Initial checkin of GCC 4.9.0 from trunk (r208799).

Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba

1 files changed, 1171 insertions, 0 deletions

diff --git a/gcc-4.9/gcc/tree-cfgcleanup.c b/gcc-4.9/gcc/tree-cfgcleanup.c
new file mode 100644
index 000000000..08401dd2d
--- /dev/null
+++ b/gcc-4.9/gcc/tree-cfgcleanup.c
@@ -0,0 +1,1171 @@
+/* CFG cleanup for trees.
+   Copyright (C) 2001-2014 Free Software Foundation, Inc.
+
+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 "diagnostic-core.h"
+#include "flags.h"
+#include "function.h"
+#include "langhooks.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "tree-eh.h"
+#include "gimple-expr.h"
+#include "is-a.h"
+#include "gimple.h"
+#include "gimplify.h"
+#include "gimple-iterator.h"
+#include "gimple-ssa.h"
+#include "tree-cfg.h"
+#include "tree-phinodes.h"
+#include "ssa-iterators.h"
+#include "stringpool.h"
+#include "tree-ssanames.h"
+#include "tree-ssa-loop-manip.h"
+#include "expr.h"
+#include "tree-dfa.h"
+#include "tree-ssa.h"
+#include "tree-pass.h"
+#include "except.h"
+#include "cfgloop.h"
+#include "hashtab.h"
+#include "tree-ssa-propagate.h"
+#include "tree-scalar-evolution.h"
+
+/* The set of blocks in that at least one of the following changes happened:
+   -- the statement at the end of the block was changed
+   -- the block was newly created
+   -- the set of the predecessors of the block changed
+   -- the set of the successors of the block changed
+   ??? Maybe we could track these changes separately, since they determine
+       what cleanups it makes sense to try on the block.  */
+bitmap cfgcleanup_altered_bbs;
+
+/* Remove any fallthru edge from EV.  Return true if an edge was removed.  */
+
+static bool
+remove_fallthru_edge (vec<edge, va_gc> *ev)
+{
+  edge_iterator ei;
+  edge e;
+
+  FOR_EACH_EDGE (e, ei, ev)
+    if ((e->flags & EDGE_FALLTHRU) != 0)
+      {
+	if (e->flags & EDGE_COMPLEX)
+	  e->flags &= ~EDGE_FALLTHRU;
+	else
+	  remove_edge_and_dominated_blocks (e);
+	return true;
+      }
+  return false;
+}
+
+
+/* Disconnect an unreachable block in the control expression starting
+   at block BB.  */
+
+static bool
+cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
+{
+  edge taken_edge;
+  bool retval = false;
+  gimple stmt = gsi_stmt (gsi);
+  tree val;
+
+  if (!single_succ_p (bb))
+    {
+      edge e;
+      edge_iterator ei;
+      bool warned;
+      location_t loc;
+
+      fold_defer_overflow_warnings ();
+      loc = gimple_location (stmt);
+      switch (gimple_code (stmt))
+	{
+	case GIMPLE_COND:
+	  val = fold_binary_loc (loc, gimple_cond_code (stmt),
+				 boolean_type_node,
+			         gimple_cond_lhs (stmt),
+				 gimple_cond_rhs (stmt));
+	  break;
+
+	case GIMPLE_SWITCH:
+	  val = gimple_switch_index (stmt);
+	  break;
+
+	default:
+	  val = NULL_TREE;
+	}
+      taken_edge = find_taken_edge (bb, val);
+      if (!taken_edge)
+	{
+	  fold_undefer_and_ignore_overflow_warnings ();
+	  return false;
+	}
+
+      /* Remove all the edges except the one that is always executed.  */
+      warned = false;
+      for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
+	{
+	  if (e != taken_edge)
+	    {
+	      if (!warned)
+		{
+		  fold_undefer_overflow_warnings
+		    (true, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
+		  warned = true;
+		}
+
+	      taken_edge->probability += e->probability;
+	      taken_edge->count += e->count;
+	      remove_edge_and_dominated_blocks (e);
+	      retval = true;
+	    }
+	  else
+	    ei_next (&ei);
+	}
+      if (!warned)
+	fold_undefer_and_ignore_overflow_warnings ();
+      if (taken_edge->probability > REG_BR_PROB_BASE)
+	taken_edge->probability = REG_BR_PROB_BASE;
+    }
+  else
+    taken_edge = single_succ_edge (bb);
+
+  bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
+  gsi_remove (&gsi, true);
+  taken_edge->flags = EDGE_FALLTHRU;
+
+  return retval;
+}
+
+/* Try to remove superfluous control structures in basic block BB.  Returns
+   true if anything changes.  */
