1 /* ef_acos.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 "fdlibm.h" 17 18 #ifdef __STDC__ 19 static const float 20 #else 21 static float 22 #endif 23 one = 1.0000000000e+00, /* 0x3F800000 */ 24 pi = 3.1415925026e+00, /* 0x40490fda */ 25 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ 26 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ 27 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ 28 pS1 = -3.2556581497e-01, /* 0xbea6b090 */ 29 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ 30 pS3 = -4.0055535734e-02, /* 0xbd241146 */ 31 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ 32 pS5 = 3.4793309169e-05, /* 0x3811ef08 */ 33 qS1 = -2.4033949375e+00, /* 0xc019d139 */ 34 qS2 = 2.0209457874e+00, /* 0x4001572d */ 35 qS3 = -6.8828397989e-01, /* 0xbf303361 */ 36 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ 37 38 #ifdef __STDC__ __ieee754_acosf(float x)39 float __ieee754_acosf(float x) 40 #else 41 float __ieee754_acosf(x) 42 float x; 43 #endif 44 { 45 float z,p,q,r,w,s,c,df; 46 __int32_t hx,ix; 47 GET_FLOAT_WORD(hx,x); 48 ix = hx&0x7fffffff; 49 if(ix==0x3f800000) { /* |x|==1 */ 50 if(hx>0) return 0.0; /* acos(1) = 0 */ 51 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 52 } else if(ix>0x3f800000) { /* |x| >= 1 */ 53 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 54 } 55 if(ix<0x3f000000) { /* |x| < 0.5 */ 56 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ 57 z = x*x; 58 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 59 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 60 r = p/q; 61 return pio2_hi - (x - (pio2_lo-x*r)); 62 } else if (hx<0) { /* x < -0.5 */ 63 z = (one+x)*(float)0.5; 64 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 65 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 66 s = __ieee754_sqrtf(z); 67 r = p/q; 68 w = r*s-pio2_lo; 69 return pi - (float)2.0*(s+w); 70 } else { /* x > 0.5 */ 71 __int32_t idf; 72 z = (one-x)*(float)0.5; 73 s = __ieee754_sqrtf(z); 74 df = s; 75 GET_FLOAT_WORD(idf,df); 76 SET_FLOAT_WORD(df,idf&0xfffff000); 77 c = (z-df*df)/(s+df); 78 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); 79 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); 80 r = p/q; 81 w = r*s+c; 82 return (float)2.0*(df+w); 83 } 84 } 85