Check in gcc sources for prebuilt toolchains in Eclair.

1 files changed, 1382 insertions, 0 deletions

diff --git a/gcc-4.3.1/gcc/tree-ssa-forwprop.c b/gcc-4.3.1/gcc/tree-ssa-forwprop.c
new file mode 100644
index 000000000..1b901f1b2
--- /dev/null
+++ b/gcc-4.3.1/gcc/tree-ssa-forwprop.c
@@ -0,0 +1,1382 @@
+/* Forward propagation of expressions for single use variables.
+   Copyright (C) 2004, 2005, 2007 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 "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 "flags.h"
+
+/* This pass propagates the RHS of assignment statements into use
+   sites of the LHS of the assignment.  It's basically a specialized
+   form of tree combination.   It is hoped all of this can disappear
+   when we have a generalized tree combiner.
+
+   Note carefully that after propagation the resulting statement
+   must still be a proper gimple statement.  Right now we simply
+   only perform propagations we know will result in valid gimple
+   code.  One day we'll want to generalize this code.
+
+   One class of common cases we handle is forward propagating a single use
+   variable into a COND_EXPR.  
+
+     bb0:
+       x = a COND b;
+       if (x) goto ... else goto ...
+
+   Will be transformed into:
+
+     bb0:
+       if (a COND b) goto ... else goto ...
+ 
+   Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+
+   Or (assuming c1 and c2 are constants):
+
+     bb0:
+       x = a + c1;  
+       if (x EQ/NEQ c2) goto ... else goto ...
+
+   Will be transformed into:
+
+     bb0:
+        if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
+
+   Similarly for x = a - c1.
+    
+   Or
+
+     bb0:
+       x = !a
+       if (x) goto ... else goto ...
+
+   Will be transformed into:
+
+     bb0:
+        if (a == 0) goto ... else goto ...
+
+   Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+   For these cases, we propagate A into all, possibly more than one,
+   COND_EXPRs that use X.
+
+   Or
+
+     bb0:
+       x = (typecast) a
+       if (x) goto ... else goto ...
+
+   Will be transformed into:
+
+     bb0:
+        if (a != 0) goto ... else goto ...
+
+   (Assuming a is an integral type and x is a boolean or x is an
+    integral and a is a boolean.)
+
+   Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+   For these cases, we propagate A into all, possibly more than one,
+   COND_EXPRs that use X.
+
+   In addition to eliminating the variable and the statement which assigns
+   a value to the variable, we may be able to later thread the jump without
+   adding insane complexity in the dominator optimizer.
+
+   Also note these transformations can cascade.  We handle this by having
+   a worklist of COND_EXPR statements to examine.  As we make a change to
+   a statement, we put it back on the worklist to examine on the next
+   iteration of the main loop.
+
+   A second class of propagation opportunities arises for ADDR_EXPR
+   nodes.
+
+     ptr = &x->y->z;
+     res = *ptr;
+
+   Will get turned into
+
+     res = x->y->z;
+
+   Or
+
+     ptr = &x[0];
+     ptr2 = ptr + <constant>;
+
+   Will get turned into
+
+     ptr2 = &x[constant/elementsize];
+
+  Or
+
+     ptr = &x[0];
+     offset = index * element_size;
+     offset_p = (pointer) offset;
+     ptr2 = ptr + offset_p
+
+  Will get turned into:
+
+     ptr2 = &x[index];
+
+  We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
+  allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
+  {NOT_EXPR,NEG_EXPR}.
+
+   This will (of course) be extended as other needs arise.  */
+
+static bool forward_propagate_addr_expr (tree name, tree rhs);
+
+/* Set to true if we delete EH edges during the optimization.  */
+static bool cfg_changed;
+
+
+/* Get the next statement we can propagate NAME's value into skipping
+   trivial copies.  Returns the statement that is suitable as a
+   propagation destination or NULL_TREE if there is no such one.
+   This only returns destinations in a single-use chain.  FINAL_NAME_P
+   if non-NULL is written to the ssa name that represents the use.  */
+
+static tree
+get_prop_dest_stmt (tree name, tree *final_name_p)
+{
+  use_operand_p use;
+  tree use_stmt;
+
+  do {
+    /* If name has multiple uses, bail out.  */
+    if (!single_imm_use (name, &use, &use_stmt))
+      return NULL_TREE;
+
+    /* If this is not a trivial copy, we found it.  */
+    if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT
+	|| TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) != SSA_NAME
+	|| GIMPLE_STMT_OPERAND (use_stmt, 1) != name)
+      break;
+
+    /* Continue searching uses of the copy destination.  */
+    name = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  } while (1);
+
+  if (final_name_p)
+    *final_name_p = name;
+
+  return use_stmt;
+}
+
+/* Get the statement we can propagate from into NAME skipping
+   trivial copies.  Returns the statement which defines the
+   propagation source or NULL_TREE if there is no such one.
