Add a JITEventListener interface that gets called back when a new function is

emitted or the machine code for a function is freed.  Chris mentioned that we
may also want a notification when a stub is emitted, but that'll be a future
change.  I intend to use this to tell oprofile where functions are emitted and
what lines correspond to what addresses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74157 91177308-0d34-0410-b5e6-96231b3b80d8

11 files changed, 600 insertions, 170 deletions

diff --git a/include/llvm/ExecutionEngine/ExecutionEngine.h b/include/llvm/ExecutionEngine/ExecutionEngine.h
index 170e18477a..613adb574e 100644
--- a/include/llvm/ExecutionEngine/ExecutionEngine.h
+++ b/include/llvm/ExecutionEngine/ExecutionEngine.h
@@ -29,13 +29,14 @@ class Constant;
 class Function;
 class GlobalVariable;
 class GlobalValue;
+class JITEventListener;
+class JITMemoryManager;
+class MachineCodeInfo;
 class Module;
 class ModuleProvider;
+class MutexGuard;
 class TargetData;
 class Type;
-class MutexGuard;
-class JITMemoryManager;
-class MachineCodeInfo;
 
 class ExecutionEngineState {
 private:
@@ -276,7 +277,14 @@ public:
   virtual void *getOrEmitGlobalVariable(const GlobalVariable *GV) {
     return getPointerToGlobal((GlobalValue*)GV);
   }
-  
+
+  /// Registers a listener to be called back on various events within
+  /// the JIT.  See JITEventListener.h for more details.  Does not
+  /// take ownership of the argument.  The argument may be NULL, in
+  /// which case these functions do nothing.
+  virtual void RegisterJITEventListener(JITEventListener *L) {}
+  virtual void UnregisterJITEventListener(JITEventListener *L) {}
+
   /// DisableLazyCompilation - If called, the JIT will abort if lazy compilation
   /// is ever attempted.
   void DisableLazyCompilation(bool Disabled = true) {
diff --git a/include/llvm/ExecutionEngine/JITEventListener.h b/include/llvm/ExecutionEngine/JITEventListener.h
new file mode 100644
index 0000000000..dd76f26c87
--- /dev/null
+++ b/include/llvm/ExecutionEngine/JITEventListener.h
@@ -0,0 +1,59 @@
+//===- JITEventListener.h - Exposes events from JIT compilation -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the JITEventListener interface, which lets users get
+// callbacks when significant events happen during the JIT compilation process.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTION_ENGINE_JIT_EVENTLISTENER_H
+#define LLVM_EXECUTION_ENGINE_JIT_EVENTLISTENER_H
+
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+class Function;
+
+/// Empty for now, but this object will contain all details about the
+/// generated machine code that a Listener might care about.
+struct JITEvent_EmittedFunctionDetails {
+};
+
+/// JITEventListener - This interface is used by the JIT to notify clients about
+/// significant events during compilation.  For example, we could have
+/// implementations for profilers and debuggers that need to know where
+/// functions have been emitted.
+///
+/// Each method defaults to doing nothing, so you only need to override the ones
+/// you care about.
+class JITEventListener {
+public:
+  JITEventListener() {}
+  virtual ~JITEventListener();  // Defined in JIT.cpp.
+
+  typedef JITEvent_EmittedFunctionDetails EmittedFunctionDetails;
+  /// NotifyFunctionEmitted - Called after a function has been successfully
+  /// emitted to memory.  The function still has its MachineFunction attached,
+  /// if you should happen to need that.
+  virtual void NotifyFunctionEmitted(const Function &F,
+                                     void *Code, size_t Size,
+                                     const EmittedFunctionDetails &Details) {}
+
+  /// NotifyFreeingMachineCode - This is called inside of
+  /// freeMachineCodeForFunction(), after the global mapping is removed, but
+  /// before the machine code is returned to the allocator.  OldPtr is the
+  /// address of the machine code.
+  virtual void NotifyFreeingMachineCode(const Function &F, void *OldPtr) {}
+};
+
+JITEventListener *createMacOSJITEventListener();
+
+} // end namespace llvm.
+
+#endif
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 14d8d5b12a..db5a306bad 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -20,8 +20,9 @@
 #include "llvm/Instructions.h"
 #include "llvm/ModuleProvider.h"
 #include "llvm/CodeGen/JITCodeEmitter.h"
-#include "llvm/ExecutionEngine/GenericValue.h"
 #include "llvm/CodeGen/MachineCodeInfo.h"
+#include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetJITInfo.h"
@@ -507,6 +508,40 @@ GenericValue JIT::runFunction(Function *F,
   return runFunction(Stub, std::vector<GenericValue>());
 }
 
