gcc/tree-ssa-copy.c

   1 /* Copy propagation and SSA_NAME replacement support routines.
   2    Copyright (C) 2004-2015 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
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License 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 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "input.h"
  25 #include "alias.h"
  26 #include "symtab.h"
  27 #include "tree.h"
  28 #include "fold-const.h"
  29 #include "flags.h"
  30 #include "tm_p.h"
  31 #include "predict.h"
  32 #include "hard-reg-set.h"
  33 #include "input.h"
  34 #include "function.h"
  35 #include "dominance.h"
  36 #include "cfg.h"
  37 #include "basic-block.h"
  38 #include "gimple-pretty-print.h"
  39 #include "tree-ssa-alias.h"
  40 #include "internal-fn.h"
  41 #include "gimple-expr.h"
  42 #include "is-a.h"
  43 #include "gimple.h"
  44 #include "gimple-iterator.h"
  45 #include "gimple-ssa.h"
  46 #include "tree-cfg.h"
  47 #include "tree-phinodes.h"
  48 #include "ssa-iterators.h"
  49 #include "stringpool.h"
  50 #include "tree-ssanames.h"
  51 #include "tree-pass.h"
  52 #include "tree-ssa-propagate.h"
  53 #include "langhooks.h"
  54 #include "cfgloop.h"
  55 #include "tree-scalar-evolution.h"
  56 #include "tree-ssa-dom.h"
  57 #include "tree-ssa-loop-niter.h"
  58
  59
  60 /* This file implements the copy propagation pass and provides a
  61    handful of interfaces for performing const/copy propagation and
  62    simple expression replacement which keep variable annotations
  63    up-to-date.
  64
  65    We require that for any copy operation where the RHS and LHS have
  66    a non-null memory tag the memory tag be the same.   It is OK
  67    for one or both of the memory tags to be NULL.
  68
  69    We also require tracking if a variable is dereferenced in a load or
  70    store operation.
  71
  72    We enforce these requirements by having all copy propagation and
  73    replacements of one SSA_NAME with a different SSA_NAME to use the
  74    APIs defined in this file.  */
  75
  76 /*---------------------------------------------------------------------------
  77                                 Copy propagation
  78 ---------------------------------------------------------------------------*/
  79 /* Lattice for copy-propagation.  The lattice is initialized to
  80    UNDEFINED (value == NULL) for SSA names that can become a copy
  81    of something or VARYING (value == self) if not (see get_copy_of_val
  82    and stmt_may_generate_copy).  Other values make the name a COPY
  83    of that value.
  84
  85    When visiting a statement or PHI node the lattice value for an
  86    SSA name can transition from UNDEFINED to COPY to VARYING.  */
  87
  88 struct prop_value_t {
  89     /* Copy-of value.  */
  90     tree value;
  91 };
  92
  93 static prop_value_t *copy_of;
  94 static unsigned n_copy_of;
  95
  96
  97 /* Return true if this statement may generate a useful copy.  */
  98
  99 static bool
 100 stmt_may_generate_copy (gimple stmt)
 101 {
 102   if (gimple_code (stmt) == GIMPLE_PHI)
 103     return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt));
 104
 105   if (gimple_code (stmt) != GIMPLE_ASSIGN)
 106     return false;
 107
 108   /* If the statement has volatile operands, it won't generate a
 109      useful copy.  */
 110   if (gimple_has_volatile_ops (stmt))
 111     return false;
 112
 113   /* Statements with loads and/or stores will never generate a useful copy.  */
 114   if (gimple_vuse (stmt))
 115     return false;
 116
 117   /* Otherwise, the only statements that generate useful copies are
 118      assignments whose RHS is just an SSA name that doesn't flow
 119      through abnormal edges.  */
