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/* Basic IPA optimizations and utilities.

   Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010

   Free Software Foundation, Inc.

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/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "cgraph.h"

#include "tree-pass.h"

#include "timevar.h"

#include "gimple.h"

#include "ggc.h"

/* Fill array order with all nodes with output flag set in the reverse

   topological order.  */

int

cgraph_postorder (struct cgraph_node **order)

{

  struct cgraph_node *node, *node2;

  int stack_size = 0;

  int order_pos = 0;

  struct cgraph_edge *edge, last;

  int pass;

  struct cgraph_node **stack =

    XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);

  /* We have to deal with cycles nicely, so use a depth first traversal

     output algorithm.  Ignore the fact that some functions won't need

     to be output and put them into order as well, so we get dependencies

     right through inline functions.  */

  for (node = cgraph_nodes; node; node = node->next)

    node->aux = NULL;

  for (pass = 0; pass < 2; pass++)

    for (node = cgraph_nodes; node; node = node->next)

      if (!node->aux

          && (pass

              || (!cgraph_only_called_directly_p (node)

                  && !node->address_taken)))

        {

          node2 = node;

          if (!node->callers)

            node->aux = &last;

          else

            node->aux = node->callers;

          while (node2)

            {

              while (node2->aux != &last)

                {

                  edge = (struct cgraph_edge *) node2->aux;

                  if (edge->next_caller)

                    node2->aux = edge->next_caller;

                  else

                    node2->aux = &last;

                  if (!edge->caller->aux)

                    {

                      if (!edge->caller->callers)

                        edge->caller->aux = &last;

                      else

                        edge->caller->aux = edge->caller->callers;

                      stack[stack_size++] = node2;

                      node2 = edge->caller;

                      break;

                    }

                }

              if (node2->aux == &last)

                {

                  order[order_pos++] = node2;

                  if (stack_size)

                    node2 = stack[--stack_size];

                  else

                    node2 = NULL;

                }

            }

        }

  free (stack);

  for (node = cgraph_nodes; node; node = node->next)

    node->aux = NULL;

  return order_pos;

}

/* Look for all functions inlined to NODE and update their inlined_to pointers

   to INLINED_TO.  */

static void

update_inlined_to_pointer (struct cgraph_node *node, struct cgraph_node *inlined_to)

{

  struct cgraph_edge *e;

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

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

      {

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

        update_inlined_to_pointer (e->callee, inlined_to);

      }

}

/* Perform reachability analysis and reclaim all unreachable nodes.

   If BEFORE_INLINING_P is true this function is called before inlining

   decisions has been made.  If BEFORE_INLINING_P is false this function also

   removes unneeded bodies of extern inline functions.  */

bool

cgraph_remove_unreachable_nodes (bool before_inlining_p, FILE *file)

{

  struct cgraph_node *first = (struct cgraph_node *) (void *) 1;

  struct cgraph_node *processed = (struct cgraph_node *) (void *) 2;

  struct cgraph_node *node, *next;

  bool changed = false;

#ifdef ENABLE_CHECKING

  verify_cgraph ();

#endif

  if (file)

    fprintf (file, "\nReclaiming functions:");

#ifdef ENABLE_CHECKING

  for (node = cgraph_nodes; node; node = node->next)

    gcc_assert (!node->aux);

#endif

  for (node = cgraph_nodes; node; node = node->next)

    if (!cgraph_can_remove_if_no_direct_calls_p (node)

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

            || !node->analyzed

            || before_inlining_p))

      {

        gcc_assert (!node->global.inlined_to);

        node->aux = first;

        first = node;

        node->reachable = true;

      }

    else

      {

        gcc_assert (!node->aux);

        node->reachable = false;

      }

  /* Perform reachability analysis.  As a special case do not consider

     extern inline functions not inlined as live because we won't output

     them at all.  */

  while (first != (void *) 1)

    {

      struct cgraph_edge *e;

      node = first;

      first = (struct cgraph_node *) first->aux;

      node->aux = processed;

      if (node->reachable)

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

          if (!e->callee->reachable

              && node->analyzed

              && (!e->inline_failed || !e->callee->analyzed

                  || (!DECL_EXTERNAL (e->callee->decl))

                  || before_inlining_p))