+   If SINGLE_USE_ONLY is set considers only sources which have
+   a single use chain up to NAME.  If SINGLE_USE_P is non-null,
+   it is set to whether the chain to NAME is a single use chain
+   or not.  SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set.  */
+
+static tree
+get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
+{
+  bool single_use = true;
+
+  do {
+    tree def_stmt = SSA_NAME_DEF_STMT (name);
+
+    if (!has_single_use (name))
+      {
+	single_use = false;
+	if (single_use_only)
+	  return NULL_TREE;
+      }
+
+    /* If name is defined by a PHI node or is the default def, bail out.  */
+    if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
+      return NULL_TREE;
+
+    /* If name is not a simple copy destination, we found it.  */
+    if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
+      {
+	if (!single_use_only && single_use_p)
+	  *single_use_p = single_use;
+
+	return def_stmt;
+      }
+
+    /* Continue searching the def of the copy source name.  */
+    name = GIMPLE_STMT_OPERAND (def_stmt, 1);
+  } while (1);
+}
+
+/* Checks if the destination ssa name in DEF_STMT can be used as
+   propagation source.  Returns true if so, otherwise false.  */
+
+static bool
+can_propagate_from (tree def_stmt)
+{
+  tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+
+  /* If the rhs has side-effects we cannot propagate from it.  */
+  if (TREE_SIDE_EFFECTS (rhs))
+    return false;
+
+  /* If the rhs is a load we cannot propagate from it.  */
+  if (REFERENCE_CLASS_P (rhs))
+    return false;
+
+  /* We cannot propagate ssa names that occur in abnormal phi nodes.  */
+  switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
+    {
+    case 3:
+      if (TREE_OPERAND (rhs, 2) != NULL_TREE
+	  && TREE_CODE (TREE_OPERAND (rhs, 2)) == SSA_NAME
+	  && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 2)))
+	return false;
+    case 2:
+      if (TREE_OPERAND (rhs, 1) != NULL_TREE
+	  && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
+	  && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 1)))
+	return false;
+    case 1:
+      if (TREE_OPERAND (rhs, 0) != NULL_TREE
+	  && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
+	  && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 0)))
+	return false;
+      break;
+
+    default:
+      return false;
+    }
+
+  /* If the definition is a conversion of a pointer to a function type,
+     then we can not apply optimizations as some targets require function
+     pointers to be canonicalized and in this case this optimization could
+     eliminate a necessary canonicalization.  */
+  if ((TREE_CODE (rhs) == NOP_EXPR
+       || TREE_CODE (rhs) == CONVERT_EXPR)
+      && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
+      && TREE_CODE (TREE_TYPE (TREE_TYPE
+			        (TREE_OPERAND (rhs, 0)))) == FUNCTION_TYPE)
+    return false;
+
+  return true;
+}
+
+/* Remove a copy chain ending in NAME along the defs but not
+   further or including UP_TO_STMT.  If NAME was replaced in
+   its only use then this function can be used to clean up
+   dead stmts.  Returns true if UP_TO_STMT can be removed
+   as well, otherwise false.  */
+
+static bool
+remove_prop_source_from_use (tree name, tree up_to_stmt)
+{
+  block_stmt_iterator bsi;
+  tree stmt;
+
+  do {
+    if (!has_zero_uses (name))
+      return false;
+
+    stmt = SSA_NAME_DEF_STMT (name);
+    if (stmt == up_to_stmt)
+      return true;
+
+    bsi = bsi_for_stmt (stmt);
+    release_defs (stmt);
+    bsi_remove (&bsi, true);
+
+    name = GIMPLE_STMT_OPERAND (stmt, 1);
+  } while (TREE_CODE (name) == SSA_NAME);
+
+  return false;
+}
+
+/* Combine OP0 CODE OP1 in the context of a COND_EXPR.  Returns
+   the folded result in a form suitable for COND_EXPR_COND or
+   NULL_TREE, if there is no suitable simplified form.  If
+   INVARIANT_ONLY is true only gimple_min_invariant results are
+   considered simplified.  */
+
+static tree
+combine_cond_expr_cond (enum tree_code code, tree type,
+			tree op0, tree op1, bool invariant_only)
+{
+  tree t;
+
+  gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
+
+  t = fold_binary (code, type, op0, op1);
+  if (!t)
+    return NULL_TREE;
+
+  /* Require that we got a boolean type out if we put one in.  */
+  gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
+
+  /* Canonicalize the combined condition for use in a COND_EXPR.  */
+  t = canonicalize_cond_expr_cond (t);
+
+  /* Bail out if we required an invariant but didn't get one.  */
+  if (!t
+      || (invariant_only
+	  && !is_gimple_min_invariant (t)))
+    return NULL_TREE;
+
+  return t;
+}
+
+/* Propagate from the ssa name definition statements of COND_EXPR
+   in statement STMT into the conditional if that simplifies it.