+
+static bool
+cleanup_control_flow_bb (basic_block bb)
+{
+  gimple_stmt_iterator gsi;
+  bool retval = false;
+  gimple stmt;
+
+  /* If the last statement of the block could throw and now cannot,
+     we need to prune cfg.  */
+  retval |= gimple_purge_dead_eh_edges (bb);
+
+  gsi = gsi_last_bb (bb);
+  if (gsi_end_p (gsi))
+    return retval;
+
+  stmt = gsi_stmt (gsi);
+
+  if (gimple_code (stmt) == GIMPLE_COND
+      || gimple_code (stmt) == GIMPLE_SWITCH)
+    retval |= cleanup_control_expr_graph (bb, gsi);
+  else if (gimple_code (stmt) == GIMPLE_GOTO
+	   && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR
+	   && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt), 0))
+	       == LABEL_DECL))
+    {
+      /* If we had a computed goto which has a compile-time determinable
+	 destination, then we can eliminate the goto.  */
+      edge e;
+      tree label;
+      edge_iterator ei;
+      basic_block target_block;
+
+      /* First look at all the outgoing edges.  Delete any outgoing
+	 edges which do not go to the right block.  For the one
+	 edge which goes to the right block, fix up its flags.  */
+      label = TREE_OPERAND (gimple_goto_dest (stmt), 0);
+      target_block = label_to_block (label);
+      for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
+	{
+	  if (e->dest != target_block)
+	    remove_edge_and_dominated_blocks (e);
+	  else
+	    {
+	      /* Turn off the EDGE_ABNORMAL flag.  */
+	      e->flags &= ~EDGE_ABNORMAL;
+
+	      /* And set EDGE_FALLTHRU.  */
+	      e->flags |= EDGE_FALLTHRU;
+	      ei_next (&ei);
+	    }
+	}
+
+      bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
+      bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index);
+
+      /* Remove the GOTO_EXPR as it is not needed.  The CFG has all the
+	 relevant information we need.  */
+      gsi_remove (&gsi, true);
+      retval = true;
+    }
+
+  /* Check for indirect calls that have been turned into
+     noreturn calls.  */
+  else if (is_gimple_call (stmt)
+           && gimple_call_noreturn_p (stmt)
+           && remove_fallthru_edge (bb->succs))
+    retval = true;
+
+  return retval;
+}
+
+/* Return true if basic block BB does nothing except pass control
+   flow to another block and that we can safely insert a label at
+   the start of the successor block.
+
+   As a precondition, we require that BB be not equal to
+   the entry block.  */
+
+static bool
+tree_forwarder_block_p (basic_block bb, bool phi_wanted)
+{
+  gimple_stmt_iterator gsi;
+  location_t locus;
+
+  /* BB must have a single outgoing edge.  */
+  if (single_succ_p (bb) != 1
+      /* If PHI_WANTED is false, BB must not have any PHI nodes.
+	 Otherwise, BB must have PHI nodes.  */
+      || gimple_seq_empty_p (phi_nodes (bb)) == phi_wanted
+      /* BB may not be a predecessor of the exit block.  */
+      || single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)
+      /* Nor should this be an infinite loop.  */
+      || single_succ (bb) == bb
+      /* BB may not have an abnormal outgoing edge.  */
+      || (single_succ_edge (bb)->flags & EDGE_ABNORMAL))
+    return false;
+
+  gcc_checking_assert (bb != ENTRY_BLOCK_PTR_FOR_FN (cfun));
+
+  locus = single_succ_edge (bb)->goto_locus;
+
+  /* There should not be an edge coming from entry, or an EH edge.  */
+  {
+    edge_iterator ei;
+    edge e;
+
+    FOR_EACH_EDGE (e, ei, bb->preds)
+      if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun) || (e->flags & EDGE_EH))
+	return false;
+      /* If goto_locus of any of the edges differs, prevent removing
+	 the forwarder block for -O0.  */
+      else if (optimize == 0 && e->goto_locus != locus)
+	return false;
+  }
+
+  /* Now walk through the statements backward.  We can ignore labels,
+     anything else means this is not a forwarder block.  */
+  for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
+    {
+      gimple stmt = gsi_stmt (gsi);
+
+      switch (gimple_code (stmt))
+	{
+	case GIMPLE_LABEL:
+	  if (DECL_NONLOCAL (gimple_label_label (stmt)))
+	    return false;
+	  if (optimize == 0 && gimple_location (stmt) != locus)
+	    return false;
+	  break;
+
+	  /* ??? For now, hope there's a corresponding debug
+	     assignment at the destination.  */
+	case GIMPLE_DEBUG:
+	  break;
+
+	default:
+	  return false;
+	}
+    }
+
+  if (current_loops)
+    {
+      basic_block dest;
+      /* Protect loop headers.  */
+      if (bb->loop_father->header == bb)
+	return false;
+
+      dest = EDGE_SUCC (bb, 0)->dest;
+      /* Protect loop preheaders and latches if requested.  */
+      if (dest->loop_father->header == dest)
+	{
+	  if (bb->loop_father == dest->loop_father)
+	    {
+	      if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
+		return false;
+	      /* If bb doesn't have a single predecessor we'd make this
+		 loop have multiple latches.  Don't do that if that
+		 would in turn require disambiguating them.  */
+	      return (single_pred_p (bb)
+		      || loops_state_satisfies_p
+		      	   (LOOPS_MAY_HAVE_MULTIPLE_LATCHES));
+	    }
+	  else if (bb->loop_father == loop_outer (dest->loop_father))
+	    return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS);
+	  /* Always preserve other edges into loop headers that are
+	     not simple latches or preheaders.  */
+	  return false;
+	}
+    }
+
+  return true;
+}
+
+/* If all the PHI nodes in DEST have alternatives for E1 and E2 and
+   those alternatives are equal in each of the PHI nodes, then return
+   true, else return false.  */
+
+static bool
+phi_alternatives_equal (basic_block dest, edge e1, edge e2)
+{
+  int n1 = e1->dest_idx;
+  int n2 = e2->dest_idx;
+  gimple_stmt_iterator gsi;
+
+  for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple phi = gsi_stmt (gsi);
+      tree val1 = gimple_phi_arg_def (phi, n1);
+      tree val2 = gimple_phi_arg_def (phi, n2);
+
+      gcc_assert (val1 != NULL_TREE);
+      gcc_assert (val2 != NULL_TREE);
+
+      if (!operand_equal_for_phi_arg_p (val1, val2))
+	return false;
+    }
+
+  return true;
+}
+
+/* Removes forwarder block BB.  Returns false if this failed.  */
+
+static bool
+remove_forwarder_block (basic_block bb)
+{
+  edge succ = single_succ_edge (bb), e, s;
+  basic_block dest = succ->dest;
+  gimple label;
+  edge_iterator ei;
+  gimple_stmt_iterator gsi, gsi_to;
+  bool can_move_debug_stmts;
+
+  /* We check for infinite loops already in tree_forwarder_block_p.
+     However it may happen that the infinite loop is created
+     afterwards due to removal of forwarders.  */
+  if (dest == bb)
+    return false;
+
+  /* If the destination block consists of a nonlocal label or is a
+     EH landing pad, do not merge it.  */
+  label = first_stmt (dest);
+  if (label
+      && gimple_code (label) == GIMPLE_LABEL
+      && (DECL_NONLOCAL (gimple_label_label (label))
+	  || EH_LANDING_PAD_NR (gimple_label_label (label)) != 0))
+    return false;
+
+  /* If there is an abnormal edge to basic block BB, but not into
+     dest, problems might occur during removal of the phi node at out
+     of ssa due to overlapping live ranges of registers.
+
+     If there is an abnormal edge in DEST, the problems would occur
+     anyway since cleanup_dead_labels would then merge the labels for
+     two different eh regions, and rest of exception handling code
+     does not like it.
+
+     So if there is an abnormal edge to BB, proceed only if there is
+     no abnormal edge to DEST and there are no phi nodes in DEST.  */
+  if (bb_has_abnormal_pred (bb)
+      && (bb_has_abnormal_pred (dest)
+	  || !gimple_seq_empty_p (phi_nodes (dest))))
+    return false;
+
+  /* If there are phi nodes in DEST, and some of the blocks that are
+     predecessors of BB are also predecessors of DEST, check that the
+     phi node arguments match.  */
+  if (!gimple_seq_empty_p (phi_nodes (dest)))
+    {
+      FOR_EACH_EDGE (e, ei, bb->preds)
+	{
+	  s = find_edge (e->src, dest);
+	  if (!s)
+	    continue;
+
+	  if (!phi_alternatives_equal (dest, succ, s))
