| 1 | /* ef_acos.c -- float version of e_acos.c. |
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| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |
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| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | */ |
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| 15 | |
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| 16 | #include "fdlibm.h" |
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| 17 | |
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| 18 | #ifdef __STDC__ |
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| 19 | static const float |
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| 20 | #else |
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| 21 | static float |
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| 22 | #endif |
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| 23 | one = 1.0000000000e+00, /* 0x3F800000 */ |
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| 24 | pi = 3.1415925026e+00, /* 0x40490fda */ |
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| 25 | pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ |
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| 26 | pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ |
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| 27 | pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ |
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| 28 | pS1 = -3.2556581497e-01, /* 0xbea6b090 */ |
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| 29 | pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ |
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| 30 | pS3 = -4.0055535734e-02, /* 0xbd241146 */ |
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| 31 | pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ |
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| 32 | pS5 = 3.4793309169e-05, /* 0x3811ef08 */ |
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| 33 | qS1 = -2.4033949375e+00, /* 0xc019d139 */ |
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| 34 | qS2 = 2.0209457874e+00, /* 0x4001572d */ |
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| 35 | qS3 = -6.8828397989e-01, /* 0xbf303361 */ |
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| 36 | qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ |
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| 37 | |
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| 38 | #ifdef __STDC__ |
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| 39 | float __ieee754_acosf(float x) |
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| 40 | #else |
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| 41 | float __ieee754_acosf(x) |
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| 42 | float x; |
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| 43 | #endif |
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| 44 | { |
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| 45 | float z,p,q,r,w,s,c,df; |
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| 46 | __int32_t hx,ix; |
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| 47 | GET_FLOAT_WORD(hx,x); |
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| 48 | ix = hx&0x7fffffff; |
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| 49 | if(ix==0x3f800000) { /* |x|==1 */ |
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| 50 | if(hx>0) return 0.0; /* acos(1) = 0 */ |
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| 51 | else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ |
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| 52 | } else if(ix>0x3f800000) { /* |x| >= 1 */ |
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| 53 | return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
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| 54 | } |
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| 55 | if(ix<0x3f000000) { /* |x| < 0.5 */ |
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| 56 | if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ |
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| 57 | z = x*x; |
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| 58 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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| 59 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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| 60 | r = p/q; |
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| 61 | return pio2_hi - (x - (pio2_lo-x*r)); |
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| 62 | } else if (hx<0) { /* x < -0.5 */ |
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| 63 | z = (one+x)*(float)0.5; |
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| 64 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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| 65 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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| 66 | s = __ieee754_sqrtf(z); |
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| 67 | r = p/q; |
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| 68 | w = r*s-pio2_lo; |
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| 69 | return pi - (float)2.0*(s+w); |
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| 70 | } else { /* x > 0.5 */ |
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| 71 | __int32_t idf; |
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| 72 | z = (one-x)*(float)0.5; |
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| 73 | s = __ieee754_sqrtf(z); |
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| 74 | df = s; |
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| 75 | GET_FLOAT_WORD(idf,df); |
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| 76 | SET_FLOAT_WORD(df,idf&0xfffff000); |
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| 77 | c = (z-df*df)/(s+df); |
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| 78 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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| 79 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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| 80 | r = p/q; |
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| 81 | w = r*s+c; |
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| 82 | return (float)2.0*(df+w); |
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| 83 | } |
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| 84 | } |
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