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