* tree-pass.h (pass_split_functions): Declare.

	* opts.c (decode_options): Enable function splitting at -O2
	* timevar.def (TV_IPA_FNSPLIT): New macro.
	* ipa-split.c: New file.
	* common.opt (-fpartial-inlining): New flag.
	* Makefile.in (ipa-split.o): New object file.
	* passes.c (init_optimization_passes): Add ipa-split.
	* params.def (max-inline-insns-auto): Reduce max-inline-insns-auto to 40.
	(partial-inlining-entry-probability): New parameters.
	* doc/invoke.texi (-fpartial-inlining): New.
	
	* testsuite/gcc.dg/tree-ssa/ipa-split.c


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@161382 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 1070 insertions, 0 deletions

diff --git a/gcc/ipa-split.c b/gcc/ipa-split.c
index e69de29bb2d..6085e0b677c 100644
--- a/gcc/ipa-split.c
+++ b/gcc/ipa-split.c
@@ -0,0 +1,1070 @@
+/* Function splitting pass
+   Copyright (C) 2010
+   Free Software Foundation, Inc.
+   Contributed by Jan Hubicka  <jh@suse.cz>
+
+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 purpose of this pass is to split function bodies to improve
+   inlining.  I.e. for function of the form:
+
+   func (...)
+     {
+       if (cheap_test)
+	 something_small
+       else
+	 something_big
+     }
+
+   Produce:
+
+   func.part (...)
+     {
+	something_big
+     }
+
+   func (...)
+     {
+       if (cheap_test)
+	 something_small
+       else
+	 func.part (...);
+     }
+
+   When func becomes inlinable and when cheap_test is often true, inlining func,
+   but not fund.part leads to performance imrovement similar as inlining
+   original func while the code size growth is smaller.
+
+   The pass is organized in three stages:
+   1) Collect local info about basic block into BB_INFO structure and
+      compute function body estimated size and time.
+   2) Via DFS walk find all possible basic blocks where we can split
+      and chose best one.
+   3) If split point is found, split at the specified BB by creating a clone
+      and updating function to call it.  
+
+   The decisions what functions to split are in execute_split_functions
+   and consider_split.  
+
+   There are several possible future improvements for this pass including:
+
+   1) Splitting to break up large functions
+   2) Splitting to reduce stack frame usage
+   3) Allow split part of function to use values computed in the header part.
+      The values needs to be passed to split function, perhaps via same
+      interface as for nested functions or as argument.
+   4) Support for simple rematerialization.  I.e. when split part use
+      value computed in header from function parameter in very cheap way, we
+      can just recompute it.
+   5) Support splitting of nested functions.
+   6) Support non-SSA arguments.  
+   7) There is nothing preventing us from producing multiple parts of single function
+      when needed or splitting also the parts.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "target.h"
+#include "cgraph.h"
+#include "ipa-prop.h"
+#include "tree-flow.h"
+#include "tree-pass.h"
+#include "flags.h"
+#include "timevar.h"
+#include "diagnostic.h"
+#include "tree-dump.h"
+#include "tree-inline.h"
+#include "fibheap.h"
+#include "params.h"
+#include "gimple-pretty-print.h"
+
+/* Per basic block info.  */
+
+typedef struct
+{
+  unsigned int size;
+  unsigned int time;
+} bb_info;
+DEF_VEC_O(bb_info);
+DEF_VEC_ALLOC_O(bb_info,heap);
+
+static VEC(bb_info, heap) *bb_info_vec;
+
+/* Description of split point.  */
+
+struct split_point
+{
+  /* Size of the partitions.  */
+  unsigned int header_time, header_size, split_time, split_size;
+
+  /* SSA names that need to be passed into spit funciton.  */
+  bitmap ssa_names_to_pass;
+
+  /* Basic block where we split (that will become entry point of new function.  */
+  basic_block entry_bb;
+
+  /* Basic blocks we are splitting away.  */
+  bitmap split_bbs;
+};
+
+/* Best split point found.  */
+
+struct split_point best_split_point;
+
+/* Callback for walk_stmt_load_store_addr_ops.  If T is non-ssa automatic
+   variable, check it if it is present in bitmap passed via DATA.  */
+
+static bool
+test_nonssa_use (gimple stmt ATTRIBUTE_UNUSED, tree t,
+	         void *data ATTRIBUTE_UNUSED)
+{
+  t = get_base_address (t);
+
+  if (t && !is_gimple_reg (t)
+      && ((TREE_CODE (t) == VAR_DECL
+	  && auto_var_in_fn_p (t, current_function_decl))
+	  || (TREE_CODE (t) == PARM_DECL)))
+    return bitmap_bit_p ((bitmap)data, DECL_UID (t));
+  return false;
+}
+
+/* Dump split point CURRENT.  */
+
+static void
+dump_split_point (FILE * file, struct split_point *current)
+{
+  fprintf (file,
+	   "Split point at BB %i header time:%i header size: %i"
+	   " split time: %i split size: %i\n  bbs: ",
+	   current->entry_bb->index, current->header_time,
+	   current->header_size, current->split_time, current->split_size);
+  dump_bitmap (file, current->split_bbs);
+  fprintf (file, "  SSA names to pass: ");
+  dump_bitmap (file, current->ssa_names_to_pass);
+}
+
+/* We found an split_point CURRENT.  NON_SSA_VARS is bitmap of all non ssa
+   variables used and RETURN_BB is return basic block.
