| 1 | /* Round to nearest integer value, rounding halfway cases to even. |
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| 2 | ldbl-128ibm version. |
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| 3 | Copyright (C) 2016-2024 Free Software Foundation, Inc. |
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| 4 | This file is part of the GNU C Library. |
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| 5 | |
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| 6 | The GNU C Library is free software; you can redistribute it and/or |
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| 7 | modify it under the terms of the GNU Lesser General Public |
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| 8 | License as published by the Free Software Foundation; either |
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| 9 | version 2.1 of the License, or (at your option) any later version. |
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| 10 | |
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| 11 | The GNU C Library is distributed in the hope that it will be useful, |
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| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 14 | Lesser General Public License for more details. |
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| 15 | |
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| 16 | You should have received a copy of the GNU Lesser General Public |
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| 17 | License along with the GNU C Library; if not, see |
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| 18 | <https://www.gnu.org/licenses/>. */ |
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| 19 | |
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| 20 | #define NO_MATH_REDIRECT |
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| 21 | #include <math.h> |
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| 22 | #include <math_private.h> |
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| 23 | |
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| 24 | long double |
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| 25 | __roundevenl (long double x) |
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| 26 | { |
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| 27 | double xh, xl, hi; |
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| 28 | |
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| 29 | ldbl_unpack (x, &xh, &xl); |
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| 30 | |
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| 31 | if (xh != 0 && isfinite (xh)) |
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| 32 | { |
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| 33 | hi = __roundeven (x: xh); |
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| 34 | if (hi != xh) |
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| 35 | { |
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| 36 | /* The high part is not an integer; the low part only |
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| 37 | affects the result if the high part is exactly half way |
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| 38 | between two integers and the low part is nonzero in the |
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| 39 | opposite direction to the rounding of the high part. */ |
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| 40 | double diff = hi - xh; |
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| 41 | if (fabs (x: diff) == 0.5) |
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| 42 | { |
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| 43 | if (xl < 0 && diff > 0) |
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| 44 | xh = hi - 1; |
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| 45 | else if (xl > 0 && diff < 0) |
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| 46 | xh = hi + 1; |
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| 47 | else |
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| 48 | xh = hi; |
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| 49 | } |
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| 50 | else |
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| 51 | xh = hi; |
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| 52 | xl = 0; |
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| 53 | } |
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| 54 | else |
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| 55 | { |
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| 56 | /* The high part is a nonzero integer. Rounding the low |
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| 57 | part to nearest, ties round to even, is always correct, |
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| 58 | as a high part that is an odd integer together with a low |
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| 59 | part with magnitude 0.5 is not a valid long double. */ |
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| 60 | xl = __roundeven (x: xl); |
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| 61 | xh = hi; |
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| 62 | ldbl_canonicalize_int (&xh, &xl); |
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| 63 | } |
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| 64 | } |
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| 65 | else |
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| 66 | /* Quiet signaling NaN arguments. */ |
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| 67 | xh += xh; |
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| 68 | |
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| 69 | return ldbl_pack (xh, xl); |
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| 70 | } |
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| 71 | weak_alias (__roundevenl, roundevenl) |
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| 72 | |
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