gcc/tree-cfg.c

/* Control flow functions for trees.
   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
   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 3, or (at your option)
any later version.

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

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

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.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 "tree-ssa-propagate.h"
#include "value-prof.h"
#include "pointer-set.h"
#include "tree-inline.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 GIMPLE_SWITCHes.

   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).  */

static struct pointer_map_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 void make_blocks (gimple_seq);
static void factor_computed_gotos (void);

/* Edges.  */
static void make_edges (void);
static void make_cond_expr_edges (basic_block);
static void make_gimple_switch_edges (basic_block);
static void make_goto_expr_edges (basic_block);
static edge gimple_redirect_edge_and_branch (edge, basic_block);
static edge gimple_try_redirect_by_replacing_jump (edge, basic_block);
static unsigned int split_critical_edges (void);

/* Various helpers.  */
static inline bool stmt_starts_bb_p (gimple, gimple);
static int gimple_verify_flow_info (void);
static void gimple_make_forwarder_block (edge);
static void gimple_cfg2vcg (FILE *);

/* Flowgraph optimization and cleanup.  */
static void gimple_merge_blocks (basic_block, basic_block);
static bool gimple_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
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 (gimple, tree);

void
init_empty_tree_cfg_for_function (struct function *fn)
{
  /* Initialize the basic block array.  */
  init_flow (fn);
  profile_status_for_function (fn) = PROFILE_ABSENT;
  n_basic_blocks_for_function (fn) = NUM_FIXED_BLOCKS;
  last_basic_block_for_function (fn) = NUM_FIXED_BLOCKS;
  basic_block_info_for_function (fn)
    = VEC_alloc (basic_block, gc, initial_cfg_capacity);
  VEC_safe_grow_cleared (basic_block, gc,
			 basic_block_info_for_function (fn),
			 initial_cfg_capacity);

  /* Build a mapping of labels to their associated blocks.  */
  label_to_block_map_for_function (fn)
    = VEC_alloc (basic_block, gc, initial_cfg_capacity);
  VEC_safe_grow_cleared (basic_block, gc,
			 label_to_block_map_for_function (fn),
			 initial_cfg_capacity);

  SET_BASIC_BLOCK_FOR_FUNCTION (fn, ENTRY_BLOCK, 
				ENTRY_BLOCK_PTR_FOR_FUNCTION (fn));
  SET_BASIC_BLOCK_FOR_FUNCTION (fn, EXIT_BLOCK, 
		   EXIT_BLOCK_PTR_FOR_FUNCTION (fn));

  ENTRY_BLOCK_PTR_FOR_FUNCTION (fn)->next_bb
    = EXIT_BLOCK_PTR_FOR_FUNCTION (fn);
  EXIT_BLOCK_PTR_FOR_FUNCTION (fn)->prev_bb
    = ENTRY_BLOCK_PTR_FOR_FUNCTION (fn);
}

void
init_empty_tree_cfg (void)
{
  init_empty_tree_cfg_for_function (cfun);
}

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

/* Entry point to the CFG builder for trees.  SEQ is the sequence of
   statements to be added to the flowgraph.  */

static void
build_gimple_cfg (gimple_seq seq)
{
  /* Register specific gimple functions.  */
  gimple_register_cfg_hooks ();

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

  init_empty_tree_cfg ();

  found_computed_goto = 0;
  make_blocks (seq);

  /* 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 == NUM_FIXED_BLOCKS)
    create_empty_bb (ENTRY_BLOCK_PTR);

  /* Adjust the size of the array.  */
  if (VEC_length (basic_block, basic_block_info) < (size_t) n_basic_blocks)
    VEC_safe_grow_cleared (basic_block, gc, 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 ();
  cleanup_dead_labels ();

  /* Debugging dumps.  */

  /* Write the flowgraph to a VCG file.  */
  {
    int local_dump_flags;
    FILE *vcg_file = dump_begin (TDI_vcg, &local_dump_flags);
    if (vcg_file)
      {
	gimple_cfg2vcg (vcg_file);
	dump_end (TDI_vcg, vcg_file);
      }
  }

#ifdef ENABLE_CHECKING
  verify_stmts ();
#endif
}

static unsigned int
execute_build_cfg (void)
{
  gimple_seq body = gimple_body (current_function_decl);

  build_gimple_cfg (body);
  gimple_set_body (current_function_decl, NULL);
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Scope blocks:\n");
      dump_scope_blocks (dump_file, dump_flags);
    }
  return 0;
}

struct gimple_opt_pass pass_build_cfg =
{
 {
  GIMPLE_PASS,
  "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_cleanup_cfg
  | TODO_dump_func			/* todo_flags_finish */
 }
};


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

static bool
computed_goto_p (gimple t)
{
  return (gimple_code (t) == GIMPLE_GOTO
	  && TREE_CODE (gimple_goto_dest (t)) != LABEL_DECL);
}


/* 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;
  gimple factored_computed_goto_label = NULL;
  gimple 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)
    {
      gimple_stmt_iterator gsi = gsi_last_bb (bb);
      gimple last;

      if (gsi_end_p (gsi))
	continue;

      last = gsi_stmt (gsi);

      /* 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))
	{
	  gimple 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);
	      gimple_stmt_iterator new_gsi = gsi_start_bb (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
		= gimple_build_label (factored_label_decl);
	      gsi_insert_after (&new_gsi, factored_computed_goto_label,
				GSI_NEW_STMT);

	      /* Build our new computed goto.  */
	      factored_computed_goto = gimple_build_goto (var);
	      gsi_insert_after (&new_gsi, factored_computed_goto, GSI_NEW_STMT);
	    }

	  /* Copy the original computed goto's destination into VAR.  */
	  assignment = gimple_build_assign (var, gimple_goto_dest (last));
	  gsi_insert_before (&gsi, assignment, GSI_SAME_STMT);

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


/* Build a flowgraph for the sequence of stmts SEQ.  */

static void
make_blocks (gimple_seq seq)
{
  gimple_stmt_iterator i = gsi_start (seq);
  gimple stmt = NULL;
  bool start_new_block = true;
  bool first_stmt_of_seq = true;
  basic_block bb = ENTRY_BLOCK_PTR;

  while (!gsi_end_p (i))
    {
      gimple prev_stmt;

      prev_stmt = stmt;
      stmt = gsi_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_seq)
	    seq = gsi_split_seq_before (&i);
	  bb = create_basic_block (seq, NULL, bb);
	  start_new_block = false;
	}

      /* Now add STMT to BB and create the subgraphs for special statement
	 codes.  */
      gimple_set_bb (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;

      gsi_next (&i);
      first_stmt_of_seq = 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->il.gimple = GGC_CNEW (struct gimple_bb_info);
  set_bb_seq (bb, h ? (gimple_seq) h : gimple_seq_alloc ());

  /* 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 == VEC_length (basic_block, basic_block_info))
    {
      size_t new_size = last_basic_block + (last_basic_block + 3) / 4;
      VEC_safe_grow_cleared (basic_block, gc, basic_block_info, new_size);
    }

  /* Add the newly created block to the array.  */
  SET_BASIC_BLOCK (last_basic_block, bb);

  n_basic_blocks++;
  last_basic_block++;

  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)
    {
      gimple stmt = last_stmt (bb);

      if (stmt && gimple_code (stmt) == GIMPLE_COND)
	{
	  tree cond;
	  bool zerop, onep;

	  fold_defer_overflow_warnings ();
	  cond = fold_binary (gimple_cond_code (stmt), boolean_type_node,
			      gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
	  if (cond)
	    {
	      zerop = integer_zerop (cond);
	      onep = integer_onep (cond);
	    }
	  else
	    zerop = onep = false;

	  fold_undefer_overflow_warnings (zerop || onep,
					  stmt,
					  WARN_STRICT_OVERFLOW_CONDITIONAL);
	  if (zerop)
	    gimple_cond_make_false (stmt);
	  else if (onep)
	    gimple_cond_make_true (stmt);
	}
    }
}

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

static void
make_edges (void)
{
  basic_block bb;
  struct omp_region *cur_region = NULL;

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

  /* Traverse the basic block array placing edges.  */
  FOR_EACH_BB (bb)
    {
      gimple last = last_stmt (bb);
      bool fallthru;

      if (last)
	{
	  enum gimple_code code = gimple_code (last);
	  switch (code)
	    {
	    case GIMPLE_GOTO:
	      make_goto_expr_edges (bb);
	      fallthru = false;
	      break;
	    case GIMPLE_RETURN:
	      make_edge (bb, EXIT_BLOCK_PTR, 0);
	      fallthru = false;
	      break;
	    case GIMPLE_COND:
	      make_cond_expr_edges (bb);
	      fallthru = false;
	      break;
	    case GIMPLE_SWITCH:
	      make_gimple_switch_edges (bb);
	      fallthru = false;
	      break;
	    case GIMPLE_RESX:
	      make_eh_edges (last);
	      fallthru = false;
	      break;

	    case GIMPLE_CALL:
	      /* If this function receives a nonlocal goto, then we need to
		 make edges from this call site to all the nonlocal goto
		 handlers.  */
	      if (stmt_can_make_abnormal_goto (last))
		make_abnormal_goto_edges (bb, true);

