--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/tree-ssa-phiopt.c	Fri Jul 17 14:47:48 2009 +0900
@@ -0,0 +1,1318 @@
+/* Optimization of PHI nodes by converting them into straightline code.
+   Copyright (C) 2004, 2005, 2006, 2007, 2008 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 "ggc.h"
+#include "tree.h"
+#include "rtl.h"
+#include "flags.h"
+#include "tm_p.h"
+#include "basic-block.h"
+#include "timevar.h"
+#include "diagnostic.h"
+#include "tree-flow.h"
+#include "tree-pass.h"
+#include "tree-dump.h"
+#include "langhooks.h"
+#include "pointer-set.h"
+#include "domwalk.h"
+
+static unsigned int tree_ssa_phiopt (void);
+static unsigned int tree_ssa_phiopt_worker (bool);
+static bool conditional_replacement (basic_block, basic_block,
+				     edge, edge, gimple, tree, tree);
+static bool value_replacement (basic_block, basic_block,
+			       edge, edge, gimple, tree, tree);
+static bool minmax_replacement (basic_block, basic_block,
+				edge, edge, gimple, tree, tree);
+static bool abs_replacement (basic_block, basic_block,
+			     edge, edge, gimple, tree, tree);
+static bool cond_store_replacement (basic_block, basic_block, edge, edge,
+				    struct pointer_set_t *);
+static struct pointer_set_t * get_non_trapping (void);
+static void replace_phi_edge_with_variable (basic_block, edge, gimple, tree);
+
+/* This pass tries to replaces an if-then-else block with an
+   assignment.  We have four kinds of transformations.  Some of these
+   transformations are also performed by the ifcvt RTL optimizer.
+
+   Conditional Replacement
+   -----------------------
+
+   This transformation, implemented in conditional_replacement,
+   replaces
+
+     bb0:
+      if (cond) goto bb2; else goto bb1;
+     bb1:
+     bb2:
+      x = PHI <0 (bb1), 1 (bb0), ...>;
+
+   with
+
+     bb0:
+      x' = cond;
+      goto bb2;
+     bb2:
+      x = PHI <x' (bb0), ...>;
+
+   We remove bb1 as it becomes unreachable.  This occurs often due to
+   gimplification of conditionals.
+
+   Value Replacement
+   -----------------
+
+   This transformation, implemented in value_replacement, replaces
+
+     bb0:
+       if (a != b) goto bb2; else goto bb1;
+     bb1:
+     bb2:
+       x = PHI <a (bb1), b (bb0), ...>;
+
+   with
+
+     bb0:
+     bb2:
+       x = PHI <b (bb0), ...>;
+
+   This opportunity can sometimes occur as a result of other
+   optimizations.
+
+   ABS Replacement
+   ---------------
+
+   This transformation, implemented in abs_replacement, replaces
+
+     bb0:
+       if (a >= 0) goto bb2; else goto bb1;
+     bb1:
+       x = -a;
+     bb2:
+       x = PHI <x (bb1), a (bb0), ...>;
+
+   with
+
+     bb0:
+       x' = ABS_EXPR< a >;
+     bb2:
+       x = PHI <x' (bb0), ...>;
+
+   MIN/MAX Replacement
+   -------------------
+
+   This transformation, minmax_replacement replaces
+
+     bb0:
+       if (a <= b) goto bb2; else goto bb1;
+     bb1:
+     bb2:
+       x = PHI <b (bb1), a (bb0), ...>;
+
+   with
+
+     bb0:
+       x' = MIN_EXPR (a, b)
+     bb2:
+       x = PHI <x' (bb0), ...>;
+
+   A similar transformation is done for MAX_EXPR.  */
+
+static unsigned int
+tree_ssa_phiopt (void)
+{
+  return tree_ssa_phiopt_worker (false);
+}
+
+/* This pass tries to transform conditional stores into unconditional
+   ones, enabling further simplifications with the simpler then and else
+   blocks.  In particular it replaces this:
+
+     bb0:
+       if (cond) goto bb2; else goto bb1;
+     bb1:
+       *p = RHS
+     bb2:
+
+   with
+
+     bb0:
+       if (cond) goto bb1; else goto bb2;
+     bb1:
+       condtmp' = *p;
+     bb2:
+       condtmp = PHI <RHS, condtmp'>
+       *p = condtmp
+
+   This transformation can only be done under several constraints,
+   documented below.  */
+
+static unsigned int
+tree_ssa_cs_elim (void)
+{
+  return tree_ssa_phiopt_worker (true);
+}
+
+/* For conditional store replacement we need a temporary to
+   put the old contents of the memory in.  */
+static tree condstoretemp;
+
+/* The core routine of conditional store replacement and normal
+   phi optimizations.  Both share much of the infrastructure in how
+   to match applicable basic block patterns.  DO_STORE_ELIM is true
+   when we want to do conditional store replacement, false otherwise.  */
+static unsigned int
+tree_ssa_phiopt_worker (bool do_store_elim)
+{
+  basic_block bb;
+  basic_block *bb_order;
+  unsigned n, i;
+  bool cfgchanged = false;
+  struct pointer_set_t *nontrap = 0;
+
+  if (do_store_elim)
+    {
+      condstoretemp = NULL_TREE;
+      /* Calculate the set of non-trapping memory accesses.  */
+      nontrap = get_non_trapping ();
+    }
+
+  /* Search every basic block for COND_EXPR we may be able to optimize.
+
+     We walk the blocks in order that guarantees that a block with
+     a single predecessor is processed before the predecessor.
