backport: ChangeLog.tuples: ChangeLog from gimple-tuples-branch.

[gcc.git] / gcc / tree-ssa-live.c

/* Liveness for SSA trees.
   Copyright (C) 2003, 2004, 2005, 2007, 2008 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 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "diagnostic.h"
#include "bitmap.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "tree-ssa-live.h"
#include "toplev.h"
#include "debug.h"
#include "flags.h"

#ifdef ENABLE_CHECKING
static void  verify_live_on_entry (tree_live_info_p);
#endif


/* VARMAP maintains a mapping from SSA version number to real variables.

   All SSA_NAMES are divided into partitions.  Initially each ssa_name is the
   only member of it's own partition.  Coalescing will attempt to group any
   ssa_names which occur in a copy or in a PHI node into the same partition.

   At the end of out-of-ssa, each partition becomes a "real" variable and is
   rewritten as a compiler variable.

   The var_map data structure is used to manage these partitions.  It allows
   partitions to be combined, and determines which partition belongs to what
   ssa_name or variable, and vice versa.  */


/* This routine will initialize the basevar fields of MAP.  */

static void
var_map_base_init (var_map map)
{
  int x, num_part, num;
  tree var;
  var_ann_t ann;
  
  num = 0;
  num_part = num_var_partitions (map);

  /* If a base table already exists, clear it, otherwise create it.  */
  if (map->partition_to_base_index != NULL)
    {
      free (map->partition_to_base_index);
      VEC_truncate (tree, map->basevars, 0);
    }
  else
    map->basevars = VEC_alloc (tree, heap, MAX (40, (num_part / 10)));

  map->partition_to_base_index = (int *) xmalloc (sizeof (int) * num_part);

  /* Build the base variable list, and point partitions at their bases.  */
  for (x = 0; x < num_part; x++)
    {
      var = partition_to_var (map, x);
      if (TREE_CODE (var) == SSA_NAME)
         var = SSA_NAME_VAR (var);
      ann = var_ann (var);
      /* If base variable hasn't been seen, set it up.  */
      if (!ann->base_var_processed)
        {
          ann->base_var_processed = 1;
          VAR_ANN_BASE_INDEX (ann) = num++;
          VEC_safe_push (tree, heap, map->basevars, var);
        }
      map->partition_to_base_index[x] = VAR_ANN_BASE_INDEX (ann);
    }

  map->num_basevars = num;

  /* Now clear the processed bit.  */
  for (x = 0; x < num; x++)
    {
       var = VEC_index (tree, map->basevars, x);
       var_ann (var)->base_var_processed = 0;
    }

#ifdef ENABLE_CHECKING
  for (x = 0; x < num_part; x++)
    {
      tree var2;
      var = SSA_NAME_VAR (partition_to_var (map, x));
      var2 = VEC_index (tree, map->basevars, basevar_index (map, x));
      gcc_assert (var == var2);
    }
#endif
}


/* Remove the base table in MAP.  */

static void
var_map_base_fini (var_map map)
{
  /* Free the basevar info if it is present.  */
  if (map->partition_to_base_index != NULL)
    {
      VEC_free (tree, heap, map->basevars);
      free (map->partition_to_base_index);
      map->partition_to_base_index = NULL;
      map->num_basevars = 0;
    }
}
/* Create a variable partition map of SIZE, initialize and return it.  */

var_map
init_var_map (int size)
{
  var_map map;

  map = (var_map) xmalloc (sizeof (struct _var_map));
  map->var_partition = partition_new (size);
  map->partition_to_var 
              = (tree *)xmalloc (size * sizeof (tree));
  memset (map->partition_to_var, 0, size * sizeof (tree));

  map->partition_to_view = NULL;
  map->view_to_partition = NULL;
  map->num_partitions = size;
  map->partition_size = size;
  map->num_basevars = 0;
  map->partition_to_base_index = NULL;
  map->basevars = NULL;
  return map;
}


/* Free memory associated with MAP.  */

void
delete_var_map (var_map map)
{
  var_map_base_fini (map);
  free (map->partition_to_var);
  partition_delete (map->var_partition);
  if (map->partition_to_view)
    free (map->partition_to_view);
  if (map->view_to_partition)
    free (map->view_to_partition);
  free (map);
}


