diff --git a/llvm/include/llvm/ExecutionEngine/Orc/CompileUtils.h b/llvm/include/llvm/ExecutionEngine/Orc/CompileUtils.h
index 213a59124c85..3d02f9d05e49 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/CompileUtils.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/CompileUtils.h
@@ -16,7 +16,7 @@
 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ExecutionEngine/ObjectCache.h"
-#include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/ObjectFile.h"
diff --git a/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h b/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h
index 6a9731655b77..5c58d4b36062 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h
@@ -21,7 +21,6 @@
 #include "llvm/ExecutionEngine/Orc/OrcError.h"
 #include "llvm/ExecutionEngine/RuntimeDyld.h"
 #include "llvm/Support/DynamicLibrary.h"
-#include "llvm/Target/TargetOptions.h"
 #include <algorithm>
 #include <cstdint>
 #include <string>
@@ -39,48 +38,6 @@ class Value;
 
 namespace orc {
 
-/// A utility class for building TargetMachines for JITs.
-class JITTargetMachineBuilder {
-public:
-  JITTargetMachineBuilder(Triple TT);
-  static Expected<JITTargetMachineBuilder> detectHost();
-  Expected<std::unique_ptr<TargetMachine>> createTargetMachine();
-
-  JITTargetMachineBuilder &setArch(std::string Arch) {
-    this->Arch = std::move(Arch);
-    return *this;
-  }
-  JITTargetMachineBuilder &setCPU(std::string CPU) {
-    this->CPU = std::move(CPU);
-    return *this;
-  }
-  JITTargetMachineBuilder &setRelocationModel(Optional<Reloc::Model> RM) {
-    this->RM = std::move(RM);
-    return *this;
-  }
-  JITTargetMachineBuilder &setCodeModel(Optional<CodeModel::Model> CM) {
-    this->CM = std::move(CM);
-    return *this;
-  }
-  JITTargetMachineBuilder &
-  addFeatures(const std::vector<std::string> &FeatureVec);
-  SubtargetFeatures &getFeatures() { return Features; }
-  TargetOptions &getOptions() { return Options; }
-
-  Triple& getTargetTriple() { return TT; }
-  const Triple& getTargetTriple() const { return TT; }
-
-private:
-  Triple TT;
-  std::string Arch;
-  std::string CPU;
-  SubtargetFeatures Features;
-  TargetOptions Options;
-  Optional<Reloc::Model> RM;
-  Optional<CodeModel::Model> CM;
-  CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
-};
-
 /// This iterator provides a convenient way to iterate over the elements
 ///        of an llvm.global_ctors/llvm.global_dtors instance.
 ///
diff --git a/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h b/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h
new file mode 100644
index 000000000000..327941d52fe2
--- /dev/null
+++ b/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h
@@ -0,0 +1,118 @@
+//===- JITTargetMachineBuilder.h - Build TargetMachines for JIT -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A utitily for building TargetMachines for JITs.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_JITTARGETMACHINEBUILDER_H
+#define LLVM_EXECUTIONENGINE_ORC_JITTARGETMACHINEBUILDER_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/Support/CodeGen.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace llvm {
+namespace orc {
+
+/// A utility class for building TargetMachines for JITs.
+class JITTargetMachineBuilder {
+public:
+  /// Create a JITTargetMachineBuilder based on the given triple.
+  ///
+  /// Note: TargetOptions is default-constructed, then EmulatedTLS and
+  /// ExplicitEmulatedTLS are set to true. If EmulatedTLS is not
+  /// required, these values should be reset before calling
+  /// createTargetMachine.
+  JITTargetMachineBuilder(Triple TT);
+
+  /// Create a JITTargetMachineBuilder for the host system.
+  ///
+  /// Note: TargetOptions is default-constructed, then EmulatedTLS and
+  /// ExplicitEmulatedTLS are set to true. If EmulatedTLS is not
+  /// required, these values should be reset before calling
+  /// createTargetMachine.
+  static Expected<JITTargetMachineBuilder> detectHost();
+
+  /// Create a TargetMachine.
