// Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/compiler/frontend/bytecode_reader.h"

#include "vm/bootstrap.h"
#include "vm/class_finalizer.h"
#include "vm/code_descriptors.h"
#include "vm/compiler/assembler/disassembler_kbc.h"
#include "vm/constants_kbc.h"
#include "vm/dart_entry.h"
#include "vm/longjump.h"
#include "vm/object_store.h"
#include "vm/timeline.h"

#if !defined(DART_PRECOMPILED_RUNTIME)

#define Z (zone_)
#define H (translation_helper_)
#define T (type_translator_)
#define I Isolate::Current()

namespace dart {

DEFINE_FLAG(bool, dump_kernel_bytecode, false, "Dump kernel bytecode");

namespace kernel {

BytecodeMetadataHelper::BytecodeMetadataHelper(KernelReaderHelper* helper,
                                               TypeTranslator* type_translator,
                                               ActiveClass* active_class)
    : MetadataHelper(helper, tag(), /* precompiler_only = */ false),
      type_translator_(*type_translator),
      active_class_(active_class) {}

void BytecodeMetadataHelper::ReadMetadata(const Function& function) {
#if !defined(PRODUCT)
  TimelineDurationScope tds(Thread::Current(), Timeline::GetCompilerStream(),
                            "BytecodeMetadataHelper::ReadMetadata");
#endif  // !defined(PRODUCT)

  const intptr_t node_offset = function.kernel_offset();
  const intptr_t md_offset = GetNextMetadataPayloadOffset(node_offset);
  if (md_offset < 0) {
    return;
  }

  AlternativeReadingScope alt(&helper_->reader_, &H.metadata_payloads(),
                              md_offset);

  const int kHasExceptionsTableFlag = 1 << 0;
  const int kHasNullableFieldsFlag = 1 << 1;
  const int kHasClosuresFlag = 1 << 2;

  const intptr_t flags = helper_->reader_.ReadUInt();
  const bool has_exceptions_table = (flags & kHasExceptionsTableFlag) != 0;
  const bool has_nullable_fields = (flags & kHasNullableFieldsFlag) != 0;
  const bool has_closures = (flags & kHasClosuresFlag) != 0;

  // Create object pool and read pool entries.
  const intptr_t obj_count = helper_->reader_.ReadListLength();
  const ObjectPool& pool =
      ObjectPool::Handle(helper_->zone_, ObjectPool::New(obj_count));

  {
    // While reading pool entries, deopt_ids are allocated for
    // ICData objects.
    //
    // TODO(alexmarkov): allocate deopt_ids for closures separately
    DeoptIdScope deopt_id_scope(H.thread(), 0);

    ReadPoolEntries(function, function, pool, 0);
  }

  // Read bytecode and attach to function.
  const Code& bytecode = Code::Handle(helper_->zone_, ReadBytecode(pool));
  function.AttachBytecode(bytecode);

  // Read exceptions table.
  ReadExceptionsTable(bytecode, has_exceptions_table);

  if (FLAG_dump_kernel_bytecode) {
    KernelBytecodeDisassembler::Disassemble(function);
  }

  // Initialization of fields with null literal is elided from bytecode.
  // Record the corresponding stores if field guards are enabled.
  if (has_nullable_fields) {
    ASSERT(function.IsGenerativeConstructor());
    const intptr_t num_fields = helper_->ReadListLength();
    if (I->use_field_guards()) {
      Field& field = Field::Handle(helper_->zone_);
      for (intptr_t i = 0; i < num_fields; i++) {
        NameIndex name_index = helper_->ReadCanonicalNameReference();
        field = H.LookupFieldByKernelField(name_index);
        field.RecordStore(Object::null_object());
      }
    } else {
      for (intptr_t i = 0; i < num_fields; i++) {
        helper_->SkipCanonicalNameReference();
      }
    }
  }

  // Read closures.
  if (has_closures) {
    Function& closure = Function::Handle(helper_->zone_);
    Code& closure_bytecode = Code::Handle(helper_->zone_);
    const intptr_t num_closures = helper_->ReadListLength();
    for (intptr_t i = 0; i < num_closures; i++) {
      intptr_t closure_index = helper_->ReadUInt();
      ASSERT(closure_index < obj_count);
      closure ^= pool.ObjectAt(closure_index);

      // Read closure bytecode and attach to closure function.
      closure_bytecode = ReadBytecode(pool);
      closure.AttachBytecode(closure_bytecode);

