runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc

// Copyright (c) 2016, 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/kernel_binary_flowgraph.h"

#include "vm/compiler/ffi/callback.h"
#include "vm/compiler/frontend/bytecode_flow_graph_builder.h"
#include "vm/compiler/frontend/bytecode_reader.h"
#include "vm/compiler/frontend/flow_graph_builder.h"  // For dart::FlowGraphBuilder::SimpleInstanceOfType.
#include "vm/compiler/frontend/prologue_builder.h"
#include "vm/compiler/jit/compiler.h"
#include "vm/object_store.h"
#include "vm/resolver.h"
#include "vm/stack_frame.h"

namespace dart {

DECLARE_FLAG(bool, enable_interpreter);

namespace kernel {

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

Class& StreamingFlowGraphBuilder::GetSuperOrDie() {
  Class& klass = Class::Handle(Z, parsed_function()->function().Owner());
  ASSERT(!klass.IsNull());
  klass = klass.SuperClass();
  ASSERT(!klass.IsNull());
  return klass;
}

FlowGraph* StreamingFlowGraphBuilder::BuildGraphOfFieldInitializer() {
  FieldHelper field_helper(this);
  field_helper.ReadUntilExcluding(FieldHelper::kInitializer);

  Tag initializer_tag = ReadTag();  // read first part of initializer.
  if (initializer_tag != kSomething) {
    UNREACHABLE();
  }

  B->graph_entry_ = new (Z) GraphEntryInstr(*parsed_function(), B->osr_id_);

  auto normal_entry = B->BuildFunctionEntry(B->graph_entry_);
  B->graph_entry_->set_normal_entry(normal_entry);

  Fragment body(normal_entry);
  body += B->CheckStackOverflowInPrologue(field_helper.position_);
  if (field_helper.IsConst()) {
    // This will read the initializer.
    body += Constant(
        Instance::ZoneHandle(Z, constant_reader_.ReadConstantExpression()));
  } else {
    body += SetupCapturedParameters(parsed_function()->function());
    body += BuildExpression();  // read initializer.
  }
  body += Return(TokenPosition::kNoSource);

  PrologueInfo prologue_info(-1, -1);
  if (B->IsCompiledForOsr()) {
    B->graph_entry_->RelinkToOsrEntry(Z, B->last_used_block_id_ + 1);
  }
  return new (Z) FlowGraph(*parsed_function(), B->graph_entry_,
                           B->last_used_block_id_, prologue_info);
}

void StreamingFlowGraphBuilder::EvaluateConstFieldValue(const Field& field) {
  ASSERT(field.is_const() && field.IsUninitialized());

  FieldHelper field_helper(this);
  field_helper.ReadUntilExcluding(FieldHelper::kInitializer);
  Tag initializer_tag = ReadTag();  // read first part of initializer.

  ASSERT(initializer_tag == kSomething);

  Instance& value =
      Instance::Handle(Z, constant_reader_.ReadConstantExpression());
  field.SetStaticValue(value);
}

void StreamingFlowGraphBuilder::SetupDefaultParameterValues() {
  intptr_t optional_parameter_count =
      parsed_function()->function().NumOptionalParameters();
  if (optional_parameter_count > 0) {
    ZoneGrowableArray<const Instance*>* default_values =
        new ZoneGrowableArray<const Instance*>(Z, optional_parameter_count);

    AlternativeReadingScope alt(&reader_);
    FunctionNodeHelper function_node_helper(this);
    function_node_helper.ReadUntilExcluding(
        FunctionNodeHelper::kPositionalParameters);

    if (parsed_function()->function().HasOptionalNamedParameters()) {
      // List of positional.
      intptr_t list_length = ReadListLength();  // read list length.
      for (intptr_t i = 0; i < list_length; ++i) {
        SkipVariableDeclaration();  // read ith variable declaration.
      }

      // List of named.
      list_length = ReadListLength();  // read list length.
      ASSERT(optional_parameter_count == list_length);
      ASSERT(!parsed_function()->function().HasOptionalPositionalParameters());
      for (intptr_t i = 0; i < list_length; ++i) {
        Instance* default_value;

        // Read ith variable declaration
        VariableDeclarationHelper helper(this);
        helper.ReadUntilExcluding(VariableDeclarationHelper::kInitializer);
        Tag tag = ReadTag();  // read (first part of) initializer.
        if (tag == kSomething) {
          // This will read the initializer.
          default_value = &Instance::ZoneHandle(
              Z, constant_reader_.ReadConstantExpression());
        } else {
          default_value = &Instance::ZoneHandle(Z, Instance::null());
        }
        default_values->Add(default_value);
      }
    } else {
      // List of positional.
      intptr_t list_length = ReadListLength();  // read list length.
      ASSERT(list_length == function_node_helper.required_parameter_count_ +
                                optional_parameter_count);
      ASSERT(parsed_function()->function().HasOptionalPositionalParameters());
      for (intptr_t i = 0; i < function_node_helper.required_parameter_count_;
           ++i) {
        SkipVariableDeclaration();  // read ith variable declaration.
      }
      for (intptr_t i = 0; i < optional_parameter_count; ++i) {
        Instance* default_value;

        // Read ith variable declaration
        VariableDeclarationHelper helper(this);
        helper.ReadUntilExcluding(VariableDeclarationHelper::kInitializer);
        Tag tag = ReadTag();  // read (first part of) initializer.
        if (tag == kSomething) {
          // This will read the initializer.
          default_value = &Instance::ZoneHandle(
              Z, constant_reader_.ReadConstantExpression());
        } else {
          default_value = &Instance::ZoneHandle(Z, Instance::null());
        }
        default_values->Add(default_value);
      }

      // List of named.
      list_length = ReadListLength();  // read list length.
      ASSERT(list_length == 0);
    }
    parsed_function()->set_default_parameter_values(default_values);
  }
}

Fragment StreamingFlowGraphBuilder::BuildFieldInitializer(
    const Field& field,
    bool only_for_side_effects) {
  ASSERT(Error::Handle(Z, H.thread()->sticky_error()).IsNull());
  if (PeekTag() == kNullLiteral) {
    SkipExpression();  // read past the null literal.
    if (H.thread()->IsMutatorThread()) {
      field.RecordStore(Object::null_object());
    } else {
      ASSERT(field.is_nullable(/* silence_assert = */ true));
    }
    return Fragment();
  }

  Fragment instructions;
  if (!only_for_side_effects) {
    instructions += LoadLocal(parsed_function()->receiver_var());
  }
  // All closures created inside BuildExpression will have
  // field.RawOwner() as its owner.
  closure_owner_ = field.RawOwner();
  instructions += BuildExpression();
  closure_owner_ = Object::null();
  if (only_for_side_effects) {
    instructions += Drop();
  } else {
    instructions += flow_graph_builder_->StoreInstanceFieldGuarded(
        field, StoreInstanceFieldInstr::Kind::kInitializing);
  }
  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildLateFieldInitializer(
    const Field& field,
    bool has_initializer) {
  if (has_initializer && PeekTag() == kNullLiteral) {
    SkipExpression();  // read past the null literal.
    if (H.thread()->IsMutatorThread()) {
      field.RecordStore(Object::null_object());
    } else {
      ASSERT(field.is_nullable(/* silence_assert = */ true));
    }
    return Fragment();
  }

  Fragment instructions;
  instructions += LoadLocal(parsed_function()->receiver_var());
  instructions += flow_graph_builder_->Constant(Object::sentinel());
  instructions += flow_graph_builder_->StoreInstanceField(
      field, StoreInstanceFieldInstr::Kind::kInitializing);
  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildInitializers(
    const Class& parent_class) {
  ASSERT(Error::Handle(Z, H.thread()->sticky_error()).IsNull());
  Fragment instructions;

  // Start by getting the position of the constructors initializer.
  intptr_t initializers_offset = -1;
  {
    AlternativeReadingScope alt(&reader_);
    SkipFunctionNode();  // read constructors function node.
    initializers_offset = ReaderOffset();
  }

  bool is_redirecting_constructor = false;

  // Field which will be initialized by the initializer with the given index.
  GrowableArray<const Field*> initializer_fields(5);

  // Check if this is a redirecting constructor and collect all fields which
  // will be initialized by the constructor initializer list.
  {
    AlternativeReadingScope alt(&reader_, initializers_offset);

    const intptr_t list_length =
        ReadListLength();  // read initializers list length.
    initializer_fields.EnsureLength(list_length, nullptr);

    bool has_field_initializers = false;
    for (intptr_t i = 0; i < list_length; ++i) {
      if (PeekTag() == kRedirectingInitializer) {
        is_redirecting_constructor = true;
      } else if (PeekTag() == kFieldInitializer) {
        has_field_initializers = true;
        ReadTag();
        ReadBool();
        const NameIndex field_name = ReadCanonicalNameReference();
        const Field& field =
            Field::Handle(Z, H.LookupFieldByKernelField(field_name));
        initializer_fields[i] = &field;
        SkipExpression();
        continue;
      }
      SkipInitializer();
    }
    ASSERT(!is_redirecting_constructor || !has_field_initializers);
  }

  // These come from:
  //
  //   class A {
  //     var x = (expr);
  //   }
  //
  // We don't want to do that when this is a Redirecting Constructors though
  // (i.e. has a single initializer being of type kRedirectingInitializer).
  if (!is_redirecting_constructor) {
    // Sort list of fields (represented as their kernel offsets) which will
    // be initialized by the constructor initializer list. We will not emit
    // StoreInstanceField instructions for those initializers though we will
    // still evaluate initialization expression for its side effects.
    GrowableArray<intptr_t> constructor_initialized_field_offsets(
        initializer_fields.length());
    for (auto field : initializer_fields) {
      if (field != nullptr) {
        constructor_initialized_field_offsets.Add(field->kernel_offset());
      }
    }

    constructor_initialized_field_offsets.Sort(
        [](const intptr_t* a, const intptr_t* b) {
          return static_cast<int>(*a) - static_cast<int>(*b);
        });
    constructor_initialized_field_offsets.Add(-1);

    ExternalTypedData& kernel_data = ExternalTypedData::Handle(Z);
    Array& class_fields = Array::Handle(Z, parent_class.fields());
    Field& class_field = Field::Handle(Z);
    intptr_t next_constructor_initialized_field_index = 0;
    for (intptr_t i = 0; i < class_fields.Length(); ++i) {
      class_field ^= class_fields.At(i);
      if (!class_field.is_static()) {
        const intptr_t field_offset = class_field.kernel_offset();

        // Check if this field will be initialized by the constructor
        // initializer list.
        // Note that both class_fields and the list of initialized fields
        // are sorted by their kernel offset (by construction) -
        // so we don't need to perform the search.
        bool is_constructor_initialized = false;
        const intptr_t constructor_initialized_field_offset =
            constructor_initialized_field_offsets
                [next_constructor_initialized_field_index];
        if (constructor_initialized_field_offset == field_offset) {
          next_constructor_initialized_field_index++;
          is_constructor_initialized = true;
        }

        kernel_data = class_field.KernelData();
        ASSERT(!kernel_data.IsNull());
        AlternativeReadingScopeWithNewData alt(&reader_, &kernel_data,
                                               field_offset);
        FieldHelper field_helper(this);
        field_helper.ReadUntilExcluding(FieldHelper::kInitializer);
        const Tag initializer_tag = ReadTag();
        if (class_field.is_late()) {
          if (!is_constructor_initialized) {
            instructions += BuildLateFieldInitializer(
                Field::ZoneHandle(Z, class_field.raw()),
                initializer_tag == kSomething);
          }
        } else if (initializer_tag == kSomething) {
          EnterScope(field_offset);
          // If this field is initialized in constructor then we can ignore the
          // value produced by the field initializer. However we still need to
          // execute it for its side effects.
          instructions += BuildFieldInitializer(
              Field::ZoneHandle(Z, class_field.raw()),
              /*only_for_side_effects=*/is_constructor_initialized);
          ExitScope(field_offset);
        }
      }
    }
  }

  // These to come from:
  //   class A {
  //     var x;
  //     var y;
  //     A(this.x) : super(expr), y = (expr);
  //   }
  {
    AlternativeReadingScope alt(&reader_, initializers_offset);
    intptr_t list_length = ReadListLength();  // read initializers list length.
    for (intptr_t i = 0; i < list_length; ++i) {
      Tag tag = ReadTag();
      bool isSynthetic = ReadBool();  // read isSynthetic flag.
      switch (tag) {
        case kInvalidInitializer:
          UNIMPLEMENTED();
          return Fragment();
        case kFieldInitializer: {
          ReadCanonicalNameReference();
          instructions += BuildFieldInitializer(
              Field::ZoneHandle(Z, initializer_fields[i]->raw()),
              /*only_for_size_effects=*/false);
          break;
        }
        case kAssertInitializer: {
          instructions += BuildStatement();
          break;
        }
        case kSuperInitializer: {
          TokenPosition position = ReadPosition();  // read position.
          NameIndex canonical_target =
              ReadCanonicalNameReference();  // read target_reference.

          instructions += LoadLocal(parsed_function()->receiver_var());

