* timevar.def (TV_SCEV_CONST): New timevar.

[pf3gnuchains/gcc-fork.git] / gcc / tree-cfg.c

/* Control flow functions for trees.
   Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   Contributed by Diego Novillo <dnovillo@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 "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "ggc.h"
#include "langhooks.h"
#include "diagnostic.h"
#include "tree-flow.h"
#include "timevar.h"
#include "tree-dump.h"
#include "tree-pass.h"
#include "toplev.h"
#include "except.h"
#include "cfgloop.h"
#include "cfglayout.h"
#include "hashtab.h"

/* This file contains functions for building the Control Flow Graph (CFG)
   for a function tree.  */

/* Local declarations.  */

/* Initial capacity for the basic block array.  */
static const int initial_cfg_capacity = 20;

/* This hash table allows us to efficiently lookup all CASE_LABEL_EXPRs
   which use a particular edge.  The CASE_LABEL_EXPRs are chained together
   via their TREE_CHAIN field, which we clear after we're done with the
   hash table to prevent problems with duplication of SWITCH_EXPRs.

   Access to this list of CASE_LABEL_EXPRs allows us to efficiently
   update the case vector in response to edge redirections.

   Right now this table is set up and torn down at key points in the
   compilation process.  It would be nice if we could make the table
   more persistent.  The key is getting notification of changes to
   the CFG (particularly edge removal, creation and redirection).  */

struct edge_to_cases_elt
{
  /* The edge itself.  Necessary for hashing and equality tests.  */
  edge e;

  /* The case labels associated with this edge.  We link these up via
     their TREE_CHAIN field, then we wipe out the TREE_CHAIN fields
     when we destroy the hash table.  This prevents problems when copying
     SWITCH_EXPRs.  */
  tree case_labels;
};

static htab_t edge_to_cases;

/* CFG statistics.  */
struct cfg_stats_d
{
  long num_merged_labels;
};

static struct cfg_stats_d cfg_stats;

/* Nonzero if we found a computed goto while building basic blocks.  */
static bool found_computed_goto;

/* Basic blocks and flowgraphs.  */
static basic_block create_bb (void *, void *, basic_block);
static void create_block_annotation (basic_block);
static void free_blocks_annotations (void);
static void clear_blocks_annotations (void);
static void make_blocks (tree);
static void factor_computed_gotos (void);

/* Edges.  */
static void make_edges (void);
static void make_ctrl_stmt_edges (basic_block);
static void make_exit_edges (basic_block);
static void make_cond_expr_edges (basic_block);
static void make_switch_expr_edges (basic_block);
static void make_goto_expr_edges (basic_block);
static edge tree_redirect_edge_and_branch (edge, basic_block);
static edge tree_try_redirect_by_replacing_jump (edge, basic_block);
static void split_critical_edges (void);
static bool remove_fallthru_edge (VEC(edge,gc) *);

/* Various helpers.  */
static inline bool stmt_starts_bb_p (tree, tree);
static int tree_verify_flow_info (void);
static void tree_make_forwarder_block (edge);
static bool tree_forwarder_block_p (basic_block, bool);
static void tree_cfg2vcg (FILE *);

/* Flowgraph optimization and cleanup.  */
static void tree_merge_blocks (basic_block, basic_block);
static bool tree_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
static bool cleanup_control_flow (void);
static bool cleanup_control_expr_graph (basic_block, block_stmt_iterator);
static edge find_taken_edge_computed_goto (basic_block, tree);
static edge find_taken_edge_cond_expr (basic_block, tree);
static edge find_taken_edge_switch_expr (basic_block, tree);
static tree find_case_label_for_value (tree, tree);
static bool phi_alternatives_equal (basic_block, edge, edge);
static bool cleanup_forwarder_blocks (void);

void
init_empty_tree_cfg (void)
{
  /* Initialize the basic block array.  */
  init_flow ();
  profile_status = PROFILE_ABSENT;
  n_basic_blocks = 0;
  last_basic_block = 0;
  VARRAY_BB_INIT (basic_block_info, initial_cfg_capacity, "basic_block_info");

  /* Build a mapping of labels to their associated blocks.  */
  VARRAY_BB_INIT (label_to_block_map, initial_cfg_capacity,
                  "label to block map");

  ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
  EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;

  create_block_annotation (ENTRY_BLOCK_PTR);
  create_block_annotation (EXIT_BLOCK_PTR);
}

/*---------------------------------------------------------------------------
                              Create basic blocks
---------------------------------------------------------------------------*/

/* Entry point to the CFG builder for trees.  TP points to the list of
   statements to be added to the flowgraph.  */

static void
build_tree_cfg (tree *tp)
{
  /* Register specific tree functions.  */
  tree_register_cfg_hooks ();

  memset ((void *) &cfg_stats, 0, sizeof (cfg_stats));

  init_empty_tree_cfg ();

  found_computed_goto = 0;
  make_blocks (*tp);

  /* Computed gotos are hell to deal with, especially if there are
     lots of them with a large number of destinations.  So we factor
     them to a common computed goto location before we build the
     edge list.  After we convert back to normal form, we will un-factor
     the computed gotos since factoring introduces an unwanted jump.  */
  if (found_computed_goto)
    factor_computed_gotos ();

  /* Make sure there is always at least one block, even if it's empty.  */
  if (n_basic_blocks == 0)
    create_empty_bb (ENTRY_BLOCK_PTR);

  /* Adjust the size of the array.  */
  VARRAY_GROW (basic_block_info, n_basic_blocks);

  /* To speed up statement iterator walks, we first purge dead labels.  */
  cleanup_dead_labels ();

  /* Group case nodes to reduce the number of edges.
     We do this after cleaning up dead labels because otherwise we miss
     a lot of obvious case merging opportunities.  */
  group_case_labels ();

  /* Create the edges of the flowgraph.  */
  make_edges ();

  /* Debugging dumps.  */

  /* Write the flowgraph to a VCG file.  */
  {
    int local_dump_flags;
    FILE *dump_file = dump_begin (TDI_vcg, &local_dump_flags);
    if (dump_file)
      {
        tree_cfg2vcg (dump_file);
        dump_end (TDI_vcg, dump_file);
      }
  }

#ifdef ENABLE_CHECKING
  verify_stmts ();
#endif

  /* Dump a textual representation of the flowgraph.  */
  if (dump_file)
    dump_tree_cfg (dump_file, dump_flags);
}

static void
execute_build_cfg (void)
{
  build_tree_cfg (&DECL_SAVED_TREE (current_function_decl));
}

struct tree_opt_pass pass_build_cfg =
{
  "cfg",                                /* name */
  NULL,                                 /* gate */
  execute_build_cfg,                    /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_TREE_CFG,                          /* tv_id */
  PROP_gimple_leh,                      /* properties_required */
  PROP_cfg,                             /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_stmts,                    /* todo_flags_finish */
  0                                     /* letter */
};

/* Search the CFG for any computed gotos.  If found, factor them to a 
   common computed goto site.  Also record the location of that site so
   that we can un-factor the gotos after we have converted back to 
   normal form.  */

static void
factor_computed_gotos (void)
{
  basic_block bb;
  tree factored_label_decl = NULL;
  tree var = NULL;
  tree factored_computed_goto_label = NULL;
  tree factored_computed_goto = NULL;

  /* We know there are one or more computed gotos in this function.
     Examine the last statement in each basic block to see if the block
     ends with a computed goto.  */
        
  FOR_EACH_BB (bb)
    {
      block_stmt_iterator bsi = bsi_last (bb);
      tree last;

      if (bsi_end_p (bsi))
        continue;
      last = bsi_stmt (bsi);

      /* Ignore the computed goto we create when we factor the original
         computed gotos.  */
      if (last == factored_computed_goto)
        continue;

      /* If the last statement is a computed goto, factor it.  */
      if (computed_goto_p (last))
        {
          tree assignment;

          /* The first time we find a computed goto we need to create
             the factored goto block and the variable each original
             computed goto will use for their goto destination.  */
          if (! factored_computed_goto)
            {
              basic_block new_bb = create_empty_bb (bb);
              block_stmt_iterator new_bsi = bsi_start (new_bb);

              /* Create the destination of the factored goto.  Each original
                 computed goto will put its desired destination into this
                 variable and jump to the label we create immediately
                 below.  */
              var = create_tmp_var (ptr_type_node, "gotovar");

              /* Build a label for the new block which will contain the
                 factored computed goto.  */
              factored_label_decl = create_artificial_label ();
              factored_computed_goto_label
                = build1 (LABEL_EXPR, void_type_node, factored_label_decl);
              bsi_insert_after (&new_bsi, factored_computed_goto_label,
                                BSI_NEW_STMT);

              /* Build our new computed goto.  */
              factored_computed_goto = build1 (GOTO_EXPR, void_type_node, var);
              bsi_insert_after (&new_bsi, factored_computed_goto,
                                BSI_NEW_STMT);
            }

          /* Copy the original computed goto's destination into VAR.  */
          assignment = build (MODIFY_EXPR, ptr_type_node,
                              var, GOTO_DESTINATION (last));
          bsi_insert_before (&bsi, assignment, BSI_SAME_STMT);

          /* And re-vector the computed goto to the new destination.  */
          GOTO_DESTINATION (last) = factored_label_decl;
        }
    }
}


/* Create annotations for a single basic block.  */

static void
create_block_annotation (basic_block bb)
{
  /* Verify that the tree_annotations field is clear.  */
  gcc_assert (!bb->tree_annotations);
  bb->tree_annotations = ggc_alloc_cleared (sizeof (struct bb_ann_d));
}


/* Free the annotations for all the basic blocks.  */

static void free_blocks_annotations (void)
{
  clear_blocks_annotations ();  
}


/* Clear the annotations for all the basic blocks.  */

static void
clear_blocks_annotations (void)
{
  basic_block bb;

  FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
    bb->tree_annotations = NULL;
}


/* Build a flowgraph for the statement_list STMT_LIST.  */

static void
make_blocks (tree stmt_list)
{
  tree_stmt_iterator i = tsi_start (stmt_list);
  tree stmt = NULL;
  bool start_new_block = true;
  bool first_stmt_of_list = true;
  basic_block bb = ENTRY_BLOCK_PTR;

  while (!tsi_end_p (i))
    {
      tree prev_stmt;

      prev_stmt = stmt;
      stmt = tsi_stmt (i);

      /* If the statement starts a new basic block or if we have determined
         in a previous pass that we need to create a new block for STMT, do
         so now.  */
      if (start_new_block || stmt_starts_bb_p (stmt, prev_stmt))
        {
          if (!first_stmt_of_list)
            stmt_list = tsi_split_statement_list_before (&i);
          bb = create_basic_block (stmt_list, NULL, bb);
          start_new_block = false;
        }

      /* Now add STMT to BB and create the subgraphs for special statement
         codes.  */
      set_bb_for_stmt (stmt, bb);

      if (computed_goto_p (stmt))
        found_computed_goto = true;

      /* If STMT is a basic block terminator, set START_NEW_BLOCK for the
         next iteration.  */
      if (stmt_ends_bb_p (stmt))
        start_new_block = true;

      tsi_next (&i);
      first_stmt_of_list = false;
    }
}


/* Create and return a new empty basic block after bb AFTER.  */

static basic_block
create_bb (void *h, void *e, basic_block after)
{
  basic_block bb;

  gcc_assert (!e);

  /* Create and initialize a new basic block.  Since alloc_block uses
     ggc_alloc_cleared to allocate a basic block, we do not have to
     clear the newly allocated basic block here.  */
  bb = alloc_block ();

  bb->index = last_basic_block;
  bb->flags = BB_NEW;
  bb->stmt_list = h ? h : alloc_stmt_list ();

  /* Add the new block to the linked list of blocks.  */
  link_block (bb, after);

  /* Grow the basic block array if needed.  */
  if ((size_t) last_basic_block == VARRAY_SIZE (basic_block_info))
    {
      size_t new_size = last_basic_block + (last_basic_block + 3) / 4;
      VARRAY_GROW (basic_block_info, new_size);
    }

  /* Add the newly created block to the array.  */
  BASIC_BLOCK (last_basic_block) = bb;

  create_block_annotation (bb);

  n_basic_blocks++;
  last_basic_block++;

  initialize_bb_rbi (bb);
  return bb;
}


/*---------------------------------------------------------------------------
                                 Edge creation
---------------------------------------------------------------------------*/

/* Fold COND_EXPR_COND of each COND_EXPR.  */

void
fold_cond_expr_cond (void)
{
  basic_block bb;

  FOR_EACH_BB (bb)
    {
      tree stmt = last_stmt (bb);

      if (stmt
          && TREE_CODE (stmt) == COND_EXPR)
        {
          tree cond = fold (COND_EXPR_COND (stmt));
          if (integer_zerop (cond))
            COND_EXPR_COND (stmt) = boolean_false_node;
          else if (integer_onep (cond))
            COND_EXPR_COND (stmt) = boolean_true_node;
        }
    }
}

/* Join all the blocks in the flowgraph.  */

static void
make_edges (void)
{
  basic_block bb;

