feat(engine): Implement interleaved garbage collection (#443)

An interleaved, exact, stop-the-world GC implementation.

At present the GC is (mostly?) memory safe but not very reference-correct or useful. The collection is just "after every 256 instructions in the same bytecode" and the rest of the engine has no lifetime hints about when it's safe or unsafe to retain JS Values.

Author: aapoalas

nova_vm/Cargo.toml

@@ -25,14 +25,15 @@ wtf8 = { workspace = true }
 
 [features]
 default = ["math", "json", "date", "array-buffer", "shared-array-buffer", "weak-refs", "atomics"]
-math = []
-json = ["sonic-rs"]
-date = []
 array-buffer = []
-shared-array-buffer = []
-weak-refs = []
 atomics = ["array-buffer", "shared-array-buffer"]
+date = []
+interleaved-gc = []
+json = ["sonic-rs"]
+math = []
+shared-array-buffer = []
 typescript = []
+weak-refs = []
 
 [build-dependencies]
 small_string = { path = "../small_string" }

nova_vm/src/ecmascript/abstract_operations/operations_on_iterator_objects.rs

@@ -451,12 +451,22 @@ pub(crate) fn iterator_to_list(
 
 impl HeapMarkAndSweep for IteratorRecord {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.iterator.mark_values(queues);
-        self.next_method.mark_values(queues);
+        let Self {
+            iterator,
+            next_method,
+            done: _,
+        } = self;
+        iterator.mark_values(queues);
+        next_method.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.iterator.sweep_values(compactions);
-        self.next_method.sweep_values(compactions);
+        let Self {
+            iterator,
+            next_method,
+            done: _,
+        } = self;
+        iterator.sweep_values(compactions);
+        next_method.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/abstract_operations/operations_on_objects.rs

@@ -907,7 +907,6 @@ pub(crate) fn initialize_instance_elements(
         // To do this, we need a new execution context that points to a new
         // Function environment. The function environment should be lexically a
         // child of the class constructor's creating environment.
-        let bytecode = unsafe { bytecode.as_ref() };
         let f = constructor.into_function();
         let outer_env = constructor_data.environment;
         let outer_priv_env = constructor_data.private_environment;

nova_vm/src/ecmascript/builtins/array/data.rs

@@ -127,27 +127,33 @@ pub struct ArrayHeapData {
 
 impl HeapMarkAndSweep for SealableElementsVector {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        let item = *self;
-        let elements: ElementsVector = item.into();
+        let elements: ElementsVector = (*self).into();
         elements.mark_values(queues)
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        let item = *self;
-        let mut elements: ElementsVector = item.into();
+        let mut elements: ElementsVector = (*self).into();
         elements.sweep_values(compactions);
         self.elements_index = elements.elements_index;
     }
 }
 
 impl HeapMarkAndSweep for ArrayHeapData {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.object_index.mark_values(queues);
-        self.elements.mark_values(queues);
+        let Self {
+            object_index,
+            elements,
+        } = self;
+        object_index.mark_values(queues);
+        elements.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.object_index.sweep_values(compactions);
-        self.elements.sweep_values(compactions);
+        let Self {
+            object_index,
+            elements,
+        } = self;
+        object_index.sweep_values(compactions);
+        elements.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/builtins/array_buffer/data.rs

@@ -149,10 +149,18 @@ impl ArrayBufferHeapData {
 
 impl HeapMarkAndSweep for ArrayBufferHeapData {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.object_index.mark_values(queues);
+        let Self {
+            object_index,
+            buffer: _,
+        } = self;
+        object_index.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.object_index.sweep_values(compactions);
+        let Self {
+            object_index,
+            buffer: _,
+        } = self;
+        object_index.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/builtins/bound_function.rs

