It's not necessary to do rounding for alloca operations when the requested

alignment is equal to the stack alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 1802 insertions, 0 deletions

diff --git a/lib/ExecutionEngine/JIT/Intercept.cpp b/lib/ExecutionEngine/JIT/Intercept.cpp
new file mode 100644
index 0000000..f370e5b
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/Intercept.cpp
@@ -0,0 +1,121 @@
+//===-- Intercept.cpp - System function interception routines -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// If a function call occurs to an external function, the JIT is designed to use
+// the dynamic loader interface to find a function to call.  This is useful for
+// calling system calls and library functions that are not available in LLVM.
+// Some system calls, however, need to be handled specially.  For this reason,
+// we intercept some of them here and use our own stubs to handle them.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JIT.h"
+#include "llvm/System/DynamicLibrary.h"
+#include "llvm/Config/config.h"
+using namespace llvm;
+
+// AtExitHandlers - List of functions to call when the program exits,
+// registered with the atexit() library function.
+static std::vector<void (*)()> AtExitHandlers;
+
+/// runAtExitHandlers - Run any functions registered by the program's
+/// calls to atexit(3), which we intercept and store in
+/// AtExitHandlers.
+///
+static void runAtExitHandlers() {
+  while (!AtExitHandlers.empty()) {
+    void (*Fn)() = AtExitHandlers.back();
+    AtExitHandlers.pop_back();
+    Fn();
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// Function stubs that are invoked instead of certain library calls
+//===----------------------------------------------------------------------===//
+
+// Force the following functions to be linked in to anything that uses the
+// JIT. This is a hack designed to work around the all-too-clever Glibc
+// strategy of making these functions work differently when inlined vs. when
+// not inlined, and hiding their real definitions in a separate archive file
+// that the dynamic linker can't see. For more info, search for
+// 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
+#if defined(__linux__)
+#if defined(HAVE_SYS_STAT_H)
+#include <sys/stat.h>
+#endif
+void *FunctionPointers[] = {
+  (void *)(intptr_t) stat,
+  (void *)(intptr_t) fstat,
+  (void *)(intptr_t) lstat,
+  (void *)(intptr_t) stat64,
+  (void *)(intptr_t) fstat64,
+  (void *)(intptr_t) lstat64,
+  (void *)(intptr_t) atexit,
+  (void *)(intptr_t) mknod
+};
+#endif // __linux__
+
+// __mainFunc - If the program does not have a linked in __main function, allow
+// it to run, but print a warning.
+static void __mainFunc() {
+  fprintf(stderr, "WARNING: Program called __main but was not linked to "
+          "libcrtend.a.\nThis probably won't hurt anything unless the "
+          "program is written in C++.\n");
+}
+
+// jit_exit - Used to intercept the "exit" library call.
+static void jit_exit(int Status) {
+  runAtExitHandlers();   // Run atexit handlers...
+  exit(Status);
+}
+
+// jit_atexit - Used to intercept the "atexit" library call.
+static int jit_atexit(void (*Fn)(void)) {
+  AtExitHandlers.push_back(Fn);    // Take note of atexit handler...
+  return 0;  // Always successful
+}
+
+//===----------------------------------------------------------------------===//
+//
+/// getPointerToNamedFunction - This method returns the address of the specified
+/// function by using the dynamic loader interface.  As such it is only useful
+/// for resolving library symbols, not code generated symbols.
+///
+void *JIT::getPointerToNamedFunction(const std::string &Name) {
+  // Check to see if this is one of the functions we want to intercept.  Note,
+  // we cast to intptr_t here to silence a -pedantic warning that complains
+  // about casting a function pointer to a normal pointer.
+  if (Name == "exit") return (void*)(intptr_t)&jit_exit;
+  if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
+
+  // If the program does not have a linked in __main function, allow it to run,
+  // but print a warning.
+  if (Name == "__main") return (void*)(intptr_t)&__mainFunc;
+
+  const char *NameStr = Name.c_str();
+  // If this is an asm specifier, skip the sentinal.
+  if (NameStr[0] == 1) ++NameStr;
+  
+  // If it's an external function, look it up in the process image...
+  void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
+  if (Ptr) return Ptr;
+  
+  // If it wasn't found and if it starts with an underscore ('_') character, and
+  // has an asm specifier, try again without the underscore.
+  if (Name[0] == 1 && NameStr[0] == '_') {
+    Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
+    if (Ptr) return Ptr;
+  }
+
+  cerr << "ERROR: Program used external function '" << Name
+       << "' which could not be resolved!\n";
+  abort();
+  return 0;
+}
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
new file mode 100644
index 0000000..603f8ec
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -0,0 +1,369 @@
+//===-- JIT.cpp - LLVM Just in Time Compiler ------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This tool implements a just-in-time compiler for LLVM, allowing direct
+// execution of LLVM bitcode in an efficient manner.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JIT.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/Instructions.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/Support/MutexGuard.h"
+#include "llvm/System/DynamicLibrary.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetJITInfo.h"
+using namespace llvm;
+
+#ifdef __APPLE__ 
+#include <AvailabilityMacros.h>
+#if defined(MAC_OS_X_VERSION_10_4) && \
+    ((MAC_OS_X_VERSION_MIN_REQUIRED > MAC_OS_X_VERSION_10_4) || \
+     (MAC_OS_X_VERSION_MIN_REQUIRED == MAC_OS_X_VERSION_10_4 && \
+      __APPLE_CC__ >= 5330))
+// __dso_handle is resolved by Mac OS X dynamic linker.
+extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
+#endif
+#endif
+
+static struct RegisterJIT {
+  RegisterJIT() { JIT::Register(); }
+} JITRegistrator;
+
+namespace llvm {
+  void LinkInJIT() {
+  }
+}
+
+JIT::JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji)
+  : ExecutionEngine(MP), TM(tm), TJI(tji), jitstate(MP) {
+  setTargetData(TM.getTargetData());
+
+  // Initialize MCE
+  MCE = createEmitter(*this);
+
+  // Add target data
+  MutexGuard locked(lock);
+  FunctionPassManager &PM = jitstate.getPM(locked);
+  PM.add(new TargetData(*TM.getTargetData()));
+
+  // Turn the machine code intermediate representation into bytes in memory that
+  // may be executed.
+  if (TM.addPassesToEmitMachineCode(PM, *MCE, false /*fast*/)) {
+    cerr << "Target does not support machine code emission!\n";
+    abort();
+  }
+  
+  // Initialize passes.
+  PM.doInitialization();
+}
+
+JIT::~JIT() {
+  delete MCE;
+  delete &TM;
+}
+
+/// run - Start execution with the specified function and arguments.
+///
+GenericValue JIT::runFunction(Function *F,
+                              const std::vector<GenericValue> &ArgValues) {
+  assert(F && "Function *F was null at entry to run()");
+
+  void *FPtr = getPointerToFunction(F);
+  assert(FPtr && "Pointer to fn's code was null after getPointerToFunction");
+  const FunctionType *FTy = F->getFunctionType();
+  const Type *RetTy = FTy->getReturnType();
+
+  assert((FTy->getNumParams() <= ArgValues.size() || FTy->isVarArg()) &&
+         "Too many arguments passed into function!");
+  assert(FTy->getNumParams() == ArgValues.size() &&
+         "This doesn't support passing arguments through varargs (yet)!");
+
+  // Handle some common cases first.  These cases correspond to common `main'
+  // prototypes.
+  if (RetTy == Type::Int32Ty || RetTy == Type::Int32Ty || RetTy == Type::VoidTy) {
+    switch (ArgValues.size()) {
+    case 3:
+      if ((FTy->getParamType(0) == Type::Int32Ty ||
+           FTy->getParamType(0) == Type::Int32Ty) &&
+          isa<PointerType>(FTy->getParamType(1)) &&
+          isa<PointerType>(FTy->getParamType(2))) {
+        int (*PF)(int, char **, const char **) =
+          (int(*)(int, char **, const char **))(intptr_t)FPtr;
+
+        // Call the function.
+        GenericValue rv;
+        rv.IntVal = APInt(32, PF(ArgValues[0].IntVal.getZExtValue(), 
+                                 (char **)GVTOP(ArgValues[1]),
+                                 (const char **)GVTOP(ArgValues[2])));
+        return rv;
+      }
+      break;
+    case 2:
+      if ((FTy->getParamType(0) == Type::Int32Ty ||
+           FTy->getParamType(0) == Type::Int32Ty) &&
+          isa<PointerType>(FTy->getParamType(1))) {
+        int (*PF)(int, char **) = (int(*)(int, char **))(intptr_t)FPtr;
+
+        // Call the function.
