c/8224: Incorrect joining of signed and unsigned division

[Glen Nakamura]

I'm testing the following patch as a fix to PR c/8224:

	* fold-const.c (extract_muldiv_1): Don't pass through type conversions
	when signedness changes for division or modulus.

diff -Nru3p gcc-3.3.orig/gcc/fold-const.c gcc-3.3/gcc/fold-const.c
--- gcc-3.3.orig/gcc/fold-const.c	2003-02-16 08:25:20.000000000 +0000
+++ gcc-3.3/gcc/fold-const.c	2003-02-16 08:25:20.000000000 +0000
@@ -4117,7 +4117,12 @@ extract_muldiv_1 (t, c, code, wide_type)
 	      /* ... or its type is larger than ctype,
 		 then we cannot pass through this truncation.  */
 	      || (GET_MODE_SIZE (TYPE_MODE (ctype))
-		  < GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0))))))
+		  < GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0))))
+	      /* ... or signedness changes for division or modulus,
+		 then we cannot pass through this conversion.  */
+	      || (code != MULT_EXPR
+		  && (TREE_UNSIGNED (ctype)
+		      != TREE_UNSIGNED (TREE_TYPE (op0))))))
 	break;
 
       /* Pass the constant down and see if we can make a simplification.  If