ref: 1c30bd451e1813f1cf9f9db4d7c1a4f3f95d1e37 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