+     This ensures that we collapse inner ifs before visiting the
+     outer ones, and also that we do not try to visit a removed
+     block.  */
+  bb_order = blocks_in_phiopt_order ();
+  n = n_basic_blocks - NUM_FIXED_BLOCKS;
+
+  for (i = 0; i < n; i++) 
+    {
+      gimple cond_stmt, phi;
+      basic_block bb1, bb2;
+      edge e1, e2;
+      tree arg0, arg1;
+
+      bb = bb_order[i];
+
+      cond_stmt = last_stmt (bb);
+      /* Check to see if the last statement is a GIMPLE_COND.  */
+      if (!cond_stmt
+          || gimple_code (cond_stmt) != GIMPLE_COND)
+        continue;
+
+      e1 = EDGE_SUCC (bb, 0);
+      bb1 = e1->dest;
+      e2 = EDGE_SUCC (bb, 1);
+      bb2 = e2->dest;
+
+      /* We cannot do the optimization on abnormal edges.  */
+      if ((e1->flags & EDGE_ABNORMAL) != 0
+          || (e2->flags & EDGE_ABNORMAL) != 0)
+       continue;
+
+      /* If either bb1's succ or bb2 or bb2's succ is non NULL.  */
+      if (EDGE_COUNT (bb1->succs) == 0
+          || bb2 == NULL
+	  || EDGE_COUNT (bb2->succs) == 0)
+        continue;
+
+      /* Find the bb which is the fall through to the other.  */
+      if (EDGE_SUCC (bb1, 0)->dest == bb2)
+        ;
+      else if (EDGE_SUCC (bb2, 0)->dest == bb1)
+        {
+	  basic_block bb_tmp = bb1;
+	  edge e_tmp = e1;
+	  bb1 = bb2;
+	  bb2 = bb_tmp;
+	  e1 = e2;
+	  e2 = e_tmp;
+	}
+      else
+        continue;
+
+      e1 = EDGE_SUCC (bb1, 0);
+
+      /* Make sure that bb1 is just a fall through.  */
+      if (!single_succ_p (bb1)
+	  || (e1->flags & EDGE_FALLTHRU) == 0)
+        continue;
+
+      /* Also make sure that bb1 only have one predecessor and that it
+	 is bb.  */
+      if (!single_pred_p (bb1)
+          || single_pred (bb1) != bb)
+	continue;
+
+      if (do_store_elim)
+	{
+	  /* bb1 is the middle block, bb2 the join block, bb the split block,
+	     e1 the fallthrough edge from bb1 to bb2.  We can't do the
+	     optimization if the join block has more than two predecessors.  */
+	  if (EDGE_COUNT (bb2->preds) > 2)
+	    continue;
+	  if (cond_store_replacement (bb1, bb2, e1, e2, nontrap))
+	    cfgchanged = true;
+	}
+      else
+	{
+	  gimple_seq phis = phi_nodes (bb2);
+
+	  /* Check to make sure that there is only one PHI node.
+	     TODO: we could do it with more than one iff the other PHI nodes
+	     have the same elements for these two edges.  */
+	  if (! gimple_seq_singleton_p (phis))
+	    continue;
+
+	  phi = gsi_stmt (gsi_start (phis));
+	  arg0 = gimple_phi_arg_def (phi, e1->dest_idx);
+	  arg1 = gimple_phi_arg_def (phi, e2->dest_idx);
+
+	  /* Something is wrong if we cannot find the arguments in the PHI
+	     node.  */
+	  gcc_assert (arg0 != NULL && arg1 != NULL);
+
+	  /* Do the replacement of conditional if it can be done.  */
+	  if (conditional_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
+	    cfgchanged = true;
+	  else if (value_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
+	    cfgchanged = true;
+	  else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
+	    cfgchanged = true;
+	  else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
+	    cfgchanged = true;
+	}
+    }
+
+  free (bb_order);
+  
+  if (do_store_elim)
+    pointer_set_destroy (nontrap);
+  /* If the CFG has changed, we should cleanup the CFG.  */
+  if (cfgchanged && do_store_elim)
+    {
+      /* In cond-store replacement we have added some loads on edges
+         and new VOPS (as we moved the store, and created a load).  */
+      gsi_commit_edge_inserts ();
+      return TODO_cleanup_cfg | TODO_update_ssa_only_virtuals;
+    }
+  else if (cfgchanged)
+    return TODO_cleanup_cfg;
+  return 0;
+}
+
+/* Returns the list of basic blocks in the function in an order that guarantees
+   that if a block X has just a single predecessor Y, then Y is after X in the
+   ordering.  */
+
+basic_block *
+blocks_in_phiopt_order (void)
+{
+  basic_block x, y;
+  basic_block *order = XNEWVEC (basic_block, n_basic_blocks);
+  unsigned n = n_basic_blocks - NUM_FIXED_BLOCKS; 
+  unsigned np, i;
+  sbitmap visited = sbitmap_alloc (last_basic_block); 
+
+#define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index)) 
+#define VISITED_P(BB) (TEST_BIT (visited, (BB)->index)) 
+
+  sbitmap_zero (visited);
+
+  MARK_VISITED (ENTRY_BLOCK_PTR);
+  FOR_EACH_BB (x)
+    {
+      if (VISITED_P (x))
+	continue;
+
+      /* Walk the predecessors of x as long as they have precisely one
+	 predecessor and add them to the list, so that they get stored
+	 after x.  */
+      for (y = x, np = 1;
+	   single_pred_p (y) && !VISITED_P (single_pred (y));
+	   y = single_pred (y))
+	np++;
+      for (y = x, i = n - np;
+	   single_pred_p (y) && !VISITED_P (single_pred (y));
+	   y = single_pred (y), i++)
+	{
+	  order[i] = y;
+	  MARK_VISITED (y);
+	}
+      order[i] = y;
+      MARK_VISITED (y);
+
+      gcc_assert (i == n - 1);
+      n -= np;
+    }
+
+  sbitmap_free (visited);
+  gcc_assert (n == 0);
+  return order;
+
+#undef MARK_VISITED
+#undef VISITED_P
+}
+
+
+/* Return TRUE if block BB has no executable statements, otherwise return
+   FALSE.  */
+
+bool
+empty_block_p (basic_block bb)
+{
+  /* BB must have no executable statements.  */
+  return gsi_end_p (gsi_after_labels (bb));
+}
+
+/* Replace PHI node element whose edge is E in block BB with variable NEW.
