ref: 6361c0a2f202ae56f70cb4a7e8b6f45d54abe1e8 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