2011-11-09 Richard Guenther <rguenther@suse.de>

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

/* Control flow functions for trees.
   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
   2010, 2011  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 "tm_p.h"
#include "basic-block.h"
#include "output.h"
#include "flags.h"
#include "function.h"
#include "ggc.h"
#include "langhooks.h"
#include "tree-pretty-print.h"
#include "gimple-pretty-print.h"
#include "tree-flow.h"
#include "timevar.h"
#include "tree-dump.h"
#include "tree-pass.h"
#include "diagnostic-core.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;

/* If we record edge_to_cases, this bitmap will hold indexes
   of basic blocks that end in a GIMPLE_SWITCH which we touched
   due to edge manipulations.  */

static bitmap touched_switch_bbs;

/* 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;

/* Hash table to store last discriminator assigned for each locus.  */
struct locus_discrim_map
{
  location_t locus;
  int discriminator;
};
static htab_t discriminator_per_locus;

/* 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 void make_gimple_asm_edges (basic_block);
static unsigned int locus_map_hash (const void *);
static int locus_map_eq (const void *, const void *);
static void assign_discriminator (location_t, 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 *);
static gimple first_non_label_stmt (basic_block);
static bool verify_gimple_transaction (gimple);

/* 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);
static void group_case_labels_stmt (gimple);

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.  */
  discriminator_per_locus = htab_create (13, locus_map_hash, locus_map_eq,
                                         free);
  make_edges ();
  cleanup_dead_labels ();
  htab_delete (discriminator_per_locus);

  /* 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);
      }
  }
}

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_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 (UNKNOWN_LOCATION);
              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))
        {
          /* If the stmt can make abnormal goto use a new temporary
             for the assignment to the LHS.  This makes sure the old value
             of the LHS is available on the abnormal edge.  Otherwise
             we will end up with overlapping life-ranges for abnormal
             SSA names.  */
          if (gimple_has_lhs (stmt)
              && stmt_can_make_abnormal_goto (stmt)
              && is_gimple_reg_type (TREE_TYPE (gimple_get_lhs (stmt))))
            {
              tree lhs = gimple_get_lhs (stmt);
              tree tmp = create_tmp_var (TREE_TYPE (lhs), NULL);
              gimple s = gimple_build_assign (lhs, tmp);
              gimple_set_location (s, gimple_location (stmt));
              gimple_set_block (s, gimple_block (stmt));
              gimple_set_lhs (stmt, tmp);
              if (TREE_CODE (TREE_TYPE (tmp)) == COMPLEX_TYPE
                  || TREE_CODE (TREE_TYPE (tmp)) == VECTOR_TYPE)
                DECL_GIMPLE_REG_P (tmp) = 1;
              gsi_insert_after (&i, s, GSI_SAME_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
     GC allocation that clears memory 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_alloc_cleared_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)
        {
          location_t loc = gimple_location (stmt);
          tree cond;
          bool zerop, onep;

          fold_defer_overflow_warnings ();
          cond = fold_binary_loc (loc, 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_EH_DISPATCH:
              fallthru = make_eh_dispatch_edges (last);
              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);

              /* BUILTIN_RETURN is really a return statement.  */
              if (gimple_call_builtin_p (last, BUILT_IN_RETURN))
                make_edge (bb, EXIT_BLOCK_PTR, 0), fallthru = false;
              /* Some calls are known not to return.  */
              else
                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_ASM:
              make_gimple_asm_edges (bb);
              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;

            case GIMPLE_TRANSACTION:
              {
                tree abort_label = gimple_transaction_label (last);
                if (abort_label)
                  make_edge (bb, label_to_block (abort_label), 0);
                fallthru = true;
              }
              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 (last)
            assign_discriminator (gimple_location (last), bb->next_bb);
        }
    }

  if (root_omp_region)
    free_omp_regions ();

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

/* Trivial hash function for a location_t.  ITEM is a pointer to
   a hash table entry that maps a location_t to a discriminator.  */

static unsigned int
locus_map_hash (const void *item)
{
  return ((const struct locus_discrim_map *) item)->locus;
}

/* Equality function for the locus-to-discriminator map.  VA and VB
   point to the two hash table entries to compare.  */

static int
locus_map_eq (const void *va, const void *vb)
{
  const struct locus_discrim_map *a = (const struct locus_discrim_map *) va;
  const struct locus_discrim_map *b = (const struct locus_discrim_map *) vb;
  return a->locus == b->locus;
}