@@ -321,18 +321,34 @@ impl HeapMarkAndSweep for BoundFunction {
 
 impl HeapMarkAndSweep for BoundFunctionHeapData {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.name.mark_values(queues);
-        self.bound_target_function.mark_values(queues);
-        self.object_index.mark_values(queues);
-        self.bound_this.mark_values(queues);
-        self.bound_arguments.mark_values(queues);
+        let Self {
+            object_index,
+            length: _,
+            bound_target_function,
+            bound_this,
+            bound_arguments,
+            name,
+        } = self;
+        name.mark_values(queues);
+        bound_target_function.mark_values(queues);
+        object_index.mark_values(queues);
+        bound_this.mark_values(queues);
+        bound_arguments.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.name.sweep_values(compactions);
-        self.bound_target_function.sweep_values(compactions);
-        self.object_index.sweep_values(compactions);
-        self.bound_this.sweep_values(compactions);
-        self.bound_arguments.sweep_values(compactions);
+        let Self {
+            object_index,
+            length: _,
+            bound_target_function,
+            bound_this,
+            bound_arguments,
+            name,
+        } = self;
+        name.sweep_values(compactions);
+        bound_target_function.sweep_values(compactions);
+        object_index.sweep_values(compactions);
+        bound_this.sweep_values(compactions);
+        bound_arguments.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/builtins/builtin_constructor.rs

@@ -2,10 +2,7 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
-use std::{
-    ops::{Index, IndexMut},
-    ptr::NonNull,
-};
+use std::ops::{Index, IndexMut};
 
 use oxc_span::Span;
 
@@ -339,7 +336,7 @@ pub(crate) struct BuiltinConstructorArgs {
     pub(crate) class_name: String,
     pub(crate) prototype: Option<Object>,
     pub(crate) prototype_property: Object,
-    pub(crate) compiled_initializer_bytecode: Option<Box<Executable>>,
+    pub(crate) compiled_initializer_bytecode: Option<Executable>,
     pub(crate) env: EnvironmentIndex,
     pub(crate) private_env: Option<PrivateEnvironmentIndex>,
     pub(crate) source_code: SourceCode,
@@ -414,17 +411,13 @@ pub(crate) fn create_builtin_constructor(
         agent.heap.create_null_object(&entries)
     };
 
-    let compiled_initializer_bytecode = args
-        .compiled_initializer_bytecode
-        .map(|bytecode| NonNull::from(Box::leak(bytecode)));
-
     // 13. Return func.
     agent.heap.create(BuiltinConstructorHeapData {
         // 10. Perform SetFunctionLength(func, length).
         // Skipped as length of builtin constructors is always 0.
         // 8. Set func.[[Realm]] to realm.
         realm,
-        compiled_initializer_bytecode,
+        compiled_initializer_bytecode: args.compiled_initializer_bytecode,
         is_derived: args.is_derived,
         object_index: Some(backing_object),
         environment: args.env,
@@ -453,34 +446,40 @@ impl HeapMarkAndSweep for BuiltinConstructorFunction {
 
 impl HeapMarkAndSweep for BuiltinConstructorHeapData {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.realm.mark_values(queues);
-        self.object_index.mark_values(queues);
-        self.environment.mark_values(queues);
-        self.private_environment.mark_values(queues);
-        self.source_code.mark_values(queues);
-        if let Some(exe) = &self.compiled_initializer_bytecode {
-            // SAFETY: This is a valid, non-null pointer to an owned Executable
-            // that cannot have any live mutable references to it.
-            unsafe { exe.as_ref() }.mark_values(queues);
-        }
+        let Self {
+            object_index,
+            realm,
+            is_derived: _,
+            compiled_initializer_bytecode,
+            environment,
+            private_environment,
+            source_text: _,
+            source_code,
+        } = self;
+        realm.mark_values(queues);
+        object_index.mark_values(queues);
+        environment.mark_values(queues);
+        private_environment.mark_values(queues);
+        source_code.mark_values(queues);
+        compiled_initializer_bytecode.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.realm.sweep_values(compactions);
-        self.object_index.sweep_values(compactions);
-        self.environment.sweep_values(compactions);
-        self.private_environment.sweep_values(compactions);
-        self.source_code.sweep_values(compactions);
-        if let Some(exe) = &mut self.compiled_initializer_bytecode {
-            // SAFETY: This is a valid, non-null pointer to an owned Executable
-            // that cannot have any live references to it.
-            // References to this Executable are only created above for marking
-            // and in function_definition for running the function. Both of the
-            // references only live for the duration of a synchronous call and
-            // no longer. Sweeping cannot run concurrently with marking or with
-            // ECMAScript code execution. Hence we can be sure that this is not
-            // an aliasing violation.
-            unsafe { exe.as_mut() }.sweep_values(compactions);
-        }
+        let Self {
+            object_index,
+            realm,
+            is_derived: _,
+            compiled_initializer_bytecode,
+            environment,
+            private_environment,
+            source_text: _,
+            source_code,
+        } = self;
+        realm.sweep_values(compactions);
+        object_index.sweep_values(compactions);
+        environment.sweep_values(compactions);
+        private_environment.sweep_values(compactions);
+        source_code.sweep_values(compactions);
+        compiled_initializer_bytecode.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/builtins/builtin_function.rs

