Remove assert in get_def_bb_for_const

[official-gcc.git] / gcc / reginfo.c

/* Compute different info about registers.
   Copyright (C) 1987-2016 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 3, 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 COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */


/* This file contains regscan pass of the compiler and passes for
   dealing with info about modes of pseudo-registers inside
   subregisters.  It also defines some tables of information about the
   hardware registers, function init_reg_sets to initialize the
   tables, and other auxiliary functions to deal with info about
   registers and their classes.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "df.h"
#include "tm_p.h"
#include "insn-config.h"
#include "regs.h"
#include "ira.h"
#include "recog.h"
#include "diagnostic-core.h"
#include "reload.h"
#include "output.h"
#include "tree-pass.h"

/* Maximum register number used in this function, plus one.  */

int max_regno;

/* Used to cache the results of simplifiable_subregs.  SHAPE is the input
   parameter and SIMPLIFIABLE_REGS is the result.  */
struct simplifiable_subreg
{
  simplifiable_subreg (const subreg_shape &);

  subreg_shape shape;
  HARD_REG_SET simplifiable_regs;
};
\f
struct target_hard_regs default_target_hard_regs;
struct target_regs default_target_regs;
#if SWITCHABLE_TARGET
struct target_hard_regs *this_target_hard_regs = &default_target_hard_regs;
struct target_regs *this_target_regs = &default_target_regs;
#endif

/* Data for initializing fixed_regs.  */
static const char initial_fixed_regs[] = FIXED_REGISTERS;

/* Data for initializing call_used_regs.  */
static const char initial_call_used_regs[] = CALL_USED_REGISTERS;

#ifdef CALL_REALLY_USED_REGISTERS
/* Data for initializing call_really_used_regs.  */
static const char initial_call_really_used_regs[] = CALL_REALLY_USED_REGISTERS;
#endif

#ifdef CALL_REALLY_USED_REGISTERS
#define CALL_REALLY_USED_REGNO_P(X)  call_really_used_regs[X]
#else
#define CALL_REALLY_USED_REGNO_P(X)  call_used_regs[X]
#endif

/* Indexed by hard register number, contains 1 for registers
   that are being used for global register decls.
   These must be exempt from ordinary flow analysis
   and are also considered fixed.  */
char global_regs[FIRST_PSEUDO_REGISTER];

/* Declaration for the global register. */
tree global_regs_decl[FIRST_PSEUDO_REGISTER];

/* Same information as REGS_INVALIDATED_BY_CALL but in regset form to be used
   in dataflow more conveniently.  */
regset regs_invalidated_by_call_regset;

/* Same information as FIXED_REG_SET but in regset form.  */
regset fixed_reg_set_regset;

/* The bitmap_obstack is used to hold some static variables that
   should not be reset after each function is compiled.  */
static bitmap_obstack persistent_obstack;

/* Used to initialize reg_alloc_order.  */
#ifdef REG_ALLOC_ORDER
static int initial_reg_alloc_order[FIRST_PSEUDO_REGISTER] = REG_ALLOC_ORDER;
#endif

/* The same information, but as an array of unsigned ints.  We copy from
   these unsigned ints to the table above.  We do this so the tm.h files
   do not have to be aware of the wordsize for machines with <= 64 regs.
   Note that we hard-code 32 here, not HOST_BITS_PER_INT.  */
#define N_REG_INTS  \
  ((FIRST_PSEUDO_REGISTER + (32 - 1)) / 32)

static const unsigned int_reg_class_contents[N_REG_CLASSES][N_REG_INTS]
  = REG_CLASS_CONTENTS;

/* Array containing all of the register names.  */
static const char *const initial_reg_names[] = REGISTER_NAMES;

/* Array containing all of the register class names.  */
const char * reg_class_names[] = REG_CLASS_NAMES;

/* No more global register variables may be declared; true once
   reginfo has been initialized.  */
static int no_global_reg_vars = 0;

/* Given a register bitmap, turn on the bits in a HARD_REG_SET that
   correspond to the hard registers, if any, set in that map.  This
   could be done far more efficiently by having all sorts of special-cases
   with moving single words, but probably isn't worth the trouble.  */
void
reg_set_to_hard_reg_set (HARD_REG_SET *to, const_bitmap from)
{
  unsigned i;
  bitmap_iterator bi;

  EXECUTE_IF_SET_IN_BITMAP (from, 0, i, bi)
    {
      if (i >= FIRST_PSEUDO_REGISTER)
        return;
      SET_HARD_REG_BIT (*to, i);
    }
}

/* Function called only once per target_globals to initialize the
   target_hard_regs structure.  Once this is done, various switches
   may override.  */
void
init_reg_sets (void)
{
  int i, j;

  /* First copy the register information from the initial int form into
     the regsets.  */

  for (i = 0; i < N_REG_CLASSES; i++)
    {
      CLEAR_HARD_REG_SET (reg_class_contents[i]);

      /* Note that we hard-code 32 here, not HOST_BITS_PER_INT.  */
      for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)
        if (int_reg_class_contents[i][j / 32]
            & ((unsigned) 1 << (j % 32)))
          SET_HARD_REG_BIT (reg_class_contents[i], j);
    }