+	    return false;
+	}
+    }
+
+  can_move_debug_stmts = MAY_HAVE_DEBUG_STMTS && single_pred_p (dest);
+
+  basic_block pred = NULL;
+  if (single_pred_p (bb))
+    pred = single_pred (bb);
+
+  /* Redirect the edges.  */
+  for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
+    {
+      bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index);
+
+      if (e->flags & EDGE_ABNORMAL)
+	{
+	  /* If there is an abnormal edge, redirect it anyway, and
+	     move the labels to the new block to make it legal.  */
+	  s = redirect_edge_succ_nodup (e, dest);
+	}
+      else
+	s = redirect_edge_and_branch (e, dest);
+
+      if (s == e)
+	{
+	  /* Create arguments for the phi nodes, since the edge was not
+	     here before.  */
+	  for (gsi = gsi_start_phis (dest);
+	       !gsi_end_p (gsi);
+	       gsi_next (&gsi))
+	    {
+	      gimple phi = gsi_stmt (gsi);
+	      source_location l = gimple_phi_arg_location_from_edge (phi, succ);
+	      tree def = gimple_phi_arg_def (phi, succ->dest_idx);
+	      add_phi_arg (phi, unshare_expr (def), s, l);
+	    }
+	}
+    }
+
+  /* Move nonlocal labels and computed goto targets as well as user
+     defined labels and labels with an EH landing pad number to the
+     new block, so that the redirection of the abnormal edges works,
+     jump targets end up in a sane place and debug information for
+     labels is retained.  */
+  gsi_to = gsi_start_bb (dest);
+  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
+    {
+      tree decl;
+      label = gsi_stmt (gsi);
+      if (is_gimple_debug (label))
+	break;
+      decl = gimple_label_label (label);
+      if (EH_LANDING_PAD_NR (decl) != 0
+	  || DECL_NONLOCAL (decl)
+	  || FORCED_LABEL (decl)
+	  || !DECL_ARTIFICIAL (decl))
+	{
+	  gsi_remove (&gsi, false);
+	  gsi_insert_before (&gsi_to, label, GSI_SAME_STMT);
+	}
+      else
+	gsi_next (&gsi);
+    }
+
+  /* Move debug statements if the destination has a single predecessor.  */
+  if (can_move_debug_stmts)
+    {
+      gsi_to = gsi_after_labels (dest);
+      for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); )
+	{
+	  gimple debug = gsi_stmt (gsi);
+	  if (!is_gimple_debug (debug))
+	    break;
+	  gsi_remove (&gsi, false);
+	  gsi_insert_before (&gsi_to, debug, GSI_SAME_STMT);
+	}
+    }
+
+  bitmap_set_bit (cfgcleanup_altered_bbs, dest->index);
+
+  /* Update the dominators.  */
+  if (dom_info_available_p (CDI_DOMINATORS))
+    {
+      basic_block dom, dombb, domdest;
+
+      dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
+      domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
+      if (domdest == bb)
+	{
+	  /* Shortcut to avoid calling (relatively expensive)
+	     nearest_common_dominator unless necessary.  */
+	  dom = dombb;
+	}
+      else
+	dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
+
+      set_immediate_dominator (CDI_DOMINATORS, dest, dom);
+    }
+
+  /* Adjust latch infomation of BB's parent loop as otherwise
+     the cfg hook has a hard time not to kill the loop.  */
+  if (current_loops && bb->loop_father->latch == bb)
+    bb->loop_father->latch = pred;
+
+  /* And kill the forwarder block.  */
+  delete_basic_block (bb);
+
+  return true;
+}
+
+/* STMT is a call that has been discovered noreturn.  Fixup the CFG
+   and remove LHS.  Return true if something changed.  */
+
+bool
+fixup_noreturn_call (gimple stmt)
+{
+  basic_block bb = gimple_bb (stmt);
+  bool changed = false;
+
+  if (gimple_call_builtin_p (stmt, BUILT_IN_RETURN))
+    return false;
+
+  /* First split basic block if stmt is not last.  */
+  if (stmt != gsi_stmt (gsi_last_bb (bb)))
+    split_block (bb, stmt);
+
+  changed |= remove_fallthru_edge (bb->succs);
+
+  /* If there is LHS, remove it.  */
+  if (gimple_call_lhs (stmt))
+    {
+      tree op = gimple_call_lhs (stmt);
+      gimple_call_set_lhs (stmt, NULL_TREE);
+
+      /* We need to remove SSA name to avoid checking errors.
+	 All uses are dominated by the noreturn and thus will
+	 be removed afterwards.
