diff --git a/lib/CodeGen/ELFWriter.h b/lib/CodeGen/ELFWriter.h
index e44ab3f..b61b484 100644
--- a/lib/CodeGen/ELFWriter.h
+++ b/lib/CodeGen/ELFWriter.h
@@ -28,6 +28,7 @@
   class ELFSection;
   struct ELFSym;
   class GlobalVariable;
+  class JITDebugRegisterer;
   class Mangler;
   class MachineCodeEmitter;
   class MachineConstantPoolEntry;
@@ -51,6 +52,7 @@
   ///
   class ELFWriter : public MachineFunctionPass {
     friend class ELFCodeEmitter;
+    friend class JITDebugRegisterer;
   public:
     static char ID;
 
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 3743350..b2a268b 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -234,7 +234,7 @@
   jitstate = new JITState(MP);
 
   // Initialize JCE
-  JCE = createEmitter(*this, JMM);
+  JCE = createEmitter(*this, JMM, TM);
 
   // Add target data
   MutexGuard locked(lock);
diff --git a/lib/ExecutionEngine/JIT/JIT.h b/lib/ExecutionEngine/JIT/JIT.h
index e3ab9e2..dfeffb5 100644
--- a/lib/ExecutionEngine/JIT/JIT.h
+++ b/lib/ExecutionEngine/JIT/JIT.h
@@ -185,7 +185,8 @@
   void NotifyFreeingMachineCode(const Function &F, void *OldPtr);
 