+   Returns zero if no statement was changed, one if there were
+   changes and two if cfg_cleanup needs to run.  */
+
+static int
+forward_propagate_into_cond (tree cond_expr, tree stmt)
+{
+  int did_something = 0;
+
+  do {
+    tree tmp = NULL_TREE;
+    tree cond = COND_EXPR_COND (cond_expr);
+    tree name, def_stmt, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
+    bool single_use0_p = false, single_use1_p = false;
+
+    /* We can do tree combining on SSA_NAME and comparison expressions.  */
+    if (COMPARISON_CLASS_P (cond)
+	&& TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
+      {
+	/* For comparisons use the first operand, that is likely to
+	   simplify comparisons against constants.  */
+	name = TREE_OPERAND (cond, 0);
+	def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
+	if (def_stmt != NULL_TREE
+	    && can_propagate_from (def_stmt))
+	  {
+	    tree op1 = TREE_OPERAND (cond, 1);
+	    rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+				          fold_convert (TREE_TYPE (op1), rhs0),
+				          op1, !single_use0_p);
+	  }
+	/* If that wasn't successful, try the second operand.  */
+	if (tmp == NULL_TREE
+	    && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
+	  {
+	    tree op0 = TREE_OPERAND (cond, 0);
+	    name = TREE_OPERAND (cond, 1);
+	    def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
+	    if (def_stmt == NULL_TREE
+	        || !can_propagate_from (def_stmt))
+	      return did_something;
+
+	    rhs1 = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+					  op0,
+				          fold_convert (TREE_TYPE (op0), rhs1),
+					  !single_use1_p);
+	  }
+	/* If that wasn't successful either, try both operands.  */
+	if (tmp == NULL_TREE
+	    && rhs0 != NULL_TREE
+	    && rhs1 != NULL_TREE)
+	  tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+					rhs0,
+				        fold_convert (TREE_TYPE (rhs0), rhs1),
+					!(single_use0_p && single_use1_p));
+      }
+    else if (TREE_CODE (cond) == SSA_NAME)
+      {
+	name = cond;
+	def_stmt = get_prop_source_stmt (name, true, NULL);
+	if (def_stmt == NULL_TREE
+	    || !can_propagate_from (def_stmt))
+	  return did_something;
+
+	rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs0,
+				      build_int_cst (TREE_TYPE (rhs0), 0),
+				      false);
+      }
+
+    if (tmp)
+      {
+	if (dump_file && tmp)
+	  {
+	    fprintf (dump_file, "  Replaced '");
+	    print_generic_expr (dump_file, cond, 0);
+	    fprintf (dump_file, "' with '");
+	    print_generic_expr (dump_file, tmp, 0);
+	    fprintf (dump_file, "'\n");
+	  }
+
+	COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
+	update_stmt (stmt);
+
+	/* Remove defining statements.  */
+	remove_prop_source_from_use (name, NULL);
+
+	if (is_gimple_min_invariant (tmp))
+	  did_something = 2;
+	else if (did_something == 0)
+	  did_something = 1;
+
+	/* Continue combining.  */
+	continue;
+      }
+
+    break;
+  } while (1);
+
+  return did_something;
+}
+
+/* We've just substituted an ADDR_EXPR into stmt.  Update all the 
+   relevant data structures to match.  */
+
+static void
+tidy_after_forward_propagate_addr (tree stmt)
+{
+  /* We may have turned a trapping insn into a non-trapping insn.  */
+  if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
+      && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
+    cfg_changed = true;
+
+  if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
+     recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
+
+  mark_symbols_for_renaming (stmt);
+}
+
+/* DEF_RHS contains the address of the 0th element in an array. 
+   USE_STMT uses type of DEF_RHS to compute the address of an
+   arbitrary element within the array.  The (variable) byte offset
+   of the element is contained in OFFSET.
+
+   We walk back through the use-def chains of OFFSET to verify that
+   it is indeed computing the offset of an element within the array
+   and extract the index corresponding to the given byte offset.
+
+   We then try to fold the entire address expression into a form
+   &array[index].
+
+   If we are successful, we replace the right hand side of USE_STMT
+   with the new address computation.  */
+
+static bool
+forward_propagate_addr_into_variable_array_index (tree offset,
+						  tree def_rhs, tree use_stmt)
+{
+  tree index;
+
+  /* Try to find an expression for a proper index.  This is either
+     a multiplication expression by the element size or just the
+     ssa name we came along in case the element size is one.  */
+  if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+    index = offset;
+  else
+    {
+      /* Get the offset's defining statement.  */
+      offset = SSA_NAME_DEF_STMT (offset);
+
+      /* The statement which defines OFFSET before type conversion
+         must be a simple GIMPLE_MODIFY_STMT.  */
+      if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
+	return false;
+
+      /* The RHS of the statement which defines OFFSET must be a
+	 multiplication of an object by the size of the array elements. 
+	 This implicitly verifies that the size of the array elements
+	 is constant.  */
+     offset = GIMPLE_STMT_OPERAND (offset, 1);
+      if (TREE_CODE (offset) != MULT_EXPR
+	  || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
+	  || !simple_cst_equal (TREE_OPERAND (offset, 1),
+				TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+	return false;
+
+      /* The first operand to the MULT_EXPR is the desired index.  */
+      index = TREE_OPERAND (offset, 0);
+    }
+
+  /* Replace the pointer addition with array indexing.  */
+  GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
+  TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
+    = index;
+
+  /* That should have created gimple, so there is no need to
+     record information to undo the propagation.  */
+  fold_stmt_inplace (use_stmt);
+  tidy_after_forward_propagate_addr (use_stmt);
+  return true;
+}
+
+/* NAME is a SSA_NAME representing DEF_RHS which is of the form
+   ADDR_EXPR <whatever>.
+
+   Try to forward propagate the ADDR_EXPR into the use USE_STMT.
+   Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+   node or for recovery of array indexing from pointer arithmetic.
