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-inline.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/%i to %s/%i\n",
 410                xstrdup_for_dump (src->name ()), src->order,
 411                xstrdup_for_dump (dst->name ()), dst->order);
 412     }
 413   dst->count += src->count;
 414
 415   /* This is ugly.  We need to get both function bodies into memory.
 416      If declaration is merged, we need to duplicate it to be able
 417      to load body that is being replaced.  This makes symbol table
 418      temporarily inconsistent.  */
 419   if (src->decl == dst->decl)
 420     {
 421       struct lto_in_decl_state temp;
 422       struct lto_in_decl_state *state;
 423
 424       /* We are going to move the decl, we want to remove its file decl data.
 425          and link these with the new decl. */
 426       temp.fn_decl = src->decl;
 427       lto_in_decl_state **slot
 428         = src->lto_file_data->function_decl_states->find_slot (&temp,
 429                                                                NO_INSERT);
 430       state = *slot;
 431       src->lto_file_data->function_decl_states->clear_slot (slot);
 432       gcc_assert (state);
 433
 434       /* Duplicate the decl and be sure it does not link into body of DST.  */
 435       src->decl = copy_node (src->decl);
 436       DECL_STRUCT_FUNCTION (src->decl) = NULL;
 437       DECL_ARGUMENTS (src->decl) = NULL;
 438       DECL_INITIAL (src->decl) = NULL;
 439       DECL_RESULT (src->decl) = NULL;
 440
 441       /* Associate the decl state with new declaration, so LTO streamer
 442          can look it up.  */
 443       state->fn_decl = src->decl;
 444       slot
 445         = src->lto_file_data->function_decl_states->find_slot (state, INSERT);
 446       gcc_assert (!*slot);
 447       *slot = state;
 448     }
 449   src->get_untransformed_body ();
 450   dst->get_untransformed_body ();
 451   srccfun = DECL_STRUCT_FUNCTION (src->decl);
 452   dstcfun = DECL_STRUCT_FUNCTION (dst->decl);
 453   if (n_basic_blocks_for_fn (srccfun)
 454       != n_basic_blocks_for_fn (dstcfun))
 455     {
 456       if (symtab->dump_file)
 457         fprintf (symtab->dump_file,
 458                  "Giving up; number of basic block mismatch.\n");
 459       match = false;
 460     }
 461   else if (last_basic_block_for_fn (srccfun)
 462            != last_basic_block_for_fn (dstcfun))
 463     {
 464       if (symtab->dump_file)
 465         fprintf (symtab->dump_file,
 466                  "Giving up; last block mismatch.\n");
 467       match = false;
 468     }
 469   else
 470     {
 471       basic_block srcbb, dstbb;
 472
 473       FOR_ALL_BB_FN (srcbb, srccfun)
 474         {
 475           unsigned int i;
 476
 477           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 478           if (dstbb == NULL)
 479             {
 480               if (symtab->dump_file)
 481                 fprintf (symtab->dump_file,
 482                          "No matching block for bb %i.\n",
 483                          srcbb->index);
 484               match = false;
 485               break;
 486             }
 487           if (EDGE_COUNT (srcbb->succs) != EDGE_COUNT (dstbb->succs))
 488             {
 489               if (symtab->dump_file)
 490                 fprintf (symtab->dump_file,
 491                          "Edge count mistmatch for bb %i.\n",
 492                          srcbb->index);
 493               match = false;
 494               break;
 495             }
 496           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 497             {
 498               edge srce = EDGE_SUCC (srcbb, i);
 499               edge dste = EDGE_SUCC (dstbb, i);
 500               if (srce->dest->index != dste->dest->index)
 501                 {
 502                   if (symtab->dump_file)
 503                     fprintf (symtab->dump_file,
 504                              "Succ edge mistmatch for bb %i.\n",
 505                              srce->dest->index);
 506                   match = false;
 507                   break;
 508                 }
 509             }
 510         }
 511     }
 512   if (match)
 513     {
 514       struct cgraph_edge *e, *e2;
 515       basic_block srcbb, dstbb;
 516
 517       /* TODO: merge also statement histograms.  */
 518       FOR_ALL_BB_FN (srcbb, srccfun)
 519         {
 520           unsigned int i;
 521
 522           dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
 523           dstbb->count += srcbb->count;
 524           for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
 525             {
 526               edge srce = EDGE_SUCC (srcbb, i);
 527               edge dste = EDGE_SUCC (dstbb, i);
 528               dste->count += srce->count;
 529             }
 530         }
 531       push_cfun (dstcfun);
 532       counts_to_freqs ();
 533       compute_function_frequency ();
 534       pop_cfun ();
 535       for (e = dst->callees; e; e = e->next_callee)
 536         {
 537           if (e->speculative)
 538             continue;
 539           e->count = gimple_bb (e->call_stmt)->count;
 540           e->frequency = compute_call_stmt_bb_frequency
 541                              (dst->decl,
 542                               gimple_bb (e->call_stmt));
