ref: 4d22dbb0f5a0cd4d3202a01a8cc18b632b5c9b01 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