fold-const.c (fold_binary): When comparing two simple ADDR_EXPR expressions...

        * fold-const.c (fold_binary): When comparing two simple ADDR_EXPR
        expressions, test their _DECL operands for pointer equality rather
        than using operand_equal_p.

        * gcc.dg/tree-ssa/pr22321.c: New test.

From-SVN: r101974

gcc/ChangeLog

+2005-07-13  Jeff Law  <law@redhat.com>
+
+	* fold-const.c (fold_binary): When comparing two simple ADDR_EXPR
+	expressions, test their _DECL operands for pointer equality rather
+	than using operand_equal_p.
+
 2005-07-13  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* config/alpha/linux.h (TARGET_HAS_F_SETLKW): Renamed to ...

gcc/fold-const.c

@@ -8757,9 +8757,23 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	  && ! lookup_attribute ("alias",
 				 DECL_ATTRIBUTES (TREE_OPERAND (arg1, 0)))
 	  && ! DECL_EXTERNAL (TREE_OPERAND (arg1, 0)))
-	return constant_boolean_node (operand_equal_p (arg0, arg1, 0)
-				      ? code == EQ_EXPR : code != EQ_EXPR,
-				      type);
+	{
+	  /* We know that we're looking at the address of two
+	     non-weak, unaliased, static _DECL nodes.
+
+	     It is both wasteful and incorrect to call operand_equal_p
+	     to compare the two ADDR_EXPR nodes.  It is wasteful in that
+	     all we need to do is test pointer equality for the arguments
+	     to the two ADDR_EXPR nodes.  It is incorrect to use
+	     operand_equal_p as that function is NOT equivalent to a
+	     C equality test.  It can in fact return false for two
+	     objects which would test as equal using the C equality
+	     operator.  */
+	  bool equal = TREE_OPERAND (arg0, 0) == TREE_OPERAND (arg1, 0);
+	  return constant_boolean_node (equal
+				        ? code == EQ_EXPR : code != EQ_EXPR,
+				        type);
+	}
 
       /* If this is a comparison of two exprs that look like an
 	 ARRAY_REF of the same object, then we can fold this to a

gcc/testsuite/ChangeLog

+2005-07-13  Jeff Law  <law@redhat.com>
+
+	* gcc.dg/tree-ssa/pr22321.c: New test
+
 2005-07-13  Paolo Bonzini  <bonzini@gnu.org>
 
 	PR tree-optimization/21921

gcc/testsuite/gcc.dg/tree-ssa/pr22321.c

+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-vrp -fno-tree-copy-prop -fno-tree-ccp -fdump-tree-optimized" } */
+
+
+volatile int x;
+
+int main ()
+{
+  volatile int *vip;
+  vip = &x;
+  volatile int *cvip;
+  cvip = vip;
+
+  if (vip != cvip) return -1;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
+