ref: 332f070e5a51e5fcc1f2f17f15f67aa98a01b5f4 dir: /sys/src/libc/arm/tas.s/
TEXT _tas(SB), $-4 MOVW R0,R1 MOVW $1,R0 SWPW R0,(R1) /* fix: deprecated in armv7 */ RET