path: root/deps/v8/src/wasm/wasm-objects.cc

// Copyright 2015 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/wasm/wasm-objects.h"

#include "src/base/iterator.h"
#include "src/codegen/assembler-inl.h"
#include "src/codegen/code-factory.h"
#include "src/compiler/wasm-compiler.h"
#include "src/debug/debug-interface.h"
#include "src/logging/counters.h"
#include "src/objects/debug-objects-inl.h"
#include "src/objects/objects-inl.h"
#include "src/objects/shared-function-info.h"
#include "src/objects/struct-inl.h"
#include "src/trap-handler/trap-handler.h"
#include "src/utils/utils.h"
#include "src/utils/vector.h"
#include "src/wasm/jump-table-assembler.h"
#include "src/wasm/module-compiler.h"
#include "src/wasm/module-decoder.h"
#include "src/wasm/module-instantiate.h"
#include "src/wasm/value-type.h"
#include "src/wasm/wasm-code-manager.h"
#include "src/wasm/wasm-engine.h"
#include "src/wasm/wasm-limits.h"
#include "src/wasm/wasm-module.h"
#include "src/wasm/wasm-objects-inl.h"
#include "src/wasm/wasm-subtyping.h"
#include "src/wasm/wasm-value.h"

#define TRACE_IFT(...)              \
  do {                              \
    if (false) PrintF(__VA_ARGS__); \
  } while (false)

namespace v8 {
namespace internal {

// Import a few often used types from the wasm namespace.
using WasmFunction = wasm::WasmFunction;
using WasmModule = wasm::WasmModule;

namespace {

// Manages the natively-allocated memory for a WasmInstanceObject. Since
// an instance finalizer is not guaranteed to run upon isolate shutdown,
// we must use a Managed<WasmInstanceNativeAllocations> to guarantee
// it is freed.
// Native allocations are the signature ids and targets for indirect call
// targets, as well as the call targets for imported functions.
class WasmInstanceNativeAllocations {
 public:
// Helper macro to set an internal field and the corresponding field
// on an instance.
#define SET(instance, field, value) \
  instance->set_##field((this->field##_ = value).get());

  // Allocates initial native storage for a given instance.
  WasmInstanceNativeAllocations(Handle<WasmInstanceObject> instance,
                                size_t num_imported_functions,
                                size_t num_imported_mutable_globals,
                                size_t num_data_segments,
                                size_t num_elem_segments) {
    SET(instance, imported_function_targets,
        std::make_unique<Address[]>(num_imported_functions));
    SET(instance, imported_mutable_globals,
        std::make_unique<Address[]>(num_imported_mutable_globals));
    SET(instance, data_segment_starts,
        std::make_unique<Address[]>(num_data_segments));
    SET(instance, data_segment_sizes,
        std::make_unique<uint32_t[]>(num_data_segments));
    SET(instance, dropped_elem_segments,
        std::make_unique<uint8_t[]>(num_elem_segments));
  }

  uint32_t indirect_function_table_capacity() const {
    return indirect_function_table_capacity_;
  }

  // Resizes the indirect function table.
  void resize_indirect_function_table(Isolate* isolate,
                                      Handle<WasmInstanceObject> instance,
                                      uint32_t new_capacity) {
    uint32_t old_capacity = indirect_function_table_capacity_;
    DCHECK_LT(old_capacity, new_capacity);
    // Grow exponentially to support repeated re-allocation.
    new_capacity = std::max(new_capacity, 2 * old_capacity);
    CHECK_GE(kMaxInt, old_capacity);
    CHECK_GE(kMaxInt, new_capacity);

    SET(instance, indirect_function_table_sig_ids,
        grow(indirect_function_table_sig_ids_.get(), old_capacity,
             new_capacity));
    SET(instance, indirect_function_table_targets,
        grow(indirect_function_table_targets_.get(), old_capacity,
             new_capacity));

    Handle<FixedArray> old_refs(instance->indirect_function_table_refs(),
                                isolate);
    Handle<FixedArray> new_refs = isolate->factory()->CopyFixedArrayAndGrow(
        old_refs, static_cast<int>(new_capacity - old_capacity));
    instance->set_indirect_function_table_refs(*new_refs);
    indirect_function_table_capacity_ = new_capacity;
  }

 private:
  template <typename T>
  std::unique_ptr<T[]> grow(T* old_arr, size_t old_size, size_t new_size) {
    std::unique_ptr<T[]> new_arr = std::make_unique<T[]>(new_size);
    std::copy_n(old_arr, old_size, new_arr.get());
    return new_arr;
  }

  uint32_t indirect_function_table_capacity_ = 0;
  std::unique_ptr<uint32_t[]> indirect_function_table_sig_ids_;
  std::unique_ptr<Address[]> indirect_function_table_targets_;
  std::unique_ptr<Address[]> imported_function_targets_;
  std::unique_ptr<Address[]> imported_mutable_globals_;
  std::unique_ptr<Address[]> data_segment_starts_;
  std::unique_ptr<uint32_t[]> data_segment_sizes_;
  std::unique_ptr<uint8_t[]> dropped_elem_segments_;
#undef SET
};

size_t EstimateNativeAllocationsSize(const WasmModule* module) {
  size_t estimate =
      sizeof(WasmInstanceNativeAllocations) +
      (1 * kSystemPointerSize * module->num_imported_mutable_globals) +
      (2 * kSystemPointerSize * module->num_imported_functions) +
      ((kSystemPointerSize + sizeof(uint32_t) + sizeof(uint8_t)) *
       module->num_declared_data_segments);
  for (auto& table : module->tables) {
    estimate += 3 * kSystemPointerSize * table.initial_size;
  }
  return estimate;
}

WasmInstanceNativeAllocations* GetNativeAllocations(
    WasmInstanceObject instance) {
  return Managed<WasmInstanceNativeAllocations>::cast(
             instance.managed_native_allocations())
      .raw();
}

enum DispatchTableElements : int {
  kDispatchTableInstanceOffset,
  kDispatchTableIndexOffset,
  kDispatchTableFunctionTableOffset,
  // Marker:
  kDispatchTableNumElements
};

}  // namespace

// static
Handle<WasmModuleObject> WasmModuleObject::New(
    Isolate* isolate, std::shared_ptr<wasm::NativeModule> native_module,
    Handle<Script> script) {
  Handle<FixedArray> export_wrappers = isolate->factory()->NewFixedArray(0);
  return New(isolate, std::move(native_module), script, export_wrappers);
}

// static
Handle<WasmModuleObject> WasmModuleObject::New(
    Isolate* isolate, std::shared_ptr<wasm::NativeModule> native_module,
    Handle<Script> script, Handle<FixedArray> export_wrappers) {
  Handle<Managed<wasm::NativeModule>> managed_native_module;
  if (script->type() == Script::TYPE_WASM) {
    managed_native_module = handle(
        Managed<wasm::NativeModule>::cast(script->wasm_managed_native_module()),
        isolate);
  } else {
    const WasmModule* module = native_module->module();
    size_t memory_estimate =
        native_module->committed_code_space() +
        wasm::WasmCodeManager::EstimateNativeModuleMetaDataSize(module);
    managed_native_module = Managed<wasm::NativeModule>::FromSharedPtr(
        isolate, memory_estimate, std::move(native_module));
  }
  Handle<WasmModuleObject> module_object = Handle<WasmModuleObject>::cast(
      isolate->factory()->NewJSObject(isolate->wasm_module_constructor()));
  module_object->set_export_wrappers(*export_wrappers);
  module_object->set_managed_native_module(*managed_native_module);
  module_object->set_script(*script);
  return module_object;
}

Handle<String> WasmModuleObject::ExtractUtf8StringFromModuleBytes(
    Isolate* isolate, Handle<WasmModuleObject> module_object,
    wasm::WireBytesRef ref, InternalizeString internalize) {
  Vector<const uint8_t> wire_bytes =
      module_object->native_module()->wire_bytes();
  return ExtractUtf8StringFromModuleBytes(isolate, wire_bytes, ref,
                                          internalize);
}

Handle<String> WasmModuleObject::ExtractUtf8StringFromModuleBytes(
    Isolate* isolate, Vector<const uint8_t> wire_bytes, wasm::WireBytesRef ref,
    InternalizeString internalize) {
  Vector<const uint8_t> name_vec =
      wire_bytes.SubVector(ref.offset(), ref.end_offset());
  // UTF8 validation happens at decode time.
  DCHECK(unibrow::Utf8::ValidateEncoding(name_vec.begin(), name_vec.length()));
  auto* factory = isolate->factory();
  return internalize
             ? factory->InternalizeUtf8String(
                   Vector<const char>::cast(name_vec))
             : factory->NewStringFromUtf8(Vector<const char>::cast(name_vec))
                   .ToHandleChecked();
}

MaybeHandle<String> WasmModuleObject::GetModuleNameOrNull(
    Isolate* isolate, Handle<WasmModuleObject> module_object) {
  const WasmModule* module = module_object->module();
  if (!module->name.is_set()) return {};
  return ExtractUtf8StringFromModuleBytes(isolate, module_object, module->name,
                                          kNoInternalize);
}

MaybeHandle<String> WasmModuleObject::GetFunctionNameOrNull(
    Isolate* isolate, Handle<WasmModuleObject> module_object,
    uint32_t func_index) {
  DCHECK_LT(func_index, module_object->module()->functions.size());
  wasm::WireBytesRef name =
      module_object->module()->lazily_generated_names.LookupFunctionName(
          wasm::ModuleWireBytes(module_object->native_module()->wire_bytes()),
          func_index, VectorOf(module_object->module()->export_table));
  if (!name.is_set()) return {};
  return ExtractUtf8StringFromModuleBytes(isolate, module_object, name,
                                          kNoInternalize);
}

Handle<String> WasmModuleObject::GetFunctionName(
    Isolate* isolate, Handle<WasmModuleObject> module_object,
    uint32_t func_index) {
  MaybeHandle<String> name =
      GetFunctionNameOrNull(isolate, module_object, func_index);
  if (!name.is_null()) return name.ToHandleChecked();
  EmbeddedVector<char, 32> buffer;
  DCHECK_GE(func_index, module_object->module()->num_imported_functions);
  int length = SNPrintF(buffer, "func%u", func_index);
  return isolate->factory()
      ->NewStringFromOneByte(Vector<uint8_t>::cast(buffer.SubVector(0, length)))
      .ToHandleChecked();
}

Vector<const uint8_t> WasmModuleObject::GetRawFunctionName(
    uint32_t func_index) {
  DCHECK_GT(module()->functions.size(), func_index);
  wasm::ModuleWireBytes wire_bytes(native_module()->wire_bytes());
  wasm::WireBytesRef name_ref =
      module()->lazily_generated_names.LookupFunctionName(
          wire_bytes, func_index, VectorOf(module()->export_table));
  wasm::WasmName name = wire_bytes.GetNameOrNull(name_ref);
  return Vector<const uint8_t>::cast(name);
}

Handle<WasmTableObject> WasmTableObject::New(
    Isolate* isolate, Handle<WasmInstanceObject> instance, wasm::ValueType type,
    uint32_t initial, bool has_maximum, uint32_t maximum,
    Handle<FixedArray>* entries) {
  // TODO(7748): Make this work with other types when spec clears up.
  {
    const WasmModule* module =
        instance.is_null() ? nullptr : instance->module();
    CHECK(wasm::WasmTable::IsValidTableType(type, module));
  }

  Handle<FixedArray> backing_store = isolate->factory()->NewFixedArray(initial);
  Object null = ReadOnlyRoots(isolate).null_value();
  for (int i = 0; i < static_cast<int>(initial); ++i) {
    backing_store->set(i, null);
  }

  Handle<Object> max;
  if (has_maximum) {
    max = isolate->factory()->NewNumberFromUint(maximum);
  } else {
    max = isolate->factory()->undefined_value();
  }

  Handle<JSFunction> table_ctor(
      isolate->native_context()->wasm_table_constructor(), isolate);
  auto table_obj = Handle<WasmTableObject>::cast(
      isolate->factory()->NewJSObject(table_ctor));
  DisallowHeapAllocation no_gc;

  if (!instance.is_null()) table_obj->set_instance(*instance);
  table_obj->set_entries(*backing_store);
  table_obj->set_current_length(initial);
  table_obj->set_maximum_length(*max);
  table_obj->set_raw_type(static_cast<int>(type.heap_representation()));

  table_obj->set_dispatch_tables(ReadOnlyRoots(isolate).empty_fixed_array());
  if (entries != nullptr) {
    *entries = backing_store;
  }
  return Handle<WasmTableObject>::cast(table_obj);
}

void WasmTableObject::AddDispatchTable(Isolate* isolate,
                                       Handle<WasmTableObject> table_obj,
                                       Handle<WasmInstanceObject> instance,
                                       int table_index) {
  Handle<FixedArray> dispatch_tables(table_obj->dispatch_tables(), isolate);
  int old_length = dispatch_tables->length();
  DCHECK_EQ(0, old_length % kDispatchTableNumElements);

  if (instance.is_null()) return;
  // TODO(titzer): use weak cells here to avoid leaking instances.