+        GenericValue rv;
+        rv.IntVal = APInt(32, PF(ArgValues[0].IntVal.getZExtValue(), 
+                                 (char **)GVTOP(ArgValues[1])));
+        return rv;
+      }
+      break;
+    case 1:
+      if (FTy->getNumParams() == 1 &&
+          (FTy->getParamType(0) == Type::Int32Ty ||
+           FTy->getParamType(0) == Type::Int32Ty)) {
+        GenericValue rv;
+        int (*PF)(int) = (int(*)(int))(intptr_t)FPtr;
+        rv.IntVal = APInt(32, PF(ArgValues[0].IntVal.getZExtValue()));
+        return rv;
+      }
+      break;
+    }
+  }
+
+  // Handle cases where no arguments are passed first.
+  if (ArgValues.empty()) {
+    GenericValue rv;
+    switch (RetTy->getTypeID()) {
+    default: assert(0 && "Unknown return type for function call!");
+    case Type::IntegerTyID: {
+      unsigned BitWidth = cast<IntegerType>(RetTy)->getBitWidth();
+      if (BitWidth == 1)
+        rv.IntVal = APInt(BitWidth, ((bool(*)())(intptr_t)FPtr)());
+      else if (BitWidth <= 8)
+        rv.IntVal = APInt(BitWidth, ((char(*)())(intptr_t)FPtr)());
+      else if (BitWidth <= 16)
+        rv.IntVal = APInt(BitWidth, ((short(*)())(intptr_t)FPtr)());
+      else if (BitWidth <= 32)
+        rv.IntVal = APInt(BitWidth, ((int(*)())(intptr_t)FPtr)());
+      else if (BitWidth <= 64)
+        rv.IntVal = APInt(BitWidth, ((int64_t(*)())(intptr_t)FPtr)());
+      else 
+        assert(0 && "Integer types > 64 bits not supported");
+      return rv;
+    }
+    case Type::VoidTyID:
+      rv.IntVal = APInt(32, ((int(*)())(intptr_t)FPtr)());
+      return rv;
+    case Type::FloatTyID:
+      rv.FloatVal = ((float(*)())(intptr_t)FPtr)();
+      return rv;
+    case Type::DoubleTyID:
+      rv.DoubleVal = ((double(*)())(intptr_t)FPtr)();
+      return rv;
+    case Type::PointerTyID:
+      return PTOGV(((void*(*)())(intptr_t)FPtr)());
+    }
+  }
+
+  // Okay, this is not one of our quick and easy cases.  Because we don't have a
+  // full FFI, we have to codegen a nullary stub function that just calls the
+  // function we are interested in, passing in constants for all of the
+  // arguments.  Make this function and return.
+
+  // First, create the function.
+  FunctionType *STy=FunctionType::get(RetTy, std::vector<const Type*>(), false);
+  Function *Stub = new Function(STy, Function::InternalLinkage, "",
+                                F->getParent());
+
+  // Insert a basic block.
+  BasicBlock *StubBB = new BasicBlock("", Stub);
+
+  // Convert all of the GenericValue arguments over to constants.  Note that we
+  // currently don't support varargs.
+  SmallVector<Value*, 8> Args;
+  for (unsigned i = 0, e = ArgValues.size(); i != e; ++i) {
+    Constant *C = 0;
+    const Type *ArgTy = FTy->getParamType(i);
+    const GenericValue &AV = ArgValues[i];
+    switch (ArgTy->getTypeID()) {
+    default: assert(0 && "Unknown argument type for function call!");
+    case Type::IntegerTyID: C = ConstantInt::get(AV.IntVal); break;
+    case Type::FloatTyID:   C = ConstantFP ::get(ArgTy, AV.FloatVal);  break;
+    case Type::DoubleTyID:  C = ConstantFP ::get(ArgTy, AV.DoubleVal); break;
+    case Type::PointerTyID:
+      void *ArgPtr = GVTOP(AV);
+      if (sizeof(void*) == 4) {
+        C = ConstantInt::get(Type::Int32Ty, (int)(intptr_t)ArgPtr);
+      } else {
+        C = ConstantInt::get(Type::Int64Ty, (intptr_t)ArgPtr);
+      }
+      C = ConstantExpr::getIntToPtr(C, ArgTy);  // Cast the integer to pointer
+      break;
+    }
+    Args.push_back(C);
+  }
+
+  CallInst *TheCall = new CallInst(F, &Args[0], Args.size(), "", StubBB);
+  TheCall->setTailCall();
+  if (TheCall->getType() != Type::VoidTy)
+    new ReturnInst(TheCall, StubBB);             // Return result of the call.
+  else
+    new ReturnInst(StubBB);                      // Just return void.
+
+  // Finally, return the value returned by our nullary stub function.
+  return runFunction(Stub, std::vector<GenericValue>());
+}
+
+/// 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.
+///
+void JIT::runJITOnFunction(Function *F) {
+  static bool isAlreadyCodeGenerating = false;
+  assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
+
+  MutexGuard locked(lock);
+
+  // JIT the function
+  isAlreadyCodeGenerating = true;
+  jitstate.getPM(locked).run(*F);
+  isAlreadyCodeGenerating = false;
+
+  // If the function referred to a global variable that had not yet been
+  // emitted, it allocates memory for the global, but doesn't emit it yet.  Emit
+  // all of these globals now.
+  while (!jitstate.getPendingGlobals(locked).empty()) {
+    const GlobalVariable *GV = jitstate.getPendingGlobals(locked).back();
+    jitstate.getPendingGlobals(locked).pop_back();
+    EmitGlobalVariable(GV);
+  }
+}
+
+/// getPointerToFunction - This method is used to get the address of the
+/// specified function, compiling it if neccesary.
+///
+void *JIT::getPointerToFunction(Function *F) {
+  MutexGuard locked(lock);
+
+  if (void *Addr = getPointerToGlobalIfAvailable(F))
+    return Addr;   // Check if function already code gen'd
+
+  // Make sure we read in the function if it exists in this Module.
+  if (F->hasNotBeenReadFromBitcode()) {
+    // Determine the module provider this function is provided by.
+    Module *M = F->getParent();
+    ModuleProvider *MP = 0;
+    for (unsigned i = 0, e = Modules.size(); i != e; ++i) {
+      if (Modules[i]->getModule() == M) {
+        MP = Modules[i];
+        break;
+      }
+    }
+    assert(MP && "Function isn't in a module we know about!");
+    
+    std::string ErrorMsg;
+    if (MP->materializeFunction(F, &ErrorMsg)) {
+      cerr << "Error reading function '" << F->getName()
+           << "' from bitcode file: " << ErrorMsg << "\n";
+      abort();
+    }
+  }
+
+  if (F->isDeclaration()) {
+    void *Addr = getPointerToNamedFunction(F->getName());
+    addGlobalMapping(F, Addr);
+    return Addr;
+  }
+
+  runJITOnFunction(F);
+
+  void *Addr = getPointerToGlobalIfAvailable(F);
+  assert(Addr && "Code generation didn't add function to GlobalAddress table!");
+  return Addr;
+}
+
+/// getOrEmitGlobalVariable - Return the address of the specified global
+/// variable, possibly emitting it to memory if needed.  This is used by the
+/// Emitter.
+void *JIT::getOrEmitGlobalVariable(const GlobalVariable *GV) {
+  MutexGuard locked(lock);
+
+  void *Ptr = getPointerToGlobalIfAvailable(GV);
+  if (Ptr) return Ptr;
+
+  // If the global is external, just remember the address.
+  if (GV->isDeclaration()) {
+#if defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_4) && \
+    ((MAC_OS_X_VERSION_MIN_REQUIRED > MAC_OS_X_VERSION_10_4) || \
+     (MAC_OS_X_VERSION_MIN_REQUIRED == MAC_OS_X_VERSION_10_4 && \
+      __APPLE_CC__ >= 5330))
+    // Apple gcc defaults to -fuse-cxa-atexit (i.e. calls __cxa_atexit instead
+    // of atexit). It passes the address of linker generated symbol __dso_handle
+    // to the function.
+    // This configuration change happened at version 5330.
+    if (GV->getName() == "__dso_handle")
+      return (void*)&__dso_handle;
+#endif
+    Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(GV->getName().c_str());
+    if (Ptr == 0) {
+      cerr << "Could not resolve external global address: "
+           << GV->getName() << "\n";
+      abort();
+    }
+  } else {
+    // If the global hasn't been emitted to memory yet, allocate space.  We will
+    // actually initialize the global after current function has finished
+    // compilation.
