gcc/simplify-rtx.c

   1 /* RTL simplification functions for GNU compiler.
   2    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, USA.  */
  21
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "tm.h"
  27 #include "rtl.h"
  28 #include "tree.h"
  29 #include "tm_p.h"
  30 #include "regs.h"
  31 #include "hard-reg-set.h"
  32 #include "flags.h"
  33 #include "real.h"
  34 #include "insn-config.h"
  35 #include "recog.h"
  36 #include "function.h"
  37 #include "expr.h"
  38 #include "toplev.h"
  39 #include "output.h"
  40 #include "ggc.h"
  41 #include "target.h"
  42
  43 /* Simplification and canonicalization of RTL.  */
  44
  45 /* Much code operates on (low, high) pairs; the low value is an
  46    unsigned wide int, the high value a signed wide int.  We
  47    occasionally need to sign extend from low to high as if low were a
  48    signed wide int.  */
  49 #define HWI_SIGN_EXTEND(low) \
  50  ((((HOST_WIDE_INT) low) < 0) ? ((HOST_WIDE_INT) -1) : ((HOST_WIDE_INT) 0))
  51
  52 static rtx neg_const_int PARAMS ((enum machine_mode, rtx));
  53 static int simplify_plus_minus_op_data_cmp PARAMS ((const void *,
  54                                                     const void *));
  55 static rtx simplify_plus_minus          PARAMS ((enum rtx_code,
  56                                                  enum machine_mode, rtx,
  57                                                  rtx, int));
  58 \f
  59 /* Negate a CONST_INT rtx, truncating (because a conversion from a
  60    maximally negative number can overflow).  */
  61 static rtx
  62 neg_const_int (mode, i)
  63      enum machine_mode mode;
  64      rtx i;
  65 {
  66   return gen_int_mode (- INTVAL (i), mode);
  67 }
  68
  69 \f
  70 /* Make a binary operation by properly ordering the operands and
  71    seeing if the expression folds.  */
  72
  73 rtx
  74 simplify_gen_binary (code, mode, op0, op1)
  75      enum rtx_code code;
  76      enum machine_mode mode;
  77      rtx op0, op1;
  78 {
  79   rtx tem;
  80
  81   /* Put complex operands first and constants second if commutative.  */
  82   if (GET_RTX_CLASS (code) == 'c'
  83       && swap_commutative_operands_p (op0, op1))
  84     tem = op0, op0 = op1, op1 = tem;
  85
  86   /* If this simplifies, do it.  */
  87   tem = simplify_binary_operation (code, mode, op0, op1);
  88   if (tem)
  89     return tem;
  90
  91   /* Handle addition and subtraction specially.  Otherwise, just form
  92      the operation.  */
  93
  94   if (code == PLUS || code == MINUS)
  95     {
  96       tem = simplify_plus_minus (code, mode, op0, op1, 1);
  97       if (tem)
  98         return tem;
  99     }
 100
 101   return gen_rtx_fmt_ee (code, mode, op0, op1);
 102 }
 103 \f
 104 /* If X is a MEM referencing the constant pool, return the real value.
 105    Otherwise return X.  */
 106 rtx
 107 avoid_constant_pool_reference (x)
 108      rtx x;
 109 {
 110   rtx c, tmp, addr;
 111   enum machine_mode cmode;
 112
 113   switch (GET_CODE (x))
 114     {
 115     case MEM:
 116       break;
 117
 118     case FLOAT_EXTEND:
 119       /* Handle float extensions of constant pool references.  */
 120       tmp = XEXP (x, 0);
 121       c = avoid_constant_pool_reference (tmp);
 122       if (c != tmp && GET_CODE (c) == CONST_DOUBLE)
 123         {
 124           REAL_VALUE_TYPE d;
 125
 126           REAL_VALUE_FROM_CONST_DOUBLE (d, c);
 127           return CONST_DOUBLE_FROM_REAL_VALUE (d, GET_MODE (x));
 128         }
 129       return x;
 130
 131     default:
 132       return x;
 133     }
 134
 135   addr = XEXP (x, 0);
 136
 137   /* Call target hook to avoid the effects of -fpic etc...  */
 138   addr = (*targetm.delegitimize_address) (addr);
 139
 140   if (GET_CODE (addr) == LO_SUM)
 141     addr = XEXP (addr, 1);
 142
 143   if (GET_CODE (addr) != SYMBOL_REF
 144       || ! CONSTANT_POOL_ADDRESS_P (addr))
 145     return x;
 146
 147   c = get_pool_constant (addr);
 148   cmode = get_pool_mode (addr);
 149
 150   /* If we're accessing the constant in a different mode than it was
 151      originally stored, attempt to fix that up via subreg simplifications.
 152      If that fails we have no choice but to return the original memory.  */
 153   if (cmode != GET_MODE (x))
 154     {
 155       c = simplify_subreg (GET_MODE (x), c, cmode, 0);
 156       return c ? c : x;
 157     }
 158
 159   return c;
 160 }
 161 \f
 162 /* Make a unary operation by first seeing if it folds and otherwise making
 163    the specified operation.  */
 164
 165 rtx
 166 simplify_gen_unary (code, mode, op, op_mode)
 167      enum rtx_code code;
 168      enum machine_mode mode;
 169      rtx op;
 170      enum machine_mode op_mode;
 171 {
 172   rtx tem;
 173
 174   /* If this simplifies, use it.  */
 175   if ((tem = simplify_unary_operation (code, mode, op, op_mode)) != 0)
 176     return tem;
 177
 178   return gen_rtx_fmt_e (code, mode, op);
 179 }
 180
 181 /* Likewise for ternary operations.  */
 182
 183 rtx
 184 simplify_gen_ternary (code, mode, op0_mode, op0, op1, op2)
 185      enum rtx_code code;
 186      enum machine_mode mode, op0_mode;
 187      rtx op0, op1, op2;
 188 {
 189   rtx tem;
 190
 191   /* If this simplifies, use it.  */
 192   if (0 != (tem = simplify_ternary_operation (code, mode, op0_mode,
 193                                               op0, op1, op2)))
 194     return tem;
 195
 196   return gen_rtx_fmt_eee (code, mode, op0, op1, op2);
 197 }
 198 \f
 199 /* Likewise, for relational operations.
 200    CMP_MODE specifies mode comparison is done in.
 201   */
 202
 203 rtx
 204 simplify_gen_relational (code, mode, cmp_mode, op0, op1)
 205      enum rtx_code code;
 206      enum machine_mode mode;
 207      enum machine_mode cmp_mode;
 208      rtx op0, op1;
 209 {
 210   rtx tem;
 211
 212   if ((tem = simplify_relational_operation (code, cmp_mode, op0, op1)) != 0)
 213     return tem;
 214
 215   /* For the following tests, ensure const0_rtx is op1.  */
 216   if (op0 == const0_rtx && swap_commutative_operands_p (op0, op1))
 217     tem = op0, op0 = op1, op1 = tem, code = swap_condition (code);
 218
 219   /* If op0 is a compare, extract the comparison arguments from it.  */
 220   if (GET_CODE (op0) == COMPARE && op1 == const0_rtx)
 221     op1 = XEXP (op0, 1), op0 = XEXP (op0, 0);
 222
 223   /* If op0 is a comparison, extract the comparison arguments form it.  */
 224   if (code == NE && op1 == const0_rtx
 225       && GET_RTX_CLASS (GET_CODE (op0)) == '<')
 226     return op0;
 227   else if (code == EQ && op1 == const0_rtx)
 228     {
 229       /* The following tests GET_RTX_CLASS (GET_CODE (op0)) == '<'.  */
 230       enum rtx_code new = reversed_comparison_code (op0, NULL_RTX);
 231       if (new != UNKNOWN)
 232         {
 233           code = new;
 234           mode = cmp_mode;
 235           op1 = XEXP (op0, 1);
 236           op0 = XEXP (op0, 0);
 237         }
 238     }
 239
 240   /* Put complex operands first and constants second.  */
 241   if (swap_commutative_operands_p (op0, op1))
 242     tem = op0, op0 = op1, op1 = tem, code = swap_condition (code);
 243
 244   return gen_rtx_fmt_ee (code, mode, op0, op1);
 245 }
 246 \f
 247 /* Replace all occurrences of OLD in X with NEW and try to simplify the
 248    resulting RTX.  Return a new RTX which is as simplified as possible.  */
 249
 250 rtx
 251 simplify_replace_rtx (x, old, new)
 252      rtx x;
 253      rtx old;
 254      rtx new;
 255 {
 256   enum rtx_code code = GET_CODE (x);
 257   enum machine_mode mode = GET_MODE (x);
 258
 259   /* If X is OLD, return NEW.  Otherwise, if this is an expression, try
 260      to build a new expression substituting recursively.  If we can't do
 261      anything, return our input.  */
 262
 263   if (x == old)
 264     return new;
 265
 266   switch (GET_RTX_CLASS (code))
 267     {
 268     case '1':
 269       {
 270         enum machine_mode op_mode = GET_MODE (XEXP (x, 0));
 271         rtx op = (XEXP (x, 0) == old
 272                   ? new : simplify_replace_rtx (XEXP (x, 0), old, new));
 273
 274         return simplify_gen_unary (code, mode, op, op_mode);
 275       }
 276
 277     case '2':
 278     case 'c':
 279       return
 280         simplify_gen_binary (code, mode,
 281                              simplify_replace_rtx (XEXP (x, 0), old, new),
 282                              simplify_replace_rtx (XEXP (x, 1), old, new));
 283     case '<':
 284       {
 285         enum machine_mode op_mode = (GET_MODE (XEXP (x, 0)) != VOIDmode
 286                                      ? GET_MODE (XEXP (x, 0))
 287                                      : GET_MODE (XEXP (x, 1)));
 288         rtx op0 = simplify_replace_rtx (XEXP (x, 0), old, new);
 289         rtx op1 = simplify_replace_rtx (XEXP (x, 1), old, new);
 290
 291         return
 292           simplify_gen_relational (code, mode,
 293                                    (op_mode != VOIDmode
 294                                     ? op_mode
 295                                     : GET_MODE (op0) != VOIDmode
 296                                     ? GET_MODE (op0)
 297                                     : GET_MODE (op1)),
 298                                    op0, op1);
 299       }
 300
 301     case '3':
 302     case 'b':
 303       {
 304         enum machine_mode op_mode = GET_MODE (XEXP (x, 0));
 305         rtx op0 = simplify_replace_rtx (XEXP (x, 0), old, new);
 306
 307         return
 308           simplify_gen_ternary (code, mode,
 309                                 (op_mode != VOIDmode
 310                                  ? op_mode
 311                                  : GET_MODE (op0)),
 312                                 op0,
 313                                 simplify_replace_rtx (XEXP (x, 1), old, new),
 314                                 simplify_replace_rtx (XEXP (x, 2), old, new));
 315       }
 316
 317     case 'x':
 318       /* The only case we try to handle is a SUBREG.  */
 319       if (code == SUBREG)
 320         {
 321           rtx exp;
 322           exp = simplify_gen_subreg (GET_MODE (x),
 323                                      simplify_replace_rtx (SUBREG_REG (x),
 324                                                            old, new),
 325                                      GET_MODE (SUBREG_REG (x)),
 326                                      SUBREG_BYTE (x));
 327           if (exp)
 328             x = exp;
 329         }
 330       return x;
 331
 332     case 'o':
 333       if (code == MEM)
 334         return replace_equiv_address_nv (x,
 335                                          simplify_replace_rtx (XEXP (x, 0),
 336                                                                old, new));
 337       else if (code == LO_SUM)
 338         {
 339           rtx op0 = simplify_replace_rtx (XEXP (x, 0), old, new);
 340           rtx op1 = simplify_replace_rtx (XEXP (x, 1), old, new);
 341
 342           /* (lo_sum (high x) x) -> x  */
 343           if (GET_CODE (op0) == HIGH && rtx_equal_p (XEXP (op0, 0), op1))
 344             return op1;
 345
 346           return gen_rtx_LO_SUM (mode, op0, op1);
 347         }
 348       else if (code == REG)
 349         {
 350           if (REG_P (old) && REGNO (x) == REGNO (old))
 351             return new;
 352         }
 353
 354       return x;
 355
 356     default:
 357       return x;
 358     }
 359   return x;
