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/* $OpenBSD: s_logbl.c,v 1.1 2008/12/09 20:00:35 martynas Exp $ */ |
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/* |
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* From: @(#)s_ilogb.c 5.1 93/09/24 |
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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 <sys/types.h> |
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#include <machine/ieee.h> |
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#include <float.h> |
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#include <limits.h> |
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#include <math.h> |
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long double |
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logbl(long double x) |
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{ |
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union { |
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long double e; |
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struct ieee_ext bits; |
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} u; |
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unsigned long m; |
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int b; |
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u.e = x; |
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if (u.bits.ext_exp == 0) { |
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if ((u.bits.ext_fracl |
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#ifdef EXT_FRACLMBITS |
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| u.bits.ext_fraclm |
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#endif /* EXT_FRACLMBITS */ |
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#ifdef EXT_FRACHMBITS |
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| u.bits.ext_frachm |
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#endif /* EXT_FRACHMBITS */ |
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| u.bits.ext_frach) == 0) { /* x == 0 */ |
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u.bits.ext_sign = 1; |
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return (1.0L / u.e); |
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} |
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/* denormalized */ |
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if (u.bits.ext_frach == 0 |
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#ifdef EXT_FRACHMBITS |
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&& u.bits.ext_frachm == 0 |
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#endif |
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) { |
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m = 1lu << (EXT_FRACLBITS - 1); |
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for (b = EXT_FRACHBITS; !(u.bits.ext_fracl & m); m >>= 1) |
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b++; |
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#if defined(EXT_FRACHMBITS) && defined(EXT_FRACLMBITS) |
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m = 1lu << (EXT_FRACLMBITS - 1); |
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for (b += EXT_FRACHMBITS; !(u.bits.ext_fraclm & m); |
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m >>= 1) |
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b++; |
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#endif /* defined(EXT_FRACHMBITS) && defined(EXT_FRACLMBITS) */ |
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} else { |
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m = 1lu << (EXT_FRACHBITS - 1); |
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for (b = 0; !(u.bits.ext_frach & m); m >>= 1) |
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b++; |
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#ifdef EXT_FRACHMBITS |
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m = 1lu << (EXT_FRACHMBITS - 1); |
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for (; !(u.bits.ext_frachm & m); m >>= 1) |
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b++; |
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#endif /* EXT_FRACHMBITS */ |
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} |
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#ifdef EXT_IMPLICIT_NBIT |
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b++; |
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#endif |
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return ((long double)(LDBL_MIN_EXP - b - 1)); |
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} |
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if (u.bits.ext_exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ |
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return ((long double)(u.bits.ext_exp - LDBL_MAX_EXP + 1)); |
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else /* +/- inf or nan */ |
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return (x * x); |
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} |