/* This function will combine the partitions in MAP for VAR1 and VAR2.  It 
   Returns the partition which represents the new partition.  If the two 
   partitions cannot be combined, NO_PARTITION is returned.  */

int
var_union (var_map map, tree var1, tree var2)
{
  int p1, p2, p3;
  tree root_var = NULL_TREE;
  tree other_var = NULL_TREE;

  /* This is independent of partition_to_view. If partition_to_view is 
     on, then whichever one of these partitions is absorbed will never have a
     dereference into the partition_to_view array any more.  */

  if (TREE_CODE (var1) == SSA_NAME)
    p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1));
  else
    {
      p1 = var_to_partition (map, var1);
      if (map->view_to_partition)
        p1 = map->view_to_partition[p1];
      root_var = var1;
    }
  
  if (TREE_CODE (var2) == SSA_NAME)
    p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2));
  else
    {
      p2 = var_to_partition (map, var2);
      if (map->view_to_partition)
        p2 = map->view_to_partition[p2];

      /* If there is no root_var set, or it's not a user variable, set the
         root_var to this one.  */
      if (!root_var || (DECL_P (root_var) && DECL_IGNORED_P (root_var)))
        {
          other_var = root_var;
          root_var = var2;
        }
      else 
        other_var = var2;
    }

  gcc_assert (p1 != NO_PARTITION);
  gcc_assert (p2 != NO_PARTITION);

  if (p1 == p2)
    p3 = p1;
  else
    p3 = partition_union (map->var_partition, p1, p2);

  if (map->partition_to_view)
    p3 = map->partition_to_view[p3];

  if (root_var)
    change_partition_var (map, root_var, p3);
  if (other_var)
    change_partition_var (map, other_var, p3);

  return p3;
}

 
/* Compress the partition numbers in MAP such that they fall in the range 
   0..(num_partitions-1) instead of wherever they turned out during
   the partitioning exercise.  This removes any references to unused
   partitions, thereby allowing bitmaps and other vectors to be much
   denser.  

   This is implemented such that compaction doesn't affect partitioning.
   Ie., once partitions are created and possibly merged, running one
   or more different kind of compaction will not affect the partitions
   themselves.  Their index might change, but all the same variables will
   still be members of the same partition group.  This allows work on reduced
   sets, and no loss of information when a larger set is later desired.

   In particular, coalescing can work on partitions which have 2 or more
   definitions, and then 'recompact' later to include all the single
   definitions for assignment to program variables.  */


/* Set MAP back to the initial state of having no partition view.  Return a 
   bitmap which has a bit set for each partition number which is in use in the 
   varmap.  */

static bitmap
partition_view_init (var_map map)
{
  bitmap used;
  int tmp;
  unsigned int x;

  used = BITMAP_ALLOC (NULL);

  /* Already in a view? Abandon the old one.  */
  if (map->partition_to_view)
    {
      free (map->partition_to_view);
      map->partition_to_view = NULL;
    }
  if (map->view_to_partition)
    {
      free (map->view_to_partition);
      map->view_to_partition = NULL;
    }

  /* Find out which partitions are actually referenced.  */
  for (x = 0; x < map->partition_size; x++)
    {
      tmp = partition_find (map->var_partition, x);
      if (map->partition_to_var[tmp] != NULL_TREE && !bitmap_bit_p (used, tmp))
        bitmap_set_bit (used, tmp);
    }

  map->num_partitions = map->partition_size;
  return used;
}


/* This routine will finalize the view data for MAP based on the partitions
   set in SELECTED.  This is either the same bitmap returned from 
   partition_view_init, or a trimmed down version if some of those partitions
   were not desired in this view.  SELECTED is freed before returning.  */

static void 
partition_view_fini (var_map map, bitmap selected)
{
  bitmap_iterator bi;
  unsigned count, i, x, limit;
  tree var;

  gcc_assert (selected);

  count = bitmap_count_bits (selected);
  limit = map->partition_size;

  /* If its a one-to-one ratio, we don't need any view compaction.  */
  if (count < limit)
    {
      map->partition_to_view = (int *)xmalloc (limit * sizeof (int));
      memset (map->partition_to_view, 0xff, (limit * sizeof (int)));
      map->view_to_partition = (int *)xmalloc (count * sizeof (int));

      i = 0;
      /* Give each selected partition an index.  */
      EXECUTE_IF_SET_IN_BITMAP (selected, 0, x, bi)
        {
          map->partition_to_view[x] = i;
          map->view_to_partition[i] = x;
          var = map->partition_to_var[x];
          /* If any one of the members of a partition is not an SSA_NAME, make
             sure it is the representative.  */
          if (TREE_CODE (var) != SSA_NAME)
            change_partition_var (map, var, i);
          i++;
        }
      gcc_assert (i == count);
      map->num_partitions = i;
    }

