gcc/ipa-pure-const.c

   1 /* Callgraph based analysis of static variables.
   2    Copyright (C) 2004, 2005 Free Software Foundation, Inc.
   3    Contributed by Kenneth Zadeck <zadeck@naturalbridge.com>
   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, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22 /* This file mark functions as being either const (TREE_READONLY) or
  23    pure (DECL_IS_PURE).
  24
  25    This must be run after inlining decisions have been made since
  26    otherwise, the local sets will not contain information that is
  27    consistent with post inlined state.  The global sets are not prone
  28    to this problem since they are by definition transitive.  */
  29
  30 /* The code in this module is called by the ipa pass manager. It
  31    should be one of the later passes since it's information is used by
  32    the rest of the compilation. */
  33
  34 #include "config.h"
  35 #include "system.h"
  36 #include "coretypes.h"
  37 #include "tm.h"
  38 #include "tree.h"
  39 #include "tree-flow.h"
  40 #include "tree-inline.h"
  41 #include "tree-pass.h"
  42 #include "langhooks.h"
  43 #include "pointer-set.h"
  44 #include "ggc.h"
  45 #include "ipa-utils.h"
  46 #include "c-common.h"
  47 #include "tree-gimple.h"
  48 #include "cgraph.h"
  49 #include "output.h"
  50 #include "flags.h"
  51 #include "timevar.h"
  52 #include "diagnostic.h"
  53 #include "langhooks.h"
  54 #include "target.h"
  55
  56 static struct pointer_set_t *visited_nodes;
  57
  58 /* Lattice values for const and pure functions.  Everything starts out
  59    being const, then may drop to pure and then neither depending on
  60    what is found.  */
  61 enum pure_const_state_e
  62 {
  63   IPA_CONST,
  64   IPA_PURE,
  65   IPA_NEITHER
  66 };
  67
  68 /* Holder inserted into the ipa_dfs_info aux field to hold the
  69    const_state.  */
  70 struct funct_state_d
  71 {
  72   enum pure_const_state_e pure_const_state;
  73   bool state_set_in_source;
  74 };
  75
  76 typedef struct funct_state_d * funct_state;
  77
  78 /* Return the function state from NODE.  */
  79
  80 static inline funct_state
  81 get_function_state (struct cgraph_node *node)
  82 {
  83   struct ipa_dfs_info * info = node->aux;
  84   return info->aux;
  85 }
  86
  87 /* Check to see if the use (or definition when CHECHING_WRITE is true)
  88    variable T is legal in a function that is either pure or const.  */
  89
  90 static inline void
  91 check_decl (funct_state local,
  92             tree t, bool checking_write)
  93 {
  94   /* If the variable has the "used" attribute, treat it as if it had a
  95      been touched by the devil.  */
  96   if (lookup_attribute ("used", DECL_ATTRIBUTES (t)))
  97     {
  98       local->pure_const_state = IPA_NEITHER;
  99       return;
 100     }
 101
 102   /* Do not want to do anything with volatile except mark any
 103      function that uses one to be not const or pure.  */
 104   if (TREE_THIS_VOLATILE (t))
 105     {
 106       local->pure_const_state = IPA_NEITHER;
 107       return;
 108     }
 109
 110   /* Do not care about a local automatic that is not static.  */
 111   if (!TREE_STATIC (t) && !DECL_EXTERNAL (t))
 112     return;
 113
 114   /* Since we have dealt with the locals and params cases above, if we
 115      are CHECKING_WRITE, this cannot be a pure or constant
 116      function.  */
 117   if (checking_write)
 118     local->pure_const_state = IPA_NEITHER;
 119
 120   if (DECL_EXTERNAL (t) || TREE_PUBLIC (t))
 121     {
 122       /* If the front end set the variable to be READONLY and
 123          constant, we can allow this variable in pure or const
 124          functions but the scope is too large for our analysis to set
 125          these bits ourselves.  */
 126
 127       if (TREE_READONLY (t)
 128           && DECL_INITIAL (t)
 129           && is_gimple_min_invariant (DECL_INITIAL (t)))
