LibJS: Lazily collect stack trace information

The previous implementation was calling `backtrace()` for every
function call, which is quite slow.

Instead, this implementation provides VM::stack_trace() which unwinds
the native stack, maps it through NativeExecutable::get_source_range
and combines it with source ranges from interpreted call frames.

Userland/Libraries/LibJS/Runtime/Error.cpp

@@ -75,13 +75,13 @@ ThrowCompletionOr<void> Error::install_error_cause(Value options)
 
 void Error::populate_stack()
 {
-    auto& vm = this->vm();
-    m_traceback.ensure_capacity(vm.execution_context_stack().size());
-    for (ssize_t i = vm.execution_context_stack().size() - 1; i >= 0; i--) {
-        auto context = vm.execution_context_stack()[i];
+    auto stack_trace = vm().stack_trace();
+    m_traceback.ensure_capacity(stack_trace.size());
+    for (auto& element : stack_trace) {
+        auto* context = element.execution_context;
         UnrealizedSourceRange range = {};
-        if (context->instruction_stream_iterator.has_value())
-            range = context->instruction_stream_iterator->source_range();
+        if (element.source_range.has_value())
+            range = element.source_range.value();
         TracebackFrame frame {
             .function_name = context->function_name,
             .source_range_storage = range,

Userland/Libraries/LibJS/Runtime/ExecutionContext.h

@@ -51,9 +51,16 @@ public:
     MarkedVector<Value> local_variables;
     bool is_strict_mode { false };
 
+    RefPtr<Bytecode::Executable> executable;
+
     // https://html.spec.whatwg.org/multipage/webappapis.html#skip-when-determining-incumbent-counter
     // FIXME: Move this out of LibJS (e.g. by using the CustomData concept), as it's used exclusively by LibWeb.
     size_t skip_when_determining_incumbent_counter { 0 };
 };
 
+struct StackTraceElement {
+    ExecutionContext* execution_context;
+    Optional<UnrealizedSourceRange> source_range;
+};
+
 }

Userland/Libraries/LibJS/Runtime/VM.cpp

@@ -15,6 +15,7 @@
 #include <LibFileSystem/FileSystem.h>
 #include <LibJS/AST.h>
 #include <LibJS/Bytecode/Interpreter.h>
+#include <LibJS/JIT/NativeExecutable.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/BoundFunction.h>
@@ -1135,4 +1136,66 @@ void VM::pop_execution_context()
         on_call_stack_emptied();
 }
 
+#if ARCH(X86_64)
+struct [[gnu::packed]] NativeStackFrame {
+    NativeStackFrame* prev;
+    FlatPtr return_address;
+};
+#endif
+
+Vector<FlatPtr> VM::get_native_stack_trace() const
+{
+    Vector<FlatPtr> buffer;
+#if ARCH(X86_64)
+    // Manually walk the stack, because backtrace() does not traverse through JIT frames.
+    auto* frame = bit_cast<NativeStackFrame*>(__builtin_frame_address(0));
+    while (bit_cast<FlatPtr>(frame) < m_stack_info.top() && bit_cast<FlatPtr>(frame) >= m_stack_info.base()) {
+        buffer.append(frame->return_address);
+        frame = frame->prev;
+    }
+#endif
+    return buffer;
+}
+
+static Optional<UnrealizedSourceRange> get_source_range(ExecutionContext const* context, Vector<FlatPtr> const& native_stack)
+{
+    // native function
+    if (!context->executable)
+        return {};
+
+    auto const* native_executable = context->executable->native_executable();
+    if (!native_executable) {
+        // Interpreter frame
+        if (context->instruction_stream_iterator.has_value())
+            return context->instruction_stream_iterator->source_range();
+        return {};
+    }
+
+    // JIT frame
+    for (auto address : native_stack) {
+        auto range = native_executable->get_source_range(*context->executable, address);
+        if (range.has_value()) {
+            auto realized = range->realize();
+            return range;
+        }
+    }
+
+    return {};
+}
+
+Vector<StackTraceElement> VM::stack_trace() const
+{
+    auto native_stack = get_native_stack_trace();
+    Vector<StackTraceElement> stack_trace;
+    for (ssize_t i = m_execution_context_stack.size() - 1; i >= 0; i--) {
+        auto* context = m_execution_context_stack[i];
+        stack_trace.append({
+            .execution_context = context,
+            .source_range = get_source_range(context, native_stack).value_or({}),
+        });
+    }
+
+    return stack_trace;
+}
+
 }

Userland/Libraries/LibJS/Runtime/VM.h

@@ -254,6 +254,8 @@ public:
     // NOTE: This is meant as a temporary stopgap until everything is bytecode.
     ThrowCompletionOr<Value> execute_ast_node(ASTNode const&);
 
+    Vector<StackTraceElement> stack_trace() const;
+
 private:
     using ErrorMessages = AK::Array<String, to_underlying(ErrorMessage::__Count)>;
 
@@ -277,6 +279,8 @@ private:
 
     void set_well_known_symbols(WellKnownSymbols well_known_symbols) { m_well_known_symbols = move(well_known_symbols); }
 
+    Vector<FlatPtr> get_native_stack_trace() const;
+
     HashMap<String, GCPtr<PrimitiveString>> m_string_cache;
     HashMap<DeprecatedString, GCPtr<PrimitiveString>> m_deprecated_string_cache;