From 5d03df9431833ad992c1507fedc7daee3e232443 Mon Sep 17 00:00:00 2001 From: bjorn3 <17426603+bjorn3@users.noreply.github.com> Date: Wed, 5 Mar 2025 15:35:51 +0000 Subject: [PATCH] Remove support for the lazy jit mode I might re-implement it in the future, but would probably do so by replacing cranelift-jit. cranelift-jit's api doesn't quite work well for lazy jitting. And even so it adds complexity to cranelift-jit and breaks cranelift-jit outside of x86_64. --- build_system/tests.rs | 14 --- docs/usage.md | 9 +- scripts/cargo-clif.rs | 13 --- src/config.rs | 7 -- src/driver/jit.rs | 214 ++++-------------------------------------- src/lib.rs | 2 +- 6 files changed, 18 insertions(+), 241 deletions(-) diff --git a/build_system/tests.rs b/build_system/tests.rs index ea7e94c345ad..1b1f0f483a33 100644 --- a/build_system/tests.rs +++ b/build_system/tests.rs @@ -384,20 +384,6 @@ impl<'a> TestRunner<'a> { jit_cmd.env("CG_CLIF_JIT_ARGS", args); } spawn_and_wait(jit_cmd); - - eprintln!("[JIT-lazy] {testname}"); - let mut jit_cmd = self.rustc_command([ - "-Zunstable-options", - "-Cllvm-args=mode=jit-lazy", - "-Cprefer-dynamic", - source, - "--cfg", - "jit", - ]); - if !args.is_empty() { - jit_cmd.env("CG_CLIF_JIT_ARGS", args); - } - spawn_and_wait(jit_cmd); } } } diff --git a/docs/usage.md b/docs/usage.md index 785adbbdf9a8..dbe36109f83e 100644 --- a/docs/usage.md +++ b/docs/usage.md @@ -41,20 +41,13 @@ or $ $cg_clif_dir/dist/rustc-clif -Cllvm-args=jit-mode -Cprefer-dynamic my_crate.rs ``` -There is also an experimental lazy jit mode. In this mode functions are only compiled once they are -first called. - -```bash -$ $cg_clif_dir/dist/cargo-clif lazy-jit -``` - ## Shell These are a few functions that allow you to easily run rust code from the shell using cg_clif as jit. ```bash function jit_naked() { - echo "$@" | $cg_clif_dir/dist/rustc-clif - -Zunstable-options -Cllvm-args=jit-mode -Cllvm-args=jit-lazy -Cprefer-dynamic + echo "$@" | $cg_clif_dir/dist/rustc-clif - -Zunstable-options -Cllvm-args=jit-mode-Cprefer-dynamic } function jit() { diff --git a/scripts/cargo-clif.rs b/scripts/cargo-clif.rs index 1ca02bc6a2ce..e6c63bf5e650 100644 --- a/scripts/cargo-clif.rs +++ b/scripts/cargo-clif.rs @@ -54,19 +54,6 @@ fn main() { ]) .collect() } - Some("lazy-jit") => { - rustflags.push("-Cprefer-dynamic".to_owned()); - args.remove(0); - IntoIterator::into_iter(["rustc".to_string()]) - .chain(args) - .chain([ - "--".to_string(), - "-Zunstable-options".to_string(), - "-Cllvm-args=jit-mode".to_string(), - "-Cllvm-args=jit-lazy".to_string(), - ]) - .collect() - } _ => args, }; diff --git a/src/config.rs b/src/config.rs index 30b48786cdc4..d328b33a704f 100644 --- a/src/config.rs +++ b/src/config.rs @@ -6,11 +6,6 @@ pub struct BackendConfig { /// Defaults to AOT compilation. Can be set using `-Cllvm-args=jit-mode`. pub jit_mode: bool, - /// When JIT executing should the lazy JIT mode be used. - /// - /// Defaults to false. Can be set using `-Cllvm-args=jit-lazy`. - pub lazy_jit: bool, - /// When JIT mode is enable pass these arguments to the program. /// /// Defaults to the value of `CG_CLIF_JIT_ARGS`. @@ -22,7 +17,6 @@ impl BackendConfig { pub fn from_opts(opts: &[String]) -> Result { let mut config = BackendConfig { jit_mode: false, - lazy_jit: false, jit_args: match std::env::var("CG_CLIF_JIT_ARGS") { Ok(args) => args.split(' ').map(|arg| arg.to_string()).collect(), Err(std::env::VarError::NotPresent) => vec![], @@ -40,7 +34,6 @@ impl BackendConfig { } match &**opt { "jit-mode" => config.jit_mode = true, - "jit-lazy" => config.lazy_jit = true, _ => return Err(format!