+   See if we can split function here.  */
+
+static void
+consider_split (struct split_point *current, bitmap non_ssa_vars,
+		basic_block return_bb)
+{
+  tree parm;
+  unsigned int num_args = 0;
+  unsigned int call_overhead;
+  edge e;
+  edge_iterator ei;
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    dump_split_point (dump_file, current);
+
+  /* Do not split when we would end up calling function anyway.  */
+  if (current->entry_bb->frequency
+      >= (ENTRY_BLOCK_PTR->frequency
+	  * PARAM_VALUE (PARAM_PARTIAL_INLINING_ENTRY_PROBABILITY) / 100))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "  Refused: split BB frequency is too large.\n");
+      return;
+    }
+
+  if (!current->header_size)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "  Refused: header empty\n");
+      gcc_unreachable ();
+      return;
+    }
+
+  /* FIXME: We can do better: if the split region start with a loop and there
+     is only one entry point from outer wrold, we can update PHI.  */
+  if (!gsi_end_p (gsi_start_phis (current->entry_bb)))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "  Refused: entry BB has PHI\n");
+      return;
+    }
+
+
+  /* See what argument we will pass to the split function and compute
+     call overhead.  */
+  call_overhead = eni_size_weights.call_cost;
+  for (parm = DECL_ARGUMENTS (current_function_decl); parm;
+       parm = TREE_CHAIN (parm))
+    {
+      if (!is_gimple_reg (parm))
+	{
+	  if (bitmap_bit_p (non_ssa_vars, DECL_UID (parm)))
+	    {
+	      if (dump_file && (dump_flags & TDF_DETAILS))
+		fprintf (dump_file,
+			 "  Refused: need to pass non-ssa param values\n");
+	      return;
+	    }
+	}
+      else if (gimple_default_def (cfun, parm)
+	       && bitmap_bit_p (current->ssa_names_to_pass,
+				SSA_NAME_VERSION (gimple_default_def
+						  (cfun, parm))))
+	{
+	  if (!VOID_TYPE_P (TREE_TYPE (parm)))
+	    call_overhead += estimate_move_cost (TREE_TYPE (parm));
+	  num_args++;
+	}
+    }
+  if (!VOID_TYPE_P (TREE_TYPE (current_function_decl)))
+    call_overhead += estimate_move_cost (TREE_TYPE (current_function_decl));
+
+  if (current->split_size <= call_overhead)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "  Refused: split size is smaller than call overhead\n");
+      return;
+    }
+  if (current->header_size + call_overhead
+      >= (unsigned int)(DECL_DECLARED_INLINE_P (current_function_decl)
+			? MAX_INLINE_INSNS_SINGLE
+			: MAX_INLINE_INSNS_AUTO))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "  Refused: header size is too large for inline candidate\n");
+      return;
+    }
+
+  /* FIXME: we currently can pass only SSA function parameters to the split
+     arguments.  Once parm_adjustment infrastructure is supported by clonning,
+     we can pass more than that.  */
+  if (num_args != bitmap_count_bits (current->ssa_names_to_pass))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "  Refused: need to pass non-param values\n");
+      return;
+    }
+
+  /* When there are non-ssa vars used in the split region, see if they
+     are used in the header region.  If so, reject the split.