 120   return ((gimple_assign_rhs_code (stmt) == SSA_NAME
 121            && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt)))
 122           || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)));
 123 }
 124
 125
 126 /* Return the copy-of value for VAR.  */
 127
 128 static inline prop_value_t *
 129 get_copy_of_val (tree var)
 130 {
 131   prop_value_t *val = &copy_of[SSA_NAME_VERSION (var)];
 132
 133   if (val->value == NULL_TREE
 134       && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var)))
 135     {
 136       /* If the variable will never generate a useful copy relation,
 137          make it its own copy.  */
 138       val->value = var;
 139     }
 140
 141   return val;
 142 }
 143
 144 /* Return the variable VAR is a copy of or VAR if VAR isn't the result
 145    of a copy.  */
 146
 147 static inline tree
 148 valueize_val (tree var)
 149 {
 150   if (TREE_CODE (var) == SSA_NAME)
 151     {
 152       tree val = get_copy_of_val (var)->value;
 153       if (val)
 154         return val;
 155     }
 156   return var;
 157 }
 158
 159 /* Set VAL to be the copy of VAR.  If that changed return true.  */
 160
 161 static inline bool
 162 set_copy_of_val (tree var, tree val)
 163 {
 164   unsigned int ver = SSA_NAME_VERSION (var);
 165   tree old;
 166
 167   /* Set FIRST to be the first link in COPY_OF[DEST].  If that
 168      changed, return true.  */
 169   old = copy_of[ver].value;
 170   copy_of[ver].value = val;
 171
 172   if (old != val
 173       || (val && !operand_equal_p (old, val, 0)))
 174     return true;
 175
 176   return false;
 177 }
 178
 179
 180 /* Dump the copy-of value for variable VAR to FILE.  */
 181
 182 static void
 183 dump_copy_of (FILE *file, tree var)
 184 {
 185   tree val;
 186
 187   print_generic_expr (file, var, dump_flags);
 188   if (TREE_CODE (var) != SSA_NAME)
 189     return;
 190
 191   val = copy_of[SSA_NAME_VERSION (var)].value;
 192   fprintf (file, " copy-of chain: ");
 193   print_generic_expr (file, var, 0);
 194   fprintf (file, " ");
 195   if (!val)
 196     fprintf (file, "[UNDEFINED]");
 197   else if (val == var)
 198     fprintf (file, "[NOT A COPY]");
 199   else
 200     {
 201       fprintf (file, "-> ");
 202       print_generic_expr (file, val, 0);
 203       fprintf (file, " ");
 204       fprintf (file, "[COPY]");
 205     }
 206 }
 207
 208
 209 /* Evaluate the RHS of STMT.  If it produces a valid copy, set the LHS
 210    value and store the LHS into *RESULT_P.  */
 211
 212 static enum ssa_prop_result
 213 copy_prop_visit_assignment (gimple stmt, tree *result_p)
 214 {
 215   tree lhs, rhs;
 216
 217   lhs = gimple_assign_lhs (stmt);
 218   rhs = valueize_val (gimple_assign_rhs1 (stmt));
 219
 220   if (TREE_CODE (lhs) == SSA_NAME)
 221     {
 222       /* Straight copy between two SSA names.  First, make sure that
 223          we can propagate the RHS into uses of LHS.  */
 224       if (!may_propagate_copy (lhs, rhs))
 225         return SSA_PROP_VARYING;
 226
 227       *result_p = lhs;
 228       if (set_copy_of_val (*result_p, rhs))
 229         return SSA_PROP_INTERESTING;
 230       else
 231         return SSA_PROP_NOT_INTERESTING;
 232     }
 233
 234   return SSA_PROP_VARYING;
 235 }
 236
 237
 238 /* Visit the GIMPLE_COND STMT.  Return SSA_PROP_INTERESTING
 239    if it can determine which edge will be taken.  Otherwise, return
 240    SSA_PROP_VARYING.  */
 241
 242 static enum ssa_prop_result
 243 copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p)
 244 {
 245   enum ssa_prop_result retval = SSA_PROP_VARYING;
 246   location_t loc = gimple_location (stmt);
 247
 248   tree op0 = valueize_val (gimple_cond_lhs (stmt));
 249   tree op1 = valueize_val (gimple_cond_rhs (stmt));
