and H1; the other, L2 and H2.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
mul_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT l2, HOST_WIDE_INT h2,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  HOST_WIDE_INT arg1[4];
  HOST_WIDE_INT arg2[4];
  HOST_WIDE_INT prod[4 * 2];
  unsigned HOST_WIDE_INT carry;
  int i, j, k;
  unsigned HOST_WIDE_INT toplow, neglow;
  HOST_WIDE_INT tophigh, neghigh;

  encode (arg1, l1, h1);
  encode (arg2, l2, h2);

  memset (prod, 0, sizeof prod);

  for (i = 0; i < 4; i++)
    {
      carry = 0;
      for (j = 0; j < 4; j++)
        {
          k = i + j;
          /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000.  */
          carry += arg1[i] * arg2[j];
          /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF.  */
          carry += prod[k];
          prod[k] = LOWPART (carry);
          carry = HIGHPART (carry);
        }
      prod[i + 4] = carry;
    }

  decode (prod, lv, hv);        /* This ignores prod[4] through prod[4*2-1] */

  /* Check for overflow by calculating the top half of the answer in full;
     it should agree with the low half's sign bit.  */
  decode (prod + 4, &toplow, &tophigh);
  if (h1 < 0)
    {
      neg_double (l2, h2, &neglow, &neghigh);
      add_double (neglow, neghigh, toplow, tophigh, &toplow, &tophigh);
    }
  if (h2 < 0)
    {
      neg_double (l1, h1, &neglow, &neghigh);
      add_double (neglow, neghigh, toplow, tophigh, &toplow, &tophigh);
    }
  return (*hv < 0 ? ~(toplow & tophigh) : toplow | tophigh) != 0;
}
\f
/* Shift the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.
   Shift right if COUNT is negative.
   ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
lshift_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
               HOST_WIDE_INT count, unsigned int prec,
               unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv, int arith)
{
  unsigned HOST_WIDE_INT signmask;

  if (count < 0)
    {
      rshift_double (l1, h1, -count, prec, lv, hv, arith);
      return;
    }

  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;

  if (count >= 2 * HOST_BITS_PER_WIDE_INT)
    {
      /* Shifting by the host word size is undefined according to the
         ANSI standard, so we must handle this as a special case.  */
      *hv = 0;
      *lv = 0;
    }
  else if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = l1 << (count - HOST_BITS_PER_WIDE_INT);
      *lv = 0;
    }
  else
    {
      *hv = (((unsigned HOST_WIDE_INT) h1 << count)
             | (l1 >> (HOST_BITS_PER_WIDE_INT - count - 1) >> 1));
      *lv = l1 << count;
    }

  /* Sign extend all bits that are beyond the precision.  */

  signmask = -((prec > HOST_BITS_PER_WIDE_INT
                ? ((unsigned HOST_WIDE_INT) *hv
                   >> (prec - HOST_BITS_PER_WIDE_INT - 1))
                : (*lv >> (prec - 1))) & 1);

  if (prec >= 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if (prec >= HOST_BITS_PER_WIDE_INT)
    {
      *hv &= ~((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
      *hv |= signmask << (prec - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = signmask;
      *lv &= ~((unsigned HOST_WIDE_INT) (-1) << prec);
      *lv |= signmask << prec;
    }
}

/* Shift the doubleword integer in L1, H1 right by COUNT places
   keeping only PREC bits of result.  COUNT must be positive.
   ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
rshift_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
               HOST_WIDE_INT count, unsigned int prec,
               unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv,
               int arith)
{
  unsigned HOST_WIDE_INT signmask;

  signmask = (arith
              ? -((unsigned HOST_WIDE_INT) h1 >> (HOST_BITS_PER_WIDE_INT - 1))
              : 0);

  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;

  if (count >= 2 * HOST_BITS_PER_WIDE_INT)
    {
      /* Shifting by the host word size is undefined according to the
         ANSI standard, so we must handle this as a special case.  */
      *hv = 0;
      *lv = 0;
    }
  else if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = 0;
      *lv = (unsigned HOST_WIDE_INT) h1 >> (count - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = (unsigned HOST_WIDE_INT) h1 >> count;
      *lv = ((l1 >> count)
             | ((unsigned HOST_WIDE_INT) h1 << (HOST_BITS_PER_WIDE_INT - count - 1) << 1));
    }

  /* Zero / sign extend all bits that are beyond the precision.  */

  if (count >= (HOST_WIDE_INT)prec)
    {
      *hv = signmask;
      *lv = signmask;
    }
  else if ((prec - count) >= 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if ((prec - count) >= HOST_BITS_PER_WIDE_INT)
    {
      *hv &= ~((HOST_WIDE_INT) (-1) << (prec - count - HOST_BITS_PER_WIDE_INT));
      *hv |= signmask << (prec - count - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = signmask;
      *lv &= ~((unsigned HOST_WIDE_INT) (-1) << (prec - count));
      *lv |= signmask << (prec - count);
    }
}
\f
/* Rotate the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.
   Rotate right if COUNT is negative.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
lrotate_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
                HOST_WIDE_INT count, unsigned int prec,
                unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT s1l, s2l;
  HOST_WIDE_INT s1h, s2h;

  count %= prec;
  if (count < 0)
    count += prec;

  lshift_double (l1, h1, count, prec, &s1l, &s1h, 0);
  rshift_double (l1, h1, prec - count, prec, &s2l, &s2h, 0);
  *lv = s1l | s2l;
  *hv = s1h | s2h;
}

/* Rotate the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.  COUNT must be positive.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
rrotate_double (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
                HOST_WIDE_INT count, unsigned int prec,
                unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT s1l, s2l;
  HOST_WIDE_INT s1h, s2h;

  count %= prec;
  if (count < 0)
    count += prec;

  rshift_double (l1, h1, count, prec, &s1l, &s1h, 0);
  lshift_double (l1, h1, prec - count, prec, &s2l, &s2h, 0);
  *lv = s1l | s2l;
  *hv = s1h | s2h;
}
\f
/* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
   for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
   CODE is a tree code for a kind of division, one of
   TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
   or EXACT_DIV_EXPR
   It controls how the quotient is rounded to an integer.
   Return nonzero if the operation overflows.
   UNS nonzero says do unsigned division.  */

int
div_and_round_double (enum tree_code code, int uns,
                      unsigned HOST_WIDE_INT lnum_orig, /* num == numerator == dividend */
                      HOST_WIDE_INT hnum_orig,
                      unsigned HOST_WIDE_INT lden_orig, /* den == denominator == divisor */
                      HOST_WIDE_INT hden_orig,
                      unsigned HOST_WIDE_INT *lquo,
                      HOST_WIDE_INT *hquo, unsigned HOST_WIDE_INT *lrem,
                      HOST_WIDE_INT *hrem)
{
  int quo_neg = 0;
  HOST_WIDE_INT num[4 + 1];     /* extra element for scaling.  */
  HOST_WIDE_INT den[4], quo[4];
  int i, j;
  unsigned HOST_WIDE_INT work;
  unsigned HOST_WIDE_INT carry = 0;
  unsigned HOST_WIDE_INT lnum = lnum_orig;
  HOST_WIDE_INT hnum = hnum_orig;
  unsigned HOST_WIDE_INT lden = lden_orig;
  HOST_WIDE_INT hden = hden_orig;
  int overflow = 0;

  if (hden == 0 && lden == 0)
    overflow = 1, lden = 1;

  /* Calculate quotient sign and convert operands to unsigned.  */
  if (!uns)
    {
      if (hnum < 0)
        {
          quo_neg = ~ quo_neg;
          /* (minimum integer) / (-1) is the only overflow case.  */
          if (neg_double (lnum, hnum, &lnum, &hnum)
              && ((HOST_WIDE_INT) lden & hden) == -1)
            overflow = 1;
        }
      if (hden < 0)
        {
          quo_neg = ~ quo_neg;
          neg_double (lden, hden, &lden, &hden);
        }
    }

  if (hnum == 0 && hden == 0)
    {                           /* single precision */
      *hquo = *hrem = 0;
      /* This unsigned division rounds toward zero.  */
      *lquo = lnum / lden;
      goto finish_up;
    }

  if (hnum == 0)
    {                           /* trivial case: dividend < divisor */
      /* hden != 0 already checked.  */
      *hquo = *lquo = 0;
      *hrem = hnum;
      *lrem = lnum;
      goto finish_up;
    }

  memset (quo, 0, sizeof quo);

  memset (num, 0, sizeof num);  /* to zero 9th element */
  memset (den, 0, sizeof den);

  encode (num, lnum, hnum);
  encode (den, lden, hden);

  /* Special code for when the divisor < BASE.  */
  if (hden == 0 && lden < (unsigned HOST_WIDE_INT) BASE)
    {
      /* hnum != 0 already checked.  */
      for (i = 4 - 1; i >= 0; i--)
        {
          work = num[i] + carry * BASE;
          quo[i] = work / lden;
          carry = work % lden;
        }
    }
  else
    {
      /* Full double precision division,
         with thanks to Don Knuth's "Seminumerical Algorithms".  */
      int num_hi_sig, den_hi_sig;
      unsigned HOST_WIDE_INT quo_est, scale;

      /* Find the highest nonzero divisor digit.  */
      for (i = 4 - 1;; i--)
        if (den[i] != 0)
          {
            den_hi_sig = i;
            break;
          }

      /* Insure that the first digit of the divisor is at least BASE/2.
         This is required by the quotient digit estimation algorithm.  */

      scale = BASE / (den[den_hi_sig] + 1);
      if (scale > 1)
        {               /* scale divisor and dividend */
          carry = 0;
          for (i = 0; i <= 4 - 1; i++)
            {
              work = (num[i] * scale) + carry;
              num[i] = LOWPART (work);
              carry = HIGHPART (work);
            }

          num[4] = carry;
          carry = 0;
          for (i = 0; i <= 4 - 1; i++)
            {
              work = (den[i] * scale) + carry;
              den[i] = LOWPART (work);
              carry = HIGHPART (work);
              if (den[i] != 0) den_hi_sig = i;
            }
        }

      num_hi_sig = 4;

      /* Main loop */
      for (i = num_hi_sig - den_hi_sig - 1; i >= 0; i--)
        {
          /* Guess the next quotient digit, quo_est, by dividing the first
             two remaining dividend digits by the high order quotient digit.
             quo_est is never low and is at most 2 high.  */
          unsigned HOST_WIDE_INT tmp;

          num_hi_sig = i + den_hi_sig + 1;
          work = num[num_hi_sig] * BASE + num[num_hi_sig - 1];
          if (num[num_hi_sig] != den[den_hi_sig])
            quo_est = work / den[den_hi_sig];
          else
            quo_est = BASE - 1;

          /* Refine quo_est so it's usually correct, and at most one high.  */
          tmp = work - quo_est * den[den_hi_sig];
          if (tmp < BASE
              && (den[den_hi_sig - 1] * quo_est
                  > (tmp * BASE + num[num_hi_sig - 2])))
            quo_est--;

          /* Try QUO_EST as the quotient digit, by multiplying the
             divisor by QUO_EST and subtracting from the remaining dividend.
             Keep in mind that QUO_EST is the I - 1st digit.  */

          carry = 0;
          for (j = 0; j <= den_hi_sig; j++)
            {
              work = quo_est * den[j] + carry;
              carry = HIGHPART (work);
              work = num[i + j] - LOWPART (work);
              num[i + j] = LOWPART (work);
              carry += HIGHPART (work) != 0;
            }

          /* If quo_est was high by one, then num[i] went negative and
             we need to correct things.  */
          if (num[num_hi_sig] < (HOST_WIDE_INT) carry)
            {
              quo_est--;
              carry = 0;                /* add divisor back in */
              for (j = 0; j <= den_hi_sig; j++)
                {
                  work = num[i + j] + den[j] + carry;
                  carry = HIGHPART (work);
                  num[i + j] = LOWPART (work);
                }

              num [num_hi_sig] += carry;
            }

          /* Store the quotient digit.  */
          quo[i] = quo_est;
        }
    }

  decode (quo, lquo, hquo);

 finish_up:
  /* If result is negative, make it so.  */
  if (quo_neg)
    neg_double (*lquo, *hquo, lquo, hquo);

  /* Compute trial remainder:  rem = num - (quo * den)  */
  mul_double (*lquo, *hquo, lden_orig, hden_orig, lrem, hrem);
  neg_double (*lrem, *hrem, lrem, hrem);
  add_double (lnum_orig, hnum_orig, *lrem, *hrem, lrem, hrem);

  switch (code)
    {
    case TRUNC_DIV_EXPR:
    case TRUNC_MOD_EXPR:        /* round toward zero */
    case EXACT_DIV_EXPR:        /* for this one, it shouldn't matter */
      return overflow;

    case FLOOR_DIV_EXPR:
    case FLOOR_MOD_EXPR:        /* round toward negative infinity */
      if (quo_neg && (*lrem != 0 || *hrem != 0))   /* ratio < 0 && rem != 0 */
        {
          /* quo = quo - 1;  */
          add_double (*lquo, *hquo, (HOST_WIDE_INT) -1, (HOST_WIDE_INT)  -1,
                      lquo, hquo);
        }
      else
        return overflow;
      break;

    case CEIL_DIV_EXPR:
    case CEIL_MOD_EXPR:         /* round toward positive infinity */
      if (!quo_neg && (*lrem != 0 || *hrem != 0))  /* ratio > 0 && rem != 0 */
        {
          add_double (*lquo, *hquo, (HOST_WIDE_INT) 1, (HOST_WIDE_INT) 0,
                      lquo, hquo);
        }
      else
        return overflow;
      break;

    case ROUND_DIV_EXPR:
    case ROUND_MOD_EXPR:        /* round to closest integer */
      {
        unsigned HOST_WIDE_INT labs_rem = *lrem;
        HOST_WIDE_INT habs_rem = *hrem;
        unsigned HOST_WIDE_INT labs_den = lden, ltwice;
        HOST_WIDE_INT habs_den = hden, htwice;

        /* Get absolute values.  */
        if (*hrem < 0)
          neg_double (*lrem, *hrem, &labs_rem, &habs_rem);
        if (hden < 0)
          neg_double (lden, hden, &labs_den, &habs_den);

        /* If (2 * abs (lrem) >= abs (lden)) */
        mul_double ((HOST_WIDE_INT) 2, (HOST_WIDE_INT) 0,
                    labs_rem, habs_rem, &ltwice, &htwice);

        if (((unsigned HOST_WIDE_INT) habs_den
             < (unsigned HOST_WIDE_INT) htwice)
            || (((unsigned HOST_WIDE_INT) habs_den
                 == (unsigned HOST_WIDE_INT) htwice)
                && (labs_den < ltwice)))
          {
            if (*hquo < 0)
              /* quo = quo - 1;  */
              add_double (*lquo, *hquo,
                          (HOST_WIDE_INT) -1, (HOST_WIDE_INT) -1, lquo, hquo);
            else
              /* quo = quo + 1; */
              add_double (*lquo, *hquo, (HOST_WIDE_INT) 1, (HOST_WIDE_INT) 0,
                          lquo, hquo);
          }
        else
          return overflow;
      }
      break;

    default:
      abort ();
    }

  /* Compute true remainder:  rem = num - (quo * den)  */
  mul_double (*lquo, *hquo, lden_orig, hden_orig, lrem, hrem);
  neg_double (*lrem, *hrem, lrem, hrem);
  add_double (lnum_orig, hnum_orig, *lrem, *hrem, lrem, hrem);
  return overflow;
}
\f
/* Return true if built-in mathematical function specified by CODE
   preserves the sign of it argument, i.e. -f(x) == f(-x).  */

static bool
negate_mathfn_p (enum built_in_function code)
{
  switch (code)
    {
    case BUILT_IN_ASIN:
    case BUILT_IN_ASINF:
    case BUILT_IN_ASINL:
    case BUILT_IN_ATAN:
    case BUILT_IN_ATANF:
    case BUILT_IN_ATANL:
    case BUILT_IN_SIN:
    case BUILT_IN_SINF:
    case BUILT_IN_SINL:
    case BUILT_IN_TAN:
    case BUILT_IN_TANF:
    case BUILT_IN_TANL:
      return true;

    default:
      break;
    }
  return false;
}

/* Determine whether an expression T can be cheaply negated using
   the function negate_expr.  */

static bool
negate_expr_p (tree t)
{
  unsigned HOST_WIDE_INT val;
  unsigned int prec;
  tree type;

  if (t == 0)
    return false;

  type = TREE_TYPE (t);

  STRIP_SIGN_NOPS (t);
  switch (TREE_CODE (t))
    {
    case INTEGER_CST:
      if (TYPE_UNSIGNED (type) || ! flag_trapv)
        return true;

      /* Check that -CST will not overflow type.  */
      prec = TYPE_PRECISION (type);
      if (prec > HOST_BITS_PER_WIDE_INT)
        {
          if (TREE_INT_CST_LOW (t) != 0)
            return true;
          prec -= HOST_BITS_PER_WIDE_INT;
          val = TREE_INT_CST_HIGH (t);
        }
      else
        val = TREE_INT_CST_LOW (t);
      if (prec < HOST_BITS_PER_WIDE_INT)
        val &= ((unsigned HOST_WIDE_INT) 1 << prec) - 1;
      return val != ((unsigned HOST_WIDE_INT) 1 << (prec - 1));

    case REAL_CST:
    case NEGATE_EXPR:
      return true;

    case COMPLEX_CST:
      return negate_expr_p (TREE_REALPART (t))
             && negate_expr_p (TREE_IMAGPART (t));

    case PLUS_EXPR:
      if (FLOAT_TYPE_P (type) && !flag_unsafe_math_optimizations)
        return false;
      /* -(A + B) -> (-B) - A.  */
      if (negate_expr_p (TREE_OPERAND (t, 1))
          && reorder_operands_p (TREE_OPERAND (t, 0),
                                 TREE_OPERAND (t, 1)))
        return true;
      /* -(A + B) -> (-A) - B.  */
      return negate_expr_p (TREE_OPERAND (t, 0));

    case MINUS_EXPR:
      /* We can't turn -(A-B) into B-A when we honor signed zeros.  */
      return (! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
             && reorder_operands_p (TREE_OPERAND (t, 0),
                                    TREE_OPERAND (t, 1));

    case MULT_EXPR:
      if (TYPE_UNSIGNED (TREE_TYPE (t)))
        break;

      /* Fall through.  */

    case RDIV_EXPR:
      if (! HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (TREE_TYPE (t))))
        return negate_expr_p (TREE_OPERAND (t, 1))
               || negate_expr_p (TREE_OPERAND (t, 0));
      break;

    case NOP_EXPR:
      /* Negate -((double)float) as (double)(-float).  */
      if (TREE_CODE (type) == REAL_TYPE)
        {
          tree tem = strip_float_extensions (t);
          if (tem != t)
            return negate_expr_p (tem);
        }
      break;

    case CALL_EXPR:
      /* Negate -f(x) as f(-x).  */
      if (negate_mathfn_p (builtin_mathfn_code (t)))
        return negate_expr_p (TREE_VALUE (TREE_OPERAND (t, 1)));
      break;

    case RSHIFT_EXPR:
      /* Optimize -((int)x >> 31) into (unsigned)x >> 31.  */
      if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
        {
          tree op1 = TREE_OPERAND (t, 1);
          if (TREE_INT_CST_HIGH (op1) == 0
              && (unsigned HOST_WIDE_INT) (TYPE_PRECISION (type) - 1)
                 == TREE_INT_CST_LOW (op1))
            return true;
        }
      break;

    default:
      break;
    }
  return false;
}

/* Given T, an expression, return the negation of T.  Allow for T to be
   null, in which case return null.  */

static tree
negate_expr (tree t)
{
  tree type;
  tree tem;

  if (t == 0)
    return 0;

  type = TREE_TYPE (t);
  STRIP_SIGN_NOPS (t);

  switch (TREE_CODE (t))
    {
    case INTEGER_CST:
      tem = fold_negate_const (t, type);
      if (! TREE_OVERFLOW (tem)
          || TYPE_UNSIGNED (type)
          || ! flag_trapv)
        return tem;
      break;

    case REAL_CST:
      tem = fold_negate_const (t, type);
      /* Two's complement FP formats, such as c4x, may overflow.  */
      if (! TREE_OVERFLOW (tem) || ! flag_trapping_math)
        return fold_convert (type, tem);
      break;

    case COMPLEX_CST:
      {
        tree rpart = negate_expr (TREE_REALPART (t));
        tree ipart = negate_expr (TREE_IMAGPART (t));

        if ((TREE_CODE (rpart) == REAL_CST
             && TREE_CODE (ipart) == REAL_CST)
            || (TREE_CODE (rpart) == INTEGER_CST
                && TREE_CODE (ipart) == INTEGER_CST))
          return build_complex (type, rpart, ipart);
      }
      break;

    case NEGATE_EXPR:
      return fold_convert (type, TREE_OPERAND (t, 0));

    case PLUS_EXPR:
      if (! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
        {
          /* -(A + B) -> (-B) - A.  */
          if (negate_expr_p (TREE_OPERAND (t, 1))
              && reorder_operands_p (TREE_OPERAND (t, 0),
                                     TREE_OPERAND (t, 1)))
            {
              tem = negate_expr (TREE_OPERAND (t, 1));
              tem = fold (build2 (MINUS_EXPR, TREE_TYPE (t),
                                  tem, TREE_OPERAND (t, 0)));
              return fold_convert (type, tem);
            }

          /* -(A + B) -> (-A) - B.  */
          if (negate_expr_p (TREE_OPERAND (t, 0)))
            {
              tem = negate_expr (TREE_OPERAND (t, 0));
              tem = fold (build2 (MINUS_EXPR, TREE_TYPE (t),
                                  tem, TREE_OPERAND (t, 1)));
              return fold_convert (type, tem);
            }
        }
      break;

    case MINUS_EXPR:
      /* - (A - B) -> B - A  */
      if ((! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
          && reorder_operands_p (TREE_OPERAND (t, 0), TREE_OPERAND (t, 1)))
        return fold_convert (type,
                             fold (build2 (MINUS_EXPR, TREE_TYPE (t),
                                           TREE_OPERAND (t, 1),
                                           TREE_OPERAND (t, 0))));
      break;

    case MULT_EXPR:
      if (TYPE_UNSIGNED (TREE_TYPE (t)))
        break;

      /* Fall through.  */

    case RDIV_EXPR:
      if (! HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (TREE_TYPE (t))))
        {
          tem = TREE_OPERAND (t, 1);
          if (negate_expr_p (tem))
            return fold_convert (type,
                                 fold (build2 (TREE_CODE (t), TREE_TYPE (t),
                                               TREE_OPERAND (t, 0),
                                               negate_expr (tem))));
          tem = TREE_OPERAND (t, 0);
          if (negate_expr_p (tem))
            return fold_convert (type,
                                 fold (build2 (TREE_CODE (t), TREE_TYPE (t),
                                               negate_expr (tem),
                                               TREE_OPERAND (t, 1))));
        }
      break;

    case NOP_EXPR:
      /* Convert -((double)float) into (double)(-float).  */
      if (TREE_CODE (type) == REAL_TYPE)
        {
          tem = strip_float_extensions (t);
          if (tem != t && negate_expr_p (tem))
            return fold_convert (type, negate_expr (tem));
        }
      break;

    case CALL_EXPR:
      /* Negate -f(x) as f(-x).  */
      if (negate_mathfn_p (builtin_mathfn_code (t))
          && negate_expr_p (TREE_VALUE (TREE_OPERAND (t, 1))))
        {
          tree fndecl, arg, arglist;

          fndecl = get_callee_fndecl (t);
          arg = negate_expr (TREE_VALUE (TREE_OPERAND (t, 1)));
          arglist = build_tree_list (NULL_TREE, arg);
          return build_function_call_expr (fndecl, arglist);
        }
      break;

    case RSHIFT_EXPR:
      /* Optimize -((int)x >> 31) into (unsigned)x >> 31.  */
      if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
        {
          tree op1 = TREE_OPERAND (t, 1);
          if (TREE_INT_CST_HIGH (op1) == 0
              && (unsigned HOST_WIDE_INT) (TYPE_PRECISION (type) - 1)
                 == TREE_INT_CST_LOW (op1))
            {
              tree ntype = TYPE_UNSIGNED (type)
                           ? lang_hooks.types.signed_type (type)
                           : lang_hooks.types.unsigned_type (type);
              tree temp = fold_convert (ntype, TREE_OPERAND (t, 0));
              temp = fold (build2 (RSHIFT_EXPR, ntype, temp, op1));
              return fold_convert (type, temp);
            }
        }
      break;

    default:
      break;
    }

  tem = fold (build1 (NEGATE_EXPR, TREE_TYPE (t), t));
  return fold_convert (type, tem);
}
\f
/* Split a tree IN into a constant, literal and variable parts that could be
   combined with CODE to make IN.  "constant" means an expression with
   TREE_CONSTANT but that isn't an actual constant.  CODE must be a
   commutative arithmetic operation.  Store the constant part into *CONP,
   the literal in *LITP and return the variable part.  If a part isn't
   present, set it to null.  If the tree does not decompose in this way,
   return the entire tree as the variable part and the other parts as null.

   If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR.  In that
   case, we negate an operand that was subtracted.  Except if it is a
   literal for which we use *MINUS_LITP instead.

   If NEGATE_P is true, we are negating all of IN, again except a literal
   for which we use *MINUS_LITP instead.

   If IN is itself a literal or constant, return it as appropriate.

   Note that we do not guarantee that any of the three values will be the
   same type as IN, but they will have the same signedness and mode.  */

static tree
split_tree (tree in, enum tree_code code, tree *conp, tree *litp,
            tree *minus_litp, int negate_p)
{
  tree var = 0;

  *conp = 0;
  *litp = 0;
  *minus_litp = 0;

  /* Strip any conversions that don't change the machine mode or signedness.  */
  STRIP_SIGN_NOPS (in);

  if (TREE_CODE (in) == INTEGER_CST || TREE_CODE (in) == REAL_CST)
    *litp = in;
  else if (TREE_CODE (in) == code
           || (! FLOAT_TYPE_P (TREE_TYPE (in))
               /* We can associate addition and subtraction together (even
                  though the C standard doesn't say so) for integers because
                  the value is not affected.  For reals, the value might be
                  affected, so we can't.  */
               && ((code == PLUS_EXPR && TREE_CODE (in) == MINUS_EXPR)
                   || (code == MINUS_EXPR && TREE_CODE (in) == PLUS_EXPR))))
    {
      tree op0 = TREE_OPERAND (in, 0);
      tree op1 = TREE_OPERAND (in, 1);
      int neg1_p = TREE_CODE (in) == MINUS_EXPR;
      int neg_litp_p = 0, neg_conp_p = 0, neg_var_p = 0;

      /* First see if either of the operands is a literal, then a constant.  */
      if (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST)
        *litp = op0, op0 = 0;
      else if (TREE_CODE (op1) == INTEGER_CST || TREE_CODE (op1) == REAL_CST)
        *litp = op1, neg_litp_p = neg1_p, op1 = 0;

      if (op0 != 0 && TREE_CONSTANT (op0))
        *conp = op0, op0 = 0;
      else if (op1 != 0 && TREE_CONSTANT (op1))
        *conp = op1, neg_conp_p = neg1_p, op1 = 0;

      /* If we haven't dealt with either operand, this is not a case we can
         decompose.  Otherwise, VAR is either of the ones remaining, if any.  */
      if (op0 != 0 && op1 != 0)
        var = in;
      else if (op0 != 0)
        var = op0;
      else
        var = op1, neg_var_p = neg1_p;

      /* Now do any needed negations.  */
      if (neg_litp_p)
        *minus_litp = *litp, *litp = 0;
      if (neg_conp_p)
        *conp = negate_expr (*conp);
      if (neg_var_p)
        var = negate_expr (var);
    }
  else if (TREE_CONSTANT (in))
    *conp = in;
  else
    var = in;

  if (negate_p)
    {
      if (*litp)
        *minus_litp = *litp, *litp = 0;
      else if (*minus_litp)
        *litp = *minus_litp, *minus_litp = 0;
      *conp = negate_expr (*conp);
      var = negate_expr (var);
    }

  return var;
}

/* Re-associate trees split by the above function.  T1 and T2 are either
   expressions to associate or null.  Return the new expression, if any.  If
   we build an operation, do it in TYPE and with CODE.  */

static tree
associate_trees (tree t1, tree t2, enum tree_code code, tree type)
{
  if (t1 == 0)
    return t2;
  else if (t2 == 0)
    return t1;

  /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
     try to fold this since we will have infinite recursion.  But do
     deal with any NEGATE_EXPRs.  */
  if (TREE_CODE (t1) == code || TREE_CODE (t2) == code
      || TREE_CODE (t1) == MINUS_EXPR || TREE_CODE (t2) == MINUS_EXPR)
    {
      if (code == PLUS_EXPR)
        {
          if (TREE_CODE (t1) == NEGATE_EXPR)
            return build2 (MINUS_EXPR, type, fold_convert (type, t2),
                           fold_convert (type, TREE_OPERAND (t1, 0)));
          else if (TREE_CODE (t2) == NEGATE_EXPR)
            return build2 (MINUS_EXPR, type, fold_convert (type, t1),
                           fold_convert (type, TREE_OPERAND (t2, 0)));
        }
      return build2 (code, type, fold_convert (type, t1),
                     fold_convert (type, t2));
    }

  return fold (build2 (code, type, fold_convert (type, t1),
                       fold_convert (type, t2)));
}
\f
/* Combine two integer constants ARG1 and ARG2 under operation CODE
   to produce a new constant.

   If NOTRUNC is nonzero, do not truncate the result to fit the data type.  */

tree
int_const_binop (enum tree_code code, tree arg1, tree arg2, int notrunc)
{
  unsigned HOST_WIDE_INT int1l, int2l;
  HOST_WIDE_INT int1h, int2h;
  unsigned HOST_WIDE_INT low;
  HOST_WIDE_INT hi;
  unsigned HOST_WIDE_INT garbagel;
  HOST_WIDE_INT garbageh;
  tree t;
  tree type = TREE_TYPE (arg1);
  int uns = TYPE_UNSIGNED (type);
  int is_sizetype
    = (TREE_CODE (type) == INTEGER_TYPE && TYPE_IS_SIZETYPE (type));
  int overflow = 0;
  int no_overflow = 0;

  int1l = TREE_INT_CST_LOW (arg1);
  int1h = TREE_INT_CST_HIGH (arg1);
  int2l = TREE_INT_CST_LOW (arg2);
  int2h = TREE_INT_CST_HIGH (arg2);

  switch (code)
    {
    case BIT_IOR_EXPR:
      low = int1l | int2l, hi = int1h | int2h;
      break;

    case BIT_XOR_EXPR:
      low = int1l ^ int2l, hi = int1h ^ int2h;
      break;

    case BIT_AND_EXPR:
      low = int1l & int2l, hi = int1h & int2h;
      break;

    case RSHIFT_EXPR:
      int2l = -int2l;
    case LSHIFT_EXPR:
      /* It's unclear from the C standard whether shifts can overflow.
         The following code ignores overflow; perhaps a C standard
         interpretation ruling is needed.  */
      lshift_double (int1l, int1h, int2l, TYPE_PRECISION (type),
                     &low, &hi, !uns);
      no_overflow = 1;
      break;

    case RROTATE_EXPR:
      int2l = - int2l;
    case LROTATE_EXPR:
      lrotate_double (int1l, int1h, int2l, TYPE_PRECISION (type),
                      &low, &hi);
      break;

    case PLUS_EXPR:
      overflow = add_double (int1l, int1h, int2l, int2h, &low, &hi);
      break;

    case MINUS_EXPR:
      neg_double (int2l, int2h, &low, &hi);
      add_double (int1l, int1h, low, hi, &low, &hi);
      overflow = OVERFLOW_SUM_SIGN (hi, int2h, int1h);
      break;

    case MULT_EXPR:
      overflow = mul_double (int1l, int1h, int2l, int2h, &low, &hi);
      break;

    case TRUNC_DIV_EXPR:
    case FLOOR_DIV_EXPR: case CEIL_DIV_EXPR:
    case EXACT_DIV_EXPR:
      /* This is a shortcut for a common special case.  */
      if (int2h == 0 && (HOST_WIDE_INT) int2l > 0
          && ! TREE_CONSTANT_OVERFLOW (arg1)
          && ! TREE_CONSTANT_OVERFLOW (arg2)
          && int1h == 0 && (HOST_WIDE_INT) int1l >= 0)
        {
          if (code == CEIL_DIV_EXPR)
            int1l += int2l - 1;

          low = int1l / int2l, hi = 0;
          break;
        }

      /* ... fall through ...  */

    case ROUND_DIV_EXPR:
      if (int2h == 0 && int2l == 1)
        {
          low = int1l, hi = int1h;
          break;
        }
      if (int1l == int2l && int1h == int2h
          && ! (int1l == 0 && int1h == 0))
        {
          low = 1, hi = 0;
          break;
        }
      overflow = div_and_round_double (code, uns, int1l, int1h, int2l, int2h,
                                       &low, &hi, &garbagel, &garbageh);
      break;

    case TRUNC_MOD_EXPR:
    case FLOOR_MOD_EXPR: case CEIL_MOD_EXPR:
      /* This is a shortcut for a common special case.  */
      if (int2h == 0 && (HOST_WIDE_INT) int2l > 0
          && ! TREE_CONSTANT_OVERFLOW (arg1)
          && ! TREE_CONSTANT_OVERFLOW (arg2)
          && int1h == 0 && (HOST_WIDE_INT) int1l >= 0)
        {
          if (code == CEIL_MOD_EXPR)
            int1l += int2l - 1;
          low = int1l % int2l, hi = 0;
          break;
        }

      /* ... fall through ...  */

    case ROUND_MOD_EXPR:
      overflow = div_and_round_double (code, uns,
                                       int1l, int1h, int2l, int2h,
                                       &garbagel, &garbageh, &low, &hi);
      break;

    case MIN_EXPR:
    case MAX_EXPR:
      if (uns)
        low = (((unsigned HOST_WIDE_INT) int1h
                < (unsigned HOST_WIDE_INT) int2h)
               || (((unsigned HOST_WIDE_INT) int1h
                    == (unsigned HOST_WIDE_INT) int2h)
                   && int1l < int2l));
      else
        low = (int1h < int2h
               || (int1h == int2h && int1l < int2l));

      if (low == (code == MIN_EXPR))
        low = int1l, hi = int1h;
      else
        low = int2l, hi = int2h;
      break;

    default:
      abort ();
    }

  /* If this is for a sizetype, can be represented as one (signed)
     HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
     constants.  */
  if (is_sizetype
      && ((hi == 0 && (HOST_WIDE_INT) low >= 0)
          || (hi == -1 && (HOST_WIDE_INT) low < 0))
      && overflow == 0 && ! TREE_OVERFLOW (arg1) && ! TREE_OVERFLOW (arg2))
    return size_int_type_wide (low, type);
  else
    {
      t = build_int_2 (low, hi);
      TREE_TYPE (t) = TREE_TYPE (arg1);
    }

  TREE_OVERFLOW (t)
    = ((notrunc
        ? (!uns || is_sizetype) && overflow
        : (force_fit_type (t, (!uns || is_sizetype) && overflow)
           && ! no_overflow))
       | TREE_OVERFLOW (arg1)
       | TREE_OVERFLOW (arg2));

  /* If we're doing a size calculation, unsigned arithmetic does overflow.
     So check if force_fit_type truncated the value.  */
  if (is_sizetype
      && ! TREE_OVERFLOW (t)
      && (TREE_INT_CST_HIGH (t) != hi
          || TREE_INT_CST_LOW (t) != low))
    TREE_OVERFLOW (t) = 1;

  TREE_CONSTANT_OVERFLOW (t) = (TREE_OVERFLOW (t)
                                | TREE_CONSTANT_OVERFLOW (arg1)
                                | TREE_CONSTANT_OVERFLOW (arg2));
  return t;
}

/* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
   constant.  We assume ARG1 and ARG2 have the same data type, or at least
   are the same kind of constant and the same machine mode.

   If NOTRUNC is nonzero, do not truncate the result to fit the data type.  */

static tree
const_binop (enum tree_code code, tree arg1, tree arg2, int notrunc)
{
  STRIP_NOPS (arg1);
  STRIP_NOPS (arg2);

  if (TREE_CODE (arg1) == INTEGER_CST)
    return int_const_binop (code, arg1, arg2, notrunc);

  if (TREE_CODE (arg1) == REAL_CST)
    {
      enum machine_mode mode;
      REAL_VALUE_TYPE d1;
      REAL_VALUE_TYPE d2;
      REAL_VALUE_TYPE value;
      tree t, type;

      d1 = TREE_REAL_CST (arg1);
      d2 = TREE_REAL_CST (arg2);

      type = TREE_TYPE (arg1);
      mode = TYPE_MODE (type);

      /* Don't perform operation if we honor signaling NaNs and
         either operand is a NaN.  */
      if (HONOR_SNANS (mode)
          && (REAL_VALUE_ISNAN (d1) || REAL_VALUE_ISNAN (d2)))
        return NULL_TREE;

      /* Don't perform operation if it would raise a division
         by zero exception.  */
      if (code == RDIV_EXPR
          && REAL_VALUES_EQUAL (d2, dconst0)
          && (flag_trapping_math || ! MODE_HAS_INFINITIES (mode)))
        return NULL_TREE;

      /* If either operand is a NaN, just return it.  Otherwise, set up
         for floating-point trap; we return an overflow.  */
      if (REAL_VALUE_ISNAN (d1))
        return arg1;
      else if (REAL_VALUE_ISNAN (d2))
        return arg2;

      REAL_ARITHMETIC (value, code, d1, d2);

      t = build_real (type, real_value_truncate (mode, value));

      TREE_OVERFLOW (t)
        = (force_fit_type (t, 0)
           | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2));
      TREE_CONSTANT_OVERFLOW (t)
        = TREE_OVERFLOW (t)
          | TREE_CONSTANT_OVERFLOW (arg1)
          | TREE_CONSTANT_OVERFLOW (arg2);
      return t;
    }
  if (TREE_CODE (arg1) == COMPLEX_CST)
    {
      tree type = TREE_TYPE (arg1);
      tree r1 = TREE_REALPART (arg1);
      tree i1 = TREE_IMAGPART (arg1);
      tree r2 = TREE_REALPART (arg2);
      tree i2 = TREE_IMAGPART (arg2);
      tree t;

      switch (code)
        {
        case PLUS_EXPR:
          t = build_complex (type,
                             const_binop (PLUS_EXPR, r1, r2, notrunc),
                             const_binop (PLUS_EXPR, i1, i2, notrunc));
          break;

        case MINUS_EXPR:
          t = build_complex (type,
                             const_binop (MINUS_EXPR, r1, r2, notrunc),
                             const_binop (MINUS_EXPR, i1, i2, notrunc));
          break;

        case MULT_EXPR:
          t = build_complex (type,
                             const_binop (MINUS_EXPR,
                                          const_binop (MULT_EXPR,
                                                       r1, r2, notrunc),
                                          const_binop (MULT_EXPR,
                                                       i1, i2, notrunc),
                                          notrunc),
                             const_binop (PLUS_EXPR,
                                          const_binop (MULT_EXPR,
                                                       r1, i2, notrunc),
                                          const_binop (MULT_EXPR,
                                                       i1, r2, notrunc),
                                          notrunc));
          break;

        case RDIV_EXPR:
          {
            tree magsquared
              = const_binop (PLUS_EXPR,
                             const_binop (MULT_EXPR, r2, r2, notrunc),
                             const_binop (MULT_EXPR, i2, i2, notrunc),
                             notrunc);

            t = build_complex (type,
                               const_binop
                               (INTEGRAL_TYPE_P (TREE_TYPE (r1))
                                ? TRUNC_DIV_EXPR : RDIV_EXPR,
                                const_binop (PLUS_EXPR,
                                             const_binop (MULT_EXPR, r1, r2,
                                                          notrunc),
                                             const_binop (MULT_EXPR, i1, i2,
                                                          notrunc),
                                             notrunc),
                                magsquared, notrunc),
                               const_binop
                               (INTEGRAL_TYPE_P (TREE_TYPE (r1))
                                ? TRUNC_DIV_EXPR : RDIV_EXPR,
                                const_binop (MINUS_EXPR,
                                             const_binop (MULT_EXPR, i1, r2,
                                                          notrunc),
                                             const_binop (MULT_EXPR, r1, i2,
                                                          notrunc),
                                             notrunc),
                                magsquared, notrunc));
          }
          break;

        default:
          abort ();
        }
      return t;
    }
  return 0;
}

/* These are the hash table functions for the hash table of INTEGER_CST
   nodes of a sizetype.  */

/* Return the hash code code X, an INTEGER_CST.  */

static hashval_t
size_htab_hash (const void *x)
{
  tree t = (tree) x;

  return (TREE_INT_CST_HIGH (t) ^ TREE_INT_CST_LOW (t)
          ^ htab_hash_pointer (TREE_TYPE (t))
          ^ (TREE_OVERFLOW (t) << 20));
}

/* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
   is the same as that given by *Y, which is the same.  */

static int
size_htab_eq (const void *x, const void *y)
{
  tree xt = (tree) x;
  tree yt = (tree) y;

  return (TREE_INT_CST_HIGH (xt) == TREE_INT_CST_HIGH (yt)
          && TREE_INT_CST_LOW (xt) == TREE_INT_CST_LOW (yt)
          && TREE_TYPE (xt) == TREE_TYPE (yt)
          && TREE_OVERFLOW (xt) == TREE_OVERFLOW (yt));
}
\f
/* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
   bits are given by NUMBER and of the sizetype represented by KIND.  */

tree
size_int_wide (HOST_WIDE_INT number, enum size_type_kind kind)
{
  return size_int_type_wide (number, sizetype_tab[(int) kind]);
}

/* Likewise, but the desired type is specified explicitly.  */

static GTY (()) tree new_const;
static GTY ((if_marked ("ggc_marked_p"), param_is (union tree_node)))
     htab_t size_htab;

tree
size_int_type_wide (HOST_WIDE_INT number, tree type)
{
  void **slot;

  if (size_htab == 0)
    {
      size_htab = htab_create_ggc (1024, size_htab_hash, size_htab_eq, NULL);
      new_const = make_node (INTEGER_CST);
    }

  /* Adjust NEW_CONST to be the constant we want.  If it's already in the
     hash table, we return the value from the hash table.  Otherwise, we
     place that in the hash table and make a new node for the next time.  */
  TREE_INT_CST_LOW (new_const) = number;
  TREE_INT_CST_HIGH (new_const) = number < 0 ? -1 : 0;
  TREE_TYPE (new_const) = type;
  TREE_OVERFLOW (new_const) = TREE_CONSTANT_OVERFLOW (new_const)
    = force_fit_type (new_const, 0);

  slot = htab_find_slot (size_htab, new_const, INSERT);
  if (*slot == 0)
    {
      tree t = new_const;

      *slot = new_const;
      new_const = make_node (INTEGER_CST);
      return t;
    }
  else
    return (tree) *slot;
}

/* Combine operands OP1 and OP2 with arithmetic operation CODE.  CODE
   is a tree code.  The type of the result is taken from the operands.
   Both must be the same type integer type and it must be a size type.
   If the operands are constant, so is the result.  */

tree
size_binop (enum tree_code code, tree arg0, tree arg1)
{
  tree type = TREE_TYPE (arg0);

  if (TREE_CODE (type) != INTEGER_TYPE || ! TYPE_IS_SIZETYPE (type)
      || type != TREE_TYPE (arg1))
    abort ();

  /* Handle the special case of two integer constants faster.  */
  if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST)
    {
      /* And some specific cases even faster than that.  */
      if (code == PLUS_EXPR && integer_zerop (arg0))
        return arg1;
      else if ((code == MINUS_EXPR || code == PLUS_EXPR)
               && integer_zerop (arg1))
        return arg0;
      else if (code == MULT_EXPR && integer_onep (arg0))
        return arg1;