+   
+   Return true if the propagation was successful (the propagation can
+   be not totally successful, yet things may have been changed).  */
+
+static bool
+forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt,
+			       bool single_use_p)
+{
+  tree lhs, rhs, array_ref;
+  tree *rhsp, *lhsp;
+
+  gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
+
+  lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
+
+  /* Trivial cases.  The use statement could be a trivial copy or a
+     useless conversion.  Recurse to the uses of the lhs as copyprop does
+     not copy through different variant pointers and FRE does not catch
+     all useless conversions.  Treat the case of a single-use name and
+     a conversion to def_rhs type separate, though.  */
+  if (TREE_CODE (lhs) == SSA_NAME
+      && (rhs == name
+	  || TREE_CODE (rhs) == NOP_EXPR
+	  || TREE_CODE (rhs) == CONVERT_EXPR)
+      && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (def_rhs)))
+    {
+      /* Only recurse if we don't deal with a single use.  */
+      if (!single_use_p)
+	return forward_propagate_addr_expr (lhs, def_rhs);
+
+      GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
+      return true;
+    }
+
+  /* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS. 
+     ADDR_EXPR will not appear on the LHS.  */
+  lhsp = &GIMPLE_STMT_OPERAND (use_stmt, 0);
+  while (handled_component_p (*lhsp))
+    lhsp = &TREE_OPERAND (*lhsp, 0);
+  lhs = *lhsp;
+
+  /* Now see if the LHS node is an INDIRECT_REF using NAME.  If so, 
+     propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+  if (TREE_CODE (lhs) == INDIRECT_REF
+      && TREE_OPERAND (lhs, 0) == name
+      /* This will not allow stripping const qualification from
+	 pointers which we want to allow specifically here to clean up
+	 the IL for initialization of constant objects.   */
+      && (useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (lhs, 0)),
+				     TREE_TYPE (def_rhs))
+	  /* So explicitly check for this here.  */
+	  || (TYPE_QUALS (TREE_TYPE (TREE_TYPE (TREE_OPERAND (lhs, 0))))
+	      ^ TYPE_QUALS (TREE_TYPE (TREE_TYPE (def_rhs)))) == TYPE_QUAL_CONST)
+      /* ???  This looks redundant, but is required for bogus types
+	 that can sometimes occur.  */
+      && useless_type_conversion_p (TREE_TYPE (lhs),
+				    TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
+    {
+      *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
+      fold_stmt_inplace (use_stmt);
+      tidy_after_forward_propagate_addr (use_stmt);
+
+      /* Continue propagating into the RHS if this was not the only use.  */
+      if (single_use_p)
+	return true;
+    }
+
+  /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
+     nodes from the RHS.  */
+  rhsp = &GIMPLE_STMT_OPERAND (use_stmt, 1);
+  while (handled_component_p (*rhsp)
+	 || TREE_CODE (*rhsp) == ADDR_EXPR)
+    rhsp = &TREE_OPERAND (*rhsp, 0);
+  rhs = *rhsp;
+
+  /* Now see if the RHS node is an INDIRECT_REF using NAME.  If so, 
+     propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+  if (TREE_CODE (rhs) == INDIRECT_REF
+      && TREE_OPERAND (rhs, 0) == name
+      /* ???  This doesn't allow stripping const qualification to
+	 streamline the IL for reads from non-constant objects.  */
+      && (useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (rhs, 0)),
+				     TREE_TYPE (def_rhs))
+	  /* So explicitly check for this here.  */
+	  || (TYPE_QUALS (TREE_TYPE (TREE_TYPE (TREE_OPERAND (rhs, 0))))
+	      ^ TYPE_QUALS (TREE_TYPE (TREE_TYPE (def_rhs)))) == TYPE_QUAL_CONST)
+      && useless_type_conversion_p (TREE_TYPE (rhs),
+				    TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
+    {
+      *rhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
+      fold_stmt_inplace (use_stmt);
+      tidy_after_forward_propagate_addr (use_stmt);
+      return true;
+    }
+
+  /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
+     is nothing to do. */
+  if (TREE_CODE (rhs) != POINTER_PLUS_EXPR
+      || TREE_OPERAND (rhs, 0) != name)
+    return false;
+
+  /* The remaining cases are all for turning pointer arithmetic into
+     array indexing.  They only apply when we have the address of
+     element zero in an array.  If that is not the case then there
+     is nothing to do.  */
+  array_ref = TREE_OPERAND (def_rhs, 0);
+  if (TREE_CODE (array_ref) != ARRAY_REF
+      || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
+      || !integer_zerop (TREE_OPERAND (array_ref, 1)))
+    return false;
+
+  /* Try to optimize &x[0] p+ C where C is a multiple of the size
+     of the elements in X into &x[C/element size].  */
+  if (TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
+    {
+      tree orig = unshare_expr (rhs);
+      TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
+
+      /* If folding succeeds, then we have just exposed new variables
+	 in USE_STMT which will need to be renamed.  If folding fails,
+	 then we need to put everything back the way it was.  */
+      if (fold_stmt_inplace (use_stmt))
+	{
+	  tidy_after_forward_propagate_addr (use_stmt);
+	  return true;
+	}
+      else
+	{
+	  GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
+	  update_stmt (use_stmt);
+	  return false;
+	}
+    }
+
+  /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
+     converting a multiplication of an index by the size of the
+     array elements, then the result is converted into the proper
+     type for the arithmetic.  */
+  if (TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
+      /* Avoid problems with IVopts creating PLUS_EXPRs with a
+	 different type than their operands.  */
+      && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (name)))
+    {
+      bool res;
+      
+      res = forward_propagate_addr_into_variable_array_index (TREE_OPERAND (rhs, 1),
+							      def_rhs, use_stmt);
+      return res;
+    }
+  return false;
+}
+
+/* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
+
+   Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
+   Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+   node or for recovery of array indexing from pointer arithmetic.