      // Read closure exceptions table.
      ReadExceptionsTable(closure_bytecode);

      if (FLAG_dump_kernel_bytecode) {
        KernelBytecodeDisassembler::Disassemble(closure);
      }
    }
  }
}

intptr_t BytecodeMetadataHelper::ReadPoolEntries(const Function& function,
                                                 const Function& inner_function,
                                                 const ObjectPool& pool,
                                                 intptr_t from_index) {
#if !defined(PRODUCT)
  TimelineDurationScope tds(Thread::Current(), Timeline::GetCompilerStream(),
                            "BytecodeMetadataHelper::ReadPoolEntries");
#endif  // !defined(PRODUCT)

  // These enums and the code below reading the constant pool from kernel must
  // be kept in sync with pkg/vm/lib/bytecode/constant_pool.dart.
  enum ConstantPoolTag {
    kInvalid,
    kNull,
    kString,
    kInt,
    kDouble,
    kBool,
    kArgDesc,
    kICData,
    kStaticICData,
    kStaticField,
    kInstanceField,
    kClass,
    kTypeArgumentsField,
    kTearOff,
    kType,
    kTypeArguments,
    kList,
    kInstance,
    kTypeArgumentsForInstanceAllocation,
    kClosureFunction,
    kEndClosureFunctionScope,
    kNativeEntry,
    kSubtypeTestCache,
    kPartialTearOffInstantiation,
    kEmptyTypeArguments,
    kSymbol,
  };

  enum InvocationKind {
    method,  // x.foo(...) or foo(...)
    getter,  // x.foo
    setter   // x.foo = ...
  };

  const int kInvocationKindMask = 0x3;
  const int kFlagDynamic = 1 << 2;

