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   if (!dst->count)
 406     return;
 407   if (symtab->dump_file)
 408     {
 409       fprintf (symtab->dump_file, "Merging profiles of %s to %s\n",
 410                src->dump_name (), dst->dump_name ());
 411     }
 412   dst->count += src->count;
 413
 414   /* This is ugly.  We need to get both function bodies into memory.
 415      If declaration is merged, we need to duplicate it to be able
 416      to load body that is being replaced.  This makes symbol table
 417      temporarily inconsistent.  */
 418   if (src->decl == dst->decl)
 419     {
 420       struct lto_in_decl_state temp;
 421       struct lto_in_decl_state *state;
 422
 423       /* We are going to move the decl, we want to remove its file decl data.
 424          and link these with the new decl. */
 425       temp.fn_decl = src->decl;
 426       lto_in_decl_state **slot
 427         = src->lto_file_data->function_decl_states->find_slot (&temp,
 428                                                                NO_INSERT);
 429       state = *slot;
 430       src->lto_file_data->function_decl_states->clear_slot (slot);
 431       gcc_assert (state);
 432
 433       /* Duplicate the decl and be sure it does not link into body of DST.  */
 434       src->decl = copy_node (src->decl);
 435       DECL_STRUCT_FUNCTION (src->decl) = NULL;
 436       DECL_ARGUMENTS (src->decl) = NULL;
 437       DECL_INITIAL (src->decl) = NULL;
 438       DECL_RESULT (src->decl) = NULL;
 439
 440       /* Associate the decl state with new declaration, so LTO streamer
 441          can look it up.  */
 442       state->fn_decl = src->decl;
 443       slot
 444         = src->lto_file_data->function_decl_states->find_slot (state, INSERT);
 445       gcc_assert (!*slot);
 446       *slot = state;
 447     }
 448   src->get_untransformed_body ();
 449   dst->get_untransformed_body ();
 450   srccfun = DECL_STRUCT_FUNCTION (src->decl);
 451   dstcfun = DECL_STRUCT_FUNCTION (dst->decl);
 452   if (n_basic_blocks_for_fn (srccfun)
 453       != n_basic_blocks_for_fn (dstcfun))
 454     {
 455       if (symtab->dump_file)
 456         fprintf (symtab->dump_file,
 457                  "Giving up; number of basic block mismatch.\n");
 458       match = false;
 459     }
 460   else if (last_basic_block_for_fn (srccfun)
 461            != last_basic_block_for_fn (dstcfun))
 462     {
 463       if (symtab->dump_file)
 464         fprintf (symtab->dump_file,
 465                  "Giving up; last block mismatch.\n");
 466       match = false;
 467     }
 468   else
 469     {
 470       basic_block srcbb, dstbb;
 471
 472       FOR_ALL_BB_FN (srcbb, srccfun)
 473         {
 474           unsigned int i;
 475
 476           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 477           if (dstbb == NULL)
 478             {
 479               if (symtab->dump_file)
 480                 fprintf (symtab->dump_file,
 481                          "No matching block for bb %i.\n",
 482                          srcbb->index);
 483               match = false;
 484               break;
 485             }
 486           if (EDGE_COUNT (srcbb->succs) != EDGE_COUNT (dstbb->succs))
 487             {
 488               if (symtab->dump_file)
 489                 fprintf (symtab->dump_file,
 490                          "Edge count mistmatch for bb %i.\n",
 491                          srcbb->index);
 492               match = false;
 493               break;
 494             }
 495           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 496             {
 497               edge srce = EDGE_SUCC (srcbb, i);
 498               edge dste = EDGE_SUCC (dstbb, i);
 499               if (srce->dest->index != dste->dest->index)
 500                 {
 501                   if (symtab->dump_file)
 502                     fprintf (symtab->dump_file,
 503                              "Succ edge mistmatch for bb %i.\n",
 504                              srce->dest->index);
 505                   match = false;
 506                   break;
 507                 }
 508             }
 509         }
 510     }
 511   if (match)
 512     {
 513       struct cgraph_edge *e, *e2;
 514       basic_block srcbb, dstbb;
 515
 516       /* TODO: merge also statement histograms.  */
 517       FOR_ALL_BB_FN (srcbb, srccfun)
 518         {
 519           unsigned int i;
 520
 521           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 522           dstbb->count += srcbb->count;
 523           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 524             {
 525               edge srce = EDGE_SUCC (srcbb, i);
 526               edge dste = EDGE_SUCC (dstbb, i);
 527               dste->count += srce->count;
 528             }
 529         }
 530       push_cfun (dstcfun);
 531       counts_to_freqs ();
 532       compute_function_frequency ();
 533       pop_cfun ();
 534       for (e = dst->callees; e; e = e->next_callee)
 535         {
 536           if (e->speculative)
 537             continue;
 538           e->count = gimple_bb (e->call_stmt)->count;
 539           e->frequency = compute_call_stmt_bb_frequency
 540                              (dst->decl,
 541                               gimple_bb (e->call_stmt));
