gcc/ipa-inline-transform.c

   1 /* Callgraph transformations to handle inlining
   2    Copyright (C) 2003-2015 Free Software Foundation, Inc.
   3    Contributed by Jan Hubicka
   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 /* The inline decisions are stored in callgraph in "inline plan" and
  22    applied later.
  23
  24    To mark given call inline, use inline_call function.
  25    The function marks the edge inlinable and, if necessary, produces
  26    virtual clone in the callgraph representing the new copy of callee's
  27    function body.
  28
  29    The inline plan is applied on given function body by inline_transform.  */
  30
  31 #include "config.h"
  32 #include "system.h"
  33 #include "coretypes.h"
  34 #include "tm.h"
  35 #include "hash-set.h"
  36 #include "machmode.h"
  37 #include "vec.h"
  38 #include "double-int.h"
  39 #include "input.h"
  40 #include "alias.h"
  41 #include "symtab.h"
  42 #include "wide-int.h"
  43 #include "inchash.h"
  44 #include "tree.h"
  45 #include "langhooks.h"
  46 #include "intl.h"
  47 #include "coverage.h"
  48 #include "ggc.h"
  49 #include "tree-cfg.h"
  50 #include "hash-map.h"
  51 #include "is-a.h"
  52 #include "plugin-api.h"
  53 #include "hard-reg-set.h"
  54 #include "input.h"
  55 #include "function.h"
  56 #include "ipa-ref.h"
  57 #include "cgraph.h"
  58 #include "alloc-pool.h"
  59 #include "symbol-summary.h"
  60 #include "ipa-prop.h"
  61 #include "ipa-inline.h"
  62 #include "tree-inline.h"
  63 #include "tree-pass.h"
  64
  65 int ncalls_inlined;
  66 int nfunctions_inlined;
  67 bool speculation_removed;
  68
  69 /* Scale frequency of NODE edges by FREQ_SCALE.  */
  70
  71 static void
  72 update_noncloned_frequencies (struct cgraph_node *node,
  73                               int freq_scale)
  74 {
  75   struct cgraph_edge *e;
  76
  77   /* We do not want to ignore high loop nest after freq drops to 0.  */
  78   if (!freq_scale)
  79     freq_scale = 1;
  80   for (e = node->callees; e; e = e->next_callee)
  81     {
  82       e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;
  83       if (e->frequency > CGRAPH_FREQ_MAX)
  84         e->frequency = CGRAPH_FREQ_MAX;
  85       if (!e->inline_failed)
  86         update_noncloned_frequencies (e->callee, freq_scale);
  87     }
  88   for (e = node->indirect_calls; e; e = e->next_callee)
  89     {
  90       e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;
  91       if (e->frequency > CGRAPH_FREQ_MAX)
  92         e->frequency = CGRAPH_FREQ_MAX;
  93     }
  94 }
  95
  96 /* We removed or are going to remove the last call to NODE.
  97    Return true if we can and want proactively remove the NODE now.
  98    This is important to do, since we want inliner to know when offline
  99    copy of function was removed.  */
 100
 101 static bool
 102 can_remove_node_now_p_1 (struct cgraph_node *node, struct cgraph_edge *e)
 103 {
 104   ipa_ref *ref;
 105
 106   FOR_EACH_ALIAS (node, ref)
 107     {
 108       cgraph_node *alias = dyn_cast <cgraph_node *> (ref->referring);
 109       if ((alias->callers && alias->callers != e)
 110           || !can_remove_node_now_p_1 (alias, e))
 111         return false;
 112     }
 113   /* FIXME: When address is taken of DECL_EXTERNAL function we still
 114      can remove its offline copy, but we would need to keep unanalyzed node in
 115      the callgraph so references can point to it.  */
 116   return (!node->address_taken
 117           && node->can_remove_if_no_direct_calls_p ()
 118           /* Inlining might enable more devirtualizing, so we want to remove
 119              those only after all devirtualizable virtual calls are processed.