/* Find the next available discriminator value for LOCUS.  The
   discriminator distinguishes among several basic blocks that
   share a common locus, allowing for more accurate sample-based
   profiling.  */

static int
next_discriminator_for_locus (location_t locus)
{
  struct locus_discrim_map item;
  struct locus_discrim_map **slot;

  item.locus = locus;
  item.discriminator = 0;
  slot = (struct locus_discrim_map **)
      htab_find_slot_with_hash (discriminator_per_locus, (void *) &item,
                                (hashval_t) locus, INSERT);
  gcc_assert (slot);
  if (*slot == HTAB_EMPTY_ENTRY)
    {
      *slot = XNEW (struct locus_discrim_map);
      gcc_assert (*slot);
      (*slot)->locus = locus;
      (*slot)->discriminator = 0;
    }
  (*slot)->discriminator++;
  return (*slot)->discriminator;
}

/* Return TRUE if LOCUS1 and LOCUS2 refer to the same source line.  */

static bool
same_line_p (location_t locus1, location_t locus2)
{
  expanded_location from, to;

  if (locus1 == locus2)
    return true;

  from = expand_location (locus1);
  to = expand_location (locus2);

  if (from.line != to.line)
    return false;
  if (from.file == to.file)
    return true;
  return (from.file != NULL
          && to.file != NULL
          && filename_cmp (from.file, to.file) == 0);
}

/* Assign a unique discriminator value to block BB if it begins at the same
   LOCUS as its predecessor block.  */

static void
assign_discriminator (location_t locus, basic_block bb)
{
  gimple first_in_to_bb, last_in_to_bb;

  if (locus == 0 || bb->discriminator != 0)
    return;

  first_in_to_bb = first_non_label_stmt (bb);
  last_in_to_bb = last_stmt (bb);
  if ((first_in_to_bb && same_line_p (locus, gimple_location (first_in_to_bb)))
      || (last_in_to_bb && same_line_p (locus, gimple_location (last_in_to_bb))))
    bb->discriminator = next_discriminator_for_locus (locus);
}

/* 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;
  location_t entry_locus;

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

  entry_locus = gimple_location (entry);

  /* 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);
  assign_discriminator (entry_locus, then_bb);
  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)
    {
      assign_discriminator (entry_locus, else_bb);
      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 = CASE_CHAIN (t);
      CASE_CHAIN (t) = NULL;
    }

  *value = NULL;
  return true;
}

/* 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 ();
  touched_switch_bbs = BITMAP_ALLOC (NULL);
}

/* 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)
{
  bitmap_iterator bi;
  unsigned i;
  pointer_map_traverse (edge_to_cases, edge_to_cases_cleanup, NULL);
  pointer_map_destroy (edge_to_cases);
  edge_to_cases = NULL;
  EXECUTE_IF_SET_IN_BITMAP (touched_switch_bbs, 0, i, bi)
    {
      basic_block bb = BASIC_BLOCK (i);
      if (bb)
        {
          gimple stmt = last_stmt (bb);
          if (stmt && gimple_code (stmt) == GIMPLE_SWITCH)
            group_case_labels_stmt (stmt);
        }
    }
  BITMAP_FREE (touched_switch_bbs);
}

/* 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);
      CASE_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);
  location_t entry_locus;
  size_t i, n;

  entry_locus = gimple_location (entry);

  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);
      assign_discriminator (entry_locus, label_bb);
    }
}


/* 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 (seen_error () && 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);
      basic_block label_bb = label_to_block (dest);
      edge e = make_edge (bb, label_bb, EDGE_FALLTHRU);
      e->goto_locus = gimple_location (goto_t);
      assign_discriminator (e->goto_locus, label_bb);
      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);
}

/* Create edges for an asm statement with labels at block BB.  */

static void
make_gimple_asm_edges (basic_block bb)
{
  gimple stmt = last_stmt (bb);
  location_t stmt_loc = gimple_location (stmt);
  int i, n = gimple_asm_nlabels (stmt);

  for (i = 0; i < n; ++i)
    {
      tree label = TREE_VALUE (gimple_asm_label_op (stmt, i));
      basic_block label_bb = label_to_block (label);
      make_edge (bb, label_bb, 0);
      assign_discriminator (stmt_loc, label_bb);
    }
}

/*---------------------------------------------------------------------------
                               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;

/* 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;
}

/* Clean up redundant labels within the exception tree.  */

static void
cleanup_dead_labels_eh (void)
{
  eh_landing_pad lp;
  eh_region r;
  tree lab;
  int i;

  if (cfun->eh == NULL)
    return;

  for (i = 1; VEC_iterate (eh_landing_pad, cfun->eh->lp_array, i, lp); ++i)
    if (lp && lp->post_landing_pad)
      {
        lab = main_block_label (lp->post_landing_pad);
        if (lab != lp->post_landing_pad)
          {
            EH_LANDING_PAD_NR (lp->post_landing_pad) = 0;
            EH_LANDING_PAD_NR (lab) = lp->index;
          }
      }

