1/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */ 2/* 3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 4 * Optimized by Bruce D. Evans. 5 */ 6/* 7 * ==================================================== 8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 9 * 10 * Developed at SunPro, a Sun Microsystems, Inc. business. 11 * Permission to use, copy, modify, and distribute this 12 * software is freely granted, provided that this notice 13 * is preserved. 14 * ==================================================== 15 */ 16 17#include "libm.h" 18 19/* Small multiples of pi/2 rounded to double precision. */ 20static const double t1pio2 = 1 * M_PI_2, /* 0x3FF921FB, 0x54442D18 */ 21 t2pio2 = 2 * M_PI_2, /* 0x400921FB, 0x54442D18 */ 22 t3pio2 = 3 * M_PI_2, /* 0x4012D97C, 0x7F3321D2 */ 23 t4pio2 = 4 * M_PI_2; /* 0x401921FB, 0x54442D18 */ 24 25float tanf(float x) { 26 double y; 27 uint32_t ix; 28 unsigned n, sign; 29 30 GET_FLOAT_WORD(ix, x); 31 sign = ix >> 31; 32 ix &= 0x7fffffff; 33 34 if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */ 35 if (ix < 0x39800000) { /* |x| < 2**-12 */ 36 /* raise inexact if x!=0 and underflow if subnormal */ 37 FORCE_EVAL(ix < 0x00800000 ? x / 0x1p120f : x + 0x1p120f); 38 return x; 39 } 40 return __tandf(x, 0); 41 } 42 if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */ 43 if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */ 44 return __tandf((sign ? x + t1pio2 : x - t1pio2), 1); 45 else 46 return __tandf((sign ? x + t2pio2 : x - t2pio2), 0); 47 } 48 if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */ 49 if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */ 50 return __tandf((sign ? x + t3pio2 : x - t3pio2), 1); 51 else 52 return __tandf((sign ? x + t4pio2 : x - t4pio2), 0); 53 } 54 55 /* tan(Inf or NaN) is NaN */ 56 if (ix >= 0x7f800000) 57 return x - x; 58 59 /* argument reduction */ 60 n = __rem_pio2f(x, &y); 61 return __tandf(y, n & 1); 62} 63