 542         }
 543       for (e = dst->indirect_calls, e2 = src->indirect_calls; e;
 544            e2 = (e2 ? e2->next_callee : NULL), e = e->next_callee)
 545         {
 546           gcov_type count = gimple_bb (e->call_stmt)->count;
 547           int freq = compute_call_stmt_bb_frequency
 548                         (dst->decl,
 549                          gimple_bb (e->call_stmt));
 550           /* When call is speculative, we need to re-distribute probabilities
 551              the same way as they was.  This is not really correct because
 552              in the other copy the speculation may differ; but probably it
 553              is not really worth the effort.  */
 554           if (e->speculative)
 555             {
 556               cgraph_edge *direct, *indirect;
 557               cgraph_edge *direct2 = NULL, *indirect2 = NULL;
 558               ipa_ref *ref;
 559
 560               e->speculative_call_info (direct, indirect, ref);
 561               gcc_assert (e == indirect);
 562               if (e2 && e2->speculative)
 563                 e2->speculative_call_info (direct2, indirect2, ref);
 564               if (indirect->count || direct->count)
 565                 {
 566                   /* We should mismatch earlier if there is no matching
 567                      indirect edge.  */
 568                   if (!e2)
 569                     {
 570                       if (dump_file)
 571                         fprintf (dump_file,
 572                                  "Mismatch in merging indirect edges\n");
 573                     }
 574                   else if (!e2->speculative)
 575                     indirect->count += e2->count;
 576                   else if (e2->speculative)
 577                     {
 578                       if (DECL_ASSEMBLER_NAME (direct2->callee->decl)
 579                           != DECL_ASSEMBLER_NAME (direct->callee->decl))
 580                         {
 581                           if (direct2->count >= direct->count)
 582                             {
 583                               direct->redirect_callee (direct2->callee);
 584                               indirect->count += indirect2->count
 585                                                  + direct->count;
 586                               direct->count = direct2->count;
 587                             }
 588                           else
 589                             indirect->count += indirect2->count + direct2->count;
 590                         }
 591                       else
 592                         {
 593                            direct->count += direct2->count;
 594                            indirect->count += indirect2->count;
 595                         }
 596                     }
 597                   int  prob = RDIV (direct->count * REG_BR_PROB_BASE ,
 598                                     direct->count + indirect->count);
 599                   direct->frequency = RDIV (freq * prob, REG_BR_PROB_BASE);
 600                   indirect->frequency = RDIV (freq * (REG_BR_PROB_BASE - prob),
 601                                               REG_BR_PROB_BASE);
 602                 }
 603               else
 604                 /* At the moment we should have only profile feedback based
 605                    speculations when merging.  */
 606                 gcc_unreachable ();
 607             }
 608           else if (e2 && e2->speculative)
 609             {
 610               cgraph_edge *direct, *indirect;
 611               ipa_ref *ref;
 612
 613               e2->speculative_call_info (direct, indirect, ref);
 614               e->count = count;
 615               e->frequency = freq;
 616               int prob = RDIV (direct->count * REG_BR_PROB_BASE, e->count);
 617               e->make_speculative (direct->callee, direct->count,
 618                                    RDIV (freq * prob, REG_BR_PROB_BASE));
 619             }
 620           else
 621             {
 622               e->count = count;
 623               e->frequency = freq;
 624             }
 625         }
 626       if (!preserve_body)
 627         src->release_body ();
 628       ipa_update_overall_fn_summary (dst);
 629     }
 630   /* TODO: if there is no match, we can scale up.  */
 631   src->decl = oldsrcdecl;
 632 }
 633
 634 /* Return true if call to DEST is known to be self-recusive call withing FUNC.   */
 635
 636 bool
 637 recursive_call_p (tree func, tree dest)
 638 {
 639   struct cgraph_node *dest_node = cgraph_node::get_create (dest);
 640   struct cgraph_node *cnode = cgraph_node::get_create (func);
 641   ipa_ref *alias;
 642   enum availability avail;
 643
 644   gcc_assert (!cnode->alias);
 645   if (cnode != dest_node->ultimate_alias_target (&avail))
 646     return false;
 647   if (avail >= AVAIL_AVAILABLE)
 648     return true;
 649   if (!dest_node->semantically_equivalent_p (cnode))
 650     return false;
 651   /* If there is only one way to call the fuction or we know all of them
 652      are semantically equivalent, we still can consider call recursive.  */
 653   FOR_EACH_ALIAS (cnode, alias)
 654     if (!dest_node->semantically_equivalent_p (alias->referring))
 655       return false;
 656   return true;
 657 }