      /* Handle general case of two integer constants.  */
      return int_const_binop (code, arg0, arg1, 0);
    }

  if (arg0 == error_mark_node || arg1 == error_mark_node)
    return error_mark_node;

  return fold (build2 (code, type, arg0, arg1));
}

/* Given two values, either both of sizetype or both of bitsizetype,
   compute the difference between the two values.  Return the value
   in signed type corresponding to the type of the operands.  */

tree
size_diffop (tree arg0, tree arg1)
{
  tree type = TREE_TYPE (arg0);
  tree ctype;

  if (TREE_CODE (type) != INTEGER_TYPE || ! TYPE_IS_SIZETYPE (type)
      || type != TREE_TYPE (arg1))
    abort ();

  /* If the type is already signed, just do the simple thing.  */
  if (!TYPE_UNSIGNED (type))
    return size_binop (MINUS_EXPR, arg0, arg1);

  ctype = (type == bitsizetype || type == ubitsizetype
           ? sbitsizetype : ssizetype);

  /* If either operand is not a constant, do the conversions to the signed
     type and subtract.  The hardware will do the right thing with any
     overflow in the subtraction.  */
  if (TREE_CODE (arg0) != INTEGER_CST || TREE_CODE (arg1) != INTEGER_CST)
    return size_binop (MINUS_EXPR, fold_convert (ctype, arg0),
                       fold_convert (ctype, arg1));

  /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
     Otherwise, subtract the other way, convert to CTYPE (we know that can't
     overflow) and negate (which can't either).  Special-case a result
     of zero while we're here.  */
  if (tree_int_cst_equal (arg0, arg1))
    return fold_convert (ctype, integer_zero_node);
  else if (tree_int_cst_lt (arg1, arg0))
    return fold_convert (ctype, size_binop (MINUS_EXPR, arg0, arg1));
  else
    return size_binop (MINUS_EXPR, fold_convert (ctype, integer_zero_node),
                       fold_convert (ctype, size_binop (MINUS_EXPR,
                                                        arg1, arg0)));
}
\f

/* Attempt to fold type conversion operation CODE of expression ARG1 to
   type TYPE.  If no simplification can be done return NULL_TREE.  */

static tree
fold_convert_const (enum tree_code code, tree type, tree arg1)
{
  int overflow = 0;
  tree t;

  if (TREE_TYPE (arg1) == type)
    return arg1;

  if (POINTER_TYPE_P (type) || INTEGRAL_TYPE_P (type))
    {
      if (TREE_CODE (arg1) == INTEGER_CST)
        {
          /* If we would build a constant wider than GCC supports,
             leave the conversion unfolded.  */
          if (TYPE_PRECISION (type) > 2 * HOST_BITS_PER_WIDE_INT)
            return NULL_TREE;

          /* If we are trying to make a sizetype for a small integer, use
             size_int to pick up cached types to reduce duplicate nodes.  */
          if (TREE_CODE (type) == INTEGER_TYPE && TYPE_IS_SIZETYPE (type)
              && !TREE_CONSTANT_OVERFLOW (arg1)
              && compare_tree_int (arg1, 10000) < 0)
            return size_int_type_wide (TREE_INT_CST_LOW (arg1), type);

          /* Given an integer constant, make new constant with new type,
             appropriately sign-extended or truncated.  */
          t = build_int_2 (TREE_INT_CST_LOW (arg1),
                           TREE_INT_CST_HIGH (arg1));
          TREE_TYPE (t) = type;
          /* Indicate an overflow if (1) ARG1 already overflowed,
             or (2) force_fit_type indicates an overflow.
             Tell force_fit_type that an overflow has already occurred
             if ARG1 is a too-large unsigned value and T is signed.
             But don't indicate an overflow if converting a pointer.  */
          TREE_OVERFLOW (t)
            = ((force_fit_type (t,
                                (TREE_INT_CST_HIGH (arg1) < 0
                                 && (TYPE_UNSIGNED (type)
                                    < TYPE_UNSIGNED (TREE_TYPE (arg1)))))
                && ! POINTER_TYPE_P (TREE_TYPE (arg1)))
               || TREE_OVERFLOW (arg1));
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
          return t;
        }
      else if (TREE_CODE (arg1) == REAL_CST)
        {
          /* The following code implements the floating point to integer
             conversion rules required by the Java Language Specification,
             that IEEE NaNs are mapped to zero and values that overflow
             the target precision saturate, i.e. values greater than
             INT_MAX are mapped to INT_MAX, and values less than INT_MIN
             are mapped to INT_MIN.  These semantics are allowed by the
             C and C++ standards that simply state that the behavior of
             FP-to-integer conversion is unspecified upon overflow.  */

          HOST_WIDE_INT high, low;

          REAL_VALUE_TYPE r;
          REAL_VALUE_TYPE x = TREE_REAL_CST (arg1);

          switch (code)
            {
            case FIX_TRUNC_EXPR:
              real_trunc (&r, VOIDmode, &x);
              break;

            case FIX_CEIL_EXPR:
              real_ceil (&r, VOIDmode, &x);
              break;

            case FIX_FLOOR_EXPR:
              real_floor (&r, VOIDmode, &x);
              break;

            case FIX_ROUND_EXPR:
              real_round (&r, VOIDmode, &x);
              break;

            default:
              abort ();
            }

          /* If R is NaN, return zero and show we have an overflow.  */
          if (REAL_VALUE_ISNAN (r))
            {
              overflow = 1;
              high = 0;
              low = 0;
            }

          /* See if R is less than the lower bound or greater than the
             upper bound.  */

          if (! overflow)
            {
              tree lt = TYPE_MIN_VALUE (type);
              REAL_VALUE_TYPE l = real_value_from_int_cst (NULL_TREE, lt);
              if (REAL_VALUES_LESS (r, l))
                {
                  overflow = 1;
                  high = TREE_INT_CST_HIGH (lt);
                  low = TREE_INT_CST_LOW (lt);
                }
            }

          if (! overflow)
            {
              tree ut = TYPE_MAX_VALUE (type);
              if (ut)
                {
                  REAL_VALUE_TYPE u = real_value_from_int_cst (NULL_TREE, ut);
                  if (REAL_VALUES_LESS (u, r))
                    {
                      overflow = 1;
                      high = TREE_INT_CST_HIGH (ut);
                      low = TREE_INT_CST_LOW (ut);
                    }
                }
            }

          if (! overflow)
            REAL_VALUE_TO_INT (&low, &high, r);

          t = build_int_2 (low, high);
          TREE_TYPE (t) = type;
          TREE_OVERFLOW (t)
            = TREE_OVERFLOW (arg1) | force_fit_type (t, overflow);
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
          return t;
        }
    }
  else if (TREE_CODE (type) == REAL_TYPE)
    {
      if (TREE_CODE (arg1) == INTEGER_CST)
        return build_real_from_int_cst (type, arg1);
      if (TREE_CODE (arg1) == REAL_CST)
        {
          if (REAL_VALUE_ISNAN (TREE_REAL_CST (arg1)))
            {
              /* We make a copy of ARG1 so that we don't modify an
                 existing constant tree.  */
              t = copy_node (arg1);
              TREE_TYPE (t) = type;
              return t;
            }

          t = build_real (type,
                          real_value_truncate (TYPE_MODE (type),
                                               TREE_REAL_CST (arg1)));

          TREE_OVERFLOW (t)
            = TREE_OVERFLOW (arg1) | force_fit_type (t, 0);
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
          return t;
        }
    }
  return NULL_TREE;
}

/* Convert expression ARG to type TYPE.  Used by the middle-end for
   simple conversions in preference to calling the front-end's convert.  */

tree
fold_convert (tree type, tree arg)
{
  tree orig = TREE_TYPE (arg);
  tree tem;

  if (type == orig)
    return arg;

  if (TREE_CODE (arg) == ERROR_MARK
      || TREE_CODE (type) == ERROR_MARK
      || TREE_CODE (orig) == ERROR_MARK)
    return error_mark_node;

  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (orig))
    return fold (build1 (NOP_EXPR, type, arg));

  if (INTEGRAL_TYPE_P (type) || POINTER_TYPE_P (type))
    {
      if (TREE_CODE (arg) == INTEGER_CST)
        {
          tem = fold_convert_const (NOP_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }
      if (INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
        return fold (build1 (NOP_EXPR, type, arg));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tem = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          return fold_convert (type, tem);
        }
      if (TREE_CODE (orig) == VECTOR_TYPE
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
    }
  else if (TREE_CODE (type) == REAL_TYPE)
    {
      if (TREE_CODE (arg) == INTEGER_CST)
        {
          tem = fold_convert_const (FLOAT_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }
      else if (TREE_CODE (arg) == REAL_CST)
        {
          tem = fold_convert_const (NOP_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }

      if (INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
        return fold (build1 (FLOAT_EXPR, type, arg));
      if (TREE_CODE (orig) == REAL_TYPE)
        return fold (build1 (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
                             type, arg));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tem = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          return fold_convert (type, tem);
        }
    }
  else if (TREE_CODE (type) == COMPLEX_TYPE)
    {
      if (INTEGRAL_TYPE_P (orig)
          || POINTER_TYPE_P (orig)
          || TREE_CODE (orig) == REAL_TYPE)
        return build2 (COMPLEX_EXPR, type,
                       fold_convert (TREE_TYPE (type), arg),
                       fold_convert (TREE_TYPE (type), integer_zero_node));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tree rpart, ipart;

          if (TREE_CODE (arg) == COMPLEX_EXPR)
            {
              rpart = fold_convert (TREE_TYPE (type), TREE_OPERAND (arg, 0));
              ipart = fold_convert (TREE_TYPE (type), TREE_OPERAND (arg, 1));
              return fold (build2 (COMPLEX_EXPR, type, rpart, ipart));
            }

          arg = save_expr (arg);
          rpart = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          ipart = fold (build1 (IMAGPART_EXPR, TREE_TYPE (orig), arg));
          rpart = fold_convert (TREE_TYPE (type), rpart);
          ipart = fold_convert (TREE_TYPE (type), ipart);
          return fold (build2 (COMPLEX_EXPR, type, rpart, ipart));
        }
    }
  else if (TREE_CODE (type) == VECTOR_TYPE)
    {
      if ((INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
      if (TREE_CODE (orig) == VECTOR_TYPE
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
    }
  else if (VOID_TYPE_P (type))
    return fold (build1 (CONVERT_EXPR, type, arg));
  abort ();
}
\f
/* Return an expr equal to X but certainly not valid as an lvalue.  */

tree
non_lvalue (tree x)
{
  /* These things are certainly not lvalues.  */
  if (TREE_CODE (x) == NON_LVALUE_EXPR
      || TREE_CODE (x) == INTEGER_CST
      || TREE_CODE (x) == REAL_CST
      || TREE_CODE (x) == STRING_CST
      || TREE_CODE (x) == ADDR_EXPR)
    return x;

  return build1 (NON_LVALUE_EXPR, TREE_TYPE (x), x);
}

/* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
   Zero means allow extended lvalues.  */

int pedantic_lvalues;

/* When pedantic, return an expr equal to X but certainly not valid as a
   pedantic lvalue.  Otherwise, return X.  */

tree
pedantic_non_lvalue (tree x)
{
  if (pedantic_lvalues)
    return non_lvalue (x);
  else
    return x;
}
\f
/* Given a tree comparison code, return the code that is the logical inverse
   of the given code.  It is not safe to do this for floating-point
   comparisons, except for NE_EXPR and EQ_EXPR.  */

static enum tree_code
invert_tree_comparison (enum tree_code code)
{
  switch (code)
    {
    case EQ_EXPR:
      return NE_EXPR;
    case NE_EXPR:
      return EQ_EXPR;
    case GT_EXPR:
      return LE_EXPR;
    case GE_EXPR:
      return LT_EXPR;
    case LT_EXPR:
      return GE_EXPR;
    case LE_EXPR:
      return GT_EXPR;
    default:
      abort ();
    }
}

/* Similar, but return the comparison that results if the operands are
   swapped.  This is safe for floating-point.  */

static enum tree_code
swap_tree_comparison (enum tree_code code)
{
  switch (code)
    {
    case EQ_EXPR:
    case NE_EXPR:
      return code;
    case GT_EXPR:
      return LT_EXPR;
    case GE_EXPR:
      return LE_EXPR;
    case LT_EXPR:
      return GT_EXPR;
    case LE_EXPR:
      return GE_EXPR;
    default:
      abort ();
    }
}


/* Convert a comparison tree code from an enum tree_code representation
   into a compcode bit-based encoding.  This function is the inverse of
   compcode_to_comparison.  */

static int
comparison_to_compcode (enum tree_code code)
{
  switch (code)
    {
    case LT_EXPR:
      return COMPCODE_LT;
    case EQ_EXPR:
      return COMPCODE_EQ;
    case LE_EXPR:
      return COMPCODE_LE;
    case GT_EXPR:
      return COMPCODE_GT;
    case NE_EXPR:
      return COMPCODE_NE;
    case GE_EXPR:
      return COMPCODE_GE;
    default:
      abort ();
    }
}

/* Convert a compcode bit-based encoding of a comparison operator back
   to GCC's enum tree_code representation.  This function is the
   inverse of comparison_to_compcode.  */

static enum tree_code
compcode_to_comparison (int code)
{
  switch (code)
    {
    case COMPCODE_LT:
      return LT_EXPR;
    case COMPCODE_EQ:
      return EQ_EXPR;
    case COMPCODE_LE:
      return LE_EXPR;
    case COMPCODE_GT:
      return GT_EXPR;
    case COMPCODE_NE:
      return NE_EXPR;
    case COMPCODE_GE:
      return GE_EXPR;
    default:
      abort ();
    }
}

/* Return nonzero if CODE is a tree code that represents a truth value.  */

static int
truth_value_p (enum tree_code code)
{
  return (TREE_CODE_CLASS (code) == '<'
          || code == TRUTH_AND_EXPR || code == TRUTH_ANDIF_EXPR
          || code == TRUTH_OR_EXPR || code == TRUTH_ORIF_EXPR
          || code == TRUTH_XOR_EXPR || code == TRUTH_NOT_EXPR);
}
\f
/* Return nonzero if two operands (typically of the same tree node)
   are necessarily equal.  If either argument has side-effects this
   function returns zero.  FLAGS modifies behaviour as follows:

   If OEP_ONLY_CONST is set, only return nonzero for constants.
   This function tests whether the operands are indistinguishable;
   it does not test whether they are equal using C's == operation.
   The distinction is important for IEEE floating point, because
   (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
   (2) two NaNs may be indistinguishable, but NaN!=NaN.

   If OEP_ONLY_CONST is unset, a VAR_DECL is considered equal to itself
   even though it may hold multiple values during a function.
   This is because a GCC tree node guarantees that nothing else is
   executed between the evaluation of its "operands" (which may often
   be evaluated in arbitrary order).  Hence if the operands themselves
   don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
   same value in each operand/subexpression.  Hence a zero value for
   ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
   If comparing arbitrary expression trees, such as from different
   statements, ONLY_CONST must usually be nonzero.

   If OEP_PURE_SAME is set, then pure functions with identical arguments
   are considered the same.  It is used when the caller has other ways
   to ensure that global memory is unchanged in between.  */

int
operand_equal_p (tree arg0, tree arg1, unsigned int flags)
{
  /* If either is ERROR_MARK, they aren't equal.  */
  if (TREE_CODE (arg0) == ERROR_MARK || TREE_CODE (arg1) == ERROR_MARK)
    return 0;

  /* If both types don't have the same signedness, then we can't consider
     them equal.  We must check this before the STRIP_NOPS calls
     because they may change the signedness of the arguments.  */
  if (TYPE_UNSIGNED (TREE_TYPE (arg0)) != TYPE_UNSIGNED (TREE_TYPE (arg1)))
    return 0;

  STRIP_NOPS (arg0);
  STRIP_NOPS (arg1);

  if (TREE_CODE (arg0) != TREE_CODE (arg1)
      /* This is needed for conversions and for COMPONENT_REF.
         Might as well play it safe and always test this.  */
      || TREE_CODE (TREE_TYPE (arg0)) == ERROR_MARK
      || TREE_CODE (TREE_TYPE (arg1)) == ERROR_MARK
      || TYPE_MODE (TREE_TYPE (arg0)) != TYPE_MODE (TREE_TYPE (arg1)))
    return 0;

  /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
     We don't care about side effects in that case because the SAVE_EXPR
     takes care of that for us. In all other cases, two expressions are
     equal if they have no side effects.  If we have two identical
     expressions with side effects that should be treated the same due
     to the only side effects being identical SAVE_EXPR's, that will
     be detected in the recursive calls below.  */
  if (arg0 == arg1 && ! (flags & OEP_ONLY_CONST)
      && (TREE_CODE (arg0) == SAVE_EXPR
          || (! TREE_SIDE_EFFECTS (arg0) && ! TREE_SIDE_EFFECTS (arg1))))
    return 1;

  /* Next handle constant cases, those for which we can return 1 even
     if ONLY_CONST is set.  */
  if (TREE_CONSTANT (arg0) && TREE_CONSTANT (arg1))
    switch (TREE_CODE (arg0))
      {
      case INTEGER_CST:
        return (! TREE_CONSTANT_OVERFLOW (arg0)
                && ! TREE_CONSTANT_OVERFLOW (arg1)
                && tree_int_cst_equal (arg0, arg1));

      case REAL_CST:
        return (! TREE_CONSTANT_OVERFLOW (arg0)
                && ! TREE_CONSTANT_OVERFLOW (arg1)
                && REAL_VALUES_IDENTICAL (TREE_REAL_CST (arg0),
                                          TREE_REAL_CST (arg1)));

      case VECTOR_CST:
        {
          tree v1, v2;

          if (TREE_CONSTANT_OVERFLOW (arg0)
              || TREE_CONSTANT_OVERFLOW (arg1))
            return 0;

          v1 = TREE_VECTOR_CST_ELTS (arg0);
          v2 = TREE_VECTOR_CST_ELTS (arg1);
          while (v1 && v2)
            {
              if (!operand_equal_p (TREE_VALUE (v1), TREE_VALUE (v2),
                                    flags))
                return 0;
              v1 = TREE_CHAIN (v1);
              v2 = TREE_CHAIN (v2);
            }

          return 1;
        }

      case COMPLEX_CST:
        return (operand_equal_p (TREE_REALPART (arg0), TREE_REALPART (arg1),
                                 flags)
                && operand_equal_p (TREE_IMAGPART (arg0), TREE_IMAGPART (arg1),
                                    flags));

      case STRING_CST:
        return (TREE_STRING_LENGTH (arg0) == TREE_STRING_LENGTH (arg1)
                && ! memcmp (TREE_STRING_POINTER (arg0),
                              TREE_STRING_POINTER (arg1),
                              TREE_STRING_LENGTH (arg0)));

      case ADDR_EXPR:
        return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0),
                                0);
      default:
        break;
      }

  if (flags & OEP_ONLY_CONST)
    return 0;

  switch (TREE_CODE_CLASS (TREE_CODE (arg0)))
    {
    case '1':
      /* Two conversions are equal only if signedness and modes match.  */
      if ((TREE_CODE (arg0) == NOP_EXPR || TREE_CODE (arg0) == CONVERT_EXPR)
          && (TYPE_UNSIGNED (TREE_TYPE (arg0))
              != TYPE_UNSIGNED (TREE_TYPE (arg1))))
        return 0;

      return operand_equal_p (TREE_OPERAND (arg0, 0),
                              TREE_OPERAND (arg1, 0), flags);

    case '<':
    case '2':
      if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), 0)
          && operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 1),
                              0))
        return 1;

      /* For commutative ops, allow the other order.  */
      return (commutative_tree_code (TREE_CODE (arg0))
              && operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 1), flags)
              && operand_equal_p (TREE_OPERAND (arg0, 1),
                                  TREE_OPERAND (arg1, 0), flags));

    case 'r':
      /* If either of the pointer (or reference) expressions we are
         dereferencing contain a side effect, these cannot be equal.  */
      if (TREE_SIDE_EFFECTS (arg0)
          || TREE_SIDE_EFFECTS (arg1))
        return 0;

      switch (TREE_CODE (arg0))
        {
        case INDIRECT_REF:
          return operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 0), flags);

        case COMPONENT_REF:
        case ARRAY_REF:
        case ARRAY_RANGE_REF:
          return (operand_equal_p (TREE_OPERAND (arg0, 0),
                                   TREE_OPERAND (arg1, 0), flags)
                  && operand_equal_p (TREE_OPERAND (arg0, 1),
                                      TREE_OPERAND (arg1, 1), flags));

        case BIT_FIELD_REF:
          return (operand_equal_p (TREE_OPERAND (arg0, 0),
                                   TREE_OPERAND (arg1, 0), flags)
                  && operand_equal_p (TREE_OPERAND (arg0, 1),
                                      TREE_OPERAND (arg1, 1), flags)
                  && operand_equal_p (TREE_OPERAND (arg0, 2),
                                      TREE_OPERAND (arg1, 2), flags));
        default:
          return 0;
        }

    case 'e':
      switch (TREE_CODE (arg0))
        {
        case ADDR_EXPR:
        case TRUTH_NOT_EXPR:
          return operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 0), flags);

        case RTL_EXPR:
          return rtx_equal_p (RTL_EXPR_RTL (arg0), RTL_EXPR_RTL (arg1));

        case CALL_EXPR:
          /* If the CALL_EXPRs call different functions, then they
             clearly can not be equal.  */
          if (! operand_equal_p (TREE_OPERAND (arg0, 0),
                                 TREE_OPERAND (arg1, 0), flags))
            return 0;

          {
            unsigned int cef = call_expr_flags (arg0);
            if (flags & OEP_PURE_SAME)
              cef &= ECF_CONST | ECF_PURE;
            else
              cef &= ECF_CONST;
            if (!cef)
              return 0;
          }

          /* Now see if all the arguments are the same.  operand_equal_p
             does not handle TREE_LIST, so we walk the operands here
             feeding them to operand_equal_p.  */
          arg0 = TREE_OPERAND (arg0, 1);
          arg1 = TREE_OPERAND (arg1, 1);
          while (arg0 && arg1)
            {
              if (! operand_equal_p (TREE_VALUE (arg0), TREE_VALUE (arg1),
                                     flags))
                return 0;

              arg0 = TREE_CHAIN (arg0);
              arg1 = TREE_CHAIN (arg1);
            }

          /* If we get here and both argument lists are exhausted
             then the CALL_EXPRs are equal.  */
          return ! (arg0 || arg1);

        default:
          return 0;
        }

    case 'd':
      /* Consider __builtin_sqrt equal to sqrt.  */
      return (TREE_CODE (arg0) == FUNCTION_DECL
              && DECL_BUILT_IN (arg0) && DECL_BUILT_IN (arg1)
              && DECL_BUILT_IN_CLASS (arg0) == DECL_BUILT_IN_CLASS (arg1)
              && DECL_FUNCTION_CODE (arg0) == DECL_FUNCTION_CODE (arg1));

    default:
      return 0;
    }
}
\f
/* Similar to operand_equal_p, but see if ARG0 might have been made by
   shorten_compare from ARG1 when ARG1 was being compared with OTHER.

   When in doubt, return 0.  */

static int
operand_equal_for_comparison_p (tree arg0, tree arg1, tree other)
{
  int unsignedp1, unsignedpo;
  tree primarg0, primarg1, primother;
  unsigned int correct_width;

  if (operand_equal_p (arg0, arg1, 0))
    return 1;

  if (! INTEGRAL_TYPE_P (TREE_TYPE (arg0))
      || ! INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
    return 0;

  /* Discard any conversions that don't change the modes of ARG0 and ARG1
     and see if the inner values are the same.  This removes any
     signedness comparison, which doesn't matter here.  */
  primarg0 = arg0, primarg1 = arg1;
  STRIP_NOPS (primarg0);
  STRIP_NOPS (primarg1);
  if (operand_equal_p (primarg0, primarg1, 0))
    return 1;

  /* Duplicate what shorten_compare does to ARG1 and see if that gives the
     actual comparison operand, ARG0.

     First throw away any conversions to wider types
     already present in the operands.  */

  primarg1 = get_narrower (arg1, &unsignedp1);
  primother = get_narrower (other, &unsignedpo);

  correct_width = TYPE_PRECISION (TREE_TYPE (arg1));
  if (unsignedp1 == unsignedpo
      && TYPE_PRECISION (TREE_TYPE (primarg1)) < correct_width
      && TYPE_PRECISION (TREE_TYPE (primother)) < correct_width)
    {
      tree type = TREE_TYPE (arg0);

      /* Make sure shorter operand is extended the right way
         to match the longer operand.  */
      primarg1 = fold_convert (lang_hooks.types.signed_or_unsigned_type
                               (unsignedp1, TREE_TYPE (primarg1)), primarg1);

      if (operand_equal_p (arg0, fold_convert (type, primarg1), 0))
        return 1;
    }

  return 0;
}
\f
/* See if ARG is an expression that is either a comparison or is performing
   arithmetic on comparisons.  The comparisons must only be comparing
   two different values, which will be stored in *CVAL1 and *CVAL2; if
   they are nonzero it means that some operands have already been found.
   No variables may be used anywhere else in the expression except in the
   comparisons.  If SAVE_P is true it means we removed a SAVE_EXPR around
   the expression and save_expr needs to be called with CVAL1 and CVAL2.

   If this is true, return 1.  Otherwise, return zero.  */

static int
twoval_comparison_p (tree arg, tree *cval1, tree *cval2, int *save_p)
{
  enum tree_code code = TREE_CODE (arg);
  char class = TREE_CODE_CLASS (code);

  /* We can handle some of the 'e' cases here.  */
  if (class == 'e' && code == TRUTH_NOT_EXPR)
    class = '1';
  else if (class == 'e'
           && (code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR
               || code == COMPOUND_EXPR))
    class = '2';

  else if (class == 'e' && code == SAVE_EXPR && SAVE_EXPR_RTL (arg) == 0
           && ! TREE_SIDE_EFFECTS (TREE_OPERAND (arg, 0)))
    {
      /* If we've already found a CVAL1 or CVAL2, this expression is
         two complex to handle.  */
      if (*cval1 || *cval2)
        return 0;

      class = '1';
      *save_p = 1;
    }

  switch (class)
    {
    case '1':
      return twoval_comparison_p (TREE_OPERAND (arg, 0), cval1, cval2, save_p);

    case '2':
      return (twoval_comparison_p (TREE_OPERAND (arg, 0), cval1, cval2, save_p)
              && twoval_comparison_p (TREE_OPERAND (arg, 1),
                                      cval1, cval2, save_p));

    case 'c':
      return 1;

    case 'e':
      if (code == COND_EXPR)
        return (twoval_comparison_p (TREE_OPERAND (arg, 0),
                                     cval1, cval2, save_p)
                && twoval_comparison_p (TREE_OPERAND (arg, 1),
                                        cval1, cval2, save_p)
                && twoval_comparison_p (TREE_OPERAND (arg, 2),
                                        cval1, cval2, save_p));
      return 0;

    case '<':
      /* First see if we can handle the first operand, then the second.  For
         the second operand, we know *CVAL1 can't be zero.  It must be that
         one side of the comparison is each of the values; test for the
         case where this isn't true by failing if the two operands
         are the same.  */

      if (operand_equal_p (TREE_OPERAND (arg, 0),
                           TREE_OPERAND (arg, 1), 0))
        return 0;

      if (*cval1 == 0)
        *cval1 = TREE_OPERAND (arg, 0);
      else if (operand_equal_p (*cval1, TREE_OPERAND (arg, 0), 0))
        ;
      else if (*cval2 == 0)
        *cval2 = TREE_OPERAND (arg, 0);
      else if (operand_equal_p (*cval2, TREE_OPERAND (arg, 0), 0))
        ;
      else
        return 0;

      if (operand_equal_p (*cval1, TREE_OPERAND (arg, 1), 0))
        ;
      else if (*cval2 == 0)
        *cval2 = TREE_OPERAND (arg, 1);
      else if (operand_equal_p (*cval2, TREE_OPERAND (arg, 1), 0))
        ;
      else
        return 0;

      return 1;

    default:
      return 0;
    }
}
\f
/* ARG is a tree that is known to contain just arithmetic operations and
   comparisons.  Evaluate the operations in the tree substituting NEW0 for
   any occurrence of OLD0 as an operand of a comparison and likewise for
   NEW1 and OLD1.  */

static tree
eval_subst (tree arg, tree old0, tree new0, tree old1, tree new1)
{
  tree type = TREE_TYPE (arg);
  enum tree_code code = TREE_CODE (arg);
  char class = TREE_CODE_CLASS (code);

  /* We can handle some of the 'e' cases here.  */
  if (class == 'e' && code == TRUTH_NOT_EXPR)
    class = '1';
  else if (class == 'e'
           && (code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR))
    class = '2';

  switch (class)
    {
    case '1':
      return fold (build1 (code, type,
                           eval_subst (TREE_OPERAND (arg, 0),
                                       old0, new0, old1, new1)));

    case '2':
      return fold (build2 (code, type,
                           eval_subst (TREE_OPERAND (arg, 0),
                                       old0, new0, old1, new1),
                           eval_subst (TREE_OPERAND (arg, 1),
                                       old0, new0, old1, new1)));

    case 'e':
      switch (code)
        {
        case SAVE_EXPR:
          return eval_subst (TREE_OPERAND (arg, 0), old0, new0, old1, new1);

        case COMPOUND_EXPR:
          return eval_subst (TREE_OPERAND (arg, 1), old0, new0, old1, new1);

        case COND_EXPR:
          return fold (build3 (code, type,
                               eval_subst (TREE_OPERAND (arg, 0),
                                           old0, new0, old1, new1),
                               eval_subst (TREE_OPERAND (arg, 1),
                                           old0, new0, old1, new1),
                               eval_subst (TREE_OPERAND (arg, 2),
                                           old0, new0, old1, new1)));
        default:
          break;
        }
      /* Fall through - ???  */

    case '<':
      {
        tree arg0 = TREE_OPERAND (arg, 0);
        tree arg1 = TREE_OPERAND (arg, 1);

        /* We need to check both for exact equality and tree equality.  The
           former will be true if the operand has a side-effect.  In that
           case, we know the operand occurred exactly once.  */

        if (arg0 == old0 || operand_equal_p (arg0, old0, 0))
          arg0 = new0;
        else if (arg0 == old1 || operand_equal_p (arg0, old1, 0))
          arg0 = new1;

        if (arg1 == old0 || operand_equal_p (arg1, old0, 0))
          arg1 = new0;
        else if (arg1 == old1 || operand_equal_p (arg1, old1, 0))
          arg1 = new1;

        return fold (build2 (code, type, arg0, arg1));
      }

    default:
      return arg;
    }
}
\f
/* Return a tree for the case when the result of an expression is RESULT
   converted to TYPE and OMITTED was previously an operand of the expression
   but is now not needed (e.g., we folded OMITTED * 0).

   If OMITTED has side effects, we must evaluate it.  Otherwise, just do
   the conversion of RESULT to TYPE.  */

tree
omit_one_operand (tree type, tree result, tree omitted)
{
  tree t = fold_convert (type, result);

  if (TREE_SIDE_EFFECTS (omitted))
    return build2 (COMPOUND_EXPR, type, omitted, t);

  return non_lvalue (t);
}

/* Similar, but call pedantic_non_lvalue instead of non_lvalue.  */

static tree
pedantic_omit_one_operand (tree type, tree result, tree omitted)
{
  tree t = fold_convert (type, result);

  if (TREE_SIDE_EFFECTS (omitted))
    return build2 (COMPOUND_EXPR, type, omitted, t);

  return pedantic_non_lvalue (t);
}
\f
/* Return a simplified tree node for the truth-negation of ARG.  This
   never alters ARG itself.  We assume that ARG is an operation that
   returns a truth value (0 or 1).  */

tree
invert_truthvalue (tree arg)
{
  tree type = TREE_TYPE (arg);
  enum tree_code code = TREE_CODE (arg);

  if (code == ERROR_MARK)
    return arg;

  /* If this is a comparison, we can simply invert it, except for
     floating-point non-equality comparisons, in which case we just
     enclose a TRUTH_NOT_EXPR around what we have.  */

  if (TREE_CODE_CLASS (code) == '<')
    {
      if (FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (arg, 0)))
          && !flag_unsafe_math_optimizations
          && code != NE_EXPR
          && code != EQ_EXPR)
        return build1 (TRUTH_NOT_EXPR, type, arg);
      else if (code == UNORDERED_EXPR
               || code == ORDERED_EXPR
               || code == UNEQ_EXPR
               || code == UNLT_EXPR
               || code == UNLE_EXPR
               || code == UNGT_EXPR
               || code == UNGE_EXPR)
        return build1 (TRUTH_NOT_EXPR, type, arg);
      else
        return build2 (invert_tree_comparison (code), type,
                       TREE_OPERAND (arg, 0), TREE_OPERAND (arg, 1));
    }

  switch (code)
    {
    case INTEGER_CST:
      return fold_convert (type, build_int_2 (integer_zerop (arg), 0));

    case TRUTH_AND_EXPR:
      return build2 (TRUTH_OR_EXPR, type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)),
                     invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_OR_EXPR:
      return build2 (TRUTH_AND_EXPR, type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)),
                     invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_XOR_EXPR:
      /* Here we can invert either operand.  We invert the first operand
         unless the second operand is a TRUTH_NOT_EXPR in which case our
         result is the XOR of the first operand with the inside of the
         negation of the second operand.  */

      if (TREE_CODE (TREE_OPERAND (arg, 1)) == TRUTH_NOT_EXPR)
        return build2 (TRUTH_XOR_EXPR, type, TREE_OPERAND (arg, 0),
                       TREE_OPERAND (TREE_OPERAND (arg, 1), 0));
      else
        return build2 (TRUTH_XOR_EXPR, type,
                       invert_truthvalue (TREE_OPERAND (arg, 0)),
                       TREE_OPERAND (arg, 1));

    case TRUTH_ANDIF_EXPR:
      return build2 (TRUTH_ORIF_EXPR, type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)),
                     invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_ORIF_EXPR:
      return build2 (TRUTH_ANDIF_EXPR, type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)),
                     invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_NOT_EXPR:
      return TREE_OPERAND (arg, 0);

    case COND_EXPR:
      return build3 (COND_EXPR, type, TREE_OPERAND (arg, 0),
                     invert_truthvalue (TREE_OPERAND (arg, 1)),
                     invert_truthvalue (TREE_OPERAND (arg, 2)));

    case COMPOUND_EXPR:
      return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg, 0),
                     invert_truthvalue (TREE_OPERAND (arg, 1)));

    case NON_LVALUE_EXPR:
      return invert_truthvalue (TREE_OPERAND (arg, 0));

    case NOP_EXPR:
      if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE)
        break;

    case CONVERT_EXPR:
    case FLOAT_EXPR:
      return build1 (TREE_CODE (arg), type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)));

    case BIT_AND_EXPR:
      if (!integer_onep (TREE_OPERAND (arg, 1)))
        break;
      return build2 (EQ_EXPR, type, arg,
                     fold_convert (type, integer_zero_node));

    case SAVE_EXPR:
      return build1 (TRUTH_NOT_EXPR, type, arg);

    case CLEANUP_POINT_EXPR:
      return build1 (CLEANUP_POINT_EXPR, type,
                     invert_truthvalue (TREE_OPERAND (arg, 0)));

    default:
      break;
    }
  if (TREE_CODE (TREE_TYPE (arg)) != BOOLEAN_TYPE)
    abort ();
  return build1 (TRUTH_NOT_EXPR, type, arg);
}

/* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
   operands are another bit-wise operation with a common input.  If so,
   distribute the bit operations to save an operation and possibly two if
   constants are involved.  For example, convert
        (A | B) & (A | C) into A | (B & C)
   Further simplification will occur if B and C are constants.

   If this optimization cannot be done, 0 will be returned.  */

static tree
distribute_bit_expr (enum tree_code code, tree type, tree arg0, tree arg1)
{
  tree common;
  tree left, right;

  if (TREE_CODE (arg0) != TREE_CODE (arg1)
      || TREE_CODE (arg0) == code
      || (TREE_CODE (arg0) != BIT_AND_EXPR
          && TREE_CODE (arg0) != BIT_IOR_EXPR))
    return 0;

  if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), 0))
    {
      common = TREE_OPERAND (arg0, 0);
      left = TREE_OPERAND (arg0, 1);
      right = TREE_OPERAND (arg1, 1);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 1), 0))
    {
      common = TREE_OPERAND (arg0, 0);
      left = TREE_OPERAND (arg0, 1);
      right = TREE_OPERAND (arg1, 0);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 0), 0))
    {
      common = TREE_OPERAND (arg0, 1);
      left = TREE_OPERAND (arg0, 0);
      right = TREE_OPERAND (arg1, 1);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 1), 0))
    {
      common = TREE_OPERAND (arg0, 1);
      left = TREE_OPERAND (arg0, 0);
      right = TREE_OPERAND (arg1, 0);
    }
  else
    return 0;

  return fold (build2 (TREE_CODE (arg0), type, common,
                       fold (build2 (code, type, left, right))));
}
\f
/* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
   starting at BITPOS.  The field is unsigned if UNSIGNEDP is nonzero.  */

static tree
make_bit_field_ref (tree inner, tree type, int bitsize, int bitpos,
                    int unsignedp)
{
  tree result = build3 (BIT_FIELD_REF, type, inner,
                        size_int (bitsize), bitsize_int (bitpos));

  BIT_FIELD_REF_UNSIGNED (result) = unsignedp;

  return result;
}

/* Optimize a bit-field compare.

   There are two cases:  First is a compare against a constant and the
   second is a comparison of two items where the fields are at the same
   bit position relative to the start of a chunk (byte, halfword, word)
   large enough to contain it.  In these cases we can avoid the shift
   implicit in bitfield extractions.

   For constants, we emit a compare of the shifted constant with the
   BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
   compared.  For two fields at the same position, we do the ANDs with the
   similar mask and compare the result of the ANDs.

   CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
   COMPARE_TYPE is the type of the comparison, and LHS and RHS
   are the left and right operands of the comparison, respectively.

   If the optimization described above can be done, we return the resulting
   tree.  Otherwise we return zero.  */

static tree
optimize_bit_field_compare (enum tree_code code, tree compare_type,
                            tree lhs, tree rhs)
{
  HOST_WIDE_INT lbitpos, lbitsize, rbitpos, rbitsize, nbitpos, nbitsize;
  tree type = TREE_TYPE (lhs);
  tree signed_type, unsigned_type;
  int const_p = TREE_CODE (rhs) == INTEGER_CST;
  enum machine_mode lmode, rmode, nmode;
  int lunsignedp, runsignedp;
  int lvolatilep = 0, rvolatilep = 0;
  tree linner, rinner = NULL_TREE;
  tree mask;
  tree offset;

  /* Get all the information about the extractions being done.  If the bit size
     if the same as the size of the underlying object, we aren't doing an
     extraction at all and so can do nothing.  We also don't want to
     do anything if the inner expression is a PLACEHOLDER_EXPR since we
     then will no longer be able to replace it.  */
  linner = get_inner_reference (lhs, &lbitsize, &lbitpos, &offset, &lmode,
                                &lunsignedp, &lvolatilep);
  if (linner == lhs || lbitsize == GET_MODE_BITSIZE (lmode) || lbitsize < 0
      || offset != 0 || TREE_CODE (linner) == PLACEHOLDER_EXPR)
    return 0;

 if (!const_p)
   {
     /* If this is not a constant, we can only do something if bit positions,
        sizes, and signedness are the same.  */
     rinner = get_inner_reference (rhs, &rbitsize, &rbitpos, &offset, &rmode,
                                   &runsignedp, &rvolatilep);

     if (rinner == rhs || lbitpos != rbitpos || lbitsize != rbitsize
         || lunsignedp != runsignedp || offset != 0
         || TREE_CODE (rinner) == PLACEHOLDER_EXPR)
       return 0;
   }

  /* See if we can find a mode to refer to this field.  We should be able to,
     but fail if we can't.  */
  nmode = get_best_mode (lbitsize, lbitpos,
                         const_p ? TYPE_ALIGN (TREE_TYPE (linner))
                         : MIN (TYPE_ALIGN (TREE_TYPE (linner)),
                                TYPE_ALIGN (TREE_TYPE (rinner))),
                         word_mode, lvolatilep || rvolatilep);
  if (nmode == VOIDmode)
    return 0;

  /* Set signed and unsigned types of the precision of this mode for the
     shifts below.  */
  signed_type = lang_hooks.types.type_for_mode (nmode, 0);
  unsigned_type = lang_hooks.types.type_for_mode (nmode, 1);

  /* Compute the bit position and size for the new reference and our offset
     within it. If the new reference is the same size as the original, we
     won't optimize anything, so return zero.  */
  nbitsize = GET_MODE_BITSIZE (nmode);
  nbitpos = lbitpos & ~ (nbitsize - 1);
  lbitpos -= nbitpos;
  if (nbitsize == lbitsize)
    return 0;

  if (BYTES_BIG_ENDIAN)
    lbitpos = nbitsize - lbitsize - lbitpos;

  /* Make the mask to be used against the extracted field.  */
  mask = build_int_2 (~0, ~0);
  TREE_TYPE (mask) = unsigned_type;
  force_fit_type (mask, 0);
  mask = fold_convert (unsigned_type, mask);
  mask = const_binop (LSHIFT_EXPR, mask, size_int (nbitsize - lbitsize), 0);
  mask = const_binop (RSHIFT_EXPR, mask,
                      size_int (nbitsize - lbitsize - lbitpos), 0);

  if (! const_p)
    /* If not comparing with constant, just rework the comparison
       and return.  */
    return build2 (code, compare_type,
                   build2 (BIT_AND_EXPR, unsigned_type,
                           make_bit_field_ref (linner, unsigned_type,
                                               nbitsize, nbitpos, 1),
                           mask),
                   build2 (BIT_AND_EXPR, unsigned_type,
                           make_bit_field_ref (rinner, unsigned_type,
                                               nbitsize, nbitpos, 1),
                           mask));

  /* Otherwise, we are handling the constant case. See if the constant is too
     big for the field.  Warn and return a tree of for 0 (false) if so.  We do
     this not only for its own sake, but to avoid having to test for this
     error case below.  If we didn't, we might generate wrong code.

     For unsigned fields, the constant shifted right by the field length should
     be all zero.  For signed fields, the high-order bits should agree with
     the sign bit.  */

  if (lunsignedp)
    {
      if (! integer_zerop (const_binop (RSHIFT_EXPR,
                                        fold_convert (unsigned_type, rhs),
                                        size_int (lbitsize), 0)))
        {
          warning ("comparison is always %d due to width of bit-field",
                   code == NE_EXPR);
          return fold_convert (compare_type,
                               (code == NE_EXPR
                                ? integer_one_node : integer_zero_node));
        }
    }
  else
    {
      tree tem = const_binop (RSHIFT_EXPR, fold_convert (signed_type, rhs),
                              size_int (lbitsize - 1), 0);
      if (! integer_zerop (tem) && ! integer_all_onesp (tem))
        {
          warning ("comparison is always %d due to width of bit-field",
                   code == NE_EXPR);
          return fold_convert (compare_type,
                               (code == NE_EXPR
                                ? integer_one_node : integer_zero_node));
        }
    }

  /* Single-bit compares should always be against zero.  */
  if (lbitsize == 1 && ! integer_zerop (rhs))
    {
      code = code == EQ_EXPR ? NE_EXPR : EQ_EXPR;
      rhs = fold_convert (type, integer_zero_node);
    }

  /* Make a new bitfield reference, shift the constant over the
     appropriate number of bits and mask it with the computed mask
     (in case this was a signed field).  If we changed it, make a new one.  */
  lhs = make_bit_field_ref (linner, unsigned_type, nbitsize, nbitpos, 1);
  if (lvolatilep)
    {
      TREE_SIDE_EFFECTS (lhs) = 1;
      TREE_THIS_VOLATILE (lhs) = 1;
    }

  rhs = fold (const_binop (BIT_AND_EXPR,
                           const_binop (LSHIFT_EXPR,
                                        fold_convert (unsigned_type, rhs),
                                        size_int (lbitpos), 0),
                           mask, 0));

  return build2 (code, compare_type,
                 build2 (BIT_AND_EXPR, unsigned_type, lhs, mask),
                 rhs);
}
\f
/* Subroutine for fold_truthop: decode a field reference.