 130         ; /* Read of a constant, do not change the function state.  */
 131       else
 132         {
 133           /* Just a regular read.  */
 134           if (local->pure_const_state == IPA_CONST)
 135             local->pure_const_state = IPA_PURE;
 136         }
 137     }
 138
 139   /* Compilation level statics can be read if they are readonly
 140      variables.  */
 141   if (TREE_READONLY (t))
 142     return;
 143
 144   /* Just a regular read.  */
 145   if (local->pure_const_state == IPA_CONST)
 146     local->pure_const_state = IPA_PURE;
 147 }
 148
 149 /* If T is a VAR_DECL check to see if it is an allowed reference.  */
 150
 151 static void
 152 check_operand (funct_state local,
 153                tree t, bool checking_write)
 154 {
 155   if (!t) return;
 156
 157   if (TREE_CODE (t) == VAR_DECL)
 158     check_decl (local, t, checking_write);
 159 }
 160
 161 /* Examine tree T for references.  */
 162
 163 static void
 164 check_tree (funct_state local, tree t, bool checking_write)
 165 {
 166   if ((TREE_CODE (t) == EXC_PTR_EXPR) || (TREE_CODE (t) == FILTER_EXPR))
 167     return;
 168
 169   /* Any tree which is volatile disqualifies thie function from being
 170      const or pure. */
 171   if (TREE_THIS_VOLATILE (t))
 172     {
 173       local->pure_const_state = IPA_NEITHER;
 174       return;
 175     }
 176
 177   while (TREE_CODE (t) == REALPART_EXPR
 178          || TREE_CODE (t) == IMAGPART_EXPR
 179          || handled_component_p (t))
 180     {
 181       if (TREE_CODE (t) == ARRAY_REF)
 182         check_operand (local, TREE_OPERAND (t, 1), false);
 183       t = TREE_OPERAND (t, 0);
 184     }
 185
 186   /* The bottom of an indirect reference can only be read, not
 187      written.  */
 188   if (INDIRECT_REF_P (t))
 189     {
 190       check_tree (local, TREE_OPERAND (t, 0), false);
 191
 192       /* Any indirect reference that occurs on the lhs
 193          disqualifies the function from being pure or const. Any
 194          indirect reference that occurs on the rhs disqualifies the
 195          function from being const.  */
 196       if (checking_write)
 197         {
 198           local->pure_const_state = IPA_NEITHER;
 199           return;
 200         }
 201       else if (local->pure_const_state == IPA_CONST)
 202         local->pure_const_state = IPA_PURE;
 203     }
 204
 205   if (SSA_VAR_P (t))
 206     check_operand (local, t, checking_write);
 207 }
 208
 209 /* Scan tree T to see if there are any addresses taken in within T.  */
 210
 211 static void
 212 look_for_address_of (funct_state local, tree t)
 213 {
 214   if (TREE_CODE (t) == ADDR_EXPR)
 215     {
 216       tree x = get_base_var (t);
 217       if (TREE_CODE (x) == VAR_DECL)
 218         {
 219           check_decl (local, x, false);
 220
 221           /* Taking the address of something appears to be reasonable
 222              in PURE code.  Not allowed in const.  */
 223           if (local->pure_const_state == IPA_CONST)
 224             local->pure_const_state = IPA_PURE;
 225         }
 226     }
 227 }
 228
 229 /* Check to see if T is a read or address of operation on a var we are
 230    interested in analyzing.  LOCAL is passed in to get access to its
 231    bit vectors.  */
 232
 233 static void
 234 check_rhs_var (funct_state local, tree t)
 235 {
 236   look_for_address_of (local, t);
 237
 238   /* Memcmp and strlen can both trap and they are declared pure.  */
 239   if (tree_could_trap_p (t)
 240       && local->pure_const_state == IPA_CONST)
 241     local->pure_const_state = IPA_PURE;
 242
 243   check_tree(local, t, false);
 244 }
 245
 246 /* Check to see if T is an assignment to a var we are interested in
 247    analyzing.  LOCAL is passed in to get access to its bit vectors. */
 248
 249 static void
 250 check_lhs_var (funct_state local, tree t)
 251 {
 252   /* Memcmp and strlen can both trap and they are declared pure.
