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e2310a27be
The ldbl-128ibm implementation of truncl is only correct in round-to-nearest mode (in other modes, there are incorrect results and overflow exceptions in some cases). It is also unnecessarily complicated, rounding both high and low parts to the nearest integer and then adjusting for the semantics of trunc, when it seems more natural to take the truncation of the high part (__trunc optimized inline versions can be used), and the floor or ceiling of the low part (depending on the sign of the high part) if the high part is an integer, as was done for floorl and ceill. This patch makes it use that simpler approach. Tested for powerpc. [BZ #19593] * sysdeps/ieee754/ldbl-128ibm/s_truncl.c (__truncl): Use __trunc on high part and __floor or __ceil on low part then use ldbl_canonicalize_int if needed.
60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
/* Truncate (toward zero) 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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__truncl (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 = __trunc (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 = xh > 0 ? __floor (xl) : __ceil (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, __truncl, truncl);
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