* tree-ssa-pre.c (grand_bitmap_obstack): New.

[official-gcc.git] / gcc / tree-outof-ssa.c

/* Convert a program in SSA form into Normal form.
   Copyright (C) 2004 Free Software Foundation, Inc.
   Contributed by Andrew Macleod <amacleod@redhat.com>

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 "flags.h"
#include "rtl.h"
#include "tm_p.h"
#include "ggc.h"
#include "langhooks.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "expr.h"
#include "function.h"
#include "diagnostic.h"
#include "bitmap.h"
#include "tree-flow.h"
#include "tree-gimple.h"
#include "tree-inline.h"
#include "varray.h"
#include "timevar.h"
#include "tree-alias-common.h"
#include "hashtab.h"
#include "tree-dump.h"
#include "tree-ssa-live.h"
#include "tree-pass.h"

/* Flags to pass to remove_ssa_form.  */

#define SSANORM_PERFORM_TER             0x1
#define SSANORM_COMBINE_TEMPS           0x2
#define SSANORM_REMOVE_ALL_PHIS         0x4
#define SSANORM_COALESCE_PARTITIONS     0x8
#define SSANORM_USE_COALESCE_LIST       0x10

/* Used to hold all the components required to do SSA PHI elimination.
   The node and pred/succ list is a simple linear list of nodes and
   edges represented as pairs of nodes.

   The predecessor and successor list:  Nodes are entered in pairs, where
   [0] ->PRED, [1]->SUCC.  All the even indexes in the array represent 
   predecessors, all the odd elements are successors. 
   
   Rationale:
   When implemented as bitmaps, very large programs SSA->Normal times were 
   being dominated by clearing the interference graph.

   Typically this list of edges is extremely small since it only includes 
   PHI results and uses from a single edge which have not coalesced with 
   each other.  This means that no virtual PHI nodes are included, and
   empirical evidence suggests that the number of edges rarely exceed
   3, and in a bootstrap of GCC, the maximum size encountered was 7.
   This also limits the number of possible nodes that are involved to
   rarely more than 6, and in the bootstrap of gcc, the maximum number
   of nodes encountered was 12.  */
 
typedef struct _elim_graph {
  /* Size of the elimination vectors.  */
  int size;

  /* List of nodes in the elimination graph.  */
  varray_type nodes;

  /*  The predecessor and successor edge list.  */
  varray_type edge_list;

  /* Visited vector.  */
  sbitmap visited;

  /* Stack for visited nodes.  */
  varray_type stack;
  
  /* The variable partition map.  */
  var_map map;

  /* Edge being eliminated by this graph.  */
  edge e;

  /* List of constant copies to emit.  These are pushed on in pairs.  */
  varray_type  const_copies;
} *elim_graph;


/* Local functions.  */
static tree create_temp (tree);
static void insert_copy_on_edge (edge, tree, tree);
static elim_graph new_elim_graph (int);
static inline void delete_elim_graph (elim_graph);
static inline void clear_elim_graph (elim_graph);
static inline int elim_graph_size (elim_graph);
static inline void elim_graph_add_node (elim_graph, tree);
static inline void elim_graph_add_edge (elim_graph, int, int);
static inline int elim_graph_remove_succ_edge (elim_graph, int);

static inline void eliminate_name (elim_graph, tree);
static void eliminate_build (elim_graph, basic_block, int);
static void elim_forward (elim_graph, int);
static int elim_unvisited_predecessor (elim_graph, int);
static void elim_backward (elim_graph, int);
static void elim_create (elim_graph, int);
static void eliminate_phi (edge, int, elim_graph);
static tree_live_info_p coalesce_ssa_name (var_map, int);
static void assign_vars (var_map);
static bool replace_use_variable (var_map, use_operand_p, tree *);
static bool replace_def_variable (var_map, def_operand_p, tree *);
static void eliminate_virtual_phis (void);
static void coalesce_abnormal_edges (var_map, conflict_graph, root_var_p);
static void print_exprs (FILE *, const char *, tree, const char *, tree,
                         const char *);
static void print_exprs_edge (FILE *, edge, const char *, tree, const char *,
                              tree);


/* Create a temporary variable based on the type of variable T.  Use T's name
   as the prefix.  */

static tree
create_temp (tree t)
{
  tree tmp;
  const char *name = NULL;
  tree type;

  if (TREE_CODE (t) == SSA_NAME)
    t = SSA_NAME_VAR (t);
 
  if (TREE_CODE (t) != VAR_DECL 
      && TREE_CODE (t) != PARM_DECL)
    abort ();

  type = TREE_TYPE (t);
  tmp = DECL_NAME (t);
  if (tmp)
    name = IDENTIFIER_POINTER (tmp);

  if (name == NULL)
    name = "temp";
  tmp = create_tmp_var (type, name);
  DECL_ARTIFICIAL (tmp) = DECL_ARTIFICIAL (t);
  add_referenced_tmp_var (tmp);

  /* add_referenced_tmp_var will create the annotation and set up some
     of the flags in the annotation.  However, some flags we need to
     inherit from our original variable.  */
  var_ann (tmp)->type_mem_tag = var_ann (t)->type_mem_tag;
  if (is_call_clobbered (t))
    mark_call_clobbered (tmp);

  return tmp;
}


/* This helper function fill insert a copy from a constant or variable SRC to 
   variable DEST on edge E.  */

static void
insert_copy_on_edge (edge e, tree dest, tree src)
{
  tree copy;

  copy = build (MODIFY_EXPR, TREE_TYPE (dest), dest, src);
  set_is_used (dest);

  if (TREE_CODE (src) == ADDR_EXPR)
    src = TREE_OPERAND (src, 0);
  if (TREE_CODE (src) == VAR_DECL || TREE_CODE (src) == PARM_DECL)
    set_is_used (src);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file,
               "Inserting a copy on edge BB%d->BB%d :",
               e->src->index,
               e->dest->index);
      print_generic_expr (dump_file, copy, dump_flags);
      fprintf (dump_file, "\n");
    }

  bsi_insert_on_edge (e, copy);
}


/* Create an elimination graph with SIZE nodes and associated data
   structures.  */

static elim_graph
new_elim_graph (int size)
{
  elim_graph g = (elim_graph) xmalloc (sizeof (struct _elim_graph));

  VARRAY_TREE_INIT (g->nodes, 30, "Elimination Node List");
  VARRAY_TREE_INIT (g->const_copies, 20, "Elimination Constant Copies");
  VARRAY_INT_INIT (g->edge_list, 20, "Elimination Edge List");
  VARRAY_INT_INIT (g->stack, 30, " Elimination Stack");
  
  g->visited = sbitmap_alloc (size);

  return g;
}


/* Empty elimination graph G.  */

static inline void
clear_elim_graph (elim_graph g)
{
  VARRAY_POP_ALL (g->nodes);
  VARRAY_POP_ALL (g->edge_list);
}


/* Delete elimination graph G.  */

static inline void
delete_elim_graph (elim_graph g)
{
  sbitmap_free (g->visited);
  free (g);
}


/* Return the number of nodes in graph G.  */

static inline int
elim_graph_size (elim_graph g)
{
  return VARRAY_ACTIVE_SIZE (g->nodes);
}


/* Add NODE to graph G, if it doesn't exist already.  */

static inline void 
elim_graph_add_node (elim_graph g, tree node)
{
  int x;
  for (x = 0; x < elim_graph_size (g); x++)
    if (VARRAY_TREE (g->nodes, x) == node)
      return;
  VARRAY_PUSH_TREE (g->nodes, node);
}


/* Add the edge PRED->SUCC to graph G.  */

static inline void
elim_graph_add_edge (elim_graph g, int pred, int succ)
{
  VARRAY_PUSH_INT (g->edge_list, pred);
  VARRAY_PUSH_INT (g->edge_list, succ);
}