            {

              bool prev_reachable = e->callee->reachable;

              e->callee->reachable |= node->reachable;

              if (!e->callee->aux

                  || (e->callee->aux == processed

                      && prev_reachable != e->callee->reachable))

                {

                  e->callee->aux = first;

                  first = e->callee;

                }

            }

      /* If any function in a comdat group is reachable, force

         all other functions in the same comdat group to be

         also reachable.  */

      if (node->same_comdat_group

          && node->reachable

          && !node->global.inlined_to)

        {

          for (next = node->same_comdat_group;

               next != node;

               next = next->same_comdat_group)

            if (!next->reachable)

              {

                next->aux = first;

                first = next;

                next->reachable = true;

              }

        }

      /* We can freely remove inline clones even if they are cloned, however if

         function is clone of real clone, we must keep it around in order to

         make materialize_clones produce function body with the changes

         applied.  */

      while (node->clone_of && !node->clone_of->aux && !gimple_has_body_p (node->decl))

        {

          bool noninline = node->clone_of->decl != node->decl;

          node = node->clone_of;

          if (noninline)

            {

              node->aux = first;

              first = node;

              break;

            }

        }

    }

  /* Remove unreachable nodes.  Extern inline functions need special care;

     Unreachable extern inline functions shall be removed.

     Reachable extern inline functions we never inlined shall get their bodies

     eliminated.

     Reachable extern inline functions we sometimes inlined will be turned into

     unanalyzed nodes so they look like for true extern functions to the rest

     of code.  Body of such functions is released via remove_node once the

     inline clones are eliminated.  */

  for (node = cgraph_nodes; node; node = next)

    {

      next = node->next;

      if (node->aux && !node->reachable)

        {

          cgraph_node_remove_callees (node);

          node->analyzed = false;

          node->local.inlinable = false;

        }

      if (!node->aux)

        {

          node->global.inlined_to = NULL;

          if (file)

            fprintf (file, " %s", cgraph_node_name (node));

          if (!node->analyzed || !DECL_EXTERNAL (node->decl) || before_inlining_p)

            cgraph_remove_node (node);

          else

            {

              struct cgraph_edge *e;

              /* See if there is reachable caller.  */

              for (e = node->callers; e; e = e->next_caller)

                if (e->caller->aux)

                  break;

              /* If so, we need to keep node in the callgraph.  */

              if (e || node->needed)

                {

                  struct cgraph_node *clone;

                  /* If there are still clones, we must keep body around.

                     Otherwise we can just remove the body but keep the clone.  */

                  for (clone = node->clones; clone;

                       clone = clone->next_sibling_clone)

                    if (clone->aux)

                      break;

                  if (!clone)

                    {

                      cgraph_release_function_body (node);

                      node->analyzed = false;

                      node->local.inlinable = false;

                    }

                  cgraph_node_remove_callees (node);

                  if (node->prev_sibling_clone)

                    node->prev_sibling_clone->next_sibling_clone = node->next_sibling_clone;

                  else if (node->clone_of)

                    node->clone_of->clones = node->next_sibling_clone;

                  if (node->next_sibling_clone)

                    node->next_sibling_clone->prev_sibling_clone = node->prev_sibling_clone;

                  node->clone_of = NULL;

                  node->next_sibling_clone = NULL;

                  node->prev_sibling_clone = NULL;

                }

              else

                cgraph_remove_node (node);

            }

          changed = true;

        }

    }

  for (node = cgraph_nodes; node; node = node->next)

    {

      /* Inline clones might be kept around so their materializing allows further

         cloning.  If the function the clone is inlined into is removed, we need

         to turn it into normal cone.  */

      if (node->global.inlined_to

          && !node->callers)

        {

          gcc_assert (node->clones);

          node->global.inlined_to = NULL;

          update_inlined_to_pointer (node, node);

        }

      node->aux = NULL;

    }

#ifdef ENABLE_CHECKING

  verify_cgraph ();

#endif

  /* Reclaim alias pairs for functions that have disappeared from the

     call graph.  */

  remove_unreachable_alias_pairs ();

  return changed;

}

static bool

cgraph_externally_visible_p (struct cgraph_node *node, bool whole_program)

