ref: a5a8a92adf39b1a4525d6b0ddebc75e6db03e5b3 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