LibWasm+Meta: Implement instantiation/execution primitives in test-wasm

This also optionally generates a test suite from the WebAssembly
testsuite, which can be enabled via passing `INCLUDE_WASM_SPEC_TESTS`
to cmake, which will generate test-wasm-compatible tests and the
required fixtures.
The generated directories are excluded from git since there's no point
in committing them.

Tests/LibWasm/test-wasm.cpp

@@ -27,6 +27,36 @@ TESTJS_GLOBAL_FUNCTION(read_binary_wasm_file, readBinaryWasmFile)
     return array;
 }
 
+class WebAssemblyModule final : public JS::Object {
+    JS_OBJECT(WebAssemblyModule, JS::Object);
+
+public:
+    // FIXME: This should only contain an instantiated module, not the entire abstract machine!
+    explicit WebAssemblyModule(JS::Object& prototype)
+        : JS::Object(prototype)
+    {
+    }
+
+    static WebAssemblyModule* create(JS::GlobalObject& global_object, Wasm::Module module)
+    {
+        auto instance = global_object.heap().allocate<WebAssemblyModule>(global_object, *global_object.object_prototype());
+        instance->m_module = move(module);
+        if (auto result = instance->m_machine.instantiate(*instance->m_module, {}); result.is_error())
+            global_object.vm().throw_exception<JS::TypeError>(global_object, result.release_error().error);
+        return instance;
+    }
+    void initialize(JS::GlobalObject&) override;
+
+    ~WebAssemblyModule() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(get_export);
+    JS_DECLARE_NATIVE_FUNCTION(wasm_invoke);
+
+    Wasm::AbstractMachine m_machine;
+    Optional<Wasm::Module> m_module;
+};
+
 TESTJS_GLOBAL_FUNCTION(parse_webassembly_module, parseWebAssemblyModule)
 {
     auto object = vm.argument(0).to_object(global_object);
@@ -43,9 +73,12 @@ TESTJS_GLOBAL_FUNCTION(parse_webassembly_module, parseWebAssemblyModule)
         vm.throw_exception<JS::SyntaxError>(global_object, Wasm::parse_error_to_string(result.error()));
         return {};
     }
-    if (stream.handle_any_error())
-        return JS::js_undefined();
-    return JS::js_null();
+
+    if (stream.handle_any_error()) {
+        vm.throw_exception<JS::SyntaxError>(global_object, "Bianry stream contained errors");
+        return {};
+    }
+    return WebAssemblyModule::create(global_object, result.release_value());
 }
 
 TESTJS_GLOBAL_FUNCTION(compare_typed_arrays, compareTypedArrays)
@@ -68,3 +101,112 @@ TESTJS_GLOBAL_FUNCTION(compare_typed_arrays, compareTypedArrays)
     auto& rhs_array = static_cast<JS::TypedArrayBase&>(*rhs);
     return JS::Value(lhs_array.viewed_array_buffer()->buffer() == rhs_array.viewed_array_buffer()->buffer());
 }
+
+void WebAssemblyModule::initialize(JS::GlobalObject& global_object)
+{
+    Base::initialize(global_object);
+    define_native_function("getExport", get_export);
+    define_native_function("invoke", wasm_invoke);
+}
+
+JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::get_export)
+{
+    auto name = vm.argument(0).to_string(global_object);
+    if (vm.exception())
+        return {};
+    auto this_value = vm.this_value(global_object);
+    auto object = this_value.to_object(global_object);
+    if (vm.exception())
+        return {};
+    if (!object || !is<WebAssemblyModule>(object)) {
+        vm.throw_exception<JS::TypeError>(global_object, "Not a WebAssemblyModule");
+        return {};
+    }
+    auto instance = static_cast<WebAssemblyModule*>(object);
+    for (auto& entry : instance->m_machine.module_instance().exports()) {
+        if (entry.name() == name) {
+            auto& value = entry.value();
+            if (auto ptr = value.get_pointer<Wasm::FunctionAddress>())
+                return JS::Value(static_cast<unsigned long>(ptr->value()));
+            vm.throw_exception<JS::TypeError>(global_object, String::formatted("'{}' does not refer to a function", name));
+            return {};
+        }
+    }
+    vm.throw_exception<JS::TypeError>(global_object, String::formatted("'{}' could not be found", name));
+    return {};
+}
+
+JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::wasm_invoke)
+{
+    auto address = static_cast<unsigned long>(vm.argument(0).to_double(global_object));
+    if (vm.exception())
+        return {};
+    auto this_value = vm.this_value(global_object);
+    auto object = this_value.to_object(global_object);
+    if (vm.exception())
+        return {};
+    if (!object || !is<WebAssemblyModule>(object)) {
+        vm.throw_exception<JS::TypeError>(global_object, "Not a WebAssemblyModule");
+        return {};
+    }
+    auto instance = static_cast<WebAssemblyModule*>(object);
+    Wasm::FunctionAddress function_address { address };
+    auto function_instance = instance->m_machine.store().get(function_address);
+    if (!function_instance) {
+        vm.throw_exception<JS::TypeError>(global_object, "Invalid function address");
+        return {};
+    }
+
+    const Wasm::FunctionType* type { nullptr };
+    function_instance->visit([&](auto& value) { type = &value.type(); });
+    if (!type) {
+        vm.throw_exception<JS::TypeError>(global_object, "Invalid function found at given address");
+        return {};
+    }
+
+    Vector<Wasm::Value> arguments;
+    if (type->parameters().size() + 1 > vm.argument_count()) {
+        vm.throw_exception<JS::TypeError>(global_object, String::formatted("Expected {} arguments for call, but found {}", type->parameters().size() + 1, vm.argument_count()));
+        return {};
+    }
+    size_t index = 1;
+    for (auto& param : type->parameters()) {
+        auto value = vm.argument(index++).to_double(global_object);
+        switch (param.kind()) {
+        case Wasm::ValueType::Kind::I32:
+            arguments.append(Wasm::Value(static_cast<i32>(value)));
+            break;
+        case Wasm::ValueType::Kind::I64:
+            arguments.append(Wasm::Value(static_cast<i64>(value)));
+            break;
+        case Wasm::ValueType::Kind::F32:
+            arguments.append(Wasm::Value(static_cast<float>(value)));
+            break;
+        case Wasm::ValueType::Kind::F64:
+            arguments.append(Wasm::Value(static_cast<double>(value)));
+            break;
+        case Wasm::ValueType::Kind::FunctionReference:
+            arguments.append(Wasm::Value(Wasm::FunctionAddress { static_cast<u64>(value) }));
+            break;
+        case Wasm::ValueType::Kind::ExternReference:
+            arguments.append(Wasm::Value(Wasm::ExternAddress { static_cast<u64>(value) }));
+            break;
+        }
+    }
+
+    auto result = instance->m_machine.invoke(function_address, arguments);
+    if (result.is_trap()) {
+        vm.throw_exception<JS::TypeError>(global_object, "Execution trapped");
+        return {};
+    }
+
+    if (result.values().is_empty())
+        return JS::js_null();
+
+    JS::Value return_value;
+    result.values().first().value().visit(
+        [&](const auto& value) { return_value = JS::Value(static_cast<double>(value)); },
+        [&](const Wasm::FunctionAddress& index) { return_value = JS::Value(static_cast<double>(index.value())); },
+        [&](const Wasm::ExternAddress& index) { return_value = JS::Value(static_cast<double>(index.value())); });
+    return return_value;
+}