  Object& obj = Object::Handle(helper_->zone_);
  Object& elem = Object::Handle(helper_->zone_);
  Array& array = Array::Handle(helper_->zone_);
  Field& field = Field::Handle(helper_->zone_);
  Class& cls = Class::Handle(helper_->zone_);
  Library& lib = Library::Handle(helper_->zone_);
  String& name = String::Handle(helper_->zone_);
  TypeArguments& type_args = TypeArguments::Handle(helper_->zone_);
  Class* symbol_class = nullptr;
  Field* symbol_name_field = nullptr;
  const intptr_t obj_count = pool.Length();
  for (intptr_t i = from_index; i < obj_count; ++i) {
    const intptr_t tag = helper_->ReadTag();
    switch (tag) {
      case ConstantPoolTag::kInvalid:
        UNREACHABLE();
      case ConstantPoolTag::kNull:
        obj = Object::null();
        break;
      case ConstantPoolTag::kString:
        obj = H.DartString(helper_->ReadStringReference()).raw();
        ASSERT(obj.IsString());
        obj = H.Canonicalize(String::Cast(obj));
        break;
      case ConstantPoolTag::kInt: {
        uint32_t low_bits = helper_->ReadUInt32();
        int64_t value = helper_->ReadUInt32();
        value = (value << 32) | low_bits;
        obj = Integer::New(value, Heap::kOld);
        obj = H.Canonicalize(Integer::Cast(obj));
      } break;
      case ConstantPoolTag::kDouble: {
        uint32_t low_bits = helper_->ReadUInt32();
        uint64_t bits = helper_->ReadUInt32();
        bits = (bits << 32) | low_bits;
        double value = bit_cast<double, uint64_t>(bits);
        obj = Double::New(value, Heap::kOld);
        obj = H.Canonicalize(Double::Cast(obj));
      } break;
      case ConstantPoolTag::kBool:
        if (helper_->ReadUInt() == 1) {
          obj = Bool::True().raw();
        } else {
          obj = Bool::False().raw();
        }
        break;
      case ConstantPoolTag::kArgDesc: {
        intptr_t num_arguments = helper_->ReadUInt();
        intptr_t num_type_args = helper_->ReadUInt();
        intptr_t num_arg_names = helper_->ReadListLength();
        if (num_arg_names == 0) {
          obj = ArgumentsDescriptor::New(num_type_args, num_arguments);
        } else {
          array = Array::New(num_arg_names);
          for (intptr_t j = 0; j < num_arg_names; j++) {
            array.SetAt(j, H.DartSymbolPlain(helper_->ReadStringReference()));
          }
          obj = ArgumentsDescriptor::New(num_type_args, num_arguments, array);
        }
      } break;
      case ConstantPoolTag::kICData: {
        intptr_t flags = helper_->ReadByte();
        InvocationKind kind =
            static_cast<InvocationKind>(flags & kInvocationKindMask);
        bool isDynamic = (flags & kFlagDynamic) != 0;
        if (kind == InvocationKind::getter) {
          name = helper_->ReadNameAsGetterName().raw();
        } else if (kind == InvocationKind::setter) {
          name = helper_->ReadNameAsSetterName().raw();
        } else {
          ASSERT(kind == InvocationKind::method);
          name = helper_->ReadNameAsMethodName().raw();
        }
        intptr_t arg_desc_index = helper_->ReadUInt();
        ASSERT(arg_desc_index < i);
        array ^= pool.ObjectAt(arg_desc_index);
        intptr_t checked_argument_count = 1;
        if ((kind == InvocationKind::method) &&
            (MethodTokenRecognizer::RecognizeTokenKind(name) !=
             Token::kILLEGAL)) {
          intptr_t argument_count = ArgumentsDescriptor(array).Count();
          ASSERT(argument_count <= 2);
          checked_argument_count = argument_count;
        }
        // Do not mangle == or call:
        //   * operator == takes an Object so its either not checked or checked
        //     at the entry because the parameter is marked covariant, neither
        //     of those cases require a dynamic invocation forwarder;
        //   * we assume that all closures are entered in a checked way.
        if (isDynamic && (kind != InvocationKind::getter) &&
            !FLAG_precompiled_mode && I->should_emit_strong_mode_checks() &&
            (name.raw() != Symbols::EqualOperator().raw()) &&
            (name.raw() != Symbols::Call().raw())) {
          name = Function::CreateDynamicInvocationForwarderName(name);
        }
        obj =
            ICData::New(function, name,
                        array,  // Arguments descriptor.
                        H.thread()->compiler_state().GetNextDeoptId(),
                        checked_argument_count, ICData::RebindRule::kInstance);
#if defined(TAG_IC_DATA)
        ICData::Cast(obj).set_tag(ICData::Tag::kInstanceCall);
#endif
      } break;
      case ConstantPoolTag::kStaticICData: {
        InvocationKind kind = static_cast<InvocationKind>(helper_->ReadByte());
        NameIndex target = helper_->ReadCanonicalNameReference();
        if (H.IsConstructor(target)) {
          name = H.DartConstructorName(target).raw();
          elem = H.LookupConstructorByKernelConstructor(target);
        } else if (H.IsField(target)) {
          if (kind == InvocationKind::getter) {
            name = H.DartGetterName(target).raw();
          } else if (kind == InvocationKind::setter) {
            name = H.DartSetterName(target).raw();
          } else {
            ASSERT(kind == InvocationKind::method);
            UNIMPLEMENTED();  // TODO(regis): Revisit.
          }
          field = H.LookupFieldByKernelField(target);
          cls = field.Owner();
