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diff --git a/js/src/vm/InvalidatingFuse.h b/js/src/vm/InvalidatingFuse.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/. */
+
+#ifndef vm_InvalidatingFuse_h
+#define vm_InvalidatingFuse_h
+
+#include "gc/Barrier.h"
+#include "gc/SweepingAPI.h"
+#include "vm/GuardFuse.h"
+#include "vm/JSScript.h"
+
+namespace js {
+
+// [SMDOC] Invalidating Fuses
+//
+// An invalidating fuse will invalidate a set of dependent IonScripts when the
+// fuse is popped. In this way Ion can choose to ignore fuse guarded
+// possibilities when doing compilation.
+class InvalidatingFuse : public GuardFuse {
+ public:
+  // Register a script's IonScript as having a dependency on this fuse.
+  virtual bool addFuseDependency(JSContext* cx, Handle<JSScript*> script) = 0;
+};
+
+// [SMDOC] Invalidating Runtime Fuses
+//
+// A specialized sublass for handling runtime wide fuses. This provides a
+// version of addFuseDependency which records scripts into sets associated with
+// their home zone, and invalidates all sets across all zones linked to this
+// specific fuse.
+class InvalidatingRuntimeFuse : public InvalidatingFuse {
+ public:
+  virtual bool addFuseDependency(JSContext* cx,
+                                 Handle<JSScript*> script) override;
+  virtual void popFuse(JSContext* cx) override;
+};
+
+// A (weak) set of scripts which are dependent on an associated fuse.
+//
+// These are typically stored in a vector at the moment, due to the low number
+// of invalidating fuses, and so the associated fuse is stored along with the
+// set.
+//
+// Because it uses JS::WeakCache, GC tracing is taken care of without any need
+// for tracing in this class.
+class DependentScriptSet {
+ public:
+  DependentScriptSet(JSContext* cx, InvalidatingFuse* fuse);
+
+  InvalidatingFuse* associatedFuse;
+  bool addScriptForFuse(InvalidatingFuse* fuse, Handle<JSScript*> script);
+  void invalidateForFuse(JSContext* cx, InvalidatingFuse* fuse);
+
+ private:
+  using WeakScriptSet = GCHashSet<WeakHeapPtr<JSScript*>,
+                                  StableCellHasher<WeakHeapPtr<JSScript*>>,
+                                  js::SystemAllocPolicy>;
+  js::WeakCache<WeakScriptSet> weakScripts;
+};
+
+}  // namespace js
+
+#endif  // vm_InvalidatingFuse_h