  BITMAP_FREE (selected);
}


/* Create a partition view which includes all the used partitions in MAP.  If 
   WANT_BASES is true, create the base variable map as well.  */

extern void
partition_view_normal (var_map map, bool want_bases)
{
  bitmap used;

  used = partition_view_init (map);
  partition_view_fini (map, used);

  if (want_bases)
    var_map_base_init (map);
  else
    var_map_base_fini (map);
}


/* Create a partition view in MAP which includes just partitions which occur in 
   the bitmap ONLY. If WANT_BASES is true, create the base variable map 
   as well.  */

extern void
partition_view_bitmap (var_map map, bitmap only, bool want_bases)
{
  bitmap used;
  bitmap new_partitions = BITMAP_ALLOC (NULL);
  unsigned x, p;
  bitmap_iterator bi;

  used = partition_view_init (map);
  EXECUTE_IF_SET_IN_BITMAP (only, 0, x, bi)
    {
      p = partition_find (map->var_partition, x);
      gcc_assert (bitmap_bit_p (used, p));
      bitmap_set_bit (new_partitions, p);
    }
  partition_view_fini (map, new_partitions);

  BITMAP_FREE (used);
  if (want_bases)
    var_map_base_init (map);
  else
    var_map_base_fini (map);
}


/* This function is used to change the representative variable in MAP for VAR's 
   partition to a regular non-ssa variable.  This allows partitions to be 
   mapped back to real variables.  */
  
void 
change_partition_var (var_map map, tree var, int part)
{
  var_ann_t ann;

  gcc_assert (TREE_CODE (var) != SSA_NAME);

  ann = var_ann (var);
  ann->out_of_ssa_tag = 1;
  VAR_ANN_PARTITION (ann) = part;
  if (map->view_to_partition)
    map->partition_to_var[map->view_to_partition[part]] = var;
}


static inline void mark_all_vars_used (tree *, void *data);

/* Helper function for mark_all_vars_used, called via walk_tree.  */

static tree
mark_all_vars_used_1 (tree *tp, int *walk_subtrees, void *data)
{
  tree t = *tp;
  enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t));
  tree b;

  if (TREE_CODE (t) == SSA_NAME)
    t = SSA_NAME_VAR (t);

  if (IS_EXPR_CODE_CLASS (c)
      && (b = TREE_BLOCK (t)) != NULL)
    TREE_USED (b) = true;

  /* Ignore TREE_ORIGINAL for TARGET_MEM_REFS, as well as other
     fields that do not contain vars.  */
  if (TREE_CODE (t) == TARGET_MEM_REF)
    {
      mark_all_vars_used (&TMR_SYMBOL (t), data);
      mark_all_vars_used (&TMR_BASE (t), data);
      mark_all_vars_used (&TMR_INDEX (t), data);
      *walk_subtrees = 0;
      return NULL;
    }

  /* Only need to mark VAR_DECLS; parameters and return results are not
     eliminated as unused.  */
  if (TREE_CODE (t) == VAR_DECL)
    {
      if (data != NULL && bitmap_bit_p ((bitmap) data, DECL_UID (t)))
        {
          bitmap_clear_bit ((bitmap) data, DECL_UID (t));
          mark_all_vars_used (&DECL_INITIAL (t), data);
        }
      set_is_used (t);
    }

  if (IS_TYPE_OR_DECL_P (t))
    *walk_subtrees = 0;

  return NULL;
}

/* Mark the scope block SCOPE and its subblocks unused when they can be
   possibly eliminated if dead.  */

static void
mark_scope_block_unused (tree scope)
{
  tree t;
  TREE_USED (scope) = false;
  if (!(*debug_hooks->ignore_block) (scope))
    TREE_USED (scope) = true;
  for (t = BLOCK_SUBBLOCKS (scope); t ; t = BLOCK_CHAIN (t))
    mark_scope_block_unused (t);
}