 253      Which seems to imply that we can apply the same rule here.  */
 254   if (tree_could_trap_p (t)
 255       && local->pure_const_state == IPA_CONST)
 256     local->pure_const_state = IPA_PURE;
 257
 258   check_tree(local, t, true);
 259 }
 260
 261 /* This is a scaled down version of get_asm_expr_operands from
 262    tree_ssa_operands.c.  The version there runs much later and assumes
 263    that aliasing information is already available. Here we are just
 264    trying to find if the set of inputs and outputs contain references
 265    or address of operations to local static variables.  STMT is the
 266    actual asm statement.  */
 267
 268 static void
 269 get_asm_expr_operands (funct_state local, tree stmt)
 270 {
 271   int noutputs = list_length (ASM_OUTPUTS (stmt));
 272   const char **oconstraints
 273     = (const char **) alloca ((noutputs) * sizeof (const char *));
 274   int i;
 275   tree link;
 276   const char *constraint;
 277   bool allows_mem, allows_reg, is_inout;
 278
 279   for (i=0, link = ASM_OUTPUTS (stmt); link; ++i, link = TREE_CHAIN (link))
 280     {
 281       oconstraints[i] = constraint
 282         = TREE_STRING_POINTER (TREE_VALUE (TREE_PURPOSE (link)));
 283       parse_output_constraint (&constraint, i, 0, 0,
 284                                &allows_mem, &allows_reg, &is_inout);
 285
 286       check_lhs_var (local, TREE_VALUE (link));
 287     }
 288
 289   for (link = ASM_INPUTS (stmt); link; link = TREE_CHAIN (link))
 290     {
 291       constraint
 292         = TREE_STRING_POINTER (TREE_VALUE (TREE_PURPOSE (link)));
 293       parse_input_constraint (&constraint, 0, 0, noutputs, 0,
 294                               oconstraints, &allows_mem, &allows_reg);
 295
 296       check_rhs_var (local, TREE_VALUE (link));
 297     }
 298
 299   for (link = ASM_CLOBBERS (stmt); link; link = TREE_CHAIN (link))
 300     if (simple_cst_equal(TREE_VALUE (link), memory_identifier_string) == 1)
 301       /* Abandon all hope, ye who enter here. */
 302       local->pure_const_state = IPA_NEITHER;
 303
 304   if (ASM_VOLATILE_P (stmt))
 305     local->pure_const_state = IPA_NEITHER;
 306 }
 307
 308 /* Check the parameters of a function call to CALL_EXPR to see if
 309    there are any references in the parameters that are not allowed for
 310    pure or const functions.  Also check to see if this is either an
 311    indirect call, a call outside the compilation unit, or has special
 312    attributes that may also effect the purity.  The CALL_EXPR node for
 313    the entire call expression.  */
 314
 315 static void
 316 check_call (funct_state local, tree call_expr)
 317 {
 318   int flags = call_expr_flags(call_expr);
 319   tree operand_list = TREE_OPERAND (call_expr, 1);
 320   tree operand;
 321   tree callee_t = get_callee_fndecl (call_expr);
 322   struct cgraph_node* callee;
 323   enum availability avail = AVAIL_NOT_AVAILABLE;
 324
 325   for (operand = operand_list;
 326        operand != NULL_TREE;
 327        operand = TREE_CHAIN (operand))
 328     {
 329       tree argument = TREE_VALUE (operand);
 330       check_rhs_var (local, argument);
 331     }
 332
 333   /* The const and pure flags are set by a variety of places in the
 334      compiler (including here).  If someone has already set the flags
 335      for the callee, (such as for some of the builtins) we will use
 336      them, otherwise we will compute our own information.
 337
 338      Const and pure functions have less clobber effects than other
 339      functions so we process these first.  Otherwise if it is a call
 340      outside the compilation unit or an indirect call we punt.  This
 341      leaves local calls which will be processed by following the call
 342      graph.  */
 343   if (callee_t)
 344     {
 345       callee = cgraph_node(callee_t);
 346       avail = cgraph_function_body_availability (callee);
 347
 348       /* When bad things happen to bad functions, they cannot be const
 349          or pure.  */
 350       if (setjmp_call_p (callee_t))
 351         local->pure_const_state = IPA_NEITHER;
 352
 353       if (DECL_BUILT_IN_CLASS (callee_t) == BUILT_IN_NORMAL)
 354         switch (DECL_FUNCTION_CODE (callee_t))
 355           {
 356           case BUILT_IN_LONGJMP:
 357           case BUILT_IN_NONLOCAL_GOTO:
 358             local->pure_const_state = IPA_NEITHER;
 359             break;
 360           default:
 361             break;
 362           }
 363     }
 364
 365   /* The callee is either unknown (indirect call) or there is just no
 366      scannable code for it (external call) .  We look to see if there
 367      are any bits available for the callee (such as by declaration or
 368      because it is builtin) and process solely on the basis of those
 369      bits. */
 370   if (avail == AVAIL_NOT_AVAILABLE || avail == AVAIL_OVERWRITABLE)
 371     {
 372       if (flags & ECF_PURE)
 373         {
 374           if (local->pure_const_state == IPA_CONST)
 375             local->pure_const_state = IPA_PURE;
 376         }
 377       else
 378         local->pure_const_state = IPA_NEITHER;
 379     }
 380   else
 381     {
 382       /* We have the code and we will scan it for the effects. */
 383       if (flags & ECF_PURE)
 384         {
 385           if (local->pure_const_state == IPA_CONST)
 386             local->pure_const_state = IPA_PURE;
 387         }
 388     }
 389 }
 390
 391 /* TP is the part of the tree currently under the microscope.