  FOR_ALL_EH_REGION (r)
    switch (r->type)
      {
      case ERT_CLEANUP:
      case ERT_MUST_NOT_THROW:
        break;

      case ERT_TRY:
        {
          eh_catch c;
          for (c = r->u.eh_try.first_catch; c ; c = c->next_catch)
            {
              lab = c->label;
              if (lab)
                c->label = main_block_label (lab);
            }
        }
        break;

      case ERT_ALLOWED_EXCEPTIONS:
        lab = r->u.allowed.label;
        if (lab)
          r->u.allowed.label = main_block_label (lab);
        break;
      }
}


/* 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);
      tree label, new_label;

      if (!stmt)
        continue;

      switch (gimple_code (stmt))
        {
        case GIMPLE_COND:
          label = gimple_cond_true_label (stmt);
          if (label)
            {
              new_label = main_block_label (label);
              if (new_label != label)
                gimple_cond_set_true_label (stmt, new_label);
            }

          label = gimple_cond_false_label (stmt);
          if (label)
            {
              new_label = main_block_label (label);
              if (new_label != label)
                gimple_cond_set_false_label (stmt, new_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);
                label = CASE_LABEL (case_label);
                new_label = main_block_label (label);
                if (new_label != label)
                  CASE_LABEL (case_label) = new_label;
              }
            break;
          }

        case GIMPLE_ASM:
          {
            int i, n = gimple_asm_nlabels (stmt);

            for (i = 0; i < n; ++i)
              {
                tree cons = gimple_asm_label_op (stmt, i);
                tree label = main_block_label (TREE_VALUE (cons));
                TREE_VALUE (cons) = 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))
            {
              label = gimple_goto_dest (stmt);
              new_label = main_block_label (label);
              if (new_label != label)
                gimple_goto_set_dest (stmt, new_label);
            }
          break;

        case GIMPLE_TRANSACTION:
          {
            tree label = gimple_transaction_label (stmt);
            if (label)
              {
                tree new_label = main_block_label (label);
                if (new_label != label)
                  gimple_transaction_set_label (stmt, new_label);
              }
          }
          break;

        default:
          break;
      }
    }

  /* Do the same for the exception region tree labels.  */
  cleanup_dead_labels_eh ();

  /* 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);
}

/* Scan the sorted vector of cases in STMT (a GIMPLE_SWITCH) and combine
   the ones jumping to the same label.
   Eg. three separate entries 1: 2: 3: become one entry 1..3:  */

static void
group_case_labels_stmt (gimple stmt)
{
  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);
          double_int bhp1 = double_int_add (tree_to_double_int (base_high),
                                            double_int_one);

          /* Merge the cases if they jump to the same place,
             and their ranges are consecutive.  */
          if (merge_label == base_label
              && double_int_equal_p (tree_to_double_int (CASE_LOW (merge_case)),
                                     bhp1))
            {
              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);
}

/* Look for blocks ending in a multiway branch (a GIMPLE_SWITCH),
   and scan the sorted vector of cases.  Combine the ones jumping to the
   same label.  */

void
group_case_labels (void)
{
  basic_block bb;

  FOR_EACH_BB (bb)
    {
      gimple stmt = last_stmt (bb);
      if (stmt && gimple_code (stmt) == GIMPLE_SWITCH)
        group_case_labels_stmt (stmt);
    }
}

/* 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 | EDGE_EH | EDGE_PRESERVE))
    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;

  /* Examine the labels at the beginning of B.  */
  for (gsi = gsi_start_bb (b); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      tree lab;
      stmt = gsi_stmt (gsi);
      if (gimple_code (stmt) != GIMPLE_LABEL)
        break;
      lab = gimple_label_label (stmt);

      /* Do not remove user forced labels or for -O0 any user labels.  */
      if (!DECL_ARTIFICIAL (lab) && (!optimize || FORCED_LABEL (lab)))
        return false;
    }

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

  /* It must be possible to eliminate all phi nodes in B.  If ssa form
     is not up-to-date and a name-mapping is registered, we cannot eliminate
     any phis.  Symbols marked for renaming are never a problem though.  */
  phis = phi_nodes (b);
  if (!gimple_seq_empty_p (phis)
      && name_mappings_registered_p ())
    return false;