 private:
-  static JITCodeEmitter *createEmitter(JIT &J, JITMemoryManager *JMM);
+  static JITCodeEmitter *createEmitter(JIT &J, JITMemoryManager *JMM,
+                                       TargetMachine &tm);
   void runJITOnFunctionUnlocked(Function *F, const MutexGuard &locked);
   void updateFunctionStub(Function *F);
   void updateDlsymStubTable();
diff --git a/lib/ExecutionEngine/JIT/JITDebugRegisterer.cpp b/lib/ExecutionEngine/JIT/JITDebugRegisterer.cpp
new file mode 100644
index 0000000..62d66d5
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JITDebugRegisterer.cpp
@@ -0,0 +1,208 @@
+//===-- JITDebugRegisterer.cpp - Register debug symbols for JIT -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a JITDebugRegisterer object that is used by the JIT to
+// register debug info with debuggers like GDB.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JITDebugRegisterer.h"
+#include "../../CodeGen/ELF.h"
+#include "../../CodeGen/ELFWriter.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Function.h"
+#include "llvm/Module.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/System/Mutex.h"
+#include <string>
+#include <vector>
+
+namespace llvm {
+
+// This must be kept in sync with gdb/gdb/jit.h .
+extern "C" {
+
+  // Debuggers puts a breakpoint in this function.
+  void __attribute__((noinline)) __jit_debug_register_code() { }
+
+  // We put information about the JITed function in this global, which the
+  // debugger reads.  Make sure to specify the version statically, because the
+  // debugger checks the version before we can set it during runtime.
+  struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
+
+}
+
+namespace {
+
+  /// JITDebugLock - Used to serialize all code registration events, since they
+  /// modify global variables.
+  sys::Mutex JITDebugLock;
+
+}
+
+JITDebugRegisterer::JITDebugRegisterer(TargetMachine &tm) : TM(tm), FnMap() { }
+
+JITDebugRegisterer::~JITDebugRegisterer() {
+  // Free all ELF memory.
+  for (RegisteredFunctionsMap::iterator I = FnMap.begin(), E = FnMap.end();
+       I != E; ++I) {
+    // Call the private method that doesn't update the map so our iterator
+    // doesn't break.
+    UnregisterFunctionInternal(I);
+  }
+  FnMap.clear();
+}
+
+std::string JITDebugRegisterer::MakeELF(const Function *F, DebugInfo &I) {
+  // Stack allocate an empty module with an empty LLVMContext for the ELFWriter
+  // API.  We don't use the real module because then the ELFWriter would write
+  // out unnecessary GlobalValues during finalization.
+  LLVMContext Context;
+  Module M("", Context);
+
+  // Make a buffer for the ELF in memory.
+  std::string Buffer;
+  raw_string_ostream O(Buffer);
+  ELFWriter EW(O, TM);
+  EW.doInitialization(M);
+
+  // Copy the binary into the .text section.  This isn't necessary, but it's
+  // useful to be able to disassemble the ELF by hand.
+  ELFSection &Text = EW.getTextSection((Function *)F);
+  Text.Addr = (uint64_t)I.FnStart;
+  // TODO: We could eliminate this copy if we somehow used a pointer/size pair
+  // instead of a vector.
+  Text.getData().assign(I.FnStart, I.FnEnd);
+
+  // Copy the exception handling call frame information into the .eh_frame
+  // section.  This allows GDB to get a good stack trace, particularly on
+  // linux x86_64.  Mark this as a PROGBITS section that needs to be loaded
+  // into memory at runtime.
+  ELFSection &EH = EW.getSection(".eh_frame", ELFSection::SHT_PROGBITS,
+                                 ELFSection::SHF_ALLOC);
+  // Pointers in the DWARF EH info are all relative to the EH frame start,
+  // which is stored here.
+  EH.Addr = (uint64_t)I.EhStart;
+  // TODO: We could eliminate this copy if we somehow used a pointer/size pair
+  // instead of a vector.
+  EH.getData().assign(I.EhStart, I.EhEnd);
+
+  // Add this single function to the symbol table, so the debugger prints the
+  // name instead of '???'.  We give the symbol default global visibility.
+  ELFSym *FnSym = ELFSym::getGV(F,
+                                ELFSym::STB_GLOBAL,
+                                ELFSym::STT_FUNC,
+                                ELFSym::STV_DEFAULT);
+  FnSym->SectionIdx = Text.SectionIdx;
+  FnSym->Size = I.FnEnd - I.FnStart;
+  FnSym->Value = 0;  // Offset from start of section.
+  EW.SymbolList.push_back(FnSym);
+
+  EW.doFinalization(M);
+  O.flush();
+
+  // When trying to debug why GDB isn't getting the debug info right, it's
+  // awfully helpful to write the object file to disk so that it can be
+  // inspected with readelf and objdump.
+  if (JITEmitDebugInfoToDisk) {
+    std::string Filename;
+    raw_string_ostream O2(Filename);
+    O2 << "/tmp/llvm_function_" << I.FnStart << "_" << F->getNameStr() << ".o";
+    O2.flush();
+    std::string Errors;
+    raw_fd_ostream O3(Filename.c_str(), Errors);
+    O3 << Buffer;
+    O3.close();
+  }
+
+  return Buffer;
+}
+
+void JITDebugRegisterer::RegisterFunction(const Function *F, DebugInfo &I) {
+  // TODO: Support non-ELF platforms.
+  if (!TM.getELFWriterInfo())
+    return;
+
+  std::string Buffer = MakeELF(F, I);
+
+  jit_code_entry *JITCodeEntry = new jit_code_entry();
+  JITCodeEntry->symfile_addr = Buffer.c_str();
+  JITCodeEntry->symfile_size = Buffer.size();
+
+  // Add a mapping from F to the entry and buffer, so we can delete this
+  // info later.
+  FnMap[F] = std::make_pair<std::string, jit_code_entry*>(Buffer, JITCodeEntry);
+
+  // Acquire the lock and do the registration.
+  {
+    MutexGuard locked(JITDebugLock);
+    __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
+
+    // Insert this entry at the head of the list.
+    JITCodeEntry->prev_entry = NULL;
+    jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
+    JITCodeEntry->next_entry = NextEntry;
+    if (NextEntry != NULL) {
+      NextEntry->prev_entry = JITCodeEntry;
+    }
+    __jit_debug_descriptor.first_entry = JITCodeEntry;
+    __jit_debug_descriptor.relevant_entry = JITCodeEntry;
