8343810: [s390x] is_uimm* methods should take unsigned arguments

Reviewed-by: lucy

src/hotspot/cpu/s390/assembler_s390.hpp

@@ -56,24 +56,23 @@ class Immediate {
     }
 
     // Test if x is within signed immediate range for nbits.
-    static bool is_uimm(int64_t x, unsigned int nbits) {
+    static bool is_uimm(uint64_t x, unsigned int nbits) {
       // nbits == 0  --> false
       // nbits >= 64 --> true
       assert(1 <= nbits && nbits < 64, "don't call, use statically known result");
-      const uint64_t xu       = (unsigned long)x;
       const uint64_t maxplus1 = 1UL << nbits;
-      return xu < maxplus1; // Unsigned comparison. Negative inputs appear to be very large.
+      return x < maxplus1; // Unsigned comparison. Negative inputs appear to be very large.
     }
-    static bool is_uimm32(int64_t x) {
+    static bool is_uimm32(uint64_t x) {
       return is_uimm(x, 32);
     }
-    static bool is_uimm16(int64_t x) {
+    static bool is_uimm16(uint64_t x) {
       return is_uimm(x, 16);
     }
-    static bool is_uimm12(int64_t x) {
+    static bool is_uimm12(uint64_t x) {
       return is_uimm(x, 12);
     }
-    static bool is_uimm8(int64_t x) {
+    static bool is_uimm8(uint64_t x) {
       return is_uimm(x,  8);
     }
 };