ref: 7efba9bdc777541330e1b8fcd4a9e6e61a7a2b2d dir: /sys/src/libc/386/387/tan.s/
TEXT tan(SB), $0 FMOVD a+0(FP), F0 FPTAN FMOVDP F0, F0 /* get rid of extra 1.0 */ RET