/* Remove an edge from graph G for which NODE is the predecessor, and
   return the successor node.  -1 is returned if there is no such edge.  */

static inline int
elim_graph_remove_succ_edge (elim_graph g, int node)
{
  int y;
  unsigned x;
  for (x = 0; x < VARRAY_ACTIVE_SIZE (g->edge_list); x += 2)
    if (VARRAY_INT (g->edge_list, x) == node)
      {
        VARRAY_INT (g->edge_list, x) = -1;
        y = VARRAY_INT (g->edge_list, x + 1);
        VARRAY_INT (g->edge_list, x + 1) = -1;
        return y;
      }
  return -1;
}


/* Find all the nodes in GRAPH which are successors to NODE in the
   edge list.  VAR will hold the partition number found.  CODE is the
   code fragment executed for every node found.  */

#define FOR_EACH_ELIM_GRAPH_SUCC(GRAPH, NODE, VAR, CODE)                \
do {                                                                    \
  unsigned x_;                                                          \
  int y_;                                                               \
  for (x_ = 0; x_ < VARRAY_ACTIVE_SIZE ((GRAPH)->edge_list); x_ += 2)   \
    {                                                                   \
      y_ = VARRAY_INT ((GRAPH)->edge_list, x_);                         \
      if (y_ != (NODE))                                                 \
        continue;                                                       \
      (VAR) = VARRAY_INT ((GRAPH)->edge_list, x_ + 1);                  \
      CODE;                                                             \
    }                                                                   \
} while (0)


/* Find all the nodes which are predecessors of NODE in the edge list for
   GRAPH.  VAR will hold the partition number found.  CODE is the
   code fragment executed for every node found.  */

#define FOR_EACH_ELIM_GRAPH_PRED(GRAPH, NODE, VAR, CODE)                \
do {                                                                    \
  unsigned x_;                                                          \
  int y_;                                                               \
  for (x_ = 0; x_ < VARRAY_ACTIVE_SIZE ((GRAPH)->edge_list); x_ += 2)   \
    {                                                                   \
      y_ = VARRAY_INT ((GRAPH)->edge_list, x_ + 1);                     \
      if (y_ != (NODE))                                                 \
        continue;                                                       \
      (VAR) = VARRAY_INT ((GRAPH)->edge_list, x_);                      \
      CODE;                                                             \
    }                                                                   \
} while (0)


/* Add T to elimination graph G.  */

static inline void
eliminate_name (elim_graph g, tree T)
{
  elim_graph_add_node (g, T);
}


/* Build elimination graph G for basic block BB on incoming PHI edge I.  */

static void
eliminate_build (elim_graph g, basic_block B, int i)
{
  tree phi;
  tree T0, Ti;
  int p0, pi;

  clear_elim_graph (g);
  
  for (phi = phi_nodes (B); phi; phi = PHI_CHAIN (phi))
    {
      T0 = var_to_partition_to_var (g->map, PHI_RESULT (phi));
      
      /* Ignore results which are not in partitions.  */
      if (T0 == NULL_TREE)
        continue;

      if (PHI_ARG_EDGE (phi, i) == g->e)
        Ti = PHI_ARG_DEF (phi, i);
      else
        {
          /* On rare occasions, a PHI node may not have the arguments
             in the same order as all of the other PHI nodes. If they don't 
             match, find the appropriate index here.  */
          pi = phi_arg_from_edge (phi, g->e);
          if (pi == -1)
            abort();
          Ti = PHI_ARG_DEF (phi, pi);
        }

      /* If this argument is a constant, or a SSA_NAME which is being
         left in SSA form, just queue a copy to be emitted on this
         edge.  */
      if (!phi_ssa_name_p (Ti)
          || (TREE_CODE (Ti) == SSA_NAME
              && var_to_partition (g->map, Ti) == NO_PARTITION))
        {
          /* Save constant copies until all other copies have been emitted
             on this edge.  */
          VARRAY_PUSH_TREE (g->const_copies, T0);
          VARRAY_PUSH_TREE (g->const_copies, Ti);
        }
      else
        {
          Ti = var_to_partition_to_var (g->map, Ti);
          if (T0 != Ti)
            {
              eliminate_name (g, T0);
              eliminate_name (g, Ti);
              p0 = var_to_partition (g->map, T0);
              pi = var_to_partition (g->map, Ti);
              elim_graph_add_edge (g, p0, pi);
            }
        }
    }
}


/* Push successors of T onto the elimination stack for G.  */

static void 
elim_forward (elim_graph g, int T)
{
  int S;
  SET_BIT (g->visited, T);
  FOR_EACH_ELIM_GRAPH_SUCC (g, T, S,
    {
      if (!TEST_BIT (g->visited, S))
        elim_forward (g, S);
    });
  VARRAY_PUSH_INT (g->stack, T);
}


/* Return 1 if there unvisited predecessors of T in graph G.  */

static int
elim_unvisited_predecessor (elim_graph g, int T)
{
  int P;
  FOR_EACH_ELIM_GRAPH_PRED (g, T, P, 
    {
      if (!TEST_BIT (g->visited, P))
        return 1;
    });
  return 0;
}

/* Process predecessors first, and insert a copy.  */

static void
elim_backward (elim_graph g, int T)
{
  int P;
  SET_BIT (g->visited, T);
  FOR_EACH_ELIM_GRAPH_PRED (g, T, P, 
    {
      if (!TEST_BIT (g->visited, P))
        {
          elim_backward (g, P);
          insert_copy_on_edge (g->e, 
                               partition_to_var (g->map, P), 
                               partition_to_var (g->map, T));
        }
    });
}

/* Insert required copies for T in graph G.  Check for a strongly connected 
   region, and create a temporary to break the cycle if one is found.  */

static void 
elim_create (elim_graph g, int T)
{
  tree U;
  int P, S;

  if (elim_unvisited_predecessor (g, T))
    {
      U = create_temp (partition_to_var (g->map, T));
      insert_copy_on_edge (g->e, U, partition_to_var (g->map, T));
      FOR_EACH_ELIM_GRAPH_PRED (g, T, P, 
        {
          if (!TEST_BIT (g->visited, P))
            {
              elim_backward (g, P);
              insert_copy_on_edge (g->e, partition_to_var (g->map, P), U);
            }
        });
    }
  else
    {
      S = elim_graph_remove_succ_edge (g, T);
      if (S != -1)
        {
          SET_BIT (g->visited, T);
          insert_copy_on_edge (g->e, 
                               partition_to_var (g->map, T), 
                               partition_to_var (g->map, S));
        }
    }
  
}

/* Eliminate all the phi nodes on edge E in graph G. I is the usual PHI
   index that edge E's values are found on.  */

static void
eliminate_phi (edge e, int i, elim_graph g)
{
  int num_nodes = 0;
  int x;
  basic_block B = e->dest;

#if defined ENABLE_CHECKING
  if (i == -1)
    abort ();
  if (VARRAY_ACTIVE_SIZE (g->const_copies) != 0)
    abort ();
#endif

  /* Abnormal edges already have everything coalesced, or the coalescer
     would have aborted.  */
  if (e->flags & EDGE_ABNORMAL)
    return;

  num_nodes = num_var_partitions (g->map);
  g->e = e;

  eliminate_build (g, B, i);

  if (elim_graph_size (g) != 0)
    {
      sbitmap_zero (g->visited);
      VARRAY_POP_ALL (g->stack);

      for (x = 0; x < elim_graph_size (g); x++)
        {
          tree var = VARRAY_TREE (g->nodes, x);
          int p = var_to_partition (g->map, var);
          if (!TEST_BIT (g->visited, p))
            elim_forward (g, p);
        }
       
      sbitmap_zero (g->visited);
      while (VARRAY_ACTIVE_SIZE (g->stack) > 0)
        {
          x = VARRAY_TOP_INT (g->stack);
          VARRAY_POP (g->stack);
          if (!TEST_BIT (g->visited, x))
            elim_create (g, x);
        }
    }

