Stub implementation of unwinding for AMD GCN.

2019-06-07  Andrew Stubbs  <ams@codesourcery.com>

	libgcc/
	* config/gcn/t-amdgcn (LIB2ADD): Add unwind-gcn.c.
	* config/gcn/unwind-gcn.c: New file.

diff --git a/libgcc/config/gcn/t-amdgcn b/libgcc/config/gcn/t-amdgcn
index 8687c9f3d9f..adbd866a1d9 100644
--- a/libgcc/config/gcn/t-amdgcn
+++ b/libgcc/config/gcn/t-amdgcn
@@ -1,5 +1,6 @@
 LIB2ADD += $(srcdir)/config/gcn/lib2-divmod.c \
-	   $(srcdir)/config/gcn/lib2-divmod-hi.c
+	   $(srcdir)/config/gcn/lib2-divmod-hi.c \
+	   $(srcdir)/config/gcn/unwind-gcn.c
 
 LIB2ADDEH=
 LIB2FUNCS_EXCLUDE=__main
diff --git a/libgcc/config/gcn/unwind-gcn.c b/libgcc/config/gcn/unwind-gcn.c
new file mode 100644
index 00000000000..8aa84d372c3
--- /dev/null
+++ b/libgcc/config/gcn/unwind-gcn.c
@@ -0,0 +1,37 @@
+/* Stub unwinding implementation.
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   Contributed by Mentor Graphics
+
+   This file is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3, or (at your option) any
+   later version.
+
+   This file 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
+   General Public License for more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "unwind.h"
+
+_Unwind_Reason_Code
+_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument)
+{
+  return 0;
+}
+
+_Unwind_Ptr
+_Unwind_GetIPInfo (struct _Unwind_Context *c, int *ip_before_insn)
+{
+  return 0;
+}