ref: 9c2e8e2b13b0d01b7adf88b61af6edfbddd872c1 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