  /* If there are any pending constant copies, issue them now.  */
  while (VARRAY_ACTIVE_SIZE (g->const_copies) > 0)
    {
      tree src, dest;
      src = VARRAY_TOP_TREE (g->const_copies);
      VARRAY_POP (g->const_copies);
      dest = VARRAY_TOP_TREE (g->const_copies);
      VARRAY_POP (g->const_copies);
      insert_copy_on_edge (e, dest, src);
    }
}


/* Shortcut routine to print messages to file F of the form:
   "STR1 EXPR1 STR2 EXPR2 STR3."  */

static void
print_exprs (FILE *f, const char *str1, tree expr1, const char *str2,
             tree expr2, const char *str3)
{
  fprintf (f, "%s", str1);
  print_generic_expr (f, expr1, TDF_SLIM);
  fprintf (f, "%s", str2);
  print_generic_expr (f, expr2, TDF_SLIM);
  fprintf (f, "%s", str3);
}


/* Shortcut routine to print abnormal edge messages to file F of the form:
   "STR1 EXPR1 STR2 EXPR2 across edge E.  */

static void
print_exprs_edge (FILE *f, edge e, const char *str1, tree expr1, 
                  const char *str2, tree expr2)
{
  print_exprs (f, str1, expr1, str2, expr2, " across an abnormal edge");
  fprintf (f, " from BB%d->BB%d\n", e->src->index,
               e->dest->index);
}


/* Coalesce partitions in MAP which are live across abnormal edges in GRAPH.
   RV is the root variable groupings of the partitions in MAP.  Since code 
   cannot be inserted on these edges, failure to coalesce something across
   an abnormal edge is an error.  */

static void
coalesce_abnormal_edges (var_map map, conflict_graph graph, root_var_p rv)
{
  basic_block bb;
  edge e;
  tree phi, var, tmp;
  int x, y;

  /* Code cannot be inserted on abnormal edges. Look for all abnormal 
     edges, and coalesce any PHI results with their arguments across 
     that edge.  */

  FOR_EACH_BB (bb)
    for (e = bb->succ; e; e = e->succ_next)
      if (e->dest != EXIT_BLOCK_PTR && e->flags & EDGE_ABNORMAL)
        for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
          {
            /* Visit each PHI on the destination side of this abnormal
               edge, and attempt to coalesce the argument with the result.  */
            var = PHI_RESULT (phi);
            x = var_to_partition (map, var);

            /* Ignore results which are not relevant.  */
            if (x == NO_PARTITION)
              continue;

            y = phi_arg_from_edge (phi, e);
            if (y == -1)
              abort ();

            tmp = PHI_ARG_DEF (phi, y);
            if (!phi_ssa_name_p (tmp))
              {
                print_exprs_edge (stderr, e,
                                  "\nConstant argument in PHI. Can't insert :",
                                  var, " = ", tmp);
                abort ();
              }
            y = var_to_partition (map, tmp);
            if (x == NO_PARTITION || y == NO_PARTITION)
              abort ();
            if (root_var_find (rv, x) != root_var_find (rv, y))
              {
                print_exprs_edge (stderr, e, "\nDifferent root vars: ",
                                  root_var (rv, root_var_find (rv, x)), 
                                  " and ", 
                                  root_var (rv, root_var_find (rv, y)));
                abort ();
              }

            if (x != y)
              {
                if (!conflict_graph_conflict_p (graph, x, y))
                  {
                    /* Now map the partitions back to their real variables.  */
                    var = partition_to_var (map, x);
                    tmp = partition_to_var (map, y);
                    if (dump_file 
                        && (dump_flags & TDF_DETAILS))
                      {
                        print_exprs_edge (dump_file, e, 
                                          "ABNORMAL: Coalescing ",
                                          var, " and ", tmp);
                      }
                    if (var_union (map, var, tmp) == NO_PARTITION)
                      {
                        print_exprs_edge (stderr, e, "\nUnable to coalesce", 
                                          partition_to_var (map, x), " and ", 
                                          partition_to_var (map, y));
                        abort ();
                      }
                    conflict_graph_merge_regs (graph, x, y);
                  }
                else
                  {
                    print_exprs_edge (stderr, e, "\n Conflict ", 
                                      partition_to_var (map, x),
                                      " and ", partition_to_var (map, y));
                    abort ();
                  }
              }
          }
}


/* Reduce the number of live ranges in MAP.  Live range information is 
   returned if FLAGS indicates that we are combining temporaries, otherwise 
   NULL is returned.  The only partitions which are associated with actual 
   variables at this point are those which are forced to be coalesced for 
   various reason. (live on entry, live across abnormal edges, etc.).  */

static tree_live_info_p
coalesce_ssa_name (var_map map, int flags)
{
  int num, x, i;
  sbitmap live;
  tree var, phi;
  root_var_p rv;
  tree_live_info_p liveinfo;
  var_ann_t ann;
  conflict_graph graph;
  basic_block bb;
  coalesce_list_p cl = NULL;

  if (num_var_partitions (map) <= 1)
    return NULL;

  /* If no preference given, use cheap coalescing of all partitions.  */
  if ((flags & (SSANORM_COALESCE_PARTITIONS | SSANORM_USE_COALESCE_LIST)) == 0)
    flags |= SSANORM_COALESCE_PARTITIONS;
  
  liveinfo = calculate_live_on_entry (map);
  calculate_live_on_exit (liveinfo);
  rv = root_var_init (map);

  /* Remove single element variable from the list.  */
  root_var_compact (rv);

  if (flags & SSANORM_USE_COALESCE_LIST)
    {
      cl = create_coalesce_list (map);
      
      /* Add all potential copies via PHI arguments to the list.  */
      FOR_EACH_BB (bb)
        {
          for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
            {
              tree res = PHI_RESULT (phi);
              int p = var_to_partition (map, res);
              if (p == NO_PARTITION)
                continue;
              for (x = 0; x < PHI_NUM_ARGS (phi); x++)
                {
                  tree arg = PHI_ARG_DEF (phi, x);
                  int p2;

                  if (TREE_CODE (arg) != SSA_NAME)
                    continue;
                  if (SSA_NAME_VAR (res) != SSA_NAME_VAR (arg))
                    continue;
                  p2 = var_to_partition (map, PHI_ARG_DEF (phi, x));
                  if (p2 != NO_PARTITION)
                    add_coalesce (cl, p, p2, 1);
                }
            }
        }

      /* Coalesce all the result decls together.  */
      var = NULL_TREE;
      i = 0;
      for (x = 0; x < num_var_partitions (map); x++)
        {
          tree p = partition_to_var (map, x);
          if (TREE_CODE (SSA_NAME_VAR(p)) == RESULT_DECL)
            {
              if (var == NULL_TREE)
                {
                  var = p;
                  i = x;
                }
              else
                add_coalesce (cl, i, x, 1);
            }
        }
    }

  /* Build a conflict graph.  */
  graph = build_tree_conflict_graph (liveinfo, rv, cl);

  if (cl)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
        {
          fprintf (dump_file, "Before sorting:\n");
          dump_coalesce_list (dump_file, cl);
        }

      sort_coalesce_list (cl);

      if (dump_file && (dump_flags & TDF_DETAILS))
        {
          fprintf (dump_file, "\nAfter sorting:\n");
          dump_coalesce_list (dump_file, cl);
        }
    }

  /* Put the single element variables back in.  */
  root_var_decompact (rv);

