ref: 59d978eeb6d9f987d2c2b17d2799f3c15655284f dir: /sys/src/libc/arm64/tas.s/
TEXT _tas(SB), 1, $-4 MOVW $1, R2 _tas1: LDXRW (R0), R1 STXRW R2, (R0), R3 CBNZ R3, _tas1 MOVW R1, R0 B _barrier(SB) TEXT _barrier(SB), 1, $-4 DMB $0xB // ISH RETURN