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

	      /* Some calls are known not to return.  */
	      fallthru = !(gimple_call_flags (last) & ECF_NORETURN);
	      break;

	    case GIMPLE_ASSIGN:
	       /* A GIMPLE_ASSIGN may throw internally and thus be considered
		  control-altering. */
	      if (is_ctrl_altering_stmt (last))
		{
		  make_eh_edges (last);
		}
	      fallthru = true;
	      break;

	    case GIMPLE_OMP_PARALLEL:
	    case GIMPLE_OMP_TASK:
	    case GIMPLE_OMP_FOR:
	    case GIMPLE_OMP_SINGLE:
	    case GIMPLE_OMP_MASTER:
	    case GIMPLE_OMP_ORDERED:
	    case GIMPLE_OMP_CRITICAL:
	    case GIMPLE_OMP_SECTION:
	      cur_region = new_omp_region (bb, code, cur_region);
	      fallthru = true;
	      break;

	    case GIMPLE_OMP_SECTIONS:
	      cur_region = new_omp_region (bb, code, cur_region);
	      fallthru = true;
	      break;

	    case GIMPLE_OMP_SECTIONS_SWITCH:
	      fallthru = false;
	      break;


            case GIMPLE_OMP_ATOMIC_LOAD:
            case GIMPLE_OMP_ATOMIC_STORE:
               fallthru = true;
               break;


	    case GIMPLE_OMP_RETURN:
	      /* In the case of a GIMPLE_OMP_SECTION, the edge will go
		 somewhere other than the next block.  This will be
		 created later.  */
	      cur_region->exit = bb;
	      fallthru = cur_region->type != GIMPLE_OMP_SECTION;
	      cur_region = cur_region->outer;
	      break;

	    case GIMPLE_OMP_CONTINUE:
	      cur_region->cont = bb;
	      switch (cur_region->type)
		{
		case GIMPLE_OMP_FOR:
		  /* Mark all GIMPLE_OMP_FOR and GIMPLE_OMP_CONTINUE
		     succs edges as abnormal to prevent splitting
		     them.  */
		  single_succ_edge (cur_region->entry)->flags |= EDGE_ABNORMAL;
		  /* Make the loopback edge.  */
		  make_edge (bb, single_succ (cur_region->entry),
			     EDGE_ABNORMAL);

		  /* Create an edge from GIMPLE_OMP_FOR to exit, which
		     corresponds to the case that the body of the loop
		     is not executed at all.  */
		  make_edge (cur_region->entry, bb->next_bb, EDGE_ABNORMAL);
		  make_edge (bb, bb->next_bb, EDGE_FALLTHRU | EDGE_ABNORMAL);
		  fallthru = false;
		  break;

		case GIMPLE_OMP_SECTIONS:
		  /* Wire up the edges into and out of the nested sections.  */
		  {
		    basic_block switch_bb = single_succ (cur_region->entry);

		    struct omp_region *i;
		    for (i = cur_region->inner; i ; i = i->next)
		      {
			gcc_assert (i->type == GIMPLE_OMP_SECTION);
			make_edge (switch_bb, i->entry, 0);
			make_edge (i->exit, bb, EDGE_FALLTHRU);
		      }

		    /* Make the loopback edge to the block with
		       GIMPLE_OMP_SECTIONS_SWITCH.  */
		    make_edge (bb, switch_bb, 0);

		    /* Make the edge from the switch to exit.  */
		    make_edge (switch_bb, bb->next_bb, 0);
		    fallthru = false;
		  }
		  break;

		default:
		  gcc_unreachable ();
		}
	      break;

	    default:
	      gcc_assert (!stmt_ends_bb_p (last));
	      fallthru = true;
	    }
	}
      else
	fallthru = true;

      if (fallthru)
	make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
    }

  if (root_omp_region)
    free_omp_regions ();

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


/* Create the edges for a GIMPLE_COND starting at block BB.  */

static void
make_cond_expr_edges (basic_block bb)
{
  gimple entry = last_stmt (bb);
  gimple then_stmt, else_stmt;
  basic_block then_bb, else_bb;
  tree then_label, else_label;
  edge e;

  gcc_assert (entry);
  gcc_assert (gimple_code (entry) == GIMPLE_COND);

  /* Entry basic blocks for each component.  */
  then_label = gimple_cond_true_label (entry);
  else_label = gimple_cond_false_label (entry);
  then_bb = label_to_block (then_label);
  else_bb = label_to_block (else_label);
  then_stmt = first_stmt (then_bb);
  else_stmt = first_stmt (else_bb);

  e = make_edge (bb, then_bb, EDGE_TRUE_VALUE);
  e->goto_locus = gimple_location (then_stmt);
  if (e->goto_locus)
    e->goto_block = gimple_block (then_stmt);
  e = make_edge (bb, else_bb, EDGE_FALSE_VALUE);
  if (e)
    {
      e->goto_locus = gimple_location (else_stmt);
      if (e->goto_locus)
	e->goto_block = gimple_block (else_stmt);
    }

  /* We do not need the labels anymore.  */
  gimple_cond_set_true_label (entry, NULL_TREE);
  gimple_cond_set_false_label (entry, NULL_TREE);
}


/* 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 bool
edge_to_cases_cleanup (const void *key ATTRIBUTE_UNUSED, void **value,
		       void *data ATTRIBUTE_UNUSED)
{
  tree t, next;

  for (t = (tree) *value; t; t = next)
    {
      next = TREE_CHAIN (t);
      TREE_CHAIN (t) = NULL;
    }

  *value = NULL;
  return false;
}

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

void
start_recording_case_labels (void)
{
  gcc_assert (edge_to_cases == NULL);
  edge_to_cases = pointer_map_create ();
}

/* 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.  */
void
end_recording_case_labels (void)
{
  pointer_map_traverse (edge_to_cases, edge_to_cases_cleanup, NULL);
  pointer_map_destroy (edge_to_cases);
  edge_to_cases = NULL;
}

/* 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, gimple t)
{
  void **slot;
  size_t i, n;

  /* 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;

  slot = pointer_map_contains (edge_to_cases, e);
  if (slot)
    return (tree) *slot;

  /* 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.  */

  n = gimple_switch_num_labels (t);
  for (i = 0; i < n; i++)
    {
      tree elt = gimple_switch_label (t, i);
      tree lab = CASE_LABEL (elt);
      basic_block label_bb = label_to_block (lab);
      edge this_edge = find_edge (e->src, label_bb);

      /* Add it to the chain of CASE_LABEL_EXPRs referencing E, or create
	 a new chain.  */
      slot = pointer_map_insert (edge_to_cases, this_edge);
      TREE_CHAIN (elt) = (tree) *slot;
      *slot = elt;
    }

  return (tree) *pointer_map_contains (edge_to_cases, e);
}

/* Create the edges for a GIMPLE_SWITCH starting at block BB.  */

static void
make_gimple_switch_edges (basic_block bb)
{
  gimple entry = last_stmt (bb);
  size_t i, n;

  n = gimple_switch_num_labels (entry);

  for (i = 0; i < n; ++i)
    {
      tree lab = CASE_LABEL (gimple_switch_label (entry, 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)
    {
      gimple_stmt_iterator gsi = gsi_start_bb (BASIC_BLOCK (NUM_FIXED_BLOCKS));
      gimple stmt;

      stmt = gimple_build_label (dest);
      gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
      uid = LABEL_DECL_UID (dest);
    }
  if (VEC_length (basic_block, ifun->cfg->x_label_to_block_map)
      <= (unsigned int) uid)
    return NULL;
  return VEC_index (basic_block, ifun->cfg->x_label_to_block_map, uid);
}

/* Create edges for an abnormal goto statement at block BB.  If FOR_CALL
   is true, the source statement is a CALL_EXPR instead of a GOTO_EXPR.  */

void
make_abnormal_goto_edges (basic_block bb, bool for_call)
{
  basic_block target_bb;
  gimple_stmt_iterator gsi;

  FOR_EACH_BB (target_bb)
    for (gsi = gsi_start_bb (target_bb); !gsi_end_p (gsi); gsi_next (&gsi))
      {
	gimple label_stmt = gsi_stmt (gsi);
	tree target;

	if (gimple_code (label_stmt) != GIMPLE_LABEL)
	  break;

	target = gimple_label_label (label_stmt);

	/* Make an edge to every label block that has been marked as a
	   potential target for a computed goto or a non-local goto.  */
	if ((FORCED_LABEL (target) && !for_call)
	    || (DECL_NONLOCAL (target) && for_call))
	  {
	    make_edge (bb, target_bb, EDGE_ABNORMAL);
	    break;
	  }
      }
}

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

static void
make_goto_expr_edges (basic_block bb)
{
  gimple_stmt_iterator last = gsi_last_bb (bb);
  gimple goto_t = gsi_stmt (last);

