ref: c1cf36fbb4a5b7a47f773e95fb8efe0b6d5c3c28 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