Implement the JIT side of the GDB JIT debugging interface. To enable this

feature, either build the JIT in debug mode to enable it by default or pass
-jit-emit-debug to lli.

Right now, the only debug information that this communicates to GDB is call
frame information, since it's already being generated to support exceptions in
the JIT.  Eventually, when DWARF generation isn't tied so tightly to AsmPrinter,
it will be easy to push that information to GDB through this interface.

Here's a step-by-step breakdown of how the feature works:

- The JIT generates the machine code and DWARF call frame info
  (.eh_frame/.debug_frame) for a function into memory.
- The JIT copies that info into an in-memory ELF file with a symbol for the
  function.
- The JIT creates a code entry pointing to the ELF buffer and adds it to a
  linked list hanging off of a global descriptor at a special symbol that GDB
  knows about.
- The JIT calls a function marked noinline that GDB knows about and has put an
  internal breakpoint in.
- GDB catches the breakpoint and reads the global descriptor to look for new
  code.
- When sees there is new code, it reads the ELF from the inferior's memory and
  adds it to itself as an object file.
- The JIT continues, and the next time we stop the program, we are able to
  produce a proper backtrace.

Consider running the following program through the JIT:

#include <stdio.h>
void baz(short z) {
  long w = z + 1;
  printf("%d, %x\n", w, *((int*)NULL));  // SEGFAULT here
}
void bar(short y) {
  int z = y + 1;
  baz(z);
}
void foo(char x) {
  short y = x + 1;
  bar(y);
}
int main(int argc, char** argv) {
  char x = 1;
  foo(x);
}

Here is a backtrace before this patch:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x2aaaabdfbd10 (LWP 25476)]
0x00002aaaabe7d1a8 in ?? ()
(gdb) bt
#0  0x00002aaaabe7d1a8 in ?? ()
#1  0x0000000000000003 in ?? ()
#2  0x0000000000000004 in ?? ()
#3  0x00032aaaabe7cfd0 in ?? ()
#4  0x00002aaaabe7d12c in ?? ()
#5  0x00022aaa00000003 in ?? ()
#6  0x00002aaaabe7d0aa in ?? ()
#7  0x01000002abe7cff0 in ?? ()
#8  0x00002aaaabe7d02c in ?? ()
#9  0x0100000000000001 in ?? ()
#10 0x00000000014388e0 in ?? ()
#11 0x00007fff00000001 in ?? ()
#12 0x0000000000b870a2 in llvm::JIT::runFunction (this=0x1405b70,
F=0x14024e0, ArgValues=@0x7fffffffe050)
   at /home/rnk/llvm-gdb/lib/ExecutionEngine/JIT/JIT.cpp:395
#13 0x0000000000baa4c5 in llvm::ExecutionEngine::runFunctionAsMain
(this=0x1405b70, Fn=0x14024e0, argv=@0x13f06f8, envp=0x7fffffffe3b0)
   at /home/rnk/llvm-gdb/lib/ExecutionEngine/ExecutionEngine.cpp:377
#14 0x00000000007ebd52 in main (argc=2, argv=0x7fffffffe398,
envp=0x7fffffffe3b0) at /home/rnk/llvm-gdb/tools/lli/lli.cpp:208

And a backtrace after this patch:
Program received signal SIGSEGV, Segmentation fault.
0x00002aaaabe7d1a8 in baz ()
(gdb) bt
#0  0x00002aaaabe7d1a8 in baz ()
#1  0x00002aaaabe7d12c in bar ()
#2  0x00002aaaabe7d0aa in foo ()
#3  0x00002aaaabe7d02c in main ()
#4  0x0000000000b870a2 in llvm::JIT::runFunction (this=0x1405b70,
F=0x14024e0, ArgValues=...)
   at /home/rnk/llvm-gdb/lib/ExecutionEngine/JIT/JIT.cpp:395
#5  0x0000000000baa4c5 in llvm::ExecutionEngine::runFunctionAsMain
(this=0x1405b70, Fn=0x14024e0, argv=..., envp=0x7fffffffe3c0)
   at /home/rnk/llvm-gdb/lib/ExecutionEngine/ExecutionEngine.cpp:377
#6  0x00000000007ebd52 in main (argc=2, argv=0x7fffffffe3a8,
envp=0x7fffffffe3c0) at /home/rnk/llvm-gdb/tools/lli/lli.cpp:208


