gcc/optabs-query.c

   1 /* IR-agnostic target query functions relating to optabs
   2    Copyright (C) 1987-2017 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "target.h"
  25 #include "insn-codes.h"
  26 #include "optabs-query.h"
  27 #include "optabs-libfuncs.h"
  28 #include "insn-config.h"
  29 #include "rtl.h"
  30 #include "recog.h"
  31
  32 struct target_optabs default_target_optabs;
  33 struct target_optabs *this_fn_optabs = &default_target_optabs;
  34 #if SWITCHABLE_TARGET
  35 struct target_optabs *this_target_optabs = &default_target_optabs;
  36 #endif
  37
  38 /* Return the insn used to perform conversion OP from mode FROM_MODE
  39    to mode TO_MODE; return CODE_FOR_nothing if the target does not have
  40    such an insn, or if it is unsuitable for optimization type OPT_TYPE.  */
  41
  42 insn_code
  43 convert_optab_handler (convert_optab optab, machine_mode to_mode,
  44                        machine_mode from_mode, optimization_type opt_type)
  45 {
  46   insn_code icode = convert_optab_handler (optab, to_mode, from_mode);
  47   if (icode == CODE_FOR_nothing
  48       || !targetm.optab_supported_p (optab, to_mode, from_mode, opt_type))
  49     return CODE_FOR_nothing;
  50   return icode;
  51 }
  52
  53 /* Return the insn used to implement mode MODE of OP; return
  54    CODE_FOR_nothing if the target does not have such an insn,
  55    or if it is unsuitable for optimization type OPT_TYPE.  */
  56
  57 insn_code
  58 direct_optab_handler (convert_optab optab, machine_mode mode,
  59                       optimization_type opt_type)
  60 {
  61   insn_code icode = direct_optab_handler (optab, mode);
  62   if (icode == CODE_FOR_nothing
  63       || !targetm.optab_supported_p (optab, mode, mode, opt_type))
  64     return CODE_FOR_nothing;
  65   return icode;
  66 }
  67
  68 /* Enumerates the possible types of structure operand to an
  69    extraction_insn.  */
  70 enum extraction_type { ET_unaligned_mem, ET_reg };
  71
  72 /* Check whether insv, extv or extzv pattern ICODE can be used for an
  73    insertion or extraction of type TYPE on a structure of mode MODE.
  74    Return true if so and fill in *INSN accordingly.  STRUCT_OP is the
  75    operand number of the structure (the first sign_extract or zero_extract
  76    operand) and FIELD_OP is the operand number of the field (the other
  77    side of the set from the sign_extract or zero_extract).  */
  78
  79 static bool
  80 get_traditional_extraction_insn (extraction_insn *insn,
  81                                  enum extraction_type type,
  82                                  machine_mode mode,
  83                                  enum insn_code icode,
  84                                  int struct_op, int field_op)
  85 {
  86   const struct insn_data_d *data = &insn_data[icode];
  87
  88   machine_mode struct_mode = data->operand[struct_op].mode;
  89   if (struct_mode == VOIDmode)
  90     struct_mode = word_mode;
  91   if (mode != struct_mode)
  92     return false;
  93
  94   machine_mode field_mode = data->operand[field_op].mode;
  95   if (field_mode == VOIDmode)
  96     field_mode = word_mode;
  97
  98   machine_mode pos_mode = data->operand[struct_op + 2].mode;
  99   if (pos_mode == VOIDmode)
 100     pos_mode = word_mode;
 101
 102   insn->icode = icode;
 103   insn->field_mode = as_a <scalar_int_mode> (field_mode);
 104   if (type == ET_unaligned_mem)
 105     insn->struct_mode = byte_mode;
 106   else if (struct_mode == BLKmode)
 107     insn->struct_mode = opt_scalar_int_mode ();
 108   else
 109     insn->struct_mode = as_a <scalar_int_mode> (struct_mode);
 110   insn->pos_mode = as_a <scalar_int_mode> (pos_mode);
 111   return true;
 112 }
 113
 114 /* Return true if an optab exists to perform an insertion or extraction
 115    of type TYPE in mode MODE.  Describe the instruction in *INSN if so.
