gcc/ipa-inline-analysis.c

   1 /* Analysis used by inlining decision heuristics.
   2    Copyright (C) 2003-2017 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 #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 "alloc-pool.h"
  28 #include "tree-pass.h"
  29 #include "ssa.h"
  30 #include "tree-streamer.h"
  31 #include "cgraph.h"
  32 #include "diagnostic.h"
  33 #include "fold-const.h"
  34 #include "print-tree.h"
  35 #include "tree-inline.h"
  36 #include "gimple-pretty-print.h"
  37 #include "params.h"
  38 #include "cfganal.h"
  39 #include "gimple-iterator.h"
  40 #include "tree-cfg.h"
  41 #include "tree-ssa-loop-niter.h"
  42 #include "tree-ssa-loop.h"
  43 #include "symbol-summary.h"
  44 #include "ipa-prop.h"
  45 #include "ipa-fnsummary.h"
  46 #include "ipa-inline.h"
  47 #include "cfgloop.h"
  48 #include "tree-scalar-evolution.h"
  49 #include "ipa-utils.h"
  50 #include "cfgexpand.h"
  51 #include "gimplify.h"
  52
  53 /* Cached node/edge growths.  */
  54 vec<edge_growth_cache_entry> edge_growth_cache;
  55 static struct cgraph_edge_hook_list *edge_removal_hook_holder;
  56
  57
  58 /* Give initial reasons why inlining would fail on EDGE.  This gets either
  59    nullified or usually overwritten by more precise reasons later.  */
  60
  61 void
  62 initialize_inline_failed (struct cgraph_edge *e)
  63 {
  64   struct cgraph_node *callee = e->callee;
  65
  66   if (e->inline_failed && e->inline_failed != CIF_BODY_NOT_AVAILABLE
  67       && cgraph_inline_failed_type (e->inline_failed) == CIF_FINAL_ERROR)
  68     ;
  69   else if (e->indirect_unknown_callee)
  70     e->inline_failed = CIF_INDIRECT_UNKNOWN_CALL;
  71   else if (!callee->definition)
  72     e->inline_failed = CIF_BODY_NOT_AVAILABLE;
  73   else if (callee->local.redefined_extern_inline)
  74     e->inline_failed = CIF_REDEFINED_EXTERN_INLINE;
  75   else
  76     e->inline_failed = CIF_FUNCTION_NOT_CONSIDERED;
  77   gcc_checking_assert (!e->call_stmt_cannot_inline_p
  78                        || cgraph_inline_failed_type (e->inline_failed)
  79                             == CIF_FINAL_ERROR);
  80 }
  81
  82
  83 /* Keep edge cache consistent across edge removal.  */
  84
  85 static void
  86 inline_edge_removal_hook (struct cgraph_edge *edge,
  87                           void *data ATTRIBUTE_UNUSED)
  88 {
  89   reset_edge_growth_cache (edge);
  90 }
  91
  92
  93 /* Initialize growth caches.  */
  94
  95 void
  96 initialize_growth_caches (void)
  97 {
  98   if (!edge_removal_hook_holder)
  99     edge_removal_hook_holder =
 100       symtab->add_edge_removal_hook (&inline_edge_removal_hook, NULL);
 101   if (symtab->edges_max_uid)
 102     edge_growth_cache.safe_grow_cleared (symtab->edges_max_uid);
 103 }
 104
 105
 106 /* Free growth caches.  */
 107
 108 void
 109 free_growth_caches (void)
 110 {
 111   if (edge_removal_hook_holder)
 112     {
 113       symtab->remove_edge_removal_hook (edge_removal_hook_holder);
 114       edge_removal_hook_holder = NULL;
 115     }
 116   edge_growth_cache.release ();
 117 }
 118
 119 /* Return hints derrived from EDGE.   */
 120
 121 int
 122 simple_edge_hints (struct cgraph_edge *edge)
 123 {
 124   int hints = 0;
 125   struct cgraph_node *to = (edge->caller->global.inlined_to
 126                             ? edge->caller->global.inlined_to : edge->caller);
 127   struct cgraph_node *callee = edge->callee->ultimate_alias_target ();
 128   if (ipa_fn_summaries->get (to)->scc_no
 129       && ipa_fn_summaries->get (to)->scc_no
 130          == ipa_fn_summaries->get (callee)->scc_no
 131       && !edge->recursive_p ())
 132     hints |= INLINE_HINT_same_scc;
 133
 134   if (callee->lto_file_data && edge->caller->lto_file_data
 135       && edge->caller->lto_file_data != callee->lto_file_data
 136       && !callee->merged_comdat && !callee->icf_merged)
 137     hints |= INLINE_HINT_cross_module;
 138
 139   return hints;
 140 }
 141
 142 /* Estimate the time cost for the caller when inlining EDGE.