  /* Sanity check: make sure the target macros FIXED_REGISTERS and
     CALL_USED_REGISTERS had the right number of initializers.  */
  gcc_assert (sizeof fixed_regs == sizeof initial_fixed_regs);
  gcc_assert (sizeof call_used_regs == sizeof initial_call_used_regs);
#ifdef CALL_REALLY_USED_REGISTERS
  gcc_assert (sizeof call_really_used_regs
              == sizeof initial_call_really_used_regs);
#endif
#ifdef REG_ALLOC_ORDER
  gcc_assert (sizeof reg_alloc_order == sizeof initial_reg_alloc_order);
#endif
  gcc_assert (sizeof reg_names == sizeof initial_reg_names);

  memcpy (fixed_regs, initial_fixed_regs, sizeof fixed_regs);
  memcpy (call_used_regs, initial_call_used_regs, sizeof call_used_regs);
#ifdef CALL_REALLY_USED_REGISTERS
  memcpy (call_really_used_regs, initial_call_really_used_regs,
          sizeof call_really_used_regs);
#endif
#ifdef REG_ALLOC_ORDER
  memcpy (reg_alloc_order, initial_reg_alloc_order, sizeof reg_alloc_order);
#endif
  memcpy (reg_names, initial_reg_names, sizeof reg_names);

  SET_HARD_REG_SET (accessible_reg_set);
  SET_HARD_REG_SET (operand_reg_set);
}

/* We need to save copies of some of the register information which
   can be munged by command-line switches so we can restore it during
   subsequent back-end reinitialization.  */
static char saved_fixed_regs[FIRST_PSEUDO_REGISTER];
static char saved_call_used_regs[FIRST_PSEUDO_REGISTER];
#ifdef CALL_REALLY_USED_REGISTERS
static char saved_call_really_used_regs[FIRST_PSEUDO_REGISTER];
#endif
static const char *saved_reg_names[FIRST_PSEUDO_REGISTER];
static HARD_REG_SET saved_accessible_reg_set;
static HARD_REG_SET saved_operand_reg_set;

/* Save the register information.  */
void
save_register_info (void)
{
  /* Sanity check:  make sure the target macros FIXED_REGISTERS and
     CALL_USED_REGISTERS had the right number of initializers.  */
  gcc_assert (sizeof fixed_regs == sizeof saved_fixed_regs);
  gcc_assert (sizeof call_used_regs == sizeof saved_call_used_regs);
  memcpy (saved_fixed_regs, fixed_regs, sizeof fixed_regs);
  memcpy (saved_call_used_regs, call_used_regs, sizeof call_used_regs);

  /* Likewise for call_really_used_regs.  */
#ifdef CALL_REALLY_USED_REGISTERS
  gcc_assert (sizeof call_really_used_regs
              == sizeof saved_call_really_used_regs);
  memcpy (saved_call_really_used_regs, call_really_used_regs,
          sizeof call_really_used_regs);
#endif

  /* And similarly for reg_names.  */
  gcc_assert (sizeof reg_names == sizeof saved_reg_names);
  memcpy (saved_reg_names, reg_names, sizeof reg_names);
  COPY_HARD_REG_SET (saved_accessible_reg_set, accessible_reg_set);
  COPY_HARD_REG_SET (saved_operand_reg_set, operand_reg_set);
}

/* Restore the register information.  */
static void
restore_register_info (void)
{
  memcpy (fixed_regs, saved_fixed_regs, sizeof fixed_regs);
  memcpy (call_used_regs, saved_call_used_regs, sizeof call_used_regs);

#ifdef CALL_REALLY_USED_REGISTERS
  memcpy (call_really_used_regs, saved_call_really_used_regs,
          sizeof call_really_used_regs);
#endif

  memcpy (reg_names, saved_reg_names, sizeof reg_names);
  COPY_HARD_REG_SET (accessible_reg_set, saved_accessible_reg_set);
  COPY_HARD_REG_SET (operand_reg_set, saved_operand_reg_set);
}

/* After switches have been processed, which perhaps alter
   `fixed_regs' and `call_used_regs', convert them to HARD_REG_SETs.  */
static void
init_reg_sets_1 (void)
{
  unsigned int i, j;
  unsigned int /* machine_mode */ m;

  restore_register_info ();

#ifdef REG_ALLOC_ORDER
  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    inv_reg_alloc_order[reg_alloc_order[i]] = i;
#endif

  /* Let the target tweak things if necessary.  */

  targetm.conditional_register_usage ();

  /* Compute number of hard regs in each class.  */

  memset (reg_class_size, 0, sizeof reg_class_size);
  for (i = 0; i < N_REG_CLASSES; i++)
    {
      bool any_nonfixed = false;
      for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)       
        if (TEST_HARD_REG_BIT (reg_class_contents[i], j))
          {
            reg_class_size[i]++;
            if (!fixed_regs[j])
              any_nonfixed = true;
          }
      class_only_fixed_regs[i] = !any_nonfixed;
    }

  /* Initialize the table of subunions.
     reg_class_subunion[I][J] gets the largest-numbered reg-class
     that is contained in the union of classes I and J.  */

  memset (reg_class_subunion, 0, sizeof reg_class_subunion);
  for (i = 0; i < N_REG_CLASSES; i++)
    {
      for (j = 0; j < N_REG_CLASSES; j++)
        {
          HARD_REG_SET c;
          int k;

          COPY_HARD_REG_SET (c, reg_class_contents[i]);
          IOR_HARD_REG_SET (c, reg_class_contents[j]);
          for (k = 0; k < N_REG_CLASSES; k++)
            if (hard_reg_set_subset_p (reg_class_contents[k], c)
                && !hard_reg_set_subset_p (reg_class_contents[k],
                                          reg_class_contents
                                          [(int) reg_class_subunion[i][j]]))
              reg_class_subunion[i][j] = (enum reg_class) k;
        }
    }

  /* Initialize the table of superunions.
     reg_class_superunion[I][J] gets the smallest-numbered reg-class
     containing the union of classes I and J.  */

  memset (reg_class_superunion, 0, sizeof reg_class_superunion);
  for (i = 0; i < N_REG_CLASSES; i++)
    {
      for (j = 0; j < N_REG_CLASSES; j++)
        {
          HARD_REG_SET c;
          int k;

