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float128: Add signbit alternative for old compilers 

In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
e.g.: __builtin_signbitf128, before GCC 6.  However, there has never
been a __builtin_signbitf128 in GCC and the type-generic builtin is
only available since GCC 6.  For older GCC, this patch defines
__builtin_signbitf128 to __signbitf128, so that the internal function
is used instead of the non-existent builtin.

This patch also changes the implementation of __signbitf128, because
it was reusing the implementation of __signbitl from ldbl-128, which
calls __builtin_signbitl.  Using the long double version of the
builtin is not correct on machines where _Float128 is ABI-distinct
from long double (i.e.: ia64, powerpc64le, x86, x86_84).  The new
implementation does not rely on builtins when being built with GCC
versions older than 6.0.

The new code does not currently affect powerpc64le builds, because
only GCC 6.2 fulfills the requirements from configure.  It might
affect powerpc64le builds if those requirements are backported to
older versions of the compiler.  The new code affects x86_64 builds,
since glibc is supposed to build correctly with older versions of GCC.

Tested for powerpc64le and x86_64.

	* include/math.h (__signbitf128): Define as hidden.
	* sysdeps/ieee754/float128/s_signbitf128.c (__signbitf128):
	Reimplement without builtins.
	* sysdeps/ia64/bits/floatn.h [!__GNUC_PREREQ (6, 0)]
	(__builtin_signbitf128): Define to __signbitf128.
	* sysdeps/powerpc/bits/floatn.h: Likewise.
	* sysdeps/x86/bits/floatn.h: Likewise.
This commit is contained in:
Gabriel F. T. Gomes 2017-06-29 15:34:05 -03:00
parent 9b8f8593e5
commit 8466ee1cb7
6 changed files with 71 additions and 1 deletions
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10
ChangeLog
View File

@ -1,3 +1,13 @@
2017-06-30 Gabriel F. T. Gomes <gftg@linux.vnet.ibm.com>
* include/math.h (__signbitf128): Define as hidden.
* sysdeps/ieee754/float128/s_signbitf128.c (__signbitf128):
Reimplement without builtins.
* sysdeps/ia64/bits/floatn.h [!__GNUC_PREREQ (6, 0)]
(__builtin_signbitf128): Define to __signbitf128.
* sysdeps/powerpc/bits/floatn.h: Likewise.
* sysdeps/x86/bits/floatn.h: Likewise.
2017-06-30 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* sysdeps/unix/sysv/linux/arm/fcntl.c: Remove file.

1
include/math.h
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@ -31,6 +31,7 @@ hidden_proto (__isnanl)
hidden_proto (__finitef128)
hidden_proto (__isinff128)
hidden_proto (__isnanf128)
hidden_proto (__signbitf128)
# endif
# endif

8
sysdeps/ia64/bits/floatn.h
View File

@ -89,6 +89,14 @@ typedef __float128 _Float128;
# define __builtin_nansf128(x) ((_Float128) __builtin_nans (x))
# endif
/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
e.g.: __builtin_signbitf128, before GCC 6. However, there has never
been a __builtin_signbitf128 in GCC and the type-generic builtin is
only available since GCC 6. */
# if !__GNUC_PREREQ (6, 0)
# define __builtin_signbitf128 __signbitf128
# endif
#endif
#endif /* _BITS_FLOATN_H */

37
sysdeps/ieee754/float128/s_signbitf128.c
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@ -1,2 +1,37 @@
/* Return nonzero value if number is negative.
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/>. */
#include <float128_private.h>
#include "../ldbl-128/s_signbitl.c"
#include <math.h>
#include <math_private.h>
/* Once GCC >= 6.0 is required for building glibc, this implementation can
be removed and replaced with an inclusion of ldbl-128/s_signbitl.c. */
int
__signbitf128 (_Float128 x)
{
#if __GNUC_PREREQ (6, 0)
return __builtin_signbit (x);
#else
int64_t e;
GET_FLOAT128_MSW64 (e, x);
return e < 0;
#endif
}
hidden_def (__signbitf128)

8
sysdeps/powerpc/bits/floatn.h
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@ -87,6 +87,14 @@ typedef __float128 _Float128;
# define __builtin_nansf128 __builtin_nansq
# endif
/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
e.g.: __builtin_signbitf128, before GCC 6. However, there has never
been a __builtin_signbitf128 in GCC and the type-generic builtin is
only available since GCC 6. */
# if !__GNUC_PREREQ (6, 0)
# define __builtin_signbitf128 __signbitf128
# endif
#endif
#endif /* _BITS_FLOATN_H */

8
sysdeps/x86/bits/floatn.h
View File

@ -91,6 +91,14 @@ typedef __float128 _Float128;
# define __builtin_nansf128(x) ((_Float128) __builtin_nans (x))
# endif
/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
e.g.: __builtin_signbitf128, before GCC 6. However, there has never
been a __builtin_signbitf128 in GCC and the type-generic builtin is
only available since GCC 6. */
# if !__GNUC_PREREQ (6, 0)
# define __builtin_signbitf128 __signbitf128
# endif
#endif
#endif /* _BITS_FLOATN_H */