  /* A simple GOTO creates normal edges.  */
  if (simple_goto_p (goto_t))
    {
      tree dest = gimple_goto_dest (goto_t);
      edge e = make_edge (bb, label_to_block (dest), EDGE_FALLTHRU);
      e->goto_locus = gimple_location (goto_t);
      if (e->goto_locus)
	e->goto_block = gimple_block (goto_t);
      gsi_remove (&last, true);
      return;
    }

  /* A computed GOTO creates abnormal edges.  */
  make_abnormal_goto_edges (bb, false);
}


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

/* 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 rerun this pass after CFG is created, to get rid of the labels that
   are no longer referenced.  After then we do not run it any more, since
   (almost) no new labels should be created.  */

/* A map from basic block index to the leading label of that block.  */
static struct label_record
{
  /* The label.  */
  tree label;

  /* True if the label is referenced from somewhere.  */
  bool used;
} *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].label;
      label_for_bb[bb->index].used = true;
      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);
  tree main_label = label_for_bb[bb->index].label;

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

  label_for_bb[bb->index].used = true;
  return main_label;
}

/* 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 = XCNEWVEC (struct label_record, last_basic_block);

  /* 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)
    {
      gimple_stmt_iterator i;

      for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
	{
	  tree label;
	  gimple stmt = gsi_stmt (i);

	  if (gimple_code (stmt) != GIMPLE_LABEL)
	    break;

	  label = gimple_label_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)
	    {
	      label_for_bb[bb->index].label = 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))
	    {
	      label_for_bb[bb->index].label = 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)
    {
      gimple stmt = last_stmt (bb);
      if (!stmt)
	continue;

      switch (gimple_code (stmt))
	{
	case GIMPLE_COND:
	  {
	    tree true_label = gimple_cond_true_label (stmt);
	    tree false_label = gimple_cond_false_label (stmt);

	    if (true_label)
	      gimple_cond_set_true_label (stmt, main_block_label (true_label));
	    if (false_label)
	      gimple_cond_set_false_label (stmt, main_block_label (false_label));
	    break;
	  }

	case GIMPLE_SWITCH:
	  {
	    size_t i, n = gimple_switch_num_labels (stmt);

	    /* Replace all destination labels.  */
	    for (i = 0; i < n; ++i)
	      {
		tree case_label = gimple_switch_label (stmt, i);
		tree label = main_block_label (CASE_LABEL (case_label));
		CASE_LABEL (case_label) = label;
	      }
	    break;
	  }

	/* We have to handle gotos until they're removed, and we don't
	   remove them until after we've created the CFG edges.  */
	case GIMPLE_GOTO:
          if (!computed_goto_p (stmt))
	    {
	      tree new_dest = main_block_label (gimple_goto_dest (stmt));
	      gimple_goto_set_dest (stmt, new_dest);
	      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 and labels which have their
     address taken are preserved.  */
  FOR_EACH_BB (bb)
    {
      gimple_stmt_iterator i;
      tree label_for_this_bb = label_for_bb[bb->index].label;

      if (!label_for_this_bb)
	continue;

      /* If the main label of the block is unused, we may still remove it.  */
      if (!label_for_bb[bb->index].used)
	label_for_this_bb = NULL;

      for (i = gsi_start_bb (bb); !gsi_end_p (i); )
	{
	  tree label;
	  gimple stmt = gsi_stmt (i);

	  if (gimple_code (stmt) != GIMPLE_LABEL)
	    break;

	  label = gimple_label_label (stmt);

	  if (label == label_for_this_bb
	      || !DECL_ARTIFICIAL (label)
	      || DECL_NONLOCAL (label)
	      || FORCED_LABEL (label))
	    gsi_next (&i);
	  else
	    gsi_remove (&i, true);
	}
    }

  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)
    {
      gimple stmt = last_stmt (bb);
      if (stmt && gimple_code (stmt) == GIMPLE_SWITCH)
	{
	  int old_size = gimple_switch_num_labels (stmt);
	  int i, j, new_size = old_size;
	  tree default_case = NULL_TREE;
	  tree default_label = NULL_TREE;
	  bool has_default;

	  /* The default label is always the first case in a switch
	     statement after gimplification if it was not optimized
	     away */
	  if (!CASE_LOW (gimple_switch_default_label (stmt))
	      && !CASE_HIGH (gimple_switch_default_label (stmt)))
	    {
	      default_case = gimple_switch_default_label (stmt);
	      default_label = CASE_LABEL (default_case);
	      has_default = true;
	    }
	  else
	    has_default = false;

	  /* Look for possible opportunities to merge cases.  */
	  if (has_default)
	    i = 1;
	  else
	    i = 0;
	  while (i < old_size)
	    {
	      tree base_case, base_label, base_high;
	      base_case = gimple_switch_label (stmt, 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)
		{
		  gimple_switch_set_label (stmt, 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)
		{
		  tree merge_case = gimple_switch_label (stmt, 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;
		      gimple_switch_set_label (stmt, 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 (! gimple_switch_label (stmt, j))
		j++;
	      gimple_switch_set_label (stmt, i,
				       gimple_switch_label (stmt, j++));
	    }

	  gcc_assert (new_size <= old_size);
	  gimple_switch_set_num_labels (stmt, new_size);
	}
    }
}

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

static bool
gimple_can_merge_blocks_p (basic_block a, basic_block b)
{
  gimple stmt;
  gimple_stmt_iterator gsi;
  gimple_seq phis;

  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
      && gimple_code (stmt) == GIMPLE_LABEL
      && DECL_NONLOCAL (gimple_label_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; however, if only
     some symbols as whole are marked for renaming, this is not a problem,
     as phi nodes for those symbols are irrelevant in updating anyway.  */
  phis = phi_nodes (b);
  if (!gimple_seq_empty_p (phis))
    {
      gimple_stmt_iterator i;

      if (name_mappings_registered_p ())
	return false;

      for (i = gsi_start (phis); !gsi_end_p (i); gsi_next (&i))
	{
	  gimple phi = gsi_stmt (i);

	  if (!is_gimple_reg (gimple_phi_result (phi))
	      && !may_propagate_copy (gimple_phi_result (phi),
				      gimple_phi_arg_def (phi, 0)))
	    return false;
	}
    }

  /* Do not remove user labels.  */
  for (gsi = gsi_start_bb (b); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      stmt = gsi_stmt (gsi);
      if (gimple_code (stmt) != GIMPLE_LABEL)
	break;
      if (!DECL_ARTIFICIAL (gimple_label_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;
  gimple stmt;
  edge e;

  FOR_EACH_IMM_USE_STMT (stmt, imm_iter, name)
    {
      if (gimple_code (stmt) != GIMPLE_PHI)
	push_stmt_changes (&stmt);

      FOR_EACH_IMM_USE_ON_STMT (use, imm_iter)
        {
	  replace_exp (use, val);

	  if (gimple_code (stmt) == GIMPLE_PHI)
	    {
	      e = gimple_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;
		}
	    }
	}

      if (gimple_code (stmt) != GIMPLE_PHI)
	{
	  size_t i;

	  fold_stmt_inplace (stmt);
	  if (cfgcleanup_altered_bbs)
	    bitmap_set_bit (cfgcleanup_altered_bbs, gimple_bb (stmt)->index);

	  /* FIXME.  This should go in pop_stmt_changes.  */
	  for (i = 0; i < gimple_num_ops (stmt); i++)
	    {
	      tree op = gimple_op (stmt, i);
              /* Operands may be empty here.  For example, the labels
                 of a GIMPLE_COND are nulled out following the creation
                 of the corresponding CFG edges.  */
	      if (op && TREE_CODE (op) == ADDR_EXPR)
		recompute_tree_invariant_for_addr_expr (op);
	    }

	  maybe_clean_or_replace_eh_stmt (stmt, stmt);

	  pop_stmt_changes (&stmt);
	}
    }

  gcc_assert (has_zero_uses (name));

  /* Also update the trees stored in loop structures.  */
  if (current_loops)
    {
      struct loop *loop;
      loop_iterator li;

      FOR_EACH_LOOP (li, loop, 0)
	{
	  substitute_in_loop_info (loop, name, val);
	}
    }
}

/* Merge block B into block A.  */

static void
gimple_merge_blocks (basic_block a, basic_block b)
{
  gimple_stmt_iterator last, gsi, psi;
  gimple_seq phis = phi_nodes (b);

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

  /* Remove all single-valued PHI nodes from block B of the form
     V_i = PHI <V_j> by propagating V_j to all the uses of V_i.  */
  gsi = gsi_last_bb (a);
  for (psi = gsi_start (phis); !gsi_end_p (psi); )
    {
      gimple phi = gsi_stmt (psi);
      tree def = gimple_phi_result (phi), use = gimple_phi_arg_def (phi, 0);
      gimple copy;
      bool may_replace_uses = !is_gimple_reg (def)
			      || may_propagate_copy (def, use);

