gcc/ipa-utils.c

   1 /* Utilities for ipa analysis.
   2    Copyright (C) 2005-2017 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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "backend.h"
  25 #include "tree.h"
  26 #include "gimple.h"
  27 #include "predict.h"
  28 #include "alloc-pool.h"
  29 #include "cgraph.h"
  30 #include "lto-streamer.h"
  31 #include "dumpfile.h"
  32 #include "splay-tree.h"
  33 #include "ipa-utils.h"
  34 #include "symbol-summary.h"
  35 #include "tree-vrp.h"
  36 #include "ipa-prop.h"
  37 #include "ipa-fnsummary.h"
  38
  39 /* Debugging function for postorder and inorder code. NOTE is a string
  40    that is printed before the nodes are printed.  ORDER is an array of
  41    cgraph_nodes that has COUNT useful nodes in it.  */
  42
  43 void
  44 ipa_print_order (FILE* out,
  45                  const char * note,
  46                  struct cgraph_node** order,
  47                  int count)
  48 {
  49   int i;
  50   fprintf (out, "\n\n ordered call graph: %s\n", note);
  51
  52   for (i = count - 1; i >= 0; i--)
  53     order[i]->dump (out);
  54   fprintf (out, "\n");
  55   fflush (out);
  56 }
  57
  58
  59 struct searchc_env {
  60   struct cgraph_node **stack;
  61   struct cgraph_node **result;
  62   int stack_size;
  63   int order_pos;
  64   splay_tree nodes_marked_new;
  65   bool reduce;
  66   bool allow_overwritable;
  67   int count;
  68 };
  69
  70 /* This is an implementation of Tarjan's strongly connected region
  71    finder as reprinted in Aho Hopcraft and Ullman's The Design and
  72    Analysis of Computer Programs (1975) pages 192-193.  This version
  73    has been customized for cgraph_nodes.  The env parameter is because
  74    it is recursive and there are no nested functions here.  This
  75    function should only be called from itself or
  76    ipa_reduced_postorder.  ENV is a stack env and would be
  77    unnecessary if C had nested functions.  V is the node to start
  78    searching from.  */
  79
  80 static void
  81 searchc (struct searchc_env* env, struct cgraph_node *v,
  82          bool (*ignore_edge) (struct cgraph_edge *))
  83 {
  84   struct cgraph_edge *edge;
  85   struct ipa_dfs_info *v_info = (struct ipa_dfs_info *) v->aux;
  86
  87   /* mark node as old */
  88   v_info->new_node = false;
  89   splay_tree_remove (env->nodes_marked_new, v->uid);
  90
  91   v_info->dfn_number = env->count;
  92   v_info->low_link = env->count;
  93   env->count++;
  94   env->stack[(env->stack_size)++] = v;
  95   v_info->on_stack = true;
  96
  97   for (edge = v->callees; edge; edge = edge->next_callee)
  98     {
  99       struct ipa_dfs_info * w_info;
 100       enum availability avail;
 101       struct cgraph_node *w = edge->callee->ultimate_alias_target (&avail);
 102
 103       if (!w || (ignore_edge && ignore_edge (edge)))
 104         continue;
 105
 106       if (w->aux
 107           && (avail > AVAIL_INTERPOSABLE
 108               || (env->allow_overwritable && avail == AVAIL_INTERPOSABLE)))
 109         {
 110           w_info = (struct ipa_dfs_info *) w->aux;
 111           if (w_info->new_node)
 112             {
 113               searchc (env, w, ignore_edge);
 114               v_info->low_link =
 115                 (v_info->low_link < w_info->low_link) ?
 116                 v_info->low_link : w_info->low_link;
 117             }
 118           else
 119             if ((w_info->dfn_number < v_info->dfn_number)
 120                 && (w_info->on_stack))
 121               v_info->low_link =
 122                 (w_info->dfn_number < v_info->low_link) ?
