/* Callgraph handling code.
   Copyright (C) 2003 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 2, 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 COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "tree-inline.h"
#include "langhooks.h"
#include "hashtab.h"
#include "toplev.h"
#include "flags.h"
#include "ggc.h"
#include "debug.h"
#include "target.h"
#include "cgraph.h"

static void cgraph_expand_functions PARAMS ((void));
static void cgraph_mark_functions_to_output PARAMS ((void));
static void cgraph_expand_function PARAMS ((struct cgraph_node *));
static tree record_call_1 PARAMS ((tree *, int *, void *));

/* Analyze function once it is parsed.  Set up the local information
   available - create cgraph edges for function calles via BODY.  */

void
cgraph_finalize_function (decl, body)
     tree decl;
     tree body ATTRIBUTE_UNUSED;
{
  struct cgraph_node *node = cgraph_node (decl);

  node->decl = decl;

  /* Set TREE_UNINLINABLE flag.  */
  tree_inlinable_function_p (decl);

  (*debug_hooks->deferred_inline_function) (decl);
}

static struct cgraph_node *queue = NULL;

/* Notify finalize_compilation_unit that given node is reachable
   or needed.  */
void
cgraph_mark_needed_node (node, needed)
     struct cgraph_node *node;
     int needed;
{
  if (needed)
    {
      if (DECL_SAVED_TREE (node->decl))
        announce_function (node->decl);
      node->needed = 1;
    }
  if (!node->reachable)
    {
      node->reachable = 1;
      if (DECL_SAVED_TREE (node->decl))
	{
	  node->aux = queue;
	  queue = node;
        }
    }
}

/* Walk tree and record all calls.  Called via walk_tree.  */
static tree
record_call_1 (tp, walk_subtrees, data)
     tree *tp;
     int *walk_subtrees;
     void *data;
{
  /* Record dereferences to the functions.  This makes the functions
     reachable unconditionally.  */
  if (TREE_CODE (*tp) == ADDR_EXPR)
    {
      tree decl = TREE_OPERAND (*tp, 0);
      if (TREE_CODE (decl) == FUNCTION_DECL)
        cgraph_mark_needed_node (cgraph_node (decl), 1);
    }
  else if (TREE_CODE (*tp) == CALL_EXPR)
    {
      tree decl = TREE_OPERAND (*tp, 0);
      if (TREE_CODE (decl) == ADDR_EXPR)
	decl = TREE_OPERAND (decl, 0);
      if (TREE_CODE (decl) == FUNCTION_DECL)
	{
	  if (DECL_BUILT_IN (decl))
	    return NULL;
	  cgraph_record_call (data, decl);
	  walk_tree (&TREE_OPERAND (*tp, 1), record_call_1, data, NULL);
	  *walk_subtrees = 0;
	}
    }
  return NULL;
}

/* Create cgraph edges for function calles via BODY.  */

void
cgraph_create_edges (decl, body)
     tree decl;
     tree body;
{
  walk_tree (&body, record_call_1, decl, NULL);
}

/* Analyze the whole compilation unit once it is parsed completely.  */

void
cgraph_finalize_compilation_unit ()
{
  struct cgraph_node *node;
  struct cgraph_edge *edge;

  /* Collect entry points to the unit.  */

  if (!quiet_flag)
    fprintf (stderr, "\n\nUnit entry points:");

  for (node = cgraph_nodes; node; node = node->next)
    {
      tree decl = node->decl;

      if (!DECL_SAVED_TREE (decl))
	continue;
      if ((TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
	  || (DECL_ASSEMBLER_NAME_SET_P (decl)
	      && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl))))
	{
          cgraph_mark_needed_node (node, 1);
	}
    }

  /*  Propagate reachability flag and lower representation of all reachable
      functions.  In the future, lowering will introduce new functions and
      new entry points on the way (by template instantiation and virtual
      method table generation for instance).  */
  while (queue)
    {
      tree decl = queue->decl;

      node = queue;
      queue = queue->aux;
      if (node->lowered || !node->reachable || !DECL_SAVED_TREE (decl))
	abort ();