   If EXP is a comparison reference, we return the innermost reference.

   *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
   set to the starting bit number.

   If the innermost field can be completely contained in a mode-sized
   unit, *PMODE is set to that mode.  Otherwise, it is set to VOIDmode.

   *PVOLATILEP is set to 1 if the any expression encountered is volatile;
   otherwise it is not changed.

   *PUNSIGNEDP is set to the signedness of the field.

   *PMASK is set to the mask used.  This is either contained in a
   BIT_AND_EXPR or derived from the width of the field.

   *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.

   Return 0 if this is not a component reference or is one that we can't
   do anything with.  */

static tree
decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize,
                        HOST_WIDE_INT *pbitpos, enum machine_mode *pmode,
                        int *punsignedp, int *pvolatilep,
                        tree *pmask, tree *pand_mask)
{
  tree outer_type = 0;
  tree and_mask = 0;
  tree mask, inner, offset;
  tree unsigned_type;
  unsigned int precision;

  /* All the optimizations using this function assume integer fields.
     There are problems with FP fields since the type_for_size call
     below can fail for, e.g., XFmode.  */
  if (! INTEGRAL_TYPE_P (TREE_TYPE (exp)))
    return 0;

  /* We are interested in the bare arrangement of bits, so strip everything
     that doesn't affect the machine mode.  However, record the type of the
     outermost expression if it may matter below.  */
  if (TREE_CODE (exp) == NOP_EXPR
      || TREE_CODE (exp) == CONVERT_EXPR
      || TREE_CODE (exp) == NON_LVALUE_EXPR)
    outer_type = TREE_TYPE (exp);
  STRIP_NOPS (exp);

  if (TREE_CODE (exp) == BIT_AND_EXPR)
    {
      and_mask = TREE_OPERAND (exp, 1);
      exp = TREE_OPERAND (exp, 0);
      STRIP_NOPS (exp); STRIP_NOPS (and_mask);
      if (TREE_CODE (and_mask) != INTEGER_CST)
        return 0;
    }

  inner = get_inner_reference (exp, pbitsize, pbitpos, &offset, pmode,
                               punsignedp, pvolatilep);
  if ((inner == exp && and_mask == 0)
      || *pbitsize < 0 || offset != 0
      || TREE_CODE (inner) == PLACEHOLDER_EXPR)
    return 0;

  /* If the number of bits in the reference is the same as the bitsize of
     the outer type, then the outer type gives the signedness. Otherwise
     (in case of a small bitfield) the signedness is unchanged.  */
  if (outer_type && *pbitsize == tree_low_cst (TYPE_SIZE (outer_type), 1))
    *punsignedp = TYPE_UNSIGNED (outer_type);

  /* Compute the mask to access the bitfield.  */
  unsigned_type = lang_hooks.types.type_for_size (*pbitsize, 1);
  precision = TYPE_PRECISION (unsigned_type);

  mask = build_int_2 (~0, ~0);
  TREE_TYPE (mask) = unsigned_type;
  force_fit_type (mask, 0);
  mask = const_binop (LSHIFT_EXPR, mask, size_int (precision - *pbitsize), 0);
  mask = const_binop (RSHIFT_EXPR, mask, size_int (precision - *pbitsize), 0);

  /* Merge it with the mask we found in the BIT_AND_EXPR, if any.  */
  if (and_mask != 0)
    mask = fold (build2 (BIT_AND_EXPR, unsigned_type,
                         fold_convert (unsigned_type, and_mask), mask));

  *pmask = mask;
  *pand_mask = and_mask;
  return inner;
}

/* Return nonzero if MASK represents a mask of SIZE ones in the low-order
   bit positions.  */

static int
all_ones_mask_p (tree mask, int size)
{
  tree type = TREE_TYPE (mask);
  unsigned int precision = TYPE_PRECISION (type);
  tree tmask;

  tmask = build_int_2 (~0, ~0);
  TREE_TYPE (tmask) = lang_hooks.types.signed_type (type);
  force_fit_type (tmask, 0);
  return
    tree_int_cst_equal (mask,
                        const_binop (RSHIFT_EXPR,
                                     const_binop (LSHIFT_EXPR, tmask,
                                                  size_int (precision - size),
                                                  0),
                                     size_int (precision - size), 0));
}

/* Subroutine for fold: determine if VAL is the INTEGER_CONST that
   represents the sign bit of EXP's type.  If EXP represents a sign
   or zero extension, also test VAL against the unextended type.
   The return value is the (sub)expression whose sign bit is VAL,
   or NULL_TREE otherwise.  */

static tree
sign_bit_p (tree exp, tree val)
{
  unsigned HOST_WIDE_INT mask_lo, lo;
  HOST_WIDE_INT mask_hi, hi;
  int width;
  tree t;

  /* Tree EXP must have an integral type.  */
  t = TREE_TYPE (exp);
  if (! INTEGRAL_TYPE_P (t))
    return NULL_TREE;

  /* Tree VAL must be an integer constant.  */
  if (TREE_CODE (val) != INTEGER_CST
      || TREE_CONSTANT_OVERFLOW (val))
    return NULL_TREE;

  width = TYPE_PRECISION (t);
  if (width > HOST_BITS_PER_WIDE_INT)
    {
      hi = (unsigned HOST_WIDE_INT) 1 << (width - HOST_BITS_PER_WIDE_INT - 1);
      lo = 0;

      mask_hi = ((unsigned HOST_WIDE_INT) -1
                 >> (2 * HOST_BITS_PER_WIDE_INT - width));
      mask_lo = -1;
    }
  else
    {
      hi = 0;
      lo = (unsigned HOST_WIDE_INT) 1 << (width - 1);

      mask_hi = 0;
      mask_lo = ((unsigned HOST_WIDE_INT) -1
                 >> (HOST_BITS_PER_WIDE_INT - width));
    }

  /* We mask off those bits beyond TREE_TYPE (exp) so that we can
     treat VAL as if it were unsigned.  */
  if ((TREE_INT_CST_HIGH (val) & mask_hi) == hi
      && (TREE_INT_CST_LOW (val) & mask_lo) == lo)
    return exp;

  /* Handle extension from a narrower type.  */
  if (TREE_CODE (exp) == NOP_EXPR
      && TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (exp, 0))) < width)
    return sign_bit_p (TREE_OPERAND (exp, 0), val);

  return NULL_TREE;
}

/* Subroutine for fold_truthop: determine if an operand is simple enough
   to be evaluated unconditionally.  */

static int
simple_operand_p (tree exp)
{
  /* Strip any conversions that don't change the machine mode.  */
  while ((TREE_CODE (exp) == NOP_EXPR
          || TREE_CODE (exp) == CONVERT_EXPR)
         && (TYPE_MODE (TREE_TYPE (exp))
             == TYPE_MODE (TREE_TYPE (TREE_OPERAND (exp, 0)))))
    exp = TREE_OPERAND (exp, 0);

  return (TREE_CODE_CLASS (TREE_CODE (exp)) == 'c'
          || (DECL_P (exp)
              && ! TREE_ADDRESSABLE (exp)
              && ! TREE_THIS_VOLATILE (exp)
              && ! DECL_NONLOCAL (exp)
              /* Don't regard global variables as simple.  They may be
                 allocated in ways unknown to the compiler (shared memory,
                 #pragma weak, etc).  */
              && ! TREE_PUBLIC (exp)
              && ! DECL_EXTERNAL (exp)
              /* Loading a static variable is unduly expensive, but global
                 registers aren't expensive.  */
              && (! TREE_STATIC (exp) || DECL_REGISTER (exp))));
}
\f
/* The following functions are subroutines to fold_range_test and allow it to
   try to change a logical combination of comparisons into a range test.

   For example, both
        X == 2 || X == 3 || X == 4 || X == 5
   and
        X >= 2 && X <= 5
   are converted to
        (unsigned) (X - 2) <= 3

   We describe each set of comparisons as being either inside or outside
   a range, using a variable named like IN_P, and then describe the
   range with a lower and upper bound.  If one of the bounds is omitted,
   it represents either the highest or lowest value of the type.

   In the comments below, we represent a range by two numbers in brackets
   preceded by a "+" to designate being inside that range, or a "-" to
   designate being outside that range, so the condition can be inverted by
   flipping the prefix.  An omitted bound is represented by a "-".  For
   example, "- [-, 10]" means being outside the range starting at the lowest
   possible value and ending at 10, in other words, being greater than 10.
   The range "+ [-, -]" is always true and hence the range "- [-, -]" is
   always false.

   We set up things so that the missing bounds are handled in a consistent
   manner so neither a missing bound nor "true" and "false" need to be
   handled using a special case.  */

/* Return the result of applying CODE to ARG0 and ARG1, but handle the case
   of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
   and UPPER1_P are nonzero if the respective argument is an upper bound
   and zero for a lower.  TYPE, if nonzero, is the type of the result; it
   must be specified for a comparison.  ARG1 will be converted to ARG0's
   type if both are specified.  */

static tree
range_binop (enum tree_code code, tree type, tree arg0, int upper0_p,
             tree arg1, int upper1_p)
{
  tree tem;
  int result;
  int sgn0, sgn1;

  /* If neither arg represents infinity, do the normal operation.
     Else, if not a comparison, return infinity.  Else handle the special
     comparison rules. Note that most of the cases below won't occur, but
     are handled for consistency.  */

  if (arg0 != 0 && arg1 != 0)
    {
      tem = fold (build2 (code, type != 0 ? type : TREE_TYPE (arg0),
                          arg0, fold_convert (TREE_TYPE (arg0), arg1)));
      STRIP_NOPS (tem);
      return TREE_CODE (tem) == INTEGER_CST ? tem : 0;
    }

  if (TREE_CODE_CLASS (code) != '<')
    return 0;

  /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
     for neither.  In real maths, we cannot assume open ended ranges are
     the same. But, this is computer arithmetic, where numbers are finite.
     We can therefore make the transformation of any unbounded range with
     the value Z, Z being greater than any representable number. This permits
     us to treat unbounded ranges as equal.  */
  sgn0 = arg0 != 0 ? 0 : (upper0_p ? 1 : -1);
  sgn1 = arg1 != 0 ? 0 : (upper1_p ? 1 : -1);
  switch (code)
    {
    case EQ_EXPR:
      result = sgn0 == sgn1;
      break;
    case NE_EXPR:
      result = sgn0 != sgn1;
      break;
    case LT_EXPR:
      result = sgn0 < sgn1;
      break;
    case LE_EXPR:
      result = sgn0 <= sgn1;
      break;
    case GT_EXPR:
      result = sgn0 > sgn1;
      break;
    case GE_EXPR:
      result = sgn0 >= sgn1;
      break;
    default:
      abort ();
    }

  return fold_convert (type, result ? integer_one_node : integer_zero_node);
}
\f
/* Given EXP, a logical expression, set the range it is testing into
   variables denoted by PIN_P, PLOW, and PHIGH.  Return the expression
   actually being tested.  *PLOW and *PHIGH will be made of the same type
   as the returned expression.  If EXP is not a comparison, we will most
   likely not be returning a useful value and range.  */

static tree
make_range (tree exp, int *pin_p, tree *plow, tree *phigh)
{
  enum tree_code code;
  tree arg0 = NULL_TREE, arg1 = NULL_TREE, type = NULL_TREE;
  tree orig_type = NULL_TREE;
  int in_p, n_in_p;
  tree low, high, n_low, n_high;

  /* Start with simply saying "EXP != 0" and then look at the code of EXP
     and see if we can refine the range.  Some of the cases below may not
     happen, but it doesn't seem worth worrying about this.  We "continue"
     the outer loop when we've changed something; otherwise we "break"
     the switch, which will "break" the while.  */

  in_p = 0;
  low = high = fold_convert (TREE_TYPE (exp), integer_zero_node);

  while (1)
    {
      code = TREE_CODE (exp);

      if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
        {
          if (first_rtl_op (code) > 0)
            arg0 = TREE_OPERAND (exp, 0);
          if (TREE_CODE_CLASS (code) == '<'
              || TREE_CODE_CLASS (code) == '1'
              || TREE_CODE_CLASS (code) == '2')
            type = TREE_TYPE (arg0);
          if (TREE_CODE_CLASS (code) == '2'
              || TREE_CODE_CLASS (code) == '<'
              || (TREE_CODE_CLASS (code) == 'e'
                  && TREE_CODE_LENGTH (code) > 1))
            arg1 = TREE_OPERAND (exp, 1);
        }

      /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
         lose a cast by accident.  */
      if (type != NULL_TREE && orig_type == NULL_TREE)
        orig_type = type;

      switch (code)
        {
        case TRUTH_NOT_EXPR:
          in_p = ! in_p, exp = arg0;
          continue;

        case EQ_EXPR: case NE_EXPR:
        case LT_EXPR: case LE_EXPR: case GE_EXPR: case GT_EXPR:
          /* We can only do something if the range is testing for zero
             and if the second operand is an integer constant.  Note that
             saying something is "in" the range we make is done by
             complementing IN_P since it will set in the initial case of
             being not equal to zero; "out" is leaving it alone.  */
          if (low == 0 || high == 0
              || ! integer_zerop (low) || ! integer_zerop (high)
              || TREE_CODE (arg1) != INTEGER_CST)
            break;

          switch (code)
            {
            case NE_EXPR:  /* - [c, c]  */
              low = high = arg1;
              break;
            case EQ_EXPR:  /* + [c, c]  */
              in_p = ! in_p, low = high = arg1;
              break;
            case GT_EXPR:  /* - [-, c] */
              low = 0, high = arg1;
              break;
            case GE_EXPR:  /* + [c, -] */
              in_p = ! in_p, low = arg1, high = 0;
              break;
            case LT_EXPR:  /* - [c, -] */
              low = arg1, high = 0;
              break;
            case LE_EXPR:  /* + [-, c] */
              in_p = ! in_p, low = 0, high = arg1;
              break;
            default:
              abort ();
            }

          exp = arg0;

          /* If this is an unsigned comparison, we also know that EXP is
             greater than or equal to zero.  We base the range tests we make
             on that fact, so we record it here so we can parse existing
             range tests.  */
          if (TYPE_UNSIGNED (type) && (low == 0 || high == 0))
            {
              if (! merge_ranges (&n_in_p, &n_low, &n_high, in_p, low, high,
                                  1, fold_convert (type, integer_zero_node),
                                  NULL_TREE))
                break;

              in_p = n_in_p, low = n_low, high = n_high;

              /* If the high bound is missing, but we have a nonzero low
                 bound, reverse the range so it goes from zero to the low bound
                 minus 1.  */
              if (high == 0 && low && ! integer_zerop (low))
                {
                  in_p = ! in_p;
                  high = range_binop (MINUS_EXPR, NULL_TREE, low, 0,
                                      integer_one_node, 0);
                  low = fold_convert (type, integer_zero_node);
                }
            }
          continue;

        case NEGATE_EXPR:
          /* (-x) IN [a,b] -> x in [-b, -a]  */
          n_low = range_binop (MINUS_EXPR, type,
                               fold_convert (type, integer_zero_node),
                               0, high, 1);
          n_high = range_binop (MINUS_EXPR, type,
                                fold_convert (type, integer_zero_node),
                                0, low, 0);
          low = n_low, high = n_high;
          exp = arg0;
          continue;

        case BIT_NOT_EXPR:
          /* ~ X -> -X - 1  */
          exp = build2 (MINUS_EXPR, type, negate_expr (arg0),
                        fold_convert (type, integer_one_node));
          continue;

        case PLUS_EXPR:  case MINUS_EXPR:
          if (TREE_CODE (arg1) != INTEGER_CST)
            break;

          /* If EXP is signed, any overflow in the computation is undefined,
             so we don't worry about it so long as our computations on
             the bounds don't overflow.  For unsigned, overflow is defined
             and this is exactly the right thing.  */
          n_low = range_binop (code == MINUS_EXPR ? PLUS_EXPR : MINUS_EXPR,
                               type, low, 0, arg1, 0);
          n_high = range_binop (code == MINUS_EXPR ? PLUS_EXPR : MINUS_EXPR,
                                type, high, 1, arg1, 0);
          if ((n_low != 0 && TREE_OVERFLOW (n_low))
              || (n_high != 0 && TREE_OVERFLOW (n_high)))
            break;

          /* Check for an unsigned range which has wrapped around the maximum
             value thus making n_high < n_low, and normalize it.  */
          if (n_low && n_high && tree_int_cst_lt (n_high, n_low))
            {
              low = range_binop (PLUS_EXPR, type, n_high, 0,
                                 integer_one_node, 0);
              high = range_binop (MINUS_EXPR, type, n_low, 0,
                                  integer_one_node, 0);

              /* If the range is of the form +/- [ x+1, x ], we won't
                 be able to normalize it.  But then, it represents the
                 whole range or the empty set, so make it
                 +/- [ -, - ].  */
              if (tree_int_cst_equal (n_low, low)
                  && tree_int_cst_equal (n_high, high))
                low = high = 0;
              else
                in_p = ! in_p;
            }
          else
            low = n_low, high = n_high;

          exp = arg0;
          continue;

        case NOP_EXPR:  case NON_LVALUE_EXPR:  case CONVERT_EXPR:
          if (TYPE_PRECISION (type) > TYPE_PRECISION (orig_type))
            break;

          if (! INTEGRAL_TYPE_P (type)
              || (low != 0 && ! int_fits_type_p (low, type))
              || (high != 0 && ! int_fits_type_p (high, type)))
            break;

          n_low = low, n_high = high;

          if (n_low != 0)
            n_low = fold_convert (type, n_low);

          if (n_high != 0)
            n_high = fold_convert (type, n_high);

          /* If we're converting from an unsigned to a signed type,
             we will be doing the comparison as unsigned.  The tests above
             have already verified that LOW and HIGH are both positive.

             So we have to make sure that the original unsigned value will
             be interpreted as positive.  */
          if (TYPE_UNSIGNED (type) && ! TYPE_UNSIGNED (TREE_TYPE (exp)))
            {
              tree equiv_type = lang_hooks.types.type_for_mode
                (TYPE_MODE (type), 1);
              tree high_positive;

              /* A range without an upper bound is, naturally, unbounded.
                 Since convert would have cropped a very large value, use
                 the max value for the destination type.  */
              high_positive
                = TYPE_MAX_VALUE (equiv_type) ? TYPE_MAX_VALUE (equiv_type)
                  : TYPE_MAX_VALUE (type);

              if (TYPE_PRECISION (type) == TYPE_PRECISION (TREE_TYPE (exp)))
                high_positive = fold (build2 (RSHIFT_EXPR, type,
                                              fold_convert (type,
                                                            high_positive),
                                              fold_convert (type,
                                                            integer_one_node)));

              /* If the low bound is specified, "and" the range with the
                 range for which the original unsigned value will be
                 positive.  */
              if (low != 0)
                {
                  if (! merge_ranges (&n_in_p, &n_low, &n_high,
                                      1, n_low, n_high, 1,
                                      fold_convert (type, integer_zero_node),
                                      high_positive))
                    break;

                  in_p = (n_in_p == in_p);
                }
              else
                {
                  /* Otherwise, "or" the range with the range of the input
                     that will be interpreted as negative.  */
                  if (! merge_ranges (&n_in_p, &n_low, &n_high,
                                      0, n_low, n_high, 1,
                                      fold_convert (type, integer_zero_node),
                                      high_positive))
                    break;

                  in_p = (in_p != n_in_p);
                }
            }

          exp = arg0;
          low = n_low, high = n_high;
          continue;

        default:
          break;
        }

      break;
    }

  /* If EXP is a constant, we can evaluate whether this is true or false.  */
  if (TREE_CODE (exp) == INTEGER_CST)
    {
      in_p = in_p == (integer_onep (range_binop (GE_EXPR, integer_type_node,
                                                 exp, 0, low, 0))
                      && integer_onep (range_binop (LE_EXPR, integer_type_node,
                                                    exp, 1, high, 1)));
      low = high = 0;
      exp = 0;
    }

  *pin_p = in_p, *plow = low, *phigh = high;
  return exp;
}
\f
/* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
   type, TYPE, return an expression to test if EXP is in (or out of, depending
   on IN_P) the range.  */

static tree
build_range_check (tree type, tree exp, int in_p, tree low, tree high)
{
  tree etype = TREE_TYPE (exp);
  tree value;

  if (! in_p
      && (0 != (value = build_range_check (type, exp, 1, low, high))))
    return invert_truthvalue (value);

  if (low == 0 && high == 0)
    return fold_convert (type, integer_one_node);

  if (low == 0)
    return fold (build2 (LE_EXPR, type, exp, high));

  if (high == 0)
    return fold (build2 (GE_EXPR, type, exp, low));

  if (operand_equal_p (low, high, 0))
    return fold (build2 (EQ_EXPR, type, exp, low));

  if (integer_zerop (low))
    {
      if (! TYPE_UNSIGNED (etype))
        {
          etype = lang_hooks.types.unsigned_type (etype);
          high = fold_convert (etype, high);
          exp = fold_convert (etype, exp);
        }
      return build_range_check (type, exp, 1, 0, high);
    }

  /* Optimize (c>=1) && (c<=127) into (signed char)c > 0.  */
  if (integer_onep (low) && TREE_CODE (high) == INTEGER_CST)
    {
      unsigned HOST_WIDE_INT lo;
      HOST_WIDE_INT hi;
      int prec;

      prec = TYPE_PRECISION (etype);
      if (prec <= HOST_BITS_PER_WIDE_INT)
        {
          hi = 0;
          lo = ((unsigned HOST_WIDE_INT) 1 << (prec - 1)) - 1;
        }
      else
        {
          hi = ((HOST_WIDE_INT) 1 << (prec - HOST_BITS_PER_WIDE_INT - 1)) - 1;
          lo = (unsigned HOST_WIDE_INT) -1;
        }

      if (TREE_INT_CST_HIGH (high) == hi && TREE_INT_CST_LOW (high) == lo)
        {
          if (TYPE_UNSIGNED (etype))
            {
              etype = lang_hooks.types.signed_type (etype);
              exp = fold_convert (etype, exp);
            }
          return fold (build2 (GT_EXPR, type, exp,
                               fold_convert (etype, integer_zero_node)));
        }
    }

  if (0 != (value = const_binop (MINUS_EXPR, high, low, 0))
      && ! TREE_OVERFLOW (value))
    return build_range_check (type,
                              fold (build2 (MINUS_EXPR, etype, exp, low)),
                              1, fold_convert (etype, integer_zero_node),
                              value);

  return 0;
}
\f
/* Given two ranges, see if we can merge them into one.  Return 1 if we
   can, 0 if we can't.  Set the output range into the specified parameters.  */

static int
merge_ranges (int *pin_p, tree *plow, tree *phigh, int in0_p, tree low0,
              tree high0, int in1_p, tree low1, tree high1)
{
  int no_overlap;
  int subset;
  int temp;
  tree tem;
  int in_p;
  tree low, high;
  int lowequal = ((low0 == 0 && low1 == 0)
                  || integer_onep (range_binop (EQ_EXPR, integer_type_node,
                                                low0, 0, low1, 0)));
  int highequal = ((high0 == 0 && high1 == 0)
                   || integer_onep (range_binop (EQ_EXPR, integer_type_node,
                                                 high0, 1, high1, 1)));

  /* Make range 0 be the range that starts first, or ends last if they
     start at the same value.  Swap them if it isn't.  */
  if (integer_onep (range_binop (GT_EXPR, integer_type_node,
                                 low0, 0, low1, 0))
      || (lowequal
          && integer_onep (range_binop (GT_EXPR, integer_type_node,
                                        high1, 1, high0, 1))))
    {
      temp = in0_p, in0_p = in1_p, in1_p = temp;
      tem = low0, low0 = low1, low1 = tem;
      tem = high0, high0 = high1, high1 = tem;
    }

  /* Now flag two cases, whether the ranges are disjoint or whether the
     second range is totally subsumed in the first.  Note that the tests
     below are simplified by the ones above.  */
  no_overlap = integer_onep (range_binop (LT_EXPR, integer_type_node,
                                          high0, 1, low1, 0));
  subset = integer_onep (range_binop (LE_EXPR, integer_type_node,
                                      high1, 1, high0, 1));

  /* We now have four cases, depending on whether we are including or
     excluding the two ranges.  */
  if (in0_p && in1_p)
    {
      /* If they don't overlap, the result is false.  If the second range
         is a subset it is the result.  Otherwise, the range is from the start
         of the second to the end of the first.  */
      if (no_overlap)
        in_p = 0, low = high = 0;
      else if (subset)
        in_p = 1, low = low1, high = high1;
      else
        in_p = 1, low = low1, high = high0;
    }

  else if (in0_p && ! in1_p)
    {
      /* If they don't overlap, the result is the first range.  If they are
         equal, the result is false.  If the second range is a subset of the
         first, and the ranges begin at the same place, we go from just after
         the end of the first range to the end of the second.  If the second
         range is not a subset of the first, or if it is a subset and both
         ranges end at the same place, the range starts at the start of the
         first range and ends just before the second range.
         Otherwise, we can't describe this as a single range.  */
      if (no_overlap)
        in_p = 1, low = low0, high = high0;
      else if (lowequal && highequal)
        in_p = 0, low = high = 0;
      else if (subset && lowequal)
        {
          in_p = 1, high = high0;
          low = range_binop (PLUS_EXPR, NULL_TREE, high1, 0,
                             integer_one_node, 0);
        }
      else if (! subset || highequal)
        {
          in_p = 1, low = low0;
          high = range_binop (MINUS_EXPR, NULL_TREE, low1, 0,
                              integer_one_node, 0);
        }
      else
        return 0;
    }

  else if (! in0_p && in1_p)
    {
      /* If they don't overlap, the result is the second range.  If the second
         is a subset of the first, the result is false.  Otherwise,
         the range starts just after the first range and ends at the
         end of the second.  */
      if (no_overlap)
        in_p = 1, low = low1, high = high1;
      else if (subset || highequal)
        in_p = 0, low = high = 0;
      else
        {
          in_p = 1, high = high1;
          low = range_binop (PLUS_EXPR, NULL_TREE, high0, 1,
                             integer_one_node, 0);
        }
    }

  else
    {
      /* The case where we are excluding both ranges.  Here the complex case
         is if they don't overlap.  In that case, the only time we have a
         range is if they are adjacent.  If the second is a subset of the
         first, the result is the first.  Otherwise, the range to exclude
         starts at the beginning of the first range and ends at the end of the
         second.  */
      if (no_overlap)
        {
          if (integer_onep (range_binop (EQ_EXPR, integer_type_node,
                                         range_binop (PLUS_EXPR, NULL_TREE,
                                                      high0, 1,
                                                      integer_one_node, 1),
                                         1, low1, 0)))
            in_p = 0, low = low0, high = high1;
          else
            return 0;
        }
      else if (subset)
        in_p = 0, low = low0, high = high0;
      else
        in_p = 0, low = low0, high = high1;
    }

  *pin_p = in_p, *plow = low, *phigh = high;
  return 1;
}
\f
#ifndef RANGE_TEST_NON_SHORT_CIRCUIT
#define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
#endif

/* EXP is some logical combination of boolean tests.  See if we can
   merge it into some range test.  Return the new tree if so.  */

static tree
fold_range_test (tree exp)
{
  int or_op = (TREE_CODE (exp) == TRUTH_ORIF_EXPR
               || TREE_CODE (exp) == TRUTH_OR_EXPR);
  int in0_p, in1_p, in_p;
  tree low0, low1, low, high0, high1, high;
  tree lhs = make_range (TREE_OPERAND (exp, 0), &in0_p, &low0, &high0);
  tree rhs = make_range (TREE_OPERAND (exp, 1), &in1_p, &low1, &high1);
  tree tem;

  /* If this is an OR operation, invert both sides; we will invert
     again at the end.  */
  if (or_op)
    in0_p = ! in0_p, in1_p = ! in1_p;

  /* If both expressions are the same, if we can merge the ranges, and we
     can build the range test, return it or it inverted.  If one of the
     ranges is always true or always false, consider it to be the same
     expression as the other.  */
  if ((lhs == 0 || rhs == 0 || operand_equal_p (lhs, rhs, 0))
      && merge_ranges (&in_p, &low, &high, in0_p, low0, high0,
                       in1_p, low1, high1)
      && 0 != (tem = (build_range_check (TREE_TYPE (exp),
                                         lhs != 0 ? lhs
                                         : rhs != 0 ? rhs : integer_zero_node,
                                         in_p, low, high))))
    return or_op ? invert_truthvalue (tem) : tem;

  /* On machines where the branch cost is expensive, if this is a
     short-circuited branch and the underlying object on both sides
     is the same, make a non-short-circuit operation.  */
  else if (RANGE_TEST_NON_SHORT_CIRCUIT
           && lhs != 0 && rhs != 0
           && (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
               || TREE_CODE (exp) == TRUTH_ORIF_EXPR)
           && operand_equal_p (lhs, rhs, 0))
    {
      /* If simple enough, just rewrite.  Otherwise, make a SAVE_EXPR
         unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
         which cases we can't do this.  */
      if (simple_operand_p (lhs))
        return build2 (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
                       ? TRUTH_AND_EXPR : TRUTH_OR_EXPR,
                       TREE_TYPE (exp), TREE_OPERAND (exp, 0),
                       TREE_OPERAND (exp, 1));

      else if (lang_hooks.decls.global_bindings_p () == 0
               && ! CONTAINS_PLACEHOLDER_P (lhs))
        {
          tree common = save_expr (lhs);

          if (0 != (lhs = build_range_check (TREE_TYPE (exp), common,
                                             or_op ? ! in0_p : in0_p,
                                             low0, high0))
              && (0 != (rhs = build_range_check (TREE_TYPE (exp), common,
                                                 or_op ? ! in1_p : in1_p,
                                                 low1, high1))))
            return build2 (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
                           ? TRUTH_AND_EXPR : TRUTH_OR_EXPR,
                           TREE_TYPE (exp), lhs, rhs);
        }
    }

  return 0;
}
\f
/* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
   bit value.  Arrange things so the extra bits will be set to zero if and
   only if C is signed-extended to its full width.  If MASK is nonzero,
   it is an INTEGER_CST that should be AND'ed with the extra bits.  */

static tree
unextend (tree c, int p, int unsignedp, tree mask)
{
  tree type = TREE_TYPE (c);
  int modesize = GET_MODE_BITSIZE (TYPE_MODE (type));
  tree temp;

  if (p == modesize || unsignedp)
    return c;

  /* We work by getting just the sign bit into the low-order bit, then
     into the high-order bit, then sign-extend.  We then XOR that value
     with C.  */
  temp = const_binop (RSHIFT_EXPR, c, size_int (p - 1), 0);
  temp = const_binop (BIT_AND_EXPR, temp, size_int (1), 0);

  /* We must use a signed type in order to get an arithmetic right shift.
     However, we must also avoid introducing accidental overflows, so that
     a subsequent call to integer_zerop will work.  Hence we must
     do the type conversion here.  At this point, the constant is either
     zero or one, and the conversion to a signed type can never overflow.
     We could get an overflow if this conversion is done anywhere else.  */
  if (TYPE_UNSIGNED (type))
    temp = fold_convert (lang_hooks.types.signed_type (type), temp);

  temp = const_binop (LSHIFT_EXPR, temp, size_int (modesize - 1), 0);
  temp = const_binop (RSHIFT_EXPR, temp, size_int (modesize - p - 1), 0);
  if (mask != 0)
    temp = const_binop (BIT_AND_EXPR, temp,
                        fold_convert (TREE_TYPE (c), mask), 0);
  /* If necessary, convert the type back to match the type of C.  */
  if (TYPE_UNSIGNED (type))
    temp = fold_convert (type, temp);

  return fold_convert (type, const_binop (BIT_XOR_EXPR, c, temp, 0));
}
\f
/* Find ways of folding logical expressions of LHS and RHS:
   Try to merge two comparisons to the same innermost item.
   Look for range tests like "ch >= '0' && ch <= '9'".
   Look for combinations of simple terms on machines with expensive branches
   and evaluate the RHS unconditionally.

   For example, if we have p->a == 2 && p->b == 4 and we can make an
   object large enough to span both A and B, we can do this with a comparison
   against the object ANDed with the a mask.

   If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
   operations to do this with one comparison.

   We check for both normal comparisons and the BIT_AND_EXPRs made this by
   function and the one above.

   CODE is the logical operation being done.  It can be TRUTH_ANDIF_EXPR,
   TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.

   TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
   two operands.

   We return the simplified tree or 0 if no optimization is possible.  */

static tree
fold_truthop (enum tree_code code, tree truth_type, tree lhs, tree rhs)
{
  /* If this is the "or" of two comparisons, we can do something if
     the comparisons are NE_EXPR.  If this is the "and", we can do something
     if the comparisons are EQ_EXPR.  I.e.,
        (a->b == 2 && a->c == 4) can become (a->new == NEW).

     WANTED_CODE is this operation code.  For single bit fields, we can
     convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
     comparison for one-bit fields.  */

  enum tree_code wanted_code;
  enum tree_code lcode, rcode;
  tree ll_arg, lr_arg, rl_arg, rr_arg;
  tree ll_inner, lr_inner, rl_inner, rr_inner;
  HOST_WIDE_INT ll_bitsize, ll_bitpos, lr_bitsize, lr_bitpos;
  HOST_WIDE_INT rl_bitsize, rl_bitpos, rr_bitsize, rr_bitpos;
  HOST_WIDE_INT xll_bitpos, xlr_bitpos, xrl_bitpos, xrr_bitpos;
  HOST_WIDE_INT lnbitsize, lnbitpos, rnbitsize, rnbitpos;
  int ll_unsignedp, lr_unsignedp, rl_unsignedp, rr_unsignedp;
  enum machine_mode ll_mode, lr_mode, rl_mode, rr_mode;
  enum machine_mode lnmode, rnmode;
  tree ll_mask, lr_mask, rl_mask, rr_mask;
  tree ll_and_mask, lr_and_mask, rl_and_mask, rr_and_mask;
  tree l_const, r_const;
  tree lntype, rntype, result;
  int first_bit, end_bit;
  int volatilep;

  /* Start by getting the comparison codes.  Fail if anything is volatile.
     If one operand is a BIT_AND_EXPR with the constant one, treat it as if
     it were surrounded with a NE_EXPR.  */

  if (TREE_SIDE_EFFECTS (lhs) || TREE_SIDE_EFFECTS (rhs))
    return 0;

  lcode = TREE_CODE (lhs);
  rcode = TREE_CODE (rhs);

  if (lcode == BIT_AND_EXPR && integer_onep (TREE_OPERAND (lhs, 1)))
    {
      lhs = build2 (NE_EXPR, truth_type, lhs, integer_zero_node);
      lcode = NE_EXPR;
    }

  if (rcode == BIT_AND_EXPR && integer_onep (TREE_OPERAND (rhs, 1)))
    {
      rhs = build2 (NE_EXPR, truth_type, rhs, integer_zero_node);
      rcode = NE_EXPR;
    }

  if (TREE_CODE_CLASS (lcode) != '<' || TREE_CODE_CLASS (rcode) != '<')
    return 0;

  code = ((code == TRUTH_AND_EXPR || code == TRUTH_ANDIF_EXPR)
          ? TRUTH_AND_EXPR : TRUTH_OR_EXPR);

  ll_arg = TREE_OPERAND (lhs, 0);
  lr_arg = TREE_OPERAND (lhs, 1);
  rl_arg = TREE_OPERAND (rhs, 0);
  rr_arg = TREE_OPERAND (rhs, 1);

  /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations.  */
  if (simple_operand_p (ll_arg)
      && simple_operand_p (lr_arg)
      && !FLOAT_TYPE_P (TREE_TYPE (ll_arg)))
    {
      int compcode;

      if (operand_equal_p (ll_arg, rl_arg, 0)
          && operand_equal_p (lr_arg, rr_arg, 0))
        {
          int lcompcode, rcompcode;

          lcompcode = comparison_to_compcode (lcode);
          rcompcode = comparison_to_compcode (rcode);
          compcode = (code == TRUTH_AND_EXPR)
                     ? lcompcode & rcompcode
                     : lcompcode | rcompcode;
        }
      else if (operand_equal_p (ll_arg, rr_arg, 0)
               && operand_equal_p (lr_arg, rl_arg, 0))
        {
          int lcompcode, rcompcode;

          rcode = swap_tree_comparison (rcode);
          lcompcode = comparison_to_compcode (lcode);
          rcompcode = comparison_to_compcode (rcode);
          compcode = (code == TRUTH_AND_EXPR)
                     ? lcompcode & rcompcode
                     : lcompcode | rcompcode;
        }
      else
        compcode = -1;

      if (compcode == COMPCODE_TRUE)
        return fold_convert (truth_type, integer_one_node);
      else if (compcode == COMPCODE_FALSE)
        return fold_convert (truth_type, integer_zero_node);
      else if (compcode != -1)
        return build2 (compcode_to_comparison (compcode),
                       truth_type, ll_arg, lr_arg);
    }

  /* If the RHS can be evaluated unconditionally and its operands are
     simple, it wins to evaluate the RHS unconditionally on machines
     with expensive branches.  In this case, this isn't a comparison
     that can be merged.  Avoid doing this if the RHS is a floating-point
     comparison since those can trap.  */

  if (BRANCH_COST >= 2
      && ! FLOAT_TYPE_P (TREE_TYPE (rl_arg))
      && simple_operand_p (rl_arg)
      && simple_operand_p (rr_arg))
    {
      /* Convert (a != 0) || (b != 0) into (a | b) != 0.  */
      if (code == TRUTH_OR_EXPR
          && lcode == NE_EXPR && integer_zerop (lr_arg)
          && rcode == NE_EXPR && integer_zerop (rr_arg)
          && TREE_TYPE (ll_arg) == TREE_TYPE (rl_arg))
        return build2 (NE_EXPR, truth_type,
                       build2 (BIT_IOR_EXPR, TREE_TYPE (ll_arg),
                               ll_arg, rl_arg),
                       integer_zero_node);

      /* Convert (a == 0) && (b == 0) into (a | b) == 0.  */
      if (code == TRUTH_AND_EXPR
          && lcode == EQ_EXPR && integer_zerop (lr_arg)
          && rcode == EQ_EXPR && integer_zerop (rr_arg)
          && TREE_TYPE (ll_arg) == TREE_TYPE (rl_arg))
        return build2 (EQ_EXPR, truth_type,
                       build2 (BIT_IOR_EXPR, TREE_TYPE (ll_arg),
                               ll_arg, rl_arg),
                       integer_zero_node);

      return build2 (code, truth_type, lhs, rhs);
    }

  /* See if the comparisons can be merged.  Then get all the parameters for
     each side.  */

  if ((lcode != EQ_EXPR && lcode != NE_EXPR)
      || (rcode != EQ_EXPR && rcode != NE_EXPR))
    return 0;

  volatilep = 0;
  ll_inner = decode_field_reference (ll_arg,
                                     &ll_bitsize, &ll_bitpos, &ll_mode,
                                     &ll_unsignedp, &volatilep, &ll_mask,
                                     &ll_and_mask);
  lr_inner = decode_field_reference (lr_arg,
                                     &lr_bitsize, &lr_bitpos, &lr_mode,
                                     &lr_unsignedp, &volatilep, &lr_mask,
                                     &lr_and_mask);
  rl_inner = decode_field_reference (rl_arg,
                                     &rl_bitsize, &rl_bitpos, &rl_mode,
                                     &rl_unsignedp, &volatilep, &rl_mask,
                                     &rl_and_mask);
  rr_inner = decode_field_reference (rr_arg,
                                     &rr_bitsize, &rr_bitpos, &rr_mode,
                                     &rr_unsignedp, &volatilep, &rr_mask,
                                     &rr_and_mask);

  /* It must be true that the inner operation on the lhs of each
     comparison must be the same if we are to be able to do anything.
     Then see if we have constants.  If not, the same must be true for
     the rhs's.  */
  if (volatilep || ll_inner == 0 || rl_inner == 0
      || ! operand_equal_p (ll_inner, rl_inner, 0))
    return 0;

  if (TREE_CODE (lr_arg) == INTEGER_CST
      && TREE_CODE (rr_arg) == INTEGER_CST)
    l_const = lr_arg, r_const = rr_arg;
  else if (lr_inner == 0 || rr_inner == 0
           || ! operand_equal_p (lr_inner, rr_inner, 0))
    return 0;
  else
    l_const = r_const = 0;

  /* If either comparison code is not correct for our logical operation,
     fail.  However, we can convert a one-bit comparison against zero into
     the opposite comparison against that bit being set in the field.  */

  wanted_code = (code == TRUTH_AND_EXPR ? EQ_EXPR : NE_EXPR);
  if (lcode != wanted_code)
    {
      if (l_const && integer_zerop (l_const) && integer_pow2p (ll_mask))
        {
          /* Make the left operand unsigned, since we are only interested
             in the value of one bit.  Otherwise we are doing the wrong
             thing below.  */
          ll_unsignedp = 1;
          l_const = ll_mask;
        }
      else
        return 0;
    }

  /* This is analogous to the code for l_const above.  */
  if (rcode != wanted_code)
    {
      if (r_const && integer_zerop (r_const) && integer_pow2p (rl_mask))
        {
          rl_unsignedp = 1;
          r_const = rl_mask;
        }
      else
        return 0;
    }

  /* After this point all optimizations will generate bit-field
     references, which we might not want.  */
  if (! lang_hooks.can_use_bit_fields_p ())
    return 0;

  /* See if we can find a mode that contains both fields being compared on
     the left.  If we can't, fail.  Otherwise, update all constants and masks
     to be relative to a field of that size.  */
  first_bit = MIN (ll_bitpos, rl_bitpos);
  end_bit = MAX (ll_bitpos + ll_bitsize, rl_bitpos + rl_bitsize);
  lnmode = get_best_mode (end_bit - first_bit, first_bit,
                          TYPE_ALIGN (TREE_TYPE (ll_inner)), word_mode,
                          volatilep);
  if (lnmode == VOIDmode)
    return 0;

  lnbitsize = GET_MODE_BITSIZE (lnmode);
  lnbitpos = first_bit & ~ (lnbitsize - 1);
  lntype = lang_hooks.types.type_for_size (lnbitsize, 1);
  xll_bitpos = ll_bitpos - lnbitpos, xrl_bitpos = rl_bitpos - lnbitpos;

  if (BYTES_BIG_ENDIAN)
    {
      xll_bitpos = lnbitsize - xll_bitpos - ll_bitsize;
      xrl_bitpos = lnbitsize - xrl_bitpos - rl_bitsize;
    }

  ll_mask = const_binop (LSHIFT_EXPR, fold_convert (lntype, ll_mask),
                         size_int (xll_bitpos), 0);
  rl_mask = const_binop (LSHIFT_EXPR, fold_convert (lntype, rl_mask),
                         size_int (xrl_bitpos), 0);

  if (l_const)
    {
      l_const = fold_convert (lntype, l_const);
      l_const = unextend (l_const, ll_bitsize, ll_unsignedp, ll_and_mask);
      l_const = const_binop (LSHIFT_EXPR, l_const, size_int (xll_bitpos), 0);
      if (! integer_zerop (const_binop (BIT_AND_EXPR, l_const,
                                        fold (build1 (BIT_NOT_EXPR,
                                                      lntype, ll_mask)),
                                        0)))
        {
          warning ("comparison is always %d", wanted_code == NE_EXPR);

          return fold_convert (truth_type,
                               wanted_code == NE_EXPR
                               ? integer_one_node : integer_zero_node);
        }
    }
  if (r_const)
    {
      r_const = fold_convert (lntype, r_const);
      r_const = unextend (r_const, rl_bitsize, rl_unsignedp, rl_and_mask);
      r_const = const_binop (LSHIFT_EXPR, r_const, size_int (xrl_bitpos), 0);
      if (! integer_zerop (const_binop (BIT_AND_EXPR, r_const,
                                        fold (build1 (BIT_NOT_EXPR,
                                                      lntype, rl_mask)),
                                        0)))
        {
          warning ("comparison is always %d", wanted_code == NE_EXPR);

          return fold_convert (truth_type,
                               wanted_code == NE_EXPR
                               ? integer_one_node : integer_zero_node);
        }
    }

  /* If the right sides are not constant, do the same for it.  Also,
     disallow this optimization if a size or signedness mismatch occurs
     between the left and right sides.  */
  if (l_const == 0)
    {
      if (ll_bitsize != lr_bitsize || rl_bitsize != rr_bitsize
          || ll_unsignedp != lr_unsignedp || rl_unsignedp != rr_unsignedp
          /* Make sure the two fields on the right
             correspond to the left without being swapped.  */
          || ll_bitpos - rl_bitpos != lr_bitpos - rr_bitpos)
        return 0;

      first_bit = MIN (lr_bitpos, rr_bitpos);
      end_bit = MAX (lr_bitpos + lr_bitsize, rr_bitpos + rr_bitsize);
      rnmode = get_best_mode (end_bit - first_bit, first_bit,
                              TYPE_ALIGN (TREE_TYPE (lr_inner)), word_mode,
                              volatilep);
      if (rnmode == VOIDmode)
        return 0;

      rnbitsize = GET_MODE_BITSIZE (rnmode);
      rnbitpos = first_bit & ~ (rnbitsize - 1);
      rntype = lang_hooks.types.type_for_size (rnbitsize, 1);
      xlr_bitpos = lr_bitpos - rnbitpos, xrr_bitpos = rr_bitpos - rnbitpos;

      if (BYTES_BIG_ENDIAN)
        {
          xlr_bitpos = rnbitsize - xlr_bitpos - lr_bitsize;
          xrr_bitpos = rnbitsize - xrr_bitpos - rr_bitsize;
        }

      lr_mask = const_binop (LSHIFT_EXPR, fold_convert (rntype, lr_mask),
                             size_int (xlr_bitpos), 0);
      rr_mask = const_binop (LSHIFT_EXPR, fold_convert (rntype, rr_mask),
                             size_int (xrr_bitpos), 0);

      /* Make a mask that corresponds to both fields being compared.
         Do this for both items being compared.  If the operands are the
         same size and the bits being compared are in the same position
         then we can do this by masking both and comparing the masked
         results.  */
      ll_mask = const_binop (BIT_IOR_EXPR, ll_mask, rl_mask, 0);
      lr_mask = const_binop (BIT_IOR_EXPR, lr_mask, rr_mask, 0);
      if (lnbitsize == rnbitsize && xll_bitpos == xlr_bitpos)
        {
          lhs = make_bit_field_ref (ll_inner, lntype, lnbitsize, lnbitpos,
                                    ll_unsignedp || rl_unsignedp);
          if (! all_ones_mask_p (ll_mask, lnbitsize))
            lhs = build2 (BIT_AND_EXPR, lntype, lhs, ll_mask);

          rhs = make_bit_field_ref (lr_inner, rntype, rnbitsize, rnbitpos,
                                    lr_unsignedp || rr_unsignedp);
          if (! all_ones_mask_p (lr_mask, rnbitsize))
            rhs = build2 (BIT_AND_EXPR, rntype, rhs, lr_mask);

          return build2 (wanted_code, truth_type, lhs, rhs);
        }

      /* There is still another way we can do something:  If both pairs of
         fields being compared are adjacent, we may be able to make a wider
         field containing them both.