 143    Only to be called via estimate_edge_time, that handles the
 144    caching mechanism.
 145
 146    When caching, also update the cache entry.  Compute both time and
 147    size, since we always need both metrics eventually.  */
 148
 149 sreal
 150 do_estimate_edge_time (struct cgraph_edge *edge)
 151 {
 152   sreal time, nonspec_time;
 153   int size;
 154   ipa_hints hints;
 155   struct cgraph_node *callee;
 156   clause_t clause, nonspec_clause;
 157   vec<tree> known_vals;
 158   vec<ipa_polymorphic_call_context> known_contexts;
 159   vec<ipa_agg_jump_function_p> known_aggs;
 160   struct ipa_call_summary *es = ipa_call_summaries->get (edge);
 161   int min_size;
 162
 163   callee = edge->callee->ultimate_alias_target ();
 164
 165   gcc_checking_assert (edge->inline_failed);
 166   evaluate_properties_for_edge (edge, true,
 167                                 &clause, &nonspec_clause, &known_vals,
 168                                 &known_contexts, &known_aggs);
 169   estimate_node_size_and_time (callee, clause, nonspec_clause, known_vals,
 170                                known_contexts, known_aggs, &size, &min_size,
 171                                &time, &nonspec_time, &hints, es->param);
 172
 173   /* When we have profile feedback, we can quite safely identify hot
 174      edges and for those we disable size limits.  Don't do that when
 175      probability that caller will call the callee is low however, since it
 176      may hurt optimization of the caller's hot path.  */
 177   if (edge->count.ipa ().initialized_p () && edge->maybe_hot_p ()
 178       && (edge->count.ipa ().apply_scale (2, 1)
 179           > (edge->caller->global.inlined_to
 180              ? edge->caller->global.inlined_to->count.ipa ()
 181              : edge->caller->count.ipa ())))
 182     hints |= INLINE_HINT_known_hot;
 183
 184   known_vals.release ();
 185   known_contexts.release ();
 186   known_aggs.release ();
 187   gcc_checking_assert (size >= 0);
 188   gcc_checking_assert (time >= 0);
 189
 190   /* When caching, update the cache entry.  */
 191   if (edge_growth_cache.exists ())
 192     {
 193       ipa_fn_summaries->get (edge->callee)->min_size = min_size;
 194       if ((int) edge_growth_cache.length () <= edge->uid)
 195         edge_growth_cache.safe_grow_cleared (symtab->edges_max_uid);
 196       edge_growth_cache[edge->uid].time = time;
 197       edge_growth_cache[edge->uid].nonspec_time = nonspec_time;
 198
 199       edge_growth_cache[edge->uid].size = size + (size >= 0);
 200       hints |= simple_edge_hints (edge);
 201       edge_growth_cache[edge->uid].hints = hints + 1;
 202     }
 203   return time;
 204 }
 205
 206
 207 /* Return estimated callee growth after inlining EDGE.