 123                 w_info->dfn_number : v_info->low_link;
 124         }
 125     }
 126
 127
 128   if (v_info->low_link == v_info->dfn_number)
 129     {
 130       struct cgraph_node *last = NULL;
 131       struct cgraph_node *x;
 132       struct ipa_dfs_info *x_info;
 133       do {
 134         x = env->stack[--(env->stack_size)];
 135         x_info = (struct ipa_dfs_info *) x->aux;
 136         x_info->on_stack = false;
 137         x_info->scc_no = v_info->dfn_number;
 138
 139         if (env->reduce)
 140           {
 141             x_info->next_cycle = last;
 142             last = x;
 143           }
 144         else
 145           env->result[env->order_pos++] = x;
 146       }
 147       while (v != x);
 148       if (env->reduce)
 149         env->result[env->order_pos++] = v;
 150     }
 151 }
 152
 153 /* Topsort the call graph by caller relation.  Put the result in ORDER.
 154
 155    The REDUCE flag is true if you want the cycles reduced to single nodes.
 156    You can use ipa_get_nodes_in_cycle to obtain a vector containing all real
 157    call graph nodes in a reduced node.
 158
 159    Set ALLOW_OVERWRITABLE if nodes with such availability should be included.
 160    IGNORE_EDGE, if non-NULL is a hook that may make some edges insignificant
 161    for the topological sort.   */
 162
 163 int
 164 ipa_reduced_postorder (struct cgraph_node **order,
 165                        bool reduce, bool allow_overwritable,
 166                        bool (*ignore_edge) (struct cgraph_edge *))
 167 {
 168   struct cgraph_node *node;
 169   struct searchc_env env;
 170   splay_tree_node result;
 171   env.stack = XCNEWVEC (struct cgraph_node *, symtab->cgraph_count);
 172   env.stack_size = 0;
 173   env.result = order;
 174   env.order_pos = 0;
 175   env.nodes_marked_new = splay_tree_new (splay_tree_compare_ints, 0, 0);
 176   env.count = 1;
 177   env.reduce = reduce;
 178   env.allow_overwritable = allow_overwritable;
 179
 180   FOR_EACH_DEFINED_FUNCTION (node)
 181     {
 182       enum availability avail = node->get_availability ();
 183
 184       if (avail > AVAIL_INTERPOSABLE
 185           || (allow_overwritable
 186               && (avail == AVAIL_INTERPOSABLE)))
 187         {
 188           /* Reuse the info if it is already there.  */
 189           struct ipa_dfs_info *info = (struct ipa_dfs_info *) node->aux;
 190           if (!info)
 191             info = XCNEW (struct ipa_dfs_info);
 192           info->new_node = true;
 193           info->on_stack = false;
 194           info->next_cycle = NULL;
 195           node->aux = info;
 196
 197           splay_tree_insert (env.nodes_marked_new,
 198                              (splay_tree_key)node->uid,
 199                              (splay_tree_value)node);
 200         }
 201       else
 202         node->aux = NULL;
 203     }
 204   result = splay_tree_min (env.nodes_marked_new);
 205   while (result)
 206     {
 207       node = (struct cgraph_node *)result->value;
 208       searchc (&env, node, ignore_edge);
 209       result = splay_tree_min (env.nodes_marked_new);
 210     }
 211   splay_tree_delete (env.nodes_marked_new);
 212   free (env.stack);
 213
 214   return env.order_pos;
 215 }
 216
 217 /* Deallocate all ipa_dfs_info structures pointed to by the aux pointer of call
 218    graph nodes.  */
 219
 220 void
 221 ipa_free_postorder_info (void)
 222 {
 223   struct cgraph_node *node;
 224   FOR_EACH_DEFINED_FUNCTION (node)
 225     {
 226       /* Get rid of the aux information.  */
 227       if (node->aux)
 228         {
