bcc.cpp

/*
 * Bitcode compiler (bcc) for Android:
 * This is an eager-compilation JIT running on Android.
 *
 */

#define LOG_TAG "bcc"
#include <cutils/log.h>

#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <cutils/hashmap.h>

#if defined(__i386__)
#include <sys/mman.h>
#endif

#if defined(__arm__)
  #define DEFAULT_ARM_CODEGEN
  #define PROVIDE_ARM_CODEGEN
#elif defined(__i386__)
  #define DEFAULT_X86_CODEGEN
  #define PROVIDE_X86_CODEGEN
#elif defined(__x86_64__)
  #define DEFAULT_X64_CODEGEN
  #define PROVIDE_X64_CODEGEN
#endif

#if defined(FORCE_ARM_CODEGEN)
  #define DEFAULT_ARM_CODEGEN
  #undef DEFAULT_X86_CODEGEN
  #undef DEFAULT_X64_CODEGEN
  #define PROVIDE_ARM_CODEGEN
  #undef PROVIDE_X86_CODEGEN
  #undef PROVIDE_X64_CODEGEN
#elif defined(FORCE_X86_CODEGEN)
  #undef DEFAULT_ARM_CODEGEN
  #define DEFAULT_X86_CODEGEN
  #undef DEFAULT_X64_CODEGEN
  #undef PROVIDE_ARM_CODEGEN
  #define PROVIDE_X86_CODEGEN
  #undef PROVIDE_X64_CODEGEN
#elif defined(FORCE_X64_CODEGEN)
  #undef DEFAULT_ARM_CODEGEN
  #undef DEFAULT_X86_CODEGEN
  #define DEFAULT_X64_CODEGEN
  #undef PROVIDE_ARM_CODEGEN
  #undef PROVIDE_X86_CODEGEN
  #define PROVIDE_X64_CODEGEN
#endif

#if defined(DEFAULT_ARM_CODEGEN)
  #define TARGET_TRIPLE_STRING    "armv7-none-linux-gnueabi"
#elif defined(DEFAULT_X86_CODEGEN)
  #define TARGET_TRIPLE_STRING    "i686-unknown-linux"
#elif defined(DEFAULT_X64_CODEGEN)
  #define  TARGET_TRIPLE_STRING   "x86_64-unknown-linux"
#endif

#if (defined(__VFP_FP__) && !defined(__SOFTFP__))
#define ARM_USE_VFP
#endif

#include <bcc/bcc.h>
#include "bcc_runtime.h"

#define LOG_API(...) do {} while(0)
// #define LOG_API(...) fprintf (stderr, __VA_ARGS__)

#define LOG_STACK(...) do {} while(0)
// #define LOG_STACK(...) fprintf (stderr, __VA_ARGS__)

// #define PROVIDE_TRACE_CODEGEN

#if defined(USE_DISASSEMBLER)
#   include "disassembler/dis-asm.h"
#   include <cstdio>
#endif

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>                    /* for std::reverse */

// Basic
#include "llvm/Use.h"                   /* for class llvm::Use */
#include "llvm/User.h"                  /* for class llvm::User */
#include "llvm/Module.h"                /* for class llvm::Module */
#include "llvm/Function.h"              /* for class llvm::Function */
#include "llvm/Constant.h"              /* for class llvm::Constant */
#include "llvm/Constants.h"             /* for class llvm::ConstantExpr */
#include "llvm/Instruction.h"           /* for class llvm::Instruction */
#include "llvm/PassManager.h"           /* for class llvm::PassManager and
                                         * llvm::FunctionPassManager
                                         */
#include "llvm/LLVMContext.h"           /* for llvm::getGlobalContext() */
#include "llvm/GlobalValue.h"           /* for class llvm::GlobalValue */
#include "llvm/Instructions.h"          /* for class llvm::CallInst */
#include "llvm/OperandTraits.h"         /* for macro
                                         * DECLARE_TRANSPARENT_OPERAND_ACCESSORS
                                         * and macro
                                         * DEFINE_TRANSPARENT_OPERAND_ACCESSORS
                                         */
#include "llvm/TypeSymbolTable.h"       /* for Type Reflection */

// System
#include "llvm/System/Host.h"           /* for function
                                         * llvm::sys::isLittleEndianHost()
                                         */
#include "llvm/System/Memory.h"         /* for class llvm::sys::MemoryBlock */