 360 }
 361 \f
 362 /* Try to simplify a unary operation CODE whose output mode is to be
 363    MODE with input operand OP whose mode was originally OP_MODE.
 364    Return zero if no simplification can be made.  */
 365 rtx
 366 simplify_unary_operation (code, mode, op, op_mode)
 367      enum rtx_code code;
 368      enum machine_mode mode;
 369      rtx op;
 370      enum machine_mode op_mode;
 371 {
 372   unsigned int width = GET_MODE_BITSIZE (mode);
 373   rtx trueop = avoid_constant_pool_reference (op);
 374
 375   if (code == VEC_DUPLICATE)
 376     {
 377       if (!VECTOR_MODE_P (mode))
 378         abort ();
 379       if (GET_MODE (trueop) != VOIDmode
 380           && !VECTOR_MODE_P (GET_MODE (trueop))
 381           && GET_MODE_INNER (mode) != GET_MODE (trueop))
 382         abort ();
 383       if (GET_MODE (trueop) != VOIDmode
 384           && VECTOR_MODE_P (GET_MODE (trueop))
 385           && GET_MODE_INNER (mode) != GET_MODE_INNER (GET_MODE (trueop)))
 386         abort ();
 387       if (GET_CODE (trueop) == CONST_INT || GET_CODE (trueop) == CONST_DOUBLE
 388           || GET_CODE (trueop) == CONST_VECTOR)
 389         {
 390           int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
 391           unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
 392           rtvec v = rtvec_alloc (n_elts);
 393           unsigned int i;
 394
 395           if (GET_CODE (trueop) != CONST_VECTOR)
 396             for (i = 0; i < n_elts; i++)
 397               RTVEC_ELT (v, i) = trueop;
 398           else
 399             {
 400               enum machine_mode inmode = GET_MODE (trueop);
 401               int in_elt_size = GET_MODE_SIZE (GET_MODE_INNER (inmode));
 402               unsigned in_n_elts = (GET_MODE_SIZE (inmode) / in_elt_size);
 403
 404               if (in_n_elts >= n_elts || n_elts % in_n_elts)
 405                 abort ();
 406               for (i = 0; i < n_elts; i++)
 407                 RTVEC_ELT (v, i) = CONST_VECTOR_ELT (trueop, i % in_n_elts);
 408             }
 409           return gen_rtx_CONST_VECTOR (mode, v);
 410         }
 411     }
 412
 413   if (VECTOR_MODE_P (mode) && GET_CODE (trueop) == CONST_VECTOR)
 414     {
 415       int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
 416       unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
 417       enum machine_mode opmode = GET_MODE (trueop);
 418       int op_elt_size = GET_MODE_SIZE (GET_MODE_INNER (opmode));
 419       unsigned op_n_elts = (GET_MODE_SIZE (opmode) / op_elt_size);
 420       rtvec v = rtvec_alloc (n_elts);
 421       unsigned int i;
 422
 423       if (op_n_elts != n_elts)
 424         abort ();
 425
 426       for (i = 0; i < n_elts; i++)
 427         {
 428           rtx x = simplify_unary_operation (code, GET_MODE_INNER (mode),
 429                                             CONST_VECTOR_ELT (trueop, i),
 430                                             GET_MODE_INNER (opmode));
 431           if (!x)
 432             return 0;
 433           RTVEC_ELT (v, i) = x;
 434         }
 435       return gen_rtx_CONST_VECTOR (mode, v);
 436     }
 437
 438   /* The order of these tests is critical so that, for example, we don't
 439      check the wrong mode (input vs. output) for a conversion operation,
 440      such as FIX.  At some point, this should be simplified.  */
 441
 442   if (code == FLOAT && GET_MODE (trueop) == VOIDmode
 443       && (GET_CODE (trueop) == CONST_DOUBLE || GET_CODE (trueop) == CONST_INT))
 444     {
 445       HOST_WIDE_INT hv, lv;
 446       REAL_VALUE_TYPE d;
 447
 448       if (GET_CODE (trueop) == CONST_INT)
 449         lv = INTVAL (trueop), hv = HWI_SIGN_EXTEND (lv);
 450       else
 451         lv = CONST_DOUBLE_LOW (trueop),  hv = CONST_DOUBLE_HIGH (trueop);
 452
 453       REAL_VALUE_FROM_INT (d, lv, hv, mode);
 454       d = real_value_truncate (mode, d);
 455       return CONST_DOUBLE_FROM_REAL_VALUE (d, mode);
 456     }
 457   else if (code == UNSIGNED_FLOAT && GET_MODE (trueop) == VOIDmode
 458            && (GET_CODE (trueop) == CONST_DOUBLE
 459                || GET_CODE (trueop) == CONST_INT))
 460     {
 461       HOST_WIDE_INT hv, lv;
 462       REAL_VALUE_TYPE d;
 463
 464       if (GET_CODE (trueop) == CONST_INT)
 465         lv = INTVAL (trueop), hv = HWI_SIGN_EXTEND (lv);
 466       else
 467         lv = CONST_DOUBLE_LOW (trueop),  hv = CONST_DOUBLE_HIGH (trueop);
 468
 469       if (op_mode == VOIDmode)
 470         {
 471           /* We don't know how to interpret negative-looking numbers in
 472              this case, so don't try to fold those.  */
 473           if (hv < 0)
 474             return 0;
 475         }
 476       else if (GET_MODE_BITSIZE (op_mode) >= HOST_BITS_PER_WIDE_INT * 2)
 477         ;
 478       else
 479         hv = 0, lv &= GET_MODE_MASK (op_mode);
 480
 481       REAL_VALUE_FROM_UNSIGNED_INT (d, lv, hv, mode);
 482       d = real_value_truncate (mode, d);
 483       return CONST_DOUBLE_FROM_REAL_VALUE (d, mode);
 484     }
 485
 486   if (GET_CODE (trueop) == CONST_INT
 487       && width <= HOST_BITS_PER_WIDE_INT && width > 0)
 488     {
 489       HOST_WIDE_INT arg0 = INTVAL (trueop);
 490       HOST_WIDE_INT val;
 491
 492       switch (code)
 493         {
 494         case NOT:
 495           val = ~ arg0;
 496           break;
 497
 498         case NEG:
 499           val = - arg0;
 500           break;
 501
 502         case ABS:
 503           val = (arg0 >= 0 ? arg0 : - arg0);
 504           break;
 505
 506         case FFS:
 507           /* Don't use ffs here.  Instead, get low order bit and then its
 508              number.  If arg0 is zero, this will return 0, as desired.  */
 509           arg0 &= GET_MODE_MASK (mode);
 510           val = exact_log2 (arg0 & (- arg0)) + 1;
 511           break;
 512
 513         case CLZ:
 514           arg0 &= GET_MODE_MASK (mode);
 515           if (arg0 == 0 && CLZ_DEFINED_VALUE_AT_ZERO (mode, val))
 516             ;
 517           else
 518             val = GET_MODE_BITSIZE (mode) - floor_log2 (arg0) - 1;
 519           break;
 520
 521         case CTZ:
 522           arg0 &= GET_MODE_MASK (mode);
 523           if (arg0 == 0)
 524             {
 525               /* Even if the value at zero is undefined, we have to come
 526                  up with some replacement.  Seems good enough.  */
 527               if (! CTZ_DEFINED_VALUE_AT_ZERO (mode, val))
 528                 val = GET_MODE_BITSIZE (mode);
 529             }
 530           else
 531             val = exact_log2 (arg0 & -arg0);
 532           break;
 533
 534         case POPCOUNT:
 535           arg0 &= GET_MODE_MASK (mode);
 536           val = 0;
 537           while (arg0)
 538             val++, arg0 &= arg0 - 1;
 539           break;
 540
 541         case PARITY:
 542           arg0 &= GET_MODE_MASK (mode);
 543           val = 0;
 544           while (arg0)
 545             val++, arg0 &= arg0 - 1;
 546           val &= 1;
 547           break;
 548
 549         case TRUNCATE:
 550           val = arg0;
 551           break;
 552
 553         case ZERO_EXTEND:
 554           /* When zero-extending a CONST_INT, we need to know its
 555              original mode.  */
 556           if (op_mode == VOIDmode)
 557             abort ();
 558           if (GET_MODE_BITSIZE (op_mode) == HOST_BITS_PER_WIDE_INT)
 559             {
 560               /* If we were really extending the mode,
 561                  we would have to distinguish between zero-extension
 562                  and sign-extension.  */
 563               if (width != GET_MODE_BITSIZE (op_mode))
 564                 abort ();
 565               val = arg0;
 566             }
 567           else if (GET_MODE_BITSIZE (op_mode) < HOST_BITS_PER_WIDE_INT)
 568             val = arg0 & ~((HOST_WIDE_INT) (-1) << GET_MODE_BITSIZE (op_mode));
 569           else
 570             return 0;
 571           break;
 572
 573         case SIGN_EXTEND:
 574           if (op_mode == VOIDmode)
 575             op_mode = mode;
 576           if (GET_MODE_BITSIZE (op_mode) == HOST_BITS_PER_WIDE_INT)
 577             {
 578               /* If we were really extending the mode,
 579                  we would have to distinguish between zero-extension
 580                  and sign-extension.  */
 581               if (width != GET_MODE_BITSIZE (op_mode))
 582                 abort ();
 583               val = arg0;
 584             }
 585           else if (GET_MODE_BITSIZE (op_mode) < HOST_BITS_PER_WIDE_INT)
 586             {
 587               val
 588                 = arg0 & ~((HOST_WIDE_INT) (-1) << GET_MODE_BITSIZE (op_mode));
 589               if (val
 590                   & ((HOST_WIDE_INT) 1 << (GET_MODE_BITSIZE (op_mode) - 1)))
 591                 val -= (HOST_WIDE_INT) 1 << GET_MODE_BITSIZE (op_mode);
 592             }
 593           else
 594             return 0;
 595           break;
 596
 597         case SQRT:
 598         case FLOAT_EXTEND:
 599         case FLOAT_TRUNCATE:
 600         case SS_TRUNCATE:
 601         case US_TRUNCATE:
 602           return 0;
 603
 604         default:
 605           abort ();
 606         }
 607
 608       val = trunc_int_for_mode (val, mode);
 609
 610       return GEN_INT (val);
 611     }
 612
 613   /* We can do some operations on integer CONST_DOUBLEs.  Also allow
 614      for a DImode operation on a CONST_INT.  */
 615   else if (GET_MODE (trueop) == VOIDmode
 616            && width <= HOST_BITS_PER_WIDE_INT * 2
 617            && (GET_CODE (trueop) == CONST_DOUBLE
 618                || GET_CODE (trueop) == CONST_INT))
 619     {
 620       unsigned HOST_WIDE_INT l1, lv;
 621       HOST_WIDE_INT h1, hv;
 622
 623       if (GET_CODE (trueop) == CONST_DOUBLE)
 624         l1 = CONST_DOUBLE_LOW (trueop), h1 = CONST_DOUBLE_HIGH (trueop);
 625       else
 626         l1 = INTVAL (trueop), h1 = HWI_SIGN_EXTEND (l1);
 627
 628       switch (code)
 629         {
 630         case NOT:
 631           lv = ~ l1;
 632           hv = ~ h1;
 633           break;
 634
 635         case NEG:
 636           neg_double (l1, h1, &lv, &hv);
 637           break;
 638
 639         case ABS:
 640           if (h1 < 0)
 641             neg_double (l1, h1, &lv, &hv);
 642           else
 643             lv = l1, hv = h1;
 644           break;
 645
 646         case FFS:
 647           hv = 0;
 648           if (l1 == 0)
 649             {
 650               if (h1 == 0)
 651                 lv = 0;
 652               else
 653                 lv = HOST_BITS_PER_WIDE_INT + exact_log2 (h1 & -h1) + 1;
 654             }
 655           else
 656             lv = exact_log2 (l1 & -l1) + 1;
 657           break;
 658
 659         case CLZ:
 660           hv = 0;
 661           if (h1 == 0)
 662             lv = GET_MODE_BITSIZE (mode) - floor_log2 (l1) - 1;
 663           else
 664             lv = GET_MODE_BITSIZE (mode) - floor_log2 (h1) - 1
 665               - HOST_BITS_PER_WIDE_INT;
 666           break;
 667
 668         case CTZ:
 669           hv = 0;
 670           if (l1 == 0)
 671             {
 672               if (h1 == 0)
 673                 lv = GET_MODE_BITSIZE (mode);
 674               else
 675                 lv = HOST_BITS_PER_WIDE_INT + exact_log2 (h1 & -h1);
 676             }
 677           else
 678             lv = exact_log2 (l1 & -l1);
 679           break;
 680
 681         case POPCOUNT:
 682           hv = 0;
 683           lv = 0;
 684           while (l1)
 685             lv++, l1 &= l1 - 1;
 686           while (h1)
 687             lv++, h1 &= h1 - 1;
 688           break;
 689
 690         case PARITY:
 691           hv = 0;
 692           lv = 0;
 693           while (l1)
 694             lv++, l1 &= l1 - 1;
 695           while (h1)
 696             lv++, h1 &= h1 - 1;
 697           lv &= 1;
 698           break;
 699
 700         case TRUNCATE:
 701           /* This is just a change-of-mode, so do nothing.  */
 702           lv = l1, hv = h1;
 703           break;
 704
 705         case ZERO_EXTEND:
 706           if (op_mode == VOIDmode)
 707             abort ();
 708
 709           if (GET_MODE_BITSIZE (op_mode) > HOST_BITS_PER_WIDE_INT)
 710             return 0;
 711
 712           hv = 0;
 713           lv = l1 & GET_MODE_MASK (op_mode);
 714           break;
 715
 716         case SIGN_EXTEND:
 717           if (op_mode == VOIDmode
 718               || GET_MODE_BITSIZE (op_mode) > HOST_BITS_PER_WIDE_INT)
 719             return 0;
 720           else
 721             {
 722               lv = l1 & GET_MODE_MASK (op_mode);
 723               if (GET_MODE_BITSIZE (op_mode) < HOST_BITS_PER_WIDE_INT
 724                   && (lv & ((HOST_WIDE_INT) 1
 725                             << (GET_MODE_BITSIZE (op_mode) - 1))) != 0)
 726                 lv -= (HOST_WIDE_INT) 1 << GET_MODE_BITSIZE (op_mode);
 727
 728               hv = HWI_SIGN_EXTEND (lv);
 729             }
 730           break;
 731
 732         case SQRT:
 733           return 0;
 734
 735         default:
 736           return 0;
 737         }
 738
 739       return immed_double_const (lv, hv, mode);
 740     }
 741
 742   else if (GET_CODE (trueop) == CONST_DOUBLE
 743            && GET_MODE_CLASS (mode) == MODE_FLOAT)
 744     {
 745       REAL_VALUE_TYPE d, t;
 746       REAL_VALUE_FROM_CONST_DOUBLE (d, trueop);
 747
 748       switch (code)
 749         {
 750         case SQRT:
 751           if (HONOR_SNANS (mode) && real_isnan (&d))
 752             return 0;
 753           real_sqrt (&t, mode, &d);
 754           d = t;
 755           break;
 756         case ABS:
 757           d = REAL_VALUE_ABS (d);
 758           break;
 759         case NEG:
 760           d = REAL_VALUE_NEGATE (d);
 761           break;
 762         case FLOAT_TRUNCATE:
 763           d = real_value_truncate (mode, d);
 764           break;
 765         case FLOAT_EXTEND:
 766           /* All this does is change the mode.  */
 767           break;
 768         case FIX:
 769           real_arithmetic (&d, FIX_TRUNC_EXPR, &d, NULL);
 770           break;
 771
 772         default:
 773           abort ();
 774         }
 775       return CONST_DOUBLE_FROM_REAL_VALUE (d, mode);
 776     }
 777
 778   else if (GET_CODE (trueop) == CONST_DOUBLE
 779            && GET_MODE_CLASS (GET_MODE (trueop)) == MODE_FLOAT
 780            && GET_MODE_CLASS (mode) == MODE_INT
 781            && width <= HOST_BITS_PER_WIDE_INT && width > 0)
 782     {
 783       HOST_WIDE_INT i;
 784       REAL_VALUE_TYPE d;
 785       REAL_VALUE_FROM_CONST_DOUBLE (d, trueop);
 786       switch (code)
 787         {
 788         case FIX:               i = REAL_VALUE_FIX (d);           break;
 789         case UNSIGNED_FIX:      i = REAL_VALUE_UNSIGNED_FIX (d);  break;
 790         default:
 791           abort ();
 792         }
 793       return gen_int_mode (i, mode);
 794     }
 795
 796   /* This was formerly used only for non-IEEE float.
 797      eggert@twinsun.com says it is safe for IEEE also.  */
 798   else
 799     {
 800       enum rtx_code reversed;
 801       /* There are some simplifications we can do even if the operands
 802          aren't constant.  */
 803       switch (code)
 804         {
 805         case NOT:
 806           /* (not (not X)) == X.  */
 807           if (GET_CODE (op) == NOT)
 808             return XEXP (op, 0);
 809
 810           /* (not (eq X Y)) == (ne X Y), etc.  */
 811           if (mode == BImode && GET_RTX_CLASS (GET_CODE (op)) == '<'
 812               && ((reversed = reversed_comparison_code (op, NULL_RTX))
 813                   != UNKNOWN))
 814             return gen_rtx_fmt_ee (reversed,
 815                                    op_mode, XEXP (op, 0), XEXP (op, 1));
 816           break;
 817
 818         case NEG:
 819           /* (neg (neg X)) == X.  */
 820           if (GET_CODE (op) == NEG)
 821             return XEXP (op, 0);
 822           break;
 823
 824         case SIGN_EXTEND:
 825           /* (sign_extend (truncate (minus (label_ref L1) (label_ref L2))))
 826              becomes just the MINUS if its mode is MODE.  This allows
 827              folding switch statements on machines using casesi (such as
 828              the VAX).  */
 829           if (GET_CODE (op) == TRUNCATE
 830               && GET_MODE (XEXP (op, 0)) == mode
 831               && GET_CODE (XEXP (op, 0)) == MINUS
 832               && GET_CODE (XEXP (XEXP (op, 0), 0)) == LABEL_REF
 833               && GET_CODE (XEXP (XEXP (op, 0), 1)) == LABEL_REF)
 834             return XEXP (op, 0);
 835
 836 #if defined(POINTERS_EXTEND_UNSIGNED) && !defined(HAVE_ptr_extend)
 837           if (! POINTERS_EXTEND_UNSIGNED
 838               && mode == Pmode && GET_MODE (op) == ptr_mode
 839               && (CONSTANT_P (op)
 840                   || (GET_CODE (op) == SUBREG
 841                       && GET_CODE (SUBREG_REG (op)) == REG
 842                       && REG_POINTER (SUBREG_REG (op))
 843                       && GET_MODE (SUBREG_REG (op)) == Pmode)))
 844             return convert_memory_address (Pmode, op);
 845 #endif
 846           break;
 847
 848 #if defined(POINTERS_EXTEND_UNSIGNED) && !defined(HAVE_ptr_extend)
 849         case ZERO_EXTEND:
 850           if (POINTERS_EXTEND_UNSIGNED > 0
 851               && mode == Pmode && GET_MODE (op) == ptr_mode
 852               && (CONSTANT_P (op)
 853                   || (GET_CODE (op) == SUBREG
 854                       && GET_CODE (SUBREG_REG (op)) == REG
 855                       && REG_POINTER (SUBREG_REG (op))
 856                       && GET_MODE (SUBREG_REG (op)) == Pmode)))
 857             return convert_memory_address (Pmode, op);
 858           break;
 859 #endif
 860
 861         default:
 862           break;
 863         }
 864
 865       return 0;
 866     }
 867 }
 868 \f
 869 /* Simplify a binary operation CODE with result mode MODE, operating on OP0
 870    and OP1.  Return 0 if no simplification is possible.