  /* When not optimizing, don't merge if we'd lose goto_locus.  */
  if (!optimize
      && single_succ_edge (a)->goto_locus != UNKNOWN_LOCATION)
    {
      location_t goto_locus = single_succ_edge (a)->goto_locus;
      gimple_stmt_iterator prev, next;
      prev = gsi_last_nondebug_bb (a);
      next = gsi_after_labels (b);
      if (!gsi_end_p (next) && is_gimple_debug (gsi_stmt (next)))
        gsi_next_nondebug (&next);
      if ((gsi_end_p (prev)
           || gimple_location (gsi_stmt (prev)) != goto_locus)
          && (gsi_end_p (next)
              || gimple_location (gsi_stmt (next)) != goto_locus))
        return false;
    }

  return true;
}

/* Return true if the var whose chain of uses starts at PTR has no
   nondebug uses.  */
bool
has_zero_uses_1 (const ssa_use_operand_t *head)
{
  const ssa_use_operand_t *ptr;

  for (ptr = head->next; ptr != head; ptr = ptr->next)
    if (!is_gimple_debug (USE_STMT (ptr)))
      return false;

  return true;
}

/* Return true if the var whose chain of uses starts at PTR has a
   single nondebug use.  Set USE_P and STMT to that single nondebug
   use, if so, or to NULL otherwise.  */
bool
single_imm_use_1 (const ssa_use_operand_t *head,
                  use_operand_p *use_p, gimple *stmt)
{
  ssa_use_operand_t *ptr, *single_use = 0;

  for (ptr = head->next; ptr != head; ptr = ptr->next)
    if (!is_gimple_debug (USE_STMT (ptr)))
      {
        if (single_use)
          {
            single_use = NULL;
            break;
          }
        single_use = ptr;
      }

  if (use_p)
    *use_p = single_use;

  if (stmt)
    *stmt = single_use ? single_use->loc.stmt : NULL;

  return !!single_use;
}

/* 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)
    {
      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)
        {
          gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
          size_t i;

          fold_stmt (&gsi);
          stmt = gsi_stmt (gsi);
          if (cfgcleanup_altered_bbs && !is_gimple_debug (stmt))
            bitmap_set_bit (cfgcleanup_altered_bbs, gimple_bb (stmt)->index);

          /* FIXME.  This should go in update_stmt.  */
          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);
          update_stmt (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);

              if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def))
                SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use) = 1;
            }
          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);)
    {
      gimple stmt = gsi_stmt (gsi);
      if (gimple_code (stmt) == GIMPLE_LABEL)
        {
          tree label = gimple_label_label (stmt);
          int lp_nr;

          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 (label))
            {
              gimple_stmt_iterator dest_gsi = gsi_start_bb (a);
              gsi_insert_before (&dest_gsi, stmt, GSI_NEW_STMT);
            }
          /* Other user labels keep around in a form of a debug stmt.  */
          else if (!DECL_ARTIFICIAL (label) && MAY_HAVE_DEBUG_STMTS)
            {
              gimple dbg = gimple_build_debug_bind (label,
                                                    integer_zero_node,
                                                    stmt);
              gimple_debug_bind_reset_value (dbg);
              gsi_insert_before (&gsi, dbg, GSI_SAME_STMT);
            }

          lp_nr = EH_LANDING_PAD_NR (label);
          if (lp_nr)
            {
              eh_landing_pad lp = get_eh_landing_pad_from_number (lp_nr);
              lp->post_landing_pad = NULL;
            }
        }
      else
        {
          gimple_set_bb (stmt, 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
   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;
}

/* 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 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;

  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)
    {
      /* Walk backwards so as to get a chance to substitute all
         released DEFs into debug stmts.  See
         eliminate_unnecessary_stmts() in tree-ssa-dce.c for more
         details.  */
      for (i = gsi_last_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);
            }

          if (gsi_end_p (i))
            i = gsi_last_bb (bb);
          else
            gsi_prev (&i);
        }
    }

  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)
    {
      dump_function_header (file, current_function_decl, flags);
      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.  */

DEBUG_FUNCTION 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)
{
  switch (gimple_code (t))
    {
    case GIMPLE_COND:
    case GIMPLE_SWITCH:
    case GIMPLE_GOTO:
    case GIMPLE_RETURN:
    case GIMPLE_RESX:
      return true;
    default:
      return false;
    }
}


/* 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);

  switch (gimple_code (t))
    {
    case GIMPLE_CALL:
      {
        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 | ECF_LEAF))
            && cfun->has_nonlocal_label)
          return true;

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

        /* TM ending statements have backedges out of the transaction.
           Return true so we split the basic block containing them.
           Note that the TM_BUILTIN test is merely an optimization.  */
        if ((flags & ECF_TM_BUILTIN)
            && is_tm_ending_fndecl (gimple_call_fndecl (t)))
          return true;

        /* BUILT_IN_RETURN call is same as return statement.  */
        if (gimple_call_builtin_p (t, BUILT_IN_RETURN))
          return true;
      }
      break;

    case GIMPLE_EH_DISPATCH:
      /* EH_DISPATCH branches to the individual catch handlers at
         this level of a try or allowed-exceptions region.  It can
         fallthru to the next statement as well.  */
      return true;

    case GIMPLE_ASM:
      if (gimple_asm_nlabels (t) > 0)
        return true;
      break;

