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tools/clang/blink_gc_plugin/Edge.h

+// Copyright 2014 The Chromium 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 TOOLS_BLINK_GC_PLUGIN_EDGE_H_
+#define TOOLS_BLINK_GC_PLUGIN_EDGE_H_
+
+#include <cassert>
+#include <deque>
+#include <vector>
+
+#include "TracingStatus.h"
+
+class RecordInfo;
+
+class Edge;
+class Value;
+class RawPtr;
+class RefPtr;
+class OwnPtr;
+class Member;
+class WeakMember;
+class Persistent;
+class Collection;
+
+// Bare-bones visitor.
+class EdgeVisitor {
+ public:
+  virtual ~EdgeVisitor() {}
+  virtual void VisitValue(Value*) {}
+  virtual void VisitRawPtr(RawPtr*) {}
+  virtual void VisitRefPtr(RefPtr*) {}
+  virtual void VisitOwnPtr(OwnPtr*) {}
+  virtual void VisitMember(Member*) {}
+  virtual void VisitWeakMember(WeakMember*) {}
+  virtual void VisitPersistent(Persistent*) {}
+  virtual void VisitCollection(Collection*) {}
+};
+
+// Recursive edge visitor. The traversed path is accessible in context.
+class RecursiveEdgeVisitor : public EdgeVisitor {
+ public:
+  // Overrides that recursively walk the edges and record the path.
+  void VisitValue(Value*) override;
+  void VisitRawPtr(RawPtr*) override;
+  void VisitRefPtr(RefPtr*) override;
+  void VisitOwnPtr(OwnPtr*) override;
+  void VisitMember(Member*) override;
+  void VisitWeakMember(WeakMember*) override;
+  void VisitPersistent(Persistent*) override;
+  void VisitCollection(Collection*) override;
+
+ protected:
+  typedef std::deque<Edge*> Context;
+  Context& context() { return context_; }
+  Edge* Parent() { return context_.empty() ? 0 : context_.front(); }
+  void Enter(Edge* e) { return context_.push_front(e); }
+  void Leave() { context_.pop_front(); }
+
+  // Default callback to overwrite in visitor subclass.
+  virtual void AtValue(Value*);
+  virtual void AtRawPtr(RawPtr*);
+  virtual void AtRefPtr(RefPtr*);
+  virtual void AtOwnPtr(OwnPtr*);
+  virtual void AtMember(Member*);
+  virtual void AtWeakMember(WeakMember*);
+  virtual void AtPersistent(Persistent*);
+  virtual void AtCollection(Collection*);
+
+ private:
+  Context context_;
+};
+
+// Base class for all edges.
+class Edge {
+ public:
+  enum NeedsTracingOption { kRecursive, kNonRecursive };
+  enum LivenessKind { kWeak, kStrong, kRoot };
+
+  virtual ~Edge() {}
+  virtual LivenessKind Kind() = 0;
+  virtual void Accept(EdgeVisitor*) = 0;
+  virtual bool NeedsFinalization() = 0;
+  virtual TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Unknown();
+  }
+
+  virtual bool IsValue() { return false; }
+  virtual bool IsRawPtr() { return false; }
+  virtual bool IsRawPtrClass() { return false; }
+  virtual bool IsRefPtr() { return false; }
+  virtual bool IsOwnPtr() { return false; }
+  virtual bool IsMember() { return false; }
+  virtual bool IsWeakMember() { return false; }
+  virtual bool IsPersistent() { return false; }
+  virtual bool IsCollection() { return false; }
+};
+
+// A value edge is a direct edge to some type, eg, part-object edges.
+class Value : public Edge {
+ public:
+  explicit Value(RecordInfo* value) : value_(value) {};
+  bool IsValue() override { return true; }
+  LivenessKind Kind() override { return kStrong; }
+  bool NeedsFinalization() override;
+  TracingStatus NeedsTracing(NeedsTracingOption) override;
+  void Accept(EdgeVisitor* visitor) override { visitor->VisitValue(this); }
+  RecordInfo* value() { return value_; }
+
+ private:
+  RecordInfo* value_;
+};
+
+// Shared base for smart-pointer edges.
