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/* Callgraph transformations to handle inlining

   Copyright (C) 2003, 2004, 2007, 2008, 2009, 2010, 2011

   Free Software Foundation, Inc.

   Contributed by Jan Hubicka

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 3, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING3.  If not see

<http://www.gnu.org/licenses/>.  */

/* The inline decisions are stored in callgraph in "inline plan" and

   applied later.

   To mark given call inline, use inline_call function.

   The function marks the edge inlinable and, if necessary, produces

   virtual clone in the callgraph representing the new copy of callee's

   function body.

   The inline plan is applied on given function body by inline_transform.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "langhooks.h"

#include "cgraph.h"

#include "timevar.h"

#include "output.h"

#include "intl.h"

#include "coverage.h"

#include "ggc.h"

#include "tree-flow.h"

#include "ipa-prop.h"

#include "ipa-inline.h"

#include "tree-inline.h"

#include "tree-pass.h"

int ncalls_inlined;

int nfunctions_inlined;

/* Scale frequency of NODE edges by FREQ_SCALE.  */

static void

update_noncloned_frequencies (struct cgraph_node *node,

                              int freq_scale)

{

  struct cgraph_edge *e;

  /* We do not want to ignore high loop nest after freq drops to 0.  */

  if (!freq_scale)

    freq_scale = 1;

  for (e = node->callees; e; e = e->next_callee)

    {

      e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;

      if (e->frequency > CGRAPH_FREQ_MAX)

        e->frequency = CGRAPH_FREQ_MAX;

      if (!e->inline_failed)

        update_noncloned_frequencies (e->callee, freq_scale);

    }

  for (e = node->indirect_calls; e; e = e->next_callee)

    {

      e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;

      if (e->frequency > CGRAPH_FREQ_MAX)

        e->frequency = CGRAPH_FREQ_MAX;

    }

}

/* We removed or are going to remove the last call to NODE.

   Return true if we can and want proactively remove the NODE now.

   This is important to do, since we want inliner to know when offline

   copy of function was removed.  */

static bool

can_remove_node_now_p_1 (struct cgraph_node *node)

{

  /* FIXME: When address is taken of DECL_EXTERNAL function we still

     can remove its offline copy, but we would need to keep unanalyzed node in

     the callgraph so references can point to it.  */

  return (!node->address_taken

          && !ipa_ref_has_aliases_p (&node->ref_list)

          && cgraph_can_remove_if_no_direct_calls_p (node)

          /* Inlining might enable more devirtualizing, so we want to remove

             those only after all devirtualizable virtual calls are processed.

             Lacking may edges in callgraph we just preserve them post

             inlining.  */

          && (!DECL_VIRTUAL_P (node->decl)

              || (!DECL_COMDAT (node->decl)

                  && !DECL_EXTERNAL (node->decl)))

          /* During early inlining some unanalyzed cgraph nodes might be in the

             callgraph and they might reffer the function in question.  */

          && !cgraph_new_nodes);

}

/* We are going to eliminate last direct call to NODE (or alias of it) via edge E.

   Verify that the NODE can be removed from unit and if it is contained in comdat

   group that the whole comdat group is removable.  */

static bool

can_remove_node_now_p (struct cgraph_node *node, struct cgraph_edge *e)

{

  struct cgraph_node *next;

  if (!can_remove_node_now_p_1 (node))

    return false;

  /* When we see same comdat group, we need to be sure that all

     items can be removed.  */

  if (!node->same_comdat_group)

    return true;

  for (next = node->same_comdat_group;

       next != node; next = next->same_comdat_group)

    if ((next->callers && next->callers != e)

        || !can_remove_node_now_p_1 (next))

      return false;

  return true;

}

/* E is expected to be an edge being inlined.  Clone destination node of

   the edge and redirect it to the new clone.

   DUPLICATE is used for bookkeeping on whether we are actually creating new

   clones or re-using node originally representing out-of-line function call.

   */

void

clone_inlined_nodes (struct cgraph_edge *e, bool duplicate,

                     bool update_original, int *overall_size)

{

  if (duplicate)

    {

      /* We may eliminate the need for out-of-line copy to be output.

