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LibJS: Allocate ExecutionContext memory using alloca() when possible

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This should be faster than heap allocation. However, heap allocation is
still necessary in some cases, such as with generators and async
functions.
This commit is contained in:
Aliaksandr Kalenik 2025-04-23 23:44:24 +02:00 • committed by Andreas Kling
commit a329868c1b
Notes: github-actions[bot] 2025-04-24 08:32:11 +00:00
10 changed files with 42 additions and 12 deletions
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3
Libraries/LibJS/Runtime/AbstractOperations.cpp
View file

@ -662,7 +662,8 @@ ThrowCompletionOr<Value> perform_eval(VM& vm, Value x, CallerMode strict_caller,
executable->dump();
// 20. Let evalContext be a new ECMAScript code execution context.
auto eval_context = ExecutionContext::create(executable->number_of_registers + executable->constants.size() + executable->local_variable_names.size(), 0);
ExecutionContext* eval_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(eval_context, executable->number_of_registers + executable->constants.size() + executable->local_variable_names.size(), 0);
// 21. Set evalContext's Function to null.
// NOTE: This was done in the construction of eval_context.

8
Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
View file

@ -501,7 +501,9 @@ ThrowCompletionOr<Value> ECMAScriptFunctionObject::internal_call(Value this_argu
}
u32 arguments_count = max(arguments_list.size(), formal_parameters().size());
auto callee_context = ExecutionContext::create(m_bytecode_executable->number_of_registers + m_bytecode_executable->constants.size() + m_bytecode_executable->local_variable_names.size(), arguments_count);
auto registers_and_constants_and_locals_count = m_bytecode_executable->number_of_registers + m_bytecode_executable->constants.size() + m_bytecode_executable->local_variable_names.size();
ExecutionContext* callee_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(callee_context, registers_and_constants_and_locals_count, arguments_count);
// Non-standard
auto arguments = callee_context->arguments();
@ -571,7 +573,9 @@ ThrowCompletionOr<GC::Ref<Object>> ECMAScriptFunctionObject::internal_construct(
}
u32 arguments_count = max(arguments_list.size(), formal_parameters().size());
auto callee_context = ExecutionContext::create(m_bytecode_executable->number_of_registers + m_bytecode_executable->constants.size() + m_bytecode_executable->local_variable_names.size(), arguments_count);
auto registers_and_constants_and_locals_count = m_bytecode_executable->number_of_registers + m_bytecode_executable->constants.size() + m_bytecode_executable->local_variable_names.size();
ExecutionContext* callee_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(callee_context, registers_and_constants_and_locals_count, arguments_count);
// Non-standard
auto arguments = callee_context->arguments();

18
Libraries/LibJS/Runtime/ExecutionContext.h
View file

@ -43,9 +43,9 @@ struct ExecutionContext {
private:
friend class ExecutionContextAllocator;
public:
ExecutionContext(u32 registers_and_constants_and_locals_count, u32 arguments_count);
public:
void operator delete(void* ptr);
GC::Ptr<FunctionObject> function; // [[Function]]
@ -123,6 +123,22 @@ private:
u32 registers_and_constants_and_locals_and_arguments_count { 0 };
};
#define ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(execution_context, \
registers_and_constants_and_locals_count, \
arguments_count) \
auto execution_context_size = sizeof(JS::ExecutionContext) \
+ ((registers_and_constants_and_locals_count) + (arguments_count)) \
* sizeof(JS::Value); \
\
void* execution_context_memory = alloca(execution_context_size); \
\
execution_context = new (execution_context_memory) \
JS::ExecutionContext((registers_and_constants_and_locals_count), (arguments_count)); \
\
ScopeGuard run_execution_context_destructor([execution_context] { \
execution_context->~ExecutionContext(); \
})
struct StackTraceElement {
ExecutionContext* execution_context;
RefPtr<CachedSourceRange> source_range;

6
Libraries/LibJS/Runtime/NativeFunction.cpp
View file

@ -119,7 +119,8 @@ ThrowCompletionOr<Value> NativeFunction::internal_call(Value this_argument, Read
// 2. If callerContext is not already suspended, suspend callerContext.
// 3. Let calleeContext be a new execution context.
auto callee_context = ExecutionContext::create(0, arguments_list.size());
ExecutionContext* callee_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(callee_context, 0, arguments_list.size());
// 4. Set the Function of calleeContext to F.
callee_context->function = this;
@ -181,7 +182,8 @@ ThrowCompletionOr<GC::Ref<Object>> NativeFunction::internal_construct(ReadonlySp
// 2. If callerContext is not already suspended, suspend callerContext.
// 3. Let calleeContext be a new execution context.
auto callee_context = ExecutionContext::create(0, arguments_list.size());
ExecutionContext* callee_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(callee_context, 0, arguments_list.size());
// 4. Set the Function of calleeContext to F.
callee_context->function = this;

4
Libraries/LibJS/Runtime/WrappedFunction.cpp
View file

@ -62,7 +62,9 @@ ThrowCompletionOr<Value> WrappedFunction::internal_call(Value this_argument, Rea
// NOTE: No-op, kept by the VM in its execution context stack.
// 2. Let calleeContext be PrepareForWrappedFunctionCall(F).
auto callee_context = ExecutionContext::create(0, 0);
ExecutionContext* callee_context = nullptr;
ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(callee_context, 0, 0);
prepare_for_wrapped_function_call(*this, *callee_context);
// 3. Assert: calleeContext is now the running execution context.