          // TODO(jensj): ASSERT(init->arguments()->types().length() == 0);
          Array& argument_names = Array::ZoneHandle(Z);
          intptr_t argument_count;
          instructions += BuildArguments(
              &argument_names, &argument_count,
              /* positional_parameter_count = */ NULL);  // read arguments.
          argument_count += 1;

          Class& parent_klass = GetSuperOrDie();

          const Function& target = Function::ZoneHandle(
              Z, H.LookupConstructorByKernelConstructor(
                     parent_klass, H.CanonicalNameString(canonical_target)));
          instructions += StaticCall(
              isSynthetic ? TokenPosition::kNoSource : position, target,
              argument_count, argument_names, ICData::kStatic);
          instructions += Drop();
          break;
        }
        case kRedirectingInitializer: {
          TokenPosition position = ReadPosition();  // read position.
          NameIndex canonical_target =
              ReadCanonicalNameReference();  // read target_reference.

          instructions += LoadLocal(parsed_function()->receiver_var());

          // TODO(jensj): ASSERT(init->arguments()->types().length() == 0);
          Array& argument_names = Array::ZoneHandle(Z);
          intptr_t argument_count;
          instructions += BuildArguments(
              &argument_names, &argument_count,
              /* positional_parameter_count = */ NULL);  // read arguments.
          argument_count += 1;

          const Function& target = Function::ZoneHandle(
              Z, H.LookupConstructorByKernelConstructor(canonical_target));
          instructions += StaticCall(
              isSynthetic ? TokenPosition::kNoSource : position, target,
              argument_count, argument_names, ICData::kStatic);
          instructions += Drop();
          break;
        }
        case kLocalInitializer: {
          // The other initializers following this one might read the variable.
          // This is used e.g. for evaluating the arguments to a super call
          // first, run normal field initializers next and then make the actual
          // super call:
          //
          //   The frontend converts
          //
          //      class A {
          //        var x;
          //        A(a, b) : super(a + b), x = 2*b {}
          //      }
          //
          //   to
          //
          //      class A {
          //        var x;
          //        A(a, b) : tmp = a + b, x = 2*b, super(tmp) {}
          //      }
          //
          // (This is strictly speaking not what one should do in terms of the
          //  specification but that is how it is currently implemented.)
          LocalVariable* variable =
              LookupVariable(ReaderOffset() + data_program_offset_);

          // Variable declaration
          VariableDeclarationHelper helper(this);
          helper.ReadUntilExcluding(VariableDeclarationHelper::kInitializer);
          ASSERT(!helper.IsConst());
          Tag tag = ReadTag();  // read (first part of) initializer.
          if (tag != kSomething) {
            UNREACHABLE();
          }

          instructions += BuildExpression();  // read initializer.
          instructions += StoreLocal(TokenPosition::kNoSource, variable);
          instructions += Drop();
          break;
        }
        default:
          ReportUnexpectedTag("initializer", tag);
          UNREACHABLE();
      }
    }
  }
  return instructions;
}

void StreamingFlowGraphBuilder::ReadDefaultFunctionTypeArguments(
    const Function& function) {
  if (!function.IsGeneric()) {
    return;
  }
  AlternativeReadingScope alt(&reader_);
  FunctionNodeHelper function_node_helper(this);
  function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kTypeParameters);
  intptr_t num_type_params = ReadListLength();
  ASSERT(num_type_params == function.NumTypeParameters());
  TypeArguments& default_types =
      TypeArguments::Handle(Z, TypeArguments::New(num_type_params));
  for (intptr_t i = 0; i < num_type_params; ++i) {
    TypeParameterHelper helper(this);
    helper.ReadUntilExcludingAndSetJustRead(TypeParameterHelper::kDefaultType);
    if (ReadTag() == kSomething) {
      default_types.SetTypeAt(i, T.BuildType());
    } else {
      default_types.SetTypeAt(i, Object::dynamic_type());
    }
    helper.Finish();
  }
  default_types = default_types.Canonicalize();
  parsed_function()->SetDefaultFunctionTypeArguments(default_types);
}

Fragment StreamingFlowGraphBuilder::DebugStepCheckInPrologue(
    const Function& dart_function,
    TokenPosition position) {
  if (!NeedsDebugStepCheck(dart_function, position)) {
    return {};
  }

  // Place this check at the last parameter to ensure parameters
  // are in scope in the debugger at method entry.
  const int parameter_count = dart_function.NumParameters();
  TokenPosition check_pos = TokenPosition::kNoSource;
  if (parameter_count > 0) {
    const LocalVariable& parameter =
        *parsed_function()->ParameterVariable(parameter_count - 1);
    check_pos = parameter.token_pos();
  }
  if (!check_pos.IsDebugPause()) {
    // No parameters or synthetic parameters.
    check_pos = position;
    ASSERT(check_pos.IsDebugPause());
  }

  return DebugStepCheck(check_pos);
}

Fragment StreamingFlowGraphBuilder::SetAsyncStackTrace(
    const Function& dart_function) {
  if (!FLAG_causal_async_stacks ||
      !(dart_function.IsAsyncClosure() || dart_function.IsAsyncGenClosure())) {
    return {};
  }

  // The code we are building will be executed right after we enter
  // the function and before any nested contexts are allocated.
  ASSERT(B->context_depth_ ==
         scopes()->yield_jump_variable->owner()->context_level());

  Fragment instructions;
  LocalScope* scope = parsed_function()->scope();

  const Function& target = Function::ZoneHandle(
      Z, I->object_store()->async_set_thread_stack_trace());
  ASSERT(!target.IsNull());

  // Fetch and load :async_stack_trace
  LocalVariable* async_stack_trace_var =
      scope->LookupVariable(Symbols::AsyncStackTraceVar(), false);
  ASSERT((async_stack_trace_var != NULL) &&
         async_stack_trace_var->is_captured());

  Fragment code;
  code += LoadLocal(async_stack_trace_var);
  // Call _asyncSetThreadStackTrace
  code += StaticCall(TokenPosition::kNoSource, target,
                     /* argument_count = */ 1, ICData::kStatic);
  code += Drop();
  return code;
}

Fragment StreamingFlowGraphBuilder::TypeArgumentsHandling(
    const Function& dart_function) {
  Fragment prologue = B->BuildDefaultTypeHandling(dart_function);

  if (dart_function.IsClosureFunction() &&
      dart_function.NumParentTypeParameters() > 0) {
    LocalVariable* closure = parsed_function()->ParameterVariable(0);

    // Function with yield points can not be generic itself but the outer
    // function can be.
    ASSERT(yield_continuations().is_empty() || !dart_function.IsGeneric());

    LocalVariable* fn_type_args = parsed_function()->function_type_arguments();
    ASSERT(fn_type_args != NULL && closure != NULL);

    if (dart_function.IsGeneric()) {
      prologue += LoadLocal(fn_type_args);

      prologue += LoadLocal(closure);
      prologue += LoadNativeField(Slot::Closure_function_type_arguments());

      prologue += IntConstant(dart_function.NumParentTypeParameters());

      prologue += IntConstant(dart_function.NumTypeParameters() +
                              dart_function.NumParentTypeParameters());

      const Library& dart_internal =
          Library::Handle(Z, Library::InternalLibrary());
      const Function& prepend_function =
          Function::ZoneHandle(Z, dart_internal.LookupFunctionAllowPrivate(
                                      Symbols::PrependTypeArguments()));
      ASSERT(!prepend_function.IsNull());

      prologue += StaticCall(TokenPosition::kNoSource, prepend_function, 4,
                             ICData::kStatic);
      prologue += StoreLocal(TokenPosition::kNoSource, fn_type_args);
      prologue += Drop();
    } else {
      prologue += LoadLocal(closure);
      prologue += LoadNativeField(Slot::Closure_function_type_arguments());
      prologue += StoreLocal(TokenPosition::kNoSource, fn_type_args);
      prologue += Drop();
    }
  }

  return prologue;
}

Fragment StreamingFlowGraphBuilder::CompleteBodyWithYieldContinuations(
    Fragment body) {
  // The code we are building will be executed right after we enter
  // the function and before any nested contexts are allocated.
  // Reset current context_depth_ to match this.
  const intptr_t current_context_depth = B->context_depth_;
  B->context_depth_ = scopes()->yield_jump_variable->owner()->context_level();

  // Prepend an entry corresponding to normal entry to the function.
  yield_continuations().InsertAt(
      0, YieldContinuation(new (Z) DropTempsInstr(0, NULL), kInvalidTryIndex));
  yield_continuations()[0].entry->LinkTo(body.entry);

  // Load :await_jump_var into a temporary.
  Fragment dispatch;
  dispatch += LoadLocal(scopes()->yield_jump_variable);
  dispatch += StoreLocal(TokenPosition::kNoSource, scopes()->switch_variable);
  dispatch += Drop();

  const intptr_t continuation_count = yield_continuations().length();

  IndirectGotoInstr* indirect_goto;
  if (FLAG_async_igoto_threshold >= 0 &&
      continuation_count >= FLAG_async_igoto_threshold) {
    const auto& offsets = TypedData::ZoneHandle(
        Z, TypedData::New(kTypedDataInt32ArrayCid, continuation_count,
                          Heap::kOld));

    dispatch += Constant(offsets);
    dispatch += LoadLocal(scopes()->switch_variable);

    // Ideally this would just be LoadIndexedTypedData(kTypedDataInt32ArrayCid),
    // but that doesn't work in unoptimised code.
    // The optimiser will turn this into that in any case.
    dispatch += InstanceCall(TokenPosition::kNoSource, Symbols::IndexToken(),
                             Token::kINDEX, /*argument_count=*/2);

    Value* offset_from_start = Pop();

    indirect_goto = new (Z) IndirectGotoInstr(&offsets, offset_from_start);
    dispatch <<= indirect_goto;

    for (intptr_t i = 0; i < continuation_count; i++) {
      if (i >= 1) {
        Fragment resumption;
        // Every continuation after the first is not a normal entry but a
        // resumption.
        // Restore :current_context_var from :await_ctx_var.
        // Note: after this point context_depth_ does not match current context
        // depth so we should not access any local variables anymore.
        resumption += LoadLocal(scopes()->yield_context_variable);
        resumption += StoreLocal(TokenPosition::kNoSource,
                                 parsed_function()->current_context_var());
        resumption += Drop();

        Instruction* next = yield_continuations()[i].entry->next();
        yield_continuations()[i].entry->LinkTo(resumption.entry);
        resumption <<= next;
      }

      IndirectEntryInstr* indirect_entry = B->BuildIndirectEntry(
          /*indirect_id=*/i, yield_continuations()[i].try_index);
      indirect_entry->LinkTo(yield_continuations()[i].entry->next());

      TargetEntryInstr* target = B->BuildTargetEntry();
      Fragment(target) + Goto(indirect_entry);

      indirect_goto->AddSuccessor(target);
    }
  } else {
    BlockEntryInstr* block = nullptr;
    for (intptr_t i = 0; i < continuation_count; i++) {
      if (i == 1) {
        // This is not a normal entry but a resumption.  Restore
        // :current_context_var from :await_ctx_var.
        // Note: after this point context_depth_ does not match current context
        // depth so we should not access any local variables anymore.
        dispatch += LoadLocal(scopes()->yield_context_variable);
        dispatch += StoreLocal(TokenPosition::kNoSource,
                               parsed_function()->current_context_var());
        dispatch += Drop();
      }
      if (i == (continuation_count - 1)) {
        // We reached the last possibility, no need to build more ifs.
        // Continue to the last continuation.
        // Note: continuations start with nop DropTemps instruction
        // which acts like an anchor, so we need to skip it.
        block->set_try_index(yield_continuations()[i].try_index);
        dispatch <<= yield_continuations()[i].entry->next();
        break;
      }

      // Build comparison:
      //
      //   if (:await_jump_var == i) {
      //     -> yield_continuations()[i]
      //   } else ...
      //
      TargetEntryInstr* then;
      TargetEntryInstr* otherwise;
      dispatch += LoadLocal(scopes()->switch_variable);
      dispatch += IntConstant(i);
      dispatch += B->BranchIfStrictEqual(&then, &otherwise);

      // True branch is linked to appropriate continuation point.
      // Note: continuations start with nop DropTemps instruction
      // which acts like an anchor, so we need to skip it.
      then->LinkTo(yield_continuations()[i].entry->next());
      then->set_try_index(yield_continuations()[i].try_index);
      // False branch will contain the next comparison.
      dispatch = Fragment(dispatch.entry, otherwise);
      block = otherwise;
    }
  }
  B->context_depth_ = current_context_depth;
  return dispatch;
}

Fragment StreamingFlowGraphBuilder::CheckStackOverflowInPrologue(
    const Function& dart_function) {
  if (dart_function.is_native()) return {};
  return B->CheckStackOverflowInPrologue(dart_function.token_pos());
}

Fragment StreamingFlowGraphBuilder::SetupCapturedParameters(
    const Function& dart_function) {
  Fragment body;
  const LocalScope* scope = parsed_function()->scope();
  if (scope->num_context_variables() > 0) {
    body += flow_graph_builder_->PushContext(scope);
    LocalVariable* context = MakeTemporary();