/* Look if the block is dead (by possibly eliminating its dead subblocks)
   and return true if so.  
   Block is declared dead if:
     1) No statements are associated with it.
     2) Declares no live variables
     3) All subblocks are dead
        or there is precisely one subblocks and the block
        has same abstract origin as outer block and declares
        no variables, so it is pure wrapper.
   When we are not outputting full debug info, we also eliminate dead variables
   out of scope blocks to let them to be recycled by GGC and to save copying work
   done by the inliner.  */

static bool
remove_unused_scope_block_p (tree scope)
{
  tree *t, *next;
  bool unused = !TREE_USED (scope);
  var_ann_t ann;
  int nsubblocks = 0;

  for (t = &BLOCK_VARS (scope); *t; t = next)
    {
      next = &TREE_CHAIN (*t);

      /* Debug info of nested function refers to the block of the
         function.  */
      if (TREE_CODE (*t) == FUNCTION_DECL)
        unused = false;

      /* When we are outputting debug info, we usually want to output
         info about optimized-out variables in the scope blocks.
         Exception are the scope blocks not containing any instructions
         at all so user can't get into the scopes at first place.  */
      else if ((ann = var_ann (*t)) != NULL
                && ann->used)
        unused = false;

      /* When we are not doing full debug info, we however can keep around
         only the used variables for cfgexpand's memory packing saving quite
         a lot of memory.  */
      else if (debug_info_level == DINFO_LEVEL_NORMAL
               || debug_info_level == DINFO_LEVEL_VERBOSE
               /* Removing declarations before inlining is going to affect
                  DECL_UID that in turn is going to affect hashtables and
                  code generation.  */
               || !cfun->after_inlining)
        unused = false;

      else
        {
          *t = TREE_CHAIN (*t);
          next = t;
        }
    }

  for (t = &BLOCK_SUBBLOCKS (scope); *t ;)
    if (remove_unused_scope_block_p (*t))
      {
        if (BLOCK_SUBBLOCKS (*t))
          {
            tree next = BLOCK_CHAIN (*t);
            tree supercontext = BLOCK_SUPERCONTEXT (*t);
            *t = BLOCK_SUBBLOCKS (*t);
            gcc_assert (!BLOCK_CHAIN (*t));
            BLOCK_CHAIN (*t) = next;
            BLOCK_SUPERCONTEXT (*t) = supercontext;
            t = &BLOCK_CHAIN (*t);
            nsubblocks ++;
          }
        else
          {
            gcc_assert (!BLOCK_VARS (*t));
            *t = BLOCK_CHAIN (*t);
          }
      }
    else
      {
        t = &BLOCK_CHAIN (*t);
        nsubblocks ++;
      }
   /* Outer scope is always used.  */
   if (!BLOCK_SUPERCONTEXT (scope)
       || TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL)
     unused = false;
   /* If there are more than one live subblocks, it is used.  */
   else if (nsubblocks > 1)
     unused = false;
   /* When there is only one subblock, see if it is just wrapper we can
      ignore.  Wrappers are not declaring any variables and not changing
      abstract origin.  */
   else if (nsubblocks == 1
            && (BLOCK_VARS (scope)
                || ((debug_info_level == DINFO_LEVEL_NORMAL
                     || debug_info_level == DINFO_LEVEL_VERBOSE)
                    && ((BLOCK_ABSTRACT_ORIGIN (scope)
                        != BLOCK_ABSTRACT_ORIGIN (BLOCK_SUPERCONTEXT (scope)))))))
     unused = false;
   return unused;
}

/* Mark all VAR_DECLS under *EXPR_P as used, so that they won't be 
   eliminated during the tree->rtl conversion process.  */

static inline void
mark_all_vars_used (tree *expr_p, void *data)
{
  walk_tree (expr_p, mark_all_vars_used_1, data, NULL);
}


/* Remove local variables that are not referenced in the IL.  */

void
remove_unused_locals (void)
{
  basic_block bb;
  tree t, *cell;
  referenced_var_iterator rvi;
  var_ann_t ann;
  bitmap global_unused_vars = NULL;

  if (optimize)
    mark_scope_block_unused (DECL_INITIAL (current_function_decl));

  /* Assume all locals are unused.  */
  FOR_EACH_REFERENCED_VAR (t, rvi)
    var_ann (t)->used = false;

  /* Walk the CFG marking all referenced symbols.  */
  FOR_EACH_BB (bb)
    {
      gimple_stmt_iterator gsi;
      size_t i;