+    const Type *GlobalType = GV->getType()->getElementType();
+    size_t S = getTargetData()->getTypeSize(GlobalType);
+    size_t A = getTargetData()->getPrefTypeAlignment(GlobalType);
+    if (A <= 8) {
+      Ptr = malloc(S);
+    } else {
+      // Allocate S+A bytes of memory, then use an aligned pointer within that
+      // space.
+      Ptr = malloc(S+A);
+      unsigned MisAligned = ((intptr_t)Ptr & (A-1));
+      Ptr = (char*)Ptr + (MisAligned ? (A-MisAligned) : 0);
+    }
+    jitstate.getPendingGlobals(locked).push_back(GV);
+  }
+  addGlobalMapping(GV, Ptr);
+  return Ptr;
+}
+
+
+/// recompileAndRelinkFunction - This method is used to force a function
+/// which has already been compiled, to be compiled again, possibly
+/// after it has been modified. Then the entry to the old copy is overwritten
+/// with a branch to the new copy. If there was no old copy, this acts
+/// just like JIT::getPointerToFunction().
+///
+void *JIT::recompileAndRelinkFunction(Function *F) {
+  void *OldAddr = getPointerToGlobalIfAvailable(F);
+
+  // If it's not already compiled there is no reason to patch it up.
+  if (OldAddr == 0) { return getPointerToFunction(F); }
+
+  // Delete the old function mapping.
+  addGlobalMapping(F, 0);
+
+  // Recodegen the function
+  runJITOnFunction(F);
+
+  // Update state, forward the old function to the new function.
+  void *Addr = getPointerToGlobalIfAvailable(F);
+  assert(Addr && "Code generation didn't add function to GlobalAddress table!");
+  TJI.replaceMachineCodeForFunction(OldAddr, Addr);
+  return Addr;
+}
+
diff --git a/lib/ExecutionEngine/JIT/JIT.h b/lib/ExecutionEngine/JIT/JIT.h
new file mode 100644
index 0000000..5a3d661
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JIT.h
@@ -0,0 +1,130 @@
+//===-- JIT.h - Class definition for the JIT --------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the top-level JIT data structure.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef JIT_H
+#define JIT_H
+
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/PassManager.h"
+#include <map>
+
+namespace llvm {
+
+class Function;
+class GlobalValue;
+class Constant;
+class TargetMachine;
+class TargetJITInfo;
+class MachineCodeEmitter;
+
+class JITState {
+private:
+  FunctionPassManager PM;  // Passes to compile a function
+
+  /// PendingGlobals - Global variables which have had memory allocated for them
+  /// while a function was code generated, but which have not been initialized
+  /// yet.
+  std::vector<const GlobalVariable*> PendingGlobals;
+
+public:
+  JITState(ModuleProvider *MP) : PM(MP) {}
+
+  FunctionPassManager &getPM(const MutexGuard &L) {
+    return PM;
+  }
+
+  std::vector<const GlobalVariable*> &getPendingGlobals(const MutexGuard &L) {
+    return PendingGlobals;
+  }
+};
+
+
+class JIT : public ExecutionEngine {
+  TargetMachine &TM;       // The current target we are compiling to
+  TargetJITInfo &TJI;      // The JITInfo for the target we are compiling to
+  MachineCodeEmitter *MCE; // MCE object
+
+  JITState jitstate;
+
+  JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji);
+public:
+  ~JIT();
+
+  static void Register() {
+    JITCtor = create;
+  }
+  
+  /// getJITInfo - Return the target JIT information structure.
+  ///
+  TargetJITInfo &getJITInfo() const { return TJI; }
+
+  /// create - Create an return a new JIT compiler if there is one available
+  /// for the current target.  Otherwise, return null.
+  ///
+  static ExecutionEngine *create(ModuleProvider *MP, std::string* = 0);
+
+  /// run - Start execution with the specified function and arguments.
+  ///
+  virtual GenericValue runFunction(Function *F,
+                                   const std::vector<GenericValue> &ArgValues);
+
+  /// getPointerToNamedFunction - This method returns the address of the
+  /// specified function by using the dlsym function call.  As such it is only
+  /// useful for resolving library symbols, not code generated symbols.
+  ///
+  void *getPointerToNamedFunction(const std::string &Name);
+
+  // CompilationCallback - Invoked the first time that a call site is found,
+  // which causes lazy compilation of the target function.
+  //
+  static void CompilationCallback();
+
+  /// getPointerToFunction - This returns the address of the specified function,
+  /// compiling it if necessary.
+  ///
+  void *getPointerToFunction(Function *F);
+
+  /// getOrEmitGlobalVariable - Return the address of the specified global
+  /// variable, possibly emitting it to memory if needed.  This is used by the
+  /// Emitter.
+  void *getOrEmitGlobalVariable(const GlobalVariable *GV);
+
+  /// getPointerToFunctionOrStub - If the specified function has been
+  /// code-gen'd, return a pointer to the function.  If not, compile it, or use
+  /// a stub to implement lazy compilation if available.
+  ///
+  void *getPointerToFunctionOrStub(Function *F);
+
+  /// recompileAndRelinkFunction - This method is used to force a function
+  /// which has already been compiled, to be compiled again, possibly
+  /// after it has been modified. Then the entry to the old copy is overwritten
+  /// with a branch to the new copy. If there was no old copy, this acts
+  /// just like JIT::getPointerToFunction().
+  ///
+  void *recompileAndRelinkFunction(Function *F);
+
+  /// freeMachineCodeForFunction - deallocate memory used to code-generate this
+  /// Function.
+  ///
+  void freeMachineCodeForFunction(Function *F);
+
+  /// getCodeEmitter - Return the code emitter this JIT is emitting into.
+  MachineCodeEmitter *getCodeEmitter() const { return MCE; }
+private:
+  static MachineCodeEmitter *createEmitter(JIT &J);
+  void runJITOnFunction (Function *F);
+};
+
+} // End llvm namespace
+
+#endif
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
new file mode 100644
index 0000000..484af48
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -0,0 +1,1067 @@
+//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a MachineCodeEmitter object that is used by the JIT to
+// write machine code to memory and remember where relocatable values are.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "jit"
+#include "JIT.h"
+#include "llvm/Constant.h"
+#include "llvm/Module.h"
+#include "llvm/Type.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/MachineRelocation.h"
+#include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetJITInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MutexGuard.h"
+#include "llvm/System/Disassembler.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/System/Memory.h"
+#include <algorithm>
+using namespace llvm;
+
+STATISTIC(NumBytes, "Number of bytes of machine code compiled");
+STATISTIC(NumRelos, "Number of relocations applied");
+static JIT *TheJIT = 0;
+
+//===----------------------------------------------------------------------===//
+// JITMemoryManager code.
+//
+namespace {
+  /// MemoryRangeHeader - For a range of memory, this is the header that we put
+  /// on the block of memory.  It is carefully crafted to be one word of memory.
+  /// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
+  /// which starts with this.
+  struct FreeRangeHeader;
+  struct MemoryRangeHeader {
+    /// ThisAllocated - This is true if this block is currently allocated.  If
+    /// not, this can be converted to a FreeRangeHeader.
+    intptr_t ThisAllocated : 1;
+    
+    /// PrevAllocated - Keep track of whether the block immediately before us is
+    /// allocated.  If not, the word immediately before this header is the size
+    /// of the previous block.
+    intptr_t PrevAllocated : 1;
+    
+    /// BlockSize - This is the size in bytes of this memory block,
+    /// including this header.
+    uintptr_t BlockSize : (sizeof(intptr_t)*8 - 2);
+    
+
+    /// getBlockAfter - Return the memory block immediately after this one.
+    ///
+    MemoryRangeHeader &getBlockAfter() const {
+      return *(MemoryRangeHeader*)((char*)this+BlockSize);
+    }
+    
+    /// getFreeBlockBefore - If the block before this one is free, return it,
+    /// otherwise return null.
+    FreeRangeHeader *getFreeBlockBefore() const {
+      if (PrevAllocated) return 0;
+      intptr_t PrevSize = ((intptr_t *)this)[-1];
+      return (FreeRangeHeader*)((char*)this-PrevSize);
+    }
+    
+    /// FreeBlock - Turn an allocated block into a free block, adjusting
+    /// bits in the object headers, and adding an end of region memory block.
+    FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
+    
+    /// TrimAllocationToSize - If this allocated block is significantly larger
+    /// than NewSize, split it into two pieces (where the former is NewSize
+    /// bytes, including the header), and add the new block to the free list.
+    FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList, 
+                                          uint64_t NewSize);
+  };
+
+  /// FreeRangeHeader - For a memory block that isn't already allocated, this
+  /// keeps track of the current block and has a pointer to the next free block.