// ADT
#include "llvm/ADT/APInt.h"             /* for class llvm::APInt */
#include "llvm/ADT/APFloat.h"           /* for class llvm::APFloat */
#include "llvm/ADT/DenseMap.h"          /* for class llvm::DenseMap */
#include "llvm/ADT/ValueMap.h"          /* for class llvm::ValueMap and
                                         * class llvm::ValueMapConfig
                                         */
#include "llvm/ADT/StringMap.h"         /* for class llvm::StringMap */
#include "llvm/ADT/OwningPtr.h"         /* for class llvm::OwningPtr */
#include "llvm/ADT/SmallString.h"       /* for class llvm::SmallString */

// Target
#include "llvm/Target/TargetData.h"     /* for class llvm::TargetData */
#include "llvm/Target/TargetSelect.h"   /* for function
                                         * LLVMInitialize[ARM|X86]
                                         * [TargetInfo|Target]()
                                         */
#include "llvm/Target/TargetOptions.h"  /* for
                                         *  variable bool llvm::UseSoftFloat
                                         *  FloatABI::ABIType llvm::FloatABIType
                                         *  bool llvm::NoZerosInBSS
                                         */
#include "llvm/Target/TargetMachine.h"  /* for class llvm::TargetMachine and
                                         * llvm::TargetMachine::AssemblyFile
                                         */
#include "llvm/Target/TargetJITInfo.h"  /* for class llvm::TargetJITInfo */
#include "llvm/Target/TargetRegistry.h" /* for class llvm::TargetRegistry */
#include "llvm/Target/SubtargetFeature.h"
                                        /* for class llvm::SubtargetFeature */

// Support
#include "llvm/Support/Casting.h"       /* for class cast<> */
#include "llvm/Support/raw_ostream.h"   /* for class llvm::raw_ostream and
                                         * llvm::raw_string_ostream
                                         */
#include "llvm/Support/ValueHandle.h"   /* for class AssertingVH<> */
#include "llvm/Support/MemoryBuffer.h"  /* for class llvm::MemoryBuffer */
#include "llvm/Support/ManagedStatic.h" /* for class llvm::llvm_shutdown */
#include "llvm/Support/ErrorHandling.h" /* for function
                                         * llvm::llvm_install_error_handler()
                                         * and macro llvm_unreachable()
                                         */
#include "llvm/Support/StandardPasses.h"/* for function
                                         * llvm::createStandardFunctionPasses()
                                         * and
                                         * llvm::createStandardModulePasses()
                                         */
#include "llvm/Support/FormattedStream.h"
                                        /* for
                                         * class llvm::formatted_raw_ostream
                                         * llvm::formatted_raw_ostream::
                                         * PRESERVE_STREAM
                                         * llvm::FileModel::Error
                                         */

// Bitcode
#include "llvm/Bitcode/ReaderWriter.h"  /* for function
                                         * llvm::ParseBitcodeFile()
                                         */

// CodeGen
#include "llvm/CodeGen/Passes.h"        /* for
                                         * llvm::createLocalRegisterAllocator()
                                         * and
                                         * llvm::
                                         * createLinearScanRegisterAllocator()
                                         */
#include "llvm/CodeGen/JITCodeEmitter.h"/* for class llvm::JITCodeEmitter */
#include "llvm/CodeGen/MachineFunction.h"
                                        /* for class llvm::MachineFunction */
#include "llvm/CodeGen/RegAllocRegistry.h"
                                        /* for class llvm::RegisterRegAlloc */
#include "llvm/CodeGen/SchedulerRegistry.h"
                                        /* for class llvm::RegisterScheduler
                                         * and llvm::createDefaultScheduler()
                                         */
#include "llvm/CodeGen/MachineRelocation.h"
                                        /* for class llvm::MachineRelocation */
#include "llvm/CodeGen/MachineModuleInfo.h"
                                        /* for class llvm::MachineModuleInfo */
#include "llvm/CodeGen/MachineCodeEmitter.h"
                                        /* for class llvm::MachineCodeEmitter */
#include "llvm/CodeGen/MachineConstantPool.h"
                                        /* for class llvm::MachineConstantPool
                                         */
#include "llvm/CodeGen/MachineJumpTableInfo.h"
                                        /* for class llvm::MachineJumpTableInfo
                                         */

// ExecutionEngine
#include "llvm/ExecutionEngine/GenericValue.h"
                                        /* for struct llvm::GenericValue */
#include "llvm/ExecutionEngine/JITMemoryManager.h"
                                        /* for class llvm::JITMemoryManager */


/*
 * Compilation class that suits Android's needs.
 * (Support: no argument passed, ...)
 */

namespace bcc {

class Compiler {
  /*
   * This part is designed to be orthogonal to those exported bcc*() functions
   * implementation and internal struct BCCscript.
   */


