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// Copyright 2017 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_VISITORS_H_
#define V8_VISITORS_H_
#include "src/globals.h"
namespace v8 {
namespace internal {
class CodeDataContainer;
class MaybeObject;
class Object;
#define ROOT_ID_LIST(V) \
V(kStringTable, "(Internalized strings)") \
V(kExternalStringsTable, "(External strings)") \
V(kStrongRootList, "(Strong roots)") \
V(kSmiRootList, "(Smi roots)") \
V(kBootstrapper, "(Bootstrapper)") \
V(kTop, "(Isolate)") \
V(kRelocatable, "(Relocatable)") \
V(kDebug, "(Debugger)") \
V(kCompilationCache, "(Compilation cache)") \
V(kHandleScope, "(Handle scope)") \
V(kDispatchTable, "(Dispatch table)") \
V(kBuiltins, "(Builtins)") \
V(kGlobalHandles, "(Global handles)") \
V(kEternalHandles, "(Eternal handles)") \
V(kThreadManager, "(Thread manager)") \
V(kStrongRoots, "(Strong roots)") \
V(kExtensions, "(Extensions)") \
V(kCodeFlusher, "(Code flusher)") \
V(kPartialSnapshotCache, "(Partial snapshot cache)") \
V(kWeakCollections, "(Weak collections)") \
V(kWrapperTracing, "(Wrapper tracing)") \
V(kUnknown, "(Unknown)")
class VisitorSynchronization : public AllStatic {
public:
#define DECLARE_ENUM(enum_item, ignore) enum_item,
enum SyncTag { ROOT_ID_LIST(DECLARE_ENUM) kNumberOfSyncTags };
#undef DECLARE_ENUM
};
enum class Root {
#define DECLARE_ENUM(enum_item, ignore) enum_item,
ROOT_ID_LIST(DECLARE_ENUM)
#undef DECLARE_ENUM
kNumberOfRoots
};
// Abstract base class for visiting, and optionally modifying, the
// pointers contained in roots. Used in GC and serialization/deserialization.
class RootVisitor {
public:
virtual ~RootVisitor() = default;
// Visits a contiguous arrays of pointers in the half-open range
// [start, end). Any or all of the values may be modified on return.
virtual void VisitRootPointers(Root root, const char* description,
Object** start, Object** end) = 0;
// Handy shorthand for visiting a single pointer.
virtual void VisitRootPointer(Root root, const char* description,
Object** p) {
VisitRootPointers(root, description, p, p + 1);
}
// Intended for serialization/deserialization checking: insert, or
// check for the presence of, a tag at this position in the stream.
// Also used for marking up GC roots in heap snapshots.
// TODO(ulan): Remove this.
virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
static const char* RootName(Root root);
};
class RelocIterator;
// Abstract base class for visiting, and optionally modifying, the
// pointers contained in Objects. Used in GC and serialization/deserialization.
class ObjectVisitor {
public:
virtual ~ObjectVisitor() = default;
// Visits a contiguous arrays of pointers in the half-open range
// [start, end). Any or all of the values may be modified on return.
virtual void VisitPointers(HeapObject* host, Object** start,
Object** end) = 0;
virtual void VisitPointers(HeapObject* host, MaybeObject** start,
MaybeObject** end) = 0;
// Custom weak pointers must be ignored by the GC but not other
// visitors. They're used for e.g., lists that are recreated after GC. The
// default implementation treats them as strong pointers. Visitors who want to
// ignore them must override this function with empty.
virtual void VisitCustomWeakPointers(HeapObject* host, Object** start,
Object** end) {
VisitPointers(host, start, end);
}
// Handy shorthand for visiting a single pointer.
virtual void VisitPointer(HeapObject* host, Object** p) {
VisitPointers(host, p, p + 1);
}
virtual void VisitPointer(HeapObject* host, MaybeObject** p) {
VisitPointers(host, p, p + 1);
}
virtual void VisitCustomWeakPointer(HeapObject* host, Object** p) {
VisitCustomWeakPointers(host, p, p + 1);
}
// To allow lazy clearing of inline caches the visitor has
// a rich interface for iterating over Code objects ...
// Visits a code target in the instruction stream.
virtual void VisitCodeTarget(Code* host, RelocInfo* rinfo);
// Visits a runtime entry in the instruction stream.
virtual void VisitRuntimeEntry(Code* host, RelocInfo* rinfo) {}
// Visit pointer embedded into a code object.
virtual void VisitEmbeddedPointer(Code* host, RelocInfo* rinfo);
// Visits an external reference embedded into a code object.
virtual void VisitExternalReference(Code* host, RelocInfo* rinfo) {}
// Visits an external reference.
virtual void VisitExternalReference(Foreign* host, Address* p) {}
// Visits an (encoded) internal reference.
virtual void VisitInternalReference(Code* host, RelocInfo* rinfo) {}
// Visits an off-heap target in the instruction stream.
virtual void VisitOffHeapTarget(Code* host, RelocInfo* rinfo) {}
// Visits the relocation info using the given iterator.
virtual void VisitRelocInfo(RelocIterator* it);
};
} // namespace internal
} // namespace v8
#endif // V8_VISITORS_H_
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