+   Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK
+   is known to have two edges, one of which must reach BB).  */
+
+static void
+replace_phi_edge_with_variable (basic_block cond_block,
+				edge e, gimple phi, tree new_tree)
+{
+  basic_block bb = gimple_bb (phi);
+  basic_block block_to_remove;
+  gimple_stmt_iterator gsi;
+
+  /* Change the PHI argument to new.  */
+  SET_USE (PHI_ARG_DEF_PTR (phi, e->dest_idx), new_tree);
+
+  /* Remove the empty basic block.  */
+  if (EDGE_SUCC (cond_block, 0)->dest == bb)
+    {
+      EDGE_SUCC (cond_block, 0)->flags |= EDGE_FALLTHRU;
+      EDGE_SUCC (cond_block, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
+      EDGE_SUCC (cond_block, 0)->probability = REG_BR_PROB_BASE;
+      EDGE_SUCC (cond_block, 0)->count += EDGE_SUCC (cond_block, 1)->count;
+
+      block_to_remove = EDGE_SUCC (cond_block, 1)->dest;
+    }
+  else
+    {
+      EDGE_SUCC (cond_block, 1)->flags |= EDGE_FALLTHRU;
+      EDGE_SUCC (cond_block, 1)->flags
+	&= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
+      EDGE_SUCC (cond_block, 1)->probability = REG_BR_PROB_BASE;
+      EDGE_SUCC (cond_block, 1)->count += EDGE_SUCC (cond_block, 0)->count;
+
+      block_to_remove = EDGE_SUCC (cond_block, 0)->dest;
+    }
+  delete_basic_block (block_to_remove);
+
+  /* Eliminate the COND_EXPR at the end of COND_BLOCK.  */
+  gsi = gsi_last_bb (cond_block);
+  gsi_remove (&gsi, true);
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file,
+	      "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n",
+	      cond_block->index,
+	      bb->index);
+}
+
+/*  The function conditional_replacement does the main work of doing the
+    conditional replacement.  Return true if the replacement is done.
+    Otherwise return false.
+    BB is the basic block where the replacement is going to be done on.  ARG0
+    is argument 0 from PHI.  Likewise for ARG1.  */
+
+static bool
+conditional_replacement (basic_block cond_bb, basic_block middle_bb,
+			 edge e0, edge e1, gimple phi,
+			 tree arg0, tree arg1)
+{
+  tree result;
+  gimple stmt, new_stmt;
+  tree cond;
+  gimple_stmt_iterator gsi;
+  edge true_edge, false_edge;
+  tree new_var, new_var2;
+
+  /* FIXME: Gimplification of complex type is too hard for now.  */
+  if (TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
+      || TREE_CODE (TREE_TYPE (arg1)) == COMPLEX_TYPE)
+    return false;
+
+  /* The PHI arguments have the constants 0 and 1, then convert
+     it to the conditional.  */
+  if ((integer_zerop (arg0) && integer_onep (arg1))
+      || (integer_zerop (arg1) && integer_onep (arg0)))
+    ;
+  else
+    return false;
+
+  if (!empty_block_p (middle_bb))
+    return false;
+
+  /* At this point we know we have a GIMPLE_COND with two successors.
+     One successor is BB, the other successor is an empty block which
+     falls through into BB.
+
+     There is a single PHI node at the join point (BB) and its arguments
+     are constants (0, 1).
+
+     So, given the condition COND, and the two PHI arguments, we can
+     rewrite this PHI into non-branching code:
+
+       dest = (COND) or dest = COND'
+
+     We use the condition as-is if the argument associated with the
+     true edge has the value one or the argument associated with the
+     false edge as the value zero.  Note that those conditions are not
+     the same since only one of the outgoing edges from the GIMPLE_COND
+     will directly reach BB and thus be associated with an argument.  */
+
+  stmt = last_stmt (cond_bb);
+  result = PHI_RESULT (phi);
+
+  /* To handle special cases like floating point comparison, it is easier and
+     less error-prone to build a tree and gimplify it on the fly though it is
+     less efficient.  */
+  cond = fold_build2 (gimple_cond_code (stmt), boolean_type_node,
+		      gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
+
+  /* We need to know which is the true edge and which is the false
+     edge so that we know when to invert the condition below.  */
+  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
+  if ((e0 == true_edge && integer_zerop (arg0))
+      || (e0 == false_edge && integer_onep (arg0))
+      || (e1 == true_edge && integer_zerop (arg1))
+      || (e1 == false_edge && integer_onep (arg1)))
+    cond = fold_build1 (TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
+
+  /* Insert our new statements at the end of conditional block before the
+     COND_STMT.  */
+  gsi = gsi_for_stmt (stmt);
+  new_var = force_gimple_operand_gsi (&gsi, cond, true, NULL, true,
+				      GSI_SAME_STMT);
+
+  if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (new_var)))
+    {
+      new_var2 = create_tmp_var (TREE_TYPE (result), NULL);
+      add_referenced_var (new_var2);
+      new_stmt = gimple_build_assign_with_ops (CONVERT_EXPR, new_var2,
+					       new_var, NULL);
+      new_var2 = make_ssa_name (new_var2, new_stmt);
+      gimple_assign_set_lhs (new_stmt, new_var2);
+      gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
+      new_var = new_var2;
+    }
+
+  replace_phi_edge_with_variable (cond_bb, e1, phi, new_var);
+
+  /* Note that we optimized this PHI.  */
+  return true;
+}
+
+/*  The function value_replacement does the main work of doing the value
+    replacement.  Return true if the replacement is done.  Otherwise return
+    false.