 250
 251   /* See if we can determine the predicate's value.  */
 252   if (dump_file && (dump_flags & TDF_DETAILS))
 253     {
 254       fprintf (dump_file, "Trying to determine truth value of ");
 255       fprintf (dump_file, "predicate ");
 256       print_gimple_stmt (dump_file, stmt, 0, 0);
 257     }
 258
 259   /* Fold COND and see whether we get a useful result.  */
 260   tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt),
 261                                       boolean_type_node, op0, op1);
 262   if (folded_cond)
 263     {
 264       basic_block bb = gimple_bb (stmt);
 265       *taken_edge_p = find_taken_edge (bb, folded_cond);
 266       if (*taken_edge_p)
 267         retval = SSA_PROP_INTERESTING;
 268     }
 269
 270   if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p)
 271     fprintf (dump_file, "\nConditional will always take edge %d->%d\n",
 272              (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index);
 273
 274   return retval;
 275 }
 276
 277
 278 /* Evaluate statement STMT.  If the statement produces a new output
 279    value, return SSA_PROP_INTERESTING and store the SSA_NAME holding
 280    the new value in *RESULT_P.
 281
 282    If STMT is a conditional branch and we can determine its truth
 283    value, set *TAKEN_EDGE_P accordingly.
 284
 285    If the new value produced by STMT is varying, return
 286    SSA_PROP_VARYING.  */
 287
 288 static enum ssa_prop_result
 289 copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p)
 290 {
 291   enum ssa_prop_result retval;
 292
 293   if (dump_file && (dump_flags & TDF_DETAILS))
 294     {
 295       fprintf (dump_file, "\nVisiting statement:\n");
 296       print_gimple_stmt (dump_file, stmt, 0, dump_flags);
 297       fprintf (dump_file, "\n");
 298     }
 299
 300   if (gimple_assign_single_p (stmt)
 301       && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
 302       && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
 303           || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
 304     {
 305       /* If the statement is a copy assignment, evaluate its RHS to
 306          see if the lattice value of its output has changed.  */
 307       retval = copy_prop_visit_assignment (stmt, result_p);
 308     }
 309   else if (gimple_code (stmt) == GIMPLE_COND)
 310     {
 311       /* See if we can determine which edge goes out of a conditional
 312          jump.  */
 313       retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p);
 314     }
 315   else
 316     retval = SSA_PROP_VARYING;
 317
 318   if (retval == SSA_PROP_VARYING)
 319     {
 320       tree def;
 321       ssa_op_iter i;
 322
 323       /* Any other kind of statement is not interesting for constant
 324          propagation and, therefore, not worth simulating.  */
 325       if (dump_file && (dump_flags & TDF_DETAILS))
 326         fprintf (dump_file, "No interesting values produced.\n");
 327
 328       /* The assignment is not a copy operation.  Don't visit this
 329          statement again and mark all the definitions in the statement
 330          to be copies of nothing.  */
 331       FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS)
 332         set_copy_of_val (def, def);
 333     }
 334
 335   return retval;
 336 }
 337
 338
 339 /* Visit PHI node PHI.  If all the arguments produce the same value,
 340    set it to be the value of the LHS of PHI.  */
 341
 342 static enum ssa_prop_result
 343 copy_prop_visit_phi_node (gphi *phi)
 344 {
 345   enum ssa_prop_result retval;
 346   unsigned i;
 347   prop_value_t phi_val = { NULL_TREE };
 348
 349   tree lhs = gimple_phi_result (phi);
 350
 351   if (dump_file && (dump_flags & TDF_DETAILS))