+     FIXME: we can use nested function support to access both.  */
+  if (!bitmap_empty_p (non_ssa_vars))
+    {
+      basic_block bb;
+      FOR_EACH_BB (bb)
+	{
+	  gimple_stmt_iterator bsi;
+	  if (!bitmap_bit_p (current->split_bbs, bb->index))
+	    continue;
+	  for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+	    {
+	      if (is_gimple_debug (gsi_stmt (bsi)))
+		continue;
+	      if (walk_stmt_load_store_addr_ops
+		  (gsi_stmt (bsi), non_ssa_vars, test_nonssa_use,
+		   test_nonssa_use, test_nonssa_use))
+		{
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    fprintf (dump_file,
+			     "  Refused: split part has non-ssa uses\n");
+		  return;
+		}
+	    }
+	  for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+	    {
+	      if (is_gimple_debug (gsi_stmt (bsi)))
+		continue;
+	      if (walk_stmt_load_store_addr_ops
+		  (gsi_stmt (bsi), non_ssa_vars, test_nonssa_use,
+		   test_nonssa_use, test_nonssa_use))
+		{
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    fprintf (dump_file,
+			     "  Refused: split part has non-ssa uses\n");
+		  return;
+		}
+	    }
+	  FOR_EACH_EDGE (e, ei, bb->succs)
+	    {
+	      if (e->dest != return_bb)
+		continue;
+	      for (bsi = gsi_start_phis (return_bb); !gsi_end_p (bsi);
+		   gsi_next (&bsi))
+		{
+		  gimple stmt = gsi_stmt (bsi);
+		  tree op = gimple_phi_arg_def (stmt, e->dest_idx);
+
+		  if (!is_gimple_reg (gimple_phi_result (stmt)))
+		    continue;
+		  if (TREE_CODE (op) != SSA_NAME
+		      && test_nonssa_use (stmt, op, non_ssa_vars))
+		    {
+		      if (dump_file && (dump_flags & TDF_DETAILS))
+			fprintf (dump_file,
+				 "  Refused: split part has non-ssa uses\n");
+		      return;
+		    }
+		}
+	    }
+	  }
+      return;
+    }
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, "  Accepted!\n");
+
+  /* At the moment chose split point with lowest frequency and that leaves
+     out smallest size of header.
+     In future we might re-consider this heuristics.  */
+  if (!best_split_point.split_bbs
+      || best_split_point.entry_bb->frequency > current->entry_bb->frequency
+      || (best_split_point.entry_bb->frequency == current->entry_bb->frequency
+	  && best_split_point.split_size < current->split_size))
+	
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "  New best split point!\n");
+      if (best_split_point.ssa_names_to_pass)
+	{
+	  BITMAP_FREE (best_split_point.ssa_names_to_pass);
+	  BITMAP_FREE (best_split_point.split_bbs);
+	}
+      best_split_point = *current;
+      best_split_point.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+      bitmap_copy (best_split_point.ssa_names_to_pass,
+		   current->ssa_names_to_pass);
+      best_split_point.split_bbs = BITMAP_ALLOC (NULL);
+      bitmap_copy (best_split_point.split_bbs, current->split_bbs);
+    }
+}
+
+/* Return basic block containing RETURN statement, or EXIT_BLOCK_PTR if none
+   found. 
+   When there are multiple RETURN statement, chose one with return value,
+   since that one is more likely shared by multiple code paths.
+   TODO: We might support multiple return blocks.  */
+
+static basic_block
+find_return_bb (void)
+{
+  edge e;
+  edge_iterator ei;
+  basic_block return_bb = EXIT_BLOCK_PTR;
+
+  if (EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 1)
+    FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
+      {
+	gimple_stmt_iterator bsi;
+	bool found_return = false;
+	tree retval = NULL_TREE;
+
+	for (bsi = gsi_start_bb (e->src); !gsi_end_p (bsi); gsi_next (&bsi))
+	  if (gimple_code (gsi_stmt (bsi)) != GIMPLE_RETURN
+	      && gimple_code (gsi_stmt (bsi)) != GIMPLE_LABEL
+	      && !is_gimple_debug (gsi_stmt (bsi)))
+	    break;
+	  else if (gimple_code (gsi_stmt (bsi)) == GIMPLE_RETURN)
+	    {
+	      found_return = true;
+	      retval = gimple_return_retval (gsi_stmt (bsi));
+	    }
+	if (gsi_end_p (bsi) && found_return)
+	  {
+	    if (retval)
+	      return e->src;
+	    else
+	      return_bb = e->src;
+	  }
+      }
+  return return_bb;
+}
+
+/* Callback for walk_stmt_load_store_addr_ops.  If T is non-ssa automatic
+   variable, mark it as used in bitmap passed via DATA. 
+   Return true when access to T prevents splitting the function.  */
+
+static bool
+mark_nonssa_use (gimple stmt ATTRIBUTE_UNUSED, tree t,
+	         void *data ATTRIBUTE_UNUSED)
+{
+  t = get_base_address (t);
+
+  if (!t || is_gimple_reg (t))
+    return false;
+
+  /* At present we can't pass non-SSA arguments to split function.
+     FIXME: this can be relaxed by passing references to arguments.  */
+  if (TREE_CODE (t) == PARM_DECL)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "Can not split use of non-ssa function parameter.\n");
+      return true;
+    }
+
+  if (TREE_CODE (t) == VAR_DECL && auto_var_in_fn_p (t, current_function_decl))
+    bitmap_set_bit ((bitmap)data, DECL_UID (t));
+  return false;
+}
+
+/* Compute local properties of basic block BB we collect when looking for
+   split points.  We look for ssa defs and store them in SET_SSA_NAMES,
+   for ssa uses and store them in USED_SSA_NAMES and for any non-SSA automatic
+   vars stored in NON_SSA_VARS.