{

  if (!node->local.finalized)

    return false;

  if (!DECL_COMDAT (node->decl)

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

    return false;

  if (!whole_program)

    return true;

  if (DECL_PRESERVE_P (node->decl))

    return true;

  /* COMDAT functions must be shared only if they have address taken,

     otherwise we can produce our own private implementation with

     -fwhole-program.  */

  if (DECL_COMDAT (node->decl))

    {

      if (node->address_taken || !node->analyzed)

        return true;

      if (node->same_comdat_group)

        {

          struct cgraph_node *next;

          /* If more than one function is in the same COMDAT group, it must

             be shared even if just one function in the comdat group has

             address taken.  */

          for (next = node->same_comdat_group;

               next != node;

               next = next->same_comdat_group)

            if (next->address_taken || !next->analyzed)

              return true;

        }

    }

  if (MAIN_NAME_P (DECL_NAME (node->decl)))

    return true;

  if (lookup_attribute ("externally_visible", DECL_ATTRIBUTES (node->decl)))

    return true;

  return false;

}

/* Dissolve the same_comdat_group list in which NODE resides.  */

static void

dissolve_same_comdat_group_list (struct cgraph_node *node)

{

  struct cgraph_node *n = node, *next;

  do

    {

      next = n->same_comdat_group;

      n->same_comdat_group = NULL;

      n = next;

    }

  while (n != node);

}

/* Mark visibility of all functions.

   A local function is one whose calls can occur only in the current

   compilation unit and all its calls are explicit, so we can change

   its calling convention.  We simply mark all static functions whose

   address is not taken as local.

   We also change the TREE_PUBLIC flag of all declarations that are public

   in language point of view but we want to overwrite this default

   via visibilities for the backend point of view.  */

static unsigned int

function_and_variable_visibility (bool whole_program)

{

  struct cgraph_node *node;

  struct varpool_node *vnode;

  for (node = cgraph_nodes; node; node = node->next)

    {

      /* C++ FE on lack of COMDAT support create local COMDAT functions

         (that ought to be shared but can not due to object format

         limitations).  It is neccesary to keep the flag to make rest of C++ FE

         happy.  Clear the flag here to avoid confusion in middle-end.  */

      if (DECL_COMDAT (node->decl) && !TREE_PUBLIC (node->decl))

        DECL_COMDAT (node->decl) = 0;

      /* For external decls stop tracking same_comdat_group, it doesn't matter

         what comdat group they are in when they won't be emitted in this TU,

         and simplifies later passes.  */

      if (node->same_comdat_group && DECL_EXTERNAL (node->decl))

        {

#ifdef ENABLE_CHECKING

          struct cgraph_node *n;

          for (n = node->same_comdat_group;

               n != node;

               n = n->same_comdat_group)

              /* If at least one of same comdat group functions is external,

                 all of them have to be, otherwise it is a front-end bug.  */

              gcc_assert (DECL_EXTERNAL (n->decl));

#endif

          dissolve_same_comdat_group_list (node);

        }

      gcc_assert ((!DECL_WEAK (node->decl) && !DECL_COMDAT (node->decl))

                  || TREE_PUBLIC (node->decl) || DECL_EXTERNAL (node->decl));

      if (cgraph_externally_visible_p (node, whole_program))

        {

          gcc_assert (!node->global.inlined_to);

          node->local.externally_visible = true;

        }

      else

        node->local.externally_visible = false;

      if (!node->local.externally_visible && node->analyzed

          && !DECL_EXTERNAL (node->decl))

        {

          gcc_assert (whole_program || !TREE_PUBLIC (node->decl));

          cgraph_make_decl_local (node->decl);

          if (node->same_comdat_group)

            /* cgraph_externally_visible_p has already checked all other nodes

               in the group and they will all be made local.  We need to

               dissolve the group at once so that the predicate does not

               segfault though. */

            dissolve_same_comdat_group_list (node);

        }

      node->local.local = (cgraph_only_called_directly_p (node)

                           && node->analyzed

                           && !DECL_EXTERNAL (node->decl)

                           && !node->local.externally_visible);

    }

  for (vnode = varpool_nodes; vnode; vnode = vnode->next)

    {

      /* weak flag makes no sense on local variables.  */

      gcc_assert (!DECL_WEAK (vnode->decl)

                  || TREE_PUBLIC (vnode->decl) || DECL_EXTERNAL (vnode->decl));

      /* In several cases declarations can not be common:

         - when declaration has initializer

         - when it is in weak

         - when it has specific section

         - when it resides in non-generic address space.