    // Copy captured parameters from the stack into the context.
    LocalScope* scope = parsed_function()->scope();
    intptr_t parameter_count = dart_function.NumParameters();
    const ParsedFunction& pf = *flow_graph_builder_->parsed_function_;
    const Function& function = pf.function();

    for (intptr_t i = 0; i < parameter_count; ++i) {
      LocalVariable* variable = pf.ParameterVariable(i);
      if (variable->is_captured()) {
        LocalVariable& raw_parameter = *pf.RawParameterVariable(i);
        ASSERT((function.HasOptionalParameters() &&
                raw_parameter.owner() == scope) ||
               (!function.HasOptionalParameters() &&
                raw_parameter.owner() == NULL));
        ASSERT(!raw_parameter.is_captured());

        // Copy the parameter from the stack to the context.
        body += LoadLocal(context);
        body += LoadLocal(&raw_parameter);
        body += flow_graph_builder_->StoreInstanceField(
            TokenPosition::kNoSource,
            Slot::GetContextVariableSlotFor(thread(), *variable),
            StoreInstanceFieldInstr::Kind::kInitializing);
      }
    }
    body += Drop();  // The context.
  }
  return body;
}

// If we run in checked mode or strong mode, we have to check the type of the
// passed arguments.
//
// TODO(#34162): If we're building an extra entry-point to skip
// type checks, we should substitute Redefinition nodes for the AssertAssignable
// instructions to ensure that the argument types are known.
void StreamingFlowGraphBuilder::CheckArgumentTypesAsNecessary(
    const Function& dart_function,
    intptr_t type_parameters_offset,
    Fragment* explicit_checks,
    Fragment* implicit_checks,
    Fragment* implicit_redefinitions) {
  if (!dart_function.NeedsArgumentTypeChecks()) return;

  // Check if parent function was annotated with no-dynamic-invocations.
  const ProcedureAttributesMetadata attrs =
      procedure_attributes_metadata_helper_.GetProcedureAttributes(
          dart_function.kernel_offset());

  AlternativeReadingScope _(&reader_);
  SetOffset(type_parameters_offset);
  B->BuildArgumentTypeChecks(
      MethodCanSkipTypeChecksForNonCovariantArguments(dart_function, attrs)
          ? TypeChecksToBuild::kCheckCovariantTypeParameterBounds
          : TypeChecksToBuild::kCheckAllTypeParameterBounds,
      explicit_checks, implicit_checks, implicit_redefinitions);
}

Fragment StreamingFlowGraphBuilder::ShortcutForUserDefinedEquals(
    const Function& dart_function,
    LocalVariable* first_parameter) {
  // The specification defines the result of `a == b` to be:
  //
  //   a) if either side is `null` then the result is `identical(a, b)`.
  //   b) else the result is `a.operator==(b)`
  //
  // For user-defined implementations of `operator==` we need therefore
  // implement the handling of a).
  //
  // The default `operator==` implementation in `Object` is implemented in terms
  // of identical (which we assume here!) which means that case a) is actually
  // included in b).  So we just use the normal implementation in the body.
  Fragment body;
  if ((dart_function.NumParameters() == 2) &&
      (dart_function.name() == Symbols::EqualOperator().raw()) &&
      (dart_function.Owner() != I->object_store()->object_class())) {
    TargetEntryInstr* null_entry;
    TargetEntryInstr* non_null_entry;

    body += LoadLocal(first_parameter);
    body += BranchIfNull(&null_entry, &non_null_entry);

    // The argument was `null` and the receiver is not the null class (we only
    // go into this branch for user-defined == operators) so we can return
    // false.
    Fragment null_fragment(null_entry);
    null_fragment += Constant(Bool::False());
    null_fragment += Return(dart_function.end_token_pos());

    body = Fragment(body.entry, non_null_entry);
  }
  return body;
}

Fragment StreamingFlowGraphBuilder::BuildFunctionBody(
    const Function& dart_function,
    LocalVariable* first_parameter,
    bool constructor) {
  Fragment body;

  // TODO(27590): Currently the [VariableDeclaration]s from the
  // initializers will be visible inside the entire body of the constructor.
  // We should make a separate scope for them.
  if (constructor) {
    body += BuildInitializers(Class::Handle(Z, dart_function.Owner()));
  }

  if (body.is_closed()) return body;

  FunctionNodeHelper function_node_helper(this);
  function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kBody);

  const bool has_body = ReadTag() == kSomething;  // read first part of body.

  if (dart_function.is_native()) {
    body += B->NativeFunctionBody(dart_function, first_parameter);
  } else if (has_body) {
    body += BuildStatement();
  } else if (dart_function.is_external()) {
    body += ThrowNoSuchMethodError(dart_function);
  }

  if (body.is_open()) {
    body += NullConstant();
    body += Return(dart_function.end_token_pos());
  }

  return body;
}

Fragment StreamingFlowGraphBuilder::BuildEveryTimePrologue(
    const Function& dart_function,
    TokenPosition token_position,
    intptr_t type_parameters_offset) {
  Fragment F;
  F += CheckStackOverflowInPrologue(dart_function);
  F += DebugStepCheckInPrologue(dart_function, token_position);
  F += SetAsyncStackTrace(dart_function);
  F += B->InitConstantParameters();
  return F;
}

Fragment StreamingFlowGraphBuilder::BuildFirstTimePrologue(
    const Function& dart_function,
    LocalVariable* first_parameter,
    intptr_t type_parameters_offset) {
  Fragment F;
  F += SetupCapturedParameters(dart_function);
  F += ShortcutForUserDefinedEquals(dart_function, first_parameter);
  return F;
}

Fragment StreamingFlowGraphBuilder::ClearRawParameters(
    const Function& dart_function) {
  const ParsedFunction& pf = *flow_graph_builder_->parsed_function_;
  Fragment code;
  for (intptr_t i = 0; i < dart_function.NumParameters(); ++i) {
    LocalVariable* variable = pf.ParameterVariable(i);

    if (!variable->is_captured()) continue;

    // Captured 'this' is immutable, so within the outer method we don't need to
    // load it from the context. Therefore we don't reset it to null.
    if (pf.function().HasThisParameter() && pf.has_receiver_var() &&
        variable == pf.receiver_var()) {
      ASSERT(i == 0);
      continue;
    }

    variable = pf.RawParameterVariable(i);
    code += NullConstant();
    code += StoreLocal(TokenPosition::kNoSource, variable);
    code += Drop();
  }
  return code;
}

UncheckedEntryPointStyle StreamingFlowGraphBuilder::ChooseEntryPointStyle(
    const Function& dart_function,
    const Fragment& implicit_type_checks,
    const Fragment& first_time_prologue,
    const Fragment& every_time_prologue,
    const Fragment& type_args_handling) {
  ASSERT(!dart_function.IsImplicitClosureFunction());
  if (!dart_function.MayHaveUncheckedEntryPoint() ||
      implicit_type_checks.is_empty()) {
    return UncheckedEntryPointStyle::kNone;
  }

  // Record which entry-point was taken into a variable and test it later if
  // either:
  //
  // 1. There is a non-empty PrologueBuilder-prologue.
  //
  // 2. There is a non-empty "first-time" prologue.
  //
  // 3. The "every-time" prologue has more than two instructions (DebugStepCheck
  //    and CheckStackOverflow).
  //
  // TODO(#34162): For regular closures we can often avoid the
  // PrologueBuilder-prologue on non-dynamic invocations.
  if (!PrologueBuilder::HasEmptyPrologue(dart_function) ||
      !type_args_handling.is_empty() || !first_time_prologue.is_empty() ||
      !(every_time_prologue.entry == every_time_prologue.current ||
        every_time_prologue.current->previous() == every_time_prologue.entry)) {
    return UncheckedEntryPointStyle::kSharedWithVariable;
  }

  return UncheckedEntryPointStyle::kSeparate;
}

FlowGraph* StreamingFlowGraphBuilder::BuildGraphOfFunction(
    bool is_constructor) {
  const Function& dart_function = parsed_function()->function();

  intptr_t type_parameters_offset = 0;
  LocalVariable* first_parameter = nullptr;
  TokenPosition token_position = TokenPosition::kNoSource;
  {
    AlternativeReadingScope alt(&reader_);
    FunctionNodeHelper function_node_helper(this);
    function_node_helper.ReadUntilExcluding(
        FunctionNodeHelper::kTypeParameters);
    type_parameters_offset = ReaderOffset();
    function_node_helper.ReadUntilExcluding(
        FunctionNodeHelper::kPositionalParameters);
    intptr_t list_length = ReadListLength();  // read number of positionals.
    if (list_length > 0) {
      intptr_t first_parameter_offset = ReaderOffset() + data_program_offset_;
      first_parameter = LookupVariable(first_parameter_offset);
    }
    token_position = function_node_helper.position_;
  }

  auto graph_entry = flow_graph_builder_->graph_entry_ =
      new (Z) GraphEntryInstr(*parsed_function(), flow_graph_builder_->osr_id_);

  auto normal_entry = flow_graph_builder_->BuildFunctionEntry(graph_entry);
  graph_entry->set_normal_entry(normal_entry);

  PrologueInfo prologue_info(-1, -1);
  BlockEntryInstr* instruction_cursor =
      flow_graph_builder_->BuildPrologue(normal_entry, &prologue_info);

  // The 'every_time_prologue' runs first and is run when resuming from yield
  // points.
  const Fragment every_time_prologue = BuildEveryTimePrologue(
      dart_function, token_position, type_parameters_offset);

  // The 'first_time_prologue' run after 'every_time_prologue' and is *not* run
  // when resuming from yield points.
  const Fragment first_time_prologue = BuildFirstTimePrologue(
      dart_function, first_parameter, type_parameters_offset);

  // TODO(#34162): We can remove the default type handling (and
  // shorten the prologue type handling sequence) for non-dynamic invocations of
  // regular methods.
  const Fragment type_args_handling = TypeArgumentsHandling(dart_function);

  Fragment explicit_type_checks;
  Fragment implicit_type_checks;
  Fragment implicit_redefinitions;
  CheckArgumentTypesAsNecessary(dart_function, type_parameters_offset,
                                &explicit_type_checks, &implicit_type_checks,
                                &implicit_redefinitions);

  // The RawParameter variables should be set to null to avoid retaining more
  // objects than necessary during GC.
  const Fragment body =
      ClearRawParameters(dart_function) + B->BuildNullAssertions() +
      BuildFunctionBody(dart_function, first_parameter, is_constructor);

  auto extra_entry_point_style = ChooseEntryPointStyle(
      dart_function, implicit_type_checks, first_time_prologue,
      every_time_prologue, type_args_handling);

  Fragment function(instruction_cursor);
  if (yield_continuations().is_empty()) {
    FunctionEntryInstr* extra_entry = nullptr;
    switch (extra_entry_point_style) {
      case UncheckedEntryPointStyle::kNone: {
        function += every_time_prologue + first_time_prologue +
                    type_args_handling + implicit_type_checks +
                    explicit_type_checks + body;
        break;
      }
      case UncheckedEntryPointStyle::kSeparate: {
        ASSERT(instruction_cursor == normal_entry);
        ASSERT(first_time_prologue.is_empty());
        ASSERT(type_args_handling.is_empty());

        const Fragment prologue_copy = BuildEveryTimePrologue(
            dart_function, token_position, type_parameters_offset);

        extra_entry = B->BuildSeparateUncheckedEntryPoint(
            normal_entry,
            /*normal_prologue=*/every_time_prologue + implicit_type_checks,
            /*extra_prologue=*/prologue_copy,
            /*shared_prologue=*/explicit_type_checks,
            /*body=*/body);
        break;
      }
      case UncheckedEntryPointStyle::kSharedWithVariable: {
        Fragment prologue(normal_entry, instruction_cursor);
        prologue += every_time_prologue;
        prologue += first_time_prologue;
        prologue += type_args_handling;
        prologue += explicit_type_checks;
        extra_entry = B->BuildSharedUncheckedEntryPoint(
            /*shared_prologue_linked_in=*/prologue,
            /*skippable_checks=*/implicit_type_checks,
            /*redefinitions_if_skipped=*/implicit_redefinitions,
            /*body=*/body);
        break;
      }
    }
    if (extra_entry != nullptr) {
      B->RecordUncheckedEntryPoint(graph_entry, extra_entry);
    }
  } else {
    // If the function's body contains any yield points, build switch statement
    // that selects a continuation point based on the value of :await_jump_var.
    ASSERT(explicit_type_checks.is_empty());

    // If the function is generic, type_args_handling might require access to
    // (possibly captured) 'this' for preparing default type arguments, in which
    // case we can't run it before the 'first_time_prologue'.
    ASSERT(!dart_function.IsGeneric());

    // TODO(#34162): We can probably ignore the implicit checks
    // here as well since the arguments are passed from generated code.
    function += every_time_prologue + type_args_handling +
                CompleteBodyWithYieldContinuations(first_time_prologue +
                                                   implicit_type_checks + body);
  }

  // When compiling for OSR, use a depth first search to find the OSR
  // entry and make graph entry jump to it instead of normal entry.
  // Catch entries are always considered reachable, even if they
  // become unreachable after OSR.
  if (flow_graph_builder_->IsCompiledForOsr()) {
    graph_entry->RelinkToOsrEntry(Z,
                                  flow_graph_builder_->last_used_block_id_ + 1);
  }
  return new (Z)
      FlowGraph(*parsed_function(), graph_entry,
                flow_graph_builder_->last_used_block_id_, prologue_info);
}

