Use unsigned shift instead of signed shift.

From-SVN: r29621

gcc/ChangeLog

+Thu Sep 23 15:54:12 1999  Nick Clifton  <nickc@cygnus.com>
+
+	* combine.c (simplify_comparison): Use an unsigned shift to adjust
+	the constant.
+
 Thu Sep 23 08:46:21 1999  Guy Harris  <guy@netapp.com>
 
 	* gcc.1: Fix a formatting error.

gcc/combine.c

@@ -10362,8 +10362,12 @@ simplify_comparison (code, pop0, pop1)
 		  & ~ (mask >> (INTVAL (XEXP (op0, 1))
 				+ ! equality_comparison_p))) == 0)
 	    {
-	      const_op >>= INTVAL (XEXP (op0, 1));
-	      op1 = GEN_INT (const_op);
+	      /* We must perform a logical shift, not an arithmetic one,
+		 as we want the top N bits of C to be zero.  */
+	      unsigned HOST_WIDE_INT temp = const_op;
+	      
+	      temp >>= INTVAL (XEXP (op0, 1));
+	      op1 = GEN_INT (temp);
 	      op0 = XEXP (op0, 0);
 	      continue;
 	    }