+    BB is the basic block where the replacement is going to be done on.  ARG0
+    is argument 0 from the PHI.  Likewise for ARG1.  */
+
+static bool
+value_replacement (basic_block cond_bb, basic_block middle_bb,
+		   edge e0, edge e1, gimple phi,
+		   tree arg0, tree arg1)
+{
+  gimple cond;
+  edge true_edge, false_edge;
+  enum tree_code code;
+
+  /* If the type says honor signed zeros we cannot do this
+     optimization.  */
+  if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
+    return false;
+
+  if (!empty_block_p (middle_bb))
+    return false;
+
+  cond = last_stmt (cond_bb);
+  code = gimple_cond_code (cond);
+
+  /* This transformation is only valid for equality comparisons.  */
+  if (code != NE_EXPR && code != EQ_EXPR)
+    return false;
+
+  /* We need to know which is the true edge and which is the false
+      edge so that we know if have abs or negative abs.  */
+  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
+
+  /* At this point we know we have a COND_EXPR with two successors.
+     One successor is BB, the other successor is an empty block which
+     falls through into BB.
+
+     The condition for the COND_EXPR is known to be NE_EXPR or EQ_EXPR.
+
+     There is a single PHI node at the join point (BB) with two arguments.
+
+     We now need to verify that the two arguments in the PHI node match
+     the two arguments to the equality comparison.  */
+
+  if ((operand_equal_for_phi_arg_p (arg0, gimple_cond_lhs (cond))
+       && operand_equal_for_phi_arg_p (arg1, gimple_cond_rhs (cond)))
+      || (operand_equal_for_phi_arg_p (arg1, gimple_cond_lhs (cond))
+	  && operand_equal_for_phi_arg_p (arg0, gimple_cond_rhs (cond))))
+    {
+      edge e;
+      tree arg;
+
+      /* For NE_EXPR, we want to build an assignment result = arg where
+	 arg is the PHI argument associated with the true edge.  For
+	 EQ_EXPR we want the PHI argument associated with the false edge.  */
+      e = (code == NE_EXPR ? true_edge : false_edge);
+
+      /* Unfortunately, E may not reach BB (it may instead have gone to
+	 OTHER_BLOCK).  If that is the case, then we want the single outgoing
+	 edge from OTHER_BLOCK which reaches BB and represents the desired
+	 path from COND_BLOCK.  */
+      if (e->dest == middle_bb)
+	e = single_succ_edge (e->dest);
+
+      /* Now we know the incoming edge to BB that has the argument for the
+	 RHS of our new assignment statement.  */
+      if (e0 == e)
+	arg = arg0;
+      else
+	arg = arg1;
+
+      replace_phi_edge_with_variable (cond_bb, e1, phi, arg);
+
+      /* Note that we optimized this PHI.  */
+      return true;
+    }
+  return false;
+}
+
+/*  The function minmax_replacement does the main work of doing the minmax
+    replacement.  Return true if the replacement is done.  Otherwise return
+    false.
+    BB is the basic block where the replacement is going to be done on.  ARG0
+    is argument 0 from the PHI.  Likewise for ARG1.  */
+
+static bool
+minmax_replacement (basic_block cond_bb, basic_block middle_bb,
+		    edge e0, edge e1, gimple phi,
+		    tree arg0, tree arg1)
+{
+  tree result, type;
+  gimple cond, new_stmt;
+  edge true_edge, false_edge;
+  enum tree_code cmp, minmax, ass_code;
+  tree smaller, larger, arg_true, arg_false;
+  gimple_stmt_iterator gsi, gsi_from;
+
+  type = TREE_TYPE (PHI_RESULT (phi));
+
+  /* The optimization may be unsafe due to NaNs.  */
+  if (HONOR_NANS (TYPE_MODE (type)))
+    return false;
+
+  cond = last_stmt (cond_bb);
+  cmp = gimple_cond_code (cond);
+  result = PHI_RESULT (phi);
+
+  /* This transformation is only valid for order comparisons.  Record which
+     operand is smaller/larger if the result of the comparison is true.  */
+  if (cmp == LT_EXPR || cmp == LE_EXPR)
+    {
+      smaller = gimple_cond_lhs (cond);
+      larger = gimple_cond_rhs (cond);
+    }
+  else if (cmp == GT_EXPR || cmp == GE_EXPR)
+    {
+      smaller = gimple_cond_rhs (cond);
+      larger = gimple_cond_lhs (cond);
+    }
+  else
+    return false;
+
+  /* We need to know which is the true edge and which is the false
+      edge so that we know if have abs or negative abs.  */
+  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
+
+  /* Forward the edges over the middle basic block.  */
+  if (true_edge->dest == middle_bb)
+    true_edge = EDGE_SUCC (true_edge->dest, 0);
+  if (false_edge->dest == middle_bb)
+    false_edge = EDGE_SUCC (false_edge->dest, 0);
+
+  if (true_edge == e0)
+    {
+      gcc_assert (false_edge == e1);
+      arg_true = arg0;
+      arg_false = arg1;
+    }
+  else
+    {
+      gcc_assert (false_edge == e0);
+      gcc_assert (true_edge == e1);
+      arg_true = arg1;
+      arg_false = arg0;
+    }
+
+  if (empty_block_p (middle_bb))
+    {