      /* Walk the statements.  */
      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
        {
          gimple stmt = gsi_stmt (gsi);
          tree b = gimple_block (stmt);

          if (b)
            TREE_USED (b) = true;

          for (i = 0; i < gimple_num_ops (stmt); i++)
            mark_all_vars_used (gimple_op_ptr (gsi_stmt (gsi), i), NULL);
        }

      for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
        {
          use_operand_p arg_p;
          ssa_op_iter i;
          tree def;
          gimple phi = gsi_stmt (gsi);

          /* No point processing globals.  */
          if (is_global_var (SSA_NAME_VAR (gimple_phi_result (phi))))
            continue;

          def = gimple_phi_result (phi);
          mark_all_vars_used (&def, NULL);

          FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_ALL_USES)
            {
              tree arg = USE_FROM_PTR (arg_p);
              mark_all_vars_used (&arg, NULL);
            }
        }
    }

  /* Remove unmarked local vars from local_decls.  */
  for (cell = &cfun->local_decls; *cell; )
    {
      tree var = TREE_VALUE (*cell);

      if (TREE_CODE (var) != FUNCTION_DECL
          && (!(ann = var_ann (var))
              || !ann->used))
        {
          if (is_global_var (var))
            {
              if (global_unused_vars == NULL)
                global_unused_vars = BITMAP_ALLOC (NULL);
              bitmap_set_bit (global_unused_vars, DECL_UID (var));
            }
          else
            {
              *cell = TREE_CHAIN (*cell);
              continue;
            }
        }
      cell = &TREE_CHAIN (*cell);
    }

  /* Remove unmarked global vars from local_decls.  */
  if (global_unused_vars != NULL)
    {
      for (t = cfun->local_decls; t; t = TREE_CHAIN (t))
        {
          tree var = TREE_VALUE (t);

          if (TREE_CODE (var) == VAR_DECL
              && is_global_var (var)
              && (ann = var_ann (var)) != NULL
              && ann->used)
            mark_all_vars_used (&DECL_INITIAL (var), global_unused_vars);
        }

      for (cell = &cfun->local_decls; *cell; )
        {
          tree var = TREE_VALUE (*cell);

          if (TREE_CODE (var) == VAR_DECL
              && is_global_var (var)
              && bitmap_bit_p (global_unused_vars, DECL_UID (var))
              && (optimize || DECL_ARTIFICIAL (var)))
            *cell = TREE_CHAIN (*cell);
          else
            cell = &TREE_CHAIN (*cell);
        }
      BITMAP_FREE (global_unused_vars);
    }

  /* Remove unused variables from REFERENCED_VARs.  As a special
     exception keep the variables that are believed to be aliased.
     Those can't be easily removed from the alias sets and operand
     caches.  They will be removed shortly after the next may_alias
     pass is performed.  */
  FOR_EACH_REFERENCED_VAR (t, rvi)
    if (!is_global_var (t)
        && !MTAG_P (t)
        && TREE_CODE (t) != PARM_DECL
        && TREE_CODE (t) != RESULT_DECL
        && !(ann = var_ann (t))->used
        && !ann->symbol_mem_tag
        && !TREE_ADDRESSABLE (t)
        && (optimize || DECL_ARTIFICIAL (t)))
      remove_referenced_var (t);
  if (optimize)
    remove_unused_scope_block_p (DECL_INITIAL (current_function_decl));
}


/* Allocate and return a new live range information object base on MAP.  */

static tree_live_info_p
new_tree_live_info (var_map map)
{
  tree_live_info_p live;
  unsigned x;

  live = (tree_live_info_p) xmalloc (sizeof (struct tree_live_info_d));
  live->map = map;
  live->num_blocks = last_basic_block;

  live->livein = (bitmap *)xmalloc (last_basic_block * sizeof (bitmap));
  for (x = 0; x < (unsigned)last_basic_block; x++)
    live->livein[x] = BITMAP_ALLOC (NULL);

  live->liveout = (bitmap *)xmalloc (last_basic_block * sizeof (bitmap));
  for (x = 0; x < (unsigned)last_basic_block; x++)
    live->liveout[x] = BITMAP_ALLOC (NULL);

  live->work_stack = XNEWVEC (int, last_basic_block);
  live->stack_top = live->work_stack;

  live->global = BITMAP_ALLOC (NULL);
  return live;
}


/* Free storage for live range info object LIVE.  */

void 
delete_tree_live_info (tree_live_info_p live)
{
  int x;

