ref: 361b65e4df0b4a3562a6e57b0f7b8009c59c3f2b 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