Makefile.in (bb-reoder.o): Add depdendency on cfglayout.h; remove unneded depdendencies;

	* Makefile.in (bb-reoder.o): Add depdendency on cfglayout.h;
	remove unneded depdendencies;
	(cfglayout.o): New.
	* cfglayout.c, cfglayout.h: New files; break out from ...
	* bb-reorder.c: ... here; Remove unneeded includes;

From-SVN: r46786

1 files changed, 1079 insertions, 0 deletions

diff --git a/gcc/cfglayout.c b/gcc/cfglayout.c
new file mode 100644
index 0000000..896eda6
--- /dev/null
+++ b/gcc/cfglayout.c
@@ -0,0 +1,1079 @@
+/* Basic block reordering routines for the GNU compiler.
+   Copyright (C) 2000 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 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 "rtl.h"
+#include "hard-reg-set.h"
+#include "basic-block.h"
+#include "insn-config.h"
+#include "output.h"
+#include "function.h"
+#include "obstack.h"
+#include "cfglayout.h"
+
+/* The contents of the current function definition are allocated
+   in this obstack, and all are freed at the end of the function.
+   For top-level functions, this is temporary_obstack.
+   Separate obstacks are made for nested functions.  */
+
+extern struct obstack flow_obstack;
+
+/* Structure to hold information about lexical scopes.  */
+struct scope_def
+{
+  int level;
+
+  /* The NOTE_INSN_BLOCK_BEG that started this scope.  */
+  rtx note_beg;
+
+  /* The NOTE_INSN_BLOCK_END that ended this scope.  */
+  rtx note_end;
+
+  /* The bb containing note_beg (if any).  */
+  basic_block bb_beg;
+
+  /* The bb containing note_end (if any).  */
+  basic_block bb_end;
+
+  /* List of basic blocks contained within this scope.  */
+  basic_block *bbs;
+
+  /* Number of blocks contained within this scope.  */
+  int num_bbs;
+
+  /* The outer scope or NULL if outermost scope.  */
+  struct scope_def *outer;
+
+  /* The first inner scope or NULL if innermost scope.  */
+  struct scope_def *inner;
+
+  /* The last inner scope or NULL if innermost scope.  */
+  struct scope_def *inner_last;
+
+  /* Link to the next (sibling) scope.  */
+  struct scope_def *next;
+};
+
+/* Structure to hold information about the scope forest.  */
+typedef struct
+{
+  /* Number of trees in forest.  */
+  int num_trees;
+
+  /* List of tree roots.  */
+  scope *trees;
+} scope_forest_info;
+
+/* Holds the interesting trailing notes for the function.  */
+static rtx function_tail_eff_head;
+
+/* The scope forst of current function.  */
+static scope_forest_info forest;
+
+static rtx skip_insns_after_block	PARAMS ((basic_block));
+static void record_effective_endpoints	PARAMS ((void));
+static rtx label_for_bb			PARAMS ((basic_block));
+static void fixup_reorder_chain		PARAMS ((void));
+
+static void relate_bbs_with_scopes	PARAMS ((scope));
+static scope make_new_scope		PARAMS ((int, rtx));
+static void build_scope_forest		PARAMS ((scope_forest_info *));
+static void remove_scope_notes		PARAMS ((void));
+static void insert_intra_1		PARAMS ((scope, rtx *, basic_block));
+static void insert_intra_bb_scope_notes PARAMS ((basic_block));
+static void insert_inter_bb_scope_notes PARAMS ((basic_block, basic_block));
+static void rebuild_scope_notes		PARAMS ((scope_forest_info *));
+static void free_scope_forest_1		PARAMS ((scope));
+static void free_scope_forest		PARAMS ((scope_forest_info *));
+void dump_scope_forest			PARAMS ((scope_forest_info *));
+static void dump_scope_forest_1		PARAMS ((scope, int));
+
+static rtx get_next_bb_note		PARAMS ((rtx));
+static rtx get_prev_bb_note		PARAMS ((rtx));
+
+void verify_insn_chain			PARAMS ((void));
+
+/* Skip over inter-block insns occurring after BB which are typically
+   associated with BB (e.g., barriers). If there are any such insns,
+   we return the last one. Otherwise, we return the end of BB.  */