  /* Create an edge from entry to the first block with executable
     statements in it.  */
  make_edge (ENTRY_BLOCK_PTR, BASIC_BLOCK (0), EDGE_FALLTHRU);

  /* Traverse the basic block array placing edges.  */
  FOR_EACH_BB (bb)
    {
      tree first = first_stmt (bb);
      tree last = last_stmt (bb);

      if (first)
        {
          /* Edges for statements that always alter flow control.  */
          if (is_ctrl_stmt (last))
            make_ctrl_stmt_edges (bb);

          /* Edges for statements that sometimes alter flow control.  */
          if (is_ctrl_altering_stmt (last))
            make_exit_edges (bb);
        }

      /* Finally, if no edges were created above, this is a regular
         basic block that only needs a fallthru edge.  */
      if (EDGE_COUNT (bb->succs) == 0)
        make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
    }

  /* We do not care about fake edges, so remove any that the CFG
     builder inserted for completeness.  */
  remove_fake_exit_edges ();

  /* Fold COND_EXPR_COND of each COND_EXPR.  */
  fold_cond_expr_cond ();

  /* Clean up the graph and warn for unreachable code.  */
  cleanup_tree_cfg ();
}


/* Create edges for control statement at basic block BB.  */

static void
make_ctrl_stmt_edges (basic_block bb)
{
  tree last = last_stmt (bb);

  gcc_assert (last);
  switch (TREE_CODE (last))
    {
    case GOTO_EXPR:
      make_goto_expr_edges (bb);
      break;

    case RETURN_EXPR:
      make_edge (bb, EXIT_BLOCK_PTR, 0);
      break;

    case COND_EXPR:
      make_cond_expr_edges (bb);
      break;

    case SWITCH_EXPR:
      make_switch_expr_edges (bb);
      break;

    case RESX_EXPR:
      make_eh_edges (last);
      /* Yet another NORETURN hack.  */
      if (EDGE_COUNT (bb->succs) == 0)
        make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
      break;

    default:
      gcc_unreachable ();
    }
}


/* Create exit edges for statements in block BB that alter the flow of
   control.  Statements that alter the control flow are 'goto', 'return'
   and calls to non-returning functions.  */

static void
make_exit_edges (basic_block bb)
{
  tree last = last_stmt (bb), op;

  gcc_assert (last);
  switch (TREE_CODE (last))
    {
    case RESX_EXPR:
      break;
    case CALL_EXPR:
      /* If this function receives a nonlocal goto, then we need to
         make edges from this call site to all the nonlocal goto
         handlers.  */
      if (TREE_SIDE_EFFECTS (last)
          && current_function_has_nonlocal_label)
        make_goto_expr_edges (bb);

      /* If this statement has reachable exception handlers, then
         create abnormal edges to them.  */
      make_eh_edges (last);

      /* Some calls are known not to return.  For such calls we create
         a fake edge.

         We really need to revamp how we build edges so that it's not
         such a bloody pain to avoid creating edges for this case since
         all we do is remove these edges when we're done building the
         CFG.  */
      if (call_expr_flags (last) & ECF_NORETURN)
        {
          make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
          return;
        }

      /* Don't forget the fall-thru edge.  */
      make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
      break;

    case MODIFY_EXPR:
      /* A MODIFY_EXPR may have a CALL_EXPR on its RHS and the CALL_EXPR
         may have an abnormal edge.  Search the RHS for this case and
         create any required edges.  */
      op = get_call_expr_in (last);
      if (op && TREE_SIDE_EFFECTS (op)
          && current_function_has_nonlocal_label)
        make_goto_expr_edges (bb);

      make_eh_edges (last);
      make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
      break;

    default:
      gcc_unreachable ();
    }
}


/* Create the edges for a COND_EXPR starting at block BB.
   At this point, both clauses must contain only simple gotos.  */

static void
make_cond_expr_edges (basic_block bb)
{
  tree entry = last_stmt (bb);
  basic_block then_bb, else_bb;
  tree then_label, else_label;

  gcc_assert (entry);
  gcc_assert (TREE_CODE (entry) == COND_EXPR);

  /* Entry basic blocks for each component.  */
  then_label = GOTO_DESTINATION (COND_EXPR_THEN (entry));
  else_label = GOTO_DESTINATION (COND_EXPR_ELSE (entry));
  then_bb = label_to_block (then_label);
  else_bb = label_to_block (else_label);

  make_edge (bb, then_bb, EDGE_TRUE_VALUE);
  make_edge (bb, else_bb, EDGE_FALSE_VALUE);
}

/* Hashing routine for EDGE_TO_CASES.  */

static hashval_t
edge_to_cases_hash (const void *p)
{
  edge e = ((struct edge_to_cases_elt *)p)->e;

  /* Hash on the edge itself (which is a pointer).  */
  return htab_hash_pointer (e);
}

/* Equality routine for EDGE_TO_CASES, edges are unique, so testing
   for equality is just a pointer comparison.  */

static int
edge_to_cases_eq (const void *p1, const void *p2)
{
  edge e1 = ((struct edge_to_cases_elt *)p1)->e;
  edge e2 = ((struct edge_to_cases_elt *)p2)->e;

  return e1 == e2;
}

/* Called for each element in the hash table (P) as we delete the
   edge to cases hash table.

   Clear all the TREE_CHAINs to prevent problems with copying of 
   SWITCH_EXPRs and structure sharing rules, then free the hash table
   element.  */

static void
edge_to_cases_cleanup (void *p)
{
  struct edge_to_cases_elt *elt = p;
  tree t, next;

  for (t = elt->case_labels; t; t = next)
    {
      next = TREE_CHAIN (t);
      TREE_CHAIN (t) = NULL;
    }
  free (p);
}

/* Start recording information mapping edges to case labels.  */

static void
start_recording_case_labels (void)
{
  gcc_assert (edge_to_cases == NULL);

  edge_to_cases = htab_create (37,
                               edge_to_cases_hash,
                               edge_to_cases_eq,
                               edge_to_cases_cleanup);
}

/* Return nonzero if we are recording information for case labels.  */

static bool
recording_case_labels_p (void)
{
  return (edge_to_cases != NULL);
}

/* Stop recording information mapping edges to case labels and
   remove any information we have recorded.  */
static void
end_recording_case_labels (void)
{
  htab_delete (edge_to_cases);
  edge_to_cases = NULL;
}

/* Record that CASE_LABEL (a CASE_LABEL_EXPR) references edge E.  */

static void
record_switch_edge (edge e, tree case_label)
{
  struct edge_to_cases_elt *elt;
  void **slot;

  /* Build a hash table element so we can see if E is already
     in the table.  */
  elt = xmalloc (sizeof (struct edge_to_cases_elt));
  elt->e = e;
  elt->case_labels = case_label;

  slot = htab_find_slot (edge_to_cases, elt, INSERT);

  if (*slot == NULL)
    {
      /* E was not in the hash table.  Install E into the hash table.  */
      *slot = (void *)elt;
    }
  else
    {
      /* E was already in the hash table.  Free ELT as we do not need it
         anymore.  */
      free (elt);

      /* Get the entry stored in the hash table.  */
      elt = (struct edge_to_cases_elt *) *slot;

      /* Add it to the chain of CASE_LABEL_EXPRs referencing E.  */
      TREE_CHAIN (case_label) = elt->case_labels;
      elt->case_labels = case_label;
    }
}

/* If we are inside a {start,end}_recording_cases block, then return
   a chain of CASE_LABEL_EXPRs from T which reference E.

   Otherwise return NULL.  */

static tree
get_cases_for_edge (edge e, tree t)
{
  struct edge_to_cases_elt elt, *elt_p;
  void **slot;
  size_t i, n;
  tree vec;

  /* If we are not recording cases, then we do not have CASE_LABEL_EXPR
     chains available.  Return NULL so the caller can detect this case.  */
  if (!recording_case_labels_p ())
    return NULL;
  
restart:
  elt.e = e;
  elt.case_labels = NULL;
  slot = htab_find_slot (edge_to_cases, &elt, NO_INSERT);

  if (slot)
    {
      elt_p = (struct edge_to_cases_elt *)*slot;
      return elt_p->case_labels;
    }

  /* If we did not find E in the hash table, then this must be the first
     time we have been queried for information about E & T.  Add all the
     elements from T to the hash table then perform the query again.  */

  vec = SWITCH_LABELS (t);
  n = TREE_VEC_LENGTH (vec);
  for (i = 0; i < n; i++)
    {
      tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
      basic_block label_bb = label_to_block (lab);
      record_switch_edge (find_edge (e->src, label_bb), TREE_VEC_ELT (vec, i));
    }
  goto restart;
}

/* Create the edges for a SWITCH_EXPR starting at block BB.
   At this point, the switch body has been lowered and the
   SWITCH_LABELS filled in, so this is in effect a multi-way branch.  */

static void
make_switch_expr_edges (basic_block bb)
{
  tree entry = last_stmt (bb);
  size_t i, n;
  tree vec;

  vec = SWITCH_LABELS (entry);
  n = TREE_VEC_LENGTH (vec);

  for (i = 0; i < n; ++i)
    {
      tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
      basic_block label_bb = label_to_block (lab);
      make_edge (bb, label_bb, 0);
    }
}


/* Return the basic block holding label DEST.  */

basic_block
label_to_block_fn (struct function *ifun, tree dest)
{
  int uid = LABEL_DECL_UID (dest);

  /* We would die hard when faced by an undefined label.  Emit a label to
     the very first basic block.  This will hopefully make even the dataflow
     and undefined variable warnings quite right.  */
  if ((errorcount || sorrycount) && uid < 0)
    {
      block_stmt_iterator bsi = bsi_start (BASIC_BLOCK (0));
      tree stmt;

      stmt = build1 (LABEL_EXPR, void_type_node, dest);
      bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
      uid = LABEL_DECL_UID (dest);
    }
  if (VARRAY_SIZE (ifun->cfg->x_label_to_block_map) <= (unsigned int)uid)
    return NULL;
  return VARRAY_BB (ifun->cfg->x_label_to_block_map, uid);
}

/* Create edges for a goto statement at block BB.  */

static void
make_goto_expr_edges (basic_block bb)
{
  tree goto_t;
  basic_block target_bb;
  int for_call;
  block_stmt_iterator last = bsi_last (bb);

  goto_t = bsi_stmt (last);

  /* If the last statement is not a GOTO (i.e., it is a RETURN_EXPR,
     CALL_EXPR or MODIFY_EXPR), then the edge is an abnormal edge resulting
     from a nonlocal goto.  */
  if (TREE_CODE (goto_t) != GOTO_EXPR)
    for_call = 1;
  else
    {
      tree dest = GOTO_DESTINATION (goto_t);
      for_call = 0;

      /* A GOTO to a local label creates normal edges.  */
      if (simple_goto_p (goto_t))
        {
          edge e = make_edge (bb, label_to_block (dest), EDGE_FALLTHRU);
#ifdef USE_MAPPED_LOCATION
          e->goto_locus = EXPR_LOCATION (goto_t);
#else
          e->goto_locus = EXPR_LOCUS (goto_t);
#endif
          bsi_remove (&last);
          return;
        }

      /* Nothing more to do for nonlocal gotos.  */
      if (TREE_CODE (dest) == LABEL_DECL)
        return;

      /* Computed gotos remain.  */
    }

  /* Look for the block starting with the destination label.  In the
     case of a computed goto, make an edge to any label block we find
     in the CFG.  */
  FOR_EACH_BB (target_bb)
    {
      block_stmt_iterator bsi;

      for (bsi = bsi_start (target_bb); !bsi_end_p (bsi); bsi_next (&bsi))
        {
          tree target = bsi_stmt (bsi);

          if (TREE_CODE (target) != LABEL_EXPR)
            break;

          if (
              /* Computed GOTOs.  Make an edge to every label block that has
                 been marked as a potential target for a computed goto.  */
              (FORCED_LABEL (LABEL_EXPR_LABEL (target)) && for_call == 0)
              /* Nonlocal GOTO target.  Make an edge to every label block
                 that has been marked as a potential target for a nonlocal
                 goto.  */
              || (DECL_NONLOCAL (LABEL_EXPR_LABEL (target)) && for_call == 1))
            {
              make_edge (bb, target_bb, EDGE_ABNORMAL);
              break;
            }
        }
    }

  /* Degenerate case of computed goto with no labels.  */
  if (!for_call && EDGE_COUNT (bb->succs) == 0)
    make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
}


/*---------------------------------------------------------------------------
                               Flowgraph analysis
---------------------------------------------------------------------------*/

/* Remove unreachable blocks and other miscellaneous clean up work.  */

bool
cleanup_tree_cfg (void)
{
  bool retval = false;

  timevar_push (TV_TREE_CLEANUP_CFG);

  retval = cleanup_control_flow ();
  retval |= delete_unreachable_blocks ();

  /* cleanup_forwarder_blocks can redirect edges out of SWITCH_EXPRs,
     which can get expensive.  So we want to enable recording of edge
     to CASE_LABEL_EXPR mappings around the call to
     cleanup_forwarder_blocks.  */
  start_recording_case_labels ();
  retval |= cleanup_forwarder_blocks ();
  end_recording_case_labels ();