 871
 872    Don't use this for relational operations such as EQ or LT.
 873    Use simplify_relational_operation instead.  */
 874 rtx
 875 simplify_binary_operation (code, mode, op0, op1)
 876      enum rtx_code code;
 877      enum machine_mode mode;
 878      rtx op0, op1;
 879 {
 880   HOST_WIDE_INT arg0, arg1, arg0s, arg1s;
 881   HOST_WIDE_INT val;
 882   unsigned int width = GET_MODE_BITSIZE (mode);
 883   rtx tem;
 884   rtx trueop0 = avoid_constant_pool_reference (op0);
 885   rtx trueop1 = avoid_constant_pool_reference (op1);
 886
 887   /* Relational operations don't work here.  We must know the mode
 888      of the operands in order to do the comparison correctly.
 889      Assuming a full word can give incorrect results.
 890      Consider comparing 128 with -128 in QImode.  */
 891
 892   if (GET_RTX_CLASS (code) == '<')
 893     abort ();
 894
 895   /* Make sure the constant is second.  */
 896   if (GET_RTX_CLASS (code) == 'c'
 897       && swap_commutative_operands_p (trueop0, trueop1))
 898     {
 899       tem = op0, op0 = op1, op1 = tem;
 900       tem = trueop0, trueop0 = trueop1, trueop1 = tem;
 901     }
 902
 903   if (VECTOR_MODE_P (mode)
 904       && GET_CODE (trueop0) == CONST_VECTOR
 905       && GET_CODE (trueop1) == CONST_VECTOR)
 906     {
 907       int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
 908       unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
 909       enum machine_mode op0mode = GET_MODE (trueop0);
 910       int op0_elt_size = GET_MODE_SIZE (GET_MODE_INNER (op0mode));
 911       unsigned op0_n_elts = (GET_MODE_SIZE (op0mode) / op0_elt_size);
 912       enum machine_mode op1mode = GET_MODE (trueop1);
 913       int op1_elt_size = GET_MODE_SIZE (GET_MODE_INNER (op1mode));
 914       unsigned op1_n_elts = (GET_MODE_SIZE (op1mode) / op1_elt_size);
 915       rtvec v = rtvec_alloc (n_elts);
 916       unsigned int i;
 917
 918       if (op0_n_elts != n_elts || op1_n_elts != n_elts)
 919         abort ();
 920
 921       for (i = 0; i < n_elts; i++)
 922         {
 923           rtx x = simplify_binary_operation (code, GET_MODE_INNER (mode),
 924                                              CONST_VECTOR_ELT (trueop0, i),
 925                                              CONST_VECTOR_ELT (trueop1, i));
 926           if (!x)
 927             return 0;
 928           RTVEC_ELT (v, i) = x;
 929         }
 930
 931       return gen_rtx_CONST_VECTOR (mode, v);
 932     }
 933
 934   if (GET_MODE_CLASS (mode) == MODE_FLOAT
 935       && GET_CODE (trueop0) == CONST_DOUBLE
 936       && GET_CODE (trueop1) == CONST_DOUBLE
 937       && mode == GET_MODE (op0) && mode == GET_MODE (op1))
 938     {
 939       REAL_VALUE_TYPE f0, f1, value;
 940
 941       REAL_VALUE_FROM_CONST_DOUBLE (f0, trueop0);
 942       REAL_VALUE_FROM_CONST_DOUBLE (f1, trueop1);
 943       f0 = real_value_truncate (mode, f0);
 944       f1 = real_value_truncate (mode, f1);
 945
 946       if (code == DIV
 947           && !MODE_HAS_INFINITIES (mode)
 948           && REAL_VALUES_EQUAL (f1, dconst0))
 949         return 0;
 950
 951       REAL_ARITHMETIC (value, rtx_to_tree_code (code), f0, f1);
 952
 953       value = real_value_truncate (mode, value);
 954       return CONST_DOUBLE_FROM_REAL_VALUE (value, mode);
 955     }
 956
 957   /* We can fold some multi-word operations.  */
 958   if (GET_MODE_CLASS (mode) == MODE_INT
 959       && width == HOST_BITS_PER_WIDE_INT * 2
 960       && (GET_CODE (trueop0) == CONST_DOUBLE
 961           || GET_CODE (trueop0) == CONST_INT)
 962       && (GET_CODE (trueop1) == CONST_DOUBLE
 963           || GET_CODE (trueop1) == CONST_INT))
 964     {
 965       unsigned HOST_WIDE_INT l1, l2, lv;
 966       HOST_WIDE_INT h1, h2, hv;
 967
 968       if (GET_CODE (trueop0) == CONST_DOUBLE)
 969         l1 = CONST_DOUBLE_LOW (trueop0), h1 = CONST_DOUBLE_HIGH (trueop0);
 970       else
 971         l1 = INTVAL (trueop0), h1 = HWI_SIGN_EXTEND (l1);
 972
 973       if (GET_CODE (trueop1) == CONST_DOUBLE)
 974         l2 = CONST_DOUBLE_LOW (trueop1), h2 = CONST_DOUBLE_HIGH (trueop1);
 975       else
 976         l2 = INTVAL (trueop1), h2 = HWI_SIGN_EXTEND (l2);
 977
 978       switch (code)
 979         {
 980         case MINUS:
 981           /* A - B == A + (-B).  */
 982           neg_double (l2, h2, &lv, &hv);
 983           l2 = lv, h2 = hv;
 984
 985           /* .. fall through ...  */
 986
 987         case PLUS:
 988           add_double (l1, h1, l2, h2, &lv, &hv);
 989           break;
 990
 991         case MULT:
 992           mul_double (l1, h1, l2, h2, &lv, &hv);
 993           break;
 994
 995         case DIV:  case MOD:   case UDIV:  case UMOD:
 996           /* We'd need to include tree.h to do this and it doesn't seem worth
 997              it.  */
 998           return 0;
 999
1000         case AND:
1001           lv = l1 & l2, hv = h1 & h2;
1002           break;
1003
1004         case IOR:
1005           lv = l1 | l2, hv = h1 | h2;
1006           break;
1007
1008         case XOR:
1009           lv = l1 ^ l2, hv = h1 ^ h2;
1010           break;
1011
1012         case SMIN:
1013           if (h1 < h2
1014               || (h1 == h2
1015                   && ((unsigned HOST_WIDE_INT) l1
1016                       < (unsigned HOST_WIDE_INT) l2)))
1017             lv = l1, hv = h1;
1018           else
1019             lv = l2, hv = h2;
1020           break;
1021
1022         case SMAX:
1023           if (h1 > h2
1024               || (h1 == h2
1025                   && ((unsigned HOST_WIDE_INT) l1
1026                       > (unsigned HOST_WIDE_INT) l2)))
1027             lv = l1, hv = h1;
1028           else
1029             lv = l2, hv = h2;
1030           break;
1031
1032         case UMIN:
1033           if ((unsigned HOST_WIDE_INT) h1 < (unsigned HOST_WIDE_INT) h2
1034               || (h1 == h2
1035                   && ((unsigned HOST_WIDE_INT) l1
1036                       < (unsigned HOST_WIDE_INT) l2)))
1037             lv = l1, hv = h1;
1038           else
1039             lv = l2, hv = h2;
1040           break;
1041
1042         case UMAX:
1043           if ((unsigned HOST_WIDE_INT) h1 > (unsigned HOST_WIDE_INT) h2
1044               || (h1 == h2
1045                   && ((unsigned HOST_WIDE_INT) l1
1046                       > (unsigned HOST_WIDE_INT) l2)))
1047             lv = l1, hv = h1;
1048           else
1049             lv = l2, hv = h2;
1050           break;
1051
1052         case LSHIFTRT:   case ASHIFTRT:
1053         case ASHIFT:
1054         case ROTATE:     case ROTATERT:
1055 #ifdef SHIFT_COUNT_TRUNCATED
1056           if (SHIFT_COUNT_TRUNCATED)
1057             l2 &= (GET_MODE_BITSIZE (mode) - 1), h2 = 0;
1058 #endif
1059
1060           if (h2 != 0 || l2 >= GET_MODE_BITSIZE (mode))
1061             return 0;
1062
1063           if (code == LSHIFTRT || code == ASHIFTRT)
1064             rshift_double (l1, h1, l2, GET_MODE_BITSIZE (mode), &lv, &hv,
1065                            code == ASHIFTRT);
1066           else if (code == ASHIFT)
1067             lshift_double (l1, h1, l2, GET_MODE_BITSIZE (mode), &lv, &hv, 1);
1068           else if (code == ROTATE)
1069             lrotate_double (l1, h1, l2, GET_MODE_BITSIZE (mode), &lv, &hv);
1070           else /* code == ROTATERT */
1071             rrotate_double (l1, h1, l2, GET_MODE_BITSIZE (mode), &lv, &hv);
1072           break;
1073
1074         default:
1075           return 0;
1076         }
1077
1078       return immed_double_const (lv, hv, mode);
1079     }
1080
1081   if (GET_CODE (op0) != CONST_INT || GET_CODE (op1) != CONST_INT
1082       || width > HOST_BITS_PER_WIDE_INT || width == 0)
1083     {
1084       /* Even if we can't compute a constant result,
1085          there are some cases worth simplifying.  */
1086
1087       switch (code)
1088         {
1089         case PLUS:
1090           /* Maybe simplify x + 0 to x.  The two expressions are equivalent
1091              when x is NaN, infinite, or finite and nonzero.  They aren't
1092              when x is -0 and the rounding mode is not towards -infinity,
1093              since (-0) + 0 is then 0.  */
1094           if (!HONOR_SIGNED_ZEROS (mode) && trueop1 == CONST0_RTX (mode))
1095             return op0;
1096
1097           /* ((-a) + b) -> (b - a) and similarly for (a + (-b)).  These
1098              transformations are safe even for IEEE.  */
1099           if (GET_CODE (op0) == NEG)
1100             return simplify_gen_binary (MINUS, mode, op1, XEXP (op0, 0));
1101           else if (GET_CODE (op1) == NEG)
1102             return simplify_gen_binary (MINUS, mode, op0, XEXP (op1, 0));
1103
1104           /* (~a) + 1 -> -a */
1105           if (INTEGRAL_MODE_P (mode)
1106               && GET_CODE (op0) == NOT
1107               && trueop1 == const1_rtx)
1108             return gen_rtx_NEG (mode, XEXP (op0, 0));
1109
1110           /* Handle both-operands-constant cases.  We can only add
1111              CONST_INTs to constants since the sum of relocatable symbols
1112              can't be handled by most assemblers.  Don't add CONST_INT
1113              to CONST_INT since overflow won't be computed properly if wider
1114              than HOST_BITS_PER_WIDE_INT.  */
1115
1116           if (CONSTANT_P (op0) && GET_MODE (op0) != VOIDmode
1117               && GET_CODE (op1) == CONST_INT)
1118             return plus_constant (op0, INTVAL (op1));
1119           else if (CONSTANT_P (op1) && GET_MODE (op1) != VOIDmode
1120                    && GET_CODE (op0) == CONST_INT)
1121             return plus_constant (op1, INTVAL (op0));
1122
1123           /* See if this is something like X * C - X or vice versa or
1124              if the multiplication is written as a shift.  If so, we can
1125              distribute and make a new multiply, shift, or maybe just
1126              have X (if C is 2 in the example above).  But don't make
1127              real multiply if we didn't have one before.  */
1128
1129           if (! FLOAT_MODE_P (mode))
1130             {
1131               HOST_WIDE_INT coeff0 = 1, coeff1 = 1;
1132               rtx lhs = op0, rhs = op1;
1133               int had_mult = 0;
1134
1135               if (GET_CODE (lhs) == NEG)
1136                 coeff0 = -1, lhs = XEXP (lhs, 0);
1137               else if (GET_CODE (lhs) == MULT
1138                        && GET_CODE (XEXP (lhs, 1)) == CONST_INT)
1139                 {
1140                   coeff0 = INTVAL (XEXP (lhs, 1)), lhs = XEXP (lhs, 0);
1141                   had_mult = 1;
1142                 }
1143               else if (GET_CODE (lhs) == ASHIFT
1144                        && GET_CODE (XEXP (lhs, 1)) == CONST_INT
1145                        && INTVAL (XEXP (lhs, 1)) >= 0
1146                        && INTVAL (XEXP (lhs, 1)) < HOST_BITS_PER_WIDE_INT)
1147                 {
1148                   coeff0 = ((HOST_WIDE_INT) 1) << INTVAL (XEXP (lhs, 1));
1149                   lhs = XEXP (lhs, 0);
1150                 }
1151
1152               if (GET_CODE (rhs) == NEG)
1153                 coeff1 = -1, rhs = XEXP (rhs, 0);
1154               else if (GET_CODE (rhs) == MULT
1155                        && GET_CODE (XEXP (rhs, 1)) == CONST_INT)
1156                 {
1157                   coeff1 = INTVAL (XEXP (rhs, 1)), rhs = XEXP (rhs, 0);
1158                   had_mult = 1;
1159                 }
1160               else if (GET_CODE (rhs) == ASHIFT
1161                        && GET_CODE (XEXP (rhs, 1)) == CONST_INT
1162                        && INTVAL (XEXP (rhs, 1)) >= 0
1163                        && INTVAL (XEXP (rhs, 1)) < HOST_BITS_PER_WIDE_INT)
1164                 {
1165                   coeff1 = ((HOST_WIDE_INT) 1) << INTVAL (XEXP (rhs, 1));
1166                   rhs = XEXP (rhs, 0);
1167                 }
1168
1169               if (rtx_equal_p (lhs, rhs))
1170                 {
1171                   tem = simplify_gen_binary (MULT, mode, lhs,
1172                                         GEN_INT (coeff0 + coeff1));
1173                   return (GET_CODE (tem) == MULT && ! had_mult) ? 0 : tem;
1174                 }
1175             }
1176
1177           /* If one of the operands is a PLUS or a MINUS, see if we can
1178              simplify this by the associative law.
1179              Don't use the associative law for floating point.
1180              The inaccuracy makes it nonassociative,
1181              and subtle programs can break if operations are associated.  */
1182
1183           if (INTEGRAL_MODE_P (mode)
1184               && (GET_CODE (op0) == PLUS || GET_CODE (op0) == MINUS
1185                   || GET_CODE (op1) == PLUS || GET_CODE (op1) == MINUS
1186                   || (GET_CODE (op0) == CONST
1187                       && GET_CODE (XEXP (op0, 0)) == PLUS)
1188                   || (GET_CODE (op1) == CONST
1189                       && GET_CODE (XEXP (op1, 0)) == PLUS))
1190               && (tem = simplify_plus_minus (code, mode, op0, op1, 0)) != 0)
1191             return tem;
1192           break;
1193
1194         case COMPARE:
1195 #ifdef HAVE_cc0
1196           /* Convert (compare FOO (const_int 0)) to FOO unless we aren't
1197              using cc0, in which case we want to leave it as a COMPARE
1198              so we can distinguish it from a register-register-copy.
