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. */ 20 static const double 21 t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */ 22 t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */ 23 t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */ 24 t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */ 25 26 float tanf(float x) 27 { 28 double y; 29 uint32_t ix; 30 unsigned n, sign; 31 32 GET_FLOAT_WORD(ix, x); 33 sign = ix >> 31; 34 ix &= 0x7fffffff; 35 36 if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */ 37 if (ix < 0x39800000) { /* |x| < 2**-12 */ 38 /* raise inexact if x!=0 and underflow if subnormal */ 39 FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f); 40 return x; 41 } 42 return __tandf(x, 0); 43 } 44 if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */ 45 if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */ 46 return __tandf((sign ? x+t1pio2 : x-t1pio2), 1); 47 else 48 return __tandf((sign ? x+t2pio2 : x-t2pio2), 0); 49 } 50 if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */ 51 if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */ 52 return __tandf((sign ? x+t3pio2 : x-t3pio2), 1); 53 else 54 return __tandf((sign ? x+t4pio2 : x-t4pio2), 0); 55 } 56 57 /* tan(Inf or NaN) is NaN */ 58 if (ix >= 0x7f800000) 59 return x - x; 60 61 /* argument reduction */ 62 n = __rem_pio2f(x, &y); 63 return __tandf(y, n&1); 64 } 65