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 #include "vec-perm-indices.h"
  32
  33 struct target_optabs default_target_optabs;
  34 struct target_optabs *this_fn_optabs = &default_target_optabs;
  35 #if SWITCHABLE_TARGET
  36 struct target_optabs *this_target_optabs = &default_target_optabs;
  37 #endif
  38
  39 /* Return the insn used to perform conversion OP from mode FROM_MODE
  40    to mode TO_MODE; return CODE_FOR_nothing if the target does not have
  41    such an insn, or if it is unsuitable for optimization type OPT_TYPE.  */
  42
  43 insn_code
  44 convert_optab_handler (convert_optab optab, machine_mode to_mode,
  45                        machine_mode from_mode, optimization_type opt_type)
  46 {
  47   insn_code icode = convert_optab_handler (optab, to_mode, from_mode);
  48   if (icode == CODE_FOR_nothing
  49       || !targetm.optab_supported_p (optab, to_mode, from_mode, opt_type))
  50     return CODE_FOR_nothing;
  51   return icode;
  52 }
  53
  54 /* Return the insn used to implement mode MODE of OP; return
  55    CODE_FOR_nothing if the target does not have such an insn,
  56    or if it is unsuitable for optimization type OPT_TYPE.  */
  57
  58 insn_code
  59 direct_optab_handler (convert_optab optab, machine_mode mode,
  60                       optimization_type opt_type)
  61 {
  62   insn_code icode = direct_optab_handler (optab, mode);
  63   if (icode == CODE_FOR_nothing
  64       || !targetm.optab_supported_p (optab, mode, mode, opt_type))
  65     return CODE_FOR_nothing;
  66   return icode;
  67 }
  68
  69 /* Enumerates the possible types of structure operand to an
  70    extraction_insn.  */
  71 enum extraction_type { ET_unaligned_mem, ET_reg };
  72
  73 /* Check whether insv, extv or extzv pattern ICODE can be used for an
  74    insertion or extraction of type TYPE on a structure of mode MODE.
  75    Return true if so and fill in *INSN accordingly.  STRUCT_OP is the
  76    operand number of the structure (the first sign_extract or zero_extract
  77    operand) and FIELD_OP is the operand number of the field (the other
  78    side of the set from the sign_extract or zero_extract).  */
  79
  80 static bool
  81 get_traditional_extraction_insn (extraction_insn *insn,
  82                                  enum extraction_type type,
  83                                  machine_mode mode,
  84                                  enum insn_code icode,
  85                                  int struct_op, int field_op)
  86 {
  87   const struct insn_data_d *data = &insn_data[icode];
  88
  89   machine_mode struct_mode = data->operand[struct_op].mode;
  90   if (struct_mode == VOIDmode)
  91     struct_mode = word_mode;
  92   if (mode != struct_mode)
  93     return false;
  94
  95   machine_mode field_mode = data->operand[field_op].mode;
  96   if (field_mode == VOIDmode)
  97     field_mode = word_mode;
  98
  99   machine_mode pos_mode = data->operand[struct_op + 2].mode;
 100   if (pos_mode == VOIDmode)
 101     pos_mode = word_mode;
 102
 103   insn->icode = icode;
 104   insn->field_mode = as_a <scalar_int_mode> (field_mode);
 105   if (type == ET_unaligned_mem)
 106     insn->struct_mode = byte_mode;
 107   else if (struct_mode == BLKmode)
 108     insn->struct_mode = opt_scalar_int_mode ();
 109   else
 110     insn->struct_mode = as_a <scalar_int_mode> (struct_mode);
 111   insn->pos_mode = as_a <scalar_int_mode> (pos_mode);
 112   return true;
 113 }
 114
 115 /* Return true if an optab exists to perform an insertion or extraction
 116    of type TYPE in mode MODE.  Describe the instruction in *INSN if so.