+  /// Free blocks are kept on a circularly linked list.
+  struct FreeRangeHeader : public MemoryRangeHeader {
+    FreeRangeHeader *Prev;
+    FreeRangeHeader *Next;
+    
+    /// getMinBlockSize - Get the minimum size for a memory block.  Blocks
+    /// smaller than this size cannot be created.
+    static unsigned getMinBlockSize() {
+      return sizeof(FreeRangeHeader)+sizeof(intptr_t);
+    }
+    
+    /// SetEndOfBlockSizeMarker - The word at the end of every free block is
+    /// known to be the size of the free block.  Set it for this block.
+    void SetEndOfBlockSizeMarker() {
+      void *EndOfBlock = (char*)this + BlockSize;
+      ((intptr_t *)EndOfBlock)[-1] = BlockSize;
+    }
+
+    FreeRangeHeader *RemoveFromFreeList() {
+      assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
+      Next->Prev = Prev;
+      return Prev->Next = Next;
+    }
+    
+    void AddToFreeList(FreeRangeHeader *FreeList) {
+      Next = FreeList;
+      Prev = FreeList->Prev;
+      Prev->Next = this;
+      Next->Prev = this;
+    }
+
+    /// GrowBlock - The block after this block just got deallocated.  Merge it
+    /// into the current block.
+    void GrowBlock(uintptr_t NewSize);
+    
+    /// AllocateBlock - Mark this entire block allocated, updating freelists
+    /// etc.  This returns a pointer to the circular free-list.
+    FreeRangeHeader *AllocateBlock();
+  };
+}
+
+
+/// AllocateBlock - Mark this entire block allocated, updating freelists
+/// etc.  This returns a pointer to the circular free-list.
+FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
+  assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
+         "Cannot allocate an allocated block!");
+  // Mark this block allocated.
+  ThisAllocated = 1;
+  getBlockAfter().PrevAllocated = 1;
+ 
+  // Remove it from the free list.
+  return RemoveFromFreeList();
+}
+
+/// FreeBlock - Turn an allocated block into a free block, adjusting
+/// bits in the object headers, and adding an end of region memory block.
+/// If possible, coalesce this block with neighboring blocks.  Return the
+/// FreeRangeHeader to allocate from.
+FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
+  MemoryRangeHeader *FollowingBlock = &getBlockAfter();
+  assert(ThisAllocated && "This block is already allocated!");
+  assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
+  
+  FreeRangeHeader *FreeListToReturn = FreeList;
+  
+  // If the block after this one is free, merge it into this block.
+  if (!FollowingBlock->ThisAllocated) {
+    FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
+    // "FreeList" always needs to be a valid free block.  If we're about to
+    // coalesce with it, update our notion of what the free list is.
+    if (&FollowingFreeBlock == FreeList) {
+      FreeList = FollowingFreeBlock.Next;
+      FreeListToReturn = 0;
+      assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
+    }
+    FollowingFreeBlock.RemoveFromFreeList();
+    
+    // Include the following block into this one.
+    BlockSize += FollowingFreeBlock.BlockSize;
+    FollowingBlock = &FollowingFreeBlock.getBlockAfter();
+    
+    // Tell the block after the block we are coalescing that this block is
+    // allocated.
+    FollowingBlock->PrevAllocated = 1;
+  }
+  
+  assert(FollowingBlock->ThisAllocated && "Missed coalescing?");
+  
+  if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
+    PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
+    return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
+  }
+
+  // Otherwise, mark this block free.
+  FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
+  FollowingBlock->PrevAllocated = 0;
+  FreeBlock.ThisAllocated = 0;
+
+  // Link this into the linked list of free blocks.
+  FreeBlock.AddToFreeList(FreeList);
+
+  // Add a marker at the end of the block, indicating the size of this free
+  // block.
+  FreeBlock.SetEndOfBlockSizeMarker();
+  return FreeListToReturn ? FreeListToReturn : &FreeBlock;
+}
+
+/// GrowBlock - The block after this block just got deallocated.  Merge it
+/// into the current block.
+void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
+  assert(NewSize > BlockSize && "Not growing block?");
+  BlockSize = NewSize;
+  SetEndOfBlockSizeMarker();
+  getBlockAfter().PrevAllocated = 0;
+}
+
+/// TrimAllocationToSize - If this allocated block is significantly larger
+/// than NewSize, split it into two pieces (where the former is NewSize
+/// bytes, including the header), and add the new block to the free list.
+FreeRangeHeader *MemoryRangeHeader::
+TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
+  assert(ThisAllocated && getBlockAfter().PrevAllocated &&
+         "Cannot deallocate part of an allocated block!");
+
+  // Round up size for alignment of header.
+  unsigned HeaderAlign = __alignof(FreeRangeHeader);
+  NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
+  
+  // Size is now the size of the block we will remove from the start of the
+  // current block.
+  assert(NewSize <= BlockSize &&
+         "Allocating more space from this block than exists!");
+  
+  // If splitting this block will cause the remainder to be too small, do not
+  // split the block.
+  if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
+    return FreeList;
+  
+  // Otherwise, we splice the required number of bytes out of this block, form
+  // a new block immediately after it, then mark this block allocated.
+  MemoryRangeHeader &FormerNextBlock = getBlockAfter();
+  
+  // Change the size of this block.
+  BlockSize = NewSize;
+  
+  // Get the new block we just sliced out and turn it into a free block.
+  FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
+  NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
+  NewNextBlock.ThisAllocated = 0;
+  NewNextBlock.PrevAllocated = 1;
+  NewNextBlock.SetEndOfBlockSizeMarker();
+  FormerNextBlock.PrevAllocated = 0;
+  NewNextBlock.AddToFreeList(FreeList);
+  return &NewNextBlock;
+}
+
+ 
+namespace {  
+  /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
+  /// sane way.  This splits a large block of MAP_NORESERVE'd memory into two
+  /// sections, one for function stubs, one for the functions themselves.  We
+  /// have to do this because we may need to emit a function stub while in the
+  /// middle of emitting a function, and we don't know how large the function we
+  /// are emitting is.  This never bothers to release the memory, because when
+  /// we are ready to destroy the JIT, the program exits.
+  class JITMemoryManager {
+    std::vector<sys::MemoryBlock> Blocks; // Memory blocks allocated by the JIT
+    FreeRangeHeader *FreeMemoryList;      // Circular list of free blocks.
+    
+    // When emitting code into a memory block, this is the block.
+    MemoryRangeHeader *CurBlock;
+    
+    unsigned char *CurStubPtr, *StubBase;
+    unsigned char *GOTBase;      // Target Specific reserved memory
+
+    // Centralize memory block allocation.
+    sys::MemoryBlock getNewMemoryBlock(unsigned size);
+    
+    std::map<const Function*, MemoryRangeHeader*> FunctionBlocks;
+  public:
+    JITMemoryManager(bool useGOT);
+    ~JITMemoryManager();
+
+    inline unsigned char *allocateStub(unsigned StubSize, unsigned Alignment);
+    
+    /// startFunctionBody - When a function starts, allocate a block of free
+    /// executable memory, returning a pointer to it and its actual size.
+    unsigned char *startFunctionBody(uintptr_t &ActualSize) {
+      CurBlock = FreeMemoryList;
+      
+      // Allocate the entire memory block.
+      FreeMemoryList = FreeMemoryList->AllocateBlock();
+      ActualSize = CurBlock->BlockSize-sizeof(MemoryRangeHeader);
+      return (unsigned char *)(CurBlock+1);
+    }
+    
+    /// endFunctionBody - The function F is now allocated, and takes the memory
+    /// in the range [FunctionStart,FunctionEnd).
+    void endFunctionBody(const Function *F, unsigned char *FunctionStart,
+                         unsigned char *FunctionEnd) {
+      assert(FunctionEnd > FunctionStart);
+      assert(FunctionStart == (unsigned char *)(CurBlock+1) &&
+             "Mismatched function start/end!");
+      
+      uintptr_t BlockSize = FunctionEnd - (unsigned char *)CurBlock;
+      FunctionBlocks[F] = CurBlock;
+
+      // Release the memory at the end of this block that isn't needed.
+      FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
+    }
+    
+    unsigned char *getGOTBase() const {
+      return GOTBase;
+    }
+    bool isManagingGOT() const {
+      return GOTBase != NULL;
+    }
+    
+    /// deallocateMemForFunction - Deallocate all memory for the specified
+    /// function body.
+    void deallocateMemForFunction(const Function *F) {
+      std::map<const Function*, MemoryRangeHeader*>::iterator
+        I = FunctionBlocks.find(F);
+      if (I == FunctionBlocks.end()) return;
+      
+      // Find the block that is allocated for this function.