 229           free (node->aux);
 230           node->aux = NULL;
 231         }
 232     }
 233 }
 234
 235 /* Get the set of nodes for the cycle in the reduced call graph starting
 236    from NODE.  */
 237
 238 vec<cgraph_node *>
 239 ipa_get_nodes_in_cycle (struct cgraph_node *node)
 240 {
 241   vec<cgraph_node *> v = vNULL;
 242   struct ipa_dfs_info *node_dfs_info;
 243   while (node)
 244     {
 245       v.safe_push (node);
 246       node_dfs_info = (struct ipa_dfs_info *) node->aux;
 247       node = node_dfs_info->next_cycle;
 248     }
 249   return v;
 250 }
 251
 252 /* Return true iff the CS is an edge within a strongly connected component as
 253    computed by ipa_reduced_postorder.  */
 254
 255 bool
 256 ipa_edge_within_scc (struct cgraph_edge *cs)
 257 {
 258   struct ipa_dfs_info *caller_dfs = (struct ipa_dfs_info *) cs->caller->aux;
 259   struct ipa_dfs_info *callee_dfs;
 260   struct cgraph_node *callee = cs->callee->function_symbol ();
 261
 262   callee_dfs = (struct ipa_dfs_info *) callee->aux;
 263   return (caller_dfs
 264           && callee_dfs
 265           && caller_dfs->scc_no == callee_dfs->scc_no);
 266 }
 267
 268 struct postorder_stack
 269 {
 270   struct cgraph_node *node;
 271   struct cgraph_edge *edge;
 272   int ref;
 273 };
 274
 275 /* Fill array order with all nodes with output flag set in the reverse
 276    topological order.  Return the number of elements in the array.
 277    FIXME: While walking, consider aliases, too.  */
 278
 279 int
 280 ipa_reverse_postorder (struct cgraph_node **order)
 281 {
 282   struct cgraph_node *node, *node2;
 283   int stack_size = 0;
 284   int order_pos = 0;
 285   struct cgraph_edge *edge;
 286   int pass;
 287   struct ipa_ref *ref = NULL;
 288
 289   struct postorder_stack *stack =
 290     XCNEWVEC (struct postorder_stack, symtab->cgraph_count);
 291
 292   /* We have to deal with cycles nicely, so use a depth first traversal
 293      output algorithm.  Ignore the fact that some functions won't need
 294      to be output and put them into order as well, so we get dependencies
 295      right through inline functions.  */
 296   FOR_EACH_FUNCTION (node)
 297     node->aux = NULL;
 298   for (pass = 0; pass < 2; pass++)
 299     FOR_EACH_FUNCTION (node)
 300       if (!node->aux
 301           && (pass
 302               || (!node->address_taken
 303                   && !node->global.inlined_to
 304                   && !node->alias && !node->thunk.thunk_p
 305                   && !node->only_called_directly_p ())))
 306         {
 307           stack_size = 0;
 308           stack[stack_size].node = node;
 309           stack[stack_size].edge = node->callers;
 310           stack[stack_size].ref = 0;
 311           node->aux = (void *)(size_t)1;
 312           while (stack_size >= 0)
 313             {
 314               while (true)
 315                 {
 316                   node2 = NULL;
 317                   while (stack[stack_size].edge && !node2)
 318                     {
 319                       edge = stack[stack_size].edge;
 320                       node2 = edge->caller;
 321                       stack[stack_size].edge = edge->next_caller;
 322                       /* Break possible cycles involving always-inline
 323                          functions by ignoring edges from always-inline
 324                          functions to non-always-inline functions.  */
 325                       if (DECL_DISREGARD_INLINE_LIMITS (edge->caller->decl)
 326                           && !DECL_DISREGARD_INLINE_LIMITS