FlowGraph* StreamingFlowGraphBuilder::BuildGraph() {
  ASSERT(Error::Handle(Z, H.thread()->sticky_error()).IsNull());
  ASSERT(flow_graph_builder_ != nullptr);

  const Function& function = parsed_function()->function();

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

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

  if (function.is_declared_in_bytecode()) {
    bytecode_metadata_helper_.ParseBytecodeFunction(parsed_function());

    switch (function.kind()) {
      case FunctionLayout::kImplicitClosureFunction:
        return B->BuildGraphOfImplicitClosureFunction(function);
      case FunctionLayout::kImplicitGetter:
      case FunctionLayout::kImplicitSetter:
        return B->BuildGraphOfFieldAccessor(function);
      case FunctionLayout::kImplicitStaticGetter: {
        if (IsStaticFieldGetterGeneratedAsInitializer(function, Z)) {
          break;
        }
        return B->BuildGraphOfFieldAccessor(function);
      }
      case FunctionLayout::kDynamicInvocationForwarder:
        return B->BuildGraphOfDynamicInvocationForwarder(function);
      case FunctionLayout::kMethodExtractor:
        return B->BuildGraphOfMethodExtractor(function);
      case FunctionLayout::kNoSuchMethodDispatcher:
        return B->BuildGraphOfNoSuchMethodDispatcher(function);
      default:
        break;
    }

    ASSERT(function.HasBytecode());

    BytecodeFlowGraphBuilder bytecode_compiler(
        flow_graph_builder_, parsed_function(),
        &(flow_graph_builder_->ic_data_array_));

    if (B->IsRecognizedMethodForFlowGraph(function)) {
      bytecode_compiler.CreateParameterVariables();
      return B->BuildGraphOfRecognizedMethod(function);
    }

    return bytecode_compiler.BuildGraph();
  }

  // Certain special functions could have a VM-internal bytecode
  // attached to them.
  ASSERT((!function.HasBytecode()) ||
         (function.kind() == FunctionLayout::kImplicitGetter) ||
         (function.kind() == FunctionLayout::kImplicitSetter) ||
         (function.kind() == FunctionLayout::kImplicitStaticGetter) ||
         (function.kind() == FunctionLayout::kMethodExtractor) ||
         (function.kind() == FunctionLayout::kInvokeFieldDispatcher) ||
         (function.kind() == FunctionLayout::kNoSuchMethodDispatcher));

  ParseKernelASTFunction();

  switch (function.kind()) {
    case FunctionLayout::kRegularFunction:
    case FunctionLayout::kGetterFunction:
    case FunctionLayout::kSetterFunction:
    case FunctionLayout::kClosureFunction:
    case FunctionLayout::kConstructor: {
      if (B->IsRecognizedMethodForFlowGraph(function)) {
        return B->BuildGraphOfRecognizedMethod(function);
      }
      return BuildGraphOfFunction(function.IsGenerativeConstructor());
    }
    case FunctionLayout::kImplicitGetter:
    case FunctionLayout::kImplicitStaticGetter:
    case FunctionLayout::kImplicitSetter: {
      const Field& field = Field::Handle(Z, function.accessor_field());
      if (field.is_const() && field.IsUninitialized()) {
        EvaluateConstFieldValue(field);
      }
      return B->BuildGraphOfFieldAccessor(function);
    }
    case FunctionLayout::kFieldInitializer:
      return BuildGraphOfFieldInitializer();
    case FunctionLayout::kDynamicInvocationForwarder:
      return B->BuildGraphOfDynamicInvocationForwarder(function);
    case FunctionLayout::kMethodExtractor:
      return flow_graph_builder_->BuildGraphOfMethodExtractor(function);
    case FunctionLayout::kNoSuchMethodDispatcher:
      return flow_graph_builder_->BuildGraphOfNoSuchMethodDispatcher(function);
    case FunctionLayout::kInvokeFieldDispatcher:
      return flow_graph_builder_->BuildGraphOfInvokeFieldDispatcher(function);
    case FunctionLayout::kImplicitClosureFunction:
      return flow_graph_builder_->BuildGraphOfImplicitClosureFunction(function);
    case FunctionLayout::kFfiTrampoline:
      return flow_graph_builder_->BuildGraphOfFfiTrampoline(function);
    case FunctionLayout::kSignatureFunction:
    case FunctionLayout::kIrregexpFunction:
      break;
  }
  UNREACHABLE();
  return NULL;
}

void StreamingFlowGraphBuilder::ParseKernelASTFunction() {
  const Function& function = parsed_function()->function();

  const intptr_t kernel_offset = function.kernel_offset();
  ASSERT(kernel_offset >= 0);

  SetOffset(kernel_offset);

  // Mark forwarding stubs.
  switch (function.kind()) {
    case FunctionLayout::kRegularFunction:
    case FunctionLayout::kImplicitClosureFunction:
    case FunctionLayout::kGetterFunction:
    case FunctionLayout::kSetterFunction:
    case FunctionLayout::kClosureFunction:
    case FunctionLayout::kConstructor:
    case FunctionLayout::kDynamicInvocationForwarder:
      ReadForwardingStubTarget(function);
      break;
    default:
      break;
  }

  set_scopes(parsed_function()->EnsureKernelScopes());

  switch (function.kind()) {
    case FunctionLayout::kRegularFunction:
    case FunctionLayout::kGetterFunction:
    case FunctionLayout::kSetterFunction:
    case FunctionLayout::kClosureFunction:
    case FunctionLayout::kConstructor:
    case FunctionLayout::kImplicitClosureFunction:
      ReadUntilFunctionNode();
      SetupDefaultParameterValues();
      ReadDefaultFunctionTypeArguments(function);
      break;
    case FunctionLayout::kImplicitGetter:
    case FunctionLayout::kImplicitStaticGetter:
    case FunctionLayout::kImplicitSetter:
    case FunctionLayout::kFieldInitializer:
    case FunctionLayout::kMethodExtractor:
    case FunctionLayout::kNoSuchMethodDispatcher:
    case FunctionLayout::kInvokeFieldDispatcher:
    case FunctionLayout::kFfiTrampoline:
      break;
    case FunctionLayout::kDynamicInvocationForwarder:
      if (PeekTag() != kField) {
        ReadUntilFunctionNode();
        SetupDefaultParameterValues();
        ReadDefaultFunctionTypeArguments(function);
      }
      break;
    case FunctionLayout::kSignatureFunction:
    case FunctionLayout::kIrregexpFunction:
      UNREACHABLE();
      break;
  }
}

void StreamingFlowGraphBuilder::ReadForwardingStubTarget(
    const Function& function) {
  if (PeekTag() == kProcedure) {
    AlternativeReadingScope alt(&reader_);
    ProcedureHelper procedure_helper(this);
    procedure_helper.ReadUntilExcluding(ProcedureHelper::kFunction);
    if (procedure_helper.IsForwardingStub() && !procedure_helper.IsAbstract()) {
      const NameIndex target_name =
          procedure_helper.forwarding_stub_super_target_;
      ASSERT(target_name != NameIndex::kInvalidName);
      const String& name = function.IsSetterFunction()
                               ? H.DartSetterName(target_name)
                               : H.DartProcedureName(target_name);
      const Function* forwarding_target =
          &Function::ZoneHandle(Z, H.LookupMethodByMember(target_name, name));
      ASSERT(!forwarding_target->IsNull());
      parsed_function()->MarkForwardingStub(forwarding_target);
    }
  }
}

Fragment StreamingFlowGraphBuilder::BuildStatementAt(intptr_t kernel_offset) {
  SetOffset(kernel_offset);
  return BuildStatement();  // read statement.
}

Fragment StreamingFlowGraphBuilder::BuildExpression(TokenPosition* position) {
  uint8_t payload = 0;
  Tag tag = ReadTag(&payload);  // read tag.
  switch (tag) {
    case kInvalidExpression:
      return BuildInvalidExpression(position);
    case kVariableGet:
      return BuildVariableGet(position);
    case kSpecializedVariableGet:
      return BuildVariableGet(payload, position);
    case kVariableSet:
      return BuildVariableSet(position);
    case kSpecializedVariableSet:
      return BuildVariableSet(payload, position);
    case kPropertyGet:
      return BuildPropertyGet(position);
    case kPropertySet:
      return BuildPropertySet(position);
    case kDirectPropertyGet:
      return BuildDirectPropertyGet(position);
    case kDirectPropertySet:
      return BuildDirectPropertySet(position);
    case kSuperPropertyGet:
      return BuildSuperPropertyGet(position);
    case kSuperPropertySet:
      return BuildSuperPropertySet(position);
    case kStaticGet:
      return BuildStaticGet(position);
    case kStaticSet:
      return BuildStaticSet(position);
    case kMethodInvocation:
      return BuildMethodInvocation(position);
    case kSuperMethodInvocation:
      return BuildSuperMethodInvocation(position);
    case kDirectMethodInvocation:
      return BuildDirectMethodInvocation(position);
    case kStaticInvocation:
      return BuildStaticInvocation(position);
    case kConstructorInvocation:
      return BuildConstructorInvocation(position);
    case kNot:
      return BuildNot(position);
    case kNullCheck:
      return BuildNullCheck(position);
    case kLogicalExpression:
      return BuildLogicalExpression(position);
    case kConditionalExpression:
      return BuildConditionalExpression(position);
    case kStringConcatenation:
      return BuildStringConcatenation(position);
    case kIsExpression:
      return BuildIsExpression(position);
    case kAsExpression:
      return BuildAsExpression(position);
    case kTypeLiteral:
      return BuildTypeLiteral(position);
    case kThisExpression:
      return BuildThisExpression(position);
    case kRethrow:
      return BuildRethrow(position);
    case kThrow:
      return BuildThrow(position);
    case kListLiteral:
      return BuildListLiteral(position);
    case kSetLiteral:
      // Set literals are currently desugared in the frontend and will not
      // reach the VM. See http://dartbug.com/35124 for discussion.
      UNREACHABLE();
      break;
    case kMapLiteral:
      return BuildMapLiteral(position);
    case kFunctionExpression:
      return BuildFunctionExpression();
    case kLet:
      return BuildLet(position);
    case kBlockExpression:
      return BuildBlockExpression();
    case kBigIntLiteral:
      return BuildBigIntLiteral(position);
    case kStringLiteral:
      return BuildStringLiteral(position);
    case kSpecializedIntLiteral:
      return BuildIntLiteral(payload, position);
    case kNegativeIntLiteral:
      return BuildIntLiteral(true, position);
    case kPositiveIntLiteral:
      return BuildIntLiteral(false, position);
    case kDoubleLiteral:
      return BuildDoubleLiteral(position);
    case kTrueLiteral:
      return BuildBoolLiteral(true, position);
    case kFalseLiteral:
      return BuildBoolLiteral(false, position);
    case kNullLiteral:
      return BuildNullLiteral(position);
    case kConstantExpression:
      return BuildConstantExpression(position, tag);
    case kInstantiation:
      return BuildPartialTearoffInstantiation(position);
    case kLoadLibrary:
      return BuildLibraryPrefixAction(position, Symbols::LoadLibrary());
    case kCheckLibraryIsLoaded:
      return BuildLibraryPrefixAction(position, Symbols::CheckLoaded());
    case kConstStaticInvocation:
    case kConstConstructorInvocation:
    case kConstListLiteral:
    case kConstSetLiteral:
    case kConstMapLiteral:
    case kSymbolLiteral:
      // Const invocations and const literals are removed by the
      // constant evaluator.
    case kListConcatenation:
    case kSetConcatenation:
    case kMapConcatenation:
    case kInstanceCreation:
    case kFileUriExpression:
      // Collection concatenation, instance creation operations and
      // in-expression URI changes are internal to the front end and
      // removed by the constant evaluator.
    default:
      ReportUnexpectedTag("expression", tag);
      UNREACHABLE();
  }

  return Fragment();
}

Fragment StreamingFlowGraphBuilder::BuildStatement() {
  Tag tag = ReadTag();  // read tag.
  switch (tag) {
    case kExpressionStatement:
      return BuildExpressionStatement();
    case kBlock:
      return BuildBlock();
    case kEmptyStatement:
      return BuildEmptyStatement();
    case kAssertBlock:
      return BuildAssertBlock();
    case kAssertStatement:
      return BuildAssertStatement();
    case kLabeledStatement:
      return BuildLabeledStatement();
    case kBreakStatement:
      return BuildBreakStatement();
    case kWhileStatement:
      return BuildWhileStatement();
    case kDoStatement:
      return BuildDoStatement();
    case kForStatement:
      return BuildForStatement();
    case kForInStatement:
      return BuildForInStatement(false);
    case kAsyncForInStatement:
      return BuildForInStatement(true);
    case kSwitchStatement:
      return BuildSwitchStatement();
    case kContinueSwitchStatement:
      return BuildContinueSwitchStatement();
    case kIfStatement:
      return BuildIfStatement();
    case kReturnStatement:
      return BuildReturnStatement();
    case kTryCatch:
      return BuildTryCatch();
    case kTryFinally:
      return BuildTryFinally();
    case kYieldStatement:
      return BuildYieldStatement();
    case kVariableDeclaration:
      return BuildVariableDeclaration();
    case kFunctionDeclaration:
      return BuildFunctionDeclaration();
    default:
      ReportUnexpectedTag("statement", tag);
      UNREACHABLE();
  }
  return Fragment();
}

void StreamingFlowGraphBuilder::ReportUnexpectedTag(const char* variant,
                                                    Tag tag) {
  if ((flow_graph_builder_ == NULL) || (parsed_function() == NULL)) {
    KernelReaderHelper::ReportUnexpectedTag(variant, tag);
  } else {
    H.ReportError(script_, TokenPosition::kNoSource,
                  "Unexpected tag %d (%s) in %s, expected %s", tag,
                  Reader::TagName(tag),
                  parsed_function()->function().ToQualifiedCString(), variant);
  }
}