          COPY_HARD_REG_SET (c, reg_class_contents[i]);
          IOR_HARD_REG_SET (c, reg_class_contents[j]);
          for (k = 0; k < N_REG_CLASSES; k++)
            if (hard_reg_set_subset_p (c, reg_class_contents[k]))
              break;

          reg_class_superunion[i][j] = (enum reg_class) k;
        }
    }

  /* Initialize the tables of subclasses and superclasses of each reg class.
     First clear the whole table, then add the elements as they are found.  */

  for (i = 0; i < N_REG_CLASSES; i++)
    {
      for (j = 0; j < N_REG_CLASSES; j++)
        reg_class_subclasses[i][j] = LIM_REG_CLASSES;
    }

  for (i = 0; i < N_REG_CLASSES; i++)
    {
      if (i == (int) NO_REGS)
        continue;

      for (j = i + 1; j < N_REG_CLASSES; j++)
        if (hard_reg_set_subset_p (reg_class_contents[i],
                                  reg_class_contents[j]))
          {
            /* Reg class I is a subclass of J.
               Add J to the table of superclasses of I.  */
            enum reg_class *p;

            /* Add I to the table of superclasses of J.  */
            p = &reg_class_subclasses[j][0];
            while (*p != LIM_REG_CLASSES) p++;
            *p = (enum reg_class) i;
          }
    }

  /* Initialize "constant" tables.  */

  CLEAR_HARD_REG_SET (fixed_reg_set);
  CLEAR_HARD_REG_SET (call_used_reg_set);
  CLEAR_HARD_REG_SET (call_fixed_reg_set);
  CLEAR_HARD_REG_SET (regs_invalidated_by_call);
  if (!regs_invalidated_by_call_regset)
    {
      bitmap_obstack_initialize (&persistent_obstack);
      regs_invalidated_by_call_regset = ALLOC_REG_SET (&persistent_obstack);
    }
  else
    CLEAR_REG_SET (regs_invalidated_by_call_regset);
  if (!fixed_reg_set_regset)
    fixed_reg_set_regset = ALLOC_REG_SET (&persistent_obstack);
  else
    CLEAR_REG_SET (fixed_reg_set_regset);

  AND_HARD_REG_SET (operand_reg_set, accessible_reg_set);
  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    {
      /* As a special exception, registers whose class is NO_REGS are
         not accepted by `register_operand'.  The reason for this change
         is to allow the representation of special architecture artifacts
         (such as a condition code register) without extending the rtl
         definitions.  Since registers of class NO_REGS cannot be used
         as registers in any case where register classes are examined,
         it is better to apply this exception in a target-independent way.  */
      if (REGNO_REG_CLASS (i) == NO_REGS)
        CLEAR_HARD_REG_BIT (operand_reg_set, i);

      /* If a register is too limited to be treated as a register operand,
         then it should never be allocated to a pseudo.  */
      if (!TEST_HARD_REG_BIT (operand_reg_set, i))
        {
          fixed_regs[i] = 1;
          call_used_regs[i] = 1;
        }

      /* call_used_regs must include fixed_regs.  */
      gcc_assert (!fixed_regs[i] || call_used_regs[i]);
#ifdef CALL_REALLY_USED_REGISTERS
      /* call_used_regs must include call_really_used_regs.  */
      gcc_assert (!call_really_used_regs[i] || call_used_regs[i]);
#endif

      if (fixed_regs[i])
        {
          SET_HARD_REG_BIT (fixed_reg_set, i);
          SET_REGNO_REG_SET (fixed_reg_set_regset, i);
        }

      if (call_used_regs[i])
        SET_HARD_REG_BIT (call_used_reg_set, i);

      /* There are a couple of fixed registers that we know are safe to
         exclude from being clobbered by calls:

         The frame pointer is always preserved across calls.  The arg
         pointer is if it is fixed.  The stack pointer usually is,
         unless TARGET_RETURN_POPS_ARGS, in which case an explicit
         CLOBBER will be present.  If we are generating PIC code, the
         PIC offset table register is preserved across calls, though the
         target can override that.  */

      if (i == STACK_POINTER_REGNUM)
        ;
      else if (global_regs[i])
        {
          SET_HARD_REG_BIT (regs_invalidated_by_call, i);
          SET_REGNO_REG_SET (regs_invalidated_by_call_regset, i);
        }
      else if (i == FRAME_POINTER_REGNUM)
        ;
      else if (!HARD_FRAME_POINTER_IS_FRAME_POINTER
               && i == HARD_FRAME_POINTER_REGNUM)
        ;
      else if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
               && i == ARG_POINTER_REGNUM && fixed_regs[i])
        ;
      else if (!PIC_OFFSET_TABLE_REG_CALL_CLOBBERED
               && i == (unsigned) PIC_OFFSET_TABLE_REGNUM && fixed_regs[i])
        ;
      else if (CALL_REALLY_USED_REGNO_P (i))
        {
          SET_HARD_REG_BIT (regs_invalidated_by_call, i);
          SET_REGNO_REG_SET (regs_invalidated_by_call_regset, i);
        }
    }

  COPY_HARD_REG_SET (call_fixed_reg_set, fixed_reg_set);
  COPY_HARD_REG_SET (fixed_nonglobal_reg_set, fixed_reg_set);

