X-Git-Url: http://git.sourceforge.jp/view?p=pf3gnuchains%2Fgcc-fork.git;a=blobdiff_plain;f=gcc%2Ftree-ssa-copy.c;h=4c6d9927bbd23c8f72cc9530ef1ae6c94f886199;hp=12aaff81d94c55a3c5a02f28317e43b39304233a;hb=c11301e89c1e80887b6b9bb795a0038cadee8bbe;hpb=591c2a30f69726711c0e075a3a3e46882d9eb6ad

diff --git a/gcc/tree-ssa-copy.c b/gcc/tree-ssa-copy.c
index 12aaff81d94..4c6d9927bbd 100644
--- a/gcc/tree-ssa-copy.c
+++ b/gcc/tree-ssa-copy.c
@@ -1,11 +1,12 @@
-/* Const/copy propagation and SSA_NAME replacement support routines.
-   Copyright (C) 2004 Free Software Foundation, Inc.
+/* Copy propagation and SSA_NAME replacement support routines.
+   Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010
+   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 2, or (at your option)
+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,
@@ -14,9 +15,8 @@ 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 COPYING.  If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA.  */
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
 
 #include "config.h"
 #include "system.h"
@@ -24,27 +24,27 @@ Boston, MA 02111-1307, USA.  */
 #include "tm.h"
 #include "tree.h"
 #include "flags.h"
-#include "rtl.h"
 #include "tm_p.h"
-#include "ggc.h"
 #include "basic-block.h"
 #include "output.h"
-#include "errors.h"
-#include "expr.h"
 #include "function.h"
-#include "diagnostic.h"
+#include "tree-pretty-print.h"
+#include "gimple-pretty-print.h"
 #include "timevar.h"
 #include "tree-dump.h"
 #include "tree-flow.h"
 #include "tree-pass.h"
+#include "tree-ssa-propagate.h"
 #include "langhooks.h"
+#include "cfgloop.h"
 
-/* This file provides a handful of interfaces for performing const/copy
-   propagation and simple expression replacement which keep variable
-   annotations up-to-date.
+/* This file implements the copy propagation pass and provides a
+   handful of interfaces for performing const/copy propagation and
+   simple expression replacement which keep variable annotations
+   up-to-date.
 
    We require that for any copy operation where the RHS and LHS have
-   a non-null memory tag that the memory tag be the same.   It is OK
+   a non-null memory tag the memory tag be the same.   It is OK
    for one or both of the memory tags to be NULL.
 
    We also require tracking if a variable is dereferenced in a load or
@@ -54,66 +54,129 @@ Boston, MA 02111-1307, USA.  */
    replacements of one SSA_NAME with a different SSA_NAME to use the
    APIs defined in this file.  */
 
+/* Return true if we may propagate ORIG into DEST, false otherwise.  */
 
-/* Given two SSA_NAMEs, replace the annotations for the one referred to by OP 
-   with VAR's annmoptations.
+bool
+may_propagate_copy (tree dest, tree orig)
+{
+  tree type_d = TREE_TYPE (dest);
+  tree type_o = TREE_TYPE (orig);
+
+  /* If ORIG flows in from an abnormal edge, it cannot be propagated.  */
+  if (TREE_CODE (orig) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
+    return false;
+
+  /* If DEST is an SSA_NAME that flows from an abnormal edge, then it
+     cannot be replaced.  */
+  if (TREE_CODE (dest) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest))
+    return false;
+
+  /* Do not copy between types for which we *do* need a conversion.  */
+  if (!useless_type_conversion_p (type_d, type_o))
+    return false;
+
+  /* Propagating virtual operands is always ok.  */
+  if (TREE_CODE (dest) == SSA_NAME && !is_gimple_reg (dest))
+    {
+      /* But only between virtual operands.  */
+      gcc_assert (TREE_CODE (orig) == SSA_NAME && !is_gimple_reg (orig));
+
+      return true;
+    }
 
