ref: 5f7a6b7ea3c4ae1b51beffe3309e9b6b0491e71f 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