ref: 7c7c7a23512be8c2f3100b61a5ea95f1d5e76d93 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