+
+   When BB has edge to RETURN_BB, collect uses in RETURN_BB too.  
+
+   Return false when BB contains something that prevents it from being put into
+   split function.  */
+
+static bool
+visit_bb (basic_block bb, basic_block return_bb,
+	  bitmap set_ssa_names, bitmap used_ssa_names,
+	  bitmap non_ssa_vars)
+{
+  gimple_stmt_iterator bsi;
+  edge e;
+  edge_iterator ei;
+  bool can_split = true;
+
+  for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+    {
+      gimple stmt = gsi_stmt (bsi);
+      tree op;
+      ssa_op_iter iter;
+      tree decl;
+
+      if (is_gimple_debug (stmt))
+	continue;
+
+      /* FIXME: We can split regions containing EH.  We can not however
+	 split RESX, EH_DISPATCH and EH_POINTER referring to same region
+	 into different partitions.  This would require tracking of
+	 EH regions and checking in consider_split_point if they 
+	 are not used elsewhere.  */
+      if (gimple_code (stmt) == GIMPLE_RESX
+	  && stmt_can_throw_external (stmt))
+	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "Can not split external resx.\n");
+	  can_split = false;
+	}
+      if (gimple_code (stmt) == GIMPLE_EH_DISPATCH)
+	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "Can not split eh dispatch.\n");
+	  can_split = false;
+	}
+
+      /* Check builtins that prevent splitting.  */
+      if (gimple_code (stmt) == GIMPLE_CALL
+	  && (decl = gimple_call_fndecl (stmt)) != NULL_TREE
+	  && DECL_BUILT_IN (decl)
+	  && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL)
+	switch (DECL_FUNCTION_CODE (decl))
+	  {
+	  /* FIXME: once we will allow passing non-parm values to split part,
+	     we need to be sure to handle correct builtin_stack_save and
+	     builtin_stack_restore.  At the moment we are safe; there is no
+	     way to store builtin_stack_save result in non-SSA variable
+	     since all calls to those are compiler generated.  */
+	  case BUILT_IN_APPLY:
+	  case BUILT_IN_VA_START:
+	    if (dump_file && (dump_flags & TDF_DETAILS))
+	      fprintf (dump_file, "Can not split builtin_apply and va_start.\n");
+	    can_split = false;
+	    break;
+	  case BUILT_IN_EH_POINTER:
+	    if (dump_file && (dump_flags & TDF_DETAILS))
+	      fprintf (dump_file, "Can not split builtin_eh_pointer.\n");
+	    can_split = false;
+	    break;
+	  default:
+	    break;
+	  }
+
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
+	bitmap_set_bit (set_ssa_names, SSA_NAME_VERSION (op));
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+	bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+      can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+						   mark_nonssa_use,
+						   mark_nonssa_use,
+						   mark_nonssa_use);
+    }
+  for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+    {
+      gimple stmt = gsi_stmt (bsi);
+      tree op;
+      ssa_op_iter iter;
+
+      if (is_gimple_debug (stmt))
+	continue;
+      if (!is_gimple_reg (gimple_phi_result (stmt)))
+	continue;
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
+	bitmap_set_bit (set_ssa_names, SSA_NAME_VERSION (op));
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+	bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+      can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+						   mark_nonssa_use,
+						   mark_nonssa_use,
+						   mark_nonssa_use);
+    }
+  /* Record also uses comming from PHI operand in return BB.  */
+  FOR_EACH_EDGE (e, ei, bb->succs)
+    if (e->dest == return_bb)
+      {
+	bool found_phi = false;
+	for (bsi = gsi_start_phis (return_bb); !gsi_end_p (bsi); gsi_next (&bsi))
+	  {
+	    gimple stmt = gsi_stmt (bsi);
+	    tree op = gimple_phi_arg_def (stmt, e->dest_idx);
+
+	    if (is_gimple_debug (stmt))
+	      continue;
+	    if (!is_gimple_reg (gimple_phi_result (stmt)))
+	      continue;
+	    found_phi = true;
+	    if (TREE_CODE (op) == SSA_NAME)
+	      bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+	    else
+	      can_split &= !mark_nonssa_use (stmt, op, non_ssa_vars);
+	  }
+	if (!gsi_end_p (gsi_last_bb (return_bb)))
+	  {
+	    ssa_op_iter iter;
+	    gimple stmt = gsi_stmt (gsi_last_bb (return_bb));
+	    tree op;
+	    if (!found_phi)
+	      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+		bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+	    can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+							 mark_nonssa_use,
+							 mark_nonssa_use,
+							 mark_nonssa_use);
+	  }
+      }
+  return can_split;
+}
+
+/* Stack entry for recursive DFS walk in find_split_point.  */
+
+typedef struct
+{
+  /* Basic block we are examining.  */
+  basic_block bb;
+
+  /* SSA names set and used by the BB and all BBs reachable
+     from it via DFS walk.  */
+  bitmap set_ssa_names, used_ssa_names;
+  bitmap non_ssa_vars;
+
+  /* All BBS visited from this BB via DFS walk.  */
+  bitmap bbs_visited;
+
+  /* Last examined edge in DFS walk.  Since we walk unoriented graph,
+     the value is up to sum of incomming and outgoing edges of BB.  */
+  unsigned int edge_num;
+
+  /* Stack entry index of earliest BB reachable from current BB
+     or any BB visited later in DFS valk.  */
+  int earliest;
+
+  /* Overall time and size of all BBs reached from this BB in DFS walk.  */
+  int overall_time, overall_size;
+
+  /* When false we can not split on this BB.  */
+  bool can_split;
+} stack_entry;
+DEF_VEC_O(stack_entry);
+DEF_VEC_ALLOC_O(stack_entry,heap);
+
+
+/* Find all articulations and call consider_split on them.