    CASE_GIMPLE_OMP:
      /* OpenMP directives alter control flow.  */
      return true;

    case GIMPLE_TRANSACTION:
      /* A transaction start alters control flow.  */
      return true;

    default:
      break;
    }

  /* 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
            && !(gimple_call_flags (t) & ECF_LEAF));
  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);
  gimple stmt = NULL;

  while (!gsi_end_p (i) && is_gimple_debug ((stmt = gsi_stmt (i))))
    {
      gsi_next (&i);
      stmt = NULL;
    }
  return stmt;
}

/* Return the first non-label statement in basic block BB.  */

static gimple
first_non_label_stmt (basic_block bb)
{
  gimple_stmt_iterator i = gsi_start_bb (bb);
  while (!gsi_end_p (i) && gimple_code (gsi_stmt (i)) == GIMPLE_LABEL)
    gsi_next (&i);
  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 i = gsi_last_bb (bb);
  gimple stmt = NULL;

  while (!gsi_end_p (i) && is_gimple_debug ((stmt = gsi_stmt (i))))
    {
      gsi_prev (&i);
      stmt = NULL;
    }
  return stmt;
}

/* 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_nondebug_bb (bb);
  gimple last, prev;

  if (gsi_end_p (i))
    return NULL;

  last = gsi_stmt (i);
  gsi_prev_nondebug (&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_location (vm));
    }

  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;
  basic_block dest_prev = dest->prev_bb;

  if (dest_prev)
    {
      edge e = find_edge (dest_prev, dest);
      if (e && !(e->flags & EDGE_COMPLEX))
        return edge_in->src;
    }
  return dest_prev;
}

/* 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;
}


/* Verify properties of the address expression T with base object BASE.  */

static tree
verify_address (tree t, tree base)
{
  bool old_constant;
  bool old_side_effects;
  bool new_constant;
  bool new_side_effects;

  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;
    }

  if (!(TREE_CODE (base) == VAR_DECL
        || TREE_CODE (base) == PARM_DECL
        || TREE_CODE (base) == RESULT_DECL))
    return NULL_TREE;

  if (DECL_GIMPLE_REG_P (base))
    {
      error ("DECL_GIMPLE_REG_P set on a variable with address taken");
      return base;
    }

  return NULL_TREE;
}

/* 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:
      error ("INDIRECT_REF in gimple IL");
      return t;

    case MEM_REF:
      x = TREE_OPERAND (t, 0);
      if (!POINTER_TYPE_P (TREE_TYPE (x))
          || !is_gimple_mem_ref_addr (x))
        {
          error ("invalid first operand of MEM_REF");
          return x;
        }
      if (TREE_CODE (TREE_OPERAND (t, 1)) != INTEGER_CST
          || !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (t, 1))))
        {
          error ("invalid offset operand of MEM_REF");
          return TREE_OPERAND (t, 1);
        }
      if (TREE_CODE (x) == ADDR_EXPR
          && (x = verify_address (x, TREE_OPERAND (x, 0))))
        return x;
      *walk_subtrees = 0;
      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:
      {
        tree tem;

        gcc_assert (is_gimple_address (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 ((tem = verify_address (t, x)))
          return tem;

        if (!(TREE_CODE (x) == VAR_DECL
              || TREE_CODE (x) == PARM_DECL
              || TREE_CODE (x) == RESULT_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:
    case TRUTH_NOT_EXPR:
      gcc_unreachable ();

    CASE_CONVERT:
    case FIX_TRUNC_EXPR:
    case FLOAT_EXPR:
    case NEGATE_EXPR:
    case ABS_EXPR:
    case BIT_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 a ptrofftype.  */
      if (!ptrofftype_p (TREE_TYPE (TREE_OPERAND (t, 1))))
        {
          error ("invalid operand to pointer plus, second operand is not an "
                 "integer type of appropriate width");
          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;

    case CASE_LABEL_EXPR:
      if (CASE_CHAIN (t))
        {
          error ("invalid CASE_CHAIN");
          return t;
        }
      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 (TREE_CODE (expr) != TARGET_MEM_REF
      && TREE_CODE (expr) != 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;
    }
  /* Memory references now generally can involve a value conversion.  */

  return false;
}

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

static bool
verify_types_in_gimple_reference (tree expr, bool require_lvalue)
{
  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;
        }

