Do not redirect calls to __GI_* symbols, when redirecting to *ieee128

On platforms where long double has IEEE binary128 format as a third
option (initially, only powerpc64le), many exported functions are
redirected to their __*ieee128 equivalents.  This redirection is
provided by installed headers such as stdio-ldbl.h, and is supposed to
work correctly with user code.

However, during the build of glibc, similar redirections are employed,
in internal headers, such as include/stdio.h, in order to avoid extra
PLT entries.  These redirections conflict with the redirections to
__*ieee128, and must be avoided during the build.  This patch protects
the second redirections with a test for __LONG_DOUBLE_USES_FLOAT128, a
new macro that is defined to 1 when functions that deal with long double
typed values reuses the _Float128 implementation (this is currently only
true for powerpc64le).

Tested for powerpc64le, x86_64, and with build-many-glibcs.py.

Co-authored-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm-compat/bits/long-double.h b/sysdeps/ieee754/ldbl-128ibm-compat/bits/long-double.h
new file mode 100644
index 0000000000..02d1b40169
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm-compat/bits/long-double.h
@@ -0,0 +1,29 @@
+/* Properties of long double type.  ldbl-opt version.
+   Copyright (C) 2019 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef __NO_LONG_DOUBLE_MATH
+# define __LONG_DOUBLE_MATH_OPTIONAL	1
+# ifndef __LONG_DOUBLE_128__
+#  define __NO_LONG_DOUBLE_MATH		1
+# endif
+#endif
+/* On platforms that reuse the _Float128 implementation for IEEE long
+   double, access to the correct long double functions is selected based
+   on the long double mode being used during the compilation.  On
+   powerpc64le, this is true when -mabi=ieeelongdouble is in use.  */
+#define __LONG_DOUBLE_USES_FLOAT128 (__LDBL_MANT_DIG__ == 113)