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C99 and C11 allow but do not require ceil, floor, round and trunc to raise the "inexact" exception for noninteger arguments. TS 18661-1 requires that this exception not be raised by these functions. This aligns them with general IEEE semantics, where "inexact" is only raised if the final step of rounding the infinite-precision result to the result type is inexact; for these functions, the infinite-precision integer result is always representable in the result type, so "inexact" should never be raised. The generic implementations of ceil, floor and round functions contain code to force "inexact" to be raised. This patch removes it for round functions to align them with TS 18661-1 in this regard. The tests *are* updated by this patch; there are fewer architecture-specific versions than for ceil and floor, and I fixed the powerpc ones some time ago. If any others still have the issue, as shown by tests for round failing with spurious exceptions, they can be fixed separately by architecture maintainers or others. Tested for x86_64, x86 and mips64. [BZ #15479] * sysdeps/ieee754/dbl-64/s_round.c (huge): Remove variable. (__round): Do not force "inexact" exception. * sysdeps/ieee754/dbl-64/wordsize-64/s_round.c (huge): Remove variable. (__round): Do not force "inexact" exception. * sysdeps/ieee754/flt-32/s_roundf.c (huge): Remove variable. (__roundf): Do not force "inexact" exception. * sysdeps/ieee754/ldbl-128/s_roundl.c (huge): Remove variable. (__roundl): Do not force "inexact" exception. * sysdeps/ieee754/ldbl-96/s_roundl.c (huge): Remove variable. (__roundl): Do not force "inexact" exception. * math/libm-test.inc (round_test_data): Do not allow spurious "inexact" exceptions.
84 lines
1.8 KiB
C
84 lines
1.8 KiB
C
/* Round double to integer away from zero.
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Copyright (C) 1997-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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double
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__round (double x)
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{
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int32_t i0, j0;
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u_int32_t i1;
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EXTRACT_WORDS (i0, i1, x);
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j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
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if (j0 < 20)
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{
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if (j0 < 0)
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{
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i0 &= 0x80000000;
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if (j0 == -1)
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i0 |= 0x3ff00000;
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i1 = 0;
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}
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else
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{
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u_int32_t i = 0x000fffff >> j0;
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if (((i0 & i) | i1) == 0)
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/* X is integral. */
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return x;
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i0 += 0x00080000 >> j0;
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i0 &= ~i;
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i1 = 0;
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}
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}
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else if (j0 > 51)
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{
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if (j0 == 0x400)
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/* Inf or NaN. */
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return x + x;
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else
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return x;
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}
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else
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{
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u_int32_t i = 0xffffffff >> (j0 - 20);
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if ((i1 & i) == 0)
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/* X is integral. */
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return x;
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u_int32_t j = i1 + (1 << (51 - j0));
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if (j < i1)
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i0 += 1;
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i1 = j;
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i1 &= ~i;
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}
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INSERT_WORDS (x, i0, i1);
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return x;
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}
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weak_alias (__round, round)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__round, __roundl)
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weak_alias (__round, roundl)
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#endif
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