+void JIT::RegisterJITEventListener(JITEventListener *L) {
+  if (L == NULL)
+    return;
+  MutexGuard locked(lock);
+  EventListeners.push_back(L);
+}
+void JIT::UnregisterJITEventListener(JITEventListener *L) {
+  if (L == NULL)
+    return;
+  MutexGuard locked(lock);
+  std::vector<JITEventListener*>::reverse_iterator I=
+      std::find(EventListeners.rbegin(), EventListeners.rend(), L);
+  if (I != EventListeners.rend()) {
+    std::swap(*I, EventListeners.back());
+    EventListeners.pop_back();
+  }
+}
+void JIT::NotifyFunctionEmitted(
+    const Function &F,
+    void *Code, size_t Size,
+    const JITEvent_EmittedFunctionDetails &Details) {
+  MutexGuard locked(lock);
+  for (unsigned I = 0, S = EventListeners.size(); I < S; ++I) {
+    EventListeners[I]->NotifyFunctionEmitted(F, Code, Size, Details);
+  }
+}
+
+void JIT::NotifyFreeingMachineCode(const Function &F, void *OldPtr) {
+  MutexGuard locked(lock);
+  for (unsigned I = 0, S = EventListeners.size(); I < S; ++I) {
+    EventListeners[I]->NotifyFreeingMachineCode(F, OldPtr);
+  }
+}
+
 /// runJITOnFunction - Run the FunctionPassManager full of
 /// just-in-time compilation passes on F, hopefully filling in
 /// GlobalAddress[F] with the address of F's machine code.
@@ -514,11 +549,23 @@ GenericValue JIT::runFunction(Function *F,
 void JIT::runJITOnFunction(Function *F, MachineCodeInfo *MCI) {
   MutexGuard locked(lock);
 
-  registerMachineCodeInfo(MCI);
+  class MCIListener : public JITEventListener {
+    MachineCodeInfo *const MCI;
+   public:
+    MCIListener(MachineCodeInfo *mci) : MCI(mci) {}
+    virtual void NotifyFunctionEmitted(const Function &,
+                                       void *Code, size_t Size,
+                                       const EmittedFunctionDetails &) {
+      MCI->setAddress(Code);
+      MCI->setSize(Size);
+    }
+  };
+  MCIListener MCIL(MCI);
+  RegisterJITEventListener(&MCIL);
 
   runJITOnFunctionUnlocked(F, locked);
 
-  registerMachineCodeInfo(0);
+  UnregisterJITEventListener(&MCIL);
 }
 
 void JIT::runJITOnFunctionUnlocked(Function *F, const MutexGuard &locked) {
@@ -709,3 +756,6 @@ void JIT::addPendingFunction(Function *F) {
   MutexGuard locked(lock);
   jitstate->getPendingFunctions(locked).push_back(F);
 }
+
+
+JITEventListener::~JITEventListener() {}
diff --git a/lib/ExecutionEngine/JIT/JIT.h b/lib/ExecutionEngine/JIT/JIT.h
index 3ccb2dd812..66417a71b2 100644
--- a/lib/ExecutionEngine/JIT/JIT.h
+++ b/lib/ExecutionEngine/JIT/JIT.h
@@ -20,10 +20,11 @@
 namespace llvm {
 
 class Function;
-class TargetMachine;
-class TargetJITInfo;
+class JITEvent_EmittedFunctionDetails;
 class MachineCodeEmitter;
 class MachineCodeInfo;
+class TargetJITInfo;
+class TargetMachine;
 
 class JITState {
 private:
@@ -52,6 +53,7 @@ class JIT : public ExecutionEngine {
   TargetMachine &TM;       // The current target we are compiling to
   TargetJITInfo &TJI;      // The JITInfo for the target we are compiling to
   JITCodeEmitter *JCE;     // JCE object
+  std::vector<JITEventListener*> EventListeners;
 
   JITState *jitstate;
 
@@ -157,9 +159,18 @@ public:
   // Run the JIT on F and return information about the generated code
   void runJITOnFunction(Function *F, MachineCodeInfo *MCI = 0);
 
+  virtual void RegisterJITEventListener(JITEventListener *L);
+  virtual void UnregisterJITEventListener(JITEventListener *L);
+  /// These functions correspond to the methods on JITEventListener.  They
+  /// iterate over the registered listeners and call the corresponding method on
+  /// each.
+  void NotifyFunctionEmitted(
+      const Function &F, void *Code, size_t Size,
+      const JITEvent_EmittedFunctionDetails &Details);
+  void NotifyFreeingMachineCode(const Function &F, void *OldPtr);
+
 private:
   static JITCodeEmitter *createEmitter(JIT &J, JITMemoryManager *JMM);
-  void registerMachineCodeInfo(MachineCodeInfo *MCI);
   void runJITOnFunctionUnlocked(Function *F, const MutexGuard &locked);
   void updateFunctionStub(Function *F);
   void updateDlsymStubTable();
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 43f23e4434..8fe7ab848b 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -24,8 +24,9 @@
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRelocation.h"
-#include "llvm/ExecutionEngine/JITMemoryManager.h"
 #include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
+#include "llvm/ExecutionEngine/JITMemoryManager.h"
 #include "llvm/CodeGen/MachineCodeInfo.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetJITInfo.h"
@@ -411,136 +412,6 @@ void *JITResolver::JITCompilerFn(void *Stub) {
 }
 