+      if (operand_equal_for_phi_arg_p (arg_true, smaller)
+	  && operand_equal_for_phi_arg_p (arg_false, larger))
+	{
+	  /* Case
+	 
+	     if (smaller < larger)
+	     rslt = smaller;
+	     else
+	     rslt = larger;  */
+	  minmax = MIN_EXPR;
+	}
+      else if (operand_equal_for_phi_arg_p (arg_false, smaller)
+	       && operand_equal_for_phi_arg_p (arg_true, larger))
+	minmax = MAX_EXPR;
+      else
+	return false;
+    }
+  else
+    {
+      /* Recognize the following case, assuming d <= u:
+
+	 if (a <= u)
+	   b = MAX (a, d);
+	 x = PHI <b, u>
+
+	 This is equivalent to
+
+	 b = MAX (a, d);
+	 x = MIN (b, u);  */
+
+      gimple assign = last_and_only_stmt (middle_bb);
+      tree lhs, op0, op1, bound;
+
+      if (!assign
+	  || gimple_code (assign) != GIMPLE_ASSIGN)
+	return false;
+
+      lhs = gimple_assign_lhs (assign);
+      ass_code = gimple_assign_rhs_code (assign);
+      if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)
+	return false;
+      op0 = gimple_assign_rhs1 (assign);
+      op1 = gimple_assign_rhs2 (assign);
+
+      if (true_edge->src == middle_bb)
+	{
+	  /* We got here if the condition is true, i.e., SMALLER < LARGER.  */
+	  if (!operand_equal_for_phi_arg_p (lhs, arg_true))
+	    return false;
+
+	  if (operand_equal_for_phi_arg_p (arg_false, larger))
+	    {
+	      /* Case
+
+		 if (smaller < larger)
+		   {
+		     r' = MAX_EXPR (smaller, bound)
+		   }
+		 r = PHI <r', larger>  --> to be turned to MIN_EXPR.  */
+	      if (ass_code != MAX_EXPR)
+		return false;
+
+	      minmax = MIN_EXPR;
+	      if (operand_equal_for_phi_arg_p (op0, smaller))
+		bound = op1;
+	      else if (operand_equal_for_phi_arg_p (op1, smaller))
+		bound = op0;
+	      else
+		return false;
+
+	      /* We need BOUND <= LARGER.  */
+	      if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node,
+						  bound, larger)))
+		return false;
+	    }
+	  else if (operand_equal_for_phi_arg_p (arg_false, smaller))
+	    {
+	      /* Case
+
+		 if (smaller < larger)
+		   {
+		     r' = MIN_EXPR (larger, bound)
+		   }
+		 r = PHI <r', smaller>  --> to be turned to MAX_EXPR.  */
+	      if (ass_code != MIN_EXPR)
+		return false;
+
+	      minmax = MAX_EXPR;
+	      if (operand_equal_for_phi_arg_p (op0, larger))
+		bound = op1;
+	      else if (operand_equal_for_phi_arg_p (op1, larger))
+		bound = op0;
+	      else
+		return false;
+
+	      /* We need BOUND >= SMALLER.  */
+	      if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node,
+						  bound, smaller)))
+		return false;
+	    }
+	  else
+	    return false;
+	}
+      else
+	{
+	  /* We got here if the condition is false, i.e., SMALLER > LARGER.  */
+	  if (!operand_equal_for_phi_arg_p (lhs, arg_false))
+	    return false;
+
+	  if (operand_equal_for_phi_arg_p (arg_true, larger))
+	    {
+	      /* Case
+
+		 if (smaller > larger)
+		   {
+		     r' = MIN_EXPR (smaller, bound)
+		   }
+		 r = PHI <r', larger>  --> to be turned to MAX_EXPR.  */
+	      if (ass_code != MIN_EXPR)
+		return false;
+
+	      minmax = MAX_EXPR;
+	      if (operand_equal_for_phi_arg_p (op0, smaller))
+		bound = op1;
+	      else if (operand_equal_for_phi_arg_p (op1, smaller))
+		bound = op0;
+	      else
+		return false;
+
+	      /* We need BOUND >= LARGER.  */
+	      if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node,
+						  bound, larger)))
+		return false;
+	    }
+	  else if (operand_equal_for_phi_arg_p (arg_true, smaller))
+	    {
+	      /* Case
+
+		 if (smaller > larger)
+		   {
+		     r' = MAX_EXPR (larger, bound)
+		   }
+		 r = PHI <r', smaller>  --> to be turned to MIN_EXPR.  */
+	      if (ass_code != MAX_EXPR)
+		return false;
+
+	      minmax = MIN_EXPR;
+	      if (operand_equal_for_phi_arg_p (op0, larger))
+		bound = op1;
+	      else if (operand_equal_for_phi_arg_p (op1, larger))
+		bound = op0;
+	      else
+		return false;
+
+	      /* We need BOUND <= SMALLER.  */
+	      if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node,
+						  bound, smaller)))
+		return false;
+	    }
+	  else
+	    return false;
+	}
+
+      /* Move the statement from the middle block.  */
+      gsi = gsi_last_bb (cond_bb);
+      gsi_from = gsi_last_bb (middle_bb);
+      gsi_move_before (&gsi_from, &gsi);
+    }
+
+  /* Emit the statement to compute min/max.  */
+  result = duplicate_ssa_name (PHI_RESULT (phi), NULL);
+  new_stmt = gimple_build_assign_with_ops (minmax, result, arg0, arg1);
+  gsi = gsi_last_bb (cond_bb);
+  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
+
+  replace_phi_edge_with_variable (cond_bb, e1, phi, result);
+  return true;
+}
+
+/*  The function absolute_replacement does the main work of doing the absolute
+    replacement.  Return true if the replacement is done.  Otherwise return
+    false.