  BITMAP_FREE (live->global);
  free (live->work_stack);

  for (x = live->num_blocks - 1; x >= 0; x--)
    BITMAP_FREE (live->liveout[x]);
  free (live->liveout);

  for (x = live->num_blocks - 1; x >= 0; x--)
    BITMAP_FREE (live->livein[x]);
  free (live->livein);

  free (live);
}


/* Visit basic block BB and propagate any required live on entry bits from 
   LIVE into the predecessors.  VISITED is the bitmap of visited blocks.  
   TMP is a temporary work bitmap which is passed in to avoid reallocating
   it each time.  */

static void 
loe_visit_block (tree_live_info_p live, basic_block bb, sbitmap visited,
                 bitmap tmp)
{
  edge e;
  bool change;
  edge_iterator ei;
  basic_block pred_bb;
  bitmap loe;
  gcc_assert (!TEST_BIT (visited, bb->index));

  SET_BIT (visited, bb->index);
  loe = live_on_entry (live, bb);

  FOR_EACH_EDGE (e, ei, bb->preds)
    {
      pred_bb = e->src;
      if (pred_bb == ENTRY_BLOCK_PTR)
        continue;
      /* TMP is variables live-on-entry from BB that aren't defined in the
         predecessor block.  This should be the live on entry vars to pred.  
         Note that liveout is the DEFs in a block while live on entry is
         being calculated.  */
      bitmap_and_compl (tmp, loe, live->liveout[pred_bb->index]);

      /* Add these bits to live-on-entry for the pred. if there are any 
         changes, and pred_bb has been visited already, add it to the
         revisit stack.  */
      change = bitmap_ior_into (live_on_entry (live, pred_bb), tmp);
      if (TEST_BIT (visited, pred_bb->index) && change)
        {
          RESET_BIT (visited, pred_bb->index);
          *(live->stack_top)++ = pred_bb->index;
        }
    }
}


/* Using LIVE, fill in all the live-on-entry blocks between the defs and uses 
   of all the variables.  */

static void
live_worklist (tree_live_info_p live)
{
  unsigned b;
  basic_block bb;
  sbitmap visited = sbitmap_alloc (last_basic_block + 1);
  bitmap tmp = BITMAP_ALLOC (NULL);

  sbitmap_zero (visited);

  /* Visit all the blocks in reverse order and propagate live on entry values
     into the predecessors blocks.  */
  FOR_EACH_BB_REVERSE (bb)
    loe_visit_block (live, bb, visited, tmp);

  /* Process any blocks which require further iteration.  */
  while (live->stack_top != live->work_stack)
    {
      b = *--(live->stack_top);
      loe_visit_block (live, BASIC_BLOCK (b), visited, tmp);
    }

  BITMAP_FREE (tmp);
  sbitmap_free (visited);
}


/* Calculate the initial live on entry vector for SSA_NAME using immediate_use
   links.  Set the live on entry fields in LIVE.  Def's are marked temporarily
   in the liveout vector.  */

static void
set_var_live_on_entry (tree ssa_name, tree_live_info_p live)
{
  int p;
  gimple stmt;
  use_operand_p use;
  basic_block def_bb = NULL;
  imm_use_iterator imm_iter;
  bool global = false;

  p = var_to_partition (live->map, ssa_name);
  if (p == NO_PARTITION)
    return;

  stmt = SSA_NAME_DEF_STMT (ssa_name);
  if (stmt)
    {
      def_bb = gimple_bb (stmt);
      /* Mark defs in liveout bitmap temporarily.  */
      if (def_bb)
        bitmap_set_bit (live->liveout[def_bb->index], p);
    }
  else
    def_bb = ENTRY_BLOCK_PTR;

  /* Visit each use of SSA_NAME and if it isn't in the same block as the def,
     add it to the list of live on entry blocks.  */
  FOR_EACH_IMM_USE_FAST (use, imm_iter, ssa_name)
    {
      gimple use_stmt = USE_STMT (use);
      basic_block add_block = NULL;

      if (gimple_code (use_stmt) == GIMPLE_PHI)
        {
          /* Uses in PHI's are considered to be live at exit of the SRC block
             as this is where a copy would be inserted.  Check to see if it is
             defined in that block, or whether its live on entry.  */
          int index = PHI_ARG_INDEX_FROM_USE (use);
          edge e = gimple_phi_arg_edge (use_stmt, index);
          if (e->src != ENTRY_BLOCK_PTR)
            {
              if (e->src != def_bb)
                add_block = e->src;
            }
        }
      else
        {
          /* If its not defined in this block, its live on entry.  */
          basic_block use_bb = gimple_bb (use_stmt);
          if (use_bb != def_bb)
            add_block = use_bb;
        }  