 117
 118    REG_OPTAB is the optab to use for register structures and
 119    MISALIGN_OPTAB is the optab to use for misaligned memory structures.
 120    POS_OP is the operand number of the bit position.  */
 121
 122 static bool
 123 get_optab_extraction_insn (struct extraction_insn *insn,
 124                            enum extraction_type type,
 125                            machine_mode mode, direct_optab reg_optab,
 126                            direct_optab misalign_optab, int pos_op)
 127 {
 128   direct_optab optab = (type == ET_unaligned_mem ? misalign_optab : reg_optab);
 129   enum insn_code icode = direct_optab_handler (optab, mode);
 130   if (icode == CODE_FOR_nothing)
 131     return false;
 132
 133   const struct insn_data_d *data = &insn_data[icode];
 134
 135   machine_mode pos_mode = data->operand[pos_op].mode;
 136   if (pos_mode == VOIDmode)
 137     pos_mode = word_mode;
 138
 139   insn->icode = icode;
 140   insn->field_mode = as_a <scalar_int_mode> (mode);
 141   if (type == ET_unaligned_mem)
 142     insn->struct_mode = opt_scalar_int_mode ();
 143   else
 144     insn->struct_mode = insn->field_mode;
 145   insn->pos_mode = as_a <scalar_int_mode> (pos_mode);
 146   return true;
 147 }
 148
 149 /* Return true if an instruction exists to perform an insertion or
 150    extraction (PATTERN says which) of type TYPE in mode MODE.
 151    Describe the instruction in *INSN if so.  */
 152
 153 static bool
 154 get_extraction_insn (extraction_insn *insn,
 155                      enum extraction_pattern pattern,
 156                      enum extraction_type type,
 157                      machine_mode mode)
 158 {
 159   switch (pattern)
 160     {
 161     case EP_insv:
 162       if (targetm.have_insv ()
 163           && get_traditional_extraction_insn (insn, type, mode,
 164                                               targetm.code_for_insv, 0, 3))
 165         return true;
 166       return get_optab_extraction_insn (insn, type, mode, insv_optab,
 167                                         insvmisalign_optab, 2);
 168
 169     case EP_extv:
 170       if (targetm.have_extv ()
 171           && get_traditional_extraction_insn (insn, type, mode,
 172                                               targetm.code_for_extv, 1, 0))
 173         return true;
 174       return get_optab_extraction_insn (insn, type, mode, extv_optab,
 175                                         extvmisalign_optab, 3);
 176
 177     case EP_extzv:
 178       if (targetm.have_extzv ()
 179           && get_traditional_extraction_insn (insn, type, mode,
 180                                               targetm.code_for_extzv, 1, 0))
 181         return true;
 182       return get_optab_extraction_insn (insn, type, mode, extzv_optab,
 183                                         extzvmisalign_optab, 3);
 184
 185     default:
 186       gcc_unreachable ();
 187     }
 188 }
 189
 190 /* Return true if an instruction exists to access a field of mode
 191    FIELDMODE in a structure that has STRUCT_BITS significant bits.
 192    Describe the "best" such instruction in *INSN if so.  PATTERN and
 193    TYPE describe the type of insertion or extraction we want to perform.
 194
 195    For an insertion, the number of significant structure bits includes
 196    all bits of the target.  For an extraction, it need only include the
 197    most significant bit of the field.  Larger widths are acceptable
 198    in both cases.  */
 199
 200 static bool
 201 get_best_extraction_insn (extraction_insn *insn,
 202                           enum extraction_pattern pattern,
 203                           enum extraction_type type,
 204                           unsigned HOST_WIDE_INT struct_bits,
 205                           machine_mode field_mode)
 206 {
 207   opt_scalar_int_mode mode_iter;
 208   FOR_EACH_MODE_FROM (mode_iter, smallest_int_mode_for_size (struct_bits))
 209     {
 210       scalar_int_mode mode = mode_iter.require ();
 211       if (get_extraction_insn (insn, pattern, type, mode))
 212         {
 213           FOR_EACH_MODE_FROM (mode_iter, mode)
 214             {
 215               mode = mode_iter.require ();
 216               if (GET_MODE_SIZE (mode) > GET_MODE_SIZE (field_mode)
 217                   || TRULY_NOOP_TRUNCATION_MODES_P (insn->field_mode,
 218                                                     field_mode))
 219                 break;
 220               get_extraction_insn (insn, pattern, type, mode);
 221             }
 222           return true;
 223         }
 224     }
 225   return false;
