diff --git a/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h b/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h
index 3b6becd2853a9..c4109a8de82eb 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h
@@ -25,6 +25,9 @@
 #include <vector>
 
 namespace llvm {
+
+class raw_ostream;
+
 namespace orc {
 
 /// A utility class for building TargetMachines for JITs.
@@ -136,6 +139,12 @@ class JITTargetMachineBuilder {
   /// Access Triple.
   const Triple &getTargetTriple() const { return TT; }
 
+#ifndef NDEBUG
+  /// Debug-dump a JITTargetMachineBuilder.
+  friend raw_ostream &operator<<(raw_ostream &OS,
+                                 const JITTargetMachineBuilder &JTMB);
+#endif
+
 private:
   Triple TT;
   std::string CPU;
diff --git a/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp b/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp
index 3eda0fa1360c7..8cf66c9e759a3 100644
--- a/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/JITTargetMachineBuilder.cpp
@@ -10,6 +10,7 @@
 
 #include "llvm/Support/Host.h"
 #include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
 namespace orc {
@@ -63,5 +64,78 @@ JITTargetMachineBuilder &JITTargetMachineBuilder::addFeatures(
   return *this;
 }
 
+#ifndef NDEBUG
+raw_ostream &operator<<(raw_ostream &OS, const JITTargetMachineBuilder &JTMB) {
+  OS << "{ Triple = \"" << JTMB.TT.str() << "\", CPU = \"" << JTMB.CPU
+     << "\", Options = <not-printable>, Relocation Model = ";
+
+  if (JTMB.RM) {
+    switch (*JTMB.RM) {
+    case Reloc::Static:
+      OS << "Static";
+      break;
+    case Reloc::PIC_:
+      OS << "PIC_";
+      break;
+    case Reloc::DynamicNoPIC:
+      OS << "DynamicNoPIC";
+      break;
+    case Reloc::ROPI:
+      OS << "ROPI";
+      break;
+    case Reloc::RWPI:
+      OS << "RWPI";
+      break;
+    case Reloc::ROPI_RWPI:
+      OS << "ROPI_RWPI";
+      break;
+    }
+  } else
+    OS << "unspecified";
+
+  OS << ", Code Model = ";
+
+  if (JTMB.CM) {
+    switch (*JTMB.CM) {
+    case CodeModel::Tiny:
+      OS << "Tiny";
+      break;
+    case CodeModel::Small:
+      OS << "Small";
+      break;
+    case CodeModel::Kernel:
+      OS << "Kernel";
+      break;
+    case CodeModel::Medium:
+      OS << "Medium";
+      break;
+    case CodeModel::Large:
+      OS << "Large";
+      break;
+    }
+  } else
+    OS << "unspecified";
+
+  OS << ", Optimization Level = ";
+  switch (JTMB.OptLevel) {
+  case CodeGenOpt::None:
+    OS << "None";
+    break;
+  case CodeGenOpt::Less:
+    OS << "Less";
+    break;
+  case CodeGenOpt::Default:
+    OS << "Default";
+    break;
+  case CodeGenOpt::Aggressive:
+    OS << "Aggressive";
+    break;
+  }
+
+  OS << " }";
+  return OS;
+}
+#endif // NDEBUG
+
 } // End namespace orc.
 } // End namespace llvm.
diff --git a/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp b/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
index 79e502775f799..0e51ba1dff352 100644
--- a/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
@@ -927,13 +927,42 @@ LLJIT::PlatformSupport::~PlatformSupport() {}
 
 Error LLJITBuilderState::prepareForConstruction() {
 
+  LLVM_DEBUG(dbgs() << "Preparing to create LLIT instance...\n");
+
   if (!JTMB) {
+    LLVM_DEBUG({
+      dbgs() << "  No explicitly set JITTargetMachineBuilder. "
+                "Detecting host...\n";
+    });
     if (auto JTMBOrErr = JITTargetMachineBuilder::detectHost())
       JTMB = std::move(*JTMBOrErr);
     else
       return JTMBOrErr.takeError();
   }
 
+  LLVM_DEBUG({
+    dbgs() << "  JITTargetMachineBuilder is " << JTMB << "\n"
+           << "  Pre-constructed ExecutionSession: " << (ES ? "Yes" : "No")
+           << "\n"
+           << "  DataLayout: ";
+    if (DL)
+      dbgs() << DL->getStringRepresentation() << "\n";
+    else
+      dbgs() << "None (will be created by JITTargetMachineBuilder)\n";
+
+    dbgs() << "  Custom object-linking-layer creator: "
+           << (CreateObjectLinkingLayer ? "Yes" : "No") << "\n"
+           << "  Custom compile-function creator: "
+           << (CreateCompileFunction ? "Yes" : "No") << "\n"
+           << "  Custom platform-setup function: "
+           << (SetUpPlatform ? "Yes" : "No") << "\n"
+           << "  Number of compile threads: " << NumCompileThreads;
+    if (!NumCompileThreads)
+      dbgs() << " (code will be compiled on the execution thread)\n";
+    else
+      dbgs() << "\n";
+  });
+
   // If the client didn't configure any linker options then auto-configure the
   // JIT linker.
   if (!CreateObjectLinkingLayer && JTMB->getCodeModel() == None &&