Index: lib/ExecutionEngine/MCJIT/MCJIT.cpp
===================================================================
--- lib/ExecutionEngine/MCJIT/MCJIT.cpp
+++ lib/ExecutionEngine/MCJIT/MCJIT.cpp
@@ -371,9 +371,11 @@
 
   Mangler Mang(TM->getDataLayout());
   SmallString<128> Name;
-  TM->getNameWithPrefix(Name, F, Mang);
 
   if (F->isDeclaration() || F->hasAvailableExternallyLinkage()) {
+    if (F->hasPrivateLinkage())
+      return nullptr;
+    TM->getNameWithPrefix(Name, F, Mang);
     bool AbortOnFailure = !F->hasExternalWeakLinkage();
     void *Addr = getPointerToNamedFunction(Name, AbortOnFailure);
     updateGlobalMapping(F, Addr);
@@ -394,6 +396,10 @@
     return nullptr;
   }
 
+  // Do not move this earlier - this function may rely on the target machine
+  // having been initialized by code generation.
+  TM->getNameWithPrefix(Name, F, Mang);
+
   // FIXME: Should the Dyld be retaining module information? Probably not.
   //
   // This is the accessor for the target address, so make sure to check the
Index: unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
===================================================================
--- unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
+++ unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
@@ -199,4 +199,16 @@
   EXPECT_EQ(A, B) << "Repeat calls to getPointerToFunction fail.";
 }
 
+TEST_F(MCJITTest, private_function_lookup) {
+  SKIP_UNSUPPORTED_PLATFORM;
+
+  Function *Foo = insertMainFunction(M.get(), 0, GlobalValue::PrivateLinkage);
+  createJIT(std::move(M));
+  void *A = TheJIT->getPointerToFunction(Foo);
+  void *B = TheJIT->getPointerToFunction(Foo);
+
+  EXPECT_TRUE(A != 0) << "Failed lookup - test not correctly configured.";
+  EXPECT_EQ(A, B)
+      << "Repeat calls to getPointerToFunction fail for private function.";
+}
 }
Index: unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
===================================================================
--- unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
+++ unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
@@ -46,11 +46,12 @@
     return M;
   }
 
-  template<typename FuncType>
-  Function *startFunction(Module *M, StringRef Name) {
+  template <typename FuncType>
+  Function *startFunction(
+      Module *M, StringRef Name,
+      GlobalValue::LinkageTypes linkage = GlobalValue::ExternalLinkage) {
     Function *Result = Function::Create(
-      TypeBuilder<FuncType, false>::get(Context),
-      GlobalValue::ExternalLinkage, Name, M);
+        TypeBuilder<FuncType, false>::get(Context), linkage, Name, M);
 
     BasicBlock *BB = BasicBlock::Create(Context, Name, Result);
     Builder.SetInsertPoint(BB);
@@ -82,8 +83,10 @@
   // Inserts a function named 'main' that returns a uint32_t:
   //    int32_t main() { return X; }
   // where X is given by returnCode
-  Function *insertMainFunction(Module *M, uint32_t returnCode) {
-    Function *Result = startFunction<int32_t(void)>(M, "main");
+  Function *insertMainFunction(
+      Module *M, uint32_t returnCode,
+      GlobalValue::LinkageTypes linkage = GlobalValue::ExternalLinkage) {
+    Function *Result = startFunction<int32_t(void)>(M, "main", linkage);
 
     Value *ReturnVal = ConstantInt::get(Context, APInt(32, returnCode));
     endFunctionWithRet(Result, ReturnVal);