  /* Preserve global registers if called more than once.  */
  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    {
      if (global_regs[i])
        {
          fixed_regs[i] = call_used_regs[i] = 1;
          SET_HARD_REG_BIT (fixed_reg_set, i);
          SET_HARD_REG_BIT (call_used_reg_set, i);
          SET_HARD_REG_BIT (call_fixed_reg_set, i);
        }
    }

  memset (have_regs_of_mode, 0, sizeof (have_regs_of_mode));
  memset (contains_reg_of_mode, 0, sizeof (contains_reg_of_mode));
  for (m = 0; m < (unsigned int) MAX_MACHINE_MODE; m++)
    {
      HARD_REG_SET ok_regs;
      CLEAR_HARD_REG_SET (ok_regs);
      for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)
        if (!fixed_regs [j] && HARD_REGNO_MODE_OK (j, (machine_mode) m))
          SET_HARD_REG_BIT (ok_regs, j);

      for (i = 0; i < N_REG_CLASSES; i++)
        if ((targetm.class_max_nregs ((reg_class_t) i, (machine_mode) m)
             <= reg_class_size[i])
            && hard_reg_set_intersect_p (ok_regs, reg_class_contents[i]))
          {
             contains_reg_of_mode [i][m] = 1;
             have_regs_of_mode [m] = 1;
          }
     }
}

/* Compute the table of register modes.
   These values are used to record death information for individual registers
   (as opposed to a multi-register mode).
   This function might be invoked more than once, if the target has support
   for changing register usage conventions on a per-function basis.
*/
void
init_reg_modes_target (void)
{
  int i, j;

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    for (j = 0; j < MAX_MACHINE_MODE; j++)
      hard_regno_nregs[i][j] = HARD_REGNO_NREGS (i, (machine_mode)j);

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    {
      reg_raw_mode[i] = choose_hard_reg_mode (i, 1, false);

      /* If we couldn't find a valid mode, just use the previous mode
         if it is suitable, otherwise fall back on word_mode.  */
      if (reg_raw_mode[i] == VOIDmode)
        {
          if (i > 0 && hard_regno_nregs[i][reg_raw_mode[i - 1]] == 1)
            reg_raw_mode[i] = reg_raw_mode[i - 1];
          else
            reg_raw_mode[i] = word_mode;
        }
    }
}

/* Finish initializing the register sets and initialize the register modes.
   This function might be invoked more than once, if the target has support
   for changing register usage conventions on a per-function basis.
*/
void
init_regs (void)
{
  /* This finishes what was started by init_reg_sets, but couldn't be done
     until after register usage was specified.  */
  init_reg_sets_1 ();
}

/* The same as previous function plus initializing IRA.  */
void
reinit_regs (void)
{
  init_regs ();
  /* caller_save needs to be re-initialized.  */
  caller_save_initialized_p = false;
  if (this_target_rtl->target_specific_initialized)
    {
      ira_init ();
      recog_init ();
    }
}

/* Initialize some fake stack-frame MEM references for use in
   memory_move_secondary_cost.  */
void
init_fake_stack_mems (void)
{
  int i;

  for (i = 0; i < MAX_MACHINE_MODE; i++)
    top_of_stack[i] = gen_rtx_MEM ((machine_mode) i, stack_pointer_rtx);
}


/* Compute cost of moving data from a register of class FROM to one of
   TO, using MODE.  */

int
register_move_cost (machine_mode mode, reg_class_t from, reg_class_t to)
{
  return targetm.register_move_cost (mode, from, to);
}

/* Compute cost of moving registers to/from memory.  */

int
memory_move_cost (machine_mode mode, reg_class_t rclass, bool in)
{
  return targetm.memory_move_cost (mode, rclass, in);
}

/* Compute extra cost of moving registers to/from memory due to reloads.
   Only needed if secondary reloads are required for memory moves.  */
int
memory_move_secondary_cost (machine_mode mode, reg_class_t rclass,
                            bool in)
{
  reg_class_t altclass;
  int partial_cost = 0;
  /* We need a memory reference to feed to SECONDARY... macros.  */
  /* mem may be unused even if the SECONDARY_ macros are defined.  */
  rtx mem ATTRIBUTE_UNUSED = top_of_stack[(int) mode];

  altclass = secondary_reload_class (in ? 1 : 0, rclass, mode, mem);

  if (altclass == NO_REGS)
    return 0;

  if (in)
    partial_cost = register_move_cost (mode, altclass, rclass);
  else
    partial_cost = register_move_cost (mode, rclass, altclass);

  if (rclass == altclass)
    /* This isn't simply a copy-to-temporary situation.  Can't guess
       what it is, so TARGET_MEMORY_MOVE_COST really ought not to be
       calling here in that case.

       I'm tempted to put in an assert here, but returning this will
       probably only give poor estimates, which is what we would've
       had before this code anyways.  */
    return partial_cost;

  /* Check if the secondary reload register will also need a
     secondary reload.  */
  return memory_move_secondary_cost (mode, altclass, in) + partial_cost;
}

/* Return a machine mode that is legitimate for hard reg REGNO and large
   enough to save nregs.  If we can't find one, return VOIDmode.
   If CALL_SAVED is true, only consider modes that are call saved.  */
machine_mode
choose_hard_reg_mode (unsigned int regno ATTRIBUTE_UNUSED,
                      unsigned int nregs, bool call_saved)
{
  unsigned int /* machine_mode */ m;
  machine_mode found_mode = VOIDmode, mode;

  /* We first look for the largest integer mode that can be validly
     held in REGNO.  If none, we look for the largest floating-point mode.
     If we still didn't find a valid mode, try CCmode.  */

  for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT);
       mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if ((unsigned) hard_regno_nregs[regno][mode] == nregs
        && HARD_REGNO_MODE_OK (regno, mode)
        && (! call_saved || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode))
        && GET_MODE_SIZE (mode) > GET_MODE_SIZE (found_mode))
      found_mode = mode;

  for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT);
       mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if ((unsigned) hard_regno_nregs[regno][mode] == nregs
        && HARD_REGNO_MODE_OK (regno, mode)
        && (! call_saved || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode))
        && GET_MODE_SIZE (mode) > GET_MODE_SIZE (found_mode))
      found_mode = mode;

  for (mode = GET_CLASS_NARROWEST_MODE (MODE_VECTOR_FLOAT);
       mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if ((unsigned) hard_regno_nregs[regno][mode] == nregs
        && HARD_REGNO_MODE_OK (regno, mode)
        && (! call_saved || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode))
        && GET_MODE_SIZE (mode) > GET_MODE_SIZE (found_mode))
      found_mode = mode;

  for (mode = GET_CLASS_NARROWEST_MODE (MODE_VECTOR_INT);
       mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if ((unsigned) hard_regno_nregs[regno][mode] == nregs
        && HARD_REGNO_MODE_OK (regno, mode)
        && (! call_saved || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode))
        && GET_MODE_SIZE (mode) > GET_MODE_SIZE (found_mode))
      found_mode = mode;

  if (found_mode != VOIDmode)
    return found_mode;