+	 We proactively remove affected non-PHI statements to avoid
+	 fixup_cfg from trying to update them and crashing.  */
+      if (TREE_CODE (op) == SSA_NAME)
+	{
+	  use_operand_p use_p;
+          imm_use_iterator iter;
+	  gimple use_stmt;
+	  bitmap_iterator bi;
+	  unsigned int bb_index;
+
+	  bitmap blocks = BITMAP_ALLOC (NULL);
+
+          FOR_EACH_IMM_USE_STMT (use_stmt, iter, op)
+	    {
+	      if (gimple_code (use_stmt) != GIMPLE_PHI)
+	        bitmap_set_bit (blocks, gimple_bb (use_stmt)->index);
+	      else
+		FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+		  SET_USE (use_p, error_mark_node);
+	    }
+	  EXECUTE_IF_SET_IN_BITMAP (blocks, 0, bb_index, bi)
+	    delete_basic_block (BASIC_BLOCK_FOR_FN (cfun, bb_index));
+	  BITMAP_FREE (blocks);
+	  release_ssa_name (op);
+	}
+      update_stmt (stmt);
+      changed = true;
+    }
+  /* Similarly remove VDEF if there is any.  */
+  else if (gimple_vdef (stmt))
+    update_stmt (stmt);
+  return changed;
+}
+
+
+/* Split basic blocks on calls in the middle of a basic block that are now
+   known not to return, and remove the unreachable code.  */
+
+static bool
+split_bbs_on_noreturn_calls (void)
+{
+  bool changed = false;
+  gimple stmt;
+  basic_block bb;
+
+  /* Detect cases where a mid-block call is now known not to return.  */
+  if (cfun->gimple_df)
+    while (vec_safe_length (MODIFIED_NORETURN_CALLS (cfun)))
+      {
+	stmt = MODIFIED_NORETURN_CALLS (cfun)->pop ();
+	bb = gimple_bb (stmt);
+	/* BB might be deleted at this point, so verify first
+	   BB is present in the cfg.  */
+	if (bb == NULL
+	    || bb->index < NUM_FIXED_BLOCKS
+	    || bb->index >= last_basic_block_for_fn (cfun)
+	    || BASIC_BLOCK_FOR_FN (cfun, bb->index) != bb
+	    || !gimple_call_noreturn_p (stmt))
+	  continue;
+
+	changed |= fixup_noreturn_call (stmt);
+      }
+
+  return changed;
+}
+
+/* Tries to cleanup cfg in basic block BB.  Returns true if anything
+   changes.  */
+
+static bool
+cleanup_tree_cfg_bb (basic_block bb)
+{
+  bool retval = cleanup_control_flow_bb (bb);
+
+  if (tree_forwarder_block_p (bb, false)
+      && remove_forwarder_block (bb))
+    return true;
+
+  /* Merging the blocks may create new opportunities for folding
+     conditional branches (due to the elimination of single-valued PHI
+     nodes).  */
+  if (single_succ_p (bb)
+      && can_merge_blocks_p (bb, single_succ (bb)))
+    {
+      merge_blocks (bb, single_succ (bb));
+      return true;
+    }
+
+  return retval;
+}
+
+/* Iterate the cfg cleanups, while anything changes.  */
+
+static bool
+cleanup_tree_cfg_1 (void)
+{
+  bool retval = false;
+  basic_block bb;
+  unsigned i, n;
+
+  retval |= split_bbs_on_noreturn_calls ();
+
+  /* Prepare the worklists of altered blocks.  */
+  cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL);
+
+  /* During forwarder block cleanup, we may redirect edges out of
+     SWITCH_EXPRs, which can get expensive.  So we want to enable
+     recording of edge to CASE_LABEL_EXPR.  */
+  start_recording_case_labels ();
+
+  /* Start by iterating over all basic blocks.  We cannot use FOR_EACH_BB_FN,
+     since the basic blocks may get removed.  */
+  n = last_basic_block_for_fn (cfun);
+  for (i = NUM_FIXED_BLOCKS; i < n; i++)
+    {
+      bb = BASIC_BLOCK_FOR_FN (cfun, i);
+      if (bb)
+	retval |= cleanup_tree_cfg_bb (bb);
+    }
+
+  /* Now process the altered blocks, as long as any are available.  */
+  while (!bitmap_empty_p (cfgcleanup_altered_bbs))
+    {
+      i = bitmap_first_set_bit (cfgcleanup_altered_bbs);
+      bitmap_clear_bit (cfgcleanup_altered_bbs, i);
+      if (i < NUM_FIXED_BLOCKS)
+	continue;
+
+      bb = BASIC_BLOCK_FOR_FN (cfun, i);
+      if (!bb)
+	continue;
+
+      retval |= cleanup_tree_cfg_bb (bb);
+
+      /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn
+	 calls.  */
+      retval |= split_bbs_on_noreturn_calls ();
+    }
+
+  end_recording_case_labels ();
+  BITMAP_FREE (cfgcleanup_altered_bbs);
+  return retval;
+}
+
+
+/* Remove unreachable blocks and other miscellaneous clean up work.
+   Return true if the flowgraph was modified, false otherwise.  */
+
+static bool
+cleanup_tree_cfg_noloop (void)
+{
+  bool changed;
+
+  timevar_push (TV_TREE_CLEANUP_CFG);
+
+  /* Iterate until there are no more cleanups left to do.  If any
+     iteration changed the flowgraph, set CHANGED to true.