-   If OP is a pointer, copy the memory tag used originally by OP into
-   VAR.  This is needed in cases where VAR had never been dereferenced in the
-   program.
+  /* Anything else is OK.  */
+  return true;
+}
 
-   If FOR_PROPAGATION is true, then perform additional checks to ensure
-   that const/copy propagation of var for OP is valid.  */
-   
-static void
-replace_ssa_names_ann (tree op,
-		   tree var,
-		   bool for_propagation ATTRIBUTE_UNUSED)
+/* Like may_propagate_copy, but use as the destination expression
+   the principal expression (typically, the RHS) contained in
+   statement DEST.  This is more efficient when working with the
+   gimple tuples representation.  */
+
+bool
+may_propagate_copy_into_stmt (gimple dest, tree orig)
 {
-#if defined ENABLE_CHECKING
-  if (for_propagation && !may_propagate_copy (op, var))
-    abort ();
-#endif
+  tree type_d;
+  tree type_o;
+
+  /* If the statement is a switch or a single-rhs assignment,
+     then the expression to be replaced by the propagation may
+     be an SSA_NAME.  Fortunately, there is an explicit tree
+     for the expression, so we delegate to may_propagate_copy.  */
+
+  if (gimple_assign_single_p (dest))
+    return may_propagate_copy (gimple_assign_rhs1 (dest), orig);
+  else if (gimple_code (dest) == GIMPLE_SWITCH)
+    return may_propagate_copy (gimple_switch_index (dest), orig);
+
+  /* In other cases, the expression is not materialized, so there
+     is no destination to pass to may_propagate_copy.  On the other
+     hand, the expression cannot be an SSA_NAME, so the analysis
+     is much simpler.  */
+
+  if (TREE_CODE (orig) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
+    return false;
+
+  if (is_gimple_assign (dest))
+    type_d = TREE_TYPE (gimple_assign_lhs (dest));
+  else if (gimple_code (dest) == GIMPLE_COND)
+    type_d = boolean_type_node;
+  else if (is_gimple_call (dest)
+           && gimple_call_lhs (dest) != NULL_TREE)
+    type_d = TREE_TYPE (gimple_call_lhs (dest));
+  else
+    gcc_unreachable ();
 
-  /* If VAR doesn't have a memory tag, copy the one from the original
-     operand.  Also copy the dereferenced flags.  */
-  if (POINTER_TYPE_P (TREE_TYPE (op)))
-    {
-      var_ann_t new_ann = var_ann (SSA_NAME_VAR (var));
-      var_ann_t orig_ann = var_ann (SSA_NAME_VAR (op));
+  type_o = TREE_TYPE (orig);
 
-      if (new_ann->type_mem_tag == NULL_TREE)
-	new_ann->type_mem_tag = orig_ann->type_mem_tag;
-      else if (orig_ann->type_mem_tag == NULL_TREE)
-	orig_ann->type_mem_tag = new_ann->type_mem_tag;
-      else if (new_ann->type_mem_tag != orig_ann->type_mem_tag)
-	abort ();
-    }
+  if (!useless_type_conversion_p (type_d, type_o))
+    return false;
 
-}   
+  return true;
+}
+
+/* Similarly, but we know that we're propagating into an ASM_EXPR.  */
+
+bool
+may_propagate_copy_into_asm (tree dest)
+{
+  /* Hard register operands of asms are special.  Do not bypass.  */
+  return !(TREE_CODE (dest) == SSA_NAME
+	   && TREE_CODE (SSA_NAME_VAR (dest)) == VAR_DECL
+	   && DECL_HARD_REGISTER (SSA_NAME_VAR (dest)));
+}
 
 
 /* Common code for propagate_value and replace_exp.
 