 208    Only to be called via estimate_edge_size.  */
 209
 210 int
 211 do_estimate_edge_size (struct cgraph_edge *edge)
 212 {
 213   int size;
 214   struct cgraph_node *callee;
 215   clause_t clause, nonspec_clause;
 216   vec<tree> known_vals;
 217   vec<ipa_polymorphic_call_context> known_contexts;
 218   vec<ipa_agg_jump_function_p> known_aggs;
 219
 220   /* When we do caching, use do_estimate_edge_time to populate the entry.  */
 221
 222   if (edge_growth_cache.exists ())
 223     {
 224       do_estimate_edge_time (edge);
 225       size = edge_growth_cache[edge->uid].size;
 226       gcc_checking_assert (size);
 227       return size - (size > 0);
 228     }
 229
 230   callee = edge->callee->ultimate_alias_target ();
 231
 232   /* Early inliner runs without caching, go ahead and do the dirty work.  */
 233   gcc_checking_assert (edge->inline_failed);
 234   evaluate_properties_for_edge (edge, true,
 235                                 &clause, &nonspec_clause,
 236                                 &known_vals, &known_contexts,
 237                                 &known_aggs);
 238   estimate_node_size_and_time (callee, clause, nonspec_clause, known_vals,
 239                                known_contexts, known_aggs, &size, NULL, NULL,
 240                                NULL, NULL, vNULL);
 241   known_vals.release ();
 242   known_contexts.release ();
 243   known_aggs.release ();
 244   return size;
 245 }
 246
 247
 248 /* Estimate the growth of the caller when inlining EDGE.
 249    Only to be called via estimate_edge_size.  */
 250
 251 ipa_hints
 252 do_estimate_edge_hints (struct cgraph_edge *edge)
 253 {
 254   ipa_hints hints;
 255   struct cgraph_node *callee;
 256   clause_t clause, nonspec_clause;
 257   vec<tree> known_vals;
 258   vec<ipa_polymorphic_call_context> known_contexts;
 259   vec<ipa_agg_jump_function_p> known_aggs;
 260
 261   /* When we do caching, use do_estimate_edge_time to populate the entry.  */
 262
 263   if (edge_growth_cache.exists ())
 264     {
 265       do_estimate_edge_time (edge);
 266       hints = edge_growth_cache[edge->uid].hints;
 267       gcc_checking_assert (hints);
 268       return hints - 1;
 269     }
 270
 271   callee = edge->callee->ultimate_alias_target ();
 272
 273   /* Early inliner runs without caching, go ahead and do the dirty work.  */
 274   gcc_checking_assert (edge->inline_failed);
 275   evaluate_properties_for_edge (edge, true,
 276                                 &clause, &nonspec_clause,
 277                                 &known_vals, &known_contexts,
 278                                 &known_aggs);
 279   estimate_node_size_and_time (callee, clause, nonspec_clause, known_vals,
 280                                known_contexts, known_aggs, NULL, NULL,
 281                                NULL, NULL, &hints, vNULL);
 282   known_vals.release ();
 283   known_contexts.release ();
 284   known_aggs.release ();
 285   hints |= simple_edge_hints (edge);
 286   return hints;
 287 }
 288
 289 /* Estimate the size of NODE after inlining EDGE which should be an
 290    edge to either NODE or a call inlined into NODE.  */
 291
 292 int
 293 estimate_size_after_inlining (struct cgraph_node *node,
 294                               struct cgraph_edge *edge)
 295 {
 296   struct ipa_call_summary *es = ipa_call_summaries->get (edge);
 297   if (!es->predicate || *es->predicate != false)
 298     {
 299       int size = ipa_fn_summaries->get (node)->size + estimate_edge_growth (edge);
 300       gcc_assert (size >= 0);
 301       return size;
 302     }
 303   return ipa_fn_summaries->get (node)->size;
 304 }
 305
 306
 307 struct growth_data
 308 {
 309   struct cgraph_node *node;
 310   bool self_recursive;
 311   bool uninlinable;
 312   int growth;
 313 };
 314
 315
 316 /* Worker for do_estimate_growth.  Collect growth for all callers.  */
 317
 318 static bool
 319 do_estimate_growth_1 (struct cgraph_node *node, void *data)
 320 {
 321   struct cgraph_edge *e;
 322   struct growth_data *d = (struct growth_data *) data;
 323
 324   for (e = node->callers; e; e = e->next_caller)
 325     {
 326       gcc_checking_assert (e->inline_failed);
 327
 328       if (cgraph_inline_failed_type (e->inline_failed) == CIF_FINAL_ERROR
 329           || !opt_for_fn (e->caller->decl, optimize))
 330         {
 331           d->uninlinable = true;
 332           continue;
 333         }
 334
 335       if (e->recursive_p ())
 336         {
 337           d->self_recursive = true;
 338           continue;
 339         }
 340       d->growth += estimate_edge_growth (e);
 341     }
 342   return false;
 343 }
 344
 345
 346 /* Estimate the growth caused by inlining NODE into all callees.  */
 347
 348 int
 349 estimate_growth (struct cgraph_node *node)
 350 {
 351   struct growth_data d = { node, false, false, 0 };
 352   struct ipa_fn_summary *info = ipa_fn_summaries->get (node);
 353
 354   node->call_for_symbol_and_aliases (do_estimate_growth_1, &d, true);
 355
 356   /* For self recursive functions the growth estimation really should be
 357      infinity.  We don't want to return very large values because the growth
 358      plays various roles in badness computation fractions.  Be sure to not
 359      return zero or negative growths. */
 360   if (d.self_recursive)
 361     d.growth = d.growth < info->size ? info->size : d.growth;
 362   else if (DECL_EXTERNAL (node->decl) || d.uninlinable)
 363     ;
 364   else
 365     {
 366       if (node->will_be_removed_from_program_if_no_direct_calls_p ())
 367         d.growth -= info->size;
 368       /* COMDAT functions are very often not shared across multiple units
 369          since they come from various template instantiations.