  /* First, coalesce all live on entry variables to their root variable. 
     This will ensure the first use is coming from the correct location.  */

  live = sbitmap_alloc (num_var_partitions (map));
  sbitmap_zero (live);

  /* Set 'live' vector to indicate live on entry partitions.  */
  num = num_var_partitions (map);
  for (x = 0 ; x < num; x++)
    {
      var = partition_to_var (map, x);
      if (default_def (SSA_NAME_VAR (var)) == var)
        SET_BIT (live, x);
    }

  if ((flags & SSANORM_COMBINE_TEMPS) == 0)
    {
      delete_tree_live_info (liveinfo);
      liveinfo = NULL;
    }

  /* Assign root variable as partition representative for each live on entry
     partition.  */
  EXECUTE_IF_SET_IN_SBITMAP (live, 0, x, 
    {
      var = root_var (rv, root_var_find (rv, x));
      ann = var_ann (var);
      /* If these aren't already coalesced...  */
      if (partition_to_var (map, x) != var)
        {
          if (ann->out_of_ssa_tag)
            {
              /* This root variable has already been assigned to another
                 partition which is not coalesced with this one.  */
              abort ();
            }

          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              print_exprs (dump_file, "Must coalesce ", 
                           partition_to_var (map, x),
                           " with the root variable ", var, ".\n");
            }

          change_partition_var (map, var, x);
        }
    });

  sbitmap_free (live);

  /* Coalesce partitions live across abnormal edges.  */
  coalesce_abnormal_edges (map, graph, rv);

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_var_map (dump_file, map);

  /* Coalesce partitions.  */
  if (flags & SSANORM_USE_COALESCE_LIST)
    coalesce_tpa_members (rv, graph, map, cl, 
                          ((dump_flags & TDF_DETAILS) ? dump_file 
                                                           : NULL));

  
  if (flags & SSANORM_COALESCE_PARTITIONS)
    coalesce_tpa_members (rv, graph, map, NULL, 
                          ((dump_flags & TDF_DETAILS) ? dump_file 
                                                           : NULL));
  if (cl)
    delete_coalesce_list (cl);
  root_var_delete (rv);
  conflict_graph_delete (graph);

  return liveinfo;
}


/* Take the ssa-name var_map MAP, and assign real variables to each 
   partition.  */

static void
assign_vars (var_map map)
{
  int x, i, num, rep;
  tree t, var;
  var_ann_t ann;
  root_var_p rv;

  rv = root_var_init (map);
  if (!rv) 
    return;

  /* Coalescing may already have forced some partitions to their root 
     variable. Find these and tag them.  */

  num = num_var_partitions (map);
  for (x = 0; x < num; x++)
    {
      var = partition_to_var (map, x);
      if (TREE_CODE (var) != SSA_NAME)
        {
          /* Coalescing will already have verified that more than one
             partition doesn't have the same root variable. Simply marked
             the variable as assigned.  */
          ann = var_ann (var);
          ann->out_of_ssa_tag = 1;
          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              fprintf (dump_file, "partition %d has variable ", x);
              print_generic_expr (dump_file, var, TDF_SLIM);
              fprintf (dump_file, " assigned to it.\n");
            }

        }
    }

  num = root_var_num (rv);
  for (x = 0; x < num; x++)
    {
      var = root_var (rv, x);
      ann = var_ann (var);
      for (i = root_var_first_partition (rv, x);
           i != ROOT_VAR_NONE;
           i = root_var_next_partition (rv, i))
        {
          t = partition_to_var (map, i);

          if (t == var || TREE_CODE (t) != SSA_NAME)
            continue;

          rep = var_to_partition (map, t);
          
          if (!ann->out_of_ssa_tag)
            {
              if (dump_file && (dump_flags & TDF_DETAILS))
                print_exprs (dump_file, "", t, "  --> ", var, "\n");
              change_partition_var (map, var, rep);
              continue;
            }

          if (dump_file && (dump_flags & TDF_DETAILS))
            print_exprs (dump_file, "", t, " not coalesced with ", var, 
                         "");

          var = create_temp (t);
          change_partition_var (map, var, rep);
          ann = var_ann (var);

          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              fprintf (dump_file, " -->  New temp:  '");
              print_generic_expr (dump_file, var, TDF_SLIM);
              fprintf (dump_file, "'\n");
            }
        }
    }

  root_var_delete (rv);
}


/* Replace use operand P with whatever variable it has been rewritten to based 
   on the partitions in MAP.  EXPR is an optional expression vector over SSA 
   versions which is used to replace P with an expression instead of a variable.
   If the stmt is changed, return true.  */ 

static inline bool
replace_use_variable (var_map map, use_operand_p p, tree *expr)
{
  tree new_var;
  tree var = USE_FROM_PTR (p);

  /* Check if we are replacing this variable with an expression.  */
  if (expr)
    {
      int version = SSA_NAME_VERSION (var);
      if (expr[version])
        {
          tree new_expr = TREE_OPERAND (expr[version], 1);
          SET_USE (p, new_expr);
          /* Clear the stmt's RHS, or GC might bite us.  */
          TREE_OPERAND (expr[version], 1) = NULL_TREE;
          return true;
        }
    }

  new_var = var_to_partition_to_var (map, var);
  if (new_var)
    {
      SET_USE (p, new_var);
      set_is_used (new_var);
      return true;
    }
  return false;
}


/* Replace def operand DEF_P with whatever variable it has been rewritten to 
   based on the partitions in MAP.  EXPR is an optional expression vector over
   SSA versions which is used to replace DEF_P with an expression instead of a 
   variable.  If the stmt is changed, return true.  */ 

static inline bool
replace_def_variable (var_map map, def_operand_p def_p, tree *expr)
{
  tree new_var;
  tree var = DEF_FROM_PTR (def_p);

  /* Check if we are replacing this variable with an expression.  */
  if (expr)
    {
      int version = SSA_NAME_VERSION (var);
      if (expr[version])
        {
          tree new_expr = TREE_OPERAND (expr[version], 1);
          SET_DEF (def_p, new_expr);
          /* Clear the stmt's RHS, or GC might bite us.  */
          TREE_OPERAND (expr[version], 1) = NULL_TREE;
          return true;
        }
    }

  new_var = var_to_partition_to_var (map, var);
  if (new_var)
    {
      SET_DEF (def_p, new_var);
      set_is_used (new_var);
      return true;
    }
  return false;
}


/* Remove any PHI node which is a virtual PHI.  */

static void
eliminate_virtual_phis (void)
{
  basic_block bb;
  tree phi, next;

  FOR_EACH_BB (bb)
    {
      for (phi = phi_nodes (bb); phi; phi = next)
        {
          next = PHI_CHAIN (phi);
          if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi))))
            {
#ifdef ENABLE_CHECKING
              int i;
              /* There should be no arguments of this PHI which are in
                 the partition list, or we get incorrect results.  */
              for (i = 0; i < PHI_NUM_ARGS (phi); i++)
                {
                  tree arg = PHI_ARG_DEF (phi, i);
                  if (TREE_CODE (arg) == SSA_NAME 
                      && is_gimple_reg (SSA_NAME_VAR (arg)))
                    {
                      fprintf (stderr, "Argument of PHI is not virtual (");
                      print_generic_expr (stderr, arg, TDF_SLIM);
                      fprintf (stderr, "), but the result is :");
                      print_generic_stmt (stderr, phi, TDF_SLIM);
                      abort();
                    }
                }
#endif
              remove_phi_node (phi, NULL_TREE, bb);
            }
        }
    }
}


/* This routine will coalesce variables in MAP of the same type which do not 
   interfere with each other. LIVEINFO is the live range info for variables
   of interest.  This will both reduce the memory footprint of the stack, and 
   allow us to coalesce together local copies of globals and scalarized 
   component refs.  */

static void
coalesce_vars (var_map map, tree_live_info_p liveinfo)
{
  basic_block bb;
  type_var_p tv;
  tree var;
  int x, p, p2;
  coalesce_list_p cl;
  conflict_graph graph;

  cl = create_coalesce_list (map);

