88 lines
2.2 KiB
C
88 lines
2.2 KiB
C
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/* @(#)e_acos.c 1.3 95/01/18 */
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/* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include "cdefs-compat.h"
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//__FBSDID("$FreeBSD: src/lib/msun/src/e_acosl.c,v 1.2 2008/08/02 03:56:22 das Exp $");
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/*
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* See comments in e_acos.c.
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* Converted to long double by David Schultz <das@FreeBSD.ORG>.
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*/
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#include <float.h>
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#include <openlibm_math.h>
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#include "invtrig.h"
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#include "math_private.h"
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static const long double
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one= 1.00000000000000000000e+00;
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#ifdef __i386__
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/* XXX Work around the fact that gcc truncates long double constants on i386 */
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static volatile double
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pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */
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pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */
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#define pi ((long double)pi1 + pi2)
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#else
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static const long double
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pi = 3.14159265358979323846264338327950280e+00L;
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#endif
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OLM_DLLEXPORT long double
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acosl(long double x)
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{
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union IEEEl2bits u;
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long double z,p,q,r,w,s,c,df;
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int16_t expsign, expt;
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u.e = x;
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expsign = u.xbits.expsign;
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expt = expsign & 0x7fff;
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if(expt >= BIAS) { /* |x| >= 1 */
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if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0) {
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if (expsign>0) return 0.0; /* acos(1) = 0 */
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else return pi+2.0*pio2_lo; /* acos(-1)= pi */
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}
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return (x-x)/(x-x); /* acos(|x|>1) is NaN */
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}
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if(expt<BIAS-1) { /* |x| < 0.5 */
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if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/
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z = x*x;
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p = P(z);
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q = Q(z);
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r = p/q;
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return pio2_hi - (x - (pio2_lo-x*r));
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} else if (expsign<0) { /* x < -0.5 */
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z = (one+x)*0.5;
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p = P(z);
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q = Q(z);
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s = sqrtl(z);
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r = p/q;
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w = r*s-pio2_lo;
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return pi - 2.0*(s+w);
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} else { /* x > 0.5 */
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z = (one-x)*0.5;
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s = sqrtl(z);
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u.e = s;
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u.bits.manl = 0;
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df = u.e;
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c = (z-df*df)/(s+df);
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p = P(z);
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q = Q(z);
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r = p/q;
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w = r*s+c;
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return 2.0*(df+w);
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}
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}
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