ref: c28f07b5840216c4e83e1d3b21d8a9ed7c41f8f9 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