+
+static rtx
+skip_insns_after_block (bb)
+     basic_block bb;
+{
+  rtx insn, last_insn, next_head, prev;
+
+  next_head = NULL_RTX;
+  if (bb->index + 1 != n_basic_blocks)
+    next_head = BASIC_BLOCK (bb->index + 1)->head;
+
+  for (last_insn = insn = bb->end; (insn = NEXT_INSN (insn)); )
+    {
+      if (insn == next_head)
+	break;
+
+      switch (GET_CODE (insn))
+	{
+	case BARRIER:
+	  last_insn = insn;
+	  continue;
+
+	case NOTE:
+	  switch (NOTE_LINE_NUMBER (insn))
+	    {
+	    case NOTE_INSN_LOOP_END:
+	    case NOTE_INSN_BLOCK_END:
+	      last_insn = insn;
+	      continue;
+	    case NOTE_INSN_DELETED:
+	    case NOTE_INSN_DELETED_LABEL:
+	      continue;
+
+	    default:
+	      continue;
+	      break;
+	    }
+	  break;
+
+	case CODE_LABEL:
+	  if (NEXT_INSN (insn)
+	      && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
+	      && (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
+	          || GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
+	    {
+	      insn = NEXT_INSN (insn);
+	      last_insn = insn;
+	      continue;
+	    }
+          break;
+
+	default:
+	  break;
+	}
+
+      break;
+    }
+  /* It is possible to hit contradicting sequence.  For instance:
+    
+     jump_insn
+     NOTE_INSN_LOOP_BEG
+     barrier
+
+     Where barrier belongs to jump_insn, but the note does not.
+     This can be created by removing the basic block originally
+     following NOTE_INSN_LOOP_BEG.
+
+     In such case reorder the notes.  */
+  for (insn = last_insn; insn != bb->end; insn = prev)
+    {
+    prev = PREV_INSN (insn);
+    if (GET_CODE (insn) == NOTE)
+      switch (NOTE_LINE_NUMBER (insn))
+        {
+          case NOTE_INSN_LOOP_END:
+          case NOTE_INSN_BLOCK_END:
+          case NOTE_INSN_DELETED:
+          case NOTE_INSN_DELETED_LABEL:
+    	continue;
+          default:
+    	reorder_insns (insn, insn, last_insn);
+        }
+    }
+
+  return last_insn;
+}
+
+/* Locate or create a label for a given basic block.  */
+
+static rtx
+label_for_bb (bb)
+     basic_block bb;
+{
+  rtx label = bb->head;
+
+  if (GET_CODE (label) != CODE_LABEL)
+    {
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, "Emitting label for block %d\n",
+		 bb->index);
+
+      label = block_label (bb);
+      if (bb->head == PREV_INSN (RBI (bb)->eff_head))
+	RBI (bb)->eff_head = label;
+    }
+
+  return label;
+}
+
+/* Locate the effective beginning and end of the insn chain for each
+   block, as defined by skip_insns_after_block above.  */
+
+static void
+record_effective_endpoints ()
+{
+  rtx next_insn = get_insns ();
+  int i;
+  
+  for (i = 0; i < n_basic_blocks; ++i)
+    {
+      basic_block bb = BASIC_BLOCK (i);
+      rtx end;
+
+      RBI (bb)->eff_head = next_insn;
+      end = skip_insns_after_block (bb);
+      RBI (bb)->eff_end = end;
+      next_insn = NEXT_INSN (end);
+    }
+  function_tail_eff_head = next_insn;
+}
+
+static rtx
+get_next_bb_note (x)
+     rtx x;
+{
+  while (x)
+    {
+      if (NOTE_INSN_BASIC_BLOCK_P (x))
+	return x;
+      x = NEXT_INSN (x);
+    }
+  return NULL;
+}
+
+static rtx
+get_prev_bb_note (x)
+     rtx x;
+{
+  while (x)
+    {
+      if (NOTE_INSN_BASIC_BLOCK_P (x))
+	return x;
+      x = PREV_INSN (x);
+    }
+  return NULL;
+}
+
+/* Determine and record the relationships between basic blocks and
+   scopes in scope tree S.  */
+
+static void
+relate_bbs_with_scopes (s)
+     scope s;
+{
+  scope p;
+  int i, bbi1, bbi2, bbs_spanned;
+  rtx bbnote;
+
+  for (p = s->inner; p; p = p->next)
+    relate_bbs_with_scopes (p);
+
+  bbi1 = bbi2 = -1;
+  bbs_spanned = 0;
+
+  /* If the begin and end notes are both inside the same basic block,
+     or if they are both outside of basic blocks, then we know immediately