      /* In case we maintain loop closed ssa form, do not propagate arguments
	 of loop exit phi nodes.  */
      if (current_loops
	  && loops_state_satisfies_p (LOOP_CLOSED_SSA)
	  && is_gimple_reg (def)
	  && TREE_CODE (use) == SSA_NAME
	  && a->loop_father != b->loop_father)
	may_replace_uses = false;

      if (!may_replace_uses)
	{
	  gcc_assert (is_gimple_reg (def));

	  /* Note that just emitting 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 = gimple_build_assign (def, use);
	  gsi_insert_after (&gsi, copy, GSI_NEW_STMT);
          remove_phi_node (&psi, false);
	}
      else
        {
	  /* If we deal with a PHI for virtual operands, we can simply
	     propagate these without fussing with folding or updating
	     the stmt.  */
	  if (!is_gimple_reg (def))
	    {
	      imm_use_iterator iter;
	      use_operand_p use_p;
	      gimple stmt;

	      FOR_EACH_IMM_USE_STMT (stmt, iter, def)
		FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
		  SET_USE (use_p, use);
	    }
	  else
            replace_uses_by (def, use);

          remove_phi_node (&psi, true);
        }
    }

  /* 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 gimple_bb to A for other statements.  */
  for (gsi = gsi_start_bb (b); !gsi_end_p (gsi);)
    {
      if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
	{
	  gimple label = gsi_stmt (gsi);

	  gsi_remove (&gsi, false);

	  /* 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 (gimple_label_label (label)))
	    {
	      gimple_stmt_iterator dest_gsi = gsi_start_bb (a);
	      gsi_insert_before (&dest_gsi, label, GSI_NEW_STMT);
	    }
	}
      else
	{
	  gimple_set_bb (gsi_stmt (gsi), a);
	  gsi_next (&gsi);
	}
    }

  /* Merge the sequences.  */
  last = gsi_last_bb (a);
  gsi_insert_seq_after (&last, bb_seq (b), GSI_NEW_STMT);
  set_bb_seq (b, NULL);

  if (cfgcleanup_altered_bbs)
    bitmap_set_bit (cfgcleanup_altered_bbs, a->index);
}


/* Return the one of two successors of BB that is not reachable by a
   reached by a complex edge, if there is one.  Else, return BB.  We use
   this in optimizations that use post-dominators for their heuristics,
   to catch the cases in C++ where function calls are involved.  */

basic_block
single_noncomplex_succ (basic_block bb)
{
  edge e0, e1;
  if (EDGE_COUNT (bb->succs) != 2)
    return bb;

  e0 = EDGE_SUCC (bb, 0);
  e1 = EDGE_SUCC (bb, 1);
  if (e0->flags & EDGE_COMPLEX)
    return e1->dest;
  if (e1->flags & EDGE_COMPLEX)
    return e0->dest;

  return bb;
}


/* 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

     * GOTO_EXPRs immediately preceding destination 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
{
  bool repeat;
  bool may_throw;
  bool may_branch;
  bool has_label;
  bool last_was_goto;
  gimple_stmt_iterator last_goto_gsi;
};


static void remove_useless_stmts_1 (gimple_stmt_iterator *gsi, struct rus_data *);

/* Given a statement sequence, find the first executable statement with
   location information, and warn that it is unreachable.  When searching,
   descend into containers in execution order.  */

static bool
remove_useless_stmts_warn_notreached (gimple_seq stmts)
{
  gimple_stmt_iterator gsi;

  for (gsi = gsi_start (stmts); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      gimple stmt = gsi_stmt (gsi);

      if (gimple_has_location (stmt))
        {
          location_t loc = gimple_location (stmt);
          if (LOCATION_LINE (loc) > 0)
	    {
              warning (OPT_Wunreachable_code, "%Hwill never be executed", &loc);
              return true;
            }
        }

      switch (gimple_code (stmt))
        {
        /* Unfortunately, we need the CFG now to detect unreachable
           branches in a conditional, so conditionals are not handled here.  */

        case GIMPLE_TRY:
          if (remove_useless_stmts_warn_notreached (gimple_try_eval (stmt)))
            return true;
          if (remove_useless_stmts_warn_notreached (gimple_try_cleanup (stmt)))
            return true;
          break;

        case GIMPLE_CATCH:
          return remove_useless_stmts_warn_notreached (gimple_catch_handler (stmt));

        case GIMPLE_EH_FILTER:
          return remove_useless_stmts_warn_notreached (gimple_eh_filter_failure (stmt));

        case GIMPLE_BIND:
          return remove_useless_stmts_warn_notreached (gimple_bind_body (stmt));

        default:
          break;
        }
    }

  return false;
}

/* Helper for remove_useless_stmts_1.  Handle GIMPLE_COND statements.  */

static void
remove_useless_stmts_cond (gimple_stmt_iterator *gsi, struct rus_data *data)
{
  gimple stmt = gsi_stmt (*gsi);

  /* The folded result must still be a conditional statement.  */
  fold_stmt_inplace (stmt);

  data->may_branch = true;

  /* Replace trivial conditionals with gotos. */
  if (gimple_cond_true_p (stmt))
    {
      /* Goto THEN label.  */
      tree then_label = gimple_cond_true_label (stmt);

      gsi_replace (gsi, gimple_build_goto (then_label), false);
      data->last_goto_gsi = *gsi;
      data->last_was_goto = true;
      data->repeat = true;
    }
  else if (gimple_cond_false_p (stmt))
    {
      /* Goto ELSE label.  */
      tree else_label = gimple_cond_false_label (stmt);

      gsi_replace (gsi, gimple_build_goto (else_label), false);
      data->last_goto_gsi = *gsi;
      data->last_was_goto = true;
      data->repeat = true;
    }
  else
    {
      tree then_label = gimple_cond_true_label (stmt);
      tree else_label = gimple_cond_false_label (stmt);

      if (then_label == else_label)
        {
          /* Goto common destination.  */
          gsi_replace (gsi, gimple_build_goto (then_label), false);
          data->last_goto_gsi = *gsi;
          data->last_was_goto = true;
	  data->repeat = true;
	}
    }

  gsi_next (gsi);

  data->last_was_goto = false;
}

/* Helper for remove_useless_stmts_1. 
   Handle the try-finally case for GIMPLE_TRY statements.  */

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

  gimple_seq eval_seq, cleanup_seq;
  gimple_stmt_iterator eval_gsi, cleanup_gsi;

  gimple stmt = gsi_stmt (*gsi);

  /* 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_was_goto = false;

  eval_seq = gimple_try_eval (stmt);
  eval_gsi = gsi_start (eval_seq);
  remove_useless_stmts_1 (&eval_gsi, 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_was_goto = false;

  cleanup_seq = gimple_try_cleanup (stmt);
  cleanup_gsi = gsi_start (cleanup_seq);
  remove_useless_stmts_1 (&cleanup_gsi, data);

  /* If the body is empty, then we can emit the FINALLY block without
     the enclosing TRY_FINALLY_EXPR.  */
  if (gimple_seq_empty_p (eval_seq))
    {
      gsi_insert_seq_before (gsi, cleanup_seq, GSI_SAME_STMT);
      gsi_remove (gsi, false);
      data->repeat = true;
    }

  /* If the handler is empty, then we can emit the TRY block without
     the enclosing TRY_FINALLY_EXPR.  */
  else if (gimple_seq_empty_p (cleanup_seq))
    {
      gsi_insert_seq_before (gsi, eval_seq, GSI_SAME_STMT);
      gsi_remove (gsi, false);
      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)
    {
      gsi_insert_seq_before (gsi, eval_seq, GSI_SAME_STMT);
      gsi_insert_seq_before (gsi, cleanup_seq, GSI_SAME_STMT);
      gsi_remove (gsi, false);
      data->repeat = true;
    }
  else
    gsi_next (gsi);
}

/* Helper for remove_useless_stmts_1. 
   Handle the try-catch case for GIMPLE_TRY statements.  */

static void
remove_useless_stmts_tc (gimple_stmt_iterator *gsi, struct rus_data *data)
{
  bool save_may_throw, this_may_throw;

  gimple_seq eval_seq, cleanup_seq, handler_seq, failure_seq;
  gimple_stmt_iterator eval_gsi, cleanup_gsi, handler_gsi, failure_gsi;

  gimple stmt = gsi_stmt (*gsi);

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

  eval_seq = gimple_try_eval (stmt);
  eval_gsi = gsi_start (eval_seq);
  remove_useless_stmts_1 (&eval_gsi, data);

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

  cleanup_seq = gimple_try_cleanup (stmt);

