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111
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1 /* s_logbl.c -- long double version of s_logb.c.
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2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
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3 */
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4
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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
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145
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16 #if defined(LIBM_SCCS) && !defined(lint)
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17 static char rcsid[] = "$NetBSD: $";
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18 #endif
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19
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111
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20 /*
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145
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21 * long double logbq(x)
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111
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22 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
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23 * Use ilogb instead.
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24 */
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25
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26 #include "quadmath-imp.h"
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27
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28 __float128
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29 logbq (__float128 x)
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30 {
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31 int64_t lx, hx, ex;
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32
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33 GET_FLT128_WORDS64 (hx, lx, x);
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34 hx &= 0x7fffffffffffffffLL; /* high |x| */
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35 if ((hx | lx) == 0)
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36 return -1.0 / fabsq (x);
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37 if (hx >= 0x7fff000000000000LL)
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38 return x * x;
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39 if ((ex = hx >> 48) == 0) /* IEEE 754 logb */
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40 {
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41 /* POSIX specifies that denormal number is treated as
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42 though it were normalized. */
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43 int ma;
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44 if (hx == 0)
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45 ma = __builtin_clzll (lx) + 64;
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46 else
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47 ma = __builtin_clzll (hx);
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48 ex -= ma - 16;
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49 }
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50 return (__float128) (ex - 16383);
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51 }
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