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82418 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetOptions.h

@@ -103,6 +103,15 @@ namespace llvm {
   /// information should be emitted.
   extern bool SjLjExceptionHandling;
 
+  /// JITEmitDebugInfo - This flag indicates that the JIT should try to emit
+  /// debug information and notify a debugger about it.
+  extern bool JITEmitDebugInfo;
+
+  /// JITEmitDebugInfoToDisk - This flag indicates that the JIT should write
+  /// the object files generated by the JITEmitDebugInfo flag to disk.  This
+  /// flag is hidden and is only for debugging the debug info.
+  extern bool JITEmitDebugInfoToDisk;
+
   /// UnwindTablesMandatory - This flag indicates that unwind tables should
   /// be emitted for all functions.
   extern bool UnwindTablesMandatory;

lib/CodeGen/ELFWriter.h

@@ -28,6 +28,7 @@ namespace llvm {
   class ELFSection;
   struct ELFSym;
   class GlobalVariable;
+  class JITDebugRegisterer;
   class Mangler;
   class MachineCodeEmitter;
   class MachineConstantPoolEntry;
@@ -51,6 +52,7 @@ namespace llvm {
   ///
   class ELFWriter : public MachineFunctionPass {
     friend class ELFCodeEmitter;
+    friend class JITDebugRegisterer;
   public:
     static char ID;
 

lib/ExecutionEngine/JIT/JIT.cpp

@@ -234,7 +234,7 @@ JIT::JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji,
   jitstate = new JITState(MP);
 
   // Initialize JCE
-  JCE = createEmitter(*this, JMM);
+  JCE = createEmitter(*this, JMM, TM);
 
   // Add target data
   MutexGuard locked(lock);

lib/ExecutionEngine/JIT/JIT.h

@@ -185,7 +185,8 @@ public:
   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();

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

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

lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp

@@ -36,7 +36,8 @@ JITDwarfEmitter::JITDwarfEmitter(JIT& theJit) : Jit(theJit) {}
 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 @@ unsigned char* JITDwarfEmitter::EmitDwarfTable(MachineFunction& F,
                                                      EndFunction);
       
   unsigned char* Result = 0;
-  unsigned char* EHFramePtr = 0;
 
   const std::vector<Function *> Personalities = MMI->getPersonalities();
   EHFramePtr = EmitCommonEHFrame(Personalities[MMI->getPersonalityIndex()]);

lib/ExecutionEngine/JIT/JITDwarfEmitter.h

@@ -67,7 +67,8 @@ public:
   unsigned char* EmitDwarfTable(MachineFunction& F, 
                                 JITCodeEmitter& JCE,
                                 unsigned char* StartFunction,
-                                unsigned char* EndFunction);
+                                unsigned char* EndFunction,
+                                unsigned char* &EHFramePtr);
   
   
   unsigned GetDwarfTableSizeInBytes(MachineFunction& F, 

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 @@ namespace {
 
     /// 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 @@ namespace {
     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 @@ namespace {
         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 @@ namespace {
  
     virtual void setModuleInfo(MachineModuleInfo* Info) {
       MMI = Info;
-      if (DwarfExceptionHandling) DE->setModuleInfo(Info);
+      if (DE.get()) DE->setModuleInfo(Info);
     }
 
     void setMemoryExecutable() {
@@ -1124,12 +1133,12 @@ bool JITEmitter::finishFunction(MachineFunction &F) {
     }
         );
 
-  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 @@ bool JITEmitter::finishFunction(MachineFunction &F) {
     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::retryWithMoreMemory(MachineFunction &F) {
 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 @@ uintptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
 //  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

lib/Target/TargetMachine.cpp

@@ -35,6 +35,8 @@ namespace llvm {
   bool NoZerosInBSS;
   bool DwarfExceptionHandling;
   bool SjLjExceptionHandling;
+  bool JITEmitDebugInfo;
+  bool JITEmitDebugInfoToDisk;
   bool UnwindTablesMandatory;
   Reloc::Model RelocationModel;
   CodeModel::Model CMModel;
@@ -114,6 +116,24 @@ EnableSjLjExceptionHandling("enable-sjlj-eh",
   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 @@ namespace llvm {
     return !UnsafeFPMath && HonorSignDependentRoundingFPMathOption;
   }
 }
-