1199
1200              In IEEE floating point, x-0 is not the same as x.  */
1201
1202           if ((TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
1203                || ! FLOAT_MODE_P (mode) || flag_unsafe_math_optimizations)
1204               && trueop1 == CONST0_RTX (mode))
1205             return op0;
1206 #endif
1207
1208           /* Convert (compare (gt (flags) 0) (lt (flags) 0)) to (flags).  */
1209           if (((GET_CODE (op0) == GT && GET_CODE (op1) == LT)
1210                || (GET_CODE (op0) == GTU && GET_CODE (op1) == LTU))
1211               && XEXP (op0, 1) == const0_rtx && XEXP (op1, 1) == const0_rtx)
1212             {
1213               rtx xop00 = XEXP (op0, 0);
1214               rtx xop10 = XEXP (op1, 0);
1215
1216 #ifdef HAVE_cc0
1217               if (GET_CODE (xop00) == CC0 && GET_CODE (xop10) == CC0)
1218 #else
1219               if (GET_CODE (xop00) == REG && GET_CODE (xop10) == REG
1220                   && GET_MODE (xop00) == GET_MODE (xop10)
1221                   && REGNO (xop00) == REGNO (xop10)
1222                   && GET_MODE_CLASS (GET_MODE (xop00)) == MODE_CC
1223                   && GET_MODE_CLASS (GET_MODE (xop10)) == MODE_CC)
1224 #endif
1225                 return xop00;
1226             }
1227           break;
1228
1229         case MINUS:
1230           /* We can't assume x-x is 0 even with non-IEEE floating point,
1231              but since it is zero except in very strange circumstances, we
1232              will treat it as zero with -funsafe-math-optimizations.  */
1233           if (rtx_equal_p (trueop0, trueop1)
1234               && ! side_effects_p (op0)
1235               && (! FLOAT_MODE_P (mode) || flag_unsafe_math_optimizations))
1236             return CONST0_RTX (mode);
1237
1238           /* Change subtraction from zero into negation.  (0 - x) is the
1239              same as -x when x is NaN, infinite, or finite and nonzero.
1240              But if the mode has signed zeros, and does not round towards
1241              -infinity, then 0 - 0 is 0, not -0.  */
1242           if (!HONOR_SIGNED_ZEROS (mode) && trueop0 == CONST0_RTX (mode))
1243             return gen_rtx_NEG (mode, op1);
1244
1245           /* (-1 - a) is ~a.  */
1246           if (trueop0 == constm1_rtx)
1247             return gen_rtx_NOT (mode, op1);
1248
1249           /* Subtracting 0 has no effect unless the mode has signed zeros
1250              and supports rounding towards -infinity.  In such a case,
1251              0 - 0 is -0.  */
1252           if (!(HONOR_SIGNED_ZEROS (mode)
1253                 && HONOR_SIGN_DEPENDENT_ROUNDING (mode))
1254               && trueop1 == CONST0_RTX (mode))
1255             return op0;
1256
1257           /* See if this is something like X * C - X or vice versa or
1258              if the multiplication is written as a shift.  If so, we can
1259              distribute and make a new multiply, shift, or maybe just
1260              have X (if C is 2 in the example above).  But don't make
1261              real multiply if we didn't have one before.  */
1262
1263           if (! FLOAT_MODE_P (mode))
1264             {
1265               HOST_WIDE_INT coeff0 = 1, coeff1 = 1;
1266               rtx lhs = op0, rhs = op1;
1267               int had_mult = 0;
1268
1269               if (GET_CODE (lhs) == NEG)
1270                 coeff0 = -1, lhs = XEXP (lhs, 0);
1271               else if (GET_CODE (lhs) == MULT
1272                        && GET_CODE (XEXP (lhs, 1)) == CONST_INT)
1273                 {
1274                   coeff0 = INTVAL (XEXP (lhs, 1)), lhs = XEXP (lhs, 0);
1275                   had_mult = 1;
1276                 }
1277               else if (GET_CODE (lhs) == ASHIFT
1278                        && GET_CODE (XEXP (lhs, 1)) == CONST_INT
1279                        && INTVAL (XEXP (lhs, 1)) >= 0
1280                        && INTVAL (XEXP (lhs, 1)) < HOST_BITS_PER_WIDE_INT)
1281                 {
1282                   coeff0 = ((HOST_WIDE_INT) 1) << INTVAL (XEXP (lhs, 1));
1283                   lhs = XEXP (lhs, 0);
1284                 }
1285
1286               if (GET_CODE (rhs) == NEG)
1287                 coeff1 = - 1, rhs = XEXP (rhs, 0);
1288               else if (GET_CODE (rhs) == MULT
1289                        && GET_CODE (XEXP (rhs, 1)) == CONST_INT)
1290                 {
1291                   coeff1 = INTVAL (XEXP (rhs, 1)), rhs = XEXP (rhs, 0);
1292                   had_mult = 1;
1293                 }
1294               else if (GET_CODE (rhs) == ASHIFT
1295                        && GET_CODE (XEXP (rhs, 1)) == CONST_INT
1296                        && INTVAL (XEXP (rhs, 1)) >= 0
1297                        && INTVAL (XEXP (rhs, 1)) < HOST_BITS_PER_WIDE_INT)
1298                 {
1299                   coeff1 = ((HOST_WIDE_INT) 1) << INTVAL (XEXP (rhs, 1));
1300                   rhs = XEXP (rhs, 0);
1301                 }
1302
1303               if (rtx_equal_p (lhs, rhs))
1304                 {
1305                   tem = simplify_gen_binary (MULT, mode, lhs,
1306                                              GEN_INT (coeff0 - coeff1));
1307                   return (GET_CODE (tem) == MULT && ! had_mult) ? 0 : tem;
1308                 }
1309             }
1310
1311           /* (a - (-b)) -> (a + b).  True even for IEEE.  */
1312           if (GET_CODE (op1) == NEG)
1313             return simplify_gen_binary (PLUS, mode, op0, XEXP (op1, 0));
1314
1315           /* If one of the operands is a PLUS or a MINUS, see if we can
1316              simplify this by the associative law.
1317              Don't use the associative law for floating point.
1318              The inaccuracy makes it nonassociative,
1319              and subtle programs can break if operations are associated.  */
1320
1321           if (INTEGRAL_MODE_P (mode)
1322               && (GET_CODE (op0) == PLUS || GET_CODE (op0) == MINUS
1323                   || GET_CODE (op1) == PLUS || GET_CODE (op1) == MINUS
1324                   || (GET_CODE (op0) == CONST
1325                       && GET_CODE (XEXP (op0, 0)) == PLUS)
1326                   || (GET_CODE (op1) == CONST
1327                       && GET_CODE (XEXP (op1, 0)) == PLUS))
1328               && (tem = simplify_plus_minus (code, mode, op0, op1, 0)) != 0)
1329             return tem;
1330
1331           /* Don't let a relocatable value get a negative coeff.  */
1332           if (GET_CODE (op1) == CONST_INT && GET_MODE (op0) != VOIDmode)
1333             return simplify_gen_binary (PLUS, mode,
1334                                         op0,
1335                                         neg_const_int (mode, op1));
1336
1337           /* (x - (x & y)) -> (x & ~y) */
1338           if (GET_CODE (op1) == AND)
1339             {
1340               if (rtx_equal_p (op0, XEXP (op1, 0)))
1341                 {
1342                   tem = simplify_gen_unary (NOT, mode, XEXP (op1, 1),
1343                                             GET_MODE (XEXP (op1, 1)));
1344                   return simplify_gen_binary (AND, mode, op0, tem);
1345                 }
1346               if (rtx_equal_p (op0, XEXP (op1, 1)))
1347                 {
1348                   tem = simplify_gen_unary (NOT, mode, XEXP (op1, 0),
1349                                             GET_MODE (XEXP (op1, 0)));
1350                   return simplify_gen_binary (AND, mode, op0, tem);
1351                 }
1352             }
1353           break;
1354
1355         case MULT:
1356           if (trueop1 == constm1_rtx)
1357             {
1358               tem = simplify_unary_operation (NEG, mode, op0, mode);
1359
1360               return tem ? tem : gen_rtx_NEG (mode, op0);
1361             }
1362
1363           /* Maybe simplify x * 0 to 0.  The reduction is not valid if
1364              x is NaN, since x * 0 is then also NaN.  Nor is it valid
1365              when the mode has signed zeros, since multiplying a negative
1366              number by 0 will give -0, not 0.  */
1367           if (!HONOR_NANS (mode)
1368               && !HONOR_SIGNED_ZEROS (mode)
1369               && trueop1 == CONST0_RTX (mode)
1370               && ! side_effects_p (op0))
1371             return op1;
1372
1373           /* In IEEE floating point, x*1 is not equivalent to x for
1374              signalling NaNs.  */
1375           if (!HONOR_SNANS (mode)
1376               && trueop1 == CONST1_RTX (mode))
1377             return op0;
1378
1379           /* Convert multiply by constant power of two into shift unless
1380              we are still generating RTL.  This test is a kludge.  */
1381           if (GET_CODE (trueop1) == CONST_INT
1382               && (val = exact_log2 (INTVAL (trueop1))) >= 0
1383               /* If the mode is larger than the host word size, and the
1384                  uppermost bit is set, then this isn't a power of two due
1385                  to implicit sign extension.  */
1386               && (width <= HOST_BITS_PER_WIDE_INT
1387                   || val != HOST_BITS_PER_WIDE_INT - 1)
1388               && ! rtx_equal_function_value_matters)
1389             return gen_rtx_ASHIFT (mode, op0, GEN_INT (val));
1390
1391           /* x*2 is x+x and x*(-1) is -x */
1392           if (GET_CODE (trueop1) == CONST_DOUBLE
1393               && GET_MODE_CLASS (GET_MODE (trueop1)) == MODE_FLOAT
1394               && GET_MODE (op0) == mode)
1395             {
1396               REAL_VALUE_TYPE d;
1397               REAL_VALUE_FROM_CONST_DOUBLE (d, trueop1);
1398
1399               if (REAL_VALUES_EQUAL (d, dconst2))
1400                 return gen_rtx_PLUS (mode, op0, copy_rtx (op0));
1401
1402               if (REAL_VALUES_EQUAL (d, dconstm1))
1403                 return gen_rtx_NEG (mode, op0);
1404             }
1405           break;
1406
1407         case IOR:
1408           if (trueop1 == const0_rtx)
1409             return op0;
1410           if (GET_CODE (trueop1) == CONST_INT
1411               && ((INTVAL (trueop1) & GET_MODE_MASK (mode))
1412                   == GET_MODE_MASK (mode)))
1413             return op1;
1414           if (rtx_equal_p (trueop0, trueop1) && ! side_effects_p (op0))
1415             return op0;
1416           /* A | (~A) -> -1 */
1417           if (((GET_CODE (op0) == NOT && rtx_equal_p (XEXP (op0, 0), op1))
1418                || (GET_CODE (op1) == NOT && rtx_equal_p (XEXP (op1, 0), op0)))
1419               && ! side_effects_p (op0)
1420               && GET_MODE_CLASS (mode) != MODE_CC)
1421             return constm1_rtx;
1422           break;
1423
1424         case XOR:
1425           if (trueop1 == const0_rtx)
1426             return op0;
1427           if (GET_CODE (trueop1) == CONST_INT
1428               && ((INTVAL (trueop1) & GET_MODE_MASK (mode))
1429                   == GET_MODE_MASK (mode)))
1430             return gen_rtx_NOT (mode, op0);
1431           if (trueop0 == trueop1 && ! side_effects_p (op0)
1432               && GET_MODE_CLASS (mode) != MODE_CC)
1433             return const0_rtx;
1434           break;
1435
1436         case AND:
1437           if (trueop1 == const0_rtx && ! side_effects_p (op0))
1438             return const0_rtx;
1439           if (GET_CODE (trueop1) == CONST_INT
1440               && ((INTVAL (trueop1) & GET_MODE_MASK (mode))
1441                   == GET_MODE_MASK (mode)))
1442             return op0;
1443           if (trueop0 == trueop1 && ! side_effects_p (op0)
1444               && GET_MODE_CLASS (mode) != MODE_CC)
1445             return op0;
1446           /* A & (~A) -> 0 */
1447           if (((GET_CODE (op0) == NOT && rtx_equal_p (XEXP (op0, 0), op1))
1448                || (GET_CODE (op1) == NOT && rtx_equal_p (XEXP (op1, 0), op0)))
1449               && ! side_effects_p (op0)
1450               && GET_MODE_CLASS (mode) != MODE_CC)
1451             return const0_rtx;
1452           break;
1453
1454         case UDIV:
1455           /* Convert divide by power of two into shift (divide by 1 handled
1456              below).  */
1457           if (GET_CODE (trueop1) == CONST_INT
1458               && (arg1 = exact_log2 (INTVAL (trueop1))) > 0)
1459             return gen_rtx_LSHIFTRT (mode, op0, GEN_INT (arg1));
1460
1461           /* ... fall through ...  */
1462
1463         case DIV:
1464           if (trueop1 == CONST1_RTX (mode))
1465             {
1466               /* On some platforms DIV uses narrower mode than its
1467                  operands.  */
1468               rtx x = gen_lowpart_common (mode, op0);
1469               if (x)
1470                 return x;
1471               else if (mode != GET_MODE (op0) && GET_MODE (op0) != VOIDmode)
1472                 return gen_lowpart_SUBREG (mode, op0);
1473               else
1474                 return op0;
1475             }
1476
1477           /* Maybe change 0 / x to 0.  This transformation isn't safe for
1478              modes with NaNs, since 0 / 0 will then be NaN rather than 0.