  // Grow the dispatch table and add a new entry at the end.
  Handle<FixedArray> new_dispatch_tables =
      isolate->factory()->CopyFixedArrayAndGrow(dispatch_tables,
                                                kDispatchTableNumElements);

  new_dispatch_tables->set(old_length + kDispatchTableInstanceOffset,
                           *instance);
  new_dispatch_tables->set(old_length + kDispatchTableIndexOffset,
                           Smi::FromInt(table_index));

  table_obj->set_dispatch_tables(*new_dispatch_tables);
}

int WasmTableObject::Grow(Isolate* isolate, Handle<WasmTableObject> table,
                          uint32_t count, Handle<Object> init_value) {
  uint32_t old_size = table->current_length();
  if (count == 0) return old_size;  // Degenerate case: nothing to do.

  // Check if growing by {count} is valid.
  uint32_t max_size;
  if (!table->maximum_length().ToUint32(&max_size)) {
    max_size = FLAG_wasm_max_table_size;
  }
  max_size = std::min(max_size, FLAG_wasm_max_table_size);
  DCHECK_LE(old_size, max_size);
  if (max_size - old_size < count) return -1;

  uint32_t new_size = old_size + count;
  // Even with 2x over-allocation, there should not be an integer overflow.
  STATIC_ASSERT(wasm::kV8MaxWasmTableSize <= kMaxInt / 2);
  DCHECK_GE(kMaxInt, new_size);
  int old_capacity = table->entries().length();
  if (new_size > static_cast<uint32_t>(old_capacity)) {
    int grow = static_cast<int>(new_size) - old_capacity;
    // Grow at least by the old capacity, to implement exponential growing.
    grow = std::max(grow, old_capacity);
    // Never grow larger than the max size.
    grow = std::min(grow, static_cast<int>(max_size - old_capacity));
    auto new_store = isolate->factory()->CopyFixedArrayAndGrow(
        handle(table->entries(), isolate), grow);
    table->set_entries(*new_store, WriteBarrierMode::UPDATE_WRITE_BARRIER);
  }
  table->set_current_length(new_size);

  Handle<FixedArray> dispatch_tables(table->dispatch_tables(), isolate);
  DCHECK_EQ(0, dispatch_tables->length() % kDispatchTableNumElements);
  // Tables are stored in the instance object, no code patching is
  // necessary. We simply have to grow the raw tables in each instance
  // that has imported this table.

  // TODO(titzer): replace the dispatch table with a weak list of all
  // the instances that import a given table.
  for (int i = 0; i < dispatch_tables->length();
       i += kDispatchTableNumElements) {
    int table_index =
        Smi::cast(dispatch_tables->get(i + kDispatchTableIndexOffset)).value();

    Handle<WasmInstanceObject> instance(
        WasmInstanceObject::cast(dispatch_tables->get(i)), isolate);

    DCHECK_EQ(old_size, WasmInstanceObject::IndirectFunctionTableSize(
                            isolate, instance, table_index));
    WasmInstanceObject::EnsureIndirectFunctionTableWithMinimumSize(
        instance, table_index, new_size);
  }

  for (uint32_t entry = old_size; entry < new_size; ++entry) {
    WasmTableObject::Set(isolate, table, entry, init_value);
  }
  return old_size;
}

bool WasmTableObject::IsInBounds(Isolate* isolate,
                                 Handle<WasmTableObject> table,
                                 uint32_t entry_index) {
  return entry_index < static_cast<uint32_t>(table->current_length());
}

bool WasmTableObject::IsValidElement(Isolate* isolate,
                                     Handle<WasmTableObject> table,
                                     Handle<Object> entry) {
  const char* error_message;
  const WasmModule* module =
      !table->instance().IsUndefined()
          ? WasmInstanceObject::cast(table->instance()).module()
          : nullptr;
  return wasm::TypecheckJSObject(isolate, module, entry, table->type(),
                                 &error_message);
}

void WasmTableObject::SetFunctionTableEntry(Isolate* isolate,
                                            Handle<WasmTableObject> table,
                                            Handle<FixedArray> entries,
                                            int entry_index,
                                            Handle<Object> entry) {
  if (entry->IsNull(isolate)) {
    ClearDispatchTables(isolate, table, entry_index);  // Degenerate case.
    entries->set(entry_index, ReadOnlyRoots(isolate).null_value());
    return;
  }

  if (WasmExportedFunction::IsWasmExportedFunction(*entry)) {
    auto exported_function = Handle<WasmExportedFunction>::cast(entry);
    Handle<WasmInstanceObject> target_instance(exported_function->instance(),
                                               isolate);
    int func_index = exported_function->function_index();
    auto* wasm_function = &target_instance->module()->functions[func_index];
    DCHECK_NOT_NULL(wasm_function);
    DCHECK_NOT_NULL(wasm_function->sig);
    UpdateDispatchTables(isolate, table, entry_index, wasm_function->sig,
                         target_instance, func_index);
  } else if (WasmJSFunction::IsWasmJSFunction(*entry)) {
    UpdateDispatchTables(isolate, table, entry_index,
                         Handle<WasmJSFunction>::cast(entry));
  } else {
    DCHECK(WasmCapiFunction::IsWasmCapiFunction(*entry));
    UpdateDispatchTables(isolate, table, entry_index,
                         Handle<WasmCapiFunction>::cast(entry));
  }
  entries->set(entry_index, *entry);
}

void WasmTableObject::Set(Isolate* isolate, Handle<WasmTableObject> table,
                          uint32_t index, Handle<Object> entry) {
  // Callers need to perform bounds checks, type check, and error handling.
  DCHECK(IsInBounds(isolate, table, index));
  DCHECK(IsValidElement(isolate, table, entry));

  Handle<FixedArray> entries(table->entries(), isolate);
  // The FixedArray is addressed with int's.
  int entry_index = static_cast<int>(index);

  switch (table->type().heap_representation()) {
    case wasm::HeapType::kExtern:
    case wasm::HeapType::kExn:
      entries->set(entry_index, *entry);
      return;
    case wasm::HeapType::kFunc:
      SetFunctionTableEntry(isolate, table, entries, entry_index, entry);
      return;
    case wasm::HeapType::kEq:
    case wasm::HeapType::kI31:
      // TODO(7748): Implement once we have a story for struct/arrays/i31ref in
      // JS.
      UNIMPLEMENTED();
    case wasm::HeapType::kBottom:
      UNREACHABLE();
    default:
      DCHECK(!table->instance().IsUndefined());
      if (WasmInstanceObject::cast(table->instance())
              .module()
              ->has_signature(entry_index)) {
        SetFunctionTableEntry(isolate, table, entries, entry_index, entry);
        return;
      }
      // TODO(7748): Implement once we have a story for struct/arrays in JS.
      UNIMPLEMENTED();
  }
}

Handle<Object> WasmTableObject::Get(Isolate* isolate,
                                    Handle<WasmTableObject> table,
                                    uint32_t index) {
  Handle<FixedArray> entries(table->entries(), isolate);
  // Callers need to perform bounds checks and error handling.
  DCHECK(IsInBounds(isolate, table, index));

  // The FixedArray is addressed with int's.
  int entry_index = static_cast<int>(index);

  Handle<Object> entry(entries->get(entry_index), isolate);

  if (entry->IsNull(isolate)) {
    return entry;
  }

  switch (table->type().heap_representation()) {
    case wasm::HeapType::kExtern:
    case wasm::HeapType::kExn:
      return entry;
    case wasm::HeapType::kFunc:
      if (WasmExportedFunction::IsWasmExportedFunction(*entry) ||
          WasmJSFunction::IsWasmJSFunction(*entry) ||
          WasmCapiFunction::IsWasmCapiFunction(*entry)) {
        return entry;
      }
      break;
    case wasm::HeapType::kEq:
    case wasm::HeapType::kI31:
      // TODO(7748): Implement once we have a story for struct/arrays/i31ref in
      // JS.
      UNIMPLEMENTED();
    case wasm::HeapType::kBottom:
      UNREACHABLE();
    default:
      DCHECK(!table->instance().IsUndefined());
      if (WasmInstanceObject::cast(table->instance())
              .module()
              ->has_signature(entry_index)) {
        if (WasmExportedFunction::IsWasmExportedFunction(*entry) ||
            WasmJSFunction::IsWasmJSFunction(*entry) ||
            WasmCapiFunction::IsWasmCapiFunction(*entry)) {
          return entry;
        }
        break;
      }
      // TODO(7748): Implement once we have a story for struct/arrays in JS.
      UNIMPLEMENTED();
  }

  // {entry} is not a valid entry in the table. It has to be a placeholder
  // for lazy initialization.
  Handle<Tuple2> tuple = Handle<Tuple2>::cast(entry);
  auto instance = handle(WasmInstanceObject::cast(tuple->value1()), isolate);
  int function_index = Smi::cast(tuple->value2()).value();