 116
 117    REG_OPTAB is the optab to use for register structures and
 118    MISALIGN_OPTAB is the optab to use for misaligned memory structures.
 119    POS_OP is the operand number of the bit position.  */
 120
 121 static bool
 122 get_optab_extraction_insn (struct extraction_insn *insn,
 123                            enum extraction_type type,
 124                            machine_mode mode, direct_optab reg_optab,
 125                            direct_optab misalign_optab, int pos_op)
 126 {
 127   direct_optab optab = (type == ET_unaligned_mem ? misalign_optab : reg_optab);
 128   enum insn_code icode = direct_optab_handler (optab, mode);
 129   if (icode == CODE_FOR_nothing)
 130     return false;
 131
 132   const struct insn_data_d *data = &insn_data[icode];
 133
 134   machine_mode pos_mode = data->operand[pos_op].mode;
 135   if (pos_mode == VOIDmode)
 136     pos_mode = word_mode;
 137
 138   insn->icode = icode;
 139   insn->field_mode = as_a <scalar_int_mode> (mode);
 140   if (type == ET_unaligned_mem)
 141     insn->struct_mode = opt_scalar_int_mode ();
 142   else
 143     insn->struct_mode = insn->field_mode;
 144   insn->pos_mode = as_a <scalar_int_mode> (pos_mode);
 145   return true;
 146 }
 147
 148 /* Return true if an instruction exists to perform an insertion or
 149    extraction (PATTERN says which) of type TYPE in mode MODE.
 150    Describe the instruction in *INSN if so.  */
 151
 152 static bool
 153 get_extraction_insn (extraction_insn *insn,
 154                      enum extraction_pattern pattern,
 155                      enum extraction_type type,
 156                      machine_mode mode)
 157 {
 158   switch (pattern)
 159     {
 160     case EP_insv:
 161       if (targetm.have_insv ()
 162           && get_traditional_extraction_insn (insn, type, mode,
 163                                               targetm.code_for_insv, 0, 3))
 164         return true;
 165       return get_optab_extraction_insn (insn, type, mode, insv_optab,
 166                                         insvmisalign_optab, 2);
 167
 168     case EP_extv:
 169       if (targetm.have_extv ()
 170           && get_traditional_extraction_insn (insn, type, mode,
 171                                               targetm.code_for_extv, 1, 0))
 172         return true;
 173       return get_optab_extraction_insn (insn, type, mode, extv_optab,
 174                                         extvmisalign_optab, 3);
 175
 176     case EP_extzv:
 177       if (targetm.have_extzv ()
 178           && get_traditional_extraction_insn (insn, type, mode,
 179                                               targetm.code_for_extzv, 1, 0))
 180         return true;
 181       return get_optab_extraction_insn (insn, type, mode, extzv_optab,
 182                                         extzvmisalign_optab, 3);
 183
 184     default:
 185       gcc_unreachable ();
 186     }
 187 }
 188
 189 /* Return true if an instruction exists to access a field of mode
 190    FIELDMODE in a structure that has STRUCT_BITS significant bits.
 191    Describe the "best" such instruction in *INSN if so.  PATTERN and
 192    TYPE describe the type of insertion or extraction we want to perform.
 193
 194    For an insertion, the number of significant structure bits includes
 195    all bits of the target.  For an extraction, it need only include the
 196    most significant bit of the field.  Larger widths are acceptable
 197    in both cases.  */
 198
 199 static bool
 200 get_best_extraction_insn (extraction_insn *insn,
 201                           enum extraction_pattern pattern,
 202                           enum extraction_type type,
 203                           unsigned HOST_WIDE_INT struct_bits,
 204                           machine_mode field_mode)
 205 {
 206   opt_scalar_int_mode mode_iter;
 207   FOR_EACH_MODE_FROM (mode_iter, smallest_int_mode_for_size (struct_bits))
 208     {
 209       scalar_int_mode mode = mode_iter.require ();
 210       if (get_extraction_insn (insn, pattern, type, mode))
 211         {
 212           FOR_EACH_MODE_FROM (mode_iter, mode)
 213             {
 214               mode = mode_iter.require ();
 215               if (GET_MODE_SIZE (mode) > GET_MODE_SIZE (field_mode)
 216                   || TRULY_NOOP_TRUNCATION_MODES_P (insn->field_mode,
 217                                                     field_mode))
 218                 break;
 219               get_extraction_insn (insn, pattern, type, mode);
 220             }
 221           return true;
 222         }
 223     }
 224   return false;
 225 }
 226
 227 /* Return true if an instruction exists to access a field of mode
 228    FIELDMODE in a register structure that has STRUCT_BITS significant bits.
 229    Describe the "best" such instruction in *INSN if so.  PATTERN describes
 230    the type of insertion or extraction we want to perform.