  /* Iterate over all of the CCmodes.  */
  for (m = (unsigned int) CCmode; m < (unsigned int) NUM_MACHINE_MODES; ++m)
    {
      mode = (machine_mode) m;
      if ((unsigned) hard_regno_nregs[regno][mode] == nregs
          && HARD_REGNO_MODE_OK (regno, mode)
          && (! call_saved || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode)))
        return mode;
    }

  /* We can't find a mode valid for this register.  */
  return VOIDmode;
}

/* Specify the usage characteristics of the register named NAME.
   It should be a fixed register if FIXED and a
   call-used register if CALL_USED.  */
void
fix_register (const char *name, int fixed, int call_used)
{
  int i;
  int reg, nregs;

  /* Decode the name and update the primary form of
     the register info.  */

  if ((reg = decode_reg_name_and_count (name, &nregs)) >= 0)
    {
      gcc_assert (nregs >= 1);
      for (i = reg; i < reg + nregs; i++)
        {
          if ((i == STACK_POINTER_REGNUM
#ifdef HARD_FRAME_POINTER_REGNUM
               || i == HARD_FRAME_POINTER_REGNUM
#else
               || i == FRAME_POINTER_REGNUM
#endif
               )
              && (fixed == 0 || call_used == 0))
            {
              switch (fixed)
                {
                case 0:
                  switch (call_used)
                    {
                    case 0:
                      error ("can%'t use %qs as a call-saved register", name);
                      break;

                    case 1:
                      error ("can%'t use %qs as a call-used register", name);
                      break;

                    default:
                      gcc_unreachable ();
                    }
                  break;

                case 1:
                  switch (call_used)
                    {
                    case 1:
                      error ("can%'t use %qs as a fixed register", name);
                      break;

                    case 0:
                    default:
                      gcc_unreachable ();
                    }
                  break;

                default:
                  gcc_unreachable ();
                }
            }
          else
            {
              fixed_regs[i] = fixed;
              call_used_regs[i] = call_used;
#ifdef CALL_REALLY_USED_REGISTERS
              if (fixed == 0)
                call_really_used_regs[i] = call_used;
#endif
            }
        }
    }
  else
    {
      warning (0, "unknown register name: %s", name);
    }
}

/* Mark register number I as global.  */
void
globalize_reg (tree decl, int i)
{
  location_t loc = DECL_SOURCE_LOCATION (decl);

#ifdef STACK_REGS
  if (IN_RANGE (i, FIRST_STACK_REG, LAST_STACK_REG))
    {
      error ("stack register used for global register variable");
      return;
    }
#endif

  if (fixed_regs[i] == 0 && no_global_reg_vars)
    error_at (loc, "global register variable follows a function definition");

  if (global_regs[i])
    {
      warning_at (loc, 0, 
                  "register of %qD used for multiple global register variables",
                  decl);
      inform (DECL_SOURCE_LOCATION (global_regs_decl[i]),
              "conflicts with %qD", global_regs_decl[i]); 
      return;
    }

  if (call_used_regs[i] && ! fixed_regs[i])
    warning_at (loc, 0, "call-clobbered register used for global register variable");

  global_regs[i] = 1;
  global_regs_decl[i] = decl;

  /* If we're globalizing the frame pointer, we need to set the
     appropriate regs_invalidated_by_call bit, even if it's already
     set in fixed_regs.  */
  if (i != STACK_POINTER_REGNUM)
    {
      SET_HARD_REG_BIT (regs_invalidated_by_call, i);
      SET_REGNO_REG_SET (regs_invalidated_by_call_regset, i);
    }

  /* If already fixed, nothing else to do.  */
  if (fixed_regs[i])
    return;

  fixed_regs[i] = call_used_regs[i] = 1;
#ifdef CALL_REALLY_USED_REGISTERS
  call_really_used_regs[i] = 1;
#endif

  SET_HARD_REG_BIT (fixed_reg_set, i);
  SET_HARD_REG_BIT (call_used_reg_set, i);
  SET_HARD_REG_BIT (call_fixed_reg_set, i);

  reinit_regs ();
}
\f

/* Structure used to record preferences of given pseudo.  */
struct reg_pref
{
  /* (enum reg_class) prefclass is the preferred class.  May be
     NO_REGS if no class is better than memory.  */
  char prefclass;

  /* altclass is a register class that we should use for allocating
     pseudo if no register in the preferred class is available.
     If no register in this class is available, memory is preferred.

