ref: 1f15f469f9a659fe26f2ad3f8c1f9db3d49d79c5 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