+      MemoryRangeHeader *MemRange = I->second;
+      assert(MemRange->ThisAllocated && "Block isn't allocated!");
+      
+      // Fill the buffer with garbage!
+      DEBUG(memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange)));
+      
+      // Free the memory.
+      FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
+      
+      // Finally, remove this entry from FunctionBlocks.
+      FunctionBlocks.erase(I);
+    }
+  };
+}
+
+JITMemoryManager::JITMemoryManager(bool useGOT) {
+  // Allocate a 16M block of memory for functions.
+  sys::MemoryBlock MemBlock = getNewMemoryBlock(16 << 20);
+
+  unsigned char *MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
+
+  // Allocate stubs backwards from the base, allocate functions forward
+  // from the base.
+  StubBase   = MemBase;
+  CurStubPtr = MemBase + 512*1024; // Use 512k for stubs, working backwards.
+  
+  // We set up the memory chunk with 4 mem regions, like this:
+  //  [ START
+  //    [ Free      #0 ] -> Large space to allocate functions from.
+  //    [ Allocated #1 ] -> Tiny space to separate regions.
+  //    [ Free      #2 ] -> Tiny space so there is always at least 1 free block.
+  //    [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
+  //  END ]
+  //
+  // The last three blocks are never deallocated or touched.
+  
+  // Add MemoryRangeHeader to the end of the memory region, indicating that
+  // the space after the block of memory is allocated.  This is block #3.
+  MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
+  Mem3->ThisAllocated = 1;
+  Mem3->PrevAllocated = 0;
+  Mem3->BlockSize     = 0;
+  
+  /// Add a tiny free region so that the free list always has one entry.
+  FreeRangeHeader *Mem2 = 
+    (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
+  Mem2->ThisAllocated = 0;
+  Mem2->PrevAllocated = 1;
+  Mem2->BlockSize     = FreeRangeHeader::getMinBlockSize();
+  Mem2->SetEndOfBlockSizeMarker();
+  Mem2->Prev = Mem2;   // Mem2 *is* the free list for now.
+  Mem2->Next = Mem2;
+
+  /// Add a tiny allocated region so that Mem2 is never coalesced away.
+  MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
+  Mem1->ThisAllocated = 1;
+  Mem1->PrevAllocated = 0;
+  Mem1->BlockSize     = (char*)Mem2 - (char*)Mem1;
+  
+  // Add a FreeRangeHeader to the start of the function body region, indicating
+  // that the space is free.  Mark the previous block allocated so we never look
+  // at it.
+  FreeRangeHeader *Mem0 = (FreeRangeHeader*)CurStubPtr;
+  Mem0->ThisAllocated = 0;
+  Mem0->PrevAllocated = 1;
+  Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
+  Mem0->SetEndOfBlockSizeMarker();
+  Mem0->AddToFreeList(Mem2);
+  
+  // Start out with the freelist pointing to Mem0.
+  FreeMemoryList = Mem0;
+
+  // Allocate the GOT.
+  GOTBase = NULL;
+  if (useGOT) GOTBase = new unsigned char[sizeof(void*) * 8192];
+}
+
+JITMemoryManager::~JITMemoryManager() {
+  for (unsigned i = 0, e = Blocks.size(); i != e; ++i)
+    sys::Memory::ReleaseRWX(Blocks[i]);
+  
+  delete[] GOTBase;
+  Blocks.clear();
+}
+
+unsigned char *JITMemoryManager::allocateStub(unsigned StubSize,
+                                              unsigned Alignment) {
+  CurStubPtr -= StubSize;
+  CurStubPtr = (unsigned char*)(((intptr_t)CurStubPtr) &
+                                ~(intptr_t)(Alignment-1));
+  if (CurStubPtr < StubBase) {
+    // FIXME: allocate a new block
+    cerr << "JIT ran out of memory for function stubs!\n";
+    abort();
+  }
+  return CurStubPtr;
+}
+
+sys::MemoryBlock JITMemoryManager::getNewMemoryBlock(unsigned size) {
+  // Allocate a new block close to the last one.
+  const sys::MemoryBlock *BOld = Blocks.empty() ? 0 : &Blocks.front();
+  std::string ErrMsg;
+  sys::MemoryBlock B = sys::Memory::AllocateRWX(size, BOld, &ErrMsg);
+  if (B.base() == 0) {
+    cerr << "Allocation failed when allocating new memory in the JIT\n";
+    cerr << ErrMsg << "\n";
+    abort();
+  }
+  Blocks.push_back(B);
+  return B;
+}
+
+//===----------------------------------------------------------------------===//
+// JIT lazy compilation code.
+//
+namespace {
+  class JITResolverState {
+  private:
+    /// FunctionToStubMap - Keep track of the stub created for a particular
+    /// function so that we can reuse them if necessary.
+    std::map<Function*, void*> FunctionToStubMap;
+
+    /// StubToFunctionMap - Keep track of the function that each stub
+    /// corresponds to.
+    std::map<void*, Function*> StubToFunctionMap;
+
+  public:
+    std::map<Function*, void*>& getFunctionToStubMap(const MutexGuard& locked) {
+      assert(locked.holds(TheJIT->lock));
+      return FunctionToStubMap;
+    }
+
+    std::map<void*, Function*>& getStubToFunctionMap(const MutexGuard& locked) {
+      assert(locked.holds(TheJIT->lock));
+      return StubToFunctionMap;
+    }
+  };
+
+  /// JITResolver - Keep track of, and resolve, call sites for functions that
+  /// have not yet been compiled.
+  class JITResolver {
+    /// LazyResolverFn - The target lazy resolver function that we actually
+    /// rewrite instructions to use.
+    TargetJITInfo::LazyResolverFn LazyResolverFn;
+
+    JITResolverState state;
+
+    /// ExternalFnToStubMap - This is the equivalent of FunctionToStubMap for
+    /// external functions.
+    std::map<void*, void*> ExternalFnToStubMap;
+
+    //map addresses to indexes in the GOT
+    std::map<void*, unsigned> revGOTMap;
+    unsigned nextGOTIndex;
+
+    static JITResolver *TheJITResolver;
+  public:
+    JITResolver(JIT &jit) : nextGOTIndex(0) {
+      TheJIT = &jit;
+
+      LazyResolverFn = jit.getJITInfo().getLazyResolverFunction(JITCompilerFn);
+      assert(TheJITResolver == 0 && "Multiple JIT resolvers?");
+      TheJITResolver = this;
+    }
+    
+    ~JITResolver() {
+      TheJITResolver = 0;
+    }
+
+    /// getFunctionStub - This returns a pointer to a function stub, creating
+    /// one on demand as needed.
+    void *getFunctionStub(Function *F);
+
+    /// getExternalFunctionStub - Return a stub for the function at the
+    /// specified address, created lazily on demand.
+    void *getExternalFunctionStub(void *FnAddr);
+
+    /// AddCallbackAtLocation - If the target is capable of rewriting an
+    /// instruction without the use of a stub, record the location of the use so
+    /// we know which function is being used at the location.
+    void *AddCallbackAtLocation(Function *F, void *Location) {
+      MutexGuard locked(TheJIT->lock);
+      /// Get the target-specific JIT resolver function.
+      state.getStubToFunctionMap(locked)[Location] = F;
+      return (void*)(intptr_t)LazyResolverFn;
+    }
+
+    /// getGOTIndexForAddress - Return a new or existing index in the GOT for
+    /// and address.  This function only manages slots, it does not manage the
+    /// contents of the slots or the memory associated with the GOT.
+    unsigned getGOTIndexForAddr(void* addr);
+
+    /// JITCompilerFn - This function is called to resolve a stub to a compiled
+    /// address.  If the LLVM Function corresponding to the stub has not yet
+    /// been compiled, this function compiles it first.
+    static void *JITCompilerFn(void *Stub);
+  };
+}
+
+JITResolver *JITResolver::TheJITResolver = 0;
+
+#if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
+    defined(__APPLE__)
+extern "C" void sys_icache_invalidate(const void *Addr, size_t len);
+#endif
+
+/// synchronizeICache - On some targets, the JIT emitted code must be
+/// explicitly refetched to ensure correct execution.
+static void synchronizeICache(const void *Addr, size_t len) {
+#if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
+    defined(__APPLE__)
+  sys_icache_invalidate(Addr, len);
+#endif
+}
+
+/// getFunctionStub - This returns a pointer to a function stub, creating
+/// one on demand as needed.
+void *JITResolver::getFunctionStub(Function *F) {
+  MutexGuard locked(TheJIT->lock);
+
+  // If we already have a stub for this function, recycle it.