+  ///
+  /// This operation will fail if the requested target is not registered,
+  /// in which case see llvm/Support/TargetSelect.h. To JIT IR the Target and
+  /// the target's AsmPrinter must both be registered. To JIT assembly
+  /// (including inline and module level assembly) the target's AsmParser must
+  /// also be registered.
+  Expected<std::unique_ptr<TargetMachine>> createTargetMachine();
+
+  /// Set the CPU string.
+  JITTargetMachineBuilder &setCPU(std::string CPU) {
+    this->CPU = std::move(CPU);
+    return *this;
+  }
+
+  /// Set the relocation model.
+  JITTargetMachineBuilder &setRelocationModel(Optional<Reloc::Model> RM) {
+    this->RM = std::move(RM);
+    return *this;
+  }
+
+  /// Set the code model.
+  JITTargetMachineBuilder &setCodeModel(Optional<CodeModel::Model> CM) {
+    this->CM = std::move(CM);
+    return *this;
+  }
+
+  /// Set the LLVM CodeGen optimization level.
+  JITTargetMachineBuilder &setCodeGenOptLevel(CodeGenOpt::Level OptLevel) {
+    this->OptLevel = OptLevel;
+    return *this;
+  }
+
+  /// Add subtarget features.
+  JITTargetMachineBuilder &
+  addFeatures(const std::vector<std::string> &FeatureVec);
+
+  /// Access subtarget features.
+  SubtargetFeatures &getFeatures() { return Features; }
+
+  /// Access subtarget features.
+  const SubtargetFeatures &getFeatures() const { return Features; }
+
+  /// Access TargetOptions.
+  TargetOptions &getOptions() { return Options; }
+
+  /// Access TargetOptions.
+  const TargetOptions &getOptions() const { return Options; }
+
+  /// Access Triple.
+  Triple &getTargetTriple() { return TT; }
+
+  /// Access Triple.
+  const Triple &getTargetTriple() const { return TT; }
+
+private:
+  Triple TT;
+  std::string CPU;
+  SubtargetFeatures Features;
+  TargetOptions Options;
+  Optional<Reloc::Model> RM;
+  Optional<CodeModel::Model> CM;
+  CodeGenOpt::Level OptLevel = CodeGenOpt::None;
+};
+
+} // end namespace orc
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_JITTARGETMACHINEBUILDER_H
diff --git a/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h b/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h
index 7e113b8ace38..01dae538b8e2 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h
@@ -19,6 +19,7 @@
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
 #include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
 #include "llvm/ExecutionEngine/Orc/IRTransformLayer.h"
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
 #include "llvm/ExecutionEngine/Orc/ObjectTransformLayer.h"
 #include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
 #include "llvm/ExecutionEngine/Orc/ThreadSafeModule.h"
@@ -51,6 +52,8 @@ public:
   /// Convenience method for defining an absolute symbol.
   Error defineAbsolute(StringRef Name, JITEvaluatedSymbol Address);
 
+  /// Convenience method for defining an
+
   /// Adds an IR module to the given JITDylib.