      /* If there was a live on entry use, set the bit.  */
      if (add_block)
        {
          global = true;
          bitmap_set_bit (live->livein[add_block->index], p);
        }
    }

  /* If SSA_NAME is live on entry to at least one block, fill in all the live
     on entry blocks between the def and all the uses.  */
  if (global)
    bitmap_set_bit (live->global, p);
}


/* Calculate the live on exit vectors based on the entry info in LIVEINFO.  */

void
calculate_live_on_exit (tree_live_info_p liveinfo)
{
  basic_block bb;
  edge e;
  edge_iterator ei;

  /* live on entry calculations used liveout vectors for defs, clear them.  */
  FOR_EACH_BB (bb)
    bitmap_clear (liveinfo->liveout[bb->index]);

  /* Set all the live-on-exit bits for uses in PHIs.  */
  FOR_EACH_BB (bb)
    {
      gimple_stmt_iterator gsi;
      size_t i;

      /* Mark the PHI arguments which are live on exit to the pred block.  */
      for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
        {
          gimple phi = gsi_stmt (gsi);
          for (i = 0; i < gimple_phi_num_args (phi); i++)
            { 
              tree t = PHI_ARG_DEF (phi, i);
              int p;

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

              p = var_to_partition (liveinfo->map, t);
              if (p == NO_PARTITION)
                continue;
              e = gimple_phi_arg_edge (phi, i);
              if (e->src != ENTRY_BLOCK_PTR)
                bitmap_set_bit (liveinfo->liveout[e->src->index], p);
            }
        }

      /* Add each successors live on entry to this bock live on exit.  */
      FOR_EACH_EDGE (e, ei, bb->succs)
        if (e->dest != EXIT_BLOCK_PTR)
          bitmap_ior_into (liveinfo->liveout[bb->index],
                           live_on_entry (liveinfo, e->dest));
    }
}


/* Given partition map MAP, calculate all the live on entry bitmaps for 
   each partition.  Return a new live info object.  */

tree_live_info_p 
calculate_live_ranges (var_map map)
{
  tree var;
  unsigned i;
  tree_live_info_p live;

  live = new_tree_live_info (map);
  for (i = 0; i < num_var_partitions (map); i++)
    {
      var = partition_to_var (map, i);
      if (var != NULL_TREE)
        set_var_live_on_entry (var, live);
    }

  live_worklist (live);

#ifdef ENABLE_CHECKING
  verify_live_on_entry (live);
#endif

  calculate_live_on_exit (live);
  return live;
}


/* Output partition map MAP to file F.  */

void
dump_var_map (FILE *f, var_map map)
{
  int t;
  unsigned x, y;
  int p;

  fprintf (f, "\nPartition map \n\n");

  for (x = 0; x < map->num_partitions; x++)
    {
      if (map->view_to_partition != NULL)
        p = map->view_to_partition[x];
      else
        p = x;

      if (map->partition_to_var[p] == NULL_TREE)
        continue;

      t = 0;
      for (y = 1; y < num_ssa_names; y++)
        {
          p = partition_find (map->var_partition, y);
          if (map->partition_to_view)
            p = map->partition_to_view[p];
          if (p == (int)x)
            {
              if (t++ == 0)
                {
                  fprintf(f, "Partition %d (", x);
                  print_generic_expr (f, partition_to_var (map, p), TDF_SLIM);
                  fprintf (f, " - ");
                }
              fprintf (f, "%d ", y);
            }
        }
      if (t != 0)
        fprintf (f, ")\n");
    }
  fprintf (f, "\n");
}


/* Output live range info LIVE to file F, controlled by FLAG.  */

void
dump_live_info (FILE *f, tree_live_info_p live, int flag)
{
  basic_block bb;
  unsigned i;
  var_map map = live->map;
  bitmap_iterator bi;

  if ((flag & LIVEDUMP_ENTRY) && live->livein)
    {
      FOR_EACH_BB (bb)
        {
          fprintf (f, "\nLive on entry to BB%d : ", bb->index);
          EXECUTE_IF_SET_IN_BITMAP (live->livein[bb->index], 0, i, bi)
            {
              print_generic_expr (f, partition_to_var (map, i), TDF_SLIM);
              fprintf (f, "  ");
            }
          fprintf (f, "\n");
        }
    }

  if ((flag & LIVEDUMP_EXIT) && live->liveout)
    {
      FOR_EACH_BB (bb)
        {
          fprintf (f, "\nLive on exit from BB%d : ", bb->index);
          EXECUTE_IF_SET_IN_BITMAP (live->liveout[bb->index], 0, i, bi)
            {
              print_generic_expr (f, partition_to_var (map, i), TDF_SLIM);
              fprintf (f, "  ");
            }
          fprintf (f, "\n");
        }
    }
}