+
+     If dominance information is available, there cannot be any unreachable
+     blocks.  */
+  if (!dom_info_available_p (CDI_DOMINATORS))
+    {
+      changed = delete_unreachable_blocks ();
+      calculate_dominance_info (CDI_DOMINATORS);
+    }
+  else
+    {
+#ifdef ENABLE_CHECKING
+      verify_dominators (CDI_DOMINATORS);
+#endif
+      changed = false;
+    }
+
+  changed |= cleanup_tree_cfg_1 ();
+
+  gcc_assert (dom_info_available_p (CDI_DOMINATORS));
+  compact_blocks ();
+
+#ifdef ENABLE_CHECKING
+  verify_flow_info ();
+#endif
+
+  timevar_pop (TV_TREE_CLEANUP_CFG);
+
+  if (changed && current_loops)
+    loops_state_set (LOOPS_NEED_FIXUP);
+
+  return changed;
+}
+
+/* Repairs loop structures.  */
+
+static void
+repair_loop_structures (void)
+{
+  bitmap changed_bbs;
+  unsigned n_new_loops;
+
+  calculate_dominance_info (CDI_DOMINATORS);
+
+  timevar_push (TV_REPAIR_LOOPS);
+  changed_bbs = BITMAP_ALLOC (NULL);
+  n_new_loops = fix_loop_structure (changed_bbs);
+
+  /* This usually does nothing.  But sometimes parts of cfg that originally
+     were inside a loop get out of it due to edge removal (since they
+     become unreachable by back edges from latch).  Also a former
+     irreducible loop can become reducible - in this case force a full
+     rewrite into loop-closed SSA form.  */
+  if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
+    rewrite_into_loop_closed_ssa (n_new_loops ? NULL : changed_bbs,
+				  TODO_update_ssa);
+
+  BITMAP_FREE (changed_bbs);
+
+#ifdef ENABLE_CHECKING
+  verify_loop_structure ();
+#endif
+  scev_reset ();
+
+  timevar_pop (TV_REPAIR_LOOPS);
+}
+
+/* Cleanup cfg and repair loop structures.  */
+
+bool
+cleanup_tree_cfg (void)
+{
+  bool changed = cleanup_tree_cfg_noloop ();
+
+  if (current_loops != NULL
+      && loops_state_satisfies_p (LOOPS_NEED_FIXUP))
+    repair_loop_structures ();
+
+  return changed;
+}
+
+/* Tries to merge the PHI nodes at BB into those at BB's sole successor.
+   Returns true if successful.  */
+
+static bool
+remove_forwarder_block_with_phi (basic_block bb)
+{
+  edge succ = single_succ_edge (bb);
+  basic_block dest = succ->dest;
+  gimple label;
+  basic_block dombb, domdest, dom;
+
+  /* We check for infinite loops already in tree_forwarder_block_p.
+     However it may happen that the infinite loop is created
+     afterwards due to removal of forwarders.  */
+  if (dest == bb)
+    return false;
+
+  /* If the destination block consists of a nonlocal label, do not
+     merge it.  */
+  label = first_stmt (dest);
+  if (label
+      && gimple_code (label) == GIMPLE_LABEL
+      && DECL_NONLOCAL (gimple_label_label (label)))
+    return false;
+
+  /* Record BB's single pred in case we need to update the father
+     loop's latch information later.  */
+  basic_block pred = NULL;
+  if (single_pred_p (bb))
+    pred = single_pred (bb);
+
+  /* Redirect each incoming edge to BB to DEST.  */
+  while (EDGE_COUNT (bb->preds) > 0)
+    {
+      edge e = EDGE_PRED (bb, 0), s;
+      gimple_stmt_iterator gsi;
+
+      s = find_edge (e->src, dest);
+      if (s)
+	{
+	  /* We already have an edge S from E->src to DEST.  If S and
+	     E->dest's sole successor edge have the same PHI arguments
+	     at DEST, redirect S to DEST.  */
+	  if (phi_alternatives_equal (dest, s, succ))
+	    {
+	      e = redirect_edge_and_branch (e, dest);
+	      redirect_edge_var_map_clear (e);
+	      continue;
+	    }
+
+	  /* PHI arguments are different.  Create a forwarder block by
+	     splitting E so that we can merge PHI arguments on E to
+	     DEST.  */
+	  e = single_succ_edge (split_edge (e));
+	}
+
+      s = redirect_edge_and_branch (e, dest);
+
+      /* redirect_edge_and_branch must not create a new edge.  */
+      gcc_assert (s == e);
+
+      /* Add to the PHI nodes at DEST each PHI argument removed at the
+	 destination of E.  */
+      for (gsi = gsi_start_phis (dest);
+	   !gsi_end_p (gsi);
+	   gsi_next (&gsi))
+	{