+     how they are related. Otherwise, we need to poke around to make the
+     determination.  */
+  if (s->bb_beg != s->bb_end)
+    {
+      if (s->bb_beg && s->bb_end)
+        {
+	  /* Both notes are in different bbs. This implies that all the
+	     basic blocks spanned by the pair of notes are contained in
+             this scope.  */
+	  bbi1 = s->bb_beg->index;
+	  bbi2 = s->bb_end->index;
+	  bbs_spanned = 1;
+	}
+      else if (! s->bb_beg)
+        {
+	  /* First note is outside of a bb. If the scope spans more than
+	     one basic block, then they all are contained within this
+             scope. Otherwise, this scope is contained within the basic
+	     block.  */
+	  bbnote = get_next_bb_note (s->note_beg);
+	  if (! bbnote)
+	    abort ();
+	  if (NOTE_BASIC_BLOCK (bbnote) == s->bb_end)
+	    {
+	      bbs_spanned = 0;
+	      s->bb_beg = NOTE_BASIC_BLOCK (bbnote);
+	    }
+	  else
+	    {
+	      bbi1 = NOTE_BASIC_BLOCK (bbnote)->index;
+	      bbi2 = s->bb_end->index;
+	      s->bb_end = NULL;
+	      bbs_spanned = 1;
+	    }
+	}
+      else /* ! s->bb_end */
+        {
+	  /* Second note is outside of a bb. If the scope spans more than
+	     one basic block, then they all are contained within this
+             scope. Otherwise, this scope is contained within the basic
+	     block.  */
+	  bbnote = get_prev_bb_note (s->note_end);
+	  if (! bbnote)
+	    abort ();
+	  if (NOTE_BASIC_BLOCK (bbnote) == s->bb_beg)
+	    {
+	      bbs_spanned = 0;
+	      s->bb_end = NOTE_BASIC_BLOCK (bbnote);
+	    }
+	  else
+	    {
+	      bbi1 = s->bb_beg->index;
+	      bbi2 = NOTE_BASIC_BLOCK (bbnote)->index;
+	      s->bb_beg = NULL;
+	      bbs_spanned = 1;
+	    }
+	}
+    }
+  else
+    {
+      if (s->bb_beg)
+        /* Both notes are in the same bb, which implies the block
+	   contains this scope.  */
+	bbs_spanned = 0;
+      else
+	{
+          rtx x1, x2;
+	  /* Both notes are outside of any bbs. This implies that all the
+	     basic blocks spanned by the pair of notes are contained in
+             this scope. 
+	     There is a degenerate case to consider. If the notes do not
+	     span any basic blocks, then it is an empty scope that can
+	     safely be deleted or ignored. Mark these with level = -1.  */
+
+	  x1 = get_next_bb_note (s->note_beg);
+	  x2 = get_prev_bb_note (s->note_end);
+	  if (! (x1 && x2))
+	    {
+	      s->level = -1; 
+	      bbs_spanned = 0; 
+	    }
+	  else
+	    {
+	      bbi1 = NOTE_BASIC_BLOCK (x1)->index;
+	      bbi2 = NOTE_BASIC_BLOCK (x2)->index;
+	      bbs_spanned = 1;
+	    }
+	}
+    }
+
+  /* If the scope spans one or more basic blocks, we record them. We
+     only record the bbs that are immediately contained within this
+     scope. Note that if a scope is contained within a bb, we can tell
+     by checking that bb_beg = bb_end and that they are non-null.  */
+  if (bbs_spanned)
+    {
+      int j = 0;
+
+      s->num_bbs = 0;
+      for (i = bbi1; i <= bbi2; i++)
+	if (! RBI (BASIC_BLOCK (i))->scope)
+	  s->num_bbs++;
+
+      s->bbs = xmalloc (s->num_bbs * sizeof (basic_block));
+      for (i = bbi1; i <= bbi2; i++)
+	{
+	  basic_block curr_bb = BASIC_BLOCK (i);
+	  if (! RBI (curr_bb)->scope)
+	    {
+	      s->bbs[j++] = curr_bb;
+	      RBI (curr_bb)->scope = s;
+	    }
+	}
+    }
+  else
+    s->num_bbs = 0;
+}
+
+/* Allocate and initialize a new scope structure with scope level LEVEL,
+   and record the NOTE beginning the scope.  */
+
+static scope 
+make_new_scope (level, note)
+     int level;
+     rtx note;
+{
+  scope new_scope = xcalloc (1, sizeof (struct scope_def));
+  new_scope->level = level;
+  new_scope->note_beg = note;
+  return new_scope;
+}
+
+
+/* Build a forest representing the scope structure of the function.