-   Replace use operand OP_P with VAL.  FOR_PROPAGATION indicates if the 
+   Replace use operand OP_P with VAL.  FOR_PROPAGATION indicates if the
    replacement is done to propagate a value or not.  */
 
 static void
-replace_exp_1 (use_operand_p op_p, tree val, bool for_propagation)
+replace_exp_1 (use_operand_p op_p, tree val,
+    	       bool for_propagation ATTRIBUTE_UNUSED)
 {
+#if defined ENABLE_CHECKING
+  tree op = USE_FROM_PTR (op_p);
+
+  gcc_assert (!(for_propagation
+		&& TREE_CODE (op) == SSA_NAME
+		&& TREE_CODE (val) == SSA_NAME
+		&& !may_propagate_copy (op, val)));
+#endif
+
   if (TREE_CODE (val) == SSA_NAME)
-    {
-      if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
-	replace_ssa_names_ann (USE_FROM_PTR (op_p), val, for_propagation);
-      SET_USE (op_p, val);
-    }
+    SET_USE (op_p, val);
   else
-    SET_USE (op_p, lhd_unsave_expr_now (val));
+    SET_USE (op_p, unsave_expr_now (val));
 }
 
 
 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
-   into the operand pointed by OP_P.
+   into the operand pointed to by OP_P.
 
    Use this version for const/copy propagation as it will perform additional
    checks to ensure validity of the const/copy propagation.  */
@@ -124,37 +187,669 @@ propagate_value (use_operand_p op_p, tree val)
   replace_exp_1 (op_p, val, true);
 }
 
+/* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME).
+
+   Use this version when not const/copy propagating values.  For example,
+   PRE uses this version when building expressions as they would appear
+   in specific blocks taking into account actions of PHI nodes.
+
+   The statement in which an expression has been replaced should be
+   folded using fold_stmt_inplace.  */
+
+void
+replace_exp (use_operand_p op_p, tree val)
+{
+  replace_exp_1 (op_p, val, false);
+}
+
 
 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
-   into the tree pointed by OP_P.
+   into the tree pointed to by OP_P.
 
-   Use this version for const/copy propagation when SSA operands are not 
-   available.  It will perform the additional checks to ensure validity of 
+   Use this version for const/copy propagation when SSA operands are not
+   available.  It will perform the additional checks to ensure validity of
    the const/copy propagation, but will not update any operand information.
    Be sure to mark the stmt as modified.  */
 
 void
 propagate_tree_value (tree *op_p, tree val)
 {
+  gcc_checking_assert (!(TREE_CODE (val) == SSA_NAME
+			 && *op_p
+			 && TREE_CODE (*op_p) == SSA_NAME
+			 && !may_propagate_copy (*op_p, val)));
+
   if (TREE_CODE (val) == SSA_NAME)
+    *op_p = val;
+  else
+    *op_p = unsave_expr_now (val);
+}
+
+
+/* Like propagate_tree_value, but use as the operand to replace
+   the principal expression (typically, the RHS) contained in the
+   statement referenced by iterator GSI.  Note that it is not
+   always possible to update the statement in-place, so a new
+   statement may be created to replace the original.  */
+
+void
+propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val)
+{
+  gimple stmt = gsi_stmt (*gsi);
+
+  if (is_gimple_assign (stmt))
+    {
+      tree expr = NULL_TREE;
+      if (gimple_assign_single_p (stmt))
+        expr = gimple_assign_rhs1 (stmt);
+      propagate_tree_value (&expr, val);
+      gimple_assign_set_rhs_from_tree (gsi, expr);
+    }
+  else if (gimple_code (stmt) == GIMPLE_COND)
+    {
+      tree lhs = NULL_TREE;
+      tree rhs = build_zero_cst (TREE_TYPE (val));
+      propagate_tree_value (&lhs, val);
+      gimple_cond_set_code (stmt, NE_EXPR);
+      gimple_cond_set_lhs (stmt, lhs);
+      gimple_cond_set_rhs (stmt, rhs);
+    }
+  else if (is_gimple_call (stmt)
+           && gimple_call_lhs (stmt) != NULL_TREE)
     {
-      if (TREE_CODE (*op_p) == SSA_NAME)
-	replace_ssa_names_ann (*op_p, val, true);
-      *op_p = val;
+      gimple new_stmt;
+
+      tree expr = NULL_TREE;
+      propagate_tree_value (&expr, val);
+      new_stmt = gimple_build_assign (gimple_call_lhs (stmt), expr);
+      move_ssa_defining_stmt_for_defs (new_stmt, stmt);
+      gsi_replace (gsi, new_stmt, false);
     }
+  else if (gimple_code (stmt) == GIMPLE_SWITCH)
+    propagate_tree_value (gimple_switch_index_ptr (stmt), val);
   else
-    *op_p = lhd_unsave_expr_now (val);
+    gcc_unreachable ();
 }
 