         Note that we still must mask the lhs/rhs expressions.  Furthermore,
         the mask must be shifted to account for the shift done by
         make_bit_field_ref.  */
      if ((ll_bitsize + ll_bitpos == rl_bitpos
           && lr_bitsize + lr_bitpos == rr_bitpos)
          || (ll_bitpos == rl_bitpos + rl_bitsize
              && lr_bitpos == rr_bitpos + rr_bitsize))
        {
          tree type;

          lhs = make_bit_field_ref (ll_inner, lntype, ll_bitsize + rl_bitsize,
                                    MIN (ll_bitpos, rl_bitpos), ll_unsignedp);
          rhs = make_bit_field_ref (lr_inner, rntype, lr_bitsize + rr_bitsize,
                                    MIN (lr_bitpos, rr_bitpos), lr_unsignedp);

          ll_mask = const_binop (RSHIFT_EXPR, ll_mask,
                                 size_int (MIN (xll_bitpos, xrl_bitpos)), 0);
          lr_mask = const_binop (RSHIFT_EXPR, lr_mask,
                                 size_int (MIN (xlr_bitpos, xrr_bitpos)), 0);

          /* Convert to the smaller type before masking out unwanted bits.  */
          type = lntype;
          if (lntype != rntype)
            {
              if (lnbitsize > rnbitsize)
                {
                  lhs = fold_convert (rntype, lhs);
                  ll_mask = fold_convert (rntype, ll_mask);
                  type = rntype;
                }
              else if (lnbitsize < rnbitsize)
                {
                  rhs = fold_convert (lntype, rhs);
                  lr_mask = fold_convert (lntype, lr_mask);
                  type = lntype;
                }
            }

          if (! all_ones_mask_p (ll_mask, ll_bitsize + rl_bitsize))
            lhs = build2 (BIT_AND_EXPR, type, lhs, ll_mask);

          if (! all_ones_mask_p (lr_mask, lr_bitsize + rr_bitsize))
            rhs = build2 (BIT_AND_EXPR, type, rhs, lr_mask);

          return build2 (wanted_code, truth_type, lhs, rhs);
        }

      return 0;
    }

  /* Handle the case of comparisons with constants.  If there is something in
     common between the masks, those bits of the constants must be the same.
     If not, the condition is always false.  Test for this to avoid generating
     incorrect code below.  */
  result = const_binop (BIT_AND_EXPR, ll_mask, rl_mask, 0);
  if (! integer_zerop (result)
      && simple_cst_equal (const_binop (BIT_AND_EXPR, result, l_const, 0),
                           const_binop (BIT_AND_EXPR, result, r_const, 0)) != 1)
    {
      if (wanted_code == NE_EXPR)
        {
          warning ("`or' of unmatched not-equal tests is always 1");
          return fold_convert (truth_type, integer_one_node);
        }
      else
        {
          warning ("`and' of mutually exclusive equal-tests is always 0");
          return fold_convert (truth_type, integer_zero_node);
        }
    }

  /* Construct the expression we will return.  First get the component
     reference we will make.  Unless the mask is all ones the width of
     that field, perform the mask operation.  Then compare with the
     merged constant.  */
  result = make_bit_field_ref (ll_inner, lntype, lnbitsize, lnbitpos,
                               ll_unsignedp || rl_unsignedp);

  ll_mask = const_binop (BIT_IOR_EXPR, ll_mask, rl_mask, 0);
  if (! all_ones_mask_p (ll_mask, lnbitsize))
    result = build2 (BIT_AND_EXPR, lntype, result, ll_mask);

  return build2 (wanted_code, truth_type, result,
                 const_binop (BIT_IOR_EXPR, l_const, r_const, 0));
}
\f
/* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
   constant.  */

static tree
optimize_minmax_comparison (tree t)
{
  tree type = TREE_TYPE (t);
  tree arg0 = TREE_OPERAND (t, 0);
  enum tree_code op_code;
  tree comp_const = TREE_OPERAND (t, 1);
  tree minmax_const;
  int consts_equal, consts_lt;
  tree inner;

  STRIP_SIGN_NOPS (arg0);

  op_code = TREE_CODE (arg0);
  minmax_const = TREE_OPERAND (arg0, 1);
  consts_equal = tree_int_cst_equal (minmax_const, comp_const);
  consts_lt = tree_int_cst_lt (minmax_const, comp_const);
  inner = TREE_OPERAND (arg0, 0);

  /* If something does not permit us to optimize, return the original tree.  */
  if ((op_code != MIN_EXPR && op_code != MAX_EXPR)
      || TREE_CODE (comp_const) != INTEGER_CST
      || TREE_CONSTANT_OVERFLOW (comp_const)
      || TREE_CODE (minmax_const) != INTEGER_CST
      || TREE_CONSTANT_OVERFLOW (minmax_const))
    return t;

  /* Now handle all the various comparison codes.  We only handle EQ_EXPR
     and GT_EXPR, doing the rest with recursive calls using logical
     simplifications.  */
  switch (TREE_CODE (t))
    {
    case NE_EXPR:  case LT_EXPR:  case LE_EXPR:
      return
        invert_truthvalue (optimize_minmax_comparison (invert_truthvalue (t)));

    case GE_EXPR:
      return
        fold (build2 (TRUTH_ORIF_EXPR, type,
                      optimize_minmax_comparison
                      (build2 (EQ_EXPR, type, arg0, comp_const)),
                      optimize_minmax_comparison
                      (build2 (GT_EXPR, type, arg0, comp_const))));

    case EQ_EXPR:
      if (op_code == MAX_EXPR && consts_equal)
        /* MAX (X, 0) == 0  ->  X <= 0  */
        return fold (build2 (LE_EXPR, type, inner, comp_const));

      else if (op_code == MAX_EXPR && consts_lt)
        /* MAX (X, 0) == 5  ->  X == 5   */
        return fold (build2 (EQ_EXPR, type, inner, comp_const));

      else if (op_code == MAX_EXPR)
        /* MAX (X, 0) == -1  ->  false  */
        return omit_one_operand (type, integer_zero_node, inner);

      else if (consts_equal)
        /* MIN (X, 0) == 0  ->  X >= 0  */
        return fold (build2 (GE_EXPR, type, inner, comp_const));

      else if (consts_lt)
        /* MIN (X, 0) == 5  ->  false  */
        return omit_one_operand (type, integer_zero_node, inner);

      else
        /* MIN (X, 0) == -1  ->  X == -1  */
        return fold (build2 (EQ_EXPR, type, inner, comp_const));

    case GT_EXPR:
      if (op_code == MAX_EXPR && (consts_equal || consts_lt))
        /* MAX (X, 0) > 0  ->  X > 0
           MAX (X, 0) > 5  ->  X > 5  */
        return fold (build2 (GT_EXPR, type, inner, comp_const));

      else if (op_code == MAX_EXPR)
        /* MAX (X, 0) > -1  ->  true  */
        return omit_one_operand (type, integer_one_node, inner);

      else if (op_code == MIN_EXPR && (consts_equal || consts_lt))
        /* MIN (X, 0) > 0  ->  false
           MIN (X, 0) > 5  ->  false  */
        return omit_one_operand (type, integer_zero_node, inner);

      else
        /* MIN (X, 0) > -1  ->  X > -1  */
        return fold (build2 (GT_EXPR, type, inner, comp_const));

    default:
      return t;
    }
}
\f
/* T is an integer expression that is being multiplied, divided, or taken a
   modulus (CODE says which and what kind of divide or modulus) by a
   constant C.  See if we can eliminate that operation by folding it with
   other operations already in T.  WIDE_TYPE, if non-null, is a type that
   should be used for the computation if wider than our type.

   For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
   (X * 2) + (Y * 4).  We must, however, be assured that either the original
   expression would not overflow or that overflow is undefined for the type
   in the language in question.

   We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
   the machine has a multiply-accumulate insn or that this is part of an
   addressing calculation.

   If we return a non-null expression, it is an equivalent form of the
   original computation, but need not be in the original type.  */

static tree
extract_muldiv (tree t, tree c, enum tree_code code, tree wide_type)
{
  /* To avoid exponential search depth, refuse to allow recursion past
     three levels.  Beyond that (1) it's highly unlikely that we'll find
     something interesting and (2) we've probably processed it before
     when we built the inner expression.  */

  static int depth;
  tree ret;

  if (depth > 3)
    return NULL;

  depth++;
  ret = extract_muldiv_1 (t, c, code, wide_type);
  depth--;

  return ret;
}

static tree
extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type)
{
  tree type = TREE_TYPE (t);
  enum tree_code tcode = TREE_CODE (t);
  tree ctype = (wide_type != 0 && (GET_MODE_SIZE (TYPE_MODE (wide_type))
                                   > GET_MODE_SIZE (TYPE_MODE (type)))
                ? wide_type : type);
  tree t1, t2;
  int same_p = tcode == code;
  tree op0 = NULL_TREE, op1 = NULL_TREE;

  /* Don't deal with constants of zero here; they confuse the code below.  */
  if (integer_zerop (c))
    return NULL_TREE;

  if (TREE_CODE_CLASS (tcode) == '1')
    op0 = TREE_OPERAND (t, 0);

  if (TREE_CODE_CLASS (tcode) == '2')
    op0 = TREE_OPERAND (t, 0), op1 = TREE_OPERAND (t, 1);

  /* Note that we need not handle conditional operations here since fold
     already handles those cases.  So just do arithmetic here.  */
  switch (tcode)
    {
    case INTEGER_CST:
      /* For a constant, we can always simplify if we are a multiply
         or (for divide and modulus) if it is a multiple of our constant.  */
      if (code == MULT_EXPR
          || integer_zerop (const_binop (TRUNC_MOD_EXPR, t, c, 0)))
        return const_binop (code, fold_convert (ctype, t),
                            fold_convert (ctype, c), 0);
      break;

    case CONVERT_EXPR:  case NON_LVALUE_EXPR:  case NOP_EXPR:
      /* If op0 is an expression ...  */
      if ((TREE_CODE_CLASS (TREE_CODE (op0)) == '<'
           || TREE_CODE_CLASS (TREE_CODE (op0)) == '1'
           || TREE_CODE_CLASS (TREE_CODE (op0)) == '2'
           || TREE_CODE_CLASS (TREE_CODE (op0)) == 'e')
          /* ... and is unsigned, and its type is smaller than ctype,
             then we cannot pass through as widening.  */
          && ((TYPE_UNSIGNED (TREE_TYPE (op0))
               && ! (TREE_CODE (TREE_TYPE (op0)) == INTEGER_TYPE
                     && TYPE_IS_SIZETYPE (TREE_TYPE (op0)))
               && (GET_MODE_SIZE (TYPE_MODE (ctype))
                   > GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0)))))
              /* ... or its type is larger than ctype,
                 then we cannot pass through this truncation.  */
              || (GET_MODE_SIZE (TYPE_MODE (ctype))
                  < GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0))))
              /* ... or signedness changes for division or modulus,
                 then we cannot pass through this conversion.  */
              || (code != MULT_EXPR
                  && (TYPE_UNSIGNED (ctype)
                      != TYPE_UNSIGNED (TREE_TYPE (op0))))))
        break;

      /* Pass the constant down and see if we can make a simplification.  If
         we can, replace this expression with the inner simplification for
         possible later conversion to our or some other type.  */
      if ((t2 = fold_convert (TREE_TYPE (op0), c)) != 0
          && TREE_CODE (t2) == INTEGER_CST
          && ! TREE_CONSTANT_OVERFLOW (t2)
          && (0 != (t1 = extract_muldiv (op0, t2, code,
                                         code == MULT_EXPR
                                         ? ctype : NULL_TREE))))
        return t1;
      break;

    case NEGATE_EXPR:  case ABS_EXPR:
      if ((t1 = extract_muldiv (op0, c, code, wide_type)) != 0)
        return fold (build1 (tcode, ctype, fold_convert (ctype, t1)));
      break;

    case MIN_EXPR:  case MAX_EXPR:
      /* If widening the type changes the signedness, then we can't perform
         this optimization as that changes the result.  */
      if (TYPE_UNSIGNED (ctype) != TYPE_UNSIGNED (type))
        break;

      /* MIN (a, b) / 5 -> MIN (a / 5, b / 5)  */
      if ((t1 = extract_muldiv (op0, c, code, wide_type)) != 0
          && (t2 = extract_muldiv (op1, c, code, wide_type)) != 0)
        {
          if (tree_int_cst_sgn (c) < 0)
            tcode = (tcode == MIN_EXPR ? MAX_EXPR : MIN_EXPR);

          return fold (build2 (tcode, ctype, fold_convert (ctype, t1),
                               fold_convert (ctype, t2)));
        }
      break;

    case LSHIFT_EXPR:  case RSHIFT_EXPR:
      /* If the second operand is constant, this is a multiplication
         or floor division, by a power of two, so we can treat it that
         way unless the multiplier or divisor overflows.  */
      if (TREE_CODE (op1) == INTEGER_CST
          /* const_binop may not detect overflow correctly,
             so check for it explicitly here.  */
          && TYPE_PRECISION (TREE_TYPE (size_one_node)) > TREE_INT_CST_LOW (op1)
          && TREE_INT_CST_HIGH (op1) == 0
          && 0 != (t1 = fold_convert (ctype,
                                      const_binop (LSHIFT_EXPR,
                                                   size_one_node,
                                                   op1, 0)))
          && ! TREE_OVERFLOW (t1))
        return extract_muldiv (build2 (tcode == LSHIFT_EXPR
                                       ? MULT_EXPR : FLOOR_DIV_EXPR,
                                       ctype, fold_convert (ctype, op0), t1),
                               c, code, wide_type);
      break;

    case PLUS_EXPR:  case MINUS_EXPR:
      /* See if we can eliminate the operation on both sides.  If we can, we
         can return a new PLUS or MINUS.  If we can't, the only remaining
         cases where we can do anything are if the second operand is a
         constant.  */
      t1 = extract_muldiv (op0, c, code, wide_type);
      t2 = extract_muldiv (op1, c, code, wide_type);
      if (t1 != 0 && t2 != 0
          && (code == MULT_EXPR
              /* If not multiplication, we can only do this if both operands
                 are divisible by c.  */
              || (multiple_of_p (ctype, op0, c)
                  && multiple_of_p (ctype, op1, c))))
        return fold (build2 (tcode, ctype, fold_convert (ctype, t1),
                             fold_convert (ctype, t2)));

      /* If this was a subtraction, negate OP1 and set it to be an addition.
         This simplifies the logic below.  */
      if (tcode == MINUS_EXPR)
        tcode = PLUS_EXPR, op1 = negate_expr (op1);

      if (TREE_CODE (op1) != INTEGER_CST)
        break;

      /* If either OP1 or C are negative, this optimization is not safe for
         some of the division and remainder types while for others we need
         to change the code.  */
      if (tree_int_cst_sgn (op1) < 0 || tree_int_cst_sgn (c) < 0)
        {
          if (code == CEIL_DIV_EXPR)
            code = FLOOR_DIV_EXPR;
          else if (code == FLOOR_DIV_EXPR)
            code = CEIL_DIV_EXPR;
          else if (code != MULT_EXPR
                   && code != CEIL_MOD_EXPR && code != FLOOR_MOD_EXPR)
            break;
        }

      /* If it's a multiply or a division/modulus operation of a multiple
         of our constant, do the operation and verify it doesn't overflow.  */
      if (code == MULT_EXPR
          || integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
        {
          op1 = const_binop (code, fold_convert (ctype, op1),
                             fold_convert (ctype, c), 0);
          /* We allow the constant to overflow with wrapping semantics.  */
          if (op1 == 0
              || (TREE_OVERFLOW (op1) && ! flag_wrapv))
            break;
        }
      else
        break;

      /* If we have an unsigned type is not a sizetype, we cannot widen
         the operation since it will change the result if the original
         computation overflowed.  */
      if (TYPE_UNSIGNED (ctype)
          && ! (TREE_CODE (ctype) == INTEGER_TYPE && TYPE_IS_SIZETYPE (ctype))
          && ctype != type)
        break;

      /* If we were able to eliminate our operation from the first side,
         apply our operation to the second side and reform the PLUS.  */
      if (t1 != 0 && (TREE_CODE (t1) != code || code == MULT_EXPR))
        return fold (build2 (tcode, ctype, fold_convert (ctype, t1), op1));

      /* The last case is if we are a multiply.  In that case, we can
         apply the distributive law to commute the multiply and addition
         if the multiplication of the constants doesn't overflow.  */
      if (code == MULT_EXPR)
        return fold (build2 (tcode, ctype,
                             fold (build2 (code, ctype,
                                           fold_convert (ctype, op0),
                                           fold_convert (ctype, c))),
                             op1));

      break;

    case MULT_EXPR:
      /* We have a special case here if we are doing something like
         (C * 8) % 4 since we know that's zero.  */
      if ((code == TRUNC_MOD_EXPR || code == CEIL_MOD_EXPR
           || code == FLOOR_MOD_EXPR || code == ROUND_MOD_EXPR)
          && TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST
          && integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
        return omit_one_operand (type, integer_zero_node, op0);

      /* ... fall through ...  */

    case TRUNC_DIV_EXPR:  case CEIL_DIV_EXPR:  case FLOOR_DIV_EXPR:
    case ROUND_DIV_EXPR:  case EXACT_DIV_EXPR:
      /* If we can extract our operation from the LHS, do so and return a
         new operation.  Likewise for the RHS from a MULT_EXPR.  Otherwise,
         do something only if the second operand is a constant.  */
      if (same_p
          && (t1 = extract_muldiv (op0, c, code, wide_type)) != 0)
        return fold (build2 (tcode, ctype, fold_convert (ctype, t1),
                             fold_convert (ctype, op1)));
      else if (tcode == MULT_EXPR && code == MULT_EXPR
               && (t1 = extract_muldiv (op1, c, code, wide_type)) != 0)
        return fold (build2 (tcode, ctype, fold_convert (ctype, op0),
                             fold_convert (ctype, t1)));
      else if (TREE_CODE (op1) != INTEGER_CST)
        return 0;

      /* If these are the same operation types, we can associate them
         assuming no overflow.  */
      if (tcode == code
          && 0 != (t1 = const_binop (MULT_EXPR, fold_convert (ctype, op1),
                                     fold_convert (ctype, c), 0))
          && ! TREE_OVERFLOW (t1))
        return fold (build2 (tcode, ctype, fold_convert (ctype, op0), t1));

      /* If these operations "cancel" each other, we have the main
         optimizations of this pass, which occur when either constant is a
         multiple of the other, in which case we replace this with either an
         operation or CODE or TCODE.

         If we have an unsigned type that is not a sizetype, we cannot do
         this since it will change the result if the original computation
         overflowed.  */
      if ((! TYPE_UNSIGNED (ctype)
           || (TREE_CODE (ctype) == INTEGER_TYPE && TYPE_IS_SIZETYPE (ctype)))
          && ! flag_wrapv
          && ((code == MULT_EXPR && tcode == EXACT_DIV_EXPR)
              || (tcode == MULT_EXPR
                  && code != TRUNC_MOD_EXPR && code != CEIL_MOD_EXPR
                  && code != FLOOR_MOD_EXPR && code != ROUND_MOD_EXPR)))
        {
          if (integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
            return fold (build2 (tcode, ctype, fold_convert (ctype, op0),
                                 fold_convert (ctype,
                                               const_binop (TRUNC_DIV_EXPR,
                                                            op1, c, 0))));
          else if (integer_zerop (const_binop (TRUNC_MOD_EXPR, c, op1, 0)))
            return fold (build2 (code, ctype, fold_convert (ctype, op0),
                                 fold_convert (ctype,
                                               const_binop (TRUNC_DIV_EXPR,
                                                            c, op1, 0))));
        }
      break;

    default:
      break;
    }

  return 0;
}
\f
/* Return a node which has the indicated constant VALUE (either 0 or
   1), and is of the indicated TYPE.  */

static tree
constant_boolean_node (int value, tree type)
{
  if (type == integer_type_node)
    return value ? integer_one_node : integer_zero_node;
  else if (TREE_CODE (type) == BOOLEAN_TYPE)
    return lang_hooks.truthvalue_conversion (value ? integer_one_node
                                                   : integer_zero_node);
  else
    {
      tree t = build_int_2 (value, 0);

      TREE_TYPE (t) = type;
      return t;
    }
}

/* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
   Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'.  Here
   CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
   expression, and ARG to `a'.  If COND_FIRST_P is nonzero, then the
   COND is the first argument to CODE; otherwise (as in the example
   given here), it is the second argument.  TYPE is the type of the
   original expression.  Return NULL_TREE if no simplification is
   possible.  */

static tree
fold_binary_op_with_conditional_arg (enum tree_code code, tree type,
                                     tree cond, tree arg, int cond_first_p)
{
  tree test, true_value, false_value;
  tree lhs = NULL_TREE;
  tree rhs = NULL_TREE;

  /* This transformation is only worthwhile if we don't have to wrap
     arg in a SAVE_EXPR, and the operation can be simplified on atleast
     one of the branches once its pushed inside the COND_EXPR.  */
  if (!TREE_CONSTANT (arg))
    return NULL_TREE;

  if (TREE_CODE (cond) == COND_EXPR)
    {
      test = TREE_OPERAND (cond, 0);
      true_value = TREE_OPERAND (cond, 1);
      false_value = TREE_OPERAND (cond, 2);
      /* If this operand throws an expression, then it does not make
         sense to try to perform a logical or arithmetic operation
         involving it.  */
      if (VOID_TYPE_P (TREE_TYPE (true_value)))
        lhs = true_value;
      if (VOID_TYPE_P (TREE_TYPE (false_value)))
        rhs = false_value;
    }
  else
    {
      tree testtype = TREE_TYPE (cond);
      test = cond;
      true_value = fold_convert (testtype, integer_one_node);
      false_value = fold_convert (testtype, integer_zero_node);
    }

  if (lhs == 0)
    lhs = fold (cond_first_p ? build2 (code, type, true_value, arg)
                             : build2 (code, type, arg, true_value));
  if (rhs == 0)
    rhs = fold (cond_first_p ? build2 (code, type, false_value, arg)
                             : build2 (code, type, arg, false_value));

  test = fold (build3 (COND_EXPR, type, test, lhs, rhs));
  return fold_convert (type, test);
}

\f
/* Subroutine of fold() that checks for the addition of +/- 0.0.

   If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
   TYPE, X + ADDEND is the same as X.  If NEGATE, return true if X -
   ADDEND is the same as X.

   X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
   and finite.  The problematic cases are when X is zero, and its mode
   has signed zeros.  In the case of rounding towards -infinity,
   X - 0 is not the same as X because 0 - 0 is -0.  In other rounding
   modes, X + 0 is not the same as X because -0 + 0 is 0.  */

static bool
fold_real_zero_addition_p (tree type, tree addend, int negate)
{
  if (!real_zerop (addend))
    return false;

  /* Don't allow the fold with -fsignaling-nans.  */
  if (HONOR_SNANS (TYPE_MODE (type)))
    return false;

  /* Allow the fold if zeros aren't signed, or their sign isn't important.  */
  if (!HONOR_SIGNED_ZEROS (TYPE_MODE (type)))
    return true;

  /* Treat x + -0 as x - 0 and x - -0 as x + 0.  */
  if (TREE_CODE (addend) == REAL_CST
      && REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (addend)))
    negate = !negate;

  /* The mode has signed zeros, and we have to honor their sign.
     In this situation, there is only one case we can return true for.
     X - 0 is the same as X unless rounding towards -infinity is
     supported.  */
  return negate && !HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (type));
}

/* Subroutine of fold() that checks comparisons of built-in math
   functions against real constants.

   FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
   operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR.  TYPE
   is the type of the result and ARG0 and ARG1 are the operands of the
   comparison.  ARG1 must be a TREE_REAL_CST.

   The function returns the constant folded tree if a simplification
   can be made, and NULL_TREE otherwise.  */

static tree
fold_mathfn_compare (enum built_in_function fcode, enum tree_code code,
                     tree type, tree arg0, tree arg1)
{
  REAL_VALUE_TYPE c;

  if (BUILTIN_SQRT_P (fcode))
    {
      tree arg = TREE_VALUE (TREE_OPERAND (arg0, 1));
      enum machine_mode mode = TYPE_MODE (TREE_TYPE (arg0));

      c = TREE_REAL_CST (arg1);
      if (REAL_VALUE_NEGATIVE (c))
        {
          /* sqrt(x) < y is always false, if y is negative.  */
          if (code == EQ_EXPR || code == LT_EXPR || code == LE_EXPR)
            return omit_one_operand (type,
                                     fold_convert (type, integer_zero_node),
                                     arg);

          /* sqrt(x) > y is always true, if y is negative and we
             don't care about NaNs, i.e. negative values of x.  */
          if (code == NE_EXPR || !HONOR_NANS (mode))
            return omit_one_operand (type,
                                     fold_convert (type, integer_one_node),
                                     arg);

          /* sqrt(x) > y is the same as x >= 0, if y is negative.  */
          return fold (build2 (GE_EXPR, type, arg,
                               build_real (TREE_TYPE (arg), dconst0)));
        }
      else if (code == GT_EXPR || code == GE_EXPR)
        {
          REAL_VALUE_TYPE c2;

          REAL_ARITHMETIC (c2, MULT_EXPR, c, c);
          real_convert (&c2, mode, &c2);

          if (REAL_VALUE_ISINF (c2))
            {
              /* sqrt(x) > y is x == +Inf, when y is very large.  */
              if (HONOR_INFINITIES (mode))
                return fold (build2 (EQ_EXPR, type, arg,
                                     build_real (TREE_TYPE (arg), c2)));

              /* sqrt(x) > y is always false, when y is very large
                 and we don't care about infinities.  */
              return omit_one_operand (type,
                                       fold_convert (type, integer_zero_node),
                                       arg);
            }

          /* sqrt(x) > c is the same as x > c*c.  */
          return fold (build2 (code, type, arg,
                               build_real (TREE_TYPE (arg), c2)));
        }
      else if (code == LT_EXPR || code == LE_EXPR)
        {
          REAL_VALUE_TYPE c2;

          REAL_ARITHMETIC (c2, MULT_EXPR, c, c);
          real_convert (&c2, mode, &c2);

          if (REAL_VALUE_ISINF (c2))
            {
              /* sqrt(x) < y is always true, when y is a very large
                 value and we don't care about NaNs or Infinities.  */
              if (! HONOR_NANS (mode) && ! HONOR_INFINITIES (mode))
                return omit_one_operand (type,
                                         fold_convert (type, integer_one_node),
                                         arg);

              /* sqrt(x) < y is x != +Inf when y is very large and we
                 don't care about NaNs.  */
              if (! HONOR_NANS (mode))
                return fold (build2 (NE_EXPR, type, arg,
                                     build_real (TREE_TYPE (arg), c2)));

              /* sqrt(x) < y is x >= 0 when y is very large and we
                 don't care about Infinities.  */
              if (! HONOR_INFINITIES (mode))
                return fold (build2 (GE_EXPR, type, arg,
                                     build_real (TREE_TYPE (arg), dconst0)));

              /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large.  */
              if (lang_hooks.decls.global_bindings_p () != 0
                  || CONTAINS_PLACEHOLDER_P (arg))
                return NULL_TREE;

              arg = save_expr (arg);
              return fold (build2 (TRUTH_ANDIF_EXPR, type,
                                   fold (build2 (GE_EXPR, type, arg,
                                                 build_real (TREE_TYPE (arg),
                                                             dconst0))),
                                   fold (build2 (NE_EXPR, type, arg,
                                                 build_real (TREE_TYPE (arg),
                                                             c2)))));
            }

          /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs.  */
          if (! HONOR_NANS (mode))
            return fold (build2 (code, type, arg,
                                 build_real (TREE_TYPE (arg), c2)));

          /* sqrt(x) < c is the same as x >= 0 && x < c*c.  */
          if (lang_hooks.decls.global_bindings_p () == 0
              && ! CONTAINS_PLACEHOLDER_P (arg))
            {
              arg = save_expr (arg);
              return fold (build2 (TRUTH_ANDIF_EXPR, type,
                                   fold (build2 (GE_EXPR, type, arg,
                                                 build_real (TREE_TYPE (arg),
                                                             dconst0))),
                                   fold (build2 (code, type, arg,
                                                 build_real (TREE_TYPE (arg),
                                                             c2)))));
            }
        }
    }

  return NULL_TREE;
}

/* Subroutine of fold() that optimizes comparisons against Infinities,
   either +Inf or -Inf.

   CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
   GE_EXPR or LE_EXPR.  TYPE is the type of the result and ARG0 and ARG1
   are the operands of the comparison.  ARG1 must be a TREE_REAL_CST.

   The function returns the constant folded tree if a simplification
   can be made, and NULL_TREE otherwise.  */

static tree
fold_inf_compare (enum tree_code code, tree type, tree arg0, tree arg1)
{
  enum machine_mode mode;
  REAL_VALUE_TYPE max;
  tree temp;
  bool neg;

  mode = TYPE_MODE (TREE_TYPE (arg0));

  /* For negative infinity swap the sense of the comparison.  */
  neg = REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg1));
  if (neg)
    code = swap_tree_comparison (code);

  switch (code)
    {
    case GT_EXPR:
      /* x > +Inf is always false, if with ignore sNANs.  */
      if (HONOR_SNANS (mode))
        return NULL_TREE;
      return omit_one_operand (type,
                               fold_convert (type, integer_zero_node),
                               arg0);

    case LE_EXPR:
      /* x <= +Inf is always true, if we don't case about NaNs.  */
      if (! HONOR_NANS (mode))
        return omit_one_operand (type,
                                 fold_convert (type, integer_one_node),
                                 arg0);

      /* x <= +Inf is the same as x == x, i.e. isfinite(x).  */
      if (lang_hooks.decls.global_bindings_p () == 0
          && ! CONTAINS_PLACEHOLDER_P (arg0))
        {
          arg0 = save_expr (arg0);
          return fold (build2 (EQ_EXPR, type, arg0, arg0));
        }
      break;

    case EQ_EXPR:
    case GE_EXPR:
      /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX.  */
      real_maxval (&max, neg, mode);
      return fold (build2 (neg ? LT_EXPR : GT_EXPR, type,
                           arg0, build_real (TREE_TYPE (arg0), max)));

    case LT_EXPR:
      /* x < +Inf is always equal to x <= DBL_MAX.  */
      real_maxval (&max, neg, mode);
      return fold (build2 (neg ? GE_EXPR : LE_EXPR, type,
                           arg0, build_real (TREE_TYPE (arg0), max)));

    case NE_EXPR:
      /* x != +Inf is always equal to !(x > DBL_MAX).  */
      real_maxval (&max, neg, mode);
      if (! HONOR_NANS (mode))
        return fold (build2 (neg ? GE_EXPR : LE_EXPR, type,
                             arg0, build_real (TREE_TYPE (arg0), max)));
      temp = fold (build2 (neg ? LT_EXPR : GT_EXPR, type,
                           arg0, build_real (TREE_TYPE (arg0), max)));
      return fold (build1 (TRUTH_NOT_EXPR, type, temp));

    default:
      break;
    }

  return NULL_TREE;
}

/* Subroutine of fold() that optimizes comparisons of a division by
   a non-zero integer constant against an integer constant, i.e.
   X/C1 op C2.

   CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
   GE_EXPR or LE_EXPR.  TYPE is the type of the result and ARG0 and ARG1
   are the operands of the comparison.  ARG1 must be a TREE_REAL_CST.

   The function returns the constant folded tree if a simplification
   can be made, and NULL_TREE otherwise.  */

static tree
fold_div_compare (enum tree_code code, tree type, tree arg0, tree arg1)
{
  tree prod, tmp, hi, lo;
  tree arg00 = TREE_OPERAND (arg0, 0);
  tree arg01 = TREE_OPERAND (arg0, 1);
  unsigned HOST_WIDE_INT lpart;
  HOST_WIDE_INT hpart;
  int overflow;

  /* We have to do this the hard way to detect unsigned overflow.
     prod = int_const_binop (MULT_EXPR, arg01, arg1, 0);  */
  overflow = mul_double (TREE_INT_CST_LOW (arg01),
                         TREE_INT_CST_HIGH (arg01),
                         TREE_INT_CST_LOW (arg1),
                         TREE_INT_CST_HIGH (arg1), &lpart, &hpart);
  prod = build_int_2 (lpart, hpart);
  TREE_TYPE (prod) = TREE_TYPE (arg00);
  TREE_OVERFLOW (prod) = force_fit_type (prod, overflow)
                         || TREE_INT_CST_HIGH (prod) != hpart
                         || TREE_INT_CST_LOW (prod) != lpart;
  TREE_CONSTANT_OVERFLOW (prod) = TREE_OVERFLOW (prod);

  if (TYPE_UNSIGNED (TREE_TYPE (arg0)))
    {
      tmp = int_const_binop (MINUS_EXPR, arg01, integer_one_node, 0);
      lo = prod;

      /* Likewise hi = int_const_binop (PLUS_EXPR, prod, tmp, 0).  */
      overflow = add_double (TREE_INT_CST_LOW (prod),
                             TREE_INT_CST_HIGH (prod),
                             TREE_INT_CST_LOW (tmp),
                             TREE_INT_CST_HIGH (tmp),
                             &lpart, &hpart);
      hi = build_int_2 (lpart, hpart);
      TREE_TYPE (hi) = TREE_TYPE (arg00);
      TREE_OVERFLOW (hi) = force_fit_type (hi, overflow)
                           || TREE_INT_CST_HIGH (hi) != hpart
                           || TREE_INT_CST_LOW (hi) != lpart
                           || TREE_OVERFLOW (prod);
      TREE_CONSTANT_OVERFLOW (hi) = TREE_OVERFLOW (hi);
    }
  else if (tree_int_cst_sgn (arg01) >= 0)
    {
      tmp = int_const_binop (MINUS_EXPR, arg01, integer_one_node, 0);
      switch (tree_int_cst_sgn (arg1))
        {
        case -1:
          lo = int_const_binop (MINUS_EXPR, prod, tmp, 0);
          hi = prod;
          break;

        case  0:
          lo = fold_negate_const (tmp, TREE_TYPE (arg0));
          hi = tmp;
          break;

        case  1:
          hi = int_const_binop (PLUS_EXPR, prod, tmp, 0);
          lo = prod;
          break;

        default:
          abort ();
        }
    }
  else
    {
      tmp = int_const_binop (PLUS_EXPR, arg01, integer_one_node, 0);
      switch (tree_int_cst_sgn (arg1))
        {
        case -1:
          hi = int_const_binop (MINUS_EXPR, prod, tmp, 0);
          lo = prod;
          break;

        case  0:
          hi = fold_negate_const (tmp, TREE_TYPE (arg0));
          lo = tmp;
          break;

        case  1:
          lo = int_const_binop (PLUS_EXPR, prod, tmp, 0);
          hi = prod;
          break;

        default:
          abort ();
        }
    }

  switch (code)
    {
    case EQ_EXPR:
      if (TREE_OVERFLOW (lo) && TREE_OVERFLOW (hi))
        return omit_one_operand (type, integer_zero_node, arg00);
      if (TREE_OVERFLOW (hi))
        return fold (build2 (GE_EXPR, type, arg00, lo));
      if (TREE_OVERFLOW (lo))
        return fold (build2 (LE_EXPR, type, arg00, hi));
      return build_range_check (type, arg00, 1, lo, hi);

    case NE_EXPR:
      if (TREE_OVERFLOW (lo) && TREE_OVERFLOW (hi))
        return omit_one_operand (type, integer_one_node, arg00);
      if (TREE_OVERFLOW (hi))
        return fold (build2 (LT_EXPR, type, arg00, lo));
      if (TREE_OVERFLOW (lo))
        return fold (build2 (GT_EXPR, type, arg00, hi));
      return build_range_check (type, arg00, 0, lo, hi);

    case LT_EXPR:
      if (TREE_OVERFLOW (lo))
        return omit_one_operand (type, integer_zero_node, arg00);
      return fold (build2 (LT_EXPR, type, arg00, lo));

    case LE_EXPR:
      if (TREE_OVERFLOW (hi))
        return omit_one_operand (type, integer_one_node, arg00);
      return fold (build2 (LE_EXPR, type, arg00, hi));

    case GT_EXPR:
      if (TREE_OVERFLOW (hi))
        return omit_one_operand (type, integer_zero_node, arg00);
      return fold (build2 (GT_EXPR, type, arg00, hi));

    case GE_EXPR:
      if (TREE_OVERFLOW (lo))
        return omit_one_operand (type, integer_one_node, arg00);
      return fold (build2 (GE_EXPR, type, arg00, lo));

    default:
      break;
    }

  return NULL_TREE;
}


/* If CODE with arguments ARG0 and ARG1 represents a single bit
   equality/inequality test, then return a simplified form of
   the test using shifts and logical operations.  Otherwise return
   NULL.  TYPE is the desired result type.  */
 
tree
fold_single_bit_test (enum tree_code code, tree arg0, tree arg1,
                      tree result_type)
{
  /* If this is a TRUTH_NOT_EXPR, it may have a single bit test inside
     operand 0.  */
  if (code == TRUTH_NOT_EXPR)
    {
      code = TREE_CODE (arg0);
      if (code != NE_EXPR && code != EQ_EXPR)
        return NULL_TREE;

      /* Extract the arguments of the EQ/NE.  */
      arg1 = TREE_OPERAND (arg0, 1);
      arg0 = TREE_OPERAND (arg0, 0);

      /* This requires us to invert the code.  */ 
      code = (code == EQ_EXPR ? NE_EXPR : EQ_EXPR);
    }

  /* If this is testing a single bit, we can optimize the test.  */
  if ((code == NE_EXPR || code == EQ_EXPR)
      && TREE_CODE (arg0) == BIT_AND_EXPR && integer_zerop (arg1)
      && integer_pow2p (TREE_OPERAND (arg0, 1)))
    {
      tree inner = TREE_OPERAND (arg0, 0);
      tree type = TREE_TYPE (arg0);
      int bitnum = tree_log2 (TREE_OPERAND (arg0, 1));
      enum machine_mode operand_mode = TYPE_MODE (type);
      int ops_unsigned;
      tree signed_type, unsigned_type, intermediate_type;
      tree arg00;
  
      /* If we have (A & C) != 0 where C is the sign bit of A, convert
         this into A < 0.  Similarly for (A & C) == 0 into A >= 0.  */
      arg00 = sign_bit_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg0, 1));
      if (arg00 != NULL_TREE)
        {
          tree stype = lang_hooks.types.signed_type (TREE_TYPE (arg00));
          return fold (build2 (code == EQ_EXPR ? GE_EXPR : LT_EXPR,
                               result_type, fold_convert (stype, arg00),
                               fold_convert (stype, integer_zero_node)));
        }

      /* At this point, we know that arg0 is not testing the sign bit.  */
      if (TYPE_PRECISION (type) - 1 == bitnum)
        abort ();
      
      /* Otherwise we have (A & C) != 0 where C is a single bit, 
         convert that into ((A >> C2) & 1).  Where C2 = log2(C).
         Similarly for (A & C) == 0.  */

      /* If INNER is a right shift of a constant and it plus BITNUM does
         not overflow, adjust BITNUM and INNER.  */
      if (TREE_CODE (inner) == RSHIFT_EXPR
          && TREE_CODE (TREE_OPERAND (inner, 1)) == INTEGER_CST
          && TREE_INT_CST_HIGH (TREE_OPERAND (inner, 1)) == 0
          && bitnum < TYPE_PRECISION (type)
          && 0 > compare_tree_int (TREE_OPERAND (inner, 1),
                                   bitnum - TYPE_PRECISION (type)))
        {
          bitnum += TREE_INT_CST_LOW (TREE_OPERAND (inner, 1));
          inner = TREE_OPERAND (inner, 0);
        }

      /* If we are going to be able to omit the AND below, we must do our
         operations as unsigned.  If we must use the AND, we have a choice.
         Normally unsigned is faster, but for some machines signed is.  */
#ifdef LOAD_EXTEND_OP
      ops_unsigned = (LOAD_EXTEND_OP (operand_mode) == SIGN_EXTEND ? 0 : 1);
#else
      ops_unsigned = 1;
#endif

      signed_type = lang_hooks.types.type_for_mode (operand_mode, 0);
      unsigned_type = lang_hooks.types.type_for_mode (operand_mode, 1);
      intermediate_type = ops_unsigned ? unsigned_type : signed_type;
      inner = fold_convert (intermediate_type, inner);

      if (bitnum != 0)
        inner = build2 (RSHIFT_EXPR, intermediate_type,
                        inner, size_int (bitnum));

      if (code == EQ_EXPR)
        inner = build2 (BIT_XOR_EXPR, intermediate_type,
                        inner, integer_one_node);

      /* Put the AND last so it can combine with more things.  */
      inner = build2 (BIT_AND_EXPR, intermediate_type,
                      inner, integer_one_node);

      /* Make sure to return the proper type.  */
      inner = fold_convert (result_type, inner);

      return inner;
    }
  return NULL_TREE;
}

/* Check whether we are allowed to reorder operands arg0 and arg1,
   such that the evaluation of arg1 occurs before arg0.  */

static bool
reorder_operands_p (tree arg0, tree arg1)
{
  if (! flag_evaluation_order)
    return true;
  if (TREE_CONSTANT (arg0) || TREE_CONSTANT (arg1))
    return true;
  return ! TREE_SIDE_EFFECTS (arg0)
         && ! TREE_SIDE_EFFECTS (arg1);
}

/* Test whether it is preferable two swap two operands, ARG0 and
   ARG1, for example because ARG0 is an integer constant and ARG1
   isn't.  If REORDER is true, only recommend swapping if we can
   evaluate the operands in reverse order.  */

static bool
tree_swap_operands_p (tree arg0, tree arg1, bool reorder)
{
  STRIP_SIGN_NOPS (arg0);
  STRIP_SIGN_NOPS (arg1);

  if (TREE_CODE (arg1) == INTEGER_CST)
    return 0;
  if (TREE_CODE (arg0) == INTEGER_CST)
    return 1;

  if (TREE_CODE (arg1) == REAL_CST)
    return 0;
  if (TREE_CODE (arg0) == REAL_CST)
    return 1;

  if (TREE_CODE (arg1) == COMPLEX_CST)
    return 0;
  if (TREE_CODE (arg0) == COMPLEX_CST)
    return 1;

  if (TREE_CONSTANT (arg1))
    return 0;
  if (TREE_CONSTANT (arg0))
    return 1;
    
  if (optimize_size)
    return 0;

  if (reorder && flag_evaluation_order
      && (TREE_SIDE_EFFECTS (arg0) || TREE_SIDE_EFFECTS (arg1)))
    return 0;

  if (DECL_P (arg1))
    return 0;
  if (DECL_P (arg0))
    return 1;

  if (reorder && flag_evaluation_order
      && (TREE_SIDE_EFFECTS (arg0) || TREE_SIDE_EFFECTS (arg1)))
    return 0;

  if (DECL_P (arg1))
    return 0;
  if (DECL_P (arg0))
    return 1;

  return 0;
}

/* Perform constant folding and related simplification of EXPR.
   The related simplifications include x*1 => x, x*0 => 0, etc.,
   and application of the associative law.
   NOP_EXPR conversions may be removed freely (as long as we
   are careful not to change the type of the overall expression).
   We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
   but we can constant-fold them if they have constant operands.  */

#ifdef ENABLE_FOLD_CHECKING
# define fold(x) fold_1 (x)
static tree fold_1 (tree);
static
#endif
tree
fold (tree expr)
{
  const tree t = expr;
  const tree type = TREE_TYPE (expr);
  tree t1 = NULL_TREE;
  tree tem;
  tree arg0 = NULL_TREE, arg1 = NULL_TREE;
  enum tree_code code = TREE_CODE (t);
  int kind = TREE_CODE_CLASS (code);

  /* WINS will be nonzero when the switch is done
     if all operands are constant.  */
  int wins = 1;

  /* Don't try to process an RTL_EXPR since its operands aren't trees.
     Likewise for a SAVE_EXPR that's already been evaluated.  */
  if (code == RTL_EXPR || (code == SAVE_EXPR && SAVE_EXPR_RTL (t) != 0))
    return t;

  /* Return right away if a constant.  */
  if (kind == 'c')
    return t;

  if (code == NOP_EXPR || code == FLOAT_EXPR || code == CONVERT_EXPR)
    {
      tree subop;

      /* Special case for conversion ops that can have fixed point args.  */
      arg0 = TREE_OPERAND (t, 0);

      /* Don't use STRIP_NOPS, because signedness of argument type matters.  */
      if (arg0 != 0)
        STRIP_SIGN_NOPS (arg0);

      if (arg0 != 0 && TREE_CODE (arg0) == COMPLEX_CST)
        subop = TREE_REALPART (arg0);
      else
        subop = arg0;

      if (subop != 0 && TREE_CODE (subop) != INTEGER_CST
          && TREE_CODE (subop) != REAL_CST)
        /* Note that TREE_CONSTANT isn't enough:
           static var addresses are constant but we can't
           do arithmetic on them.  */
        wins = 0;
    }
  else if (IS_EXPR_CODE_CLASS (kind))
    {
      int len = first_rtl_op (code);
      int i;
      for (i = 0; i < len; i++)
        {
          tree op = TREE_OPERAND (t, i);
          tree subop;

          if (op == 0)
            continue;           /* Valid for CALL_EXPR, at least.  */

          /* Strip any conversions that don't change the mode.  This is
             safe for every expression, except for a comparison expression
             because its signedness is derived from its operands.  So, in
             the latter case, only strip conversions that don't change the
             signedness.