 352     {
 353       fprintf (dump_file, "\nVisiting PHI node: ");
 354       print_gimple_stmt (dump_file, phi, 0, dump_flags);
 355     }
 356
 357   for (i = 0; i < gimple_phi_num_args (phi); i++)
 358     {
 359       prop_value_t *arg_val;
 360       tree arg_value;
 361       tree arg = gimple_phi_arg_def (phi, i);
 362       edge e = gimple_phi_arg_edge (phi, i);
 363
 364       /* We don't care about values flowing through non-executable
 365          edges.  */
 366       if (!(e->flags & EDGE_EXECUTABLE))
 367         continue;
 368
 369       /* Names that flow through abnormal edges cannot be used to
 370          derive copies.  */
 371       if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg))
 372         {
 373           phi_val.value = lhs;
 374           break;
 375         }
 376
 377       if (dump_file && (dump_flags & TDF_DETAILS))
 378         {
 379           fprintf (dump_file, "\tArgument #%d: ", i);
 380           dump_copy_of (dump_file, arg);
 381           fprintf (dump_file, "\n");
 382         }
 383
 384       if (TREE_CODE (arg) == SSA_NAME)
 385         {
 386           arg_val = get_copy_of_val (arg);
 387
 388           /* If we didn't visit the definition of arg yet treat it as
 389              UNDEFINED.  This also handles PHI arguments that are the
 390              same as lhs.  We'll come here again.  */
 391           if (!arg_val->value)
 392             continue;
 393
 394           arg_value = arg_val->value;
 395         }
 396       else
 397         arg_value = valueize_val (arg);
 398
 399       /* In loop-closed SSA form do not copy-propagate SSA-names across
 400          loop exit edges.  */
 401       if (loops_state_satisfies_p (LOOP_CLOSED_SSA)
 402           && TREE_CODE (arg_value) == SSA_NAME
 403           && loop_exit_edge_p (e->src->loop_father, e))
 404         {
 405           phi_val.value = lhs;
 406           break;
 407         }
 408
 409       /* If the LHS didn't have a value yet, make it a copy of the
 410          first argument we find.   */
 411       if (phi_val.value == NULL_TREE)
 412         {
 413           phi_val.value = arg_value;
 414           continue;
 415         }
 416
 417       /* If PHI_VAL and ARG don't have a common copy-of chain, then
 418          this PHI node cannot be a copy operation.  */
 419       if (phi_val.value != arg_value
 420           && !operand_equal_p (phi_val.value, arg_value, 0))
 421         {
 422           phi_val.value = lhs;
 423           break;
 424         }
 425     }
 426
 427   if (phi_val.value
 428       && may_propagate_copy (lhs, phi_val.value)
 429       && set_copy_of_val (lhs, phi_val.value))
 430     retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING;
 431   else
 432     retval = SSA_PROP_NOT_INTERESTING;
 433
 434   if (dump_file && (dump_flags & TDF_DETAILS))
 435     {
 436       fprintf (dump_file, "PHI node ");
 437       dump_copy_of (dump_file, lhs);
 438       fprintf (dump_file, "\nTelling the propagator to ");
 439       if (retval == SSA_PROP_INTERESTING)
 440         fprintf (dump_file, "add SSA edges out of this PHI and continue.");
 441       else if (retval == SSA_PROP_VARYING)
 442         fprintf (dump_file, "add SSA edges out of this PHI and never visit again.");
 443       else
 444         fprintf (dump_file, "do nothing with SSA edges and keep iterating.");
 445       fprintf (dump_file, "\n\n");
 446     }
 447
 448   return retval;
 449 }
 450
 451
 452 /* Initialize structures used for copy propagation.  */
 453
 454 static void
 455 init_copy_prop (void)
 456 {
 457   basic_block bb;
 458
 459   n_copy_of = num_ssa_names;
 460   copy_of = XCNEWVEC (prop_value_t, n_copy_of);
 461
 462   FOR_EACH_BB_FN (bb, cfun)