Tag KernelReaderHelper::ReadTag(uint8_t* payload) {
  return reader_.ReadTag(payload);
}

Tag KernelReaderHelper::PeekTag(uint8_t* payload) {
  return reader_.PeekTag(payload);
}

Nullability KernelReaderHelper::ReadNullability() {
  return reader_.ReadNullability();
}

Variance KernelReaderHelper::ReadVariance() {
  if (translation_helper_.info().kernel_binary_version() >= 34) {
    return reader_.ReadVariance();
  }
  return kCovariant;
}

void StreamingFlowGraphBuilder::loop_depth_inc() {
  ++flow_graph_builder_->loop_depth_;
}

void StreamingFlowGraphBuilder::loop_depth_dec() {
  --flow_graph_builder_->loop_depth_;
}

intptr_t StreamingFlowGraphBuilder::for_in_depth() {
  return flow_graph_builder_->for_in_depth_;
}

void StreamingFlowGraphBuilder::for_in_depth_inc() {
  ++flow_graph_builder_->for_in_depth_;
}

void StreamingFlowGraphBuilder::for_in_depth_dec() {
  --flow_graph_builder_->for_in_depth_;
}

void StreamingFlowGraphBuilder::catch_depth_inc() {
  ++flow_graph_builder_->catch_depth_;
}

void StreamingFlowGraphBuilder::catch_depth_dec() {
  --flow_graph_builder_->catch_depth_;
}

void StreamingFlowGraphBuilder::try_depth_inc() {
  ++flow_graph_builder_->try_depth_;
}

void StreamingFlowGraphBuilder::try_depth_dec() {
  --flow_graph_builder_->try_depth_;
}

intptr_t StreamingFlowGraphBuilder::block_expression_depth() {
  return flow_graph_builder_->block_expression_depth_;
}

void StreamingFlowGraphBuilder::block_expression_depth_inc() {
  ++flow_graph_builder_->block_expression_depth_;
}

void StreamingFlowGraphBuilder::block_expression_depth_dec() {
  --flow_graph_builder_->block_expression_depth_;
}

intptr_t StreamingFlowGraphBuilder::CurrentTryIndex() {
  return flow_graph_builder_->CurrentTryIndex();
}

intptr_t StreamingFlowGraphBuilder::AllocateTryIndex() {
  return flow_graph_builder_->AllocateTryIndex();
}

LocalVariable* StreamingFlowGraphBuilder::CurrentException() {
  return flow_graph_builder_->CurrentException();
}

LocalVariable* StreamingFlowGraphBuilder::CurrentStackTrace() {
  return flow_graph_builder_->CurrentStackTrace();
}

CatchBlock* StreamingFlowGraphBuilder::catch_block() {
  return flow_graph_builder_->catch_block_;
}

ActiveClass* StreamingFlowGraphBuilder::active_class() {
  return active_class_;
}

ScopeBuildingResult* StreamingFlowGraphBuilder::scopes() {
  return flow_graph_builder_->scopes_;
}

void StreamingFlowGraphBuilder::set_scopes(ScopeBuildingResult* scope) {
  flow_graph_builder_->scopes_ = scope;
}

ParsedFunction* StreamingFlowGraphBuilder::parsed_function() {
  return flow_graph_builder_->parsed_function_;
}

TryFinallyBlock* StreamingFlowGraphBuilder::try_finally_block() {
  return flow_graph_builder_->try_finally_block_;
}

SwitchBlock* StreamingFlowGraphBuilder::switch_block() {
  return flow_graph_builder_->switch_block_;
}

BreakableBlock* StreamingFlowGraphBuilder::breakable_block() {
  return flow_graph_builder_->breakable_block_;
}

GrowableArray<YieldContinuation>&
StreamingFlowGraphBuilder::yield_continuations() {
  return flow_graph_builder_->yield_continuations_;
}

Value* StreamingFlowGraphBuilder::stack() {
  return flow_graph_builder_->stack_;
}

void StreamingFlowGraphBuilder::Push(Definition* definition) {
  flow_graph_builder_->Push(definition);
}

Value* StreamingFlowGraphBuilder::Pop() {
  return flow_graph_builder_->Pop();
}

Tag StreamingFlowGraphBuilder::PeekArgumentsFirstPositionalTag() {
  // read parts of arguments, then go back to before doing so.
  AlternativeReadingScope alt(&reader_);
  ReadUInt();  // read number of arguments.

  SkipListOfDartTypes();  // Read list of types.

  // List of positional.
  intptr_t list_length = ReadListLength();  // read list length.
  if (list_length > 0) {
    return ReadTag();  // read first tag.
  }

  UNREACHABLE();
  return kNothing;
}

const TypeArguments& StreamingFlowGraphBuilder::PeekArgumentsInstantiatedType(
    const Class& klass) {
  // read parts of arguments, then go back to before doing so.
  AlternativeReadingScope alt(&reader_);
  ReadUInt();                               // read argument count.
  intptr_t list_length = ReadListLength();  // read types list length.
  return T.BuildInstantiatedTypeArguments(klass, list_length);  // read types.
}

intptr_t StreamingFlowGraphBuilder::PeekArgumentsCount() {
  return PeekUInt();
}

LocalVariable* StreamingFlowGraphBuilder::LookupVariable(
    intptr_t kernel_offset) {
  return flow_graph_builder_->LookupVariable(kernel_offset);
}

LocalVariable* StreamingFlowGraphBuilder::MakeTemporary() {
  return flow_graph_builder_->MakeTemporary();
}

Function& StreamingFlowGraphBuilder::FindMatchingFunction(
    const Class& klass,
    const String& name,
    int type_args_len,
    int argument_count,
    const Array& argument_names) {
  // Search the superclass chain for the selector.
  ArgumentsDescriptor args_desc(
      Array::Handle(Z, ArgumentsDescriptor::NewBoxed(
                           type_args_len, argument_count, argument_names)));
  Function& function =
      Function::Handle(Z, Resolver::ResolveDynamicForReceiverClassAllowPrivate(
                              klass, name, args_desc, /*allow_add=*/false));
  return function;
}

bool StreamingFlowGraphBuilder::NeedsDebugStepCheck(const Function& function,
                                                    TokenPosition position) {
  return flow_graph_builder_->NeedsDebugStepCheck(function, position);
}

bool StreamingFlowGraphBuilder::NeedsDebugStepCheck(Value* value,
                                                    TokenPosition position) {
  return flow_graph_builder_->NeedsDebugStepCheck(value, position);
}

void StreamingFlowGraphBuilder::InlineBailout(const char* reason) {
  flow_graph_builder_->InlineBailout(reason);
}

Fragment StreamingFlowGraphBuilder::DebugStepCheck(TokenPosition position) {
  return flow_graph_builder_->DebugStepCheck(position);
}

Fragment StreamingFlowGraphBuilder::LoadLocal(LocalVariable* variable) {
  return flow_graph_builder_->LoadLocal(variable);
}

Fragment StreamingFlowGraphBuilder::Return(TokenPosition position,
                                           intptr_t yield_index) {
  return flow_graph_builder_->Return(position, /*omit_result_type_check=*/false,
                                     yield_index);
}

Fragment StreamingFlowGraphBuilder::EvaluateAssertion() {
  return flow_graph_builder_->EvaluateAssertion();
}

Fragment StreamingFlowGraphBuilder::RethrowException(TokenPosition position,
                                                     int catch_try_index) {
  return flow_graph_builder_->RethrowException(position, catch_try_index);
}

Fragment StreamingFlowGraphBuilder::ThrowNoSuchMethodError(
    const Function& target) {
  return flow_graph_builder_->ThrowNoSuchMethodError(target);
}

Fragment StreamingFlowGraphBuilder::Constant(const Object& value) {
  return flow_graph_builder_->Constant(value);
}

Fragment StreamingFlowGraphBuilder::IntConstant(int64_t value) {
  return flow_graph_builder_->IntConstant(value);
}

Fragment StreamingFlowGraphBuilder::LoadStaticField(const Field& field,
                                                    bool calls_initializer) {
  return flow_graph_builder_->LoadStaticField(field, calls_initializer);
}

Fragment StreamingFlowGraphBuilder::RedefinitionWithType(
    const AbstractType& type) {
  return flow_graph_builder_->RedefinitionWithType(type);
}

Fragment StreamingFlowGraphBuilder::CheckNull(
    TokenPosition position,
    LocalVariable* receiver,
    const String& function_name,
    bool clear_the_temp /* = true */) {
  return flow_graph_builder_->CheckNull(position, receiver, function_name,
                                        clear_the_temp);
}

Fragment StreamingFlowGraphBuilder::StaticCall(TokenPosition position,
                                               const Function& target,
                                               intptr_t argument_count,
                                               ICData::RebindRule rebind_rule) {
  if (!target.AreValidArgumentCounts(0, argument_count, 0, nullptr)) {
    return flow_graph_builder_->ThrowNoSuchMethodError(target);
  }
  return flow_graph_builder_->StaticCall(position, target, argument_count,
                                         rebind_rule);
}

Fragment StreamingFlowGraphBuilder::StaticCall(
    TokenPosition position,
    const Function& target,
    intptr_t argument_count,
    const Array& argument_names,
    ICData::RebindRule rebind_rule,
    const InferredTypeMetadata* result_type,
    intptr_t type_args_count,
    bool use_unchecked_entry) {
  if (!target.AreValidArguments(type_args_count, argument_count, argument_names,
                                nullptr)) {
    return flow_graph_builder_->ThrowNoSuchMethodError(target);
  }
  return flow_graph_builder_->StaticCall(
      position, target, argument_count, argument_names, rebind_rule,
      result_type, type_args_count, use_unchecked_entry);
}

Fragment StreamingFlowGraphBuilder::InstanceCall(
    TokenPosition position,
    const String& name,
    Token::Kind kind,
    intptr_t argument_count,
    intptr_t checked_argument_count) {
  const intptr_t kTypeArgsLen = 0;
  return flow_graph_builder_->InstanceCall(position, name, kind, kTypeArgsLen,
                                           argument_count, Array::null_array(),
                                           checked_argument_count);
}

Fragment StreamingFlowGraphBuilder::InstanceCall(
    TokenPosition position,
    const String& name,
    Token::Kind kind,
    intptr_t type_args_len,
    intptr_t argument_count,
    const Array& argument_names,
    intptr_t checked_argument_count,
    const Function& interface_target,
    const Function& tearoff_interface_target,
    const InferredTypeMetadata* result_type,
    bool use_unchecked_entry,
    const CallSiteAttributesMetadata* call_site_attrs,
    bool receiver_is_not_smi) {
  return flow_graph_builder_->InstanceCall(
      position, name, kind, type_args_len, argument_count, argument_names,
      checked_argument_count, interface_target, tearoff_interface_target,
      result_type, use_unchecked_entry, call_site_attrs, receiver_is_not_smi);
}

Fragment StreamingFlowGraphBuilder::ThrowException(TokenPosition position) {
  return flow_graph_builder_->ThrowException(position);
}

Fragment StreamingFlowGraphBuilder::BooleanNegate() {
  return flow_graph_builder_->BooleanNegate();
}

Fragment StreamingFlowGraphBuilder::TranslateInstantiatedTypeArguments(
    const TypeArguments& type_arguments) {
  return flow_graph_builder_->TranslateInstantiatedTypeArguments(
      type_arguments);
}

Fragment StreamingFlowGraphBuilder::StrictCompare(TokenPosition position,
                                                  Token::Kind kind,
                                                  bool number_check) {
  return flow_graph_builder_->StrictCompare(position, kind, number_check);
}

Fragment StreamingFlowGraphBuilder::AllocateObject(TokenPosition position,
                                                   const Class& klass,
                                                   intptr_t argument_count) {
  return flow_graph_builder_->AllocateObject(position, klass, argument_count);
}

Fragment StreamingFlowGraphBuilder::AllocateContext(
    const ZoneGrowableArray<const Slot*>& context_slots) {
  return flow_graph_builder_->AllocateContext(context_slots);
}

Fragment StreamingFlowGraphBuilder::LoadNativeField(const Slot& field) {
  return flow_graph_builder_->LoadNativeField(field);
}

Fragment StreamingFlowGraphBuilder::StoreLocal(TokenPosition position,
                                               LocalVariable* variable) {
  return flow_graph_builder_->StoreLocal(position, variable);
}