     It might appear to be more general to have a bitmask of classes here,
     but since it is recommended that there be a class corresponding to the
     union of most major pair of classes, that generality is not required.  */
  char altclass;

  /* allocnoclass is a register class that IRA uses for allocating
     the pseudo.  */
  char allocnoclass;
};

/* Record preferences of each pseudo.  This is available after RA is
   run.  */
static struct reg_pref *reg_pref;

/* Current size of reg_info.  */
static int reg_info_size;
/* Max_reg_num still last resize_reg_info call.  */
static int max_regno_since_last_resize;

/* Return the reg_class in which pseudo reg number REGNO is best allocated.
   This function is sometimes called before the info has been computed.
   When that happens, just return GENERAL_REGS, which is innocuous.  */
enum reg_class
reg_preferred_class (int regno)
{
  if (reg_pref == 0)
    return GENERAL_REGS;

  gcc_assert (regno < reg_info_size);
  return (enum reg_class) reg_pref[regno].prefclass;
}

enum reg_class
reg_alternate_class (int regno)
{
  if (reg_pref == 0)
    return ALL_REGS;

  gcc_assert (regno < reg_info_size);
  return (enum reg_class) reg_pref[regno].altclass;
}

/* Return the reg_class which is used by IRA for its allocation.  */
enum reg_class
reg_allocno_class (int regno)
{
  if (reg_pref == 0)
    return NO_REGS;

  gcc_assert (regno < reg_info_size);
  return (enum reg_class) reg_pref[regno].allocnoclass;
}

\f

/* Allocate space for reg info and initilize it.  */
static void
allocate_reg_info (void)
{
  int i;

  max_regno_since_last_resize = max_reg_num ();
  reg_info_size = max_regno_since_last_resize * 3 / 2 + 1;
  gcc_assert (! reg_pref && ! reg_renumber);
  reg_renumber = XNEWVEC (short, reg_info_size);
  reg_pref = XCNEWVEC (struct reg_pref, reg_info_size);
  memset (reg_renumber, -1, reg_info_size * sizeof (short));
  for (i = 0; i < reg_info_size; i++)
    {
      reg_pref[i].prefclass = GENERAL_REGS;
      reg_pref[i].altclass = ALL_REGS;
      reg_pref[i].allocnoclass = GENERAL_REGS;
    }
}


/* Resize reg info. The new elements will be initialized.  Return TRUE
   if new pseudos were added since the last call.  */
bool
resize_reg_info (void)
{
  int old, i;
  bool change_p;

  if (reg_pref == NULL)
    {
      allocate_reg_info ();
      return true;
    }
  change_p = max_regno_since_last_resize != max_reg_num ();
  max_regno_since_last_resize = max_reg_num ();
  if (reg_info_size >= max_reg_num ())
    return change_p;
  old = reg_info_size;
  reg_info_size = max_reg_num () * 3 / 2 + 1;
  gcc_assert (reg_pref && reg_renumber);
  reg_renumber = XRESIZEVEC (short, reg_renumber, reg_info_size);
  reg_pref = XRESIZEVEC (struct reg_pref, reg_pref, reg_info_size);
  memset (reg_pref + old, -1,
          (reg_info_size - old) * sizeof (struct reg_pref));
  memset (reg_renumber + old, -1, (reg_info_size - old) * sizeof (short));
  for (i = old; i < reg_info_size; i++)
    {
      reg_pref[i].prefclass = GENERAL_REGS;
      reg_pref[i].altclass = ALL_REGS;
      reg_pref[i].allocnoclass = GENERAL_REGS;
    }
  return true;
}


/* Free up the space allocated by allocate_reg_info.  */
void
free_reg_info (void)
{
  if (reg_pref)
    {
      free (reg_pref);
      reg_pref = NULL;
    }

  if (reg_renumber)
    {
      free (reg_renumber);
      reg_renumber = NULL;
    }
}

/* Initialize some global data for this pass.  */
static unsigned int
reginfo_init (void)
{
  if (df)
    df_compute_regs_ever_live (true);

  /* This prevents dump_reg_info from losing if called
     before reginfo is run.  */
  reg_pref = NULL;
  reg_info_size = max_regno_since_last_resize = 0;
  /* No more global register variables may be declared.  */
  no_global_reg_vars = 1;
  return 1;
}

namespace {

const pass_data pass_data_reginfo_init =
{
  RTL_PASS, /* type */
  "reginfo", /* name */
  OPTGROUP_NONE, /* optinfo_flags */
  TV_NONE, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_reginfo_init : public rtl_opt_pass
{
public:
  pass_reginfo_init (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_reginfo_init, ctxt)
  {}

  /* opt_pass methods: */
  virtual unsigned int execute (function *) { return reginfo_init (); }

}; // class pass_reginfo_init

} // anon namespace

rtl_opt_pass *
make_pass_reginfo_init (gcc::context *ctxt)
{
  return new pass_reginfo_init (ctxt);
}

\f

/* Set up preferred, alternate, and allocno classes for REGNO as
   PREFCLASS, ALTCLASS, and ALLOCNOCLASS.  */
void
setup_reg_classes (int regno,
                   enum reg_class prefclass, enum reg_class altclass,
                   enum reg_class allocnoclass)
{
  if (reg_pref == NULL)
    return;
  gcc_assert (reg_info_size >= max_reg_num ());
  reg_pref[regno].prefclass = prefclass;
  reg_pref[regno].altclass = altclass;
  reg_pref[regno].allocnoclass = allocnoclass;
}