 //===----------------------------------------------------------------------===//
-// Function Index Support
-
-// On MacOS we generate an index of currently JIT'd functions so that
-// performance tools can determine a symbol name and accurate code range for a
-// PC value.  Because performance tools are generally asynchronous, the code
-// below is written with the hope that it could be interrupted at any time and
-// have useful answers.  However, we don't go crazy with atomic operations, we
-// just do a "reasonable effort".
-#ifdef __APPLE__ 
-#define ENABLE_JIT_SYMBOL_TABLE 0
-#endif
-
-/// JitSymbolEntry - Each function that is JIT compiled results in one of these
-/// being added to an array of symbols.  This indicates the name of the function
-/// as well as the address range it occupies.  This allows the client to map
-/// from a PC value to the name of the function.
-struct JitSymbolEntry {
-  const char *FnName;   // FnName - a strdup'd string.
-  void *FnStart;
-  intptr_t FnSize;
-};
-
-
-struct JitSymbolTable {
-  /// NextPtr - This forms a linked list of JitSymbolTable entries.  This
-  /// pointer is not used right now, but might be used in the future.  Consider
-  /// it reserved for future use.
-  JitSymbolTable *NextPtr;
-  
-  /// Symbols - This is an array of JitSymbolEntry entries.  Only the first
-  /// 'NumSymbols' symbols are valid.
-  JitSymbolEntry *Symbols;
-  
-  /// NumSymbols - This indicates the number entries in the Symbols array that
-  /// are valid.
-  unsigned NumSymbols;
-  
-  /// NumAllocated - This indicates the amount of space we have in the Symbols
-  /// array.  This is a private field that should not be read by external tools.
-  unsigned NumAllocated;
-};
-
-#if ENABLE_JIT_SYMBOL_TABLE 
-JitSymbolTable *__jitSymbolTable;
-#endif
-
-static void AddFunctionToSymbolTable(const char *FnName, 
-                                     void *FnStart, intptr_t FnSize) {
-  assert(FnName != 0 && FnStart != 0 && "Bad symbol to add");
-  JitSymbolTable **SymTabPtrPtr = 0;
-#if !ENABLE_JIT_SYMBOL_TABLE
-  return;
-#else
-  SymTabPtrPtr = &__jitSymbolTable;
-#endif
-  
-  // If this is the first entry in the symbol table, add the JitSymbolTable
-  // index.
-  if (*SymTabPtrPtr == 0) {
-    JitSymbolTable *New = new JitSymbolTable();
-    New->NextPtr = 0;
-    New->Symbols = 0;
-    New->NumSymbols = 0;
-    New->NumAllocated = 0;
-    *SymTabPtrPtr = New;
-  }
-  
-  JitSymbolTable *SymTabPtr = *SymTabPtrPtr;
-  
-  // If we have space in the table, reallocate the table.
-  if (SymTabPtr->NumSymbols >= SymTabPtr->NumAllocated) {
-    // If we don't have space, reallocate the table.
-    unsigned NewSize = std::max(64U, SymTabPtr->NumAllocated*2);
-    JitSymbolEntry *NewSymbols = new JitSymbolEntry[NewSize];
-    JitSymbolEntry *OldSymbols = SymTabPtr->Symbols;
-    
-    // Copy the old entries over.
-    memcpy(NewSymbols, OldSymbols, SymTabPtr->NumSymbols*sizeof(OldSymbols[0]));
-    
-    // Swap the new symbols in, delete the old ones.
-    SymTabPtr->Symbols = NewSymbols;
-    SymTabPtr->NumAllocated = NewSize;
-    delete [] OldSymbols;
-  }
-  
-  // Otherwise, we have enough space, just tack it onto the end of the array.
-  JitSymbolEntry &Entry = SymTabPtr->Symbols[SymTabPtr->NumSymbols];
-  Entry.FnName = strdup(FnName);
-  Entry.FnStart = FnStart;
-  Entry.FnSize = FnSize;
-  ++SymTabPtr->NumSymbols;
-}
-
-static void RemoveFunctionFromSymbolTable(void *FnStart) {
-  assert(FnStart && "Invalid function pointer");
-  JitSymbolTable **SymTabPtrPtr = 0;
-#if !ENABLE_JIT_SYMBOL_TABLE
-  return;
-#else
-  SymTabPtrPtr = &__jitSymbolTable;
-#endif
-  
-  JitSymbolTable *SymTabPtr = *SymTabPtrPtr;
-  JitSymbolEntry *Symbols = SymTabPtr->Symbols;
-  
-  // Scan the table to find its index.  The table is not sorted, so do a linear
-  // scan.
-  unsigned Index;
-  for (Index = 0; Symbols[Index].FnStart != FnStart; ++Index)
-    assert(Index != SymTabPtr->NumSymbols && "Didn't find function!");
-  
-  // Once we have an index, we know to nuke this entry, overwrite it with the
-  // entry at the end of the array, making the last entry redundant.
-  const char *OldName = Symbols[Index].FnName;
-  Symbols[Index] = Symbols[SymTabPtr->NumSymbols-1];
-  free((void*)OldName);
-  
-  // Drop the number of symbols in the table.
-  --SymTabPtr->NumSymbols;
-
-  // Finally, if we deleted the final symbol, deallocate the table itself.
-  if (SymTabPtr->NumSymbols != 0) 
-    return;
-  
-  *SymTabPtrPtr = 0;
-  delete [] Symbols;
-  delete SymTabPtr;
-}
-
-//===----------------------------------------------------------------------===//
 // JITEmitter code.
 //
 namespace {
@@ -616,11 +487,8 @@ namespace {
     // in the JITResolver's ExternalFnToStubMap.
     StringMap<void *> ExtFnStubs;
 
