75 lines
2.4 KiB
C
75 lines
2.4 KiB
C
/* Construct a signalling NaN 'double' with a given payload.
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Copyright 2024 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation, either version 3 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible. */
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#include <config.h>
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/* Specification. */
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#include <math.h>
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#include <float.h>
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#include <stdint.h>
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#include <string.h>
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#include "signed-snan.h"
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int
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setpayloadsig (double *result, double payload)
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{
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#if DBL_MANT_DIG == 53
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if (
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# if defined __hppa || (defined __mips__ && !MIPS_NAN2008_DOUBLE) || defined __sh__
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payload >= 0.0
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# else
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/* A zero payload is not allowed, because that would denote Infinity.
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Cf. snan.h. */
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payload > 0.0
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# endif
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&& payload < 2251799813685248.0 /* (double) (1ULL << (DBL_MANT_DIG - 2)) */
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&& payload == (double) (int64_t) payload)
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{
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memory_double x = memory_positive_SNaNd ();
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uint64_t pl = (int64_t) payload;
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uint32_t pl_hi = (uint32_t) (pl >> 32);
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uint32_t pl_lo = (uint32_t) pl;
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x.word[DBL_EXPBIT0_WORD] =
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(x.word[DBL_EXPBIT0_WORD] & ~((1U << (DBL_MANT_DIG - 2 - 32)) - 1))
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| pl_hi;
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x.word[DBL_EXPBIT0_WORD + (DBL_EXPBIT0_WORD == 0 ? 1 : -1)] = pl_lo;
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# if 0
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*result = x.value;
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# else
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/* On 32-bit x86 processors, as well as on x86_64 processors with
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CC="gcc -mfpmath=387", the evaluation of *x and *y above is done
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through an 'fldl' instruction, which converts a signalling NaN to
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a quiet NaN. See
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<https://lists.gnu.org/archive/html/bug-gnulib/2023-10/msg00060.html>
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for details. Use memcpy to avoid this. */
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memcpy (result, &x.value, sizeof (double));
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# endif
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return 0;
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}
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else
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{
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*result = 0.0;
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return -1;
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}
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#else
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# error "Please port gnulib setpayloadsig.c to your platform!"
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#endif
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}
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