1479              Nor is it safe for modes with signed zeros, since dividing
1480              0 by a negative number gives -0, not 0.  */
1481           if (!HONOR_NANS (mode)
1482               && !HONOR_SIGNED_ZEROS (mode)
1483               && trueop0 == CONST0_RTX (mode)
1484               && ! side_effects_p (op1))
1485             return op0;
1486
1487           /* Change division by a constant into multiplication.  Only do
1488              this with -funsafe-math-optimizations.  */
1489           else if (GET_CODE (trueop1) == CONST_DOUBLE
1490                    && GET_MODE_CLASS (GET_MODE (trueop1)) == MODE_FLOAT
1491                    && trueop1 != CONST0_RTX (mode)
1492                    && flag_unsafe_math_optimizations)
1493             {
1494               REAL_VALUE_TYPE d;
1495               REAL_VALUE_FROM_CONST_DOUBLE (d, trueop1);
1496
1497               if (! REAL_VALUES_EQUAL (d, dconst0))
1498                 {
1499                   REAL_ARITHMETIC (d, rtx_to_tree_code (DIV), dconst1, d);
1500                   return gen_rtx_MULT (mode, op0,
1501                                        CONST_DOUBLE_FROM_REAL_VALUE (d, mode));
1502                 }
1503             }
1504           break;
1505
1506         case UMOD:
1507           /* Handle modulus by power of two (mod with 1 handled below).  */
1508           if (GET_CODE (trueop1) == CONST_INT
1509               && exact_log2 (INTVAL (trueop1)) > 0)
1510             return gen_rtx_AND (mode, op0, GEN_INT (INTVAL (op1) - 1));
1511
1512           /* ... fall through ...  */
1513
1514         case MOD:
1515           if ((trueop0 == const0_rtx || trueop1 == const1_rtx)
1516               && ! side_effects_p (op0) && ! side_effects_p (op1))
1517             return const0_rtx;
1518           break;
1519
1520         case ROTATERT:
1521         case ROTATE:
1522         case ASHIFTRT:
1523           /* Rotating ~0 always results in ~0.  */
1524           if (GET_CODE (trueop0) == CONST_INT && width <= HOST_BITS_PER_WIDE_INT
1525               && (unsigned HOST_WIDE_INT) INTVAL (trueop0) == GET_MODE_MASK (mode)
1526               && ! side_effects_p (op1))
1527             return op0;
1528
1529           /* ... fall through ...  */
1530
1531         case ASHIFT:
1532         case LSHIFTRT:
1533           if (trueop1 == const0_rtx)
1534             return op0;
1535           if (trueop0 == const0_rtx && ! side_effects_p (op1))
1536             return op0;
1537           break;
1538
1539         case SMIN:
1540           if (width <= HOST_BITS_PER_WIDE_INT && GET_CODE (trueop1) == CONST_INT
1541               && INTVAL (trueop1) == (HOST_WIDE_INT) 1 << (width -1)
1542               && ! side_effects_p (op0))
1543             return op1;
1544           else if (rtx_equal_p (trueop0, trueop1) && ! side_effects_p (op0))
1545             return op0;
1546           break;
1547
1548         case SMAX:
1549           if (width <= HOST_BITS_PER_WIDE_INT && GET_CODE (trueop1) == CONST_INT
1550               && ((unsigned HOST_WIDE_INT) INTVAL (trueop1)
1551                   == (unsigned HOST_WIDE_INT) GET_MODE_MASK (mode) >> 1)
1552               && ! side_effects_p (op0))
1553             return op1;
1554           else if (rtx_equal_p (trueop0, trueop1) && ! side_effects_p (op0))
1555             return op0;
1556           break;
1557
1558         case UMIN:
1559           if (trueop1 == const0_rtx && ! side_effects_p (op0))
1560             return op1;
1561           else if (rtx_equal_p (trueop0, trueop1) && ! side_effects_p (op0))
1562             return op0;
1563           break;
1564
1565         case UMAX:
1566           if (trueop1 == constm1_rtx && ! side_effects_p (op0))
1567             return op1;
1568           else if (rtx_equal_p (trueop0, trueop1) && ! side_effects_p (op0))
1569             return op0;
1570           break;
1571
1572         case SS_PLUS:
1573         case US_PLUS:
1574         case SS_MINUS:
1575         case US_MINUS:
1576           /* ??? There are simplifications that can be done.  */
1577           return 0;
1578
1579         case VEC_SELECT:
1580           if (!VECTOR_MODE_P (mode))
1581             {
1582               if (!VECTOR_MODE_P (GET_MODE (trueop0))
1583                   || (mode
1584                       != GET_MODE_INNER (GET_MODE (trueop0)))
1585                   || GET_CODE (trueop1) != PARALLEL
1586                   || XVECLEN (trueop1, 0) != 1
1587                   || GET_CODE (XVECEXP (trueop1, 0, 0)) != CONST_INT)
1588                 abort ();
1589
1590               if (GET_CODE (trueop0) == CONST_VECTOR)
1591                 return CONST_VECTOR_ELT (trueop0, INTVAL (XVECEXP (trueop1, 0, 0)));
1592             }
1593           else
1594             {
1595               if (!VECTOR_MODE_P (GET_MODE (trueop0))
1596                   || (GET_MODE_INNER (mode)
1597                       != GET_MODE_INNER (GET_MODE (trueop0)))
1598                   || GET_CODE (trueop1) != PARALLEL)
1599                 abort ();
1600
1601               if (GET_CODE (trueop0) == CONST_VECTOR)
1602                 {
1603                   int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
1604                   unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
1605                   rtvec v = rtvec_alloc (n_elts);
1606                   unsigned int i;
1607
1608                   if (XVECLEN (trueop1, 0) != (int) n_elts)
1609                     abort ();
1610                   for (i = 0; i < n_elts; i++)
1611                     {
1612                       rtx x = XVECEXP (trueop1, 0, i);
1613
1614                       if (GET_CODE (x) != CONST_INT)
1615                         abort ();
1616                       RTVEC_ELT (v, i) = CONST_VECTOR_ELT (trueop0, INTVAL (x));
1617                     }
1618
1619                   return gen_rtx_CONST_VECTOR (mode, v);
1620                 }
1621             }
1622           return 0;
1623         case VEC_CONCAT:
1624           {
1625             enum machine_mode op0_mode = (GET_MODE (trueop0) != VOIDmode
1626                                           ? GET_MODE (trueop0)
1627                                           : GET_MODE_INNER (mode));
1628             enum machine_mode op1_mode = (GET_MODE (trueop1) != VOIDmode
1629                                           ? GET_MODE (trueop1)
1630                                           : GET_MODE_INNER (mode));
1631
1632             if (!VECTOR_MODE_P (mode)
1633                 || (GET_MODE_SIZE (op0_mode) + GET_MODE_SIZE (op1_mode)
1634                     != GET_MODE_SIZE (mode)))
1635               abort ();
1636
1637             if ((VECTOR_MODE_P (op0_mode)
1638                  && (GET_MODE_INNER (mode)
1639                      != GET_MODE_INNER (op0_mode)))
1640                 || (!VECTOR_MODE_P (op0_mode)
1641                     && GET_MODE_INNER (mode) != op0_mode))
1642               abort ();
1643
1644             if ((VECTOR_MODE_P (op1_mode)
1645                  && (GET_MODE_INNER (mode)
1646                      != GET_MODE_INNER (op1_mode)))
1647                 || (!VECTOR_MODE_P (op1_mode)
1648                     && GET_MODE_INNER (mode) != op1_mode))
1649               abort ();
1650
1651             if ((GET_CODE (trueop0) == CONST_VECTOR
1652                  || GET_CODE (trueop0) == CONST_INT
1653                  || GET_CODE (trueop0) == CONST_DOUBLE)
1654                 && (GET_CODE (trueop1) == CONST_VECTOR
1655                     || GET_CODE (trueop1) == CONST_INT
1656                     || GET_CODE (trueop1) == CONST_DOUBLE))
1657               {
1658                 int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
1659                 unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
1660                 rtvec v = rtvec_alloc (n_elts);
1661                 unsigned int i;
1662                 unsigned in_n_elts = 1;
1663
1664                 if (VECTOR_MODE_P (op0_mode))
1665                   in_n_elts = (GET_MODE_SIZE (op0_mode) / elt_size);
1666                 for (i = 0; i < n_elts; i++)
1667                   {
1668                     if (i < in_n_elts)
1669                       {
1670                         if (!VECTOR_MODE_P (op0_mode))
1671                           RTVEC_ELT (v, i) = trueop0;
1672                         else
1673                           RTVEC_ELT (v, i) = CONST_VECTOR_ELT (trueop0, i);
1674                       }
1675                     else
1676                       {
1677                         if (!VECTOR_MODE_P (op1_mode))
1678                           RTVEC_ELT (v, i) = trueop1;
1679                         else
1680                           RTVEC_ELT (v, i) = CONST_VECTOR_ELT (trueop1,
1681                                                                i - in_n_elts);
1682                       }
1683                   }
1684
1685                 return gen_rtx_CONST_VECTOR (mode, v);
1686               }
1687           }
1688           return 0;
1689
1690         default:
1691           abort ();
1692         }
1693
1694       return 0;
1695     }
1696
1697   /* Get the integer argument values in two forms:
1698      zero-extended in ARG0, ARG1 and sign-extended in ARG0S, ARG1S.  */
1699
1700   arg0 = INTVAL (trueop0);
1701   arg1 = INTVAL (trueop1);
1702
1703   if (width < HOST_BITS_PER_WIDE_INT)
1704     {
1705       arg0 &= ((HOST_WIDE_INT) 1 << width) - 1;
1706       arg1 &= ((HOST_WIDE_INT) 1 << width) - 1;
1707
1708       arg0s = arg0;
1709       if (arg0s & ((HOST_WIDE_INT) 1 << (width - 1)))
1710         arg0s |= ((HOST_WIDE_INT) (-1) << width);
1711
1712       arg1s = arg1;
1713       if (arg1s & ((HOST_WIDE_INT) 1 << (width - 1)))
1714         arg1s |= ((HOST_WIDE_INT) (-1) << width);
1715     }
1716   else
1717     {
1718       arg0s = arg0;
1719       arg1s = arg1;
1720     }
1721
1722   /* Compute the value of the arithmetic.  */
1723
1724   switch (code)
1725     {
1726     case PLUS:
1727       val = arg0s + arg1s;
1728       break;
1729
1730     case MINUS:
1731       val = arg0s - arg1s;
1732       break;
1733
1734     case MULT:
1735       val = arg0s * arg1s;
1736       break;
1737
1738     case DIV:
1739       if (arg1s == 0
1740           || (arg0s == (HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)
1741               && arg1s == -1))
1742         return 0;
1743       val = arg0s / arg1s;
1744       break;
1745
1746     case MOD:
1747       if (arg1s == 0
1748           || (arg0s == (HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)
1749               && arg1s == -1))
1750         return 0;
1751       val = arg0s % arg1s;
1752       break;
1753
1754     case UDIV:
1755       if (arg1 == 0
1756           || (arg0s == (HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)
1757               && arg1s == -1))
1758         return 0;
1759       val = (unsigned HOST_WIDE_INT) arg0 / arg1;
1760       break;
1761
1762     case UMOD:
1763       if (arg1 == 0
1764           || (arg0s == (HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)
1765               && arg1s == -1))
1766         return 0;
1767       val = (unsigned HOST_WIDE_INT) arg0 % arg1;
1768       break;
1769
1770     case AND:
1771       val = arg0 & arg1;
1772       break;
1773
1774     case IOR:
1775       val = arg0 | arg1;
1776       break;
1777
1778     case XOR:
1779       val = arg0 ^ arg1;
1780       break;
1781
1782     case LSHIFTRT:
1783       /* If shift count is undefined, don't fold it; let the machine do
1784          what it wants.  But truncate it if the machine will do that.  */
1785       if (arg1 < 0)
1786         return 0;
1787
1788 #ifdef SHIFT_COUNT_TRUNCATED
1789       if (SHIFT_COUNT_TRUNCATED)
1790         arg1 %= width;
1791 #endif
1792
1793       val = ((unsigned HOST_WIDE_INT) arg0) >> arg1;
1794       break;
1795
1796     case ASHIFT:
1797       if (arg1 < 0)
1798         return 0;
1799
1800 #ifdef SHIFT_COUNT_TRUNCATED
1801       if (SHIFT_COUNT_TRUNCATED)
1802         arg1 %= width;
1803 #endif
1804
1805       val = ((unsigned HOST_WIDE_INT) arg0) << arg1;
1806       break;
1807
1808     case ASHIFTRT:
1809       if (arg1 < 0)
1810         return 0;
1811
1812 #ifdef SHIFT_COUNT_TRUNCATED
1813       if (SHIFT_COUNT_TRUNCATED)
1814         arg1 %= width;
1815 #endif
1816
1817       val = arg0s >> arg1;
1818
1819       /* Bootstrap compiler may not have sign extended the right shift.
1820          Manually extend the sign to insure bootstrap cc matches gcc.  */
1821       if (arg0s < 0 && arg1 > 0)
1822         val |= ((HOST_WIDE_INT) -1) << (HOST_BITS_PER_WIDE_INT - arg1);
1823
1824       break;
1825
1826     case ROTATERT:
1827       if (arg1 < 0)
1828         return 0;
1829
1830       arg1 %= width;
1831       val = ((((unsigned HOST_WIDE_INT) arg0) << (width - arg1))
1832              | (((unsigned HOST_WIDE_INT) arg0) >> arg1));
1833       break;
1834
1835     case ROTATE:
1836       if (arg1 < 0)
1837         return 0;
1838
1839       arg1 %= width;
1840       val = ((((unsigned HOST_WIDE_INT) arg0) << arg1)
1841              | (((unsigned HOST_WIDE_INT) arg0) >> (width - arg1)));
1842       break;
1843
1844     case COMPARE:
1845       /* Do nothing here.  */
1846       return 0;
1847
1848     case SMIN:
1849       val = arg0s <= arg1s ? arg0s : arg1s;
1850       break;
1851
1852     case UMIN:
1853       val = ((unsigned HOST_WIDE_INT) arg0
1854              <= (unsigned HOST_WIDE_INT) arg1 ? arg0 : arg1);
1855       break;
1856
1857     case SMAX:
1858       val = arg0s > arg1s ? arg0s : arg1s;
1859       break;
1860
1861     case UMAX:
1862       val = ((unsigned HOST_WIDE_INT) arg0
1863              > (unsigned HOST_WIDE_INT) arg1 ? arg0 : arg1);
1864       break;
1865
1866     case SS_PLUS:
1867     case US_PLUS:
1868     case SS_MINUS:
1869     case US_MINUS:
1870       /* ??? There are simplifications that can be done.  */
1871       return 0;
1872
1873     default:
1874       abort ();
1875     }
1876
1877   val = trunc_int_for_mode (val, mode);
1878
1879   return GEN_INT (val);
1880 }
1881 \f
1882 /* Simplify a PLUS or MINUS, at least one of whose operands may be another
1883    PLUS or MINUS.
1884
1885    Rather than test for specific case, we do this by a brute-force method
1886    and do all possible simplifications until no more changes occur.  Then
1887    we rebuild the operation.