("Unknown option `{}`", opt)), } } diff --git a/src/driver/jit.rs b/src/driver/jit.rs index 17d55a82e8b5..4a08937f4aa9 100644 --- a/src/driver/jit.rs +++ b/src/driver/jit.rs @@ -1,12 +1,9 @@ //! The JIT driver uses [`cranelift_jit`] to JIT execute programs without writing any object //! files. -use std::cell::RefCell; use std::ffi::CString; use std::os::raw::{c_char, c_int}; -use std::sync::{Mutex, OnceLock, mpsc}; -use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext}; use cranelift_jit::{JITBuilder, JITModule}; use rustc_codegen_ssa::CrateInfo; use rustc_middle::mir::mono::MonoItem; @@ -18,58 +15,13 @@ use crate::debuginfo::TypeDebugContext; use crate::prelude::*; use crate::unwind_module::UnwindModule; -struct JitState { - jit_module: UnwindModule, -} - -thread_local! { - static LAZY_JIT_STATE: RefCell> = const { RefCell::new(None) }; -} - -/// The Sender owned by the rustc thread -static GLOBAL_MESSAGE_SENDER: OnceLock>> = OnceLock::new(); - -/// A message that is sent from the jitted runtime to the rustc thread. -/// Senders are responsible for upholding `Send` semantics. -enum UnsafeMessage { - /// Request that the specified `Instance` be lazily jitted. - /// - /// Nothing accessible through `instance_ptr` may be moved or mutated by the sender after - /// this message is sent. - JitFn { - instance_ptr: *const Instance<'static>, - trampoline_ptr: *const u8, - tx: mpsc::Sender<*const u8>, - }, -} -unsafe impl Send for UnsafeMessage {} - -impl UnsafeMessage { - /// Send the message. - fn send(self) { - thread_local! { - /// The Sender owned by the local thread - static LOCAL_MESSAGE_SENDER: mpsc::Sender = - GLOBAL_MESSAGE_SENDER - .get().unwrap() - .lock().unwrap() - .clone(); - } - LOCAL_MESSAGE_SENDER.with(|sender| { - sender.send(self).expect("rustc thread hung up before lazy JIT request was sent") - }) - } -} - -fn create_jit_module(tcx: TyCtxt<'_>, hotswap: bool) -> (UnwindModule, CodegenCx) { +fn create_jit_module(tcx: TyCtxt<'_>) -> (UnwindModule, CodegenCx) { let crate_info = CrateInfo::new(tcx, "dummy_target_cpu".to_string()); let isa = crate::build_isa(tcx.sess); let mut jit_builder = JITBuilder::with_isa(isa, cranelift_module::default_libcall_names()); - jit_builder.hotswap(hotswap); crate::compiler_builtins::register_functions_for_jit(&mut jit_builder); jit_builder.symbol_lookup_fn(dep_symbol_lookup_fn(tcx.sess, crate_info)); - jit_builder.symbol("__clif_jit_fn", clif_jit_fn as *const u8); let mut jit_module = UnwindModule::new(JITModule::new(jit_builder), false); let cx = crate::CodegenCx::new(tcx, jit_module.isa(), false, sym::dummy_cgu_name); @@ -79,7 +31,7 @@ fn create_jit_module(tcx: TyCtxt<'_>, hotswap: bool) -> (UnwindModule (jit_module, cx) } -pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_lazy: bool, jit_args: Vec) -> ! { +pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_args: Vec) -> ! { if !tcx.sess.opts.output_types.should_codegen() { tcx.dcx().fatal("JIT mode doesn't work with `cargo check`"); } @@ -88,7 +40,7 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_lazy: bool, jit_args: Vec) -> tcx.dcx().fatal("can't jit non-executable crate"); } - let (mut jit_module, mut cx) = create_jit_module(tcx, jit_lazy); + let (mut jit_module, mut cx) = create_jit_module(tcx); let mut cached_context = Context::new(); let cgus = tcx.collect_and_partition_mono_items(()).codegen_units; @@ -105,17 +57,13 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_lazy: bool, jit_args: Vec) -> for (mono_item, _) in mono_items { match mono_item { MonoItem::Fn(inst) => { - if jit_lazy { - codegen_shim(tcx, &mut cached_context, &mut jit_module, inst) - } else { - codegen_and_compile_fn( - tcx, - &mut cx, - &mut cached_context, - &mut jit_module, - inst, - ); - } + codegen_and_compile_fn( + tcx, + &mut cx, + &mut cached_context, + &mut jit_module, + inst, + ); } MonoItem::Static(def_id) => { crate::constant::codegen_static(tcx, &mut jit_module, def_id); @@ -158,41 +106,17 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_lazy: bool, jit_args: Vec) -> let start_func_id = jit_module.declare_function("main", Linkage::Import, &start_sig).unwrap(); let finalized_start: *const u8 = jit_module.module.get_finalized_function(start_func_id); - LAZY_JIT_STATE.with(|lazy_jit_state| { - let mut lazy_jit_state = lazy_jit_state.borrow_mut(); - assert!(lazy_jit_state.is_none()); - *lazy_jit_state = Some(JitState { jit_module }); - }); - let f: extern "C" fn(c_int, *const *const c_char) -> c_int = unsafe { ::std::mem::transmute(finalized_start) }; - let (tx, rx) = mpsc::channel(); - GLOBAL_MESSAGE_SENDER.set(Mutex::new(tx)).unwrap(); + let mut argv = args.iter().map(|arg| arg.as_ptr()).collect::>(); - // Spawn the jitted runtime in a new thread so that this rustc thread can handle messages - // (eg to lazily JIT further functions as required) - std::thread::spawn(move || { - let mut argv = args.iter().map(|arg| arg.as_ptr()).collect::>(); + // Push a null pointer as a terminating argument. This is required by POSIX and + // useful as some dynamic linkers use it as a marker to jump over. + argv.push(std::ptr::null()); - // Push a null pointer as a terminating argument. This is required by POSIX and - // useful as some dynamic linkers use it as a marker to jump over. - argv.push(std::ptr::null()); - - let ret = f(args.len() as c_int, argv.as_ptr()); - std::process::exit(ret); - }); - - // Handle messages - loop { - match rx.recv().unwrap() { - // lazy JIT compilation request - compile requested instance and return pointer to result - UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx } => { - tx.send(jit_fn(instance_ptr, trampoline_ptr)) - .expect("jitted runtime hung up before response to lazy JIT request was sent"); - } - } - } + let ret = f(args.len() as c_int, argv.as_ptr()); + std::process::exit(ret); } pub(crate) fn codegen_and_compile_fn<'tcx>( @@ -224,58 +148,6 @@ pub(crate) fn codegen_and_compile_fn<'tcx>( }); } -extern "C" fn clif_jit_fn( - instance_ptr: *const Instance<'static>, - trampoline_ptr: *const u8, -) -> *const u8 { - // send the JIT request to the rustc thread, with a channel for the response - let (tx, rx) = mpsc::channel(); - UnsafeMessage::JitFn { instance_ptr, trampoline_ptr, tx }.send(); - - // block on JIT compilation result - rx.recv().expect("rustc thread hung up before responding to sent lazy JIT request") -} - -fn jit_fn(instance_ptr: *const Instance<'static>, trampoline_ptr: *const u8) -> *const u8 { - rustc_middle::ty::tls::with(|tcx| { - // lift is used to ensure the correct lifetime for instance. - let instance = tcx.lift(unsafe { *instance_ptr }).unwrap(); - - LAZY_JIT_STATE.with(|lazy_jit_state| { - let mut lazy_jit_state = lazy_jit_state.borrow_mut(); - let lazy_jit_state = lazy_jit_state.as_mut().unwrap(); - let jit_module = &mut lazy_jit_state.jit_module; - - let name = tcx.symbol_name(instance).name; - let sig = crate::abi::get_function_sig( - tcx, - jit_module.target_config().default_call_conv, - instance, - ); - let func_id = jit_module.declare_function(name, Linkage::Export, &sig).unwrap(); - - let current_ptr = jit_module.module.read_got_entry(func_id); - - // If the function's GOT entry has already been updated to point at something other - // than the shim trampoline, don't re-jit but just return the new pointer instead. - // This does not need synchronization as this code is executed only by a sole rustc - // thread. - if current_ptr != trampoline_ptr { - return current_ptr; - } - - jit_module.module.prepare_for_function_redefine(func_id).unwrap(); - - let mut cx = crate::CodegenCx::new(tcx, jit_module.isa(), false, sym::dummy_cgu_name); - codegen_and_compile_fn(tcx, &mut cx, &mut Context::new(), jit_module, instance); - - assert!(cx.global_asm.is_empty()); - jit_module.finalize_definitions(); - jit_module.module.get_finalized_function(func_id) - }) - }) -} - fn dep_symbol_lookup_fn( sess: &Session, crate_info: CrateInfo, @@ -323,57 +195,3 @@ fn dep_symbol_lookup_fn( None }) } - -fn codegen_shim<'tcx>( - tcx: TyCtxt<'tcx>, - cached_context: &mut Context, - module: &mut UnwindModule, - inst: Instance<'tcx>, -) { - let pointer_type = module.target_config().pointer_type(); - - let name = tcx.symbol_name(inst).name; - let sig = crate::abi::get_function_sig(tcx, module.target_config().default_call_conv, inst); - let func_id = module.declare_function(name, Linkage::Export, &sig).unwrap(); - - let instance_ptr = Box::into_raw(Box::new(inst)); - - let jit_fn = module - .declare_function( - "__clif_jit_fn", - Linkage::Import, - &Signature { - call_conv: module.target_config().default_call_conv, - params: vec![AbiParam::new(pointer_type), AbiParam::new(pointer_type)], - returns: vec![AbiParam::new(pointer_type)], - }, - ) - .unwrap(); - - let context = cached_context; - context.clear(); - let trampoline = &mut context.func; - trampoline.signature = sig.clone(); - - let mut builder_ctx = FunctionBuilderContext::new(); - let mut trampoline_builder = FunctionBuilder::new(trampoline, &mut builder_ctx); - - let trampoline_fn = module.declare_func_in_func(func_id, trampoline_builder.func); - let jit_fn = module.declare_func_in_func(jit_fn, trampoline_builder.func); - let sig_ref = trampoline_builder.func.import_signature(sig); - - let entry_block = trampoline_builder.create_block(); - trampoline_builder.append_block_params_for_function_params(entry_block); - let fn_args = trampoline_builder.func.dfg.block_params(entry_block).to_vec(); - - trampoline_builder.switch_to_block(entry_block); - let instance_ptr = trampoline_builder.ins().iconst(pointer_type, instance_ptr as u64 as i64); - let trampoline_ptr = trampoline_builder.ins().func_addr(pointer_type, trampoline_fn); - let jitted_fn = trampoline_builder.ins().call(jit_fn, &[instance_ptr, trampoline_ptr]); - let jitted_fn = trampoline_builder.func.dfg.inst_results(jitted_fn)[0]; - let call_inst = trampoline_builder.ins().call_indirect(sig_ref, jitted_fn, &fn_args); - let ret_vals = trampoline_builder.func.dfg.inst_results(call_inst).to_vec(); - trampoline_builder.ins().return_(&ret_vals); - - module.define_function(func_id, context).unwrap(); -} diff --git a/src/lib.rs b/src/lib.rs index c5ca6565a86b..4d97c3ae6048 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -215,7 +215,7 @@ impl CodegenBackend for CraneliftCodegenBackend { }); if config.jit_mode { #[cfg(feature = "jit")] - driver::jit::run_jit(tcx, config.lazy_jit, config.jit_args); + driver::jit::run_jit(tcx, config.jit_args); #[cfg(not(feature = "jit"))] tcx.dcx().fatal("jit support was disabled when compiling rustc_codegen_cranelift");