ref: 1ae5fc01a6e9c6fb1a1befd4c60653a6af10a9e0 dir: /sys/src/ape/lib/ap/386/tas.s/
TEXT tas(SB),$0 MOVL $0xdeadead,AX MOVL l+0(FP),BX XCHGL AX,(BX) RET