+/*---------------------------------------------------------------------------
+				Copy propagation
+---------------------------------------------------------------------------*/
+/* Lattice for copy-propagation.  The lattice is initialized to
+   UNDEFINED (value == NULL) for SSA names that can become a copy
+   of something or VARYING (value == self) if not (see get_copy_of_val
+   and stmt_may_generate_copy).  Other values make the name a COPY
+   of that value.
 
-/* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME).
+   When visiting a statement or PHI node the lattice value for an
+   SSA name can transition from UNDEFINED to COPY to VARYING.  */
 
-   Use this version when not const/copy propagating values.  For example,
-   PRE uses this version when building expressions as they would appear
-   in specific blocks taking into account actions of PHI nodes.  */
+struct prop_value_d {
+    /* Copy-of value.  */
+    tree value;
+};
+typedef struct prop_value_d prop_value_t;
 
-void
-replace_exp (use_operand_p op_p, tree val)
+static prop_value_t *copy_of;
+
+
+/* Return true if this statement may generate a useful copy.  */
+
+static bool
+stmt_may_generate_copy (gimple stmt)
 {
-  replace_exp_1 (op_p, val, false);
+  if (gimple_code (stmt) == GIMPLE_PHI)
+    return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt));
+
+  if (gimple_code (stmt) != GIMPLE_ASSIGN)
+    return false;
+
+  /* If the statement has volatile operands, it won't generate a
+     useful copy.  */
+  if (gimple_has_volatile_ops (stmt))
+    return false;
+
+  /* Statements with loads and/or stores will never generate a useful copy.  */
+  if (gimple_vuse (stmt))
+    return false;
+
+  /* Otherwise, the only statements that generate useful copies are
+     assignments whose RHS is just an SSA name that doesn't flow
+     through abnormal edges.  */
+  return ((gimple_assign_rhs_code (stmt) == SSA_NAME
+	   && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt)))
+	  || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)));
+}
+
+
+/* Return the copy-of value for VAR.  */
+
+static inline prop_value_t *
+get_copy_of_val (tree var)
+{
+  prop_value_t *val = &copy_of[SSA_NAME_VERSION (var)];
+
+  if (val->value == NULL_TREE
+      && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var)))
+    {
+      /* If the variable will never generate a useful copy relation,
+	 make it its own copy.  */
+      val->value = var;
+    }
+
+  return val;
+}
+
+/* Return the variable VAR is a copy of or VAR if VAR isn't the result
+   of a copy.  */
+
+static inline tree
+valueize_val (tree var)
+{
+  if (TREE_CODE (var) == SSA_NAME)
+    {
+      tree val = get_copy_of_val (var)->value;
+      if (val)
+	return val;
+    }
+  return var;
+}
+
+/* Set VAL to be the copy of VAR.  If that changed return true.  */
+
+static inline bool
+set_copy_of_val (tree var, tree val)
+{
+  unsigned int ver = SSA_NAME_VERSION (var);
+  tree old;
+
+  /* Set FIRST to be the first link in COPY_OF[DEST].  If that
+     changed, return true.  */
+  old = copy_of[ver].value;
+  copy_of[ver].value = val;
+
+  if (old != val
+      || (val && !operand_equal_p (old, val, 0)))
+    return true;
+
+  return false;
+}
+
+
+/* Dump the copy-of value for variable VAR to FILE.  */
+
+static void
+dump_copy_of (FILE *file, tree var)
+{
+  tree val;
+
+  print_generic_expr (file, var, dump_flags);
+  if (TREE_CODE (var) != SSA_NAME)
+    return;
+
+  val = copy_of[SSA_NAME_VERSION (var)].value;
+  fprintf (file, " copy-of chain: ");