+   Return a pointer to a structure describing the forest.  */
+
+static void
+build_scope_forest (forest)
+    scope_forest_info *forest;
+{
+  rtx x;
+  int level, bbi, i;
+  basic_block curr_bb;
+  scope root, curr_scope = 0;
+
+  forest->num_trees = 0;
+  forest->trees = NULL;
+  level = -1;
+  root = NULL;
+  curr_bb = NULL;
+  bbi = 0;
+  for (x = get_insns (); x; x = NEXT_INSN (x))
+    {
+      if (bbi < n_basic_blocks && x == BASIC_BLOCK (bbi)->head)
+	curr_bb = BASIC_BLOCK (bbi);
+
+      if (GET_CODE (x) == NOTE)
+	{
+	  if (NOTE_LINE_NUMBER (x) == NOTE_INSN_BLOCK_BEG)
+	    {
+	      if (root)
+		{
+		  scope new_scope;
+		  if (! curr_scope)
+		    abort();
+		  level++;
+		  new_scope = make_new_scope (level, x);
+		  new_scope->outer = curr_scope;
+		  new_scope->next = NULL;
+		  if (! curr_scope->inner)
+		    {
+		      curr_scope->inner = new_scope;
+		      curr_scope->inner_last = new_scope;
+		    }
+		  else
+		    {
+		      curr_scope->inner_last->next = new_scope;
+		      curr_scope->inner_last = new_scope;
+		    }
+		  curr_scope = curr_scope->inner_last;
+		}
+	      else
+		{
+		  int ntrees = forest->num_trees;
+		  level++;
+	          curr_scope = make_new_scope (level, x);
+		  root = curr_scope;
+		  forest->trees = xrealloc (forest->trees,
+					    sizeof (scope) * (ntrees + 1));
+		  forest->trees[forest->num_trees++] = root;
+		}
+	      curr_scope->bb_beg = curr_bb;
+	    }
+	  else if (NOTE_LINE_NUMBER (x) == NOTE_INSN_BLOCK_END)
+	    {
+	      curr_scope->bb_end = curr_bb;
+	      curr_scope->note_end = x;
+	      level--;
+	      curr_scope = curr_scope->outer;
+	      if (level == -1)
+		root = NULL;
+	    }
+	} /* if note */
+
+      if (curr_bb && curr_bb->end == x)
+	{
+	  curr_bb = NULL;
+	  bbi++;
+	}
+
+    } /* for */
+
+  for (i = 0; i < forest->num_trees; i++)
+    relate_bbs_with_scopes (forest->trees[i]);
+}
+
+/* Remove all the NOTE_INSN_BLOCK_BEG and NOTE_INSN_BLOCK_END notes from
+   the insn chain.  */
+
+static void
+remove_scope_notes ()
+{
+  rtx x, next;
+  basic_block currbb = NULL;
+
+  for (x = get_insns (); x; x = next)
+    {
+      next = NEXT_INSN (x);
+      if (NOTE_INSN_BASIC_BLOCK_P (x))
+	currbb = NOTE_BASIC_BLOCK (x);
+
+      if (GET_CODE (x) == NOTE
+	  && (NOTE_LINE_NUMBER (x) == NOTE_INSN_BLOCK_BEG
+	      || NOTE_LINE_NUMBER (x) == NOTE_INSN_BLOCK_END))
+	{
+	  /* Check if the scope note happens to be the end of a bb.  */
+	  if (currbb && x == currbb->end)
+	    currbb->end = PREV_INSN (x);
+	  if (currbb && x == currbb->head)
+	    abort ();
+
+	  if (PREV_INSN (x))
+	    {
+	      NEXT_INSN (PREV_INSN (x)) = next;
+	      PREV_INSN (next) = PREV_INSN (x);
+
+              NEXT_INSN (x) = NULL;
+              PREV_INSN (x) = NULL;
+	    }
+	  else
+	    abort ();
+	}
+    }
+}
+
+/* Insert scope note pairs for a contained scope tree S after insn IP.  */
+
+static void
+insert_intra_1 (s, ip, bb)
+     scope s;
+     rtx *ip;
+     basic_block bb;
+{
+  scope p;
+
+  if (NOTE_BLOCK (s->note_beg))
+    {  
+      *ip = emit_note_after (NOTE_INSN_BLOCK_BEG, *ip);
+      NOTE_BLOCK (*ip) = NOTE_BLOCK (s->note_beg);