+    bb is the basic block where the replacement is going to be done on.  arg0
+    is argument 0 from the phi.  Likewise for arg1.  */
+
+static bool
+abs_replacement (basic_block cond_bb, basic_block middle_bb,
+		 edge e0 ATTRIBUTE_UNUSED, edge e1,
+		 gimple phi, tree arg0, tree arg1)
+{
+  tree result;
+  gimple new_stmt, cond;
+  gimple_stmt_iterator gsi;
+  edge true_edge, false_edge;
+  gimple assign;
+  edge e;
+  tree rhs, lhs;
+  bool negate;
+  enum tree_code cond_code;
+
+  /* If the type says honor signed zeros we cannot do this
+     optimization.  */
+  if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
+    return false;
+
+  /* OTHER_BLOCK must have only one executable statement which must have the
+     form arg0 = -arg1 or arg1 = -arg0.  */
+
+  assign = last_and_only_stmt (middle_bb);
+  /* If we did not find the proper negation assignment, then we can not
+     optimize.  */
+  if (assign == NULL)
+    return false;
+      
+  /* If we got here, then we have found the only executable statement
+     in OTHER_BLOCK.  If it is anything other than arg = -arg1 or
+     arg1 = -arg0, then we can not optimize.  */
+  if (gimple_code (assign) != GIMPLE_ASSIGN)
+    return false;
+
+  lhs = gimple_assign_lhs (assign);
+
+  if (gimple_assign_rhs_code (assign) != NEGATE_EXPR)
+    return false;
+
+  rhs = gimple_assign_rhs1 (assign);
+              
+  /* The assignment has to be arg0 = -arg1 or arg1 = -arg0.  */
+  if (!(lhs == arg0 && rhs == arg1)
+      && !(lhs == arg1 && rhs == arg0))
+    return false;
+
+  cond = last_stmt (cond_bb);
+  result = PHI_RESULT (phi);
+
+  /* Only relationals comparing arg[01] against zero are interesting.  */
+  cond_code = gimple_cond_code (cond);
+  if (cond_code != GT_EXPR && cond_code != GE_EXPR
+      && cond_code != LT_EXPR && cond_code != LE_EXPR)
+    return false;
+
+  /* Make sure the conditional is arg[01] OP y.  */
+  if (gimple_cond_lhs (cond) != rhs)
+    return false;
+
+  if (FLOAT_TYPE_P (TREE_TYPE (gimple_cond_rhs (cond)))
+	       ? real_zerop (gimple_cond_rhs (cond))
+	       : integer_zerop (gimple_cond_rhs (cond)))
+    ;
+  else
+    return false;
+
+  /* We need to know which is the true edge and which is the false
+     edge so that we know if have abs or negative abs.  */
+  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
+
+  /* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
+     will need to negate the result.  Similarly for LT_EXPR/LE_EXPR if
+     the false edge goes to OTHER_BLOCK.  */
+  if (cond_code == GT_EXPR || cond_code == GE_EXPR)
+    e = true_edge;
+  else
+    e = false_edge;
+
+  if (e->dest == middle_bb)
+    negate = true;
+  else
+    negate = false;
+
+  result = duplicate_ssa_name (result, NULL);
+
+  if (negate)
+    {
+      tree tmp = create_tmp_var (TREE_TYPE (result), NULL);
+      add_referenced_var (tmp);
+      lhs = make_ssa_name (tmp, NULL);
+    }
+  else
+    lhs = result;
+
+  /* Build the modify expression with abs expression.  */
+  new_stmt = gimple_build_assign_with_ops (ABS_EXPR, lhs, rhs, NULL);
+
+  gsi = gsi_last_bb (cond_bb);
+  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
+
+  if (negate)
+    {
+      /* Get the right GSI.  We want to insert after the recently
+	 added ABS_EXPR statement (which we know is the first statement
+	 in the block.  */
+      new_stmt = gimple_build_assign_with_ops (NEGATE_EXPR, result, lhs, NULL);
+
+      gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
+    }
+
+  replace_phi_edge_with_variable (cond_bb, e1, phi, result);
+
+  /* Note that we optimized this PHI.  */
+  return true;
+}
+
+/* Auxiliary functions to determine the set of memory accesses which
+   can't trap because they are preceded by accesses to the same memory
+   portion.  We do that for INDIRECT_REFs, so we only need to track
+   the SSA_NAME of the pointer indirectly referenced.  The algorithm
+   simply is a walk over all instructions in dominator order.  When
+   we see an INDIRECT_REF we determine if we've already seen a same
+   ref anywhere up to the root of the dominator tree.  If we do the
+   current access can't trap.  If we don't see any dominating access
+   the current access might trap, but might also make later accesses
+   non-trapping, so we remember it.  We need to be careful with loads
+   or stores, for instance a load might not trap, while a store would,
+   so if we see a dominating read access this doesn't mean that a later
+   write access would not trap.  Hence we also need to differentiate the
+   type of access(es) seen.