#ifdef ENABLE_CHECKING
  if (retval)
    {
      gcc_assert (!cleanup_control_flow ());
      gcc_assert (!delete_unreachable_blocks ());
      gcc_assert (!cleanup_forwarder_blocks ());
    }
#endif

  /* Merging the blocks creates no new opportunities for the other
     optimizations, so do it here.  */
  retval |= merge_seq_blocks ();

  compact_blocks ();

#ifdef ENABLE_CHECKING
  verify_flow_info ();
#endif
  timevar_pop (TV_TREE_CLEANUP_CFG);
  return retval;
}


/* Cleanup cfg and repair loop structures.  */

void
cleanup_tree_cfg_loop (void)
{
  bitmap changed_bbs = BITMAP_ALLOC (NULL);

  cleanup_tree_cfg ();

  fix_loop_structure (current_loops, changed_bbs);
  calculate_dominance_info (CDI_DOMINATORS);

  /* This usually does nothing.  But sometimes parts of cfg that originally
     were inside a loop get out of it due to edge removal (since they
     become unreachable by back edges from latch).  */
  rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa);

  BITMAP_FREE (changed_bbs);

#ifdef ENABLE_CHECKING
  verify_loop_structure (current_loops);
#endif
}

/* Cleanup useless labels in basic blocks.  This is something we wish
   to do early because it allows us to group case labels before creating
   the edges for the CFG, and it speeds up block statement iterators in
   all passes later on.
   We only run this pass once, running it more than once is probably not
   profitable.  */

/* A map from basic block index to the leading label of that block.  */
static tree *label_for_bb;

/* Callback for for_each_eh_region.  Helper for cleanup_dead_labels.  */
static void
update_eh_label (struct eh_region *region)
{
  tree old_label = get_eh_region_tree_label (region);
  if (old_label)
    {
      tree new_label;
      basic_block bb = label_to_block (old_label);

      /* ??? After optimizing, there may be EH regions with labels
         that have already been removed from the function body, so
         there is no basic block for them.  */
      if (! bb)
        return;

      new_label = label_for_bb[bb->index];
      set_eh_region_tree_label (region, new_label);
    }
}

/* Given LABEL return the first label in the same basic block.  */
static tree
main_block_label (tree label)
{
  basic_block bb = label_to_block (label);

  /* label_to_block possibly inserted undefined label into the chain.  */
  if (!label_for_bb[bb->index])
    label_for_bb[bb->index] = label;
  return label_for_bb[bb->index];
}

/* Cleanup redundant labels.  This is a three-step process:
     1) Find the leading label for each block.
     2) Redirect all references to labels to the leading labels.
     3) Cleanup all useless labels.  */

void
cleanup_dead_labels (void)
{
  basic_block bb;
  label_for_bb = xcalloc (last_basic_block, sizeof (tree));

  /* Find a suitable label for each block.  We use the first user-defined
     label if there is one, or otherwise just the first label we see.  */
  FOR_EACH_BB (bb)
    {
      block_stmt_iterator i;

      for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
        {
          tree label, stmt = bsi_stmt (i);

          if (TREE_CODE (stmt) != LABEL_EXPR)
            break;

          label = LABEL_EXPR_LABEL (stmt);

          /* If we have not yet seen a label for the current block,
             remember this one and see if there are more labels.  */
          if (! label_for_bb[bb->index])
            {
              label_for_bb[bb->index] = label;
              continue;
            }

          /* If we did see a label for the current block already, but it
             is an artificially created label, replace it if the current
             label is a user defined label.  */
          if (! DECL_ARTIFICIAL (label)
              && DECL_ARTIFICIAL (label_for_bb[bb->index]))
            {
              label_for_bb[bb->index] = label;
              break;
            }
        }
    }

  /* Now redirect all jumps/branches to the selected label.
     First do so for each block ending in a control statement.  */
  FOR_EACH_BB (bb)
    {
      tree stmt = last_stmt (bb);
      if (!stmt)
        continue;

      switch (TREE_CODE (stmt))
        {
        case COND_EXPR:
          {
            tree true_branch, false_branch;

            true_branch = COND_EXPR_THEN (stmt);
            false_branch = COND_EXPR_ELSE (stmt);

            GOTO_DESTINATION (true_branch)
              = main_block_label (GOTO_DESTINATION (true_branch));
            GOTO_DESTINATION (false_branch)
              = main_block_label (GOTO_DESTINATION (false_branch));

            break;
          }
  
        case SWITCH_EXPR:
          {
            size_t i;
            tree vec = SWITCH_LABELS (stmt);
            size_t n = TREE_VEC_LENGTH (vec);
  
            /* Replace all destination labels.  */
            for (i = 0; i < n; ++i)
              {
                tree elt = TREE_VEC_ELT (vec, i);
                tree label = main_block_label (CASE_LABEL (elt));
                CASE_LABEL (elt) = label;
              }
            break;
          }

        /* We have to handle GOTO_EXPRs until they're removed, and we don't
           remove them until after we've created the CFG edges.  */
        case GOTO_EXPR:
          if (! computed_goto_p (stmt))
            {
              GOTO_DESTINATION (stmt)
                = main_block_label (GOTO_DESTINATION (stmt));
              break;
            }

        default:
          break;
      }
    }

  for_each_eh_region (update_eh_label);

  /* Finally, purge dead labels.  All user-defined labels and labels that
     can be the target of non-local gotos are preserved.  */
  FOR_EACH_BB (bb)
    {
      block_stmt_iterator i;
      tree label_for_this_bb = label_for_bb[bb->index];

      if (! label_for_this_bb)
        continue;

      for (i = bsi_start (bb); !bsi_end_p (i); )
        {
          tree label, stmt = bsi_stmt (i);

          if (TREE_CODE (stmt) != LABEL_EXPR)
            break;

          label = LABEL_EXPR_LABEL (stmt);

          if (label == label_for_this_bb
              || ! DECL_ARTIFICIAL (label)
              || DECL_NONLOCAL (label))
            bsi_next (&i);
          else
            bsi_remove (&i);
        }
    }

  free (label_for_bb);
}

/* Look for blocks ending in a multiway branch (a SWITCH_EXPR in GIMPLE),
   and scan the sorted vector of cases.  Combine the ones jumping to the
   same label.
   Eg. three separate entries 1: 2: 3: become one entry 1..3:  */

void
group_case_labels (void)
{
  basic_block bb;

  FOR_EACH_BB (bb)
    {
      tree stmt = last_stmt (bb);
      if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
        {
          tree labels = SWITCH_LABELS (stmt);
          int old_size = TREE_VEC_LENGTH (labels);
          int i, j, new_size = old_size;
          tree default_case = TREE_VEC_ELT (labels, old_size - 1);
          tree default_label;

          /* The default label is always the last case in a switch
             statement after gimplification.  */
          default_label = CASE_LABEL (default_case);

          /* Look for possible opportunities to merge cases.
             Ignore the last element of the label vector because it
             must be the default case.  */
          i = 0;
          while (i < old_size - 1)
            {
              tree base_case, base_label, base_high;
              base_case = TREE_VEC_ELT (labels, i);

              gcc_assert (base_case);
              base_label = CASE_LABEL (base_case);

              /* Discard cases that have the same destination as the
                 default case.  */
              if (base_label == default_label)
                {
                  TREE_VEC_ELT (labels, i) = NULL_TREE;
                  i++;
                  new_size--;
                  continue;
                }

              base_high = CASE_HIGH (base_case) ?
                CASE_HIGH (base_case) : CASE_LOW (base_case);
              i++;
              /* Try to merge case labels.  Break out when we reach the end
                 of the label vector or when we cannot merge the next case
                 label with the current one.  */
              while (i < old_size - 1)
                {
                  tree merge_case = TREE_VEC_ELT (labels, i);
                  tree merge_label = CASE_LABEL (merge_case);
                  tree t = int_const_binop (PLUS_EXPR, base_high,
                                            integer_one_node, 1);

                  /* Merge the cases if they jump to the same place,
                     and their ranges are consecutive.  */
                  if (merge_label == base_label
                      && tree_int_cst_equal (CASE_LOW (merge_case), t))
                    {
                      base_high = CASE_HIGH (merge_case) ?
                        CASE_HIGH (merge_case) : CASE_LOW (merge_case);
                      CASE_HIGH (base_case) = base_high;
                      TREE_VEC_ELT (labels, i) = NULL_TREE;
                      new_size--;
                      i++;
                    }
                  else
                    break;
                }
            }

          /* Compress the case labels in the label vector, and adjust the
             length of the vector.  */
          for (i = 0, j = 0; i < new_size; i++)
            {
              while (! TREE_VEC_ELT (labels, j))
                j++;
              TREE_VEC_ELT (labels, i) = TREE_VEC_ELT (labels, j++);
            }
          TREE_VEC_LENGTH (labels) = new_size;
        }
    }
}

/* Checks whether we can merge block B into block A.  */

static bool
tree_can_merge_blocks_p (basic_block a, basic_block b)
{
  tree stmt;
  block_stmt_iterator bsi;
  tree phi;

  if (!single_succ_p (a))
    return false;

  if (single_succ_edge (a)->flags & EDGE_ABNORMAL)
    return false;

  if (single_succ (a) != b)
    return false;

  if (!single_pred_p (b))
    return false;

  if (b == EXIT_BLOCK_PTR)
    return false;
  
  /* If A ends by a statement causing exceptions or something similar, we
     cannot merge the blocks.  */
  stmt = last_stmt (a);
  if (stmt && stmt_ends_bb_p (stmt))
    return false;

  /* Do not allow a block with only a non-local label to be merged.  */
  if (stmt && TREE_CODE (stmt) == LABEL_EXPR
      && DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt)))
    return false;

  /* It must be possible to eliminate all phi nodes in B.  If ssa form
     is not up-to-date, we cannot eliminate any phis.  */
  phi = phi_nodes (b);
  if (phi)
    {
      if (need_ssa_update_p ())
        return false;

      for (; phi; phi = PHI_CHAIN (phi))
        if (!is_gimple_reg (PHI_RESULT (phi))
            && !may_propagate_copy (PHI_RESULT (phi), PHI_ARG_DEF (phi, 0)))
          return false;
    }

  /* Do not remove user labels.  */
  for (bsi = bsi_start (b); !bsi_end_p (bsi); bsi_next (&bsi))
    {
      stmt = bsi_stmt (bsi);
      if (TREE_CODE (stmt) != LABEL_EXPR)
        break;
      if (!DECL_ARTIFICIAL (LABEL_EXPR_LABEL (stmt)))
        return false;
    }

  /* Protect the loop latches.  */
  if (current_loops
      && b->loop_father->latch == b)
    return false;

  return true;
}

/* Replaces all uses of NAME by VAL.  */

void
replace_uses_by (tree name, tree val)
{
  imm_use_iterator imm_iter;
  use_operand_p use;
  tree stmt;
  edge e;
  unsigned i;
  VEC(tree,heap) *stmts = VEC_alloc (tree, heap, 20);

  FOR_EACH_IMM_USE_SAFE (use, imm_iter, name)
    {
      stmt = USE_STMT (use);

      SET_USE (use, val);

      if (TREE_CODE (stmt) == PHI_NODE)
        {
          e = PHI_ARG_EDGE (stmt, PHI_ARG_INDEX_FROM_USE (use));
          if (e->flags & EDGE_ABNORMAL)
            {
              /* This can only occur for virtual operands, since
                 for the real ones SSA_NAME_OCCURS_IN_ABNORMAL_PHI (name))
                 would prevent replacement.  */
              gcc_assert (!is_gimple_reg (name));
              SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val) = 1;
            }
        }
      else
        VEC_safe_push (tree, heap, stmts, stmt);
    }
 
  /* We do not update the statements in the loop above.  Consider
     x = w * w;

     If we performed the update in the first loop, the statement
     would be rescanned after first occurence of w is replaced,
     the new uses would be placed to the beginning of the list,
     and we would never process them.  */
  for (i = 0; VEC_iterate (tree, stmts, i, stmt); i++)
    {
      fold_stmt_inplace (stmt);
      update_stmt (stmt);
    }

  VEC_free (tree, heap, stmts);
}

/* Merge block B into block A.  */

static void
tree_merge_blocks (basic_block a, basic_block b)
{
  block_stmt_iterator bsi;
  tree_stmt_iterator last;
  tree phi;

  if (dump_file)
    fprintf (dump_file, "Merging blocks %d and %d\n", a->index, b->index);

  /* Remove the phi nodes.  */
  bsi = bsi_last (a);
  for (phi = phi_nodes (b); phi; phi = phi_nodes (b))
    {
      tree def = PHI_RESULT (phi), use = PHI_ARG_DEF (phi, 0);
      tree copy;
      
      if (!may_propagate_copy (def, use)
          /* Propagating pointers might cause the set of vops for statements
             to be changed, and thus require ssa form update.  */
          || (is_gimple_reg (def)
              && POINTER_TYPE_P (TREE_TYPE (def))))
        {
          gcc_assert (is_gimple_reg (def));

          /* Note that just emiting the copies is fine -- there is no problem
             with ordering of phi nodes.  This is because A is the single
             predecessor of B, therefore results of the phi nodes cannot
             appear as arguments of the phi nodes.  */
          copy = build2 (MODIFY_EXPR, void_type_node, def, use);
          bsi_insert_after (&bsi, copy, BSI_NEW_STMT);
          SET_PHI_RESULT (phi, NULL_TREE);
          SSA_NAME_DEF_STMT (def) = copy;
        }
      else
        replace_uses_by (def, use);
      remove_phi_node (phi, NULL);
    }

  /* Ensure that B follows A.  */
  move_block_after (b, a);

  gcc_assert (single_succ_edge (a)->flags & EDGE_FALLTHRU);
  gcc_assert (!last_stmt (a) || !stmt_ends_bb_p (last_stmt (a)));

  /* Remove labels from B and set bb_for_stmt to A for other statements.  */
  for (bsi = bsi_start (b); !bsi_end_p (bsi);)
    {
      if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
        {
          tree label = bsi_stmt (bsi);

          bsi_remove (&bsi);
          /* Now that we can thread computed gotos, we might have
             a situation where we have a forced label in block B
             However, the label at the start of block B might still be
             used in other ways (think about the runtime checking for
             Fortran assigned gotos).  So we can not just delete the
             label.  Instead we move the label to the start of block A.  */
          if (FORCED_LABEL (LABEL_EXPR_LABEL (label)))
            {
              block_stmt_iterator dest_bsi = bsi_start (a);
              bsi_insert_before (&dest_bsi, label, BSI_NEW_STMT);
            }
        }
      else
        {
          set_bb_for_stmt (bsi_stmt (bsi), a);
          bsi_next (&bsi);
        }
    }

  /* Merge the chains.  */
  last = tsi_last (a->stmt_list);
  tsi_link_after (&last, b->stmt_list, TSI_NEW_STMT);
  b->stmt_list = NULL;
}


/* Walk the function tree removing unnecessary statements.

