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diff --git a/js/src/gc/Marking.h b/js/src/gc/Marking.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Marking and sweeping APIs for use by implementations of different GC cell
+ * kinds.
+ */
+
+#ifndef gc_Marking_h
+#define gc_Marking_h
+
+#include "gc/Barrier.h"
+#include "gc/Tracer.h"
+#include "js/TypeDecls.h"
+
+class JSTracer;
+struct JSClass;
+
+namespace js {
+class GCMarker;
+class Shape;
+class WeakMapBase;
+
+namespace gc {
+
+struct Cell;
+
+/*** Liveness ***/
+
+// The IsMarkedInternal and IsAboutToBeFinalizedInternal function templates are
+// used to implement the IsMarked and IsAboutToBeFinalized set of functions.
+// These internal functions are instantiated for the base GC types and should
+// not be called directly.
+//
+// Note that there are two function templates declared for each, not one
+// template and a specialization. This is necessary so that pointer arguments
+// (e.g. JSObject**) and tagged value arguments (e.g. JS::Value*) are routed to
+// separate implementations.
+
+template <typename T>
+bool IsMarkedInternal(JSRuntime* rt, T* thing);
+
+template <typename T>
+bool IsAboutToBeFinalizedInternal(T* thing);
+template <typename T>
+bool IsAboutToBeFinalizedInternal(const T& thing);
+
+// Report whether a GC thing has been marked with any color. Things which are in
+// zones that are not currently being collected or are owned by another runtime
+// are always reported as being marked.
+template <typename T>
+inline bool IsMarked(JSRuntime* rt, const BarrieredBase<T>& thing) {
+  return IsMarkedInternal(rt, *ConvertToBase(thing.unbarrieredAddress()));
+}
+template <typename T>
+inline bool IsMarkedUnbarriered(JSRuntime* rt, T thing) {
+  return IsMarkedInternal(rt, *ConvertToBase(&thing));
+}
+
+// Report whether a GC thing is dead and will be finalized in the current sweep
+// group. This is mainly used in read barriers for incremental sweeping.
+//
+// This no longer updates pointers moved by the GC (tracing should be used for
+// this instead).
+template <typename T>
+inline bool IsAboutToBeFinalized(const BarrieredBase<T>& thing) {
+  return IsAboutToBeFinalizedInternal(
+      *ConvertToBase(thing.unbarrieredAddress()));
+}
+template <typename T>
+inline bool IsAboutToBeFinalizedUnbarriered(T* thing) {
+  return IsAboutToBeFinalizedInternal(*ConvertToBase(&thing));
+}
+template <typename T>
+inline bool IsAboutToBeFinalizedUnbarriered(const T& thing) {
+  return IsAboutToBeFinalizedInternal(thing);
+}
+
+inline bool IsAboutToBeFinalizedDuringMinorSweep(Cell* cell);
+
+inline Cell* ToMarkable(const Value& v) {
+  if (v.isGCThing()) {
+    return (Cell*)v.toGCThing();
+  }
+  return nullptr;
+}
+
+inline Cell* ToMarkable(Cell* cell) { return cell; }
+
+bool UnmarkGrayGCThingUnchecked(GCMarker* marker, JS::GCCellPtr thing);
+
+} /* namespace gc */
+
+// The return value indicates if anything was unmarked.
+bool UnmarkGrayShapeRecursively(Shape* shape);
+
+namespace gc {
+
+// Functions for checking and updating GC thing pointers that might have been
+// moved by compacting GC. Overloads are also provided that work with Values.
+//
+// IsForwarded    - check whether a pointer refers to an GC thing that has been
+//                  moved.
+//
+// Forwarded      - return a pointer to the new location of a GC thing given a
+//                  pointer to old location.
+//
+// MaybeForwarded - used before dereferencing a pointer that may refer to a
+//                  moved GC thing without updating it. For JSObjects this will
+//                  also update the object's shape pointer if it has been moved
+//                  to allow slots to be accessed.
+
+template <typename T>
+inline bool IsForwarded(const T* t);
+
+template <typename T>
+inline T* Forwarded(const T* t);
+
+inline Value Forwarded(const JS::Value& value);
+
+template <typename T>
+inline T MaybeForwarded(T t);
+
+// Helper functions for use in situations where the object's group might be
+// forwarded, for example while marking.
+
+inline const JSClass* MaybeForwardedObjectClass(const JSObject* obj);
+
+template <typename T>
+inline bool MaybeForwardedObjectIs(const JSObject* obj);
+
+template <typename T>
+inline T& MaybeForwardedObjectAs(JSObject* obj);
+
+#ifdef JSGC_HASH_TABLE_CHECKS
+
+template <typename T>
+inline bool IsGCThingValidAfterMovingGC(T* t);
+
+template <typename T>
+inline void CheckGCThingAfterMovingGC(T* t);
+
+template <typename T>
+inline void CheckGCThingAfterMovingGC(const WeakHeapPtr<T*>& t);
+
+#endif  // JSGC_HASH_TABLE_CHECKS
+
+} /* namespace gc */
+
+} /* namespace js */
+
+#endif /* gc_Marking_h */