          elem = cls.LookupFunctionAllowPrivate(name);
        } else {
          if ((kind == InvocationKind::method) && H.IsGetter(target)) {
            UNIMPLEMENTED();  // TODO(regis): Revisit.
          }
          name = H.DartProcedureName(target).raw();
          elem = H.LookupStaticMethodByKernelProcedure(target);
          if ((kind == InvocationKind::getter) && !H.IsGetter(target)) {
            // Tear-off
            name = H.DartGetterName(target).raw();
            elem = Function::Cast(elem).GetMethodExtractor(name);
          }
        }
        const int num_args_checked =
            MethodRecognizer::NumArgsCheckedForStaticCall(Function::Cast(elem));
        ASSERT(elem.IsFunction());
        intptr_t arg_desc_index = helper_->ReadUInt();
        ASSERT(arg_desc_index < i);
        array ^= pool.ObjectAt(arg_desc_index);
        obj = ICData::New(function, name,
                          array,  // Arguments descriptor.
                          H.thread()->compiler_state().GetNextDeoptId(),
                          num_args_checked, ICData::RebindRule::kStatic);
        ICData::Cast(obj).AddTarget(Function::Cast(elem));
#if defined(TAG_IC_DATA)
        ICData::Cast(obj).set_tag(ICData::Tag::kStaticCall);
#endif
      } break;
      case ConstantPoolTag::kStaticField:
        obj = H.LookupFieldByKernelField(helper_->ReadCanonicalNameReference());
        ASSERT(obj.IsField());
        break;
      case ConstantPoolTag::kInstanceField:
        field =
            H.LookupFieldByKernelField(helper_->ReadCanonicalNameReference());
        // InstanceField constant occupies 2 entries.
        // The first entry is used for field offset.
        obj = Smi::New(field.Offset() / kWordSize);
        pool.SetTypeAt(i, ObjectPool::kTaggedObject, ObjectPool::kNotPatchable);
        pool.SetObjectAt(i, obj);
        ++i;
        ASSERT(i < obj_count);
        // The second entry is used for field object.
        obj = field.raw();
        break;
      case ConstantPoolTag::kClass:
        obj = H.LookupClassByKernelClass(helper_->ReadCanonicalNameReference());
        ASSERT(obj.IsClass());
        break;
      case ConstantPoolTag::kTypeArgumentsField:
        cls = H.LookupClassByKernelClass(helper_->ReadCanonicalNameReference());
        obj = Smi::New(cls.type_arguments_field_offset() / kWordSize);
        break;
      case ConstantPoolTag::kTearOff:
        obj = H.LookupStaticMethodByKernelProcedure(
            helper_->ReadCanonicalNameReference());
        ASSERT(obj.IsFunction());
        obj = Function::Cast(obj).ImplicitClosureFunction();
        ASSERT(obj.IsFunction());
        obj = Function::Cast(obj).ImplicitStaticClosure();
        ASSERT(obj.IsInstance());
        obj = H.Canonicalize(Instance::Cast(obj));
        break;
      case ConstantPoolTag::kType:
        obj = type_translator_.BuildType().raw();
        ASSERT(obj.IsAbstractType());
        break;
      case ConstantPoolTag::kTypeArguments:
        obj = type_translator_.BuildTypeArguments(helper_->ReadListLength())
                  .raw();
        ASSERT(obj.IsNull() || obj.IsTypeArguments());
        break;
      case ConstantPoolTag::kList: {
        obj = type_translator_.BuildType().raw();
        ASSERT(obj.IsAbstractType());
        const intptr_t length = helper_->ReadListLength();
        array = Array::New(length, AbstractType::Cast(obj));
        for (intptr_t j = 0; j < length; j++) {
          intptr_t elem_index = helper_->ReadUInt();
          ASSERT(elem_index < i);
          elem = pool.ObjectAt(elem_index);
          array.SetAt(j, elem);
        }
        array.MakeImmutable();
        obj = H.Canonicalize(Array::Cast(array));
        ASSERT(!obj.IsNull());
      } break;
      case ConstantPoolTag::kInstance: {
        cls = H.LookupClassByKernelClass(helper_->ReadCanonicalNameReference());
        obj = Instance::New(cls, Heap::kOld);
        intptr_t type_args_index = helper_->ReadUInt();
        ASSERT(type_args_index < i);
        type_args ^= pool.ObjectAt(type_args_index);
        if (!type_args.IsNull()) {
          Instance::Cast(obj).SetTypeArguments(type_args);
        }
        intptr_t num_fields = helper_->ReadUInt();
        for (intptr_t j = 0; j < num_fields; j++) {
          NameIndex field_name = helper_->ReadCanonicalNameReference();
          ASSERT(H.IsField(field_name));
          field = H.LookupFieldByKernelField(field_name);
          intptr_t elem_index = helper_->ReadUInt();
          ASSERT(elem_index < i);
          elem = pool.ObjectAt(elem_index);
          Instance::Cast(obj).SetField(field, elem);
        }
        obj = H.Canonicalize(Instance::Cast(obj));
      } break;
      case ConstantPoolTag::kTypeArgumentsForInstanceAllocation: {
        cls = H.LookupClassByKernelClass(helper_->ReadCanonicalNameReference());
        obj =
            type_translator_
                .BuildInstantiatedTypeArguments(cls, helper_->ReadListLength())
                .raw();
        ASSERT(obj.IsNull() || obj.IsTypeArguments());
      } break;
      case ConstantPoolTag::kClosureFunction: {
        name = H.DartSymbolPlain(helper_->ReadStringReference()).raw();
        const Function& closure = Function::Handle(
            helper_->zone_,
            Function::NewClosureFunction(name, inner_function,
                                         TokenPosition::kNoSource));

