Index: include/llvm/ExecutionEngine/Orc/LLJIT.h
===================================================================
--- include/llvm/ExecutionEngine/Orc/LLJIT.h
+++ include/llvm/ExecutionEngine/Orc/LLJIT.h
@@ -29,10 +29,13 @@
 /// A pre-fabricated ORC JIT stack that can serve as an alternative to MCJIT.
 class LLJIT {
 public:
+  using CompileFtor = IRCompileLayer2::CompileFunction;
+  using CompileFtorFactory = std::function<CompileFtor(TargetMachine &)>;
+
   /// Create an LLJIT instance.
   static Expected<std::unique_ptr<LLJIT>>
   Create(std::unique_ptr<ExecutionSession> ES,
-         std::unique_ptr<TargetMachine> TM, DataLayout DL);
+         JITTargetMachineBuilder JTMB, DataLayout DL, bool Multithreaded);
 
   /// Returns a reference to the ExecutionSession for this JIT instance.
   ExecutionSession &getExecutionSession() { return *ES; }
@@ -89,7 +92,7 @@
 
 protected:
   LLJIT(std::unique_ptr<ExecutionSession> ES, std::unique_ptr<TargetMachine> TM,
-        DataLayout DL);
+        DataLayout DL, CompileFtorFactory MakeCompileFtor);
 
   std::shared_ptr<RuntimeDyld::MemoryManager> getMemoryManager(VModuleKey K);
 
@@ -136,7 +139,8 @@
 
 private:
   LLLazyJIT(std::unique_ptr<ExecutionSession> ES,
-            std::unique_ptr<TargetMachine> TM, DataLayout DL, LLVMContext &Ctx,
+            std::unique_ptr<TargetMachine> TM, DataLayout DL,
+            CompileFtorFactory MakeCompileFtor, LLVMContext &Ctx,
             std::unique_ptr<JITCompileCallbackManager> CCMgr,
             std::function<std::unique_ptr<IndirectStubsManager>()> ISMBuilder);
 
Index: lib/ExecutionEngine/Orc/LLJIT.cpp
===================================================================
--- lib/ExecutionEngine/Orc/LLJIT.cpp
+++ lib/ExecutionEngine/Orc/LLJIT.cpp
@@ -17,9 +17,25 @@
 
 Expected<std::unique_ptr<LLJIT>>
 LLJIT::Create(std::unique_ptr<ExecutionSession> ES,
-              std::unique_ptr<TargetMachine> TM, DataLayout DL) {
+              JITTargetMachineBuilder JTMB, DataLayout DL, bool Multithreaded) {
+  auto TM = JTMB.createTargetMachine();
+  if (!TM)
+    return TM.takeError();
+  
+  CompileFtorFactory MakeCompileFtor;
+  if (Multithreaded) {
+    MakeCompileFtor = [JTMB](TargetMachine &) -> CompileFtor {
+      return MultiThreadedSimpleCompiler(JTMB);
+    };
+  } else {
+    MakeCompileFtor = [](TargetMachine &TM) -> CompileFtor {
+      return SimpleCompiler(TM);
+    };
+  }
+
   return std::unique_ptr<LLJIT>(
-      new LLJIT(std::move(ES), std::move(TM), std::move(DL)));
+      new LLJIT(std::move(ES), std::move(*TM), std::move(DL),
+                std::move(MakeCompileFtor)));
 }
 
 Error LLJIT::defineAbsolute(StringRef Name, JITEvaluatedSymbol Sym) {
@@ -51,12 +67,13 @@
 }
 
 LLJIT::LLJIT(std::unique_ptr<ExecutionSession> ES,
-             std::unique_ptr<TargetMachine> TM, DataLayout DL)
+             std::unique_ptr<TargetMachine> TM, DataLayout DL,
+             CompileFtorFactory MakeCompileFtor)
     : ES(std::move(ES)), Main(this->ES->createJITDylib("main")),
       TM(std::move(TM)), DL(std::move(DL)),
       ObjLinkingLayer(*this->ES,
                       [this](VModuleKey K) { return getMemoryManager(K); }),
-      CompileLayer(*this->ES, ObjLinkingLayer, SimpleCompiler(*this->TM)),
+      CompileLayer(*this->ES, ObjLinkingLayer, MakeCompileFtor(*this->TM)),
       CtorRunner(Main), DtorRunner(Main) {}
 
 std::shared_ptr<RuntimeDyld::MemoryManager>
@@ -108,8 +125,13 @@
         std::string("No indirect stubs manager builder for ") + TT.str(),
         inconvertibleErrorCode());
 
+  auto MakeCompileFtor = [](TargetMachine &TM) -> CompileFtor {
+    return SimpleCompiler(TM);
+  };
+
   return std::unique_ptr<LLLazyJIT>(
-      new LLLazyJIT(std::move(ES), std::move(TM), std::move(DL), Ctx,
+      new LLLazyJIT(std::move(ES), std::move(TM), std::move(DL),
+                    std::move(MakeCompileFtor), Ctx,
                     std::move(CCMgr), std::move(ISMBuilder)));
 }
 
@@ -129,10 +151,11 @@
 
 LLLazyJIT::LLLazyJIT(
     std::unique_ptr<ExecutionSession> ES, std::unique_ptr<TargetMachine> TM,
-    DataLayout DL, LLVMContext &Ctx,
+    DataLayout DL, CompileFtorFactory MakeCompileFtor, LLVMContext &Ctx,
     std::unique_ptr<JITCompileCallbackManager> CCMgr,
     std::function<std::unique_ptr<IndirectStubsManager>()> ISMBuilder)
-    : LLJIT(std::move(ES), std::move(TM), std::move(DL)),
+    : LLJIT(std::move(ES), std::move(TM), std::move(DL),
+            std::move(MakeCompileFtor)),
       CCMgr(std::move(CCMgr)), TransformLayer(*this->ES, CompileLayer),
       CODLayer(*this->ES, TransformLayer, *this->CCMgr, std::move(ISMBuilder),
                [&]() -> LLVMContext & { return Ctx; }) {}