 226 }
 227
 228 /* Return true if an instruction exists to access a field of mode
 229    FIELDMODE in a register structure that has STRUCT_BITS significant bits.
 230    Describe the "best" such instruction in *INSN if so.  PATTERN describes
 231    the type of insertion or extraction we want to perform.
 232
 233    For an insertion, the number of significant structure bits includes
 234    all bits of the target.  For an extraction, it need only include the
 235    most significant bit of the field.  Larger widths are acceptable
 236    in both cases.  */
 237
 238 bool
 239 get_best_reg_extraction_insn (extraction_insn *insn,
 240                               enum extraction_pattern pattern,
 241                               unsigned HOST_WIDE_INT struct_bits,
 242                               machine_mode field_mode)
 243 {
 244   return get_best_extraction_insn (insn, pattern, ET_reg, struct_bits,
 245                                    field_mode);
 246 }
 247
 248 /* Return true if an instruction exists to access a field of BITSIZE
 249    bits starting BITNUM bits into a memory structure.  Describe the
 250    "best" such instruction in *INSN if so.  PATTERN describes the type
 251    of insertion or extraction we want to perform and FIELDMODE is the
 252    natural mode of the extracted field.
 253
 254    The instructions considered here only access bytes that overlap
 255    the bitfield; they do not touch any surrounding bytes.  */
 256
 257 bool
 258 get_best_mem_extraction_insn (extraction_insn *insn,
 259                               enum extraction_pattern pattern,
 260                               HOST_WIDE_INT bitsize, HOST_WIDE_INT bitnum,
 261                               machine_mode field_mode)
 262 {
 263   unsigned HOST_WIDE_INT struct_bits = (bitnum % BITS_PER_UNIT
 264                                         + bitsize
 265                                         + BITS_PER_UNIT - 1);
 266   struct_bits -= struct_bits % BITS_PER_UNIT;
 267   return get_best_extraction_insn (insn, pattern, ET_unaligned_mem,
 268                                    struct_bits, field_mode);
 269 }
 270
 271 /* Return the insn code used to extend FROM_MODE to TO_MODE.
 272    UNSIGNEDP specifies zero-extension instead of sign-extension.  If
 273    no such operation exists, CODE_FOR_nothing will be returned.  */
 274
 275 enum insn_code
 276 can_extend_p (machine_mode to_mode, machine_mode from_mode,
 277               int unsignedp)
 278 {
 279   if (unsignedp < 0 && targetm.have_ptr_extend ())
 280     return targetm.code_for_ptr_extend;
 281
 282   convert_optab tab = unsignedp ? zext_optab : sext_optab;
 283   return convert_optab_handler (tab, to_mode, from_mode);
 284 }
 285
 286 /* Return the insn code to convert fixed-point mode FIXMODE to floating-point
 287    mode FLTMODE, or CODE_FOR_nothing if no such instruction exists.
 288    UNSIGNEDP specifies whether FIXMODE is unsigned.  */
 289
 290 enum insn_code
 291 can_float_p (machine_mode fltmode, machine_mode fixmode,
 292              int unsignedp)
 293 {
 294   convert_optab tab = unsignedp ? ufloat_optab : sfloat_optab;
 295   return convert_optab_handler (tab, fltmode, fixmode);
 296 }
 297
 298 /* Return the insn code to convert floating-point mode FLTMODE to fixed-point
 299    mode FIXMODE, or CODE_FOR_nothing if no such instruction exists.
