1 //! The JIT driver uses [`cranelift_jit`] to JIT execute programs without writing any object
4 use std::cell::RefCell;
6 use std::lazy::{Lazy, SyncOnceCell};
7 use std::os::raw::{c_char, c_int};
8 use std::sync::{mpsc, Mutex};
10 use cranelift_codegen::binemit::{NullStackMapSink, NullTrapSink};
11 use rustc_codegen_ssa::CrateInfo;
12 use rustc_middle::mir::mono::MonoItem;
14 use cranelift_jit::{JITBuilder, JITModule};
16 use crate::{prelude::*, BackendConfig};
17 use crate::{CodegenCx, CodegenMode};
20 backend_config: BackendConfig,
21 jit_module: JITModule,
25 static LAZY_JIT_STATE: RefCell<Option<JitState>> = RefCell::new(None);
28 /// The Sender owned by the rustc thread
29 static GLOBAL_MESSAGE_SENDER: SyncOnceCell<Mutex<mpsc::Sender<UnsafeMessage>>> =
32 /// A message that is sent from the jitted runtime to the rustc thread.
33 /// Senders are responsible for upholding `Send` semantics.
35 /// Request that the specified `Instance` be lazily jitted.
37 /// Nothing accessible through `instance_ptr` may be moved or mutated by the sender after
38 /// this message is sent.
40 instance_ptr: *const Instance<'static>,
41 trampoline_ptr: *const u8,
42 tx: mpsc::Sender<*const u8>,
45 unsafe impl Send for UnsafeMessage {}
49 fn send(self) -> Result<(), mpsc::SendError<UnsafeMessage>> {
51 /// The Sender owned by the local thread
52 static LOCAL_MESSAGE_SENDER: Lazy<mpsc::Sender<UnsafeMessage>> = Lazy::new(||
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 imported_symbols = load_imported_symbols_for_jit(tcx);
70 let isa = crate::build_isa(tcx.sess, backend_config);
71 let mut jit_builder = JITBuilder::with_isa(isa, cranelift_module::default_libcall_names());
72 jit_builder.hotswap(hotswap);
73 crate::compiler_builtins::register_functions_for_jit(&mut jit_builder);
74 jit_builder.symbols(imported_symbols);
75 let mut jit_module = JITModule::new(jit_builder);
77 let mut cx = crate::CodegenCx::new(tcx, backend_config.clone(), jit_module.isa(), false);
79 crate::allocator::codegen(tcx, &mut jit_module, &mut cx.unwind_context);
80 crate::main_shim::maybe_create_entry_wrapper(
83 &mut cx.unwind_context,
91 pub(crate) fn run_jit(tcx: TyCtxt<'_>, backend_config: BackendConfig) -> ! {
92 if !tcx.sess.opts.output_types.should_codegen() {
93 tcx.sess.fatal("JIT mode doesn't work with `cargo check`");
96 if !tcx.sess.crate_types().contains(&rustc_session::config::CrateType::Executable) {
97 tcx.sess.fatal("can't jit non-executable crate");
100 let (mut jit_module, mut cx) = create_jit_module(
103 matches!(backend_config.codegen_mode, CodegenMode::JitLazy),
106 let (_, cgus) = tcx.collect_and_partition_mono_items(());
107 let mono_items = cgus
109 .map(|cgu| cgu.items_in_deterministic_order(tcx).into_iter())
111 .collect::<FxHashMap<_, (_, _)>>()
113 .collect::<Vec<(_, (_, _))>>();
115 super::time(tcx, backend_config.display_cg_time, "codegen mono items", || {
116 super::predefine_mono_items(tcx, &mut jit_module, &mono_items);
117 for (mono_item, _) in mono_items {
119 MonoItem::Fn(inst) => match backend_config.codegen_mode {
120 CodegenMode::Aot => unreachable!(),
121 CodegenMode::Jit => {
122 cx.tcx.sess.time("codegen fn", || {
123 crate::base::codegen_fn(&mut cx, &mut jit_module, inst)
126 CodegenMode::JitLazy => codegen_shim(&mut cx, &mut jit_module, inst),
128 MonoItem::Static(def_id) => {
129 crate::constant::codegen_static(tcx, &mut jit_module, def_id);
131 MonoItem::GlobalAsm(item_id) => {
132 let item = tcx.hir().item(item_id);
133 tcx.sess.span_fatal(item.span, "Global asm is not supported in JIT mode");
139 if !cx.global_asm.is_empty() {
140 tcx.sess.fatal("Inline asm is not supported in JIT mode");