 231
 232    For an insertion, the number of significant structure bits includes
 233    all bits of the target.  For an extraction, it need only include the
 234    most significant bit of the field.  Larger widths are acceptable
 235    in both cases.  */
 236
 237 bool
 238 get_best_reg_extraction_insn (extraction_insn *insn,
 239                               enum extraction_pattern pattern,
 240                               unsigned HOST_WIDE_INT struct_bits,
 241                               machine_mode field_mode)
 242 {
 243   return get_best_extraction_insn (insn, pattern, ET_reg, struct_bits,
 244                                    field_mode);
 245 }
 246
 247 /* Return true if an instruction exists to access a field of BITSIZE
 248    bits starting BITNUM bits into a memory structure.  Describe the
 249    "best" such instruction in *INSN if so.  PATTERN describes the type
 250    of insertion or extraction we want to perform and FIELDMODE is the
 251    natural mode of the extracted field.
 252
 253    The instructions considered here only access bytes that overlap
 254    the bitfield; they do not touch any surrounding bytes.  */
 255
 256 bool
 257 get_best_mem_extraction_insn (extraction_insn *insn,
 258                               enum extraction_pattern pattern,
 259                               HOST_WIDE_INT bitsize, HOST_WIDE_INT bitnum,
 260                               machine_mode field_mode)
 261 {
 262   unsigned HOST_WIDE_INT struct_bits = (bitnum % BITS_PER_UNIT
 263                                         + bitsize
 264                                         + BITS_PER_UNIT - 1);
 265   struct_bits -= struct_bits % BITS_PER_UNIT;
 266   return get_best_extraction_insn (insn, pattern, ET_unaligned_mem,
 267                                    struct_bits, field_mode);
 268 }
 269
 270 /* Return the insn code used to extend FROM_MODE to TO_MODE.
 271    UNSIGNEDP specifies zero-extension instead of sign-extension.  If
 272    no such operation exists, CODE_FOR_nothing will be returned.  */
 273
 274 enum insn_code
 275 can_extend_p (machine_mode to_mode, machine_mode from_mode,
 276               int unsignedp)
 277 {
 278   if (unsignedp < 0 && targetm.have_ptr_extend ())
 279     return targetm.code_for_ptr_extend;
 280
 281   convert_optab tab = unsignedp ? zext_optab : sext_optab;
 282   return convert_optab_handler (tab, to_mode, from_mode);
 283 }
 284
 285 /* Return the insn code to convert fixed-point mode FIXMODE to floating-point
 286    mode FLTMODE, or CODE_FOR_nothing if no such instruction exists.
 287    UNSIGNEDP specifies whether FIXMODE is unsigned.  */
 288
 289 enum insn_code
 290 can_float_p (machine_mode fltmode, machine_mode fixmode,
 291              int unsignedp)
 292 {
 293   convert_optab tab = unsignedp ? ufloat_optab : sfloat_optab;
 294   return convert_optab_handler (tab, fltmode, fixmode);
 295 }
 296
 297 /* Return the insn code to convert floating-point mode FLTMODE to fixed-point
 298    mode FIXMODE, or CODE_FOR_nothing if no such instruction exists.
 299    UNSIGNEDP specifies whether FIXMODE is unsigned.
 300
 301    On a successful return, set *TRUNCP_PTR to true if it is necessary to
 302    output an explicit FTRUNC before the instruction.  */
 303
 304 enum insn_code
 305 can_fix_p (machine_mode fixmode, machine_mode fltmode,
 306            int unsignedp, bool *truncp_ptr)
 307 {
 308   convert_optab tab;
 309   enum insn_code icode;
 310
 311   tab = unsignedp ? ufixtrunc_optab : sfixtrunc_optab;
 312   icode = convert_optab_handler (tab, fixmode, fltmode);
 313   if (icode != CODE_FOR_nothing)
 314     {
 315       *truncp_ptr = false;
 316       return icode;
 317     }
 318
 319   /* FIXME: This requires a port to define both FIX and FTRUNC pattern
 320      for this to work.  We need to rework the fix* and ftrunc* patterns
 321      and documentation.  */
 322   tab = unsignedp ? ufix_optab : sfix_optab;
 323   icode = convert_optab_handler (tab, fixmode, fltmode);
 324   if (icode != CODE_FOR_nothing
 325       && optab_handler (ftrunc_optab, fltmode) != CODE_FOR_nothing)
 326     {
 327       *truncp_ptr = true;
 328       return icode;
 329     }
 330
 331   return CODE_FOR_nothing;
 332 }
 333
 334 /* Return nonzero if a conditional move of mode MODE is supported.