         In that case just go ahead and re-use it.  This is not just an

         memory optimization.  Making offline copy of fuction disappear

         from the program will improve future decisions on inlining.  */

      if (!e->callee->callers->next_caller

          /* Recursive inlining never wants the master clone to

             be overwritten.  */

          && update_original

          && can_remove_node_now_p (e->callee, e))

        {

          /* TODO: When callee is in a comdat group, we could remove all of it,

             including all inline clones inlined into it.  That would however

             need small function inlining to register edge removal hook to

             maintain the priority queue.

             For now we keep the ohter functions in the group in program until

             cgraph_remove_unreachable_functions gets rid of them.  */

          gcc_assert (!e->callee->global.inlined_to);

          if (e->callee->analyzed && !DECL_EXTERNAL (e->callee->decl))

            {

              if (overall_size)

                *overall_size -= inline_summary (e->callee)->size;

              nfunctions_inlined++;

            }

          duplicate = false;

          e->callee->local.externally_visible = false;

          update_noncloned_frequencies (e->callee, e->frequency);

        }

      else

        {

          struct cgraph_node *n;

          n = cgraph_clone_node (e->callee, e->callee->decl,

                                 e->count, e->frequency,

                                 update_original, NULL, true);

          cgraph_redirect_edge_callee (e, n);

        }

    }

  if (e->caller->global.inlined_to)

    e->callee->global.inlined_to = e->caller->global.inlined_to;

  else

    e->callee->global.inlined_to = e->caller;

  /* Recursively clone all bodies.  */

  for (e = e->callee->callees; e; e = e->next_callee)

    if (!e->inline_failed)

      clone_inlined_nodes (e, duplicate, update_original, overall_size);

}

/* Mark edge E as inlined and update callgraph accordingly.  UPDATE_ORIGINAL

   specify whether profile of original function should be updated.  If any new

   indirect edges are discovered in the process, add them to NEW_EDGES, unless

   it is NULL.  Return true iff any new callgraph edges were discovered as a

   result of inlining.  */

bool

inline_call (struct cgraph_edge *e, bool update_original,

             VEC (cgraph_edge_p, heap) **new_edges,

             int *overall_size)

{

  int old_size = 0, new_size = 0;

  struct cgraph_node *to = NULL;

  struct cgraph_edge *curr = e;

  struct cgraph_node *callee = cgraph_function_or_thunk_node (e->callee, NULL);

  /* Don't inline inlined edges.  */

  gcc_assert (e->inline_failed);

  /* Don't even think of inlining inline clone.  */

  gcc_assert (!callee->global.inlined_to);

  e->inline_failed = CIF_OK;

  DECL_POSSIBLY_INLINED (callee->decl) = true;

  to = e->caller;

  if (to->global.inlined_to)

    to = to->global.inlined_to;

  /* If aliases are involved, redirect edge to the actual destination and

     possibly remove the aliases.  */

  if (e->callee != callee)

    {

      struct cgraph_node *alias = e->callee, *next_alias;

      cgraph_redirect_edge_callee (e, callee);

      while (alias && alias != callee)

        {

          if (!alias->callers

              && can_remove_node_now_p (alias, e))

            {

              next_alias = cgraph_alias_aliased_node (alias);

              cgraph_remove_node (alias);

              alias = next_alias;

            }

          else

            break;

        }

    }

  clone_inlined_nodes (e, true, update_original, overall_size);

  gcc_assert (curr->callee->global.inlined_to == to);

  old_size = inline_summary (to)->size;

  inline_merge_summary (e);

  new_size = inline_summary (to)->size;

  if (overall_size)

    *overall_size += new_size - old_size;

  ncalls_inlined++;

  /* This must happen after inline_merge_summary that rely on jump

     functions of callee to not be updated.  */

  if (optimize)

    return ipa_propagate_indirect_call_infos (curr, new_edges);

  else

    return false;

}

/* Copy function body of NODE and redirect all inline clones to it.

   This is done before inline plan is applied to NODE when there are

   still some inline clones if it.