+   OVERALL_TIME and OVERALL_SIZE is time and size of the function.
+
+   We perform basic algorithm for finding an articulation in a graph
+   created from CFG by considering it to be an unoriented graph.
+
+   The articulation is discovered via DFS walk. We collect earliest
+   basic block on stack that is reachable via backward edge.  Articulation
+   is any basic block such that there is no backward edge bypassing it.
+   To reduce stack usage we maintain heap allocated stack in STACK vector.
+   AUX pointer of BB is set to index it appears in the stack or -1 once
+   it is visited and popped off the stack.
+
+   The algorithm finds articulation after visiting the whole component
+   reachable by it.  This makes it convenient to collect information about
+   the component used by consider_split.  */
+
+static void
+find_split_points (int overall_time, int overall_size)
+{
+  stack_entry first;
+  VEC(stack_entry, heap) *stack = NULL;
+  basic_block bb;
+  basic_block return_bb = find_return_bb ();
+  struct split_point current;
+
+  current.header_time = overall_time;
+  current.header_size = overall_size;
+  current.split_time = 0;
+  current.split_size = 0;
+  current.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+
+  first.bb = ENTRY_BLOCK_PTR;
+  first.edge_num = 0;
+  first.overall_time = 0;
+  first.overall_size = 0;
+  first.earliest = INT_MAX;
+  first.set_ssa_names = 0;
+  first.used_ssa_names = 0;
+  first.bbs_visited = 0;
+  VEC_safe_push (stack_entry, heap, stack, &first);
+  ENTRY_BLOCK_PTR->aux = (void *)(intptr_t)-1;
+
+  while (!VEC_empty (stack_entry, stack))
+    {
+      stack_entry *entry = VEC_last (stack_entry, stack);
+
+      /* We are walking an acyclic graph, so edge_num counts
+	 succ and pred edges together.  However when considering
+         articulation, we want to have processed everything reachable
+	 from articulation but nothing that reaches into it.  */
+      if (entry->edge_num == EDGE_COUNT (entry->bb->succs)
+	  && entry->bb != ENTRY_BLOCK_PTR)
+	{
+	  int pos = VEC_length (stack_entry, stack);
+	  entry->can_split &= visit_bb (entry->bb, return_bb,
+					entry->set_ssa_names,
+					entry->used_ssa_names,
+					entry->non_ssa_vars);
+	  if (pos <= entry->earliest && !entry->can_split
+	      && dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file,
+		     "found articulation at bb %i but can not split\n",
+		     entry->bb->index);
+	  if (pos <= entry->earliest && entry->can_split)
+	     {
+	       if (dump_file && (dump_flags & TDF_DETAILS))
+		 fprintf (dump_file, "found articulation at bb %i\n",
+			  entry->bb->index);
+	       current.entry_bb = entry->bb;
+	       current.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+	       bitmap_and_compl (current.ssa_names_to_pass,
+				 entry->used_ssa_names, entry->set_ssa_names);
+	       current.header_time = overall_time - entry->overall_time;
+	       current.header_size = overall_size - entry->overall_size;
+	       current.split_time = entry->overall_time;
+	       current.split_size = entry->overall_size;
+	       current.split_bbs = entry->bbs_visited;
+	       consider_split (&current, entry->non_ssa_vars, return_bb);
+	       BITMAP_FREE (current.ssa_names_to_pass);
+	     }
+	}
+      /* Do actual DFS walk.  */
+      if (entry->edge_num
+	  < (EDGE_COUNT (entry->bb->succs)
+	     + EDGE_COUNT (entry->bb->preds)))
+	{
+          edge e;
+	  basic_block dest;
+	  if (entry->edge_num < EDGE_COUNT (entry->bb->succs))
+	    {
+	      e = EDGE_SUCC (entry->bb, entry->edge_num);
+	      dest = e->dest;
+	    }
+	  else
+	    {
+	      e = EDGE_PRED (entry->bb, entry->edge_num
+			     - EDGE_COUNT (entry->bb->succs));
+	      dest = e->src;
+	    }
+
+	  entry->edge_num++;
+
+	  /* New BB to visit, push it to the stack.  */
+	  if (dest != return_bb && dest != EXIT_BLOCK_PTR
+	      && !dest->aux)
+	    {
+	      stack_entry new_entry;
+
+	      new_entry.bb = dest;
+	      new_entry.edge_num = 0;