+
+   ??? We currently are very conservative and assume that a load might
+   trap even if a store doesn't (write-only memory).  This probably is
+   overly conservative.  */
+
+/* A hash-table of SSA_NAMEs, and in which basic block an INDIRECT_REF
+   through it was seen, which would constitute a no-trap region for
+   same accesses.  */
+struct name_to_bb
+{
+  tree ssa_name;
+  basic_block bb;
+  unsigned store : 1;
+};
+
+/* The hash table for remembering what we've seen.  */
+static htab_t seen_ssa_names;
+
+/* The set of INDIRECT_REFs which can't trap.  */
+static struct pointer_set_t *nontrap_set;
+
+/* The hash function, based on the pointer to the pointer SSA_NAME.  */
+static hashval_t
+name_to_bb_hash (const void *p)
+{
+  const_tree n = ((const struct name_to_bb *)p)->ssa_name;
+  return htab_hash_pointer (n) ^ ((const struct name_to_bb *)p)->store;
+}
+
+/* The equality function of *P1 and *P2.  SSA_NAMEs are shared, so
+   it's enough to simply compare them for equality.  */
+static int
+name_to_bb_eq (const void *p1, const void *p2)
+{
+  const struct name_to_bb *n1 = (const struct name_to_bb *)p1;
+  const struct name_to_bb *n2 = (const struct name_to_bb *)p2;
+
+  return n1->ssa_name == n2->ssa_name && n1->store == n2->store;
+}
+
+/* We see the expression EXP in basic block BB.  If it's an interesting
+   expression (an INDIRECT_REF through an SSA_NAME) possibly insert the
+   expression into the set NONTRAP or the hash table of seen expressions.
+   STORE is true if this expression is on the LHS, otherwise it's on
+   the RHS.  */
+static void
+add_or_mark_expr (basic_block bb, tree exp,
+		  struct pointer_set_t *nontrap, bool store)
+{
+  if (INDIRECT_REF_P (exp)
+      && TREE_CODE (TREE_OPERAND (exp, 0)) == SSA_NAME)
+    {
+      tree name = TREE_OPERAND (exp, 0);
+      struct name_to_bb map;
+      void **slot;
+      struct name_to_bb *n2bb;
+      basic_block found_bb = 0;
+
+      /* Try to find the last seen INDIRECT_REF through the same
+         SSA_NAME, which can trap.  */
+      map.ssa_name = name;
+      map.bb = 0;
+      map.store = store;
+      slot = htab_find_slot (seen_ssa_names, &map, INSERT);
+      n2bb = (struct name_to_bb *) *slot;
+      if (n2bb)
+        found_bb = n2bb->bb;
+
+      /* If we've found a trapping INDIRECT_REF, _and_ it dominates EXP
+         (it's in a basic block on the path from us to the dominator root)
+	 then we can't trap.  */
+      if (found_bb && found_bb->aux == (void *)1)
+	{
+	  pointer_set_insert (nontrap, exp);
+	}
+      else
+        {
+	  /* EXP might trap, so insert it into the hash table.  */
+	  if (n2bb)
+	    {
+	      n2bb->bb = bb;
+	    }
+	  else
+	    {
+	      n2bb = XNEW (struct name_to_bb);
+	      n2bb->ssa_name = name;
+	      n2bb->bb = bb;
+	      n2bb->store = store;
+	      *slot = n2bb;
+	    }
+	}
+    }
+}
+
+/* Called by walk_dominator_tree, when entering the block BB.  */
+static void
+nt_init_block (struct dom_walk_data *data ATTRIBUTE_UNUSED, basic_block bb)
+{
+  gimple_stmt_iterator gsi;
+  /* Mark this BB as being on the path to dominator root.  */
+  bb->aux = (void*)1;
+
+  /* And walk the statements in order.  */
+  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple stmt = gsi_stmt (gsi);
+
+      if (is_gimple_assign (stmt))
+	{
+	  add_or_mark_expr (bb, gimple_assign_lhs (stmt), nontrap_set, true);
+	  add_or_mark_expr (bb, gimple_assign_rhs1 (stmt), nontrap_set, false);
+	  if (get_gimple_rhs_num_ops (gimple_assign_rhs_code (stmt)) > 1)
+	    add_or_mark_expr (bb, gimple_assign_rhs2 (stmt), nontrap_set,
+			      false);
+	}
+    }
+}
+
+/* Called by walk_dominator_tree, when basic block BB is exited.  */
+static void
+nt_fini_block (struct dom_walk_data *data ATTRIBUTE_UNUSED, basic_block bb)
+{
+  /* This BB isn't on the path to dominator root anymore.  */
+  bb->aux = NULL;
+}
+
+/* This is the entry point of gathering non trapping memory accesses.
+   It will do a dominator walk over the whole function, and it will
+   make use of the bb->aux pointers.  It returns a set of trees
+   (the INDIRECT_REFs itself) which can't trap.  */
+static struct pointer_set_t *
+get_non_trapping (void)
+{
+  struct pointer_set_t *nontrap;
+  struct dom_walk_data walk_data;
+
+  nontrap = pointer_set_create ();
+  seen_ssa_names = htab_create (128, name_to_bb_hash, name_to_bb_eq,
+				free);
+  /* We're going to do a dominator walk, so ensure that we have
+     dominance information.  */
+  calculate_dominance_info (CDI_DOMINATORS);
+
+  /* Setup callbacks for the generic dominator tree walker.  */
+  nontrap_set = nontrap;
+  walk_data.walk_stmts_backward = false;
+  walk_data.dom_direction = CDI_DOMINATORS;
+  walk_data.initialize_block_local_data = NULL;
+  walk_data.before_dom_children_before_stmts = nt_init_block;
+  walk_data.before_dom_children_walk_stmts = NULL;
+  walk_data.before_dom_children_after_stmts = NULL;
+  walk_data.after_dom_children_before_stmts = NULL;
+  walk_data.after_dom_children_walk_stmts = NULL;
+  walk_data.after_dom_children_after_stmts = nt_fini_block;