Fragment StreamingFlowGraphBuilder::StoreStaticField(TokenPosition position,
                                                     const Field& field) {
  return flow_graph_builder_->StoreStaticField(position, field);
}

Fragment StreamingFlowGraphBuilder::StringInterpolate(TokenPosition position) {
  return flow_graph_builder_->StringInterpolate(position);
}

Fragment StreamingFlowGraphBuilder::StringInterpolateSingle(
    TokenPosition position) {
  return flow_graph_builder_->StringInterpolateSingle(position);
}

Fragment StreamingFlowGraphBuilder::ThrowTypeError() {
  return flow_graph_builder_->ThrowTypeError();
}

Fragment StreamingFlowGraphBuilder::LoadInstantiatorTypeArguments() {
  return flow_graph_builder_->LoadInstantiatorTypeArguments();
}

Fragment StreamingFlowGraphBuilder::LoadFunctionTypeArguments() {
  return flow_graph_builder_->LoadFunctionTypeArguments();
}

Fragment StreamingFlowGraphBuilder::InstantiateType(const AbstractType& type) {
  return flow_graph_builder_->InstantiateType(type);
}

Fragment StreamingFlowGraphBuilder::CreateArray() {
  return flow_graph_builder_->CreateArray();
}

Fragment StreamingFlowGraphBuilder::StoreIndexed(intptr_t class_id) {
  return flow_graph_builder_->StoreIndexed(class_id);
}

Fragment StreamingFlowGraphBuilder::CheckStackOverflow(TokenPosition position) {
  return flow_graph_builder_->CheckStackOverflow(
      position, flow_graph_builder_->GetStackDepth(),
      flow_graph_builder_->loop_depth_);
}

Fragment StreamingFlowGraphBuilder::CloneContext(
    const ZoneGrowableArray<const Slot*>& context_slots) {
  return flow_graph_builder_->CloneContext(context_slots);
}

Fragment StreamingFlowGraphBuilder::TranslateFinallyFinalizers(
    TryFinallyBlock* outer_finally,
    intptr_t target_context_depth) {
  // TranslateFinallyFinalizers can move the readers offset.
  // Save the current position and restore it afterwards.
  AlternativeReadingScope alt(&reader_);

  // Save context.
  TryFinallyBlock* const saved_finally_block = B->try_finally_block_;
  TryCatchBlock* const saved_try_catch_block = B->CurrentTryCatchBlock();
  const intptr_t saved_context_depth = B->context_depth_;
  const ProgramState state(B->breakable_block_, B->switch_block_,
                           B->loop_depth_, B->for_in_depth_, B->try_depth_,
                           B->catch_depth_, B->block_expression_depth_);

  Fragment instructions;

  // While translating the body of a finalizer we need to set the try-finally
  // block which is active when translating the body.
  while (B->try_finally_block_ != outer_finally) {
    ASSERT(B->try_finally_block_ != nullptr);
    // Adjust program context to finalizer's position.
    B->try_finally_block_->state().assignTo(B);

    // Potentially restore the context to what is expected for the finally
    // block.
    instructions += B->AdjustContextTo(B->try_finally_block_->context_depth());

    // The to-be-translated finalizer has to have the correct try-index (namely
    // the one outside the try-finally block).
    bool changed_try_index = false;
    intptr_t target_try_index = B->try_finally_block_->try_index();
    while (B->CurrentTryIndex() != target_try_index) {
      B->SetCurrentTryCatchBlock(B->CurrentTryCatchBlock()->outer());
      changed_try_index = true;
    }
    if (changed_try_index) {
      JoinEntryInstr* entry = BuildJoinEntry();
      instructions += Goto(entry);
      instructions = Fragment(instructions.entry, entry);
    }

    intptr_t finalizer_kernel_offset =
        B->try_finally_block_->finalizer_kernel_offset();
    B->try_finally_block_ = B->try_finally_block_->outer();
    instructions += BuildStatementAt(finalizer_kernel_offset);

    // We only need to make sure that if the finalizer ended normally, we
    // continue towards the next outer try-finally.
    if (!instructions.is_open()) break;
  }

  if (instructions.is_open() && target_context_depth != -1) {
    // A target context depth of -1 indicates that the code after this
    // will not care about the context chain so we can leave it any way we
    // want after the last finalizer.  That is used when returning.
    instructions += B->AdjustContextTo(target_context_depth);
  }

  // Restore.
  B->try_finally_block_ = saved_finally_block;
  B->SetCurrentTryCatchBlock(saved_try_catch_block);
  B->context_depth_ = saved_context_depth;
  state.assignTo(B);

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BranchIfTrue(
    TargetEntryInstr** then_entry,
    TargetEntryInstr** otherwise_entry,
    bool negate) {
  return flow_graph_builder_->BranchIfTrue(then_entry, otherwise_entry, negate);
}

Fragment StreamingFlowGraphBuilder::BranchIfEqual(
    TargetEntryInstr** then_entry,
    TargetEntryInstr** otherwise_entry,
    bool negate) {
  return flow_graph_builder_->BranchIfEqual(then_entry, otherwise_entry,
                                            negate);
}

Fragment StreamingFlowGraphBuilder::BranchIfNull(
    TargetEntryInstr** then_entry,
    TargetEntryInstr** otherwise_entry,
    bool negate) {
  return flow_graph_builder_->BranchIfNull(then_entry, otherwise_entry, negate);
}

Fragment StreamingFlowGraphBuilder::CatchBlockEntry(const Array& handler_types,
                                                    intptr_t handler_index,
                                                    bool needs_stacktrace,
                                                    bool is_synthesized) {
  return flow_graph_builder_->CatchBlockEntry(handler_types, handler_index,
                                              needs_stacktrace, is_synthesized);
}

Fragment StreamingFlowGraphBuilder::TryCatch(int try_handler_index) {
  return flow_graph_builder_->TryCatch(try_handler_index);
}

Fragment StreamingFlowGraphBuilder::Drop() {
  return flow_graph_builder_->Drop();
}

Fragment StreamingFlowGraphBuilder::DropTempsPreserveTop(
    intptr_t num_temps_to_drop) {
  return flow_graph_builder_->DropTempsPreserveTop(num_temps_to_drop);
}

Fragment StreamingFlowGraphBuilder::MakeTemp() {
  return flow_graph_builder_->MakeTemp();
}

Fragment StreamingFlowGraphBuilder::NullConstant() {
  return flow_graph_builder_->NullConstant();
}

JoinEntryInstr* StreamingFlowGraphBuilder::BuildJoinEntry() {
  return flow_graph_builder_->BuildJoinEntry();
}

JoinEntryInstr* StreamingFlowGraphBuilder::BuildJoinEntry(intptr_t try_index) {
  return flow_graph_builder_->BuildJoinEntry(try_index);
}

Fragment StreamingFlowGraphBuilder::Goto(JoinEntryInstr* destination) {
  return flow_graph_builder_->Goto(destination);
}

Fragment StreamingFlowGraphBuilder::BuildImplicitClosureCreation(
    const Function& target) {
  return flow_graph_builder_->BuildImplicitClosureCreation(target);
}

Fragment StreamingFlowGraphBuilder::CheckBoolean(TokenPosition position) {
  return flow_graph_builder_->CheckBoolean(position);
}

Fragment StreamingFlowGraphBuilder::CheckArgumentType(
    LocalVariable* variable,
    const AbstractType& type) {
  return flow_graph_builder_->CheckAssignable(
      type, variable->name(), AssertAssignableInstr::kParameterCheck);
}

Fragment StreamingFlowGraphBuilder::EnterScope(
    intptr_t kernel_offset,
    const LocalScope** scope /* = nullptr */) {
  return flow_graph_builder_->EnterScope(kernel_offset, scope);
}

Fragment StreamingFlowGraphBuilder::ExitScope(intptr_t kernel_offset) {
  return flow_graph_builder_->ExitScope(kernel_offset);
}

TestFragment StreamingFlowGraphBuilder::TranslateConditionForControl() {
  // Skip all negations and go directly to the expression.
  bool negate = false;
  while (PeekTag() == kNot) {
    SkipBytes(1);
    negate = !negate;
  }

  TestFragment result;
  if (PeekTag() == kLogicalExpression) {
    // Handle '&&' and '||' operators specially to implement short circuit
    // evaluation.
    SkipBytes(1);  // tag.

    TestFragment left = TranslateConditionForControl();
    LogicalOperator op = static_cast<LogicalOperator>(ReadByte());
    TestFragment right = TranslateConditionForControl();

    result.entry = left.entry;
    if (op == kAnd) {
      left.CreateTrueSuccessor(flow_graph_builder_)->LinkTo(right.entry);
      result.true_successor_addresses = right.true_successor_addresses;
      result.false_successor_addresses = left.false_successor_addresses;
      result.false_successor_addresses->AddArray(
          *right.false_successor_addresses);
    } else {
      ASSERT(op == kOr);
      left.CreateFalseSuccessor(flow_graph_builder_)->LinkTo(right.entry);
      result.true_successor_addresses = left.true_successor_addresses;
      result.true_successor_addresses->AddArray(
          *right.true_successor_addresses);
      result.false_successor_addresses = right.false_successor_addresses;
    }
  } else {
    // Other expressions.
    TokenPosition position = TokenPosition::kNoSource;
    Fragment instructions = BuildExpression(&position);  // read expression.

    // Check if the top of the stack is already a StrictCompare that
    // can be merged with a branch. Otherwise compare TOS with
    // true value and branch on that.
    BranchInstr* branch;
    if (stack()->definition()->IsStrictCompare() &&
        stack()->definition() == instructions.current) {
      StrictCompareInstr* compare = Pop()->definition()->AsStrictCompare();
      if (negate) {
        compare->NegateComparison();
        negate = false;
      }
      branch =
          new (Z) BranchInstr(compare, flow_graph_builder_->GetNextDeoptId());
      branch->comparison()->ClearTempIndex();
      ASSERT(instructions.current->previous() != nullptr);
      instructions.current = instructions.current->previous();
    } else {
      instructions += CheckBoolean(position);
      instructions += Constant(Bool::True());
      Value* right_value = Pop();
      Value* left_value = Pop();
      StrictCompareInstr* compare = new (Z) StrictCompareInstr(
          TokenPosition::kNoSource,
          negate ? Token::kNE_STRICT : Token::kEQ_STRICT, left_value,
          right_value, false, flow_graph_builder_->GetNextDeoptId());
      branch =
          new (Z) BranchInstr(compare, flow_graph_builder_->GetNextDeoptId());
      negate = false;
    }
    instructions <<= branch;

    result = TestFragment(instructions.entry, branch);
  }

  return result.Negate(negate);
}

const TypeArguments& StreamingFlowGraphBuilder::BuildTypeArguments() {
  ReadUInt();                               // read arguments count.
  intptr_t type_count = ReadListLength();   // read type count.
  return T.BuildTypeArguments(type_count);  // read types.
}

Fragment StreamingFlowGraphBuilder::BuildArguments(Array* argument_names,
                                                   intptr_t* argument_count,
                                                   intptr_t* positional_count) {
  intptr_t dummy;
  if (argument_count == NULL) argument_count = &dummy;
  *argument_count = ReadUInt();  // read arguments count.

  // List of types.
  SkipListOfDartTypes();  // read list of types.