      if (TREE_CODE (expr) == VIEW_CONVERT_EXPR)
        {
          /* For VIEW_CONVERT_EXPRs which are allowed here too, we only check
             that their operand is not an SSA name or an invariant when
             requiring an lvalue (this usually means there is a SRA or IPA-SRA
             bug).  Otherwise there is nothing to verify, gross mismatches at
             most invoke undefined behavior.  */
          if (require_lvalue
              && (TREE_CODE (op) == SSA_NAME
                  || is_gimple_min_invariant (op)))
            {
              error ("conversion of an SSA_NAME on the left hand side");
              debug_generic_stmt (expr);
              return true;
            }
          else if (TREE_CODE (op) == SSA_NAME
                   && TYPE_SIZE (TREE_TYPE (expr)) != TYPE_SIZE (TREE_TYPE (op)))
            {
              error ("conversion of register to a different size");
              debug_generic_stmt (expr);
              return true;
            }
          else if (!handled_component_p (op))
            return false;
        }

      expr = op;
    }

  if (TREE_CODE (expr) == MEM_REF)
    {
      if (!is_gimple_mem_ref_addr (TREE_OPERAND (expr, 0)))
        {
          error ("invalid address operand in MEM_REF");
          debug_generic_stmt (expr);
          return true;
        }
      if (TREE_CODE (TREE_OPERAND (expr, 1)) != INTEGER_CST
          || !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 1))))
        {
          error ("invalid offset operand in MEM_REF");
          debug_generic_stmt (expr);
          return true;
        }
    }
  else if (TREE_CODE (expr) == TARGET_MEM_REF)
    {
      if (!TMR_BASE (expr)
          || !is_gimple_mem_ref_addr (TMR_BASE (expr)))
        {
          error ("invalid address operand in TARGET_MEM_REF");
          return true;
        }
      if (!TMR_OFFSET (expr)
          || TREE_CODE (TMR_OFFSET (expr)) != INTEGER_CST
          || !POINTER_TYPE_P (TREE_TYPE (TMR_OFFSET (expr))))
        {
          error ("invalid offset operand in TARGET_MEM_REF");
          debug_generic_stmt (expr);
          return true;
        }
    }

  return ((require_lvalue || !is_gimple_min_invariant (expr))
          && 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, fndecl;
  unsigned i;

  if (gimple_call_internal_p (stmt))
    {
      if (fn)
        {
          error ("gimple call has two targets");
          debug_generic_stmt (fn);
          return true;
        }
    }
  else
    {
      if (!fn)
        {
          error ("gimple call has no target");
          return true;
        }
    }

  if (fn && !is_gimple_call_addr (fn))
    {
      error ("invalid function in gimple call");
      debug_generic_stmt (fn);
      return true;
    }

  if (fn
      && (!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;
    }

   fndecl = gimple_call_fndecl (stmt);
   if (fndecl
       && TREE_CODE (fndecl) == FUNCTION_DECL
       && DECL_LOOPING_CONST_OR_PURE_P (fndecl)
       && !DECL_PURE_P (fndecl)
       && !TREE_READONLY (fndecl))
     {
       error ("invalid pure const state for function");
       return true;
     }

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

  if (gimple_call_lhs (stmt) && gimple_call_noreturn_p (stmt))
    {
      error ("LHS in noreturn call");
      return true;
    }

  fntype = gimple_call_fntype (stmt);
  if (fntype
      && 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;
    }

  if (gimple_call_chain (stmt)
      && !is_gimple_val (gimple_call_chain (stmt)))
    {
      error ("invalid static chain in gimple call");
      debug_generic_stmt (gimple_call_chain (stmt));
      return true;
    }

  /* If there is a static chain argument, this should not be an indirect
     call, and the decl should have DECL_STATIC_CHAIN set.  */
  if (gimple_call_chain (stmt))
    {
      if (!gimple_call_fndecl (stmt))
        {
          error ("static chain in indirect gimple call");
          return true;
        }
      fn = TREE_OPERAND (fn, 0);

      if (!DECL_STATIC_CHAIN (fn))
        {
          error ("static chain with function that doesn%'t use one");
          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 mostly unverified.  Once we gimplify
     unit-at-a-time we have a chance to fix this.  */

  for (i = 0; i < gimple_call_num_args (stmt); ++i)
    {
      tree arg = gimple_call_arg (stmt, i);
      if ((is_gimple_reg_type (TREE_TYPE (arg))
           && !is_gimple_val (arg))
          || (!is_gimple_reg_type (TREE_TYPE (arg))
              && !is_gimple_lvalue (arg)))
        {
          error ("invalid argument to gimple call");
          debug_generic_expr (arg);
          return true;
        }
    }

  /* Verify that if we have a direct call and the argument/return
     types have mismatches the call is properly marked as noninlinable.  */
  if (fndecl
      && !gimple_call_cannot_inline_p (stmt)
      && !gimple_check_call_matching_types (stmt, fndecl))
    {
      error ("gimple call cannot be inlined but is not marked so");
      return true;
    }

