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/* ef_exp.c -- float version of e_exp.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */
 
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
 
#include "fdlibm.h"
 
#ifdef __v810__
#define const
#endif
 
#ifdef __STDC__
static const float
#else
static float
#endif
one     = 1.0,
halF[2] = {0.5,-0.5,},
huge    = 1.0e+30,
twom100 = 7.8886090522e-31,      /* 2**-100=0x0d800000 */
ln2HI[2]   ={ 6.9313812256e-01,         /* 0x3f317180 */
             -6.9313812256e-01,},       /* 0xbf317180 */
ln2LO[2]   ={ 9.0580006145e-06,         /* 0x3717f7d1 */
             -9.0580006145e-06,},       /* 0xb717f7d1 */
invln2 =  1.4426950216e+00,             /* 0x3fb8aa3b */
P1   =  1.6666667163e-01, /* 0x3e2aaaab */
P2   = -2.7777778450e-03, /* 0xbb360b61 */
P3   =  6.6137559770e-05, /* 0x388ab355 */
P4   = -1.6533901999e-06, /* 0xb5ddea0e */
P5   =  4.1381369442e-08; /* 0x3331bb4c */
 
#ifdef __STDC__
        float __ieee754_expf(float x)   /* default IEEE double exp */
#else
        float __ieee754_expf(x) /* default IEEE double exp */
        float x;
#endif
{
        float y,hi,lo,c,t;
        __int32_t k,xsb,sx;
        __uint32_t hx;
 
        GET_FLOAT_WORD(sx,x);
        xsb = (sx>>31)&1;               /* sign bit of x */
        hx = sx & 0x7fffffff;           /* high word of |x| */
 
    /* filter out non-finite argument */
        if(FLT_UWORD_IS_NAN(hx))
            return x+x;         /* NaN */
        if(FLT_UWORD_IS_INFINITE(hx))
            return (xsb==0)? x:0.0;              /* exp(+-inf)={inf,0} */
        if(sx > FLT_UWORD_LOG_MAX)
            return huge*huge; /* overflow */
        if(sx < 0 && hx > FLT_UWORD_LOG_MIN)
            return twom100*twom100; /* underflow */
 
    /* argument reduction */
        if(hx > 0x3eb17218) {           /* if  |x| > 0.5 ln2 */
            if(hx < 0x3F851592) {       /* and |x| < 1.5 ln2 */
                hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb;
            } else {
                k  = invln2*x+halF[xsb];
                t  = k;
                hi = x - t*ln2HI[0];     /* t*ln2HI is exact here */
                lo = t*ln2LO[0];
            }
            x  = hi - lo;
        }
        else if(hx < 0x31800000)  {     /* when |x|<2**-28 */
            if(huge+x>one) return one+x;/* trigger inexact */
        }
        else k = 0;
 
    /* x is now in primary range */
        t  = x*x;
        c  = x - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
        if(k==0)         return one-((x*c)/(c-(float)2.0)-x);
        else            y = one-((lo-(x*c)/((float)2.0-c))-hi);
        if(k >= -125) {
            __uint32_t hy;
            GET_FLOAT_WORD(hy,y);
            SET_FLOAT_WORD(y,hy+(k<<23));       /* add k to y's exponent */
            return y;
        } else {
            __uint32_t hy;
            GET_FLOAT_WORD(hy,y);
            SET_FLOAT_WORD(y,hy+((k+100)<<23)); /* add k to y's exponent */
            return y*twom100;
        }
}