  {
    AlternativeReadingScope _(&reader_);
    if (positional_count == NULL) positional_count = &dummy;
    *positional_count = ReadListLength();  // read length of expression list
  }
  return BuildArgumentsFromActualArguments(argument_names);
}

Fragment StreamingFlowGraphBuilder::BuildArgumentsFromActualArguments(
    Array* argument_names) {
  Fragment instructions;

  // List of positional.
  intptr_t list_length = ReadListLength();  // read list length.
  for (intptr_t i = 0; i < list_length; ++i) {
    instructions += BuildExpression();  // read ith expression.
  }

  // List of named.
  list_length = ReadListLength();  // read list length.
  if (argument_names != NULL && list_length > 0) {
    *argument_names = Array::New(list_length, Heap::kOld);
  }
  for (intptr_t i = 0; i < list_length; ++i) {
    String& name =
        H.DartSymbolObfuscate(ReadStringReference());  // read ith name index.
    instructions += BuildExpression();                 // read ith expression.
    if (argument_names != NULL) {
      argument_names->SetAt(i, name);
    }
  }

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildInvalidExpression(
    TokenPosition* position) {
  // The frontend will take care of emitting normal errors (like
  // [NoSuchMethodError]s) and only emit [InvalidExpression]s in very special
  // situations (e.g. an invalid annotation).
  TokenPosition pos = ReadPosition();
  if (position != NULL) *position = pos;
  const String& message = H.DartString(ReadStringReference());
  // Invalid expression message has pointer to the source code, no need to
  // report it twice.
  H.ReportError(script(), TokenPosition::kNoSource, "%s", message.ToCString());
  return Fragment();
}

Fragment StreamingFlowGraphBuilder::BuildVariableGet(TokenPosition* position) {
  const TokenPosition pos = ReadPosition();
  if (position != nullptr) *position = pos;
  intptr_t variable_kernel_position = ReadUInt();  // read kernel position.
  ReadUInt();              // read relative variable index.
  SkipOptionalDartType();  // read promoted type.
  return BuildVariableGetImpl(variable_kernel_position, pos);
}

Fragment StreamingFlowGraphBuilder::BuildVariableGet(uint8_t payload,
                                                     TokenPosition* position) {
  const TokenPosition pos = ReadPosition();
  if (position != nullptr) *position = pos;
  intptr_t variable_kernel_position = ReadUInt();  // read kernel position.
  return BuildVariableGetImpl(variable_kernel_position, pos);
}

Fragment StreamingFlowGraphBuilder::BuildVariableGetImpl(
    intptr_t variable_kernel_position,
    TokenPosition position) {
  LocalVariable* variable = LookupVariable(variable_kernel_position);
  if (!variable->is_late()) {
    return LoadLocal(variable);
  }

  // Late variable, so check whether it has been initialized already.
  Fragment instructions = LoadLocal(variable);
  TargetEntryInstr *is_uninitialized, *is_initialized;
  instructions += Constant(Object::sentinel());
  instructions += flow_graph_builder_->BranchIfStrictEqual(&is_uninitialized,
                                                           &is_initialized);
  JoinEntryInstr* join = BuildJoinEntry();

  {
    AlternativeReadingScope alt(&reader_, variable->late_init_offset());
    const bool has_initializer = (ReadTag() != kNothing);

    if (has_initializer) {
      // If the variable isn't initialized, call the initializer and set it.
      Fragment initialize(is_uninitialized);
      initialize += BuildExpression();
      initialize += StoreLocal(position, variable);
      initialize += Drop();
      initialize += Goto(join);
    } else {
      // The variable has no initializer, so throw a LateInitializationError.
      Fragment initialize(is_uninitialized);
      initialize += flow_graph_builder_->ThrowLateInitializationError(
          position, variable->name());
      initialize += Goto(join);
    }
  }

  {
    // Already initialized, so there's nothing to do.
    Fragment already_initialized(is_initialized);
    already_initialized += Goto(join);
  }

  Fragment done = Fragment(instructions.entry, join);
  done += LoadLocal(variable);
  return done;
}

Fragment StreamingFlowGraphBuilder::BuildVariableSet(TokenPosition* p) {
  TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  intptr_t variable_kernel_position = ReadUInt();  // read kernel position.
  ReadUInt();  // read relative variable index.
  return BuildVariableSetImpl(position, variable_kernel_position);
}

Fragment StreamingFlowGraphBuilder::BuildVariableSet(uint8_t payload,
                                                     TokenPosition* p) {
  TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  intptr_t variable_kernel_position = ReadUInt();  // read kernel position.
  return BuildVariableSetImpl(position, variable_kernel_position);
}

Fragment StreamingFlowGraphBuilder::BuildVariableSetImpl(
    TokenPosition position,
    intptr_t variable_kernel_position) {
  Fragment instructions = BuildExpression();  // read expression.
  if (NeedsDebugStepCheck(stack(), position)) {
    instructions = DebugStepCheck(position) + instructions;
  }

  LocalVariable* variable = LookupVariable(variable_kernel_position);
  if (variable->is_late() && variable->is_final()) {
    // Late final variable, so check whether it has been initialized.
    LocalVariable* expr_temp = MakeTemporary();
    instructions += LoadLocal(variable);
    TargetEntryInstr *is_uninitialized, *is_initialized;
    instructions += Constant(Object::sentinel());
    instructions += flow_graph_builder_->BranchIfStrictEqual(&is_uninitialized,
                                                             &is_initialized);
    JoinEntryInstr* join = BuildJoinEntry();

    {
      // The variable is uninitialized, so store the expression value.
      Fragment initialize(is_uninitialized);
      initialize += LoadLocal(expr_temp);
      initialize += StoreLocal(position, variable);
      initialize += Drop();
      initialize += Goto(join);
    }

    {
      // Already initialized, so throw a LateInitializationError.
      Fragment already_initialized(is_initialized);
      already_initialized += flow_graph_builder_->ThrowLateInitializationError(
          position, variable->name());
      already_initialized += Goto(join);
    }

    instructions = Fragment(instructions.entry, join);
  } else {
    instructions += StoreLocal(position, variable);
  }

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildPropertyGet(TokenPosition* p) {
  const intptr_t offset = ReaderOffset() - 1;     // Include the tag.
  const TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  const DirectCallMetadata direct_call =
      direct_call_metadata_helper_.GetDirectTargetForPropertyGet(offset);
  const InferredTypeMetadata result_type =
      inferred_type_metadata_helper_.GetInferredType(offset);

  Fragment instructions = BuildExpression();  // read receiver.

  LocalVariable* receiver = NULL;
  if (direct_call.check_receiver_for_null_) {
    // Duplicate receiver for CheckNull before it is consumed by PushArgument.
    receiver = MakeTemporary();
    instructions += LoadLocal(receiver);
  }

  const String& getter_name = ReadNameAsGetterName();  // read name.

  const Function* interface_target = &Function::null_function();
  const Function* tearoff_interface_target = &Function::null_function();
  const NameIndex itarget_name =
      ReadInterfaceMemberNameReference();  // read interface_target_reference.
  if (!H.IsRoot(itarget_name) &&
      (H.IsGetter(itarget_name) || H.IsField(itarget_name))) {
    interface_target = &Function::ZoneHandle(
        Z,
        H.LookupMethodByMember(itarget_name, H.DartGetterName(itarget_name)));
    ASSERT(getter_name.raw() == interface_target->name());
  } else if (!H.IsRoot(itarget_name) && H.IsMethod(itarget_name)) {
    tearoff_interface_target = &Function::ZoneHandle(
        Z,
        H.LookupMethodByMember(itarget_name, H.DartMethodName(itarget_name)));
  }

  if (direct_call.check_receiver_for_null_) {
    instructions += CheckNull(position, receiver, getter_name);
  }

  const String* mangled_name = &getter_name;
  const Function* direct_call_target = &direct_call.target_;
  if (H.IsRoot(itarget_name)) {
    mangled_name = &String::ZoneHandle(
        Z, Function::CreateDynamicInvocationForwarderName(getter_name));
    if (!direct_call_target->IsNull()) {
      direct_call_target = &Function::ZoneHandle(
          direct_call.target_.GetDynamicInvocationForwarder(*mangled_name));
    }
  }

  if (!direct_call_target->IsNull()) {
    ASSERT(CompilerState::Current().is_aot());
    instructions +=
        StaticCall(position, *direct_call_target, 1, Array::null_array(),
                   ICData::kNoRebind, &result_type);
  } else {
    const intptr_t kTypeArgsLen = 0;
    const intptr_t kNumArgsChecked = 1;
    instructions +=
        InstanceCall(position, *mangled_name, Token::kGET, kTypeArgsLen, 1,
                     Array::null_array(), kNumArgsChecked, *interface_target,
                     *tearoff_interface_target, &result_type);
  }

  if (direct_call.check_receiver_for_null_) {
    instructions += DropTempsPreserveTop(1);  // Drop receiver, preserve result.
  }

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildPropertySet(TokenPosition* p) {
  const intptr_t offset = ReaderOffset() - 1;  // Include the tag.

  const DirectCallMetadata direct_call =
      direct_call_metadata_helper_.GetDirectTargetForPropertySet(offset);
  const CallSiteAttributesMetadata call_site_attributes =
      call_site_attributes_metadata_helper_.GetCallSiteAttributes(offset);
  const InferredTypeMetadata inferred_type =
      inferred_type_metadata_helper_.GetInferredType(offset);

  // True if callee can skip argument type checks.
  bool is_unchecked_call = inferred_type.IsSkipCheck();
  if (call_site_attributes.receiver_type != nullptr &&
      call_site_attributes.receiver_type->HasTypeClass() &&
      !Class::Handle(call_site_attributes.receiver_type->type_class())
           .IsGeneric()) {
    is_unchecked_call = true;
  }

  Fragment instructions(MakeTemp());
  LocalVariable* variable = MakeTemporary();

  const TokenPosition position = ReadPosition();  // read position.
  if (p != nullptr) *p = position;

  if (PeekTag() == kThisExpression) {
    is_unchecked_call = true;
  }
  instructions += BuildExpression();  // read receiver.

  LocalVariable* receiver = nullptr;
  if (direct_call.check_receiver_for_null_) {
    // Duplicate receiver for CheckNull before it is consumed by PushArgument.
    receiver = MakeTemporary();
    instructions += LoadLocal(receiver);
  }

  const String& setter_name = ReadNameAsSetterName();  // read name.

  instructions += BuildExpression();  // read value.
  instructions += StoreLocal(TokenPosition::kNoSource, variable);

  const Function* interface_target = &Function::null_function();
  const NameIndex itarget_name =
      ReadInterfaceMemberNameReference();  // read interface_target_reference.
  if (!H.IsRoot(itarget_name)) {
    interface_target = &Function::ZoneHandle(
        Z,
        H.LookupMethodByMember(itarget_name, H.DartSetterName(itarget_name)));
    ASSERT(setter_name.raw() == interface_target->name());
  }

  if (direct_call.check_receiver_for_null_) {
    instructions += CheckNull(position, receiver, setter_name);
  }

  const String* mangled_name = &setter_name;
  const Function* direct_call_target = &direct_call.target_;
  if (H.IsRoot(itarget_name)) {
    mangled_name = &String::ZoneHandle(
        Z, Function::CreateDynamicInvocationForwarderName(setter_name));
    if (!direct_call_target->IsNull()) {
      direct_call_target = &Function::ZoneHandle(
          direct_call.target_.GetDynamicInvocationForwarder(*mangled_name));
    }
  }

  if (!direct_call_target->IsNull()) {
    ASSERT(CompilerState::Current().is_aot());
    instructions +=
        StaticCall(position, *direct_call_target, 2, Array::null_array(),
                   ICData::kNoRebind, /*result_type=*/nullptr,
                   /*type_args_count=*/0,
                   /*use_unchecked_entry=*/is_unchecked_call);
  } else {
    const intptr_t kTypeArgsLen = 0;
    const intptr_t kNumArgsChecked = 1;

    instructions += InstanceCall(
        position, *mangled_name, Token::kSET, kTypeArgsLen, 2,
        Array::null_array(), kNumArgsChecked, *interface_target,
        Function::null_function(),
        /*result_type=*/nullptr,
        /*use_unchecked_entry=*/is_unchecked_call, &call_site_attributes);
  }

  instructions += Drop();  // Drop result of the setter invocation.

  if (direct_call.check_receiver_for_null_) {
    instructions += Drop();  // Drop receiver.
  }

  return instructions;
}

static Function& GetNoSuchMethodOrDie(Thread* thread,
                                      Zone* zone,
                                      const Class& klass) {
  Function& nsm_function = Function::Handle(zone);
  Class& iterate_klass = Class::Handle(zone, klass.raw());
  while (!iterate_klass.IsNull()) {
    if (iterate_klass.EnsureIsFinalized(thread) == Error::null()) {
      nsm_function =
          iterate_klass.LookupDynamicFunction(Symbols::NoSuchMethod());
    }
    if (!nsm_function.IsNull() && nsm_function.NumParameters() == 2 &&
        nsm_function.NumTypeParameters() == 0) {
      break;
    }
    iterate_klass = iterate_klass.SuperClass();
  }
  // We are guaranteed to find noSuchMethod of class Object.
  ASSERT(!nsm_function.IsNull());

  return nsm_function;
}

// Note, that this will always mark `super` flag to true.
Fragment StreamingFlowGraphBuilder::BuildAllocateInvocationMirrorCall(
    TokenPosition position,
    const String& name,
    intptr_t num_type_arguments,
    intptr_t num_arguments,
    const Array& argument_names,
    LocalVariable* actuals_array,
    Fragment build_rest_of_actuals) {
  Fragment instructions;

  // Populate array containing the actual arguments. Just add [this] here.
  instructions += LoadLocal(actuals_array);                      // array
  instructions += IntConstant(num_type_arguments == 0 ? 0 : 1);  // index
  instructions += LoadLocal(parsed_function()->receiver_var());  // receiver
  instructions += StoreIndexed(kArrayCid);
  instructions += build_rest_of_actuals;

  // First argument is receiver.
  instructions += LoadLocal(parsed_function()->receiver_var());

  // Push the arguments for allocating the invocation mirror:
  //   - the name.
  instructions += Constant(String::ZoneHandle(Z, name.raw()));

  //   - the arguments descriptor.
  const Array& args_descriptor =
      Array::Handle(Z, ArgumentsDescriptor::NewBoxed(
                           num_type_arguments, num_arguments, argument_names));
  instructions += Constant(Array::ZoneHandle(Z, args_descriptor.raw()));

  //   - an array containing the actual arguments.
  instructions += LoadLocal(actuals_array);

  //   - [true] indicating this is a `super` NoSuchMethod.
  instructions += Constant(Bool::True());

  const Class& mirror_class =
      Class::Handle(Z, Library::LookupCoreClass(Symbols::InvocationMirror()));
  ASSERT(!mirror_class.IsNull());
  const auto& error = mirror_class.EnsureIsFinalized(thread());
  ASSERT(error == Error::null());
  const Function& allocation_function = Function::ZoneHandle(
      Z, mirror_class.LookupStaticFunction(
             Library::PrivateCoreLibName(Symbols::AllocateInvocationMirror())));
  ASSERT(!allocation_function.IsNull());
  instructions += StaticCall(position, allocation_function,
                             /* argument_count = */ 4, ICData::kStatic);
  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildSuperPropertyGet(TokenPosition* p) {
  const intptr_t offset = ReaderOffset() - 1;     // Include the tag.
  const TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  const InferredTypeMetadata result_type =
      inferred_type_metadata_helper_.GetInferredType(offset);

  Class& klass = GetSuperOrDie();

  StringIndex name_index = ReadStringReference();  // read name index.
  NameIndex library_reference =
      ((H.StringSize(name_index) >= 1) && H.CharacterAt(name_index, 0) == '_')
          ? ReadCanonicalNameReference()  // read library index.
          : NameIndex();
  const String& getter_name = H.DartGetterName(library_reference, name_index);
  const String& method_name = H.DartMethodName(library_reference, name_index);

  SkipInterfaceMemberNameReference();  // skip target_reference.

