gcc/ipa-inline-transform.c

   1 /* Callgraph transformations to handle inlining
   2    Copyright (C) 2003, 2004, 2007, 2008, 2009, 2010, 2011
   3    Free Software Foundation, Inc.
   4    Contributed by Jan Hubicka
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 /* The inline decisions are stored in callgraph in "inline plan" and
  23    applied later.
  24
  25    To mark given call inline, use inline_call function.
  26    The function marks the edge inlinable and, if necessary, produces
  27    virtual clone in the callgraph representing the new copy of callee's
  28    function body.
  29
  30    The inline plan is applied on given function body by inline_transform.  */
  31
  32 #include "config.h"
  33 #include "system.h"
  34 #include "coretypes.h"
  35 #include "tm.h"
  36 #include "tree.h"
  37 #include "langhooks.h"
  38 #include "cgraph.h"
  39 #include "timevar.h"
  40 #include "output.h"
  41 #include "intl.h"
  42 #include "coverage.h"
  43 #include "ggc.h"
  44 #include "tree-flow.h"
  45 #include "ipa-prop.h"
  46 #include "ipa-inline.h"
  47 #include "tree-inline.h"
  48 #include "tree-pass.h"
  49
  50 int ncalls_inlined;
  51 int nfunctions_inlined;
  52
  53 /* Scale frequency of NODE edges by FREQ_SCALE.  */
  54
  55 static void
  56 update_noncloned_frequencies (struct cgraph_node *node,
  57                               int freq_scale)
  58 {
  59   struct cgraph_edge *e;
  60
  61   /* We do not want to ignore high loop nest after freq drops to 0.  */
  62   if (!freq_scale)
  63     freq_scale = 1;
  64   for (e = node->callees; e; e = e->next_callee)
  65     {
  66       e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;
  67       if (e->frequency > CGRAPH_FREQ_MAX)
  68         e->frequency = CGRAPH_FREQ_MAX;
  69       if (!e->inline_failed)
  70         update_noncloned_frequencies (e->callee, freq_scale);
  71     }
  72   for (e = node->indirect_calls; e; e = e->next_callee)
  73     {
  74       e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;
  75       if (e->frequency > CGRAPH_FREQ_MAX)
  76         e->frequency = CGRAPH_FREQ_MAX;
  77     }
  78 }
  79
  80 /* We removed or are going to remove the last call to NODE.
  81    Return true if we can and want proactively remove the NODE now.
  82    This is important to do, since we want inliner to know when offline
  83    copy of function was removed.  */
  84
  85 static bool
  86 can_remove_node_now_p_1 (struct cgraph_node *node)
  87 {
  88   /* FIXME: When address is taken of DECL_EXTERNAL function we still
  89      can remove its offline copy, but we would need to keep unanalyzed node in
  90      the callgraph so references can point to it.  */
  91   return (!node->address_taken
  92           && !ipa_ref_has_aliases_p (&node->ref_list)
  93           && cgraph_can_remove_if_no_direct_calls_p (node)
  94           /* Inlining might enable more devirtualizing, so we want to remove
  95              those only after all devirtualizable virtual calls are processed.
  96              Lacking may edges in callgraph we just preserve them post
  97              inlining.  */
  98           && (!DECL_VIRTUAL_P (node->decl)
  99               || (!DECL_COMDAT (node->decl)
 100                   && !DECL_EXTERNAL (node->decl)))
 101           /* During early inlining some unanalyzed cgraph nodes might be in the
 102              callgraph and they might reffer the function in question.  */
 103           && !cgraph_new_nodes);
 104 }
 105
 106 /* We are going to eliminate last direct call to NODE (or alias of it) via edge E.
 107    Verify that the NODE can be removed from unit and if it is contained in comdat
 108    group that the whole comdat group is removable.  */
 109
 110 static bool
 111 can_remove_node_now_p (struct cgraph_node *node, struct cgraph_edge *e)
 112 {
 113   struct cgraph_node *next;
 114   if (!can_remove_node_now_p_1 (node))
 115     return false;
 116
 117   /* When we see same comdat group, we need to be sure that all
 118      items can be removed.  */
 119   if (!node->same_comdat_group)
 120     return true;
 121   for (next = node->same_comdat_group;
 122        next != node; next = next->same_comdat_group)
 123     if ((next->callers && next->callers != e)
 124         || !can_remove_node_now_p_1 (next))
 125       return false;
 126   return true;
 127 }
 128
 129
 130 /* E is expected to be an edge being inlined.  Clone destination node of
 131    the edge and redirect it to the new clone.
 132    DUPLICATE is used for bookkeeping on whether we are actually creating new
 133    clones or re-using node originally representing out-of-line function call.