-    // MCI - A pointer to a MachineCodeInfo object to update with information.
-    MachineCodeInfo *MCI;
-
   public:
-    JITEmitter(JIT &jit, JITMemoryManager *JMM) : Resolver(jit), CurFn(0), MCI(0) {
+    JITEmitter(JIT &jit, JITMemoryManager *JMM) : Resolver(jit), CurFn(0) {
       MemMgr = JMM ? JMM : JITMemoryManager::CreateDefaultMemManager();
       if (jit.getJITInfo().needsGOT()) {
         MemMgr->AllocateGOT();
@@ -716,10 +584,6 @@ namespace {
     
     JITMemoryManager *getMemMgr(void) const { return MemMgr; }
 
-    void setMachineCodeInfo(MachineCodeInfo *mci) {
-      MCI = mci;
-    }
-
   private:
     void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
     void *getPointerToGVIndirectSym(GlobalValue *V, void *Reference,
@@ -1157,21 +1021,16 @@ bool JITEmitter::finishFunction(MachineFunction &F) {
 
   // Invalidate the icache if necessary.
   sys::Memory::InvalidateInstructionCache(FnStart, FnEnd-FnStart);
-  
-  // Add it to the JIT symbol table if the host wants it.
-  AddFunctionToSymbolTable(F.getFunction()->getNameStart(),
-                           FnStart, FnEnd-FnStart);
+
+  JITEvent_EmittedFunctionDetails Details;
+  TheJIT->NotifyFunctionEmitted(*F.getFunction(), FnStart, FnEnd-FnStart,
+                                Details);
 
   DOUT << "JIT: Finished CodeGen of [" << (void*)FnStart
        << "] Function: " << F.getFunction()->getName()
        << ": " << (FnEnd-FnStart) << " bytes of text, "
        << Relocations.size() << " relocations\n";
 
-  if (MCI) {
-    MCI->setAddress(FnStart);
-    MCI->setSize(FnEnd-FnStart);
-  }
-
   Relocations.clear();
   ConstPoolAddresses.clear();
 
@@ -1495,13 +1354,6 @@ void *JIT::getPointerToFunctionOrStub(Function *F) {
   return JE->getJITResolver().getFunctionStub(F);
 }
 
-void JIT::registerMachineCodeInfo(MachineCodeInfo *mc) {
-  assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");
-  JITEmitter *JE = cast<JITEmitter>(getCodeEmitter());
-
-  JE->setMachineCodeInfo(mc);
-}
-
 void JIT::updateFunctionStub(Function *F) {
   // Get the empty stub we generated earlier.
   assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");
@@ -1609,10 +1461,9 @@ void JIT::freeMachineCodeForFunction(Function *F) {
   void *OldPtr = updateGlobalMapping(F, 0);
 
   if (OldPtr)
-    RemoveFunctionFromSymbolTable(OldPtr);
+    TheJIT->NotifyFreeingMachineCode(*F, OldPtr);
 