  /* Merge all the live on entry vectors for coalesced partitions.  */
  for (x = 0; x < num_var_partitions (map); x++)
    {
      var = partition_to_var (map, x);
      p = var_to_partition (map, var);
      if (p != x)
        live_merge_and_clear (liveinfo, p, x);
    }

  /* When PHI nodes are turned into copies, the result of each PHI node
     becomes live on entry to the block. Mark these now.  */
  FOR_EACH_BB (bb)
    {
      tree phi, arg;
      int p;
      for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
        {
          p = var_to_partition (map, PHI_RESULT (phi));

          /* Skip virtual PHI nodes.  */
          if (p == NO_PARTITION)
            continue;

          make_live_on_entry (liveinfo, bb, p);

          /* Each argument is a potential copy operation. Add any arguments 
             which are not coalesced to the result to the coalesce list.  */
          for (x = 0; x < PHI_NUM_ARGS (phi); x++)
            {
              arg = PHI_ARG_DEF (phi, x);
              if (!phi_ssa_name_p (arg))
                continue;
              p2 = var_to_partition (map, arg);
              if (p2 == NO_PARTITION)
                continue;
              if (p != p2)
                add_coalesce (cl, p, p2, 1);
            }
        }
   }

  
  /* Re-calculate live on exit info.  */
  calculate_live_on_exit (liveinfo);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Live range info for variable memory coalescing.\n");
      dump_live_info (dump_file, liveinfo, LIVEDUMP_ALL);

      fprintf (dump_file, "Coalesce list from phi nodes:\n");
      dump_coalesce_list (dump_file, cl);
    }


  tv = type_var_init (map);
  if (dump_file)
    type_var_dump (dump_file, tv);
  type_var_compact (tv);
  if (dump_file)
    type_var_dump (dump_file, tv);

  graph = build_tree_conflict_graph (liveinfo, tv, cl);

  type_var_decompact (tv);
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "type var list now looks like:n");
      type_var_dump (dump_file, tv);

      fprintf (dump_file, "Coalesce list after conflict graph build:\n");
      dump_coalesce_list (dump_file, cl);
    }

  sort_coalesce_list (cl);
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Coalesce list after sorting:\n");
      dump_coalesce_list (dump_file, cl);
    }

  coalesce_tpa_members (tv, graph, map, cl, 
                        ((dump_flags & TDF_DETAILS) ? dump_file : NULL));

  type_var_delete (tv);
  delete_coalesce_list (cl);
}


/* Temporary Expression Replacement (TER)

   Replace SSA version variables during out-of-ssa with their defining
   expression if there is only one use of the variable.

   A pass is made through the function, one block at a time.  No cross block
   information is tracked.

   Variables which only have one use, and whose defining stmt is considered
   a replaceable expression (see check_replaceable) are entered into 
   consideration by adding a list of dependent partitions to the version_info
   vector for that ssa_name_version.  This information comes from the partition
   mapping for each USE.  At the same time, the partition_dep_list vector for 
   these partitions have this version number entered into their lists.

   When the use of a replaceable ssa_variable is encountered, the dependence
   list in version_info[] is moved to the "pending_dependence" list in case
   the current expression is also replaceable. (To be determined later in 
   processing this stmt.) version_info[] for the version is then updated to 
   point to the defining stmt and the 'replaceable' bit is set.

   Any partition which is defined by a statement 'kills' any expression which
   is dependent on this partition.  Every ssa version in the partitions' 
   dependence list is removed from future consideration.

   All virtual references are lumped together.  Any expression which is
   dependent on any virtual variable (via a VUSE) has a dependence added
   to the special partition defined by VIRTUAL_PARTITION.

   Whenever a V_MAY_DEF is seen, all expressions dependent this 
   VIRTUAL_PARTITION are removed from consideration.

   At the end of a basic block, all expression are removed from consideration
   in preparation for the next block.  
   
   The end result is a vector over SSA_NAME_VERSION which is passed back to
   rewrite_out_of_ssa.  As the SSA variables are being rewritten, instead of
   replacing the SSA_NAME tree element with the partition it was assigned, 
   it is replaced with the RHS of the defining expression.  */


/* Dependency list element.  This can contain either a partition index or a
   version number, depending on which list it is in.  */

typedef struct value_expr_d 
{
  int value;
  struct value_expr_d *next;
} *value_expr_p;


/* Temporary Expression Replacement (TER) table information.  */

typedef struct temp_expr_table_d 
{
  var_map map;
  void **version_info;          
  value_expr_p *partition_dep_list;
  bitmap replaceable;
  bool saw_replaceable;
  int virtual_partition;
  bitmap partition_in_use;
  value_expr_p free_list;
  value_expr_p pending_dependence;
} *temp_expr_table_p;

/* Used to indicate a dependency on V_MAY_DEFs.  */
#define VIRTUAL_PARTITION(table)        (table->virtual_partition)

static temp_expr_table_p new_temp_expr_table (var_map);
static tree *free_temp_expr_table (temp_expr_table_p);
static inline value_expr_p new_value_expr (temp_expr_table_p);
static inline void free_value_expr (temp_expr_table_p, value_expr_p);
static inline value_expr_p find_value_in_list (value_expr_p, int, 
                                               value_expr_p *);
static inline void add_value_to_list (temp_expr_table_p, value_expr_p *, int);
static inline void add_info_to_list (temp_expr_table_p, value_expr_p *, 
                                     value_expr_p);
static value_expr_p remove_value_from_list (value_expr_p *, int);
static void add_dependance (temp_expr_table_p, int, tree);
static bool check_replaceable (temp_expr_table_p, tree);
static void finish_expr (temp_expr_table_p, int, bool);
static void mark_replaceable (temp_expr_table_p, tree);
static inline void kill_expr (temp_expr_table_p, int, bool);
static inline void kill_virtual_exprs (temp_expr_table_p, bool);
static void find_replaceable_in_bb (temp_expr_table_p, basic_block);
static tree *find_replaceable_exprs (var_map);
static void dump_replaceable_exprs (FILE *, tree *);


/* Create a new TER table for MAP.  */

static temp_expr_table_p
new_temp_expr_table (var_map map)
{
  temp_expr_table_p t;

  t = (temp_expr_table_p) xmalloc (sizeof (struct temp_expr_table_d));
  t->map = map;

  t->version_info = xcalloc (num_ssa_names + 1, sizeof (void *));
  t->partition_dep_list = xcalloc (num_var_partitions (map) + 1, 
                                   sizeof (value_expr_p));

  t->replaceable = BITMAP_XMALLOC ();
  t->partition_in_use = BITMAP_XMALLOC ();

  t->saw_replaceable = false;
  t->virtual_partition = num_var_partitions (map);
  t->free_list = NULL;
  t->pending_dependence = NULL;

  return t;
}


/* Free TER table T.  If there are valid replacements, return the expression 
   vector.  */

static tree *
free_temp_expr_table (temp_expr_table_p t)
{
  value_expr_p p;
  tree *ret = NULL;

#ifdef ENABLE_CHECKING
  int x;
  for (x = 0; x <= num_var_partitions (t->map); x++)
    if (t->partition_dep_list[x] != NULL)
      abort();
#endif

  while ((p = t->free_list))
    {
      t->free_list = p->next;
      free (p);
    }