  /* 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 (cleanup_seq);
        }
      gsi_insert_seq_before (gsi, eval_seq, GSI_SAME_STMT);
      gsi_remove (gsi, false);
      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;
  cleanup_gsi = gsi_start (cleanup_seq);
  stmt = gsi_stmt (cleanup_gsi);
  data->last_was_goto = false;

  switch (gimple_code (stmt))
    {
    case GIMPLE_CATCH:
      /* If the first element is a catch, they all must be.  */
      while (!gsi_end_p (cleanup_gsi))
        {
	  stmt = gsi_stmt (cleanup_gsi);
	  /* If we catch all exceptions, then the body does not
	     propagate exceptions past this point.  */
	  if (gimple_catch_types (stmt) == NULL)
	    this_may_throw = false;
	  data->last_was_goto = false;
          handler_seq = gimple_catch_handler (stmt);
          handler_gsi = gsi_start (handler_seq);
	  remove_useless_stmts_1 (&handler_gsi, data);
          gsi_next (&cleanup_gsi);
	}
      gsi_next (gsi);
      break;

    case GIMPLE_EH_FILTER:
      /* If the first element is an eh_filter, it should stand alone.  */
      if (gimple_eh_filter_must_not_throw (stmt))
	this_may_throw = false;
      else if (gimple_eh_filter_types (stmt) == NULL)
	this_may_throw = false;
      failure_seq = gimple_eh_filter_failure (stmt);
      failure_gsi = gsi_start (failure_seq);
      remove_useless_stmts_1 (&failure_gsi, data);
      gsi_next (gsi);
      break;

    default:
      /* Otherwise this is a list of cleanup statements.  */
      remove_useless_stmts_1 (&cleanup_gsi, data);

      /* If the cleanup is empty, then we can emit the TRY block without
	 the enclosing TRY_CATCH_EXPR.  */
      if (gimple_seq_empty_p (cleanup_seq))
	{
          gsi_insert_seq_before (gsi, eval_seq, GSI_SAME_STMT);
          gsi_remove(gsi, false);
	  data->repeat = true;
	}
      else
        gsi_next (gsi);
      break;
    }

  data->may_throw |= this_may_throw;
}

/* Helper for remove_useless_stmts_1.  Handle GIMPLE_BIND statements.  */

static void
remove_useless_stmts_bind (gimple_stmt_iterator *gsi, struct rus_data *data ATTRIBUTE_UNUSED)
{
  tree block;
  gimple_seq body_seq, fn_body_seq;
  gimple_stmt_iterator body_gsi;

  gimple stmt = gsi_stmt (*gsi);

  /* First remove anything underneath the BIND_EXPR.  */
  
  body_seq = gimple_bind_body (stmt);
  body_gsi = gsi_start (body_seq);
  remove_useless_stmts_1 (&body_gsi, data);

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

     When this situation occurs we will want to apply this
     optimization again.  */
  block = gimple_bind_block (stmt);
  fn_body_seq = gimple_body (current_function_decl);
  if (gimple_bind_vars (stmt) == NULL_TREE
      && (gimple_seq_empty_p (fn_body_seq)
          || stmt != gimple_seq_first_stmt (fn_body_seq))
      && (! block
	  || ! BLOCK_ABSTRACT_ORIGIN (block)
	  || (TREE_CODE (BLOCK_ABSTRACT_ORIGIN (block))
	      != FUNCTION_DECL)))
    {
      tree var = NULL_TREE;
      /* Even if there are no gimple_bind_vars, there might be other
	 decls in BLOCK_VARS rendering the GIMPLE_BIND not useless.  */
      if (block && !BLOCK_NUM_NONLOCALIZED_VARS (block))
	for (var = BLOCK_VARS (block); var; var = TREE_CHAIN (var))
	  if (TREE_CODE (var) == IMPORTED_DECL)
	    break;
      if (var || (block && BLOCK_NUM_NONLOCALIZED_VARS (block)))
	gsi_next (gsi);
      else
	{
	  gsi_insert_seq_before (gsi, body_seq, GSI_SAME_STMT);
	  gsi_remove (gsi, false);
	  data->repeat = true;
	}
    }
  else
    gsi_next (gsi);
}

/* Helper for remove_useless_stmts_1.  Handle GIMPLE_GOTO statements.  */

static void
remove_useless_stmts_goto (gimple_stmt_iterator *gsi, struct rus_data *data)
{
  gimple stmt = gsi_stmt (*gsi);

  tree dest = gimple_goto_dest (stmt);

  data->may_branch = true;
  data->last_was_goto = false;

  /* Record iterator for last goto expr, so that we can delete it if unnecessary.  */
  if (TREE_CODE (dest) == LABEL_DECL)
    {
      data->last_goto_gsi = *gsi;
      data->last_was_goto = true;
    }

  gsi_next(gsi);
}

/* Helper for remove_useless_stmts_1.  Handle GIMPLE_LABEL statements.  */

static void
remove_useless_stmts_label (gimple_stmt_iterator *gsi, struct rus_data *data)
{
  gimple stmt = gsi_stmt (*gsi);

  tree label = gimple_label_label (stmt);

  data->has_label = true;

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

  else if (data->last_was_goto
           && gimple_goto_dest (gsi_stmt (data->last_goto_gsi)) == label)
    {
      /* Replace the preceding GIMPLE_GOTO statement with
         a GIMPLE_NOP, which will be subsequently removed.
         In this way, we avoid invalidating other iterators
         active on the statement sequence.  */
      gsi_replace(&data->last_goto_gsi, gimple_build_nop(), false);
      data->last_was_goto = false;
      data->repeat = true;
    }

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

  gsi_next (gsi);
}


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

void
notice_special_calls (gimple call)
{
  int flags = gimple_call_flags (call);

  if (flags & ECF_MAY_BE_ALLOCA)
    cfun->calls_alloca = true;
  if (flags & ECF_RETURNS_TWICE)
    cfun->calls_setjmp = true;
}


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

void
clear_special_calls (void)
{
  cfun->calls_alloca = false;
  cfun->calls_setjmp = false;
}

/* Remove useless statements from a statement sequence, and perform
   some preliminary simplifications.  */

static void
remove_useless_stmts_1 (gimple_stmt_iterator *gsi, struct rus_data *data)
{
  while (!gsi_end_p (*gsi))
    {
      gimple stmt = gsi_stmt (*gsi);

      switch (gimple_code (stmt))
        {
        case GIMPLE_COND:
          remove_useless_stmts_cond (gsi, data);
          break;

        case GIMPLE_GOTO:
          remove_useless_stmts_goto (gsi, data);
          break;

        case GIMPLE_LABEL:
          remove_useless_stmts_label (gsi, data);
          break;

        case GIMPLE_ASSIGN:
          fold_stmt (gsi);
          stmt = gsi_stmt (*gsi);
          data->last_was_goto = false;
          if (stmt_could_throw_p (stmt))
            data->may_throw = true;
          gsi_next (gsi);
          break;

        case GIMPLE_ASM:
          fold_stmt (gsi);
          data->last_was_goto = false;
          gsi_next (gsi);
          break;

        case GIMPLE_CALL:
          fold_stmt (gsi);
          stmt = gsi_stmt (*gsi);
          data->last_was_goto = false;
          if (is_gimple_call (stmt))
            notice_special_calls (stmt);

          /* We used to call update_gimple_call_flags here,
             which copied side-effects and nothrows status
             from the function decl to the call.  In the new
             tuplified GIMPLE, the accessors for this information
             always consult the function decl, so this copying
             is no longer necessary.  */
          if (stmt_could_throw_p (stmt))
            data->may_throw = true;
          gsi_next (gsi);
          break;

        case GIMPLE_RETURN:
          fold_stmt (gsi);
          data->last_was_goto = false;
          data->may_branch = true;
          gsi_next (gsi);
          break;

        case GIMPLE_BIND:
          remove_useless_stmts_bind (gsi, data);
          break;

        case GIMPLE_TRY:
          if (gimple_try_kind (stmt) == GIMPLE_TRY_CATCH)
            remove_useless_stmts_tc (gsi, data);
          else if (gimple_try_kind (stmt) == GIMPLE_TRY_FINALLY)
            remove_useless_stmts_tf (gsi, data);
          else
            gcc_unreachable ();
          break;

        case GIMPLE_CATCH:
          gcc_unreachable ();
          break;

        case GIMPLE_NOP:
          gsi_remove (gsi, false);
          break;

        case GIMPLE_OMP_FOR:
          {
            gimple_seq pre_body_seq = gimple_omp_for_pre_body (stmt);
            gimple_stmt_iterator pre_body_gsi = gsi_start (pre_body_seq);

            remove_useless_stmts_1 (&pre_body_gsi, data);
	    data->last_was_goto = false;
          }
          /* FALLTHROUGH */
        case GIMPLE_OMP_CRITICAL:
        case GIMPLE_OMP_CONTINUE:
        case GIMPLE_OMP_MASTER:
        case GIMPLE_OMP_ORDERED:
        case GIMPLE_OMP_SECTION:
        case GIMPLE_OMP_SECTIONS:
        case GIMPLE_OMP_SINGLE:
          {
            gimple_seq body_seq = gimple_omp_body (stmt);
            gimple_stmt_iterator body_gsi = gsi_start (body_seq);

            remove_useless_stmts_1 (&body_gsi, data);
	    data->last_was_goto = false;
	    gsi_next (gsi);
          }
          break;

        case GIMPLE_OMP_PARALLEL:
	case GIMPLE_OMP_TASK:
          {
	    /* Make sure the outermost GIMPLE_BIND isn't removed
	       as useless.  */
            gimple_seq body_seq = gimple_omp_body (stmt);
            gimple bind = gimple_seq_first_stmt (body_seq);
            gimple_seq bind_seq = gimple_bind_body (bind);
            gimple_stmt_iterator bind_gsi = gsi_start (bind_seq);

            remove_useless_stmts_1 (&bind_gsi, data);
	    data->last_was_goto = false;
	    gsi_next (gsi);
          }
          break;

        case GIMPLE_CHANGE_DYNAMIC_TYPE:
	  /* If we do not optimize remove GIMPLE_CHANGE_DYNAMIC_TYPE as
	     expansion is confused about them and we only remove them
	     during alias computation otherwise.  */
	  if (!optimize)
	    {
	      data->last_was_goto = false;
	      gsi_remove (gsi, false);
	      break;
	    }
	  /* Fallthru.  */

        default:
          data->last_was_goto = false;
          gsi_next (gsi);
          break;
        }
    }
}