 463     {
 464       for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si);
 465            gsi_next (&si))
 466         {
 467           gimple stmt = gsi_stmt (si);
 468           ssa_op_iter iter;
 469           tree def;
 470
 471           /* The only statements that we care about are those that may
 472              generate useful copies.  We also need to mark conditional
 473              jumps so that their outgoing edges are added to the work
 474              lists of the propagator.  */
 475           if (stmt_ends_bb_p (stmt))
 476             prop_set_simulate_again (stmt, true);
 477           else if (stmt_may_generate_copy (stmt))
 478             prop_set_simulate_again (stmt, true);
 479           else
 480             prop_set_simulate_again (stmt, false);
 481
 482           /* Mark all the outputs of this statement as not being
 483              the copy of anything.  */
 484           FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
 485             if (!prop_simulate_again_p (stmt))
 486               set_copy_of_val (def, def);
 487         }
 488
 489       for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si);
 490            gsi_next (&si))
 491         {
 492           gphi *phi = si.phi ();
 493           tree def;
 494
 495           def = gimple_phi_result (phi);
 496           if (virtual_operand_p (def))
 497             prop_set_simulate_again (phi, false);
 498           else
 499             prop_set_simulate_again (phi, true);
 500
 501           if (!prop_simulate_again_p (phi))
 502             set_copy_of_val (def, def);
 503         }
 504     }
 505 }
 506
 507 /* Callback for substitute_and_fold to get at the final copy-of values.  */
 508
 509 static tree
 510 get_value (tree name)
 511 {
 512   tree val;
 513   if (SSA_NAME_VERSION (name) >= n_copy_of)
 514     return NULL_TREE;
 515   val = copy_of[SSA_NAME_VERSION (name)].value;
 516   if (val && val != name)
 517     return val;
 518   return NULL_TREE;
 519 }
 520
 521 /* Deallocate memory used in copy propagation and do final
 522    substitution.  */
 523
 524 static bool
 525 fini_copy_prop (void)
 526 {
 527   unsigned i;
 528
 529   /* Set the final copy-of value for each variable by traversing the
 530      copy-of chains.  */
 531   for (i = 1; i < num_ssa_names; i++)
 532     {
 533       tree var = ssa_name (i);
 534       if (!var
 535           || !copy_of[i].value
 536           || copy_of[i].value == var)
 537         continue;
 538
 539       /* In theory the points-to solution of all members of the
 540          copy chain is their intersection.  For now we do not bother
 541          to compute this but only make sure we do not lose points-to
 542          information completely by setting the points-to solution
 543          of the representative to the first solution we find if
 544          it doesn't have one already.  */
 545       if (copy_of[i].value != var
 546           && TREE_CODE (copy_of[i].value) == SSA_NAME)
 547         {
 548           basic_block copy_of_bb
 549             = gimple_bb (SSA_NAME_DEF_STMT (copy_of[i].value));
 550           basic_block var_bb = gimple_bb (SSA_NAME_DEF_STMT (var));
 551           if (POINTER_TYPE_P (TREE_TYPE (var))
 552               && SSA_NAME_PTR_INFO (var)
 553               && !SSA_NAME_PTR_INFO (copy_of[i].value))
 554             {
 555               duplicate_ssa_name_ptr_info (copy_of[i].value,
 556                                            SSA_NAME_PTR_INFO (var));
 557               /* Points-to information is cfg insensitive,
 558                  but alignment info might be cfg sensitive, if it
 559                  e.g. is derived from VRP derived non-zero bits.
