| The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 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[] = "$FreeBSD: src/lib/msun/src/e_acosf.c,v 1.7 2002/05/28 17:03:12 alfred Exp $"; |
| 18 | #endif |
| 19 | |
| 20 | #include "math.h" |
| 21 | #include "math_private.h" |
| 22 | |
| 23 | static const float |
| 24 | one = 1.0000000000e+00, /* 0x3F800000 */ |
| 25 | pi = 3.1415925026e+00, /* 0x40490fda */ |
| 26 | pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ |
| 27 | pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ |
| 28 | pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ |
| 29 | pS1 = -3.2556581497e-01, /* 0xbea6b090 */ |
| 30 | pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ |
| 31 | pS3 = -4.0055535734e-02, /* 0xbd241146 */ |
| 32 | pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ |
| 33 | pS5 = 3.4793309169e-05, /* 0x3811ef08 */ |
| 34 | qS1 = -2.4033949375e+00, /* 0xc019d139 */ |
| 35 | qS2 = 2.0209457874e+00, /* 0x4001572d */ |
| 36 | qS3 = -6.8828397989e-01, /* 0xbf303361 */ |
| 37 | qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ |
| 38 | |
| 39 | float |
| 40 | __ieee754_acosf(float x) |
| 41 | { |
| 42 | float z,p,q,r,w,s,c,df; |
| 43 | int32_t hx,ix; |
| 44 | GET_FLOAT_WORD(hx,x); |
| 45 | ix = hx&0x7fffffff; |
| 46 | if(ix==0x3f800000) { /* |x|==1 */ |
| 47 | if(hx>0) return 0.0; /* acos(1) = 0 */ |
| 48 | else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ |
| 49 | } else if(ix>0x3f800000) { /* |x| >= 1 */ |
| 50 | return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
| 51 | } |
| 52 | if(ix<0x3f000000) { /* |x| < 0.5 */ |
| 53 | if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ |
| 54 | z = x*x; |
| 55 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
| 56 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
| 57 | r = p/q; |
| 58 | return pio2_hi - (x - (pio2_lo-x*r)); |
| 59 | } else if (hx<0) { /* x < -0.5 */ |
| 60 | z = (one+x)*(float)0.5; |
| 61 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
| 62 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
| 63 | s = __ieee754_sqrtf(z); |
| 64 | r = p/q; |
| 65 | w = r*s-pio2_lo; |
| 66 | return pi - (float)2.0*(s+w); |
| 67 | } else { /* x > 0.5 */ |
| 68 | int32_t idf; |
| 69 | z = (one-x)*(float)0.5; |
| 70 | s = __ieee754_sqrtf(z); |
| 71 | df = s; |
| 72 | GET_FLOAT_WORD(idf,df); |
| 73 | SET_FLOAT_WORD(df,idf&0xfffff000); |
| 74 | c = (z-df*df)/(s+df); |
| 75 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
| 76 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
| 77 | r = p/q; |
| 78 | w = r*s+c; |
| 79 | return (float)2.0*(df+w); |
| 80 | } |
| 81 | } |