s390/facilities: optimize test_facility()

test_facility() can be optimized for bits which must be set anyway,
due to the check in head.S. This removes a couple of superfluous
runtime checks.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/facility.h

@@ -34,6 +34,12 @@ static inline int __test_facility(unsigned long nr, void *facilities)
  */
 static inline int test_facility(unsigned long nr)
 {
+	unsigned long facilities_als[] = { FACILITIES_ALS };
+
+	if (__builtin_constant_p(nr) && nr < sizeof(facilities_als) * 8) {
+		if (__test_facility(nr, &facilities_als))
+			return 1;
+	}
 	return __test_facility(nr, &S390_lowcore.stfle_fac_list);
 }