ref: 1b9c7aa4ee5af0b10a07ffbcb5cbfb91abe262c0 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