   // Free the actual memory for the function body and related stuff.
   assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");
   cast<JITEmitter>(JCE)->deallocateMemForFunction(F);
 }
-
diff --git a/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp b/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp
new file mode 100644
index 0000000000..3b8b84ce5b
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp
@@ -0,0 +1,173 @@
+//===-- MacOSJITEventListener.cpp - Save symbol table for OSX perf tools --===//
+//
+//                     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 JITEventListener object that records JITted functions to
+// a global __jitSymbolTable linked list.  Apple's performance tools use this to
+// determine a symbol name and accurate code range for a PC value.  Because
+// performance tools are generally asynchronous, the code below is written with
+// the hope that it could be interrupted at any time and have useful answers.
+// However, we don't go crazy with atomic operations, we just do a "reasonable
+// effort".
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "macos-jit-event-listener"
+#include "llvm/Function.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
+#include <stddef.h>
+using namespace llvm;
+
+#ifdef __APPLE__
+#define ENABLE_JIT_SYMBOL_TABLE 0
+#endif
+
+#if ENABLE_JIT_SYMBOL_TABLE
+
+namespace {
+
+/// JITSymbolEntry - Each function that is JIT compiled results in one of these
+/// being added to an array of symbols.  This indicates the name of the function
+/// as well as the address range it occupies.  This allows the client to map
+/// from a PC value to the name of the function.
+struct JITSymbolEntry {
+  const char *FnName;   // FnName - a strdup'd string.
+  void *FnStart;
+  intptr_t FnSize;
+};
+
+
+struct JITSymbolTable {
+  /// NextPtr - This forms a linked list of JitSymbolTable entries.  This
+  /// pointer is not used right now, but might be used in the future.  Consider
+  /// it reserved for future use.
+  JITSymbolTable *NextPtr;
+  
+  /// Symbols - This is an array of JitSymbolEntry entries.  Only the first
+  /// 'NumSymbols' symbols are valid.
+  JITSymbolEntry *Symbols;
+  
+  /// NumSymbols - This indicates the number entries in the Symbols array that
+  /// are valid.
+  unsigned NumSymbols;
+  
+  /// NumAllocated - This indicates the amount of space we have in the Symbols
+  /// array.  This is a private field that should not be read by external tools.
+  unsigned NumAllocated;
+};
+
+class MacOSJITEventListener : public JITEventListener {
+public:
+  virtual void NotifyFunctionEmitted(const Function &F,
+                                     void *FnStart, size_t FnSize,
+                                     const EmittedFunctionDetails &Details);
+  virtual void NotifyFreeingMachineCode(const Function &F, void *OldPtr);
+};
+
+}  // anonymous namespace.
+
+// This is a public symbol so the performance tools can find it.
+JITSymbolTable *__jitSymbolTable;
+
+namespace llvm {
+JITEventListener *createMacOSJITEventListener() {
+  return new MacOSJITEventListener;
+}
+}
+
+// Adds the just-emitted function to the symbol table.
+void MacOSJITEventListener::NotifyFunctionEmitted(
+    const Function &F, void *FnStart, size_t FnSize,
+    const EmittedFunctionDetails &) {
+  const char *const FnName = F.getNameStart();
+  assert(FnName != 0 && FnStart != 0 && "Bad symbol to add");
+  JITSymbolTable **SymTabPtrPtr = 0;
+  SymTabPtrPtr = &__jitSymbolTable;
+
+  // If this is the first entry in the symbol table, add the JITSymbolTable
+  // index.
+  if (*SymTabPtrPtr == 0) {
+    JITSymbolTable *New = new JITSymbolTable();
+    New->NextPtr = 0;
+    New->Symbols = 0;
+    New->NumSymbols = 0;
+    New->NumAllocated = 0;
+    *SymTabPtrPtr = New;
+  }
+
+  JITSymbolTable *SymTabPtr = *SymTabPtrPtr;
+
+  // If we have space in the table, reallocate the table.
+  if (SymTabPtr->NumSymbols >= SymTabPtr->NumAllocated) {
+    // If we don't have space, reallocate the table.
+    unsigned NewSize = std::max(64U, SymTabPtr->NumAllocated*2);
+    JITSymbolEntry *NewSymbols = new JITSymbolEntry[NewSize];
+    JITSymbolEntry *OldSymbols = SymTabPtr->Symbols;
+
+    // Copy the old entries over.
+    memcpy(NewSymbols, OldSymbols, SymTabPtr->NumSymbols*sizeof(OldSymbols[0]));
+
+    // Swap the new symbols in, delete the old ones.
+    SymTabPtr->Symbols = NewSymbols;
+    SymTabPtr->NumAllocated = NewSize;
+    delete [] OldSymbols;
+  }
+
+  // Otherwise, we have enough space, just tack it onto the end of the array.
+  JITSymbolEntry &Entry = SymTabPtr->Symbols[SymTabPtr->NumSymbols];
+  Entry.FnName = strdup(FnName);
+  Entry.FnStart = FnStart;
+  Entry.FnSize = FnSize;
+  ++SymTabPtr->NumSymbols;
+}
+
+// Removes the to-be-deleted function from the symbol table.
+void MacOSJITEventListener::NotifyFreeingMachineCode(
+    const Function &, void *FnStart) {
+  assert(FnStart && "Invalid function pointer");
+  JITSymbolTable **SymTabPtrPtr = 0;
+  SymTabPtrPtr = &__jitSymbolTable;
+
+  JITSymbolTable *SymTabPtr = *SymTabPtrPtr;
+  JITSymbolEntry *Symbols = SymTabPtr->Symbols;
+
+  // Scan the table to find its index.  The table is not sorted, so do a linear
+  // scan.
+  unsigned Index;
+  for (Index = 0; Symbols[Index].FnStart != FnStart; ++Index)
+    assert(Index != SymTabPtr->NumSymbols && "Didn't find function!");
+
+  // Once we have an index, we know to nuke this entry, overwrite it with the
+  // entry at the end of the array, making the last entry redundant.
+  const char *OldName = Symbols[Index].FnName;
+  Symbols[Index] = Symbols[SymTabPtr->NumSymbols-1];
+  free((void*)OldName);
+
+  // Drop the number of symbols in the table.
+  --SymTabPtr->NumSymbols;
+
+  // Finally, if we deleted the final symbol, deallocate the table itself.
+  if (SymTabPtr->NumSymbols != 0)
+    return;
+
+  *SymTabPtrPtr = 0;
+  delete [] Symbols;
+  delete SymTabPtr;
+}
+
+#else  // !ENABLE_JIT_SYMBOL_TABLE
+
+namespace llvm {
+// By defining this to return NULL, we can let clients call it unconditionally,
+// even if they aren't on an Apple system.
+JITEventListener *createMacOSJITEventListener() {
+  return NULL;
+}
+}  // namespace llvm
+
+#endif  // ENABLE_JIT_SYMBOL_TABLE
diff --git a/tools/lli/lli.cpp b/tools/lli/lli.cpp
index afd3c5a71f..25536746da 100644
--- a/tools/lli/lli.cpp
+++ b/tools/lli/lli.cpp
@@ -18,9 +18,10 @@
 #include "llvm/Type.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/LinkAllCodegenComponents.h"
-#include "llvm/ExecutionEngine/JIT.h"
-#include "llvm/ExecutionEngine/Interpreter.h"
 #include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/ExecutionEngine/Interpreter.h"
+#include "llvm/ExecutionEngine/JIT.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -149,6 +150,8 @@ int main(int argc, char **argv, char * const *envp) {
     exit(1);
   }
 