/* Walk the function tree, removing useless statements and performing
   some preliminary simplifications.  */

static unsigned int
remove_useless_stmts (void)
{
  struct rus_data data;

  clear_special_calls ();

  do
    {
      gimple_stmt_iterator gsi;

      gsi = gsi_start (gimple_body (current_function_decl));
      memset (&data, 0, sizeof (data));
      remove_useless_stmts_1 (&gsi, &data);
    }
  while (data.repeat);
  return 0;
}


struct gimple_opt_pass pass_remove_useless_stmts =
{
 {
  GIMPLE_PASS,
  "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 */
 }
};

/* 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)
{
  /* Since this block is no longer reachable, we can just delete all
     of its PHI nodes.  */
  remove_phi_nodes (bb);

  /* 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)
{
  gimple_stmt_iterator i;
  source_location loc = UNKNOWN_LOCATION;

  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 (current_loops)
    {
      struct loop *loop = bb->loop_father;

      /* If a loop gets removed, clean up the information associated
	 with it.  */
      if (loop->latch == bb
	  || loop->header == bb)
	free_numbers_of_iterations_estimates_loop (loop);
    }

  /* Remove all the instructions in the block.  */
  if (bb_seq (bb) != NULL)
    {
      for (i = gsi_start_bb (bb); !gsi_end_p (i);)
	{
	  gimple stmt = gsi_stmt (i);
	  if (gimple_code (stmt) == GIMPLE_LABEL
	      && (FORCED_LABEL (gimple_label_label (stmt))
		  || DECL_NONLOCAL (gimple_label_label (stmt))))
	    {
	      basic_block new_bb;
	      gimple_stmt_iterator new_gsi;

	      /* A non-reachable non-local label may still be referenced.
		 But it no longer needs to carry the extra semantics of
		 non-locality.  */
	      if (DECL_NONLOCAL (gimple_label_label (stmt)))
		{
		  DECL_NONLOCAL (gimple_label_label (stmt)) = 0;
		  FORCED_LABEL (gimple_label_label (stmt)) = 1;
		}

	      new_bb = bb->prev_bb;
	      new_gsi = gsi_start_bb (new_bb);
	      gsi_remove (&i, false);
	      gsi_insert_before (&new_gsi, stmt, GSI_NEW_STMT);
	    }
	  else
	    {
	      /* Release SSA definitions if we are in SSA.  Note that we
		 may be called when not in SSA.  For example,
		 final_cleanup calls this function via
		 cleanup_tree_cfg.  */
	      if (gimple_in_ssa_p (cfun))
		release_defs (stmt);

	      gsi_remove (&i, true);
	    }

	  /* 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 (gimple_code (stmt) != GIMPLE_GOTO
	      && gimple_has_location (stmt)
	      && !loc)
	    loc = gimple_location (stmt);
	}
    }

  /* 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.  */
  if (loc > BUILTINS_LOCATION && LOCATION_LINE (loc) > 0)
    warning (OPT_Wunreachable_code, "%Hwill never be executed", &loc);

  remove_phi_nodes_and_edges_for_unreachable_block (bb);
  bb->il.gimple = NULL;
}


/* 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)
{
  gimple stmt;

  stmt = last_stmt (bb);

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

  if (val == NULL)
    return NULL;

  if (!is_gimple_min_invariant (val))
    return NULL;

  if (gimple_code (stmt) == GIMPLE_COND)
    return find_taken_edge_cond_expr (bb, val);

  if (gimple_code (stmt) == GIMPLE_SWITCH)
    return find_taken_edge_switch_expr (bb, val);

  if (computed_goto_p (stmt))
    {
      /* Only optimize if the argument is a label, if the argument is
	 not a label then we can not construct a proper CFG.

         It may be the case that we only need to allow the LABEL_REF to
         appear inside an ADDR_EXPR, but we also allow the LABEL_REF to
         appear inside a LABEL_EXPR just to be safe.  */
      if ((TREE_CODE (val) == ADDR_EXPR || TREE_CODE (val) == LABEL_EXPR)
	  && TREE_CODE (TREE_OPERAND (val, 0)) == LABEL_DECL)
	return find_taken_edge_computed_goto (bb, TREE_OPERAND (val, 0));
      return NULL;
    }

  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 (integer_zerop (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)
{
  basic_block dest_bb;
  edge e;
  gimple switch_stmt;
  tree taken_case;

  switch_stmt = last_stmt (bb);
  taken_case = find_case_label_for_value (switch_stmt, 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_STMT 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 (gimple switch_stmt, tree val)
{
  size_t low, high, n = gimple_switch_num_labels (switch_stmt);
  tree default_case = gimple_switch_default_label (switch_stmt);

  for (low = 0, high = n; high - low > 1; )
    {
      size_t i = (high + low) / 2;
      tree t = gimple_switch_label (switch_stmt, 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;
}


/* Dump a basic block on stderr.  */

void
gimple_debug_bb (basic_block bb)
{
  gimple_dump_bb (bb, stderr, 0, TDF_VOPS|TDF_MEMSYMS);
}


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

basic_block
gimple_debug_bb_n (int n)
{
  gimple_debug_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-pass.h).  */

void
gimple_debug_cfg (int flags)
{
  gimple_dump_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
gimple_dump_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_2 = "%-30s%13ld%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_2, "Edges", num_edges, 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
gimple_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 gimple_code head_code, end_code;
      const char *head_name, *end_name;
      int head_line = 0;
      int end_line = 0;
      gimple first = first_stmt (bb);
      gimple last = last_stmt (bb);

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

      if (last)
	{
	  end_code = gimple_code (last);
	  end_name = gimple_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 (gimple t)
{
  return gimple_code (t) == GIMPLE_COND
    || gimple_code (t) == GIMPLE_SWITCH
    || gimple_code (t) == GIMPLE_GOTO
    || gimple_code (t) == GIMPLE_RETURN
    || gimple_code (t) == GIMPLE_RESX;
}


/* 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 (gimple t)
{
  gcc_assert (t);

  if (is_gimple_call (t))
    {
      int flags = gimple_call_flags (t);

      /* A non-pure/const call alters flow control if the current
	 function has nonlocal labels.  */
      if (!(flags & (ECF_CONST | ECF_PURE))
	  && cfun->has_nonlocal_label)
	return true;

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

  /* OpenMP directives alter control flow.  */
  if (is_gimple_omp (t))
    return true;

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


/* Return true if T is a simple local goto.  */

bool
simple_goto_p (gimple t)
{
  return (gimple_code (t) == GIMPLE_GOTO
	  && TREE_CODE (gimple_goto_dest (t)) == LABEL_DECL);
}


/* Return true if T can make an abnormal transfer of control flow.
   Transfers of control flow associated with EH are excluded.  */

bool
stmt_can_make_abnormal_goto (gimple t)
{
  if (computed_goto_p (t))
    return true;
  if (is_gimple_call (t))
    return gimple_has_side_effects (t) && cfun->has_nonlocal_label;
  return false;
}


/* Return true if STMT should start a new basic block.  PREV_STMT is
   the statement preceding STMT.  It is used when STMT 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 (gimple stmt, gimple prev_stmt)
{
  if (stmt == NULL)
    return false;

  /* Labels 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 (gimple_code (stmt) == GIMPLE_LABEL)
    {
      /* Nonlocal and computed GOTO targets always start a new block.  */
      if (DECL_NONLOCAL (gimple_label_label (stmt))
	  || FORCED_LABEL (gimple_label_label (stmt)))
	return true;

      if (prev_stmt && gimple_code (prev_stmt) == GIMPLE_LABEL)
	{
	  if (DECL_NONLOCAL (gimple_label_label (prev_stmt)))
	    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 (gimple t)
{
  return is_ctrl_stmt (t) || is_ctrl_altering_stmt (t);
}