+   Returns true, if all uses have been propagated into.  */
+
+static bool
+forward_propagate_addr_expr (tree name, tree rhs)
+{
+  int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
+  imm_use_iterator iter;
+  tree use_stmt;
+  bool all = true;
+  bool single_use_p = has_single_use (name);
+
+  FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
+    {
+      bool result;
+      tree use_rhs;
+
+      /* If the use is not in a simple assignment statement, then
+	 there is nothing we can do.  */
+      if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
+	{
+	  all = false;
+	  continue;
+	}
+
+      /* If the use is in a deeper loop nest, then we do not want
+	to propagate the ADDR_EXPR into the loop as that is likely
+	adding expression evaluations into the loop.  */
+      if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
+	{
+	  all = false;
+	  continue;
+	}
+
+      push_stmt_changes (&use_stmt);
+
+      result = forward_propagate_addr_expr_1 (name, rhs, use_stmt,
+					      single_use_p);
+      all &= result;
+
+      pop_stmt_changes (&use_stmt);
+
+      /* Remove intermediate now unused copy and conversion chains.  */
+      use_rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
+      if (result
+	  && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
+	  && (TREE_CODE (use_rhs) == SSA_NAME
+	      || ((TREE_CODE (use_rhs) == NOP_EXPR
+	           || TREE_CODE (use_rhs) == CONVERT_EXPR)
+		  && TREE_CODE (TREE_OPERAND (use_rhs, 0)) == SSA_NAME)))
+	{
+	  block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
+	  release_defs (use_stmt);
+	  bsi_remove (&bsi, true);
+	}
+    }
+
+  return all;
+}
+
+/* Forward propagate the comparison COND defined in STMT like
+   cond_1 = x CMP y to uses of the form
+     a_1 = (T')cond_1
+     a_1 = !cond_1
+     a_1 = cond_1 != 0
+   Returns true if stmt is now unused.  */
+
+static bool
+forward_propagate_comparison (tree cond, tree stmt)
+{
+  tree name = GIMPLE_STMT_OPERAND (stmt, 0);
+  tree use_stmt, tmp = NULL_TREE;
+
+  /* Don't propagate ssa names that occur in abnormal phis.  */
+  if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
+       && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
+      || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
+	  && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
+    return false;
+
+  /* Do not un-cse comparisons.  But propagate through copies.  */
+  use_stmt = get_prop_dest_stmt (name, &name);
+  if (use_stmt == NULL_TREE)
+    return false;
+
+  /* Conversion of the condition result to another integral type.  */
+  if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+      && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
+	  || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
+          || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
+          || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
+      && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))
+    {
+      tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
+      tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
+
+      /* We can propagate the condition into a conversion.  */
+      if (TREE_CODE (rhs) == CONVERT_EXPR
+	  || TREE_CODE (rhs) == NOP_EXPR)
+	{
+	  /* Avoid using fold here as that may create a COND_EXPR with
+	     non-boolean condition as canonical form.  */
+	  tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
+			TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
+	}
+      /* We can propagate the condition into X op CST where op
+	 is EQ_EXRP or NE_EXPR and CST is either one or zero.  */
+      else if (COMPARISON_CLASS_P (rhs)
+	       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
+	       && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
+	{
+	  enum tree_code code = TREE_CODE (rhs);
+	  tree cst = TREE_OPERAND (rhs, 1);
+
+	  tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
+					fold_convert (TREE_TYPE (cst), cond),
+					cst, false);
+	  if (tmp == NULL_TREE)
+	    return false;
+	}
+      /* We can propagate the condition into a statement that
+	 computes the logical negation of the comparison result.  */
+      else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
+	{
+	  tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
+	  bool nans = HONOR_NANS (TYPE_MODE (type));
+	  enum tree_code code;
+	  code = invert_tree_comparison (TREE_CODE (cond), nans);
+	  if (code == ERROR_MARK)
+	    return false;
+
+	  tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
+			TREE_OPERAND (cond, 1));
+	}
+      else
+	return false;
+
+      GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
+      update_stmt (use_stmt);
+
+      /* Remove defining statements.  */
+      remove_prop_source_from_use (name, stmt);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "  Replaced '");
+	  print_generic_expr (dump_file, rhs, dump_flags);
+	  fprintf (dump_file, "' with '");
+	  print_generic_expr (dump_file, tmp, dump_flags);
+	  fprintf (dump_file, "'\n");
+	}
+
+      return true;
+    }
+
+  return false;
+}
+
+/* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
+   If so, we can change STMT into lhs = y which can later be copy
+   propagated.  Similarly for negation. 
+
+   This could trivially be formulated as a forward propagation 
+   to immediate uses.  However, we already had an implementation
+   from DOM which used backward propagation via the use-def links.
+
+   It turns out that backward propagation is actually faster as
+   there's less work to do for each NOT/NEG expression we find.