\f
/* This is the `regscan' pass of the compiler, run just before cse and
   again just before loop.  It finds the first and last use of each
   pseudo-register.  */

static void reg_scan_mark_refs (rtx, rtx_insn *);

void
reg_scan (rtx_insn *f, unsigned int nregs ATTRIBUTE_UNUSED)
{
  rtx_insn *insn;

  timevar_push (TV_REG_SCAN);

  for (insn = f; insn; insn = NEXT_INSN (insn))
    if (INSN_P (insn))
      {
        reg_scan_mark_refs (PATTERN (insn), insn);
        if (REG_NOTES (insn))
          reg_scan_mark_refs (REG_NOTES (insn), insn);
      }

  timevar_pop (TV_REG_SCAN);
}


/* X is the expression to scan.  INSN is the insn it appears in.
   NOTE_FLAG is nonzero if X is from INSN's notes rather than its body.
   We should only record information for REGs with numbers
   greater than or equal to MIN_REGNO.  */
static void
reg_scan_mark_refs (rtx x, rtx_insn *insn)
{
  enum rtx_code code;
  rtx dest;
  rtx note;

  if (!x)
    return;
  code = GET_CODE (x);
  switch (code)
    {
    case CONST:
    CASE_CONST_ANY:
    case CC0:
    case PC:
    case SYMBOL_REF:
    case LABEL_REF:
    case ADDR_VEC:
    case ADDR_DIFF_VEC:
    case REG:
      return;

    case EXPR_LIST:
      if (XEXP (x, 0))
        reg_scan_mark_refs (XEXP (x, 0), insn);
      if (XEXP (x, 1))
        reg_scan_mark_refs (XEXP (x, 1), insn);
      break;

    case INSN_LIST:
    case INT_LIST:
      if (XEXP (x, 1))
        reg_scan_mark_refs (XEXP (x, 1), insn);
      break;

    case CLOBBER:
      if (MEM_P (XEXP (x, 0)))
        reg_scan_mark_refs (XEXP (XEXP (x, 0), 0), insn);
      break;

    case SET:
      /* Count a set of the destination if it is a register.  */
      for (dest = SET_DEST (x);
           GET_CODE (dest) == SUBREG || GET_CODE (dest) == STRICT_LOW_PART
           || GET_CODE (dest) == ZERO_EXTRACT;
           dest = XEXP (dest, 0))
        ;

      /* If this is setting a pseudo from another pseudo or the sum of a
         pseudo and a constant integer and the other pseudo is known to be
         a pointer, set the destination to be a pointer as well.

         Likewise if it is setting the destination from an address or from a
         value equivalent to an address or to the sum of an address and
         something else.

         But don't do any of this if the pseudo corresponds to a user
         variable since it should have already been set as a pointer based
         on the type.  */

      if (REG_P (SET_DEST (x))
          && REGNO (SET_DEST (x)) >= FIRST_PSEUDO_REGISTER
          /* If the destination pseudo is set more than once, then other
             sets might not be to a pointer value (consider access to a
             union in two threads of control in the presence of global
             optimizations).  So only set REG_POINTER on the destination
             pseudo if this is the only set of that pseudo.  */
          && DF_REG_DEF_COUNT (REGNO (SET_DEST (x))) == 1
          && ! REG_USERVAR_P (SET_DEST (x))
          && ! REG_POINTER (SET_DEST (x))
          && ((REG_P (SET_SRC (x))
               && REG_POINTER (SET_SRC (x)))
              || ((GET_CODE (SET_SRC (x)) == PLUS
                   || GET_CODE (SET_SRC (x)) == LO_SUM)
                  && CONST_INT_P (XEXP (SET_SRC (x), 1))
                  && REG_P (XEXP (SET_SRC (x), 0))
                  && REG_POINTER (XEXP (SET_SRC (x), 0)))
              || GET_CODE (SET_SRC (x)) == CONST
              || GET_CODE (SET_SRC (x)) == SYMBOL_REF
              || GET_CODE (SET_SRC (x)) == LABEL_REF
              || (GET_CODE (SET_SRC (x)) == HIGH
                  && (GET_CODE (XEXP (SET_SRC (x), 0)) == CONST
                      || GET_CODE (XEXP (SET_SRC (x), 0)) == SYMBOL_REF
                      || GET_CODE (XEXP (SET_SRC (x), 0)) == LABEL_REF))
              || ((GET_CODE (SET_SRC (x)) == PLUS
                   || GET_CODE (SET_SRC (x)) == LO_SUM)
                  && (GET_CODE (XEXP (SET_SRC (x), 1)) == CONST
                      || GET_CODE (XEXP (SET_SRC (x), 1)) == SYMBOL_REF
                      || GET_CODE (XEXP (SET_SRC (x), 1)) == LABEL_REF))
              || ((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
                  && (GET_CODE (XEXP (note, 0)) == CONST
                      || GET_CODE (XEXP (note, 0)) == SYMBOL_REF
                      || GET_CODE (XEXP (note, 0)) == LABEL_REF))))
        REG_POINTER (SET_DEST (x)) = 1;

      /* If this is setting a register from a register or from a simple
         conversion of a register, propagate REG_EXPR.  */
      if (REG_P (dest) && !REG_ATTRS (dest))
        set_reg_attrs_from_value (dest, SET_SRC (x));

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

    default:
      {
        const char *fmt = GET_RTX_FORMAT (code);
        int i;
        for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
          {
            if (fmt[i] == 'e')
              reg_scan_mark_refs (XEXP (x, i), insn);
            else if (fmt[i] == 'E' && XVEC (x, i) != 0)
              {
                int j;
                for (j = XVECLEN (x, i) - 1; j >= 0; j--)
                  reg_scan_mark_refs (XVECEXP (x, i, j), insn);
              }
          }
      }
    }
}
\f

/* Return nonzero if C1 is a subset of C2, i.e., if every register in C1
   is also in C2.  */
int
reg_class_subset_p (reg_class_t c1, reg_class_t c2)
{
  return (c1 == c2
          || c2 == ALL_REGS
          || hard_reg_set_subset_p (reg_class_contents[(int) c1],
                                   reg_class_contents[(int) c2]));
}

/* Return nonzero if there is a register that is in both C1 and C2.  */
int
reg_classes_intersect_p (reg_class_t c1, reg_class_t c2)
{
  return (c1 == c2
          || c1 == ALL_REGS
          || c2 == ALL_REGS
          || hard_reg_set_intersect_p (reg_class_contents[(int) c1],
                                      reg_class_contents[(int) c2]));
}