  BITMAP_XFREE (t->partition_in_use);
  BITMAP_XFREE (t->replaceable);

  free (t->partition_dep_list);
  if (t->saw_replaceable)
    ret = (tree *)t->version_info;
  else
    free (t->version_info);
  
  free (t);
  return ret;
}


/* Allocate a new value list node. Take it from the free list in TABLE if 
   possible.  */

static inline value_expr_p
new_value_expr (temp_expr_table_p table)
{
  value_expr_p p;
  if (table->free_list)
    {
      p = table->free_list;
      table->free_list = p->next;
    }
  else
    p = (value_expr_p) xmalloc (sizeof (struct value_expr_d));

  return p;
}


/* Add value list node P to the free list in TABLE.  */

static inline void
free_value_expr (temp_expr_table_p table, value_expr_p p)
{
  p->next = table->free_list;
  table->free_list = p;
}


/* Find VALUE if its in LIST.  Return a pointer to the list object if found,  
   else return NULL.  If LAST_PTR is provided, it will point to the previous 
   item upon return, or NULL if this is the first item in the list.  */

static inline value_expr_p
find_value_in_list (value_expr_p list, int value, value_expr_p *last_ptr)
{
  value_expr_p curr;
  value_expr_p last = NULL;

  for (curr = list; curr; last = curr, curr = curr->next)
    {
      if (curr->value == value)
        break;
    }
  if (last_ptr)
    *last_ptr = last;
  return curr;
}


/* Add VALUE to LIST, if it isn't already present.  TAB is the expression 
   table */

static inline void
add_value_to_list (temp_expr_table_p tab, value_expr_p *list, int value)
{
  value_expr_p info;

  if (!find_value_in_list (*list, value, NULL))
    {
      info = new_value_expr (tab);
      info->value = value;
      info->next = *list;
      *list = info;
    }
}


/* Add value node INFO if it's value isn't already in LIST.  Free INFO if
   it is already in the list. TAB is the expression table.  */

static inline void
add_info_to_list (temp_expr_table_p tab, value_expr_p *list, value_expr_p info)
{
  if (find_value_in_list (*list, info->value, NULL))
    free_value_expr (tab, info);
  else
    {
      info->next = *list;
      *list = info;
    }
}


/* Look for VALUE in LIST.  If found, remove it from the list and return it's 
   pointer.  */

static value_expr_p
remove_value_from_list (value_expr_p *list, int value)
{
  value_expr_p info, last;

  info = find_value_in_list (*list, value, &last);
  if (!info)
    return NULL;
  if (!last)
    *list = info->next;
  else
    last->next = info->next;
 
  return info;
}


/* Add a dependency between the def of ssa VERSION and VAR.  If VAR is 
   replaceable by an expression, add a dependence each of the elements of the 
   expression.  These are contained in the pending list.  TAB is the
   expression table.  */

static void
add_dependance (temp_expr_table_p tab, int version, tree var)
{
  int i, x;
  value_expr_p info;

  i = SSA_NAME_VERSION (var);
  if (bitmap_bit_p (tab->replaceable, i))
    {
      /* This variable is being substituted, so use whatever dependences
         were queued up when we marked this as replaceable earlier.  */
      while ((info = tab->pending_dependence))
        {
          tab->pending_dependence = info->next;
          /* Get the partition this variable was dependent on. Reuse this
             object to represent the current  expression instead.  */
          x = info->value;
          info->value = version;
          add_info_to_list (tab, &(tab->partition_dep_list[x]), info);
          add_value_to_list (tab, 
                             (value_expr_p *)&(tab->version_info[version]), x);
          bitmap_set_bit (tab->partition_in_use, x);
        }
    }
  else
    {
      i = var_to_partition (tab->map, var);
#ifdef ENABLE_CHECKING
      if (i== NO_PARTITION)
        abort ();
#endif
      add_value_to_list (tab, &(tab->partition_dep_list[i]), version);
      add_value_to_list (tab, 
                         (value_expr_p *)&(tab->version_info[version]), i);
      bitmap_set_bit (tab->partition_in_use, i);
    }
}


/* Check if expression STMT is suitable for replacement in table TAB.  If so, 
   create an expression entry.  Return true if this stmt is replaceable.  */

static bool
check_replaceable (temp_expr_table_p tab, tree stmt)
{
  stmt_ann_t ann;
  vuse_optype vuseops;
  def_optype defs;
  use_optype uses;
  tree var, def;
  int num_use_ops, version;
  var_map map = tab->map;
  ssa_op_iter iter;

  if (TREE_CODE (stmt) != MODIFY_EXPR)
    return false;
  
  ann = stmt_ann (stmt);
  defs = DEF_OPS (ann);

  /* Punt if there is more than 1 def, or more than 1 use.  */
  if (NUM_DEFS (defs) != 1)
    return false;
  def = DEF_OP (defs, 0);
  if (version_ref_count (map, def) != 1)
    return false;

  /* Assignments to variables assigned to hard registers are not
     replaceable.  */
  if (DECL_HARD_REGISTER (SSA_NAME_VAR (def)))
    return false;

  /* There must be no V_MAY_DEFS.  */
  if (NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) != 0)
    return false;

  /* There must be no V_MUST_DEFS.  */
  if (NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) != 0)
    return false;

  /* Float expressions must go through memory if float-store is on.  */
  if (flag_float_store && FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
    return false;

  uses = USE_OPS (ann);
  num_use_ops = NUM_USES (uses);
  vuseops = VUSE_OPS (ann);

  /* Any expression which has no virtual operands and no real operands
     should have been propagated if it's possible to do anything with them. 
     If this happens here, it probably exists that way for a reason, so we 
     won't touch it.   An example is:
         b_4 = &tab
     There are no virtual uses nor any real uses, so we just leave this 
     alone to be safe.  */

  if (num_use_ops == 0 && NUM_VUSES (vuseops) == 0)
    return false;

  version = SSA_NAME_VERSION (def);

  /* Add this expression to the dependency list for each use partition.  */
  FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
    {
      add_dependance (tab, version, var);
    }

  /* If there are VUSES, add a dependence on virtual defs.  */
  if (NUM_VUSES (vuseops) != 0)
    {
      add_value_to_list (tab, (value_expr_p *)&(tab->version_info[version]), 
                         VIRTUAL_PARTITION (tab));
      add_value_to_list (tab, 
                         &(tab->partition_dep_list[VIRTUAL_PARTITION (tab)]), 
                         version);
      bitmap_set_bit (tab->partition_in_use, VIRTUAL_PARTITION (tab));
    }

  return true;
}


/* This function will remove the expression for VERSION from replacement 
   consideration.n table TAB  If 'replace' is true, it is marked as 
   replaceable, otherwise not.  */

static void
finish_expr (temp_expr_table_p tab, int version, bool replace)
{
  value_expr_p info, tmp;
  int partition;

  /* Remove this expression from its dependent lists.  The partition dependence
     list is retained and transfered later to whomever uses this version.  */
  for (info = (value_expr_p) tab->version_info[version]; info; info = tmp)
    {
      partition = info->value;
#ifdef ENABLE_CHECKING
      if (tab->partition_dep_list[partition] == NULL)
        abort ();
#endif
      tmp = remove_value_from_list (&(tab->partition_dep_list[partition]), 
                                    version);
#ifdef ENABLE_CHECKING
      if (!tmp)
        abort ();
#endif
      free_value_expr (tab, tmp);
      /* Only clear the bit when the dependency list is emptied via 
         a replacement. Otherwise kill_expr will take care of it.  */
      if (!(tab->partition_dep_list[partition]) && replace)
        bitmap_clear_bit (tab->partition_in_use, partition);
      tmp = info->next;
      if (!replace)
        free_value_expr (tab, info);
    }

  if (replace)
    {
      tab->saw_replaceable = true;
      bitmap_set_bit (tab->replaceable, version);
    }
  else
    {
#ifdef ENABLE_CHECKING
      if (bitmap_bit_p (tab->replaceable, version))
        abort ();
#endif
      tab->version_info[version] = NULL;
    }
}