+   Backwards propagation needs to look at the statement in a single
+   backlink.  Forward propagation needs to look at potentially more
+   than one forward link.  */
+
+static void
+simplify_not_neg_expr (tree stmt)
+{
+  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+  tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
+
+  /* See if the RHS_DEF_STMT has the same form as our statement.  */
+  if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
+      && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
+    {
+      tree rhs_def_operand =
+	TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);
+
+      /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME.  */
+      if (TREE_CODE (rhs_def_operand) == SSA_NAME
+	  && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
+	{
+	  GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
+	  update_stmt (stmt);
+	}
+    }
+}
+
+/* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
+   the condition which we may be able to optimize better.  */
+
+static void
+simplify_switch_expr (tree stmt)
+{
+  tree cond = SWITCH_COND (stmt);
+  tree def, to, ti;
+
+  /* The optimization that we really care about is removing unnecessary
+     casts.  That will let us do much better in propagating the inferred
+     constant at the switch target.  */
+  if (TREE_CODE (cond) == SSA_NAME)
+    {
+      def = SSA_NAME_DEF_STMT (cond);
+      if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
+	{
+	  def = GIMPLE_STMT_OPERAND (def, 1);
+	  if (TREE_CODE (def) == NOP_EXPR)
+	    {
+	      int need_precision;
+	      bool fail;
+
+	      def = TREE_OPERAND (def, 0);
+
+#ifdef ENABLE_CHECKING
+	      /* ??? Why was Jeff testing this?  We are gimple...  */
+	      gcc_assert (is_gimple_val (def));
+#endif
+
+	      to = TREE_TYPE (cond);
+	      ti = TREE_TYPE (def);
+
+	      /* If we have an extension that preserves value, then we
+		 can copy the source value into the switch.  */
+
+	      need_precision = TYPE_PRECISION (ti);
+	      fail = false;
+	      if (! INTEGRAL_TYPE_P (ti))
+		fail = true;
+	      else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
+		fail = true;
+	      else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
+		need_precision += 1;
+	      if (TYPE_PRECISION (to) < need_precision)
+		fail = true;
+
+	      if (!fail)
+		{
+		  SWITCH_COND (stmt) = def;
+		  update_stmt (stmt);
+		}
+	    }
+	}
+    }
+}
+
+/* Main entry point for the forward propagation optimizer.  */
+
+static unsigned int
+tree_ssa_forward_propagate_single_use_vars (void)
+{
+  basic_block bb;
+  unsigned int todoflags = 0;
+
+  cfg_changed = false;
+
+  FOR_EACH_BB (bb)
+    {
+      block_stmt_iterator bsi;
+
+      /* Note we update BSI within the loop as necessary.  */
+      for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
+	{
+	  tree stmt = bsi_stmt (bsi);
+
+	  /* If this statement sets an SSA_NAME to an address,
+	     try to propagate the address into the uses of the SSA_NAME.  */
+	  if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+	    {
+	      tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+	      tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+
+
+	      if (TREE_CODE (lhs) != SSA_NAME)
+		{
+		  bsi_next (&bsi);
+		  continue;
+		}
+
+	      if (TREE_CODE (rhs) == ADDR_EXPR
+		  /* Handle pointer conversions on invariant addresses
+		     as well, as this is valid gimple.  */
+		  || ((TREE_CODE (rhs) == NOP_EXPR
+		       || TREE_CODE (rhs) == CONVERT_EXPR)
+		      && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
+		      && POINTER_TYPE_P (TREE_TYPE (rhs))))
+		{
+		  STRIP_NOPS (rhs);
+		  if (!stmt_references_abnormal_ssa_name (stmt)
+		      && forward_propagate_addr_expr (lhs, rhs))
+		    {
+		      release_defs (stmt);
+		      todoflags |= TODO_remove_unused_locals;
+		      bsi_remove (&bsi, true);
+		    }
+		  else
+		    bsi_next (&bsi);
+		}
+	      else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
+		        || TREE_CODE (rhs) == NEGATE_EXPR)
+		       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
+		{
+		  simplify_not_neg_expr (stmt);
+		  bsi_next (&bsi);
+		}
+              else if (TREE_CODE (rhs) == COND_EXPR)
+                {
+		  int did_something;
+		  fold_defer_overflow_warnings ();
+                  did_something = forward_propagate_into_cond (rhs, stmt);
+		  if (did_something == 2)
+		    cfg_changed = true;
+		  fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
+		    && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
+		  bsi_next (&bsi);
+                }
+	      else if (COMPARISON_CLASS_P (rhs))
+		{
+		  if (forward_propagate_comparison (rhs, stmt))
+		    {
+		      release_defs (stmt);
+		      todoflags |= TODO_remove_unused_locals;
+		      bsi_remove (&bsi, true);
+		    }
+		  else
+		    bsi_next (&bsi);
+		}
+	      else
+		bsi_next (&bsi);
+	    }
+	  else if (TREE_CODE (stmt) == SWITCH_EXPR)
+	    {
+	      simplify_switch_expr (stmt);
+	      bsi_next (&bsi);
+	    }