 300    UNSIGNEDP specifies whether FIXMODE is unsigned.
 301
 302    On a successful return, set *TRUNCP_PTR to true if it is necessary to
 303    output an explicit FTRUNC before the instruction.  */
 304
 305 enum insn_code
 306 can_fix_p (machine_mode fixmode, machine_mode fltmode,
 307            int unsignedp, bool *truncp_ptr)
 308 {
 309   convert_optab tab;
 310   enum insn_code icode;
 311
 312   tab = unsignedp ? ufixtrunc_optab : sfixtrunc_optab;
 313   icode = convert_optab_handler (tab, fixmode, fltmode);
 314   if (icode != CODE_FOR_nothing)
 315     {
 316       *truncp_ptr = false;
 317       return icode;
 318     }
 319
 320   /* FIXME: This requires a port to define both FIX and FTRUNC pattern
 321      for this to work.  We need to rework the fix* and ftrunc* patterns
 322      and documentation.  */
 323   tab = unsignedp ? ufix_optab : sfix_optab;
 324   icode = convert_optab_handler (tab, fixmode, fltmode);
 325   if (icode != CODE_FOR_nothing
 326       && optab_handler (ftrunc_optab, fltmode) != CODE_FOR_nothing)
 327     {
 328       *truncp_ptr = true;
 329       return icode;
 330     }
 331
 332   return CODE_FOR_nothing;
 333 }
 334
 335 /* Return nonzero if a conditional move of mode MODE is supported.
 336
 337    This function is for combine so it can tell whether an insn that looks
 338    like a conditional move is actually supported by the hardware.  If we
 339    guess wrong we lose a bit on optimization, but that's it.  */
 340 /* ??? sparc64 supports conditionally moving integers values based on fp
 341    comparisons, and vice versa.  How do we handle them?  */
 342
 343 bool
 344 can_conditionally_move_p (machine_mode mode)
 345 {
 346   return direct_optab_handler (movcc_optab, mode) != CODE_FOR_nothing;
 347 }
 348
 349 /* If a target doesn't implement a permute on a vector with multibyte
 350    elements, we can try to do the same permute on byte elements.
 351    If this makes sense for vector mode MODE then return the appropriate
 352    byte vector mode.  */
 353
 354 opt_machine_mode
 355 qimode_for_vec_perm (machine_mode mode)
 356 {
 357   machine_mode qimode;
 358   if (GET_MODE_INNER (mode) != QImode
 359       && mode_for_vector (QImode, GET_MODE_SIZE (mode)).exists (&qimode)
 360       && VECTOR_MODE_P (qimode))
 361     return qimode;
 362   return opt_machine_mode ();
 363 }
 364
 365 /* Return true if selector SEL can be represented in the integer
 366    equivalent of vector mode MODE.  */
 367
 368 bool
 369 selector_fits_mode_p (machine_mode mode, const vec_perm_indices &sel)
 370 {
 371   unsigned HOST_WIDE_INT mask = GET_MODE_MASK (GET_MODE_INNER (mode));
 372   return (mask == HOST_WIDE_INT_M1U
 373           || sel.all_in_range_p (0, mask + 1));
 374 }
 375
 376 /* Return true if VEC_PERM_EXPRs with variable selector operands can be
 377    expanded using SIMD extensions of the CPU.  MODE is the mode of the
 378    vectors being permuted.  */
 379
 380 bool
 381 can_vec_perm_var_p (machine_mode mode)
 382 {
 383   /* If the target doesn't implement a vector mode for the vector type,
 384      then no operations are supported.  */
 385   if (!VECTOR_MODE_P (mode))
 386     return false;
 387
 388   if (direct_optab_handler (vec_perm_optab, mode) != CODE_FOR_nothing)
 389     return true;
 390
 391   /* We allow fallback to a QI vector mode, and adjust the mask.  */
 392   machine_mode qimode;
 393   if (!qimode_for_vec_perm (mode).exists (&qimode)
 394       || GET_MODE_NUNITS (qimode) > GET_MODE_MASK (QImode) + 1)
 395     return false;
 396
 397   if (direct_optab_handler (vec_perm_optab, qimode) == CODE_FOR_nothing)
 398     return false;
 399
 400   /* In order to support the lowering of variable permutations,
 401      we need to support shifts and adds.  */
 402   if (GET_MODE_UNIT_SIZE (mode) > 2
 403       && optab_handler (ashl_optab, mode) == CODE_FOR_nothing
 404       && optab_handler (vashl_optab, mode) == CODE_FOR_nothing)
 405     return false;
 406   if (optab_handler (add_optab, qimode) == CODE_FOR_nothing)
 407     return false;
 408
 409   return true;
 410 }
 411
 412 /* Return true if the target directly supports VEC_PERM_EXPRs on vectors
 413    of mode MODE using the selector SEL.  ALLOW_VARIABLE_P is true if it
 414    is acceptable to force the selector into a register and use a variable
 415    permute (if the target supports that).