  // Check if we already compiled a wrapper for the function but did not store
  // it in the table slot yet.
  entry = WasmInstanceObject::GetOrCreateWasmExternalFunction(isolate, instance,
                                                              function_index);
  entries->set(entry_index, *entry);
  return entry;
}

void WasmTableObject::Fill(Isolate* isolate, Handle<WasmTableObject> table,
                           uint32_t start, Handle<Object> entry,
                           uint32_t count) {
  // Bounds checks must be done by the caller.
  DCHECK_LE(start, table->current_length());
  DCHECK_LE(count, table->current_length());
  DCHECK_LE(start + count, table->current_length());

  for (uint32_t i = 0; i < count; i++) {
    WasmTableObject::Set(isolate, table, start + i, entry);
  }
}

void WasmTableObject::UpdateDispatchTables(
    Isolate* isolate, Handle<WasmTableObject> table, int entry_index,
    const wasm::FunctionSig* sig, Handle<WasmInstanceObject> target_instance,
    int target_func_index) {
  // We simply need to update the IFTs for each instance that imports
  // this table.
  Handle<FixedArray> dispatch_tables(table->dispatch_tables(), isolate);
  DCHECK_EQ(0, dispatch_tables->length() % kDispatchTableNumElements);

  for (int i = 0; i < dispatch_tables->length();
       i += kDispatchTableNumElements) {
    int table_index =
        Smi::cast(dispatch_tables->get(i + kDispatchTableIndexOffset)).value();
    Handle<WasmInstanceObject> instance(
        WasmInstanceObject::cast(
            dispatch_tables->get(i + kDispatchTableInstanceOffset)),
        isolate);
    // Note that {SignatureMap::Find} may return {-1} if the signature is
    // not found; it will simply never match any check.
    auto sig_id = instance->module()->signature_map.Find(*sig);
    IndirectFunctionTableEntry(instance, table_index, entry_index)
        .Set(sig_id, target_instance, target_func_index);
  }
}

void WasmTableObject::UpdateDispatchTables(Isolate* isolate,
                                           Handle<WasmTableObject> table,
                                           int entry_index,
                                           Handle<WasmJSFunction> function) {
  // We simply need to update the IFTs for each instance that imports
  // this table.
  Handle<FixedArray> dispatch_tables(table->dispatch_tables(), isolate);
  DCHECK_EQ(0, dispatch_tables->length() % kDispatchTableNumElements);

  for (int i = 0; i < dispatch_tables->length();
       i += kDispatchTableNumElements) {
    int table_index =
        Smi::cast(dispatch_tables->get(i + kDispatchTableIndexOffset)).value();
    Handle<WasmInstanceObject> instance(
        WasmInstanceObject::cast(
            dispatch_tables->get(i + kDispatchTableInstanceOffset)),
        isolate);
    WasmInstanceObject::ImportWasmJSFunctionIntoTable(
        isolate, instance, table_index, entry_index, function);
  }
}

void WasmTableObject::UpdateDispatchTables(
    Isolate* isolate, Handle<WasmTableObject> table, int entry_index,
    Handle<WasmCapiFunction> capi_function) {
  // We simply need to update the IFTs for each instance that imports
  // this table.
  Handle<FixedArray> dispatch_tables(table->dispatch_tables(), isolate);
  DCHECK_EQ(0, dispatch_tables->length() % kDispatchTableNumElements);

  // Reconstruct signature.
  // TODO(jkummerow): Unify with "SignatureHelper" in c-api.cc.
  PodArray<wasm::ValueType> serialized_sig =
      capi_function->GetSerializedSignature();
  int total_count = serialized_sig.length() - 1;
  std::unique_ptr<wasm::ValueType[]> reps(new wasm::ValueType[total_count]);
  int result_count;
  static const wasm::ValueType kMarker = wasm::kWasmStmt;
  for (int i = 0, j = 0; i <= total_count; i++) {
    if (serialized_sig.get(i) == kMarker) {
      result_count = i;
      continue;
    }
    reps[j++] = serialized_sig.get(i);
  }
  int param_count = total_count - result_count;
  wasm::FunctionSig sig(result_count, param_count, reps.get());

  for (int i = 0; i < dispatch_tables->length();
       i += kDispatchTableNumElements) {
    int table_index =
        Smi::cast(dispatch_tables->get(i + kDispatchTableIndexOffset)).value();
    Handle<WasmInstanceObject> instance(
        WasmInstanceObject::cast(
            dispatch_tables->get(i + kDispatchTableInstanceOffset)),
        isolate);
    // TODO(jkummerow): Find a way to avoid recompiling wrappers.
    wasm::NativeModule* native_module =
        instance->module_object().native_module();
    Address host_address = capi_function->GetHostCallTarget();
    wasm::WasmCodeRefScope code_ref_scope;
    wasm::WasmCode* wasm_code = compiler::CompileWasmCapiCallWrapper(
        isolate->wasm_engine(), native_module, &sig, host_address);
    isolate->counters()->wasm_generated_code_size()->Increment(
        wasm_code->instructions().length());
    isolate->counters()->wasm_reloc_size()->Increment(
        wasm_code->reloc_info().length());
    Handle<Tuple2> tuple = isolate->factory()->NewTuple2(
        instance, capi_function, AllocationType::kOld);
    // Note that {SignatureMap::Find} may return {-1} if the signature is
    // not found; it will simply never match any check.
    auto sig_id = instance->module()->signature_map.Find(sig);
    IndirectFunctionTableEntry(instance, table_index, entry_index)
        .Set(sig_id, wasm_code->instruction_start(), *tuple);
  }
}

void WasmTableObject::ClearDispatchTables(Isolate* isolate,
                                          Handle<WasmTableObject> table,
                                          int index) {
  Handle<FixedArray> dispatch_tables(table->dispatch_tables(), isolate);
  DCHECK_EQ(0, dispatch_tables->length() % kDispatchTableNumElements);
  for (int i = 0; i < dispatch_tables->length();
       i += kDispatchTableNumElements) {
    int table_index =
        Smi::cast(dispatch_tables->get(i + kDispatchTableIndexOffset)).value();
    Handle<WasmInstanceObject> target_instance(
        WasmInstanceObject::cast(
            dispatch_tables->get(i + kDispatchTableInstanceOffset)),
        isolate);
    DCHECK_LT(index, WasmInstanceObject::IndirectFunctionTableSize(
                         isolate, target_instance, table_index));
    IndirectFunctionTableEntry(target_instance, table_index, index).clear();
  }
}

void WasmTableObject::SetFunctionTablePlaceholder(
    Isolate* isolate, Handle<WasmTableObject> table, int entry_index,
    Handle<WasmInstanceObject> instance, int func_index) {
  // Put (instance, func_index) as a Tuple2 into the table_index.
  // The {WasmExportedFunction} will be created lazily.
  Handle<Tuple2> tuple = isolate->factory()->NewTuple2(
      instance, Handle<Smi>(Smi::FromInt(func_index), isolate),
      AllocationType::kYoung);
  table->entries().set(entry_index, *tuple);
}

void WasmTableObject::GetFunctionTableEntry(
    Isolate* isolate, const WasmModule* module, Handle<WasmTableObject> table,
    int entry_index, bool* is_valid, bool* is_null,
    MaybeHandle<WasmInstanceObject>* instance, int* function_index,
    MaybeHandle<WasmJSFunction>* maybe_js_function) {
  DCHECK(wasm::IsSubtypeOf(table->type(), wasm::kWasmFuncRef, module));
  DCHECK_LT(entry_index, table->current_length());
  // We initialize {is_valid} with {true}. We may change it later.
  *is_valid = true;
  Handle<Object> element(table->entries().get(entry_index), isolate);

  *is_null = element->IsNull(isolate);
  if (*is_null) return;

  if (WasmExportedFunction::IsWasmExportedFunction(*element)) {
    auto target_func = Handle<WasmExportedFunction>::cast(element);
    *instance = handle(target_func->instance(), isolate);
    *function_index = target_func->function_index();
    *maybe_js_function = MaybeHandle<WasmJSFunction>();
    return;
  }
  if (WasmJSFunction::IsWasmJSFunction(*element)) {
    *instance = MaybeHandle<WasmInstanceObject>();
    *maybe_js_function = Handle<WasmJSFunction>::cast(element);
    return;
  }
  if (element->IsTuple2()) {
    auto tuple = Handle<Tuple2>::cast(element);
    *instance = handle(WasmInstanceObject::cast(tuple->value1()), isolate);
    *function_index = Smi::cast(tuple->value2()).value();
    *maybe_js_function = MaybeHandle<WasmJSFunction>();
    return;
  }
  *is_valid = false;
}

namespace {
class IftNativeAllocations {
 public:
  IftNativeAllocations(Handle<WasmIndirectFunctionTable> table, uint32_t size)
      : sig_ids_(size), targets_(size) {
    table->set_sig_ids(sig_ids_.data());
    table->set_targets(targets_.data());
  }

  static size_t SizeInMemory(uint32_t size) {
    return size * (sizeof(Address) + sizeof(uint32_t));
  }

  void resize(Handle<WasmIndirectFunctionTable> table, uint32_t new_size) {
    DCHECK_GE(new_size, sig_ids_.size());
    DCHECK_EQ(this, Managed<IftNativeAllocations>::cast(
                        table->managed_native_allocations())
                        .raw());
    sig_ids_.resize(new_size);
    targets_.resize(new_size);
    table->set_sig_ids(sig_ids_.data());
    table->set_targets(targets_.data());
  }

 private:
  std::vector<uint32_t> sig_ids_;
  std::vector<Address> targets_;
};
}  // namespace

Handle<WasmIndirectFunctionTable> WasmIndirectFunctionTable::New(
    Isolate* isolate, uint32_t size) {
  auto refs = isolate->factory()->NewFixedArray(static_cast<int>(size));
  auto table = Handle<WasmIndirectFunctionTable>::cast(
      isolate->factory()->NewStruct(WASM_INDIRECT_FUNCTION_TABLE_TYPE));
  table->set_size(size);
  table->set_refs(*refs);
  auto native_allocations = Managed<IftNativeAllocations>::Allocate(
      isolate, IftNativeAllocations::SizeInMemory(size), table, size);
  table->set_managed_native_allocations(*native_allocations);
  for (uint32_t i = 0; i < size; ++i) {
    IndirectFunctionTableEntry(table, static_cast<int>(i)).clear();
  }
  return table;
}

void WasmIndirectFunctionTable::Resize(Isolate* isolate,
                                       Handle<WasmIndirectFunctionTable> table,
                                       uint32_t new_size) {
  uint32_t old_size = table->size();
  if (old_size >= new_size) return;  // Nothing to do.

  Managed<IftNativeAllocations>::cast(table->managed_native_allocations())
      .raw()
      ->resize(table, new_size);

  Handle<FixedArray> old_refs(table->refs(), isolate);
  Handle<FixedArray> new_refs = isolate->factory()->CopyFixedArrayAndGrow(
      old_refs, static_cast<int>(new_size - old_size));
  table->set_refs(*new_refs);
  table->set_size(new_size);
  for (uint32_t i = old_size; i < new_size; ++i) {
    IndirectFunctionTableEntry(table, static_cast<int>(i)).clear();
  }
}

namespace {

void SetInstanceMemory(Handle<WasmInstanceObject> instance,
                       Handle<JSArrayBuffer> buffer) {
  bool is_wasm_module = instance->module()->origin == wasm::kWasmOrigin;
  bool use_trap_handler =
      instance->module_object().native_module()->use_trap_handler();
  // Wasm modules compiled to use the trap handler don't have bounds checks,
  // so they must have a memory that has guard regions.
  CHECK_IMPLIES(is_wasm_module && use_trap_handler,
                buffer->GetBackingStore()->has_guard_regions());

  instance->SetRawMemory(reinterpret_cast<byte*>(buffer->backing_store()),
                         buffer->byte_length());
#if DEBUG
  if (!FLAG_mock_arraybuffer_allocator) {
    // To flush out bugs earlier, in DEBUG mode, check that all pages of the
    // memory are accessible by reading and writing one byte on each page.
    // Don't do this if the mock ArrayBuffer allocator is enabled.
    byte* mem_start = instance->memory_start();
    size_t mem_size = instance->memory_size();
    for (size_t offset = 0; offset < mem_size; offset += wasm::kWasmPageSize) {
      byte val = mem_start[offset];
      USE(val);
      mem_start[offset] = val;
    }
  }
#endif
}
}  // namespace

Handle<WasmMemoryObject> WasmMemoryObject::New(
    Isolate* isolate, MaybeHandle<JSArrayBuffer> maybe_buffer,
    uint32_t maximum) {
  Handle<JSArrayBuffer> buffer;
  if (!maybe_buffer.ToHandle(&buffer)) {
    // If no buffer was provided, create a zero-length one.
    auto backing_store =
        BackingStore::AllocateWasmMemory(isolate, 0, 0, SharedFlag::kNotShared);
    buffer = isolate->factory()->NewJSArrayBuffer(std::move(backing_store));
  }

