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Add C++ versions of iscanonical for ldbl-96 and ldbl-128ibm (bug 22235)

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All representations of floating-point numbers in types with IEC 60559
binary exchange format are canonical.  On the other hand, types with IEC
60559 extended formats, such as those implemented under ldbl-96 and
ldbl-128ibm, contain representations that are not canonical.

TS 18661-1 introduced the type-generic macro iscanonical, which returns
whether a floating-point value is canonical or not.  In Glibc, this
type-generic macro is implemented using the macro __MATH_TG, which, when
support for float128 is enabled, relies on __builtin_types_compatible_p
to select between floating-point types.  However, this use of
iscanonical breaks C++ applications, because the builtin is only
available in C mode.

This patch provides a C++ implementation of iscanonical that relies on
function overloading, rather than builtins, to select between
floating-point types.

Unlike the C++ implementations for iszero and issignaling, this
implementation ignores __NO_LONG_DOUBLE_MATH.  The double type always
matches IEC 60559 double format, which is always canonical.  Thus, when
double and long double are the same (__NO_LONG_DOUBLE_MATH), iscanonical
always returns 1 and is not implemented with __MATH_TG.

Tested for powerpc64, powerpc64le and x86_64.

	[BZ #22235]
	* math/math.h: Trivial fix for unbalanced parentheses in comment.
	* math/Makefile [CXX] (tests): Add test-math-iscanonical.cc.
	(CFLAGS-test-math-iscanonical.cc): New variable.
	* math/test-math-iscanonical.cc: New file.
	* sysdeps/ieee754/ldbl-96/bits/iscanonical.h (iscanonical):
	Provide a C++ implementation based on function overloading,
	rather than using __MATH_TG, which uses C-only builtins.
	* sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h (iscanonical):
	Likewise.
	* sysdeps/powerpc/powerpc64le/Makefile
	(CFLAGS-test-math-iscanonical.cc): New variable.

(cherry picked from commit aa0235dfde)
This commit is contained in:
Gabriel F. T. Gomes 2017-10-02 14:46:35 -03:00
parent 3f68c5c9b6
commit 3b10c5d2ab
8 changed files with 106 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
ChangeLog
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@ -1,3 +1,18 @@
2017-10-03 Gabriel F. T. Gomes <gabriel@inconstante.eti.br>
[BZ #22235]
* math/math.h: Trivial fix for unbalanced parentheses in comment.
* math/Makefile [CXX] (tests): Add test-math-iscanonical.cc.
(CFLAGS-test-math-iscanonical.cc): New variable.
* math/test-math-iscanonical.cc: New file.
* sysdeps/ieee754/ldbl-96/bits/iscanonical.h (iscanonical):
Provide a C++ implementation based on function overloading,
rather than using __MATH_TG, which uses C-only builtins.
* sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h (iscanonical):
Likewise.
* sysdeps/powerpc/powerpc64le/Makefile
(CFLAGS-test-math-iscanonical.cc): New variable.
2017-08-22 Joseph Myers <joseph@codesourcery.com>
[BZ #21987]

1
NEWS
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@ -35,6 +35,7 @@ The following bugs are resolved with this release:
[22096] resolv: __resolv_conf_attach must not free passed conf object
[22146] Let fpclassify use the builtin when optimizing for size in C++ mode
[22225] math: nearbyint arithmetic moved before feholdexcept
[22235] Add C++ versions of iscanonical for ldbl-96 and ldbl-128ibm
Version 2.26

4
math/Makefile
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@ -203,7 +203,8 @@ tests-static = test-fpucw-static test-fpucw-ieee-static \
test-signgam-ullong-static test-signgam-ullong-init-static
ifneq (,$(CXX))
tests += test-math-isinff test-math-iszero test-math-issignaling
tests += test-math-isinff test-math-iszero test-math-issignaling \
test-math-iscanonical
endif
ifneq (no,$(PERL))
@ -351,6 +352,7 @@ CFLAGS-test-signgam-ullong-init-static.c = -std=c99
CFLAGS-test-math-isinff.cc = -std=gnu++11
CFLAGS-test-math-iszero.cc = -std=gnu++11
CFLAGS-test-math-issignaling.cc = -std=gnu++11
CFLAGS-test-math-iscanonical.cc = -std=gnu++11
CFLAGS-test-iszero-excess-precision.c = -fexcess-precision=standard
CFLAGS-test-iseqsig-excess-precision.c = -fexcess-precision=standard

