ref: 2c1dc1aa4f374f5c8d6a13e7e82a26c4e27e6775 dir: /sys/src/libc/68020/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