   Error addIRModule(JITDylib &JD, ThreadSafeModule TSM);
 
diff --git a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
index 680ede23568c..9ca409f81cd3 100644
--- a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
+++ b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
@@ -5,6 +5,7 @@ add_llvm_library(LLVMOrcJIT
   IndirectionUtils.cpp
   IRCompileLayer.cpp
   IRTransformLayer.cpp
+  JITTargetMachineBuilder.cpp
   LazyReexports.cpp
   Legacy.cpp
   Layer.cpp
diff --git a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
index bb32b3d82e6d..e9e27453c320 100644
--- a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
@@ -19,45 +19,6 @@
 namespace llvm {
 namespace orc {
 
-JITTargetMachineBuilder::JITTargetMachineBuilder(Triple TT)
-    : TT(std::move(TT)) {}
-
-Expected<JITTargetMachineBuilder> JITTargetMachineBuilder::detectHost() {
-  return JITTargetMachineBuilder(Triple(sys::getProcessTriple()));
-}
-
-Expected<std::unique_ptr<TargetMachine>>
-JITTargetMachineBuilder::createTargetMachine() {
-  if (!Arch.empty()) {
-    Triple::ArchType Type = Triple::getArchTypeForLLVMName(Arch);
-
-    if (Type == Triple::UnknownArch)
-      return make_error<StringError>(std::string("Unknown arch: ") + Arch,
-                                     inconvertibleErrorCode());
-  }
-
-  std::string ErrMsg;
-  auto *TheTarget = TargetRegistry::lookupTarget(TT.getTriple(), ErrMsg);
-  if (!TheTarget)
-    return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
-
-  auto *TM =
-      TheTarget->createTargetMachine(TT.getTriple(), CPU, Features.getString(),
-                                     Options, RM, CM, OptLevel, /*JIT*/ true);
-  if (!TM)
-    return make_error<StringError>("Could not allocate target machine",
-                                   inconvertibleErrorCode());
-
-  return std::unique_ptr<TargetMachine>(TM);
-}
-
-JITTargetMachineBuilder &JITTargetMachineBuilder::addFeatures(
-    const std::vector<std::string> &FeatureVec) {
-  for (const auto &F : FeatureVec)
-    Features.AddFeature(F);
-  return *this;
-}
-
 CtorDtorIterator::CtorDtorIterator(const GlobalVariable *GV, bool End)
   : InitList(
       GV ? dyn_cast_or_null<ConstantArray>(GV->getInitializer()) : nullptr),
diff --git a/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp b/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp
new file mode 100644
index 000000000000..4af09d196ff9
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp
@@ -0,0 +1,55 @@
+//===----- JITTargetMachineBuilder.cpp - Build TargetMachines for JIT -----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
+
+#include "llvm/Support/TargetRegistry.h"
+
+namespace llvm {
+namespace orc {
+
+JITTargetMachineBuilder::JITTargetMachineBuilder(Triple TT)
+    : TT(std::move(TT)) {
+  Options.EmulatedTLS = true;
+  Options.ExplicitEmulatedTLS = true;
+}
+
+Expected<JITTargetMachineBuilder> JITTargetMachineBuilder::detectHost() {
+  // FIXME: getProcessTriple is bogus. It returns the host LLVM was compiled on,
+  //        rather than a valid triple for the current process.
+  return JITTargetMachineBuilder(Triple(sys::getProcessTriple()));
+}
+
+Expected<std::unique_ptr<TargetMachine>>
+JITTargetMachineBuilder::createTargetMachine() {
+
+  std::string ErrMsg;
+  auto *TheTarget = TargetRegistry::lookupTarget(TT.getTriple(), ErrMsg);
+  if (!TheTarget)
+    return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
+
+  auto *TM =
+      TheTarget->createTargetMachine(TT.getTriple(), CPU, Features.getString(),
+                                     Options, RM, CM, OptLevel, /*JIT*/ true);
+  if (!TM)
+    return make_error<StringError>("Could not allocate target machine",
+                                   inconvertibleErrorCode());
+
+  return std::unique_ptr<TargetMachine>(TM);
+}
+
+JITTargetMachineBuilder &JITTargetMachineBuilder::addFeatures(
+    const std::vector<std::string> &FeatureVec) {
+  for (const auto &F : FeatureVec)
+    Features.AddFeature(F);
+  return *this;
+}
+
+} // End namespace orc.
+} // End namespace llvm.
diff --git a/llvm/tools/lli/lli.cpp b/llvm/tools/lli/lli.cpp
index 18cb661b9ef7..9b3c7478b412 100644
--- a/llvm/tools/lli/lli.cpp
+++ b/llvm/tools/lli/lli.cpp
@@ -26,6 +26,7 @@
 #include "llvm/ExecutionEngine/MCJIT.h"
 #include "llvm/ExecutionEngine/ObjectCache.h"
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
 #include "llvm/ExecutionEngine/Orc/OrcRemoteTargetClient.h"
 #include "llvm/ExecutionEngine/OrcMCJITReplacement.h"
@@ -773,8 +774,10 @@ int runOrcLazyJIT(const char *ProgName) {
       TT.empty() ? ExitOnErr(orc::JITTargetMachineBuilder::detectHost())
                  : orc::JITTargetMachineBuilder(Triple(TT));
 
-  JTMB.setArch(MArch)
-      .setCPU(getCPUStr())
+  if (!MArch.empty())
+    JTMB.getTargetTriple().setArchName(MArch);
+
+  JTMB.setCPU(getCPUStr())
       .addFeatures(getFeatureList())
       .setRelocationModel(RelocModel.getNumOccurrences()
                               ? Optional<Reloc::Model>(RelocModel)
@@ -782,6 +785,7 @@ int runOrcLazyJIT(const char *ProgName) {
       .setCodeModel(CMModel.getNumOccurrences()
                         ? Optional<CodeModel::Model>(CMModel)
                         : None);
+
   DataLayout DL("");
   {
     // Create a throwaway TargetMachine to get the data layout.