+	  gimple phi = gsi_stmt (gsi);
+	  tree def = gimple_phi_arg_def (phi, succ->dest_idx);
+	  source_location locus = gimple_phi_arg_location_from_edge (phi, succ);
+
+	  if (TREE_CODE (def) == SSA_NAME)
+	    {
+	      edge_var_map_vector *head;
+	      edge_var_map *vm;
+	      size_t i;
+
+	      /* If DEF is one of the results of PHI nodes removed during
+		 redirection, replace it with the PHI argument that used
+		 to be on E.  */
+	      head = redirect_edge_var_map_vector (e);
+	      FOR_EACH_VEC_SAFE_ELT (head, i, vm)
+		{
+		  tree old_arg = redirect_edge_var_map_result (vm);
+		  tree new_arg = redirect_edge_var_map_def (vm);
+
+		  if (def == old_arg)
+		    {
+		      def = new_arg;
+		      locus = redirect_edge_var_map_location (vm);
+		      break;
+		    }
+		}
+	    }
+
+	  add_phi_arg (phi, def, s, locus);
+	}
+
+      redirect_edge_var_map_clear (e);
+    }
+
+  /* Update the dominators.  */
+  dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
+  domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
+  if (domdest == bb)
+    {
+      /* Shortcut to avoid calling (relatively expensive)
+	 nearest_common_dominator unless necessary.  */
+      dom = dombb;
+    }
+  else
+    dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
+
+  set_immediate_dominator (CDI_DOMINATORS, dest, dom);
+
+  /* Adjust latch infomation of BB's parent loop as otherwise
+     the cfg hook has a hard time not to kill the loop.  */
+  if (current_loops && bb->loop_father->latch == bb)
+    bb->loop_father->latch = pred;
+
+  /* Remove BB since all of BB's incoming edges have been redirected
+     to DEST.  */
+  delete_basic_block (bb);
+
+  return true;
+}
+
+/* This pass merges PHI nodes if one feeds into another.  For example,
+   suppose we have the following:
+
+  goto <bb 9> (<L9>);
+
+<L8>:;
+  tem_17 = foo ();
+
+  # tem_6 = PHI <tem_17(8), tem_23(7)>;
+<L9>:;
+
+  # tem_3 = PHI <tem_6(9), tem_2(5)>;
+<L10>:;
+
+  Then we merge the first PHI node into the second one like so:
+
+  goto <bb 9> (<L10>);
+
+<L8>:;
+  tem_17 = foo ();
+
+  # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>;
+<L10>:;
+*/
+
+static unsigned int
+merge_phi_nodes (void)
+{
+  basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
+  basic_block *current = worklist;
+  basic_block bb;
+
+  calculate_dominance_info (CDI_DOMINATORS);
+
+  /* Find all PHI nodes that we may be able to merge.  */
+  FOR_EACH_BB_FN (bb, cfun)
+    {
+      basic_block dest;
+
+      /* Look for a forwarder block with PHI nodes.  */
+      if (!tree_forwarder_block_p (bb, true))
+	continue;
+
+      dest = single_succ (bb);
+
+      /* We have to feed into another basic block with PHI
+	 nodes.  */
+      if (gimple_seq_empty_p (phi_nodes (dest))
+	  /* We don't want to deal with a basic block with
+	     abnormal edges.  */
+	  || bb_has_abnormal_pred (bb))
+	continue;
+
+      if (!dominated_by_p (CDI_DOMINATORS, dest, bb))
+	{
+	  /* If BB does not dominate DEST, then the PHI nodes at
+	     DEST must be the only users of the results of the PHI
+	     nodes at BB.  */
+	  *current++ = bb;
+	}
+      else
+	{
+	  gimple_stmt_iterator gsi;
+	  unsigned int dest_idx = single_succ_edge (bb)->dest_idx;
+
+	  /* BB dominates DEST.  There may be many users of the PHI
+	     nodes in BB.  However, there is still a trivial case we
+	     can handle.  If the result of every PHI in BB is used
+	     only by a PHI in DEST, then we can trivially merge the
+	     PHI nodes from BB into DEST.  */
+	  for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
+	       gsi_next (&gsi))
+	    {
+	      gimple phi = gsi_stmt (gsi);
+	      tree result = gimple_phi_result (phi);
+	      use_operand_p imm_use;
+	      gimple use_stmt;
+
+	      /* If the PHI's result is never used, then we can just
+		 ignore it.  */
+	      if (has_zero_uses (result))
+		continue;
+
+	      /* Get the single use of the result of this PHI node.  */
+  	      if (!single_imm_use (result, &imm_use, &use_stmt)