/* Mark the expression associated with VAR as replaceable, and enter
   the defining stmt into the version_info table TAB.  */

static void
mark_replaceable (temp_expr_table_p tab, tree var)
{
  value_expr_p info;
  int version = SSA_NAME_VERSION (var);
  finish_expr (tab, version, true);

  /* Move the dependence list to the pending list.  */
  if (tab->version_info[version])
    {
      info = (value_expr_p) tab->version_info[version]; 
      for ( ; info->next; info = info->next)
        continue;
      info->next = tab->pending_dependence;
      tab->pending_dependence = (value_expr_p)tab->version_info[version];
    }

  tab->version_info[version] = SSA_NAME_DEF_STMT (var);
}


/* This function marks any expression in TAB which is dependent on PARTITION
   as NOT replaceable.  CLEAR_BIT is used to determine whether partition_in_use
   should have its bit cleared.  Since this routine can be called within an
   EXECUTE_IF_SET_IN_BITMAP, the bit can't always be cleared.  */

static inline void
kill_expr (temp_expr_table_p tab, int partition, bool clear_bit)
{
  value_expr_p ptr;

  /* Mark every active expr dependent on this var as not replaceable.  */
  while ((ptr = tab->partition_dep_list[partition]) != NULL)
    finish_expr (tab, ptr->value, false);

  if (clear_bit)
    bitmap_clear_bit (tab->partition_in_use, partition);
}


/* This function kills all expressions in TAB which are dependent on virtual 
   DEFs.  CLEAR_BIT determines whether partition_in_use gets cleared.  */

static inline void
kill_virtual_exprs (temp_expr_table_p tab, bool clear_bit)
{
  kill_expr (tab, VIRTUAL_PARTITION (tab), clear_bit);
}


/* This function processes basic block BB, and looks for variables which can
   be replaced by their expressions.  Results are stored in TAB.  */

static void
find_replaceable_in_bb (temp_expr_table_p tab, basic_block bb)
{
  block_stmt_iterator bsi;
  tree stmt, def;
  stmt_ann_t ann;
  int partition;
  var_map map = tab->map;
  value_expr_p p;
  ssa_op_iter iter;

  for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
    {
      stmt = bsi_stmt (bsi);
      ann = stmt_ann (stmt);

      /* Determine if this stmt finishes an existing expression.  */
      FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_USE)
        {
          if (tab->version_info[SSA_NAME_VERSION (def)])
            {
              /* Mark expression as replaceable unless stmt is volatile.  */
              if (!ann->has_volatile_ops)
                mark_replaceable (tab, def);
              else
                finish_expr (tab, SSA_NAME_VERSION (def), false);
            }
        }
      
      /* Next, see if this stmt kills off an active expression.  */
      FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
        {
          partition = var_to_partition (map, def);
          if (partition != NO_PARTITION && tab->partition_dep_list[partition])
            kill_expr (tab, partition, true);
        }

      /* Now see if we are creating a new expression or not.  */
      if (!ann->has_volatile_ops)
        check_replaceable (tab, stmt);

      /* Free any unused dependency lists.  */
      while ((p = tab->pending_dependence))
        {
          tab->pending_dependence = p->next;
          free_value_expr (tab, p);
        }

      /* A V_MAY_DEF kills any expression using a virtual operand.  */
      if (NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) > 0)
        kill_virtual_exprs (tab, true);
        
      /* A V_MUST_DEF kills any expression using a virtual operand.  */
      if (NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) > 0)
        kill_virtual_exprs (tab, true);
    }
}


/* This function is the driver routine for replacement of temporary expressions
   in the SSA->normal phase, operating on MAP.  If there are replaceable 
   expressions, a table is returned which maps SSA versions to the 
   expressions they should be replaced with.  A NULL_TREE indicates no 
   replacement should take place.  If there are no replacements at all, 
   NULL is returned by the function, otherwise an expression vector indexed
   by SSA_NAME version numbers.  */

static tree *
find_replaceable_exprs (var_map map)
{
  basic_block bb;
  int i;
  temp_expr_table_p table;
  tree *ret;

  table = new_temp_expr_table (map);
  FOR_EACH_BB (bb)
    {
      find_replaceable_in_bb (table, bb);
      EXECUTE_IF_SET_IN_BITMAP ((table->partition_in_use), 0, i,
        {
          kill_expr (table, i, false);
        });
    }

  ret = free_temp_expr_table (table);
  return ret;
}


/* Dump TER expression table EXPR to file F.  */

static void
dump_replaceable_exprs (FILE *f, tree *expr)
{
  tree stmt, var;
  int x;
  fprintf (f, "\nReplacing Expressions\n");
  for (x = 0; x < (int)num_ssa_names + 1; x++)
    if (expr[x])
      {
        stmt = expr[x];
        var = DEF_OP (STMT_DEF_OPS (stmt), 0);
        print_generic_expr (f, var, TDF_SLIM);
        fprintf (f, " replace with --> ");
        print_generic_expr (f, TREE_OPERAND (stmt, 1), TDF_SLIM);
        fprintf (f, "\n");
      }
  fprintf (f, "\n");
}


/* Helper function for discover_nonconstant_array_refs. 
   Look for ARRAY_REF nodes with non-constant indexes and mark them
   addressable.  */

static tree
discover_nonconstant_array_refs_r (tree * tp, int *walk_subtrees,
                                   void *data ATTRIBUTE_UNUSED)
{
  tree t = *tp;

  if (TYPE_P (t) || DECL_P (t))
    *walk_subtrees = 0;
  else if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
    {
      while (((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
              && is_gimple_min_invariant (TREE_OPERAND (t, 1))
              && (!TREE_OPERAND (t, 2)
                  || is_gimple_min_invariant (TREE_OPERAND (t, 2))))
             || (TREE_CODE (t) == COMPONENT_REF
                 && (!TREE_OPERAND (t,2)
                     || is_gimple_min_invariant (TREE_OPERAND (t, 2))))
             || TREE_CODE (t) == BIT_FIELD_REF
             || TREE_CODE (t) == REALPART_EXPR
             || TREE_CODE (t) == IMAGPART_EXPR
             || TREE_CODE (t) == VIEW_CONVERT_EXPR
             || TREE_CODE (t) == NOP_EXPR
             || TREE_CODE (t) == CONVERT_EXPR)
        t = TREE_OPERAND (t, 0);

      if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
        {
          t = get_base_address (t);
          if (t && DECL_P (t))
            TREE_ADDRESSABLE (t) = 1;
        }

      *walk_subtrees = 0;
    }

  return NULL_TREE;
}


/* RTL expansion is not able to compile array references with variable
   offsets for arrays stored in single register.  Discover such
   expressions and mark variables as addressable to avoid this
   scenario.  */

static void
discover_nonconstant_array_refs (void)
{
  basic_block bb;
  block_stmt_iterator bsi;

  FOR_EACH_BB (bb)
    {
      for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
        walk_tree (bsi_stmt_ptr (bsi), discover_nonconstant_array_refs_r,
                   NULL , NULL);
    }
}


/* This function will rewrite the current program using the variable mapping
   found in MAP.  If the replacement vector VALUES is provided, any 
   occurrences of partitions with non-null entries in the vector will be 
   replaced with the expression in the vector instead of its mapped 
   variable.  */

static void
rewrite_trees (var_map map, tree *values)
{
  elim_graph g;
  basic_block bb;
  block_stmt_iterator si;
  edge e;
  tree phi;
  bool changed;
 