        FunctionNodeHelper function_node_helper(helper_);
        function_node_helper.ReadUntilExcluding(
            FunctionNodeHelper::kTypeParameters);
        type_translator_.LoadAndSetupTypeParameters(
            active_class_, closure, helper_->ReadListLength(), closure);
        function_node_helper.SetJustRead(FunctionNodeHelper::kTypeParameters);

        // Scope remains opened until ConstantPoolTag::kEndClosureFunctionScope.
        ActiveTypeParametersScope scope(
            active_class_, &closure,
            TypeArguments::Handle(helper_->zone_, closure.type_parameters()),
            helper_->zone_);

        function_node_helper.ReadUntilExcluding(
            FunctionNodeHelper::kPositionalParameters);

        intptr_t required_parameter_count =
            function_node_helper.required_parameter_count_;
        intptr_t total_parameter_count =
            function_node_helper.total_parameter_count_;

        intptr_t positional_parameter_count = helper_->ReadListLength();

        intptr_t named_parameter_count =
            total_parameter_count - positional_parameter_count;

        const intptr_t extra_parameters = 1;
        closure.set_num_fixed_parameters(extra_parameters +
                                         required_parameter_count);
        if (named_parameter_count > 0) {
          closure.SetNumOptionalParameters(named_parameter_count, false);
        } else {
          closure.SetNumOptionalParameters(
              positional_parameter_count - required_parameter_count, true);
        }
        intptr_t parameter_count = extra_parameters + total_parameter_count;
        closure.set_parameter_types(Array::Handle(
            helper_->zone_, Array::New(parameter_count, Heap::kOld)));
        closure.set_parameter_names(Array::Handle(
            helper_->zone_, Array::New(parameter_count, Heap::kOld)));

        intptr_t pos = 0;
        closure.SetParameterTypeAt(pos, AbstractType::dynamic_type());
        closure.SetParameterNameAt(pos, Symbols::ClosureParameter());
        pos++;

        lib = active_class_->klass->library();
        for (intptr_t j = 0; j < positional_parameter_count; ++j, ++pos) {
          VariableDeclarationHelper helper(helper_);
          helper.ReadUntilExcluding(VariableDeclarationHelper::kType);
          const AbstractType& type = type_translator_.BuildVariableType();
          Tag tag = helper_->ReadTag();  // read (first part of) initializer.
          if (tag == kSomething) {
            helper_->SkipExpression();  // read (actual) initializer.
          }

          closure.SetParameterTypeAt(pos, type);
          closure.SetParameterNameAt(pos,
                                     H.DartIdentifier(lib, helper.name_index_));
        }

        intptr_t named_parameter_count_check = helper_->ReadListLength();
        ASSERT(named_parameter_count_check == named_parameter_count);
        for (intptr_t j = 0; j < named_parameter_count; ++j, ++pos) {
          VariableDeclarationHelper helper(helper_);
          helper.ReadUntilExcluding(VariableDeclarationHelper::kType);
          const AbstractType& type = type_translator_.BuildVariableType();
          Tag tag = helper_->ReadTag();  // read (first part of) initializer.
          if (tag == kSomething) {
            helper_->SkipExpression();  // read (actual) initializer.
          }

          closure.SetParameterTypeAt(pos, type);
          closure.SetParameterNameAt(pos,
                                     H.DartIdentifier(lib, helper.name_index_));
        }

        function_node_helper.SetJustRead(FunctionNodeHelper::kNamedParameters);

        const AbstractType& return_type = type_translator_.BuildVariableType();
        closure.set_result_type(return_type);
        function_node_helper.SetJustRead(FunctionNodeHelper::kReturnType);
        // The closure has no body.
        function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kEnd);

        // Finalize function type.
        Type& signature_type =
            Type::Handle(helper_->zone_, closure.SignatureType());
        signature_type ^= ClassFinalizer::FinalizeType(*(active_class_->klass),
                                                       signature_type);
        closure.SetSignatureType(signature_type);

        pool.SetTypeAt(i, ObjectPool::kTaggedObject, ObjectPool::kNotPatchable);
        pool.SetObjectAt(i, closure);

