ref: 17b80cbcf1d5a7c6afd74c7432ab64c100dbdc2f 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