+    } 
+
+  for (p = s->inner; p; p = p->next)
+    insert_intra_1 (p, ip, bb);
+
+  if (NOTE_BLOCK (s->note_beg))
+    {  
+      *ip = emit_note_after (NOTE_INSN_BLOCK_END, *ip);
+      NOTE_BLOCK (*ip) = NOTE_BLOCK (s->note_end);
+    }
+}
+
+
+/* Insert NOTE_INSN_BLOCK_END notes and NOTE_INSN_BLOCK_BEG notes for
+   scopes that are contained within BB.  */
+
+static void
+insert_intra_bb_scope_notes (bb)
+     basic_block bb;
+{
+  scope s = RBI (bb)->scope;
+  scope p;
+  rtx ip;
+
+  if (! s)
+    return;
+
+  ip = bb->head;
+  if (GET_CODE (ip) == CODE_LABEL)
+    ip = NEXT_INSN (ip);
+
+  for (p = s->inner; p; p = p->next)
+    {
+      if (p->bb_beg != NULL && p->bb_beg == p->bb_end && p->bb_beg == bb)
+	insert_intra_1 (p, &ip, bb);
+    }
+}
+
+
+/* Given two consecutive basic blocks BB1 and BB2 with different scopes,
+   insert NOTE_INSN_BLOCK_END notes after BB1 and NOTE_INSN_BLOCK_BEG
+   notes before BB2 such that the notes are correctly balanced. If BB1 or
+   BB2 is NULL, we are inserting scope notes for the first and last basic
+   blocks, respectively.  */
+
+static void
+insert_inter_bb_scope_notes (bb1, bb2)
+     basic_block bb1;
+     basic_block bb2;
+{
+  rtx ip;
+  scope com;
+
+  /* It is possible that a basic block is not contained in any scope.
+     In that case, we either open or close a scope but not both.  */
+  if (bb1 && bb2)
+    {
+      scope s1 = RBI (bb1)->scope;
+      scope s2 = RBI (bb2)->scope;
+      if (! s1 && ! s2)
+	return;
+      if (! s1)
+	bb1 = NULL;
+      else if (! s2)
+	bb2 = NULL;
+    }
+
+  /* Find common ancestor scope.  */
+  if (bb1 && bb2)
+    {
+      scope s1 = RBI (bb1)->scope;
+      scope s2 = RBI (bb2)->scope;
+      while (s1 != s2)
+	{
+          if (! (s1 && s2))
+	    abort ();
+	  if (s1->level > s2->level)
+	    s1 = s1->outer;
+	  else if (s2->level > s1->level)
+	    s2 = s2->outer;
+	  else
+	    {
+	      s1 = s1->outer;
+	      s2 = s2->outer;
+	    }
+	}
+      com = s1;
+    }
+  else
+    com = NULL;
+
+  /* Close scopes.  */
+  if (bb1)
+    {
+      rtx end = bb1->end;
+
+      scope s = RBI (bb1)->scope;
+      ip = RBI (bb1)->eff_end;
+      while (s != com)
+	{
+	  if (NOTE_BLOCK (s->note_beg))
+	    {  
+	      ip = emit_note_after (NOTE_INSN_BLOCK_END, ip);
+	      NOTE_BLOCK (ip) = NOTE_BLOCK (s->note_end);
+	    }
+	  s = s->outer;
+	}
+      /* Emitting note may move the end of basic block to unwanted place.  */
+      bb1->end = end;
+    }
+
+  /* Open scopes.  */
+  if (bb2)
+    {
+      scope s = RBI (bb2)->scope;
+      ip = bb2->head;
+      while (s != com)
+	{
+	  if (NOTE_BLOCK (s->note_beg))
+	    {  
+	      ip = emit_note_before (NOTE_INSN_BLOCK_BEG, ip);
+	      NOTE_BLOCK (ip) = NOTE_BLOCK (s->note_beg);
+	    }
+	  s = s->outer;
+	}
+    }
+}
+
+
+/* Rebuild all the NOTE_INSN_BLOCK_BEG and NOTE_INSN_BLOCK_END notes based
+   on the scope forest and the newly reordered basic blocks.  */
+
+static void
+rebuild_scope_notes (forest)
+    scope_forest_info *forest;
+{
+  int i;
+
+  if (forest->num_trees == 0)
+    return;
+
+  /* Start by opening the scopes before the first basic block.  */