+  walk_data.global_data = NULL;
+  walk_data.block_local_data_size = 0;
+  walk_data.interesting_blocks = NULL;
+
+  init_walk_dominator_tree (&walk_data);
+  walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
+  fini_walk_dominator_tree (&walk_data);
+  htab_delete (seen_ssa_names);
+
+  return nontrap;
+}
+
+/* Do the main work of conditional store replacement.  We already know
+   that the recognized pattern looks like so:
+
+   split:
+     if (cond) goto MIDDLE_BB; else goto JOIN_BB (edge E1)
+   MIDDLE_BB:
+     something
+     fallthrough (edge E0)
+   JOIN_BB:
+     some more
+
+   We check that MIDDLE_BB contains only one store, that that store
+   doesn't trap (not via NOTRAP, but via checking if an access to the same
+   memory location dominates us) and that the store has a "simple" RHS.  */
+
+static bool
+cond_store_replacement (basic_block middle_bb, basic_block join_bb,
+			edge e0, edge e1, struct pointer_set_t *nontrap)
+{
+  gimple assign = last_and_only_stmt (middle_bb);
+  tree lhs, rhs, name;
+  gimple newphi, new_stmt;
+  gimple_stmt_iterator gsi;
+  enum tree_code code;
+
+  /* Check if middle_bb contains of only one store.  */
+  if (!assign
+      || gimple_code (assign) != GIMPLE_ASSIGN)
+    return false;
+
+  lhs = gimple_assign_lhs (assign);
+  rhs = gimple_assign_rhs1 (assign);
+  if (!INDIRECT_REF_P (lhs))
+    return false;
+
+  /* RHS is either a single SSA_NAME or a constant. */
+  code = gimple_assign_rhs_code (assign);
+  if (get_gimple_rhs_class (code) != GIMPLE_SINGLE_RHS
+      || (code != SSA_NAME && !is_gimple_min_invariant (rhs)))
+    return false;
+  /* Prove that we can move the store down.  We could also check
+     TREE_THIS_NOTRAP here, but in that case we also could move stores,
+     whose value is not available readily, which we want to avoid.  */
+  if (!pointer_set_contains (nontrap, lhs))
+    return false;
+
+  /* Now we've checked the constraints, so do the transformation:
+     1) Remove the single store.  */
+  mark_symbols_for_renaming (assign);
+  gsi = gsi_for_stmt (assign);
+  gsi_remove (&gsi, true);
+
+  /* 2) Create a temporary where we can store the old content
+        of the memory touched by the store, if we need to.  */
+  if (!condstoretemp || TREE_TYPE (lhs) != TREE_TYPE (condstoretemp))
+    {
+      condstoretemp = create_tmp_var (TREE_TYPE (lhs), "cstore");
+      get_var_ann (condstoretemp);
+      if (TREE_CODE (TREE_TYPE (lhs)) == COMPLEX_TYPE
+          || TREE_CODE (TREE_TYPE (lhs)) == VECTOR_TYPE)
+	DECL_GIMPLE_REG_P (condstoretemp) = 1;
+    }
+  add_referenced_var (condstoretemp);
+
+  /* 3) Insert a load from the memory of the store to the temporary
+        on the edge which did not contain the store.  */
+  lhs = unshare_expr (lhs);
+  new_stmt = gimple_build_assign (condstoretemp, lhs);
+  name = make_ssa_name (condstoretemp, new_stmt);
+  gimple_assign_set_lhs (new_stmt, name);
+  mark_symbols_for_renaming (new_stmt);
+  gsi_insert_on_edge (e1, new_stmt);
+
+  /* 4) Create a PHI node at the join block, with one argument
+        holding the old RHS, and the other holding the temporary
+        where we stored the old memory contents.  */
+  newphi = create_phi_node (condstoretemp, join_bb);
+  add_phi_arg (newphi, rhs, e0);
+  add_phi_arg (newphi, name, e1);
+
+  lhs = unshare_expr (lhs);
+  new_stmt = gimple_build_assign (lhs, PHI_RESULT (newphi));
+  mark_symbols_for_renaming (new_stmt);
+
+  /* 5) Insert that PHI node.  */
+  gsi = gsi_after_labels (join_bb);
+  if (gsi_end_p (gsi))
+    {
+      gsi = gsi_last_bb (join_bb);
+      gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
+    }
+  else
+    gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
+
+  return true;
+}
+
+/* Always do these optimizations if we have SSA
+   trees to work on.  */
+static bool
+gate_phiopt (void)
+{
+  return 1;
+}
+
+struct gimple_opt_pass pass_phiopt =
+{
+ {
+  GIMPLE_PASS,
+  "phiopt",				/* name */
+  gate_phiopt,				/* gate */
+  tree_ssa_phiopt,			/* execute */
+  NULL,					/* sub */
+  NULL,					/* next */
+  0,					/* static_pass_number */
+  TV_TREE_PHIOPT,			/* tv_id */
+  PROP_cfg | PROP_ssa | PROP_alias,	/* properties_required */
+  0,					/* properties_provided */
+  0,					/* properties_destroyed */
+  0,					/* todo_flags_start */
+  TODO_dump_func
+    | TODO_ggc_collect
+    | TODO_verify_ssa
+    | TODO_verify_flow
+    | TODO_verify_stmts	 		/* todo_flags_finish */
+ }
+};
+
+static bool
+gate_cselim (void)
+{
+  return flag_tree_cselim;
+}
+
+struct gimple_opt_pass pass_cselim =
+{
+ {
+  GIMPLE_PASS,
+  "cselim",				/* name */
+  gate_cselim,				/* gate */
+  tree_ssa_cs_elim,			/* execute */
+  NULL,					/* sub */
+  NULL,					/* next */
+  0,					/* static_pass_number */
+  TV_TREE_PHIOPT,			/* tv_id */
+  PROP_cfg | PROP_ssa | PROP_alias,	/* properties_required */
+  0,					/* properties_provided */
+  0,					/* properties_destroyed */
+  0,					/* todo_flags_start */
+  TODO_dump_func
+    | TODO_ggc_collect
+    | TODO_verify_ssa
+    | TODO_verify_flow
+    | TODO_verify_stmts	 		/* todo_flags_finish */
+ }
+};