s_cosf.c revision 152596
1/* s_cosf.c -- float version of s_cos.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5/* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16#ifndef lint 17static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_cosf.c 152596 2005-11-19 02:38:27Z bde $"; 18#endif 19 20#include "math.h" 21#include "math_private.h" 22 23/* Small multiples of pi/2 rounded to double precision. */ 24static const double 25c1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */ 26c2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */ 27c3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */ 28c4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */ 29 30static inline float 31__kernel_cosdf(double x) 32{ 33 return __kernel_cosf((float)x, x - (float)x); 34} 35 36static inline float 37__kernel_sindf(double x) 38{ 39 return __kernel_sinf((float)x, x - (float)x, 1); 40} 41 42float 43cosf(float x) 44{ 45 float y[2]; 46 int32_t n,ix; 47 48 x = fabsf(x); 49 GET_FLOAT_WORD(ix,x); 50 51 if(ix <= 0x3f490fda) { /* |x| ~<= pi/4 */ 52 if(ix<0x39800000) /* |x| < 2**-12 */ 53 if(((int)x)==0) return 1.0; /* 1 with inexact if x != 0 */ 54 return __kernel_cosf(x,0.0); 55 } 56 if(ix<=0x407b53d1) { /* |x| <= ~5*pi/4 */ 57 if(ix<=0x4016cbe3) /* |x| <= ~3pi/4 */ 58 return -__kernel_sindf(x - c1pio2); 59 else 60 return -__kernel_cosdf(x - c2pio2); 61 } 62 if(ix<=0x40e231d5) { /* |x| <= ~9*pi/4 */ 63 if(ix<=0x40afeddf) /* |x| <= ~7*pi/4 */ 64 return __kernel_sindf(x - c3pio2); 65 else 66 return __kernel_cosdf(x - c4pio2); 67 } 68 69 /* cos(Inf or NaN) is NaN */ 70 else if (ix>=0x7f800000) return x-x; 71 72 /* general argument reduction needed */ 73 else { 74 n = __ieee754_rem_pio2f(x,y); 75 switch(n&3) { 76 case 0: return __kernel_cosf(y[0],y[1]); 77 case 1: return -__kernel_sinf(y[0],y[1],1); 78 case 2: return -__kernel_cosf(y[0],y[1]); 79 default: 80 return __kernel_sinf(y[0],y[1],1); 81 } 82 } 83} 84