ref: 566a38b1aa0c7243a1a890a1d7bafdd7a8c8d4d2 dir: /sys/src/libc/68000/tas.s/
TEXT _tas(SB), $0 MOVL $0, R0 MOVL a+0(FP), A0 TAS (A0) BEQ tas_1 MOVL $1, R0 tas_1: RTS