  Handle<JSFunction> memory_ctor(
      isolate->native_context()->wasm_memory_constructor(), isolate);

  auto memory_object = Handle<WasmMemoryObject>::cast(
      isolate->factory()->NewJSObject(memory_ctor, AllocationType::kOld));
  memory_object->set_array_buffer(*buffer);
  memory_object->set_maximum_pages(maximum);

  if (buffer->is_shared()) {
    auto backing_store = buffer->GetBackingStore();
    backing_store->AttachSharedWasmMemoryObject(isolate, memory_object);
  }

  return memory_object;
}

MaybeHandle<WasmMemoryObject> WasmMemoryObject::New(Isolate* isolate,
                                                    uint32_t initial,
                                                    uint32_t maximum,
                                                    SharedFlag shared) {
  auto heuristic_maximum = maximum;
#ifdef V8_TARGET_ARCH_32_BIT
  // TODO(wasm): use a better heuristic for reserving more than the initial
  // number of pages on 32-bit systems. Being too greedy in reserving capacity
  // limits the number of memories that can be allocated, causing OOMs in many
  // tests. For now, on 32-bit we never reserve more than initial, unless the
  // memory is shared.
  if (shared == SharedFlag::kNotShared || !FLAG_wasm_grow_shared_memory) {
    heuristic_maximum = initial;
  }
#endif

  auto backing_store = BackingStore::AllocateWasmMemory(
      isolate, initial, heuristic_maximum, shared);

  if (!backing_store) return {};

  Handle<JSArrayBuffer> buffer =
      (shared == SharedFlag::kShared)
          ? isolate->factory()->NewJSSharedArrayBuffer(std::move(backing_store))
          : isolate->factory()->NewJSArrayBuffer(std::move(backing_store));

  return New(isolate, buffer, maximum);
}

void WasmMemoryObject::AddInstance(Isolate* isolate,
                                   Handle<WasmMemoryObject> memory,
                                   Handle<WasmInstanceObject> instance) {
  Handle<WeakArrayList> old_instances =
      memory->has_instances()
          ? Handle<WeakArrayList>(memory->instances(), isolate)
          : handle(ReadOnlyRoots(isolate->heap()).empty_weak_array_list(),
                   isolate);
  Handle<WeakArrayList> new_instances = WeakArrayList::AddToEnd(
      isolate, old_instances, MaybeObjectHandle::Weak(instance));
  memory->set_instances(*new_instances);
  Handle<JSArrayBuffer> buffer(memory->array_buffer(), isolate);
  SetInstanceMemory(instance, buffer);
}

void WasmMemoryObject::update_instances(Isolate* isolate,
                                        Handle<JSArrayBuffer> buffer) {
  if (has_instances()) {
    Handle<WeakArrayList> instances(this->instances(), isolate);
    for (int i = 0; i < instances->length(); i++) {
      MaybeObject elem = instances->Get(i);
      HeapObject heap_object;
      if (elem->GetHeapObjectIfWeak(&heap_object)) {
        Handle<WasmInstanceObject> instance(
            WasmInstanceObject::cast(heap_object), isolate);
        SetInstanceMemory(instance, buffer);
      } else {
        DCHECK(elem->IsCleared());
      }
    }
  }
  set_array_buffer(*buffer);
}

// static
int32_t WasmMemoryObject::Grow(Isolate* isolate,
                               Handle<WasmMemoryObject> memory_object,
                               uint32_t pages) {
  TRACE_EVENT0("v8.wasm", "wasm.GrowMemory");
  Handle<JSArrayBuffer> old_buffer(memory_object->array_buffer(), isolate);
  // Any buffer used as an asmjs memory cannot be detached, and
  // therefore this memory cannot be grown.
  if (old_buffer->is_asmjs_memory()) return -1;

  // Checks for maximum memory size.
  uint32_t maximum_pages = wasm::max_mem_pages();
  if (memory_object->has_maximum_pages()) {
    maximum_pages = std::min(
        maximum_pages, static_cast<uint32_t>(memory_object->maximum_pages()));
  }
  size_t old_size = old_buffer->byte_length();
  DCHECK_EQ(0, old_size % wasm::kWasmPageSize);
  size_t old_pages = old_size / wasm::kWasmPageSize;
  CHECK_GE(wasm::max_mem_pages(), old_pages);
  if (pages > maximum_pages - old_pages) return -1;
  std::shared_ptr<BackingStore> backing_store = old_buffer->GetBackingStore();
  if (!backing_store) return -1;

  // Try to handle shared memory first.
  if (old_buffer->is_shared()) {
    if (FLAG_wasm_grow_shared_memory) {
      base::Optional<size_t> result =
          backing_store->GrowWasmMemoryInPlace(isolate, pages, maximum_pages);
      // Shared memories can only be grown in place; no copying.
      if (result.has_value()) {
        BackingStore::BroadcastSharedWasmMemoryGrow(isolate, backing_store);
        // Broadcasting the update should update this memory object too.
        CHECK_NE(*old_buffer, memory_object->array_buffer());
        size_t new_pages = result.value() + pages;
        // If the allocation succeeded, then this can't possibly overflow:
        size_t new_byte_length = new_pages * wasm::kWasmPageSize;
        // This is a less than check, as it is not guaranteed that the SAB
        // length here will be equal to the stashed length above as calls to
        // grow the same memory object can come in from different workers.
        // It is also possible that a call to Grow was in progress when
        // handling this call.
        CHECK_LE(new_byte_length, memory_object->array_buffer().byte_length());
        // As {old_pages} was read racefully, we return here the synchronized
        // value provided by {GrowWasmMemoryInPlace}, to provide the atomic
        // read-modify-write behavior required by the spec.
        return static_cast<int32_t>(result.value());  // success
      }
    }
    return -1;
  }

  base::Optional<size_t> result =
      backing_store->GrowWasmMemoryInPlace(isolate, pages, maximum_pages);
  // Try to grow non-shared memory in-place.
  if (result.has_value()) {
    // Detach old and create a new one with the grown backing store.
    old_buffer->Detach(true);
    Handle<JSArrayBuffer> new_buffer =
        isolate->factory()->NewJSArrayBuffer(std::move(backing_store));
    memory_object->update_instances(isolate, new_buffer);
    DCHECK_EQ(result.value(), old_pages);
    return static_cast<int32_t>(result.value());  // success
  }

  size_t new_pages = old_pages + pages;
  // Try allocating a new backing store and copying.
  std::unique_ptr<BackingStore> new_backing_store =
      backing_store->CopyWasmMemory(isolate, new_pages);
  if (!new_backing_store) {
    // Crash on out-of-memory if the correctness fuzzer is running.
    if (FLAG_correctness_fuzzer_suppressions) {
      FATAL("could not grow wasm memory");
    }
    return -1;
  }

  // Detach old and create a new one with the new backing store.
  old_buffer->Detach(true);
  Handle<JSArrayBuffer> new_buffer =
      isolate->factory()->NewJSArrayBuffer(std::move(new_backing_store));
  memory_object->update_instances(isolate, new_buffer);
  return static_cast<int32_t>(old_pages);  // success
}

// static
MaybeHandle<WasmGlobalObject> WasmGlobalObject::New(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    MaybeHandle<JSArrayBuffer> maybe_untagged_buffer,
    MaybeHandle<FixedArray> maybe_tagged_buffer, wasm::ValueType type,
    int32_t offset, bool is_mutable) {
  Handle<JSFunction> global_ctor(
      isolate->native_context()->wasm_global_constructor(), isolate);
  auto global_obj = Handle<WasmGlobalObject>::cast(
      isolate->factory()->NewJSObject(global_ctor));
  {
    // Disallow GC until all fields have acceptable types.
    DisallowHeapAllocation no_gc;
    if (!instance.is_null()) global_obj->set_instance(*instance);
    global_obj->set_type(type);
    global_obj->set_offset(offset);
    global_obj->set_is_mutable(is_mutable);
  }

  if (type.is_reference_type()) {
    DCHECK(maybe_untagged_buffer.is_null());
    Handle<FixedArray> tagged_buffer;
    if (!maybe_tagged_buffer.ToHandle(&tagged_buffer)) {
      // If no buffer was provided, create one.
      tagged_buffer =
          isolate->factory()->NewFixedArray(1, AllocationType::kOld);
      CHECK_EQ(offset, 0);
    }
    global_obj->set_tagged_buffer(*tagged_buffer);
  } else {
    DCHECK(maybe_tagged_buffer.is_null());
    uint32_t type_size = type.element_size_bytes();

    Handle<JSArrayBuffer> untagged_buffer;
    if (!maybe_untagged_buffer.ToHandle(&untagged_buffer)) {
      MaybeHandle<JSArrayBuffer> result =
          isolate->factory()->NewJSArrayBufferAndBackingStore(
              offset + type_size, InitializedFlag::kZeroInitialized);

      if (!result.ToHandle(&untagged_buffer)) return {};
    }

    // Check that the offset is in bounds.
    CHECK_LE(offset + type_size, untagged_buffer->byte_length());

    global_obj->set_untagged_buffer(*untagged_buffer);
  }

  return global_obj;
}

void IndirectFunctionTableEntry::clear() {
  if (!instance_.is_null()) {
    instance_->indirect_function_table_sig_ids()[index_] = -1;
    instance_->indirect_function_table_targets()[index_] = 0;
    instance_->indirect_function_table_refs().set(
        index_, ReadOnlyRoots(instance_->GetIsolate()).undefined_value());
  } else {
    DCHECK(!table_.is_null());
    table_->sig_ids()[index_] = -1;
    table_->targets()[index_] = 0;
    table_->refs().set(
        index_,
        ReadOnlyRoots(GetIsolateFromWritableObject(*table_)).undefined_value());
  }
}

void IndirectFunctionTableEntry::Set(int sig_id,
                                     Handle<WasmInstanceObject> target_instance,
                                     int target_func_index) {
  TRACE_IFT("IFT entry 0x%" PRIxPTR
            "[%d] = {sig_id=%d, target_instance=0x%" PRIxPTR
            ", target_func_index=%d}\n",
            instance_->ptr(), index_, sig_id, target_instance->ptr(),
            target_func_index);

  Object ref;
  Address call_target = 0;
  if (target_func_index <
      static_cast<int>(target_instance->module()->num_imported_functions)) {
    // The function in the target instance was imported. Use its imports table,
    // which contains a tuple needed by the import wrapper.
    ImportedFunctionEntry entry(target_instance, target_func_index);
    ref = entry.object_ref();
    call_target = entry.target();
  } else {
    // The function in the target instance was not imported.
    ref = *target_instance;
    call_target = target_instance->GetCallTarget(target_func_index);
  }
  Set(sig_id, call_target, ref);
}

void IndirectFunctionTableEntry::Set(int sig_id, Address call_target,
                                     Object ref) {
  if (!instance_.is_null()) {
    instance_->indirect_function_table_sig_ids()[index_] = sig_id;
    instance_->indirect_function_table_targets()[index_] = call_target;
    instance_->indirect_function_table_refs().set(index_, ref);
  } else {
    DCHECK(!table_.is_null());
    table_->sig_ids()[index_] = sig_id;
    table_->targets()[index_] = call_target;
    table_->refs().set(index_, ref);
  }
}

Object IndirectFunctionTableEntry::object_ref() const {
  return !instance_.is_null()
             ? instance_->indirect_function_table_refs().get(index_)
             : table_->refs().get(index_);
}

int IndirectFunctionTableEntry::sig_id() const {
  return !instance_.is_null()
             ? instance_->indirect_function_table_sig_ids()[index_]
             : table_->sig_ids()[index_];
}