#ifdef ENABLE_CHECKING
/* Verify that SSA_VAR is a non-virtual SSA_NAME.  */

void
register_ssa_partition_check (tree ssa_var)
{
  gcc_assert (TREE_CODE (ssa_var) == SSA_NAME);
  if (!is_gimple_reg (SSA_NAME_VAR (ssa_var)))
    {
      fprintf (stderr, "Illegally registering a virtual SSA name :");
      print_generic_expr (stderr, ssa_var, TDF_SLIM);
      fprintf (stderr, " in the SSA->Normal phase.\n");
      internal_error ("SSA corruption");
    }
}


/* Verify that the info in LIVE matches the current cfg.  */

static void
verify_live_on_entry (tree_live_info_p live)
{
  unsigned i;
  tree var;
  gimple stmt;
  basic_block bb;
  edge e;
  int num;
  edge_iterator ei;
  var_map map = live->map;

   /* Check for live on entry partitions and report those with a DEF in
      the program. This will typically mean an optimization has done
      something wrong.  */
  bb = ENTRY_BLOCK_PTR;
  num = 0;
  FOR_EACH_EDGE (e, ei, bb->succs)
    {
      int entry_block = e->dest->index;
      if (e->dest == EXIT_BLOCK_PTR)
        continue;
      for (i = 0; i < (unsigned)num_var_partitions (map); i++)
        {
          basic_block tmp;
          tree d;
          bitmap loe;
          var = partition_to_var (map, i);
          stmt = SSA_NAME_DEF_STMT (var);
          tmp = gimple_bb (stmt);
          d = gimple_default_def (cfun, SSA_NAME_VAR (var));

          loe = live_on_entry (live, e->dest);
          if (loe && bitmap_bit_p (loe, i))
            {
              if (!gimple_nop_p (stmt))
                {
                  num++;
                  print_generic_expr (stderr, var, TDF_SLIM);
                  fprintf (stderr, " is defined ");
                  if (tmp)
                    fprintf (stderr, " in BB%d, ", tmp->index);
                  fprintf (stderr, "by:\n");
                  print_gimple_stmt (stderr, stmt, 0, TDF_SLIM);
                  fprintf (stderr, "\nIt is also live-on-entry to entry BB %d", 
                           entry_block);
                  fprintf (stderr, " So it appears to have multiple defs.\n");
                }
              else
                {
                  if (d != var)
                    {
                      num++;
                      print_generic_expr (stderr, var, TDF_SLIM);
                      fprintf (stderr, " is live-on-entry to BB%d ",
                               entry_block);
                      if (d)
                        {
                          fprintf (stderr, " but is not the default def of ");
                          print_generic_expr (stderr, d, TDF_SLIM);
                          fprintf (stderr, "\n");
                        }
                      else
                        fprintf (stderr, " and there is no default def.\n");
                    }
                }
            }
          else
            if (d == var)
              {
                /* The only way this var shouldn't be marked live on entry is 
                   if it occurs in a PHI argument of the block.  */
                size_t z;
                bool ok = false;
                gimple_stmt_iterator gsi;
                for (gsi = gsi_start_phis (e->dest);
                     !gsi_end_p (gsi) && !ok;
                     gsi_next (&gsi))
                  {
                    gimple phi = gsi_stmt (gsi);
                    for (z = 0; z < gimple_phi_num_args (phi); z++)
                      if (var == gimple_phi_arg_def (phi, z))
                        {
                          ok = true;
                          break;
                        }
                  }
                if (ok)
                  continue;
                num++;
                print_generic_expr (stderr, var, TDF_SLIM);
                fprintf (stderr, " is not marked live-on-entry to entry BB%d ", 
                         entry_block);
                fprintf (stderr, "but it is a default def so it should be.\n");
              }
        }
    }
  gcc_assert (num <= 0);
}
#endif