     * Empty statement nodes are removed

     * Unnecessary TRY_FINALLY and TRY_CATCH blocks are removed

     * Unnecessary COND_EXPRs are removed

     * Some unnecessary BIND_EXPRs are removed

   Clearly more work could be done.  The trick is doing the analysis
   and removal fast enough to be a net improvement in compile times.

   Note that when we remove a control structure such as a COND_EXPR
   BIND_EXPR, or TRY block, we will need to repeat this optimization pass
   to ensure we eliminate all the useless code.  */

struct rus_data
{
  tree *last_goto;
  bool repeat;
  bool may_throw;
  bool may_branch;
  bool has_label;
};

static void remove_useless_stmts_1 (tree *, struct rus_data *);

static bool
remove_useless_stmts_warn_notreached (tree stmt)
{
  if (EXPR_HAS_LOCATION (stmt))
    {
      location_t loc = EXPR_LOCATION (stmt);
      if (LOCATION_LINE (loc) > 0)
        {
          warning (0, "%Hwill never be executed", &loc);
          return true;
        }
    }

  switch (TREE_CODE (stmt))
    {
    case STATEMENT_LIST:
      {
        tree_stmt_iterator i;
        for (i = tsi_start (stmt); !tsi_end_p (i); tsi_next (&i))
          if (remove_useless_stmts_warn_notreached (tsi_stmt (i)))
            return true;
      }
      break;

    case COND_EXPR:
      if (remove_useless_stmts_warn_notreached (COND_EXPR_COND (stmt)))
        return true;
      if (remove_useless_stmts_warn_notreached (COND_EXPR_THEN (stmt)))
        return true;
      if (remove_useless_stmts_warn_notreached (COND_EXPR_ELSE (stmt)))
        return true;
      break;

    case TRY_FINALLY_EXPR:
    case TRY_CATCH_EXPR:
      if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 0)))
        return true;
      if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 1)))
        return true;
      break;

    case CATCH_EXPR:
      return remove_useless_stmts_warn_notreached (CATCH_BODY (stmt));
    case EH_FILTER_EXPR:
      return remove_useless_stmts_warn_notreached (EH_FILTER_FAILURE (stmt));
    case BIND_EXPR:
      return remove_useless_stmts_warn_notreached (BIND_EXPR_BLOCK (stmt));

    default:
      /* Not a live container.  */
      break;
    }

  return false;
}

static void
remove_useless_stmts_cond (tree *stmt_p, struct rus_data *data)
{
  tree then_clause, else_clause, cond;
  bool save_has_label, then_has_label, else_has_label;

  save_has_label = data->has_label;
  data->has_label = false;
  data->last_goto = NULL;

  remove_useless_stmts_1 (&COND_EXPR_THEN (*stmt_p), data);

  then_has_label = data->has_label;
  data->has_label = false;
  data->last_goto = NULL;

  remove_useless_stmts_1 (&COND_EXPR_ELSE (*stmt_p), data);

  else_has_label = data->has_label;
  data->has_label = save_has_label | then_has_label | else_has_label;

  then_clause = COND_EXPR_THEN (*stmt_p);
  else_clause = COND_EXPR_ELSE (*stmt_p);
  cond = fold (COND_EXPR_COND (*stmt_p));

  /* If neither arm does anything at all, we can remove the whole IF.  */
  if (!TREE_SIDE_EFFECTS (then_clause) && !TREE_SIDE_EFFECTS (else_clause))
    {
      *stmt_p = build_empty_stmt ();
      data->repeat = true;
    }

  /* If there are no reachable statements in an arm, then we can
     zap the entire conditional.  */
  else if (integer_nonzerop (cond) && !else_has_label)
    {
      if (warn_notreached)
        remove_useless_stmts_warn_notreached (else_clause);
      *stmt_p = then_clause;
      data->repeat = true;
    }
  else if (integer_zerop (cond) && !then_has_label)
    {
      if (warn_notreached)
        remove_useless_stmts_warn_notreached (then_clause);
      *stmt_p = else_clause;
      data->repeat = true;
    }

  /* Check a couple of simple things on then/else with single stmts.  */
  else
    {
      tree then_stmt = expr_only (then_clause);
      tree else_stmt = expr_only (else_clause);

      /* Notice branches to a common destination.  */
      if (then_stmt && else_stmt
          && TREE_CODE (then_stmt) == GOTO_EXPR
          && TREE_CODE (else_stmt) == GOTO_EXPR
          && (GOTO_DESTINATION (then_stmt) == GOTO_DESTINATION (else_stmt)))
        {
          *stmt_p = then_stmt;
          data->repeat = true;
        }

      /* If the THEN/ELSE clause merely assigns a value to a variable or
         parameter which is already known to contain that value, then
         remove the useless THEN/ELSE clause.  */
      else if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL)
        {
          if (else_stmt
              && TREE_CODE (else_stmt) == MODIFY_EXPR
              && TREE_OPERAND (else_stmt, 0) == cond
              && integer_zerop (TREE_OPERAND (else_stmt, 1)))
            COND_EXPR_ELSE (*stmt_p) = alloc_stmt_list ();
        }
      else if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
               && (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
                   || TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)
               && TREE_CONSTANT (TREE_OPERAND (cond, 1)))
        {
          tree stmt = (TREE_CODE (cond) == EQ_EXPR
                       ? then_stmt : else_stmt);
          tree *location = (TREE_CODE (cond) == EQ_EXPR
                            ? &COND_EXPR_THEN (*stmt_p)
                            : &COND_EXPR_ELSE (*stmt_p));

          if (stmt
              && TREE_CODE (stmt) == MODIFY_EXPR
              && TREE_OPERAND (stmt, 0) == TREE_OPERAND (cond, 0)
              && TREE_OPERAND (stmt, 1) == TREE_OPERAND (cond, 1))
            *location = alloc_stmt_list ();
        }
    }

  /* Protect GOTOs in the arm of COND_EXPRs from being removed.  They
     would be re-introduced during lowering.  */
  data->last_goto = NULL;
}


static void
remove_useless_stmts_tf (tree *stmt_p, struct rus_data *data)
{
  bool save_may_branch, save_may_throw;
  bool this_may_branch, this_may_throw;

  /* Collect may_branch and may_throw information for the body only.  */
  save_may_branch = data->may_branch;
  save_may_throw = data->may_throw;
  data->may_branch = false;
  data->may_throw = false;
  data->last_goto = NULL;

  remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);

  this_may_branch = data->may_branch;
  this_may_throw = data->may_throw;
  data->may_branch |= save_may_branch;
  data->may_throw |= save_may_throw;
  data->last_goto = NULL;

  remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);

  /* If the body is empty, then we can emit the FINALLY block without
     the enclosing TRY_FINALLY_EXPR.  */
  if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 0)))
    {
      *stmt_p = TREE_OPERAND (*stmt_p, 1);
      data->repeat = true;
    }

  /* If the handler is empty, then we can emit the TRY block without
     the enclosing TRY_FINALLY_EXPR.  */
  else if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
    {
      *stmt_p = TREE_OPERAND (*stmt_p, 0);
      data->repeat = true;
    }

  /* If the body neither throws, nor branches, then we can safely
     string the TRY and FINALLY blocks together.  */
  else if (!this_may_branch && !this_may_throw)
    {
      tree stmt = *stmt_p;
      *stmt_p = TREE_OPERAND (stmt, 0);
      append_to_statement_list (TREE_OPERAND (stmt, 1), stmt_p);
      data->repeat = true;
    }
}


static void
remove_useless_stmts_tc (tree *stmt_p, struct rus_data *data)
{
  bool save_may_throw, this_may_throw;
  tree_stmt_iterator i;
  tree stmt;

  /* Collect may_throw information for the body only.  */
  save_may_throw = data->may_throw;
  data->may_throw = false;
  data->last_goto = NULL;

  remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);

  this_may_throw = data->may_throw;
  data->may_throw = save_may_throw;

  /* If the body cannot throw, then we can drop the entire TRY_CATCH_EXPR.  */
  if (!this_may_throw)
    {
      if (warn_notreached)
        remove_useless_stmts_warn_notreached (TREE_OPERAND (*stmt_p, 1));
      *stmt_p = TREE_OPERAND (*stmt_p, 0);
      data->repeat = true;
      return;
    }

  /* Process the catch clause specially.  We may be able to tell that
     no exceptions propagate past this point.  */

  this_may_throw = true;
  i = tsi_start (TREE_OPERAND (*stmt_p, 1));
  stmt = tsi_stmt (i);
  data->last_goto = NULL;

  switch (TREE_CODE (stmt))
    {
    case CATCH_EXPR:
      for (; !tsi_end_p (i); tsi_next (&i))
        {
          stmt = tsi_stmt (i);
          /* If we catch all exceptions, then the body does not
             propagate exceptions past this point.  */
          if (CATCH_TYPES (stmt) == NULL)
            this_may_throw = false;
          data->last_goto = NULL;
          remove_useless_stmts_1 (&CATCH_BODY (stmt), data);
        }
      break;

    case EH_FILTER_EXPR:
      if (EH_FILTER_MUST_NOT_THROW (stmt))
        this_may_throw = false;
      else if (EH_FILTER_TYPES (stmt) == NULL)
        this_may_throw = false;
      remove_useless_stmts_1 (&EH_FILTER_FAILURE (stmt), data);
      break;

    default:
      /* Otherwise this is a cleanup.  */
      remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);

      /* If the cleanup is empty, then we can emit the TRY block without
         the enclosing TRY_CATCH_EXPR.  */
      if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
        {
          *stmt_p = TREE_OPERAND (*stmt_p, 0);
          data->repeat = true;
        }
      break;
    }
  data->may_throw |= this_may_throw;
}


static void
remove_useless_stmts_bind (tree *stmt_p, struct rus_data *data)
{
  tree block;

  /* First remove anything underneath the BIND_EXPR.  */
  remove_useless_stmts_1 (&BIND_EXPR_BODY (*stmt_p), data);

  /* If the BIND_EXPR has no variables, then we can pull everything
     up one level and remove the BIND_EXPR, unless this is the toplevel
     BIND_EXPR for the current function or an inlined function.

     When this situation occurs we will want to apply this
     optimization again.  */
  block = BIND_EXPR_BLOCK (*stmt_p);
  if (BIND_EXPR_VARS (*stmt_p) == NULL_TREE
      && *stmt_p != DECL_SAVED_TREE (current_function_decl)
      && (! block
          || ! BLOCK_ABSTRACT_ORIGIN (block)
          || (TREE_CODE (BLOCK_ABSTRACT_ORIGIN (block))
              != FUNCTION_DECL)))
    {
      *stmt_p = BIND_EXPR_BODY (*stmt_p);
      data->repeat = true;
    }
}


static void
remove_useless_stmts_goto (tree *stmt_p, struct rus_data *data)
{
  tree dest = GOTO_DESTINATION (*stmt_p);

  data->may_branch = true;
  data->last_goto = NULL;

  /* Record the last goto expr, so that we can delete it if unnecessary.  */
  if (TREE_CODE (dest) == LABEL_DECL)
    data->last_goto = stmt_p;
}


static void
remove_useless_stmts_label (tree *stmt_p, struct rus_data *data)
{
  tree label = LABEL_EXPR_LABEL (*stmt_p);

  data->has_label = true;

  /* We do want to jump across non-local label receiver code.  */
  if (DECL_NONLOCAL (label))
    data->last_goto = NULL;

  else if (data->last_goto && GOTO_DESTINATION (*data->last_goto) == label)
    {
      *data->last_goto = build_empty_stmt ();
      data->repeat = true;
    }

  /* ??? Add something here to delete unused labels.  */
}


/* If the function is "const" or "pure", then clear TREE_SIDE_EFFECTS on its
   decl.  This allows us to eliminate redundant or useless
   calls to "const" functions. 