+	  else if (TREE_CODE (stmt) == COND_EXPR)
+	    {
+	      int did_something;
+	      fold_defer_overflow_warnings ();
+	      did_something = forward_propagate_into_cond (stmt, stmt);
+	      if (did_something == 2)
+		cfg_changed = true;
+	      fold_undefer_overflow_warnings (did_something, stmt,
+					      WARN_STRICT_OVERFLOW_CONDITIONAL);
+	      bsi_next (&bsi);
+	    }
+	  else
+	    bsi_next (&bsi);
+	}
+    }
+
+  if (cfg_changed)
+    todoflags |= TODO_cleanup_cfg;
+  return todoflags;
+}
+
+
+static bool
+gate_forwprop (void)
+{
+  return 1;
+}
+
+struct tree_opt_pass pass_forwprop = {
+  "forwprop",			/* name */
+  gate_forwprop,		/* gate */
+  tree_ssa_forward_propagate_single_use_vars,	/* execute */
+  NULL,				/* sub */
+  NULL,				/* next */
+  0,				/* static_pass_number */
+  TV_TREE_FORWPROP,		/* tv_id */
+  PROP_cfg | PROP_ssa,		/* properties_required */
+  0,				/* properties_provided */
+  0,				/* properties_destroyed */
+  0,				/* todo_flags_start */
+  TODO_dump_func
+  | TODO_ggc_collect
+  | TODO_update_ssa
+  | TODO_verify_ssa,		/* todo_flags_finish */
+  0				/* letter */
+};
+
+
+/* Structure to keep track of the value of a dereferenced PHI result
+   and the set of virtual operands used for that dereference.  */
+
+struct phiprop_d
+{
+  tree value;
+  tree vop_stmt;
+};
+
+/* Verify if the value recorded for NAME in PHIVN is still valid at
+   the start of basic block BB.  */
+
+static bool
+phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
+{
+  tree vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt;
+  ssa_op_iter ui;
+  tree vuse;
+
+  /* The def stmts of all virtual uses need to be post-dominated
+     by bb.  */
+  FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE)
+    {
+      tree use_stmt;
+      imm_use_iterator ui2;
+      bool ok = true;
+
+      FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
+	{
+	  /* If BB does not dominate a VDEF, the value is invalid.  */
+	  if (((TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+	        && !ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF))
+	       || TREE_CODE (use_stmt) == PHI_NODE)
+	      && !dominated_by_p (CDI_DOMINATORS, bb_for_stmt (use_stmt), bb))
+	    {
+	      ok = false;
+	      BREAK_FROM_IMM_USE_STMT (ui2);
+	    }
+	}
+      if (!ok)
+	return false;
+    }
+
+  return true;
+}
+
+/* Insert a new phi node for the dereference of PHI at basic_block
+   BB with the virtual operands from USE_STMT.  */
+
+static tree
+phiprop_insert_phi (basic_block bb, tree phi, tree use_stmt,
+		    struct phiprop_d *phivn, size_t n)
+{
+  tree res, new_phi;
+  edge_iterator ei;
+  edge e;
+
+  /* Build a new PHI node to replace the definition of
+     the indirect reference lhs.  */
+  res = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb);
+
+  /* Add PHI arguments for each edge inserting loads of the
+     addressable operands.  */
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    {
+      tree old_arg, new_var, tmp;
+
+      old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
+      while (TREE_CODE (old_arg) == SSA_NAME
+	     && (SSA_NAME_VERSION (old_arg) >= n
+	         || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
+	{
+	  tree def_stmt = SSA_NAME_DEF_STMT (old_arg);
+	  old_arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	}
+
+      if (TREE_CODE (old_arg) == SSA_NAME)
+	/* Reuse a formerly created dereference.  */
+	new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
+      else
+	{
+	  old_arg = TREE_OPERAND (old_arg, 0);
+	  new_var = create_tmp_var (TREE_TYPE (old_arg), NULL);
+	  tmp = build2 (GIMPLE_MODIFY_STMT, void_type_node,
+			NULL_TREE, unshare_expr (old_arg));
+	  if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE
+	      || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE)
+	    DECL_GIMPLE_REG_P (new_var) = 1;
+	  add_referenced_var (new_var);
+	  new_var = make_ssa_name (new_var, tmp);
+	  GIMPLE_STMT_OPERAND (tmp, 0) = new_var;
+
+	  bsi_insert_on_edge (e, tmp);
+
+	  update_stmt (tmp);
+	  mark_symbols_for_renaming (tmp);
+	}
+
+      add_phi_arg (new_phi, new_var, e);
+    }
+
+  update_stmt (new_phi);
+
+  return res;
+}
+
+/* Propagate between the phi node arguments of PHI in BB and phi result
+   users.  For now this matches
+        # p_2 = PHI <&x, &y>
+      <Lx>:;
+	p_3 = p_2;
+	z_2 = *p_3;
+   and converts it to
+	# z_2 = PHI <x, y>
+      <Lx>:;
+   Returns true if a transformation was done and edge insertions
+   need to be committed.  Global data PHIVN and N is used to track
+   past transformation results.  We need to be especially careful here
+   with aliasing issues as we are moving memory reads.  */
+
+static bool
+propagate_with_phi (basic_block bb, tree phi, struct phiprop_d *phivn, size_t n)
+{
+  tree ptr = PHI_RESULT (phi);
+  tree use_stmt, res = NULL_TREE;
+  block_stmt_iterator bsi;
+  imm_use_iterator ui;
+  use_operand_p arg_p, use;
+  ssa_op_iter i;
+  bool phi_inserted;
+
+  if (MTAG_P (SSA_NAME_VAR (ptr))
+      || !POINTER_TYPE_P (TREE_TYPE (ptr))