             Note that this is done as an internal manipulation within the
             constant folder, in order to find the simplest representation
             of the arguments so that their form can be studied.  In any
             cases, the appropriate type conversions should be put back in
             the tree that will get out of the constant folder.  */
          if (kind == '<')
            STRIP_SIGN_NOPS (op);
          else
            STRIP_NOPS (op);

          if (TREE_CODE (op) == COMPLEX_CST)
            subop = TREE_REALPART (op);
          else
            subop = op;

          if (TREE_CODE (subop) != INTEGER_CST
              && TREE_CODE (subop) != REAL_CST)
            /* Note that TREE_CONSTANT isn't enough:
               static var addresses are constant but we can't
               do arithmetic on them.  */
            wins = 0;

          if (i == 0)
            arg0 = op;
          else if (i == 1)
            arg1 = op;
        }
    }

  /* If this is a commutative operation, and ARG0 is a constant, move it
     to ARG1 to reduce the number of tests below.  */
  if (commutative_tree_code (code)
      && tree_swap_operands_p (arg0, arg1, true))
    return fold (build2 (code, type, TREE_OPERAND (t, 1),
                         TREE_OPERAND (t, 0)));

  /* Now WINS is set as described above,
     ARG0 is the first operand of EXPR,
     and ARG1 is the second operand (if it has more than one operand).

     First check for cases where an arithmetic operation is applied to a
     compound, conditional, or comparison operation.  Push the arithmetic
     operation inside the compound or conditional to see if any folding
     can then be done.  Convert comparison to conditional for this purpose.
     The also optimizes non-constant cases that used to be done in
     expand_expr.

     Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
     one of the operands is a comparison and the other is a comparison, a
     BIT_AND_EXPR with the constant 1, or a truth value.  In that case, the
     code below would make the expression more complex.  Change it to a
     TRUTH_{AND,OR}_EXPR.  Likewise, convert a similar NE_EXPR to
     TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR.  */

  if ((code == BIT_AND_EXPR || code == BIT_IOR_EXPR
       || code == EQ_EXPR || code == NE_EXPR)
      && ((truth_value_p (TREE_CODE (arg0))
           && (truth_value_p (TREE_CODE (arg1))
               || (TREE_CODE (arg1) == BIT_AND_EXPR
                   && integer_onep (TREE_OPERAND (arg1, 1)))))
          || (truth_value_p (TREE_CODE (arg1))
              && (truth_value_p (TREE_CODE (arg0))
                  || (TREE_CODE (arg0) == BIT_AND_EXPR
                      && integer_onep (TREE_OPERAND (arg0, 1)))))))
    {
      tem = fold (build2 (code == BIT_AND_EXPR ? TRUTH_AND_EXPR
                          : code == BIT_IOR_EXPR ? TRUTH_OR_EXPR
                          : TRUTH_XOR_EXPR,
                          type, fold_convert (boolean_type_node, arg0),
                          fold_convert (boolean_type_node, arg1)));

      if (code == EQ_EXPR)
        tem = invert_truthvalue (tem);

      return tem;
    }

  if (TREE_CODE_CLASS (code) == '1')
    {
      if (TREE_CODE (arg0) == COMPOUND_EXPR)
        return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
                       fold (build1 (code, type, TREE_OPERAND (arg0, 1))));
      else if (TREE_CODE (arg0) == COND_EXPR)
        {
          tree arg01 = TREE_OPERAND (arg0, 1);
          tree arg02 = TREE_OPERAND (arg0, 2);
          if (! VOID_TYPE_P (TREE_TYPE (arg01)))
            arg01 = fold (build1 (code, type, arg01));
          if (! VOID_TYPE_P (TREE_TYPE (arg02)))
            arg02 = fold (build1 (code, type, arg02));
          tem = fold (build3 (COND_EXPR, type, TREE_OPERAND (arg0, 0),
                              arg01, arg02));

          /* If this was a conversion, and all we did was to move into
             inside the COND_EXPR, bring it back out.  But leave it if
             it is a conversion from integer to integer and the
             result precision is no wider than a word since such a
             conversion is cheap and may be optimized away by combine,
             while it couldn't if it were outside the COND_EXPR.  Then return
             so we don't get into an infinite recursion loop taking the
             conversion out and then back in.  */

          if ((code == NOP_EXPR || code == CONVERT_EXPR
               || code == NON_LVALUE_EXPR)
              && TREE_CODE (tem) == COND_EXPR
              && TREE_CODE (TREE_OPERAND (tem, 1)) == code
              && TREE_CODE (TREE_OPERAND (tem, 2)) == code
              && ! VOID_TYPE_P (TREE_OPERAND (tem, 1))
              && ! VOID_TYPE_P (TREE_OPERAND (tem, 2))
              && (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (tem, 1), 0))
                  == TREE_TYPE (TREE_OPERAND (TREE_OPERAND (tem, 2), 0)))
              && ! (INTEGRAL_TYPE_P (TREE_TYPE (tem))
                    && (INTEGRAL_TYPE_P
                        (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (tem, 1), 0))))
                    && TYPE_PRECISION (TREE_TYPE (tem)) <= BITS_PER_WORD))
            tem = build1 (code, type,
                          build3 (COND_EXPR,
                                  TREE_TYPE (TREE_OPERAND
                                             (TREE_OPERAND (tem, 1), 0)),
                                  TREE_OPERAND (tem, 0),
                                  TREE_OPERAND (TREE_OPERAND (tem, 1), 0),
                                  TREE_OPERAND (TREE_OPERAND (tem, 2), 0)));
          return tem;
        }
      else if (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<')
        {
          if (TREE_CODE (type) == BOOLEAN_TYPE)
            {
              arg0 = copy_node (arg0);
              TREE_TYPE (arg0) = type;
              return arg0;
            }
          else if (TREE_CODE (type) != INTEGER_TYPE)
            return fold (build3 (COND_EXPR, type, arg0,
                                 fold (build1 (code, type,
                                               integer_one_node)),
                                 fold (build1 (code, type,
                                               integer_zero_node))));
        }
   }
  else if (TREE_CODE_CLASS (code) == '<'
           && TREE_CODE (arg0) == COMPOUND_EXPR)
    return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
                   fold (build2 (code, type, TREE_OPERAND (arg0, 1), arg1)));
  else if (TREE_CODE_CLASS (code) == '<'
           && TREE_CODE (arg1) == COMPOUND_EXPR)
    return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg1, 0),
                   fold (build2 (code, type, arg0, TREE_OPERAND (arg1, 1))));
  else if (TREE_CODE_CLASS (code) == '2'
           || TREE_CODE_CLASS (code) == '<')
    {
      if (TREE_CODE (arg0) == COMPOUND_EXPR)
        return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
                       fold (build2 (code, type, TREE_OPERAND (arg0, 1),
                                     arg1)));
      if (TREE_CODE (arg1) == COMPOUND_EXPR
          && reorder_operands_p (arg0, TREE_OPERAND (arg1, 0)))
        return build2 (COMPOUND_EXPR, type, TREE_OPERAND (arg1, 0),
                       fold (build2 (code, type,
                                     arg0, TREE_OPERAND (arg1, 1))));

      if (TREE_CODE (arg0) == COND_EXPR
          || TREE_CODE_CLASS (TREE_CODE (arg0)) == '<')
        {
          tem = fold_binary_op_with_conditional_arg (code, type, arg0, arg1,
                                                     /*cond_first_p=*/1);
          if (tem != NULL_TREE)
            return tem;
        }

      if (TREE_CODE (arg1) == COND_EXPR
          || TREE_CODE_CLASS (TREE_CODE (arg1)) == '<')
        {
          tem = fold_binary_op_with_conditional_arg (code, type, arg1, arg0,
                                                     /*cond_first_p=*/0);
          if (tem != NULL_TREE)
            return tem;
        }
    }

  switch (code)
    {
    case CONST_DECL:
      return fold (DECL_INITIAL (t));

    case NOP_EXPR:
    case FLOAT_EXPR:
    case CONVERT_EXPR:
    case FIX_TRUNC_EXPR:
    case FIX_CEIL_EXPR:
    case FIX_FLOOR_EXPR:
    case FIX_ROUND_EXPR:
      if (TREE_TYPE (TREE_OPERAND (t, 0)) == type)
        return TREE_OPERAND (t, 0);

      /* Handle cases of two conversions in a row.  */
      if (TREE_CODE (TREE_OPERAND (t, 0)) == NOP_EXPR
          || TREE_CODE (TREE_OPERAND (t, 0)) == CONVERT_EXPR)
        {
          tree inside_type = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 0), 0));
          tree inter_type = TREE_TYPE (TREE_OPERAND (t, 0));
          int inside_int = INTEGRAL_TYPE_P (inside_type);
          int inside_ptr = POINTER_TYPE_P (inside_type);
          int inside_float = FLOAT_TYPE_P (inside_type);
          unsigned int inside_prec = TYPE_PRECISION (inside_type);
          int inside_unsignedp = TYPE_UNSIGNED (inside_type);
          int inter_int = INTEGRAL_TYPE_P (inter_type);
          int inter_ptr = POINTER_TYPE_P (inter_type);
          int inter_float = FLOAT_TYPE_P (inter_type);
          unsigned int inter_prec = TYPE_PRECISION (inter_type);
          int inter_unsignedp = TYPE_UNSIGNED (inter_type);
          int final_int = INTEGRAL_TYPE_P (type);
          int final_ptr = POINTER_TYPE_P (type);
          int final_float = FLOAT_TYPE_P (type);
          unsigned int final_prec = TYPE_PRECISION (type);
          int final_unsignedp = TYPE_UNSIGNED (type);

          /* In addition to the cases of two conversions in a row
             handled below, if we are converting something to its own
             type via an object of identical or wider precision, neither
             conversion is needed.  */
          if (TYPE_MAIN_VARIANT (inside_type) == TYPE_MAIN_VARIANT (type)
              && ((inter_int && final_int) || (inter_float && final_float))
              && inter_prec >= final_prec)
            return fold (build1 (code, type,
                                 TREE_OPERAND (TREE_OPERAND (t, 0), 0)));

          /* Likewise, if the intermediate and final types are either both
             float or both integer, we don't need the middle conversion if
             it is wider than the final type and doesn't change the signedness
             (for integers).  Avoid this if the final type is a pointer
             since then we sometimes need the inner conversion.  Likewise if
             the outer has a precision not equal to the size of its mode.  */
          if ((((inter_int || inter_ptr) && (inside_int || inside_ptr))
               || (inter_float && inside_float))
              && inter_prec >= inside_prec
              && (inter_float || inter_unsignedp == inside_unsignedp)
              && ! (final_prec != GET_MODE_BITSIZE (TYPE_MODE (type))
                    && TYPE_MODE (type) == TYPE_MODE (inter_type))
              && ! final_ptr)
            return fold (build1 (code, type,
                                 TREE_OPERAND (TREE_OPERAND (t, 0), 0)));

          /* If we have a sign-extension of a zero-extended value, we can
             replace that by a single zero-extension.  */
          if (inside_int && inter_int && final_int
              && inside_prec < inter_prec && inter_prec < final_prec
              && inside_unsignedp && !inter_unsignedp)
            return fold (build1 (code, type,
                                 TREE_OPERAND (TREE_OPERAND (t, 0), 0)));

          /* Two conversions in a row are not needed unless:
             - some conversion is floating-point (overstrict for now), or
             - the intermediate type is narrower than both initial and
               final, or
             - the intermediate type and innermost type differ in signedness,
               and the outermost type is wider than the intermediate, or
             - the initial type is a pointer type and the precisions of the
               intermediate and final types differ, or
             - the final type is a pointer type and the precisions of the
               initial and intermediate types differ.  */
          if (! inside_float && ! inter_float && ! final_float
              && (inter_prec > inside_prec || inter_prec > final_prec)
              && ! (inside_int && inter_int
                    && inter_unsignedp != inside_unsignedp
                    && inter_prec < final_prec)
              && ((inter_unsignedp && inter_prec > inside_prec)
                  == (final_unsignedp && final_prec > inter_prec))
              && ! (inside_ptr && inter_prec != final_prec)
              && ! (final_ptr && inside_prec != inter_prec)
              && ! (final_prec != GET_MODE_BITSIZE (TYPE_MODE (type))
                    && TYPE_MODE (type) == TYPE_MODE (inter_type))
              && ! final_ptr)
            return fold (build1 (code, type,
                                 TREE_OPERAND (TREE_OPERAND (t, 0), 0)));
        }

      if (TREE_CODE (TREE_OPERAND (t, 0)) == MODIFY_EXPR
          && TREE_CONSTANT (TREE_OPERAND (TREE_OPERAND (t, 0), 1))
          /* Detect assigning a bitfield.  */
          && !(TREE_CODE (TREE_OPERAND (TREE_OPERAND (t, 0), 0)) == COMPONENT_REF
               && DECL_BIT_FIELD (TREE_OPERAND (TREE_OPERAND (TREE_OPERAND (t, 0), 0), 1))))
        {
          /* Don't leave an assignment inside a conversion
             unless assigning a bitfield.  */
          tree prev = TREE_OPERAND (t, 0);
          tem = copy_node (t);
          TREE_OPERAND (tem, 0) = TREE_OPERAND (prev, 1);
          /* First do the assignment, then return converted constant.  */
          tem = build2 (COMPOUND_EXPR, TREE_TYPE (tem), prev, fold (tem));
          TREE_NO_WARNING (tem) = 1;
          TREE_USED (tem) = 1;
          return tem;
        }

      /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
         constants (if x has signed type, the sign bit cannot be set
         in c).  This folds extension into the BIT_AND_EXPR.  */
      if (INTEGRAL_TYPE_P (type)
          && TREE_CODE (type) != BOOLEAN_TYPE
          && TREE_CODE (TREE_OPERAND (t, 0)) == BIT_AND_EXPR
          && TREE_CODE (TREE_OPERAND (TREE_OPERAND (t, 0), 1)) == INTEGER_CST)
        {
          tree and = TREE_OPERAND (t, 0);
          tree and0 = TREE_OPERAND (and, 0), and1 = TREE_OPERAND (and, 1);
          int change = 0;

          if (TYPE_UNSIGNED (TREE_TYPE (and))
              || (TYPE_PRECISION (type)
                  <= TYPE_PRECISION (TREE_TYPE (and))))
            change = 1;
          else if (TYPE_PRECISION (TREE_TYPE (and1))
                   <= HOST_BITS_PER_WIDE_INT
                   && host_integerp (and1, 1))
            {
              unsigned HOST_WIDE_INT cst;

              cst = tree_low_cst (and1, 1);
              cst &= (HOST_WIDE_INT) -1
                     << (TYPE_PRECISION (TREE_TYPE (and1)) - 1);
              change = (cst == 0);
#ifdef LOAD_EXTEND_OP
              if (change
                  && (LOAD_EXTEND_OP (TYPE_MODE (TREE_TYPE (and0)))
                      == ZERO_EXTEND))
                {
                  tree uns = lang_hooks.types.unsigned_type (TREE_TYPE (and0));
                  and0 = fold_convert (uns, and0);
                  and1 = fold_convert (uns, and1);
                }
#endif
            }
          if (change)
            return fold (build2 (BIT_AND_EXPR, type,
                                 fold_convert (type, and0),
                                 fold_convert (type, and1)));
        }

      /* Convert (T1)((T2)X op Y) into (T1)X op Y, for pointer types T1 and
         T2 being pointers to types of the same size.  */
      if (POINTER_TYPE_P (TREE_TYPE (t))
          && TREE_CODE_CLASS (TREE_CODE (arg0)) == '2'
          && TREE_CODE (TREE_OPERAND (arg0, 0)) == NOP_EXPR
          && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 0))))
        {
          tree arg00 = TREE_OPERAND (arg0, 0);
          tree t0 = TREE_TYPE (t);
          tree t1 = TREE_TYPE (arg00);
          tree tt0 = TREE_TYPE (t0);
          tree tt1 = TREE_TYPE (t1);
          tree s0 = TYPE_SIZE (tt0);
          tree s1 = TYPE_SIZE (tt1);

          if (s0 && s1 && operand_equal_p (s0, s1, OEP_ONLY_CONST))
            return build2 (TREE_CODE (arg0), t0, convert (t0, arg00),
                           TREE_OPERAND (arg0, 1));
        }

      tem = fold_convert_const (code, type, arg0);
      return tem ? tem : t;

    case VIEW_CONVERT_EXPR:
      if (TREE_CODE (TREE_OPERAND (t, 0)) == VIEW_CONVERT_EXPR)
        return build1 (VIEW_CONVERT_EXPR, type,
                       TREE_OPERAND (TREE_OPERAND (t, 0), 0));
      return t;

    case COMPONENT_REF:
      if (TREE_CODE (arg0) == CONSTRUCTOR
          && ! type_contains_placeholder_p (TREE_TYPE (arg0)))
        {
          tree m = purpose_member (arg1, CONSTRUCTOR_ELTS (arg0));
          if (m)
            return TREE_VALUE (m);
        }
      return t;

    case RANGE_EXPR:
      if (TREE_CONSTANT (t) != wins)
        {
          tem = copy_node (t);
          TREE_CONSTANT (tem) = wins;
          TREE_INVARIANT (tem) = wins;
          return tem;
        }
      return t;

    case NEGATE_EXPR:
      if (negate_expr_p (arg0))
        return fold_convert (type, negate_expr (arg0));
      return t;

    case ABS_EXPR:
      if (wins
          && (TREE_CODE (arg0) == INTEGER_CST || TREE_CODE (arg0) == REAL_CST))
        return fold_abs_const (arg0, type);
      else if (TREE_CODE (arg0) == NEGATE_EXPR)
        return fold (build1 (ABS_EXPR, type, TREE_OPERAND (arg0, 0)));
      /* Convert fabs((double)float) into (double)fabsf(float).  */
      else if (TREE_CODE (arg0) == NOP_EXPR
               && TREE_CODE (type) == REAL_TYPE)
        {
          tree targ0 = strip_float_extensions (arg0);
          if (targ0 != arg0)
            return fold_convert (type, fold (build1 (ABS_EXPR,
                                                     TREE_TYPE (targ0),
                                                     targ0)));
        }
      else if (tree_expr_nonnegative_p (arg0))
        return arg0;
      return t;

    case CONJ_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
        return fold_convert (type, arg0);
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
        return build2 (COMPLEX_EXPR, type,
                       TREE_OPERAND (arg0, 0),
                       negate_expr (TREE_OPERAND (arg0, 1)));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
        return build_complex (type, TREE_REALPART (arg0),
                              negate_expr (TREE_IMAGPART (arg0)));
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
        return fold (build2 (TREE_CODE (arg0), type,
                             fold (build1 (CONJ_EXPR, type,
                                           TREE_OPERAND (arg0, 0))),
                             fold (build1 (CONJ_EXPR, type,
                                           TREE_OPERAND (arg0, 1)))));
      else if (TREE_CODE (arg0) == CONJ_EXPR)
        return TREE_OPERAND (arg0, 0);
      return t;

    case BIT_NOT_EXPR:
      if (wins)
        {
          tem = build_int_2 (~ TREE_INT_CST_LOW (arg0),
                             ~ TREE_INT_CST_HIGH (arg0));
          TREE_TYPE (tem) = type;
          force_fit_type (tem, 0);
          TREE_OVERFLOW (tem) = TREE_OVERFLOW (arg0);
          TREE_CONSTANT_OVERFLOW (tem) = TREE_CONSTANT_OVERFLOW (arg0);
          return tem;
        }
      else if (TREE_CODE (arg0) == BIT_NOT_EXPR)
        return TREE_OPERAND (arg0, 0);
      return t;

    case PLUS_EXPR:
      /* A + (-B) -> A - B */
      if (TREE_CODE (arg1) == NEGATE_EXPR)
        return fold (build2 (MINUS_EXPR, type, arg0, TREE_OPERAND (arg1, 0)));
      /* (-A) + B -> B - A */
      if (TREE_CODE (arg0) == NEGATE_EXPR
          && reorder_operands_p (TREE_OPERAND (arg0, 0), arg1))
        return fold (build2 (MINUS_EXPR, type, arg1, TREE_OPERAND (arg0, 0)));
      if (! FLOAT_TYPE_P (type))
        {
          if (integer_zerop (arg1))
            return non_lvalue (fold_convert (type, arg0));

          /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
             with a constant, and the two constants have no bits in common,
             we should treat this as a BIT_IOR_EXPR since this may produce more
             simplifications.  */
          if (TREE_CODE (arg0) == BIT_AND_EXPR
              && TREE_CODE (arg1) == BIT_AND_EXPR
              && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
              && TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST
              && integer_zerop (const_binop (BIT_AND_EXPR,
                                             TREE_OPERAND (arg0, 1),
                                             TREE_OPERAND (arg1, 1), 0)))
            {
              code = BIT_IOR_EXPR;
              goto bit_ior;
            }

          /* Reassociate (plus (plus (mult) (foo)) (mult)) as
             (plus (plus (mult) (mult)) (foo)) so that we can
             take advantage of the factoring cases below.  */
          if ((TREE_CODE (arg0) == PLUS_EXPR
               && TREE_CODE (arg1) == MULT_EXPR)
              || (TREE_CODE (arg1) == PLUS_EXPR
                  && TREE_CODE (arg0) == MULT_EXPR))
            {
              tree parg0, parg1, parg, marg;

              if (TREE_CODE (arg0) == PLUS_EXPR)
                parg = arg0, marg = arg1;
              else
                parg = arg1, marg = arg0;
              parg0 = TREE_OPERAND (parg, 0);
              parg1 = TREE_OPERAND (parg, 1);
              STRIP_NOPS (parg0);
              STRIP_NOPS (parg1);

              if (TREE_CODE (parg0) == MULT_EXPR
                  && TREE_CODE (parg1) != MULT_EXPR)
                return fold (build2 (PLUS_EXPR, type,
                                     fold (build2 (PLUS_EXPR, type,
                                                   fold_convert (type, parg0),
                                                   fold_convert (type, marg))),
                                     fold_convert (type, parg1)));
              if (TREE_CODE (parg0) != MULT_EXPR
                  && TREE_CODE (parg1) == MULT_EXPR)
                return fold (build2 (PLUS_EXPR, type,
                                     fold (build2 (PLUS_EXPR, type,
                                                   fold_convert (type, parg1),
                                                   fold_convert (type, marg))),
                                     fold_convert (type, parg0)));
            }

          if (TREE_CODE (arg0) == MULT_EXPR && TREE_CODE (arg1) == MULT_EXPR)
            {
              tree arg00, arg01, arg10, arg11;
              tree alt0 = NULL_TREE, alt1 = NULL_TREE, same;

              /* (A * C) + (B * C) -> (A+B) * C.
                 We are most concerned about the case where C is a constant,
                 but other combinations show up during loop reduction.  Since
                 it is not difficult, try all four possibilities.  */

              arg00 = TREE_OPERAND (arg0, 0);
              arg01 = TREE_OPERAND (arg0, 1);
              arg10 = TREE_OPERAND (arg1, 0);
              arg11 = TREE_OPERAND (arg1, 1);
              same = NULL_TREE;

              if (operand_equal_p (arg01, arg11, 0))
                same = arg01, alt0 = arg00, alt1 = arg10;
              else if (operand_equal_p (arg00, arg10, 0))
                same = arg00, alt0 = arg01, alt1 = arg11;
              else if (operand_equal_p (arg00, arg11, 0))
                same = arg00, alt0 = arg01, alt1 = arg10;
              else if (operand_equal_p (arg01, arg10, 0))
                same = arg01, alt0 = arg00, alt1 = arg11;

              /* No identical multiplicands; see if we can find a common
                 power-of-two factor in non-power-of-two multiplies.  This
                 can help in multi-dimensional array access.  */
              else if (TREE_CODE (arg01) == INTEGER_CST
                       && TREE_CODE (arg11) == INTEGER_CST
                       && TREE_INT_CST_HIGH (arg01) == 0
                       && TREE_INT_CST_HIGH (arg11) == 0)
                {
                  HOST_WIDE_INT int01, int11, tmp;
                  int01 = TREE_INT_CST_LOW (arg01);
                  int11 = TREE_INT_CST_LOW (arg11);

                  /* Move min of absolute values to int11.  */
                  if ((int01 >= 0 ? int01 : -int01)
                      < (int11 >= 0 ? int11 : -int11))
                    {
                      tmp = int01, int01 = int11, int11 = tmp;
                      alt0 = arg00, arg00 = arg10, arg10 = alt0;
                      alt0 = arg01, arg01 = arg11, arg11 = alt0;
                    }

                  if (exact_log2 (int11) > 0 && int01 % int11 == 0)
                    {
                      alt0 = fold (build2 (MULT_EXPR, type, arg00,
                                           build_int_2 (int01 / int11, 0)));
                      alt1 = arg10;
                      same = arg11;
                    }
                }

              if (same)
                return fold (build2 (MULT_EXPR, type,
                                     fold (build2 (PLUS_EXPR, type,
                                                   alt0, alt1)),
                                     same));
            }
        }
      else
        {
          /* See if ARG1 is zero and X + ARG1 reduces to X.  */
          if (fold_real_zero_addition_p (TREE_TYPE (arg0), arg1, 0))
            return non_lvalue (fold_convert (type, arg0));

          /* Likewise if the operands are reversed.  */
          if (fold_real_zero_addition_p (TREE_TYPE (arg1), arg0, 0))
            return non_lvalue (fold_convert (type, arg1));

          /* Convert x+x into x*2.0.  */
          if (operand_equal_p (arg0, arg1, 0)
              && SCALAR_FLOAT_TYPE_P (type))
            return fold (build2 (MULT_EXPR, type, arg0,
                                 build_real (type, dconst2)));

          /* Convert x*c+x into x*(c+1).  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg0) == MULT_EXPR
              && TREE_CODE (TREE_OPERAND (arg0, 1)) == REAL_CST
              && ! TREE_CONSTANT_OVERFLOW (TREE_OPERAND (arg0, 1))
              && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
            {
              REAL_VALUE_TYPE c;

              c = TREE_REAL_CST (TREE_OPERAND (arg0, 1));
              real_arithmetic (&c, PLUS_EXPR, &c, &dconst1);
              return fold (build2 (MULT_EXPR, type, arg1,
                                   build_real (type, c)));
            }

          /* Convert x+x*c into x*(c+1).  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg1) == MULT_EXPR
              && TREE_CODE (TREE_OPERAND (arg1, 1)) == REAL_CST
              && ! TREE_CONSTANT_OVERFLOW (TREE_OPERAND (arg1, 1))
              && operand_equal_p (TREE_OPERAND (arg1, 0), arg0, 0))
            {
              REAL_VALUE_TYPE c;

              c = TREE_REAL_CST (TREE_OPERAND (arg1, 1));
              real_arithmetic (&c, PLUS_EXPR, &c, &dconst1);
              return fold (build2 (MULT_EXPR, type, arg0,
                                   build_real (type, c)));
            }

          /* Convert x*c1+x*c2 into x*(c1+c2).  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg0) == MULT_EXPR
              && TREE_CODE (arg1) == MULT_EXPR
              && TREE_CODE (TREE_OPERAND (arg0, 1)) == REAL_CST
              && ! TREE_CONSTANT_OVERFLOW (TREE_OPERAND (arg0, 1))
              && TREE_CODE (TREE_OPERAND (arg1, 1)) == REAL_CST
              && ! TREE_CONSTANT_OVERFLOW (TREE_OPERAND (arg1, 1))
              && operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 0), 0))
            {
              REAL_VALUE_TYPE c1, c2;

              c1 = TREE_REAL_CST (TREE_OPERAND (arg0, 1));
              c2 = TREE_REAL_CST (TREE_OPERAND (arg1, 1));
              real_arithmetic (&c1, PLUS_EXPR, &c1, &c2);
              return fold (build2 (MULT_EXPR, type,
                                   TREE_OPERAND (arg0, 0),
                                   build_real (type, c1)));
            }
          /* Convert a + (b*c + d*e) into (a + b*c) + d*e */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg1) == PLUS_EXPR
              && TREE_CODE (arg0) != MULT_EXPR)
            {
              tree tree10 = TREE_OPERAND (arg1, 0);
              tree tree11 = TREE_OPERAND (arg1, 1);
              if (TREE_CODE (tree11) == MULT_EXPR
                  && TREE_CODE (tree10) == MULT_EXPR)
                {
                  tree tree0;
                  tree0 = fold (build2 (PLUS_EXPR, type, arg0, tree10));
                  return fold (build2 (PLUS_EXPR, type, tree0, tree11));
                }
            }
          /* Convert (b*c + d*e) + a into b*c + (d*e +a) */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg0) == PLUS_EXPR
              && TREE_CODE (arg1) != MULT_EXPR)
            {
              tree tree00 = TREE_OPERAND (arg0, 0);
              tree tree01 = TREE_OPERAND (arg0, 1);
              if (TREE_CODE (tree01) == MULT_EXPR
                  && TREE_CODE (tree00) == MULT_EXPR)
                {
                  tree tree0;
                  tree0 = fold (build2 (PLUS_EXPR, type, tree01, arg1));
                  return fold (build2 (PLUS_EXPR, type, tree00, tree0));
                }
            }
        }

     bit_rotate:
      /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
         is a rotate of A by C1 bits.  */
      /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
         is a rotate of A by B bits.  */
      {
        enum tree_code code0, code1;
        code0 = TREE_CODE (arg0);
        code1 = TREE_CODE (arg1);
        if (((code0 == RSHIFT_EXPR && code1 == LSHIFT_EXPR)
             || (code1 == RSHIFT_EXPR && code0 == LSHIFT_EXPR))
            && operand_equal_p (TREE_OPERAND (arg0, 0),
                                TREE_OPERAND (arg1, 0), 0)
            && TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg0, 0))))
          {
            tree tree01, tree11;
            enum tree_code code01, code11;

            tree01 = TREE_OPERAND (arg0, 1);
            tree11 = TREE_OPERAND (arg1, 1);
            STRIP_NOPS (tree01);
            STRIP_NOPS (tree11);
            code01 = TREE_CODE (tree01);
            code11 = TREE_CODE (tree11);
            if (code01 == INTEGER_CST
                && code11 == INTEGER_CST
                && TREE_INT_CST_HIGH (tree01) == 0
                && TREE_INT_CST_HIGH (tree11) == 0
                && ((TREE_INT_CST_LOW (tree01) + TREE_INT_CST_LOW (tree11))
                    == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)))))
              return build2 (LROTATE_EXPR, type, TREE_OPERAND (arg0, 0),
                             code0 == LSHIFT_EXPR ? tree01 : tree11);
            else if (code11 == MINUS_EXPR)
              {
                tree tree110, tree111;
                tree110 = TREE_OPERAND (tree11, 0);
                tree111 = TREE_OPERAND (tree11, 1);
                STRIP_NOPS (tree110);
                STRIP_NOPS (tree111);
                if (TREE_CODE (tree110) == INTEGER_CST
                    && 0 == compare_tree_int (tree110,
                                              TYPE_PRECISION
                                              (TREE_TYPE (TREE_OPERAND
                                                          (arg0, 0))))
                    && operand_equal_p (tree01, tree111, 0))
                  return build2 ((code0 == LSHIFT_EXPR
                                  ? LROTATE_EXPR
                                  : RROTATE_EXPR),
                                 type, TREE_OPERAND (arg0, 0), tree01);
              }
            else if (code01 == MINUS_EXPR)
              {
                tree tree010, tree011;
                tree010 = TREE_OPERAND (tree01, 0);
                tree011 = TREE_OPERAND (tree01, 1);
                STRIP_NOPS (tree010);
                STRIP_NOPS (tree011);
                if (TREE_CODE (tree010) == INTEGER_CST
                    && 0 == compare_tree_int (tree010,
                                              TYPE_PRECISION
                                              (TREE_TYPE (TREE_OPERAND
                                                          (arg0, 0))))
                    && operand_equal_p (tree11, tree011, 0))
                  return build2 ((code0 != LSHIFT_EXPR
                                  ? LROTATE_EXPR
                                  : RROTATE_EXPR),
                                 type, TREE_OPERAND (arg0, 0), tree11);
              }
          }
      }

    associate:
      /* In most languages, can't associate operations on floats through
         parentheses.  Rather than remember where the parentheses were, we
         don't associate floats at all, unless the user has specified
         -funsafe-math-optimizations.  */

      if (! wins
          && (! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations))
        {
          tree var0, con0, lit0, minus_lit0;
          tree var1, con1, lit1, minus_lit1;

          /* Split both trees into variables, constants, and literals.  Then
             associate each group together, the constants with literals,
             then the result with variables.  This increases the chances of
             literals being recombined later and of generating relocatable
             expressions for the sum of a constant and literal.  */
          var0 = split_tree (arg0, code, &con0, &lit0, &minus_lit0, 0);
          var1 = split_tree (arg1, code, &con1, &lit1, &minus_lit1,
                             code == MINUS_EXPR);

          /* Only do something if we found more than two objects.  Otherwise,
             nothing has changed and we risk infinite recursion.  */
          if (2 < ((var0 != 0) + (var1 != 0)
                   + (con0 != 0) + (con1 != 0)
                   + (lit0 != 0) + (lit1 != 0)
                   + (minus_lit0 != 0) + (minus_lit1 != 0)))
            {
              /* Recombine MINUS_EXPR operands by using PLUS_EXPR.  */
              if (code == MINUS_EXPR)
                code = PLUS_EXPR;

              var0 = associate_trees (var0, var1, code, type);
              con0 = associate_trees (con0, con1, code, type);
              lit0 = associate_trees (lit0, lit1, code, type);
              minus_lit0 = associate_trees (minus_lit0, minus_lit1, code, type);

              /* Preserve the MINUS_EXPR if the negative part of the literal is
                 greater than the positive part.  Otherwise, the multiplicative
                 folding code (i.e extract_muldiv) may be fooled in case
                 unsigned constants are subtracted, like in the following
                 example: ((X*2 + 4) - 8U)/2.  */
              if (minus_lit0 && lit0)
                {
                  if (TREE_CODE (lit0) == INTEGER_CST
                      && TREE_CODE (minus_lit0) == INTEGER_CST
                      && tree_int_cst_lt (lit0, minus_lit0))
                    {
                      minus_lit0 = associate_trees (minus_lit0, lit0,
                                                    MINUS_EXPR, type);
                      lit0 = 0;
                    }
                  else
                    {
                      lit0 = associate_trees (lit0, minus_lit0,
                                              MINUS_EXPR, type);
                      minus_lit0 = 0;
                    }
                }
              if (minus_lit0)
                {
                  if (con0 == 0)
                    return fold_convert (type,
                                         associate_trees (var0, minus_lit0,
                                                          MINUS_EXPR, type));
                  else
                    {
                      con0 = associate_trees (con0, minus_lit0,
                                              MINUS_EXPR, type);
                      return fold_convert (type,
                                           associate_trees (var0, con0,
                                                            PLUS_EXPR, type));
                    }
                }

              con0 = associate_trees (con0, lit0, code, type);
              return fold_convert (type, associate_trees (var0, con0,
                                                          code, type));
            }
        }

    binary:
      if (wins)
        t1 = const_binop (code, arg0, arg1, 0);
      if (t1 != NULL_TREE)
        {
          /* The return value should always have
             the same type as the original expression.  */
          if (TREE_TYPE (t1) != type)
            t1 = fold_convert (type, t1);

          return t1;
        }
      return t;

    case MINUS_EXPR:
      /* A - (-B) -> A + B */
      if (TREE_CODE (arg1) == NEGATE_EXPR)
        return fold (build2 (PLUS_EXPR, type, arg0, TREE_OPERAND (arg1, 0)));
      /* (-A) - B -> (-B) - A  where B is easily negated and we can swap.  */
      if (TREE_CODE (arg0) == NEGATE_EXPR
          && (FLOAT_TYPE_P (type)
              || (INTEGRAL_TYPE_P (type) && flag_wrapv && !flag_trapv))
          && negate_expr_p (arg1)
          && reorder_operands_p (arg0, arg1))
        return fold (build2 (MINUS_EXPR, type, negate_expr (arg1),
                             TREE_OPERAND (arg0, 0)));

      if (! FLOAT_TYPE_P (type))
        {
          if (! wins && integer_zerop (arg0))
            return negate_expr (fold_convert (type, arg1));
          if (integer_zerop (arg1))
            return non_lvalue (fold_convert (type, arg0));

          /* Fold A - (A & B) into ~B & A.  */
          if (!TREE_SIDE_EFFECTS (arg0)
              && TREE_CODE (arg1) == BIT_AND_EXPR)
            {
              if (operand_equal_p (arg0, TREE_OPERAND (arg1, 1), 0))
                return fold (build2 (BIT_AND_EXPR, type,
                                     fold (build1 (BIT_NOT_EXPR, type,
                                                   TREE_OPERAND (arg1, 0))),
                                     arg0));
              if (operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
                return fold (build2 (BIT_AND_EXPR, type,
                                     fold (build1 (BIT_NOT_EXPR, type,
                                                   TREE_OPERAND (arg1, 1))),
                                     arg0));
            }

          /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
             any power of 2 minus 1.  */
          if (TREE_CODE (arg0) == BIT_AND_EXPR
              && TREE_CODE (arg1) == BIT_AND_EXPR
              && operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 0), 0))
            {
              tree mask0 = TREE_OPERAND (arg0, 1);
              tree mask1 = TREE_OPERAND (arg1, 1);
              tree tem = fold (build1 (BIT_NOT_EXPR, type, mask0));
              
              if (operand_equal_p (tem, mask1, 0))
                {
                  tem = fold (build2 (BIT_XOR_EXPR, type,
                                      TREE_OPERAND (arg0, 0), mask1));
                  return fold (build2 (MINUS_EXPR, type, tem, mask1));
                }
            }
        }

      /* See if ARG1 is zero and X - ARG1 reduces to X.  */
      else if (fold_real_zero_addition_p (TREE_TYPE (arg0), arg1, 1))
        return non_lvalue (fold_convert (type, arg0));

      /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0).  So check whether
         ARG0 is zero and X + ARG0 reduces to X, since that would mean
         (-ARG1 + ARG0) reduces to -ARG1.  */
      else if (!wins && fold_real_zero_addition_p (TREE_TYPE (arg1), arg0, 0))
        return negate_expr (fold_convert (type, arg1));

      /* Fold &x - &x.  This can happen from &x.foo - &x.
         This is unsafe for certain floats even in non-IEEE formats.
         In IEEE, it is unsafe because it does wrong for NaNs.
         Also note that operand_equal_p is always false if an operand
         is volatile.  */

      if ((! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
          && operand_equal_p (arg0, arg1, 0))
        return fold_convert (type, integer_zero_node);