Address IndirectFunctionTableEntry::target() const {
  return !instance_.is_null()
             ? instance_->indirect_function_table_targets()[index_]
             : table_->targets()[index_];
}

void ImportedFunctionEntry::SetWasmToJs(
    Isolate* isolate, Handle<JSReceiver> callable,
    const wasm::WasmCode* wasm_to_js_wrapper) {
  TRACE_IFT("Import callable 0x%" PRIxPTR "[%d] = {callable=0x%" PRIxPTR
            ", target=%p}\n",
            instance_->ptr(), index_, callable->ptr(),
            wasm_to_js_wrapper->instructions().begin());
  DCHECK(wasm_to_js_wrapper->kind() == wasm::WasmCode::kWasmToJsWrapper ||
         wasm_to_js_wrapper->kind() == wasm::WasmCode::kWasmToCapiWrapper);
  Handle<Tuple2> tuple =
      isolate->factory()->NewTuple2(instance_, callable, AllocationType::kOld);
  instance_->imported_function_refs().set(index_, *tuple);
  instance_->imported_function_targets()[index_] =
      wasm_to_js_wrapper->instruction_start();
}

void ImportedFunctionEntry::SetWasmToWasm(WasmInstanceObject instance,
                                          Address call_target) {
  TRACE_IFT("Import Wasm 0x%" PRIxPTR "[%d] = {instance=0x%" PRIxPTR
            ", target=0x%" PRIxPTR "}\n",
            instance_->ptr(), index_, instance.ptr(), call_target);
  instance_->imported_function_refs().set(index_, instance);
  instance_->imported_function_targets()[index_] = call_target;
}

WasmInstanceObject ImportedFunctionEntry::instance() {
  // The imported reference entry is either a target instance or a tuple
  // of this instance and the target callable.
  Object value = object_ref();
  if (value.IsWasmInstanceObject()) {
    return WasmInstanceObject::cast(value);
  }
  Tuple2 tuple = Tuple2::cast(value);
  return WasmInstanceObject::cast(tuple.value1());
}

// Returns an empty Object() if no callable is available, a JSReceiver
// otherwise.
Object ImportedFunctionEntry::maybe_callable() {
  Object value = object_ref();
  if (!value.IsTuple2()) return Object();
  Tuple2 tuple = Tuple2::cast(value);
  return JSReceiver::cast(tuple.value2());
}

JSReceiver ImportedFunctionEntry::callable() {
  return JSReceiver::cast(Tuple2::cast(object_ref()).value2());
}

Object ImportedFunctionEntry::object_ref() {
  return instance_->imported_function_refs().get(index_);
}

Address ImportedFunctionEntry::target() {
  return instance_->imported_function_targets()[index_];
}

// static
constexpr uint16_t WasmInstanceObject::kTaggedFieldOffsets[];

// static
bool WasmInstanceObject::EnsureIndirectFunctionTableWithMinimumSize(
    Handle<WasmInstanceObject> instance, int table_index,
    uint32_t minimum_size) {
  Isolate* isolate = instance->GetIsolate();
  if (table_index > 0) {
    DCHECK_LT(table_index, instance->indirect_function_tables().length());
    auto table =
        handle(WasmIndirectFunctionTable::cast(
                   instance->indirect_function_tables().get(table_index)),
               isolate);
    WasmIndirectFunctionTable::Resize(isolate, table, minimum_size);
    return true;
  }

  uint32_t old_size = instance->indirect_function_table_size();
  if (old_size >= minimum_size) return false;  // Nothing to do.

  auto native_allocations = GetNativeAllocations(*instance);
  if (native_allocations->indirect_function_table_capacity() < minimum_size) {
    HandleScope scope(isolate);
    native_allocations->resize_indirect_function_table(isolate, instance,
                                                       minimum_size);
    DCHECK_GE(native_allocations->indirect_function_table_capacity(),
              minimum_size);
  }
  instance->set_indirect_function_table_size(minimum_size);
  for (uint32_t j = old_size; j < minimum_size; j++) {
    // {WasmInstanceNativeAllocations} only manages the memory of table 0.
    // Therefore we pass the {table_index} as a constant here.
    IndirectFunctionTableEntry(instance, 0, static_cast<int>(j)).clear();
  }

  return true;
}

void WasmInstanceObject::SetRawMemory(byte* mem_start, size_t mem_size) {
  CHECK_LE(mem_size, wasm::max_mem_bytes());
#if V8_HOST_ARCH_64_BIT
  uint64_t mem_mask64 = base::bits::RoundUpToPowerOfTwo64(mem_size) - 1;
  set_memory_start(mem_start);
  set_memory_size(mem_size);
  set_memory_mask(mem_mask64);
#else
  // Must handle memory > 2GiB specially.
  CHECK_LE(mem_size, size_t{kMaxUInt32});
  uint32_t mem_mask32 =
      (mem_size > 2 * size_t{GB})
          ? 0xFFFFFFFFu
          : base::bits::RoundUpToPowerOfTwo32(static_cast<uint32_t>(mem_size)) -
                1;
  set_memory_start(mem_start);
  set_memory_size(mem_size);
  set_memory_mask(mem_mask32);
#endif
}

const WasmModule* WasmInstanceObject::module() {
  return module_object().module();
}

Handle<WasmInstanceObject> WasmInstanceObject::New(
    Isolate* isolate, Handle<WasmModuleObject> module_object) {
  Handle<JSFunction> instance_cons(
      isolate->native_context()->wasm_instance_constructor(), isolate);
  Handle<JSObject> instance_object =
      isolate->factory()->NewJSObject(instance_cons, AllocationType::kOld);

  Handle<WasmInstanceObject> instance(
      WasmInstanceObject::cast(*instance_object), isolate);
  instance->clear_padding();

  // Initialize the imported function arrays.
  auto module = module_object->module();
  auto num_imported_functions = module->num_imported_functions;
  auto num_imported_mutable_globals = module->num_imported_mutable_globals;
  auto num_data_segments = module->num_declared_data_segments;
  size_t native_allocations_size = EstimateNativeAllocationsSize(module);
  auto native_allocations = Managed<WasmInstanceNativeAllocations>::Allocate(
      isolate, native_allocations_size, instance, num_imported_functions,
      num_imported_mutable_globals, num_data_segments,
      module->elem_segments.size());
  instance->set_managed_native_allocations(*native_allocations);

  Handle<FixedArray> imported_function_refs =
      isolate->factory()->NewFixedArray(num_imported_functions);
  instance->set_imported_function_refs(*imported_function_refs);

  instance->SetRawMemory(nullptr, 0);
  instance->set_isolate_root(isolate->isolate_root());
  instance->set_stack_limit_address(
      isolate->stack_guard()->address_of_jslimit());
  instance->set_real_stack_limit_address(
      isolate->stack_guard()->address_of_real_jslimit());
  instance->set_globals_start(nullptr);
  instance->set_indirect_function_table_size(0);
  instance->set_indirect_function_table_refs(
      ReadOnlyRoots(isolate).empty_fixed_array());
  instance->set_indirect_function_table_sig_ids(nullptr);
  instance->set_indirect_function_table_targets(nullptr);
  instance->set_native_context(*isolate->native_context());
  instance->set_module_object(*module_object);
  instance->set_jump_table_start(
      module_object->native_module()->jump_table_start());
  instance->set_hook_on_function_call_address(
      isolate->debug()->hook_on_function_call_address());
  instance->set_managed_object_maps(*isolate->factory()->empty_fixed_array());
  instance->set_num_liftoff_function_calls_array(
      module_object->native_module()->num_liftoff_function_calls_array());

  // Insert the new instance into the scripts weak list of instances. This list
  // is used for breakpoints affecting all instances belonging to the script.
  // TODO(wasm): Allow to reuse holes in the {WeakArrayList} below.
  if (module_object->script().type() == Script::TYPE_WASM) {
    Handle<WeakArrayList> weak_instance_list(
        module_object->script().wasm_weak_instance_list(), isolate);
    weak_instance_list = WeakArrayList::AddToEnd(
        isolate, weak_instance_list, MaybeObjectHandle::Weak(instance));
    module_object->script().set_wasm_weak_instance_list(*weak_instance_list);
  }

  InitDataSegmentArrays(instance, module_object);
  InitElemSegmentArrays(instance, module_object);

  return instance;
}

// static
void WasmInstanceObject::InitDataSegmentArrays(
    Handle<WasmInstanceObject> instance,
    Handle<WasmModuleObject> module_object) {
  auto module = module_object->module();
  auto wire_bytes = module_object->native_module()->wire_bytes();
  auto num_data_segments = module->num_declared_data_segments;
  // The number of declared data segments will be zero if there is no DataCount
  // section. These arrays will not be allocated nor initialized in that case,
  // since they cannot be used (since the validator checks that number of
  // declared data segments when validating the memory.init and memory.drop
  // instructions).
  DCHECK(num_data_segments == 0 ||
         num_data_segments == module->data_segments.size());
  for (size_t i = 0; i < num_data_segments; ++i) {
    const wasm::WasmDataSegment& segment = module->data_segments[i];
    // Initialize the pointer and size of passive segments.
    auto source_bytes = wire_bytes.SubVector(segment.source.offset(),
                                             segment.source.end_offset());
    instance->data_segment_starts()[i] =
        reinterpret_cast<Address>(source_bytes.begin());
    // Set the active segments to being already dropped, since memory.init on
    // a dropped passive segment and an active segment have the same
    // behavior.
    instance->data_segment_sizes()[i] =
        segment.active ? 0 : source_bytes.length();
  }
}

void WasmInstanceObject::InitElemSegmentArrays(
    Handle<WasmInstanceObject> instance,
    Handle<WasmModuleObject> module_object) {
  auto module = module_object->module();
  auto num_elem_segments = module->elem_segments.size();
  for (size_t i = 0; i < num_elem_segments; ++i) {
    instance->dropped_elem_segments()[i] =
        module->elem_segments[i].status ==
                wasm::WasmElemSegment::kStatusDeclarative
            ? 1
            : 0;
  }
}

Address WasmInstanceObject::GetCallTarget(uint32_t func_index) {
  wasm::NativeModule* native_module = module_object().native_module();
  if (func_index < native_module->num_imported_functions()) {
    return imported_function_targets()[func_index];
  }
  return native_module->GetCallTargetForFunction(func_index);
}

int WasmInstanceObject::IndirectFunctionTableSize(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    uint32_t table_index) {
  if (table_index == 0) {
    return instance->indirect_function_table_size();
  }
  auto table =
      handle(WasmIndirectFunctionTable::cast(
                 instance->indirect_function_tables().get(table_index)),
             isolate);
  return table->size();
}

// static
bool WasmInstanceObject::CopyTableEntries(Isolate* isolate,
                                          Handle<WasmInstanceObject> instance,
                                          uint32_t table_dst_index,
                                          uint32_t table_src_index,
                                          uint32_t dst, uint32_t src,
                                          uint32_t count) {
  CHECK_LT(table_dst_index, instance->tables().length());
  CHECK_LT(table_src_index, instance->tables().length());
  auto table_dst = handle(
      WasmTableObject::cast(instance->tables().get(table_dst_index)), isolate);
  auto table_src = handle(
      WasmTableObject::cast(instance->tables().get(table_src_index)), isolate);
  uint32_t max_dst = table_dst->current_length();
  uint32_t max_src = table_src->current_length();
  bool copy_backward = src < dst;
  if (!base::IsInBounds(dst, count, max_dst) ||
      !base::IsInBounds(src, count, max_src)) {
    return false;
  }

  // no-op
  if ((dst == src && table_dst_index == table_src_index) || count == 0) {
    return true;
  }

  for (uint32_t i = 0; i < count; ++i) {
    uint32_t src_index = copy_backward ? (src + count - i - 1) : src + i;
    uint32_t dst_index = copy_backward ? (dst + count - i - 1) : dst + i;
    auto value = WasmTableObject::Get(isolate, table_src, src_index);
    WasmTableObject::Set(isolate, table_dst, dst_index, value);
  }
  return true;
}