/* Remove block annotations and other data structures.  */

void
delete_tree_cfg_annotations (void)
{
  label_to_block_map = NULL;
}


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

gimple
first_stmt (basic_block bb)
{
  gimple_stmt_iterator i = gsi_start_bb (bb);
  return !gsi_end_p (i) ? gsi_stmt (i) : NULL;
}

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

gimple
last_stmt (basic_block bb)
{
  gimple_stmt_iterator b = gsi_last_bb (bb);
  return !gsi_end_p (b) ? gsi_stmt (b) : 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.  */

gimple
last_and_only_stmt (basic_block bb)
{
  gimple_stmt_iterator i = gsi_last_bb (bb);
  gimple last, prev;

  if (gsi_end_p (i))
    return NULL;

  last = gsi_stmt (i);
  gsi_prev (&i);
  if (gsi_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 gsi_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 = gsi_stmt (i);
  if (gimple_code (prev) == GIMPLE_LABEL)
    return last;
  else
    return NULL;
}

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

static void
reinstall_phi_args (edge new_edge, edge old_edge)
{
  edge_var_map_vector v;
  edge_var_map *vm;
  int i;
  gimple_stmt_iterator phis;
  
  v = redirect_edge_var_map_vector (old_edge);
  if (!v)
    return;
  
  for (i = 0, phis = gsi_start_phis (new_edge->dest);
       VEC_iterate (edge_var_map, v, i, vm) && !gsi_end_p (phis);
       i++, gsi_next (&phis))
    {
      gimple phi = gsi_stmt (phis);
      tree result = redirect_edge_var_map_result (vm);
      tree arg = redirect_edge_var_map_def (vm);
 
      gcc_assert (result == gimple_phi_result (phi));
  
      add_phi_arg (phi, arg, new_edge);
    }
  
  redirect_edge_var_map_clear (old_edge);
}

/* Returns the basic block after which the new basic block created
   by splitting edge EDGE_IN should be placed.  Tries to keep the new block
   near its "logical" location.  This is of most help to humans looking
   at debugging dumps.  */

static basic_block
split_edge_bb_loc (edge edge_in)
{
  basic_block dest = edge_in->dest;

  if (dest->prev_bb && find_edge (dest->prev_bb, dest))
    return edge_in->src;
  else
    return dest->prev_bb;
}

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

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

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

  dest = edge_in->dest;

  after_bb = split_edge_bb_loc (edge_in);

  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 == edge_in);
  reinstall_phi_args (new_edge, e);

  return new_bb;
}

/* 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;

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

  /* Check operand N for being valid GIMPLE and give error MSG if not.  */
#define CHECK_OP(N, MSG) \
  do { if (!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 INDIRECT_REF:
      x = TREE_OPERAND (t, 0);
      if (!is_gimple_reg (x) && !is_gimple_min_invariant (x))
	{
	  error ("Indirect reference's operand is not a register or a constant.");
	  return x;
	}
      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:
      error ("MODIFY_EXPR not expected while having tuples.");
      return *tp;

    case ADDR_EXPR:
      {
	bool old_constant;
	bool old_side_effects;
	bool new_constant;
	bool new_side_effects;

	gcc_assert (is_gimple_address (t));

	old_constant = TREE_CONSTANT (t);
	old_side_effects = TREE_SIDE_EFFECTS (t);

	recompute_tree_invariant_for_addr_expr (t);
	new_side_effects = TREE_SIDE_EFFECTS (t);
	new_constant = TREE_CONSTANT (t);

        if (old_constant != new_constant)
	  {
	    error ("constant not recomputed when ADDR_EXPR changed");
	    return t;
	  }
	if (old_side_effects != new_side_effects)
	  {
	    error ("side effects not recomputed when ADDR_EXPR changed");
	    return t;
	  }

	/* 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 (!INTEGRAL_TYPE_P (TREE_TYPE (x)))
	{
	  error ("non-integral used in condition");
	  return x;
	}
      if (!is_gimple_condexpr (x))
        {
	  error ("invalid conditional operand");
	  return x;
	}
      break;

    case NON_LVALUE_EXPR:
	gcc_unreachable ();

    CASE_CONVERT:
    case FIX_TRUNC_EXPR:
    case FLOAT_EXPR:
    case NEGATE_EXPR:
    case ABS_EXPR:
    case BIT_NOT_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)
	    {
	      if (!host_integerp (TREE_OPERAND (t, 1), 1)
		  || !host_integerp (TREE_OPERAND (t, 2), 1))
		{
		  error ("invalid position or size operand to BIT_FIELD_REF");
		  return t;
		}
	      else if (INTEGRAL_TYPE_P (TREE_TYPE (t))
		       && (TYPE_PRECISION (TREE_TYPE (t))
			   != TREE_INT_CST_LOW (TREE_OPERAND (t, 1))))
		{
		  error ("integral result type precision does not match "
			 "field size of BIT_FIELD_REF");
		  return t;
		}
	      if (!INTEGRAL_TYPE_P (TREE_TYPE (t))
		  && (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (t)))
		      != TREE_INT_CST_LOW (TREE_OPERAND (t, 1))))
		{
		  error ("mode precision of non-integral result does not "
			 "match field size of BIT_FIELD_REF");
		  return t;
		}
	    }

	  t = TREE_OPERAND (t, 0);
	}

      if (!is_gimple_min_invariant (t) && !is_gimple_lvalue (t))
	{
	  error ("invalid reference prefix");
	  return t;
	}
      *walk_subtrees = 0;
      break;
    case PLUS_EXPR:
    case MINUS_EXPR:
      /* PLUS_EXPR and MINUS_EXPR don't work on pointers, they should be done using
	 POINTER_PLUS_EXPR. */
      if (POINTER_TYPE_P (TREE_TYPE (t)))
	{
	  error ("invalid operand to plus/minus, type is a pointer");
	  return t;
	}
      CHECK_OP (0, "invalid operand to binary operator");
      CHECK_OP (1, "invalid operand to binary operator");
      break;

    case POINTER_PLUS_EXPR:
      /* Check to make sure the first operand is a pointer or reference type. */
      if (!POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (t, 0))))
	{
	  error ("invalid operand to pointer plus, first operand is not a pointer");
	  return t;
	}
      /* Check to make sure the second operand is an integer with type of
	 sizetype.  */
      if (!useless_type_conversion_p (sizetype,
				     TREE_TYPE (TREE_OPERAND (t, 1))))
	{
	  error ("invalid operand to pointer plus, second operand is not an "
		 "integer with type of sizetype.");
	  return t;
	}
      /* FALLTHROUGH */
    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 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;

    case CONSTRUCTOR:
      if (TREE_CONSTANT (t) && TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE)
	*walk_subtrees = 0;
      break;

    default:
      break;
    }
  return NULL;

#undef CHECK_OP
}


/* Verify if EXPR is either a GIMPLE ID or a GIMPLE indirect reference.
   Returns true if there is an error, otherwise false.  */

static bool
verify_types_in_gimple_min_lval (tree expr)
{
  tree op;

  if (is_gimple_id (expr))
    return false;

  if (!INDIRECT_REF_P (expr)
      && TREE_CODE (expr) != TARGET_MEM_REF)
    {
      error ("invalid expression for min lvalue");
      return true;
    }

  /* TARGET_MEM_REFs are strange beasts.  */
  if (TREE_CODE (expr) == TARGET_MEM_REF)
    return false;

  op = TREE_OPERAND (expr, 0);
  if (!is_gimple_val (op))
    {
      error ("invalid operand in indirect reference");
      debug_generic_stmt (op);
      return true;
    }
  if (!useless_type_conversion_p (TREE_TYPE (expr),
				  TREE_TYPE (TREE_TYPE (op))))
    {
      error ("type mismatch in indirect reference");
      debug_generic_stmt (TREE_TYPE (expr));
      debug_generic_stmt (TREE_TYPE (TREE_TYPE (op)));
      return true;
    }

  return false;
}

/* Verify if EXPR is a valid GIMPLE reference expression.  Returns true
   if there is an error, otherwise false.  */

static bool
verify_types_in_gimple_reference (tree expr)
{
  while (handled_component_p (expr))
    {
      tree op = TREE_OPERAND (expr, 0);

      if (TREE_CODE (expr) == ARRAY_REF
	  || TREE_CODE (expr) == ARRAY_RANGE_REF)
	{
	  if (!is_gimple_val (TREE_OPERAND (expr, 1))
	      || (TREE_OPERAND (expr, 2)
		  && !is_gimple_val (TREE_OPERAND (expr, 2)))
	      || (TREE_OPERAND (expr, 3)
		  && !is_gimple_val (TREE_OPERAND (expr, 3))))
	    {
	      error ("invalid operands to array reference");
	      debug_generic_stmt (expr);
	      return true;
	    }
	}