+  EE->RegisterJITEventListener(createMacOSJITEventListener());
+
   if (NoLazyCompilation)
     EE->DisableLazyCompilation();
 
diff --git a/unittests/ExecutionEngine/JIT/JITEventListenerTest.cpp b/unittests/ExecutionEngine/JIT/JITEventListenerTest.cpp
new file mode 100644
index 0000000000..3c9beebba6
--- /dev/null
+++ b/unittests/ExecutionEngine/JIT/JITEventListenerTest.cpp
@@ -0,0 +1,241 @@
+//===- JITEventListenerTest.cpp - Unit tests for JITEventListeners --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITEventListener.h"
+
+#include "llvm/Instructions.h"
+#include "llvm/Module.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/CodeGen/MachineCodeInfo.h"
+#include "llvm/ExecutionEngine/JIT.h"
+#include "llvm/Support/TypeBuilder.h"
+#include "llvm/Target/TargetSelect.h"
+#include "gtest/gtest.h"
+#include <vector>
+
+using namespace llvm;
+
+namespace {
+
+struct FunctionEmittedEvent {
+  // Indices are local to the RecordingJITEventListener, since the
+  // JITEventListener interface makes no guarantees about the order of
+  // calls between Listeners.
+  unsigned Index;
+  const Function *F;
+  void *Code;
+  size_t Size;
+  JITEvent_EmittedFunctionDetails Details;
+};
+struct FunctionFreedEvent {
+  unsigned Index;
+  const Function *F;
+  void *Code;
+};
+
+struct RecordingJITEventListener : public JITEventListener {
+  std::vector<FunctionEmittedEvent> EmittedEvents;
+  std::vector<FunctionFreedEvent> FreedEvents;
+
+  int NextIndex;
+
+  RecordingJITEventListener() : NextIndex(0) {}
+
+  virtual void NotifyFunctionEmitted(const Function &F,
+                                     void *Code, size_t Size,
+                                     const EmittedFunctionDetails &Details) {
+    FunctionEmittedEvent Event = {NextIndex++, &F, Code, Size, Details};
+    EmittedEvents.push_back(Event);
+  }
+
+  virtual void NotifyFreeingMachineCode(const Function &F, void *OldPtr) {
+    FunctionFreedEvent Event = {NextIndex++, &F, OldPtr};
+    FreedEvents.push_back(Event);
+  }
+};
+
+class JITEventListenerTest : public testing::Test {
+ protected:
+  JITEventListenerTest()
+      : M(new Module("module")),
+        EE(ExecutionEngine::createJIT(new ExistingModuleProvider(M))) {
+  }
+
+  Module *M;
+  const OwningPtr<ExecutionEngine> EE;
+};
+
+Function *buildFunction(Module *M) {
+  Function *Result = Function::Create(
+      TypeBuilder<int32_t(int32_t), false>::get(),
+      GlobalValue::ExternalLinkage, "id", M);
+  Value *Arg = Result->arg_begin();
+  BasicBlock *BB = BasicBlock::Create("entry", Result);
+  ReturnInst::Create(Arg, BB);
+  return Result;
+}
+
+// Tests that a single JITEventListener follows JIT events accurately.
+TEST_F(JITEventListenerTest, Simple) {
+  RecordingJITEventListener Listener;
+  EE->RegisterJITEventListener(&Listener);
+  Function *F1 = buildFunction(M);
+  Function *F2 = buildFunction(M);
+
+  void *F1_addr = EE->getPointerToFunction(F1);
+  void *F2_addr = EE->getPointerToFunction(F2);
+  EE->getPointerToFunction(F1);  // Should do nothing.
+  EE->freeMachineCodeForFunction(F1);
+  EE->freeMachineCodeForFunction(F2);
+
+  ASSERT_EQ(2U, Listener.EmittedEvents.size());