 392    WALK_SUBTREES is part of the walk_tree api but is unused here.
 393    DATA is cgraph_node of the function being walked.  */
 394
 395 /* FIXME: When this is converted to run over SSA form, this code
 396    should be converted to use the operand scanner.  */
 397
 398 static tree
 399 scan_function (tree *tp,
 400                       int *walk_subtrees,
 401                       void *data)
 402 {
 403   struct cgraph_node *fn = data;
 404   tree t = *tp;
 405   funct_state local = get_function_state (fn);
 406
 407   switch (TREE_CODE (t))
 408     {
 409     case VAR_DECL:
 410       if (DECL_INITIAL (t))
 411         walk_tree (&DECL_INITIAL (t), scan_function, fn, visited_nodes);
 412       *walk_subtrees = 0;
 413       break;
 414
 415     case MODIFY_EXPR:
 416       {
 417         /* First look on the lhs and see what variable is stored to */
 418         tree lhs = TREE_OPERAND (t, 0);
 419         tree rhs = TREE_OPERAND (t, 1);
 420         check_lhs_var (local, lhs);
 421
 422         /* For the purposes of figuring out what the cast affects */
 423
 424         /* Next check the operands on the rhs to see if they are ok. */
 425         switch (TREE_CODE_CLASS (TREE_CODE (rhs)))
 426           {
 427           case tcc_binary:
 428             {
 429               tree op0 = TREE_OPERAND (rhs, 0);
 430               tree op1 = TREE_OPERAND (rhs, 1);
 431               check_rhs_var (local, op0);
 432               check_rhs_var (local, op1);
 433             }
 434             break;
 435           case tcc_unary:
 436             {
 437               tree op0 = TREE_OPERAND (rhs, 0);
 438               check_rhs_var (local, op0);
 439             }
 440
 441             break;
 442           case tcc_reference:
 443             check_rhs_var (local, rhs);
 444             break;
 445           case tcc_declaration:
 446             check_rhs_var (local, rhs);
 447             break;
 448           case tcc_expression:
 449             switch (TREE_CODE (rhs))
 450               {
 451               case ADDR_EXPR:
 452                 check_rhs_var (local, rhs);
 453                 break;
 454               case CALL_EXPR:
 455                 check_call (local, rhs);
 456                 break;
 457               default:
 458                 break;
 459               }
 460             break;
 461           default:
 462             break;
 463           }
 464         *walk_subtrees = 0;
 465       }
 466       break;
 467
 468     case ADDR_EXPR:
 469       /* This case is here to find addresses on rhs of constructors in
 470          decl_initial of static variables. */
 471       check_rhs_var (local, t);
 472       *walk_subtrees = 0;
 473       break;
 474
 475     case LABEL_EXPR:
 476       if (DECL_NONLOCAL (TREE_OPERAND (t, 0)))
 477         /* Target of long jump. */
 478         local->pure_const_state = IPA_NEITHER;
 479       break;
 480
 481     case CALL_EXPR:
 482       check_call (local, t);
 483       *walk_subtrees = 0;
 484       break;
 485
 486     case ASM_EXPR:
 487       get_asm_expr_operands (local, t);
 488       *walk_subtrees = 0;
 489       break;
 490
 491     default:
 492       break;
 493     }
 494   return NULL;
 495 }
 496
 497 /* This is the main routine for finding the reference patterns for
 498    global variables within a function FN.  */
 499
 500 static void
 501 analyze_function (struct cgraph_node *fn)
 502 {
 503   funct_state l = XCNEW (struct funct_state_d);
 504   tree decl = fn->decl;
 505   struct ipa_dfs_info * w_info = fn->aux;
 506
 507   w_info->aux = l;
 508
 509   l->pure_const_state = IPA_CONST;
 510   l->state_set_in_source = false;
 511
 512   /* If this function does not return normally or does not bind local,