 134    */
 135
 136 void
 137 clone_inlined_nodes (struct cgraph_edge *e, bool duplicate,
 138                      bool update_original, int *overall_size)
 139 {
 140   if (duplicate)
 141     {
 142       /* We may eliminate the need for out-of-line copy to be output.
 143          In that case just go ahead and re-use it.  This is not just an
 144          memory optimization.  Making offline copy of fuction disappear
 145          from the program will improve future decisions on inlining.  */
 146       if (!e->callee->callers->next_caller
 147           /* Recursive inlining never wants the master clone to
 148              be overwritten.  */
 149           && update_original
 150           && can_remove_node_now_p (e->callee, e))
 151         {
 152           /* TODO: When callee is in a comdat group, we could remove all of it,
 153              including all inline clones inlined into it.  That would however
 154              need small function inlining to register edge removal hook to
 155              maintain the priority queue.
 156
 157              For now we keep the ohter functions in the group in program until
 158              cgraph_remove_unreachable_functions gets rid of them.  */
 159           gcc_assert (!e->callee->global.inlined_to);
 160           if (e->callee->analyzed && !DECL_EXTERNAL (e->callee->decl))
 161             {
 162               if (overall_size)
 163                 *overall_size -= inline_summary (e->callee)->size;
 164               nfunctions_inlined++;
 165             }
 166           duplicate = false;
 167           e->callee->local.externally_visible = false;
 168           update_noncloned_frequencies (e->callee, e->frequency);
 169         }
 170       else
 171         {
 172           struct cgraph_node *n;
 173           n = cgraph_clone_node (e->callee, e->callee->decl,
 174                                  e->count, e->frequency,
 175                                  update_original, NULL, true);
 176           cgraph_redirect_edge_callee (e, n);
 177         }
 178     }
 179
 180   if (e->caller->global.inlined_to)
 181     e->callee->global.inlined_to = e->caller->global.inlined_to;
 182   else
 183     e->callee->global.inlined_to = e->caller;
 184
 185   /* Recursively clone all bodies.  */
 186   for (e = e->callee->callees; e; e = e->next_callee)
 187     if (!e->inline_failed)
 188       clone_inlined_nodes (e, duplicate, update_original, overall_size);
 189 }
 190
 191
 192 /* Mark edge E as inlined and update callgraph accordingly.  UPDATE_ORIGINAL
 193    specify whether profile of original function should be updated.  If any new
 194    indirect edges are discovered in the process, add them to NEW_EDGES, unless
 195    it is NULL.  Return true iff any new callgraph edges were discovered as a
 196    result of inlining.  */
 197
 198 bool
 199 inline_call (struct cgraph_edge *e, bool update_original,
 200              VEC (cgraph_edge_p, heap) **new_edges,
 201              int *overall_size)
 202 {
 203   int old_size = 0, new_size = 0;
 204   struct cgraph_node *to = NULL;
 205   struct cgraph_edge *curr = e;
 206   struct cgraph_node *callee = cgraph_function_or_thunk_node (e->callee, NULL);
 207
 208   /* Don't inline inlined edges.  */
 209   gcc_assert (e->inline_failed);
 210   /* Don't even think of inlining inline clone.  */
 211   gcc_assert (!callee->global.inlined_to);
 212
 213   e->inline_failed = CIF_OK;
 214   DECL_POSSIBLY_INLINED (callee->decl) = true;
 215
 216   to = e->caller;
 217   if (to->global.inlined_to)
 218     to = to->global.inlined_to;
 219
 220   /* If aliases are involved, redirect edge to the actual destination and
 221      possibly remove the aliases.  */
 222   if (e->callee != callee)
 223     {
 224       struct cgraph_node *alias = e->callee, *next_alias;
 225       cgraph_redirect_edge_callee (e, callee);
 226       while (alias && alias != callee)
 227         {
 228           if (!alias->callers
 229               && can_remove_node_now_p (alias, e))
 230             {
 231               next_alias = cgraph_alias_aliased_node (alias);
 232               cgraph_remove_node (alias);
 233               alias = next_alias;
 234             }
 235           else
 236             break;
 237         }
 238     }
 239
 240   clone_inlined_nodes (e, true, update_original, overall_size);
 241
 242   gcc_assert (curr->callee->global.inlined_to == to);
 243
 244   old_size = inline_summary (to)->size;
 245   inline_merge_summary (e);
 246   new_size = inline_summary (to)->size;
 247   if (overall_size)
 248     *overall_size += new_size - old_size;
 249   ncalls_inlined++;
 250
 251   /* This must happen after inline_merge_summary that rely on jump
 252      functions of callee to not be updated.  */
 253   if (optimize)
 254     return ipa_propagate_indirect_call_infos (curr, new_edges);
 255   else
 256     return false;
 257 }
 258
 259
 260 /* Copy function body of NODE and redirect all inline clones to it.
 261    This is done before inline plan is applied to NODE when there are
 262    still some inline clones if it.