+  void *&Stub = state.getFunctionToStubMap(locked)[F];
+  if (Stub) return Stub;
+
+  // Call the lazy resolver function unless we already KNOW it is an external
+  // function, in which case we just skip the lazy resolution step.
+  void *Actual = (void*)(intptr_t)LazyResolverFn;
+  if (F->isDeclaration() && !F->hasNotBeenReadFromBitcode())
+    Actual = TheJIT->getPointerToFunction(F);
+
+  // Otherwise, codegen a new stub.  For now, the stub will call the lazy
+  // resolver function.
+  Stub = TheJIT->getJITInfo().emitFunctionStub(Actual,
+                                               *TheJIT->getCodeEmitter());
+
+  if (Actual != (void*)(intptr_t)LazyResolverFn) {
+    // If we are getting the stub for an external function, we really want the
+    // address of the stub in the GlobalAddressMap for the JIT, not the address
+    // of the external function.
+    TheJIT->updateGlobalMapping(F, Stub);
+  }
+
+  // Invalidate the icache if necessary.
+  synchronizeICache(Stub, TheJIT->getCodeEmitter()->getCurrentPCValue() -
+                          (intptr_t)Stub);
+
+  DOUT << "JIT: Stub emitted at [" << Stub << "] for function '"
+       << F->getName() << "'\n";
+
+  // Finally, keep track of the stub-to-Function mapping so that the
+  // JITCompilerFn knows which function to compile!
+  state.getStubToFunctionMap(locked)[Stub] = F;
+  return Stub;
+}
+
+/// getExternalFunctionStub - Return a stub for the function at the
+/// specified address, created lazily on demand.
+void *JITResolver::getExternalFunctionStub(void *FnAddr) {
+  // If we already have a stub for this function, recycle it.
+  void *&Stub = ExternalFnToStubMap[FnAddr];
+  if (Stub) return Stub;
+
+  Stub = TheJIT->getJITInfo().emitFunctionStub(FnAddr,
+                                               *TheJIT->getCodeEmitter());
+
+  // Invalidate the icache if necessary.
+  synchronizeICache(Stub, TheJIT->getCodeEmitter()->getCurrentPCValue() -
+                    (intptr_t)Stub);
+
+  DOUT << "JIT: Stub emitted at [" << Stub
+       << "] for external function at '" << FnAddr << "'\n";
+  return Stub;
+}
+
+unsigned JITResolver::getGOTIndexForAddr(void* addr) {
+  unsigned idx = revGOTMap[addr];
+  if (!idx) {
+    idx = ++nextGOTIndex;
+    revGOTMap[addr] = idx;
+    DOUT << "Adding GOT entry " << idx
+         << " for addr " << addr << "\n";
+    //    ((void**)MemMgr.getGOTBase())[idx] = addr;
+  }
+  return idx;
+}
+
+/// JITCompilerFn - This function is called when a lazy compilation stub has
+/// been entered.  It looks up which function this stub corresponds to, compiles
+/// it if necessary, then returns the resultant function pointer.
+void *JITResolver::JITCompilerFn(void *Stub) {
+  JITResolver &JR = *TheJITResolver;
+
+  MutexGuard locked(TheJIT->lock);
+
+  // The address given to us for the stub may not be exactly right, it might be
+  // a little bit after the stub.  As such, use upper_bound to find it.
+  std::map<void*, Function*>::iterator I =
+    JR.state.getStubToFunctionMap(locked).upper_bound(Stub);
+  assert(I != JR.state.getStubToFunctionMap(locked).begin() &&
+         "This is not a known stub!");
+  Function *F = (--I)->second;
+
+  // If we have already code generated the function, just return the address.
+  void *Result = TheJIT->getPointerToGlobalIfAvailable(F);
+  
+  if (!Result) {
+    // Otherwise we don't have it, do lazy compilation now.
+    
+    // If lazy compilation is disabled, emit a useful error message and abort.
+    if (TheJIT->isLazyCompilationDisabled()) {
+      cerr << "LLVM JIT requested to do lazy compilation of function '"
+      << F->getName() << "' when lazy compiles are disabled!\n";
+      abort();
+    }
+  
+    // We might like to remove the stub from the StubToFunction map.
+    // We can't do that! Multiple threads could be stuck, waiting to acquire the
+    // lock above. As soon as the 1st function finishes compiling the function,
+    // the next one will be released, and needs to be able to find the function
+    // it needs to call.
+    //JR.state.getStubToFunctionMap(locked).erase(I);
+
+    DOUT << "JIT: Lazily resolving function '" << F->getName()
+         << "' In stub ptr = " << Stub << " actual ptr = "
+         << I->first << "\n";
+
+    Result = TheJIT->getPointerToFunction(F);
+  }
+
+  // We don't need to reuse this stub in the future, as F is now compiled.
+  JR.state.getFunctionToStubMap(locked).erase(F);
+
+  // FIXME: We could rewrite all references to this stub if we knew them.
+
+  // What we will do is set the compiled function address to map to the
+  // same GOT entry as the stub so that later clients may update the GOT
+  // if they see it still using the stub address.
+  // Note: this is done so the Resolver doesn't have to manage GOT memory
+  // Do this without allocating map space if the target isn't using a GOT
+  if(JR.revGOTMap.find(Stub) != JR.revGOTMap.end())
+    JR.revGOTMap[Result] = JR.revGOTMap[Stub];
+
+  return Result;
+}
+
+
+//===----------------------------------------------------------------------===//
+// JITEmitter code.
+//
+namespace {
+  /// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
+  /// used to output functions to memory for execution.
+  class JITEmitter : public MachineCodeEmitter {
+    JITMemoryManager MemMgr;
+
+    // When outputting a function stub in the context of some other function, we
+    // save BufferBegin/BufferEnd/CurBufferPtr here.
+    unsigned char *SavedBufferBegin, *SavedBufferEnd, *SavedCurBufferPtr;
+
+    /// Relocations - These are the relocations that the function needs, as
+    /// emitted.
+    std::vector<MachineRelocation> Relocations;
+    
+    /// MBBLocations - This vector is a mapping from MBB ID's to their address.
+    /// It is filled in by the StartMachineBasicBlock callback and queried by
+    /// the getMachineBasicBlockAddress callback.
+    std::vector<intptr_t> MBBLocations;
+
+    /// ConstantPool - The constant pool for the current function.
+    ///
+    MachineConstantPool *ConstantPool;
+
+    /// ConstantPoolBase - A pointer to the first entry in the constant pool.
+    ///
+    void *ConstantPoolBase;
+
+    /// JumpTable - The jump tables for the current function.
+    ///
+    MachineJumpTableInfo *JumpTable;
+    
+    /// JumpTableBase - A pointer to the first entry in the jump table.
+    ///
+    void *JumpTableBase;
+    
+    /// Resolver - This contains info about the currently resolved functions.
+    JITResolver Resolver;
+  public:
+    JITEmitter(JIT &jit)
+       : MemMgr(jit.getJITInfo().needsGOT()), Resolver(jit) {
+      if (MemMgr.isManagingGOT()) DOUT << "JIT is managing a GOT\n";
+    }
+    
+    JITResolver &getJITResolver() { return Resolver; }
+
+    virtual void startFunction(MachineFunction &F);
+    virtual bool finishFunction(MachineFunction &F);
+    
+    void emitConstantPool(MachineConstantPool *MCP);
+    void initJumpTableInfo(MachineJumpTableInfo *MJTI);
+    void emitJumpTableInfo(MachineJumpTableInfo *MJTI);
+    
+    virtual void startFunctionStub(unsigned StubSize, unsigned Alignment = 1);
+    virtual void* finishFunctionStub(const Function *F);
+
+    virtual void addRelocation(const MachineRelocation &MR) {
+      Relocations.push_back(MR);
+    }
+    
+    virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
+      if (MBBLocations.size() <= (unsigned)MBB->getNumber())
+        MBBLocations.resize((MBB->getNumber()+1)*2);
+      MBBLocations[MBB->getNumber()] = getCurrentPCValue();
+    }
+
+    virtual intptr_t getConstantPoolEntryAddress(unsigned Entry) const;
+    virtual intptr_t getJumpTableEntryAddress(unsigned Entry) const;
+    
+    virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
+      assert(MBBLocations.size() > (unsigned)MBB->getNumber() && 
+             MBBLocations[MBB->getNumber()] && "MBB not emitted!");
+      return MBBLocations[MBB->getNumber()];
+    }
+
+    /// deallocateMemForFunction - Deallocate all memory for the specified
+    /// function body.
