ref: c2a5d7e3f28e86aeef1e4e37e2b88e46af90b62c 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