         - if declaration is local, it will get into .local common section

           so common flag is not needed.  Frontends still produce these in

           certain cases, such as for:

             static int a __attribute__ ((common))

         Canonicalize things here and clear the redundant flag.  */

      if (DECL_COMMON (vnode->decl)

          && (!(TREE_PUBLIC (vnode->decl) || DECL_EXTERNAL (vnode->decl))

              || (DECL_INITIAL (vnode->decl)

                  && DECL_INITIAL (vnode->decl) != error_mark_node)

              || DECL_WEAK (vnode->decl)

              || DECL_SECTION_NAME (vnode->decl) != NULL

              || ! (ADDR_SPACE_GENERIC_P

                    (TYPE_ADDR_SPACE (TREE_TYPE (vnode->decl))))))

        DECL_COMMON (vnode->decl) = 0;

    }

  for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)

    {

      if (!vnode->finalized)

        continue;

      if (vnode->needed

          && (DECL_COMDAT (vnode->decl) || TREE_PUBLIC (vnode->decl))

          && (!whole_program

              /* We can privatize comdat readonly variables whose address is not taken,

                 but doing so is not going to bring us optimization oppurtunities until

                 we start reordering datastructures.  */

              || DECL_COMDAT (vnode->decl)

              || DECL_WEAK (vnode->decl)

              || lookup_attribute ("externally_visible",

                                   DECL_ATTRIBUTES (vnode->decl))))

        vnode->externally_visible = true;

      else

        vnode->externally_visible = false;

      if (!vnode->externally_visible)

        {

          gcc_assert (whole_program || !TREE_PUBLIC (vnode->decl));

          cgraph_make_decl_local (vnode->decl);

        }

     gcc_assert (TREE_STATIC (vnode->decl));

    }

  if (dump_file)

    {

      fprintf (dump_file, "\nMarking local functions:");

      for (node = cgraph_nodes; node; node = node->next)

        if (node->local.local)

          fprintf (dump_file, " %s", cgraph_node_name (node));

      fprintf (dump_file, "\n\n");

      fprintf (dump_file, "\nMarking externally visible functions:");

      for (node = cgraph_nodes; node; node = node->next)

        if (node->local.externally_visible)

          fprintf (dump_file, " %s", cgraph_node_name (node));

      fprintf (dump_file, "\n\n");

      fprintf (dump_file, "\nMarking externally visible variables:");

      for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)

        if (vnode->externally_visible)

          fprintf (dump_file, " %s", varpool_node_name (vnode));

      fprintf (dump_file, "\n\n");

    }

  cgraph_function_flags_ready = true;

  return 0;

}

/* Local function pass handling visibilities.  This happens before LTO streaming

   so in particular -fwhole-program should be ignored at this level.  */

static unsigned int

local_function_and_variable_visibility (void)

{

  return function_and_variable_visibility (flag_whole_program && !flag_lto && !flag_whopr);

}

struct simple_ipa_opt_pass pass_ipa_function_and_variable_visibility =

{

 {

  SIMPLE_IPA_PASS,

  "visibility",                         /* name */

  NULL,                                 /* gate */

  local_function_and_variable_visibility,/* execute */

  NULL,                                 /* sub */

  NULL,                                 /* next */

  0,                                     /* static_pass_number */

  TV_CGRAPHOPT,                         /* tv_id */

  0,                                     /* properties_required */

  0,                                     /* properties_provided */

  0,                                     /* properties_destroyed */

  0,                                     /* todo_flags_start */

  TODO_remove_functions | TODO_dump_cgraph/* todo_flags_finish */

 }

};

/* Do not re-run on ltrans stage.  */

static bool

gate_whole_program_function_and_variable_visibility (void)

{

  return !flag_ltrans;

}

/* Bring functionss local at LTO time whith -fwhole-program.  */

static unsigned int

whole_program_function_and_variable_visibility (void)