 335
 336    This function is for combine so it can tell whether an insn that looks
 337    like a conditional move is actually supported by the hardware.  If we
 338    guess wrong we lose a bit on optimization, but that's it.  */
 339 /* ??? sparc64 supports conditionally moving integers values based on fp
 340    comparisons, and vice versa.  How do we handle them?  */
 341
 342 bool
 343 can_conditionally_move_p (machine_mode mode)
 344 {
 345   return direct_optab_handler (movcc_optab, mode) != CODE_FOR_nothing;
 346 }
 347
 348 /* Return true if VEC_PERM_EXPR of arbitrary input vectors can be
 349    expanded using SIMD extensions of the CPU.  SEL may be NULL, which
 350    stands for an unknown constant.  Note that additional permutations
 351    representing whole-vector shifts may also be handled via the vec_shr
 352    optab, but only where the second input vector is entirely constant
 353    zeroes; this case is not dealt with here.  */
 354
 355 bool
 356 can_vec_perm_p (machine_mode mode, bool variable, vec_perm_indices *sel)
 357 {
 358   machine_mode qimode;
 359
 360   /* If the target doesn't implement a vector mode for the vector type,
 361      then no operations are supported.  */
 362   if (!VECTOR_MODE_P (mode))
 363     return false;
 364
 365   if (!variable)
 366     {
 367       if (direct_optab_handler (vec_perm_const_optab, mode) != CODE_FOR_nothing
 368           && (sel == NULL
 369               || targetm.vectorize.vec_perm_const_ok == NULL
 370               || targetm.vectorize.vec_perm_const_ok (mode, *sel)))
 371         return true;
 372     }
 373
 374   if (direct_optab_handler (vec_perm_optab, mode) != CODE_FOR_nothing)
 375     return true;
 376
 377   /* We allow fallback to a QI vector mode, and adjust the mask.  */
 378   if (GET_MODE_INNER (mode) == QImode
 379       || !mode_for_vector (QImode, GET_MODE_SIZE (mode)).exists (&qimode)
 380       || !VECTOR_MODE_P (qimode))
 381     return false;
 382
 383   /* ??? For completeness, we ought to check the QImode version of
 384       vec_perm_const_optab.  But all users of this implicit lowering
 385       feature implement the variable vec_perm_optab.  */
 386   if (direct_optab_handler (vec_perm_optab, qimode) == CODE_FOR_nothing)
 387     return false;
 388
 389   /* In order to support the lowering of variable permutations,
 390      we need to support shifts and adds.  */
 391   if (variable)
 392     {
 393       if (GET_MODE_UNIT_SIZE (mode) > 2
 394           && optab_handler (ashl_optab, mode) == CODE_FOR_nothing
 395           && optab_handler (vashl_optab, mode) == CODE_FOR_nothing)
 396         return false;
 397       if (optab_handler (add_optab, qimode) == CODE_FOR_nothing)
 398         return false;
 399     }
 400
 401   return true;
 402 }
 403
 404 /* Like optab_handler, but for widening_operations that have a
 405    TO_MODE and a FROM_MODE.  */
 406
 407 enum insn_code
 408 widening_optab_handler (optab op, machine_mode to_mode,
 409                         machine_mode from_mode)
 410 {
 411   unsigned scode = (op << 16) | to_mode;
 412   if (to_mode != from_mode && from_mode != VOIDmode)
 413     {
 414       /* ??? Why does find_widening_optab_handler_and_mode attempt to
 415          widen things that can't be widened?  E.g. add_optab... */
 416       if (op > LAST_CONV_OPTAB)
 417         return CODE_FOR_nothing;
 418       scode |= from_mode << 8;
 419     }
 420   return raw_optab_handler (scode);
 421 }
 422
 423 /* Find a widening optab even if it doesn't widen as much as we want.
 424    E.g. if from_mode is HImode, and to_mode is DImode, and there is no
 425    direct HI->SI insn, then return SI->DI, if that exists.