 327                             (edge->callee->function_symbol ()->decl))
 328                         node2 = NULL;
 329                     }
 330                   for (; stack[stack_size].node->iterate_referring (
 331                                                        stack[stack_size].ref,
 332                                                        ref) && !node2;
 333                        stack[stack_size].ref++)
 334                     {
 335                       if (ref->use == IPA_REF_ALIAS)
 336                         node2 = dyn_cast <cgraph_node *> (ref->referring);
 337                     }
 338                   if (!node2)
 339                     break;
 340                   if (!node2->aux)
 341                     {
 342                       stack[++stack_size].node = node2;
 343                       stack[stack_size].edge = node2->callers;
 344                       stack[stack_size].ref = 0;
 345                       node2->aux = (void *)(size_t)1;
 346                     }
 347                 }
 348               order[order_pos++] = stack[stack_size--].node;
 349             }
 350         }
 351   free (stack);
 352   FOR_EACH_FUNCTION (node)
 353     node->aux = NULL;
 354   return order_pos;
 355 }
 356
 357
 358
 359 /* Given a memory reference T, will return the variable at the bottom
 360    of the access.  Unlike get_base_address, this will recurse through
 361    INDIRECT_REFS.  */
 362
 363 tree
 364 get_base_var (tree t)
 365 {
 366   while (!SSA_VAR_P (t)
 367          && (!CONSTANT_CLASS_P (t))
 368          && TREE_CODE (t) != LABEL_DECL
 369          && TREE_CODE (t) != FUNCTION_DECL
 370          && TREE_CODE (t) != CONST_DECL
 371          && TREE_CODE (t) != CONSTRUCTOR)
 372     {
 373       t = TREE_OPERAND (t, 0);
 374     }
 375   return t;
 376 }
 377
 378
 379 /* SRC and DST are going to be merged.  Take SRC's profile and merge it into
 380    DST so it is not going to be lost.  Possibly destroy SRC's body on the way
 381    unless PRESERVE_BODY is set.  */
 382
 383 void
 384 ipa_merge_profiles (struct cgraph_node *dst,
 385                     struct cgraph_node *src,
 386                     bool preserve_body)
 387 {
 388   tree oldsrcdecl = src->decl;
 389   struct function *srccfun, *dstcfun;
 390   bool match = true;
 391
 392   if (!src->definition
 393       || !dst->definition)
 394     return;
 395   if (src->frequency < dst->frequency)
 396     src->frequency = dst->frequency;
 397
 398   /* Time profiles are merged.  */
 399   if (dst->tp_first_run > src->tp_first_run && src->tp_first_run)
 400     dst->tp_first_run = src->tp_first_run;
 401
 402   if (src->profile_id && !dst->profile_id)
 403     dst->profile_id = src->profile_id;
 404
 405   /* FIXME when we merge in unknown profile, we ought to set counts as
 406      unsafe.  */
 407   if (!dst->count.initialized_p ())
 408     return;
 409   if (symtab->dump_file)
 410     {
 411       fprintf (symtab->dump_file, "Merging profiles of %s to %s\n",
 412                src->dump_name (), dst->dump_name ());
 413     }
 414   dst->count += src->count;
 415
 416   /* This is ugly.  We need to get both function bodies into memory.
 417      If declaration is merged, we need to duplicate it to be able
 418      to load body that is being replaced.  This makes symbol table
 419      temporarily inconsistent.  */
 420   if (src->decl == dst->decl)
 421     {
 422       struct lto_in_decl_state temp;
 423       struct lto_in_decl_state *state;
 424
 425       /* We are going to move the decl, we want to remove its file decl data.
