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// Copyright 2022 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/builtins/builtins-utils-inl.h"
#include "src/objects/js-struct-inl.h"
#include "src/objects/property-details.h"
namespace v8 {
namespace internal {
constexpr int kMaxJSStructFields = 999;
// Note: For Wasm structs, we currently allow 2000 fields, because there was
// specific demand for that. Ideally we'd have the same limit, but JS structs
// rely on DescriptorArrays and are hence limited to 1020 fields at most.
static_assert(kMaxJSStructFields <= kMaxNumberOfDescriptors);
BUILTIN(SharedStructTypeConstructor) {
DCHECK(v8_flags.shared_string_table);
HandleScope scope(isolate);
static const char method_name[] = "SharedStructType";
auto* factory = isolate->factory();
Handle<JSReceiver> field_names_arg;
ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
isolate, field_names_arg,
Object::ToObject(isolate, args.atOrUndefined(isolate, 1), method_name));
// Treat field_names_arg as arraylike.
Handle<Object> raw_length_number;
ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
isolate, raw_length_number,
Object::GetLengthFromArrayLike(isolate, field_names_arg));
double num_properties_double = raw_length_number->Number();
if (num_properties_double < 0 || num_properties_double > kMaxJSStructFields) {
THROW_NEW_ERROR_RETURN_FAILURE(
isolate, NewRangeError(MessageTemplate::kStructFieldCountOutOfRange));
}
int num_properties = static_cast<int>(num_properties_double);
Handle<DescriptorArray> descriptors = factory->NewDescriptorArray(
num_properties, 0, AllocationType::kSharedOld);
// Build up the descriptor array.
for (int i = 0; i < num_properties; ++i) {
Handle<Object> raw_field_name;
ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
isolate, raw_field_name,
JSReceiver::GetElement(isolate, field_names_arg, i));
Handle<Name> field_name;
ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, field_name,
Object::ToName(isolate, raw_field_name));
field_name = factory->InternalizeName(field_name);
// Shared structs' fields need to be aligned, so make it all tagged.
PropertyDetails details(
PropertyKind::kData, SEALED, PropertyLocation::kField,
PropertyConstness::kMutable, Representation::Tagged(), i);
descriptors->Set(InternalIndex(i), *field_name,
MaybeObject::FromObject(FieldType::Any()), details);
}
descriptors->Sort();
Handle<SharedFunctionInfo> info =
isolate->factory()->NewSharedFunctionInfoForBuiltin(
isolate->factory()->empty_string(), Builtin::kSharedStructConstructor,
FunctionKind::kNormalFunction);
info->set_internal_formal_parameter_count(JSParameterCount(0));
info->set_length(0);
Handle<JSFunction> constructor =
Factory::JSFunctionBuilder{isolate, info, isolate->native_context()}
.set_map(isolate->strict_function_map())
.Build();
int instance_size;
int in_object_properties;
JSFunction::CalculateInstanceSizeHelper(JS_SHARED_STRUCT_TYPE, false, 0,
num_properties, &instance_size,
&in_object_properties);
Handle<Map> instance_map = factory->NewMap(
JS_SHARED_STRUCT_TYPE, instance_size, TERMINAL_FAST_ELEMENTS_KIND,
in_object_properties, AllocationType::kSharedMap);
instance_map->InitializeDescriptors(isolate, *descriptors);
// Structs have fixed layout ahead of time, so there's no slack.
instance_map->SetInObjectUnusedPropertyFields(0);
instance_map->set_is_extensible(false);
JSFunction::SetInitialMap(isolate, constructor, instance_map,
factory->null_value());
// The constructor is not a shared object, so the shared map should not point
// to it.
instance_map->set_constructor_or_back_pointer(*factory->null_value());
return *constructor;
}
BUILTIN(SharedStructConstructor) {
HandleScope scope(isolate);
return *isolate->factory()->NewJSSharedStruct(args.target());
}
} // namespace internal
} // namespace v8
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