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1833769e19
The ldbl-128ibm implementation of floorl is only correct in round-to-nearest mode (in other modes, there are incorrect results and overflow exceptions in some cases going beyond the incorrect signs of zero results noted in bug 17899). It is also unnecessarily complicated, rounding both high and low parts to the nearest integer and then adjusting for the semantics of floor, when it seems more natural to take the floor of the high part (__floor optimized inline versions can be used), and that of the low part if the high part is an integer. This patch makes it use that simpler approach, with a canonicalization that works in all rounding modes (given that the only way the result can be noncanonical is if taking the floor of a negative noninteger low part increased its exponent). Tested for powerpc, where over a thousand failures are removed from test-ldouble.out (floorl problems affect many powl tests). [BZ #17899] * sysdeps/ieee754/ldbl-128ibm/math_ldbl.h (ldbl_canonicalize_int): New function. * sysdeps/ieee754/ldbl-128ibm/s_floorl.c (__floorl): Use __floor on high and low parts then use ldbl_canonicalize_int if needed.
60 lines
1.6 KiB
C
60 lines
1.6 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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#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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__floorl (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 = __floor (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 does not
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affect the result. */
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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 = __floor (xl);
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xh = hi;
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xl = lo;
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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, __floorl, floorl);
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