hwint.h (zext_hwi): Fix signed overflow for prec == 63.

gcc/
	* hwint.h (zext_hwi): Fix signed overflow for prec == 63.

From-SVN: r210006

gcc/ChangeLog

+2014-05-02  Richard Sandiford  <rsandifo@linux.vnet.ibm.com>
+
+	* hwint.h (zext_hwi): Fix signed overflow for prec == 63.
+
 2014-05-02  Alan Lawrence  <alan.lawrence@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_expand_vec_perm_1): Tidy bit-flip

gcc/hwint.h

@@ -344,7 +344,7 @@ zext_hwi (unsigned HOST_WIDE_INT src, unsigned int prec)
   else
     {
       gcc_checking_assert (prec < HOST_BITS_PER_WIDE_INT);
-      return src & (((HOST_WIDE_INT) 1 << prec) - 1);
+      return src & (((unsigned HOST_WIDE_INT) 1 << prec) - 1);
     }
 }