143 tcx.sess.abort_if_errors();
145 jit_module.finalize_definitions();
146 unsafe { cx.unwind_context.register_jit(&jit_module) };
149 "Rustc codegen cranelift will JIT run the executable, because -Cllvm-args=mode=jit was passed"
152 let args = std::iter::once(&*tcx.crate_name(LOCAL_CRATE).as_str().to_string())
153 .chain(backend_config.jit_args.iter().map(|arg| &**arg))
154 .map(|arg| CString::new(arg).unwrap())
155 .collect::<Vec<_>>();
157 let start_sig = Signature {
159 AbiParam::new(jit_module.target_config().pointer_type()),
160 AbiParam::new(jit_module.target_config().pointer_type()),
162 returns: vec![AbiParam::new(jit_module.target_config().pointer_type() /*isize*/)],
163 call_conv: jit_module.target_config().default_call_conv,
165 let start_func_id = jit_module.declare_function("main", Linkage::Import, &start_sig).unwrap();
166 let finalized_start: *const u8 = jit_module.get_finalized_function(start_func_id);
168 LAZY_JIT_STATE.with(|lazy_jit_state| {
169 let mut lazy_jit_state = lazy_jit_state.borrow_mut();
170 assert!(lazy_jit_state.is_none());
171 *lazy_jit_state = Some(JitState { backend_config, jit_module });
174 let f: extern "C" fn(c_int, *const *const c_char) -> c_int =
175 unsafe { ::std::mem::transmute(finalized_start) };
177 let (tx, rx) = mpsc::channel();
178 GLOBAL_MESSAGE_SENDER.set(Mutex::new(tx)).unwrap();
180 // Spawn the jitted runtime in a new thread so that this rustc thread can handle messages
181 // (eg to lazily JIT further functions as required)
182 std::thread::spawn(move || {
183 let mut argv = args.iter().map(|arg| arg.as_ptr()).collect::<Vec<_>>();
185 // Push a null pointer as a terminating argument. This is required by POSIX and
186 // useful as some dynamic linkers use it as a marker to jump over.
187 argv.push(std::ptr::null());
189 let ret = f(args.len() as c_int, argv.as_ptr());
190 std::process::exit(ret);
195 match rx.recv().unwrap() {
196 // lazy JIT compilation request - compile requested instance and return pointer to result
197 UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx } => {
198 tx.send(jit_fn(instance_ptr, trampoline_ptr))
199 .expect("jitted runtime hung up before response to lazy JIT request was sent");
206 extern "C" fn __clif_jit_fn(
207 instance_ptr: *const Instance<'static>,
208 trampoline_ptr: *const u8,
210 // send the JIT request to the rustc thread, with a channel for the response
211 let (tx, rx) = mpsc::channel();
212 UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx }
214 .expect("rustc thread hung up before lazy JIT request was sent");
216 // block on JIT compilation result
217 rx.recv().expect("rustc thread hung up before responding to sent lazy JIT request")
220 fn jit_fn(instance_ptr: *const Instance<'static>, trampoline_ptr: *const u8) -> *const u8 {
221 rustc_middle::ty::tls::with(|tcx| {
222 // lift is used to ensure the correct lifetime for instance.
223 let instance = tcx.lift(unsafe { *instance_ptr }).unwrap();
225 LAZY_JIT_STATE.with(|lazy_jit_state| {
226 let mut lazy_jit_state = lazy_jit_state.borrow_mut();
227 let lazy_jit_state = lazy_jit_state.as_mut().unwrap();
228 let jit_module = &mut lazy_jit_state.jit_module;
229 let backend_config = lazy_jit_state.backend_config.clone();
231 let name = tcx.symbol_name(instance).name;
232 let sig = crate::abi::get_function_sig(tcx, jit_module.isa().triple(), instance);
233 let func_id = jit_module.declare_function(name, Linkage::Export, &sig).unwrap();
235 let current_ptr = jit_module.read_got_entry(func_id);
237 // If the function's GOT entry has already been updated to point at something other
238 // than the shim trampoline, don't re-jit but just return the new pointer instead.