  // Search the superclass chain for the selector looking for either getter or
  // method.
  Function& function = Function::Handle(Z);
  while (!klass.IsNull()) {
    if (klass.EnsureIsFinalized(thread()) == Error::null()) {
      function = klass.LookupDynamicFunction(method_name);
      if (!function.IsNull()) {
        Function& target =
            Function::ZoneHandle(Z, function.ImplicitClosureFunction());
        ASSERT(!target.IsNull());
        // Generate inline code for allocation closure object with context
        // which captures `this`.
        return BuildImplicitClosureCreation(target);
      }
      function = klass.LookupDynamicFunction(getter_name);
      if (!function.IsNull()) break;
    }
    klass = klass.SuperClass();
  }

  Fragment instructions;
  if (klass.IsNull()) {
    instructions +=
        Constant(TypeArguments::ZoneHandle(Z, TypeArguments::null()));
    instructions += IntConstant(1);  // array size
    instructions += CreateArray();
    LocalVariable* actuals_array = MakeTemporary();

    Class& parent_klass = GetSuperOrDie();

    instructions += BuildAllocateInvocationMirrorCall(
        position, getter_name,
        /* num_type_arguments = */ 0,
        /* num_arguments = */ 1,
        /* argument_names = */ Object::empty_array(), actuals_array,
        /* build_rest_of_actuals = */ Fragment());

    Function& nsm_function = GetNoSuchMethodOrDie(thread(), Z, parent_klass);
    instructions +=
        StaticCall(position, Function::ZoneHandle(Z, nsm_function.raw()),
                   /* argument_count = */ 2, ICData::kNSMDispatch);
    instructions += DropTempsPreserveTop(1);  // Drop array
  } else {
    ASSERT(!klass.IsNull());
    ASSERT(!function.IsNull());

    instructions += LoadLocal(parsed_function()->receiver_var());

    instructions +=
        StaticCall(position, Function::ZoneHandle(Z, function.raw()),
                   /* argument_count = */ 1, Array::null_array(),
                   ICData::kSuper, &result_type);
  }

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildSuperPropertySet(TokenPosition* p) {
  const TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  Class& klass = GetSuperOrDie();

  const String& setter_name = ReadNameAsSetterName();  // read name.

  Function& function = Function::Handle(Z);
  if (klass.EnsureIsFinalized(thread()) == Error::null()) {
    function = H.LookupDynamicFunction(klass, setter_name);
  }

  Fragment instructions(MakeTemp());
  LocalVariable* value = MakeTemporary();  // this holds RHS value

  if (function.IsNull()) {
    instructions +=
        Constant(TypeArguments::ZoneHandle(Z, TypeArguments::null()));
    instructions += IntConstant(2);  // array size
    instructions += CreateArray();
    LocalVariable* actuals_array = MakeTemporary();

    Fragment build_rest_of_actuals;
    build_rest_of_actuals += LoadLocal(actuals_array);  // array
    build_rest_of_actuals += IntConstant(1);            // index
    build_rest_of_actuals += BuildExpression();         // value.
    build_rest_of_actuals += StoreLocal(position, value);
    build_rest_of_actuals += StoreIndexed(kArrayCid);

    instructions += BuildAllocateInvocationMirrorCall(
        position, setter_name, /* num_type_arguments = */ 0,
        /* num_arguments = */ 2,
        /* argument_names = */ Object::empty_array(), actuals_array,
        build_rest_of_actuals);

    SkipInterfaceMemberNameReference();  // skip target_reference.

    Function& nsm_function = GetNoSuchMethodOrDie(thread(), Z, klass);
    instructions +=
        StaticCall(position, Function::ZoneHandle(Z, nsm_function.raw()),
                   /* argument_count = */ 2, ICData::kNSMDispatch);
    instructions += Drop();  // Drop result of NoSuchMethod invocation
    instructions += Drop();  // Drop array
  } else {
    // receiver
    instructions += LoadLocal(parsed_function()->receiver_var());

    instructions += BuildExpression();  // read value.
    instructions += StoreLocal(position, value);

    SkipInterfaceMemberNameReference();  // skip target_reference.

    instructions += StaticCall(
        position, Function::ZoneHandle(Z, function.raw()),
        /* argument_count = */ 2, Array::null_array(), ICData::kSuper,
        /*result_type=*/nullptr, /*type_args_len=*/0,
        /*use_unchecked_entry=*/true);
    instructions += Drop();  // Drop result of the setter invocation.
  }

  return instructions;
}

Fragment StreamingFlowGraphBuilder::BuildDirectPropertyGet(TokenPosition* p) {
  const intptr_t offset = ReaderOffset() - 1;     // Include the tag.
  const TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  const InferredTypeMetadata result_type =
      inferred_type_metadata_helper_.GetInferredType(offset);

  const Tag receiver_tag = PeekTag();         // peek tag for receiver.
  Fragment instructions = BuildExpression();  // read receiver.
  const NameIndex kernel_name =
      ReadInterfaceMemberNameReference();  // read target_reference.

  Function& target = Function::ZoneHandle(Z);
  if (H.IsProcedure(kernel_name)) {
    if (H.IsGetter(kernel_name)) {
      target =
          H.LookupMethodByMember(kernel_name, H.DartGetterName(kernel_name));
    } else if (receiver_tag == kThisExpression) {
      // Undo stack change for the BuildExpression.
      Pop();

      target =
          H.LookupMethodByMember(kernel_name, H.DartMethodName(kernel_name));
      target = target.ImplicitClosureFunction();
      ASSERT(!target.IsNull());

      // Generate inline code for allocating closure object with context which
      // captures `this`.
      return BuildImplicitClosureCreation(target);
    } else {
      // Need to create implicit closure (tear-off), receiver != this.
      // Ensure method extractor exists and call it directly.
      const Function& target_method = Function::ZoneHandle(
          Z,
          H.LookupMethodByMember(kernel_name, H.DartMethodName(kernel_name)));
      const String& getter_name = H.DartGetterName(kernel_name);
      target = target_method.GetMethodExtractor(getter_name);
    }
  } else {
    ASSERT(H.IsField(kernel_name));
    const String& getter_name = H.DartGetterName(kernel_name);
    target = H.LookupMethodByMember(kernel_name, getter_name);
    ASSERT(target.IsGetterFunction() || target.IsImplicitGetterFunction());
  }

  // Static calls are marked as "no-rebind", which is currently safe because
  // DirectPropertyGet are only used in enums (index in toString) and enums
  // can't change their structure during hot reload.
  // If there are other sources of DirectPropertyGet in the future, this code
  // have to be adjusted.
  return instructions + StaticCall(position, target, 1, Array::null_array(),
                                   ICData::kNoRebind, &result_type);
}

Fragment StreamingFlowGraphBuilder::BuildDirectPropertySet(TokenPosition* p) {
  const TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  Fragment instructions(MakeTemp());
  LocalVariable* value = MakeTemporary();

  instructions += BuildExpression();  // read receiver.

  const NameIndex target_reference =
      ReadInterfaceMemberNameReference();  // read target_reference.
  const String& method_name = H.DartSetterName(target_reference);
  const Function& target = Function::ZoneHandle(
      Z, H.LookupMethodByMember(target_reference, method_name));
  ASSERT(target.IsSetterFunction() || target.IsImplicitSetterFunction());

  instructions += BuildExpression();  // read value.
  instructions += StoreLocal(TokenPosition::kNoSource, value);

  // Static calls are marked as "no-rebind", which is currently safe because
  // DirectPropertyGet are only used in enums (index in toString) and enums
  // can't change their structure during hot reload.
  // If there are other sources of DirectPropertyGet in the future, this code
  // have to be adjusted.
  instructions +=
      StaticCall(position, target, 2, Array::null_array(), ICData::kNoRebind,
                 /* result_type = */ NULL);

  return instructions + Drop();
}

Fragment StreamingFlowGraphBuilder::BuildStaticGet(TokenPosition* p) {
  ASSERT(Error::Handle(Z, H.thread()->sticky_error()).IsNull());
  const intptr_t offset = ReaderOffset() - 1;  // Include the tag.

  TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  const InferredTypeMetadata result_type =
      inferred_type_metadata_helper_.GetInferredType(offset);

  NameIndex target = ReadCanonicalNameReference();  // read target_reference.

  if (H.IsField(target)) {
    const Field& field =
        Field::ZoneHandle(Z, H.LookupFieldByKernelField(target));
    if (field.is_const()) {
      // Since the CFE inlines all references to const variables and fields,
      // it never emits a StaticGet of a const field.
      // This situation only arises because of the static const fields in
      // the ClassID class, which are generated internally in the VM
      // during loading. See also Class::InjectCIDFields.
      ASSERT(Class::Handle(field.Owner()).library() ==
                 Library::InternalLibrary() &&
             Class::Handle(field.Owner()).Name() == Symbols::ClassID().raw());
      return Constant(Instance::ZoneHandle(Z, field.StaticValue()));
    } else {
      const Class& owner = Class::Handle(Z, field.Owner());
      const String& getter_name = H.DartGetterName(target);
      const Function& getter =
          Function::ZoneHandle(Z, owner.LookupStaticFunction(getter_name));
      if (!getter.IsNull() && field.NeedsGetter()) {
        return StaticCall(position, getter, 0, Array::null_array(),
                          ICData::kStatic, &result_type);
      } else {
        if (result_type.IsConstant()) {
          return Constant(result_type.constant_value);
        }
        return LoadStaticField(field, /*calls_initializer=*/false);
      }
    }
  } else {
    const Function& function =
        Function::ZoneHandle(Z, H.LookupStaticMethodByKernelProcedure(target));

    if (H.IsGetter(target)) {
      return StaticCall(position, function, 0, Array::null_array(),
                        ICData::kStatic, &result_type);
    } else if (H.IsMethod(target)) {
      const auto& closure_function =
          Function::Handle(Z, function.ImplicitClosureFunction());
      const auto& static_closure =
          Instance::Handle(Z, closure_function.ImplicitStaticClosure());
      return Constant(Instance::ZoneHandle(Z, H.Canonicalize(static_closure)));
    } else {
      UNIMPLEMENTED();
    }
  }

  return Fragment();
}

Fragment StreamingFlowGraphBuilder::BuildStaticSet(TokenPosition* p) {
  TokenPosition position = ReadPosition();  // read position.
  if (p != NULL) *p = position;

  NameIndex target = ReadCanonicalNameReference();  // read target_reference.

  if (H.IsField(target)) {
    const Field& field =
        Field::ZoneHandle(Z, H.LookupFieldByKernelField(target));
    const Class& owner = Class::Handle(Z, field.Owner());
    const String& setter_name = H.DartSetterName(target);
    const Function& setter =
        Function::ZoneHandle(Z, owner.LookupStaticFunction(setter_name));
    Fragment instructions = BuildExpression();  // read expression.
    if (NeedsDebugStepCheck(stack(), position)) {
      instructions = DebugStepCheck(position) + instructions;
    }
    LocalVariable* variable = MakeTemporary();
    instructions += LoadLocal(variable);
    if (!setter.IsNull() && field.NeedsSetter()) {
      instructions += StaticCall(position, setter, 1, ICData::kStatic);
      instructions += Drop();
    } else {
      instructions += StoreStaticField(position, field);
    }
    return instructions;
  } else {
    ASSERT(H.IsProcedure(target));

    // Evaluate the expression on the right hand side.
    Fragment instructions = BuildExpression();  // read expression.
    LocalVariable* variable = MakeTemporary();

    // Prepare argument.
    instructions += LoadLocal(variable);

    // Invoke the setter function.
    const Function& function =
        Function::ZoneHandle(Z, H.LookupStaticMethodByKernelProcedure(target));
    instructions += StaticCall(position, function, 1, ICData::kStatic);

    // Drop the unused result & leave the stored value on the stack.
    return instructions + Drop();
  }
}

Fragment StreamingFlowGraphBuilder::BuildMethodInvocation(TokenPosition* p) {
  const intptr_t offset = ReaderOffset() - 1;     // Include the tag.
  const TokenPosition position = ReadPosition();  // read position.
  if