ref: 23f3d33cdbbfdf2f169f1d7c4acf1f947ed5f5c5 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