Add RTEMS support

gcc/ChangeLog

2017-07-27  Sebastian Huber  <sebastian.huber@embedded-brains.de>

	* config.gcc (riscv*-*-elf*): Add (riscv*-*-rtems*).
	* config/riscv/rtems.h: New file.

From-SVN: r250632

gcc/ChangeLog

+2017-07-27  Sebastian Huber  <sebastian.huber@embedded-brains.de>
+
+	* config.gcc (riscv*-*-elf*): Add (riscv*-*-rtems*).
+	* config/riscv/rtems.h: New file.
+
 2017-07-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 	    Sudakshina Das  <sudi.das@arm.com>
 

gcc/config.gcc

@@ -2040,7 +2040,7 @@ riscv*-*-linux*)
 	# automatically detect that GAS supports it, yet we require it.
 	gcc_cv_initfini_array=yes
 	;;
-riscv*-*-elf*)
+riscv*-*-elf* | riscv*-*-rtems*)
 	tm_file="elfos.h newlib-stdint.h ${tm_file} riscv/elf.h"
 	case "x${enable_multilib}" in
 	xno) ;;
@@ -2053,6 +2053,11 @@ riscv*-*-elf*)
 	# Force .init_array support.  The configure script cannot always
 	# automatically detect that GAS supports it, yet we require it.
 	gcc_cv_initfini_array=yes
+	case ${target} in
+	riscv*-*-rtems*)
+	  tm_file="${tm_file} rtems.h riscv/rtems.h"
+	  ;;
+	esac
 	;;
 mips*-*-netbsd*)			# NetBSD/mips, either endian.
 	target_cpu_default="MASK_ABICALLS"

gcc/config/riscv/rtems.h

+/* Definitions for RISC-V RTEMS systems with ELF format.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   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.
+
+   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/>.  */
+
+#undef TARGET_OS_CPP_BUILTINS
+#define TARGET_OS_CPP_BUILTINS()		\
+    do {					\
+	builtin_define ("__rtems__");		\
+	builtin_define ("__USE_INIT_FINI__");	\
+	builtin_assert ("system=rtems");	\
+    } while (0)