 120              Lacking may edges in callgraph we just preserve them post
 121              inlining.  */
 122           && (!DECL_VIRTUAL_P (node->decl)
 123               || !opt_for_fn (node->decl, flag_devirtualize))
 124           /* During early inlining some unanalyzed cgraph nodes might be in the
 125              callgraph and they might reffer the function in question.  */
 126           && !cgraph_new_nodes.exists ());
 127 }
 128
 129 /* We are going to eliminate last direct call to NODE (or alias of it) via edge E.
 130    Verify that the NODE can be removed from unit and if it is contained in comdat
 131    group that the whole comdat group is removable.  */
 132
 133 static bool
 134 can_remove_node_now_p (struct cgraph_node *node, struct cgraph_edge *e)
 135 {
 136   struct cgraph_node *next;
 137   if (!can_remove_node_now_p_1 (node, e))
 138     return false;
 139
 140   /* When we see same comdat group, we need to be sure that all
 141      items can be removed.  */
 142   if (!node->same_comdat_group || !node->externally_visible)
 143     return true;
 144   for (next = dyn_cast<cgraph_node *> (node->same_comdat_group);
 145        next != node; next = dyn_cast<cgraph_node *> (next->same_comdat_group))
 146     {
 147       if (next->alias)
 148         continue;
 149       if ((next->callers && next->callers != e)
 150           || !can_remove_node_now_p_1 (next, e))
 151         return false;
 152     }
 153   return true;
 154 }
 155
 156 /* Return true if NODE is a master clone with non-inline clones.  */
 157
 158 static bool
 159 master_clone_with_noninline_clones_p (struct cgraph_node *node)
 160 {
 161   if (node->clone_of)
 162     return false;
 163
 164   for (struct cgraph_node *n = node->clones; n; n = n->next_sibling_clone)
 165     if (n->decl != node->decl)
 166       return true;
 167
 168   return false;
 169 }
 170
 171 /* E is expected to be an edge being inlined.  Clone destination node of
 172    the edge and redirect it to the new clone.
 173    DUPLICATE is used for bookkeeping on whether we are actually creating new
 174    clones or re-using node originally representing out-of-line function call.
 175    By default the offline copy is removed, when it appears dead after inlining.
 176    UPDATE_ORIGINAL prevents this transformation.
 177    If OVERALL_SIZE is non-NULL, the size is updated to reflect the
 178    transformation.
 179    FREQ_SCALE specify the scaling of frequencies of call sites.  */
 180
 181 void
 182 clone_inlined_nodes (struct cgraph_edge *e, bool duplicate,
 183                      bool update_original, int *overall_size, int freq_scale)
 184 {
 185   struct cgraph_node *inlining_into;
 186   struct cgraph_edge *next;
 187
 188   if (e->caller->global.inlined_to)
 189     inlining_into = e->caller->global.inlined_to;
 190   else
 191     inlining_into = e->caller;
 192
 193   if (duplicate)
 194     {
 195       /* We may eliminate the need for out-of-line copy to be output.
 196          In that case just go ahead and re-use it.  This is not just an
 197          memory optimization.  Making offline copy of fuction disappear
 198          from the program will improve future decisions on inlining.  */
 199       if (!e->callee->callers->next_caller
 200           /* Recursive inlining never wants the master clone to
 201              be overwritten.  */
 202           && update_original
 203           && can_remove_node_now_p (e->callee, e)
 204           /* We cannot overwrite a master clone with non-inline clones
 205              until after these clones are materialized.  */
 206           && !master_clone_with_noninline_clones_p (e->callee))
 207         {
 208           /* TODO: When callee is in a comdat group, we could remove all of it,
 209              including all inline clones inlined into it.  That would however
 210              need small function inlining to register edge removal hook to
 211              maintain the priority queue.