      /* A - B -> A + (-B) if B is easily negatable.  */
      if (!wins && negate_expr_p (arg1)
          && (FLOAT_TYPE_P (type)
              || (INTEGRAL_TYPE_P (type) && flag_wrapv && !flag_trapv)))
        return fold (build2 (PLUS_EXPR, type, arg0, negate_expr (arg1)));

      if (TREE_CODE (arg0) == MULT_EXPR
          && TREE_CODE (arg1) == MULT_EXPR
          && (INTEGRAL_TYPE_P (type) || flag_unsafe_math_optimizations))
        {
          /* (A * C) - (B * C) -> (A-B) * C.  */
          if (operand_equal_p (TREE_OPERAND (arg0, 1),
                               TREE_OPERAND (arg1, 1), 0))
            return fold (build2 (MULT_EXPR, type,
                                 fold (build2 (MINUS_EXPR, type,
                                               TREE_OPERAND (arg0, 0),
                                               TREE_OPERAND (arg1, 0))),
                                 TREE_OPERAND (arg0, 1)));
          /* (A * C1) - (A * C2) -> A * (C1-C2).  */
          if (operand_equal_p (TREE_OPERAND (arg0, 0),
                               TREE_OPERAND (arg1, 0), 0))
            return fold (build2 (MULT_EXPR, type,
                                 TREE_OPERAND (arg0, 0),
                                 fold (build2 (MINUS_EXPR, type,
                                               TREE_OPERAND (arg0, 1),
                                               TREE_OPERAND (arg1, 1)))));
        }

      goto associate;

    case MULT_EXPR:
      /* (-A) * (-B) -> A * B  */
      if (TREE_CODE (arg0) == NEGATE_EXPR && negate_expr_p (arg1))
        return fold (build2 (MULT_EXPR, type,
                             TREE_OPERAND (arg0, 0),
                             negate_expr (arg1)));
      if (TREE_CODE (arg1) == NEGATE_EXPR && negate_expr_p (arg0))
        return fold (build2 (MULT_EXPR, type,
                             negate_expr (arg0),
                             TREE_OPERAND (arg1, 0)));

      if (! FLOAT_TYPE_P (type))
        {
          if (integer_zerop (arg1))
            return omit_one_operand (type, arg1, arg0);
          if (integer_onep (arg1))
            return non_lvalue (fold_convert (type, arg0));

          /* (a * (1 << b)) is (a << b)  */
          if (TREE_CODE (arg1) == LSHIFT_EXPR
              && integer_onep (TREE_OPERAND (arg1, 0)))
            return fold (build2 (LSHIFT_EXPR, type, arg0,
                                 TREE_OPERAND (arg1, 1)));
          if (TREE_CODE (arg0) == LSHIFT_EXPR
              && integer_onep (TREE_OPERAND (arg0, 0)))
            return fold (build2 (LSHIFT_EXPR, type, arg1,
                                 TREE_OPERAND (arg0, 1)));

          if (TREE_CODE (arg1) == INTEGER_CST
              && 0 != (tem = extract_muldiv (TREE_OPERAND (t, 0),
                                             fold_convert (type, arg1),
                                             code, NULL_TREE)))
            return fold_convert (type, tem);

        }
      else
        {
          /* Maybe fold x * 0 to 0.  The expressions aren't the same
             when x is NaN, since x * 0 is also NaN.  Nor are they the
             same in modes with signed zeros, since multiplying a
             negative value by 0 gives -0, not +0.  */
          if (!HONOR_NANS (TYPE_MODE (TREE_TYPE (arg0)))
              && !HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg0)))
              && real_zerop (arg1))
            return omit_one_operand (type, arg1, arg0);
          /* In IEEE floating point, x*1 is not equivalent to x for snans.  */
          if (!HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg0)))
              && real_onep (arg1))
            return non_lvalue (fold_convert (type, arg0));

          /* Transform x * -1.0 into -x.  */
          if (!HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg0)))
              && real_minus_onep (arg1))
            return fold_convert (type, negate_expr (arg0));

          /* Convert (C1/X)*C2 into (C1*C2)/X.  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg0) == RDIV_EXPR
              && TREE_CODE (arg1) == REAL_CST
              && TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST)
            {
              tree tem = const_binop (MULT_EXPR, TREE_OPERAND (arg0, 0),
                                      arg1, 0);
              if (tem)
                return fold (build2 (RDIV_EXPR, type, tem,
                                     TREE_OPERAND (arg0, 1)));
            }

          if (flag_unsafe_math_optimizations)
            {
              enum built_in_function fcode0 = builtin_mathfn_code (arg0);
              enum built_in_function fcode1 = builtin_mathfn_code (arg1);

              /* Optimizations of root(...)*root(...).  */
              if (fcode0 == fcode1 && BUILTIN_ROOT_P (fcode0))
                {
                  tree rootfn, arg, arglist;
                  tree arg00 = TREE_VALUE (TREE_OPERAND (arg0, 1));
                  tree arg10 = TREE_VALUE (TREE_OPERAND (arg1, 1));

                  /* Optimize sqrt(x)*sqrt(x) as x.  */
                  if (BUILTIN_SQRT_P (fcode0)
                      && operand_equal_p (arg00, arg10, 0)
                      && ! HONOR_SNANS (TYPE_MODE (type)))
                    return arg00;

                  /* Optimize root(x)*root(y) as root(x*y).  */
                  rootfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                  arg = fold (build2 (MULT_EXPR, type, arg00, arg10));
                  arglist = build_tree_list (NULL_TREE, arg);
                  return build_function_call_expr (rootfn, arglist);
                }

              /* Optimize expN(x)*expN(y) as expN(x+y).  */
              if (fcode0 == fcode1 && BUILTIN_EXPONENT_P (fcode0))
                {
                  tree expfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                  tree arg = build2 (PLUS_EXPR, type,
                                     TREE_VALUE (TREE_OPERAND (arg0, 1)),
                                     TREE_VALUE (TREE_OPERAND (arg1, 1)));
                  tree arglist = build_tree_list (NULL_TREE, fold (arg));
                  return build_function_call_expr (expfn, arglist);
                }

              /* Optimizations of pow(...)*pow(...).  */
              if ((fcode0 == BUILT_IN_POW && fcode1 == BUILT_IN_POW)
                  || (fcode0 == BUILT_IN_POWF && fcode1 == BUILT_IN_POWF)
                  || (fcode0 == BUILT_IN_POWL && fcode1 == BUILT_IN_POWL))
                {
                  tree arg00 = TREE_VALUE (TREE_OPERAND (arg0, 1));
                  tree arg01 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg0,
                                                                     1)));
                  tree arg10 = TREE_VALUE (TREE_OPERAND (arg1, 1));
                  tree arg11 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg1,
                                                                     1)));

                  /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y).  */
                  if (operand_equal_p (arg01, arg11, 0))
                    {
                      tree powfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                      tree arg = build2 (MULT_EXPR, type, arg00, arg10);
                      tree arglist = tree_cons (NULL_TREE, fold (arg),
                                                build_tree_list (NULL_TREE,
                                                                 arg01));
                      return build_function_call_expr (powfn, arglist);
                    }

                  /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z).  */
                  if (operand_equal_p (arg00, arg10, 0))
                    {
                      tree powfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                      tree arg = fold (build2 (PLUS_EXPR, type, arg01, arg11));
                      tree arglist = tree_cons (NULL_TREE, arg00,
                                                build_tree_list (NULL_TREE,
                                                                 arg));
                      return build_function_call_expr (powfn, arglist);
                    }
                }

              /* Optimize tan(x)*cos(x) as sin(x).  */
              if (((fcode0 == BUILT_IN_TAN && fcode1 == BUILT_IN_COS)
                   || (fcode0 == BUILT_IN_TANF && fcode1 == BUILT_IN_COSF)
                   || (fcode0 == BUILT_IN_TANL && fcode1 == BUILT_IN_COSL)
                   || (fcode0 == BUILT_IN_COS && fcode1 == BUILT_IN_TAN)
                   || (fcode0 == BUILT_IN_COSF && fcode1 == BUILT_IN_TANF)
                   || (fcode0 == BUILT_IN_COSL && fcode1 == BUILT_IN_TANL))
                  && operand_equal_p (TREE_VALUE (TREE_OPERAND (arg0, 1)),
                                      TREE_VALUE (TREE_OPERAND (arg1, 1)), 0))
                {
                  tree sinfn = mathfn_built_in (type, BUILT_IN_SIN);

                  if (sinfn != NULL_TREE)
                    return build_function_call_expr (sinfn,
                                                     TREE_OPERAND (arg0, 1));
                }

              /* Optimize x*pow(x,c) as pow(x,c+1).  */
              if (fcode1 == BUILT_IN_POW
                  || fcode1 == BUILT_IN_POWF
                  || fcode1 == BUILT_IN_POWL)
                {
                  tree arg10 = TREE_VALUE (TREE_OPERAND (arg1, 1));
                  tree arg11 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg1,
                                                                     1)));
                  if (TREE_CODE (arg11) == REAL_CST
                      && ! TREE_CONSTANT_OVERFLOW (arg11)
                      && operand_equal_p (arg0, arg10, 0))
                    {
                      tree powfn = TREE_OPERAND (TREE_OPERAND (arg1, 0), 0);
                      REAL_VALUE_TYPE c;
                      tree arg, arglist;

                      c = TREE_REAL_CST (arg11);
                      real_arithmetic (&c, PLUS_EXPR, &c, &dconst1);
                      arg = build_real (type, c);
                      arglist = build_tree_list (NULL_TREE, arg);
                      arglist = tree_cons (NULL_TREE, arg0, arglist);
                      return build_function_call_expr (powfn, arglist);
                    }
                }

              /* Optimize pow(x,c)*x as pow(x,c+1).  */
              if (fcode0 == BUILT_IN_POW
                  || fcode0 == BUILT_IN_POWF
                  || fcode0 == BUILT_IN_POWL)
                {
                  tree arg00 = TREE_VALUE (TREE_OPERAND (arg0, 1));
                  tree arg01 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg0,
                                                                     1)));
                  if (TREE_CODE (arg01) == REAL_CST
                      && ! TREE_CONSTANT_OVERFLOW (arg01)
                      && operand_equal_p (arg1, arg00, 0))
                    {
                      tree powfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                      REAL_VALUE_TYPE c;
                      tree arg, arglist;

                      c = TREE_REAL_CST (arg01);
                      real_arithmetic (&c, PLUS_EXPR, &c, &dconst1);
                      arg = build_real (type, c);
                      arglist = build_tree_list (NULL_TREE, arg);
                      arglist = tree_cons (NULL_TREE, arg1, arglist);
                      return build_function_call_expr (powfn, arglist);
                    }
                }

              /* Optimize x*x as pow(x,2.0), which is expanded as x*x.  */
              if (! optimize_size
                  && operand_equal_p (arg0, arg1, 0))
                {
                  tree powfn = mathfn_built_in (type, BUILT_IN_POW);

                  if (powfn)
                    {
                      tree arg = build_real (type, dconst2);
                      tree arglist = build_tree_list (NULL_TREE, arg);
                      arglist = tree_cons (NULL_TREE, arg0, arglist);
                      return build_function_call_expr (powfn, arglist);
                    }
                }
            }
        }
      goto associate;

    case BIT_IOR_EXPR:
    bit_ior:
      if (integer_all_onesp (arg1))
        return omit_one_operand (type, arg1, arg0);
      if (integer_zerop (arg1))
        return non_lvalue (fold_convert (type, arg0));
      if (operand_equal_p (arg0, arg1, 0))
        return non_lvalue (fold_convert (type, arg0));
      t1 = distribute_bit_expr (code, type, arg0, arg1);
      if (t1 != NULL_TREE)
        return t1;

      /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).

         This results in more efficient code for machines without a NAND
         instruction.  Combine will canonicalize to the first form
         which will allow use of NAND instructions provided by the
         backend if they exist.  */
      if (TREE_CODE (arg0) == BIT_NOT_EXPR
          && TREE_CODE (arg1) == BIT_NOT_EXPR)
        {
          return fold (build1 (BIT_NOT_EXPR, type,
                               build2 (BIT_AND_EXPR, type,
                                       TREE_OPERAND (arg0, 0),
                                       TREE_OPERAND (arg1, 0))));
        }

      /* See if this can be simplified into a rotate first.  If that
         is unsuccessful continue in the association code.  */
      goto bit_rotate;

    case BIT_XOR_EXPR:
      if (integer_zerop (arg1))
        return non_lvalue (fold_convert (type, arg0));
      if (integer_all_onesp (arg1))
        return fold (build1 (BIT_NOT_EXPR, type, arg0));
      if (operand_equal_p (arg0, arg1, 0))
        return omit_one_operand (type, integer_zero_node, arg0);

      /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
         with a constant, and the two constants have no bits in common,
         we should treat this as a BIT_IOR_EXPR since this may produce more
         simplifications.  */
      if (TREE_CODE (arg0) == BIT_AND_EXPR
          && TREE_CODE (arg1) == BIT_AND_EXPR
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
          && TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST
          && integer_zerop (const_binop (BIT_AND_EXPR,
                                         TREE_OPERAND (arg0, 1),
                                         TREE_OPERAND (arg1, 1), 0)))
        {
          code = BIT_IOR_EXPR;
          goto bit_ior;
        }

      /* See if this can be simplified into a rotate first.  If that
         is unsuccessful continue in the association code.  */
      goto bit_rotate;

    case BIT_AND_EXPR:
      if (integer_all_onesp (arg1))
        return non_lvalue (fold_convert (type, arg0));
      if (integer_zerop (arg1))
        return omit_one_operand (type, arg1, arg0);
      if (operand_equal_p (arg0, arg1, 0))
        return non_lvalue (fold_convert (type, arg0));
      t1 = distribute_bit_expr (code, type, arg0, arg1);
      if (t1 != NULL_TREE)
        return t1;
      /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char.  */
      if (TREE_CODE (arg1) == INTEGER_CST && TREE_CODE (arg0) == NOP_EXPR
          && TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg0, 0))))
        {
          unsigned int prec
            = TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)));

          if (prec < BITS_PER_WORD && prec < HOST_BITS_PER_WIDE_INT
              && (~TREE_INT_CST_LOW (arg1)
                  & (((HOST_WIDE_INT) 1 << prec) - 1)) == 0)
            return fold_convert (type, TREE_OPERAND (arg0, 0));
        }

      /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).

         This results in more efficient code for machines without a NOR
         instruction.  Combine will canonicalize to the first form
         which will allow use of NOR instructions provided by the
         backend if they exist.  */
      if (TREE_CODE (arg0) == BIT_NOT_EXPR
          && TREE_CODE (arg1) == BIT_NOT_EXPR)
        {
          return fold (build1 (BIT_NOT_EXPR, type,
                               build2 (BIT_IOR_EXPR, type,
                                       TREE_OPERAND (arg0, 0),
                                       TREE_OPERAND (arg1, 0))));
        }

      goto associate;

    case RDIV_EXPR:
      /* Don't touch a floating-point divide by zero unless the mode
         of the constant can represent infinity.  */
      if (TREE_CODE (arg1) == REAL_CST
          && !MODE_HAS_INFINITIES (TYPE_MODE (TREE_TYPE (arg1)))
          && real_zerop (arg1))
        return t;

      /* (-A) / (-B) -> A / B  */
      if (TREE_CODE (arg0) == NEGATE_EXPR && negate_expr_p (arg1))
        return fold (build2 (RDIV_EXPR, type,
                             TREE_OPERAND (arg0, 0),
                             negate_expr (arg1)));
      if (TREE_CODE (arg1) == NEGATE_EXPR && negate_expr_p (arg0))
        return fold (build2 (RDIV_EXPR, type,
                             negate_expr (arg0),
                             TREE_OPERAND (arg1, 0)));

      /* In IEEE floating point, x/1 is not equivalent to x for snans.  */
      if (!HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg0)))
          && real_onep (arg1))
        return non_lvalue (fold_convert (type, arg0));

      /* In IEEE floating point, x/-1 is not equivalent to -x for snans.  */
      if (!HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg0)))
          && real_minus_onep (arg1))
        return non_lvalue (fold_convert (type, negate_expr (arg0)));

      /* If ARG1 is a constant, we can convert this to a multiply by the
         reciprocal.  This does not have the same rounding properties,
         so only do this if -funsafe-math-optimizations.  We can actually
         always safely do it if ARG1 is a power of two, but it's hard to
         tell if it is or not in a portable manner.  */
      if (TREE_CODE (arg1) == REAL_CST)
        {
          if (flag_unsafe_math_optimizations
              && 0 != (tem = const_binop (code, build_real (type, dconst1),
                                          arg1, 0)))
            return fold (build2 (MULT_EXPR, type, arg0, tem));
          /* Find the reciprocal if optimizing and the result is exact.  */
          if (optimize)
            {
              REAL_VALUE_TYPE r;
              r = TREE_REAL_CST (arg1);
              if (exact_real_inverse (TYPE_MODE(TREE_TYPE(arg0)), &r))
                {
                  tem = build_real (type, r);
                  return fold (build2 (MULT_EXPR, type, arg0, tem));
                }
            }
        }
      /* Convert A/B/C to A/(B*C).  */
      if (flag_unsafe_math_optimizations
          && TREE_CODE (arg0) == RDIV_EXPR)
        return fold (build2 (RDIV_EXPR, type, TREE_OPERAND (arg0, 0),
                             fold (build2 (MULT_EXPR, type,
                                           TREE_OPERAND (arg0, 1), arg1))));

      /* Convert A/(B/C) to (A/B)*C.  */
      if (flag_unsafe_math_optimizations
          && TREE_CODE (arg1) == RDIV_EXPR)
        return fold (build2 (MULT_EXPR, type,
                             fold (build2 (RDIV_EXPR, type, arg0,
                                           TREE_OPERAND (arg1, 0))),
                             TREE_OPERAND (arg1, 1)));

      /* Convert C1/(X*C2) into (C1/C2)/X.  */
      if (flag_unsafe_math_optimizations
          && TREE_CODE (arg1) == MULT_EXPR
          && TREE_CODE (arg0) == REAL_CST
          && TREE_CODE (TREE_OPERAND (arg1, 1)) == REAL_CST)
        {
          tree tem = const_binop (RDIV_EXPR, arg0,
                                  TREE_OPERAND (arg1, 1), 0);
          if (tem)
            return fold (build2 (RDIV_EXPR, type, tem,
                                 TREE_OPERAND (arg1, 0)));
        }

      if (flag_unsafe_math_optimizations)
        {
          enum built_in_function fcode = builtin_mathfn_code (arg1);
          /* Optimize x/expN(y) into x*expN(-y).  */
          if (BUILTIN_EXPONENT_P (fcode))
            {
              tree expfn = TREE_OPERAND (TREE_OPERAND (arg1, 0), 0);
              tree arg = negate_expr (TREE_VALUE (TREE_OPERAND (arg1, 1)));
              tree arglist = build_tree_list (NULL_TREE,
                                              fold_convert (type, arg));
              arg1 = build_function_call_expr (expfn, arglist);
              return fold (build2 (MULT_EXPR, type, arg0, arg1));
            }

          /* Optimize x/pow(y,z) into x*pow(y,-z).  */
          if (fcode == BUILT_IN_POW
              || fcode == BUILT_IN_POWF
              || fcode == BUILT_IN_POWL)
            {
              tree powfn = TREE_OPERAND (TREE_OPERAND (arg1, 0), 0);
              tree arg10 = TREE_VALUE (TREE_OPERAND (arg1, 1));
              tree arg11 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg1, 1)));
              tree neg11 = fold_convert (type, negate_expr (arg11));
              tree arglist = tree_cons(NULL_TREE, arg10,
                                       build_tree_list (NULL_TREE, neg11));
              arg1 = build_function_call_expr (powfn, arglist);
              return fold (build2 (MULT_EXPR, type, arg0, arg1));
            }
        }

      if (flag_unsafe_math_optimizations)
        {
          enum built_in_function fcode0 = builtin_mathfn_code (arg0);
          enum built_in_function fcode1 = builtin_mathfn_code (arg1);

          /* Optimize sin(x)/cos(x) as tan(x).  */
          if (((fcode0 == BUILT_IN_SIN && fcode1 == BUILT_IN_COS)
               || (fcode0 == BUILT_IN_SINF && fcode1 == BUILT_IN_COSF)
               || (fcode0 == BUILT_IN_SINL && fcode1 == BUILT_IN_COSL))
              && operand_equal_p (TREE_VALUE (TREE_OPERAND (arg0, 1)),
                                  TREE_VALUE (TREE_OPERAND (arg1, 1)), 0))
            {
              tree tanfn = mathfn_built_in (type, BUILT_IN_TAN);

              if (tanfn != NULL_TREE)
                return build_function_call_expr (tanfn,
                                                 TREE_OPERAND (arg0, 1));
            }

          /* Optimize cos(x)/sin(x) as 1.0/tan(x).  */
          if (((fcode0 == BUILT_IN_COS && fcode1 == BUILT_IN_SIN)
               || (fcode0 == BUILT_IN_COSF && fcode1 == BUILT_IN_SINF)
               || (fcode0 == BUILT_IN_COSL && fcode1 == BUILT_IN_SINL))
              && operand_equal_p (TREE_VALUE (TREE_OPERAND (arg0, 1)),
                                  TREE_VALUE (TREE_OPERAND (arg1, 1)), 0))
            {
              tree tanfn = mathfn_built_in (type, BUILT_IN_TAN);

              if (tanfn != NULL_TREE)
                {
                  tree tmp = TREE_OPERAND (arg0, 1);
                  tmp = build_function_call_expr (tanfn, tmp);
                  return fold (build2 (RDIV_EXPR, type,
                                       build_real (type, dconst1), tmp));
                }
            }

          /* Optimize pow(x,c)/x as pow(x,c-1).  */
          if (fcode0 == BUILT_IN_POW
              || fcode0 == BUILT_IN_POWF
              || fcode0 == BUILT_IN_POWL)
            {
              tree arg00 = TREE_VALUE (TREE_OPERAND (arg0, 1));
              tree arg01 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg0, 1)));
              if (TREE_CODE (arg01) == REAL_CST
                  && ! TREE_CONSTANT_OVERFLOW (arg01)
                  && operand_equal_p (arg1, arg00, 0))
                {
                  tree powfn = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
                  REAL_VALUE_TYPE c;
                  tree arg, arglist;

                  c = TREE_REAL_CST (arg01);
                  real_arithmetic (&c, MINUS_EXPR, &c, &dconst1);
                  arg = build_real (type, c);
                  arglist = build_tree_list (NULL_TREE, arg);
                  arglist = tree_cons (NULL_TREE, arg1, arglist);
                  return build_function_call_expr (powfn, arglist);
                }
            }
        }
      goto binary;

    case TRUNC_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case EXACT_DIV_EXPR:
      if (integer_onep (arg1))
        return non_lvalue (fold_convert (type, arg0));
      if (integer_zerop (arg1))
        return t;
      /* X / -1 is -X.  */
      if (!TYPE_UNSIGNED (type)
          && TREE_CODE (arg1) == INTEGER_CST
          && TREE_INT_CST_LOW (arg1) == (unsigned HOST_WIDE_INT) -1
          && TREE_INT_CST_HIGH (arg1) == -1)
        return fold_convert (type, negate_expr (arg0));

      /* If arg0 is a multiple of arg1, then rewrite to the fastest div
         operation, EXACT_DIV_EXPR.

         Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
         At one time others generated faster code, it's not clear if they do
         after the last round to changes to the DIV code in expmed.c.  */
      if ((code == CEIL_DIV_EXPR || code == FLOOR_DIV_EXPR)
          && multiple_of_p (type, arg0, arg1))
        return fold (build2 (EXACT_DIV_EXPR, type, arg0, arg1));

      if (TREE_CODE (arg1) == INTEGER_CST
          && 0 != (tem = extract_muldiv (TREE_OPERAND (t, 0), arg1,
                                         code, NULL_TREE)))
        return fold_convert (type, tem);

      goto binary;

    case CEIL_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case ROUND_MOD_EXPR:
    case TRUNC_MOD_EXPR:
      if (integer_onep (arg1))
        return omit_one_operand (type, integer_zero_node, arg0);
      if (integer_zerop (arg1))
        return t;
      /* X % -1 is zero.  */
      if (!TYPE_UNSIGNED (type)
          && TREE_CODE (arg1) == INTEGER_CST
          && TREE_INT_CST_LOW (arg1) == (unsigned HOST_WIDE_INT) -1
          && TREE_INT_CST_HIGH (arg1) == -1)
        return omit_one_operand (type, integer_zero_node, arg0);

      if (TREE_CODE (arg1) == INTEGER_CST
          && 0 != (tem = extract_muldiv (TREE_OPERAND (t, 0), arg1,
                                         code, NULL_TREE)))
        return fold_convert (type, tem);

      goto binary;

    case LROTATE_EXPR:
    case RROTATE_EXPR:
      if (integer_all_onesp (arg0))
        return omit_one_operand (type, arg0, arg1);
      goto shift;

    case RSHIFT_EXPR:
      /* Optimize -1 >> x for arithmetic right shifts.  */
      if (integer_all_onesp (arg0) && !TYPE_UNSIGNED (type))
        return omit_one_operand (type, arg0, arg1);
      /* ... fall through ...  */

    case LSHIFT_EXPR:
    shift:
      if (integer_zerop (arg1))
        return non_lvalue (fold_convert (type, arg0));
      if (integer_zerop (arg0))
        return omit_one_operand (type, arg0, arg1);

      /* Since negative shift count is not well-defined,
         don't try to compute it in the compiler.  */
      if (TREE_CODE (arg1) == INTEGER_CST && tree_int_cst_sgn (arg1) < 0)
        return t;
      /* Rewrite an LROTATE_EXPR by a constant into an
         RROTATE_EXPR by a new constant.  */
      if (code == LROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST)
        {
          tree tem = build_int_2 (GET_MODE_BITSIZE (TYPE_MODE (type)), 0);
          tem = fold_convert (TREE_TYPE (arg1), tem);
          tem = const_binop (MINUS_EXPR, tem, arg1, 0);
          return fold (build2 (RROTATE_EXPR, type, arg0, tem));
        }

      /* If we have a rotate of a bit operation with the rotate count and
         the second operand of the bit operation both constant,
         permute the two operations.  */
      if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
          && (TREE_CODE (arg0) == BIT_AND_EXPR
              || TREE_CODE (arg0) == BIT_IOR_EXPR
              || TREE_CODE (arg0) == BIT_XOR_EXPR)
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
        return fold (build2 (TREE_CODE (arg0), type,
                             fold (build2 (code, type,
                                           TREE_OPERAND (arg0, 0), arg1)),
                             fold (build2 (code, type,
                                           TREE_OPERAND (arg0, 1), arg1))));

      /* Two consecutive rotates adding up to the width of the mode can
         be ignored.  */
      if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
          && TREE_CODE (arg0) == RROTATE_EXPR
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
          && TREE_INT_CST_HIGH (arg1) == 0
          && TREE_INT_CST_HIGH (TREE_OPERAND (arg0, 1)) == 0
          && ((TREE_INT_CST_LOW (arg1)
               + TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)))
              == (unsigned int) GET_MODE_BITSIZE (TYPE_MODE (type))))
        return TREE_OPERAND (arg0, 0);

      goto binary;

    case MIN_EXPR:
      if (operand_equal_p (arg0, arg1, 0))
        return omit_one_operand (type, arg0, arg1);
      if (INTEGRAL_TYPE_P (type)
          && operand_equal_p (arg1, TYPE_MIN_VALUE (type), OEP_ONLY_CONST))
        return omit_one_operand (type, arg1, arg0);
      goto associate;

    case MAX_EXPR:
      if (operand_equal_p (arg0, arg1, 0))
        return omit_one_operand (type, arg0, arg1);
      if (INTEGRAL_TYPE_P (type)
          && TYPE_MAX_VALUE (type)
          && operand_equal_p (arg1, TYPE_MAX_VALUE (type), OEP_ONLY_CONST))
        return omit_one_operand (type, arg1, arg0);
      goto associate;

    case TRUTH_NOT_EXPR:
      /* Note that the operand of this must be an int
         and its values must be 0 or 1.
         ("true" is a fixed value perhaps depending on the language,
         but we don't handle values other than 1 correctly yet.)  */
      tem = invert_truthvalue (arg0);
      /* Avoid infinite recursion.  */
      if (TREE_CODE (tem) == TRUTH_NOT_EXPR)
        {
          tem = fold_single_bit_test (code, arg0, arg1, type);
          if (tem)
            return tem;
          return t;
        }
      return fold_convert (type, tem);

    case TRUTH_ANDIF_EXPR:
      /* Note that the operands of this must be ints
         and their values must be 0 or 1.
         ("true" is a fixed value perhaps depending on the language.)  */
      /* If first arg is constant zero, return it.  */
      if (integer_zerop (arg0))
        return fold_convert (type, arg0);
    case TRUTH_AND_EXPR:
      /* If either arg is constant true, drop it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
        return non_lvalue (fold_convert (type, arg1));
      if (TREE_CODE (arg1) == INTEGER_CST && ! integer_zerop (arg1)
          /* Preserve sequence points.  */
          && (code != TRUTH_ANDIF_EXPR || ! TREE_SIDE_EFFECTS (arg0)))
        return non_lvalue (fold_convert (type, arg0));
      /* If second arg is constant zero, result is zero, but first arg
         must be evaluated.  */
      if (integer_zerop (arg1))
        return omit_one_operand (type, arg1, arg0);
      /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
         case will be handled here.  */
      if (integer_zerop (arg0))
        return omit_one_operand (type, arg0, arg1);

    truth_andor:
      /* We only do these simplifications if we are optimizing.  */
      if (!optimize)
        return t;

      /* Check for things like (A || B) && (A || C).  We can convert this
         to A || (B && C).  Note that either operator can be any of the four
         truth and/or operations and the transformation will still be
         valid.   Also note that we only care about order for the
         ANDIF and ORIF operators.  If B contains side effects, this
         might change the truth-value of A.  */
      if (TREE_CODE (arg0) == TREE_CODE (arg1)
          && (TREE_CODE (arg0) == TRUTH_ANDIF_EXPR
              || TREE_CODE (arg0) == TRUTH_ORIF_EXPR
              || TREE_CODE (arg0) == TRUTH_AND_EXPR
              || TREE_CODE (arg0) == TRUTH_OR_EXPR)
          && ! TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1)))
        {
          tree a00 = TREE_OPERAND (arg0, 0);
          tree a01 = TREE_OPERAND (arg0, 1);
          tree a10 = TREE_OPERAND (arg1, 0);
          tree a11 = TREE_OPERAND (arg1, 1);
          int commutative = ((TREE_CODE (arg0) == TRUTH_OR_EXPR
                              || TREE_CODE (arg0) == TRUTH_AND_EXPR)
                             && (code == TRUTH_AND_EXPR
                                 || code == TRUTH_OR_EXPR));

          if (operand_equal_p (a00, a10, 0))
            return fold (build2 (TREE_CODE (arg0), type, a00,
                                 fold (build2 (code, type, a01, a11))));
          else if (commutative && operand_equal_p (a00, a11, 0))
            return fold (build2 (TREE_CODE (arg0), type, a00,
                                 fold (build2 (code, type, a01, a10))));
          else if (commutative && operand_equal_p (a01, a10, 0))
            return fold (build2 (TREE_CODE (arg0), type, a01,
                                 fold (build2 (code, type, a00, a11))));

          /* This case if tricky because we must either have commutative
             operators or else A10 must not have side-effects.  */

          else if ((commutative || ! TREE_SIDE_EFFECTS (a10))
                   && operand_equal_p (a01, a11, 0))
            return fold (build2 (TREE_CODE (arg0), type,
                                 fold (build2 (code, type, a00, a10)),
                                 a01));
        }

      /* See if we can build a range comparison.  */
      if (0 != (tem = fold_range_test (t)))
        return tem;

      /* Check for the possibility of merging component references.  If our
         lhs is another similar operation, try to merge its rhs with our
         rhs.  Then try to merge our lhs and rhs.  */
      if (TREE_CODE (arg0) == code
          && 0 != (tem = fold_truthop (code, type,
                                       TREE_OPERAND (arg0, 1), arg1)))
        return fold (build2 (code, type, TREE_OPERAND (arg0, 0), tem));

      if ((tem = fold_truthop (code, type, arg0, arg1)) != 0)
        return tem;

      return t;

    case TRUTH_ORIF_EXPR:
      /* Note that the operands of this must be ints
         and their values must be 0 or true.
         ("true" is a fixed value perhaps depending on the language.)  */
      /* If first arg is constant true, return it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
        return fold_convert (type, arg0);
    case TRUTH_OR_EXPR:
      /* If either arg is constant zero, drop it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && integer_zerop (arg0))
        return non_lvalue (fold_convert (type, arg1));
      if (TREE_CODE (arg1) == INTEGER_CST && integer_zerop (arg1)
          /* Preserve sequence points.  */
          && (code != TRUTH_ORIF_EXPR || ! TREE_SIDE_EFFECTS (arg0)))
        return non_lvalue (fold_convert (type, arg0));
      /* If second arg is constant true, result is true, but we must
         evaluate first arg.  */
      if (TREE_CODE (arg1) == INTEGER_CST && ! integer_zerop (arg1))
        return omit_one_operand (type, arg1, arg0);
      /* Likewise for first arg, but note this only occurs here for
         TRUTH_OR_EXPR.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
        return omit_one_operand (type, arg0, arg1);
      goto truth_andor;

    case TRUTH_XOR_EXPR:
      /* If either arg is constant zero, drop it.  */
      if (integer_zerop (arg0))
        return non_lvalue (fold_convert (type, arg1));
      if (integer_zerop (arg1))
        return non_lvalue (fold_convert (type, arg0));
      /* If either arg is constant true, this is a logical inversion.  */
      if (integer_onep (arg0))
        return non_lvalue (fold_convert (type, invert_truthvalue (arg1)));
      if (integer_onep (arg1))
        return non_lvalue (fold_convert (type, invert_truthvalue (arg0)));
      /* Identical arguments cancel to zero.  */
      if (operand_equal_p (arg0, arg1, 0))
        return omit_one_operand (type, integer_zero_node, arg0);
      return t;

    case EQ_EXPR:
    case NE_EXPR:
    case LT_EXPR:
    case GT_EXPR:
    case LE_EXPR:
    case GE_EXPR:
      /* If one arg is a real or integer constant, put it last.  */
      if (tree_swap_operands_p (arg0, arg1, true))
        return fold (build2 (swap_tree_comparison (code), type, arg1, arg0));

      /* If this is an equality comparison of the address of a non-weak
         object against zero, then we know the result.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == ADDR_EXPR
          && DECL_P (TREE_OPERAND (arg0, 0))
          && ! DECL_WEAK (TREE_OPERAND (arg0, 0))
          && integer_zerop (arg1))
        {
          if (code == EQ_EXPR)
            return fold_convert (type, integer_zero_node);
          else
            return fold_convert (type, integer_one_node);
        }

      /* If this is an equality comparison of the address of two non-weak,
         unaliased symbols neither of which are extern (since we do not
         have access to attributes for externs), then we know the result.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == ADDR_EXPR
          && DECL_P (TREE_OPERAND (arg0, 0))
          && ! DECL_WEAK (TREE_OPERAND (arg0, 0))
          && ! lookup_attribute ("alias",
                                 DECL_ATTRIBUTES (TREE_OPERAND (arg0, 0)))
          && ! DECL_EXTERNAL (TREE_OPERAND (arg0, 0))
          && TREE_CODE (arg1) == ADDR_EXPR
          && DECL_P (TREE_OPERAND (arg1, 0))
          && ! DECL_WEAK (TREE_OPERAND (arg1, 0))
          && ! lookup_attribute ("alias",
                                 DECL_ATTRIBUTES (TREE_OPERAND (arg1, 0)))
          && ! DECL_EXTERNAL (TREE_OPERAND (arg1, 0)))
        {
          if (code == EQ_EXPR)
            return fold_convert (type, (operand_equal_p (arg0, arg1, 0)
                    ? integer_one_node : integer_zero_node));
          else
            return fold_convert (type, (operand_equal_p (arg0, arg1, 0)
                    ? integer_zero_node : integer_one_node));
        }

      if (FLOAT_TYPE_P (TREE_TYPE (arg0)))
        {
          tree targ0 = strip_float_extensions (arg0);
          tree targ1 = strip_float_extensions (arg1);
          tree newtype = TREE_TYPE (targ0);

          if (TYPE_PRECISION (TREE_TYPE (targ1)) > TYPE_PRECISION (newtype))
            newtype = TREE_TYPE (targ1);

          /* Fold (double)float1 CMP (double)float2 into float1 CMP float2.  */
          if (TYPE_PRECISION (newtype) < TYPE_PRECISION (TREE_TYPE (arg0)))
            return fold (build2 (code, type, fold_convert (newtype, targ0),
                                 fold_convert (newtype, targ1)));

          /* (-a) CMP (-b) -> b CMP a  */
          if (TREE_CODE (arg0) == NEGATE_EXPR
              && TREE_CODE (arg1) == NEGATE_EXPR)
            return fold (build2 (code, type, TREE_OPERAND (arg1, 0),
                                 TREE_OPERAND (arg0, 0)));

          if (TREE_CODE (arg1) == REAL_CST)
          {
            REAL_VALUE_TYPE cst;
            cst = TREE_REAL_CST (arg1);

            /* (-a) CMP CST -> a swap(CMP) (-CST)  */
            if (TREE_CODE (arg0) == NEGATE_EXPR)
              return
                fold (build2 (swap_tree_comparison (code), type,
                              TREE_OPERAND (arg0, 0),
                              build_real (TREE_TYPE (arg1),
                                          REAL_VALUE_NEGATE (cst))));

            /* IEEE doesn't distinguish +0 and -0 in comparisons.  */
            /* a CMP (-0) -> a CMP 0  */
            if (REAL_VALUE_MINUS_ZERO (cst))
              return fold (build2 (code, type, arg0,
                                   build_real (TREE_TYPE (arg1), dconst0)));

            /* x != NaN is always true, other ops are always false.  */
            if (REAL_VALUE_ISNAN (cst)
                && ! HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg1))))
              {
                tem = (code == NE_EXPR) ? integer_one_node : integer_zero_node;
                return omit_one_operand (type, fold_convert (type, tem), arg0);
              }

            /* Fold comparisons against infinity.  */
            if (REAL_VALUE_ISINF (cst))
              {
                tem = fold_inf_compare (code, type, arg0, arg1);
                if (tem != NULL_TREE)
                  return tem;
              }
          }

          /* If this is a comparison of a real constant with a PLUS_EXPR
             or a MINUS_EXPR of a real constant, we can convert it into a
             comparison with a revised real constant as long as no overflow
             occurs when unsafe_math_optimizations are enabled.  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg1) == REAL_CST
              && (TREE_CODE (arg0) == PLUS_EXPR
                  || TREE_CODE (arg0) == MINUS_EXPR)
              && TREE_CODE (TREE_OPERAND (arg0, 1)) == REAL_CST
              && 0 != (tem = const_binop (TREE_CODE (arg0) == PLUS_EXPR
                                          ? MINUS_EXPR : PLUS_EXPR,
                                          arg1, TREE_OPERAND (arg0, 1), 0))
              && ! TREE_CONSTANT_OVERFLOW (tem))
            return fold (build2 (code, type, TREE_OPERAND (arg0, 0), tem));

          /* Likewise, we can simplify a comparison of a real constant with
             a MINUS_EXPR whose first operand is also a real constant, i.e.
             (c1 - x) < c2 becomes x > c1-c2.  */
          if (flag_unsafe_math_optimizations
              && TREE_CODE (arg1) == REAL_CST
              && TREE_CODE (arg0) == MINUS_EXPR
              && TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST
              && 0 != (tem = const_binop (MINUS_EXPR, TREE_OPERAND (arg0, 0),
                                          arg1, 0))
              && ! TREE_CONSTANT_OVERFLOW (tem))
            return fold (build2 (swap_tree_comparison (code), type,
                                 TREE_OPERAND (arg0, 1), tem));

          /* Fold comparisons against built-in math functions.  */
          if (TREE_CODE (arg1) == REAL_CST
              && flag_unsafe_math_optimizations
              && ! flag_errno_math)
            {
              enum built_in_function fcode = builtin_mathfn_code (arg0);

              if (fcode != END_BUILTINS)
                {
                  tem = fold_mathfn_compare (fcode, code, type, arg0, arg1);
                  if (tem != NULL_TREE)
                    return tem;
                }
            }
        }

      /* Convert foo++ == CONST into ++foo == CONST + INCR.  */
      if (TREE_CONSTANT (arg1)
          && (TREE_CODE (arg0) == POSTINCREMENT_EXPR
              || TREE_CODE (arg0) == POSTDECREMENT_EXPR)
          /* This optimization is invalid for ordered comparisons
             if CONST+INCR overflows or if foo+incr might overflow.
             This optimization is invalid for floating point due to rounding.
             For pointer types we assume overflow doesn't happen.  */
          && (POINTER_TYPE_P (TREE_TYPE (arg0))
              || (INTEGRAL_TYPE_P (TREE_TYPE (arg0))
                  && (code == EQ_EXPR || code == NE_EXPR))))
        {
          tree varop, newconst;

          if (TREE_CODE (arg0) == POSTINCREMENT_EXPR)
            {
              newconst = fold (build2 (PLUS_EXPR, TREE_TYPE (arg0),
                                       arg1, TREE_OPERAND (arg0, 1)));
              varop = build2 (PREINCREMENT_EXPR, TREE_TYPE (arg0),
                              TREE_OPERAND (arg0, 0),
                              TREE_OPERAND (arg0, 1));
            }
          else
            {
              newconst = fold (build2 (MINUS_EXPR, TREE_TYPE (arg0),
                                       arg1, TREE_OPERAND (arg0, 1)));
              varop = build2 (PREDECREMENT_EXPR, TREE_TYPE (arg0),
                              TREE_OPERAND (arg0, 0),
                              TREE_OPERAND (arg0, 1));
            }


          /* If VAROP is a reference to a bitfield, we must mask
             the constant by the width of the field.  */
          if (TREE_CODE (TREE_OPERAND (varop, 0)) == COMPONENT_REF
              && DECL_BIT_FIELD (TREE_OPERAND (TREE_OPERAND (varop, 0), 1)))
            {
              tree fielddecl = TREE_OPERAND (TREE_OPERAND (varop, 0), 1);
              int size = TREE_INT_CST_LOW (DECL_SIZE (fielddecl));
              tree folded_compare, shift;

              /* First check whether the comparison would come out
                 always the same.  If we don't do that we would
                 change the meaning with the masking.  */
              folded_compare = fold (build2 (code, type,
                                             TREE_OPERAND (varop, 0),
                                             arg1));
              if (integer_zerop (folded_compare)
                  || integer_onep (folded_compare))
                return omit_one_operand (type, folded_compare, varop);

              shift = build_int_2 (TYPE_PRECISION (TREE_TYPE (varop)) - size,
                                   0);
              newconst = fold (build2 (LSHIFT_EXPR, TREE_TYPE (varop),
                                       newconst, shift));
              newconst = fold (build2 (RSHIFT_EXPR, TREE_TYPE (varop),
                                       newconst, shift));
            }

          return fold (build2 (code, type, varop, newconst));
        }

      /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
         This transformation affects the cases which are handled in later
         optimizations involving comparisons with non-negative constants.  */
      if (TREE_CODE (arg1) == INTEGER_CST
          && TREE_CODE (arg0) != INTEGER_CST
          && tree_int_cst_sgn (arg1) > 0)
        {
          switch (code)
            {
            case GE_EXPR:
              arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
              return fold (build2 (GT_EXPR, type, arg0, arg1));

            case LT_EXPR:
              arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
              return fold (build2 (LE_EXPR, type, arg0, arg1));

            default:
              break;
            }
        }

      /* Comparisons with the highest or lowest possible integer of
         the specified size will have known values. 

