Define and use libm_alias_ldouble.

Continuing the process of setting up common macros for libm function
aliases, with a view to using them to define _FloatN / _FloatNx
aliases in future, this patch adds a libm_alias_ldouble macro and uses
it in the type-generic templates.

Since math-type-macros-ldouble.h already did the appropriate thing for
each symbol (weak_alias or long_double_symbol), this is just a
straightforward rearrangement of code, to make the required logic
available in a place that can also be used outside of the type-generic
templates in future (in particular, to eliminate various wrappers for
functions in ldbl-opt and ldbl-64-128).

Tested for x86_64.  Also tested with build-many-glibcs.py that
installed stripped shared libraries are unchanged by the patch.

	* sysdeps/generic/libm-alias-ldouble.h: New file.
	* sysdeps/ieee754/ldbl-opt/libm-alias-ldouble.h: Likewise.
	* sysdeps/ieee754/ldbl-opt/math-type-macros-ldouble.h: Remove.
	* sysdeps/generic/math-type-macros-ldouble.h: Include
	<libm-alias-ldouble.h>.
	[!declare_mgen_alias] (declare_mgen_alias): Define to use
	libm_alias_ldouble.

2 files changed, 42 insertions, 0 deletions

diff --git a/sysdeps/generic/libm-alias-ldouble.h b/sysdeps/generic/libm-alias-ldouble.h
new file mode 100644
index 0000000000..7414b922e1
--- /dev/null
+++ b/sysdeps/generic/libm-alias-ldouble.h
@@ -0,0 +1,36 @@
+/* Define aliases for libm long double functions.
+   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/>.  */
+
+#ifndef _LIBM_ALIAS_LDOUBLE_H
+#define _LIBM_ALIAS_LDOUBLE_H
+
+/* Define aliases for a long double libm function that has internal
+   name FROM ## l ## R and public names TO ## suffix ## R for each
+   suffix of a supported floating-point type with the same format as
+   long double.  This should only be used for functions where such
+   public names exist for _FloatN types, not for
+   implementation-namespace exported names (where there is one name
+   per format, not per type) or for obsolescent functions not provided
+   for _FloatN types.  */
+#define libm_alias_ldouble_r(from, to, r)	\
+  weak_alias (from ## l ## r, to ## l ## r)
+
+/* Likewise, but without the R suffix.  */
+#define libm_alias_ldouble(from, to) libm_alias_ldouble_r (from, to, )
+
+#endif
diff --git a/sysdeps/generic/math-type-macros-ldouble.h b/sysdeps/generic/math-type-macros-ldouble.h
index 7dbd559249..750bae718a 100644
--- a/sysdeps/generic/math-type-macros-ldouble.h
+++ b/sysdeps/generic/math-type-macros-ldouble.h
@@ -27,6 +27,12 @@
 #define CFLOAT _Complex long double
 #define M_STRTO_NAN __strtold_nan
 
+#include <libm-alias-ldouble.h>
+
+#ifndef declare_mgen_alias
+# define declare_mgen_alias(from, to) libm_alias_ldouble (from, to)
+#endif
+
 /* Supply the generic macros.  */
 #include <math-type-macros.h>