1888
1889    If FORCE is true, then always generate the rtx.  This is used to
1890    canonicalize stuff emitted from simplify_gen_binary.  Note that this
1891    can still fail if the rtx is too complex.  It won't fail just because
1892    the result is not 'simpler' than the input, however.  */
1893
1894 struct simplify_plus_minus_op_data
1895 {
1896   rtx op;
1897   int neg;
1898 };
1899
1900 static int
1901 simplify_plus_minus_op_data_cmp (p1, p2)
1902      const void *p1;
1903      const void *p2;
1904 {
1905   const struct simplify_plus_minus_op_data *d1 = p1;
1906   const struct simplify_plus_minus_op_data *d2 = p2;
1907
1908   return (commutative_operand_precedence (d2->op)
1909           - commutative_operand_precedence (d1->op));
1910 }
1911
1912 static rtx
1913 simplify_plus_minus (code, mode, op0, op1, force)
1914      enum rtx_code code;
1915      enum machine_mode mode;
1916      rtx op0, op1;
1917      int force;
1918 {
1919   struct simplify_plus_minus_op_data ops[8];
1920   rtx result, tem;
1921   int n_ops = 2, input_ops = 2, input_consts = 0, n_consts;
1922   int first, negate, changed;
1923   int i, j;
1924
1925   memset ((char *) ops, 0, sizeof ops);
1926
1927   /* Set up the two operands and then expand them until nothing has been
1928      changed.  If we run out of room in our array, give up; this should
1929      almost never happen.  */
1930
1931   ops[0].op = op0;
1932   ops[0].neg = 0;
1933   ops[1].op = op1;
1934   ops[1].neg = (code == MINUS);
1935
1936   do
1937     {
1938       changed = 0;
1939
1940       for (i = 0; i < n_ops; i++)
1941         {
1942           rtx this_op = ops[i].op;
1943           int this_neg = ops[i].neg;
1944           enum rtx_code this_code = GET_CODE (this_op);
1945
1946           switch (this_code)
1947             {
1948             case PLUS:
1949             case MINUS:
1950               if (n_ops == 7)
1951                 return NULL_RTX;
1952
1953               ops[n_ops].op = XEXP (this_op, 1);
1954               ops[n_ops].neg = (this_code == MINUS) ^ this_neg;
1955               n_ops++;
1956
1957               ops[i].op = XEXP (this_op, 0);
1958               input_ops++;
1959               changed = 1;
1960               break;
1961
1962             case NEG:
1963               ops[i].op = XEXP (this_op, 0);
1964               ops[i].neg = ! this_neg;
1965               changed = 1;
1966               break;
1967
1968             case CONST:
1969               if (n_ops < 7
1970                   && GET_CODE (XEXP (this_op, 0)) == PLUS
1971                   && CONSTANT_P (XEXP (XEXP (this_op, 0), 0))
1972                   && CONSTANT_P (XEXP (XEXP (this_op, 0), 1)))
1973                 {
1974                   ops[i].op = XEXP (XEXP (this_op, 0), 0);
1975                   ops[n_ops].op = XEXP (XEXP (this_op, 0), 1);
1976                   ops[n_ops].neg = this_neg;
1977                   n_ops++;
1978                   input_consts++;
1979                   changed = 1;
1980                 }
1981               break;
1982
1983             case NOT:
1984               /* ~a -> (-a - 1) */
1985               if (n_ops != 7)
1986                 {
1987                   ops[n_ops].op = constm1_rtx;
1988                   ops[n_ops++].neg = this_neg;
1989                   ops[i].op = XEXP (this_op, 0);
1990                   ops[i].neg = !this_neg;
1991                   changed = 1;
1992                 }
1993               break;
1994
1995             case CONST_INT:
1996               if (this_neg)
1997                 {
1998                   ops[i].op = neg_const_int (mode, this_op);
1999                   ops[i].neg = 0;
2000                   changed = 1;
2001                 }
2002               break;
2003
2004             default:
2005               break;
2006             }
2007         }
2008     }
2009   while (changed);
2010
2011   /* If we only have two operands, we can't do anything.  */
2012   if (n_ops <= 2 && !force)
2013     return NULL_RTX;
2014
2015   /* Count the number of CONSTs we didn't split above.  */
2016   for (i = 0; i < n_ops; i++)
2017     if (GET_CODE (ops[i].op) == CONST)
2018       input_consts++;
2019
2020   /* Now simplify each pair of operands until nothing changes.  The first
2021      time through just simplify constants against each other.  */
2022
2023   first = 1;
2024   do
2025     {
2026       changed = first;
2027
2028       for (i = 0; i < n_ops - 1; i++)
2029         for (j = i + 1; j < n_ops; j++)
2030           {
2031             rtx lhs = ops[i].op, rhs = ops[j].op;
2032             int lneg = ops[i].neg, rneg = ops[j].neg;
2033
2034             if (lhs != 0 && rhs != 0
2035                 && (! first || (CONSTANT_P (lhs) && CONSTANT_P (rhs))))
2036               {
2037                 enum rtx_code ncode = PLUS;
2038
2039                 if (lneg != rneg)
2040                   {
2041                     ncode = MINUS;
2042                     if (lneg)
2043                       tem = lhs, lhs = rhs, rhs = tem;
2044                   }
2045                 else if (swap_commutative_operands_p (lhs, rhs))
2046                   tem = lhs, lhs = rhs, rhs = tem;
2047
2048                 tem = simplify_binary_operation (ncode, mode, lhs, rhs);
2049
2050                 /* Reject "simplifications" that just wrap the two
2051                    arguments in a CONST.  Failure to do so can result
2052                    in infinite recursion with simplify_binary_operation
2053                    when it calls us to simplify CONST operations.  */
2054                 if (tem
2055                     && ! (GET_CODE (tem) == CONST
2056                           && GET_CODE (XEXP (tem, 0)) == ncode
2057                           && XEXP (XEXP (tem, 0), 0) == lhs
2058                           && XEXP (XEXP (tem, 0), 1) == rhs)
2059                     /* Don't allow -x + -1 -> ~x simplifications in the
2060                        first pass.  This allows us the chance to combine
2061                        the -1 with other constants.  */
2062                     && ! (first
2063                           && GET_CODE (tem) == NOT
2064                           && XEXP (tem, 0) == rhs))
2065                   {
2066                     lneg &= rneg;
2067                     if (GET_CODE (tem) == NEG)
2068                       tem = XEXP (tem, 0), lneg = !lneg;
2069                     if (GET_CODE (tem) == CONST_INT && lneg)
2070                       tem = neg_const_int (mode, tem), lneg = 0;
2071
2072                     ops[i].op = tem;
2073                     ops[i].neg = lneg;
2074                     ops[j].op = NULL_RTX;
2075                     changed = 1;
2076                   }
2077               }
2078           }
2079
2080       first = 0;
2081     }
2082   while (changed);
2083
2084   /* Pack all the operands to the lower-numbered entries.  */
2085   for (i = 0, j = 0; j < n_ops; j++)
2086     if (ops[j].op)
2087       ops[i++] = ops[j];
2088   n_ops = i;
2089
2090   /* Sort the operations based on swap_commutative_operands_p.  */
2091   qsort (ops, n_ops, sizeof (*ops), simplify_plus_minus_op_data_cmp);
2092
2093   /* We suppressed creation of trivial CONST expressions in the
2094      combination loop to avoid recursion.  Create one manually now.
2095      The combination loop should have ensured that there is exactly
2096      one CONST_INT, and the sort will have ensured that it is last
2097      in the array and that any other constant will be next-to-last.  */
2098
2099   if (n_ops > 1
2100       && GET_CODE (ops[n_ops - 1].op) == CONST_INT
2101       && CONSTANT_P (ops[n_ops - 2].op))
2102     {
2103       rtx value = ops[n_ops - 1].op;
2104       if (ops[n_ops - 1].neg ^ ops[n_ops - 2].neg)
2105         value = neg_const_int (mode, value);
2106       ops[n_ops - 2].op = plus_constant (ops[n_ops - 2].op, INTVAL (value));
2107       n_ops--;
2108     }
2109
2110   /* Count the number of CONSTs that we generated.  */
2111   n_consts = 0;
2112   for (i = 0; i < n_ops; i++)
2113     if (GET_CODE (ops[i].op) == CONST)
2114       n_consts++;
2115
2116   /* Give up if we didn't reduce the number of operands we had.  Make
2117      sure we count a CONST as two operands.  If we have the same
2118      number of operands, but have made more CONSTs than before, this
2119      is also an improvement, so accept it.  */
2120   if (!force
2121       && (n_ops + n_consts > input_ops
2122           || (n_ops + n_consts == input_ops && n_consts <= input_consts)))
2123     return NULL_RTX;
2124
2125   /* Put a non-negated operand first.  If there aren't any, make all
2126      operands positive and negate the whole thing later.  */
2127
2128   negate = 0;
2129   for (i = 0; i < n_ops && ops[i].neg; i++)
2130     continue;
2131   if (i == n_ops)
2132     {
2133       for (i = 0; i < n_ops; i++)
2134         ops[i].neg = 0;
2135       negate = 1;
2136     }
2137   else if (i != 0)
2138     {
2139       tem = ops[0].op;
2140       ops[0] = ops[i];
2141       ops[i].op = tem;
2142       ops[i].neg = 1;
2143     }
2144
2145   /* Now make the result by performing the requested operations.  */
2146   result = ops[0].op;
2147   for (i = 1; i < n_ops; i++)
2148     result = gen_rtx_fmt_ee (ops[i].neg ? MINUS : PLUS,
2149                              mode, result, ops[i].op);
2150
2151   return negate ? gen_rtx_NEG (mode, result) : result;
2152 }
2153
2154 /* Like simplify_binary_operation except used for relational operators.
2155    MODE is the mode of the operands, not that of the result.  If MODE
2156    is VOIDmode, both operands must also be VOIDmode and we compare the
2157    operands in "infinite precision".
2158
2159    If no simplification is possible, this function returns zero.  Otherwise,
2160    it returns either const_true_rtx or const0_rtx.  */
2161
2162 rtx
2163 simplify_relational_operation (code, mode, op0, op1)
2164      enum rtx_code code;
2165      enum machine_mode mode;
2166      rtx op0, op1;
2167 {
2168   int equal, op0lt, op0ltu, op1lt, op1ltu;
2169   rtx tem;
2170   rtx trueop0;
2171   rtx trueop1;
2172
2173   if (mode == VOIDmode
2174       && (GET_MODE (op0) != VOIDmode
2175           || GET_MODE (op1) != VOIDmode))
2176     abort ();
2177
2178   /* If op0 is a compare, extract the comparison arguments from it.  */
2179   if (GET_CODE (op0) == COMPARE && op1 == const0_rtx)
2180     op1 = XEXP (op0, 1), op0 = XEXP (op0, 0);
2181
2182   trueop0 = avoid_constant_pool_reference (op0);
2183   trueop1 = avoid_constant_pool_reference (op1);
2184
2185   /* We can't simplify MODE_CC values since we don't know what the
2186      actual comparison is.  */
2187   if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC || CC0_P (op0))
2188     return 0;
2189
2190   /* Make sure the constant is second.  */
2191   if (swap_commutative_operands_p (trueop0, trueop1))
2192     {
2193       tem = op0, op0 = op1, op1 = tem;
2194       tem = trueop0, trueop0 = trueop1, trueop1 = tem;
2195       code = swap_condition (code);
2196     }
2197
2198   /* For integer comparisons of A and B maybe we can simplify A - B and can
2199      then simplify a comparison of that with zero.  If A and B are both either
2200      a register or a CONST_INT, this can't help; testing for these cases will
2201      prevent infinite recursion here and speed things up.
2202
2203      If CODE is an unsigned comparison, then we can never do this optimization,
2204      because it gives an incorrect result if the subtraction wraps around zero.
2205      ANSI C defines unsigned operations such that they never overflow, and
2206      thus such cases can not be ignored.  */
2207
2208   if (INTEGRAL_MODE_P (mode) && trueop1 != const0_rtx
2209       && ! ((GET_CODE (op0) == REG || GET_CODE (trueop0) == CONST_INT)
2210             && (GET_CODE (op1) == REG || GET_CODE (trueop1) == CONST_INT))
2211       && 0 != (tem = simplify_binary_operation (MINUS, mode, op0, op1))
2212       && code != GTU && code != GEU && code != LTU && code != LEU)
2213     return simplify_relational_operation (signed_condition (code),
2214                                           mode, tem, const0_rtx);
2215
2216   if (flag_unsafe_math_optimizations && code == ORDERED)
2217     return const_true_rtx;
2218
2219   if (flag_unsafe_math_optimizations && code == UNORDERED)
2220     return const0_rtx;
2221
2222   /* For modes without NaNs, if the two operands are equal, we know the
2223      result.  */
2224   if (!HONOR_NANS (GET_MODE (trueop0)) && rtx_equal_p (trueop0, trueop1))
2225     equal = 1, op0lt = 0, op0ltu = 0, op1lt = 0, op1ltu = 0;
2226
2227   /* If the operands are floating-point constants, see if we can fold
2228      the result.  */
2229   else if (GET_CODE (trueop0) == CONST_DOUBLE
2230            && GET_CODE (trueop1) == CONST_DOUBLE
2231            && GET_MODE_CLASS (GET_MODE (trueop0)) == MODE_FLOAT)
2232     {
2233       REAL_VALUE_TYPE d0, d1;
2234
2235       REAL_VALUE_FROM_CONST_DOUBLE (d0, trueop0);
2236       REAL_VALUE_FROM_CONST_DOUBLE (d1, trueop1);
2237
2238       /* Comparisons are unordered iff at least one of the values is NaN.  */
2239       if (REAL_VALUE_ISNAN (d0) || REAL_VALUE_ISNAN (d1))
2240         switch (code)
2241           {
2242           case UNEQ:
2243           case UNLT:
2244           case UNGT:
2245           case UNLE:
2246           case UNGE:
2247           case NE:
2248           case UNORDERED:
2249             return const_true_rtx;
2250           case EQ:
2251           case LT:
2252           case GT:
2253           case LE:
2254           case GE:
2255           case LTGT:
2256           case ORDERED:
2257             return const0_rtx;
2258           default:
2259             return 0;
2260           }
2261
2262       equal = REAL_VALUES_EQUAL (d0, d1);
2263       op0lt = op0ltu = REAL_VALUES_LESS (d0, d1);
2264       op1lt = op1ltu = REAL_VALUES_LESS (d1, d0);
2265     }
2266
2267   /* Otherwise, see if the operands are both integers.  */
2268   else if ((GET_MODE_CLASS (mode) == MODE_INT || mode == VOIDmode)
2269            && (GET_CODE (trueop0) == CONST_DOUBLE
2270                || GET_CODE (trueop0) == CONST_INT)
2271            && (GET_CODE (trueop1) == CONST_DOUBLE
2272                || GET_CODE (trueop1) == CONST_INT))
2273     {
2274       int width = GET_MODE_BITSIZE (mode);
2275       HOST_WIDE_INT l0s, h0s, l1s, h1s;
2276       unsigned HOST_WIDE_INT l0u, h0u, l1u, h1u;
2277
2278       /* Get the two words comprising each integer constant.  */
2279       if (GET_CODE (trueop0) == CONST_DOUBLE)
2280         {
2281           l0u = l0s = CONST_DOUBLE_LOW (trueop0);
2282           h0u = h0s = CONST_DOUBLE_HIGH (trueop0);
2283         }
2284       else
2285         {
2286           l0u = l0s = INTVAL (trueop0);
2287           h0u = h0s = HWI_SIGN_EXTEND (l0s);
2288         }
2289
2290       if (GET_CODE (trueop1) == CONST_DOUBLE)
2291         {
2292           l1u = l1s = CONST_DOUBLE_LOW (trueop1);
2293           h1u = h1s = CONST_DOUBLE_HIGH (trueop1);
2294         }
2295       else
2296         {
2297           l1u = l1s = INTVAL (trueop1);
2298           h1u = h1s = HWI_SIGN_EXTEND (l1s);
2299         }
2300
2301       /* If WIDTH is nonzero and smaller than HOST_BITS_PER_WIDE_INT,
2302          we have to sign or zero-extend the values.  */
2303       if (width != 0 && width < HOST_BITS_PER_WIDE_INT)
2304         {
2305           l0u &= ((HOST_WIDE_INT) 1 << width) - 1;
2306           l1u &= ((HOST_WIDE_INT) 1 << width) - 1;
2307
2308           if (l0s & ((HOST_WIDE_INT) 1 << (width - 1)))
2309             l0s |= ((HOST_WIDE_INT) (-1) << width);
2310
2311           if (l1s & ((HOST_WIDE_INT) 1 << (width - 1)))
2312             l1s |= ((HOST_WIDE_INT) (-1) << width);
2313         }
2314       if (width != 0 && width <= HOST_BITS_PER_WIDE_INT)
2315         h0u = h1u = 0, h0s = HWI_SIGN_EXTEND (l0s), h1s = HWI_SIGN_EXTEND (l1s);
2316
2317       equal = (h0u == h1u && l0u == l1u);
2318       op0lt = (h0s < h1s || (h0s == h1s && l0u < l1u));
2319       op1lt = (h1s < h0s || (h1s == h0s && l1u < l0u));
2320       op0ltu = (h0u < h1u || (h0u == h1u && l0u < l1u));