+  ASSERT_EQ(2U, Listener.FreedEvents.size());
+
+  EXPECT_EQ(0U, Listener.EmittedEvents[0].Index);
+  EXPECT_EQ(F1, Listener.EmittedEvents[0].F);
+  EXPECT_EQ(F1_addr, Listener.EmittedEvents[0].Code);
+  EXPECT_LT(0U, Listener.EmittedEvents[0].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(1U, Listener.EmittedEvents[1].Index);
+  EXPECT_EQ(F2, Listener.EmittedEvents[1].F);
+  EXPECT_EQ(F2_addr, Listener.EmittedEvents[1].Code);
+  EXPECT_LT(0U, Listener.EmittedEvents[1].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(2U, Listener.FreedEvents[0].Index);
+  EXPECT_EQ(F1, Listener.FreedEvents[0].F);
+  EXPECT_EQ(F1_addr, Listener.FreedEvents[0].Code);
+
+  EXPECT_EQ(3U, Listener.FreedEvents[1].Index);
+  EXPECT_EQ(F2, Listener.FreedEvents[1].F);
+  EXPECT_EQ(F2_addr, Listener.FreedEvents[1].Code);
+
+  F1->eraseFromParent();
+  F2->eraseFromParent();
+}
+
+// Tests that a single JITEventListener follows JIT events accurately.
+TEST_F(JITEventListenerTest, MultipleListenersDontInterfere) {
+  RecordingJITEventListener Listener1;
+  RecordingJITEventListener Listener2;
+  RecordingJITEventListener Listener3;
+  Function *F1 = buildFunction(M);
+  Function *F2 = buildFunction(M);
+
+  EE->RegisterJITEventListener(&Listener1);
+  EE->RegisterJITEventListener(&Listener2);
+  void *F1_addr = EE->getPointerToFunction(F1);
+  EE->RegisterJITEventListener(&Listener3);
+  EE->UnregisterJITEventListener(&Listener1);
+  void *F2_addr = EE->getPointerToFunction(F2);
+  EE->UnregisterJITEventListener(&Listener2);
+  EE->UnregisterJITEventListener(&Listener3);
+  EE->freeMachineCodeForFunction(F1);
+  EE->RegisterJITEventListener(&Listener2);
+  EE->RegisterJITEventListener(&Listener3);
+  EE->RegisterJITEventListener(&Listener1);
+  EE->freeMachineCodeForFunction(F2);
+  EE->UnregisterJITEventListener(&Listener1);
+  EE->UnregisterJITEventListener(&Listener2);
+  EE->UnregisterJITEventListener(&Listener3);
+
+  // Listener 1.
+  ASSERT_EQ(1U, Listener1.EmittedEvents.size());
+  ASSERT_EQ(1U, Listener1.FreedEvents.size());
+
+  EXPECT_EQ(0U, Listener1.EmittedEvents[0].Index);
+  EXPECT_EQ(F1, Listener1.EmittedEvents[0].F);
+  EXPECT_EQ(F1_addr, Listener1.EmittedEvents[0].Code);
+  EXPECT_LT(0U, Listener1.EmittedEvents[0].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(1U, Listener1.FreedEvents[0].Index);
+  EXPECT_EQ(F2, Listener1.FreedEvents[0].F);
+  EXPECT_EQ(F2_addr, Listener1.FreedEvents[0].Code);
+
+  // Listener 2.
+  ASSERT_EQ(2U, Listener2.EmittedEvents.size());
+  ASSERT_EQ(1U, Listener2.FreedEvents.size());
+
+  EXPECT_EQ(0U, Listener2.EmittedEvents[0].Index);
+  EXPECT_EQ(F1, Listener2.EmittedEvents[0].F);
+  EXPECT_EQ(F1_addr, Listener2.EmittedEvents[0].Code);
+  EXPECT_LT(0U, Listener2.EmittedEvents[0].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(1U, Listener2.EmittedEvents[1].Index);
+  EXPECT_EQ(F2, Listener2.EmittedEvents[1].F);
+  EXPECT_EQ(F2_addr, Listener2.EmittedEvents[1].Code);
+  EXPECT_LT(0U, Listener2.EmittedEvents[1].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(2U, Listener2.FreedEvents[0].Index);
+  EXPECT_EQ(F2, Listener2.FreedEvents[0].F);
