1 //! The JIT driver uses [`cranelift_jit`] to JIT execute programs without writing any object
4 use std::cell::RefCell;
6 use std::lazy::SyncOnceCell;
7 use std::os::raw::{c_char, c_int};
8 use std::sync::{mpsc, Mutex};
10 use rustc_codegen_ssa::CrateInfo;
11 use rustc_middle::mir::mono::MonoItem;
12 use rustc_session::Session;
13 use rustc_span::Symbol;
15 use cranelift_jit::{JITBuilder, JITModule};
17 use crate::{prelude::*, BackendConfig};
18 use crate::{CodegenCx, CodegenMode};
21 backend_config: BackendConfig,
22 jit_module: JITModule,
26 static LAZY_JIT_STATE: RefCell<Option<JitState>> = const { RefCell::new(None) };
29 /// The Sender owned by the rustc thread
30 static GLOBAL_MESSAGE_SENDER: SyncOnceCell<Mutex<mpsc::Sender<UnsafeMessage>>> =
33 /// A message that is sent from the jitted runtime to the rustc thread.
34 /// Senders are responsible for upholding `Send` semantics.
36 /// Request that the specified `Instance` be lazily jitted.
38 /// Nothing accessible through `instance_ptr` may be moved or mutated by the sender after
39 /// this message is sent.
41 instance_ptr: *const Instance<'static>,
42 trampoline_ptr: *const u8,
43 tx: mpsc::Sender<*const u8>,
46 unsafe impl Send for UnsafeMessage {}
50 fn send(self) -> Result<(), mpsc::SendError<UnsafeMessage>> {
52 /// The Sender owned by the local thread
53 static LOCAL_MESSAGE_SENDER: mpsc::Sender<UnsafeMessage> =
59 LOCAL_MESSAGE_SENDER.with(|sender| sender.send(self))
63 fn create_jit_module<'tcx>(
65 backend_config: &BackendConfig,
67 ) -> (JITModule, CodegenCx<'tcx>) {
68 let crate_info = CrateInfo::new(tcx, "dummy_target_cpu".to_string());
69 let imported_symbols = load_imported_symbols_for_jit(tcx.sess, crate_info);
71 let isa = crate::build_isa(tcx.sess, backend_config);
72 let mut jit_builder = JITBuilder::with_isa(isa, cranelift_module::default_libcall_names());
73 jit_builder.hotswap(hotswap);
74 crate::compiler_builtins::register_functions_for_jit(&mut jit_builder);
75 jit_builder.symbols(imported_symbols);
76 let mut jit_module = JITModule::new(jit_builder);
78 let mut cx = crate::CodegenCx::new(
80 backend_config.clone(),
83 Symbol::intern("dummy_cgu_name"),
86 crate::allocator::codegen(tcx, &mut jit_module, &mut cx.unwind_context);
87 crate::main_shim::maybe_create_entry_wrapper(
90 &mut cx.unwind_context,
98 pub(crate) fn run_jit(tcx: TyCtxt<'_>, backend_config: BackendConfig) -> ! {
99 if !tcx.sess.opts.output_types.should_codegen() {
100 tcx.sess.fatal("JIT mode doesn't work with `cargo check`");
103 if !tcx.sess.crate_types().contains(&rustc_session::config::CrateType::Executable) {
104 tcx.sess.fatal("can't jit non-executable crate");
107 let (mut jit_module, mut cx) = create_jit_module(
110 matches!(backend_config.codegen_mode, CodegenMode::JitLazy),
113 let (_, cgus) = tcx.collect_and_partition_mono_items(());
114 let mono_items = cgus
116 .map(|cgu| cgu.items_in_deterministic_order(tcx).into_iter())
118 .collect::<FxHashMap<_, (_, _)>>()
120 .collect::<Vec<(_, (_, _))>>();
122 super::time(tcx, backend_config.display_cg_time, "codegen mono items", || {
123 super::predefine_mono_items(tcx, &mut jit_module, &mono_items);
124 for (mono_item, _) in mono_items {
126 MonoItem::Fn(inst) => match backend_config.codegen_mode {
127 CodegenMode::Aot => unreachable!(),
128 CodegenMode::Jit => {
129 cx.tcx.sess.time("codegen fn", || {
130 crate::base::codegen_fn(&mut cx, &mut jit_module, inst)
133 CodegenMode::JitLazy => codegen_shim(&mut cx, &mut jit_module, inst),
135 MonoItem::Static(def_id) => {
136 crate::constant::codegen_static(tcx, &mut jit_module, def_id);
138 MonoItem::GlobalAsm(item_id) => {
139 let item = tcx.hir().item(item_id);
140 tcx.sess.span_fatal(item.span, "Global asm is not supported in JIT mode");