  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.
     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)))
    {
      error ("mismatching comparison operand types");
      debug_generic_expr (op0_type);
      debug_generic_expr (op1_type);
      return true;
    }

  /* The resulting type of a comparison may be an effective boolean type.  */
  if (INTEGRAL_TYPE_P (type)
      && (TREE_CODE (type) == BOOLEAN_TYPE
          || TYPE_PRECISION (type) == 1))
    ;
  /* Or an integer vector type with the same size and element count
     as the comparison operand types.  */
  else if (TREE_CODE (type) == VECTOR_TYPE
           && TREE_CODE (TREE_TYPE (type)) == INTEGER_TYPE)
    {
      if (TREE_CODE (op0_type) != VECTOR_TYPE
          || TREE_CODE (op1_type) != VECTOR_TYPE)
        {
          error ("non-vector operands in vector comparison");
          debug_generic_expr (op0_type);
          debug_generic_expr (op1_type);
          return true;
        }

      if (TYPE_VECTOR_SUBPARTS (type) != TYPE_VECTOR_SUBPARTS (op0_type)
          || (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (type)))
              != GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0_type)))))
        {
          error ("invalid vector comparison resulting type");
          debug_generic_expr (type);
          return true;
        }
    }
  else
    {
      error ("bogus comparison result type");
      debug_generic_expr (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))
    {
      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 ptrofftype doesn't match that
           of pointers we need to allow arbitrary conversions from and
           to ptrofftype.  */
        if ((POINTER_TYPE_P (lhs_type)
             && INTEGRAL_TYPE_P (rhs1_type)
             && (TYPE_PRECISION (lhs_type) >= TYPE_PRECISION (rhs1_type)
                 || ptrofftype_p (rhs1_type)))
            || (POINTER_TYPE_P (rhs1_type)
                && INTEGRAL_TYPE_P (lhs_type)
                && (TYPE_PRECISION (rhs1_type) >= TYPE_PRECISION (lhs_type)
                    || ptrofftype_p (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 ADDR_SPACE_CONVERT_EXPR:
      {
        if (!POINTER_TYPE_P (rhs1_type) || !POINTER_TYPE_P (lhs_type)
            || (TYPE_ADDR_SPACE (TREE_TYPE (rhs1_type))
                == TYPE_ADDR_SPACE (TREE_TYPE (lhs_type))))
          {
            error ("invalid types in address space 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) || !SCALAR_FLOAT_TYPE_P (lhs_type))
            && (!VECTOR_INTEGER_TYPE_P (rhs1_type)
                || !VECTOR_FLOAT_TYPE_P(lhs_type)))
          {
            error ("invalid types in conversion to floating point");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            return true;
          }

        return false;
      }

    case FIX_TRUNC_EXPR:
      {
        if ((!INTEGRAL_TYPE_P (lhs_type) || !SCALAR_FLOAT_TYPE_P (rhs1_type))
            && (!VECTOR_INTEGER_TYPE_P (lhs_type)
                || !VECTOR_FLOAT_TYPE_P(rhs1_type)))
          {
            error ("invalid types in conversion to integer");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            return true;
          }

        return false;
      }

    case VEC_UNPACK_HI_EXPR:
    case VEC_UNPACK_LO_EXPR:
    case REDUC_MAX_EXPR:
    case REDUC_MIN_EXPR:
    case REDUC_PLUS_EXPR:
    case VEC_UNPACK_FLOAT_HI_EXPR:
    case VEC_UNPACK_FLOAT_LO_EXPR:
      /* FIXME.  */
      return false;

    case NEGATE_EXPR:
    case ABS_EXPR:
    case BIT_NOT_EXPR:
    case PAREN_EXPR:
    case NON_LVALUE_EXPR:
    case CONJ_EXPR:
      break;

    default:
      gcc_unreachable ();
    }

  /* For the remaining codes assert there is no conversion involved.  */
  if (!useless_type_conversion_p (lhs_type, rhs1_type))
    {
      error ("non-trivial conversion in unary operation");
      debug_generic_expr (lhs_type);
      debug_generic_expr (rhs1_type);
      return true;
    }

  return false;
}

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

static bool
verify_gimple_assign_binary (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);
  tree rhs2 = gimple_assign_rhs2 (stmt);
  tree rhs2_type = TREE_TYPE (rhs2);

  if (!is_gimple_reg (lhs))
    {
      error ("non-register as LHS of binary operation");
      return true;
    }

  if (!is_gimple_val (rhs1)
      || !is_gimple_val (rhs2))
    {
      error ("invalid operands in binary operation");
      return true;
    }