 416
 417    Note that additional permutations representing whole-vector shifts may
 418    also be handled via the vec_shr optab, but only where the second input
 419    vector is entirely constant zeroes; this case is not dealt with here.  */
 420
 421 bool
 422 can_vec_perm_const_p (machine_mode mode, const vec_perm_indices &sel,
 423                       bool allow_variable_p)
 424 {
 425   /* If the target doesn't implement a vector mode for the vector type,
 426      then no operations are supported.  */
 427   if (!VECTOR_MODE_P (mode))
 428     return false;
 429
 430   /* It's probably cheaper to test for the variable case first.  */
 431   if (allow_variable_p && selector_fits_mode_p (mode, sel))
 432     {
 433       if (direct_optab_handler (vec_perm_optab, mode) != CODE_FOR_nothing)
 434         return true;
 435
 436       /* Unlike can_vec_perm_var_p, we don't need to test for optabs
 437          related computing the QImode selector, since that happens at
 438          compile time.  */
 439       machine_mode qimode;
 440       if (qimode_for_vec_perm (mode).exists (&qimode))
 441         {
 442           vec_perm_indices qimode_indices;
 443           qimode_indices.new_expanded_vector (sel, GET_MODE_UNIT_SIZE (mode));
 444           if (selector_fits_mode_p (qimode, qimode_indices)
 445               && (direct_optab_handler (vec_perm_optab, qimode)
 446                   != CODE_FOR_nothing))
 447             return true;
 448         }
 449     }
 450
 451   if (targetm.vectorize.vec_perm_const != NULL)
 452     {
 453       if (targetm.vectorize.vec_perm_const (mode, NULL_RTX, NULL_RTX,
 454                                             NULL_RTX, sel))
 455         return true;
 456
 457       /* ??? For completeness, we ought to check the QImode version of
 458          vec_perm_const_optab.  But all users of this implicit lowering
 459          feature implement the variable vec_perm_optab, and the ia64
 460          port specifically doesn't want us to lower V2SF operations
 461          into integer operations.  */
 462     }
 463
 464   return false;
 465 }
 466
 467 /* Find a widening optab even if it doesn't widen as much as we want.
 468    E.g. if from_mode is HImode, and to_mode is DImode, and there is no
 469    direct HI->SI insn, then return SI->DI, if that exists.  */
 470
 471 enum insn_code
 472 find_widening_optab_handler_and_mode (optab op, machine_mode to_mode,
 473                                       machine_mode from_mode,
 474                                       machine_mode *found_mode)
 475 {
 476   gcc_checking_assert (GET_MODE_CLASS (from_mode) == GET_MODE_CLASS (to_mode));
 477   gcc_checking_assert (from_mode < to_mode);
 478   FOR_EACH_MODE (from_mode, from_mode, to_mode)
 479     {
 480       enum insn_code handler = convert_optab_handler (op, to_mode, from_mode);
 481
 482       if (handler != CODE_FOR_nothing)
 483         {
 484           if (found_mode)
 485             *found_mode = from_mode;
 486           return handler;
 487         }
 488     }
 489
 490   return CODE_FOR_nothing;
 491 }
 492
 493 /* Return non-zero if a highpart multiply is supported of can be synthisized.