// static
bool WasmInstanceObject::InitTableEntries(Isolate* isolate,
                                          Handle<WasmInstanceObject> instance,
                                          uint32_t table_index,
                                          uint32_t segment_index, uint32_t dst,
                                          uint32_t src, uint32_t count) {
  // Note that this implementation just calls through to module instantiation.
  // This is intentional, so that the runtime only depends on the object
  // methods, and not the module instantiation logic.
  return wasm::LoadElemSegment(isolate, instance, table_index, segment_index,
                               dst, src, count);
}

MaybeHandle<WasmExternalFunction> WasmInstanceObject::GetWasmExternalFunction(
    Isolate* isolate, Handle<WasmInstanceObject> instance, int index) {
  MaybeHandle<WasmExternalFunction> result;
  if (instance->has_wasm_external_functions()) {
    Object val = instance->wasm_external_functions().get(index);
    if (!val.IsUndefined(isolate)) {
      result = Handle<WasmExternalFunction>(WasmExternalFunction::cast(val),
                                            isolate);
    }
  }
  return result;
}

Handle<WasmExternalFunction>
WasmInstanceObject::GetOrCreateWasmExternalFunction(
    Isolate* isolate, Handle<WasmInstanceObject> instance, int function_index) {
  MaybeHandle<WasmExternalFunction> maybe_result =
      WasmInstanceObject::GetWasmExternalFunction(isolate, instance,
                                                  function_index);

  Handle<WasmExternalFunction> result;
  if (maybe_result.ToHandle(&result)) {
    return result;
  }

  Handle<WasmModuleObject> module_object(instance->module_object(), isolate);
  const WasmModule* module = module_object->module();
  const WasmFunction& function = module->functions[function_index];
  int wrapper_index =
      GetExportWrapperIndex(module, function.sig, function.imported);

  Handle<Object> entry =
      FixedArray::get(module_object->export_wrappers(), wrapper_index, isolate);

  Handle<Code> wrapper;
  if (entry->IsCode()) {
    wrapper = Handle<Code>::cast(entry);
  } else {
    // The wrapper may not exist yet if no function in the exports section has
    // this signature. We compile it and store the wrapper in the module for
    // later use.
    wrapper = wasm::JSToWasmWrapperCompilationUnit::CompileJSToWasmWrapper(
        isolate, function.sig, instance->module(), function.imported);
    module_object->export_wrappers().set(wrapper_index, *wrapper);
  }
  result = Handle<WasmExternalFunction>::cast(WasmExportedFunction::New(
      isolate, instance, function_index,
      static_cast<int>(function.sig->parameter_count()), wrapper));

  WasmInstanceObject::SetWasmExternalFunction(isolate, instance, function_index,
                                              result);
  return result;
}

void WasmInstanceObject::SetWasmExternalFunction(
    Isolate* isolate, Handle<WasmInstanceObject> instance, int index,
    Handle<WasmExternalFunction> val) {
  Handle<FixedArray> functions;
  if (!instance->has_wasm_external_functions()) {
    // Lazily allocate the wasm external functions array.
    functions = isolate->factory()->NewFixedArray(
        static_cast<int>(instance->module()->functions.size()));
    instance->set_wasm_external_functions(*functions);
  } else {
    functions =
        Handle<FixedArray>(instance->wasm_external_functions(), isolate);
  }
  functions->set(index, *val);
}

// static
void WasmInstanceObject::ImportWasmJSFunctionIntoTable(
    Isolate* isolate, Handle<WasmInstanceObject> instance, int table_index,
    int entry_index, Handle<WasmJSFunction> js_function) {
  // Deserialize the signature encapsulated with the {WasmJSFunction}.
  // Note that {SignatureMap::Find} may return {-1} if the signature is
  // not found; it will simply never match any check.
  Zone zone(isolate->allocator(), ZONE_NAME);
  const wasm::FunctionSig* sig = js_function->GetSignature(&zone);
  auto sig_id = instance->module()->signature_map.Find(*sig);

  // Compile a wrapper for the target callable.
  Handle<JSReceiver> callable(js_function->GetCallable(), isolate);
  wasm::WasmCodeRefScope code_ref_scope;
  Address call_target = kNullAddress;
  if (sig_id >= 0) {
    wasm::NativeModule* native_module =
        instance->module_object().native_module();
    // TODO(wasm): Cache and reuse wrapper code.
    const wasm::WasmFeatures enabled = native_module->enabled_features();
    auto resolved = compiler::ResolveWasmImportCall(
        callable, sig, instance->module(), enabled);
    compiler::WasmImportCallKind kind = resolved.first;
    callable = resolved.second;  // Update to ultimate target.
    DCHECK_NE(compiler::WasmImportCallKind::kLinkError, kind);
    wasm::CompilationEnv env = native_module->CreateCompilationEnv();
    // {expected_arity} should only be used if kind != kJSFunctionArityMismatch.
    int expected_arity = -1;
    if (kind == compiler::WasmImportCallKind ::kJSFunctionArityMismatch) {
      expected_arity = Handle<JSFunction>::cast(callable)
                           ->shared()
                           .internal_formal_parameter_count();
    }
    wasm::WasmCompilationResult result = compiler::CompileWasmImportCallWrapper(
        isolate->wasm_engine(), &env, kind, sig, false, expected_arity);
    std::unique_ptr<wasm::WasmCode> wasm_code = native_module->AddCode(
        result.func_index, result.code_desc, result.frame_slot_count,
        result.tagged_parameter_slots,
        result.protected_instructions_data.as_vector(),
        result.source_positions.as_vector(), GetCodeKind(result),
        wasm::ExecutionTier::kNone, wasm::kNoDebugging);
    wasm::WasmCode* published_code =
        native_module->PublishCode(std::move(wasm_code));
    isolate->counters()->wasm_generated_code_size()->Increment(
        published_code->instructions().length());
    isolate->counters()->wasm_reloc_size()->Increment(
        published_code->reloc_info().length());
    call_target = published_code->instruction_start();
  }

  // Update the dispatch table.
  Handle<Tuple2> tuple =
      isolate->factory()->NewTuple2(instance, callable, AllocationType::kOld);
  IndirectFunctionTableEntry(instance, table_index, entry_index)
      .Set(sig_id, call_target, *tuple);
}

// static
uint8_t* WasmInstanceObject::GetGlobalStorage(
    Handle<WasmInstanceObject> instance, const wasm::WasmGlobal& global) {
  DCHECK(!global.type.is_reference_type());
  if (global.mutability && global.imported) {
    return reinterpret_cast<byte*>(
        instance->imported_mutable_globals()[global.index]);
  } else {
    return instance->globals_start() + global.offset;
  }
}

// static
std::pair<Handle<FixedArray>, uint32_t>
WasmInstanceObject::GetGlobalBufferAndIndex(Handle<WasmInstanceObject> instance,
                                            const wasm::WasmGlobal& global) {
  DCHECK(global.type.is_reference_type());
  Isolate* isolate = instance->GetIsolate();
  if (global.mutability && global.imported) {
    Handle<FixedArray> buffer(
        FixedArray::cast(
            instance->imported_mutable_globals_buffers().get(global.index)),
        isolate);
    Address idx = instance->imported_mutable_globals()[global.index];
    DCHECK_LE(idx, std::numeric_limits<uint32_t>::max());
    return {buffer, static_cast<uint32_t>(idx)};
  }
  return {handle(instance->tagged_globals_buffer(), isolate), global.offset};
}

// static
MaybeHandle<String> WasmInstanceObject::GetGlobalNameOrNull(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    uint32_t global_index) {
  return WasmInstanceObject::GetNameFromImportsAndExportsOrNull(
      isolate, instance, wasm::ImportExportKindCode::kExternalGlobal,
      global_index);
}

// static
MaybeHandle<String> WasmInstanceObject::GetMemoryNameOrNull(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    uint32_t memory_index) {
  return WasmInstanceObject::GetNameFromImportsAndExportsOrNull(
      isolate, instance, wasm::ImportExportKindCode::kExternalMemory,
      memory_index);
}

// static
MaybeHandle<String> WasmInstanceObject::GetTableNameOrNull(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    uint32_t table_index) {
  return WasmInstanceObject::GetNameFromImportsAndExportsOrNull(
      isolate, instance, wasm::ImportExportKindCode::kExternalTable,
      table_index);
}

// static
MaybeHandle<String> WasmInstanceObject::GetNameFromImportsAndExportsOrNull(
    Isolate* isolate, Handle<WasmInstanceObject> instance,
    wasm::ImportExportKindCode kind, uint32_t index) {
  DCHECK(kind == wasm::ImportExportKindCode::kExternalGlobal ||
         kind == wasm::ImportExportKindCode::kExternalMemory ||
         kind == wasm::ImportExportKindCode::kExternalTable);
  wasm::ModuleWireBytes wire_bytes(
      instance->module_object().native_module()->wire_bytes());

  // This is pair of <module_name, field_name>.
  // If field_name is not set then we don't generate a name. Else if module_name
  // is set then it is an imported one. Otherwise it is an exported one.
  std::pair<wasm::WireBytesRef, wasm::WireBytesRef> name_ref =
      instance->module()
          ->lazily_generated_names.LookupNameFromImportsAndExports(
              kind, index, VectorOf(instance->module()->import_table),
              VectorOf(instance->module()->export_table));
  if (!name_ref.second.is_set()) return {};
  Vector<const char> field_name = wire_bytes.GetNameOrNull(name_ref.second);
  if (!name_ref.first.is_set()) {
    return isolate->factory()->NewStringFromUtf8(VectorOf(field_name));
  }
  Vector<const char> module_name = wire_bytes.GetNameOrNull(name_ref.first);
  std::string full_name;
  full_name.append(module_name.begin(), module_name.end());
  full_name.append(".");
  full_name.append(field_name.begin(), field_name.end());
  return isolate->factory()->NewStringFromUtf8(VectorOf(full_name));
}

// static
wasm::WasmValue WasmInstanceObject::GetGlobalValue(
    Handle<WasmInstanceObject> instance, const wasm::WasmGlobal& global) {
  Isolate* isolate = instance->GetIsolate();
  if (global.type.is_reference_type()) {
    Handle<FixedArray> global_buffer;  // The buffer of the global.
    uint32_t global_index = 0;         // The index into the buffer.
    std::tie(global_buffer, global_index) =
        GetGlobalBufferAndIndex(instance, global);
    return wasm::WasmValue(handle(global_buffer->get(global_index), isolate));
  }
  Address ptr = reinterpret_cast<Address>(GetGlobalStorage(instance, global));
  using wasm::Simd128;
  switch (global.type.kind()) {
#define CASE_TYPE(valuetype, ctype) \
  case wasm::ValueType::valuetype:  \
    return wasm::WasmValue(base::ReadLittleEndianValue<ctype>(ptr));
    FOREACH_WASMVALUE_CTYPES(CASE_TYPE)
#undef CASE_TYPE
    default:
      UNREACHABLE();
  }
}

// static
Handle<WasmExceptionObject> WasmExceptionObject::New(
    Isolate* isolate, const wasm::FunctionSig* sig,
    Handle<HeapObject> exception_tag) {
  Handle<JSFunction> exception_cons(
      isolate->native_context()->wasm_exception_constructor(), isolate);

  // Serialize the signature.
  DCHECK_EQ(0, sig->return_count());
  DCHECK_LE(sig->parameter_count(), std::numeric_limits<int>::max());
  int sig_size = static_cast<int>(sig->parameter_count());
  Handle<PodArray<wasm::ValueType>> serialized_sig =
      PodArray<wasm::ValueType>::New(isolate, sig_size, AllocationType::kOld);
  int index = 0;  // Index into the {PodArray} above.
  for (wasm::ValueType param : sig->parameters()) {
    serialized_sig->set(index++, param);
  }

