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Fix iszero for excess precision.

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Floating-point classification macros are supposed to remove any excess
range or precision from their arguments.  This patch fixes the
non-sNaN version of iszero to do so, by casting the argument to its
own type.  (This will of course work only for standard-conforming
excess precision, not for what GCC does on 32-bit x86 by default where
the back end hides excess precision from the front end; the same
applies to most of the classification macros in that case, as showed
up when we made them use GCC built-in functions.)

(iseqsig will have the reverse issue, needing to ensure that when an
underlying function is used it's for a type wide enough not to remove
any excess precision, since comparison macros must not remove excess
precision.)

Tested for x86_64 and x86.

	* math/math.h
	[__GLIBC_USE (IEC_60559_BFP_EXT) && !__SUPPORT_SNAN__] (iszero):
	Cast argument to its own type.
	* math/test-iszero-excess-precision.c: New file.
	* math/Makefile (tests): Add test-iszero-excess-precision.
	(CFLAGS-test-iszero-excess-precision.c): New variable.
This commit is contained in:
Joseph Myers 2016-09-28 21:11:58 +00:00
parent e83be73091
commit b59ad2db99
4 changed files with 62 additions and 2 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2016-09-28 Joseph Myers <joseph@codesourcery.com>
* math/math.h
[__GLIBC_USE (IEC_60559_BFP_EXT) && !__SUPPORT_SNAN__] (iszero):
Cast argument to its own type.
* math/test-iszero-excess-precision.c: New file.
* math/Makefile (tests): Add test-iszero-excess-precision.
(CFLAGS-test-iszero-excess-precision.c): New variable.
2016-09-28 Rasmus Villemoes <rv@rasmusvillemoes.dk>
* sysdeps/unix/sysv/linux/spawni.c (posix_spawn_args): Remove pipe

4
math/Makefile
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@ -156,7 +156,7 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \
test-signgam-ullong-init test-nan-overflow test-nan-payload \
test-fexcept test-fexcept-traps test-fesetexcept \
test-fesetexcept-traps test-fetestexceptflag test-femode \
test-femode-traps $(tests-static)
test-femode-traps test-iszero-excess-precision $(tests-static)
tests-static = test-fpucw-static test-fpucw-ieee-static \
test-signgam-uchar-static test-signgam-uchar-init-static \
test-signgam-uint-static test-signgam-uint-init-static \
@ -266,6 +266,8 @@ CFLAGS-test-signgam-ullong-init-static.c = -std=c99
CFLAGS-test-math-isinff.cc = -std=gnu++11
CFLAGS-test-iszero-excess-precision.c = -fexcess-precision=standard
# The -lieee module sets the _LIB_VERSION_ switch to IEEE mode
# for error handling in the -lm functions.
install-lib += libieee.a

2
math/math.h
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@ -336,7 +336,7 @@ enum
# ifdef __SUPPORT_SNAN__
# define iszero(x) (fpclassify (x) == FP_ZERO)
# else
# define iszero(x) ((x) == 0)
# define iszero(x) (((__typeof (x)) (x)) == 0)
# endif
#endif /* Use IEC_60559_BFP_EXT. */

49
math/test-iszero-excess-precision.c Normal file
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@ -0,0 +1,49 @@
/* Test iszero with excess precision.
Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <float.h>
#include <math.h>
#include <stdio.h>
#define TEST(TYPE, TRUE_MIN) \
do \
{ \
if (iszero (TRUE_MIN / 2)) \
puts ("iszero removes excess precision for " #TYPE); \
else \
{ \
puts ("iszero fails to remove excess precision for " #TYPE); \
result = 1; \
} \
} \
while (0)
static int
do_test (void)
{
int result = 0;
TEST (float, FLT_TRUE_MIN);
TEST (double, DBL_TRUE_MIN);
TEST (long double, LDBL_TRUE_MIN);
return result;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"