 494    For the benefit of expand_mult_highpart, the return value is 1 for direct,
 495    2 for even/odd widening, and 3 for hi/lo widening.  */
 496
 497 int
 498 can_mult_highpart_p (machine_mode mode, bool uns_p)
 499 {
 500   optab op;
 501   unsigned i, nunits;
 502
 503   op = uns_p ? umul_highpart_optab : smul_highpart_optab;
 504   if (optab_handler (op, mode) != CODE_FOR_nothing)
 505     return 1;
 506
 507   /* If the mode is an integral vector, synth from widening operations.  */
 508   if (GET_MODE_CLASS (mode) != MODE_VECTOR_INT)
 509     return 0;
 510
 511   nunits = GET_MODE_NUNITS (mode);
 512
 513   op = uns_p ? vec_widen_umult_even_optab : vec_widen_smult_even_optab;
 514   if (optab_handler (op, mode) != CODE_FOR_nothing)
 515     {
 516       op = uns_p ? vec_widen_umult_odd_optab : vec_widen_smult_odd_optab;
 517       if (optab_handler (op, mode) != CODE_FOR_nothing)
 518         {
 519           /* The encoding has 2 interleaved stepped patterns.  */
 520           vec_perm_builder sel (nunits, 2, 3);
 521           for (i = 0; i < 6; ++i)
 522             sel.quick_push (!BYTES_BIG_ENDIAN
 523                             + (i & ~1)
 524                             + ((i & 1) ? nunits : 0));
 525           vec_perm_indices indices (sel, 2, nunits);
 526           if (can_vec_perm_const_p (mode, indices))
 527             return 2;
 528         }
 529     }
 530
 531   op = uns_p ? vec_widen_umult_hi_optab : vec_widen_smult_hi_optab;
 532   if (optab_handler (op, mode) != CODE_FOR_nothing)
 533     {
 534       op = uns_p ? vec_widen_umult_lo_optab : vec_widen_smult_lo_optab;
 535       if (optab_handler (op, mode) != CODE_FOR_nothing)
 536         {
 537           /* The encoding has a single stepped pattern.  */
 538           vec_perm_builder sel (nunits, 1, 3);
 539           for (int i = 0; i < 3; ++i)
 540             sel.quick_push (2 * i + (BYTES_BIG_ENDIAN ? 0 : 1));
 541           vec_perm_indices indices (sel, 2, nunits);
 542           if (can_vec_perm_const_p (mode, indices))
 543             return 3;
 544         }
 545     }
 546
 547   return 0;
 548 }
 549
 550 /* Return true if target supports vector masked load/store for mode.  */
 551
 552 bool
 553 can_vec_mask_load_store_p (machine_mode mode,
 554                            machine_mode mask_mode,
 555                            bool is_load)
 556 {
 557   optab op = is_load ? maskload_optab : maskstore_optab;
 558   machine_mode vmode;
 559
 560   /* If mode is vector mode, check it directly.  */
 561   if (VECTOR_MODE_P (mode))
 562     return convert_optab_handler (op, mode, mask_mode) != CODE_FOR_nothing;
 563
 564   /* Otherwise, return true if there is some vector mode with
 565      the mask load/store supported.  */
 566
 567   /* See if there is any chance the mask load or store might be
 568      vectorized.  If not, punt.  */
 569   scalar_mode smode;
 570   if (!is_a <scalar_mode> (mode, &smode))
 571     return false;
 572
 573   vmode = targetm.vectorize.preferred_simd_mode (smode);
 574   if (!VECTOR_MODE_P (vmode))
 575     return false;
 576
 577   if ((targetm.vectorize.get_mask_mode
 578        (GET_MODE_NUNITS (vmode), GET_MODE_SIZE (vmode)).exists (&mask_mode))
 579       && convert_optab_handler (op, vmode, mask_mode) != CODE_FOR_nothing)
 580     return true;
 581
 582   auto_vector_sizes vector_sizes;
 583   targetm.vectorize.autovectorize_vector_sizes (&vector_sizes);
 584   for (unsigned int i = 0; i < vector_sizes.length (); ++i)
 585     {
