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| Rev | Author | Line No. | Line |
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| 4349 | Serge | 1 | /* ef_log10.c -- float version of e_log10.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |||
| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | */ |
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| 15 | |||
| 16 | #include "fdlibm.h" |
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| 17 | |||
| 18 | #ifdef __STDC__ |
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| 19 | static const float |
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| 20 | #else |
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| 21 | static float |
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| 22 | #endif |
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| 23 | two25 = 3.3554432000e+07, /* 0x4c000000 */ |
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| 24 | ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */ |
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| 25 | log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */ |
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| 26 | log10_2lo = 7.9034151668e-07; /* 0x355427db */ |
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| 27 | |||
| 28 | #ifdef __STDC__ |
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| 29 | static const float zero = 0.0; |
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| 30 | #else |
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| 31 | static float zero = 0.0; |
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| 32 | #endif |
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| 33 | |||
| 34 | #ifdef __STDC__ |
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| 35 | float __ieee754_log10f(float x) |
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| 36 | #else |
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| 37 | float __ieee754_log10f(x) |
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| 38 | float x; |
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| 39 | #endif |
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| 40 | { |
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| 41 | float y,z; |
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| 42 | __int32_t i,k,hx; |
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| 43 | |||
| 44 | GET_FLOAT_WORD(hx,x); |
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| 45 | |||
| 46 | k=0; |
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| 47 | if (FLT_UWORD_IS_ZERO(hx&0x7fffffff)) |
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| 48 | return -two25/zero; /* log(+-0)=-inf */ |
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| 49 | if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ |
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| 50 | if (!FLT_UWORD_IS_FINITE(hx)) return x+x; |
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| 51 | if (FLT_UWORD_IS_SUBNORMAL(hx)) { |
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| 52 | k -= 25; x *= two25; /* subnormal number, scale up x */ |
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| 53 | GET_FLOAT_WORD(hx,x); |
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| 54 | } |
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| 55 | k += (hx>>23)-127; |
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| 56 | i = ((__uint32_t)k&0x80000000)>>31; |
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| 57 | hx = (hx&0x007fffff)|((0x7f-i)<<23); |
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| 58 | y = (float)(k+i); |
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| 59 | SET_FLOAT_WORD(x,hx); |
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| 60 | z = y*log10_2lo + ivln10*__ieee754_logf(x); |
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| 61 | return z+y*log10_2hi; |
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| 62 | } |