+  EXPECT_EQ(F2_addr, Listener2.FreedEvents[0].Code);
+
+  // Listener 3.
+  ASSERT_EQ(1U, Listener3.EmittedEvents.size());
+  ASSERT_EQ(1U, Listener3.FreedEvents.size());
+
+  EXPECT_EQ(0U, Listener3.EmittedEvents[0].Index);
+  EXPECT_EQ(F2, Listener3.EmittedEvents[0].F);
+  EXPECT_EQ(F2_addr, Listener3.EmittedEvents[0].Code);
+  EXPECT_LT(0U, Listener3.EmittedEvents[0].Size)
+      << "We don't know how big the function will be, but it had better"
+      << " contain some bytes.";
+
+  EXPECT_EQ(1U, Listener3.FreedEvents[0].Index);
+  EXPECT_EQ(F2, Listener3.FreedEvents[0].F);
+  EXPECT_EQ(F2_addr, Listener3.FreedEvents[0].Code);
+
+  F1->eraseFromParent();
+  F2->eraseFromParent();
+}
+
+TEST_F(JITEventListenerTest, MatchesMachineCodeInfo) {
+  RecordingJITEventListener Listener;
+  MachineCodeInfo MCI;
+  Function *F = buildFunction(M);
+
+  EE->RegisterJITEventListener(&Listener);
+  EE->runJITOnFunction(F, &MCI);
+  void *F_addr = EE->getPointerToFunction(F);
+  EE->freeMachineCodeForFunction(F);
+
+  ASSERT_EQ(1U, Listener.EmittedEvents.size());
+  ASSERT_EQ(1U, Listener.FreedEvents.size());
+
+  EXPECT_EQ(0U, Listener.EmittedEvents[0].Index);
+  EXPECT_EQ(F, Listener.EmittedEvents[0].F);
+  EXPECT_EQ(F_addr, Listener.EmittedEvents[0].Code);
+  EXPECT_EQ(MCI.address(), Listener.EmittedEvents[0].Code);
+  EXPECT_EQ(MCI.size(), Listener.EmittedEvents[0].Size);
+
+  EXPECT_EQ(1U, Listener.FreedEvents[0].Index);
+  EXPECT_EQ(F, Listener.FreedEvents[0].F);
+  EXPECT_EQ(F_addr, Listener.FreedEvents[0].Code);
+}
+
+class JITEnvironment : public testing::Environment {
+  virtual void SetUp() {
+    // Required for ExecutionEngine::createJIT to create a JIT.
+    InitializeNativeTarget();
+  }
+};
+testing::Environment* const jit_env =
+  testing::AddGlobalTestEnvironment(new JITEnvironment);
+
+}  // anonymous namespace
diff --git a/unittests/ExecutionEngine/JIT/Makefile b/unittests/ExecutionEngine/JIT/Makefile
new file mode 100644
index 0000000000..0069c7687a
--- /dev/null
+++ b/unittests/ExecutionEngine/JIT/Makefile
@@ -0,0 +1,15 @@
+##===- unittests/ExecutionEngine/JIT/Makefile --------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../../..
+TESTNAME = JIT
+LINK_COMPONENTS := core support jit native
+
+include $(LEVEL)/Makefile.config
+include $(LLVM_SRC_ROOT)/unittests/Makefile.unittest
diff --git a/unittests/ExecutionEngine/Makefile b/unittests/ExecutionEngine/Makefile
new file mode 100644
index 0000000000..e837a7d4fd
--- /dev/null
+++ b/unittests/ExecutionEngine/Makefile
@@ -0,0 +1,19 @@
+##===- unittests/ExecutionEngine/Makefile ------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+
+include $(LEVEL)/Makefile.config
+
+PARALLEL_DIRS = JIT
+
+include $(LEVEL)/Makefile.common
+
+clean::
+	$(Verb) $(RM) -f *Tests
diff --git a/unittests/Makefile b/unittests/Makefile
index 04d12e01ad..1eb69abbc8 100644
--- a/unittests/Makefile
+++ b/unittests/Makefile
@@ -16,7 +16,7 @@ BUILD_ARCHIVE = 1
 CPP.Flags += -I$(LLVM_SRC_ROOT)/utils/unittest/googletest/include/
 CPP.Flags += -Wno-variadic-macros
 
-PARALLEL_DIRS = ADT Support VMCore MC
+PARALLEL_DIRS = ADT ExecutionEngine Support VMCore MC
 
 include $(LEVEL)/Makefile.common