+  insert_inter_bb_scope_notes (NULL, BASIC_BLOCK (0));
+
+  /* Then, open and close scopes as needed between blocks.  */
+  for (i = 0; i < n_basic_blocks - 1; i++)
+    {
+      basic_block bb1 = BASIC_BLOCK (i);
+      basic_block bb2 = BASIC_BLOCK (i + 1);
+      if (RBI (bb1)->scope != RBI (bb2)->scope)
+	insert_inter_bb_scope_notes (bb1, bb2);
+      insert_intra_bb_scope_notes (bb1);
+    }
+
+  /* Finally, close the scopes after the last basic block.  */
+  insert_inter_bb_scope_notes (BASIC_BLOCK (n_basic_blocks - 1), NULL);
+  insert_intra_bb_scope_notes (BASIC_BLOCK (n_basic_blocks - 1));
+}
+
+/* Free the storage associated with the scope tree at S.  */
+
+static void
+free_scope_forest_1 (s)
+    scope s;
+{
+  scope p, next;
+
+  for (p = s->inner; p; p = next)
+    {
+      next = p->next;
+      free_scope_forest_1 (p);
+    }
+
+  if (s->bbs)
+    free (s->bbs);
+  free (s);
+}
+
+/* Free the storage associated with the scope forest.  */
+
+static void
+free_scope_forest (forest)
+    scope_forest_info *forest;
+{
+  int i;
+  for (i = 0; i < forest->num_trees; i++)
+    free_scope_forest_1 (forest->trees[i]);
+}
+
+/* Visualize the scope forest.  */
+
+void
+dump_scope_forest (forest)
+    scope_forest_info *forest;
+{
+  if (forest->num_trees == 0)
+    fprintf (stderr, "\n< Empty scope forest >\n");
+  else
+    {
+      int i;
+      fprintf (stderr, "\n< Scope forest >\n");
+      for (i = 0; i < forest->num_trees; i++)
+	dump_scope_forest_1 (forest->trees[i], 0);
+    }
+}
+
+/* Recursive portion of dump_scope_forest.  */
+
+static void
+dump_scope_forest_1 (s, indent)
+     scope s;
+     int indent;
+{
+  scope p;
+  int i;
+
+  if (s->bb_beg != NULL && s->bb_beg == s->bb_end
+      && RBI (s->bb_beg)->scope
+      && RBI (s->bb_beg)->scope->level + 1 == s->level)
+    {
+      fprintf (stderr, "%*s", indent, "");
+      fprintf (stderr, "BB%d:\n", s->bb_beg->index);
+    }
+
+  fprintf (stderr, "%*s", indent, "");
+  fprintf (stderr, "{ level %d (block %p)\n", s->level,
+	   (PTR) NOTE_BLOCK (s->note_beg));
+
+  fprintf (stderr, "%*s%s", indent, "", "bbs:");
+  for (i = 0; i < s->num_bbs; i++)
+    fprintf (stderr, " %d", s->bbs[i]->index);
+  fprintf (stderr, "\n");
+  
+  for (p = s->inner; p; p = p->next)
+    dump_scope_forest_1 (p, indent + 2);
+
+  fprintf (stderr, "%*s", indent, "");
+  fprintf (stderr, "}\n");
+}
+
+/* Given a reorder chain, rearrange the code to match.  */
+
+static void
+fixup_reorder_chain ()
+{
+  basic_block bb, last_bb;
+  int index;
+  rtx insn;
+  int old_n_basic_blocks = n_basic_blocks;
+
+  /* First do the bulk reordering -- rechain the blocks without regard to
+     the needed changes to jumps and labels.  */
+
+  last_bb = BASIC_BLOCK (0);
+  bb = RBI (last_bb)->next;
+  index = 1;
+  while (bb)
+    {
+      rtx last_e = RBI (last_bb)->eff_end;
+      rtx curr_h = RBI (bb)->eff_head;
+
+      NEXT_INSN (last_e) = curr_h;
+      PREV_INSN (curr_h) = last_e;
+
+      last_bb = bb;
+      bb = RBI (bb)->next;
+      index++;
+    }
+
+  if (index != n_basic_blocks)
+    abort ();
+
+  insn = RBI (last_bb)->eff_end;