{

  struct cgraph_node *node;

  struct varpool_node *vnode;

  function_and_variable_visibility (flag_whole_program);

  for (node = cgraph_nodes; node; node = node->next)

    if ((node->local.externally_visible && !DECL_COMDAT (node->decl))

        && node->local.finalized)

      cgraph_mark_needed_node (node);

  for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)

    if (vnode->externally_visible && !DECL_COMDAT (vnode->decl))

      varpool_mark_needed_node (vnode);

  if (dump_file)

    {

      fprintf (dump_file, "\nNeeded variables:");

      for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)

        if (vnode->needed)

          fprintf (dump_file, " %s", varpool_node_name (vnode));

      fprintf (dump_file, "\n\n");

    }

  return 0;

}

struct ipa_opt_pass_d pass_ipa_whole_program_visibility =

{

 {

  IPA_PASS,

  "whole-program",                      /* name */

  gate_whole_program_function_and_variable_visibility,/* gate */

  whole_program_function_and_variable_visibility,/* execute */

  NULL,                                 /* sub */

  NULL,                                 /* next */

  0,                                     /* static_pass_number */

  TV_CGRAPHOPT,                         /* tv_id */

  0,                                     /* properties_required */

  0,                                     /* properties_provided */

  0,                                     /* properties_destroyed */

  0,                                     /* todo_flags_start */

  TODO_dump_cgraph | TODO_remove_functions/* todo_flags_finish */

 },

 NULL,                                  /* generate_summary */

 NULL,                                  /* write_summary */

 NULL,                                  /* read_summary */

 NULL,                                  /* function_read_summary */

 NULL,                                  /* stmt_fixup */

 0,                                      /* TODOs */

 NULL,                                  /* function_transform */

 NULL,                                  /* variable_transform */

};

/* Hash a cgraph node set element.  */

static hashval_t

hash_cgraph_node_set_element (const void *p)

{

  const_cgraph_node_set_element element = (const_cgraph_node_set_element) p;

  return htab_hash_pointer (element->node);

}

/* Compare two cgraph node set elements.  */

static int

eq_cgraph_node_set_element (const void *p1, const void *p2)

{

  const_cgraph_node_set_element e1 = (const_cgraph_node_set_element) p1;

  const_cgraph_node_set_element e2 = (const_cgraph_node_set_element) p2;

  return e1->node == e2->node;

}

/* Create a new cgraph node set.  */

cgraph_node_set

cgraph_node_set_new (void)

{

  cgraph_node_set new_node_set;

  new_node_set = GGC_NEW (struct cgraph_node_set_def);

  new_node_set->hashtab = htab_create_ggc (10,

                                           hash_cgraph_node_set_element,

                                           eq_cgraph_node_set_element,

                                           NULL);

  new_node_set->nodes = NULL;

  return new_node_set;

}

/* Add cgraph_node NODE to cgraph_node_set SET.  */

void

cgraph_node_set_add (cgraph_node_set set, struct cgraph_node *node)

{

  void **slot;

  cgraph_node_set_element element;

  struct cgraph_node_set_element_def dummy;

  dummy.node = node;

  slot = htab_find_slot (set->hashtab, &dummy, INSERT);

  if (*slot != HTAB_EMPTY_ENTRY)

    {

      element = (cgraph_node_set_element) *slot;

      gcc_assert (node == element->node

                  && (VEC_index (cgraph_node_ptr, set->nodes, element->index)

                      == node));

      return;

    }

  /* Insert node into hash table.  */

  element =

    (cgraph_node_set_element) GGC_NEW (struct cgraph_node_set_element_def);

  element->node = node;

  element->index = VEC_length (cgraph_node_ptr, set->nodes);

  *slot = element;

  /* Insert into node vector.  */

  VEC_safe_push (cgraph_node_ptr, gc, set->nodes, node);

}

/* Remove cgraph_node NODE from cgraph_node_set SET.  */

void

cgraph_node_set_remove (cgraph_node_set set, struct cgraph_node *node)

{

  void **slot, **last_slot;

  cgraph_node_set_element element, last_element;

  struct cgraph_node *last_node;

  struct cgraph_node_set_element_def dummy;