#ifdef ENABLE_CHECKING
  /* Search for PHIs where the destination has no partition, but one
     or more arguments has a partition.  This should not happen and can
     create incorrect code.  */
  FOR_EACH_BB (bb)
    {
      tree phi;

      for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
        {
          tree T0 = var_to_partition_to_var (map, PHI_RESULT (phi));
      
          if (T0 == NULL_TREE)
            {
              int i;

              for (i = 0; i < PHI_NUM_ARGS (phi); i++)
                {
                  tree arg = PHI_ARG_DEF (phi, i);

                  if (TREE_CODE (arg) == SSA_NAME
                      && var_to_partition (map, arg) != NO_PARTITION)
                    {
                      fprintf (stderr, "Argument of PHI is in a partition :(");
                      print_generic_expr (stderr, arg, TDF_SLIM);
                      fprintf (stderr, "), but the result is not :");
                      print_generic_stmt (stderr, phi, TDF_SLIM);
                      abort();
                    }
                }
            }
        }
    }
#endif

  /* Replace PHI nodes with any required copies.  */
  g = new_elim_graph (map->num_partitions);
  g->map = map;
  FOR_EACH_BB (bb)
    {
      for (si = bsi_start (bb); !bsi_end_p (si); )
        {
          size_t num_uses, num_defs;
          use_optype uses;
          def_optype defs;
          tree stmt = bsi_stmt (si);
          use_operand_p use_p;
          def_operand_p def_p;
          int remove = 0, is_copy = 0;
          stmt_ann_t ann;
          ssa_op_iter iter;

          get_stmt_operands (stmt);
          ann = stmt_ann (stmt);
          changed = false;

          if (TREE_CODE (stmt) == MODIFY_EXPR 
              && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME))
            is_copy = 1;

          uses = USE_OPS (ann);
          num_uses = NUM_USES (uses);
          FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
            {
              if (replace_use_variable (map, use_p, values))
                changed = true;
            }

          defs = DEF_OPS (ann);
          num_defs = NUM_DEFS (defs);

          /* Mark this stmt for removal if it is the list of replaceable 
             expressions.  */
          if (values && num_defs == 1)
            {
              tree def = DEF_OP (defs, 0);
              tree val;
              val = values[SSA_NAME_VERSION (def)];
              if (val)
                remove = 1;
            }
          if (!remove)
            {
              FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF)
                {
                  if (replace_def_variable (map, def_p, NULL))
                    changed = true;

                  /* If both SSA_NAMEs coalesce to the same variable,
                     mark the now redundant copy for removal.  */
                  if (is_copy
                      && num_uses == 1
                      && (DEF_FROM_PTR (def_p) == USE_OP (uses, 0)))
                    remove = 1;
                }
              if (changed & !remove)
                modify_stmt (stmt);
            }

          /* Remove any stmts marked for removal.  */
          if (remove)
            bsi_remove (&si);
          else
            bsi_next (&si);
        }

      phi = phi_nodes (bb);
      if (phi)
        {
          for (e = bb->pred; e; e = e->pred_next)
            eliminate_phi (e, phi_arg_from_edge (phi, e), g);
        }
    }

  delete_elim_graph (g);

  /* If any copies were inserted on edges, actually insert them now.  */
  bsi_commit_edge_inserts (NULL);
}


/* Remove the variables specified in MAP from SSA form.  Any debug information
   is sent to DUMP.  FLAGS indicate what options should be used.  */

static void
remove_ssa_form (FILE *dump, var_map map, int flags)
{
  tree_live_info_p liveinfo;
  basic_block bb;
  tree phi, next;
  FILE *save;
  tree *values = NULL;

  save = dump_file;
  dump_file = dump;

  /* If we are not combining temps, don't calculate live ranges for variables
     with only one SSA version.  */
  if ((flags & SSANORM_COMBINE_TEMPS) == 0)
    compact_var_map (map, VARMAP_NO_SINGLE_DEFS);
  else
    compact_var_map (map, VARMAP_NORMAL);

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_var_map (dump_file, map);

  liveinfo = coalesce_ssa_name (map, flags);

  /* Make sure even single occurrence variables are in the list now.  */
  if ((flags & SSANORM_COMBINE_TEMPS) == 0)
    compact_var_map (map, VARMAP_NORMAL);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "After Coalescing:\n");
      dump_var_map (dump_file, map);
    }

  if (flags & SSANORM_PERFORM_TER)
    {
      values = find_replaceable_exprs (map);
      if (values && dump_file && (dump_flags & TDF_DETAILS))
        dump_replaceable_exprs (dump_file, values);
    }

  /* Assign real variables to the partitions now.  */
  assign_vars (map);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "After Root variable replacement:\n");
      dump_var_map (dump_file, map);
    }

  if ((flags & SSANORM_COMBINE_TEMPS) && liveinfo)
    {
      coalesce_vars (map, liveinfo);
      if (dump_file && (dump_flags & TDF_DETAILS))
        {
          fprintf (dump_file, "After variable memory coalescing:\n");
          dump_var_map (dump_file, map);
        }
    }
  
  if (liveinfo)
    delete_tree_live_info (liveinfo);

  rewrite_trees (map, values);

  if (values)
    free (values);

  /* Remove phi nodes which have been translated back to real variables.  */
  FOR_EACH_BB (bb)
    {
      for (phi = phi_nodes (bb); phi; phi = next)
        {
          next = PHI_CHAIN (phi);
          if ((flags & SSANORM_REMOVE_ALL_PHIS) 
              || var_to_partition (map, PHI_RESULT (phi)) != NO_PARTITION)
            remove_phi_node (phi, NULL_TREE, bb);
        }
    }

  dump_file = save;
}

/* Take the current function out of SSA form, as described in
   R. Morgan, ``Building an Optimizing Compiler'',
   Butterworth-Heinemann, Boston, MA, 1998. pp 176-186.  */

static void
rewrite_out_of_ssa (void)
{
  var_map map;
  int var_flags = 0;
  int ssa_flags = (SSANORM_REMOVE_ALL_PHIS | SSANORM_USE_COALESCE_LIST);

  if (!flag_tree_live_range_split)
    ssa_flags |= SSANORM_COALESCE_PARTITIONS;
    
  eliminate_virtual_phis ();

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_tree_cfg (dump_file, dump_flags & ~TDF_DETAILS);

  /* We cannot allow unssa to un-gimplify trees before we instrument them.  */
  if (flag_tree_ter && !flag_mudflap)
    var_flags = SSA_VAR_MAP_REF_COUNT;

  map = create_ssa_var_map (var_flags);

  if (flag_tree_combine_temps)
    ssa_flags |= SSANORM_COMBINE_TEMPS;
  if (flag_tree_ter && !flag_mudflap)
    ssa_flags |= SSANORM_PERFORM_TER;

  remove_ssa_form (dump_file, map, ssa_flags);

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_tree_cfg (dump_file, dump_flags & ~TDF_DETAILS);

  /* Do some cleanups which reduce the amount of data the
     tree->rtl expanders deal with.  */
  cfg_remove_useless_stmts ();

  /* Flush out flow graph and SSA data.  */
  delete_var_map (map);

  /* Mark arrays indexed with non-constant indices with TREE_ADDRESSABLE.  */
  discover_nonconstant_array_refs ();
}


/* Define the parameters of the out of SSA pass.  */

struct tree_opt_pass pass_del_ssa = 
{
  "optimized",                          /* name */
  NULL,                                 /* gate */
  rewrite_out_of_ssa,                   /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_TREE_SSA_TO_NORMAL,                /* tv_id */
  PROP_cfg | PROP_ssa | PROP_alias,     /* properties_required */
  0,                                    /* properties_provided */
  /* ??? If TER is enabled, we also kill gimple.  */
  PROP_ssa,                             /* properties_destroyed */
  TODO_verify_ssa | TODO_verify_flow
    | TODO_verify_stmts,                /* todo_flags_start */
  TODO_dump_func | TODO_ggc_collect,    /* todo_flags_finish */
  0                                     /* letter */
};