re PR tree-optimization/21574 (store_ccp doesn't see through a store.)

	PR tree-optimization/21574
	* tree-ssa-ccp.c (likely_value): If the right hand side is a
	constant, return CONSTANT.
	(ccp_lattice_meet): Use operand_equal_p instead of simple_cst_equal.
	(ccp_fold, visit_assignment): Likewise.
	(evaluate_stmt): Handle UNDEFINED and UNKNOWN_VAL the same way.

From-SVN: r103206

4 files changed, 41 insertions, 4 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d78ba88..226422a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2005-08-17  Steven Bosscher  <stevenb@suse.de>
+
+	PR tree-optimization/21574
+	* tree-ssa-ccp.c (likely_value): If the right hand side is a
+	constant, return CONSTANT.
+	(ccp_lattice_meet): Use operand_equal_p instead of simple_cst_equal.
+	(ccp_fold, visit_assignment): Likewise.
+	(evaluate_stmt): Handle UNDEFINED and UNKNOWN_VAL the same way.
+
 2005-08-16  James A. Morrison  <phython@gcc.gnu.org>
 
 	* c-typeck.c (build_function_call): Call fold_buildN_initializer or
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a8caf51..e631fef 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-08-17  Steven Bosscher  <stevenb@suse.de>
+
+	PR tree-optimization/21574
+	* gcc.dg/tree-ssa/pr21574.c: New test.
+
 2005-08-16  James E Wilson  <wilson@specifix.com>
 
 	* gcc.dg/large-size-array.c (DIM): Use USHRT_MAX not USHORT_MAX.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr21574.c b/gcc/testsuite/gcc.dg/tree-ssa/pr21574.c
new file mode 100644
index 0000000..6e3a5fb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr21574.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-store_ccp" } */
+
+int
+foo (int *p)
+{
+  *p = 0;
+  return *p;
+}
+
+/* The store to *p should be propagated to the return statement.  */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "store_ccp" } } */
+/* { dg-final { cleanup-tree-dump "store_ccp" } } */
diff --git a/gcc/tree-ssa-ccp.c b/gcc/tree-ssa-ccp.c
index 6ec112a..1ff1528 100644
--- a/gcc/tree-ssa-ccp.c
+++ b/gcc/tree-ssa-ccp.c
@@ -473,6 +473,9 @@ likely_value (tree stmt)
       && TREE_CODE (stmt) != SWITCH_EXPR)
     return VARYING;
 
+  if (is_gimple_min_invariant (get_rhs (stmt)))
+    return CONSTANT;
+
   found_constant = false;
   FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE|SSA_OP_VUSE)
     {
@@ -658,7 +661,8 @@ ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
 	   && val2->lattice_val == CONSTANT
 	   && simple_cst_equal (val1->value, val2->value) == 1
 	   && (!do_store_ccp
-	       || simple_cst_equal (val1->mem_ref, val2->mem_ref) == 1))
+	       || (val1->mem_ref && val2->mem_ref
+		   && operand_equal_p (val1->mem_ref, val2->mem_ref, 0))))
     {
       /* Ci M Cj = Ci		if (i == j)
 	 Ci M Cj = VARYING	if (i != j)
@@ -826,7 +830,8 @@ ccp_fold (tree stmt)
       /* If the RHS is a memory load, see if the VUSEs associated with
 	 it are a valid constant for that memory load.  */
       prop_value_t *val = get_value_loaded_by (stmt, const_val);
-      if (val && simple_cst_equal (val->mem_ref, rhs) == 1)
+      if (val && val->mem_ref
+	  && operand_equal_p (val->mem_ref, rhs, 0))
 	return val->value;
       else
 	return NULL_TREE;
@@ -1085,7 +1090,11 @@ evaluate_stmt (tree stmt)
       /* The statement produced a nonconstant value.  If the statement
 	 had UNDEFINED operands, then the result of the statement
 	 should be UNDEFINED.  Otherwise, the statement is VARYING.  */
-      val.lattice_val = (likelyvalue == UNDEFINED) ? UNDEFINED : VARYING;
+      if (likelyvalue == UNDEFINED || likelyvalue == UNKNOWN_VAL)
+	val.lattice_val = likelyvalue;
+      else
+	val.lattice_val = VARYING;
+
       val.value = NULL_TREE;
     }
 
@@ -1122,7 +1131,8 @@ visit_assignment (tree stmt, tree *output_p)
 	 we can propagate the value on the RHS.  */
       prop_value_t *nval = get_value_loaded_by (stmt, const_val);
 
-      if (nval && simple_cst_equal (nval->mem_ref, rhs) == 1)
+      if (nval && nval->mem_ref
+	  && operand_equal_p (nval->mem_ref, rhs, 0))
 	val = *nval;
       else
 	val = evaluate_stmt (stmt);