| 1 | /* s_logbl.c -- long double version of s_logb.c. |
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| 2 | */ |
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| 3 | |
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| 4 | /* |
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| 5 | * ==================================================== |
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| 6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 7 | * |
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| 8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 9 | * Permission to use, copy, modify, and distribute this |
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| 10 | * software is freely granted, provided that this notice |
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| 11 | * is preserved. |
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| 12 | * ==================================================== |
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| 13 | */ |
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| 14 | |
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| 15 | /* |
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| 16 | * long double logbl(x) |
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| 17 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
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| 18 | * Use ilogb instead. |
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| 19 | */ |
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| 20 | |
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| 21 | #include <math.h> |
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| 22 | #include <math_private.h> |
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| 23 | #include <math_ldbl_opt.h> |
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| 24 | #include <fix-int-fp-convert-zero.h> |
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| 25 | |
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| 26 | long double |
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| 27 | __logbl (long double x) |
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| 28 | { |
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| 29 | int64_t hx, hxs, rhx; |
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| 30 | double xhi, xlo; |
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| 31 | |
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| 32 | ldbl_unpack (x, &xhi, &xlo); |
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| 33 | EXTRACT_WORDS64 (hx, xhi); |
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| 34 | hxs = hx; |
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| 35 | hx &= 0x7fffffffffffffffLL; /* high |x| */ |
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| 36 | if (hx == 0) |
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| 37 | return -1.0 / fabs (x: x); |
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| 38 | if (hx >= 0x7ff0000000000000LL) |
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| 39 | return x * x; |
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| 40 | if (__glibc_unlikely ((rhx = hx >> 52) == 0)) |
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| 41 | { |
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| 42 | /* POSIX specifies that denormal number is treated as |
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| 43 | though it were normalized. */ |
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| 44 | rhx -= __builtin_clzll (hx) - 12; |
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| 45 | } |
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| 46 | else if ((hx & 0x000fffffffffffffLL) == 0) |
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| 47 | { |
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| 48 | /* If the high part is a power of 2, and the low part is nonzero |
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| 49 | with the opposite sign, the low part affects the |
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| 50 | exponent. */ |
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| 51 | int64_t lx; |
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| 52 | EXTRACT_WORDS64 (lx, xlo); |
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| 53 | if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0) |
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| 54 | rhx--; |
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| 55 | } |
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| 56 | if (FIX_INT_FP_CONVERT_ZERO && rhx == 1023) |
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| 57 | return 0.0L; |
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| 58 | return (long double) (rhx - 1023); |
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| 59 | } |
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| 60 | #ifndef __logbl |
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| 61 | long_double_symbol (libm, __logbl, logbl); |
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| 62 | #endif |
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| 63 | |
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