         This is quite similar to fold_relational_hi_lo; however, my
         attempts to share the code have been nothing but trouble.
         I give up for now.  */
      {
        int width = GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (arg1)));

        if (TREE_CODE (arg1) == INTEGER_CST
            && ! TREE_CONSTANT_OVERFLOW (arg1)
            && width <= HOST_BITS_PER_WIDE_INT
            && (INTEGRAL_TYPE_P (TREE_TYPE (arg1))
                || POINTER_TYPE_P (TREE_TYPE (arg1))))
          {
            unsigned HOST_WIDE_INT signed_max;
            unsigned HOST_WIDE_INT max, min;

            signed_max = ((unsigned HOST_WIDE_INT) 1 << (width - 1)) - 1;

            if (TYPE_UNSIGNED (TREE_TYPE (arg1)))
              {
                max = ((unsigned HOST_WIDE_INT) 2 << (width - 1)) - 1;
                min = 0;
              }
            else
              {
                max = signed_max;
                min = ((unsigned HOST_WIDE_INT) -1 << (width - 1));
              }

            if (TREE_INT_CST_HIGH (arg1) == 0
                && TREE_INT_CST_LOW (arg1) == max)
              switch (code)
                {
                case GT_EXPR:
                  return omit_one_operand (type,
                                           fold_convert (type,
                                                         integer_zero_node),
                                           arg0);
                case GE_EXPR:
                  return fold (build2 (EQ_EXPR, type, arg0, arg1));

                case LE_EXPR:
                  return omit_one_operand (type,
                                           fold_convert (type,
                                                         integer_one_node),
                                           arg0);
                case LT_EXPR:
                  return fold (build2 (NE_EXPR, type, arg0, arg1));

                /* The GE_EXPR and LT_EXPR cases above are not normally
                   reached because of previous transformations.  */

                default:
                  break;
                }
            else if (TREE_INT_CST_HIGH (arg1) == 0
                     && TREE_INT_CST_LOW (arg1) == max - 1)
              switch (code)
                {
                case GT_EXPR:
                  arg1 = const_binop (PLUS_EXPR, arg1, integer_one_node, 0);
                  return fold (build2 (EQ_EXPR, type, arg0, arg1));
                case LE_EXPR:
                  arg1 = const_binop (PLUS_EXPR, arg1, integer_one_node, 0);
                  return fold (build2 (NE_EXPR, type, arg0, arg1));
                default:
                  break;
                }
            else if (TREE_INT_CST_HIGH (arg1) == (min ? -1 : 0)
                     && TREE_INT_CST_LOW (arg1) == min)
              switch (code)
                {
                case LT_EXPR:
                  return omit_one_operand (type,
                                           fold_convert (type,
                                                         integer_zero_node),
                                           arg0);
                case LE_EXPR:
                  return fold (build2 (EQ_EXPR, type, arg0, arg1));

                case GE_EXPR:
                  return omit_one_operand (type,
                                           fold_convert (type,
                                                         integer_one_node),
                                           arg0);
                case GT_EXPR:
                  return fold (build2 (NE_EXPR, type, arg0, arg1));

                default:
                  break;
                }
            else if (TREE_INT_CST_HIGH (arg1) == (min ? -1 : 0)
                     && TREE_INT_CST_LOW (arg1) == min + 1)
              switch (code)
                {
                case GE_EXPR:
                  arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
                  return fold (build2 (NE_EXPR, type, arg0, arg1));
                case LT_EXPR:
                  arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
                  return fold (build2 (EQ_EXPR, type, arg0, arg1));
                default:
                  break;
                }

            else if (!in_gimple_form
                     && TREE_INT_CST_HIGH (arg1) == 0
                     && TREE_INT_CST_LOW (arg1) == signed_max
                     && TYPE_UNSIGNED (TREE_TYPE (arg1))
                     /* signed_type does not work on pointer types.  */
                     && INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
              {
                /* The following case also applies to X < signed_max+1
                   and X >= signed_max+1 because previous transformations.  */
                if (code == LE_EXPR || code == GT_EXPR)
                  {
                    tree st0, st1;
                    st0 = lang_hooks.types.signed_type (TREE_TYPE (arg0));
                    st1 = lang_hooks.types.signed_type (TREE_TYPE (arg1));
                    return fold
                      (build2 (code == LE_EXPR ? GE_EXPR: LT_EXPR,
                               type, fold_convert (st0, arg0),
                               fold_convert (st1, integer_zero_node)));
                  }
              }
          }
      }

      /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
         a MINUS_EXPR of a constant, we can convert it into a comparison with
         a revised constant as long as no overflow occurs.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg1) == INTEGER_CST
          && (TREE_CODE (arg0) == PLUS_EXPR
              || TREE_CODE (arg0) == MINUS_EXPR)
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
          && 0 != (tem = const_binop (TREE_CODE (arg0) == PLUS_EXPR
                                      ? MINUS_EXPR : PLUS_EXPR,
                                      arg1, TREE_OPERAND (arg0, 1), 0))
          && ! TREE_CONSTANT_OVERFLOW (tem))
        return fold (build2 (code, type, TREE_OPERAND (arg0, 0), tem));

      /* Similarly for a NEGATE_EXPR.  */
      else if ((code == EQ_EXPR || code == NE_EXPR)
               && TREE_CODE (arg0) == NEGATE_EXPR
               && TREE_CODE (arg1) == INTEGER_CST
               && 0 != (tem = negate_expr (arg1))
               && TREE_CODE (tem) == INTEGER_CST
               && ! TREE_CONSTANT_OVERFLOW (tem))
        return fold (build2 (code, type, TREE_OPERAND (arg0, 0), tem));

      /* If we have X - Y == 0, we can convert that to X == Y and similarly
         for !=.  Don't do this for ordered comparisons due to overflow.  */
      else if ((code == NE_EXPR || code == EQ_EXPR)
               && integer_zerop (arg1) && TREE_CODE (arg0) == MINUS_EXPR)
        return fold (build2 (code, type,
                             TREE_OPERAND (arg0, 0), TREE_OPERAND (arg0, 1)));

      /* If we are widening one operand of an integer comparison,
         see if the other operand is similarly being widened.  Perhaps we
         can do the comparison in the narrower type.  */
      else if (TREE_CODE (TREE_TYPE (arg0)) == INTEGER_TYPE
               && TREE_CODE (arg0) == NOP_EXPR
               && (tem = get_unwidened (arg0, NULL_TREE)) != arg0
               && (code == EQ_EXPR || code == NE_EXPR
                   || TYPE_UNSIGNED (TREE_TYPE (arg0))
                      == TYPE_UNSIGNED (TREE_TYPE (tem)))
               && (t1 = get_unwidened (arg1, TREE_TYPE (tem))) != 0
               && (TREE_TYPE (t1) == TREE_TYPE (tem)
                   || (TREE_CODE (t1) == INTEGER_CST
                       && int_fits_type_p (t1, TREE_TYPE (tem)))))
        return fold (build2 (code, type, tem,
                             fold_convert (TREE_TYPE (tem), t1)));

      /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
         constant, we can simplify it.  */
      else if (TREE_CODE (arg1) == INTEGER_CST
               && (TREE_CODE (arg0) == MIN_EXPR
                   || TREE_CODE (arg0) == MAX_EXPR)
               && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
        return optimize_minmax_comparison (t);

      /* If we are comparing an ABS_EXPR with a constant, we can
         convert all the cases into explicit comparisons, but they may
         well not be faster than doing the ABS and one comparison.
         But ABS (X) <= C is a range comparison, which becomes a subtraction
         and a comparison, and is probably faster.  */
      else if (code == LE_EXPR && TREE_CODE (arg1) == INTEGER_CST
               && TREE_CODE (arg0) == ABS_EXPR
               && ! TREE_SIDE_EFFECTS (arg0)
               && (0 != (tem = negate_expr (arg1)))
               && TREE_CODE (tem) == INTEGER_CST
               && ! TREE_CONSTANT_OVERFLOW (tem))
        return fold (build2 (TRUTH_ANDIF_EXPR, type,
                             build2 (GE_EXPR, type,
                                     TREE_OPERAND (arg0, 0), tem),
                             build2 (LE_EXPR, type,
                                     TREE_OPERAND (arg0, 0), arg1)));

      /* If this is an EQ or NE comparison with zero and ARG0 is
         (1 << foo) & bar, convert it to (bar >> foo) & 1.  Both require
         two operations, but the latter can be done in one less insn
         on machines that have only two-operand insns or on which a
         constant cannot be the first operand.  */
      if (integer_zerop (arg1) && (code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == BIT_AND_EXPR)
        {
          tree arg00 = TREE_OPERAND (arg0, 0);
          tree arg01 = TREE_OPERAND (arg0, 1);
          if (TREE_CODE (arg00) == LSHIFT_EXPR
              && integer_onep (TREE_OPERAND (arg00, 0)))
            return
              fold (build2 (code, type,
                            build2 (BIT_AND_EXPR, TREE_TYPE (arg0),
                                    build2 (RSHIFT_EXPR, TREE_TYPE (arg00),
                                            arg01, TREE_OPERAND (arg00, 1)),
                                    fold_convert (TREE_TYPE (arg0),
                                                  integer_one_node)),
                            arg1));
          else if (TREE_CODE (TREE_OPERAND (arg0, 1)) == LSHIFT_EXPR
                   && integer_onep (TREE_OPERAND (TREE_OPERAND (arg0, 1), 0)))
            return
              fold (build2 (code, type,
                            build2 (BIT_AND_EXPR, TREE_TYPE (arg0),
                                    build2 (RSHIFT_EXPR, TREE_TYPE (arg01),
                                            arg00, TREE_OPERAND (arg01, 1)),
                                    fold_convert (TREE_TYPE (arg0),
                                                  integer_one_node)),
                            arg1));
        }

      /* If this is an NE or EQ comparison of zero against the result of a
         signed MOD operation whose second operand is a power of 2, make
         the MOD operation unsigned since it is simpler and equivalent.  */
      if ((code == NE_EXPR || code == EQ_EXPR)
          && integer_zerop (arg1)
          && !TYPE_UNSIGNED (TREE_TYPE (arg0))
          && (TREE_CODE (arg0) == TRUNC_MOD_EXPR
              || TREE_CODE (arg0) == CEIL_MOD_EXPR
              || TREE_CODE (arg0) == FLOOR_MOD_EXPR
              || TREE_CODE (arg0) == ROUND_MOD_EXPR)
          && integer_pow2p (TREE_OPERAND (arg0, 1)))
        {
          tree newtype = lang_hooks.types.unsigned_type (TREE_TYPE (arg0));
          tree newmod = build2 (TREE_CODE (arg0), newtype,
                                fold_convert (newtype,
                                              TREE_OPERAND (arg0, 0)),
                                fold_convert (newtype,
                                              TREE_OPERAND (arg0, 1)));

          return build2 (code, type, newmod, fold_convert (newtype, arg1));
        }

      /* If this is an NE comparison of zero with an AND of one, remove the
         comparison since the AND will give the correct value.  */
      if (code == NE_EXPR && integer_zerop (arg1)
          && TREE_CODE (arg0) == BIT_AND_EXPR
          && integer_onep (TREE_OPERAND (arg0, 1)))
        return fold_convert (type, arg0);

      /* If we have (A & C) == C where C is a power of 2, convert this into
         (A & C) != 0.  Similarly for NE_EXPR.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == BIT_AND_EXPR
          && integer_pow2p (TREE_OPERAND (arg0, 1))
          && operand_equal_p (TREE_OPERAND (arg0, 1), arg1, 0))
        return fold (build2 (code == EQ_EXPR ? NE_EXPR : EQ_EXPR, type,
                             arg0, integer_zero_node));

      /* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
         2, then fold the expression into shifts and logical operations.  */
      tem = fold_single_bit_test (code, arg0, arg1, type);
      if (tem)
        return tem;

      /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
         Similarly for NE_EXPR.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == BIT_AND_EXPR
          && TREE_CODE (arg1) == INTEGER_CST
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
        {
          tree dandnotc
            = fold (build2 (BIT_AND_EXPR, TREE_TYPE (arg0),
                            arg1, build1 (BIT_NOT_EXPR,
                                          TREE_TYPE (TREE_OPERAND (arg0, 1)),
                                          TREE_OPERAND (arg0, 1))));
          tree rslt = code == EQ_EXPR ? integer_zero_node : integer_one_node;
          if (integer_nonzerop (dandnotc))
            return omit_one_operand (type, rslt, arg0);
        }

      /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
         Similarly for NE_EXPR.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (arg0) == BIT_IOR_EXPR
          && TREE_CODE (arg1) == INTEGER_CST
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
        {
          tree candnotd
            = fold (build2 (BIT_AND_EXPR, TREE_TYPE (arg0),
                            TREE_OPERAND (arg0, 1),
                            build1 (BIT_NOT_EXPR, TREE_TYPE (arg1), arg1)));
          tree rslt = code == EQ_EXPR ? integer_zero_node : integer_one_node;
          if (integer_nonzerop (candnotd))
            return omit_one_operand (type, rslt, arg0);
        }

      /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
         and similarly for >= into !=.  */
      if ((code == LT_EXPR || code == GE_EXPR)
          && TYPE_UNSIGNED (TREE_TYPE (arg0))
          && TREE_CODE (arg1) == LSHIFT_EXPR
          && integer_onep (TREE_OPERAND (arg1, 0)))
        return build2 (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
                       build2 (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
                               TREE_OPERAND (arg1, 1)),
                       fold_convert (TREE_TYPE (arg0), integer_zero_node));

      else if ((code == LT_EXPR || code == GE_EXPR)
               && TYPE_UNSIGNED (TREE_TYPE (arg0))
               && (TREE_CODE (arg1) == NOP_EXPR
                   || TREE_CODE (arg1) == CONVERT_EXPR)
               && TREE_CODE (TREE_OPERAND (arg1, 0)) == LSHIFT_EXPR
               && integer_onep (TREE_OPERAND (TREE_OPERAND (arg1, 0), 0)))
        return
          build2 (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
                  fold_convert (TREE_TYPE (arg0),
                                build2 (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
                                        TREE_OPERAND (TREE_OPERAND (arg1, 0),
                                                      1))),
                  fold_convert (TREE_TYPE (arg0), integer_zero_node));

      /* Simplify comparison of something with itself.  (For IEEE
         floating-point, we can only do some of these simplifications.)  */
      if (operand_equal_p (arg0, arg1, 0))
        {
          switch (code)
            {
            case EQ_EXPR:
              if (! FLOAT_TYPE_P (TREE_TYPE (arg0))
                  || ! HONOR_NANS (TYPE_MODE (TREE_TYPE (arg0))))
                return constant_boolean_node (1, type);
              break;

            case GE_EXPR:
            case LE_EXPR:
              if (! FLOAT_TYPE_P (TREE_TYPE (arg0))
                  || ! HONOR_NANS (TYPE_MODE (TREE_TYPE (arg0))))
                return constant_boolean_node (1, type);
              return fold (build2 (EQ_EXPR, type, arg0, arg1));

            case NE_EXPR:
              /* For NE, we can only do this simplification if integer
                 or we don't honor IEEE floating point NaNs.  */
              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
                  && HONOR_NANS (TYPE_MODE (TREE_TYPE (arg0))))
                break;
              /* ... fall through ...  */
            case GT_EXPR:
            case LT_EXPR:
              return constant_boolean_node (0, type);
            default:
              abort ();
            }
        }

      /* If we are comparing an expression that just has comparisons
         of two integer values, arithmetic expressions of those comparisons,
         and constants, we can simplify it.  There are only three cases
         to check: the two values can either be equal, the first can be
         greater, or the second can be greater.  Fold the expression for
         those three values.  Since each value must be 0 or 1, we have
         eight possibilities, each of which corresponds to the constant 0
         or 1 or one of the six possible comparisons.

         This handles common cases like (a > b) == 0 but also handles
         expressions like  ((x > y) - (y > x)) > 0, which supposedly
         occur in macroized code.  */

      if (TREE_CODE (arg1) == INTEGER_CST && TREE_CODE (arg0) != INTEGER_CST)
        {
          tree cval1 = 0, cval2 = 0;
          int save_p = 0;

          if (twoval_comparison_p (arg0, &cval1, &cval2, &save_p)
              /* Don't handle degenerate cases here; they should already
                 have been handled anyway.  */
              && cval1 != 0 && cval2 != 0
              && ! (TREE_CONSTANT (cval1) && TREE_CONSTANT (cval2))
              && TREE_TYPE (cval1) == TREE_TYPE (cval2)
              && INTEGRAL_TYPE_P (TREE_TYPE (cval1))
              && TYPE_MAX_VALUE (TREE_TYPE (cval1))
              && TYPE_MAX_VALUE (TREE_TYPE (cval2))
              && ! operand_equal_p (TYPE_MIN_VALUE (TREE_TYPE (cval1)),
                                    TYPE_MAX_VALUE (TREE_TYPE (cval2)), 0))
            {
              tree maxval = TYPE_MAX_VALUE (TREE_TYPE (cval1));
              tree minval = TYPE_MIN_VALUE (TREE_TYPE (cval1));

              /* We can't just pass T to eval_subst in case cval1 or cval2
                 was the same as ARG1.  */

              tree high_result
                = fold (build2 (code, type,
                                eval_subst (arg0, cval1, maxval,
                                            cval2, minval),
                                arg1));
              tree equal_result
                = fold (build2 (code, type,
                                eval_subst (arg0, cval1, maxval,
                                            cval2, maxval),
                                arg1));
              tree low_result
                = fold (build2 (code, type,
                                eval_subst (arg0, cval1, minval,
                                            cval2, maxval),
                                arg1));

              /* All three of these results should be 0 or 1.  Confirm they
                 are.  Then use those values to select the proper code
                 to use.  */

              if ((integer_zerop (high_result)
                   || integer_onep (high_result))
                  && (integer_zerop (equal_result)
                      || integer_onep (equal_result))
                  && (integer_zerop (low_result)
                      || integer_onep (low_result)))
                {
                  /* Make a 3-bit mask with the high-order bit being the
                     value for `>', the next for '=', and the low for '<'.  */
                  switch ((integer_onep (high_result) * 4)
                          + (integer_onep (equal_result) * 2)
                          + integer_onep (low_result))
                    {
                    case 0:
                      /* Always false.  */
                      return omit_one_operand (type, integer_zero_node, arg0);
                    case 1:
                      code = LT_EXPR;
                      break;
                    case 2:
                      code = EQ_EXPR;
                      break;
                    case 3:
                      code = LE_EXPR;
                      break;
                    case 4:
                      code = GT_EXPR;
                      break;
                    case 5:
                      code = NE_EXPR;
                      break;
                    case 6:
                      code = GE_EXPR;
                      break;
                    case 7:
                      /* Always true.  */
                      return omit_one_operand (type, integer_one_node, arg0);
                    }

                  tem = build2 (code, type, cval1, cval2);
                  if (save_p)
                    return save_expr (tem);
                  else
                    return fold (tem);
                }
            }
        }

      /* If this is a comparison of a field, we may be able to simplify it.  */
      if (((TREE_CODE (arg0) == COMPONENT_REF
            && lang_hooks.can_use_bit_fields_p ())
           || TREE_CODE (arg0) == BIT_FIELD_REF)
          && (code == EQ_EXPR || code == NE_EXPR)
          /* Handle the constant case even without -O
             to make sure the warnings are given.  */
          && (optimize || TREE_CODE (arg1) == INTEGER_CST))
        {
          t1 = optimize_bit_field_compare (code, type, arg0, arg1);
          if (t1)
            return t1;
        }

      /* If this is a comparison of complex values and either or both sides
         are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
         comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
         This may prevent needless evaluations.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
          && (TREE_CODE (arg0) == COMPLEX_EXPR
              || TREE_CODE (arg1) == COMPLEX_EXPR
              || TREE_CODE (arg0) == COMPLEX_CST
              || TREE_CODE (arg1) == COMPLEX_CST))
        {
          tree subtype = TREE_TYPE (TREE_TYPE (arg0));
          tree real0, imag0, real1, imag1;

          arg0 = save_expr (arg0);
          arg1 = save_expr (arg1);
          real0 = fold (build1 (REALPART_EXPR, subtype, arg0));
          imag0 = fold (build1 (IMAGPART_EXPR, subtype, arg0));
          real1 = fold (build1 (REALPART_EXPR, subtype, arg1));
          imag1 = fold (build1 (IMAGPART_EXPR, subtype, arg1));

          return fold (build2 ((code == EQ_EXPR ? TRUTH_ANDIF_EXPR
                                : TRUTH_ORIF_EXPR),
                               type,
                               fold (build2 (code, type, real0, real1)),
                               fold (build2 (code, type, imag0, imag1))));
        }

      /* Optimize comparisons of strlen vs zero to a compare of the
         first character of the string vs zero.  To wit,
                strlen(ptr) == 0   =>  *ptr == 0
                strlen(ptr) != 0   =>  *ptr != 0
         Other cases should reduce to one of these two (or a constant)
         due to the return value of strlen being unsigned.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
          && integer_zerop (arg1)
          && TREE_CODE (arg0) == CALL_EXPR)
        {
          tree fndecl = get_callee_fndecl (arg0);
          tree arglist;

          if (fndecl
              && DECL_BUILT_IN (fndecl)
              && DECL_BUILT_IN_CLASS (fndecl) != BUILT_IN_MD
              && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_STRLEN
              && (arglist = TREE_OPERAND (arg0, 1))
              && TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) == POINTER_TYPE
              && ! TREE_CHAIN (arglist))
            return fold (build2 (code, type,
                                 build1 (INDIRECT_REF, char_type_node,
                                         TREE_VALUE(arglist)),
                                 integer_zero_node));
        }

      /* We can fold X/C1 op C2 where C1 and C2 are integer constants
         into a single range test.  */
      if (TREE_CODE (arg0) == TRUNC_DIV_EXPR
          && TREE_CODE (arg1) == INTEGER_CST
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
          && !integer_zerop (TREE_OPERAND (arg0, 1))
          && !TREE_OVERFLOW (TREE_OPERAND (arg0, 1))
          && !TREE_OVERFLOW (arg1))
        {
          t1 = fold_div_compare (code, type, arg0, arg1);
          if (t1 != NULL_TREE)
            return t1;
        }

      /* Both ARG0 and ARG1 are known to be constants at this point.  */
      t1 = fold_relational_const (code, type, arg0, arg1);
      return (t1 == NULL_TREE ? t : t1);

    case COND_EXPR:
      /* Pedantic ANSI C says that a conditional expression is never an lvalue,
         so all simple results must be passed through pedantic_non_lvalue.  */
      if (TREE_CODE (arg0) == INTEGER_CST)
        {
          tem = TREE_OPERAND (t, (integer_zerop (arg0) ? 2 : 1));
          /* Only optimize constant conditions when the selected branch
             has the same type as the COND_EXPR.  This avoids optimizing
             away "c ? x : throw", where the throw has a void type.  */
          if (! VOID_TYPE_P (TREE_TYPE (tem))
              || VOID_TYPE_P (type))
            return pedantic_non_lvalue (tem);
          return t;
        }
      if (operand_equal_p (arg1, TREE_OPERAND (t, 2), 0))
        return pedantic_omit_one_operand (type, arg1, arg0);

      /* If we have A op B ? A : C, we may be able to convert this to a
         simpler expression, depending on the operation and the values
         of B and C.  Signed zeros prevent all of these transformations,
         for reasons given above each one.  */

      if (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<'
          && operand_equal_for_comparison_p (TREE_OPERAND (arg0, 0),
                                             arg1, TREE_OPERAND (arg0, 1))
          && !HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
        {
          tree arg2 = TREE_OPERAND (t, 2);
          enum tree_code comp_code = TREE_CODE (arg0);

          STRIP_NOPS (arg2);

          /* If we have A op 0 ? A : -A, consider applying the following
             transformations:

             A == 0? A : -A    same as -A
             A != 0? A : -A    same as A
             A >= 0? A : -A    same as abs (A)
             A > 0?  A : -A    same as abs (A)
             A <= 0? A : -A    same as -abs (A)
             A < 0?  A : -A    same as -abs (A)

             None of these transformations work for modes with signed
             zeros.  If A is +/-0, the first two transformations will
             change the sign of the result (from +0 to -0, or vice
             versa).  The last four will fix the sign of the result,
             even though the original expressions could be positive or
             negative, depending on the sign of A.

             Note that all these transformations are correct if A is
             NaN, since the two alternatives (A and -A) are also NaNs.  */
          if ((FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 1)))
               ? real_zerop (TREE_OPERAND (arg0, 1))
               : integer_zerop (TREE_OPERAND (arg0, 1)))
              && TREE_CODE (arg2) == NEGATE_EXPR
              && operand_equal_p (TREE_OPERAND (arg2, 0), arg1, 0))
            switch (comp_code)
              {
              case EQ_EXPR:
                tem = fold_convert (TREE_TYPE (TREE_OPERAND (t, 1)), arg1);
                tem = fold_convert (type, negate_expr (tem));
                return pedantic_non_lvalue (tem);
              case NE_EXPR:
                return pedantic_non_lvalue (fold_convert (type, arg1));
              case GE_EXPR:
              case GT_EXPR:
                if (TYPE_UNSIGNED (TREE_TYPE (arg1)))
                  arg1 = fold_convert (lang_hooks.types.signed_type
                                       (TREE_TYPE (arg1)), arg1);
                arg1 = fold (build1 (ABS_EXPR, TREE_TYPE (arg1), arg1));
                return pedantic_non_lvalue (fold_convert (type, arg1));
              case LE_EXPR:
              case LT_EXPR:
                if (TYPE_UNSIGNED (TREE_TYPE (arg1)))
                  arg1 = fold_convert (lang_hooks.types.signed_type
                                       (TREE_TYPE (arg1)), arg1);
                arg1 = fold (build1 (ABS_EXPR, TREE_TYPE (arg1), arg1));
                arg1 = negate_expr (fold_convert (type, arg1));
                return pedantic_non_lvalue (arg1);
              default:
                abort ();
              }

          /* A != 0 ? A : 0 is simply A, unless A is -0.  Likewise
             A == 0 ? A : 0 is always 0 unless A is -0.  Note that
             both transformations are correct when A is NaN: A != 0
             is then true, and A == 0 is false.  */

          if (integer_zerop (TREE_OPERAND (arg0, 1)) && integer_zerop (arg2))
            {
              if (comp_code == NE_EXPR)
                return pedantic_non_lvalue (fold_convert (type, arg1));
              else if (comp_code == EQ_EXPR)
                return pedantic_non_lvalue (fold_convert (type, integer_zero_node));
            }

          /* Try some transformations of A op B ? A : B.

             A == B? A : B    same as B
             A != B? A : B    same as A
             A >= B? A : B    same as max (A, B)
             A > B?  A : B    same as max (B, A)
             A <= B? A : B    same as min (A, B)
             A < B?  A : B    same as min (B, A)

             As above, these transformations don't work in the presence
             of signed zeros.  For example, if A and B are zeros of
             opposite sign, the first two transformations will change
             the sign of the result.  In the last four, the original
             expressions give different results for (A=+0, B=-0) and
             (A=-0, B=+0), but the transformed expressions do not.

             The first two transformations are correct if either A or B
             is a NaN.  In the first transformation, the condition will
             be false, and B will indeed be chosen.  In the case of the
             second transformation, the condition A != B will be true,
             and A will be chosen.

             The conversions to max() and min() are not correct if B is
             a number and A is not.  The conditions in the original
             expressions will be false, so all four give B.  The min()
             and max() versions would give a NaN instead.  */
          if (operand_equal_for_comparison_p (TREE_OPERAND (arg0, 1),
                                              arg2, TREE_OPERAND (arg0, 0)))
            {
              tree comp_op0 = TREE_OPERAND (arg0, 0);
              tree comp_op1 = TREE_OPERAND (arg0, 1);
              tree comp_type = TREE_TYPE (comp_op0);

              /* Avoid adding NOP_EXPRs in case this is an lvalue.  */
              if (TYPE_MAIN_VARIANT (comp_type) == TYPE_MAIN_VARIANT (type))
                {
                  comp_type = type;
                  comp_op0 = arg1;
                  comp_op1 = arg2;
                }

              switch (comp_code)
                {
                case EQ_EXPR:
                  return pedantic_non_lvalue (fold_convert (type, arg2));
                case NE_EXPR:
                  return pedantic_non_lvalue (fold_convert (type, arg1));
                case LE_EXPR:
                case LT_EXPR:
                  /* In C++ a ?: expression can be an lvalue, so put the
                     operand which will be used if they are equal first
                     so that we can convert this back to the
                     corresponding COND_EXPR.  */
                  if (!HONOR_NANS (TYPE_MODE (TREE_TYPE (arg1))))
                    return pedantic_non_lvalue (fold_convert
                      (type, fold (build2 (MIN_EXPR, comp_type,
                                           (comp_code == LE_EXPR
                                            ? comp_op0 : comp_op1),
                                           (comp_code == LE_EXPR
                                            ? comp_op1 : comp_op0)))));
                  break;
                case GE_EXPR:
                case GT_EXPR:
                  if (!HONOR_NANS (TYPE_MODE (TREE_TYPE (arg1))))
                    return pedantic_non_lvalue (fold_convert
                      (type, fold (build2 (MAX_EXPR, comp_type,
                                           (comp_code == GE_EXPR
                                            ? comp_op0 : comp_op1),
                                           (comp_code == GE_EXPR
                                            ? comp_op1 : comp_op0)))));
                  break;
                default:
                  abort ();
                }
            }

          /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
             we might still be able to simplify this.  For example,
             if C1 is one less or one more than C2, this might have started
             out as a MIN or MAX and been transformed by this function.
             Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE.  */

          if (INTEGRAL_TYPE_P (type)
              && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
              && TREE_CODE (arg2) == INTEGER_CST)
            switch (comp_code)
              {
              case EQ_EXPR:
                /* We can replace A with C1 in this case.  */
                arg1 = fold_convert (type, TREE_OPERAND (arg0, 1));
                return fold (build3 (code, type, TREE_OPERAND (t, 0), arg1,
                                     TREE_OPERAND (t, 2)));

              case LT_EXPR:
                /* If C1 is C2 + 1, this is min(A, C2).  */
                if (! operand_equal_p (arg2, TYPE_MAX_VALUE (type),
                                       OEP_ONLY_CONST)
                    && operand_equal_p (TREE_OPERAND (arg0, 1),
                                        const_binop (PLUS_EXPR, arg2,
                                                     integer_one_node, 0),
                                        OEP_ONLY_CONST))
                  return pedantic_non_lvalue
                    (fold (build2 (MIN_EXPR, type, arg1, arg2)));
                break;

              case LE_EXPR:
                /* If C1 is C2 - 1, this is min(A, C2).  */
                if (! operand_equal_p (arg2, TYPE_MIN_VALUE (type),
                                       OEP_ONLY_CONST)
                    && operand_equal_p (TREE_OPERAND (arg0, 1),
                                        const_binop (MINUS_EXPR, arg2,
                                                     integer_one_node, 0),
                                        OEP_ONLY_CONST))
                  return pedantic_non_lvalue
                    (fold (build2 (MIN_EXPR, type, arg1, arg2)));
                break;

              case GT_EXPR:
                /* If C1 is C2 - 1, this is max(A, C2).  */
                if (! operand_equal_p (arg2, TYPE_MIN_VALUE (type),
                                       OEP_ONLY_CONST)
                    && operand_equal_p (TREE_OPERAND (arg0, 1),
                                        const_binop (MINUS_EXPR, arg2,
                                                     integer_one_node, 0),
                                        OEP_ONLY_CONST))
                  return pedantic_non_lvalue
                    (fold (build2 (MAX_EXPR, type, arg1, arg2)));
                break;

              case GE_EXPR:
                /* If C1 is C2 + 1, this is max(A, C2).  */
                if (! operand_equal_p (arg2, TYPE_MAX_VALUE (type),
                                       OEP_ONLY_CONST)
                    && operand_equal_p (TREE_OPERAND (arg0, 1),
                                        const_binop (PLUS_EXPR, arg2,
                                                     integer_one_node, 0),
                                        OEP_ONLY_CONST))
                  return pedantic_non_lvalue
                    (fold (build2 (MAX_EXPR, type, arg1, arg2)));
                break;
              case NE_EXPR:
                break;
              default:
                abort ();
              }
        }

      /* If the second operand is simpler than the third, swap them
         since that produces better jump optimization results.  */
      if (tree_swap_operands_p (TREE_OPERAND (t, 1),
                                TREE_OPERAND (t, 2), false))
        {
          /* See if this can be inverted.  If it can't, possibly because
             it was a floating-point inequality comparison, don't do
             anything.  */
          tem = invert_truthvalue (arg0);

          if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
            return fold (build3 (code, type, tem,
                                 TREE_OPERAND (t, 2), TREE_OPERAND (t, 1)));
        }

      /* Convert A ? 1 : 0 to simply A.  */
      if (integer_onep (TREE_OPERAND (t, 1))
          && integer_zerop (TREE_OPERAND (t, 2))
          /* If we try to convert TREE_OPERAND (t, 0) to our type, the
             call to fold will try to move the conversion inside
             a COND, which will recurse.  In that case, the COND_EXPR
             is probably the best choice, so leave it alone.  */
          && type == TREE_TYPE (arg0))
        return pedantic_non_lvalue (arg0);

      /* Convert A ? 0 : 1 to !A.  This prefers the use of NOT_EXPR
         over COND_EXPR in cases such as floating point comparisons.  */
      if (integer_zerop (TREE_OPERAND (t, 1))
          && integer_onep (TREE_OPERAND (t, 2))
          && truth_value_p (TREE_CODE (arg0)))
        return pedantic_non_lvalue (fold_convert (type,
                                                  invert_truthvalue (arg0)));

      /* Look for expressions of the form A & 2 ? 2 : 0.  The result of this
         operation is simply A & 2.  */

      if (integer_zerop (TREE_OPERAND (t, 2))
          && TREE_CODE (arg0) == NE_EXPR
          && integer_zerop (TREE_OPERAND (arg0, 1))
          && integer_pow2p (arg1)
          && TREE_CODE (TREE_OPERAND (arg0, 0)) == BIT_AND_EXPR
          && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1),
                              arg1, OEP_ONLY_CONST))
        return pedantic_non_lvalue (fold_convert (type,
                                                  TREE_OPERAND (arg0, 0)));

      /* Convert A ? B : 0 into A && B if A and B are truth values.  */
      if (integer_zerop (TREE_OPERAND (t, 2))
          && truth_value_p (TREE_CODE (arg0))
          && truth_value_p (TREE_CODE (arg1)))
        return pedantic_non_lvalue (fold (build2 (TRUTH_ANDIF_EXPR, type,
                                                  arg0, arg1)));

      /* Convert A ? B : 1 into !A || B if A and B are truth values.  */
      if (integer_onep (TREE_OPERAND (t, 2))
          && truth_value_p (TREE_CODE (arg0))
          && truth_value_p (TREE_CODE (arg1)))
        {
          /* Only perform transformation if ARG0 is easily inverted.  */
          tem = invert_truthvalue (arg0);
          if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
            return pedantic_non_lvalue (fold (build2 (TRUTH_ORIF_EXPR, type,
                                                      tem, arg1)));
        }

      return t;

    case COMPOUND_EXPR:
      /* When pedantic, a compound expression can be neither an lvalue
         nor an integer constant expression.  */
      if (TREE_SIDE_EFFECTS (arg0) || TREE_CONSTANT (arg1))
        return t;
      /* Don't let (0, 0) be null pointer constant.  */
      tem = integer_zerop (arg1) ? build1 (NOP_EXPR, type, arg1)
                                 : fold_convert (type, arg1);
      return pedantic_non_lvalue (tem);

    case COMPLEX_EXPR:
      if (wins)
        return build_complex (type, arg0, arg1);
      return t;

    case REALPART_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
        return t;
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
        return omit_one_operand (type, TREE_OPERAND (arg0, 0),
                                 TREE_OPERAND (arg0, 1));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
        return TREE_REALPART (arg0);
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
        return fold (build2 (TREE_CODE (arg0), type,
                             fold (build1 (REALPART_EXPR, type,
                                           TREE_OPERAND (arg0, 0))),
                             fold (build1 (REALPART_EXPR, type,
                                           TREE_OPERAND (arg0, 1)))));
      return t;

    case IMAGPART_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
        return fold_convert (type, integer_zero_node);
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
        return omit_one_operand (type, TREE_OPERAND (arg0, 1),
                                 TREE_OPERAND (arg0, 0));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
        return TREE_IMAGPART (arg0);
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
        return fold (build2 (TREE_CODE (arg0), type,
                             fold (build1 (IMAGPART_EXPR, type,
                                           TREE_OPERAND (arg0, 0))),
                             fold (build1 (IMAGPART_EXPR, type,
                                           TREE_OPERAND (arg0, 1)))));
      return t;

      /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
         appropriate.  */
    case CLEANUP_POINT_EXPR:
      if (! has_cleanups (arg0))
        return TREE_OPERAND (t, 0);

      {
        enum tree_code code0 = TREE_CODE (arg0);
        int kind0 = TREE_CODE_CLASS (code0);
        tree arg00 = TREE_OPERAND (arg0, 0);
        tree arg01;

        if (kind0 == '1' || code0 == TRUTH_NOT_EXPR)
          return fold (build1 (code0, type,
                               fold (build1 (CLEANUP_POINT_EXPR,
                                             TREE_TYPE (arg00), arg00))));

        if (kind0 == '<' || kind0 == '2'
            || code0 == TRUTH_ANDIF_EXPR || code0 == TRUTH_ORIF_EXPR
            || code0 == TRUTH_AND_EXPR   || code0 == TRUTH_OR_EXPR
            || code0 == TRUTH_XOR_EXPR)
          {
            arg01 = TREE_OPERAND (arg0, 1);

            if (TREE_CONSTANT (arg00)
                || ((code0 == TRUTH_ANDIF_EXPR || code0 == TRUTH_ORIF_EXPR)
                    && ! has_cleanups (arg00)))
              return fold (build2 (code0, type, arg00,
                                   fold (build1 (CLEANUP_POINT_EXPR,
                                                 TREE_TYPE (arg01), arg01))));

            if (TREE_CONSTANT (arg01))
              return fold (build2 (code0, type,
                                   fold (build1 (CLEANUP_POINT_EXPR,
                                                 TREE_TYPE (arg00), arg00)),
                                   arg01));
          }

        return t;
      }

    case CALL_EXPR:
      /* Check for a built-in function.  */
      if (TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR
          && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (t, 0), 0))
              == FUNCTION_DECL)
          && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (t, 0), 0)))
        {
          tree tmp = fold_builtin (t);
          if (tmp)
            return tmp;
        }
      return t;

    default:
      return t;
    } /* switch (code) */
}

#ifdef ENABLE_FOLD_CHECKING
#undef fold

static void fold_checksum_tree (tree, struct md5_ctx *, htab_t);
static void fold_check_failed (tree, tree);
void print_fold_checksum (tree);

/* When --enable-checking=fold, compute a digest of expr before
   and after actual fold call to see if fold did not accidentally
   change original expr.  */

tree
fold (tree expr)
{
  tree ret;
  struct md5_ctx ctx;
  unsigned char checksum_before[16], checksum_after[16];
  htab_t ht;

  ht = htab_create (32, htab_hash_pointer, htab_eq_pointer, NULL);
  md5_init_ctx (&ctx);
  fold_checksum_tree (expr, &ctx, ht);
  md5_finish_ctx (&ctx, checksum_before);
  htab_empty (ht);

  ret = fold_1 (expr);

  md5_init_ctx (&ctx);
  fold_checksum_tree (expr, &ctx, ht);
  md5_finish_ctx (&ctx, checksum_after);
  htab_delete (ht);

  if (memcmp (checksum_before, checksum_after, 16))
    fold_check_failed (expr, ret);

  return ret;
}

void
print_fold_checksum (tree expr)
{
  struct md5_ctx ctx;
  unsigned char checksum[16], cnt;
  htab_t ht;

  ht = htab_create (32, htab_hash_pointer, htab_eq_pointer, NULL);
  md5_init_ctx (&ctx);
  fold_checksum_tree (expr, &ctx, ht);
  md5_finish_ctx (&ctx, checksum);
  htab_delete (ht);
  for (cnt = 0; cnt < 16; ++cnt)
    fprintf (stderr, "%02x", checksum[cnt]);
  putc ('\n', stderr);
}

static void
fold_check_failed (tree expr ATTRIBUTE_UNUSED, tree ret ATTRIBUTE_UNUSED)
{
  internal_error ("fold check: original tree changed by fold");
}

static void
fold_checksum_tree (tree expr, struct md5_ctx *ctx, htab_t ht)
{
  void **slot;
  enum tree_code code;
  char buf[sizeof (struct tree_decl)];
  int i, len;

  if (sizeof (struct tree_exp) + 5 * sizeof (tree)
      > sizeof (struct tree_decl)
      || sizeof (struct tree_type) > sizeof (struct tree_decl))
    abort ();
  if (expr == NULL)
    return;
  slot = htab_find_slot (ht, expr, INSERT);
  if (*slot != NULL)
    return;
  *slot = expr;
  code = TREE_CODE (expr);
  if (code == SAVE_EXPR && SAVE_EXPR_NOPLACEHOLDER (expr))
    {
      /* Allow SAVE_EXPR_NOPLACEHOLDER flag to be modified.  */
      memcpy (buf, expr, tree_size (expr));
      expr = (tree) buf;
      SAVE_EXPR_NOPLACEHOLDER (expr) = 0;
    }
  else if (TREE_CODE_CLASS (code) == 'd' && DECL_ASSEMBLER_NAME_SET_P (expr))
    {
      /* Allow DECL_ASSEMBLER_NAME to be modified.  */
      memcpy (buf, expr, tree_size (expr));
      expr = (tree) buf;
      SET_DECL_ASSEMBLER_NAME (expr, NULL);
    }
  else if (TREE_CODE_CLASS (code) == 't'
           && (TYPE_POINTER_TO (expr) || TYPE_REFERENCE_TO (expr)))
    {
      /* Allow TYPE_POINTER_TO and TYPE_REFERENCE_TO to be modified.  */
      memcpy (buf, expr, tree_size (expr));
      expr = (tree) buf;
      TYPE_POINTER_TO (expr) = NULL;
      TYPE_REFERENCE_TO (expr) = NULL;
    }
  md5_process_bytes (expr, tree_size (expr), ctx);
  fold_checksum_tree (TREE_TYPE (expr), ctx, ht);
  if (TREE_CODE_CLASS (code) != 't' && TREE_CODE_CLASS (code) != 'd')
    fold_checksum_tree (TREE_CHAIN (expr), ctx, ht);
  len = TREE_CODE_LENGTH (code);
  switch (TREE_CODE_CLASS (code))
    {
    case 'c':
      switch (code)
        {
        case STRING_CST:
          md5_process_bytes (TREE_STRING_POINTER (expr),
                             TREE_STRING_LENGTH (expr), ctx);
          break;
        case COMPLEX_CST:
          fold_checksum_tree (TREE_REALPART (expr), ctx, ht);
          fold_checksum_tree (TREE_IMAGPART (expr), ctx, ht);
          break;
        case VECTOR_CST:
          fold_checksum_tree (TREE_VECTOR_CST_ELTS (expr), ctx, ht);
          break;
        default:
          break;
        }
      break;
    case 'x':
      switch (code)
        {
        case TREE_LIST:
          fold_checksum_tree (TREE_PURPOSE (expr), ctx, ht);
          fold_checksum_tree (TREE_VALUE (expr), ctx, ht);
          break;
        case TREE_VEC:
          for (i = 0; i < TREE_VEC_LENGTH (expr); ++i)
            fold_checksum_tree (TREE_VEC_ELT (expr, i), ctx, ht);
          break;
        default:
          break;
        }
      break;
    case 'e':
      switch (code)
        {
        case SAVE_EXPR: len = 2; break;
        case GOTO_SUBROUTINE_EXPR: len = 0; break;
        case RTL_EXPR: len = 0; break;
        case WITH_CLEANUP_EXPR: len = 2; break;
        default: break;
        }
      /* Fall through.  */
    case 'r':
    case '<':
    case '1':
    case '2':
    case 's':
      for (i = 0; i < len; ++i)
        fold_checksum_tree (TREE_OPERAND (expr, i), ctx, ht);
      break;
    case 'd':
      fold_checksum_tree (DECL_SIZE (expr), ctx, ht);
      fold_checksum_tree (DECL_SIZE_UNIT (expr), ctx, ht);
      fold_checksum_tree (DECL_NAME (expr), ctx, ht);
      fold_checksum_tree (DECL_CONTEXT (expr), ctx, ht);
      fold_checksum_tree (DECL_ARGUMENTS (expr), ctx, ht);
      fold_checksum_tree (DECL_RESULT_FLD (expr), ctx, ht);
      fold_checksum_tree (DECL_INITIAL (expr), ctx, ht);
      fold_checksum_tree (DECL_ABSTRACT_ORIGIN (expr), ctx, ht);
      fold_checksum_tree (DECL_SECTION_NAME (expr), ctx, ht);
      fold_checksum_tree (DECL_ATTRIBUTES (expr), ctx, ht);
      fold_checksum_tree (DECL_VINDEX (expr), ctx, ht);
      break;
    case 't':
      fold_checksum_tree (TYPE_VALUES (expr), ctx, ht);
      fold_checksum_tree (TYPE_SIZE (expr), ctx, ht);
      fold_checksum_tree (TYPE_SIZE_UNIT (expr), ctx, ht);
      fold_checksum_tree (TYPE_ATTRIBUTES (expr), ctx, ht);
      fold_checksum_tree (TYPE_NAME (expr), ctx, ht);
      fold_checksum_tree (TYPE_MIN_VALUE (expr), ctx, ht);
      fold_checksum_tree (TYPE_MAX_VALUE (expr), ctx, ht);
      fold_checksum_tree (TYPE_MAIN_VARIANT (expr), ctx, ht);
      fold_checksum_tree (TYPE_BINFO (expr), ctx, ht);
      fold_checksum_tree (TYPE_CONTEXT (expr), ctx, ht);
      break;
    default:
      break;
    }
}

#endif

/* Perform constant folding and related simplification of initializer
   expression EXPR.  This behaves identically to "fold" but ignores
   potential run-time traps and exceptions that fold must preserve.  */

tree
fold_initializer (tree expr)
{
  int saved_signaling_nans = flag_signaling_nans;
  int saved_trapping_math = flag_trapping_math;
  int saved_trapv = flag_trapv;
  tree result;

  flag_signaling_nans = 0;
  flag_trapping_math = 0;
  flag_trapv = 0;

  result = fold (expr);

  flag_signaling_nans = saved_signaling_nans;
  flag_trapping_math = saved_trapping_math;
  flag_trapv = saved_trapv;

  return result;
}

/* Determine if first argument is a multiple of second argument.  Return 0 if
   it is not, or we cannot easily determined it to be.

