| 1 | /* Return the least floating-point number greater than X. |
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| 2 | Copyright (C) 2016-2022 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #include <float.h> |
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| 20 | #include <math.h> |
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| 21 | #include <math_private.h> |
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| 22 | #include <math_ldbl_opt.h> |
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| 23 | |
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| 24 | /* Return the least floating-point number greater than X. */ |
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| 25 | long double |
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| 26 | __nextupl (long double x) |
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| 27 | { |
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| 28 | int64_t hx, ihx, lx; |
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| 29 | double xhi, xlo, yhi; |
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| 30 | |
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| 31 | ldbl_unpack (x, &xhi, &xlo); |
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| 32 | EXTRACT_WORDS64 (hx, xhi); |
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| 33 | EXTRACT_WORDS64 (lx, xlo); |
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| 34 | ihx = hx & 0x7fffffffffffffffLL; |
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| 35 | |
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| 36 | if (ihx > 0x7ff0000000000000LL) /* x is nan. */ |
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| 37 | return x + x; /* Signal the nan. */ |
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| 38 | if (ihx == 0) |
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| 39 | return LDBL_TRUE_MIN; |
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| 40 | |
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| 41 | long double u; |
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| 42 | if ((hx == 0x7fefffffffffffffLL) && (lx == 0x7c8ffffffffffffeLL)) |
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| 43 | return INFINITY; |
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| 44 | if ((uint64_t) hx >= 0xfff0000000000000ULL) |
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| 45 | { |
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| 46 | u = -0x1.fffffffffffff7ffffffffffff8p+1023L; |
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| 47 | return u; |
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| 48 | } |
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| 49 | if (ihx <= 0x0360000000000000LL) |
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| 50 | { /* x <= LDBL_MIN. */ |
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| 51 | x += LDBL_TRUE_MIN; |
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| 52 | if (x == 0.0L) /* Handle negative LDBL_TRUE_MIN case. */ |
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| 53 | x = -0.0L; |
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| 54 | return x; |
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| 55 | } |
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| 56 | /* If the high double is an exact power of two and the low |
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| 57 | double is the opposite sign, then 1ulp is one less than |
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| 58 | what we might determine from the high double. Similarly |
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| 59 | if X is an exact power of two, and negative, because |
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| 60 | making it a little larger will result in the exponent |
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| 61 | decreasing by one and normalisation of the mantissa. */ |
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| 62 | if ((hx & 0x000fffffffffffffLL) == 0 |
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| 63 | && ((lx != 0 && lx != 0x8000000000000000LL && (hx ^ lx) < 0) |
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| 64 | || ((lx == 0 || lx == 0x8000000000000000LL) && hx < 0))) |
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| 65 | ihx -= 1LL << 52; |
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| 66 | if (ihx < (106LL << 52)) |
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| 67 | { /* ulp will denormal. */ |
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| 68 | INSERT_WORDS64 (yhi, ihx & (0x7ffLL << 52)); |
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| 69 | u = yhi * 0x1p-105; |
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| 70 | } |
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| 71 | else |
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| 72 | { |
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| 73 | INSERT_WORDS64 (yhi, (ihx & (0x7ffLL << 52)) - (105LL << 52)); |
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| 74 | u = yhi; |
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| 75 | } |
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| 76 | return x + u; |
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| 77 | } |
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| 78 | |
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| 79 | weak_alias (__nextupl, nextupl) |
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| 80 | |
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