   This is neccesary because inline decisions are not really transitive

   and the other inline clones may have different bodies.  */

static struct cgraph_node *

save_inline_function_body (struct cgraph_node *node)

{

  struct cgraph_node *first_clone, *n;

  if (dump_file)

    fprintf (dump_file, "\nSaving body of %s for later reuse\n",

             cgraph_node_name (node));

  gcc_assert (node == cgraph_get_node (node->decl));

  /* first_clone will be turned into real function.  */

  first_clone = node->clones;

  first_clone->decl = copy_node (node->decl);

  cgraph_insert_node_to_hashtable (first_clone);

  gcc_assert (first_clone == cgraph_get_node (first_clone->decl));

  /* Now reshape the clone tree, so all other clones descends from

     first_clone.  */

  if (first_clone->next_sibling_clone)

    {

      for (n = first_clone->next_sibling_clone; n->next_sibling_clone; n = n->next_sibling_clone)

        n->clone_of = first_clone;

      n->clone_of = first_clone;

      n->next_sibling_clone = first_clone->clones;

      if (first_clone->clones)

        first_clone->clones->prev_sibling_clone = n;

      first_clone->clones = first_clone->next_sibling_clone;

      first_clone->next_sibling_clone->prev_sibling_clone = NULL;

      first_clone->next_sibling_clone = NULL;

      gcc_assert (!first_clone->prev_sibling_clone);

    }

  first_clone->clone_of = NULL;

  /* Now node in question has no clones.  */

  node->clones = NULL;

  /* Inline clones share decl with the function they are cloned

     from.  Walk the whole clone tree and redirect them all to the

     new decl.  */

  if (first_clone->clones)

    for (n = first_clone->clones; n != first_clone;)

      {

        gcc_assert (n->decl == node->decl);

        n->decl = first_clone->decl;

        if (n->clones)

          n = n->clones;

        else if (n->next_sibling_clone)

          n = n->next_sibling_clone;

        else

          {

            while (n != first_clone && !n->next_sibling_clone)

              n = n->clone_of;

            if (n != first_clone)

              n = n->next_sibling_clone;

          }

      }

  /* Copy the OLD_VERSION_NODE function tree to the new version.  */

  tree_function_versioning (node->decl, first_clone->decl, NULL, true, NULL,

                            false, NULL, NULL);

  /* The function will be short lived and removed after we inline all the clones,

     but make it internal so we won't confuse ourself.  */

  DECL_EXTERNAL (first_clone->decl) = 0;

  DECL_COMDAT_GROUP (first_clone->decl) = NULL_TREE;

  TREE_PUBLIC (first_clone->decl) = 0;

  DECL_COMDAT (first_clone->decl) = 0;

  VEC_free (ipa_opt_pass, heap,

            first_clone->ipa_transforms_to_apply);

  first_clone->ipa_transforms_to_apply = NULL;

#ifdef ENABLE_CHECKING

  verify_cgraph_node (first_clone);

#endif

  return first_clone;

}

/* Apply inline plan to function.  */

unsigned int

inline_transform (struct cgraph_node *node)

{

  unsigned int todo = 0;

  struct cgraph_edge *e;

  /* FIXME: Currently the pass manager is adding inline transform more than

     once to some clones.  This needs revisiting after WPA cleanups.  */

  if (cfun->after_inlining)

    return 0;

  /* We might need the body of this function so that we can expand

     it inline somewhere else.  */

  if (cgraph_preserve_function_body_p (node))

    save_inline_function_body (node);

  for (e = node->callees; e; e = e->next_callee)

    cgraph_redirect_edge_call_stmt_to_callee (e);

  timevar_push (TV_INTEGRATION);

  if (node->callees)

    todo = optimize_inline_calls (current_function_decl);

  timevar_pop (TV_INTEGRATION);

  cfun->always_inline_functions_inlined = true;

  cfun->after_inlining = true;

  todo |= execute_fixup_cfg ();

  if (!(todo & TODO_update_ssa_any))

    /* Redirecting edges might lead to a need for vops to be recomputed.  */

    todo |= TODO_update_ssa_only_virtuals;

  return todo;

}