 513      do not touch this unless it has been marked as const or pure by the
 514      front end.  */
 515   if (TREE_THIS_VOLATILE (decl)
 516       || !targetm.binds_local_p (decl))
 517     {
 518       l->pure_const_state = IPA_NEITHER;
 519       return;
 520     }
 521
 522   if (TREE_READONLY (decl))
 523     {
 524       l->pure_const_state = IPA_CONST;
 525       l->state_set_in_source = true;
 526     }
 527   if (DECL_IS_PURE (decl))
 528     {
 529       l->pure_const_state = IPA_PURE;
 530       l->state_set_in_source = true;
 531     }
 532
 533   if (dump_file)
 534     {
 535       fprintf (dump_file, "\n local analysis of %s with initial value = %d\n ",
 536                cgraph_node_name (fn),
 537                l->pure_const_state);
 538     }
 539
 540   if (!l->state_set_in_source)
 541     {
 542       struct function *this_cfun = DECL_STRUCT_FUNCTION (decl);
 543       basic_block this_block;
 544
 545       FOR_EACH_BB_FN (this_block, this_cfun)
 546         {
 547           block_stmt_iterator bsi;
 548           for (bsi = bsi_start (this_block); !bsi_end_p (bsi); bsi_next (&bsi))
 549             {
 550               walk_tree (bsi_stmt_ptr (bsi), scan_function,
 551                          fn, visited_nodes);
 552               if (l->pure_const_state == IPA_NEITHER)
 553                 goto end;
 554             }
 555         }
 556
 557       if (l->pure_const_state != IPA_NEITHER)
 558         {
 559           tree old_decl = current_function_decl;
 560           /* Const functions cannot have back edges (an
 561              indication of possible infinite loop side
 562              effect.  */
 563
 564           current_function_decl = fn->decl;
 565
 566           /* The C++ front end, has a tendency to some times jerk away
 567              a function after it has created it.  This should have
 568              been fixed.  */
 569           gcc_assert (DECL_STRUCT_FUNCTION (fn->decl));
 570
 571           push_cfun (DECL_STRUCT_FUNCTION (fn->decl));
 572
 573           if (mark_dfs_back_edges ())
 574             l->pure_const_state = IPA_NEITHER;
 575
 576           current_function_decl = old_decl;
 577           pop_cfun ();
 578         }
 579     }
 580
 581 end:
 582   if (dump_file)
 583     {
 584       fprintf (dump_file, "after local analysis of %s with initial value = %d\n ",
 585                cgraph_node_name (fn),
 586                l->pure_const_state);
 587     }
 588 }
 589
 590 \f
 591 /* Produce the global information by preforming a transitive closure
 592    on the local information that was produced by ipa_analyze_function
 593    and ipa_analyze_variable.  */
 594
 595 static unsigned int
 596 static_execute (void)
 597 {
 598   struct cgraph_node *node;
 599   struct cgraph_node *w;
 600   struct cgraph_node **order =
 601     XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);
 602   int order_pos = order_pos = ipa_utils_reduced_inorder (order, true, false);
 603   int i;
 604   struct ipa_dfs_info * w_info;
 605
 606   if (!memory_identifier_string)
 607     memory_identifier_string = build_string(7, "memory");
 608
 609   /* There are some shared nodes, in particular the initializers on
 610      static declarations.  We do not need to scan them more than once
 611      since all we would be interested in are the addressof
 612      operations.  */
 613   visited_nodes = pointer_set_create ();
 614
 615   /* Process all of the functions.
 616
 617      We do not want to process any of the clones so we check that this
 618      is a master clone.  However, we do NOT process any
 619      AVAIL_OVERWRITABLE functions (these are never clones) we cannot
 620      guarantee that what we learn about the one we see will be true
 621      for the one that overriders it.