 426          and link these with the new decl. */
 427       temp.fn_decl = src->decl;
 428       lto_in_decl_state **slot
 429         = src->lto_file_data->function_decl_states->find_slot (&temp,
 430                                                                NO_INSERT);
 431       state = *slot;
 432       src->lto_file_data->function_decl_states->clear_slot (slot);
 433       gcc_assert (state);
 434
 435       /* Duplicate the decl and be sure it does not link into body of DST.  */
 436       src->decl = copy_node (src->decl);
 437       DECL_STRUCT_FUNCTION (src->decl) = NULL;
 438       DECL_ARGUMENTS (src->decl) = NULL;
 439       DECL_INITIAL (src->decl) = NULL;
 440       DECL_RESULT (src->decl) = NULL;
 441
 442       /* Associate the decl state with new declaration, so LTO streamer
 443          can look it up.  */
 444       state->fn_decl = src->decl;
 445       slot
 446         = src->lto_file_data->function_decl_states->find_slot (state, INSERT);
 447       gcc_assert (!*slot);
 448       *slot = state;
 449     }
 450   src->get_untransformed_body ();
 451   dst->get_untransformed_body ();
 452   srccfun = DECL_STRUCT_FUNCTION (src->decl);
 453   dstcfun = DECL_STRUCT_FUNCTION (dst->decl);
 454   if (n_basic_blocks_for_fn (srccfun)
 455       != n_basic_blocks_for_fn (dstcfun))
 456     {
 457       if (symtab->dump_file)
 458         fprintf (symtab->dump_file,
 459                  "Giving up; number of basic block mismatch.\n");
 460       match = false;
 461     }
 462   else if (last_basic_block_for_fn (srccfun)
 463            != last_basic_block_for_fn (dstcfun))
 464     {
 465       if (symtab->dump_file)
 466         fprintf (symtab->dump_file,
 467                  "Giving up; last block mismatch.\n");
 468       match = false;
 469     }
 470   else
 471     {
 472       basic_block srcbb, dstbb;
 473
 474       FOR_ALL_BB_FN (srcbb, srccfun)
 475         {
 476           unsigned int i;
 477
 478           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 479           if (dstbb == NULL)
 480             {
 481               if (symtab->dump_file)
 482                 fprintf (symtab->dump_file,
 483                          "No matching block for bb %i.\n",
 484                          srcbb->index);
 485               match = false;
 486               break;
 487             }
 488           if (EDGE_COUNT (srcbb->succs) != EDGE_COUNT (dstbb->succs))
 489             {
 490               if (symtab->dump_file)
 491                 fprintf (symtab->dump_file,
 492                          "Edge count mistmatch for bb %i.\n",
 493                          srcbb->index);
 494               match = false;
 495               break;
 496             }
 497           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 498             {
 499               edge srce = EDGE_SUCC (srcbb, i);
 500               edge dste = EDGE_SUCC (dstbb, i);
 501               if (srce->dest->index != dste->dest->index)
 502                 {
 503                   if (symtab->dump_file)
 504                     fprintf (symtab->dump_file,
 505                              "Succ edge mistmatch for bb %i.\n",
 506                              srce->dest->index);
 507                   match = false;
 508                   break;
 509                 }
 510             }
 511         }
 512     }
 513   if (match)
 514     {
 515       struct cgraph_edge *e, *e2;
 516       basic_block srcbb, dstbb;
 517
 518       /* TODO: merge also statement histograms.  */
 519       FOR_ALL_BB_FN (srcbb, srccfun)
 520         {
 521           unsigned int i;
 522
 523           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 524           dstbb->count += srcbb->count;
 525           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 526             {
 527               edge srce = EDGE_SUCC (srcbb, i);
 528               edge dste = EDGE_SUCC (dstbb, i);
 529               dste->count += srce->count;
 530             }
 531         }
 532       push_cfun (dstcfun);
 533       counts_to_freqs ();
 534       compute_function_frequency ();
 535       pop_cfun ();
 536       for (e = dst->callees; e; e = e->next_callee)
 537         {
 538           if (e->speculative)
 539             continue;
 540           e->count = gimple_bb (e->call_stmt)->count;
 541           e->frequency = compute_call_stmt_bb_frequency
 542                              (dst->decl,
 543                               gimple_bb (e->call_stmt));
 544         }
 545       for (e = dst->indirect_calls, e2 = src->indirect_calls; e;
 546            e2 = (e2 ? e2->next_callee : NULL), e = e->next_callee)
 547         {
 548           profile_count count = gimple_bb (e->call_stmt)->count;
 549           int freq = compute_call_stmt_bb_frequency
 550                         (dst->decl,
 551                          gimple_bb (e->call_stmt));