+
+  NEXT_INSN (insn) = function_tail_eff_head;
+  if (function_tail_eff_head)
+    PREV_INSN (function_tail_eff_head) = insn;
+
+  while (NEXT_INSN (insn))
+    insn = NEXT_INSN (insn);
+  set_last_insn (insn);
+#ifdef ENABLE_CHECKING
+  verify_insn_chain ();
+#endif
+
+  /* Now add jumps and labels as needed to match the blocks new
+     outgoing edges.  */
+
+  for (bb = BASIC_BLOCK (0); bb ; bb = RBI (bb)->next)
+    {
+      edge e_fall, e_taken, e;
+      rtx bb_end_insn;
+      basic_block nb;
+
+      if (bb->succ == NULL)
+	continue;
+
+      /* Find the old fallthru edge, and another non-EH edge for
+	 a taken jump.  */
+      e_taken = e_fall = NULL;
+      for (e = bb->succ; e ; e = e->succ_next)
+	if (e->flags & EDGE_FALLTHRU)
+	  e_fall = e;
+	else if (! (e->flags & EDGE_EH))
+	  e_taken = e;
+
+      bb_end_insn = bb->end;
+      if (GET_CODE (bb_end_insn) == JUMP_INSN)
+	{
+	  if (any_condjump_p (bb_end_insn))
+	    {
+	      /* If the old fallthru is still next, nothing to do.  */
+	      if (RBI (bb)->next == e_fall->dest
+	          || (!RBI (bb)->next
+		      && e_fall->dest == EXIT_BLOCK_PTR))
+		continue;
+
+	      /* There is one special case: if *neither* block is next,
+		 such as happens at the very end of a function, then we'll
+		 need to add a new unconditional jump.  Choose the taken
+		 edge based on known or assumed probability.  */
+	      if (RBI (bb)->next != e_taken->dest)
+		{
+		  rtx note = find_reg_note (bb_end_insn, REG_BR_PROB, 0);
+		  if (note
+		      && INTVAL (XEXP (note, 0)) < REG_BR_PROB_BASE / 2
+		      && invert_jump (bb_end_insn,
+				      label_for_bb (e_fall->dest), 0))
+		    {
+		      e_fall->flags &= ~EDGE_FALLTHRU;
+		      e_taken->flags |= EDGE_FALLTHRU;
+		      e = e_fall, e_fall = e_taken, e_taken = e;
+		    }
+		}
+
+	      /* Otherwise we can try to invert the jump.  This will 
+		 basically never fail, however, keep up the pretense.  */
+	      else if (invert_jump (bb_end_insn,
+				    label_for_bb (e_fall->dest), 0))
+		{
+		  e_fall->flags &= ~EDGE_FALLTHRU;
+		  e_taken->flags |= EDGE_FALLTHRU;
+		  continue;
+		}
+	    }
+	  else if (returnjump_p (bb_end_insn))
+	    continue;
+	  else
+	    {
+	      /* Otherwise we have some switch or computed jump.  In the
+		 99% case, there should not have been a fallthru edge.  */
+	      if (! e_fall)
+		continue;
+#ifdef CASE_DROPS_THROUGH
+	      /* Except for VAX.  Since we didn't have predication for the
+		 tablejump, the fallthru block should not have moved.  */
+	      if (RBI (bb)->next == e_fall->dest)
+		continue;
+	      bb_end_insn = skip_insns_after_block (bb);
+#else
+	      abort ();
+#endif
+	    }
+	}
+      else
+	{
+	  /* No fallthru implies a noreturn function with EH edges, or
+	     something similarly bizarre.  In any case, we don't need to
+	     do anything.  */
+	  if (! e_fall)
+	    continue;
+
+	  /* If the fallthru block is still next, nothing to do.  */
+	  if (RBI (bb)->next == e_fall->dest)
+	    continue;
+
+	  /* An fallthru to exit block.  */
+	  if (!RBI (bb)->next && e_fall->dest == EXIT_BLOCK_PTR)
+	    continue;
+	}
+