        // Continue reading the constant pool entries inside the opened
        // ActiveTypeParametersScope until the scope gets closed by a
        // kEndClosureFunctionScope tag, in which case control returns here.
        i = ReadPoolEntries(function, closure, pool, i + 1);
        // Pool entry at index i has been set to null, because it was a
        // kEndClosureFunctionScope.
        ASSERT(pool.ObjectAt(i) == Object::null());
        continue;
      }
      case ConstantPoolTag::kEndClosureFunctionScope: {
        // Entry is not used and set to null.
        obj = Object::null();
        pool.SetTypeAt(i, ObjectPool::kTaggedObject, ObjectPool::kNotPatchable);
        pool.SetObjectAt(i, obj);
        return i;  // The caller will close the scope.
      } break;
      case ConstantPoolTag::kNativeEntry: {
        name = H.DartString(helper_->ReadStringReference()).raw();
        obj = NativeEntry(function, name);
      } break;
      case ConstantPoolTag::kSubtypeTestCache: {
        obj = SubtypeTestCache::New();
      } break;
      case ConstantPoolTag::kPartialTearOffInstantiation: {
        intptr_t tearoff_index = helper_->ReadUInt();
        ASSERT(tearoff_index < i);
        const Closure& old_closure = Closure::CheckedHandle(
            helper_->zone_, pool.ObjectAt(tearoff_index));

        intptr_t type_args_index = helper_->ReadUInt();
        ASSERT(type_args_index < i);
        type_args ^= pool.ObjectAt(type_args_index);

        obj = Closure::New(
            TypeArguments::Handle(helper_->zone_,
                                  old_closure.instantiator_type_arguments()),
            TypeArguments::Handle(helper_->zone_,
                                  old_closure.function_type_arguments()),
            type_args, Function::Handle(helper_->zone_, old_closure.function()),
            Context::Handle(helper_->zone_, old_closure.context()), Heap::kOld);
        obj = H.Canonicalize(Instance::Cast(obj));
      } break;
      case ConstantPoolTag::kEmptyTypeArguments:
        obj = Object::empty_type_arguments().raw();
        break;
      case ConstantPoolTag::kSymbol: {
        const NameIndex lib_index = helper_->ReadCanonicalNameReference();
        lib = Library::null();
        if (!H.IsRoot(lib_index)) {
          lib = H.LookupLibraryByKernelLibrary(lib_index);
        }
        const String& symbol =
            H.DartIdentifier(lib, helper_->ReadStringReference());
        if (symbol_class == nullptr) {
          elem = Library::InternalLibrary();
          ASSERT(!elem.IsNull());
          symbol_class = &Class::Handle(
              helper_->zone_,
              Library::Cast(elem).LookupClass(Symbols::Symbol()));
          ASSERT(!symbol_class->IsNull());
          symbol_name_field = &Field::Handle(
              helper_->zone_,
              symbol_class->LookupInstanceFieldAllowPrivate(Symbols::_name()));
          ASSERT(!symbol_name_field->IsNull());
        }
        obj = Instance::New(*symbol_class, Heap::kOld);
        Instance::Cast(obj).SetField(*symbol_name_field, symbol);
        obj = H.Canonicalize(Instance::Cast(obj));
      } break;
      default:
        UNREACHABLE();
    }
    pool.SetTypeAt(i, ObjectPool::kTaggedObject, ObjectPool::kNotPatchable);
    pool.SetObjectAt(i, obj);
  }
  // Return the index of the last read pool entry.
  return obj_count - 1;
}

RawCode* BytecodeMetadataHelper::ReadBytecode(const ObjectPool& pool) {
#if !defined(PRODUCT)
  TimelineDurationScope tds(Thread::Current(), Timeline::GetCompilerStream(),
                            "BytecodeMetadataHelper::ReadBytecode");
#endif  // !defined(PRODUCT)

  intptr_t size = helper_->reader_.ReadUInt();
  intptr_t offset = helper_->reader_.offset();
  const uint8_t* data = helper_->reader_.BufferAt(offset);
  helper_->reader_.set_offset(offset + size);

  // Create and return code object.
  return Code::FinalizeBytecode(reinterpret_cast<const void*>(data), size,
                                pool);
}

void BytecodeMetadataHelper::ReadExceptionsTable(const Code& bytecode,
                                                 bool has_exceptions_table) {
#if !defined(PRODUCT)
  TimelineDurationScope tds(Thread::Current(), Timeline::GetCompilerStream(),
                            "BytecodeMetadataHelper::ReadExceptionsTable");
#endif  // !defined(PRODUCT)

  const intptr_t try_block_count =
      has_exceptions_table ? helper_->reader_.ReadListLength() : 0;
  if (try_block_count > 0) {
    const ObjectPool& pool =
        ObjectPool::Handle(helper_->zone_, bytecode.object_pool());
    AbstractType& handler_type = AbstractType::Handle(helper_->zone_);
    Array& handler_types = Array::ZoneHandle(helper_->zone_);
    DescriptorList* pc_descriptors_list =
        new (helper_->zone_) DescriptorList(64);
    ExceptionHandlerList* exception_handlers_list =
        new (helper_->zone_) ExceptionHandlerList();