+    void deallocateMemForFunction(Function *F) {
+      MemMgr.deallocateMemForFunction(F);
+    }
+  private:
+    void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
+  };
+}
+
+void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
+                                     bool DoesntNeedStub) {
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
+    /// FIXME: If we straightened things out, this could actually emit the
+    /// global immediately instead of queuing it for codegen later!
+    return TheJIT->getOrEmitGlobalVariable(GV);
+  }
+
+  // If we have already compiled the function, return a pointer to its body.
+  Function *F = cast<Function>(V);
+  void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
+  if (ResultPtr) return ResultPtr;
+
+  if (F->isDeclaration() && !F->hasNotBeenReadFromBitcode()) {
+    // If this is an external function pointer, we can force the JIT to
+    // 'compile' it, which really just adds it to the map.
+    if (DoesntNeedStub)
+      return TheJIT->getPointerToFunction(F);
+
+    return Resolver.getFunctionStub(F);
+  }
+
+  // Okay, the function has not been compiled yet, if the target callback
+  // mechanism is capable of rewriting the instruction directly, prefer to do
+  // that instead of emitting a stub.
+  if (DoesntNeedStub)
+    return Resolver.AddCallbackAtLocation(F, Reference);
+
+  // Otherwise, we have to emit a lazy resolving stub.
+  return Resolver.getFunctionStub(F);
+}
+
+void JITEmitter::startFunction(MachineFunction &F) {
+  uintptr_t ActualSize;
+  BufferBegin = CurBufferPtr = MemMgr.startFunctionBody(ActualSize);
+  BufferEnd = BufferBegin+ActualSize;
+  
+  // Ensure the constant pool/jump table info is at least 4-byte aligned.
+  emitAlignment(16);
+
+  emitConstantPool(F.getConstantPool());
+  initJumpTableInfo(F.getJumpTableInfo());
+
+  // About to start emitting the machine code for the function.
+  emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));
+  TheJIT->updateGlobalMapping(F.getFunction(), CurBufferPtr);
+
+  MBBLocations.clear();
+}
+
+bool JITEmitter::finishFunction(MachineFunction &F) {
+  if (CurBufferPtr == BufferEnd) {
+    // FIXME: Allocate more space, then try again.
+    cerr << "JIT: Ran out of space for generated machine code!\n";
+    abort();
+  }
+  
+  emitJumpTableInfo(F.getJumpTableInfo());
+  
+  // FnStart is the start of the text, not the start of the constant pool and
+  // other per-function data.
+  unsigned char *FnStart =
+    (unsigned char *)TheJIT->getPointerToGlobalIfAvailable(F.getFunction());
+  unsigned char *FnEnd   = CurBufferPtr;
+  
+  MemMgr.endFunctionBody(F.getFunction(), BufferBegin, FnEnd);
+  NumBytes += FnEnd-FnStart;
+
+  if (!Relocations.empty()) {
+    NumRelos += Relocations.size();
+
+    // Resolve the relocations to concrete pointers.
+    for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
+      MachineRelocation &MR = Relocations[i];
+      void *ResultPtr;
+      if (MR.isString()) {
+        ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
+
+        // If the target REALLY wants a stub for this function, emit it now.
+        if (!MR.doesntNeedFunctionStub())
+          ResultPtr = Resolver.getExternalFunctionStub(ResultPtr);
+      } else if (MR.isGlobalValue()) {
+        ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
+                                       BufferBegin+MR.getMachineCodeOffset(),
+                                       MR.doesntNeedFunctionStub());
+      } else if (MR.isBasicBlock()) {
+        ResultPtr = (void*)getMachineBasicBlockAddress(MR.getBasicBlock());
+      } else if (MR.isConstantPoolIndex()) {
+        ResultPtr=(void*)getConstantPoolEntryAddress(MR.getConstantPoolIndex());
+      } else {
+        assert(MR.isJumpTableIndex());
+        ResultPtr=(void*)getJumpTableEntryAddress(MR.getJumpTableIndex());
+      }
+
+      MR.setResultPointer(ResultPtr);
+
+      // if we are managing the GOT and the relocation wants an index,
+      // give it one
+      if (MemMgr.isManagingGOT() && MR.isGOTRelative()) {
+        unsigned idx = Resolver.getGOTIndexForAddr(ResultPtr);
+        MR.setGOTIndex(idx);
+        if (((void**)MemMgr.getGOTBase())[idx] != ResultPtr) {
+          DOUT << "GOT was out of date for " << ResultPtr
+               << " pointing at " << ((void**)MemMgr.getGOTBase())[idx]
+               << "\n";
+          ((void**)MemMgr.getGOTBase())[idx] = ResultPtr;
+        }
+      }
+    }
+
+    TheJIT->getJITInfo().relocate(BufferBegin, &Relocations[0],
+                                  Relocations.size(), MemMgr.getGOTBase());
+  }
+
+  // Update the GOT entry for F to point to the new code.
+  if (MemMgr.isManagingGOT()) {
+    unsigned idx = Resolver.getGOTIndexForAddr((void*)BufferBegin);
+    if (((void**)MemMgr.getGOTBase())[idx] != (void*)BufferBegin) {
+      DOUT << "GOT was out of date for " << (void*)BufferBegin
+           << " pointing at " << ((void**)MemMgr.getGOTBase())[idx] << "\n";
+      ((void**)MemMgr.getGOTBase())[idx] = (void*)BufferBegin;
+    }
+  }
+
+  // Invalidate the icache if necessary.
+  synchronizeICache(FnStart, FnEnd-FnStart);
+
+  DOUT << "JIT: Finished CodeGen of [" << (void*)FnStart
+       << "] Function: " << F.getFunction()->getName()
+       << ": " << (FnEnd-FnStart) << " bytes of text, "
+       << Relocations.size() << " relocations\n";
+  Relocations.clear();
+
+#ifndef NDEBUG
+  if (sys::hasDisassembler())
+    DOUT << "Disassembled code:\n"
+         << sys::disassembleBuffer(FnStart, FnEnd-FnStart, (uintptr_t)FnStart);
+#endif
+  
+  return false;
+}
+
+void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
+  const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
+  if (Constants.empty()) return;
+
+  MachineConstantPoolEntry CPE = Constants.back();
+  unsigned Size = CPE.Offset;
+  const Type *Ty = CPE.isMachineConstantPoolEntry()
+    ? CPE.Val.MachineCPVal->getType() : CPE.Val.ConstVal->getType();
+  Size += TheJIT->getTargetData()->getTypeSize(Ty);
+
+  ConstantPoolBase = allocateSpace(Size, 1 << MCP->getConstantPoolAlignment());
+  ConstantPool = MCP;
+
+  if (ConstantPoolBase == 0) return;  // Buffer overflow.
+
+  // Initialize the memory for all of the constant pool entries.
+  for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
+    void *CAddr = (char*)ConstantPoolBase+Constants[i].Offset;
+    if (Constants[i].isMachineConstantPoolEntry()) {
+      // FIXME: add support to lower machine constant pool values into bytes!
+      cerr << "Initialize memory with machine specific constant pool entry"
+           << " has not been implemented!\n";
+      abort();
+    }
+    TheJIT->InitializeMemory(Constants[i].Val.ConstVal, CAddr);
+  }
+}
+
+void JITEmitter::initJumpTableInfo(MachineJumpTableInfo *MJTI) {
+  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+  if (JT.empty()) return;
+  
+  unsigned NumEntries = 0;
+  for (unsigned i = 0, e = JT.size(); i != e; ++i)
+    NumEntries += JT[i].MBBs.size();
+
+  unsigned EntrySize = MJTI->getEntrySize();
+
+  // Just allocate space for all the jump tables now.  We will fix up the actual
+  // MBB entries in the tables after we emit the code for each block, since then
+  // we will know the final locations of the MBBs in memory.
+  JumpTable = MJTI;
+  JumpTableBase = allocateSpace(NumEntries * EntrySize, MJTI->getAlignment());
+}
+
+void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
+  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+  if (JT.empty() || JumpTableBase == 0) return;
+  
+  if (TargetMachine::getRelocationModel() == Reloc::PIC_) {
+    assert(MJTI->getEntrySize() == 4 && "Cross JIT'ing?");
+    // For each jump table, place the offset from the beginning of the table
+    // to the target address.
+    int *SlotPtr = (int*)JumpTableBase;
+
+    for (unsigned i = 0, e = JT.size(); i != e; ++i) {
+      const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
+      // Store the offset of the basic block for this jump table slot in the
+      // memory we allocated for the jump table in 'initJumpTableInfo'
+      intptr_t Base = (intptr_t)SlotPtr;
+      for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi)
+        *SlotPtr++ = (intptr_t)getMachineBasicBlockAddress(MBBs[mi]) - Base;
+    }
+  } else {
+    assert(MJTI->getEntrySize() == sizeof(void*) && "Cross JIT'ing?");
+    
+    // For each jump table, map each target in the jump table to the address of 
+    // an emitted MachineBasicBlock.