      /* At the moment frontend automatically emits all nested functions.  */
      if (node->nested)
	{
	  struct cgraph_node *node2;

	  for (node2 = node->nested; node2; node2 = node2->next_nested)
	    if (!node2->reachable)
	      cgraph_mark_needed_node (node2, 0);
	}

      if (lang_hooks.callgraph.lower_function)
	(*lang_hooks.callgraph.lower_function) (decl);
      /* First kill forward declaration so reverse inling works properly.  */
      cgraph_create_edges (decl, DECL_SAVED_TREE (decl));

      for (edge = node->callees; edge; edge = edge->next_callee)
	{
	  if (!edge->callee->reachable)
            cgraph_mark_needed_node (edge->callee, 0);
	}
      node->lowered = true;
    }
  if (!quiet_flag)
    fprintf (stderr, "\n\nReclaiming functions:");

  for (node = cgraph_nodes; node; node = node->next)
    {
      tree decl = node->decl;

      if (!node->reachable && DECL_SAVED_TREE (decl))
	{
	  DECL_SAVED_TREE (decl) = NULL;
	  announce_function (decl);
	}
    }
  ggc_collect ();
}

/* Figure out what functions we want to assemble.  */

static void
cgraph_mark_functions_to_output ()
{
  struct cgraph_node *node;

  /* Figure out functions we want to assemble.  */
  for (node = cgraph_nodes; node; node = node->next)
    {
      tree decl = node->decl;

      if (DECL_SAVED_TREE (decl)
	  && (node->needed
	      || (DECL_UNINLINABLE (decl) && node->reachable)
	      || TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
	  && !TREE_ASM_WRITTEN (decl) && !node->origin
	  && !DECL_EXTERNAL (decl))
	node->output = 1;
    }
}

/* Expand function specified by NODE.  */
static void
cgraph_expand_function (node)
     struct cgraph_node *node;
{
  tree decl = node->decl;

  announce_function (decl);
  if (flag_inline_trees)
    optimize_inline_calls (decl);
  (*lang_hooks.callgraph.expand_function) (decl);
  if (DECL_UNINLINABLE (decl))
    DECL_SAVED_TREE (decl) = NULL;
  current_function_decl = NULL;
}


/* Expand all functions that must be output. 
  
   Attempt to topologically sort the nodes so function is output when
   all called functions are already assembled to allow data to be propagated
   accross the callgraph.  Use stack to get smaller distance between function
   and it's callees (later we may use more sophisticated algorithm for
   function reordering, we will likely want to use subsections to make output
   functions to appear in top-down order, not bottom-up they are assembled).  */

static void
cgraph_expand_functions ()
{
  struct cgraph_node *node, *node2;
  struct cgraph_node **stack =
    xcalloc (sizeof (struct cgraph_node *), cgraph_n_nodes);
  struct cgraph_node **order =
    xcalloc (sizeof (struct cgraph_node *), cgraph_n_nodes);
  int stack_size = 0;
  int order_pos = 0;
  struct cgraph_edge *edge, last;
  int i;

  cgraph_mark_functions_to_output ();

  /*  We have to deal with cycles nicely, so use depth first traversal
      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 trought inlined
      functions.  */
  for (node = cgraph_nodes; node; node = node->next)
    node->aux = NULL;
  for (node = cgraph_nodes; node; node = node->next)
    if (node->output && !node->aux)
      {
	node2 = node;
	if (!node->callers)
	  node->aux = &last;
	else
	  node->aux = node->callers;
	while (node2)
	  {
	    while (node2->aux != &last)
	      {
		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;
	      }
	  }
      }
  for (i = order_pos - 1; i >=0; i--)
    {
      node = order[i];
      if (node->output)
	{
	  if (!node->reachable)
	    abort ();
	  node->output = 0;
	  cgraph_expand_function (node);
	}
    }
  free (stack);
  free (order);
}

/* Perform simple optimizations based on callgraph.  */

void
cgraph_optimize ()
{
  struct cgraph_node *node;
  bool changed = true;
  struct cgraph_edge *edge;

  if (!quiet_flag)
    fprintf (stderr, "\n\nAssembling functions:");

  /* Output everything.  
     ??? Our inline heuristic may decide to not inline functions previously
     marked as inlinable thus adding new function bodies that must be output.
     Later we should move all inlining decisions to callgraph code to make
     this impossible.  */
  cgraph_expand_functions ();
  while (changed)
    {
      changed = false;
      for (node = cgraph_nodes; node; node = node->next)
	{
	  if (!node->needed)
	    continue;

	  for (edge = node->callees; edge; edge = edge->next_callee)
	    if (!edge->callee->needed)
	      changed = edge->callee->needed = true;
	}
    }
  cgraph_expand_functions ();
}