s390/atomic: circumvent gcc 10 build regression

Circumvent the following gcc 10 allyesconfig build regression:

  CC      drivers/leds/trigger/ledtrig-cpu.o
In file included from ./arch/s390/include/asm/bitops.h:39,
                 from ./include/linux/bitops.h:29,
                 from ./include/linux/kernel.h:12,
                 from drivers/leds/trigger/ledtrig-cpu.c:18:
./arch/s390/include/asm/atomic_ops.h: In function 'ledtrig_cpu':
./arch/s390/include/asm/atomic_ops.h:46:2: warning: 'asm' operand 1 probably does not match constraints
   46 |  asm volatile(       \
      |  ^~~
./arch/s390/include/asm/atomic_ops.h:53:2: note: in expansion of macro '__ATOMIC_CONST_OP'
   53 |  __ATOMIC_CONST_OP(op_name, op_type, op_string, "\n")  \
      |  ^~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:56:1: note: in expansion of macro '__ATOMIC_CONST_OPS'
   56 | __ATOMIC_CONST_OPS(__atomic_add_const, int, "asi")
      | ^~~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:46:2: error: impossible constraint in 'asm'
   46 |  asm volatile(       \
      |  ^~~
./arch/s390/include/asm/atomic_ops.h:53:2: note: in expansion of macro '__ATOMIC_CONST_OP'
   53 |  __ATOMIC_CONST_OP(op_name, op_type, op_string, "\n")  \
      |  ^~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:56:1: note: in expansion of macro '__ATOMIC_CONST_OPS'
   56 | __ATOMIC_CONST_OPS(__atomic_add_const, int, "asi")
      | ^~~~~~~~~~~~~~~~~~
scripts/Makefile.build:280: recipe for target 'drivers/leds/trigger/ledtrig-cpu.o' failed

By swapping conditions as proposed here:
https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549318.html

Suggested-by: Ilya Leoshkevich <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

arch/s390/include/asm/atomic.h

@@ -45,7 +45,11 @@ static inline int atomic_fetch_add(int i, atomic_t *v)
 static inline void atomic_add(int i, atomic_t *v)
 {
 #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
-	if (__builtin_constant_p(i) && (i > -129) && (i < 128)) {
+	/*
+	 * Order of conditions is important to circumvent gcc 10 bug:
+	 * https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549318.html
+	 */
+	if ((i > -129) && (i < 128) && __builtin_constant_p(i)) {
 		__atomic_add_const(i, &v->counter);
 		return;
 	}
@@ -112,7 +116,11 @@ static inline s64 atomic64_fetch_add(s64 i, atomic64_t *v)
 static inline void atomic64_add(s64 i, atomic64_t *v)
 {
 #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
-	if (__builtin_constant_p(i) && (i > -129) && (i < 128)) {
+	/*
+	 * Order of conditions is important to circumvent gcc 10 bug:
+	 * https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549318.html
+	 */
+	if ((i > -129) && (i < 128) && __builtin_constant_p(i)) {
 		__atomic64_add_const(i, (long *)&v->counter);
 		return;
 	}