    // Encoding of ExceptionsTable is described in
    // pkg/vm/lib/bytecode/exceptions.dart.
    for (intptr_t try_index = 0; try_index < try_block_count; try_index++) {
      intptr_t outer_try_index_plus1 = helper_->reader_.ReadUInt();
      intptr_t outer_try_index = outer_try_index_plus1 - 1;
      // PcDescriptors are expressed in terms of return addresses.
      intptr_t start_pc = KernelBytecode::BytecodePcToOffset(
          helper_->reader_.ReadUInt(), /* is_return_address = */ true);
      intptr_t end_pc = KernelBytecode::BytecodePcToOffset(
          helper_->reader_.ReadUInt(), /* is_return_address = */ true);
      intptr_t handler_pc = KernelBytecode::BytecodePcToOffset(
          helper_->reader_.ReadUInt(), /* is_return_address = */ false);
      uint8_t flags = helper_->reader_.ReadByte();
      const uint8_t kFlagNeedsStackTrace = 1 << 0;
      const uint8_t kFlagIsSynthetic = 1 << 1;
      const bool needs_stacktrace = (flags & kFlagNeedsStackTrace) != 0;
      const bool is_generated = (flags & kFlagIsSynthetic) != 0;
      intptr_t type_count = helper_->reader_.ReadListLength();
      ASSERT(type_count > 0);
      handler_types = Array::New(type_count, Heap::kOld);
      for (intptr_t i = 0; i < type_count; i++) {
        intptr_t type_index = helper_->reader_.ReadUInt();
        ASSERT(type_index < pool.Length());
        handler_type ^= pool.ObjectAt(type_index);
        handler_types.SetAt(i, handler_type);
      }
      pc_descriptors_list->AddDescriptor(RawPcDescriptors::kOther, start_pc,
                                         DeoptId::kNone,
                                         TokenPosition::kNoSource, try_index);
      pc_descriptors_list->AddDescriptor(RawPcDescriptors::kOther, end_pc,
                                         DeoptId::kNone,
                                         TokenPosition::kNoSource, -1);

      exception_handlers_list->AddHandler(
          try_index, outer_try_index, handler_pc, TokenPosition::kNoSource,
          is_generated, handler_types, needs_stacktrace);
    }
    const PcDescriptors& descriptors = PcDescriptors::Handle(
        helper_->zone_,
        pc_descriptors_list->FinalizePcDescriptors(bytecode.PayloadStart()));
    bytecode.set_pc_descriptors(descriptors);
    const ExceptionHandlers& handlers = ExceptionHandlers::Handle(
        helper_->zone_, exception_handlers_list->FinalizeExceptionHandlers(
                            bytecode.PayloadStart()));
    bytecode.set_exception_handlers(handlers);
  } else {
    bytecode.set_pc_descriptors(Object::empty_descriptors());
    bytecode.set_exception_handlers(Object::empty_exception_handlers());
  }
}

