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  • Committer: Package Import Robot
  • Author(s): Dmitrijs Ledkovs
  • Date: 2013-07-05 10:12:24 UTC
  • Revision ID: package-import@ubuntu.com-20130705101224-6qo3e8jbz8p31aa1
Tags: upstream-0.20130705.1
Import upstream version 0.20130705.1

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android/bionic/libm/src/s_expm1f.c
 
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/* s_expm1f.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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#ifndef lint
 
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static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_expm1f.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
 
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#endif
 
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#include "math.h"
 
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#include "math_private.h"
 
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static const float
 
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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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o_threshold     = 8.8721679688e+01,/* 0x42b17180 */
 
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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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float
 
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expm1f(float x)
 
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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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        u_int32_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(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:-1.0;/* exp(+-inf)={inf,-1} */
 
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                if(x > o_threshold) return huge*huge; /* overflow */
 
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            }
 
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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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            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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}