ref: 68d9155e1fff6c4c2d69c96f3fd4e7dc66cdeebd 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