146 if !cx.global_asm.is_empty() {
147 tcx.sess.fatal("Inline asm is not supported in JIT mode");
150 tcx.sess.abort_if_errors();
152 jit_module.finalize_definitions();
153 unsafe { cx.unwind_context.register_jit(&jit_module) };
156 "Rustc codegen cranelift will JIT run the executable, because -Cllvm-args=mode=jit was passed"
159 let args = std::iter::once(&*tcx.crate_name(LOCAL_CRATE).as_str().to_string())
160 .chain(backend_config.jit_args.iter().map(|arg| &**arg))
161 .map(|arg| CString::new(arg).unwrap())
162 .collect::<Vec<_>>();
164 let start_sig = Signature {
166 AbiParam::new(jit_module.target_config().pointer_type()),
167 AbiParam::new(jit_module.target_config().pointer_type()),
169 returns: vec![AbiParam::new(jit_module.target_config().pointer_type() /*isize*/)],
170 call_conv: jit_module.target_config().default_call_conv,
172 let start_func_id = jit_module.declare_function("main", Linkage::Import, &start_sig).unwrap();
173 let finalized_start: *const u8 = jit_module.get_finalized_function(start_func_id);
175 LAZY_JIT_STATE.with(|lazy_jit_state| {
176 let mut lazy_jit_state = lazy_jit_state.borrow_mut();
177 assert!(lazy_jit_state.is_none());
178 *lazy_jit_state = Some(JitState { backend_config, jit_module });
181 let f: extern "C" fn(c_int, *const *const c_char) -> c_int =
182 unsafe { ::std::mem::transmute(finalized_start) };
184 let (tx, rx) = mpsc::channel();
185 GLOBAL_MESSAGE_SENDER.set(Mutex::new(tx)).unwrap();
187 // Spawn the jitted runtime in a new thread so that this rustc thread can handle messages
188 // (eg to lazily JIT further functions as required)
189 std::thread::spawn(move || {
190 let mut argv = args.iter().map(|arg| arg.as_ptr()).collect::<Vec<_>>();
192 // Push a null pointer as a terminating argument. This is required by POSIX and
193 // useful as some dynamic linkers use it as a marker to jump over.
194 argv.push(std::ptr::null());
196 let ret = f(args.len() as c_int, argv.as_ptr());
197 std::process::exit(ret);
202 match rx.recv().unwrap() {
203 // lazy JIT compilation request - compile requested instance and return pointer to result
204 UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx } => {
205 tx.send(jit_fn(instance_ptr, trampoline_ptr))
206 .expect("jitted runtime hung up before response to lazy JIT request was sent");
213 extern "C" fn __clif_jit_fn(
214 instance_ptr: *const Instance<'static>,
215 trampoline_ptr: *const u8,
217 // send the JIT request to the rustc thread, with a channel for the response
218 let (tx, rx) = mpsc::channel();
219 UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx }
221 .expect("rustc thread hung up before lazy JIT request was sent");
223 // block on JIT compilation result
224 rx.recv().expect("rustc thread hung up before responding to sent lazy JIT request")
227 fn jit_fn(instance_ptr: *const Instance<'static>, trampoline_ptr: *const u8) -> *const u8 {
228 rustc_middle::ty::tls::with(|tcx| {
229 // lift is used to ensure the correct lifetime for instance.
230 let instance = tcx.lift(unsafe { *instance_ptr }).unwrap();
232 LAZY_JIT_STATE.with(|lazy_jit_state| {
233 let mut lazy_jit_state = lazy_jit_state.borrow_mut();
234 let lazy_jit_state = lazy_jit_state.as_mut().unwrap();
235 let jit_module = &mut lazy_jit_state.jit_module;
236 let backend_config = lazy_jit_state.backend_config.clone();
238 let name = tcx.symbol_name(instance).name;
239 let sig = crate::abi::get_function_sig(tcx, jit_module.isa().triple(), instance);
240 let func_id = jit_module.declare_function(name, Linkage::Export, &sig).unwrap();
242 let current_ptr = jit_module.read_got_entry(func_id);
244 // If the function's GOT entry has already been updated to point at something other
245 // than the shim trampoline, don't re-jit but just return the new pointer instead.