 212
 213              For now we keep the ohter functions in the group in program until
 214              cgraph_remove_unreachable_functions gets rid of them.  */
 215           gcc_assert (!e->callee->global.inlined_to);
 216           e->callee->dissolve_same_comdat_group_list ();
 217           if (e->callee->definition
 218               && inline_account_function_p (e->callee))
 219             {
 220               gcc_assert (!e->callee->alias);
 221               if (overall_size)
 222                 *overall_size -= inline_summaries->get (e->callee)->size;
 223               nfunctions_inlined++;
 224             }
 225           duplicate = false;
 226           e->callee->externally_visible = false;
 227           update_noncloned_frequencies (e->callee, e->frequency);
 228         }
 229       else
 230         {
 231           struct cgraph_node *n;
 232
 233           if (freq_scale == -1)
 234             freq_scale = e->frequency;
 235           n = e->callee->create_clone (e->callee->decl,
 236                                        MIN (e->count, e->callee->count),
 237                                        freq_scale,
 238                                        update_original, vNULL, true,
 239                                        inlining_into,
 240                                        NULL);
 241           n->used_as_abstract_origin = e->callee->used_as_abstract_origin;
 242           e->redirect_callee (n);
 243         }
 244     }
 245   else
 246     e->callee->dissolve_same_comdat_group_list ();
 247
 248   e->callee->global.inlined_to = inlining_into;
 249
 250   /* Recursively clone all bodies.  */
 251   for (e = e->callee->callees; e; e = next)
 252     {
 253       next = e->next_callee;
 254       if (!e->inline_failed)
 255         clone_inlined_nodes (e, duplicate, update_original, overall_size, freq_scale);
 256       if (e->speculative && !speculation_useful_p (e, true))
 257         {
 258           e->resolve_speculation (NULL);
 259           speculation_removed = true;
 260         }
 261     }
 262 }
 263
 264 /* Mark all call graph edges coming out of NODE and all nodes that have been
 265    inlined to it as in_polymorphic_cdtor.  */
 266
 267 static void
 268 mark_all_inlined_calls_cdtor (cgraph_node *node)
 269 {
 270   for (cgraph_edge *cs = node->callees; cs; cs = cs->next_callee)
 271     {
 272       cs->in_polymorphic_cdtor = true;
 273       if (!cs->inline_failed)
 274     mark_all_inlined_calls_cdtor (cs->callee);
 275     }
 276   for (cgraph_edge *cs = node->indirect_calls; cs; cs = cs->next_callee)
 277     cs->in_polymorphic_cdtor = true;
 278 }
 279
 280
 281 /* Mark edge E as inlined and update callgraph accordingly.  UPDATE_ORIGINAL
 282    specify whether profile of original function should be updated.  If any new
 283    indirect edges are discovered in the process, add them to NEW_EDGES, unless
 284    it is NULL. If UPDATE_OVERALL_SUMMARY is false, do not bother to recompute overall
 285    size of caller after inlining. Caller is required to eventually do it via
 286    inline_update_overall_summary.
 287    If callee_removed is non-NULL, set it to true if we removed callee node.
 288
 289    Return true iff any new callgraph edges were discovered as a
 290    result of inlining.  */
 291
 292 bool
 293 inline_call (struct cgraph_edge *e, bool update_original,
 294              vec<cgraph_edge *> *new_edges,
 295              int *overall_size, bool update_overall_summary,
 296              bool *callee_removed)
 297 {
 298   int old_size = 0, new_size = 0;
 299   struct cgraph_node *to = NULL;
 300   struct cgraph_edge *curr = e;
 301   struct cgraph_node *callee = e->callee->ultimate_alias_target ();
 302   bool new_edges_found = false;
 303
 304 #ifdef ENABLE_CHECKING
 305   int estimated_growth = estimate_edge_growth (e);
 306   bool predicated = inline_edge_summary (e)->predicate != NULL;
 307 #endif
 308
 309   speculation_removed = false;
 310   /* Don't inline inlined edges.  */
 311   gcc_assert (e->inline_failed);
 312   /* Don't even think of inlining inline clone.  */
 313   gcc_assert (!callee->global.inlined_to);
 314
 315   e->inline_failed = CIF_OK;
 316   DECL_POSSIBLY_INLINED (callee->decl) = true;
 317
 318   to = e->caller;