 586       poly_uint64 cur = vector_sizes[i];
 587       poly_uint64 nunits;
 588       if (!multiple_p (cur, GET_MODE_SIZE (smode), &nunits))
 589         continue;
 590       if (mode_for_vector (smode, nunits).exists (&vmode)
 591           && VECTOR_MODE_P (vmode)
 592           && targetm.vectorize.get_mask_mode (nunits, cur).exists (&mask_mode)
 593           && convert_optab_handler (op, vmode, mask_mode) != CODE_FOR_nothing)
 594         return true;
 595     }
 596   return false;
 597 }
 598
 599 /* Return true if there is a compare_and_swap pattern.  */
 600
 601 bool
 602 can_compare_and_swap_p (machine_mode mode, bool allow_libcall)
 603 {
 604   enum insn_code icode;
 605
 606   /* Check for __atomic_compare_and_swap.  */
 607   icode = direct_optab_handler (atomic_compare_and_swap_optab, mode);
 608   if (icode != CODE_FOR_nothing)
 609     return true;
 610
 611   /* Check for __sync_compare_and_swap.  */
 612   icode = optab_handler (sync_compare_and_swap_optab, mode);
 613   if (icode != CODE_FOR_nothing)
 614     return true;
 615   if (allow_libcall && optab_libfunc (sync_compare_and_swap_optab, mode))
 616     return true;
 617
 618   /* No inline compare and swap.  */
 619   return false;
 620 }
 621
 622 /* Return true if an atomic exchange can be performed.  */
 623
 624 bool
 625 can_atomic_exchange_p (machine_mode mode, bool allow_libcall)
 626 {
 627   enum insn_code icode;
 628
 629   /* Check for __atomic_exchange.  */
 630   icode = direct_optab_handler (atomic_exchange_optab, mode);
 631   if (icode != CODE_FOR_nothing)
 632     return true;
 633
 634   /* Don't check __sync_test_and_set, as on some platforms that
 635      has reduced functionality.  Targets that really do support
 636      a proper exchange should simply be updated to the __atomics.  */
 637
 638   return can_compare_and_swap_p (mode, allow_libcall);
 639 }
 640
 641 /* Return true if an atomic load can be performed without falling back to
 642    a compare-and-swap.  */
 643
 644 bool
 645 can_atomic_load_p (machine_mode mode)
 646 {
 647   enum insn_code icode;
 648
 649   /* Does the target supports the load directly?  */
 650   icode = direct_optab_handler (atomic_load_optab, mode);
 651   if (icode != CODE_FOR_nothing)
 652     return true;
 653
 654   /* If the size of the object is greater than word size on this target,
 655      then we assume that a load will not be atomic.  Also see
 656      expand_atomic_load.  */
 657   return GET_MODE_PRECISION (mode) <= BITS_PER_WORD;
 658 }
 659
 660 /* Determine whether "1 << x" is relatively cheap in word_mode.  */
 661
 662 bool
 663 lshift_cheap_p (bool speed_p)
 664 {
 665   /* FIXME: This should be made target dependent via this "this_target"
 666      mechanism, similar to e.g. can_copy_init_p in gcse.c.  */
 667   static bool init[2] = { false, false };
 668   static bool cheap[2] = { true, true };
 669
 670   /* If the targer has no lshift in word_mode, the operation will most
 671      probably not be cheap.  ??? Does GCC even work for such targets?  */
 672   if (optab_handler (ashl_optab, word_mode) == CODE_FOR_nothing)
 673     return false;
 674
 675   if (!init[speed_p])
 676     {
 677       rtx reg = gen_raw_REG (word_mode, 10000);
 678       int cost = set_src_cost (gen_rtx_ASHIFT (word_mode, const1_rtx, reg),
 679                                word_mode, speed_p);
 680       cheap[speed_p] = cost < COSTS_N_INSNS (3);
 681       init[speed_p] = true;
 682     }
 683
 684   return cheap[speed_p];
 685 }