   An example of the sort of thing we care about (at this point; this routine
   could surely be made more general, and expanded to do what the *_DIV_EXPR's
   fold cases do now) is discovering that

     SAVE_EXPR (I) * SAVE_EXPR (J * 8)

   is a multiple of

     SAVE_EXPR (J * 8)

   when we know that the two SAVE_EXPR (J * 8) nodes are the same node.

   This code also handles discovering that

     SAVE_EXPR (I) * SAVE_EXPR (J * 8)

   is a multiple of 8 so we don't have to worry about dealing with a
   possible remainder.

   Note that we *look* inside a SAVE_EXPR only to determine how it was
   calculated; it is not safe for fold to do much of anything else with the
   internals of a SAVE_EXPR, since it cannot know when it will be evaluated
   at run time.  For example, the latter example above *cannot* be implemented
   as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
   evaluation time of the original SAVE_EXPR is not necessarily the same at
   the time the new expression is evaluated.  The only optimization of this
   sort that would be valid is changing

     SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)

   divided by 8 to

     SAVE_EXPR (I) * SAVE_EXPR (J)

   (where the same SAVE_EXPR (J) is used in the original and the
   transformed version).  */

static int
multiple_of_p (tree type, tree top, tree bottom)
{
  if (operand_equal_p (top, bottom, 0))
    return 1;

  if (TREE_CODE (type) != INTEGER_TYPE)
    return 0;

  switch (TREE_CODE (top))
    {
    case MULT_EXPR:
      return (multiple_of_p (type, TREE_OPERAND (top, 0), bottom)
              || multiple_of_p (type, TREE_OPERAND (top, 1), bottom));

    case PLUS_EXPR:
    case MINUS_EXPR:
      return (multiple_of_p (type, TREE_OPERAND (top, 0), bottom)
              && multiple_of_p (type, TREE_OPERAND (top, 1), bottom));

    case LSHIFT_EXPR:
      if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
        {
          tree op1, t1;

          op1 = TREE_OPERAND (top, 1);
          /* const_binop may not detect overflow correctly,
             so check for it explicitly here.  */
          if (TYPE_PRECISION (TREE_TYPE (size_one_node))
              > TREE_INT_CST_LOW (op1)
              && TREE_INT_CST_HIGH (op1) == 0
              && 0 != (t1 = fold_convert (type,
                                          const_binop (LSHIFT_EXPR,
                                                       size_one_node,
                                                       op1, 0)))
              && ! TREE_OVERFLOW (t1))
            return multiple_of_p (type, t1, bottom);
        }
      return 0;

    case NOP_EXPR:
      /* Can't handle conversions from non-integral or wider integral type.  */
      if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)
          || (TYPE_PRECISION (type)
              < TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (top, 0)))))
        return 0;

      /* .. fall through ...  */

    case SAVE_EXPR:
      return multiple_of_p (type, TREE_OPERAND (top, 0), bottom);

    case INTEGER_CST:
      if (TREE_CODE (bottom) != INTEGER_CST
          || (TYPE_UNSIGNED (type)
              && (tree_int_cst_sgn (top) < 0
                  || tree_int_cst_sgn (bottom) < 0)))
        return 0;
      return integer_zerop (const_binop (TRUNC_MOD_EXPR,
                                         top, bottom, 0));

    default:
      return 0;
    }
}

/* Return true if `t' is known to be non-negative.  */

int
tree_expr_nonnegative_p (tree t)
{
  switch (TREE_CODE (t))
    {
    case ABS_EXPR:
      return 1;

    case INTEGER_CST:
      return tree_int_cst_sgn (t) >= 0;

    case REAL_CST:
      return ! REAL_VALUE_NEGATIVE (TREE_REAL_CST (t));

    case PLUS_EXPR:
      if (FLOAT_TYPE_P (TREE_TYPE (t)))
        return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
               && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));

      /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
         both unsigned and at least 2 bits shorter than the result.  */
      if (TREE_CODE (TREE_TYPE (t)) == INTEGER_TYPE
          && TREE_CODE (TREE_OPERAND (t, 0)) == NOP_EXPR
          && TREE_CODE (TREE_OPERAND (t, 1)) == NOP_EXPR)
        {
          tree inner1 = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 0), 0));
          tree inner2 = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 1), 0));
          if (TREE_CODE (inner1) == INTEGER_TYPE && TYPE_UNSIGNED (inner1)
              && TREE_CODE (inner2) == INTEGER_TYPE && TYPE_UNSIGNED (inner2))
            {
              unsigned int prec = MAX (TYPE_PRECISION (inner1),
                                       TYPE_PRECISION (inner2)) + 1;
              return prec < TYPE_PRECISION (TREE_TYPE (t));
            }
        }
      break;

    case MULT_EXPR:
      if (FLOAT_TYPE_P (TREE_TYPE (t)))
        {
          /* x * x for floating point x is always non-negative.  */
          if (operand_equal_p (TREE_OPERAND (t, 0), TREE_OPERAND (t, 1), 0))
            return 1;
          return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
                 && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
        }

      /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
         both unsigned and their total bits is shorter than the result.  */
      if (TREE_CODE (TREE_TYPE (t)) == INTEGER_TYPE
          && TREE_CODE (TREE_OPERAND (t, 0)) == NOP_EXPR
          && TREE_CODE (TREE_OPERAND (t, 1)) == NOP_EXPR)
        {
          tree inner1 = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 0), 0));
          tree inner2 = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 1), 0));
          if (TREE_CODE (inner1) == INTEGER_TYPE && TYPE_UNSIGNED (inner1)
              && TREE_CODE (inner2) == INTEGER_TYPE && TYPE_UNSIGNED (inner2))
            return TYPE_PRECISION (inner1) + TYPE_PRECISION (inner2)
                   < TYPE_PRECISION (TREE_TYPE (t));
        }
      return 0;

    case TRUNC_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case ROUND_DIV_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
             && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));

    case TRUNC_MOD_EXPR:
    case CEIL_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case ROUND_MOD_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));

    case RDIV_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
             && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));

    case BIT_AND_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 1))
             || tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
    case BIT_IOR_EXPR:
    case BIT_XOR_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
             && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));

    case NOP_EXPR:
      {
        tree inner_type = TREE_TYPE (TREE_OPERAND (t, 0));
        tree outer_type = TREE_TYPE (t);

        if (TREE_CODE (outer_type) == REAL_TYPE)
          {
            if (TREE_CODE (inner_type) == REAL_TYPE)
              return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
            if (TREE_CODE (inner_type) == INTEGER_TYPE)
              {
                if (TYPE_UNSIGNED (inner_type))
                  return 1;
                return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
              }
          }
        else if (TREE_CODE (outer_type) == INTEGER_TYPE)
          {
            if (TREE_CODE (inner_type) == REAL_TYPE)
              return tree_expr_nonnegative_p (TREE_OPERAND (t,0));
            if (TREE_CODE (inner_type) == INTEGER_TYPE)
              return TYPE_PRECISION (inner_type) < TYPE_PRECISION (outer_type)
                      && TYPE_UNSIGNED (inner_type);
          }
      }
      break;

    case COND_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 1))
        && tree_expr_nonnegative_p (TREE_OPERAND (t, 2));
    case COMPOUND_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
    case MIN_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
        && tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
    case MAX_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
        || tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
    case MODIFY_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
    case BIND_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 1));
    case SAVE_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
    case NON_LVALUE_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
    case FLOAT_EXPR:
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
    case RTL_EXPR:
      return rtl_expr_nonnegative_p (RTL_EXPR_RTL (t));

    case CALL_EXPR:
      {
        tree fndecl = get_callee_fndecl (t);
        tree arglist = TREE_OPERAND (t, 1);
        if (fndecl
            && DECL_BUILT_IN (fndecl)
            && DECL_BUILT_IN_CLASS (fndecl) != BUILT_IN_MD)
          switch (DECL_FUNCTION_CODE (fndecl))
            {
#define CASE_BUILTIN_F(BUILT_IN_FN) \
  case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
#define CASE_BUILTIN_I(BUILT_IN_FN) \
  case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:

            CASE_BUILTIN_F (BUILT_IN_ACOS)
            CASE_BUILTIN_F (BUILT_IN_ACOSH)
            CASE_BUILTIN_F (BUILT_IN_CABS)
            CASE_BUILTIN_F (BUILT_IN_COSH)
            CASE_BUILTIN_F (BUILT_IN_ERFC)
            CASE_BUILTIN_F (BUILT_IN_EXP)
            CASE_BUILTIN_F (BUILT_IN_EXP10)
            CASE_BUILTIN_F (BUILT_IN_EXP2)
            CASE_BUILTIN_F (BUILT_IN_FABS)
            CASE_BUILTIN_F (BUILT_IN_FDIM)
            CASE_BUILTIN_F (BUILT_IN_FREXP)
            CASE_BUILTIN_F (BUILT_IN_HYPOT)
            CASE_BUILTIN_F (BUILT_IN_POW10)
            CASE_BUILTIN_F (BUILT_IN_SQRT)
            CASE_BUILTIN_I (BUILT_IN_FFS)
            CASE_BUILTIN_I (BUILT_IN_PARITY)
            CASE_BUILTIN_I (BUILT_IN_POPCOUNT)
              /* Always true.  */
              return 1;

            CASE_BUILTIN_F (BUILT_IN_ASINH)
            CASE_BUILTIN_F (BUILT_IN_ATAN)
            CASE_BUILTIN_F (BUILT_IN_ATANH)
            CASE_BUILTIN_F (BUILT_IN_CBRT)
            CASE_BUILTIN_F (BUILT_IN_CEIL)
            CASE_BUILTIN_F (BUILT_IN_ERF)
            CASE_BUILTIN_F (BUILT_IN_EXPM1)
            CASE_BUILTIN_F (BUILT_IN_FLOOR)
            CASE_BUILTIN_F (BUILT_IN_FMOD)
            CASE_BUILTIN_F (BUILT_IN_LDEXP)
            CASE_BUILTIN_F (BUILT_IN_LLRINT)
            CASE_BUILTIN_F (BUILT_IN_LLROUND)
            CASE_BUILTIN_F (BUILT_IN_LRINT)
            CASE_BUILTIN_F (BUILT_IN_LROUND)
            CASE_BUILTIN_F (BUILT_IN_MODF)
            CASE_BUILTIN_F (BUILT_IN_NEARBYINT)
            CASE_BUILTIN_F (BUILT_IN_POW)
            CASE_BUILTIN_F (BUILT_IN_RINT)
            CASE_BUILTIN_F (BUILT_IN_ROUND)
            CASE_BUILTIN_F (BUILT_IN_SIGNBIT)
            CASE_BUILTIN_F (BUILT_IN_SINH)
            CASE_BUILTIN_F (BUILT_IN_TANH)
            CASE_BUILTIN_F (BUILT_IN_TRUNC)
              /* True if the 1st argument is nonnegative.  */
              return tree_expr_nonnegative_p (TREE_VALUE (arglist));

            CASE_BUILTIN_F(BUILT_IN_FMAX)
              /* True if the 1st OR 2nd arguments are nonnegative.  */
              return tree_expr_nonnegative_p (TREE_VALUE (arglist))
                || tree_expr_nonnegative_p (TREE_VALUE (TREE_CHAIN (arglist)));

            CASE_BUILTIN_F(BUILT_IN_FMIN)
              /* True if the 1st AND 2nd arguments are nonnegative.  */
              return tree_expr_nonnegative_p (TREE_VALUE (arglist))
                && tree_expr_nonnegative_p (TREE_VALUE (TREE_CHAIN (arglist)));

            CASE_BUILTIN_F(BUILT_IN_COPYSIGN)
              /* True if the 2nd argument is nonnegative.  */
              return tree_expr_nonnegative_p (TREE_VALUE (TREE_CHAIN (arglist)));

            default:
              break;
#undef CASE_BUILTIN_F
#undef CASE_BUILTIN_I
            }
      }

      /* ... fall through ...  */

    default:
      if (truth_value_p (TREE_CODE (t)))
        /* Truth values evaluate to 0 or 1, which is nonnegative.  */
        return 1;
    }

  /* We don't know sign of `t', so be conservative and return false.  */
  return 0;
}

/* Return true when T is an address and is known to be nonzero.
   For floating point we further ensure that T is not denormal.
   Similar logic is present in nonzero_address in rtlanal.h  */

static bool
tree_expr_nonzero_p (tree t)
{
  tree type = TREE_TYPE (t);

  /* Doing something useful for floating point would need more work.  */
  if (!INTEGRAL_TYPE_P (type) && !POINTER_TYPE_P (type))
    return false;

  switch (TREE_CODE (t))
    {
    case ABS_EXPR:
      if (!TYPE_UNSIGNED (type) && !flag_wrapv)
        return tree_expr_nonzero_p (TREE_OPERAND (t, 0));

    case INTEGER_CST:
      return !integer_zerop (t);

    case PLUS_EXPR:
      if (!TYPE_UNSIGNED (type) && !flag_wrapv)
        {
          /* With the presence of negative values it is hard
             to say something.  */
          if (!tree_expr_nonnegative_p (TREE_OPERAND (t, 0))
              || !tree_expr_nonnegative_p (TREE_OPERAND (t, 1)))
            return false;
          /* One of operands must be positive and the other non-negative.  */
          return (tree_expr_nonzero_p (TREE_OPERAND (t, 0))
                  || tree_expr_nonzero_p (TREE_OPERAND (t, 1)));
        }
      break;

    case MULT_EXPR:
      if (!TYPE_UNSIGNED (type) && !flag_wrapv)
        {
          return (tree_expr_nonzero_p (TREE_OPERAND (t, 0))
                  && tree_expr_nonzero_p (TREE_OPERAND (t, 1)));
        }
      break;

    case NOP_EXPR:
      {
        tree inner_type = TREE_TYPE (TREE_OPERAND (t, 0));
        tree outer_type = TREE_TYPE (t);

        return (TYPE_PRECISION (inner_type) >= TYPE_PRECISION (outer_type)
                && tree_expr_nonzero_p (TREE_OPERAND (t, 0)));
      }
      break;

   case ADDR_EXPR:
      /* Weak declarations may link to NULL.  */
      if (DECL_P (TREE_OPERAND (t, 0)))
        return !DECL_WEAK (TREE_OPERAND (t, 0));
      /* Constants and all other cases are never weak.  */
      return true;

    case COND_EXPR:
      return (tree_expr_nonzero_p (TREE_OPERAND (t, 1))
              && tree_expr_nonzero_p (TREE_OPERAND (t, 2)));

    case MIN_EXPR:
      return (tree_expr_nonzero_p (TREE_OPERAND (t, 0))
              && tree_expr_nonzero_p (TREE_OPERAND (t, 1)));

    case MAX_EXPR:
      if (tree_expr_nonzero_p (TREE_OPERAND (t, 0)))
        {
          /* When both operands are nonzero, then MAX must be too.  */
          if (tree_expr_nonzero_p (TREE_OPERAND (t, 1)))
            return true;

          /* MAX where operand 0 is positive is positive.  */
          return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
        }
      /* MAX where operand 1 is positive is positive.  */
      else if (tree_expr_nonzero_p (TREE_OPERAND (t, 1))
               && tree_expr_nonnegative_p (TREE_OPERAND (t, 1)))
        return true;
      break;

    case COMPOUND_EXPR:
    case MODIFY_EXPR:
    case BIND_EXPR:
      return tree_expr_nonzero_p (TREE_OPERAND (t, 1));

    case SAVE_EXPR:
    case NON_LVALUE_EXPR:
      return tree_expr_nonzero_p (TREE_OPERAND (t, 0));

    case BIT_IOR_EXPR:
      return tree_expr_nonzero_p (TREE_OPERAND (t, 1))
             || tree_expr_nonzero_p (TREE_OPERAND (t, 0));

    default:
      break;
    }
  return false;
}

/* Return true if `r' is known to be non-negative.
   Only handles constants at the moment.  */

int
rtl_expr_nonnegative_p (rtx r)
{
  switch (GET_CODE (r))
    {
    case CONST_INT:
      return INTVAL (r) >= 0;

    case CONST_DOUBLE:
      if (GET_MODE (r) == VOIDmode)
        return CONST_DOUBLE_HIGH (r) >= 0;
      return 0;

    case CONST_VECTOR:
      {
        int units, i;
        rtx elt;

        units = CONST_VECTOR_NUNITS (r);

        for (i = 0; i < units; ++i)
          {
            elt = CONST_VECTOR_ELT (r, i);
            if (!rtl_expr_nonnegative_p (elt))
              return 0;
          }

        return 1;
      }

    case SYMBOL_REF:
    case LABEL_REF:
      /* These are always nonnegative.  */
      return 1;

    default:
      return 0;
    }
}


/* See if we are applying CODE, a relational to the highest or lowest
   possible integer of TYPE.  If so, then the result is a compile
   time constant.  */

static tree
fold_relational_hi_lo (enum tree_code *code_p, const tree type, tree *op0_p,
                       tree *op1_p)
{
  tree op0 = *op0_p;
  tree op1 = *op1_p;
  enum tree_code code = *code_p;
  int width = GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (op1)));

  if (TREE_CODE (op1) == INTEGER_CST
      && ! TREE_CONSTANT_OVERFLOW (op1)
      && width <= HOST_BITS_PER_WIDE_INT
      && (INTEGRAL_TYPE_P (TREE_TYPE (op1))
          || POINTER_TYPE_P (TREE_TYPE (op1))))
    {
      unsigned HOST_WIDE_INT signed_max;
      unsigned HOST_WIDE_INT max, min;

      signed_max = ((unsigned HOST_WIDE_INT) 1 << (width - 1)) - 1;

      if (TYPE_UNSIGNED (TREE_TYPE (op1)))
        {
          max = ((unsigned HOST_WIDE_INT) 2 << (width - 1)) - 1;
          min = 0;
        }
      else
        {
          max = signed_max;
          min = ((unsigned HOST_WIDE_INT) -1 << (width - 1));
        }

      if (TREE_INT_CST_HIGH (op1) == 0
          && TREE_INT_CST_LOW (op1) == max)
        switch (code)
          {
          case GT_EXPR:
            return omit_one_operand (type,
                                     convert (type, integer_zero_node),
                                     op0);
          case GE_EXPR:
            *code_p = EQ_EXPR;
            break;
          case LE_EXPR:
            return omit_one_operand (type,
                                     convert (type, integer_one_node),
                                     op0);
          case LT_EXPR:
            *code_p = NE_EXPR;
            break;

          /* The GE_EXPR and LT_EXPR cases above are not normally
             reached because of  previous transformations.  */

          default:
            break;
          }
      else if (TREE_INT_CST_HIGH (op1) == 0
               && TREE_INT_CST_LOW (op1) == max - 1)
        switch (code)
          {
          case GT_EXPR:
            *code_p = EQ_EXPR;
            *op1_p = const_binop (PLUS_EXPR, op1, integer_one_node, 0);
            break;
          case LE_EXPR:
            *code_p = NE_EXPR;
            *op1_p = const_binop (PLUS_EXPR, op1, integer_one_node, 0);
            break;
          default:
            break;
          }
      else if (TREE_INT_CST_HIGH (op1) == (min ? -1 : 0)
               && TREE_INT_CST_LOW (op1) == min)
       switch (code)
          {
          case LT_EXPR:
            return omit_one_operand (type,
                                     convert (type, integer_zero_node),
                                     op0);
          case LE_EXPR:
            *code_p = EQ_EXPR;
            break;

          case GE_EXPR:
            return omit_one_operand (type,
                                     convert (type, integer_one_node),
                                     op0);
          case GT_EXPR:
            *code_p = NE_EXPR;
            break;

          default:
            break;
          }
      else if (TREE_INT_CST_HIGH (op1) == (min ? -1 : 0)
               && TREE_INT_CST_LOW (op1) == min + 1)
        switch (code)
          {
          case GE_EXPR:
            *code_p = NE_EXPR;
            *op1_p = const_binop (MINUS_EXPR, op1, integer_one_node, 0);
            break;
          case LT_EXPR:
            *code_p = EQ_EXPR;
            *op1_p = const_binop (MINUS_EXPR, op1, integer_one_node, 0);
            break;
          default:
            break;
          }

      else if (TREE_INT_CST_HIGH (op1) == 0
               && TREE_INT_CST_LOW (op1) == signed_max
               && TYPE_UNSIGNED (TREE_TYPE (op1))
               /* signed_type does not work on pointer types.  */
               && INTEGRAL_TYPE_P (TREE_TYPE (op1)))
        {
          /* The following case also applies to X < signed_max+1
             and X >= signed_max+1 because previous transformations.  */
          if (code == LE_EXPR || code == GT_EXPR)
            {
              tree st0, st1, exp, retval;
              st0 = lang_hooks.types.signed_type (TREE_TYPE (op0));
              st1 = lang_hooks.types.signed_type (TREE_TYPE (op1));

              exp = build2 (code == LE_EXPR ? GE_EXPR: LT_EXPR,
                            type,
                            convert (st0, op0),
                            convert (st1, integer_zero_node));

              retval
                = nondestructive_fold_binary_to_constant (TREE_CODE (exp),
                                                          TREE_TYPE (exp),
                                                          TREE_OPERAND (exp, 0),
                                                          TREE_OPERAND (exp, 1));

              /* If we are in gimple form, then returning EXP would create
                 non-gimple expressions.  Clearing it is safe and insures
                 we do not allow a non-gimple expression to escape.  */
              if (in_gimple_form)
                exp = NULL;

              return (retval ? retval : exp);
            }
        }
    }

  return NULL_TREE;
}


/* Given the components of a binary expression CODE, TYPE, OP0 and OP1,
   attempt to fold the expression to a constant without modifying TYPE,
   OP0 or OP1.

   If the expression could be simplified to a constant, then return
   the constant.  If the expression would not be simplified to a
   constant, then return NULL_TREE.

   Note this is primarily designed to be called after gimplification
   of the tree structures and when at least one operand is a constant.
   As a result of those simplifying assumptions this routine is far
   simpler than the generic fold routine.  */

tree
nondestructive_fold_binary_to_constant (enum tree_code code, tree type,
                                        tree op0, tree op1)
{
  int wins = 1;
  tree subop0;
  tree subop1;
  tree tem;

  /* If this is a commutative operation, and ARG0 is a constant, move it
     to ARG1 to reduce the number of tests below.  */
  if (commutative_tree_code (code)
      && (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST))
    {
      tem = op0;
      op0 = op1;
      op1 = tem;
    }

  /* If either operand is a complex type, extract its real component.  */
  if (TREE_CODE (op0) == COMPLEX_CST)
    subop0 = TREE_REALPART (op0);
  else
    subop0 = op0;

  if (TREE_CODE (op1) == COMPLEX_CST)
    subop1 = TREE_REALPART (op1);
  else
    subop1 = op1;

  /* Note if either argument is not a real or integer constant.
     With a few exceptions, simplification is limited to cases
     where both arguments are constants.  */
  if ((TREE_CODE (subop0) != INTEGER_CST
       && TREE_CODE (subop0) != REAL_CST)
      || (TREE_CODE (subop1) != INTEGER_CST
          && TREE_CODE (subop1) != REAL_CST))
    wins = 0;

  switch (code)
    {
    case PLUS_EXPR:
      /* (plus (address) (const_int)) is a constant.  */
      if (TREE_CODE (op0) == PLUS_EXPR
          && TREE_CODE (op1) == INTEGER_CST
          && (TREE_CODE (TREE_OPERAND (op0, 0)) == ADDR_EXPR
              || (TREE_CODE (TREE_OPERAND (op0, 0)) == NOP_EXPR
                  && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (op0, 0), 0))
                      == ADDR_EXPR)))
          && TREE_CODE (TREE_OPERAND (op0, 1)) == INTEGER_CST)
        {
          return build2 (PLUS_EXPR, type, TREE_OPERAND (op0, 0),
                         const_binop (PLUS_EXPR, op1,
                                      TREE_OPERAND (op0, 1), 0));
        }
    case BIT_XOR_EXPR:

    binary:
      if (!wins)
        return NULL_TREE;

      /* Both arguments are constants.  Simplify.  */
      tem = const_binop (code, op0, op1, 0);
      if (tem != NULL_TREE)
        {
          /* The return value should always have the same type as
             the original expression.  */
          if (TREE_TYPE (tem) != type)
            tem = convert (type, tem);

          return tem;
        }
      return NULL_TREE;
      
    case MINUS_EXPR:
      /* Fold &x - &x.  This can happen from &x.foo - &x.
         This is unsafe for certain floats even in non-IEEE formats.
         In IEEE, it is unsafe because it does wrong for NaNs.
         Also note that operand_equal_p is always false if an
         operand is volatile.  */
      if (! FLOAT_TYPE_P (type) && operand_equal_p (op0, op1, 0))
        return convert (type, integer_zero_node);

      goto binary;

    case MULT_EXPR:
    case BIT_AND_EXPR:
      /* Special case multiplication or bitwise AND where one argument
         is zero.  */
      if (! FLOAT_TYPE_P (type) && integer_zerop (op1))
        return omit_one_operand (type, op1, op0);
      else
        if (!HONOR_NANS (TYPE_MODE (TREE_TYPE (op0)))
            && !HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (op0)))
            && real_zerop (op1))
          return omit_one_operand (type, op1, op0);

      goto binary;

    case BIT_IOR_EXPR:
      /* Special case when we know the result will be all ones.  */
      if (integer_all_onesp (op1))
        return omit_one_operand (type, op1, op0);

      goto binary;
        
    case TRUNC_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case EXACT_DIV_EXPR:
    case TRUNC_MOD_EXPR:
    case ROUND_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case CEIL_MOD_EXPR:
    case RDIV_EXPR:
      /* Division by zero is undefined.  */
      if (integer_zerop (op1))
        return NULL_TREE;

      if (TREE_CODE (op1) == REAL_CST
          && !MODE_HAS_INFINITIES (TYPE_MODE (TREE_TYPE (op1)))
          && real_zerop (op1))
        return NULL_TREE;

      goto binary;

    case MIN_EXPR:
      if (INTEGRAL_TYPE_P (type)
          && operand_equal_p (op1, TYPE_MIN_VALUE (type), OEP_ONLY_CONST))
        return omit_one_operand (type, op1, op0);

      goto binary;

    case MAX_EXPR:
      if (INTEGRAL_TYPE_P (type)
          && TYPE_MAX_VALUE (type)
          && operand_equal_p (op1, TYPE_MAX_VALUE (type), OEP_ONLY_CONST))
        return omit_one_operand (type, op1, op0);

      goto binary;

    case RSHIFT_EXPR:
      /* Optimize -1 >> x for arithmetic right shifts.  */
      if (integer_all_onesp (op0) && ! TYPE_UNSIGNED (type))
        return omit_one_operand (type, op0, op1);
      /* ... fall through ...  */

    case LSHIFT_EXPR:
      if (integer_zerop (op0))
        return omit_one_operand (type, op0, op1);

      /* Since negative shift count is not well-defined, don't
         try to compute it in the compiler.  */
      if (TREE_CODE (op1) == INTEGER_CST && tree_int_cst_sgn (op1) < 0)
        return NULL_TREE;

      goto binary;

    case LROTATE_EXPR:
    case RROTATE_EXPR:
      /* -1 rotated either direction by any amount is still -1.  */
      if (integer_all_onesp (op0))
        return omit_one_operand (type, op0, op1);

      /* 0 rotated either direction by any amount is still zero.  */
      if (integer_zerop (op0))
        return omit_one_operand (type, op0, op1);

      goto binary;

    case COMPLEX_EXPR:
      if (wins)
        return build_complex (type, op0, op1);
      return NULL_TREE;

    case LT_EXPR:
    case LE_EXPR:
    case GT_EXPR:
    case GE_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
      /* If one arg is a real or integer constant, put it last.  */
      if ((TREE_CODE (op0) == INTEGER_CST
           && TREE_CODE (op1) != INTEGER_CST)
          || (TREE_CODE (op0) == REAL_CST
              && TREE_CODE (op0) != REAL_CST))
        {
          tree temp;

          temp = op0;
          op0 = op1;
          op1 = temp;
          code = swap_tree_comparison (code);
        }

      /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
         This transformation affects the cases which are handled in later
         optimizations involving comparisons with non-negative constants.  */
      if (TREE_CODE (op1) == INTEGER_CST
          && TREE_CODE (op0) != INTEGER_CST
          && tree_int_cst_sgn (op1) > 0)
        {
          switch (code)
            {
            case GE_EXPR:
              code = GT_EXPR;
              op1 = const_binop (MINUS_EXPR, op1, integer_one_node, 0);
              break;

            case LT_EXPR:
              code = LE_EXPR;
              op1 = const_binop (MINUS_EXPR, op1, integer_one_node, 0);
              break;

            default:
              break;
            }
        }

      tem = fold_relational_hi_lo (&code, type, &op0, &op1);
      if (tem)
        return tem;

      if (!wins)
        return NULL_TREE;

      return fold_relational_const (code, type, op0, op1);

    case RANGE_EXPR:
      /* This could probably be handled.  */
      return NULL_TREE;

    case TRUTH_AND_EXPR:
      /* If second arg is constant zero, result is zero, but first arg
         must be evaluated.  */
      if (integer_zerop (op1))
        return omit_one_operand (type, op1, op0);
      /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
         case will be handled here.  */
      if (integer_zerop (op0))
        return omit_one_operand (type, op0, op1);
      if (TREE_CODE (op0) == INTEGER_CST && TREE_CODE (op1) == INTEGER_CST)
        {
          int x1 = ! integer_zerop (op0);
          int x2 = ! integer_zerop (op1);

          return ((x1 & x2) ? integer_one_node : integer_zero_node);
        }
      return NULL_TREE;

    case TRUTH_OR_EXPR:
      /* If second arg is constant true, result is true, but we must
         evaluate first arg.  */
      if (TREE_CODE (op1) == INTEGER_CST && ! integer_zerop (op1))
        return omit_one_operand (type, op1, op0);
      /* Likewise for first arg, but note this only occurs here for
         TRUTH_OR_EXPR.  */
      if (TREE_CODE (op0) == INTEGER_CST && ! integer_zerop (op0))
        return omit_one_operand (type, op0, op1);
      if (TREE_CODE (op0) == INTEGER_CST && TREE_CODE (op1) == INTEGER_CST)
        {
          int x1 = ! integer_zerop (op0);
          int x2 = ! integer_zerop (op1);

          return ((x1 | x2) ? integer_one_node : integer_zero_node);
        }
      return NULL_TREE;

    case TRUTH_XOR_EXPR:
      if (TREE_CODE (op0) == INTEGER_CST && TREE_CODE (op1) == INTEGER_CST)
        {
          int x1 = ! integer_zerop (op0);
          int x2 = ! integer_zerop (op1);

          return ((x1 ^ x2) ? integer_one_node : integer_zero_node);
        }
      return NULL_TREE;

    default:
      return NULL_TREE;
    }
}

/* Given the components of a unary expression CODE, TYPE and OP0,
   attempt to fold the expression to a constant without modifying
   TYPE or OP0. 

   If the expression could be simplified to a constant, then return
   the constant.  If the expression would not be simplified to a
   constant, then return NULL_TREE.

   Note this is primarily designed to be called after gimplification
   of the tree structures and when op0 is a constant.  As a result
   of those simplifying assumptions this routine is far simpler than
   the generic fold routine.  */

tree
nondestructive_fold_unary_to_constant (enum tree_code code, tree type,
                                       tree op0)
{
  tree t;

  /* Make sure we have a suitable constant argument.  */
  if (code == NOP_EXPR || code == FLOAT_EXPR || code == CONVERT_EXPR)
    {
      tree subop;

      if (TREE_CODE (op0) == COMPLEX_CST)
        subop = TREE_REALPART (op0);
      else
        subop = op0;

      if (TREE_CODE (subop) != INTEGER_CST && TREE_CODE (subop) != REAL_CST)
        return NULL_TREE;
    }

  switch (code)
    {
    case NOP_EXPR:
    case FLOAT_EXPR:
    case CONVERT_EXPR:
    case FIX_TRUNC_EXPR:
    case FIX_FLOOR_EXPR:
    case FIX_CEIL_EXPR:
      return fold_convert_const (code, type, op0);

    case NEGATE_EXPR:
      if (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST)
        return fold_negate_const (op0, type);
      else
        return NULL_TREE;

    case ABS_EXPR:
      if (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST)
        return fold_abs_const (op0, type);
      else
        return NULL_TREE;

    case BIT_NOT_EXPR:
      if (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST)
        {
          t = build_int_2 (~ TREE_INT_CST_LOW (op0), ~ TREE_INT_CST_HIGH (op0));
          TREE_TYPE (t) = type;
          force_fit_type (t, 0);
          TREE_OVERFLOW (t) = TREE_OVERFLOW (op0);
          TREE_CONSTANT_OVERFLOW (t) = TREE_CONSTANT_OVERFLOW (op0);
          return t;
        }
      else
        return NULL_TREE;

    case REALPART_EXPR:
      if (TREE_CODE (op0) == COMPLEX_CST)
        return TREE_REALPART (op0);
      else
        return NULL_TREE;

    case IMAGPART_EXPR:
      if (TREE_CODE (op0) == COMPLEX_CST)
        return TREE_IMAGPART (op0);
      else
        return NULL_TREE;

    case CONJ_EXPR:
      if (TREE_CODE (op0) == COMPLEX_CST
          && TREE_CODE (TREE_TYPE (op0)) == COMPLEX_TYPE)
        return build_complex (type, TREE_REALPART (op0),
                              negate_expr (TREE_IMAGPART (op0)));
      return NULL_TREE;

    default:
      return NULL_TREE;
    }
}

/* If EXP represents referencing an element in a constant string
   (either via pointer arithmetic or array indexing), return the
   tree representing the value accessed, otherwise return NULL.  */

tree
fold_read_from_constant_string (tree exp)
{
  if (TREE_CODE (exp) == INDIRECT_REF || TREE_CODE (exp) == ARRAY_REF)
    {
      tree exp1 = TREE_OPERAND (exp, 0);
      tree index;
      tree string;

      if (TREE_CODE (exp) == INDIRECT_REF)
        {
          string = string_constant (exp1, &index);
        }
      else
        {
          tree domain = TYPE_DOMAIN (TREE_TYPE (exp1));
          tree low_bound = domain ? TYPE_MIN_VALUE (domain) : integer_zero_node;
          index = convert (sizetype, TREE_OPERAND (exp, 1));
          
          /* Optimize the special-case of a zero lower bound.

             We convert the low_bound to sizetype to avoid some problems
             with constant folding.  (E.g. suppose the lower bound is 1,
             and its mode is QI.  Without the conversion,l (ARRAY
             +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
             +INDEX), which becomes (ARRAY+255+INDEX).  Opps!)  */
          if (! integer_zerop (low_bound))
            index = size_diffop (index, convert (sizetype, low_bound));

          string = exp1;
        }

      if (string
          && TREE_CODE (string) == STRING_CST
          && TREE_CODE (index) == INTEGER_CST
          && compare_tree_int (index, TREE_STRING_LENGTH (string)) < 0
          && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (string))))
              == MODE_INT)
          && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (string)))) == 1))
        return build_int_2 ((TREE_STRING_POINTER (string)
                             [TREE_INT_CST_LOW (index)]), 0);
    }
  return NULL;
}

/* Return the tree for neg (ARG0) when ARG0 is known to be either
   an integer constant or real constant.

   TYPE is the type of the result.  */

static tree
fold_negate_const (tree arg0, tree type)
{
  tree t = NULL_TREE;

  if (TREE_CODE (arg0) == INTEGER_CST)
    {
      unsigned HOST_WIDE_INT low;
      HOST_WIDE_INT high;
      int overflow = neg_double (TREE_INT_CST_LOW (arg0),
                                 TREE_INT_CST_HIGH (arg0),
                                 &low, &high);
      t = build_int_2 (low, high);
      TREE_TYPE (t) = type;
      TREE_OVERFLOW (t)
        = (TREE_OVERFLOW (arg0)
           | force_fit_type (t, overflow && !TYPE_UNSIGNED (type)));
      TREE_CONSTANT_OVERFLOW (t)
        = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg0);
    }
  else if (TREE_CODE (arg0) == REAL_CST)
    t = build_real (type, REAL_VALUE_NEGATE (TREE_REAL_CST (arg0)));
#ifdef ENABLE_CHECKING
  else
    abort ();
#endif
    
  return t;
}

/* Return the tree for abs (ARG0) when ARG0 is known to be either
   an integer constant or real constant.

   TYPE is the type of the result.  */

static tree
fold_abs_const (tree arg0, tree type)
{
  tree t = NULL_TREE;

  if (TREE_CODE (arg0) == INTEGER_CST)
    {
      /* If the value is unsigned, then the absolute value is
         the same as the ordinary value.  */
      if (TYPE_UNSIGNED (type))
        return arg0;
      /* Similarly, if the value is non-negative.  */
      else if (INT_CST_LT (integer_minus_one_node, arg0))
        return arg0;
      /* If the value is negative, then the absolute value is
         its negation.  */
      else
        {
          unsigned HOST_WIDE_INT low;
          HOST_WIDE_INT high;
          int overflow = neg_double (TREE_INT_CST_LOW (arg0),
                                     TREE_INT_CST_HIGH (arg0),
                                     &low, &high);
          t = build_int_2 (low, high);
          TREE_TYPE (t) = type;
          TREE_OVERFLOW (t)
            = (TREE_OVERFLOW (arg0)
               | force_fit_type (t, overflow));
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg0);
          return t;
        }
    }
  else if (TREE_CODE (arg0) == REAL_CST)
    {
      if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg0)))
        return build_real (type, REAL_VALUE_NEGATE (TREE_REAL_CST (arg0)));
      else
        return arg0;
    }
#ifdef ENABLE_CHECKING
  else
    abort ();
#endif
    
  return t;
}

/* Given CODE, a relational operator, the target type, TYPE and two
   constant operands OP0 and OP1, return the result of the
   relational operation.  If the result is not a compile time
   constant, then return NULL_TREE.  */

static tree
fold_relational_const (enum tree_code code, tree type, tree op0, tree op1)
{
  tree tem;
  int invert;

  /* From here on, the only cases we handle are when the result is
     known to be a constant.

     To compute GT, swap the arguments and do LT.
     To compute GE, do LT and invert the result.
     To compute LE, swap the arguments, do LT and invert the result.
     To compute NE, do EQ and invert the result.

     Therefore, the code below must handle only EQ and LT.  */

  if (code == LE_EXPR || code == GT_EXPR)
    {
      tem = op0, op0 = op1, op1 = tem;
      code = swap_tree_comparison (code);
    }

  /* Note that it is safe to invert for real values here because we
     will check below in the one case that it matters.  */

  tem = NULL_TREE;
  invert = 0;
  if (code == NE_EXPR || code == GE_EXPR)
    {
      invert = 1;
      code = invert_tree_comparison (code);
    }

  /* Compute a result for LT or EQ if args permit;
     Otherwise return T.  */
  if (TREE_CODE (op0) == INTEGER_CST && TREE_CODE (op1) == INTEGER_CST)
    {
      if (code == EQ_EXPR)
        tem = build_int_2 (tree_int_cst_equal (op0, op1), 0);
      else
        tem = build_int_2 ((TYPE_UNSIGNED (TREE_TYPE (op0))
                            ? INT_CST_LT_UNSIGNED (op0, op1)
                            : INT_CST_LT (op0, op1)),
                           0);
    }

  else if (code == EQ_EXPR && !TREE_SIDE_EFFECTS (op0)
           && integer_zerop (op1) && tree_expr_nonzero_p (op0))
    tem = build_int_2 (0, 0);

  /* Two real constants can be compared explicitly.  */
  else if (TREE_CODE (op0) == REAL_CST && TREE_CODE (op1) == REAL_CST)
    {
      /* If either operand is a NaN, the result is false with two
         exceptions: First, an NE_EXPR is true on NaNs, but that case
         is already handled correctly since we will be inverting the
         result for NE_EXPR.  Second, if we had inverted a LE_EXPR
         or a GE_EXPR into a LT_EXPR, we must return true so that it
         will be inverted into false.  */

      if (REAL_VALUE_ISNAN (TREE_REAL_CST (op0))
          || REAL_VALUE_ISNAN (TREE_REAL_CST (op1)))
        tem = build_int_2 (invert && code == LT_EXPR, 0);

      else if (code == EQ_EXPR)
        tem = build_int_2 (REAL_VALUES_EQUAL (TREE_REAL_CST (op0),
                                              TREE_REAL_CST (op1)),
                           0);
      else
        tem = build_int_2 (REAL_VALUES_LESS (TREE_REAL_CST (op0),
                                             TREE_REAL_CST (op1)),
                           0);
    }

  if (tem == NULL_TREE)
    return NULL_TREE;

  if (invert)
    TREE_INT_CST_LOW (tem) ^= 1;

  TREE_TYPE (tem) = type;
  if (TREE_CODE (type) == BOOLEAN_TYPE)
    return lang_hooks.truthvalue_conversion (tem);
  return tem;
}

#include "gt-fold-const.h"