+	      new_entry.overall_time
+		 = VEC_index (bb_info, bb_info_vec, dest->index)->time;
+	      new_entry.overall_size
+		 = VEC_index (bb_info, bb_info_vec, dest->index)->size;
+	      new_entry.earliest = INT_MAX;
+	      new_entry.set_ssa_names = BITMAP_ALLOC (NULL);
+	      new_entry.used_ssa_names = BITMAP_ALLOC (NULL);
+	      new_entry.bbs_visited = BITMAP_ALLOC (NULL);
+	      new_entry.non_ssa_vars = BITMAP_ALLOC (NULL);
+	      new_entry.can_split = true;
+	      bitmap_set_bit (new_entry.bbs_visited, dest->index);
+	      VEC_safe_push (stack_entry, heap, stack, &new_entry);
+	      dest->aux = (void *)(intptr_t)VEC_length (stack_entry, stack);
+	    }
+	  /* Back edge found, record the earliest point.  */
+	  else if ((intptr_t)dest->aux > 0
+		   && (intptr_t)dest->aux < entry->earliest)
+	    entry->earliest = (intptr_t)dest->aux;
+	}
+      /* We are done with examing the edges. pop off the value from stack and
+	 merge stuff we cummulate during the walk.  */
+      else if (entry->bb != ENTRY_BLOCK_PTR)
+	{
+	  stack_entry *prev = VEC_index (stack_entry, stack,
+					 VEC_length (stack_entry, stack) - 2);
+
+	  entry->bb->aux = (void *)(intptr_t)-1;
+	  prev->can_split &= entry->can_split;
+	  if (prev->set_ssa_names)
+	    {
+	      bitmap_ior_into (prev->set_ssa_names, entry->set_ssa_names);
+	      bitmap_ior_into (prev->used_ssa_names, entry->used_ssa_names);
+	      bitmap_ior_into (prev->bbs_visited, entry->bbs_visited);
+	      bitmap_ior_into (prev->non_ssa_vars, entry->non_ssa_vars);
+	    }
+	  if (prev->earliest > entry->earliest)
+	    prev->earliest = entry->earliest;
+	  prev->overall_time += entry->overall_time;
+	  prev->overall_size += entry->overall_size;
+	  BITMAP_FREE (entry->set_ssa_names);
+	  BITMAP_FREE (entry->used_ssa_names);
+	  BITMAP_FREE (entry->bbs_visited);
+	  BITMAP_FREE (entry->non_ssa_vars);
+	  VEC_pop (stack_entry, stack);
+	}
+      else
+        VEC_pop (stack_entry, stack);
+    }
+  ENTRY_BLOCK_PTR->aux = NULL;
+  FOR_EACH_BB (bb)
+    bb->aux = NULL;
+  BITMAP_FREE (current.ssa_names_to_pass);
+}
+
+/* Split function at SPLIT_POINT.  */
+
+static void
+split_function (struct split_point *split_point)
+{
+  VEC (tree, heap) *args_to_pass = NULL;
+  bitmap args_to_skip = BITMAP_ALLOC (NULL);
+  tree parm;
+  int num = 0;
+  struct cgraph_node *node;
+  basic_block return_bb = find_return_bb ();
+  basic_block call_bb;
+  gimple_stmt_iterator gsi;
+  gimple call;
+  edge e;
+  edge_iterator ei;
+  tree retval = NULL, real_retval = NULL;
+  bool split_part_return_p = false;
+  gimple last_stmt = NULL;
+
+  if (dump_file)
+    {
+      fprintf (dump_file, "\n\nSplitting function at:\n");
+      dump_split_point (dump_file, split_point);
+    }
+
+  /* Collect the parameters of new function and args_to_skip bitmap.  */
+  for (parm = DECL_ARGUMENTS (current_function_decl);
+       parm; parm = TREE_CHAIN (parm), num++)
+    if (!is_gimple_reg (parm)
+	|| !gimple_default_def (cfun, parm)
+	|| !bitmap_bit_p (split_point->ssa_names_to_pass,
+			  SSA_NAME_VERSION (gimple_default_def (cfun, parm))))
+      bitmap_set_bit (args_to_skip, num);
+    else
+      VEC_safe_push (tree, heap, args_to_pass, gimple_default_def (cfun, parm));
+
+  /* See if the split function will return.  */
+  FOR_EACH_EDGE (e, ei, return_bb->preds)
+    if (bitmap_bit_p (split_point->split_bbs, e->src->index))
+      break;
+  if (e)
+    split_part_return_p = true;
+
+  /* If we return, we will need the return block.  */
+  if (return_bb != EXIT_BLOCK_PTR && split_part_return_p)
+    bitmap_set_bit (split_point->split_bbs, return_bb->index);
+
+  /* Now create the actual clone.  */
+  rebuild_cgraph_edges ();
+  node = cgraph_function_versioning (cgraph_node (current_function_decl),
+				     NULL, NULL,
+				     args_to_skip,
+				     split_point->split_bbs,
+				     split_point->entry_bb, "_part");
+  cgraph_node_remove_callees (cgraph_node (current_function_decl));
