re PR rtl-optimization/11210 (optimizer drops conditional with typecast from…

re PR rtl-optimization/11210 (optimizer drops conditional with typecast from signed to unsigned char)

	PR optimization/11210
	* fold-const (decode_field_reference): Strip only NOPs that
	don't affect the sign.

From-SVN: r68524

gcc/ChangeLog

+2003-06-26  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	PR optimization/11210
+	* fold-const (decode_field_reference): Strip only NOPs that
+	don't affect the sign.
+
 2003-06-26  Dhananjay Deshpande  <dhananjayd@kpitcummins.com>
 
 	* gcc/config/sh/sh.md (push_fpscr): Enable for TARGET_SH2E.

gcc/fold-const.c

@@ -2742,7 +2742,8 @@ decode_field_reference (exp, pbitsize, pbitpos, pmode, punsignedp,
   if (! INTEGRAL_TYPE_P (TREE_TYPE (exp)))
     return 0;
 
-  STRIP_NOPS (exp);
+  /* Signedness matters here.  */
+  STRIP_SIGN_NOPS (exp);
 
   if (TREE_CODE (exp) == BIT_AND_EXPR)
     {

gcc/testsuite/ChangeLog

+2003-06-26  Eric Botcazou <ebotcazou@libertysurf.fr>
+
+	* gcc.dg/20030626-1.c: New test.
+
 2003-06-26  Neil Booth  <neil@daikokuya.co.uk>
 
 	* const-str-2.m: Update.

gcc/testsuite/gcc.dg/20030626-1.c

+/* PR optimization/11210 */
+/* Originator: Guido Classen <guido@clagi.de> */
+/* Reduced testcase by Falk Hueffner <falk@debian.org> */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+/* Verify that the constant expressions folder doesn't
+   throw away the cast operation in the comparison.  */
+
+struct str { 
+  int head; 
+  char data[8];
+};
+
+int foo(struct str t)
+{
+  return t.data[0] || (unsigned char) t.data[2] != 130; /* { dg-bogus "comparison is always 1" } */
+}