runtime/vm/compiler/cha.h

// Copyright (c) 2012, 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.

#ifndef RUNTIME_VM_COMPILER_CHA_H_
#define RUNTIME_VM_COMPILER_CHA_H_

#include "vm/allocation.h"
#include "vm/growable_array.h"
#include "vm/thread.h"

namespace dart {

class Class;
class Function;
template <typename T>
class ZoneGrowableArray;
class String;

class CHA : public StackResource {
 public:
  explicit CHA(Thread* thread)
      : StackResource(thread),
        thread_(thread),
        guarded_classes_(thread->zone(), 1),
        previous_(thread->cha()) {
    thread->set_cha(this);
  }

  ~CHA() {
    ASSERT(thread_->cha() == this);
    thread_->set_cha(previous_);
  }

  // Returns true if the class has subclasses.
  static bool HasSubclasses(const Class& cls);
  bool HasSubclasses(intptr_t cid) const;

  // Collect the concrete subclasses of 'cls' into 'class_ids'. Return true if
  // the result is valid (may be invalid because we don't track the subclasses
  // of classes allocated in the VM isolate or class Object).
  bool ConcreteSubclasses(const Class& cls, GrowableArray<intptr_t>* class_ids);

  // Return true if the class is implemented by some other class.
  static bool IsImplemented(const Class& cls);

  // Returns true if any subclass of 'cls' contains the function.
  // If no override was found subclass_count would contain total count of
  // finalized subclasses that CHA looked at.
  // This count will be used to validate CHA decision before installing
  // optimized code compiled in background.
  bool HasOverride(const Class& cls,
                   const String& function_name,
                   intptr_t* subclass_count);

  // Adds class 'cls' to the list of guarded classes, deoptimization occurs
  // if any of those classes gets subclassed through later loaded/finalized
  // libraries. Only classes that were used for CHA optimizations are added.
  void AddToGuardedClasses(const Class& cls, intptr_t subclass_count);

  // When compiling in background we need to check that no new finalized
  // subclasses were added to guarded classes.
  bool IsConsistentWithCurrentHierarchy() const;

  void RegisterDependencies(const Code& code) const;

  // Used for testing.
  bool IsGuardedClass(intptr_t cid) const;

 private:
  Thread* thread_;

  struct GuardedClassInfo {
    Class* cls;

    // Number of finalized subclasses that this class had at the moment
    // when CHA made the first decision based on this class.
    // Used to validate correctness of background compilation: if
    // any subclasses were added we will discard compiled code.
    intptr_t subclass_count;
  };

  GrowableArray<GuardedClassInfo> guarded_classes_;
  CHA* previous_;
};

}  // namespace dart

#endif  // RUNTIME_VM_COMPILER_CHA_H_