239 // This does not need synchronization as this code is executed only by a sole rustc
241 if current_ptr != trampoline_ptr {
245 jit_module.prepare_for_function_redefine(func_id).unwrap();
247 let mut cx = crate::CodegenCx::new(tcx, backend_config, jit_module.isa(), false);
248 tcx.sess.time("codegen fn", || crate::base::codegen_fn(&mut cx, jit_module, instance));
250 assert!(cx.global_asm.is_empty());
251 jit_module.finalize_definitions();
252 unsafe { cx.unwind_context.register_jit(&jit_module) };
253 jit_module.get_finalized_function(func_id)
258 fn load_imported_symbols_for_jit(tcx: TyCtxt<'_>) -> Vec<(String, *const u8)> {
259 use rustc_middle::middle::dependency_format::Linkage;
261 let mut dylib_paths = Vec::new();
263 let crate_info = CrateInfo::new(tcx);
264 let formats = tcx.dependency_formats(());
267 .find(|(crate_type, _data)| *crate_type == rustc_session::config::CrateType::Executable)
270 for &(cnum, _) in &crate_info.used_crates_dynamic {
271 let src = &crate_info.used_crate_source[&cnum];
272 match data[cnum.as_usize() - 1] {
273 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
275 let name = tcx.crate_name(cnum);
277 tcx.sess.struct_err(&format!("Can't load static lib {}", name.as_str()));
278 err.note("rustc_codegen_cranelift can only load dylibs in JIT mode.");
281 Linkage::Dynamic => {
282 dylib_paths.push(src.dylib.as_ref().unwrap().0.clone());
287 let mut imported_symbols = Vec::new();
288 for path in dylib_paths {
289 use object::{Object, ObjectSymbol};
290 let lib = libloading::Library::new(&path).unwrap();
291 let obj = std::fs::read(path).unwrap();
292 let obj = object::File::parse(&*obj).unwrap();
293 imported_symbols.extend(obj.dynamic_symbols().filter_map(|symbol| {
294 let name = symbol.name().unwrap().to_string();
295 if name.is_empty() || !symbol.is_global() || symbol.is_undefined() {
298 if name.starts_with("rust_metadata_") {
299 // The metadata is part of a section that is not loaded by the dynamic linker in
303 let dlsym_name = if cfg!(target_os = "macos") {
304 // On macOS `dlsym` expects the name without leading `_`.
305 assert!(name.starts_with('_'), "{:?}", name);
310 let symbol: libloading::Symbol<'_, *const u8> =
311 unsafe { lib.get(dlsym_name.as_bytes()) }.unwrap();
312 Some((name, *symbol))
314 std::mem::forget(lib)
317 tcx.sess.abort_if_errors();
322 fn codegen_shim<'tcx>(cx: &mut CodegenCx<'tcx>, module: &mut JITModule, inst: Instance<'tcx>) {
325 let pointer_type = module.target_config().pointer_type();
327 let name = tcx.symbol_name(inst).name;
328 let sig = crate::abi::get_function_sig(tcx, module.isa().triple(), inst);
329 let func_id = module.declare_function(name, Linkage::Export, &sig).unwrap();
331 let instance_ptr = Box::into_raw(Box::new(inst));
338 call_conv: module.target_config().default_call_conv,
339 params: vec![AbiParam::new(pointer_type), AbiParam::new(pointer_type)],
340 returns: vec![AbiParam::new(pointer_type)],
345 cx.cached_context.clear();
346 let trampoline = &mut cx.cached_context.func;
347 trampoline.signature = sig.clone();
349 let mut builder_ctx = FunctionBuilderContext::new();
350 let mut trampoline_builder = FunctionBuilder::new(trampoline, &mut builder_ctx);
352 let trampoline_fn = module.declare_func_in_func(func_id, trampoline_builder.func);
353 let jit_fn = module.declare_func_in_func(jit_fn, trampoline_builder.func);
354 let sig_ref = trampoline_builder.func.import_signature(sig);
356 let entry_block = trampoline_builder.create_block();
357 trampoline_builder.append_block_params_for_function_params(entry_block);
358 let fn_args = trampoline_builder.func.dfg.block_params(entry_block).to_vec();
360 trampoline_builder.switch_to_block(entry_block);
361 let instance_ptr = trampoline_builder.ins().iconst(pointer_type, instance_ptr as u64 as i64);
362 let trampoline_ptr = trampoline_builder.ins().func_addr(pointer_type, trampoline_fn);
363 let jitted_fn = trampoline_builder.ins().call(jit_fn, &[instance_ptr, trampoline_ptr]);
364 let jitted_fn = trampoline_builder.func.dfg.inst_results(jitted_fn)[0];
365 let call_inst = trampoline_builder.ins().call_indirect(sig_ref, jitted_fn, &fn_args);
366 let ret_vals = trampoline_builder.func.dfg.inst_results(call_inst).to_vec();
367 trampoline_builder.ins().return_(&ret_vals);
372 &mut cx.cached_context,
373 &mut NullTrapSink {},
374 &mut NullStackMapSink {},