+  print_generic_expr (file, var, 0);
+  fprintf (file, " ");
+  if (!val)
+    fprintf (file, "[UNDEFINED]");
+  else if (val == var)
+    fprintf (file, "[NOT A COPY]");
+  else
+    {
+      fprintf (file, "-> ");
+      print_generic_expr (file, val, 0);
+      fprintf (file, " ");
+      fprintf (file, "[COPY]");
+    }
+}
+
+
+/* Evaluate the RHS of STMT.  If it produces a valid copy, set the LHS
+   value and store the LHS into *RESULT_P.  */
+
+static enum ssa_prop_result
+copy_prop_visit_assignment (gimple stmt, tree *result_p)
+{
+  tree lhs, rhs;
+
+  lhs = gimple_assign_lhs (stmt);
+  rhs = valueize_val (gimple_assign_rhs1 (stmt));
+
+  if (TREE_CODE (lhs) == SSA_NAME)
+    {
+      /* Straight copy between two SSA names.  First, make sure that
+	 we can propagate the RHS into uses of LHS.  */
+      if (!may_propagate_copy (lhs, rhs))
+	return SSA_PROP_VARYING;
+
+      *result_p = lhs;
+      if (set_copy_of_val (*result_p, rhs))
+	return SSA_PROP_INTERESTING;
+      else
+	return SSA_PROP_NOT_INTERESTING;
+    }
+
+  return SSA_PROP_VARYING;
+}
+
+
+/* Visit the GIMPLE_COND STMT.  Return SSA_PROP_INTERESTING
+   if it can determine which edge will be taken.  Otherwise, return
+   SSA_PROP_VARYING.  */
+
+static enum ssa_prop_result
+copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p)
+{
+  enum ssa_prop_result retval = SSA_PROP_VARYING;
+  location_t loc = gimple_location (stmt);
+
+  tree op0 = gimple_cond_lhs (stmt);
+  tree op1 = gimple_cond_rhs (stmt);
+
+  /* The only conditionals that we may be able to compute statically
+     are predicates involving two SSA_NAMEs.  */
+  if (TREE_CODE (op0) == SSA_NAME && TREE_CODE (op1) == SSA_NAME)
+    {
+      op0 = valueize_val (op0);
+      op1 = valueize_val (op1);
+
+      /* See if we can determine the predicate's value.  */
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "Trying to determine truth value of ");
+	  fprintf (dump_file, "predicate ");
+	  print_gimple_stmt (dump_file, stmt, 0, 0);
+	}
+
+      /* We can fold COND and get a useful result only when we have
+	 the same SSA_NAME on both sides of a comparison operator.  */
+      if (op0 == op1)
+	{
+	  tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt),
+                                          boolean_type_node, op0, op1);
+	  if (folded_cond)
+	    {
+	      basic_block bb = gimple_bb (stmt);
+	      *taken_edge_p = find_taken_edge (bb, folded_cond);
+	      if (*taken_edge_p)
+		retval = SSA_PROP_INTERESTING;
+	    }
+	}
+    }
+
+  if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p)
+    fprintf (dump_file, "\nConditional will always take edge %d->%d\n",
+	     (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index);
+
+  return retval;
+}
+
+
+/* Evaluate statement STMT.  If the statement produces a new output
+   value, return SSA_PROP_INTERESTING and store the SSA_NAME holding
+   the new value in *RESULT_P.
+
+   If STMT is a conditional branch and we can determine its truth
+   value, set *TAKEN_EDGE_P accordingly.
+
+   If the new value produced by STMT is varying, return
+   SSA_PROP_VARYING.  */
+
+static enum ssa_prop_result
+copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p)
+{
+  enum ssa_prop_result retval;
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    {
+      fprintf (dump_file, "\nVisiting statement:\n");
+      print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+      fprintf (dump_file, "\n");
+    }
+
+  if (gimple_assign_single_p (stmt)
