ref: 82f0a1d2b47c3d1d7cf573a9f5008f95ddf3d092 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