@@ -540,14 +540,28 @@ impl HeapMarkAndSweep for BuiltinFunction {
 
 impl HeapMarkAndSweep for BuiltinFunctionHeapData {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.realm.mark_values(queues);
-        self.initial_name.mark_values(queues);
-        self.object_index.mark_values(queues);
+        let Self {
+            object_index,
+            length: _,
+            realm,
+            initial_name,
+            behaviour: _,
+        } = self;
+        realm.mark_values(queues);
+        initial_name.mark_values(queues);
+        object_index.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.realm.sweep_values(compactions);
-        self.initial_name.sweep_values(compactions);
-        self.object_index.sweep_values(compactions);
+        let Self {
+            object_index,
+            length: _,
+            realm,
+            initial_name,
+            behaviour: _,
+        } = self;
+        realm.sweep_values(compactions);
+        initial_name.sweep_values(compactions);
+        object_index.sweep_values(compactions);
     }
 }

nova_vm/src/ecmascript/builtins/control_abstraction_objects/async_function_objects/await_reaction.rs

@@ -68,8 +68,7 @@ impl AwaitReactionIdentifier {
         // 5. d. Resume the suspended evaluation of asyncContext using ThrowCompletion(reason) as the result of the operation that suspended it.
         let vm = agent[self].vm.take().unwrap();
         let async_function = agent[self].async_function.unwrap();
-        // SAFETY: We keep the async function alive.
-        let executable = unsafe { agent[async_function].compiled_bytecode.unwrap().as_ref() };
+        let executable = agent[async_function].compiled_bytecode.unwrap();
         let execution_result = match reaction_type {
             PromiseReactionType::Fulfill => vm.resume(agent, executable, value),
             PromiseReactionType::Reject => vm.resume_throw(agent, executable, value),
@@ -179,14 +178,28 @@ impl CreateHeapData<AwaitReaction, AwaitReactionIdentifier> for Heap {
 
 impl HeapMarkAndSweep for AwaitReaction {
     fn mark_values(&self, queues: &mut WorkQueues) {
-        self.vm.mark_values(queues);
-        self.async_function.mark_values(queues);
-        self.return_promise_capability.mark_values(queues);
+        let Self {
+            vm,
+            async_function,
+            execution_context,
+            return_promise_capability,
+        } = self;
+        vm.mark_values(queues);
+        async_function.mark_values(queues);
+        execution_context.mark_values(queues);
+        return_promise_capability.mark_values(queues);
     }
 
     fn sweep_values(&mut self, compactions: &CompactionLists) {
-        self.vm.sweep_values(compactions);
-        self.async_function.sweep_values(compactions);
-        self.return_promise_capability.sweep_values(compactions);
+        let Self {
+            vm,
+            async_function,
+            execution_context,
+            return_promise_capability,
+        } = self;
+        vm.sweep_values(compactions);
+        async_function.sweep_values(compactions);
+        execution_context.sweep_values(compactions);
+        return_promise_capability.sweep_values(compactions);
     }
 }