rust: Add skeleton support and documentation for targetrustm hooks.

gcc/ChangeLog:

	* Makefile.in (tm_rust_file_list, tm_rust_include_list, TM_RUST_H,
	RUST_TARGET_DEF, RUST_TARGET_H, RUST_TARGET_OBJS): New variables.
	(tm_rust.h, cs-tm_rust.h, default-rust.o,
	rust/rust-target-hooks-def.h, s-rust-target-hooks-def-h): New rules.
	(s-tm-texi): Also check timestamp on rust-target.def.
	(generated_files): Add TM_RUST_H and rust-target-hooks-def.h.
	(build/genhooks.o): Also depend on RUST_TARGET_DEF.
	* config.gcc (tm_rust_file, rust_target_objs, target_has_targetrustm):
	New variables.
	* configure: Regenerate.
	* configure.ac (tm_rust_file_list, tm_rust_include_list,
	rust_target_objs): Add substitutes.
	* doc/tm.texi: Regenerate.
	* doc/tm.texi.in (targetrustm): Document.
	(target_has_targetrustm): Document.
	* genhooks.cc: Include rust/rust-target.def.
	* config/default-rust.cc: New file.

gcc/rust/ChangeLog:

	* rust-target-def.h: New file.
	* rust-target.def: New file.
	* rust-target.h: New file.

3 files changed, 83 insertions, 0 deletions

diff --git a/gcc/rust/rust-target-def.h b/gcc/rust/rust-target-def.h
new file mode 100644
index 0000000..8534c4b
--- /dev/null
+++ b/gcc/rust/rust-target-def.h
@@ -0,0 +1,20 @@
+/* Default initializers for Rust target hooks.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This program 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 program 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 this program; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "rust/rust-target-hooks-def.h"
+#include "tree.h"
+#include "hooks.h"
diff --git a/gcc/rust/rust-target.def b/gcc/rust/rust-target.def
new file mode 100644
index 0000000..c800eef
--- /dev/null
+++ b/gcc/rust/rust-target.def
@@ -0,0 +1,32 @@
+/* Target hook definitions for the Rust front end.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This program 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 program 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 this program; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+/* See target-hooks-macros.h for details of macros that should be
+   provided by the including file, and how to use them here.  */
+
+#include "target-hooks-macros.h"
+
+#undef HOOK_TYPE
+#define HOOK_TYPE "Rust Target Hook"
+
+HOOK_VECTOR (TARGETRUSTM_INITIALIZER, gcc_targetrustm)
+
+#undef HOOK_PREFIX
+#define HOOK_PREFIX "TARGET_"
+
+/* Close the 'struct gcc_targetrustm' definition.  */
+HOOK_VECTOR_END (C90_EMPTY_HACK)
diff --git a/gcc/rust/rust-target.h b/gcc/rust/rust-target.h
new file mode 100644
index 0000000..79edd78
--- /dev/null
+++ b/gcc/rust/rust-target.h
@@ -0,0 +1,31 @@
+/* Data structure definitions for target-specific Rust behavior.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This program 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 program 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 this program; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_RUST_TARGET_H
+#define GCC_RUST_TARGET_H
+
+#define DEFHOOKPOD(NAME, DOC, TYPE, INIT) TYPE NAME;
+#define DEFHOOK(NAME, DOC, TYPE, PARAMS, INIT) TYPE (*NAME) PARAMS;
+#define DEFHOOK_UNDOC DEFHOOK
+#define HOOKSTRUCT(FRAGMENT) FRAGMENT
+
+#include "rust-target.def"
+
+/* Each target can provide their own.  */
+extern struct gcc_targetrustm targetrustm;
+
+#endif /* GCC_RUST_TARGET_H  */