2321       op1ltu = (h1u < h0u || (h1u == h0u && l1u < l0u));
2322     }
2323
2324   /* Otherwise, there are some code-specific tests we can make.  */
2325   else
2326     {
2327       switch (code)
2328         {
2329         case EQ:
2330           if (trueop1 == const0_rtx && nonzero_address_p (op0))
2331             return const0_rtx;
2332           break;
2333
2334         case NE:
2335           if (trueop1 == const0_rtx && nonzero_address_p (op0))
2336             return const_true_rtx;
2337           break;
2338
2339         case GEU:
2340           /* Unsigned values are never negative.  */
2341           if (trueop1 == const0_rtx)
2342             return const_true_rtx;
2343           break;
2344
2345         case LTU:
2346           if (trueop1 == const0_rtx)
2347             return const0_rtx;
2348           break;
2349
2350         case LEU:
2351           /* Unsigned values are never greater than the largest
2352              unsigned value.  */
2353           if (GET_CODE (trueop1) == CONST_INT
2354               && (unsigned HOST_WIDE_INT) INTVAL (trueop1) == GET_MODE_MASK (mode)
2355             && INTEGRAL_MODE_P (mode))
2356           return const_true_rtx;
2357           break;
2358
2359         case GTU:
2360           if (GET_CODE (trueop1) == CONST_INT
2361               && (unsigned HOST_WIDE_INT) INTVAL (trueop1) == GET_MODE_MASK (mode)
2362               && INTEGRAL_MODE_P (mode))
2363             return const0_rtx;
2364           break;
2365
2366         case LT:
2367           /* Optimize abs(x) < 0.0.  */
2368           if (trueop1 == CONST0_RTX (mode) && !HONOR_SNANS (mode))
2369             {
2370               tem = GET_CODE (trueop0) == FLOAT_EXTEND ? XEXP (trueop0, 0)
2371                                                        : trueop0;
2372               if (GET_CODE (tem) == ABS)
2373                 return const0_rtx;
2374             }
2375           break;
2376
2377         case GE:
2378           /* Optimize abs(x) >= 0.0.  */
2379           if (trueop1 == CONST0_RTX (mode) && !HONOR_NANS (mode))
2380             {
2381               tem = GET_CODE (trueop0) == FLOAT_EXTEND ? XEXP (trueop0, 0)
2382                                                        : trueop0;
2383               if (GET_CODE (tem) == ABS)
2384                 return const_true_rtx;
2385             }
2386           break;
2387
2388         case UNGE:
2389           /* Optimize ! (abs(x) < 0.0).  */
2390           if (trueop1 == CONST0_RTX (mode))
2391             {
2392               tem = GET_CODE (trueop0) == FLOAT_EXTEND ? XEXP (trueop0, 0)
2393                                                        : trueop0;
2394               if (GET_CODE (tem) == ABS)
2395                 return const_true_rtx;
2396             }
2397           break;
2398
2399         default:
2400           break;
2401         }
2402
2403       return 0;
2404     }
2405
2406   /* If we reach here, EQUAL, OP0LT, OP0LTU, OP1LT, and OP1LTU are set
2407      as appropriate.  */
2408   switch (code)
2409     {
2410     case EQ:
2411     case UNEQ:
2412       return equal ? const_true_rtx : const0_rtx;
2413     case NE:
2414     case LTGT:
2415       return ! equal ? const_true_rtx : const0_rtx;
2416     case LT:
2417     case UNLT:
2418       return op0lt ? const_true_rtx : const0_rtx;
2419     case GT:
2420     case UNGT:
2421       return op1lt ? const_true_rtx : const0_rtx;
2422     case LTU:
2423       return op0ltu ? const_true_rtx : const0_rtx;
2424     case GTU:
2425       return op1ltu ? const_true_rtx : const0_rtx;
2426     case LE:
2427     case UNLE:
2428       return equal || op0lt ? const_true_rtx : const0_rtx;
2429     case GE:
2430     case UNGE:
2431       return equal || op1lt ? const_true_rtx : const0_rtx;
2432     case LEU:
2433       return equal || op0ltu ? const_true_rtx : const0_rtx;
2434     case GEU:
2435       return equal || op1ltu ? const_true_rtx : const0_rtx;
2436     case ORDERED:
2437       return const_true_rtx;
2438     case UNORDERED:
2439       return const0_rtx;
2440     default:
2441       abort ();
2442     }
2443 }
2444 \f
2445 /* Simplify CODE, an operation with result mode MODE and three operands,
2446    OP0, OP1, and OP2.  OP0_MODE was the mode of OP0 before it became
2447    a constant.  Return 0 if no simplifications is possible.  */
2448
2449 rtx
2450 simplify_ternary_operation (code, mode, op0_mode, op0, op1, op2)
2451      enum rtx_code code;
2452      enum machine_mode mode, op0_mode;
2453      rtx op0, op1, op2;
2454 {
2455   unsigned int width = GET_MODE_BITSIZE (mode);
2456
2457   /* VOIDmode means "infinite" precision.  */
2458   if (width == 0)
2459     width = HOST_BITS_PER_WIDE_INT;
2460
2461   switch (code)
2462     {
2463     case SIGN_EXTRACT:
2464     case ZERO_EXTRACT:
2465       if (GET_CODE (op0) == CONST_INT
2466           && GET_CODE (op1) == CONST_INT
2467           && GET_CODE (op2) == CONST_INT
2468           && ((unsigned) INTVAL (op1) + (unsigned) INTVAL (op2) <= width)
2469           && width <= (unsigned) HOST_BITS_PER_WIDE_INT)
2470         {
2471           /* Extracting a bit-field from a constant */
2472           HOST_WIDE_INT val = INTVAL (op0);
2473
2474           if (BITS_BIG_ENDIAN)
2475             val >>= (GET_MODE_BITSIZE (op0_mode)
2476                      - INTVAL (op2) - INTVAL (op1));
2477           else
2478             val >>= INTVAL (op2);
2479
2480           if (HOST_BITS_PER_WIDE_INT != INTVAL (op1))
2481             {
2482               /* First zero-extend.  */
2483               val &= ((HOST_WIDE_INT) 1 << INTVAL (op1)) - 1;
2484               /* If desired, propagate sign bit.  */
2485               if (code == SIGN_EXTRACT
2486                   && (val & ((HOST_WIDE_INT) 1 << (INTVAL (op1) - 1))))
2487                 val |= ~ (((HOST_WIDE_INT) 1 << INTVAL (op1)) - 1);
2488             }
2489
2490           /* Clear the bits that don't belong in our mode,
2491              unless they and our sign bit are all one.
2492              So we get either a reasonable negative value or a reasonable
2493              unsigned value for this mode.  */
2494           if (width < HOST_BITS_PER_WIDE_INT
2495               && ((val & ((HOST_WIDE_INT) (-1) << (width - 1)))
2496                   != ((HOST_WIDE_INT) (-1) << (width - 1))))
2497             val &= ((HOST_WIDE_INT) 1 << width) - 1;
2498
2499           return GEN_INT (val);
2500         }
2501       break;
2502
2503     case IF_THEN_ELSE:
2504       if (GET_CODE (op0) == CONST_INT)
2505         return op0 != const0_rtx ? op1 : op2;
2506
2507       /* Convert a == b ? b : a to "a".  */
2508       if (GET_CODE (op0) == NE && ! side_effects_p (op0)
2509           && !HONOR_NANS (mode)
2510           && rtx_equal_p (XEXP (op0, 0), op1)
2511           && rtx_equal_p (XEXP (op0, 1), op2))
2512         return op1;
2513       else if (GET_CODE (op0) == EQ && ! side_effects_p (op0)
2514           && !HONOR_NANS (mode)
2515           && rtx_equal_p (XEXP (op0, 1), op1)
2516           && rtx_equal_p (XEXP (op0, 0), op2))
2517         return op2;
2518       else if (GET_RTX_CLASS (GET_CODE (op0)) == '<' && ! side_effects_p (op0))
2519         {
2520           enum machine_mode cmp_mode = (GET_MODE (XEXP (op0, 0)) == VOIDmode
2521                                         ? GET_MODE (XEXP (op0, 1))
2522                                         : GET_MODE (XEXP (op0, 0)));
2523           rtx temp;
2524           if (cmp_mode == VOIDmode)
2525             cmp_mode = op0_mode;
2526           temp = simplify_relational_operation (GET_CODE (op0), cmp_mode,
2527                                                 XEXP (op0, 0), XEXP (op0, 1));
2528
2529           /* See if any simplifications were possible.  */
2530           if (temp == const0_rtx)
2531             return op2;
2532           else if (temp == const1_rtx)
2533             return op1;
2534           else if (temp)
2535             op0 = temp;
2536
2537           /* Look for happy constants in op1 and op2.  */
2538           if (GET_CODE (op1) == CONST_INT && GET_CODE (op2) == CONST_INT)
2539             {
2540               HOST_WIDE_INT t = INTVAL (op1);
2541               HOST_WIDE_INT f = INTVAL (op2);
2542
2543               if (t == STORE_FLAG_VALUE && f == 0)
2544                 code = GET_CODE (op0);
2545               else if (t == 0 && f == STORE_FLAG_VALUE)
2546                 {
2547                   enum rtx_code tmp;
2548                   tmp = reversed_comparison_code (op0, NULL_RTX);
2549                   if (tmp == UNKNOWN)
2550                     break;
2551                   code = tmp;
2552                 }
2553               else
2554                 break;
2555
2556               return gen_rtx_fmt_ee (code, mode, XEXP (op0, 0), XEXP (op0, 1));
2557             }
2558         }
2559       break;
2560     case VEC_MERGE:
2561       if (GET_MODE (op0) != mode
2562           || GET_MODE (op1) != mode
2563           || !VECTOR_MODE_P (mode))
2564         abort ();
2565       op2 = avoid_constant_pool_reference (op2);
2566       if (GET_CODE (op2) == CONST_INT)
2567         {
2568           int elt_size = GET_MODE_SIZE (GET_MODE_INNER (mode));
2569           unsigned n_elts = (GET_MODE_SIZE (mode) / elt_size);
2570           int mask = (1 << n_elts) - 1;
2571
2572           if (!(INTVAL (op2) & mask))
2573             return op1;
2574           if ((INTVAL (op2) & mask) == mask)
2575             return op0;
2576
2577           op0 = avoid_constant_pool_reference (op0);
2578           op1 = avoid_constant_pool_reference (op1);
2579           if (GET_CODE (op0) == CONST_VECTOR
2580               && GET_CODE (op1) == CONST_VECTOR)
2581             {
2582               rtvec v = rtvec_alloc (n_elts);
2583               unsigned int i;
2584
2585               for (i = 0; i < n_elts; i++)
2586                 RTVEC_ELT (v, i) = (INTVAL (op2) & (1 << i)
2587                                     ? CONST_VECTOR_ELT (op0, i)
2588                                     : CONST_VECTOR_ELT (op1, i));
2589               return gen_rtx_CONST_VECTOR (mode, v);
2590             }
2591         }
2592       break;
2593
2594     default:
2595       abort ();
2596     }
2597
2598   return 0;
2599 }
2600
2601 /* Simplify SUBREG:OUTERMODE(OP:INNERMODE, BYTE)
2602    Return 0 if no simplifications is possible.  */
2603 rtx
2604 simplify_subreg (outermode, op, innermode, byte)
2605      rtx op;
2606      unsigned int byte;
2607      enum machine_mode outermode, innermode;
2608 {
2609   /* Little bit of sanity checking.  */
2610   if (innermode == VOIDmode || outermode == VOIDmode
2611       || innermode == BLKmode || outermode == BLKmode)
2612     abort ();
2613
2614   if (GET_MODE (op) != innermode
2615       && GET_MODE (op) != VOIDmode)
2616     abort ();
2617
2618   if (byte % GET_MODE_SIZE (outermode)
2619       || byte >= GET_MODE_SIZE (innermode))
2620     abort ();
2621
2622   if (outermode == innermode && !byte)
2623     return op;
2624
2625   /* Simplify subregs of vector constants.  */
2626   if (GET_CODE (op) == CONST_VECTOR)
2627     {
2628       int elt_size = GET_MODE_SIZE (GET_MODE_INNER (innermode));
2629       const unsigned int offset = byte / elt_size;
2630       rtx elt;
2631
2632       if (GET_MODE_INNER (innermode) == outermode)
2633         {
2634           elt = CONST_VECTOR_ELT (op, offset);
2635
2636           /* ?? We probably don't need this copy_rtx because constants
2637              can be shared.  ?? */
2638
2639           return copy_rtx (elt);
2640         }
2641       else if (GET_MODE_INNER (innermode) == GET_MODE_INNER (outermode)
2642                && GET_MODE_SIZE (innermode) > GET_MODE_SIZE (outermode))
2643         {
2644           return (gen_rtx_CONST_VECTOR
2645                   (outermode,
2646                    gen_rtvec_v (GET_MODE_NUNITS (outermode),
2647                                 &CONST_VECTOR_ELT (op, offset))));
2648         }
2649       else if (GET_MODE_CLASS (outermode) == MODE_INT
2650                && (GET_MODE_SIZE (outermode) % elt_size == 0))
2651         {
2652           /* This happens when the target register size is smaller then
2653              the vector mode, and we synthesize operations with vectors
2654              of elements that are smaller than the register size.  */
2655           HOST_WIDE_INT sum = 0, high = 0;
2656           unsigned n_elts = (GET_MODE_SIZE (outermode) / elt_size);
2657           unsigned i = BYTES_BIG_ENDIAN ? offset : offset + n_elts - 1;
2658           unsigned step = BYTES_BIG_ENDIAN ? 1 : -1;
2659           int shift = BITS_PER_UNIT * elt_size;
2660
2661           for (; n_elts--; i += step)
2662             {
2663               elt = CONST_VECTOR_ELT (op, i);
2664               if (GET_CODE (elt) == CONST_DOUBLE
2665                   && GET_MODE_CLASS (GET_MODE (elt)) == MODE_FLOAT)
2666                 {
2667                   elt = gen_lowpart_common (int_mode_for_mode (GET_MODE (elt)),
2668                                             elt);
2669                   if (! elt)
2670                     return NULL_RTX;
2671                 }
2672               if (GET_CODE (elt) != CONST_INT)
2673                 return NULL_RTX;
2674               /* Avoid overflow.  */
2675               if (high >> (HOST_BITS_PER_WIDE_INT - shift))
2676                 return NULL_RTX;
2677               high = high << shift | sum >> (HOST_BITS_PER_WIDE_INT - shift);
2678               sum = (sum << shift) + INTVAL (elt);
2679             }
2680           if (GET_MODE_BITSIZE (outermode) <= HOST_BITS_PER_WIDE_INT)
2681             return GEN_INT (trunc_int_for_mode (sum, outermode));
2682           else if (GET_MODE_BITSIZE (outermode) == 2* HOST_BITS_PER_WIDE_INT)
2683             return immed_double_const (sum, high, outermode);
2684           else
2685             return NULL_RTX;
2686         }
2687       else if (GET_MODE_CLASS (outermode) == MODE_INT
2688                && (elt_size % GET_MODE_SIZE (outermode) == 0))
2689         {
2690           enum machine_mode new_mode
2691             = int_mode_for_mode (GET_MODE_INNER (innermode));
2692           int subbyte = byte % elt_size;
2693
2694           op = simplify_subreg (new_mode, op, innermode, byte - subbyte);
2695           if (! op)
2696             return NULL_RTX;
2697           return simplify_subreg (outermode, op, new_mode, subbyte);
2698         }
2699       else if (GET_MODE_CLASS (outermode) == MODE_INT)
2700         /* This shouldn't happen, but let's not do anything stupid.  */
2701         return NULL_RTX;
2702     }
2703
2704   /* Attempt to simplify constant to non-SUBREG expression.  */
2705   if (CONSTANT_P (op))
2706     {
2707       int offset, part;
2708       unsigned HOST_WIDE_INT val = 0;
2709
2710       if (GET_MODE_CLASS (outermode) == MODE_VECTOR_INT
2711           || GET_MODE_CLASS (outermode) == MODE_VECTOR_FLOAT)
2712         {
2713           /* Construct a CONST_VECTOR from individual subregs.  */
2714           enum machine_mode submode = GET_MODE_INNER (outermode);
2715           int subsize = GET_MODE_UNIT_SIZE (outermode);
2716           int i, elts = GET_MODE_NUNITS (outermode);
2717           rtvec v = rtvec_alloc (elts);
2718           rtx elt;
2719
2720           for (i = 0; i < elts; i++, byte += subsize)
2721             {
2722               /* This might fail, e.g. if taking a subreg from a SYMBOL_REF.  */
2723               /* ??? It would be nice if we could actually make such subregs
2724                  on targets that allow such relocations.  */
2725               if (byte >= GET_MODE_UNIT_SIZE (innermode))
2726                 elt = CONST0_RTX (submode);
2727               else
2728                 elt = simplify_subreg (submode, op, innermode, byte);
2729               if (! elt)
2730                 return NULL_RTX;
2731               RTVEC_ELT (v, i) = elt;
2732             }
2733           return gen_rtx_CONST_VECTOR (outermode, v);
2734         }
2735
2736       /* ??? This code is partly redundant with code below, but can handle
2737          the subregs of floats and similar corner cases.