+      /* We got here if we need to add a new jump insn.  */
+
+      nb = force_nonfallthru (e_fall);
+
+      if (nb)
+	{
+	  alloc_aux_for_block (nb, sizeof (struct reorder_block_def));
+	  RBI (nb)->eff_head = nb->head;
+	  RBI (nb)->eff_end = NEXT_INSN (nb->end);
+	  RBI (nb)->scope = RBI (bb)->scope;
+	  RBI (nb)->visited = 1;
+	  RBI (nb)->next = RBI (bb)->next;
+	  RBI (bb)->next = nb;
+	  /* Don't process this new block.  */
+	  bb = nb;
+	}
+    }
+
+  /* Put basic_block_info in the new order.  */
+  bb = BASIC_BLOCK (0);
+  index = 0;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file, "Reordered sequence:\n");
+  while (bb)
+    {
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, " %i %sbb %i freq %i\n", index,
+		 bb->index >= old_n_basic_blocks ? "compensation " : "",
+		 bb->index,
+	   	 bb->frequency);
+      bb->index = index;
+      BASIC_BLOCK (index) = bb;
+
+      bb = RBI (bb)->next;
+      index++;
+    }
+}
+
+/* Perform sanity checks on the insn chain.
+   1. Check that next/prev pointers are consistent in both the forward and
+      reverse direction.
+   2. Count insns in chain, going both directions, and check if equal.
+   3. Check that get_last_insn () returns the actual end of chain.  */
+
+void
+verify_insn_chain ()
+{
+  rtx x,
+      prevx,
+      nextx;
+  int insn_cnt1,
+      insn_cnt2;
+
+  prevx = NULL;
+  insn_cnt1 = 1;
+  for (x = get_insns (); x; x = NEXT_INSN (x))
+    {
+      if (PREV_INSN (x) != prevx)
+	{
+	  fprintf (stderr, "Forward traversal: insn chain corrupt.\n");
+	  fprintf (stderr, "previous insn:\n");
+	  debug_rtx (prevx);
+	  fprintf (stderr, "current insn:\n");
+	  debug_rtx (x);
+	  abort ();
+	}
+      ++insn_cnt1;
+      prevx = x;
+    }
+
+  if (prevx != get_last_insn ())
+    {
+      fprintf (stderr, "last_insn corrupt.\n");
+      abort ();
+    }
+
+  nextx = NULL;
+  insn_cnt2 = 1;
+  for (x = get_last_insn (); x; x = PREV_INSN (x))
+    {
+      if (NEXT_INSN (x) != nextx)
+	{
+	  fprintf (stderr, "Reverse traversal: insn chain corrupt.\n");
+	  fprintf (stderr, "current insn:\n");
+	  debug_rtx (x);
+	  fprintf (stderr, "next insn:\n");
+	  debug_rtx (nextx);
+	  abort ();
+	}
+      ++insn_cnt2;
+      nextx = x;
+    }
+
+  if (insn_cnt1 != insn_cnt2)
+    {
+      fprintf (stderr, "insn_cnt1 (%d) not equal to insn_cnt2 (%d).\n",
+	       insn_cnt1, insn_cnt2);
+      abort ();
+    }
+}
+
+/* Main entry point to this module - initialize the datastructures for
+   CFG layout changes.  */
+
+void
+cfg_layout_initialize ()
+{
+  alloc_aux_for_blocks (sizeof (struct reorder_block_def));
+
+  build_scope_forest (&forest);
+  remove_scope_notes ();
+
+  record_effective_endpoints ();
+}
+
+/* Finalize the changes - reorder insn list according to the sequence,
+   enter compensation code, rebuild scope forest.  */
+
+void
+cfg_layout_finalize ()
+{
+  fixup_reorder_chain ();
+#ifdef ENABLE_CHECKING
+  verify_insn_chain ();
+#endif
+
+  rebuild_scope_notes (&forest);
+  free_scope_forest (&forest);
+  reorder_blocks ();
+
+  free_aux_for_blocks ();
+
+#ifdef ENABLE_CHECKING
+  verify_flow_info ();
+#endif
+}