Line No.	Rev	Author	Line
1	1010	ivang	`/* ef_exp.c -- float version of e_exp.c.`
2			`* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.`
3			`*/`
4
5			`/*`
6			`* ====================================================`
7			`* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.`
8			`*`
9			`* Developed at SunPro, a Sun Microsystems, Inc. business.`
10			`* Permission to use, copy, modify, and distribute this`
11			`* software is freely granted, provided that this notice`
12			`* is preserved.`
13			`* ====================================================`
14			`*/`
15
16			`#include "fdlibm.h"`
17
18			`#ifdef __v810__`
19			`#define const`
20			`#endif`
21
22			`#ifdef __STDC__`
23			`static const float`
24			`#else`
25			`static float`
26			`#endif`
27			`one = 1.0,`
28			`halF[2] = {0.5,-0.5,},`
29			`huge = 1.0e+30,`
30			`twom100 = 7.8886090522e-31, /* 2*-100=0x0d800000 /`
31			`ln2HI[2] ={ 6.9313812256e-01, /* 0x3f317180 */`
32			`-6.9313812256e-01,}, /* 0xbf317180 */`
33			`ln2LO[2] ={ 9.0580006145e-06, /* 0x3717f7d1 */`
34			`-9.0580006145e-06,}, /* 0xb717f7d1 */`
35			`invln2 = 1.4426950216e+00, /* 0x3fb8aa3b */`
36			`P1 = 1.6666667163e-01, /* 0x3e2aaaab */`
37			`P2 = -2.7777778450e-03, /* 0xbb360b61 */`
38			`P3 = 6.6137559770e-05, /* 0x388ab355 */`
39			`P4 = -1.6533901999e-06, /* 0xb5ddea0e */`
40			`P5 = 4.1381369442e-08; /* 0x3331bb4c */`
41
42			`#ifdef __STDC__`
43			`float __ieee754_expf(float x) /* default IEEE double exp */`
44			`#else`
45			`float __ieee754_expf(x) /* default IEEE double exp */`
46			`float x;`
47			`#endif`
48			`{`
49			`float y,hi,lo,c,t;`
50			`__int32_t k,xsb,sx;`
51			`__uint32_t hx;`
52
53			`GET_FLOAT_WORD(sx,x);`
54			`xsb = (sx>>31)&1; /* sign bit of x */`
55			`hx = sx & 0x7fffffff; /* high word of \|x\| */`
56
57			`/* filter out non-finite argument */`
58			`if(FLT_UWORD_IS_NAN(hx))`
59			`return x+x; /* NaN */`
60			`if(FLT_UWORD_IS_INFINITE(hx))`
61			`return (xsb==0)? x:0.0; /* exp(+-inf)={inf,0} */`
62			`if(sx > FLT_UWORD_LOG_MAX)`
63			`return hugehuge; / overflow */`
64			`if(sx < 0 && hx > FLT_UWORD_LOG_MIN)`
65			`return twom100twom100; / underflow */`
66
67			`/* argument reduction */`
68			`if(hx > 0x3eb17218) { /* if \|x\| > 0.5 ln2 */`
69			`if(hx < 0x3F851592) { /* and \|x\| < 1.5 ln2 */`
70			`hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb;`
71			`} else {`
72			`k = invln2*x+halF[xsb];`
73			`t = k;`
74			`hi = x - tln2HI[0]; / tln2HI is exact here /`
75			`lo = t*ln2LO[0];`
76			`}`
77			`x = hi - lo;`
78			`}`
79			`else if(hx < 0x31800000) { /* when \|x\|<2*-28 /`
80			`if(huge+x>one) return one+x;/* trigger inexact */`
81			`}`
82			`else k = 0;`
83
84			`/* x is now in primary range */`
85			`t = x*x;`
86			`c = x - t(P1+t(P2+t(P3+t(P4+t*P5))));`
87			`if(k==0) return one-((x*c)/(c-(float)2.0)-x);`
88			`else y = one-((lo-(x*c)/((float)2.0-c))-hi);`
89			`if(k >= -125) {`
90			`__uint32_t hy;`
91			`GET_FLOAT_WORD(hy,y);`
92			`SET_FLOAT_WORD(y,hy+(k<<23)); /* add k to y's exponent */`
93			`return y;`
94			`} else {`
95			`__uint32_t hy;`
96			`GET_FLOAT_WORD(hy,y);`
97			`SET_FLOAT_WORD(y,hy+((k+100)<<23)); /* add k to y's exponent */`
98			`return y*twom100;`
99			`}`
100			`}`

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[/] [or1k_old/] [trunk/] [newlib-1.10.0/] [newlib/] [libm/] [math/] [ef_exp.c] - Blame information for rev 1010