GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libm/src/e_expf.c Lines: 8 32 25.0 %
Date: 2017-11-13 Branches: 3 22 13.6 %

Line Branch Exec Source
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/* e_expf.c -- float version of e_exp.c.
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 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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 */
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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 SunPro, 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 "math.h"
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#include "math_private.h"
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static const volatile float huge = 1.0e+30;
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static const float
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one	= 1.0,
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halF[2]	= {0.5,-0.5,},
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twom100 = 7.8886090522e-31,      /* 2**-100=0x0d800000 */
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o_threshold=  8.8721679688e+01,  /* 0x42b17180 */
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u_threshold= -1.0397208405e+02,  /* 0xc2cff1b5 */
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ln2HI[2]   ={ 6.9313812256e-01,		/* 0x3f317180 */
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	     -6.9313812256e-01,},	/* 0xbf317180 */
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ln2LO[2]   ={ 9.0580006145e-06,  	/* 0x3717f7d1 */
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	     -9.0580006145e-06,},	/* 0xb717f7d1 */
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invln2 =  1.4426950216e+00, 		/* 0x3fb8aa3b */
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P1   =  1.6666667163e-01, /* 0x3e2aaaab */
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P2   = -2.7777778450e-03, /* 0xbb360b61 */
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P3   =  6.6137559770e-05, /* 0x388ab355 */
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P4   = -1.6533901999e-06, /* 0xb5ddea0e */
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P5   =  4.1381369442e-08; /* 0x3331bb4c */
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float
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expf(float x)	/* default IEEE double exp */
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{
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	float y,hi,lo,c,t;
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	int32_t k,xsb;
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	u_int32_t hx;
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	GET_FLOAT_WORD(hx,x);
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	xsb = (hx>>31)&1;		/* sign bit of x */
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	hx &= 0x7fffffff;		/* high word of |x| */
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	k = 0;
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    /* filter out non-finite argument */
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	if(hx >= 0x42b17218) {			/* if |x|>=88.721... */
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	    if(hx>0x7f800000)
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		 return x+x;	 		/* NaN */
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            if(hx==0x7f800000)
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		return (xsb==0)? x:0.0;		/* exp(+-inf)={inf,0} */
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	    if(x > o_threshold) return huge*huge; /* overflow */
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	    if(x < u_threshold) return twom100*twom100; /* underflow */
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	}
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    /* argument reduction */
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	if(hx > 0x3eb17218) {		/* if  |x| > 0.5 ln2 */
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	    if(hx < 0x3F851592) {	/* and |x| < 1.5 ln2 */
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		hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb;
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	    } else {
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		k  = invln2*x+halF[xsb];
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		t  = k;
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		hi = x - t*ln2HI[0];	/* t*ln2HI is exact here */
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		lo = t*ln2LO[0];
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	    }
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	    x  = hi - lo;
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	}
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	else if(hx < 0x31800000)  {	/* when |x|<2**-28 */
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	    if(huge+x>one) return one+x;/* trigger inexact */
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	}
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    /* x is now in primary range */
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	t  = x*x;
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	c  = x - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
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	if(k==0) 	return one-((x*c)/(c-(float)2.0)-x);
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	else 		y = one-((lo-(x*c)/((float)2.0-c))-hi);
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	if(k >= -125) {
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	    u_int32_t hy;
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	    GET_FLOAT_WORD(hy,y);
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	    SET_FLOAT_WORD(y,hy+(k<<23));	/* add k to y's exponent */
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	    return y;
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	} else {
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	    u_int32_t hy;
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	    GET_FLOAT_WORD(hy,y);
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	    SET_FLOAT_WORD(y,hy+((k+100)<<23));	/* add k to y's exponent */
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	    return y*twom100;
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	}
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}
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DEF_STD(expf);