+      && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
+      && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
+	  || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
+    {
+      /* If the statement is a copy assignment, evaluate its RHS to
+	 see if the lattice value of its output has changed.  */
+      retval = copy_prop_visit_assignment (stmt, result_p);
+    }
+  else if (gimple_code (stmt) == GIMPLE_COND)
+    {
+      /* See if we can determine which edge goes out of a conditional
+	 jump.  */
+      retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p);
+    }
+  else
+    retval = SSA_PROP_VARYING;
+
+  if (retval == SSA_PROP_VARYING)
+    {
+      tree def;
+      ssa_op_iter i;
+
+      /* Any other kind of statement is not interesting for constant
+	 propagation and, therefore, not worth simulating.  */
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "No interesting values produced.\n");
+
+      /* The assignment is not a copy operation.  Don't visit this
+	 statement again and mark all the definitions in the statement
+	 to be copies of nothing.  */
+      FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS)
+	set_copy_of_val (def, def);
+    }
+
+  return retval;
+}
+
+
+/* Visit PHI node PHI.  If all the arguments produce the same value,
+   set it to be the value of the LHS of PHI.  */
+
+static enum ssa_prop_result
+copy_prop_visit_phi_node (gimple phi)
+{
+  enum ssa_prop_result retval;
+  unsigned i;
+  prop_value_t phi_val = { NULL_TREE };
+
+  tree lhs = gimple_phi_result (phi);
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    {
+      fprintf (dump_file, "\nVisiting PHI node: ");
+      print_gimple_stmt (dump_file, phi, 0, dump_flags);
+    }
+
+  for (i = 0; i < gimple_phi_num_args (phi); i++)
+    {
+      prop_value_t *arg_val;
+      tree arg_value;
+      tree arg = gimple_phi_arg_def (phi, i);
+      edge e = gimple_phi_arg_edge (phi, i);
+
+      /* We don't care about values flowing through non-executable
+	 edges.  */
+      if (!(e->flags & EDGE_EXECUTABLE))
+	continue;
+
+      /* Names that flow through abnormal edges cannot be used to
+	 derive copies.  */
+      if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg))
+	{
+	  phi_val.value = lhs;
+	  break;
+	}
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "\tArgument #%d: ", i);
+	  dump_copy_of (dump_file, arg);
+	  fprintf (dump_file, "\n");
+	}
+
+      if (TREE_CODE (arg) == SSA_NAME)
+	{
+	  arg_val = get_copy_of_val (arg);
+
+	  /* If we didn't visit the definition of arg yet treat it as
+	     UNDEFINED.  This also handles PHI arguments that are the
+	     same as lhs.  We'll come here again.  */
+	  if (!arg_val->value)
+	    continue;
+
+	  arg_value = arg_val->value;
+	}
+      else
+	arg_value = valueize_val (arg);
+
+      /* Avoid copy propagation from an inner into an outer loop.
+	 Otherwise, this may move loop variant variables outside of
+	 their loops and prevent coalescing opportunities.  If the
+	 value was loop invariant, it will be hoisted by LICM and
+	 exposed for copy propagation.
+	 ???  The value will be always loop invariant.
+	 In loop-closed SSA form do not copy-propagate through
+	 PHI nodes in blocks with a loop exit edge predecessor.  */
+      if (current_loops
+	  && TREE_CODE (arg_value) == SSA_NAME
+	  && (loop_depth_of_name (arg_value) > loop_depth_of_name (lhs)
+	      || (loops_state_satisfies_p (LOOP_CLOSED_SSA)
+		  && loop_exit_edge_p (e->src->loop_father, e))))
+	{
+	  phi_val.value = lhs;
