Refactor long double information into bits/long-double.h.

Information about whether the ABI of long double is the same as that
of double is split between bits/mathdef.h and bits/wordsize.h.

When the ABIs are the same, bits/mathdef.h defines
__NO_LONG_DOUBLE_MATH.  In addition, in the case where the same glibc
binary supports both -mlong-double-64 and -mlong-double-128,
bits/wordsize.h defines __LONG_DOUBLE_MATH_OPTIONAL, along with
__NO_LONG_DOUBLE_MATH if this particular compilation is with
-mlong-double-64.

As part of the refactoring I proposed in
<https://sourceware.org/ml/libc-alpha/2016-11/msg00745.html>, this
patch puts all that information in a single header,
bits/long-double.h.  It is included from sys/cdefs.h alongside the
include of bits/wordsize.h, so other headers generally do not need to
include bits/long-double.h directly.

Previously, various bits/mathdef.h headers and bits/wordsize.h headers
had this long double information (including implicitly in some
bits/mathdef.h headers through not having the defines present in the
default version).  After the patch, it's all in six bits/long-double.h
headers.  Furthermore, most of those new headers are not
architecture-specific.  Architectures with optional long double all
use the ldbl-opt sysdeps directory, either in the order (ldbl-64-128,
ldbl-opt, ldbl-128) or (ldbl-128ibm, ldbl-opt).  Thus a generic header
for the case where long double = double, and headers in ldbl-128,
ldbl-96 and ldbl-opt, suffices to cover every architecture except for
cases where long double properties vary between different ABIs sharing
a set of installed headers; fortunately all the ldbl-opt cases share a
single compiler-predefined macro __LONG_DOUBLE_128__ that can be used
to tell whether this compilation is -mlong-double-64 or
-mlong-double-128.

The two cases where a set of headers is shared between ABIs with
different long double properties, MIPS (o32 has long double = double,
other ABIs use ldbl-128) and SPARC (32-bit has optional long double,
64-bit has required long double), need their own bits/long-double.h
headers.

As with bits/wordsize.h, multiple-include protection for this header
is generally implicit through the include guards on sys/cdefs.h, and
multiple inclusion is harmless in any case.  There is one subtlety:
the header must not define __LONG_DOUBLE_MATH_OPTIONAL if
__NO_LONG_DOUBLE_MATH was defined before its inclusion, because doing
so breaks how sysdeps/ieee754/ldbl-opt/nldbl-compat.h defines
__NO_LONG_DOUBLE_MATH itself before including system headers.  Subject
to keeping that working, it would be reasonable to move these macros
from defined/undefined #ifdef to always-defined 1/0 #if semantics, but
this patch does not attempt to do so, just rearranges where the macros
are defined.

After this patch, the only use of bits/mathdef.h is the alpha one for
modifying complex function ABIs for old GCC.  Thus, all versions of
the header other than the default and alpha versions are removed, as
is the include from math.h.

Tested for x86_64 and x86.  Also did compilation-only testing with
build-many-glibcs.py.

	* bits/long-double.h: New file.
	* sysdeps/ieee754/ldbl-128/bits/long-double.h: Likewise.
	* sysdeps/ieee754/ldbl-96/bits/long-double.h: Likewise.
	* sysdeps/ieee754/ldbl-opt/bits/long-double.h: Likewise.
	* sysdeps/mips/bits/long-double.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/bits/long-double.h: Likewise.
	* math/Makefile (headers): Add bits/long-double.h.
	* misc/sys/cdefs.h: Include <bits/long-double.h>.
	* stdlib/strtold.c: Include <bits/long-double.h> instead of
	<bits/wordsize.h>.
	* bits/mathdef.h [!_COMPLEX_H]: Do not allow inclusion.
	[!__NO_LONG_DOUBLE_MATH]: Remove conditional code.
	* math/math.h: Do not include <bits/mathdef.h>.
	* sysdeps/aarch64/bits/mathdef.h: Remove file.
	* sysdeps/alpha/bits/mathdef.h [!_COMPLEX_H]: Do not allow
	inclusion.
	* sysdeps/ia64/bits/mathdef.h: Remove file.
	* sysdeps/m68k/m680x0/bits/mathdef.h: Likewise.
	* sysdeps/mips/bits/mathdef.h: Likewise.
	* sysdeps/powerpc/bits/mathdef.h: Likewise.
	* sysdeps/s390/bits/mathdef.h: Likewise.
	* sysdeps/sparc/bits/mathdef.h: Likewise.
	* sysdeps/x86/bits/mathdef.h: Likewise.
	* sysdeps/s390/s390-32/bits/wordsize.h
	[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]: Remove
	conditional code.
	* sysdeps/s390/s390-64/bits/wordsize.h
	[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
	Likewise.
	* sysdeps/unix/sysv/linux/alpha/bits/wordsize.h
	[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/bits/wordsize.h
	[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
	Likewise.
	* sysdeps/unix/sysv/linux/sparc/bits/wordsize.h
	[!__NO_LONG_DOUBLE_MATH && !__LONG_DOUBLE_MATH_OPTIONAL]:
	Likewise.

2 files changed, 41 insertions, 8 deletions

diff --git a/bits/long-double.h b/bits/long-double.h
new file mode 100644
index 0000000000..16578571b8
--- /dev/null
+++ b/bits/long-double.h
@@ -0,0 +1,39 @@
+/* Properties of long double type.
+   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  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/>.  */
+
+/* This header is included by <sys/cdefs.h>.
+
+   If long double is ABI-compatible with double, it should define
+   __NO_LONG_DOUBLE_MATH to 1; otherwise, it should leave
+   __NO_LONG_DOUBLE_MATH undefined.
+
+   If this build of the GNU C Library supports both long double
+   ABI-compatible with double and some other long double format not
+   ABI-compatible with double, it should define
+   __LONG_DOUBLE_MATH_OPTIONAL to 1; otherwise, it should leave
+   __LONG_DOUBLE_MATH_OPTIONAL undefined.
+
+   If __NO_LONG_DOUBLE_MATH is already defined, this header must not
+   define anything; this is needed to work with the definition of
+   __NO_LONG_DOUBLE_MATH in nldbl-compat.h.  */
+
+/* In the default version of this header, long double is
+   ABI-compatible with double.  */
+#ifndef __NO_LONG_DOUBLE_MATH
+# define __NO_LONG_DOUBLE_MATH	1
+#endif
diff --git a/bits/mathdef.h b/bits/mathdef.h
index 014829790a..5e80e920b4 100644
--- a/bits/mathdef.h
+++ b/bits/mathdef.h
@@ -15,12 +15,6 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#if !defined _MATH_H && !defined _COMPLEX_H
-# error "Never use <bits/mathdef.h> directly; include <math.h> instead"
-#endif
-
-#ifndef __NO_LONG_DOUBLE_MATH
-/* Signal that we do not really have a `long double'.  The disables the
-   declaration of all the `long double' function variants.  */
-# define __NO_LONG_DOUBLE_MATH	1
+#ifndef _COMPLEX_H
+# error "Never use <bits/mathdef.h> directly; include <complex.h> instead"
 #endif