 543         }
 544       for (e = dst->indirect_calls, e2 = src->indirect_calls; e;
 545            e2 = (e2 ? e2->next_callee : NULL), e = e->next_callee)
 546         {
 547           gcov_type count = gimple_bb (e->call_stmt)->count;
 548           int freq = compute_call_stmt_bb_frequency
 549                         (dst->decl,
 550                          gimple_bb (e->call_stmt));
 551           /* When call is speculative, we need to re-distribute probabilities
 552              the same way as they was.  This is not really correct because
 553              in the other copy the speculation may differ; but probably it
 554              is not really worth the effort.  */
 555           if (e->speculative)
 556             {
 557               cgraph_edge *direct, *indirect;
 558               cgraph_edge *direct2 = NULL, *indirect2 = NULL;
 559               ipa_ref *ref;
 560
 561               e->speculative_call_info (direct, indirect, ref);
 562               gcc_assert (e == indirect);
 563               if (e2 && e2->speculative)
 564                 e2->speculative_call_info (direct2, indirect2, ref);
 565               if (indirect->count || direct->count)
 566                 {
 567                   /* We should mismatch earlier if there is no matching
 568                      indirect edge.  */
 569                   if (!e2)
 570                     {
 571                       if (dump_file)
 572                         fprintf (dump_file,
 573                                  "Mismatch in merging indirect edges\n");
 574                     }
 575                   else if (!e2->speculative)
 576                     indirect->count += e2->count;
 577                   else if (e2->speculative)
 578                     {
 579                       if (DECL_ASSEMBLER_NAME (direct2->callee->decl)
 580                           != DECL_ASSEMBLER_NAME (direct->callee->decl))
 581                         {
 582                           if (direct2->count >= direct->count)
 583                             {
 584                               direct->redirect_callee (direct2->callee);
 585                               indirect->count += indirect2->count
 586                                                  + direct->count;
 587                               direct->count = direct2->count;
 588                             }
 589                           else
 590                             indirect->count += indirect2->count + direct2->count;
 591                         }
 592                       else
 593                         {
 594                            direct->count += direct2->count;
 595                            indirect->count += indirect2->count;
 596                         }
 597                     }
 598                   int  prob = RDIV (direct->count * REG_BR_PROB_BASE ,
 599                                     direct->count + indirect->count);
 600                   direct->frequency = RDIV (freq * prob, REG_BR_PROB_BASE);
 601                   indirect->frequency = RDIV (freq * (REG_BR_PROB_BASE - prob),
 602                                               REG_BR_PROB_BASE);
 603                 }
 604               else
 605                 /* At the moment we should have only profile feedback based
 606                    speculations when merging.  */
 607                 gcc_unreachable ();
 608             }
 609           else if (e2 && e2->speculative)
 610             {
 611               cgraph_edge *direct, *indirect;
 612               ipa_ref *ref;
 613
 614               e2->speculative_call_info (direct, indirect, ref);
 615               e->count = count;
 616               e->frequency = freq;
 617               int prob = RDIV (direct->count * REG_BR_PROB_BASE, e->count);
 618               e->make_speculative (direct->callee, direct->count,
 619                                    RDIV (freq * prob, REG_BR_PROB_BASE));
 620             }
 621           else
 622             {
 623               e->count = count;
 624               e->frequency = freq;
 625             }
 626         }
 627       if (!preserve_body)
 628         src->release_body ();
 629       inline_update_overall_summary (dst);
 630     }
 631   /* TODO: if there is no match, we can scale up.  */
 632   src->decl = oldsrcdecl;
 633 }
 634
 635 /* Return true if call to DEST is known to be self-recusive call withing FUNC.   */
 636
 637 bool
 638 recursive_call_p (tree func, tree dest)
 639 {
 640   struct cgraph_node *dest_node = cgraph_node::get_create (dest);
 641   struct cgraph_node *cnode = cgraph_node::get_create (func);
 642   ipa_ref *alias;
 643   enum availability avail;
 644
 645   gcc_assert (!cnode->alias);
 646   if (cnode != dest_node->ultimate_alias_target (&avail))
 647     return false;
 648   if (avail >= AVAIL_AVAILABLE)
 649     return true;
 650   if (!dest_node->semantically_equivalent_p (cnode))
 651     return false;
 652   /* If there is only one way to call the fuction or we know all of them
 653      are semantically equivalent, we still can consider call recursive.  */
 654   FOR_EACH_ALIAS (cnode, alias)
 655     if (!dest_node->semantically_equivalent_p (alias->referring))
 656       return false;
 657   return true;
 658 }