ldbl-128ibm-compat: Add *cvt functions

This patch adds IEEE long double versions of q*cvt* functions for
powerpc64le.  Unlike all other long double to/from string conversion
functions, these do not rely on internal functions that can take
floating-point numbers with different formats and act on them
accordingly, instead, the related files are rebuilt with the
-mabi=ieeelongdouble compiler flag set.

Having -mabi=ieeelongdouble passed to the compiler causes the object
files to be marked with a .gnu_attribute that is incompatible with the
.gnu_attribute in files built with -mabi=ibmlongdouble (the default).
The difference causes error messages similar to the following:

  ld: libc_pic.a(s_isinfl.os) uses IBM long double,
      libc_pic.a(ieee128-qefgcvt_r.os) uses IEEE long double.
  collect2: error: ld returned 1 exit status
  make[2]: *** [../Makerules:649: libc_pic.os] Error 1

Although this warning is useful in other situations, the library
actually needs to have functions with different long double formats, so
.gnu_attribute generation is explicitly disabled for these files with
the use of -mno-gnu-attribute.

Tested for powerpc64le on the branch that actually enables the
sysdeps/ieee754/ldbl-128ibm-compat for powerpc64le.

Reviewed-by: Paul E. Murphy <murphyp@linux.ibm.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-qefgcvt_r.c b/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-qefgcvt_r.c
new file mode 100644
index 0000000000..1a5e43972f
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-qefgcvt_r.c
@@ -0,0 +1,34 @@
+/* IEEE binary128 versions of reentrant *cvt_r functions.
+   Copyright (C) 2018 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
+   <https://www.gnu.org/licenses/>.  */
+
+/* When in IEEE long double mode, call ___ieee128_snprintf.  */
+#include <stdio.h>
+typeof (snprintf) ___ieee128_snprintf attribute_hidden;
+#define SNPRINTF ___ieee128_snprintf
+
+#define ECVT_R __qecvtieee128_r
+#define FCVT_R __qfcvtieee128_r
+#define __ECVT_R ___qecvtieee128_r
+#define __FCVT_R ___qfcvtieee128_r
+#include <efgcvt-ldbl-macros.h>
+#include <efgcvt_r-template.c>
+
+#define cvt_symbol(local, symbol) \
+  strong_alias (local, symbol)
+cvt_symbol (___qfcvtieee128_r, __qfcvtieee128_r);
+cvt_symbol (___qecvtieee128_r, __qecvtieee128_r);