  Handle<JSObject> exception_object =
      isolate->factory()->NewJSObject(exception_cons, AllocationType::kOld);
  Handle<WasmExceptionObject> exception =
      Handle<WasmExceptionObject>::cast(exception_object);
  exception->set_serialized_signature(*serialized_sig);
  exception->set_exception_tag(*exception_tag);

  return exception;
}

// TODO(9495): Update this if function type variance is introduced.
bool WasmExceptionObject::MatchesSignature(const wasm::FunctionSig* sig) {
  DCHECK_EQ(0, sig->return_count());
  DCHECK_LE(sig->parameter_count(), std::numeric_limits<int>::max());
  int sig_size = static_cast<int>(sig->parameter_count());
  if (sig_size != serialized_signature().length()) return false;
  for (int index = 0; index < sig_size; ++index) {
    if (sig->GetParam(index) != serialized_signature().get(index)) {
      return false;
    }
  }
  return true;
}

// TODO(9495): Update this if function type variance is introduced.
bool WasmCapiFunction::MatchesSignature(const wasm::FunctionSig* sig) const {
  // TODO(jkummerow): Unify with "SignatureHelper" in c-api.cc.
  int param_count = static_cast<int>(sig->parameter_count());
  int result_count = static_cast<int>(sig->return_count());
  PodArray<wasm::ValueType> serialized_sig =
      shared().wasm_capi_function_data().serialized_signature();
  if (param_count + result_count + 1 != serialized_sig.length()) return false;
  int serialized_index = 0;
  for (int i = 0; i < result_count; i++, serialized_index++) {
    if (sig->GetReturn(i) != serialized_sig.get(serialized_index)) {
      return false;
    }
  }
  if (serialized_sig.get(serialized_index) != wasm::kWasmStmt) return false;
  serialized_index++;
  for (int i = 0; i < param_count; i++, serialized_index++) {
    if (sig->GetParam(i) != serialized_sig.get(serialized_index)) return false;
  }
  return true;
}

// static
Handle<WasmExceptionPackage> WasmExceptionPackage::New(
    Isolate* isolate, Handle<WasmExceptionTag> exception_tag, int size) {
  Handle<Object> exception = isolate->factory()->NewWasmRuntimeError(
      MessageTemplate::kWasmExceptionError);
  CHECK(!Object::SetProperty(isolate, exception,
                             isolate->factory()->wasm_exception_tag_symbol(),
                             exception_tag, StoreOrigin::kMaybeKeyed,
                             Just(ShouldThrow::kThrowOnError))
             .is_null());
  Handle<FixedArray> values = isolate->factory()->NewFixedArray(size);
  CHECK(!Object::SetProperty(isolate, exception,
                             isolate->factory()->wasm_exception_values_symbol(),
                             values, StoreOrigin::kMaybeKeyed,
                             Just(ShouldThrow::kThrowOnError))
             .is_null());
  return Handle<WasmExceptionPackage>::cast(exception);
}

// static
Handle<Object> WasmExceptionPackage::GetExceptionTag(
    Isolate* isolate, Handle<WasmExceptionPackage> exception_package) {
  Handle<Object> tag;
  if (JSReceiver::GetProperty(isolate, exception_package,
                              isolate->factory()->wasm_exception_tag_symbol())
          .ToHandle(&tag)) {
    return tag;
  }
  return ReadOnlyRoots(isolate).undefined_value_handle();
}

// static
Handle<Object> WasmExceptionPackage::GetExceptionValues(
    Isolate* isolate, Handle<WasmExceptionPackage> exception_package) {
  Handle<Object> values;
  if (JSReceiver::GetProperty(
          isolate, exception_package,
          isolate->factory()->wasm_exception_values_symbol())
          .ToHandle(&values)) {
    DCHECK(values->IsFixedArray());
    return values;
  }
  return ReadOnlyRoots(isolate).undefined_value_handle();
}

#ifdef DEBUG

namespace {

constexpr uint32_t kBytesPerExceptionValuesArrayElement = 2;

size_t ComputeEncodedElementSize(wasm::ValueType type) {
  size_t byte_size = type.element_size_bytes();
  DCHECK_EQ(byte_size % kBytesPerExceptionValuesArrayElement, 0);
  DCHECK_LE(1, byte_size / kBytesPerExceptionValuesArrayElement);
  return byte_size / kBytesPerExceptionValuesArrayElement;
}

}  // namespace

#endif  // DEBUG

// static
uint32_t WasmExceptionPackage::GetEncodedSize(
    const wasm::WasmException* exception) {
  const wasm::WasmExceptionSig* sig = exception->sig;
  uint32_t encoded_size = 0;
  for (size_t i = 0; i < sig->parameter_count(); ++i) {
    switch (sig->GetParam(i).kind()) {
      case wasm::ValueType::kI32:
      case wasm::ValueType::kF32:
        DCHECK_EQ(2, ComputeEncodedElementSize(sig->GetParam(i)));
        encoded_size += 2;
        break;
      case wasm::ValueType::kI64:
      case wasm::ValueType::kF64:
        DCHECK_EQ(4, ComputeEncodedElementSize(sig->GetParam(i)));
        encoded_size += 4;
        break;
      case wasm::ValueType::kS128:
        DCHECK_EQ(8, ComputeEncodedElementSize(sig->GetParam(i)));
        encoded_size += 8;
        break;
      case wasm::ValueType::kRef:
      case wasm::ValueType::kOptRef:
        encoded_size += 1;
        break;
      case wasm::ValueType::kRtt:
      case wasm::ValueType::kStmt:
      case wasm::ValueType::kBottom:
      case wasm::ValueType::kI8:
      case wasm::ValueType::kI16:
        UNREACHABLE();
    }
  }
  return encoded_size;
}

bool WasmExportedFunction::IsWasmExportedFunction(Object object) {
  if (!object.IsJSFunction()) return false;
  JSFunction js_function = JSFunction::cast(object);
  if (CodeKind::JS_TO_WASM_FUNCTION != js_function.code().kind() &&
      js_function.code().builtin_index() != Builtins::kGenericJSToWasmWrapper) {
    return false;
  }
  DCHECK(js_function.shared().HasWasmExportedFunctionData());
  return true;
}

bool WasmCapiFunction::IsWasmCapiFunction(Object object) {
  if (!object.IsJSFunction()) return false;
  JSFunction js_function = JSFunction::cast(object);
  // TODO(jkummerow): Enable this when there is a JavaScript wrapper
  // able to call this function.
  // if (js_function->code()->kind() != CodeKind::WASM_TO_CAPI_FUNCTION) {
  //   return false;
  // }
  // DCHECK(js_function->shared()->HasWasmCapiFunctionData());
  // return true;
  return js_function.shared().HasWasmCapiFunctionData();
}

Handle<WasmCapiFunction> WasmCapiFunction::New(
    Isolate* isolate, Address call_target, Handle<Foreign> embedder_data,
    Handle<PodArray<wasm::ValueType>> serialized_signature) {
  // TODO(jkummerow): Install a JavaScript wrapper. For now, calling
  // these functions directly is unsupported; they can only be called
  // from Wasm code.
  Handle<WasmCapiFunctionData> fun_data =
      isolate->factory()->NewWasmCapiFunctionData(
          call_target, embedder_data,
          isolate->builtins()->builtin_handle(Builtins::kIllegal),
          serialized_signature, AllocationType::kOld);
  Handle<SharedFunctionInfo> shared =
      isolate->factory()->NewSharedFunctionInfoForWasmCapiFunction(fun_data);
  return Handle<WasmCapiFunction>::cast(
      isolate->factory()->NewFunctionFromSharedFunctionInfo(
          shared, isolate->native_context()));
}

WasmInstanceObject WasmExportedFunction::instance() {
  return shared().wasm_exported_function_data().instance();
}

int WasmExportedFunction::function_index() {
  return shared().wasm_exported_function_data().function_index();
}

Handle<WasmExportedFunction> WasmExportedFunction::New(
    Isolate* isolate, Handle<WasmInstanceObject> instance, int func_index,
    int arity, Handle<Code> export_wrapper) {
  DCHECK(
      CodeKind::JS_TO_WASM_FUNCTION == export_wrapper->kind() ||
      (export_wrapper->is_builtin() &&
       export_wrapper->builtin_index() == Builtins::kGenericJSToWasmWrapper));
  int num_imported_functions = instance->module()->num_imported_functions;
  int jump_table_offset = -1;
  if (func_index >= num_imported_functions) {
    uint32_t jump_table_diff =
        instance->module_object().native_module()->GetJumpTableOffset(
            func_index);
    DCHECK_GE(kMaxInt, jump_table_diff);
    jump_table_offset = static_cast<int>(jump_table_diff);
  }
  const wasm::FunctionSig* sig = instance->module()->functions[func_index].sig;
  Handle<Foreign> sig_foreign =
      isolate->factory()->NewForeign(reinterpret_cast<Address>(sig));
  Handle<WasmExportedFunctionData> function_data =
      Handle<WasmExportedFunctionData>::cast(isolate->factory()->NewStruct(
          WASM_EXPORTED_FUNCTION_DATA_TYPE, AllocationType::kOld));
  function_data->set_wrapper_code(*export_wrapper);
  function_data->set_instance(*instance);
  function_data->set_jump_table_offset(jump_table_offset);
  function_data->set_function_index(func_index);
  function_data->set_signature(*sig_foreign);
  function_data->set_call_count(0);
  function_data->set_c_wrapper_code(Smi::zero(), SKIP_WRITE_BARRIER);
  function_data->set_wasm_call_target(Smi::zero(), SKIP_WRITE_BARRIER);
  function_data->set_packed_args_size(0);

  MaybeHandle<String> maybe_name;
  bool is_asm_js_module = instance->module_object().is_asm_js();
  if (is_asm_js_module) {
    // We can use the function name only for asm.js. For WebAssembly, the
    // function name is specified as the function_index.toString().
    maybe_name = WasmModuleObject::GetFunctionNameOrNull(
        isolate, handle(instance->module_object(), isolate), func_index);
  }
  Handle<String> name;
  if (!maybe_name.ToHandle(&name)) {
    EmbeddedVector<char, 16> buffer;
    int length = SNPrintF(buffer, "%d", func_index);
    name = isolate->factory()
               ->NewStringFromOneByte(
                   Vector<uint8_t>::cast(buffer.SubVector(0, length)))
               .ToHandleChecked();
  }
  Handle<Map> function_map;
  switch (instance->module()->origin) {
    case wasm::kWasmOrigin:
      if (instance->module_object()
              .native_module()
              ->enabled_features()
              .has_gc()) {
        uint32_t sig_index =
            instance->module()->functions[func_index].sig_index;
        function_map = handle(
            Map::cast(instance->managed_object_maps().get(sig_index)), isolate);
      } else {
        function_map = isolate->wasm_exported_function_map();
      }
      break;
    case wasm::kAsmJsSloppyOrigin:
      function_map = isolate->sloppy_function_map();
      break;
    case wasm::kAsmJsStrictOrigin:
      function_map = isolate->strict_function_map();
      break;
  }
  NewFunctionArgs args =
      NewFunctionArgs::ForWasm(name, function_data, function_map);
  Handle<JSFunction> js_function = isolate->factory()->NewFunction(args);
  // According to the spec, exported functions should not have a [[Construct]]
  // method. This does not apply to functions exported from asm.js however.
  DCHECK_EQ(is_asm_js_module, js_function->IsConstructor());
  js_function->shared().set_length(arity);
  js_function->shared().set_internal_formal_parameter_count(arity);
  js_function->shared().set_script(instance->module_object().script());
  return Handle<WasmExportedFunction>::cast(js_function);
}

