ldbl-128ibm-compat: Add tests for IBM long double functions

This patch creates test-ibm128* tests from the long double function tests.
In order to explicitly test IBM long double functions -mabi=ibmlongdouble is
added to CFLAGS.

Likewise, update the test headers to correct choose ULPs when redirects
are enabled.

Co-authored-by: Tulio Magno Quites Machado Filho  <tuliom@linux.ibm.com>
Co-authored-by: Paul E. Murphy  <murphyp@linux.vnet.ibm.com>

math/Makefile

@@ -145,10 +145,15 @@ type-float128-yes := float128
 # _Float64x may be supported, only as an alias type.
 type-float64x-yes := float64x
 
+# IBM long double support in additional to IEEE 128 long double support
+type-ibm128-suffix := l
+type-ibm128-yes := ibm128
+
 types = $(types-basic) $(type-float128-$(float128-fcts))
 test-types = $(test-types-basic) $(type-float128-$(float128-fcts)) \
 	     float32 float64 $(type-float128-$(float128-alias-fcts)) \
-	     float32x $(type-float64x-$(float64x-alias-fcts))
+	     float32x $(type-float64x-$(float64x-alias-fcts)) \
+	     $(type-ibm128-$(ibm128-fcts))
 
 # Pairs of types for which narrowing functions should be tested (this
 # variable has more entries than libm-narrow-types because it includes

math/test-ibm128.h

@@ -0,0 +1,19 @@
+/* Common definitions for libm tests for ibm long double.
+   Copyright (C) 2020 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 "test-ldouble.h"

math/test-ldouble.h

@@ -27,6 +27,13 @@
 # define TYPE_STR "double"
 # define ULP_IDX ULP_DBL
 # define ULP_I_IDX ULP_I_DBL
+/* On architectures which redirect long double to _Float128 ABI, we must
+   choose the float128 ulps.  Similarly, on such architectures, the ABI
+   used may be dependent on how the compiler was invoked.  */
+#elif __LONG_DOUBLE_USES_FLOAT128 == 1
+# define TYPE_STR "float128"
+# define ULP_IDX ULP_FLT128
+# define ULP_I_IDX ULP_I_FLT128
 #else
 # define TYPE_STR "ldouble"
 # define ULP_IDX ULP_LDBL

sysdeps/ieee754/ldbl-128ibm-compat/Makeconfig

@@ -0,0 +1,3 @@
+# Include this earlier so it can be used earlier in Makefiles,
+# and sysdep/ makefiles.
+ibm128-fcts = yes