 263
 264    This is neccesary because inline decisions are not really transitive
 265    and the other inline clones may have different bodies.  */
 266
 267 static struct cgraph_node *
 268 save_inline_function_body (struct cgraph_node *node)
 269 {
 270   struct cgraph_node *first_clone, *n;
 271
 272   if (dump_file)
 273     fprintf (dump_file, "\nSaving body of %s for later reuse\n",
 274              cgraph_node_name (node));
 275
 276   gcc_assert (node == cgraph_get_node (node->decl));
 277
 278   /* first_clone will be turned into real function.  */
 279   first_clone = node->clones;
 280   first_clone->decl = copy_node (node->decl);
 281   cgraph_insert_node_to_hashtable (first_clone);
 282   gcc_assert (first_clone == cgraph_get_node (first_clone->decl));
 283
 284   /* Now reshape the clone tree, so all other clones descends from
 285      first_clone.  */
 286   if (first_clone->next_sibling_clone)
 287     {
 288       for (n = first_clone->next_sibling_clone; n->next_sibling_clone; n = n->next_sibling_clone)
 289         n->clone_of = first_clone;
 290       n->clone_of = first_clone;
 291       n->next_sibling_clone = first_clone->clones;
 292       if (first_clone->clones)
 293         first_clone->clones->prev_sibling_clone = n;
 294       first_clone->clones = first_clone->next_sibling_clone;
 295       first_clone->next_sibling_clone->prev_sibling_clone = NULL;
 296       first_clone->next_sibling_clone = NULL;
 297       gcc_assert (!first_clone->prev_sibling_clone);
 298     }
 299   first_clone->clone_of = NULL;
 300
 301   /* Now node in question has no clones.  */
 302   node->clones = NULL;
 303
 304   /* Inline clones share decl with the function they are cloned
 305      from.  Walk the whole clone tree and redirect them all to the
 306      new decl.  */
 307   if (first_clone->clones)
 308     for (n = first_clone->clones; n != first_clone;)
 309       {
 310         gcc_assert (n->decl == node->decl);
 311         n->decl = first_clone->decl;
 312         if (n->clones)
 313           n = n->clones;
 314         else if (n->next_sibling_clone)
 315           n = n->next_sibling_clone;
 316         else
 317           {
 318             while (n != first_clone && !n->next_sibling_clone)
 319               n = n->clone_of;
 320             if (n != first_clone)
 321               n = n->next_sibling_clone;
 322           }
 323       }
 324
 325   /* Copy the OLD_VERSION_NODE function tree to the new version.  */
 326   tree_function_versioning (node->decl, first_clone->decl, NULL, true, NULL,
 327                             false, NULL, NULL);
 328
 329   /* The function will be short lived and removed after we inline all the clones,
 330      but make it internal so we won't confuse ourself.  */
 331   DECL_EXTERNAL (first_clone->decl) = 0;
 332   DECL_COMDAT_GROUP (first_clone->decl) = NULL_TREE;
 333   TREE_PUBLIC (first_clone->decl) = 0;
 334   DECL_COMDAT (first_clone->decl) = 0;
 335   VEC_free (ipa_opt_pass, heap,
 336             first_clone->ipa_transforms_to_apply);
 337   first_clone->ipa_transforms_to_apply = NULL;
 338
 339 #ifdef ENABLE_CHECKING
 340   verify_cgraph_node (first_clone);
 341 #endif
 342   return first_clone;
 343 }
 344
 345
 346 /* Apply inline plan to function.  */
 347
 348 unsigned int
 349 inline_transform (struct cgraph_node *node)
 350 {
 351   unsigned int todo = 0;
 352   struct cgraph_edge *e;
 353
 354   /* FIXME: Currently the pass manager is adding inline transform more than
 355      once to some clones.  This needs revisiting after WPA cleanups.  */
 356   if (cfun->after_inlining)
 357     return 0;
 358
 359   /* We might need the body of this function so that we can expand
 360      it inline somewhere else.  */
 361   if (cgraph_preserve_function_body_p (node))
 362     save_inline_function_body (node);
 363
 364   for (e = node->callees; e; e = e->next_callee)
 365     cgraph_redirect_edge_call_stmt_to_callee (e);
 366
 367   timevar_push (TV_INTEGRATION);
 368   if (node->callees)
 369     todo = optimize_inline_calls (current_function_decl);
 370   timevar_pop (TV_INTEGRATION);
 371
 372   cfun->always_inline_functions_inlined = true;
 373   cfun->after_inlining = true;
 374   todo |= execute_fixup_cfg ();
 375
 376   if (!(todo & TODO_update_ssa_any))
 377     /* Redirecting edges might lead to a need for vops to be recomputed.  */
 378     todo |= TODO_update_ssa_only_virtuals;
 379
 380   return todo;
 381 }