 370          Take this into account.  */
 371       else if (DECL_COMDAT (node->decl)
 372                && node->can_remove_if_no_direct_calls_p ())
 373         d.growth -= (info->size
 374                      * (100 - PARAM_VALUE (PARAM_COMDAT_SHARING_PROBABILITY))
 375                      + 50) / 100;
 376     }
 377
 378   return d.growth;
 379 }
 380
 381 /* Verify if there are fewer than MAX_CALLERS.  */
 382
 383 static bool
 384 check_callers (cgraph_node *node, int *max_callers)
 385 {
 386   ipa_ref *ref;
 387
 388   if (!node->can_remove_if_no_direct_calls_and_refs_p ())
 389     return true;
 390
 391   for (cgraph_edge *e = node->callers; e; e = e->next_caller)
 392     {
 393       (*max_callers)--;
 394       if (!*max_callers
 395           || cgraph_inline_failed_type (e->inline_failed) == CIF_FINAL_ERROR)
 396         return true;
 397     }
 398
 399   FOR_EACH_ALIAS (node, ref)
 400     if (check_callers (dyn_cast <cgraph_node *> (ref->referring), max_callers))
 401       return true;
 402
 403   return false;
 404 }
 405
 406
 407 /* Make cheap estimation if growth of NODE is likely positive knowing
 408    EDGE_GROWTH of one particular edge.
 409    We assume that most of other edges will have similar growth
 410    and skip computation if there are too many callers.  */
 411
 412 bool
 413 growth_likely_positive (struct cgraph_node *node,
 414                         int edge_growth)
 415 {
 416   int max_callers;
 417   struct cgraph_edge *e;
 418   gcc_checking_assert (edge_growth > 0);
 419
 420   /* First quickly check if NODE is removable at all.  */
 421   if (DECL_EXTERNAL (node->decl))
 422     return true;
 423   if (!node->can_remove_if_no_direct_calls_and_refs_p ()
 424       || node->address_taken)
 425     return true;
 426
 427   max_callers = ipa_fn_summaries->get (node)->size * 4 / edge_growth + 2;
 428
 429   for (e = node->callers; e; e = e->next_caller)
 430     {
 431       max_callers--;
 432       if (!max_callers
 433           || cgraph_inline_failed_type (e->inline_failed) == CIF_FINAL_ERROR)
 434         return true;
 435     }
 436
 437   ipa_ref *ref;
 438   FOR_EACH_ALIAS (node, ref)
 439     if (check_callers (dyn_cast <cgraph_node *> (ref->referring), &max_callers))
 440       return true;
 441
 442   /* Unlike for functions called once, we play unsafe with
 443      COMDATs.  We can allow that since we know functions
 444      in consideration are small (and thus risk is small) and
 445      moreover grow estimates already accounts that COMDAT
 446      functions may or may not disappear when eliminated from
 447      current unit. With good probability making aggressive
 448      choice in all units is going to make overall program
 449      smaller.  */
 450   if (DECL_COMDAT (node->decl))
 451     {
 452       if (!node->can_remove_if_no_direct_calls_p ())
 453         return true;
 454     }
 455   else if (!node->will_be_removed_from_program_if_no_direct_calls_p ())
 456     return true;
 457
 458   return estimate_growth (node) > 0;
 459 }