+class PtrEdge : public Edge {
+ public:
+  ~PtrEdge() { delete ptr_; }
+  Edge* ptr() { return ptr_; }
+ protected:
+  PtrEdge(Edge* ptr) : ptr_(ptr) {
+    assert(ptr && "EdgePtr pointer must be non-null");
+  }
+ private:
+  Edge* ptr_;
+};
+
+class RawPtr : public PtrEdge {
+ public:
+  RawPtr(Edge* ptr, bool is_ptr_class, bool is_ref_type)
+      : PtrEdge(ptr)
+      , is_ptr_class_(is_ptr_class)
+      , is_ref_type_(is_ref_type)
+  {
+      assert(!(is_ptr_class_ && is_ref_type_));
+  }
+
+  bool IsRawPtr() { return true; }
+  bool IsRawPtrClass() { return is_ptr_class_; }
+  LivenessKind Kind() { return kWeak; }
+  bool NeedsFinalization() { return false; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Unneeded();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitRawPtr(this); }
+
+  bool HasReferenceType() { return is_ref_type_; }
+ private:
+  bool is_ptr_class_;
+  bool is_ref_type_;
+};
+
+class RefPtr : public PtrEdge {
+ public:
+  explicit RefPtr(Edge* ptr) : PtrEdge(ptr) { }
+  bool IsRefPtr() { return true; }
+  LivenessKind Kind() { return kStrong; }
+  bool NeedsFinalization() { return true; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Unneeded();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitRefPtr(this); }
+};
+
+class OwnPtr : public PtrEdge {
+ public:
+  explicit OwnPtr(Edge* ptr) : PtrEdge(ptr) { }
+  bool IsOwnPtr() { return true; }
+  LivenessKind Kind() { return kStrong; }
+  bool NeedsFinalization() { return true; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Unneeded();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitOwnPtr(this); }
+};
+
+class Member : public PtrEdge {
+ public:
+  explicit Member(Edge* ptr) : PtrEdge(ptr) { }
+  bool IsMember() { return true; }
+  LivenessKind Kind() { return kStrong; }
+  bool NeedsFinalization() { return false; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Needed();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitMember(this); }
+};
+
+class WeakMember : public PtrEdge {
+ public:
+  explicit WeakMember(Edge* ptr) : PtrEdge(ptr) { }
+  bool IsWeakMember() { return true; }
+  LivenessKind Kind() { return kWeak; }
+  bool NeedsFinalization() { return false; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Needed();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitWeakMember(this); }
+};
+
+class Persistent : public PtrEdge {
+ public:
+  explicit Persistent(Edge* ptr) : PtrEdge(ptr) { }
+  bool IsPersistent() { return true; }
+  LivenessKind Kind() { return kRoot; }
+  bool NeedsFinalization() { return true; }
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    return TracingStatus::Unneeded();
+  }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitPersistent(this); }
+};
+
+class Collection : public Edge {
+ public:
+  typedef std::vector<Edge*> Members;
+  Collection(RecordInfo* info, bool on_heap, bool is_root)
+      : info_(info),
+        on_heap_(on_heap),
+        is_root_(is_root) {}
+  ~Collection() {
+    for (Members::iterator it = members_.begin(); it != members_.end(); ++it) {
+      assert(*it && "Collection-edge members must be non-null");
+      delete *it;
+    }
+  }
+  bool IsCollection() { return true; }
+  LivenessKind Kind() { return is_root_ ? kRoot : kStrong; }
+  bool on_heap() { return on_heap_; }
+  bool is_root() { return is_root_; }
+  Members& members() { return members_; }
+  void Accept(EdgeVisitor* visitor) { visitor->VisitCollection(this); }
+  void AcceptMembers(EdgeVisitor* visitor) {
+    for (Members::iterator it = members_.begin(); it != members_.end(); ++it)
+      (*it)->Accept(visitor);
+  }
+  bool NeedsFinalization();
+  TracingStatus NeedsTracing(NeedsTracingOption) {
+    if (is_root_)
+      return TracingStatus::Unneeded();
+    if (on_heap_)
+      return TracingStatus::Needed();
+    // For off-heap collections, determine tracing status of members.
+    TracingStatus status = TracingStatus::Unneeded();
+    for (Members::iterator it = members_.begin(); it != members_.end(); ++it) {
+      // Do a non-recursive test here since members could equal the holder.
+      status = status.LUB((*it)->NeedsTracing(kNonRecursive));
+    }
+    return status;
+  }
+
+ private:
+  RecordInfo* info_;
+  Members members_;
+  bool on_heap_;
+  bool is_root_;
+};
+
+#endif  // TOOLS_BLINK_GC_PLUGIN_EDGE_H_