+    __jit_debug_register_code();
+  }
+}
+
+void JITDebugRegisterer::UnregisterFunctionInternal(
+    RegisteredFunctionsMap::iterator I) {
+  jit_code_entry *JITCodeEntry = I->second.second;
+
+  // Acquire the lock and do the unregistration.
+  {
+    MutexGuard locked(JITDebugLock);
+    __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
+
+    // Remove the jit_code_entry from the linked list.
+    jit_code_entry *PrevEntry = JITCodeEntry->prev_entry;
+    jit_code_entry *NextEntry = JITCodeEntry->next_entry;
+    if (NextEntry) {
+      NextEntry->prev_entry = PrevEntry;
+    }
+    if (PrevEntry) {
+      PrevEntry->next_entry = NextEntry;
+    } else {
+      assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
+      __jit_debug_descriptor.first_entry = NextEntry;
+    }
+
+    // Tell GDB which entry we removed, and unregister the code.
+    __jit_debug_descriptor.relevant_entry = JITCodeEntry;
+    __jit_debug_register_code();
+  }
+
+  // Free the ELF file in memory.
+  std::string &Buffer = I->second.first;
+  Buffer.clear();
+}
+
+void JITDebugRegisterer::UnregisterFunction(const Function *F) {
+  // TODO: Support non-ELF platforms.
+  if (!TM.getELFWriterInfo())
+    return;
+
+  RegisteredFunctionsMap::iterator I = FnMap.find(F);
+  if (I == FnMap.end()) return;
+  UnregisterFunctionInternal(I);
+  FnMap.erase(I);
+}
+
+} // end namespace llvm
diff --git a/lib/ExecutionEngine/JIT/JITDebugRegisterer.h b/lib/ExecutionEngine/JIT/JITDebugRegisterer.h
new file mode 100644
index 0000000..832580d
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JITDebugRegisterer.h
@@ -0,0 +1,116 @@
+//===-- JITDebugRegisterer.h - Register debug symbols for JIT -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a JITDebugRegisterer object that is used by the JIT to
+// register debug info with debuggers like GDB.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H
+#define LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/DataTypes.h"
+#include <string>
+
+// This must be kept in sync with gdb/gdb/jit.h .
+extern "C" {
+
+  typedef enum {
+    JIT_NOACTION = 0,
+    JIT_REGISTER_FN,
+    JIT_UNREGISTER_FN
+  } jit_actions_t;
+
+  struct jit_code_entry {
+    struct jit_code_entry *next_entry;
+    struct jit_code_entry *prev_entry;
+    const char *symfile_addr;
+    uint64_t symfile_size;
+  };
+
+  struct jit_descriptor {
+    uint32_t version;
+    // This should be jit_actions_t, but we want to be specific about the
+    // bit-width.
+    uint32_t action_flag;
+    struct jit_code_entry *relevant_entry;
+    struct jit_code_entry *first_entry;
+  };
+
+}
+
+namespace llvm {
+
+struct ELFSection;
+class Function;
+class TargetMachine;
+
+
+/// This class encapsulates information we want to send to the debugger.
+///
+struct DebugInfo {
+  uint8_t *FnStart;
+  uint8_t *FnEnd;
+  uint8_t *EhStart;
+  uint8_t *EhEnd;
+
+  DebugInfo() : FnStart(0), FnEnd(0), EhStart(0), EhEnd(0) {}
+};
+
+typedef DenseMap< const Function*, std::pair<std::string, jit_code_entry*> >
+  RegisteredFunctionsMap;
+
+/// This class registers debug info for JITed code with an attached debugger.
+/// Without proper debug info, GDB can't do things like source level debugging
+/// or even produce a proper stack trace on linux-x86_64.  To use this class,
+/// whenever a function is JITed, create a DebugInfo struct and pass it to the
+/// RegisterFunction method.  The method will then do whatever is necessary to
+/// inform the debugger about the JITed function.
+class JITDebugRegisterer {
+
+  TargetMachine &TM;
+
+  /// FnMap - A map of functions that have been registered to the associated
+  /// temporary files.  Used for cleanup.
+  RegisteredFunctionsMap FnMap;
+
+  /// MakeELF - Builds the ELF file in memory and returns a std::string that
+  /// contains the ELF.
+  std::string MakeELF(const Function *F, DebugInfo &I);
+
+public:
+  JITDebugRegisterer(TargetMachine &tm);
+
+  /// ~JITDebugRegisterer - Unregisters all code and frees symbol files.
+  ///
+  ~JITDebugRegisterer();
+
+  /// RegisterFunction - Register debug info for the given function with an
+  /// attached debugger.  Clients must call UnregisterFunction on all
+  /// registered functions before deleting them to free the associated symbol
+  /// file and unregister it from the debugger.
+  void RegisterFunction(const Function *F, DebugInfo &I);
+
+  /// UnregisterFunction - Unregister the debug info for the given function
+  /// from the debugger and free associated memory.
+  void UnregisterFunction(const Function *F);
+
+private:
+  /// UnregisterFunctionInternal - Unregister the debug info for the given
+  /// function from the debugger and delete any temporary files.  The private
+  /// version of this method does not remove the function from FnMap so that it
+  /// can be called while iterating over FnMap.
+  void UnregisterFunctionInternal(RegisteredFunctionsMap::iterator I);
+
+};
+
+} // end namespace llvm
+
+#endif // LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H
diff --git a/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp b/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
index b902636..d9651f9 100644
--- a/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
@@ -36,7 +36,8 @@
 unsigned char* JITDwarfEmitter::EmitDwarfTable(MachineFunction& F, 
                                                JITCodeEmitter& jce,
                                                unsigned char* StartFunction,
-                                               unsigned char* EndFunction) {
+                                               unsigned char* EndFunction,
+                                               unsigned char* &EHFramePtr) {
   const TargetMachine& TM = F.getTarget();
   TD = TM.getTargetData();
   stackGrowthDirection = TM.getFrameInfo()->getStackGrowthDirection();
@@ -47,7 +48,6 @@
                                                      EndFunction);
       
