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diff --git a/include/llvm/ExecutionEngine/Orc/LookasideRTDyldMM.h b/include/llvm/ExecutionEngine/Orc/LookasideRTDyldMM.h
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+++ b/include/llvm/ExecutionEngine/Orc/LookasideRTDyldMM.h
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+//===- LookasideRTDyldMM - Redirect symbol lookup via a functor -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//   Defines an adapter for RuntimeDyldMM that allows lookups for external
+// symbols to go via a functor.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_LOOKASIDERTDYLDMM_H
+#define LLVM_EXECUTIONENGINE_ORC_LOOKASIDERTDYLDMM_H
+
+#include "llvm/ADT/STLExtras.h"
+#include <memory>
+#include <vector>
+
+namespace llvm {
+namespace orc {
+
+/// @brief Defines an adapter for RuntimeDyldMM that allows lookups for external
+///        symbols to go via a functor, before falling back to the lookup logic
+///        provided by the underlying RuntimeDyldMM instance.
+///
+///   This class is useful for redirecting symbol lookup back to various layers
+/// of a JIT component stack, e.g. to enable lazy module emission.
+///
+template <typename BaseRTDyldMM, typename ExternalLookupFtor,
+          typename DylibLookupFtor>
+class LookasideRTDyldMM : public BaseRTDyldMM {
+public:
+  /// @brief Create a LookasideRTDyldMM intance.
+  LookasideRTDyldMM(ExternalLookupFtor ExternalLookup,
+                    DylibLookupFtor DylibLookup)
+      : ExternalLookup(std::move(ExternalLookup)),
+        DylibLookup(std::move(DylibLookup)) {}
+
+  /// @brief Look up the given symbol address, first via the functor this
+  ///        instance was created with, then (if the symbol isn't found)
+  ///        via the underlying RuntimeDyldMM.
+  uint64_t getSymbolAddress(const std::string &Name) override {
+    if (uint64_t Addr = ExternalLookup(Name))
+      return Addr;
+    return BaseRTDyldMM::getSymbolAddress(Name);
+  }
+
+  uint64_t getSymbolAddressInLogicalDylib(const std::string &Name) override {
+    if (uint64_t Addr = DylibLookup(Name))
+      return Addr;
+    return BaseRTDyldMM::getSymbolAddressInLogicalDylib(Name);
+  };
+
+  /// @brief Get a reference to the ExternalLookup functor.
+  ExternalLookupFtor &getExternalLookup() { return ExternalLookup; }
+
+  /// @brief Get a const-reference to the ExternalLookup functor.
+  const ExternalLookupFtor &getExternalLookup() const { return ExternalLookup; }
+
+  /// @brief Get a reference to the DylibLookup functor.
+  DylibLookupFtor &getDylibLookup() { return DylibLookup; }
+
+  /// @brief Get a const-reference to the DylibLookup functor.
+  const DylibLookupFtor &getDylibLookup() const { return DylibLookup; }
+
+private:
+  ExternalLookupFtor ExternalLookup;
+  DylibLookupFtor DylibLookup;
+};
+
+/// @brief Create a LookasideRTDyldMM from a base memory manager type, an
+///        external lookup functor, and a dylib lookup functor.
+template <typename BaseRTDyldMM, typename ExternalLookupFtor,
+          typename DylibLookupFtor>
+std::unique_ptr<
+    LookasideRTDyldMM<BaseRTDyldMM, ExternalLookupFtor, DylibLookupFtor>>
+createLookasideRTDyldMM(ExternalLookupFtor &&ExternalLookup,
+                        DylibLookupFtor &&DylibLookup) {
+  typedef LookasideRTDyldMM<BaseRTDyldMM, ExternalLookupFtor, DylibLookupFtor>
+      ThisLookasideMM;
+  return llvm::make_unique<ThisLookasideMM>(
+      std::forward<ExternalLookupFtor>(ExternalLookup),
+      std::forward<DylibLookupFtor>(DylibLookup));
+}
+
+} // End namespace orc.
+} // End namespace llvm.
+
+#endif // LLVM_EXECUTIONENGINE_ORC_LOOKASIDERTDYLDMM_H