+      || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
+    return false;
+
+  /* Check if we can "cheaply" dereference all phi arguments.  */
+  FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
+    {
+      tree arg = USE_FROM_PTR (arg_p);
+      /* Walk the ssa chain until we reach a ssa name we already
+	 created a value for or we reach a definition of the form
+	 ssa_name_n = &var;  */
+      while (TREE_CODE (arg) == SSA_NAME
+	     && !SSA_NAME_IS_DEFAULT_DEF (arg)
+	     && (SSA_NAME_VERSION (arg) >= n
+	         || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
+	{
+	  tree def_stmt = SSA_NAME_DEF_STMT (arg);
+	  if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
+	    return false;
+	  arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	}
+      if ((TREE_CODE (arg) != ADDR_EXPR
+	   /* Avoid to have to decay *&a to a[0] later.  */
+	   || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0))))
+	  && !(TREE_CODE (arg) == SSA_NAME
+	       && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
+	       && phivn_valid_p (phivn, arg, bb)))
+	return false;
+    }
+
+  /* Find a dereferencing use.  First follow (single use) ssa
+     copy chains for ptr.  */
+  while (single_imm_use (ptr, &use, &use_stmt)
+	 && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+	 && GIMPLE_STMT_OPERAND (use_stmt, 1) == ptr
+	 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME)
+    ptr = GIMPLE_STMT_OPERAND (use_stmt, 0);
+
+  /* Replace the first dereference of *ptr if there is one and if we
+     can move the loads to the place of the ptr phi node.  */
+  phi_inserted = false;
+  FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
+    {
+      ssa_op_iter ui2;
+      tree vuse;
+
+      /* Check whether this is a load of *ptr.  */
+      if (!(TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+	    && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME 
+	    && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == INDIRECT_REF
+	    && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == ptr
+	    /* We cannot replace a load that may throw or is volatile.  */
+	    && !tree_can_throw_internal (use_stmt)))
+	continue;
+
+      /* Check if we can move the loads.  The def stmts of all virtual uses
+	 need to be post-dominated by bb.  */
+      FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE)
+	{
+	  tree def_stmt = SSA_NAME_DEF_STMT (vuse);
+	  if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
+	      && (bb_for_stmt (def_stmt) == bb
+		  || !dominated_by_p (CDI_DOMINATORS,
+				      bb, bb_for_stmt (def_stmt))))
+	    goto next;
+	}
+
+      /* Found a proper dereference.  Insert a phi node if this
+	 is the first load transformation.  */
+      if (!phi_inserted)
+	{
+	  res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
+
+	  /* Remember the value we created for *ptr.  */
+	  phivn[SSA_NAME_VERSION (ptr)].value = res;
+	  phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt;
+
+	  /* Remove old stmt.  The phi is taken care of by DCE, if we
+	     want to delete it here we also have to delete all intermediate
+	     copies.  */
+	  bsi = bsi_for_stmt (use_stmt);
+	  bsi_remove (&bsi, 0);
+
+	  phi_inserted = true;
+	}
+      else
+	{
+	  /* Further replacements are easy, just make a copy out of the
+	     load.  */
+	  GIMPLE_STMT_OPERAND (use_stmt, 1) = res;
+	  update_stmt (use_stmt);
+	}
+
+next:;
+      /* Continue searching for a proper dereference.  */
+    }
+
+  return phi_inserted;
+}
+
+/* Helper walking the dominator tree starting from BB and processing
+   phi nodes with global data PHIVN and N.  */
+
+static bool
+tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n)
+{
+  bool did_something = false; 
+  basic_block son;
+  tree phi;
+
+  for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+    did_something |= propagate_with_phi (bb, phi, phivn, n);
+
+  for (son = first_dom_son (CDI_DOMINATORS, bb);
+       son;
+       son = next_dom_son (CDI_DOMINATORS, son))
+    did_something |= tree_ssa_phiprop_1 (son, phivn, n);
+
+  return did_something;
+}
+
+/* Main entry for phiprop pass.  */
+
+static unsigned int
+tree_ssa_phiprop (void)
+{
+  struct phiprop_d *phivn;
+
+  calculate_dominance_info (CDI_DOMINATORS);
+
+  phivn = XCNEWVEC (struct phiprop_d, num_ssa_names);
+
+  if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names))
+    bsi_commit_edge_inserts ();
+
+  free (phivn);
+
+  return 0;
+}
+
+static bool
+gate_phiprop (void)
+{
+  return 1;
+}
+
+struct tree_opt_pass pass_phiprop = {
+  "phiprop",			/* name */
+  gate_phiprop,			/* gate */
+  tree_ssa_phiprop,		/* execute */
+  NULL,				/* sub */
+  NULL,				/* next */
+  0,				/* static_pass_number */
+  TV_TREE_FORWPROP,		/* tv_id */
+  PROP_cfg | PROP_ssa,		/* properties_required */
+  0,				/* properties_provided */
+  0,				/* properties_destroyed */
+  0,				/* todo_flags_start */
+  TODO_dump_func
+  | TODO_ggc_collect
+  | TODO_update_ssa
+  | TODO_verify_ssa,		/* todo_flags_finish */
+  0				/* letter */
+};