ref: 963cfc9a6f6e721f52aa949e6d1af0c3e8dc2ecc 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