RawTypedData* BytecodeMetadataHelper::NativeEntry(const Function& function,
                                                  const String& external_name) {
  Zone* zone = helper_->zone_;
  MethodRecognizer::Kind kind = MethodRecognizer::RecognizeKind(function);
  // This list of recognized methods must be kept in sync with the list of
  // methods handled specially by the NativeCall bytecode in the interpreter.
  switch (kind) {
    case MethodRecognizer::kObjectEquals:
    case MethodRecognizer::kStringBaseLength:
    case MethodRecognizer::kStringBaseIsEmpty:
    case MethodRecognizer::kGrowableArrayLength:
    case MethodRecognizer::kObjectArrayLength:
    case MethodRecognizer::kImmutableArrayLength:
    case MethodRecognizer::kTypedDataLength:
    case MethodRecognizer::kClassIDgetID:
    case MethodRecognizer::kGrowableArrayCapacity:
    case MethodRecognizer::kListFactory:
    case MethodRecognizer::kObjectArrayAllocate:
    case MethodRecognizer::kLinkedHashMap_getIndex:
    case MethodRecognizer::kLinkedHashMap_setIndex:
    case MethodRecognizer::kLinkedHashMap_getData:
    case MethodRecognizer::kLinkedHashMap_setData:
    case MethodRecognizer::kLinkedHashMap_getHashMask:
    case MethodRecognizer::kLinkedHashMap_setHashMask:
    case MethodRecognizer::kLinkedHashMap_getUsedData:
    case MethodRecognizer::kLinkedHashMap_setUsedData:
    case MethodRecognizer::kLinkedHashMap_getDeletedKeys:
    case MethodRecognizer::kLinkedHashMap_setDeletedKeys:
      break;
    default:
      kind = MethodRecognizer::kUnknown;
  }
  NativeFunctionWrapper trampoline = NULL;
  NativeFunction native_function = NULL;
  intptr_t argc_tag = 0;
  if (kind == MethodRecognizer::kUnknown) {
    if (FLAG_link_natives_lazily) {
      trampoline = &NativeEntry::BootstrapNativeCallWrapper;
      native_function =
          reinterpret_cast<NativeFunction>(&NativeEntry::LinkNativeCall);
    } else {
      const Class& cls = Class::Handle(zone, function.Owner());
      const Library& library = Library::Handle(zone, cls.library());
      Dart_NativeEntryResolver resolver = library.native_entry_resolver();
      const bool is_bootstrap_native = Bootstrap::IsBootstrapResolver(resolver);
      const int num_params =
          NativeArguments::ParameterCountForResolution(function);
      bool is_auto_scope = true;
      native_function = NativeEntry::ResolveNative(library, external_name,
                                                   num_params, &is_auto_scope);
      ASSERT(native_function != NULL);  // TODO(regis): Should we throw instead?
      if (is_bootstrap_native) {
        trampoline = &NativeEntry::BootstrapNativeCallWrapper;
      } else if (is_auto_scope) {
        trampoline = &NativeEntry::AutoScopeNativeCallWrapper;
      } else {
        trampoline = &NativeEntry::NoScopeNativeCallWrapper;
      }
    }
    argc_tag = NativeArguments::ComputeArgcTag(function);
  }
  return NativeEntryData::New(kind, trampoline, native_function, argc_tag);
}

RawError* BytecodeReader::ReadFunctionBytecode(Thread* thread,
                                               const Function& function) {
  ASSERT(!FLAG_precompiled_mode);
  ASSERT(!function.HasBytecode());
  ASSERT(thread->sticky_error() == Error::null());

  LongJumpScope jump;
  if (setjmp(*jump.Set()) == 0) {
    StackZone stack_zone(thread);
    Zone* const zone = stack_zone.GetZone();
    HANDLESCOPE(thread);
    CompilerState compiler_state(thread);

    const Script& script = Script::Handle(zone, function.script());
    TranslationHelper translation_helper(thread);
    translation_helper.InitFromScript(script);

    KernelReaderHelper reader_helper(
        zone, &translation_helper, script,
        ExternalTypedData::Handle(zone, function.KernelData()),
        function.KernelDataProgramOffset());
    ActiveClass active_class;
    TypeTranslator type_translator(&reader_helper, &active_class,
                                   /* finalize= */ true);

    BytecodeMetadataHelper bytecode_metadata_helper(
        &reader_helper, &type_translator, &active_class);

    // Setup a [ActiveClassScope] and a [ActiveMemberScope] which will be used
    // e.g. for type translation.
    const Class& klass = Class::Handle(zone, function.Owner());
    Function& outermost_function =
        Function::Handle(zone, function.GetOutermostFunction());

    ActiveClassScope active_class_scope(&active_class, &klass);
    ActiveMemberScope active_member(&active_class, &outermost_function);
    ActiveTypeParametersScope active_type_params(&active_class, function, zone);

    bytecode_metadata_helper.ReadMetadata(function);

    return Error::null();
  } else {
    StackZone stack_zone(thread);
    Error& error = Error::Handle();
    // We got an error during bytecode reading.
    error = thread->sticky_error();
    thread->clear_sticky_error();
    return error.raw();
  }
}

}  // namespace kernel
}  // namespace dart

#endif  // !defined(DART_PRECOMPILED_RUNTIME)