+  if (!split_part_return_p)
+    TREE_THIS_VOLATILE (node->decl) = 1;
+  if (dump_file)
+    dump_function_to_file (node->decl, dump_file, dump_flags);
+
+  /* Create the basic block we place call into.  It is the entry basic block
+     split after last label.  */
+  call_bb = split_point->entry_bb;
+  for (gsi = gsi_start_bb (call_bb); !gsi_end_p (gsi);)
+    if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
+      {
+	last_stmt = gsi_stmt (gsi);
+	gsi_next (&gsi);
+      }
+    else
+      break;
+  e = split_block (split_point->entry_bb, last_stmt);
+  remove_edge (e);
+
+  /* Produce the call statement.  */
+  gsi = gsi_last_bb (call_bb);
+  call = gimple_build_call_vec (node->decl, args_to_pass);
+  gimple_set_block (call, DECL_INITIAL (current_function_decl));
+
+  /* Update return value.  This is bit tricky.  When we do not return,
+     do nothing.  When we return we might need to update return_bb
+     or produce a new return statement.  */
+  if (!split_part_return_p)
+    gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+  else
+    {
+      e = make_edge (call_bb, return_bb,
+		     return_bb == EXIT_BLOCK_PTR ? 0 : EDGE_FALLTHRU);
+      e->count = call_bb->count;
+      e->probability = REG_BR_PROB_BASE;
+      if (return_bb != EXIT_BLOCK_PTR)
+	{
+	  gimple return_stmt = gsi_stmt (gsi_last_bb (return_bb));
+	  gcc_assert (gimple_code (return_stmt) == GIMPLE_RETURN);
+
+	  if ((real_retval = retval = gimple_return_retval (return_stmt))
+	      && !is_gimple_min_invariant (retval)
+	      && (TREE_CODE (retval) != SSA_NAME
+		  || !SSA_NAME_IS_DEFAULT_DEF (retval)))
+	    {
+	      gimple_stmt_iterator psi;
+
+	      /* See if there is PHI definind return value.  */
+	      for (psi = gsi_start_phis (return_bb);
+		   !gsi_end_p (psi); gsi_next (&psi))
+		if (is_gimple_reg (gimple_phi_result (gsi_stmt (psi))))
+		  break;
+
+	      /* When we have PHI, update PHI.  When there is no PHI,
+		 update the return statement itself.  */
+	      if (TREE_CODE (retval) == SSA_NAME)
+		{
+		  retval = make_ssa_name (SSA_NAME_VAR (retval), call);
+		  if (TREE_CODE (retval) == SSA_NAME
+		      && !gsi_end_p (psi))
+		    add_phi_arg (gsi_stmt (psi), retval, e, UNKNOWN_LOCATION);
+		  else if (TREE_CODE (retval) == SSA_NAME)
+		    {
+		      gimple_return_set_retval (return_stmt, retval);
+		      update_stmt (return_stmt);
+		    }
+		}
+	      gimple_call_set_lhs (call, retval);
+	    }
+          gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+	}
+      else
+	{
+	  gimple ret;
+	  if (!VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))))
+	    {
+	      retval
+	        = create_tmp_var (TREE_TYPE (TREE_TYPE (current_function_decl)),
+				  "RET");
+	      if (is_gimple_reg (retval))
+		retval = make_ssa_name (retval, call);
+	      gimple_call_set_lhs (call, retval);
+	    }
+          gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+	  ret = gimple_build_return (retval);
+	  gsi_insert_after (&gsi, ret, GSI_NEW_STMT);
+	}
+    }
+  free_dominance_info (CDI_DOMINATORS);
+  free_dominance_info (CDI_POST_DOMINATORS);
+  compute_inline_parameters (node);
+}
+
+/* Execute function splitting pass.  */
+
+static unsigned int
+execute_split_functions (void)
+{
+  gimple_stmt_iterator bsi;
+  basic_block bb;
+  int overall_time = 0, overall_size = 0;
+  int todo = 0;
+  struct cgraph_node *node = cgraph_node (current_function_decl);
+
+  if (flags_from_decl_or_type (current_function_decl) & ECF_NORETURN)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: noreturn function.\n");
+      return 0;
+    }
+  if (MAIN_NAME_P (DECL_NAME (current_function_decl)))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: main function.\n");
+      return 0;
+    }
+  /* This can be relaxed; function might become inlinable after splitting
+     away the uninlinable part.  */
+  if (!node->local.inlinable)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: not inlinable.\n");