   Gimplifier already does the same operation, but we may notice functions
   being const and pure once their calls has been gimplified, so we need
   to update the flag.  */

static void
update_call_expr_flags (tree call)
{
  tree decl = get_callee_fndecl (call);
  if (!decl)
    return;
  if (call_expr_flags (call) & (ECF_CONST | ECF_PURE))
    TREE_SIDE_EFFECTS (call) = 0;
  if (TREE_NOTHROW (decl))
    TREE_NOTHROW (call) = 1;
}


/* T is CALL_EXPR.  Set current_function_calls_* flags.  */

void
notice_special_calls (tree t)
{
  int flags = call_expr_flags (t);

  if (flags & ECF_MAY_BE_ALLOCA)
    current_function_calls_alloca = true;
  if (flags & ECF_RETURNS_TWICE)
    current_function_calls_setjmp = true;
}


/* Clear flags set by notice_special_calls.  Used by dead code removal
   to update the flags.  */

void
clear_special_calls (void)
{
  current_function_calls_alloca = false;
  current_function_calls_setjmp = false;
}


static void
remove_useless_stmts_1 (tree *tp, struct rus_data *data)
{
  tree t = *tp, op;

  switch (TREE_CODE (t))
    {
    case COND_EXPR:
      remove_useless_stmts_cond (tp, data);
      break;

    case TRY_FINALLY_EXPR:
      remove_useless_stmts_tf (tp, data);
      break;

    case TRY_CATCH_EXPR:
      remove_useless_stmts_tc (tp, data);
      break;

    case BIND_EXPR:
      remove_useless_stmts_bind (tp, data);
      break;

    case GOTO_EXPR:
      remove_useless_stmts_goto (tp, data);
      break;

    case LABEL_EXPR:
      remove_useless_stmts_label (tp, data);
      break;

    case RETURN_EXPR:
      fold_stmt (tp);
      data->last_goto = NULL;
      data->may_branch = true;
      break;

    case CALL_EXPR:
      fold_stmt (tp);
      data->last_goto = NULL;
      notice_special_calls (t);
      update_call_expr_flags (t);
      if (tree_could_throw_p (t))
        data->may_throw = true;
      break;

    case MODIFY_EXPR:
      data->last_goto = NULL;
      fold_stmt (tp);
      op = get_call_expr_in (t);
      if (op)
        {
          update_call_expr_flags (op);
          notice_special_calls (op);
        }
      if (tree_could_throw_p (t))
        data->may_throw = true;
      break;

    case STATEMENT_LIST:
      {
        tree_stmt_iterator i = tsi_start (t);
        while (!tsi_end_p (i))
          {
            t = tsi_stmt (i);
            if (IS_EMPTY_STMT (t))
              {
                tsi_delink (&i);
                continue;
              }
            
            remove_useless_stmts_1 (tsi_stmt_ptr (i), data);

            t = tsi_stmt (i);
            if (TREE_CODE (t) == STATEMENT_LIST)
              {
                tsi_link_before (&i, t, TSI_SAME_STMT);
                tsi_delink (&i);
              }
            else
              tsi_next (&i);
          }
      }
      break;
    case ASM_EXPR:
      fold_stmt (tp);
      data->last_goto = NULL;
      break;

    default:
      data->last_goto = NULL;
      break;
    }
}

static void
remove_useless_stmts (void)
{
  struct rus_data data;

  clear_special_calls ();

  do
    {
      memset (&data, 0, sizeof (data));
      remove_useless_stmts_1 (&DECL_SAVED_TREE (current_function_decl), &data);
    }
  while (data.repeat);
}


struct tree_opt_pass pass_remove_useless_stmts = 
{
  "useless",                            /* name */
  NULL,                                 /* gate */
  remove_useless_stmts,                 /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  0,                                    /* tv_id */
  PROP_gimple_any,                      /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_dump_func,                       /* todo_flags_finish */
  0                                     /* letter */
};

/* Remove PHI nodes associated with basic block BB and all edges out of BB.  */

static void
remove_phi_nodes_and_edges_for_unreachable_block (basic_block bb)
{
  tree phi;

  /* Since this block is no longer reachable, we can just delete all
     of its PHI nodes.  */
  phi = phi_nodes (bb);
  while (phi)
    {
      tree next = PHI_CHAIN (phi);
      remove_phi_node (phi, NULL_TREE);
      phi = next;
    }

  /* Remove edges to BB's successors.  */
  while (EDGE_COUNT (bb->succs) > 0)
    remove_edge (EDGE_SUCC (bb, 0));
}


/* Remove statements of basic block BB.  */

static void
remove_bb (basic_block bb)
{
  block_stmt_iterator i;
#ifdef USE_MAPPED_LOCATION
  source_location loc = UNKNOWN_LOCATION;
#else
  source_locus loc = 0;
#endif

  if (dump_file)
    {
      fprintf (dump_file, "Removing basic block %d\n", bb->index);
      if (dump_flags & TDF_DETAILS)
        {
          dump_bb (bb, dump_file, 0);
          fprintf (dump_file, "\n");
        }
    }

  /* If we remove the header or the latch of a loop, mark the loop for
     removal by setting its header and latch to NULL.  */
  if (current_loops)
    {
      struct loop *loop = bb->loop_father;

      if (loop->latch == bb
          || loop->header == bb)
        {
          loop->latch = NULL;
          loop->header = NULL;
        }
    }

  /* Remove all the instructions in the block.  */
  for (i = bsi_start (bb); !bsi_end_p (i);)
    {
      tree stmt = bsi_stmt (i);
      if (TREE_CODE (stmt) == LABEL_EXPR
          && FORCED_LABEL (LABEL_EXPR_LABEL (stmt)))
        {
          basic_block new_bb = bb->prev_bb;
          block_stmt_iterator new_bsi = bsi_start (new_bb);
                  
          bsi_remove (&i);
          bsi_insert_before (&new_bsi, stmt, BSI_NEW_STMT);
        }
      else
        {
          release_defs (stmt);

          bsi_remove (&i);
        }

      /* Don't warn for removed gotos.  Gotos are often removed due to
         jump threading, thus resulting in bogus warnings.  Not great,
         since this way we lose warnings for gotos in the original
         program that are indeed unreachable.  */
      if (TREE_CODE (stmt) != GOTO_EXPR && EXPR_HAS_LOCATION (stmt) && !loc)
        {
#ifdef USE_MAPPED_LOCATION
          if (EXPR_HAS_LOCATION (stmt))
            loc = EXPR_LOCATION (stmt);
#else
          source_locus t;
          t = EXPR_LOCUS (stmt);
          if (t && LOCATION_LINE (*t) > 0)
            loc = t;
#endif
        }
    }

  /* If requested, give a warning that the first statement in the
     block is unreachable.  We walk statements backwards in the
     loop above, so the last statement we process is the first statement
     in the block.  */
#ifdef USE_MAPPED_LOCATION
  if (warn_notreached && loc > BUILTINS_LOCATION)
    warning (0, "%Hwill never be executed", &loc);
#else
  if (warn_notreached && loc)
    warning (0, "%Hwill never be executed", loc);
#endif

  remove_phi_nodes_and_edges_for_unreachable_block (bb);
}

/* A list of all the noreturn calls passed to modify_stmt.
   cleanup_control_flow uses it to detect cases where a mid-block
   indirect call has been turned into a noreturn call.  When this
   happens, all the instructions after the call are no longer
   reachable and must be deleted as dead.  */

VEC(tree,gc) *modified_noreturn_calls;

/* Try to remove superfluous control structures.  */

static bool
cleanup_control_flow (void)
{
  basic_block bb;
  block_stmt_iterator bsi;
  bool retval = false;
  tree stmt;

  /* Detect cases where a mid-block call is now known not to return.  */
  while (VEC_length (tree, modified_noreturn_calls))
    {
      stmt = VEC_pop (tree, modified_noreturn_calls);
      bb = bb_for_stmt (stmt);
      if (bb != NULL && last_stmt (bb) != stmt && noreturn_call_p (stmt))
        split_block (bb, stmt);
    }

  FOR_EACH_BB (bb)
    {
      bsi = bsi_last (bb);

      if (bsi_end_p (bsi))
        continue;
      
      stmt = bsi_stmt (bsi);
      if (TREE_CODE (stmt) == COND_EXPR
          || TREE_CODE (stmt) == SWITCH_EXPR)
        retval |= cleanup_control_expr_graph (bb, bsi);

      /* If we had a computed goto which has a compile-time determinable
         destination, then we can eliminate the goto.  */
      if (TREE_CODE (stmt) == GOTO_EXPR
          && TREE_CODE (GOTO_DESTINATION (stmt)) == ADDR_EXPR
          && TREE_CODE (TREE_OPERAND (GOTO_DESTINATION (stmt), 0)) == LABEL_DECL)
        {
          edge e;
          tree label;
          edge_iterator ei;
          basic_block target_block;
          bool removed_edge = false;

          /* First look at all the outgoing edges.  Delete any outgoing
             edges which do not go to the right block.  For the one
             edge which goes to the right block, fix up its flags.  */
          label = TREE_OPERAND (GOTO_DESTINATION (stmt), 0);
          target_block = label_to_block (label);
          for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
            {
              if (e->dest != target_block)
                {
                  removed_edge = true;
                  remove_edge (e);
                }
              else
                {
                  /* Turn off the EDGE_ABNORMAL flag.  */
                  e->flags &= ~EDGE_ABNORMAL;

                  /* And set EDGE_FALLTHRU.  */
                  e->flags |= EDGE_FALLTHRU;
                  ei_next (&ei);
                }
            }

          /* If we removed one or more edges, then we will need to fix the
             dominators.  It may be possible to incrementally update them.  */
          if (removed_edge)
            free_dominance_info (CDI_DOMINATORS);

          /* Remove the GOTO_EXPR as it is not needed.  The CFG has all the
             relevant information we need.  */
          bsi_remove (&bsi);
          retval = true;
        }

      /* Check for indirect calls that have been turned into
         noreturn calls.  */
      if (noreturn_call_p (stmt) && remove_fallthru_edge (bb->succs))
        {
          free_dominance_info (CDI_DOMINATORS);
          retval = true;
        }
    }
  return retval;
}


/* Disconnect an unreachable block in the control expression starting
   at block BB.  */

static bool
cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi)
{
  edge taken_edge;
  bool retval = false;
  tree expr = bsi_stmt (bsi), val;

  if (!single_succ_p (bb))
    {
      edge e;
      edge_iterator ei;

      switch (TREE_CODE (expr))
        {
        case COND_EXPR:
          val = COND_EXPR_COND (expr);
          break;

        case SWITCH_EXPR:
          val = SWITCH_COND (expr);
          if (TREE_CODE (val) != INTEGER_CST)
            return false;
          break;

        default:
          gcc_unreachable ();
        }

      taken_edge = find_taken_edge (bb, val);
      if (!taken_edge)
        return false;

      /* Remove all the edges except the one that is always executed.  */
      for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
        {
          if (e != taken_edge)
            {
              taken_edge->probability += e->probability;
              taken_edge->count += e->count;
              remove_edge (e);
              retval = true;
            }
          else
            ei_next (&ei);
        }
      if (taken_edge->probability > REG_BR_PROB_BASE)
        taken_edge->probability = REG_BR_PROB_BASE;
    }
  else
    taken_edge = single_succ_edge (bb);

  bsi_remove (&bsi);
  taken_edge->flags = EDGE_FALLTHRU;

  /* We removed some paths from the cfg.  */
  free_dominance_info (CDI_DOMINATORS);

  return retval;
}

/* Remove any fallthru edge from EV.  Return true if an edge was removed.  */

static bool
remove_fallthru_edge (VEC(edge,gc) *ev)
{
  edge_iterator ei;
  edge e;

  FOR_EACH_EDGE (e, ei, ev)
    if ((e->flags & EDGE_FALLTHRU) != 0)
      {
        remove_edge (e);
        return true;
      }
  return false;
}

