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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.17.0/] [newlib/] [libm/] [common/] [sf_expm1.c] - Blame information for rev 617

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1 148 jeremybenn 
/* sf_expm1.c -- float version of s_expm1.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 "fdlibm.h"
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#ifdef __v810__
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#define const
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#endif
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#ifdef __STDC__
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static const float
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#else
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static float
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#endif
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one             = 1.0,
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huge            = 1.0e+30,
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tiny            = 1.0e-30,
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ln2_hi          = 6.9313812256e-01,/* 0x3f317180 */
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ln2_lo          = 9.0580006145e-06,/* 0x3717f7d1 */
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invln2          = 1.4426950216e+00,/* 0x3fb8aa3b */
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        /* scaled coefficients related to expm1 */
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Q1  =  -3.3333335072e-02, /* 0xbd088889 */
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Q2  =   1.5873016091e-03, /* 0x3ad00d01 */
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Q3  =  -7.9365076090e-05, /* 0xb8a670cd */
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Q4  =   4.0082177293e-06, /* 0x36867e54 */
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Q5  =  -2.0109921195e-07; /* 0xb457edbb */
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#ifdef __STDC__
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        float expm1f(float x)
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#else
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        float expm1f(x)
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        float x;
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#endif
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{
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        float y,hi,lo,c,t,e,hxs,hfx,r1;
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        __int32_t k,xsb;
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        __uint32_t hx;
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        GET_FLOAT_WORD(hx,x);
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        xsb = hx&0x80000000;            /* sign bit of x */
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        if(xsb==0) y=x; else y= -x;      /* y = |x| */
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        hx &= 0x7fffffff;               /* high word of |x| */
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    /* filter out huge and non-finite argument */
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        if(hx >= 0x4195b844) {                  /* if |x|>=27*ln2 */
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            if(FLT_UWORD_IS_NAN(hx))
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                return x+x;
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            if(FLT_UWORD_IS_INFINITE(hx))
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                return (xsb==0)? x:-1.0;/* exp(+-inf)={inf,-1} */
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            if(xsb == 0 && hx > FLT_UWORD_LOG_MAX) /* if x>=o_threshold */
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                return huge*huge; /* overflow */
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            if(xsb!=0) { /* x < -27*ln2, return -1.0 with inexact */
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                if(x+tiny<(float)0.0)   /* raise inexact */
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                return tiny-one;        /* return -1 */
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            }
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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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                if(xsb==0)
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                    {hi = x - ln2_hi; lo =  ln2_lo;  k =  1;}
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                else
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                    {hi = x + ln2_hi; lo = -ln2_lo;  k = -1;}
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            } else {
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                k  = invln2*x+((xsb==0)?(float)0.5:(float)-0.5);
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                t  = k;
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                hi = x - t*ln2_hi;      /* t*ln2_hi is exact here */
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                lo = t*ln2_lo;
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            }
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            x  = hi - lo;
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            c  = (hi-x)-lo;
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        }
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        else if(hx < 0x33000000) {      /* when |x|<2**-25, return x */
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            t = huge+x; /* return x with inexact flags when x!=0 */
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            return x - (t-(huge+x));
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        }
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        else k = 0;
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    /* x is now in primary range */
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        hfx = (float)0.5*x;
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        hxs = x*hfx;
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        r1 = one+hxs*(Q1+hxs*(Q2+hxs*(Q3+hxs*(Q4+hxs*Q5))));
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        t  = (float)3.0-r1*hfx;
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        e  = hxs*((r1-t)/((float)6.0 - x*t));
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        if(k==0) return x - (x*e-hxs);           /* c is 0 */
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        else {
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            e  = (x*(e-c)-c);
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            e -= hxs;
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            if(k== -1) return (float)0.5*(x-e)-(float)0.5;
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           if(k==1) {
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                if(x < (float)-0.25) return -(float)2.0*(e-(x+(float)0.5));
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                else          return  one+(float)2.0*(x-e);
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           }
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            if (k <= -2 || k>56) {   /* suffice to return exp(x)-1 */
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                __int32_t i;
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                y = one-(e-x);
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                GET_FLOAT_WORD(i,y);
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                SET_FLOAT_WORD(y,i+(k<<23));    /* add k to y's exponent */
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                return y-one;
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            }
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            t = one;
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            if(k<23) {
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                __int32_t i;
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                SET_FLOAT_WORD(t,0x3f800000 - (0x1000000>>k)); /* t=1-2^-k */
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                y = t-(e-x);
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                GET_FLOAT_WORD(i,y);
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                SET_FLOAT_WORD(y,i+(k<<23));    /* add k to y's exponent */
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           } else {
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                __int32_t i;
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                SET_FLOAT_WORD(t,((0x7f-k)<<23));       /* 2^-k */
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                y = x-(e+t);
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                y += one;
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                GET_FLOAT_WORD(i,y);
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                SET_FLOAT_WORD(y,i+(k<<23));    /* add k to y's exponent */
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            }
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        }
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        return y;
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}
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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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        double expm1(double x)
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#else
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        double expm1(x)
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        double x;
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#endif
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{
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        return (double) expm1f((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */

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