   unsigned char* Result = 0;
-  unsigned char* EHFramePtr = 0;
 
   const std::vector<Function *> Personalities = MMI->getPersonalities();
   EHFramePtr = EmitCommonEHFrame(Personalities[MMI->getPersonalityIndex()]);
diff --git a/lib/ExecutionEngine/JIT/JITDwarfEmitter.h b/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
index f82c700..e627550 100644
--- a/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
+++ b/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
@@ -67,7 +67,8 @@
   unsigned char* EmitDwarfTable(MachineFunction& F, 
                                 JITCodeEmitter& JCE,
                                 unsigned char* StartFunction,
-                                unsigned char* EndFunction);
+                                unsigned char* EndFunction,
+                                unsigned char* &EHFramePtr);
   
   
   unsigned GetDwarfTableSizeInBytes(MachineFunction& F, 
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index e179960..590846b 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -14,7 +14,9 @@
 
 #define DEBUG_TYPE "jit"
 #include "JIT.h"
+#include "JITDebugRegisterer.h"
 #include "JITDwarfEmitter.h"
+#include "llvm/ADT/OwningPtr.h"
 #include "llvm/Constants.h"
 #include "llvm/Module.h"
 #include "llvm/DerivedTypes.h"
@@ -464,9 +466,12 @@
 
     /// Resolver - This contains info about the currently resolved functions.
     JITResolver Resolver;
-    
+
     /// DE - The dwarf emitter for the jit.
-    JITDwarfEmitter *DE;
+    OwningPtr<JITDwarfEmitter> DE;
+
+    /// DR - The debug registerer for the jit.
+    OwningPtr<JITDebugRegisterer> DR;
 
     /// LabelLocations - This vector is a mapping from Label ID's to their 
     /// address.
@@ -504,7 +509,7 @@
     DebugLocTuple PrevDLT;
 
   public:
-    JITEmitter(JIT &jit, JITMemoryManager *JMM)
+    JITEmitter(JIT &jit, JITMemoryManager *JMM, TargetMachine &TM)
         : SizeEstimate(0), Resolver(jit), MMI(0), CurFn(0) {
       MemMgr = JMM ? JMM : JITMemoryManager::CreateDefaultMemManager();
       if (jit.getJITInfo().needsGOT()) {
@@ -512,11 +517,15 @@
         DEBUG(errs() << "JIT is managing a GOT\n");
       }
 
-      if (DwarfExceptionHandling) DE = new JITDwarfEmitter(jit);
+      if (DwarfExceptionHandling || JITEmitDebugInfo) {
+        DE.reset(new JITDwarfEmitter(jit));
+      }
+      if (JITEmitDebugInfo) {
+        DR.reset(new JITDebugRegisterer(TM));
+      }
     }
     ~JITEmitter() { 
       delete MemMgr;
-      if (DwarfExceptionHandling) delete DE;
     }
 
     /// classof - Methods for support type inquiry through isa, cast, and
@@ -604,7 +613,7 @@
  
     virtual void setModuleInfo(MachineModuleInfo* Info) {
       MMI = Info;
-      if (DwarfExceptionHandling) DE->setModuleInfo(Info);
+      if (DE.get()) DE->setModuleInfo(Info);
     }
 
     void setMemoryExecutable() {
@@ -1124,12 +1133,12 @@
     }
         );
 