 426    If PERMIT_NON_WIDENING is non-zero then this can be used with
 427    non-widening optabs also.  */
 428
 429 enum insn_code
 430 find_widening_optab_handler_and_mode (optab op, machine_mode to_mode,
 431                                       machine_mode from_mode,
 432                                       int permit_non_widening,
 433                                       machine_mode *found_mode)
 434 {
 435   for (; (permit_non_widening || from_mode != to_mode)
 436          && GET_MODE_SIZE (from_mode) <= GET_MODE_SIZE (to_mode)
 437          && from_mode != VOIDmode;
 438        from_mode = GET_MODE_WIDER_MODE (from_mode).else_void ())
 439     {
 440       enum insn_code handler = widening_optab_handler (op, to_mode,
 441                                                        from_mode);
 442
 443       if (handler != CODE_FOR_nothing)
 444         {
 445           if (found_mode)
 446             *found_mode = from_mode;
 447           return handler;
 448         }
 449     }
 450
 451   return CODE_FOR_nothing;
 452 }
 453
 454 /* Return non-zero if a highpart multiply is supported of can be synthisized.
 455    For the benefit of expand_mult_highpart, the return value is 1 for direct,
 456    2 for even/odd widening, and 3 for hi/lo widening.  */
 457
 458 int
 459 can_mult_highpart_p (machine_mode mode, bool uns_p)
 460 {
 461   optab op;
 462   unsigned i, nunits;
 463
 464   op = uns_p ? umul_highpart_optab : smul_highpart_optab;
 465   if (optab_handler (op, mode) != CODE_FOR_nothing)
 466     return 1;
 467
 468   /* If the mode is an integral vector, synth from widening operations.  */
 469   if (GET_MODE_CLASS (mode) != MODE_VECTOR_INT)
 470     return 0;
 471
 472   nunits = GET_MODE_NUNITS (mode);
 473
 474   op = uns_p ? vec_widen_umult_even_optab : vec_widen_smult_even_optab;
 475   if (optab_handler (op, mode) != CODE_FOR_nothing)
 476     {
 477       op = uns_p ? vec_widen_umult_odd_optab : vec_widen_smult_odd_optab;
 478       if (optab_handler (op, mode) != CODE_FOR_nothing)
 479         {
 480           auto_vec_perm_indices sel (nunits);
 481           for (i = 0; i < nunits; ++i)
 482             sel.quick_push (!BYTES_BIG_ENDIAN
 483                             + (i & ~1)
 484                             + ((i & 1) ? nunits : 0));
 485           if (can_vec_perm_p (mode, false, &sel))
 486             return 2;
 487         }
 488     }
 489
 490   op = uns_p ? vec_widen_umult_hi_optab : vec_widen_smult_hi_optab;
 491   if (optab_handler (op, mode) != CODE_FOR_nothing)
 492     {
 493       op = uns_p ? vec_widen_umult_lo_optab : vec_widen_smult_lo_optab;
 494       if (optab_handler (op, mode) != CODE_FOR_nothing)
 495         {
 496           auto_vec_perm_indices sel (nunits);
 497           for (i = 0; i < nunits; ++i)
 498             sel.quick_push (2 * i + (BYTES_BIG_ENDIAN ? 0 : 1));
 499           if (can_vec_perm_p (mode, false, &sel))
 500             return 3;
 501         }
 502     }
 503
 504   return 0;
 505 }
 506
 507 /* Return true if target supports vector masked load/store for mode.  */
 508
 509 bool
 510 can_vec_mask_load_store_p (machine_mode mode,
 511                            machine_mode mask_mode,
 512                            bool is_load)
 513 {
 514   optab op = is_load ? maskload_optab : maskstore_optab;
 515   machine_mode vmode;
 516   unsigned int vector_sizes;
 517
 518   /* If mode is vector mode, check it directly.  */
 519   if (VECTOR_MODE_P (mode))
 520     return convert_optab_handler (op, mode, mask_mode) != CODE_FOR_nothing;
 521
 522   /* Otherwise, return true if there is some vector mode with
 523      the mask load/store supported.  */
 524
 525   /* See if there is any chance the mask load or store might be
 526      vectorized.  If not, punt.  */
 527   scalar_mode smode;
 528   if (!is_a <scalar_mode> (mode, &smode))
 529     return false;
 530
 531   vmode = targetm.vectorize.preferred_simd_mode (smode);
