ref: 2fe3b28f86ed4aa291fb8a620b948abe9c6a1f84 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