Address WasmExportedFunction::GetWasmCallTarget() {
  return instance().GetCallTarget(function_index());
}

const wasm::FunctionSig* WasmExportedFunction::sig() {
  return instance().module()->functions[function_index()].sig;
}

bool WasmExportedFunction::MatchesSignature(
    const WasmModule* other_module, const wasm::FunctionSig* other_sig) {
  const wasm::FunctionSig* sig = this->sig();
  if (sig->parameter_count() != other_sig->parameter_count() ||
      sig->return_count() != other_sig->return_count()) {
    return false;
  }

  for (int i = 0; i < sig->all().size(); i++) {
    if (!wasm::EquivalentTypes(sig->all()[i], other_sig->all()[i],
                               this->instance().module(), other_module)) {
      return false;
    }
  }
  return true;
}

// static
bool WasmJSFunction::IsWasmJSFunction(Object object) {
  if (!object.IsJSFunction()) return false;
  JSFunction js_function = JSFunction::cast(object);
  return js_function.shared().HasWasmJSFunctionData();
}

Handle<WasmJSFunction> WasmJSFunction::New(Isolate* isolate,
                                           const wasm::FunctionSig* sig,
                                           Handle<JSReceiver> callable) {
  DCHECK_LE(sig->all().size(), kMaxInt);
  int sig_size = static_cast<int>(sig->all().size());
  int return_count = static_cast<int>(sig->return_count());
  int parameter_count = static_cast<int>(sig->parameter_count());
  Handle<PodArray<wasm::ValueType>> serialized_sig =
      PodArray<wasm::ValueType>::New(isolate, sig_size, AllocationType::kOld);
  if (sig_size > 0) {
    serialized_sig->copy_in(0, sig->all().begin(), sig_size);
  }
  // TODO(wasm): Think about caching and sharing the JS-to-JS wrappers per
  // signature instead of compiling a new one for every instantiation.
  Handle<Code> wrapper_code =
      compiler::CompileJSToJSWrapper(isolate, sig, nullptr).ToHandleChecked();

  Handle<WasmJSFunctionData> function_data =
      Handle<WasmJSFunctionData>::cast(isolate->factory()->NewStruct(
          WASM_JS_FUNCTION_DATA_TYPE, AllocationType::kOld));
  function_data->set_serialized_return_count(return_count);
  function_data->set_serialized_parameter_count(parameter_count);
  function_data->set_serialized_signature(*serialized_sig);
  function_data->set_callable(*callable);
  function_data->set_wrapper_code(*wrapper_code);
  // Use Abort() as a default value (it will never be called if not overwritten
  // below).
  function_data->set_wasm_to_js_wrapper_code(
      isolate->heap()->builtin(Builtins::kAbort));

  if (wasm::WasmFeatures::FromIsolate(isolate).has_typed_funcref()) {
    using CK = compiler::WasmImportCallKind;
    int expected_arity = parameter_count;
    CK kind = compiler::kDefaultImportCallKind;
    if (callable->IsJSFunction()) {
      SharedFunctionInfo shared = Handle<JSFunction>::cast(callable)->shared();
      expected_arity = shared.internal_formal_parameter_count();
      if (expected_arity != parameter_count) {
        kind = CK::kJSFunctionArityMismatch;
      }
    }
    // TODO(wasm): Think about caching and sharing the wasm-to-JS wrappers per
    // signature instead of compiling a new one for every instantiation.
    Handle<Code> wasm_to_js_wrapper_code =
        compiler::CompileWasmToJSWrapper(isolate, sig, kind, expected_arity)
            .ToHandleChecked();
    function_data->set_wasm_to_js_wrapper_code(*wasm_to_js_wrapper_code);
  }

  Handle<String> name = isolate->factory()->Function_string();
  if (callable->IsJSFunction()) {
    name = JSFunction::GetName(Handle<JSFunction>::cast(callable));
    name = String::Flatten(isolate, name);
  }
  Handle<Map> function_map =
      Map::Copy(isolate, isolate->wasm_exported_function_map(),
                "fresh function map for WasmJSFunction::New");
  NewFunctionArgs args =
      NewFunctionArgs::ForWasm(name, function_data, function_map);
  Handle<JSFunction> js_function = isolate->factory()->NewFunction(args);
  js_function->shared().set_internal_formal_parameter_count(parameter_count);
  return Handle<WasmJSFunction>::cast(js_function);
}

JSReceiver WasmJSFunction::GetCallable() const {
  return shared().wasm_js_function_data().callable();
}

const wasm::FunctionSig* WasmJSFunction::GetSignature(Zone* zone) {
  WasmJSFunctionData function_data = shared().wasm_js_function_data();
  int sig_size = function_data.serialized_signature().length();
  wasm::ValueType* types = zone->NewArray<wasm::ValueType>(sig_size);
  if (sig_size > 0) {
    function_data.serialized_signature().copy_out(0, types, sig_size);
  }
  int return_count = function_data.serialized_return_count();
  int parameter_count = function_data.serialized_parameter_count();
  return zone->New<wasm::FunctionSig>(return_count, parameter_count, types);
}

// TODO(9495): Update this if function type variance is introduced.
bool WasmJSFunction::MatchesSignature(const wasm::FunctionSig* sig) {
  DCHECK_LE(sig->all().size(), kMaxInt);
  int sig_size = static_cast<int>(sig->all().size());
  int return_count = static_cast<int>(sig->return_count());
  int parameter_count = static_cast<int>(sig->parameter_count());
  WasmJSFunctionData function_data = shared().wasm_js_function_data();
  if (return_count != function_data.serialized_return_count() ||
      parameter_count != function_data.serialized_parameter_count()) {
    return false;
  }
  if (sig_size == 0) return true;  // Prevent undefined behavior.
  const wasm::ValueType* expected = sig->all().begin();
  return function_data.serialized_signature().matches(expected, sig_size);
}

Address WasmCapiFunction::GetHostCallTarget() const {
  return shared().wasm_capi_function_data().call_target();
}

PodArray<wasm::ValueType> WasmCapiFunction::GetSerializedSignature() const {
  return shared().wasm_capi_function_data().serialized_signature();
}

bool WasmExternalFunction::IsWasmExternalFunction(Object object) {
  return WasmExportedFunction::IsWasmExportedFunction(object) ||
         WasmJSFunction::IsWasmJSFunction(object);
}

Handle<WasmExceptionTag> WasmExceptionTag::New(Isolate* isolate, int index) {
  Handle<WasmExceptionTag> result =
      Handle<WasmExceptionTag>::cast(isolate->factory()->NewStruct(
          WASM_EXCEPTION_TAG_TYPE, AllocationType::kOld));
  result->set_index(index);
  return result;
}

Handle<AsmWasmData> AsmWasmData::New(
    Isolate* isolate, std::shared_ptr<wasm::NativeModule> native_module,
    Handle<FixedArray> export_wrappers, Handle<HeapNumber> uses_bitset) {
  const WasmModule* module = native_module->module();
  const bool kUsesLiftoff = false;
  size_t memory_estimate =
      wasm::WasmCodeManager::EstimateNativeModuleCodeSize(module,
                                                          kUsesLiftoff) +
      wasm::WasmCodeManager::EstimateNativeModuleMetaDataSize(module);
  Handle<Managed<wasm::NativeModule>> managed_native_module =
      Managed<wasm::NativeModule>::FromSharedPtr(isolate, memory_estimate,
                                                 std::move(native_module));
  Handle<AsmWasmData> result = Handle<AsmWasmData>::cast(
      isolate->factory()->NewStruct(ASM_WASM_DATA_TYPE, AllocationType::kOld));
  result->set_managed_native_module(*managed_native_module);
  result->set_export_wrappers(*export_wrappers);
  result->set_uses_bitset(*uses_bitset);
  return result;
}

namespace wasm {

bool TypecheckJSObject(Isolate* isolate, const WasmModule* module,
                       Handle<Object> value, ValueType expected,
                       const char** error_message) {
  DCHECK(expected.is_reference_type());
  switch (expected.kind()) {
    case ValueType::kOptRef:
      if (value->IsNull(isolate)) return true;
      V8_FALLTHROUGH;
    case ValueType::kRef:
      switch (expected.heap_representation()) {
        case HeapType::kFunc: {
          if (!(WasmExternalFunction::IsWasmExternalFunction(*value) ||
                WasmCapiFunction::IsWasmCapiFunction(*value))) {
            *error_message =
                "function-typed object must be null (if nullable) or a Wasm "
                "function object";
            return false;
          }
          return true;
        }
        case HeapType::kExtern:
        case HeapType::kExn:
          return true;
        case HeapType::kEq: {
          // TODO(7748): Change this when we have a decision on the JS API for
          // structs/arrays.
          Handle<Name> key = isolate->factory()->wasm_wrapped_object_symbol();
          LookupIterator it(isolate, value, key,
                            LookupIterator::OWN_SKIP_INTERCEPTOR);
          if (it.state() == LookupIterator::DATA) return true;
          *error_message =
              "eqref object must be null (if nullable) or wrapped with wasm "
              "object wrapper";
          return false;
        }
        case HeapType::kI31:
          // TODO(7748): Implement when the JS API for i31ref is decided on.
          *error_message = "Assigning JS objects to i31ref not supported yet.";
          return false;
        default:
          // Tables defined outside a module can't refer to user-defined types.
          if (module == nullptr) return false;
          DCHECK(module->has_type(expected.ref_index()));
          if (module->has_signature(expected.ref_index())) {
            if (WasmExportedFunction::IsWasmExportedFunction(*value)) {
              WasmExportedFunction function =
                  WasmExportedFunction::cast(*value);
              const WasmModule* exporting_module = function.instance().module();
              ValueType real_type = ValueType::Ref(
                  exporting_module->functions[function.function_index()]
                      .sig_index,
                  kNonNullable);
              if (!IsSubtypeOf(real_type, expected, exporting_module, module)) {
                *error_message =
                    "assigned exported function has to be a subtype of the "
                    "expected type";
                return false;
              }
              return true;
            }

            if (WasmJSFunction::IsWasmJSFunction(*value)) {
              // Since a WasmJSFunction cannot refer to indexed types (definable
              // only in a module), we do not need to use EquivalentTypes().
              if (!WasmJSFunction::cast(*value).MatchesSignature(
                      module->signature(expected.ref_index()))) {
                *error_message =
                    "assigned WasmJSFunction has to be a subtype of the "
                    "expected type";
                return false;
              }
              return true;
            }

            if (WasmCapiFunction::IsWasmCapiFunction(*value)) {
              if (!WasmCapiFunction::cast(*value).MatchesSignature(
                      module->signature(expected.ref_index()))) {
                // Since a WasmCapiFunction cannot refer to indexed types
                // (definable in a module), we don't need to invoke
                // IsEquivalentType();
                *error_message =
                    "assigned WasmCapiFunction has to be a subtype of the "
                    "expected type";
                return false;
              }
              return true;
            }

            *error_message =
                "function-typed object must be null (if nullable) or a Wasm "
                "function object";

            return false;
          }
          // TODO(7748): Implement when the JS API for structs/arrays is decided
          // on.
          *error_message =
              "Assigning to struct/array globals not supported yet.";
          return false;
      }
    case ValueType::kRtt:
      // TODO(7748): Implement when the JS API for rtts is decided on.
      *error_message = "Assigning to rtt globals not supported yet.";
      return false;
    default:
      UNREACHABLE();
  }
}

}  // namespace wasm

}  // namespace internal
}  // namespace v8

#undef TRACE_IFT