ref: 1cd199fbd188538a7eef7bcc68e8e8d5ef2c5d9f 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