\f
inline hashval_t
simplifiable_subregs_hasher::hash (const simplifiable_subreg *value)
{
  return value->shape.unique_id ();
}

inline bool
simplifiable_subregs_hasher::equal (const simplifiable_subreg *value,
                                    const subreg_shape *compare)
{
  return value->shape == *compare;
}

inline simplifiable_subreg::simplifiable_subreg (const subreg_shape &shape_in)
  : shape (shape_in)
{
  CLEAR_HARD_REG_SET (simplifiable_regs);
}

/* Return the set of hard registers that are able to form the subreg
   described by SHAPE.  */

const HARD_REG_SET &
simplifiable_subregs (const subreg_shape &shape)
{
  if (!this_target_hard_regs->x_simplifiable_subregs)
    this_target_hard_regs->x_simplifiable_subregs
      = new hash_table <simplifiable_subregs_hasher> (30);
  simplifiable_subreg **slot
    = (this_target_hard_regs->x_simplifiable_subregs
       ->find_slot_with_hash (&shape, shape.unique_id (), INSERT));

  if (!*slot)
    {
      simplifiable_subreg *info = new simplifiable_subreg (shape);
      for (unsigned int i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
        if (HARD_REGNO_MODE_OK (i, shape.inner_mode)
            && simplify_subreg_regno (i, shape.inner_mode, shape.offset,
                                      shape.outer_mode) >= 0)
          SET_HARD_REG_BIT (info->simplifiable_regs, i);
      *slot = info;
    }
  return (*slot)->simplifiable_regs;
}

/* Passes for keeping and updating info about modes of registers
   inside subregisters.  */

static HARD_REG_SET **valid_mode_changes;
static obstack valid_mode_changes_obstack;

/* Restrict the choice of register for SUBREG_REG (SUBREG) based
   on information about SUBREG.

   If PARTIAL_DEF, SUBREG is a partial definition of a multipart inner
   register and we want to ensure that the other parts of the inner
   register are correctly preserved.  If !PARTIAL_DEF we need to
   ensure that SUBREG itself can be formed.  */

static void
record_subregs_of_mode (rtx subreg, bool partial_def)
{
  unsigned int regno;

  if (!REG_P (SUBREG_REG (subreg)))
    return;

  regno = REGNO (SUBREG_REG (subreg));
  if (regno < FIRST_PSEUDO_REGISTER)
    return;

  subreg_shape shape (shape_of_subreg (subreg));
  if (partial_def)
    {
      /* The number of independently-accessible SHAPE.outer_mode values
         in SHAPE.inner_mode is GET_MODE_SIZE (SHAPE.inner_mode) / SIZE.
         We need to check that the assignment will preserve all the other
         SIZE-byte chunks in the inner register besides the one that
         includes SUBREG.

         In practice it is enough to check whether an equivalent
         SHAPE.inner_mode value in an adjacent SIZE-byte chunk can be formed.
         If the underlying registers are small enough, both subregs will
         be valid.  If the underlying registers are too large, one of the
         subregs will be invalid.

         This relies on the fact that we've already been passed
         SUBREG with PARTIAL_DEF set to false.  */
      unsigned int size = MAX (REGMODE_NATURAL_SIZE (shape.inner_mode),
                               GET_MODE_SIZE (shape.outer_mode));
      gcc_checking_assert (size < GET_MODE_SIZE (shape.inner_mode));
      if (shape.offset >= size)
        shape.offset -= size;
      else
        shape.offset += size;
    }

  if (valid_mode_changes[regno])
    AND_HARD_REG_SET (*valid_mode_changes[regno],
                      simplifiable_subregs (shape));
  else
    {
      valid_mode_changes[regno]
        = XOBNEW (&valid_mode_changes_obstack, HARD_REG_SET);
      COPY_HARD_REG_SET (*valid_mode_changes[regno],
                         simplifiable_subregs (shape));
    }
}

/* Call record_subregs_of_mode for all the subregs in X.  */
static void
find_subregs_of_mode (rtx x)
{
  enum rtx_code code = GET_CODE (x);
  const char * const fmt = GET_RTX_FORMAT (code);
  int i;

  if (code == SUBREG)
    record_subregs_of_mode (x, false);

  /* Time for some deep diving.  */
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
        find_subregs_of_mode (XEXP (x, i));
      else if (fmt[i] == 'E')
        {
          int j;
          for (j = XVECLEN (x, i) - 1; j >= 0; j--)
            find_subregs_of_mode (XVECEXP (x, i, j));
        }
    }
}

void
init_subregs_of_mode (void)
{
  basic_block bb;
  rtx_insn *insn;

  gcc_obstack_init (&valid_mode_changes_obstack);
  valid_mode_changes = XCNEWVEC (HARD_REG_SET *, max_reg_num ());

  FOR_EACH_BB_FN (bb, cfun)
    FOR_BB_INSNS (bb, insn)
      if (NONDEBUG_INSN_P (insn))
        {
          find_subregs_of_mode (PATTERN (insn));
          df_ref def;
          FOR_EACH_INSN_DEF (def, insn)
            if (DF_REF_FLAGS_IS_SET (def, DF_REF_PARTIAL)
                && df_read_modify_subreg_p (DF_REF_REG (def)))
              record_subregs_of_mode (DF_REF_REG (def), true);
        }
}

const HARD_REG_SET *
valid_mode_changes_for_regno (unsigned int regno)
{
  return valid_mode_changes[regno];
}

void
finish_subregs_of_mode (void)
{
  XDELETEVEC (valid_mode_changes);
  obstack_free (&valid_mode_changes_obstack, NULL);
}

/* Free all data attached to the structure.  This isn't a destructor because
   we don't want to run on exit.  */

void
target_hard_regs::finalize ()
{
  delete x_simplifiable_subregs;
}