ref: 6bda784cb6a0a933a3c3bde7e6b6d60d221d88f2 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