2738          Later it we should move all simplification code here and rewrite
2739          GEN_LOWPART_IF_POSSIBLE, GEN_HIGHPART, OPERAND_SUBWORD and friends
2740          using SIMPLIFY_SUBREG.  */
2741       if (subreg_lowpart_offset (outermode, innermode) == byte
2742           && GET_CODE (op) != CONST_VECTOR)
2743         {
2744           rtx new = gen_lowpart_if_possible (outermode, op);
2745           if (new)
2746             return new;
2747         }
2748
2749       /* Similar comment as above apply here.  */
2750       if (GET_MODE_SIZE (outermode) == UNITS_PER_WORD
2751           && GET_MODE_SIZE (innermode) > UNITS_PER_WORD
2752           && GET_MODE_CLASS (outermode) == MODE_INT)
2753         {
2754           rtx new = constant_subword (op,
2755                                       (byte / UNITS_PER_WORD),
2756                                       innermode);
2757           if (new)
2758             return new;
2759         }
2760
2761       if (GET_MODE_CLASS (outermode) != MODE_INT
2762           && GET_MODE_CLASS (outermode) != MODE_CC)
2763         {
2764           enum machine_mode new_mode = int_mode_for_mode (outermode);
2765
2766           if (new_mode != innermode || byte != 0)
2767             {
2768               op = simplify_subreg (new_mode, op, innermode, byte);
2769               if (! op)
2770                 return NULL_RTX;
2771               return simplify_subreg (outermode, op, new_mode, 0);
2772             }
2773         }
2774
2775       offset = byte * BITS_PER_UNIT;
2776       switch (GET_CODE (op))
2777         {
2778         case CONST_DOUBLE:
2779           if (GET_MODE (op) != VOIDmode)
2780             break;
2781
2782           /* We can't handle this case yet.  */
2783           if (GET_MODE_BITSIZE (outermode) >= HOST_BITS_PER_WIDE_INT)
2784             return NULL_RTX;
2785
2786           part = offset >= HOST_BITS_PER_WIDE_INT;
2787           if ((BITS_PER_WORD > HOST_BITS_PER_WIDE_INT
2788                && BYTES_BIG_ENDIAN)
2789               || (BITS_PER_WORD <= HOST_BITS_PER_WIDE_INT
2790                   && WORDS_BIG_ENDIAN))
2791             part = !part;
2792           val = part ? CONST_DOUBLE_HIGH (op) : CONST_DOUBLE_LOW (op);
2793           offset %= HOST_BITS_PER_WIDE_INT;
2794
2795           /* We've already picked the word we want from a double, so
2796              pretend this is actually an integer.  */
2797           innermode = mode_for_size (HOST_BITS_PER_WIDE_INT, MODE_INT, 0);
2798
2799           /* FALLTHROUGH */
2800         case CONST_INT:
2801           if (GET_CODE (op) == CONST_INT)
2802             val = INTVAL (op);
2803
2804           /* We don't handle synthesizing of non-integral constants yet.  */
2805           if (GET_MODE_CLASS (outermode) != MODE_INT)
2806             return NULL_RTX;
2807
2808           if (BYTES_BIG_ENDIAN || WORDS_BIG_ENDIAN)
2809             {
2810               if (WORDS_BIG_ENDIAN)
2811                 offset = (GET_MODE_BITSIZE (innermode)
2812                           - GET_MODE_BITSIZE (outermode) - offset);
2813               if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN
2814                   && GET_MODE_SIZE (outermode) < UNITS_PER_WORD)
2815                 offset = (offset + BITS_PER_WORD - GET_MODE_BITSIZE (outermode)
2816                           - 2 * (offset % BITS_PER_WORD));
2817             }
2818
2819           if (offset >= HOST_BITS_PER_WIDE_INT)
2820             return ((HOST_WIDE_INT) val < 0) ? constm1_rtx : const0_rtx;
2821           else
2822             {
2823               val >>= offset;
2824               if (GET_MODE_BITSIZE (outermode) < HOST_BITS_PER_WIDE_INT)
2825                 val = trunc_int_for_mode (val, outermode);
2826               return GEN_INT (val);
2827             }
2828         default:
2829           break;
2830         }
2831     }
2832
2833   /* Changing mode twice with SUBREG => just change it once,
2834      or not at all if changing back op starting mode.  */
2835   if (GET_CODE (op) == SUBREG)
2836     {
2837       enum machine_mode innermostmode = GET_MODE (SUBREG_REG (op));
2838       int final_offset = byte + SUBREG_BYTE (op);
2839       rtx new;
2840
2841       if (outermode == innermostmode
2842           && byte == 0 && SUBREG_BYTE (op) == 0)
2843         return SUBREG_REG (op);
2844
2845       /* The SUBREG_BYTE represents offset, as if the value were stored
2846          in memory.  Irritating exception is paradoxical subreg, where
2847          we define SUBREG_BYTE to be 0.  On big endian machines, this
2848          value should be negative.  For a moment, undo this exception.  */
2849       if (byte == 0 && GET_MODE_SIZE (innermode) < GET_MODE_SIZE (outermode))
2850         {
2851           int difference = (GET_MODE_SIZE (innermode) - GET_MODE_SIZE (outermode));
2852           if (WORDS_BIG_ENDIAN)
2853             final_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
2854           if (BYTES_BIG_ENDIAN)
2855             final_offset += difference % UNITS_PER_WORD;
2856         }
2857       if (SUBREG_BYTE (op) == 0
2858           && GET_MODE_SIZE (innermostmode) < GET_MODE_SIZE (innermode))
2859         {
2860           int difference = (GET_MODE_SIZE (innermostmode) - GET_MODE_SIZE (innermode));
2861           if (WORDS_BIG_ENDIAN)
2862             final_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
2863           if (BYTES_BIG_ENDIAN)
2864             final_offset += difference % UNITS_PER_WORD;
2865         }
2866
2867       /* See whether resulting subreg will be paradoxical.  */
2868       if (GET_MODE_SIZE (innermostmode) > GET_MODE_SIZE (outermode))
2869         {
2870           /* In nonparadoxical subregs we can't handle negative offsets.  */
2871           if (final_offset < 0)
2872             return NULL_RTX;
2873           /* Bail out in case resulting subreg would be incorrect.  */
2874           if (final_offset % GET_MODE_SIZE (outermode)
2875               || (unsigned) final_offset >= GET_MODE_SIZE (innermostmode))
2876             return NULL_RTX;
2877         }
2878       else
2879         {
2880           int offset = 0;
2881           int difference = (GET_MODE_SIZE (innermostmode) - GET_MODE_SIZE (outermode));
2882
2883           /* In paradoxical subreg, see if we are still looking on lower part.
2884              If so, our SUBREG_BYTE will be 0.  */
2885           if (WORDS_BIG_ENDIAN)
2886             offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
2887           if (BYTES_BIG_ENDIAN)
2888             offset += difference % UNITS_PER_WORD;
2889           if (offset == final_offset)
2890             final_offset = 0;
2891           else
2892             return NULL_RTX;
2893         }
2894
2895       /* Recurse for futher possible simplifications.  */
2896       new = simplify_subreg (outermode, SUBREG_REG (op),
2897                              GET_MODE (SUBREG_REG (op)),
2898                              final_offset);
2899       if (new)
2900         return new;
2901       return gen_rtx_SUBREG (outermode, SUBREG_REG (op), final_offset);
2902     }
2903
2904   /* SUBREG of a hard register => just change the register number
2905      and/or mode.  If the hard register is not valid in that mode,
2906      suppress this simplification.  If the hard register is the stack,
2907      frame, or argument pointer, leave this as a SUBREG.  */
2908
2909   if (REG_P (op)
2910       && (! REG_FUNCTION_VALUE_P (op)
2911           || ! rtx_equal_function_value_matters)
2912       && REGNO (op) < FIRST_PSEUDO_REGISTER
2913 #ifdef CANNOT_CHANGE_MODE_CLASS
2914       && ! (REG_CANNOT_CHANGE_MODE_P (REGNO (op), innermode, outermode)
2915             && GET_MODE_CLASS (innermode) != MODE_COMPLEX_INT
2916             && GET_MODE_CLASS (innermode) != MODE_COMPLEX_FLOAT)
2917 #endif
2918       && ((reload_completed && !frame_pointer_needed)
2919           || (REGNO (op) != FRAME_POINTER_REGNUM
2920 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2921               && REGNO (op) != HARD_FRAME_POINTER_REGNUM
2922 #endif
2923              ))
2924 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2925       && REGNO (op) != ARG_POINTER_REGNUM
2926 #endif
2927       && REGNO (op) != STACK_POINTER_REGNUM)
2928     {
2929       int final_regno = subreg_hard_regno (gen_rtx_SUBREG (outermode, op, byte),
2930                                            0);
2931
2932       /* ??? We do allow it if the current REG is not valid for
2933          its mode.  This is a kludge to work around how float/complex
2934          arguments are passed on 32-bit SPARC and should be fixed.  */
2935       if (HARD_REGNO_MODE_OK (final_regno, outermode)
2936           || ! HARD_REGNO_MODE_OK (REGNO (op), innermode))
2937         {
2938           rtx x = gen_rtx_REG_offset (op, outermode, final_regno, byte);
2939
2940           /* Propagate original regno.  We don't have any way to specify
2941              the offset inside original regno, so do so only for lowpart.
2942              The information is used only by alias analysis that can not
2943              grog partial register anyway.  */
2944
2945           if (subreg_lowpart_offset (outermode, innermode) == byte)
2946             ORIGINAL_REGNO (x) = ORIGINAL_REGNO (op);
2947           return x;
2948         }
2949     }
2950
2951   /* If we have a SUBREG of a register that we are replacing and we are
2952      replacing it with a MEM, make a new MEM and try replacing the
2953      SUBREG with it.  Don't do this if the MEM has a mode-dependent address
2954      or if we would be widening it.  */
2955
2956   if (GET_CODE (op) == MEM
2957       && ! mode_dependent_address_p (XEXP (op, 0))
2958       /* Allow splitting of volatile memory references in case we don't
2959          have instruction to move the whole thing.  */
2960       && (! MEM_VOLATILE_P (op)
2961           || ! have_insn_for (SET, innermode))
2962       && GET_MODE_SIZE (outermode) <= GET_MODE_SIZE (GET_MODE (op)))
2963     return adjust_address_nv (op, outermode, byte);
2964
2965   /* Handle complex values represented as CONCAT
2966      of real and imaginary part.  */
2967   if (GET_CODE (op) == CONCAT)
2968     {
2969       int is_realpart = byte < GET_MODE_UNIT_SIZE (innermode);
2970       rtx part = is_realpart ? XEXP (op, 0) : XEXP (op, 1);
2971       unsigned int final_offset;
2972       rtx res;
2973
2974       final_offset = byte % (GET_MODE_UNIT_SIZE (innermode));
2975       res = simplify_subreg (outermode, part, GET_MODE (part), final_offset);
2976       if (res)
2977         return res;
2978       /* We can at least simplify it by referring directly to the relevant part.  */
2979       return gen_rtx_SUBREG (outermode, part, final_offset);
2980     }
2981
2982   return NULL_RTX;
2983 }
2984 /* Make a SUBREG operation or equivalent if it folds.  */
2985
2986 rtx
2987 simplify_gen_subreg (outermode, op, innermode, byte)
2988      rtx op;
2989      unsigned int byte;
2990      enum machine_mode outermode, innermode;
2991 {
2992   rtx new;
2993   /* Little bit of sanity checking.  */
2994   if (innermode == VOIDmode || outermode == VOIDmode
2995       || innermode == BLKmode || outermode == BLKmode)
2996     abort ();
2997
2998   if (GET_MODE (op) != innermode
2999       && GET_MODE (op) != VOIDmode)
3000     abort ();
3001
3002   if (byte % GET_MODE_SIZE (outermode)
3003       || byte >= GET_MODE_SIZE (innermode))
3004     abort ();
3005
3006   if (GET_CODE (op) == QUEUED)
3007     return NULL_RTX;
3008
3009   new = simplify_subreg (outermode, op, innermode, byte);
3010   if (new)
3011     return new;
3012
3013   if (GET_CODE (op) == SUBREG || GET_MODE (op) == VOIDmode)
3014     return NULL_RTX;
3015
3016   return gen_rtx_SUBREG (outermode, op, byte);
3017 }
3018 /* Simplify X, an rtx expression.
3019
3020    Return the simplified expression or NULL if no simplifications
3021    were possible.
3022
3023    This is the preferred entry point into the simplification routines;
3024    however, we still allow passes to call the more specific routines.
3025
3026    Right now GCC has three (yes, three) major bodies of RTL simplification
3027    code that need to be unified.
3028
3029         1. fold_rtx in cse.c.  This code uses various CSE specific
3030            information to aid in RTL simplification.
3031
3032         2. simplify_rtx in combine.c.  Similar to fold_rtx, except that
3033            it uses combine specific information to aid in RTL
3034            simplification.
3035
3036         3. The routines in this file.
3037
3038
3039    Long term we want to only have one body of simplification code; to
3040    get to that state I recommend the following steps:
3041
3042         1. Pour over fold_rtx & simplify_rtx and move any simplifications
3043            which are not pass dependent state into these routines.
3044
3045         2. As code is moved by #1, change fold_rtx & simplify_rtx to
3046            use this routine whenever possible.
3047
3048         3. Allow for pass dependent state to be provided to these
3049            routines and add simplifications based on the pass dependent
3050            state.  Remove code from cse.c & combine.c that becomes
3051            redundant/dead.
3052
3053     It will take time, but ultimately the compiler will be easier to
3054     maintain and improve.  It's totally silly that when we add a
3055     simplification that it needs to be added to 4 places (3 for RTL
3056     simplification and 1 for tree simplification.  */
3057
3058 rtx
3059 simplify_rtx (x)
3060      rtx x;
3061 {
3062   enum rtx_code code = GET_CODE (x);
3063   enum machine_mode mode = GET_MODE (x);
3064
3065   switch (GET_RTX_CLASS (code))
3066     {
3067     case '1':
3068       return simplify_unary_operation (code, mode,
3069                                        XEXP (x, 0), GET_MODE (XEXP (x, 0)));
3070     case 'c':
3071       if (swap_commutative_operands_p (XEXP (x, 0), XEXP (x, 1)))
3072         {
3073           rtx tem;
3074
3075           tem = XEXP (x, 0);
3076           XEXP (x, 0) = XEXP (x, 1);
3077           XEXP (x, 1) = tem;
3078           return simplify_binary_operation (code, mode,
3079                                             XEXP (x, 0), XEXP (x, 1));
3080         }
3081
3082     case '2':
3083       return simplify_binary_operation (code, mode, XEXP (x, 0), XEXP (x, 1));
3084
3085     case '3':
3086     case 'b':
3087       return simplify_ternary_operation (code, mode, GET_MODE (XEXP (x, 0)),
3088                                          XEXP (x, 0), XEXP (x, 1),
3089                                          XEXP (x, 2));
3090
3091     case '<':
3092       return simplify_relational_operation (code,
3093                                             ((GET_MODE (XEXP (x, 0))
3094                                               != VOIDmode)
3095                                              ? GET_MODE (XEXP (x, 0))
3096                                              : GET_MODE (XEXP (x, 1))),
3097                                             XEXP (x, 0), XEXP (x, 1));
3098     case 'x':
3099       if (code == SUBREG)
3100         return simplify_gen_subreg (mode, SUBREG_REG (x),
3101                                     GET_MODE (SUBREG_REG (x)),
3102                                     SUBREG_BYTE (x));
3103       if (code == CONSTANT_P_RTX)
3104         {
3105           if (CONSTANT_P (XEXP (x, 0)))
3106             return const1_rtx;
3107         }
3108       return NULL;
3109     default:
3110       return NULL;
3111     }
3112 }