/* Given a basic block BB ending with COND_EXPR or SWITCH_EXPR, and a
   predicate VAL, return the edge that will be taken out of the block.
   If VAL does not match a unique edge, NULL is returned.  */

edge
find_taken_edge (basic_block bb, tree val)
{
  tree stmt;

  stmt = last_stmt (bb);

  gcc_assert (stmt);
  gcc_assert (is_ctrl_stmt (stmt));
  gcc_assert (val);

  if (! is_gimple_min_invariant (val))
    return NULL;

  if (TREE_CODE (stmt) == COND_EXPR)
    return find_taken_edge_cond_expr (bb, val);

  if (TREE_CODE (stmt) == SWITCH_EXPR)
    return find_taken_edge_switch_expr (bb, val);

  if (computed_goto_p (stmt))
    return find_taken_edge_computed_goto (bb, TREE_OPERAND( val, 0));

  gcc_unreachable ();
}

/* Given a constant value VAL and the entry block BB to a GOTO_EXPR
   statement, determine which of the outgoing edges will be taken out of the
   block.  Return NULL if either edge may be taken.  */

static edge
find_taken_edge_computed_goto (basic_block bb, tree val)
{
  basic_block dest;
  edge e = NULL;

  dest = label_to_block (val);
  if (dest)
    {
      e = find_edge (bb, dest);
      gcc_assert (e != NULL);
    }

  return e;
}

/* Given a constant value VAL and the entry block BB to a COND_EXPR
   statement, determine which of the two edges will be taken out of the
   block.  Return NULL if either edge may be taken.  */

static edge
find_taken_edge_cond_expr (basic_block bb, tree val)
{
  edge true_edge, false_edge;

  extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
  
  gcc_assert (TREE_CODE (val) == INTEGER_CST);
  return (zero_p (val) ? false_edge : true_edge);
}

/* Given an INTEGER_CST VAL and the entry block BB to a SWITCH_EXPR
   statement, determine which edge will be taken out of the block.  Return
   NULL if any edge may be taken.  */

static edge
find_taken_edge_switch_expr (basic_block bb, tree val)
{
  tree switch_expr, taken_case;
  basic_block dest_bb;
  edge e;

  switch_expr = last_stmt (bb);
  taken_case = find_case_label_for_value (switch_expr, val);
  dest_bb = label_to_block (CASE_LABEL (taken_case));

  e = find_edge (bb, dest_bb);
  gcc_assert (e);
  return e;
}


/* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL.
   We can make optimal use here of the fact that the case labels are
   sorted: We can do a binary search for a case matching VAL.  */

static tree
find_case_label_for_value (tree switch_expr, tree val)
{
  tree vec = SWITCH_LABELS (switch_expr);
  size_t low, high, n = TREE_VEC_LENGTH (vec);
  tree default_case = TREE_VEC_ELT (vec, n - 1);

  for (low = -1, high = n - 1; high - low > 1; )
    {
      size_t i = (high + low) / 2;
      tree t = TREE_VEC_ELT (vec, i);
      int cmp;

      /* Cache the result of comparing CASE_LOW and val.  */
      cmp = tree_int_cst_compare (CASE_LOW (t), val);

      if (cmp > 0)
        high = i;
      else
        low = i;

      if (CASE_HIGH (t) == NULL)
        {
          /* A singe-valued case label.  */
          if (cmp == 0)
            return t;
        }
      else
        {
          /* A case range.  We can only handle integer ranges.  */
          if (cmp <= 0 && tree_int_cst_compare (CASE_HIGH (t), val) >= 0)
            return t;
        }
    }

  return default_case;
}


/* If all the PHI nodes in DEST have alternatives for E1 and E2 and
   those alternatives are equal in each of the PHI nodes, then return
   true, else return false.  */

static bool
phi_alternatives_equal (basic_block dest, edge e1, edge e2)
{
  int n1 = e1->dest_idx;
  int n2 = e2->dest_idx;
  tree phi;

  for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
    {
      tree val1 = PHI_ARG_DEF (phi, n1);
      tree val2 = PHI_ARG_DEF (phi, n2);

      gcc_assert (val1 != NULL_TREE);
      gcc_assert (val2 != NULL_TREE);

      if (!operand_equal_for_phi_arg_p (val1, val2))
        return false;
    }

  return true;
}


/*---------------------------------------------------------------------------
                              Debugging functions
---------------------------------------------------------------------------*/

/* Dump tree-specific information of block BB to file OUTF.  */

void
tree_dump_bb (basic_block bb, FILE *outf, int indent)
{
  dump_generic_bb (outf, bb, indent, TDF_VOPS);
}


/* Dump a basic block on stderr.  */

void
debug_tree_bb (basic_block bb)
{
  dump_bb (bb, stderr, 0);
}


/* Dump basic block with index N on stderr.  */

basic_block
debug_tree_bb_n (int n)
{
  debug_tree_bb (BASIC_BLOCK (n));
  return BASIC_BLOCK (n);
}        


/* Dump the CFG on stderr.

   FLAGS are the same used by the tree dumping functions
   (see TDF_* in tree.h).  */

void
debug_tree_cfg (int flags)
{
  dump_tree_cfg (stderr, flags);
}


/* Dump the program showing basic block boundaries on the given FILE.

   FLAGS are the same used by the tree dumping functions (see TDF_* in
   tree.h).  */

void
dump_tree_cfg (FILE *file, int flags)
{
  if (flags & TDF_DETAILS)
    {
      const char *funcname
        = lang_hooks.decl_printable_name (current_function_decl, 2);

      fputc ('\n', file);
      fprintf (file, ";; Function %s\n\n", funcname);
      fprintf (file, ";; \n%d basic blocks, %d edges, last basic block %d.\n\n",
               n_basic_blocks, n_edges, last_basic_block);

      brief_dump_cfg (file);
      fprintf (file, "\n");
    }

  if (flags & TDF_STATS)
    dump_cfg_stats (file);

  dump_function_to_file (current_function_decl, file, flags | TDF_BLOCKS);
}


/* Dump CFG statistics on FILE.  */

void
dump_cfg_stats (FILE *file)
{
  static long max_num_merged_labels = 0;
  unsigned long size, total = 0;
  long num_edges;
  basic_block bb;
  const char * const fmt_str   = "%-30s%-13s%12s\n";
  const char * const fmt_str_1 = "%-30s%13d%11lu%c\n";
  const char * const fmt_str_3 = "%-43s%11lu%c\n";
  const char *funcname
    = lang_hooks.decl_printable_name (current_function_decl, 2);


  fprintf (file, "\nCFG Statistics for %s\n\n", funcname);

  fprintf (file, "---------------------------------------------------------\n");
  fprintf (file, fmt_str, "", "  Number of  ", "Memory");
  fprintf (file, fmt_str, "", "  instances  ", "used ");
  fprintf (file, "---------------------------------------------------------\n");

  size = n_basic_blocks * sizeof (struct basic_block_def);
  total += size;
  fprintf (file, fmt_str_1, "Basic blocks", n_basic_blocks,
           SCALE (size), LABEL (size));

  num_edges = 0;
  FOR_EACH_BB (bb)
    num_edges += EDGE_COUNT (bb->succs);
  size = num_edges * sizeof (struct edge_def);
  total += size;
  fprintf (file, fmt_str_1, "Edges", num_edges, SCALE (size), LABEL (size));

  size = n_basic_blocks * sizeof (struct bb_ann_d);
  total += size;
  fprintf (file, fmt_str_1, "Basic block annotations", n_basic_blocks,
           SCALE (size), LABEL (size));

  fprintf (file, "---------------------------------------------------------\n");
  fprintf (file, fmt_str_3, "Total memory used by CFG data", SCALE (total),
           LABEL (total));
  fprintf (file, "---------------------------------------------------------\n");
  fprintf (file, "\n");

  if (cfg_stats.num_merged_labels > max_num_merged_labels)
    max_num_merged_labels = cfg_stats.num_merged_labels;

  fprintf (file, "Coalesced label blocks: %ld (Max so far: %ld)\n",
           cfg_stats.num_merged_labels, max_num_merged_labels);

  fprintf (file, "\n");
}


/* Dump CFG statistics on stderr.  Keep extern so that it's always
   linked in the final executable.  */

void
debug_cfg_stats (void)
{
  dump_cfg_stats (stderr);
}


/* Dump the flowgraph to a .vcg FILE.  */

static void
tree_cfg2vcg (FILE *file)
{
  edge e;
  edge_iterator ei;
  basic_block bb;
  const char *funcname
    = lang_hooks.decl_printable_name (current_function_decl, 2);

  /* Write the file header.  */
  fprintf (file, "graph: { title: \"%s\"\n", funcname);
  fprintf (file, "node: { title: \"ENTRY\" label: \"ENTRY\" }\n");
  fprintf (file, "node: { title: \"EXIT\" label: \"EXIT\" }\n");

  /* Write blocks and edges.  */
  FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
    {
      fprintf (file, "edge: { sourcename: \"ENTRY\" targetname: \"%d\"",
               e->dest->index);

      if (e->flags & EDGE_FAKE)
        fprintf (file, " linestyle: dotted priority: 10");
      else
        fprintf (file, " linestyle: solid priority: 100");

      fprintf (file, " }\n");
    }
  fputc ('\n', file);

  FOR_EACH_BB (bb)
    {
      enum tree_code head_code, end_code;
      const char *head_name, *end_name;
      int head_line = 0;
      int end_line = 0;
      tree first = first_stmt (bb);
      tree last = last_stmt (bb);

      if (first)
        {
          head_code = TREE_CODE (first);
          head_name = tree_code_name[head_code];
          head_line = get_lineno (first);
        }
      else
        head_name = "no-statement";

      if (last)
        {
          end_code = TREE_CODE (last);
          end_name = tree_code_name[end_code];
          end_line = get_lineno (last);
        }
      else
        end_name = "no-statement";

      fprintf (file, "node: { title: \"%d\" label: \"#%d\\n%s (%d)\\n%s (%d)\"}\n",
               bb->index, bb->index, head_name, head_line, end_name,
               end_line);

      FOR_EACH_EDGE (e, ei, bb->succs)
        {
          if (e->dest == EXIT_BLOCK_PTR)
            fprintf (file, "edge: { sourcename: \"%d\" targetname: \"EXIT\"", bb->index);
          else
            fprintf (file, "edge: { sourcename: \"%d\" targetname: \"%d\"", bb->index, e->dest->index);

          if (e->flags & EDGE_FAKE)
            fprintf (file, " priority: 10 linestyle: dotted");
          else
            fprintf (file, " priority: 100 linestyle: solid");

          fprintf (file, " }\n");
        }

      if (bb->next_bb != EXIT_BLOCK_PTR)
        fputc ('\n', file);
    }

  fputs ("}\n\n", file);
}



/*---------------------------------------------------------------------------
                             Miscellaneous helpers
---------------------------------------------------------------------------*/

/* Return true if T represents a stmt that always transfers control.  */

bool
is_ctrl_stmt (tree t)
{
  return (TREE_CODE (t) == COND_EXPR
          || TREE_CODE (t) == SWITCH_EXPR
          || TREE_CODE (t) == GOTO_EXPR
          || TREE_CODE (t) == RETURN_EXPR
          || TREE_CODE (t) == RESX_EXPR);
}


/* Return true if T is a statement that may alter the flow of control
   (e.g., a call to a non-returning function).  */

bool
is_ctrl_altering_stmt (tree t)
{
  tree call;

  gcc_assert (t);
  call = get_call_expr_in (t);
  if (call)
    {
      /* A non-pure/const CALL_EXPR alters flow control if the current
         function has nonlocal labels.  */
      if (TREE_SIDE_EFFECTS (call) && current_function_has_nonlocal_label)
        return true;

      /* A CALL_EXPR also alters control flow if it does not return.  */
      if (call_expr_flags (call) & ECF_NORETURN)
        return true;
    }

  /* If a statement can throw, it alters control flow.  */
  return tree_can_throw_internal (t);
}


/* Return true if T is a computed goto.  */

bool
computed_goto_p (tree t)
{
  return (TREE_CODE (t) == GOTO_EXPR
          && TREE_CODE (GOTO_DESTINATION (t)) != LABEL_DECL);
}


/* Checks whether EXPR is a simple local goto.  */

bool
simple_goto_p (tree expr)
{
  return (TREE_CODE (expr) == GOTO_EXPR
          && TREE_CODE (GOTO_DESTINATION (expr)) == LABEL_DECL);
}


/* Return true if T should start a new basic block.  PREV_T is the
   statement preceding T.  It is used when T is a label or a case label.
   Labels should only start a new basic block if their previous statement
   wasn't a label.  Otherwise, sequence of labels would generate
   unnecessary basic blocks that only contain a single label.  */

static inline bool
stmt_starts_bb_p (tree t, tree prev_t)
{
  if (t == NULL_TREE)
    return false;

  /* LABEL_EXPRs start a new basic block only if the preceding
     statement wasn't a label of the same type.  This prevents the
     creation of consecutive blocks that have nothing but a single
     label.  */
  if (TREE_CODE (t) == LABEL_EXPR)
    {
      /* Nonlocal and computed GOTO targets always start a new block.  */
      if (DECL_NONLOCAL (LABEL_EXPR_LABEL (t))
          || FORCED_LABEL (LABEL_EXPR_LABEL (t)))
        return true;

      if (prev_t && TREE_CODE (prev_t) == LABEL_EXPR)
        {
          if (DECL_NONLOCAL (LABEL_EXPR_LABEL (prev_t)))
            return true;

          cfg_stats.num_merged_labels++;
          return false;
        }
      else
        return true;
    }

  return false;
}


/* Return true if T should end a basic block.  */

bool
stmt_ends_bb_p (tree t)
{
  return is_ctrl_stmt (t) || is_ctrl_altering_stmt (t);
}