+      return 0;
+    }
+  if (node->local.disregard_inline_limits)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: disregading inline limits.\n");
+      return 0;
+    }
+  /* This can be relaxed; most of versioning tests actually prevents
+     a duplication.  */
+  if (!tree_versionable_function_p (current_function_decl))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: not versionable.\n");
+      return 0;
+    }
+  /* FIXME: we could support this.  */
+  if (DECL_STRUCT_FUNCTION (current_function_decl)->static_chain_decl)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: nested function.\n");
+      return 0;
+    }
+  /* FIXME: Should be easy to support.  */
+  if (DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: returns value by reference.\n");
+      return 0;
+    }
+
+  /* See if it makes sense to try to split.
+     It makes sense to split if we inline, that is if we have direct calls to
+     handle or direct calls are possibly going to appear as result of indirect
+     inlining or LTO.
+     Note that we are not completely conservative about disqualifying functions
+     called once.  It is possible that the caller is called more then once and
+     then inlining would still benefit.  */
+  if ((!node->callers || !node->callers->next_caller)
+      && !node->address_taken
+      && ((!flag_lto && !flag_whopr) || !node->local.externally_visible))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: not called directly "
+		 "or called once.\n");
+      return 0;
+    }
+
+  /* FIXME: We can actually split if splitting reduces call overhead.  */
+  if (!flag_inline_small_functions
+      && !DECL_DECLARED_INLINE_P (current_function_decl))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: not autoinlining and function"
+		 " is not inline.\n");
+      return 0;
+    }
+
+  /* Compute local info about basic blocks and determine function size/time.  */
+  VEC_safe_grow_cleared (bb_info, heap, bb_info_vec, last_basic_block + 1);
+  memset (&best_split_point, 0, sizeof (best_split_point));
+  FOR_EACH_BB (bb)
+    {
+      int time = 0;
+      int size = 0;
+      int freq = compute_call_stmt_bb_frequency (current_function_decl, bb);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "Basic block %i\n", bb->index);
+
+      for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+	{
+	  int this_time, this_size;
+	  gimple stmt = gsi_stmt (bsi);
+
+	  this_size = estimate_num_insns (stmt, &eni_size_weights);
+	  this_time = estimate_num_insns (stmt, &eni_time_weights) * freq;
+	  size += this_size;
+	  time += this_time;
+
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    {
+	      fprintf (dump_file, "  freq:%6i size:%3i time:%3i ",
+		       freq, this_size, this_time);
+	      print_gimple_stmt (dump_file, stmt, 0, 0);
+	    }
+	}
+      overall_time += time;
+      overall_size += size;
+      VEC_index (bb_info, bb_info_vec, bb->index)->time = time;
+      VEC_index (bb_info, bb_info_vec, bb->index)->size = size;
+    }
+  find_split_points (overall_time, overall_size);
+  if (best_split_point.split_bbs)
+    {
+      split_function (&best_split_point);
+      BITMAP_FREE (best_split_point.ssa_names_to_pass);
+      BITMAP_FREE (best_split_point.split_bbs);
+      todo = TODO_update_ssa | TODO_cleanup_cfg;
+    }
+  VEC_free (bb_info, heap, bb_info_vec);
+  bb_info_vec = NULL;
+  return todo;
+}
+
+static bool
+gate_split_functions (void)
+{
+  return flag_partial_inlining;
+}
+
+struct gimple_opt_pass pass_split_functions =
+{
+ {
+  GIMPLE_PASS,
+  "fnsplit",				/* name */
+  gate_split_functions,			/* gate */
+  execute_split_functions,		/* execute */
+  NULL,					/* sub */
+  NULL,					/* next */
+  0,					/* static_pass_number */
+  TV_IPA_FNSPLIT,			/* tv_id */
+  PROP_cfg,				/* properties_required */
+  0,					/* properties_provided */
+  0,					/* properties_destroyed */
+  0,					/* todo_flags_start */
+  TODO_dump_func			/* todo_flags_finish */
+ }
+};