Fix rtl-optimization/78596 - combine.c:12561:14: runtime error: left shift of negative value

	PR rtl-optimization/78596
	* combine.c (simplify_comparison): Cast to unsigned to avoid
	left shifting of negative value.

From-SVN: r243111

gcc/ChangeLog

+2016-12-01  Markus Trippelsdorf  <markus@trippelsdorf.de>
+
+	PR rtl-optimization/78596
+	* combine.c (simplify_comparison): Cast to unsigned to avoid
+	left shifting of negative value.
+
 2016-12-01  Matthias Klose  <doko@ubuntu.com>
 
 	* doc/install.texi: Don't use pkg-config to check for bdw-gc.

gcc/combine.c

@@ -12561,7 +12561,8 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 		  if (GET_CODE (op0) == LSHIFTRT)
 		    code = unsigned_condition (code);
 
-		  const_op <<= INTVAL (XEXP (op0, 1));
+		  const_op = (unsigned HOST_WIDE_INT) const_op
+			      << INTVAL (XEXP (op0, 1));
 		  if (low_bits != 0
 		      && (code == GT || code == GTU
 			  || code == LE || code == LEU))