-  if (DwarfExceptionHandling) {
+  if (DwarfExceptionHandling || JITEmitDebugInfo) {
     uintptr_t ActualSize = 0;
     SavedBufferBegin = BufferBegin;
     SavedBufferEnd = BufferEnd;
     SavedCurBufferPtr = CurBufferPtr;
-    
+
     if (MemMgr->NeedsExactSize()) {
       ActualSize = DE->GetDwarfTableSizeInBytes(F, *this, FnStart, FnEnd);
     }
@@ -1137,14 +1146,28 @@
     BufferBegin = CurBufferPtr = MemMgr->startExceptionTable(F.getFunction(),
                                                              ActualSize);
     BufferEnd = BufferBegin+ActualSize;
-    uint8_t* FrameRegister = DE->EmitDwarfTable(F, *this, FnStart, FnEnd);
+    uint8_t *EhStart;
+    uint8_t *FrameRegister = DE->EmitDwarfTable(F, *this, FnStart, FnEnd,
+                                                EhStart);
     MemMgr->endExceptionTable(F.getFunction(), BufferBegin, CurBufferPtr,
                               FrameRegister);
+    uint8_t *EhEnd = CurBufferPtr;
     BufferBegin = SavedBufferBegin;
     BufferEnd = SavedBufferEnd;
     CurBufferPtr = SavedCurBufferPtr;
 
-    TheJIT->RegisterTable(FrameRegister);
+    if (DwarfExceptionHandling) {
+      TheJIT->RegisterTable(FrameRegister);
+    }
+
+    if (JITEmitDebugInfo) {
+      DebugInfo I;
+      I.FnStart = FnStart;
+      I.FnEnd = FnEnd;
+      I.EhStart = EhStart;
+      I.EhEnd = EhEnd;
+      DR->RegisterFunction(F.getFunction(), I);
+    }
   }
 
   if (MMI)
@@ -1168,6 +1191,13 @@
 void JITEmitter::deallocateMemForFunction(const Function *F) {
   MemMgr->deallocateMemForFunction(F);
 
+  // TODO: Do we need to unregister exception handling information from libgcc
+  // here?
+
+  if (JITEmitDebugInfo) {
+    DR->UnregisterFunction(F);
+  }
+
   // If the function did not reference any stubs, return.
   if (CurFnStubUses.find(F) == CurFnStubUses.end())
     return;
@@ -1390,8 +1420,9 @@
 //  Public interface to this file
 //===----------------------------------------------------------------------===//
 
-JITCodeEmitter *JIT::createEmitter(JIT &jit, JITMemoryManager *JMM) {
-  return new JITEmitter(jit, JMM);
+JITCodeEmitter *JIT::createEmitter(JIT &jit, JITMemoryManager *JMM,
+                                   TargetMachine &tm) {
+  return new JITEmitter(jit, JMM, tm);
 }
 
 // getPointerToNamedFunction - This function is used as a global wrapper to
diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index fdf157a..fec59b5 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -35,6 +35,8 @@
   bool NoZerosInBSS;
   bool DwarfExceptionHandling;
   bool SjLjExceptionHandling;
+  bool JITEmitDebugInfo;
+  bool JITEmitDebugInfoToDisk;
   bool UnwindTablesMandatory;
   Reloc::Model RelocationModel;
   CodeModel::Model CMModel;
@@ -114,6 +116,24 @@
   cl::desc("Emit SJLJ exception handling (default if target supports)"),
   cl::location(SjLjExceptionHandling),
   cl::init(false));
+// In debug builds, make this default to true.
+#ifdef NDEBUG
+#define EMIT_DEBUG false
+#else
+#define EMIT_DEBUG true
+#endif
+static cl::opt<bool, true>
+EmitJitDebugInfo("jit-emit-debug",
+  cl::desc("Emit debug information to debugger"),
+  cl::location(JITEmitDebugInfo),
+  cl::init(EMIT_DEBUG));
+#undef EMIT_DEBUG
+static cl::opt<bool, true>
+EmitJitDebugInfoToDisk("jit-emit-debug-to-disk",
+  cl::Hidden,
+  cl::desc("Emit debug info objfiles to disk"),
+  cl::location(JITEmitDebugInfoToDisk),
+  cl::init(false));
 static cl::opt<bool, true>
 EnableUnwindTables("unwind-tables",
   cl::desc("Generate unwinding tables for all functions"),
@@ -243,4 +263,3 @@
     return !UnsafeFPMath && HonorSignDependentRoundingFPMathOption;
   }
 }
-