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1192a80ed1
at compile time regardless of the dynamic precision, and there's no way to disable this misfeature at compile time. Hence, it's impossible to generate the appropriate tables of constants for the long double inverse trig functions in a straightforward way on i386; this change hacks around the problem by encoding the underlying bits in the table. Note that these functions won't pass the regression test on i386, even with the FPU set to extended precision, because the regression test is similarly damaged by gcc. However, the tests all pass when compiled with a modified version of gcc. Reported by: bde
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 <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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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 "invtrig.h"
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#include "math.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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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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