1 /* e_acosf.c -- float version of e_acos.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 17 static char rcsid[] = "$Id: e_acosf.c,v 1.4 1997/02/22 15:09:55 peter Exp $"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 #ifdef __STDC__ 24 static const float 25 #else 26 static float 27 #endif 28 one = 1.0000000000e+00, /* 0x3F800000 */ 29 pi = 3.1415925026e+00, /* 0x40490fda */ 30 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ 31 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ 32 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ 33 pS1 = -3.2556581497e-01, /* 0xbea6b090 */ 34 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ 35 pS3 = -4.0055535734e-02, /* 0xbd241146 */ 36 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ 37 pS5 = 3.4793309169e-05, /* 0x3811ef08 */ 38 qS1 = -2.4033949375e+00, /* 0xc019d139 */ 39 qS2 = 2.0209457874e+00, /* 0x4001572d */ 40 qS3 = -6.8828397989e-01, /* 0xbf303361 */ 41 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ 42 43 #ifdef __STDC__ 44 float __ieee754_acosf(float x) 45 #else 46 float __ieee754_acosf(x) 47 float x; 48 #endif 49 { 50 float z,p,q,r,w,s,c,df; 51 int32_t hx,ix; 52 GET_FLOAT_WORD(hx,x); 53 ix = hx&0x7fffffff; 54 if(ix==0x3f800000) { /* |x|==1 */ 55 if(hx>0) return 0.0; /* acos(1) = 0 */ 56 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 57 } else if(ix>0x3f800000) { /* |x| >= 1 */ 58 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 59 } 60 if(ix<0x3f000000) { /* |x| < 0.5 */ 61 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ 62 z = x*x; 63 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 64 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 65 r = p/q; 66 return pio2_hi - (x - (pio2_lo-x*r)); 67 } else if (hx<0) { /* x < -0.5 */ 68 z = (one+x)*(float)0.5; 69 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 70 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 71 s = __ieee754_sqrtf(z); 72 r = p/q; 73 w = r*s-pio2_lo; 74 return pi - (float)2.0*(s+w); 75 } else { /* x > 0.5 */ 76 int32_t idf; 77 z = (one-x)*(float)0.5; 78 s = __ieee754_sqrtf(z); 79 df = s; 80 GET_FLOAT_WORD(idf,df); 81 SET_FLOAT_WORD(df,idf&0xfffff000); 82 c = (z-df*df)/(s+df); 83 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 84 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 85 r = p/q; 86 w = r*s+c; 87 return (float)2.0*(df+w); 88 } 89 } 90