+		  || gimple_code (use_stmt) != GIMPLE_PHI
+		  || gimple_bb (use_stmt) != dest
+		  || gimple_phi_arg_def (use_stmt, dest_idx) != result)
+		break;
+	    }
+
+	  /* If the loop above iterated through all the PHI nodes
+	     in BB, then we can merge the PHIs from BB into DEST.  */
+	  if (gsi_end_p (gsi))
+	    *current++ = bb;
+	}
+    }
+
+  /* Now let's drain WORKLIST.  */
+  bool changed = false;
+  while (current != worklist)
+    {
+      bb = *--current;
+      changed |= remove_forwarder_block_with_phi (bb);
+    }
+  free (worklist);
+
+  /* Removing forwarder blocks can cause formerly irreducible loops
+     to become reducible if we merged two entry blocks.  */
+  if (changed
+      && current_loops)
+    loops_state_set (LOOPS_NEED_FIXUP);
+
+  return 0;
+}
+
+static bool
+gate_merge_phi (void)
+{
+  return 1;
+}
+
+namespace {
+
+const pass_data pass_data_merge_phi =
+{
+  GIMPLE_PASS, /* type */
+  "mergephi", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  true, /* has_gate */
+  true, /* has_execute */
+  TV_TREE_MERGE_PHI, /* tv_id */
+  ( PROP_cfg | PROP_ssa ), /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  TODO_verify_ssa, /* todo_flags_finish */
+};
+
+class pass_merge_phi : public gimple_opt_pass
+{
+public:
+  pass_merge_phi (gcc::context *ctxt)
+    : gimple_opt_pass (pass_data_merge_phi, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  opt_pass * clone () { return new pass_merge_phi (m_ctxt); }
+  bool gate () { return gate_merge_phi (); }
+  unsigned int execute () { return merge_phi_nodes (); }
+
+}; // class pass_merge_phi
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_merge_phi (gcc::context *ctxt)
+{
+  return new pass_merge_phi (ctxt);
+}
+
+/* Pass: cleanup the CFG just before expanding trees to RTL.
+   This is just a round of label cleanups and case node grouping
+   because after the tree optimizers have run such cleanups may
+   be necessary.  */
+
+static unsigned int
+execute_cleanup_cfg_post_optimizing (void)
+{
+  unsigned int todo = 0;
+  if (cleanup_tree_cfg ())
+    todo |= TODO_update_ssa;
+  maybe_remove_unreachable_handlers ();
+  cleanup_dead_labels ();
+  group_case_labels ();
+  if ((flag_compare_debug_opt || flag_compare_debug)
+      && flag_dump_final_insns)
+    {
+      FILE *final_output = fopen (flag_dump_final_insns, "a");
+
+      if (!final_output)
+	{
+	  error ("could not open final insn dump file %qs: %m",
+		 flag_dump_final_insns);
+	  flag_dump_final_insns = NULL;
+	}
+      else
+	{
+	  int save_unnumbered = flag_dump_unnumbered;
+	  int save_noaddr = flag_dump_noaddr;
+
+	  flag_dump_noaddr = flag_dump_unnumbered = 1;
+	  fprintf (final_output, "\n");
+	  dump_enumerated_decls (final_output, dump_flags | TDF_NOUID);
+	  flag_dump_noaddr = save_noaddr;
+	  flag_dump_unnumbered = save_unnumbered;
+	  if (fclose (final_output))
+	    {
+	      error ("could not close final insn dump file %qs: %m",
+		     flag_dump_final_insns);
+	      flag_dump_final_insns = NULL;
+	    }
+	}
+    }
+  return todo;
+}
+
+namespace {
+
+const pass_data pass_data_cleanup_cfg_post_optimizing =
+{
+  GIMPLE_PASS, /* type */
+  "optimized", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  false, /* has_gate */
+  true, /* has_execute */
+  TV_TREE_CLEANUP_CFG, /* tv_id */
+  PROP_cfg, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  TODO_remove_unused_locals, /* todo_flags_finish */
+};
+
+class pass_cleanup_cfg_post_optimizing : public gimple_opt_pass
+{
+public:
+  pass_cleanup_cfg_post_optimizing (gcc::context *ctxt)
+    : gimple_opt_pass (pass_data_cleanup_cfg_post_optimizing, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  unsigned int execute () {
+    return execute_cleanup_cfg_post_optimizing ();
+  }
+
+}; // class pass_cleanup_cfg_post_optimizing
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_cleanup_cfg_post_optimizing (gcc::context *ctxt)
+{
+  return new pass_cleanup_cfg_post_optimizing (ctxt);
+}
+
+