gccrs: refactor builtins initialization and attributes

gccrs: refactor builtins initialization and attributes

This commit performs builtin initialization in a more "GCC-y" way,
similarly to what the D frontend is doing. This way, we no longer have
to worry about invalid attributes or types when initializing them by
hand.

Also add attributes support through LANG_HOOKS_COMMON_ATTRIBUTE_TABLE
lang hook.

Most of these changes are based on D frontend.

gcc/rust/ChangeLog:

	* Make-lang.in (GRS_OBJS): Add rust-attribs.o.
	* backend/rust-builtins.cc (builtin_const, builtin_noreturn)
	(builtin_novops): Remove.
	(BuiltinsContext::lookup_simple_builtin): Adjust.
	(BuiltinsContext::setup_overflow_fns): Remove.
	(BuiltinsContext::define_function_type): Set builtin type to
	errormark so the builtin is considered unavailable.
	(BuiltinsContext::setup_math_fns): Remove.
	(BuiltinsContext::setup_atomic_fns): Remove.
	(build_c_type_nodes): Refactor based on D frontend.
	(BuiltinsContext::define_builtin_types): Likewise.
	(DEF_PRIMITIVE_TYPE): New.
	(DEF_FUNCTION_TYPE_0): New.
	(DEF_FUNCTION_TYPE_1): New.
	(DEF_FUNCTION_TYPE_2): New.
	(DEF_FUNCTION_TYPE_3): New.
	(DEF_FUNCTION_TYPE_4): New.
	(DEF_FUNCTION_TYPE_5): New.
	(DEF_FUNCTION_TYPE_6): New.
	(DEF_FUNCTION_TYPE_7): New.
	(DEF_FUNCTION_TYPE_8): New.
	(DEF_FUNCTION_TYPE_9): New.
	(DEF_FUNCTION_TYPE_10): New.
	(DEF_FUNCTION_TYPE_11): New.
	(DEF_FUNCTION_TYPE_VAR_0): New.
	(DEF_FUNCTION_TYPE_VAR_1): New.
	(DEF_FUNCTION_TYPE_VAR_2): New.
	(DEF_FUNCTION_TYPE_VAR_3): New.
	(DEF_FUNCTION_TYPE_VAR_4): New.
	(DEF_FUNCTION_TYPE_VAR_5): New.
	(DEF_FUNCTION_TYPE_VAR_6): New.
	(DEF_FUNCTION_TYPE_VAR_7): New.
	(DEF_FUNCTION_TYPE_VAR_11): New.
	(DEF_POINTER_TYPE): New.
	(BuiltinsContext::setup): Adjust.
	(BuiltinsContext::define_builtin_attributes): New.
	(DEF_ATTR_NULL_TREE): New.
	(DEF_ATTR_INT): New.
	(DEF_ATTR_STRING): New.
	(DEF_ATTR_IDENT): New.
	(DEF_ATTR_TREE_LIST): New.
	(handle_flags): Remove.
	(BuiltinsContext::define_builtins): New.
	(DEF_BUILTIN): New.
	(BuiltinsContext::define_builtin): Remove.
	(BuiltinsContext::register_rust_mappings): New. Add all missing
	builtins.
	(BuiltinsContext::lookup_gcc_builtin): Adjust.
	* backend/rust-builtins.h (DEF_PRIMITIVE_TYPE): New.
	(DEF_FUNCTION_TYPE_0): New.
	(DEF_FUNCTION_TYPE_1): New.
	(DEF_FUNCTION_TYPE_2): New.
	(DEF_FUNCTION_TYPE_3): New.
	(DEF_FUNCTION_TYPE_4): New.
	(DEF_FUNCTION_TYPE_5): New.
	(DEF_FUNCTION_TYPE_6): New.
	(DEF_FUNCTION_TYPE_7): New.
	(DEF_FUNCTION_TYPE_8): New.
	(DEF_FUNCTION_TYPE_9): New.
	(DEF_FUNCTION_TYPE_10): New.
	(DEF_FUNCTION_TYPE_11): New.
	(DEF_FUNCTION_TYPE_VAR_0): New.
	(DEF_FUNCTION_TYPE_VAR_1): New.
	(DEF_FUNCTION_TYPE_VAR_2): New.
	(DEF_FUNCTION_TYPE_VAR_3): New.
	(DEF_FUNCTION_TYPE_VAR_4): New.
	(DEF_FUNCTION_TYPE_VAR_5): New.
	(DEF_FUNCTION_TYPE_VAR_6): New.
	(DEF_FUNCTION_TYPE_VAR_7): New.
	(DEF_FUNCTION_TYPE_VAR_11): New.
	(DEF_POINTER_TYPE): New.
	(DEF_ATTR_NULL_TREE): New.
	(DEF_ATTR_INT): New.
	(DEF_ATTR_STRING): New.
	(DEF_ATTR_IDENT): New.
	(DEF_ATTR_TREE_LIST): New.
	* backend/rust-compile-intrinsic.cc (Intrinsics::compile): Add
	comment.
	(op_with_overflow_inner): Adjust.
	(copy_handler_inner): Adjust.
	(prefetch_data_handler): Adjust.
	(build_atomic_builtin_name): Adjust.
	(atomic_load_handler_inner): Adjust.
	(uninit_handler): Adjust.
	(move_val_init_handler): Adjust.
	(expect_handler_inner): Adjust.
	* rust-gcc.cc (fetch_overflow_builtins): Adjust.
	* rust-lang.cc (rust_localize_identifier): Adjust.
	(LANG_HOOKS_COMMON_ATTRIBUTE_TABLE): New.
	* rust-attribs.cc: New file.

gcc/testsuite/ChangeLog:

	* rust/compile/torture/intrinsics-4.rs: Adjust.
	* rust/compile/torture/intrinsics-math.rs: Adjust.
	* rust/execute/torture/atomic_load.rs: Adjust.
	* rust/execute/torture/atomic_store.rs: Adjust.
	* rust/compile/torture/intrinsics-1.rs: Removed.
	* rust/compile/torture/builtin_abort.rs: New test.
	* rust/execute/torture/builtin_abort.rs: New test.

Signed-off-by: Marc Poulhiès <dkm@kataplop.net>
Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>