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 #include <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: e_acosf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $"); 19 #endif 20 21 #include "math.h" 22 #include "math_private.h" 23 24 static const float 25 one = 1.0000000000e+00, /* 0x3F800000 */ 26 pi = 3.1415925026e+00, /* 0x40490fda */ 27 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ 28 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ 29 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ 30 pS1 = -3.2556581497e-01, /* 0xbea6b090 */ 31 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ 32 pS3 = -4.0055535734e-02, /* 0xbd241146 */ 33 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ 34 pS5 = 3.4793309169e-05, /* 0x3811ef08 */ 35 qS1 = -2.4033949375e+00, /* 0xc019d139 */ 36 qS2 = 2.0209457874e+00, /* 0x4001572d */ 37 qS3 = -6.8828397989e-01, /* 0xbf303361 */ 38 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ 39 40 float 41 __ieee754_acosf(float x) 42 { 43 float z,p,q,r,w,s,c,df; 44 int32_t hx,ix; 45 GET_FLOAT_WORD(hx,x); 46 ix = hx&0x7fffffff; 47 if(ix==0x3f800000) { /* |x|==1 */ 48 if(hx>0) return 0.0; /* acos(1) = 0 */ 49 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 50 } else if(ix>0x3f800000) { /* |x| >= 1 */ 51 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 52 } 53 if(ix<0x3f000000) { /* |x| < 0.5 */ 54 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ 55 z = x*x; 56 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 57 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 58 r = p/q; 59 return pio2_hi - (x - (pio2_lo-x*r)); 60 } else if (hx<0) { /* x < -0.5 */ 61 z = (one+x)*(float)0.5; 62 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 63 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 64 s = __ieee754_sqrtf(z); 65 r = p/q; 66 w = r*s-pio2_lo; 67 return pi - (float)2.0*(s+w); 68 } else { /* x > 0.5 */ 69 int32_t idf; 70 z = (one-x)*(float)0.5; 71 s = __ieee754_sqrtf(z); 72 df = s; 73 GET_FLOAT_WORD(idf,df); 74 SET_FLOAT_WORD(df,idf&0xfffff000); 75 c = (z-df*df)/(s+df); 76 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 77 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 78 r = p/q; 79 w = r*s+c; 80 return (float)2.0*(df+w); 81 } 82 } 83