      /* Verify if the reference array element types are compatible.  */
      if (TREE_CODE (expr) == ARRAY_REF
	  && !useless_type_conversion_p (TREE_TYPE (expr),
					 TREE_TYPE (TREE_TYPE (op))))
	{
	  error ("type mismatch in array reference");
	  debug_generic_stmt (TREE_TYPE (expr));
	  debug_generic_stmt (TREE_TYPE (TREE_TYPE (op)));
	  return true;
	}
      if (TREE_CODE (expr) == ARRAY_RANGE_REF
	  && !useless_type_conversion_p (TREE_TYPE (TREE_TYPE (expr)),
					 TREE_TYPE (TREE_TYPE (op))))
	{
	  error ("type mismatch in array range reference");
	  debug_generic_stmt (TREE_TYPE (TREE_TYPE (expr)));
	  debug_generic_stmt (TREE_TYPE (TREE_TYPE (op)));
	  return true;
	}

      if ((TREE_CODE (expr) == REALPART_EXPR
	   || TREE_CODE (expr) == IMAGPART_EXPR)
	  && !useless_type_conversion_p (TREE_TYPE (expr),
					 TREE_TYPE (TREE_TYPE (op))))
	{
	  error ("type mismatch in real/imagpart reference");
	  debug_generic_stmt (TREE_TYPE (expr));
	  debug_generic_stmt (TREE_TYPE (TREE_TYPE (op)));
	  return true;
	}

      if (TREE_CODE (expr) == COMPONENT_REF
	  && !useless_type_conversion_p (TREE_TYPE (expr),
					 TREE_TYPE (TREE_OPERAND (expr, 1))))
	{
	  error ("type mismatch in component reference");
	  debug_generic_stmt (TREE_TYPE (expr));
	  debug_generic_stmt (TREE_TYPE (TREE_OPERAND (expr, 1)));
	  return true;
	}

      /* For VIEW_CONVERT_EXPRs which are allowed here, too, there
	 is nothing to verify.  Gross mismatches at most invoke
	 undefined behavior.  */
      if (TREE_CODE (expr) == VIEW_CONVERT_EXPR
	  && !handled_component_p (op))
	return false;

      expr = op;
    }

  return verify_types_in_gimple_min_lval (expr);
}

/* Returns true if there is one pointer type in TYPE_POINTER_TO (SRC_OBJ)
   list of pointer-to types that is trivially convertible to DEST.  */

static bool
one_pointer_to_useless_type_conversion_p (tree dest, tree src_obj)
{
  tree src;

  if (!TYPE_POINTER_TO (src_obj))
    return true;

  for (src = TYPE_POINTER_TO (src_obj); src; src = TYPE_NEXT_PTR_TO (src))
    if (useless_type_conversion_p (dest, src))
      return true;

  return false;
}

/* Return true if TYPE1 is a fixed-point type and if conversions to and
   from TYPE2 can be handled by FIXED_CONVERT_EXPR.  */

static bool
valid_fixed_convert_types_p (tree type1, tree type2)
{
  return (FIXED_POINT_TYPE_P (type1)
	  && (INTEGRAL_TYPE_P (type2)
	      || SCALAR_FLOAT_TYPE_P (type2)
	      || FIXED_POINT_TYPE_P (type2)));
}

/* Verify the contents of a GIMPLE_CALL STMT.  Returns true when there
   is a problem, otherwise false.  */

static bool
verify_gimple_call (gimple stmt)
{
  tree fn = gimple_call_fn (stmt);
  tree fntype;

  if (!POINTER_TYPE_P (TREE_TYPE  (fn))
      || (TREE_CODE (TREE_TYPE (TREE_TYPE (fn))) != FUNCTION_TYPE
	  && TREE_CODE (TREE_TYPE (TREE_TYPE (fn))) != METHOD_TYPE))
    {
      error ("non-function in gimple call");
      return true;
    }

  if (gimple_call_lhs (stmt)
      && !is_gimple_lvalue (gimple_call_lhs (stmt)))
    {
      error ("invalid LHS in gimple call");
      return true;
    }

  fntype = TREE_TYPE (TREE_TYPE (fn));
  if (gimple_call_lhs (stmt)
      && !useless_type_conversion_p (TREE_TYPE (gimple_call_lhs (stmt)),
				     TREE_TYPE (fntype))
      /* ???  At least C++ misses conversions at assignments from
	 void * call results.
	 ???  Java is completely off.  Especially with functions
	 returning java.lang.Object.
	 For now simply allow arbitrary pointer type conversions.  */
      && !(POINTER_TYPE_P (TREE_TYPE (gimple_call_lhs (stmt)))
	   && POINTER_TYPE_P (TREE_TYPE (fntype))))
    {
      error ("invalid conversion in gimple call");
      debug_generic_stmt (TREE_TYPE (gimple_call_lhs (stmt)));
      debug_generic_stmt (TREE_TYPE (fntype));
      return true;
    }

  /* ???  The C frontend passes unpromoted arguments in case it
     didn't see a function declaration before the call.  So for now
     leave the call arguments unverified.  Once we gimplify
     unit-at-a-time we have a chance to fix this.  */

  return false;
}

/* Verifies the gimple comparison with the result type TYPE and
   the operands OP0 and OP1.  */

static bool
verify_gimple_comparison (tree type, tree op0, tree op1)
{
  tree op0_type = TREE_TYPE (op0);
  tree op1_type = TREE_TYPE (op1);

  if (!is_gimple_val (op0) || !is_gimple_val (op1))
    {
      error ("invalid operands in gimple comparison");
      return true;
    }

  /* For comparisons we do not have the operations type as the
     effective type the comparison is carried out in.  Instead
     we require that either the first operand is trivially
     convertible into the second, or the other way around.
     The resulting type of a comparison may be any integral type.
     Because we special-case pointers to void we allow
     comparisons of pointers with the same mode as well.  */
  if ((!useless_type_conversion_p (op0_type, op1_type)
       && !useless_type_conversion_p (op1_type, op0_type)
       && (!POINTER_TYPE_P (op0_type)
	   || !POINTER_TYPE_P (op1_type)
	   || TYPE_MODE (op0_type) != TYPE_MODE (op1_type)))
      || !INTEGRAL_TYPE_P (type))
    {
      error ("type mismatch in comparison expression");
      debug_generic_expr (type);
      debug_generic_expr (op0_type);
      debug_generic_expr (op1_type);
      return true;
    }

  return false;
}

/* Verify a gimple assignment statement STMT with an unary rhs.
   Returns true if anything is wrong.  */

static bool
verify_gimple_assign_unary (gimple stmt)
{
  enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
  tree lhs = gimple_assign_lhs (stmt);
  tree lhs_type = TREE_TYPE (lhs);
  tree rhs1 = gimple_assign_rhs1 (stmt);
  tree rhs1_type = TREE_TYPE (rhs1);

  if (!is_gimple_reg (lhs)
      && !(optimize == 0
	   && TREE_CODE (lhs_type) == COMPLEX_TYPE))
    {
      error ("non-register as LHS of unary operation");
      return true;
    }

  if (!is_gimple_val (rhs1))
    {
      error ("invalid operand in unary operation");
      return true;
    }

  /* First handle conversions.  */
  switch (rhs_code)
    {
    CASE_CONVERT:
      {
	/* Allow conversions between integral types and pointers only if
	   there is no sign or zero extension involved.
	   For targets were the precision of sizetype doesn't match that
	   of pointers we need to allow arbitrary conversions from and
	   to sizetype.  */
	if ((POINTER_TYPE_P (lhs_type)
	     && INTEGRAL_TYPE_P (rhs1_type)
	     && (TYPE_PRECISION (lhs_type) >= TYPE_PRECISION (rhs1_type)
		 || rhs1_type == sizetype))
	    || (POINTER_TYPE_P (rhs1_type)
		&& INTEGRAL_TYPE_P (lhs_type)
		&& (TYPE_PRECISION (rhs1_type) >= TYPE_PRECISION (lhs_type)
		    || lhs_type == sizetype)))
	  return false;

	/* Allow conversion from integer to offset type and vice versa.  */
	if ((TREE_CODE (lhs_type) == OFFSET_TYPE
	     && TREE_CODE (rhs1_type) == INTEGER_TYPE)
	    || (TREE_CODE (lhs_type) == INTEGER_TYPE
		&& TREE_CODE (rhs1_type) == OFFSET_TYPE))
	  return false;

	/* Otherwise assert we are converting between types of the
	   same kind.  */
	if (INTEGRAL_TYPE_P (lhs_type) != INTEGRAL_TYPE_P (rhs1_type))
	  {
	    error ("invalid types in nop conversion");
	    debug_generic_expr (lhs_type);
	    debug_generic_expr (rhs1_type);
	    return true;
	  }

	return false;
      }

    case FIXED_CONVERT_EXPR:
      {
	if (!valid_fixed_convert_types_p (lhs_type, rhs1_type)
	    && !valid_fixed_convert_types_p (rhs1_type, lhs_type))
	  {
	    error ("invalid types in fixed-point conversion");
	    debug_generic_expr (lhs_type);
	    debug_generic_expr (rhs1_type);
	    return true;
	  }

	return false;
      }

    case FLOAT_EXPR:
      {
	if (!INTEGRAL_TYPE_P (rhs1_type) || !</