9173e3c0b4
Removing the use of -Wno-uninitialized for math/ shows errors for
ldbl-128ibm:
../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: In function '__nearbyintl':
../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c:119:34: error: 'low' may be used uninitialized in this function [-Werror=maybe-uninitialized]
u.d[1].d = high - u.d[0].d + low;
^
../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c:119:23: error: 'high' may be used uninitialized in this function [-Werror=maybe-uninitialized]
u.d[1].d = high - u.d[0].d + low;
^
These errors are correct: if the high part of the argument is a NaN,
and the low part is nonzero but has absolute value less than 2^52,
those variables can be used uninitialized. This patch rearranges the
code so that the variables are always initialized with the natural
values, and then possibly modified later, to avoid this uninitialized
use. (Note that there are still other issues with this code and NaNs
that are not fixed by this patch.) No bug filed in Bugzilla or
testcase added for the uninitialized use since it wasn't user-visible
with the compiler I tried (that is, I still got a NaN result).
Tested for powerpc.
* sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: Always initialize
variables for high and low parts before possibly modifying them.
125 lines
3.5 KiB
C
125 lines
3.5 KiB
C
/* Round to int long double floating-point values without raising inexact.
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IBM extended format long double version.
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Copyright (C) 2006-2015 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_private.h>
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#include <fenv.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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__nearbyintl (long double x)
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{
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fenv_t env;
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static const long double TWO52 = 4503599627370496.0L;
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union ibm_extended_long_double u;
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u.ld = x;
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if (fabs (u.d[0].d) < TWO52)
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{
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double xh = u.d[0].d;
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double high = u.d[0].d;
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feholdexcept (&env);
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if (high > 0.0)
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{
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high += TWO52;
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high -= TWO52;
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if (high == -0.0) high = 0.0;
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}
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else if (high < 0.0)
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{
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high -= TWO52;
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high += TWO52;
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if (high == 0.0) high = -0.0;
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}
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if (u.d[1].d > 0.0 && (xh - high == 0.5))
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high += 1.0;
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else if (u.d[1].d < 0.0 && (-(xh - high) == 0.5))
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high -= 1.0;
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u.d[0].d = high;
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u.d[1].d = 0.0;
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math_force_eval (u.d[0]);
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math_force_eval (u.d[1]);
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fesetenv (&env);
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}
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else if (fabs (u.d[1].d) < TWO52 && u.d[1].d != 0.0)
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{
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double high = u.d[0].d, low = u.d[1].d, tau;
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/* In this case we have to round the low double and handle any
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adjustment to the high double that may be caused by rounding
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(up). This is complicated by the fact that the high double
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may already be rounded and the low double may have the
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opposite sign to compensate. */
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feholdexcept (&env);
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if (u.d[0].d > 0.0)
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{
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if (u.d[1].d > 0.0)
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{
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/* If the high/low doubles are the same sign then simply
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round the low double. */
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}
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else if (u.d[1].d < 0.0)
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{
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/* Else the high double is pre rounded and we need to
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adjust for that. */
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tau = __nextafter (u.d[0].d, 0.0);
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tau = (u.d[0].d - tau) * 2.0;
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high -= tau;
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low += tau;
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}
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low += TWO52;
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low -= TWO52;
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}
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else if (u.d[0].d < 0.0)
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{
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if (u.d[1].d < 0.0)
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{
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/* If the high/low doubles are the same sign then simply
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round the low double. */
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}
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else if (u.d[1].d > 0.0)
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{
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/* Else the high double is pre rounded and we need to
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adjust for that. */
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tau = __nextafter (u.d[0].d, 0.0);
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tau = (u.d[0].d - tau) * 2.0;
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high -= tau;
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low += tau;
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}
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low = TWO52 - low;
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low = -(low - TWO52);
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}
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u.d[0].d = high + low;
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u.d[1].d = high - u.d[0].d + low;
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math_force_eval (u.d[0]);
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math_force_eval (u.d[1]);
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fesetenv (&env);
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}
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return u.ld;
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}
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long_double_symbol (libm, __nearbyintl, nearbyintl);
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