diff --git a/llvm/unittests/ExecutionEngine/Orc/CMakeLists.txt b/llvm/unittests/ExecutionEngine/Orc/CMakeLists.txt
index 3a47bfa20bf3..8b0d5fc24354 100644
--- a/llvm/unittests/ExecutionEngine/Orc/CMakeLists.txt
+++ b/llvm/unittests/ExecutionEngine/Orc/CMakeLists.txt
@@ -14,6 +14,7 @@ add_llvm_unittest(OrcJITTests
   CoreAPIsTest.cpp
   IndirectionUtilsTest.cpp
   GlobalMappingLayerTest.cpp
+  JITTargetMachineBuilderTest.cpp
   LazyCallThroughAndReexportsTest.cpp
   LazyEmittingLayerTest.cpp
   LegacyAPIInteropTest.cpp
diff --git a/llvm/unittests/ExecutionEngine/Orc/JITTargetMachineBuilderTest.cpp b/llvm/unittests/ExecutionEngine/Orc/JITTargetMachineBuilderTest.cpp
new file mode 100644
index 000000000000..f978a90efb3d
--- /dev/null
+++ b/llvm/unittests/ExecutionEngine/Orc/JITTargetMachineBuilderTest.cpp
@@ -0,0 +1,52 @@
+//===----------- CoreAPIsTest.cpp - Unit tests for Core ORC APIs ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
+#include "OrcTestCommon.h"
+
+using namespace llvm;
+using namespace llvm::orc;
+
+namespace {
+
+TEST(ExecutionUtilsTest, JITTargetMachineBuilder) {
+  // Tests basic API usage.
+  // Bails out on error, as it is valid to run this test without any targets
+  // built.
+
+  // Make sure LLVM has been initialized.
+  OrcNativeTarget::initialize();
+
+  auto JTMB = cantFail(JITTargetMachineBuilder::detectHost());
+
+  // Test API by performing a bunch of no-ops.
+  JTMB.setCPU("");
+  JTMB.setRelocationModel(None);
+  JTMB.setCodeModel(None);
+  JTMB.setCodeGenOptLevel(CodeGenOpt::None);
+  JTMB.addFeatures(std::vector<std::string>());
+  SubtargetFeatures &STF = JTMB.getFeatures();
+  (void)STF;
+  TargetOptions &TO = JTMB.getOptions();
+  (void)TO;
+  Triple &TT = JTMB.getTargetTriple();
+  (void)TT;
+
+  auto TM = JTMB.createTargetMachine();
+
+  if (!TM)
+    consumeError(TM.takeError());
+  else {
+    EXPECT_NE(TM.get(), nullptr)
+        << "JITTargetMachineBuilder should return a non-null TargetMachine "
+           "on success";
+  }
+}
+
+} // namespace
diff --git a/llvm/unittests/ExecutionEngine/Orc/LazyCallThroughAndReexportsTest.cpp b/llvm/unittests/ExecutionEngine/Orc/LazyCallThroughAndReexportsTest.cpp
index 7caaa767242e..c3c5703f54ba 100644
--- a/llvm/unittests/ExecutionEngine/Orc/LazyCallThroughAndReexportsTest.cpp
+++ b/llvm/unittests/ExecutionEngine/Orc/LazyCallThroughAndReexportsTest.cpp
@@ -1,5 +1,5 @@
 #include "OrcTestCommon.h"
-#include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
+#include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
 #include "llvm/ExecutionEngine/Orc/LazyReexports.h"
 #include "gtest/gtest.h"