+	  break;
+	}
+
+      /* If the LHS didn't have a value yet, make it a copy of the
+	 first argument we find.   */
+      if (phi_val.value == NULL_TREE)
+	{
+	  phi_val.value = arg_value;
+	  continue;
+	}
+
+      /* If PHI_VAL and ARG don't have a common copy-of chain, then
+	 this PHI node cannot be a copy operation.  */
+      if (phi_val.value != arg_value
+	  && !operand_equal_p (phi_val.value, arg_value, 0))
+	{
+	  phi_val.value = lhs;
+	  break;
+	}
+    }
+
+  if (phi_val.value
+      && may_propagate_copy (lhs, phi_val.value)
+      && set_copy_of_val (lhs, phi_val.value))
+    retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING;
+  else
+    retval = SSA_PROP_NOT_INTERESTING;
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    {
+      fprintf (dump_file, "PHI node ");
+      dump_copy_of (dump_file, lhs);
+      fprintf (dump_file, "\nTelling the propagator to ");
+      if (retval == SSA_PROP_INTERESTING)
+	fprintf (dump_file, "add SSA edges out of this PHI and continue.");
+      else if (retval == SSA_PROP_VARYING)
+	fprintf (dump_file, "add SSA edges out of this PHI and never visit again.");
+      else
+	fprintf (dump_file, "do nothing with SSA edges and keep iterating.");
+      fprintf (dump_file, "\n\n");
+    }
+
+  return retval;
+}
+
+
+/* Initialize structures used for copy propagation.  */
+
+static void
+init_copy_prop (void)
+{
+  basic_block bb;
+
+  copy_of = XCNEWVEC (prop_value_t, num_ssa_names);
+
+  FOR_EACH_BB (bb)
+    {
+      gimple_stmt_iterator si;
+      int depth = bb->loop_depth;
+
+      for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
+	{
+	  gimple stmt = gsi_stmt (si);
+	  ssa_op_iter iter;
+          tree def;
+
+	  /* The only statements that we care about are those that may
+	     generate useful copies.  We also need to mark conditional
+	     jumps so that their outgoing edges are added to the work
+	     lists of the propagator.
+
+	     Avoid copy propagation from an inner into an outer loop.
+	     Otherwise, this may move loop variant variables outside of
+	     their loops and prevent coalescing opportunities.  If the
+	     value was loop invariant, it will be hoisted by LICM and
+	     exposed for copy propagation.
+	     ???  This doesn't make sense.  */
+	  if (stmt_ends_bb_p (stmt))
+            prop_set_simulate_again (stmt, true);
+	  else if (stmt_may_generate_copy (stmt)
+                   /* Since we are iterating over the statements in
+                      BB, not the phi nodes, STMT will always be an
+                      assignment.  */
+                   && loop_depth_of_name (gimple_assign_rhs1 (stmt)) <= depth)
+            prop_set_simulate_again (stmt, true);
+	  else
+            prop_set_simulate_again (stmt, false);
+
+	  /* Mark all the outputs of this statement as not being
+	     the copy of anything.  */
+	  FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
+            if (!prop_simulate_again_p (stmt))
+	      set_copy_of_val (def, def);
+	}
+
+      for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si))
+	{
+          gimple phi = gsi_stmt (si);
+          tree def;
+
+	  def = gimple_phi_result (phi);
+	  if (!is_gimple_reg (def))
+            prop_set_simulate_again (phi, false);
+	  else
+            prop_set_simulate_again (phi, true);
+
+	  if (!prop_simulate_again_p (phi))
+	    set_copy_of_val (def, def);
+	}
+    }
+}
+
+/* Callback for substitute_and_fold to get at the final copy-of values.  */
+
+static tree
+get_value (tree name)