2
math/math.h
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@ -488,7 +488,7 @@ enum
other hand, overloading provides the means to distinguish between
the floating-point types. The overloading resolution will match
the correct parameter (regardless of type qualifiers (i.e.: const
and volatile). */
and volatile)). */
extern "C++" {
inline int issignaling (float __val) { return __issignalingf (__val); }
inline int issignaling (double __val) { return __issignaling (__val); }

48
math/test-math-iscanonical.cc Normal file
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@ -0,0 +1,48 @@
/* Test for the C++ implementation of iscanonical.
Copyright (C) 2017 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/>. */
#define _GNU_SOURCE 1
#include <math.h>
#include <stdio.h>
static bool errors;
template <class T>
static void
check_type ()
{
T val = 0;
/* Check if iscanonical is available in C++ mode (bug 22235). */
if (iscanonical (val) == 0)
errors++;
}
static int
do_test (void)
{
check_type<float> ();
check_type<double> ();
check_type<long double> ();
#if __HAVE_DISTINCT_FLOAT128
check_type<_Float128> ();
#endif
return errors;
}
#include <support/test-driver.c>

21
sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h
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@ -37,5 +37,22 @@ extern int __iscanonicall (long double __x)
conversion, before being discarded; in IBM long double, there are
encodings that are not consistently handled as corresponding to any
particular value of the type, and we return 0 for those. */
# define iscanonical(x) __MATH_TG ((x), __iscanonical, (x))
#endif
# ifndef __cplusplus
# define iscanonical(x) __MATH_TG ((x), __iscanonical, (x))
# else
/* In C++ mode, __MATH_TG cannot be used, because it relies on
__builtin_types_compatible_p, which is a C-only builtin. On the
other hand, overloading provides the means to distinguish between
the floating-point types. The overloading resolution will match
the correct parameter (regardless of type qualifiers (i.e.: const
and volatile)). */
extern "C++" {
inline int iscanonical (float __val) { return __iscanonicalf (__val); }
inline int iscanonical (double __val) { return __iscanonical (__val); }
inline int iscanonical (long double __val) { return __iscanonicall (__val); }
# if __HAVE_DISTINCT_FLOAT128
inline int iscanonical (_Float128 __val) { return __iscanonicalf128 (__val); }
# endif
}
# endif /* __cplusplus */
#endif /* __NO_LONG_DOUBLE_MATH */

19
sysdeps/ieee754/ldbl-96/bits/iscanonical.h
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@ -34,4 +34,21 @@ extern int __iscanonicall (long double __x)
conversion, before being discarded; in extended precision, there
are encodings that are not consistently handled as corresponding to
any particular value of the type, and we return 0 for those. */
#define iscanonical(x) __MATH_TG ((x), __iscanonical, (x))
#ifndef __cplusplus
# define iscanonical(x) __MATH_TG ((x), __iscanonical, (x))
#else
/* In C++ mode, __MATH_TG cannot be used, because it relies on
__builtin_types_compatible_p, which is a C-only builtin. On the
other hand, overloading provides the means to distinguish between
the floating-point types. The overloading resolution will match
the correct parameter (regardless of type qualifiers (i.e.: const
and volatile)). */
extern "C++" {
inline int iscanonical (float __val) { return __iscanonicalf (__val); }
inline int iscanonical (double __val) { return __iscanonical (__val); }
inline int iscanonical (long double __val) { return __iscanonicall (__val); }
# if __HAVE_DISTINCT_FLOAT128
inline int iscanonical (_Float128 __val) { return __iscanonicalf128 (__val); }
# endif
}
#endif /* __cplusplus */

1
sysdeps/powerpc/powerpc64le/Makefile
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@ -16,6 +16,7 @@ $(foreach suf,$(all-object-suffixes),%f128_r$(suf)): CFLAGS += -mfloat128
$(foreach suf,$(all-object-suffixes),$(objpfx)test-float128%$(suf)): CFLAGS += -mfloat128
$(foreach suf,$(all-object-suffixes),$(objpfx)test-ifloat128%$(suf)): CFLAGS += -mfloat128
CFLAGS-libm-test-support-float128.c += -mfloat128
CFLAGS-test-math-iscanonical.cc += -mfloat128
CFLAGS-test-math-issignaling.cc += -mfloat128
CFLAGS-test-math-iszero.cc += -mfloat128
$(objpfx)test-float128% $(objpfx)test-ifloat128% $(objpfx)test-math-iszero: \