 319   if (to->global.inlined_to)
 320     to = to->global.inlined_to;
 321
 322   /* If aliases are involved, redirect edge to the actual destination and
 323      possibly remove the aliases.  */
 324   if (e->callee != callee)
 325     {
 326       struct cgraph_node *alias = e->callee, *next_alias;
 327       e->redirect_callee (callee);
 328       while (alias && alias != callee)
 329         {
 330           if (!alias->callers
 331               && can_remove_node_now_p (alias,
 332                                         !e->next_caller && !e->prev_caller ? e : NULL))
 333             {
 334               next_alias = alias->get_alias_target ();
 335               alias->remove ();
 336               if (callee_removed)
 337                 *callee_removed = true;
 338               alias = next_alias;
 339             }
 340           else
 341             break;
 342         }
 343     }
 344
 345   clone_inlined_nodes (e, true, update_original, overall_size, e->frequency);
 346
 347   gcc_assert (curr->callee->global.inlined_to == to);
 348
 349   old_size = inline_summaries->get (to)->size;
 350   inline_merge_summary (e);
 351   if (e->in_polymorphic_cdtor)
 352     mark_all_inlined_calls_cdtor (e->callee);
 353   if (opt_for_fn (e->caller->decl, optimize))
 354     new_edges_found = ipa_propagate_indirect_call_infos (curr, new_edges);
 355   if (update_overall_summary)
 356    inline_update_overall_summary (to);
 357   new_size = inline_summaries->get (to)->size;
 358
 359   if (callee->calls_comdat_local)
 360     to->calls_comdat_local = true;
 361   else if (to->calls_comdat_local && callee->comdat_local_p ())
 362     {
 363       struct cgraph_edge *se = to->callees;
 364       for (; se; se = se->next_callee)
 365         if (se->inline_failed && se->callee->comdat_local_p ())
 366           break;
 367       if (se == NULL)
 368         to->calls_comdat_local = false;
 369     }
 370
 371 #ifdef ENABLE_CHECKING
 372   /* Verify that estimated growth match real growth.  Allow off-by-one
 373      error due to INLINE_SIZE_SCALE roudoff errors.  */
 374   gcc_assert (!update_overall_summary || !overall_size || new_edges_found
 375               || abs (estimated_growth - (new_size - old_size)) <= 1
 376               || speculation_removed
 377               /* FIXME: a hack.  Edges with false predicate are accounted
 378                  wrong, we should remove them from callgraph.  */
 379               || predicated);
 380 #endif
 381
 382   /* Account the change of overall unit size; external functions will be
 383      removed and are thus not accounted.  */
 384   if (overall_size && inline_account_function_p (to))
 385     *overall_size += new_size - old_size;
 386   ncalls_inlined++;
 387
 388   /* This must happen after inline_merge_summary that rely on jump
 389      functions of callee to not be updated.  */
 390   return new_edges_found;
 391 }
 392
 393
 394 /* Copy function body of NODE and redirect all inline clones to it.
 395    This is done before inline plan is applied to NODE when there are
 396    still some inline clones if it.
 397
 398    This is necessary because inline decisions are not really transitive
 399    and the other inline clones may have different bodies.  */
 400
 401 static struct cgraph_node *
 402 save_inline_function_body (struct cgraph_node *node)
 403 {
 404   struct cgraph_node *first_clone, *n;
 405
 406   if (dump_file)
 407     fprintf (dump_file, "\nSaving body of %s for later reuse\n",
 408              node->name ());
 409
 410   gcc_assert (node == cgraph_node::get (node->decl));
 411
 412   /* first_clone will be turned into real function.  */
 413   first_clone = node->clones;
 414   first_clone->decl = copy_node (node->decl);
 415   first_clone->decl->decl_with_vis.symtab_node = first_clone;
 416   gcc_assert (first_clone == cgraph_node::get (first_clone->decl));
 417
 418   /* Now reshape the clone tree, so all other clones descends from
 419      first_clone.  */
 420   if (first_clone->next_sibling_clone)
 421     {
 422       for (n = first_clone->next_sibling_clone; n->next_sibling_clone; n = n->next_sibling_clone)
 423         n->clone_of = first_clone;
 424       n->clone_of = first_clone;
 425       n->next_sibling_clone = first_clone->clones;
 426       if (first_clone->clones)
