GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libm/src/e_log2.c Lines: 0 33 0.0 %
Date: 2017-11-13 Branches: 0 14 0.0 %

Line Branch Exec Source
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/* @(#)e_log.c 1.3 95/01/18 */
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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 <float.h>
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#include <math.h>
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#include "math_private.h"
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static const double
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ln2 = 0.6931471805599452862268,
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two54   =  1.80143985094819840000e+16,  /* 43500000 00000000 */
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Lg1 = 6.666666666666735130e-01,  /* 3FE55555 55555593 */
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Lg2 = 3.999999999940941908e-01,  /* 3FD99999 9997FA04 */
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Lg3 = 2.857142874366239149e-01,  /* 3FD24924 94229359 */
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Lg4 = 2.222219843214978396e-01,  /* 3FCC71C5 1D8E78AF */
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Lg5 = 1.818357216161805012e-01,  /* 3FC74664 96CB03DE */
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Lg6 = 1.531383769920937332e-01,  /* 3FC39A09 D078C69F */
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Lg7 = 1.479819860511658591e-01;  /* 3FC2F112 DF3E5244 */
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static const double zero   =  0.0;
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double
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log2(double x)
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{
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	double hfsq,f,s,z,R,w,t1,t2,dk;
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	int32_t k,hx,i,j;
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	u_int32_t lx;
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	EXTRACT_WORDS(hx,lx,x);
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	k=0;
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	if (hx < 0x00100000) {			/* x < 2**-1022  */
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	    if (((hx&0x7fffffff)|lx)==0)
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		return -two54/zero;		/* log(+-0)=-inf */
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	    if (hx<0) return (x-x)/zero;	/* log(-#) = NaN */
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	    k -= 54; x *= two54; /* subnormal number, scale up x */
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	    GET_HIGH_WORD(hx,x);
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	}
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	if (hx >= 0x7ff00000) return x+x;
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	k += (hx>>20)-1023;
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	hx &= 0x000fffff;
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	i = (hx+0x95f64)&0x100000;
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	SET_HIGH_WORD(x,hx|(i^0x3ff00000));	/* normalize x or x/2 */
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	k += (i>>20);
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	f = x-1.0;
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	dk = (double)k;
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	if((0x000fffff&(2+hx))<3) {	/* |f| < 2**-20 */
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	    if (f==zero)
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		    return (dk);
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	    R = f*f*(0.5-0.33333333333333333*f);
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	    return (dk-(R-f)/ln2);
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	}
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 	s = f/(2.0+f);
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	z = s*s;
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	i = hx-0x6147a;
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	w = z*z;
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	j = 0x6b851-hx;
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	t1= w*(Lg2+w*(Lg4+w*Lg6));
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	t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
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	i |= j;
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	R = t2+t1;
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	if(i>0) {
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	    hfsq=0.5*f*f;
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	    return (dk-(hfsq-s*(hfsq+R)-f)/ln2);
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	} else
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		return (dk-((s*(f-R))-f)/ln2);
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}
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DEF_STD(log2);
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LDBL_MAYBE_UNUSED_CLONE(log2);