/* Add gotos that used to be represented implicitly in the CFG.  */

void
disband_implicit_edges (void)
{
  basic_block bb;
  block_stmt_iterator last;
  edge e;
  edge_iterator ei;
  tree stmt, label;

  FOR_EACH_BB (bb)
    {
      last = bsi_last (bb);
      stmt = last_stmt (bb);

      if (stmt && TREE_CODE (stmt) == COND_EXPR)
        {
          /* Remove superfluous gotos from COND_EXPR branches.  Moved
             from cfg_remove_useless_stmts here since it violates the
             invariants for tree--cfg correspondence and thus fits better
             here where we do it anyway.  */
          e = find_edge (bb, bb->next_bb);
          if (e)
            {
              if (e->flags & EDGE_TRUE_VALUE)
                COND_EXPR_THEN (stmt) = build_empty_stmt ();
              else if (e->flags & EDGE_FALSE_VALUE)
                COND_EXPR_ELSE (stmt) = build_empty_stmt ();
              else
                gcc_unreachable ();
              e->flags |= EDGE_FALLTHRU;
            }

          continue;
        }

      if (stmt && TREE_CODE (stmt) == RETURN_EXPR)
        {
          /* Remove the RETURN_EXPR if we may fall though to the exit
             instead.  */
          gcc_assert (single_succ_p (bb));
          gcc_assert (single_succ (bb) == EXIT_BLOCK_PTR);

          if (bb->next_bb == EXIT_BLOCK_PTR
              && !TREE_OPERAND (stmt, 0))
            {
              bsi_remove (&last);
              single_succ_edge (bb)->flags |= EDGE_FALLTHRU;
            }
          continue;
        }

      /* There can be no fallthru edge if the last statement is a control
         one.  */
      if (stmt && is_ctrl_stmt (stmt))
        continue;

      /* Find a fallthru edge and emit the goto if necessary.  */
      FOR_EACH_EDGE (e, ei, bb->succs)
        if (e->flags & EDGE_FALLTHRU)
          break;

      if (!e || e->dest == bb->next_bb)
        continue;

      gcc_assert (e->dest != EXIT_BLOCK_PTR);
      label = tree_block_label (e->dest);

      stmt = build1 (GOTO_EXPR, void_type_node, label);
#ifdef USE_MAPPED_LOCATION
      SET_EXPR_LOCATION (stmt, e->goto_locus);
#else
      SET_EXPR_LOCUS (stmt, e->goto_locus);
#endif
      bsi_insert_after (&last, stmt, BSI_NEW_STMT);
      e->flags &= ~EDGE_FALLTHRU;
    }
}

/* Remove block annotations and other datastructures.  */

void
delete_tree_cfg_annotations (void)
{
  basic_block bb;
  if (n_basic_blocks > 0)
    free_blocks_annotations ();

  label_to_block_map = NULL;
  FOR_EACH_BB (bb)
    bb->rbi = NULL;
}


/* Return the first statement in basic block BB.  */

tree
first_stmt (basic_block bb)
{
  block_stmt_iterator i = bsi_start (bb);
  return !bsi_end_p (i) ? bsi_stmt (i) : NULL_TREE;
}


/* Return the last statement in basic block BB.  */

tree
last_stmt (basic_block bb)
{
  block_stmt_iterator b = bsi_last (bb);
  return !bsi_end_p (b) ? bsi_stmt (b) : NULL_TREE;
}


/* Return a pointer to the last statement in block BB.  */

tree *
last_stmt_ptr (basic_block bb)
{
  block_stmt_iterator last = bsi_last (bb);
  return !bsi_end_p (last) ? bsi_stmt_ptr (last) : NULL;
}


/* Return the last statement of an otherwise empty block.  Return NULL
   if the block is totally empty, or if it contains more than one
   statement.  */

tree
last_and_only_stmt (basic_block bb)
{
  block_stmt_iterator i = bsi_last (bb);
  tree last, prev;

  if (bsi_end_p (i))
    return NULL_TREE;

  last = bsi_stmt (i);
  bsi_prev (&i);
  if (bsi_end_p (i))
    return last;

  /* Empty statements should no longer appear in the instruction stream.
     Everything that might have appeared before should be deleted by
     remove_useless_stmts, and the optimizers should just bsi_remove
     instead of smashing with build_empty_stmt.

     Thus the only thing that should appear here in a block containing
     one executable statement is a label.  */
  prev = bsi_stmt (i);
  if (TREE_CODE (prev) == LABEL_EXPR)
    return last;
  else
    return NULL_TREE;
}


/* Mark BB as the basic block holding statement T.  */

void
set_bb_for_stmt (tree t, basic_block bb)
{
  if (TREE_CODE (t) == PHI_NODE)
    PHI_BB (t) = bb;
  else if (TREE_CODE (t) == STATEMENT_LIST)
    {
      tree_stmt_iterator i;
      for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i))
        set_bb_for_stmt (tsi_stmt (i), bb);
    }
  else
    {
      stmt_ann_t ann = get_stmt_ann (t);
      ann->bb = bb;

      /* If the statement is a label, add the label to block-to-labels map
         so that we can speed up edge creation for GOTO_EXPRs.  */
      if (TREE_CODE (t) == LABEL_EXPR)
        {
          int uid;

          t = LABEL_EXPR_LABEL (t);
          uid = LABEL_DECL_UID (t);
          if (uid == -1)
            {
              LABEL_DECL_UID (t) = uid = cfun->last_label_uid++;
              if (VARRAY_SIZE (label_to_block_map) <= (unsigned) uid)
                VARRAY_GROW (label_to_block_map, 3 * uid / 2);
            }
          else
            /* We're moving an existing label.  Make sure that we've
                removed it from the old block.  */
            gcc_assert (!bb || !VARRAY_BB (label_to_block_map, uid));
          VARRAY_BB (label_to_block_map, uid) = bb;
        }
    }
}

/* Finds iterator for STMT.  */

extern block_stmt_iterator
bsi_for_stmt (tree stmt)
{
  block_stmt_iterator bsi;

  for (bsi = bsi_start (bb_for_stmt (stmt)); !bsi_end_p (bsi); bsi_next (&bsi))
    if (bsi_stmt (bsi) == stmt)
      return bsi;

  gcc_unreachable ();
}

/* Mark statement T as modified, and update it.  */
static inline void
update_modified_stmts (tree t)
{
  if (TREE_CODE (t) == STATEMENT_LIST)
    {
      tree_stmt_iterator i;
      tree stmt;
      for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i))
        {
          stmt = tsi_stmt (i);
          update_stmt_if_modified (stmt);
        }
    }
  else
    update_stmt_if_modified (t);
}

/* Insert statement (or statement list) T before the statement
   pointed-to by iterator I.  M specifies how to update iterator I
   after insertion (see enum bsi_iterator_update).  */

void
bsi_insert_before (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
{
  set_bb_for_stmt (t, i->bb);
  update_modified_stmts (t);
  tsi_link_before (&i->tsi, t, m);
}


/* Insert statement (or statement list) T after the statement
   pointed-to by iterator I.  M specifies how to update iterator I
   after insertion (see enum bsi_iterator_update).  */

void
bsi_insert_after (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
{
  set_bb_for_stmt (t, i->bb);
  update_modified_stmts (t);
  tsi_link_after (&i->tsi, t, m);
}


/* Remove the statement pointed to by iterator I.  The iterator is updated
   to the next statement.  */

void
bsi_remove (block_stmt_iterator *i)
{
  tree t = bsi_stmt (*i);
  set_bb_for_stmt (t, NULL);
  delink_stmt_imm_use (t);
  tsi_delink (&i->tsi);
  mark_stmt_modified (t);
}


/* Move the statement at FROM so it comes right after the statement at TO.  */

void 
bsi_move_after (block_stmt_iterator *from, block_stmt_iterator *to)
{
  tree stmt = bsi_stmt (*from);
  bsi_remove (from);
  bsi_insert_after (to, stmt, BSI_SAME_STMT);
} 


/* Move the statement at FROM so it comes right before the statement at TO.  */

void 
bsi_move_before (block_stmt_iterator *from, block_stmt_iterator *to)
{
  tree stmt = bsi_stmt (*from);
  bsi_remove (from);
  bsi_insert_before (to, stmt, BSI_SAME_STMT);
}


/* Move the statement at FROM to the end of basic block BB.  */

void
bsi_move_to_bb_end (block_stmt_iterator *from, basic_block bb)
{
  block_stmt_iterator last = bsi_last (bb);
  
  /* Have to check bsi_end_p because it could be an empty block.  */
  if (!bsi_end_p (last) && is_ctrl_stmt (bsi_stmt (last)))
    bsi_move_before (from, &last);
  else
    bsi_move_after (from, &last);
}


/* Replace the contents of the statement pointed to by iterator BSI
   with STMT.  If PRESERVE_EH_INFO is true, the exception handling
   information of the original statement is preserved.  */

void
bsi_replace (const block_stmt_iterator *bsi, tree stmt, bool preserve_eh_info)
{
  int eh_region;
  tree orig_stmt = bsi_stmt (*bsi);

  SET_EXPR_LOCUS (stmt, EXPR_LOCUS (orig_stmt));
  set_bb_for_stmt (stmt, bsi->bb);

  /* Preserve EH region information from the original statement, if
     requested by the caller.  */
  if (preserve_eh_info)
    {
      eh_region = lookup_stmt_eh_region (orig_stmt);
      if (eh_region >= 0)
        add_stmt_to_eh_region (stmt, eh_region);
    }

  delink_stmt_imm_use (orig_stmt);
  *bsi_stmt_ptr (*bsi) = stmt;
  mark_stmt_modified (stmt);
  update_modified_stmts (stmt);
}


/* Insert the statement pointed-to by BSI into edge E.  Every attempt
   is made to place the statement in an existing basic block, but
   sometimes that isn't possible.  When it isn't possible, the edge is
   split and the statement is added to the new block.

   In all cases, the returned *BSI points to the correct location.  The
   return value is true if insertion should be done after the location,
   or false if it should be done before the location.  If new basic block
   has to be created, it is stored in *NEW_BB.  */

static bool
tree_find_edge_insert_loc (edge e, block_stmt_iterator *bsi,
                           basic_block *new_bb)
{
  basic_block dest, src;
  tree tmp;

  dest = e->dest;
 restart:

  /* If the destination has one predecessor which has no PHI nodes,
     insert there.  Except for the exit block. 

     The requirement for no PHI nodes could be relaxed.  Basically we
     would have to examine the PHIs to prove that none of them used
     the value set by the statement we want to insert on E.  That
     hardly seems worth the effort.  */
  if (single_pred_p (dest)
      && ! phi_nodes (dest)
      && dest != EXIT_BLOCK_PTR)
    {
      *bsi = bsi_start (dest);
      if (bsi_end_p (*bsi))
        return true;

      /* Make sure we insert after any leading labels.  */
      tmp = bsi_stmt (*bsi);
      while (TREE_CODE (tmp) == LABEL_EXPR)
        {
          bsi_next (bsi);
          if (bsi_end_p (*bsi))
            break;
          tmp = bsi_stmt (*bsi);
        }

      if (bsi_end_p (*bsi))
        {
          *bsi = bsi_last (dest);
          return true;
        }
      else
        return false;
    }

  /* If the source has one successor, the edge is not abnormal and
     the last statement does not end a basic block, insert there.
     Except for the entry block.  */
  src = e->src;
  if ((e->flags & EDGE_ABNORMAL) == 0
      && single_succ_p (src)
      && src != ENTRY_BLOCK_PTR)
    {
      *bsi = bsi_last (src);
      if (bsi_end_p (*bsi))
        return true;

      tmp = bsi_stmt (*bsi);
      if (!stmt_ends_bb_p (tmp))
        return true;

      /* Insert code just before returning the value.  We may need to decompose
         the return in the case it contains non-trivial operand.  */
      if (TREE_CODE (tmp) == RETURN_EXPR)
        {
          tree op = TREE_OPERAND (tmp, 0);
          if (!is_gimple_val (op))
            {
              gcc_assert (TREE_CODE (op) == MODIFY_EXPR);
              bsi_insert_before (bsi, op, BSI_NEW_STMT);
              TREE_OPERAND (tmp, 0) = TREE_OPERAND (op, 0);
            }
          bsi_prev (bsi);
          return true;
        }
    }

  /* Otherwise, create a new basic block, and split this edge.  */
  dest = split_edge (e);
  if (new_bb)
    *new_bb = dest;
  e = single_pred_edge (dest);
  goto restart;
}


/* This routine will commit all pending edge insertions, creating any new
   basic blocks which are necessary.  */

void
bsi_commit_edge_inserts (void)
{
  basic_block bb;
  edge e;
  edge_iterator ei;

  bsi_commit_one_edge_insert (single_succ_edge (ENTRY_BLOCK_PTR), NULL);

  FOR_EACH_BB (bb)
    FOR_EACH_EDGE (e, ei, bb->succs)
      bsi_commit_one_edge_insert (e, NULL);
}


/* Commit insertions pending at edge E. If a new block is created, set NEW_BB
   to this block, otherwise set it to NULL.  */

void
bsi_commit_one_edge_insert (edge e, basic_block *new_bb)
{
  if (new_bb)
    *new_bb = NULL;
  if (PENDING_STMT (e))
    {
      block_stmt_iterator bsi;
      tree stmt = PENDING_STMT (e);