+    intptr_t *SlotPtr = (intptr_t*)JumpTableBase;
+
+    for (unsigned i = 0, e = JT.size(); i != e; ++i) {
+      const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
+      // Store the address of the basic block for this jump table slot in the
+      // memory we allocated for the jump table in 'initJumpTableInfo'
+      for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi)
+        *SlotPtr++ = getMachineBasicBlockAddress(MBBs[mi]);
+    }
+  }
+}
+
+void JITEmitter::startFunctionStub(unsigned StubSize, unsigned Alignment) {
+  SavedBufferBegin = BufferBegin;
+  SavedBufferEnd = BufferEnd;
+  SavedCurBufferPtr = CurBufferPtr;
+  
+  BufferBegin = CurBufferPtr = MemMgr.allocateStub(StubSize, Alignment);
+  BufferEnd = BufferBegin+StubSize+1;
+}
+
+void *JITEmitter::finishFunctionStub(const Function *F) {
+  NumBytes += getCurrentPCOffset();
+  std::swap(SavedBufferBegin, BufferBegin);
+  BufferEnd = SavedBufferEnd;
+  CurBufferPtr = SavedCurBufferPtr;
+  return SavedBufferBegin;
+}
+
+// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
+// in the constant pool that was last emitted with the 'emitConstantPool'
+// method.
+//
+intptr_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) const {
+  assert(ConstantNum < ConstantPool->getConstants().size() &&
+         "Invalid ConstantPoolIndex!");
+  return (intptr_t)ConstantPoolBase +
+         ConstantPool->getConstants()[ConstantNum].Offset;
+}
+
+// getJumpTableEntryAddress - Return the address of the JumpTable with index
+// 'Index' in the jumpp table that was last initialized with 'initJumpTableInfo'
+//
+intptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
+  const std::vector<MachineJumpTableEntry> &JT = JumpTable->getJumpTables();
+  assert(Index < JT.size() && "Invalid jump table index!");
+  
+  unsigned Offset = 0;
+  unsigned EntrySize = JumpTable->getEntrySize();
+  
+  for (unsigned i = 0; i < Index; ++i)
+    Offset += JT[i].MBBs.size();
+  
+   Offset *= EntrySize;
+  
+  return (intptr_t)((char *)JumpTableBase + Offset);
+}
+
+//===----------------------------------------------------------------------===//
+//  Public interface to this file
+//===----------------------------------------------------------------------===//
+
+MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
+  return new JITEmitter(jit);
+}
+
+// getPointerToNamedFunction - This function is used as a global wrapper to
+// JIT::getPointerToNamedFunction for the purpose of resolving symbols when
+// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
+// need to resolve function(s) that are being mis-codegenerated, so we need to
+// resolve their addresses at runtime, and this is the way to do it.
+extern "C" {
+  void *getPointerToNamedFunction(const char *Name) {
+    if (Function *F = TheJIT->FindFunctionNamed(Name))
+      return TheJIT->getPointerToFunction(F);
+    return TheJIT->getPointerToNamedFunction(Name);
+  }
+}
+
+// getPointerToFunctionOrStub - If the specified function has been
+// code-gen'd, return a pointer to the function.  If not, compile it, or use
+// a stub to implement lazy compilation if available.
+//
+void *JIT::getPointerToFunctionOrStub(Function *F) {
+  // If we have already code generated the function, just return the address.
+  if (void *Addr = getPointerToGlobalIfAvailable(F))
+    return Addr;
+  
+  // Get a stub if the target supports it.
+  assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
+  JITEmitter *JE = static_cast<JITEmitter*>(getCodeEmitter());
+  return JE->getJITResolver().getFunctionStub(F);
+}
+
+/// freeMachineCodeForFunction - release machine code memory for given Function.
+///
+void JIT::freeMachineCodeForFunction(Function *F) {
+  // Delete translation for this from the ExecutionEngine, so it will get
+  // retranslated next time it is used.
+  updateGlobalMapping(F, 0);
+
+  // Free the actual memory for the function body and related stuff.
+  assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
+  static_cast<JITEmitter*>(MCE)->deallocateMemForFunction(F);
+}
+
diff --git a/lib/ExecutionEngine/JIT/Makefile b/lib/ExecutionEngine/JIT/Makefile
new file mode 100644
index 0000000..ebbdc3f
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/Makefile
@@ -0,0 +1,37 @@
+##===- lib/ExecutionEngine/JIT/Makefile --------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file was developed by the LLVM research group and is distributed under
+# the University of Illinois Open Source License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+LEVEL = ../../..
+LIBRARYNAME = LLVMJIT
+
+# Get the $(ARCH) setting
+include $(LEVEL)/Makefile.config
+
+# Enable the X86 JIT if compiling on X86
+ifeq ($(ARCH), x86)
+  ENABLE_X86_JIT = 1
+endif
+
+# This flag can also be used on the command line to force inclusion
+# of the X86 JIT on non-X86 hosts
+ifdef ENABLE_X86_JIT
+  CPPFLAGS += -DENABLE_X86_JIT
+endif
+
+# Enable the Sparc JIT if compiling on Sparc
+ifeq ($(ARCH), Sparc)
+  ENABLE_SPARC_JIT = 1
+endif
+
+# This flag can also be used on the command line to force inclusion
+# of the Sparc JIT on non-Sparc hosts
+ifdef ENABLE_SPARC_JIT
+  CPPFLAGS += -DENABLE_SPARC_JIT
+endif
+
+include $(LEVEL)/Makefile.common
diff --git a/lib/ExecutionEngine/JIT/TargetSelect.cpp b/lib/ExecutionEngine/JIT/TargetSelect.cpp
new file mode 100644
index 0000000..bf968af
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/TargetSelect.cpp
@@ -0,0 +1,78 @@
+//===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This just asks the TargetMachineRegistry for the appropriate JIT to use, and
+// allows the user to specify a specific one on the commandline with -march=x.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JIT.h"
+#include "llvm/Module.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/Target/SubtargetFeature.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetMachineRegistry.h"
+using namespace llvm;
+
+static cl::opt<const TargetMachineRegistry::Entry*, false, TargetNameParser>
+MArch("march", cl::desc("Architecture to generate assembly for:"));
+
+static cl::opt<std::string>
+MCPU("mcpu", 
+  cl::desc("Target a specific cpu type (-mcpu=help for details)"),
+  cl::value_desc("cpu-name"),
+  cl::init(""));
+
+static cl::list<std::string>
+MAttrs("mattr", 
+  cl::CommaSeparated,
+  cl::desc("Target specific attributes (-mattr=help for details)"),
+  cl::value_desc("a1,+a2,-a3,..."));
+
+/// create - Create an return a new JIT compiler if there is one available
+/// for the current target.  Otherwise, return null.
+///
+ExecutionEngine *JIT::create(ModuleProvider *MP, std::string *ErrorStr) {
+  const TargetMachineRegistry::Entry *TheArch = MArch;
+  if (TheArch == 0) {
+    std::string Error;
+    TheArch = TargetMachineRegistry::getClosestTargetForJIT(Error);
+    if (TheArch == 0) {
+      if (ErrorStr)
+        *ErrorStr = Error;
+      return 0;
+    }
+  } else if (TheArch->JITMatchQualityFn() == 0) {
+    cerr << "WARNING: This target JIT is not designed for the host you are"
+         << " running.  If bad things happen, please choose a different "
+         << "-march switch.\n";
+  }
+
+  // Package up features to be passed to target/subtarget
+  std::string FeaturesStr;
+  if (MCPU.size() || MAttrs.size()) {
+    SubtargetFeatures Features;
+    Features.setCPU(MCPU);
+    for (unsigned i = 0; i != MAttrs.size(); ++i)
+      Features.AddFeature(MAttrs[i]);
+    FeaturesStr = Features.getString();
+  }
+
+  // Allocate a target...
+  TargetMachine *Target = TheArch->CtorFn(*MP->getModule(), FeaturesStr);
+  assert(Target && "Could not allocate target machine!");
+
+  // If the target supports JIT code generation, return a new JIT now.
+  if (TargetJITInfo *TJ = Target->getJITInfo())
+    return new JIT(MP, *Target, *TJ);
+
+  if (ErrorStr)
+    *ErrorStr = "target does not support JIT code generation";
+  return 0;
+}