  /* First handle operations that involve different types.  */
  switch (rhs_code)
    {
    case COMPLEX_EXPR:
      {
        if (TREE_CODE (lhs_type) != COMPLEX_TYPE
            || !(INTEGRAL_TYPE_P (rhs1_type)
                 || SCALAR_FLOAT_TYPE_P (rhs1_type))
            || !(INTEGRAL_TYPE_P (rhs2_type)
                 || SCALAR_FLOAT_TYPE_P (rhs2_type)))
          {
            error ("type mismatch in complex expression");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            debug_generic_expr (rhs2_type);
            return true;
          }

        return false;
      }

    case LSHIFT_EXPR:
    case RSHIFT_EXPR:
    case LROTATE_EXPR:
    case RROTATE_EXPR:
      {
        /* Shifts and rotates are ok on integral types, fixed point
           types and integer vector types.  */
        if ((!INTEGRAL_TYPE_P (rhs1_type)
             && !FIXED_POINT_TYPE_P (rhs1_type)
             && !(TREE_CODE (rhs1_type) == VECTOR_TYPE
                  && INTEGRAL_TYPE_P (TREE_TYPE (rhs1_type))))
            || (!INTEGRAL_TYPE_P (rhs2_type)
                /* Vector shifts of vectors are also ok.  */
                && !(TREE_CODE (rhs1_type) == VECTOR_TYPE
                     && INTEGRAL_TYPE_P (TREE_TYPE (rhs1_type))
                     && TREE_CODE (rhs2_type) == VECTOR_TYPE
                     && INTEGRAL_TYPE_P (TREE_TYPE (rhs2_type))))
            || !useless_type_conversion_p (lhs_type, rhs1_type))
          {
            error ("type mismatch in shift expression");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            debug_generic_expr (rhs2_type);
            return true;
          }

        return false;
      }

    case VEC_LSHIFT_EXPR:
    case VEC_RSHIFT_EXPR:
      {
        if (TREE_CODE (rhs1_type) != VECTOR_TYPE
            || !(INTEGRAL_TYPE_P (TREE_TYPE (rhs1_type))
                 || POINTER_TYPE_P (TREE_TYPE (rhs1_type))
                 || FIXED_POINT_TYPE_P (TREE_TYPE (rhs1_type))
                 || SCALAR_FLOAT_TYPE_P (TREE_TYPE (rhs1_type)))
            || (!INTEGRAL_TYPE_P (rhs2_type)
                && (TREE_CODE (rhs2_type) != VECTOR_TYPE
                    || !INTEGRAL_TYPE_P (TREE_TYPE (rhs2_type))))
            || !useless_type_conversion_p (lhs_type, rhs1_type))
          {
            error ("type mismatch in vector shift expression");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            debug_generic_expr (rhs2_type);
            return true;
          }
        /* For shifting a vector of non-integral components we
           only allow shifting by a constant multiple of the element size.  */
        if (!INTEGRAL_TYPE_P (TREE_TYPE (rhs1_type))
            && (TREE_CODE (rhs2) != INTEGER_CST
                || !div_if_zero_remainder (EXACT_DIV_EXPR, rhs2,
                                           TYPE_SIZE (TREE_TYPE (rhs1_type)))))
          {
            error ("non-element sized vector shift of floating point vector");
            return true;
          }

        return false;
      }

    case WIDEN_LSHIFT_EXPR:
      {
        if (!INTEGRAL_TYPE_P (lhs_type)
            || !INTEGRAL_TYPE_P (rhs1_type)
            || TREE_CODE (rhs2) != INTEGER_CST
            || (2 * TYPE_PRECISION (rhs1_type) > TYPE_PRECISION (lhs_type)))
          {
            error ("type mismatch in widening vector shift expression");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            debug_generic_expr (rhs2_type);
            return true;
          }

        return false;
      }

    case VEC_WIDEN_LSHIFT_HI_EXPR:
    case VEC_WIDEN_LSHIFT_LO_EXPR:
      {
        if (TREE_CODE (rhs1_type) != VECTOR_TYPE
            || TREE_CODE (lhs_type) != VECTOR_TYPE
            || !INTEGRAL_TYPE_P (TREE_TYPE (rhs1_type))
            || !INTEGRAL_TYPE_P (TREE_TYPE (lhs_type))
            || TREE_CODE (rhs2) != INTEGER_CST
            || (2 * TYPE_PRECISION (TREE_TYPE (rhs1_type))
                > TYPE_PRECISION (TREE_TYPE (lhs_type))))
          {
            error ("type mismatch in widening vector shift expression");
            debug_generic_expr (lhs_type);
            debug_generic_expr (rhs1_type);
            debug_generic_expr (rhs2_type);
            return true;
          }

        return false;