gcc/ipa.c

/* Basic IPA optimizations and utilities.
   Copyright (C) 2003, 2004, 2005, 2007, 2008 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"

/* 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;

  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 (node = cgraph_nodes; node; node = node->next)
    if (!node->aux)
      {
	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;
}

/* 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 *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 (node->needed && !node->global.inlined_to
	&& ((!DECL_EXTERNAL (node->decl)) 
            || !node->analyzed
            || before_inlining_p))
      {
	node->aux = first;
	first = node;
      }
    else
      gcc_assert (!node->aux);

  /* 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;

      for (e = node->callees; e; e = e->next_callee)
	if (!e->callee->aux
	    && node->analyzed
	    && (!e->inline_failed || !e->callee->analyzed
		|| (!DECL_EXTERNAL (e->callee->decl))
                || before_inlining_p))
	  {
	    e->callee->aux = first;
	    first = e->callee;
	  }
    }

  /* 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->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;

	      for (e = node->callers; e; e = e->next_caller)
		if (e->caller->aux)
		  break;
	      if (e || node->needed)
		{
		  struct cgraph_node *clone;

		  for (clone = node->next_clone; clone;
		       clone = clone->next_clone)
		    if (clone->aux)
		      break;
		  if (!clone)
		    {
		      cgraph_release_function_body (node);
		      node->analyzed = false;
		    }
		  cgraph_node_remove_callees (node);
		  node->analyzed = false;
		  node->local.inlinable = false;
		}
	      else
		cgraph_remove_node (node);
	    }
	  changed = true;
	}
    }
  for (node = cgraph_nodes; node; node = node->next)
    node->aux = NULL;
#ifdef ENABLE_CHECKING
  verify_cgraph ();
#endif
  return changed;
}

/* 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 (void)
{
  struct cgraph_node *node;
  struct varpool_node *vnode;

  for (node = cgraph_nodes; node; node = node->next)
    {
      if (node->reachable
	  && (DECL_COMDAT (node->decl)
	      || (!flag_whole_program
		  && TREE_PUBLIC (node->decl) && !DECL_EXTERNAL (node->decl))))
	node->local.externally_visible = true;
      if (!node->local.externally_visible && node->analyzed
	  && !DECL_EXTERNAL (node->decl))
	{
	  gcc_assert (flag_whole_program || !TREE_PUBLIC (node->decl));
	  TREE_PUBLIC (node->decl) = 0;
	}
      node->local.local = (!node->needed
			   && node->analyzed
			   && !DECL_EXTERNAL (node->decl)
			   && !node->local.externally_visible);
    }
  for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)
    {
      if (vnode->needed
	  && !flag_whole_program
	  && (DECL_COMDAT (vnode->decl) || TREE_PUBLIC (vnode->decl)))
	vnode->externally_visible = 1;
      if (!vnode->externally_visible)
	{
	  gcc_assert (flag_whole_program || !TREE_PUBLIC (vnode->decl));
	  TREE_PUBLIC (vnode->decl) = 0;
	}
     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");
    }
  cgraph_function_flags_ready = true;
  return 0;
}

struct simple_ipa_opt_pass pass_ipa_function_and_variable_visibility = 
{
 {
  SIMPLE_IPA_PASS,
  "visibility",				/* name */
  NULL,					/* gate */
  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 */
 }
};