ref: a4c6dc1d3d3a2ef3ec4d4ac49b16ec039c353cd7 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