246 // This does not need synchronization as this code is executed only by a sole rustc
248 if current_ptr != trampoline_ptr {
252 jit_module.prepare_for_function_redefine(func_id).unwrap();
254 let mut cx = crate::CodegenCx::new(
259 Symbol::intern("dummy_cgu_name"),
261 tcx.sess.time("codegen fn", || crate::base::codegen_fn(&mut cx, jit_module, instance));
263 assert!(cx.global_asm.is_empty());
264 jit_module.finalize_definitions();
265 unsafe { cx.unwind_context.register_jit(&jit_module) };
266 jit_module.get_finalized_function(func_id)
271 fn load_imported_symbols_for_jit(
273 crate_info: CrateInfo,
274 ) -> Vec<(String, *const u8)> {
275 use rustc_middle::middle::dependency_format::Linkage;
277 let mut dylib_paths = Vec::new();
279 let data = &crate_info
282 .find(|(crate_type, _data)| *crate_type == rustc_session::config::CrateType::Executable)
285 for &cnum in &crate_info.used_crates {
286 let src = &crate_info.used_crate_source[&cnum];
287 match data[cnum.as_usize() - 1] {
288 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
290 let name = &crate_info.crate_name[&cnum];
291 let mut err = sess.struct_err(&format!("Can't load static lib {}", name.as_str()));
292 err.note("rustc_codegen_cranelift can only load dylibs in JIT mode.");
295 Linkage::Dynamic => {
296 dylib_paths.push(src.dylib.as_ref().unwrap().0.clone());
301 let mut imported_symbols = Vec::new();
302 for path in dylib_paths {
303 use object::{Object, ObjectSymbol};
304 let lib = libloading::Library::new(&path).unwrap();
305 let obj = std::fs::read(path).unwrap();
306 let obj = object::File::parse(&*obj).unwrap();
307 imported_symbols.extend(obj.dynamic_symbols().filter_map(|symbol| {
308 let name = symbol.name().unwrap().to_string();
309 if name.is_empty() || !symbol.is_global() || symbol.is_undefined() {
312 if name.starts_with("rust_metadata_") {
313 // The metadata is part of a section that is not loaded by the dynamic linker in
317 let dlsym_name = if cfg!(target_os = "macos") {
318 // On macOS `dlsym` expects the name without leading `_`.
319 assert!(name.starts_with('_'), "{:?}", name);
324 let symbol: libloading::Symbol<'_, *const u8> =
325 unsafe { lib.get(dlsym_name.as_bytes()) }.unwrap();
326 Some((name, *symbol))
328 std::mem::forget(lib)
331 sess.abort_if_errors();
336 fn codegen_shim<'tcx>(cx: &mut CodegenCx<'tcx>, module: &mut JITModule, inst: Instance<'tcx>) {
339 let pointer_type = module.target_config().pointer_type();
341 let name = tcx.symbol_name(inst).name;
342 let sig = crate::abi::get_function_sig(tcx, module.isa().triple(), inst);
343 let func_id = module.declare_function(name, Linkage::Export, &sig).unwrap();
345 let instance_ptr = Box::into_raw(Box::new(inst));
352 call_conv: module.target_config().default_call_conv,
353 params: vec![AbiParam::new(pointer_type), AbiParam::new(pointer_type)],
354 returns: vec![AbiParam::new(pointer_type)],
359 cx.cached_context.clear();
360 let trampoline = &mut cx.cached_context.func;
361 trampoline.signature = sig.clone();
363 let mut builder_ctx = FunctionBuilderContext::new();
364 let mut trampoline_builder = FunctionBuilder::new(trampoline, &mut builder_ctx);
366 let trampoline_fn = module.declare_func_in_func(func_id, trampoline_builder.func);
367 let jit_fn = module.declare_func_in_func(jit_fn, trampoline_builder.func);
368 let sig_ref = trampoline_builder.func.import_signature(sig);
370 let entry_block = trampoline_builder.create_block();
371 trampoline_builder.append_block_params_for_function_params(entry_block);
372 let fn_args = trampoline_builder.func.dfg.block_params(entry_block).to_vec();
374 trampoline_builder.switch_to_block(entry_block);
375 let instance_ptr = trampoline_builder.ins().iconst(pointer_type, instance_ptr as u64 as i64);
376 let trampoline_ptr = trampoline_builder.ins().func_addr(pointer_type, trampoline_fn);
377 let jitted_fn = trampoline_builder.ins().call(jit_fn, &[instance_ptr, trampoline_ptr]);
378 let jitted_fn = trampoline_builder.func.dfg.inst_results(jitted_fn)[0];
379 let call_inst = trampoline_builder.ins().call_indirect(sig_ref, jitted_fn, &fn_args);
380 let ret_vals = trampoline_builder.func.dfg.inst_results(call_inst).to_vec();
381 trampoline_builder.ins().return_(&ret_vals);
383 module.define_function(func_id, &mut cx.cached_context).unwrap();