diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0a774b0b6b1..9c74fe25e51 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-26  Joel Sherrill <joel@rtems.org>
+
+	* config.gcc: Add x86_64-*-rtems*.
+	* gcc/config/i386/rtems-64.h: New file.
+
 2016-02-26  Joel Sherrill <joel@rtems.org>
 
 	* config.gcc: Add aarch64-*-rtems*.
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 3b280e05e70..4cc6438406f 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1421,6 +1421,9 @@ i[34567]86-*-elf*)
 x86_64-*-elf*)
 	tm_file="${tm_file} i386/unix.h i386/att.h dbxelf.h elfos.h newlib-stdint.h i386/i386elf.h i386/x86-64.h"
 	;;
+x86_64-*-rtems*)
+	tm_file="${tm_file} i386/unix.h i386/att.h dbxelf.h elfos.h newlib-stdint.h i386/i386elf.h i386/x86-64.h i386/rtems-64.h"
+	;;
 i[34567]86-*-rdos*)
     tm_file="${tm_file} i386/unix.h i386/att.h dbxelf.h elfos.h newlib-stdint.h i386/i386elf.h i386/rdos.h"
     ;;
diff --git a/gcc/config/i386/rtems-64.h b/gcc/config/i386/rtems-64.h
new file mode 100644
index 00000000000..b087d44e1a4
--- /dev/null
+++ b/gcc/config/i386/rtems-64.h
@@ -0,0 +1,30 @@
+/* Definitions for rtems targeting an x86_64
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   Contributed by Joel Sherrill (joel@OARcorp.com).
+
+This file is part of GCC.
+
+GCC 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.
+
+GCC 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.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+/* Specify predefined symbols in preprocessor.  */
+
+#define TARGET_OS_CPP_BUILTINS()		\
+  do						\
+    {						\
+	builtin_define ("__rtems__");		\
+	builtin_define ("__USE_INIT_FINI__");	\
+	builtin_assert ("system=rtems");	\
+    }						\
+  while (0)