ref: 8f44d1f6e8a47395c2ebd9b6899f1b8dc94a9b3f 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