      PENDING_STMT (e) = NULL_TREE;

      if (tree_find_edge_insert_loc (e, &bsi, new_bb))
        bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
      else
        bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
    }
}


/* Add STMT to the pending list of edge E.  No actual insertion is
   made until a call to bsi_commit_edge_inserts () is made.  */

void
bsi_insert_on_edge (edge e, tree stmt)
{
  append_to_statement_list (stmt, &PENDING_STMT (e));
}

/* Similar to bsi_insert_on_edge+bsi_commit_edge_inserts.  If a new
   block has to be created, it is returned.  */

basic_block
bsi_insert_on_edge_immediate (edge e, tree stmt)
{
  block_stmt_iterator bsi;
  basic_block new_bb = NULL;

  gcc_assert (!PENDING_STMT (e));

  if (tree_find_edge_insert_loc (e, &bsi, &new_bb))
    bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
  else
    bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);

  return new_bb;
}

/*---------------------------------------------------------------------------
             Tree specific functions for CFG manipulation
---------------------------------------------------------------------------*/

/* Reinstall those PHI arguments queued in OLD_EDGE to NEW_EDGE.  */

static void
reinstall_phi_args (edge new_edge, edge old_edge)
{
  tree var, phi;

  if (!PENDING_STMT (old_edge))
    return;
  
  for (var = PENDING_STMT (old_edge), phi = phi_nodes (new_edge->dest);
       var && phi;
       var = TREE_CHAIN (var), phi = PHI_CHAIN (phi))
    {
      tree result = TREE_PURPOSE (var);
      tree arg = TREE_VALUE (var);

      gcc_assert (result == PHI_RESULT (phi));

      add_phi_arg (phi, arg, new_edge);
    }

  PENDING_STMT (old_edge) = NULL;
}

/* Split a (typically critical) edge EDGE_IN.  Return the new block.
   Abort on abnormal edges.  */

static basic_block
tree_split_edge (edge edge_in)
{
  basic_block new_bb, after_bb, dest, src;
  edge new_edge, e;

  /* Abnormal edges cannot be split.  */
  gcc_assert (!(edge_in->flags & EDGE_ABNORMAL));

  src = edge_in->src;
  dest = edge_in->dest;

  /* Place the new block in the block list.  Try to keep the new block
     near its "logical" location.  This is of most help to humans looking
     at debugging dumps.  */
  if (dest->prev_bb && find_edge (dest->prev_bb, dest))
    after_bb = edge_in->src;
  else
    after_bb = dest->prev_bb;

  new_bb = create_empty_bb (after_bb);
  new_bb->frequency = EDGE_FREQUENCY (edge_in);
  new_bb->count = edge_in->count;
  new_edge = make_edge (new_bb, dest, EDGE_FALLTHRU);
  new_edge->probability = REG_BR_PROB_BASE;
  new_edge->count = edge_in->count;

  e = redirect_edge_and_branch (edge_in, new_bb);
  gcc_assert (e);
  reinstall_phi_args (new_edge, e);

  return new_bb;
}


/* Return true when BB has label LABEL in it.  */

static bool
has_label_p (basic_block bb, tree label)
{
  block_stmt_iterator bsi;

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

      if (TREE_CODE (stmt) != LABEL_EXPR)
        return false;
      if (LABEL_EXPR_LABEL (stmt) == label)
        return true;
    }
  return false;
}


/* Callback for walk_tree, check that all elements with address taken are
   properly noticed as such.  The DATA is an int* that is 1 if TP was seen
   inside a PHI node.  */

static tree
verify_expr (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
{
  tree t = *tp, x;
  bool in_phi = (data != NULL);

  if (TYPE_P (t))
    *walk_subtrees = 0;
  
  /* Check operand N for being valid GIMPLE and give error MSG if not. 
     We check for constants explicitly since they are not considered
     gimple invariants if they overflowed.  */
#define CHECK_OP(N, MSG) \
  do { if (!CONSTANT_CLASS_P (TREE_OPERAND (t, N))              \
         && !is_gimple_val (TREE_OPERAND (t, N)))               \
       { error (MSG); return TREE_OPERAND (t, N); }} while (0)

  switch (TREE_CODE (t))
    {
    case SSA_NAME:
      if (SSA_NAME_IN_FREE_LIST (t))
        {
          error ("SSA name in freelist but still referenced");
          return *tp;
        }
      break;

    case ASSERT_EXPR:
      x = fold (ASSERT_EXPR_COND (t));
      if (x == boolean_false_node)
        {
          error ("ASSERT_EXPR with an always-false condition");
          return *tp;
        }
      break;

    case MODIFY_EXPR:
      x = TREE_OPERAND (t, 0);
      if (TREE_CODE (x) == BIT_FIELD_REF
          && is_gimple_reg (TREE_OPERAND (x, 0)))
        {
          error ("GIMPLE register modified with BIT_FIELD_REF");
          return t;
        }
      break;

    case ADDR_EXPR:
      /* ??? tree-ssa-alias.c may have overlooked dead PHI nodes, missing
         dead PHIs that take the address of something.  But if the PHI
         result is dead, the fact that it takes the address of anything
         is irrelevant.  Because we can not tell from here if a PHI result
         is dead, we just skip this check for PHIs altogether.  This means
         we may be missing "valid" checks, but what can you do?
         This was PR19217.  */
      if (in_phi)
        break;

      /* Skip any references (they will be checked when we recurse down the
         tree) and ensure that any variable used as a prefix is marked
         addressable.  */
      for (x = TREE_OPERAND (t, 0);
           handled_component_p (x);
           x = TREE_OPERAND (x, 0))
        ;

      if (TREE_CODE (x) != VAR_DECL && TREE_CODE (x) != PARM_DECL)
        return NULL;
      if (!TREE_ADDRESSABLE (x))
        {
          error ("address taken, but ADDRESSABLE bit not set");
          return x;
        }
      break;

    case COND_EXPR:
      x = COND_EXPR_COND (t);
      if (TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE)
        {
          error ("non-boolean used in condition");
          return x;
        }
      break;

    case NOP_EXPR:
    case CONVERT_EXPR:
    case FIX_TRUNC_EXPR:
    case FIX_CEIL_EXPR:
    case FIX_FLOOR_EXPR:
    case FIX_ROUND_EXPR:
    case FLOAT_EXPR:
    case NEGATE_EXPR:
    case ABS_EXPR:
    case BIT_NOT_EXPR:
    case NON_LVALUE_EXPR:
    case TRUTH_NOT_EXPR:
      CHECK_OP (0, "Invalid operand to unary operator");
      break;

    case REALPART_EXPR:
    case IMAGPART_EXPR:
    case COMPONENT_REF:
    case ARRAY_REF:
    case ARRAY_RANGE_REF:
    case BIT_FIELD_REF:
    case VIEW_CONVERT_EXPR:
      /* We have a nest of references.  Verify that each of the operands
         that determine where to reference is either a constant or a variable,
         verify that the base is valid, and then show we've already checked
         the subtrees.  */
      while (handled_component_p (t))
        {
          if (TREE_CODE (t) == COMPONENT_REF && TREE_OPERAND (t, 2))
            CHECK_OP (2, "Invalid COMPONENT_REF offset operator");
          else if (TREE_CODE (t) == ARRAY_REF
                   || TREE_CODE (t) == ARRAY_RANGE_REF)
            {
              CHECK_OP (1, "Invalid array index.");
              if (TREE_OPERAND (t, 2))
                CHECK_OP (2, "Invalid array lower bound.");
              if (TREE_OPERAND (t, 3))
                CHECK_OP (3, "Invalid array stride.");
            }
          else if (TREE_CODE (t) == BIT_FIELD_REF)
            {
              CHECK_OP (1, "Invalid operand to BIT_FIELD_REF");
              CHECK_OP (2, "Invalid operand to BIT_FIELD_REF");
            }

          t = TREE_OPERAND (t, 0);
        }

      if (!CONSTANT_CLASS_P (t) && !is_gimple_lvalue (t))
        {
          error ("Invalid reference prefix.");
          return t;
        }
      *walk_subtrees = 0;
      break;

    case LT_EXPR:
    case LE_EXPR:
    case GT_EXPR:
    case GE_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
    case UNORDERED_EXPR:
    case ORDERED_EXPR:
    case UNLT_EXPR:
    case UNLE_EXPR:
    case UNGT_EXPR:
    case UNGE_EXPR:
    case UNEQ_EXPR:
    case LTGT_EXPR:
    case PLUS_EXPR:
    case MINUS_EXPR:
    case MULT_EXPR:
    case TRUNC_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case TRUNC_MOD_EXPR:
    case CEIL_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case ROUND_MOD_EXPR:
    case RDIV_EXPR:
    case EXACT_DIV_EXPR:
    case MIN_EXPR:
    case MAX_EXPR:
    case LSHIFT_EXPR:
    case RSHIFT_EXPR:
    case LROTATE_EXPR:
    case RROTATE_EXPR:
    case BIT_IOR_EXPR:
    case BIT_XOR_EXPR:
    case BIT_AND_EXPR:
      CHECK_OP (0, "Invalid operand to binary operator");
      CHECK_OP (1, "Invalid operand to binary operator");
      break;

    default:
      break;
    }
  return NULL;

#undef CHECK_OP
}


/* Verify STMT, return true if STMT is not in GIMPLE form.
   TODO: Implement type checking.  */

static bool
verify_stmt (tree stmt, bool last_in_block)
{
  tree addr;

  if (!is_gimple_stmt (stmt))
    {
      error ("Is not a valid GIMPLE statement.");
      goto fail;
    }

  addr = walk_tree (&stmt, verify_expr, NULL, NULL);
  if (addr)
    {
      debug_generic_stmt (addr);
      return true;
    }

  /* If the statement is marked as part of an EH region, then it is
     expected that the statement could throw.  Verify that when we
     have optimizations that simplify statements such that we prove
     that they cannot throw, that we update other data structures
     to match.  */
  if (lookup_stmt_eh_region (stmt) >= 0)
    {
      if (!tree_could_throw_p (stmt))
        {
          error ("Statement marked for throw, but doesn%'t.");
          goto fail;
        }
      if (!last_in_block && tree_can_throw_internal (stmt))
        {
          error ("Statement marked for throw in middle of block.");
          goto fail;
        }
    }

  return false;

 fail:
  debug_generic_stmt (stmt);
  return true;
}


/* Return true when the T can be shared.  */

static bool
tree_node_can_be_shared (tree t)
{
  if (IS_TYPE_OR_DECL_P (t)
      /* We check for constants explicitly since they are not considered
         gimple invariants if they overflowed.  */
      || CONSTANT_CLASS_P (t)
      || is_gimple_min_invariant (t)
      || TREE_CODE (t) == SSA_NAME
      || t == error_mark_node)
    return true;

  if (TREE_CODE (t) == CASE_LABEL_EXPR)
    return true;

  while (((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
          /* We check for constants explicitly since they are not considered
             gimple invariants if they overflowed.  */
          && (CONSTANT_CLASS_P (TREE_OPERAND (t, 1))
              || is_gimple_min_invariant (TREE_OPERAND (t, 1))))
         || (TREE_CODE (t) == COMPONENT_REF
             || TREE_CODE (t) == REALPART_EXPR
             || TREE_CODE (t) == IMAGPART_EXPR))
    t = TREE_OPERAND (t, 0);

  if (DECL_P (t))
    return true;

  return false;
}


/* Called via walk_trees.  Verify tree sharing.  */

static tree
verify_node_sharing (tree * tp, int *walk_subtrees, void *data)
{
  htab_t htab = (htab_t) data;
  void **slot;

  if (tree_node_can_be_shared (*tp))
    {
      *walk_subtrees = false;
      return NULL;
    }

  slot = htab_find_slot (htab, *tp, INSERT);
  if (*slot)
    return *slot;
  *slot = *tp;

  return NULL;
}


/* Verify the GIMPLE statement chain.  */

void
verify_stmts (void)
{
  basic_block bb;
  block_stmt_iterator bsi;
  bool err = false;
  htab_t htab;
  tree addr;

  timevar_push (TV_TREE_STMT_VERIFY);
  htab = htab_create (37, htab_hash_pointer, htab_eq_pointer, NULL);

  FOR_EACH_BB (bb)
    {
      tree phi;
      int i;

      for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
        {
          int phi_num_args = PHI_NUM_ARGS (phi);

          if (bb_for_stmt (phi) != bb)
            {
              error ("bb_for_stmt (phi) is set to a wrong basic block\n");
              err |= true;
            }

          for (i = 0; i < phi_num_args; i++)
            {
              tree t = PHI_ARG_DEF (phi, i);
              tree addr;

              /* Addressable variables do have SSA_NAMEs but they
                 are not considered gimple values.  */
              if (TREE_CODE (t) != SSA_NAME
                  && TREE_CODE (t) != FUNCTION_DECL
                  && !is_gimple_val (t))
                {
                  error ("PHI def is not a GIMPLE value");
                  debug_generic_stmt (phi);