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b9a76339be
The ldbl-128ibm implementation of roundl is only correct in round-to-nearest mode (in other modes, there are incorrect results and overflow exceptions in some cases). This patch reimplements it along the lines used for floorl, ceill and truncl, using __round on the high part, and on the low part if the high part is an integer, and then adjusting in the cases where this is incorrect. Tested for powerpc. [BZ #19594] * sysdeps/ieee754/ldbl-128ibm/s_roundl.c (__roundl): Use __round on high and low parts then adjust result and use ldbl_canonicalize_int if needed.
85 lines
2.1 KiB
C
85 lines
2.1 KiB
C
/* Round to int long double floating-point values.
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IBM extended format long double version.
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Copyright (C) 2006-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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/* This has been coded in assembler because GCC makes such a mess of it
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when it's coded in C. */
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#include <math.h>
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#include <math_ldbl_opt.h>
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#include <float.h>
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#include <ieee754.h>
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long double
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__roundl (long double x)
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{
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double xh, xl, hi, lo;
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ldbl_unpack (x, &xh, &xl);
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/* Return Inf, Nan, +/-0 unchanged. */
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if (__builtin_expect (xh != 0.0
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&& __builtin_isless (__builtin_fabs (xh),
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__builtin_inf ()), 1))
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{
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hi = __round (xh);
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if (hi != xh)
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{
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/* The high part is not an integer; the low part only
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affects the result if the high part is exactly half way
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between two integers and the low part is nonzero with the
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opposite sign. */
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if (fabs (hi - xh) == 0.5)
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{
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if (xh > 0 && xl < 0)
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xh = hi - 1;
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else if (xh < 0 && xl > 0)
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xh = hi + 1;
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else
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xh = hi;
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}
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else
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xh = hi;
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xl = 0;
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}
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else
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{
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/* The high part is a nonzero integer. */
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lo = __round (xl);
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if (fabs (lo - xl) == 0.5)
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{
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if (xh > 0 && xl < 0)
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xl = lo + 1;
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else if (xh < 0 && lo > 0)
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xl = lo - 1;
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else
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xl = lo;
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}
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else
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xl = lo;
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xh = hi;
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ldbl_canonicalize_int (&xh, &xl);
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}
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}
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return ldbl_pack (xh, xl);
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}
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long_double_symbol (libm, __roundl, roundl);
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