 622   */
 623   for (node = cgraph_nodes; node; node = node->next)
 624     if (node->analyzed && cgraph_is_master_clone (node))
 625       analyze_function (node);
 626
 627   pointer_set_destroy (visited_nodes);
 628   visited_nodes = NULL;
 629   if (dump_file)
 630     {
 631       dump_cgraph (dump_file);
 632       ipa_utils_print_order(dump_file, "reduced", order, order_pos);
 633     }
 634
 635   /* Propagate the local information thru the call graph to produce
 636      the global information.  All the nodes within a cycle will have
 637      the same info so we collapse cycles first.  Then we can do the
 638      propagation in one pass from the leaves to the roots.  */
 639   for (i = 0; i < order_pos; i++ )
 640     {
 641       enum pure_const_state_e pure_const_state = IPA_CONST;
 642       node = order[i];
 643
 644       /* Find the worst state for any node in the cycle.  */
 645       w = node;
 646       while (w)
 647         {
 648           funct_state w_l = get_function_state (w);
 649           if (pure_const_state < w_l->pure_const_state)
 650             pure_const_state = w_l->pure_const_state;
 651
 652           if (pure_const_state == IPA_NEITHER)
 653             break;
 654
 655           if (!w_l->state_set_in_source)
 656             {
 657               struct cgraph_edge *e;
 658               for (e = w->callees; e; e = e->next_callee)
 659                 {
 660                   struct cgraph_node *y = e->callee;
 661                   /* Only look at the master nodes and skip external nodes.  */
 662                   y = cgraph_master_clone (y);
 663                   if (y)
 664                     {
 665                       funct_state y_l = get_function_state (y);
 666                       if (pure_const_state < y_l->pure_const_state)
 667                         pure_const_state = y_l->pure_const_state;
 668                       if (pure_const_state == IPA_NEITHER)
 669                         break;
 670                     }
 671                 }
 672             }
 673           w_info = w->aux;
 674           w = w_info->next_cycle;
 675         }
 676
 677       /* Copy back the region's pure_const_state which is shared by
 678          all nodes in the region.  */
 679       w = node;
 680       while (w)
 681         {
 682           funct_state w_l = get_function_state (w);
 683
 684           /* All nodes within a cycle share the same info.  */
 685           if (!w_l->state_set_in_source)
 686             {
 687               w_l->pure_const_state = pure_const_state;
 688               switch (pure_const_state)
 689                 {
 690                 case IPA_CONST:
 691                   TREE_READONLY (w->decl) = 1;
 692                   if (dump_file)
 693                     fprintf (dump_file, "Function found to be const: %s\n",
 694                              lang_hooks.decl_printable_name(w->decl, 2));
 695                   break;
 696
 697                 case IPA_PURE:
 698                   DECL_IS_PURE (w->decl) = 1;
 699                   if (dump_file)
 700                     fprintf (dump_file, "Function found to be pure: %s\n",
 701                              lang_hooks.decl_printable_name(w->decl, 2));
 702                   break;
 703
 704                 default:
 705                   break;
 706                 }
 707             }
 708           w_info = w->aux;
 709           w = w_info->next_cycle;
 710         }
 711     }
 712
 713   /* Cleanup. */
 714   for (node = cgraph_nodes; node; node = node->next)
 715     /* Get rid of the aux information.  */
 716     if (node->aux)
 717       {
 718         w_info = node->aux;
 719         if (w_info->aux)
 720           free (w_info->aux);
 721         free (node->aux);
 722         node->aux = NULL;
 723       }
 724
 725   free (order);
 726   return 0;
 727 }
 728
 729 static bool
 730 gate_pure_const (void)
 731 {
 732   return (flag_unit_at_a_time != 0 && flag_ipa_pure_const
 733           /* Don't bother doing anything if the program has errors.  */
 734           && !(errorcount || sorrycount));
 735 }
 736
 737 struct tree_opt_pass pass_ipa_pure_const =
 738 {
 739   "pure-const",                         /* name */
 740   gate_pure_const,                      /* gate */
 741   static_execute,                       /* execute */
 742   NULL,                                 /* sub */
 743   NULL,                                 /* next */
 744   0,                                    /* static_pass_number */
 745   TV_IPA_PURE_CONST,                    /* tv_id */
 746   0,                                    /* properties_required */
 747   0,                                    /* properties_provided */
 748   0,                                    /* properties_destroyed */
 749   0,                                    /* todo_flags_start */
 750   0,                                    /* todo_flags_finish */
 751   0                                     /* letter */
 752 };
 753
 754