src/objects/feedback-cell.h

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_OBJECTS_FEEDBACK_CELL_H_
#define V8_OBJECTS_FEEDBACK_CELL_H_

#include <optional>

#include "src/objects/struct.h"

// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"

namespace v8::internal {

class Undefined;

// This is a special cell used to maintain both the link between a
// closure and its feedback vector, as well as a way to count the
// number of closures created for a certain function per native
// context. There's at most one FeedbackCell for each function in
// a native context.
V8_OBJECT class FeedbackCell : public Struct {
 public:
  using Value = UnionOf<Undefined, FeedbackVector, ClosureFeedbackCellArray>;

  // Accessors
  inline Tagged<Value> value() const;
  inline Tagged<Value> value(AcquireLoadTag) const;
  inline void set_value(Tagged<Value> value,
                        WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
  inline void set_value(Tagged<Value> value, ReleaseStoreTag,
                        WriteBarrierMode mode = UPDATE_WRITE_BARRIER);

  inline int32_t interrupt_budget() const;
  inline void set_interrupt_budget(int32_t value);

  inline JSDispatchHandle dispatch_handle() const;
  inline void set_dispatch_handle(JSDispatchHandle new_handle);

  inline void clear_interrupt_budget();
  inline void clear_dispatch_handle();

  inline void clear_padding();
  inline void reset_feedback_vector(
      std::optional<
          std::function<void(Tagged<HeapObject> object, ObjectSlot slot,
                             Tagged<HeapObject> target)>>
          gc_notify_updated_slot = std::nullopt);

  enum ClosureCountTransition { kNoneToOne, kOneToMany, kMany };
  // The closure count is encoded in the cell's map, which distinguishes
  // between zero, one, or many closures. This function records a new closure
  // creation by updating the map.
  inline ClosureCountTransition IncrementClosureCount(Isolate* isolate);

  DECL_PRINTER(FeedbackCell)
  DECL_VERIFIER(FeedbackCell)

  class BodyDescriptor;

 public:
  TaggedMember<Value> value_;
  JSDispatchHandleMember dispatch_handle_;
  int32_t interrupt_budget_;
} V8_OBJECT_END;

static_assert(sizeof(FeedbackCell) ==
              sizeof(Struct) + kTaggedSize + 2 * kInt32Size);

}  // namespace v8::internal

#include "src/objects/object-macros-undef.h"

#endif  // V8_OBJECTS_FEEDBACK_CELL_H_