@@ -131,25 +131,25 @@ do { \
case 1: \
asm volatile ("stlrb %w1, %0" \
: "=Q" (*__p) \
- : "r" (*(__u8 *)__u.__c) \
+ : "rZ" (*(__u8 *)__u.__c) \
: "memory"); \
break; \
case 2: \
asm volatile ("stlrh %w1, %0" \
: "=Q" (*__p) \
- : "r" (*(__u16 *)__u.__c) \
+ : "rZ" (*(__u16 *)__u.__c) \
: "memory"); \
break; \
case 4: \
asm volatile ("stlr %w1, %0" \
: "=Q" (*__p) \
- : "r" (*(__u32 *)__u.__c) \
+ : "rZ" (*(__u32 *)__u.__c) \
: "memory"); \
break; \
case 8: \
- asm volatile ("stlr %1, %0" \
+ asm volatile ("stlr %x1, %0" \
: "=Q" (*__p) \
- : "r" (*(__u64 *)__u.__c) \
+ : "rZ" (*(__u64 *)__u.__c) \
: "memory"); \
break; \
} \
Currently the asm constraints for __smp_store_release() require that the value is placed in a "real" GPR (i.e. one other than [XW]ZR or SP). This means that for cases such as: __smp_store_release(ptr, 0) ... the compiler has to move '0' into "real" GPR, e.g. mov xN, #0 stlr xN, [<addr>] This is unfortunate, as using the zero register would require fewer instructions and save a "real" GPR for other usage, allowing the compiler to generate: stlr xzr, [<addr>] Modify the asm constaints for __smp_store_release() to permit the use of the zero register for the value. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Will Deacon <will@kernel.org> --- arch/arm64/include/asm/barrier.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)