 427         first_clone->clones->prev_sibling_clone = n;
 428       first_clone->clones = first_clone->next_sibling_clone;
 429       first_clone->next_sibling_clone->prev_sibling_clone = NULL;
 430       first_clone->next_sibling_clone = NULL;
 431       gcc_assert (!first_clone->prev_sibling_clone);
 432     }
 433   first_clone->clone_of = NULL;
 434
 435   /* Now node in question has no clones.  */
 436   node->clones = NULL;
 437
 438   /* Inline clones share decl with the function they are cloned
 439      from.  Walk the whole clone tree and redirect them all to the
 440      new decl.  */
 441   if (first_clone->clones)
 442     for (n = first_clone->clones; n != first_clone;)
 443       {
 444         gcc_assert (n->decl == node->decl);
 445         n->decl = first_clone->decl;
 446         if (n->clones)
 447           n = n->clones;
 448         else if (n->next_sibling_clone)
 449           n = n->next_sibling_clone;
 450         else
 451           {
 452             while (n != first_clone && !n->next_sibling_clone)
 453               n = n->clone_of;
 454             if (n != first_clone)
 455               n = n->next_sibling_clone;
 456           }
 457       }
 458
 459   /* Copy the OLD_VERSION_NODE function tree to the new version.  */
 460   tree_function_versioning (node->decl, first_clone->decl,
 461                             NULL, true, NULL, false,
 462                             NULL, NULL);
 463
 464   /* The function will be short lived and removed after we inline all the clones,
 465      but make it internal so we won't confuse ourself.  */
 466   DECL_EXTERNAL (first_clone->decl) = 0;
 467   TREE_PUBLIC (first_clone->decl) = 0;
 468   DECL_COMDAT (first_clone->decl) = 0;
 469   first_clone->ipa_transforms_to_apply.release ();
 470
 471   /* When doing recursive inlining, the clone may become unnecessary.
 472      This is possible i.e. in the case when the recursive function is proved to be
 473      non-throwing and the recursion happens only in the EH landing pad.
 474      We can not remove the clone until we are done with saving the body.
 475      Remove it now.  */
 476   if (!first_clone->callers)
 477     {
 478       first_clone->remove_symbol_and_inline_clones ();
 479       first_clone = NULL;
 480     }
 481 #ifdef ENABLE_CHECKING
 482   else
 483     first_clone->verify ();
 484 #endif
 485   return first_clone;
 486 }
 487
 488 /* Return true when function body of DECL still needs to be kept around
 489    for later re-use.  */
 490 static bool
 491 preserve_function_body_p (struct cgraph_node *node)
 492 {
 493   gcc_assert (symtab->global_info_ready);
 494   gcc_assert (!node->alias && !node->thunk.thunk_p);
 495
 496   /* Look if there is any clone around.  */
 497   if (node->clones)
 498     return true;
 499   return false;
 500 }
 501
 502 /* Apply inline plan to function.  */
 503
 504 unsigned int
 505 inline_transform (struct cgraph_node *node)
 506 {
 507   unsigned int todo = 0;
 508   struct cgraph_edge *e, *next;
 509   bool has_inline = false;
 510
 511   /* FIXME: Currently the pass manager is adding inline transform more than
 512      once to some clones.  This needs revisiting after WPA cleanups.  */
 513   if (cfun->after_inlining)
 514     return 0;
 515
 516   /* We might need the body of this function so that we can expand
 517      it inline somewhere else.  */
 518   if (preserve_function_body_p (node))
 519     save_inline_function_body (node);
 520
 521   for (e = node->callees; e; e = next)
 522     {
 523       if (!e->inline_failed)
 524         has_inline = true;
 525       next = e->next_callee;
 526       e->redirect_call_stmt_to_callee ();
 527     }
 528   node->remove_all_references ();
 529
 530   timevar_push (TV_INTEGRATION);
 531   if (node->callees && (opt_for_fn (node->decl, optimize) || has_inline))
 532     todo = optimize_inline_calls (current_function_decl);
 533   timevar_pop (TV_INTEGRATION);
 534
 535   cfun->always_inline_functions_inlined = true;
 536   cfun->after_inlining = true;
 537   todo |= execute_fixup_cfg ();
 538
 539   if (!(todo & TODO_update_ssa_any))
 540     /* Redirecting edges might lead to a need for vops to be recomputed.  */
 541     todo |= TODO_update_ssa_only_virtuals;
 542
 543   return todo;
 544 }