 532   if (!VECTOR_MODE_P (vmode))
 533     return false;
 534
 535   if ((targetm.vectorize.get_mask_mode
 536        (GET_MODE_NUNITS (vmode), GET_MODE_SIZE (vmode)).exists (&mask_mode))
 537       && convert_optab_handler (op, vmode, mask_mode) != CODE_FOR_nothing)
 538     return true;
 539
 540   vector_sizes = targetm.vectorize.autovectorize_vector_sizes ();
 541   while (vector_sizes != 0)
 542     {
 543       unsigned int cur = 1 << floor_log2 (vector_sizes);
 544       vector_sizes &= ~cur;
 545       if (cur <= GET_MODE_SIZE (smode))
 546         continue;
 547       unsigned int nunits = cur / GET_MODE_SIZE (smode);
 548       if (mode_for_vector (smode, nunits).exists (&vmode)
 549           && VECTOR_MODE_P (vmode)
 550           && targetm.vectorize.get_mask_mode (nunits, cur).exists (&mask_mode)
 551           && convert_optab_handler (op, vmode, mask_mode) != CODE_FOR_nothing)
 552         return true;
 553     }
 554   return false;
 555 }
 556
 557 /* Return true if there is a compare_and_swap pattern.  */
 558
 559 bool
 560 can_compare_and_swap_p (machine_mode mode, bool allow_libcall)
 561 {
 562   enum insn_code icode;
 563
 564   /* Check for __atomic_compare_and_swap.  */
 565   icode = direct_optab_handler (atomic_compare_and_swap_optab, mode);
 566   if (icode != CODE_FOR_nothing)
 567     return true;
 568
 569   /* Check for __sync_compare_and_swap.  */
 570   icode = optab_handler (sync_compare_and_swap_optab, mode);
 571   if (icode != CODE_FOR_nothing)
 572     return true;
 573   if (allow_libcall && optab_libfunc (sync_compare_and_swap_optab, mode))
 574     return true;
 575
 576   /* No inline compare and swap.  */
 577   return false;
 578 }
 579
 580 /* Return true if an atomic exchange can be performed.  */
 581
 582 bool
 583 can_atomic_exchange_p (machine_mode mode, bool allow_libcall)
 584 {
 585   enum insn_code icode;
 586
 587   /* Check for __atomic_exchange.  */
 588   icode = direct_optab_handler (atomic_exchange_optab, mode);
 589   if (icode != CODE_FOR_nothing)
 590     return true;
 591
 592   /* Don't check __sync_test_and_set, as on some platforms that
 593      has reduced functionality.  Targets that really do support
 594      a proper exchange should simply be updated to the __atomics.  */
 595
 596   return can_compare_and_swap_p (mode, allow_libcall);
 597 }
 598
 599 /* Return true if an atomic load can be performed without falling back to
 600    a compare-and-swap.  */
 601
 602 bool
 603 can_atomic_load_p (machine_mode mode)
 604 {
 605   enum insn_code icode;
 606
 607   /* Does the target supports the load directly?  */
 608   icode = direct_optab_handler (atomic_load_optab, mode);
 609   if (icode != CODE_FOR_nothing)
 610     return true;
 611
 612   /* If the size of the object is greater than word size on this target,
 613      then we assume that a load will not be atomic.  Also see
 614      expand_atomic_load.  */
 615   return GET_MODE_PRECISION (mode) <= BITS_PER_WORD;
 616 }
 617
 618 /* Determine whether "1 << x" is relatively cheap in word_mode.  */
 619
 620 bool
 621 lshift_cheap_p (bool speed_p)
 622 {
 623   /* FIXME: This should be made target dependent via this "this_target"
 624      mechanism, similar to e.g. can_copy_init_p in gcse.c.  */
 625   static bool init[2] = { false, false };
 626   static bool cheap[2] = { true, true };
 627
 628   /* If the targer has no lshift in word_mode, the operation will most
 629      probably not be cheap.  ??? Does GCC even work for such targets?  */
 630   if (optab_handler (ashl_optab, word_mode) == CODE_FOR_nothing)
 631     return false;
 632
 633   if (!init[speed_p])
 634     {
 635       rtx reg = gen_raw_REG (word_mode, 10000);
 636       int cost = set_src_cost (gen_rtx_ASHIFT (word_mode, const1_rtx, reg),
 637                                word_mode, speed_p);
 638       cheap[speed_p] = cost < COSTS_N_INSNS (3);
 639       init[speed_p] = true;
 640     }
 641
 642   return cheap[speed_p];
 643 }