 560                  So, do not copy alignment info if the two SSA_NAMEs
 561                  aren't defined in the same basic block.  */
 562               if (var_bb != copy_of_bb)
 563                 mark_ptr_info_alignment_unknown
 564                                 (SSA_NAME_PTR_INFO (copy_of[i].value));
 565             }
 566           else if (!POINTER_TYPE_P (TREE_TYPE (var))
 567                    && SSA_NAME_RANGE_INFO (var)
 568                    && !SSA_NAME_RANGE_INFO (copy_of[i].value)
 569                    && var_bb == copy_of_bb)
 570             duplicate_ssa_name_range_info (copy_of[i].value,
 571                                            SSA_NAME_RANGE_TYPE (var),
 572                                            SSA_NAME_RANGE_INFO (var));
 573         }
 574     }
 575
 576   bool changed = substitute_and_fold (get_value, NULL, true);
 577   if (changed)
 578     {
 579       free_numbers_of_iterations_estimates ();
 580       if (scev_initialized_p ())
 581         scev_reset ();
 582     }
 583
 584   free (copy_of);
 585
 586   return changed;
 587 }
 588
 589
 590 /* Main entry point to the copy propagator.
 591
 592    PHIS_ONLY is true if we should only consider PHI nodes as generating
 593    copy propagation opportunities.
 594
 595    The algorithm propagates the value COPY-OF using ssa_propagate.  For
 596    every variable X_i, COPY-OF(X_i) indicates which variable is X_i created
 597    from.  The following example shows how the algorithm proceeds at a
 598    high level:
 599
 600             1   a_24 = x_1
 601             2   a_2 = PHI <a_24, x_1>
 602             3   a_5 = PHI <a_2>
 603             4   x_1 = PHI <x_298, a_5, a_2>
 604
 605    The end result should be that a_2, a_5, a_24 and x_1 are a copy of
 606    x_298.  Propagation proceeds as follows.
 607
 608    Visit #1: a_24 is copy-of x_1.  Value changed.
 609    Visit #2: a_2 is copy-of x_1.  Value changed.
 610    Visit #3: a_5 is copy-of x_1.  Value changed.
 611    Visit #4: x_1 is copy-of x_298.  Value changed.
 612    Visit #1: a_24 is copy-of x_298.  Value changed.
 613    Visit #2: a_2 is copy-of x_298.  Value changed.
 614    Visit #3: a_5 is copy-of x_298.  Value changed.
 615    Visit #4: x_1 is copy-of x_298.  Stable state reached.
 616
 617    When visiting PHI nodes, we only consider arguments that flow
 618    through edges marked executable by the propagation engine.  So,
 619    when visiting statement #2 for the first time, we will only look at
 620    the first argument (a_24) and optimistically assume that its value
 621    is the copy of a_24 (x_1).  */
 622
 623 static unsigned int
 624 execute_copy_prop (void)
 625 {
 626   init_copy_prop ();
 627   ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node);
 628   if (fini_copy_prop ())
 629     return TODO_cleanup_cfg;
 630   return 0;
 631 }
 632
 633 namespace {
 634
 635 const pass_data pass_data_copy_prop =
 636 {
 637   GIMPLE_PASS, /* type */
 638   "copyprop", /* name */
 639   OPTGROUP_NONE, /* optinfo_flags */
 640   TV_TREE_COPY_PROP, /* tv_id */
 641   ( PROP_ssa | PROP_cfg ), /* properties_required */
 642   0, /* properties_provided */
 643   0, /* properties_destroyed */
 644   0, /* todo_flags_start */
 645   0, /* todo_flags_finish */
 646 };
 647
 648 class pass_copy_prop : public gimple_opt_pass
 649 {
 650 public:
 651   pass_copy_prop (gcc::context *ctxt)
 652     : gimple_opt_pass (pass_data_copy_prop, ctxt)
 653   {}
 654
 655   /* opt_pass methods: */
 656   opt_pass * clone () { return new pass_copy_prop (m_ctxt); }
 657   virtual bool gate (function *) { return flag_tree_copy_prop != 0; }
 658   virtual unsigned int execute (function *) { return execute_copy_prop (); }
 659
 660 }; // class pass_copy_prop
 661
 662 } // anon namespace
 663
 664 gimple_opt_pass *
 665 make_pass_copy_prop (gcc::context *ctxt)
 666 {
 667   return new pass_copy_prop (ctxt);
 668 }