+{
+  tree val = copy_of[SSA_NAME_VERSION (name)].value;
+  if (val && val != name)
+    return val;
+  return NULL_TREE;
 }
+
+/* Deallocate memory used in copy propagation and do final
+   substitution.  */
+
+static void
+fini_copy_prop (void)
+{
+  unsigned i;
+
+  /* Set the final copy-of value for each variable by traversing the
+     copy-of chains.  */
+  for (i = 1; i < num_ssa_names; i++)
+    {
+      tree var = ssa_name (i);
+      if (!var
+	  || !copy_of[i].value
+	  || copy_of[i].value == var)
+	continue;
+
+      /* In theory the points-to solution of all members of the
+         copy chain is their intersection.  For now we do not bother
+	 to compute this but only make sure we do not lose points-to
+	 information completely by setting the points-to solution
+	 of the representative to the first solution we find if
+	 it doesn't have one already.  */
+      if (copy_of[i].value != var
+	  && TREE_CODE (copy_of[i].value) == SSA_NAME
+	  && POINTER_TYPE_P (TREE_TYPE (var))
+	  && SSA_NAME_PTR_INFO (var)
+	  && !SSA_NAME_PTR_INFO (copy_of[i].value))
+	duplicate_ssa_name_ptr_info (copy_of[i].value, SSA_NAME_PTR_INFO (var));
+    }
+
+  /* Don't do DCE if we have loops.  That's the simplest way to not
+     destroy the scev cache.  */
+  substitute_and_fold (get_value, NULL, !current_loops);
+
+  free (copy_of);
+}
+
+
+/* Main entry point to the copy propagator.
+
+   PHIS_ONLY is true if we should only consider PHI nodes as generating
+   copy propagation opportunities.
+
+   The algorithm propagates the value COPY-OF using ssa_propagate.  For
+   every variable X_i, COPY-OF(X_i) indicates which variable is X_i created
+   from.  The following example shows how the algorithm proceeds at a
+   high level:
+
+	    1	a_24 = x_1
+	    2	a_2 = PHI <a_24, x_1>
+	    3	a_5 = PHI <a_2>
+	    4	x_1 = PHI <x_298, a_5, a_2>
+
+   The end result should be that a_2, a_5, a_24 and x_1 are a copy of
+   x_298.  Propagation proceeds as follows.
+
+   Visit #1: a_24 is copy-of x_1.  Value changed.
+   Visit #2: a_2 is copy-of x_1.  Value changed.
+   Visit #3: a_5 is copy-of x_1.  Value changed.
+   Visit #4: x_1 is copy-of x_298.  Value changed.
+   Visit #1: a_24 is copy-of x_298.  Value changed.
+   Visit #2: a_2 is copy-of x_298.  Value changed.
+   Visit #3: a_5 is copy-of x_298.  Value changed.
+   Visit #4: x_1 is copy-of x_298.  Stable state reached.
+
+   When visiting PHI nodes, we only consider arguments that flow
+   through edges marked executable by the propagation engine.  So,
+   when visiting statement #2 for the first time, we will only look at
+   the first argument (a_24) and optimistically assume that its value
+   is the copy of a_24 (x_1).  */
+
+static unsigned int
+execute_copy_prop (void)
+{
+  init_copy_prop ();
+  ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node);
+  fini_copy_prop ();
+  return 0;
+}
+
+static bool
+gate_copy_prop (void)
+{
+  return flag_tree_copy_prop != 0;
+}
+
+struct gimple_opt_pass pass_copy_prop =
+{
+ {
+  GIMPLE_PASS,
+  "copyprop",				/* name */
+  gate_copy_prop,			/* gate */
+  execute_copy_prop,			/* execute */
+  NULL,					/* sub */
+  NULL,					/* next */
+  0,					/* static_pass_number */
+  TV_TREE_COPY_PROP,			/* tv_id */
+  PROP_ssa | PROP_cfg,			/* properties_required */
+  0,					/* properties_provided */
+  0,					/* properties_destroyed */
+  0,					/* todo_flags_start */
+  TODO_cleanup_cfg
+    | TODO_ggc_collect
+    | TODO_verify_ssa
+    | TODO_update_ssa			/* todo_flags_finish */
+ }
+};