 552           /* When call is speculative, we need to re-distribute probabilities
 553              the same way as they was.  This is not really correct because
 554              in the other copy the speculation may differ; but probably it
 555              is not really worth the effort.  */
 556           if (e->speculative)
 557             {
 558               cgraph_edge *direct, *indirect;
 559               cgraph_edge *direct2 = NULL, *indirect2 = NULL;
 560               ipa_ref *ref;
 561
 562               e->speculative_call_info (direct, indirect, ref);
 563               gcc_assert (e == indirect);
 564               if (e2 && e2->speculative)
 565                 e2->speculative_call_info (direct2, indirect2, ref);
 566               if (indirect->count > profile_count::zero ()
 567                   || direct->count > profile_count::zero ())
 568                 {
 569                   /* We should mismatch earlier if there is no matching
 570                      indirect edge.  */
 571                   if (!e2)
 572                     {
 573                       if (dump_file)
 574                         fprintf (dump_file,
 575                                  "Mismatch in merging indirect edges\n");
 576                     }
 577                   else if (!e2->speculative)
 578                     indirect->count += e2->count;
 579                   else if (e2->speculative)
 580                     {
 581                       if (DECL_ASSEMBLER_NAME (direct2->callee->decl)
 582                           != DECL_ASSEMBLER_NAME (direct->callee->decl))
 583                         {
 584                           if (direct2->count >= direct->count)
 585                             {
 586                               direct->redirect_callee (direct2->callee);
 587                               indirect->count += indirect2->count
 588                                                  + direct->count;
 589                               direct->count = direct2->count;
 590                             }
 591                           else
 592                             indirect->count += indirect2->count + direct2->count;
 593                         }
 594                       else
 595                         {
 596                            direct->count += direct2->count;
 597                            indirect->count += indirect2->count;
 598                         }
 599                     }
 600                   int  prob = direct->count.probability_in (direct->count
 601                                                             + indirect->count);
 602                   direct->frequency = RDIV (freq * prob, REG_BR_PROB_BASE);
 603                   indirect->frequency = RDIV (freq * (REG_BR_PROB_BASE - prob),
 604                                               REG_BR_PROB_BASE);
 605                 }
 606               else
 607                 /* At the moment we should have only profile feedback based
 608                    speculations when merging.  */
 609                 gcc_unreachable ();
 610             }
 611           else if (e2 && e2->speculative)
 612             {
 613               cgraph_edge *direct, *indirect;
 614               ipa_ref *ref;
 615
 616               e2->speculative_call_info (direct, indirect, ref);
 617               e->count = count;
 618               e->frequency = freq;
 619               int prob = direct->count.probability_in (e->count);
 620               e->make_speculative (direct->callee, direct->count,
 621                                    RDIV (freq * prob, REG_BR_PROB_BASE));
 622             }
 623           else
 624             {
 625               e->count = count;
 626               e->frequency = freq;
 627             }
 628         }
 629       if (!preserve_body)
 630         src->release_body ();
 631       ipa_update_overall_fn_summary (dst);
 632     }
 633   /* TODO: if there is no match, we can scale up.  */
 634   src->decl = oldsrcdecl;
 635 }
 636
 637 /* Return true if call to DEST is known to be self-recusive call withing FUNC.   */
 638
 639 bool
 640 recursive_call_p (tree func, tree dest)
 641 {
 642   struct cgraph_node *dest_node = cgraph_node::get_create (dest);
 643   struct cgraph_node *cnode = cgraph_node::get_create (func);
 644   ipa_ref *alias;
 645   enum availability avail;
 646
 647   gcc_assert (!cnode->alias);
 648   if (cnode != dest_node->ultimate_alias_target (&avail))
 649     return false;
 650   if (avail >= AVAIL_AVAILABLE)
 651     return true;
 652   if (!dest_node->semantically_equivalent_p (cnode))
 653     return false;
 654   /* If there is only one way to call the fuction or we know all of them
 655      are semantically equivalent, we still can consider call recursive.  */
 656   FOR_EACH_ALIAS (cnode, alias)
 657     if (!dest_node->semantically_equivalent_p (alias->referring))
 658       return false;
 659   return true;
 660 }