  /*********************************************
   * The variable section below (e.g., Triple, CodeGenOptLevel)
   * is initialized in GlobalInitialization()
   */
  static bool GlobalInitialized;

  /*
   * If given, this will be the name of the target triple to compile for.
   * If not given, the initial values defined in this file will be used.
   */
  static std::string Triple;

  static llvm::CodeGenOpt::Level CodeGenOptLevel;
  /*
   * End of section of GlobalInitializing variables
   **********************************************/

  /* If given, the name of the target CPU to generate code for. */
  static std::string CPU;

  /*
   * The list of target specific features to enable or disable -- this should
   * be a list of strings starting with '+' (enable) or '-' (disable).
   */
  static std::vector<std::string> Features;

  struct Runtime {
      const char* mName;
      void* mPtr;
  };
  static struct Runtime Runtimes[];

  static void GlobalInitialization() {
    if(GlobalInitialized) return;

    /* Set Triple, CPU and Features here */
    Triple = TARGET_TRIPLE_STRING;

#if defined(DEFAULT_ARM_CODEGEN) || defined(PROVIDE_ARM_CODEGEN)
    LLVMInitializeARMTargetInfo();
    LLVMInitializeARMTarget();
#endif

#if defined(DEFAULT_X86_CODEGEN) || defined(PROVIDE_X86_CODEGEN)
    LLVMInitializeX86TargetInfo();
    LLVMInitializeX86Target();
#endif

#if defined(DEFAULT_X64_CODEGEN) || defined(PROVIDE_X64_CODEGEN)
    LLVMInitializeX86TargetInfo();
    LLVMInitializeX86Target();
#endif

    /*
     * -O0: llvm::CodeGenOpt::None
     * -O1: llvm::CodeGenOpt::Less
     * -O2: llvm::CodeGenOpt::Default
     * -O3: llvm::CodeGenOpt::Aggressive
     */
    CodeGenOptLevel = llvm::CodeGenOpt::Aggressive;

    /* Below are the global settings to LLVM */

    /* Disable frame pointer elimination optimization */
    llvm::NoFramePointerElim = false;

    /*
     * Use hardfloat ABI
     *
     * FIXME: Need to detect the CPU capability and decide whether to use
     * softfp. To use softfp, change following 2 lines to
     *
     *  llvm::FloatABIType = llvm::FloatABI::Soft;
     *  llvm::UseSoftFloat = true;
     */
    llvm::FloatABIType = llvm::FloatABI::Hard;
    llvm::UseSoftFloat = false;

    /*
     * BCC needs all unknown symbols resolved at JIT/compilation time.
     * So we don't need any dynamic relocation model.
     */
    llvm::TargetMachine::setRelocationModel(llvm::Reloc::Static);

#ifdef DEFAULT_X64_CODEGEN
    /* Data address in X86_64 architecture may reside in a far-away place */
    llvm::TargetMachine::setCodeModel(llvm::CodeModel::Medium);
#else
    /*
     * This is set for the linker (specify how large of the virtual addresses
     * we can access for all unknown symbols.)
    */
    llvm::TargetMachine::setCodeModel(llvm::CodeModel::Small);
#endif

    /* Register the scheduler */
    llvm::RegisterScheduler::setDefault(llvm::createDefaultScheduler);

    /*
     * Register allocation policy:
     *  createLocalRegisterAllocator: fast but bad quality
     *  createLinearScanRegisterAllocator: not so fast but good quality
     */
    llvm::RegisterRegAlloc::setDefault
        ((CodeGenOptLevel == llvm::CodeGenOpt::None) ?
         llvm::createLocalRegisterAllocator :
         llvm::createLinearScanRegisterAllocator);

    GlobalInitialized = true;
    return;
  }

  static void LLVMErrorHandler(void *UserData, const std::string &Message) {
    // std::string* Error = static_cast<std::string*>(UserData);
    // Error->assign(Message);
    // return;
    fprintf(stderr, "%s\n", Message.c_str());
    exit(1);
  }

  static const llvm::StringRef PragmaMetadataName;

 private:
  std::string mError;

  inline bool hasError() const {
    return !mError.empty();
  }
  inline void setError(const char* Error) {
    mError.assign(Error);  // Copying
    return;
  }
  inline void setError(const std::string& Error) {
    mError = Error;
    return;
  }

  typedef std::list< std::pair<std::string, std::string> > PragmaList;
  PragmaList mPragmas;

  /* Memory manager for the code reside in memory */
  /*
   * The memory for our code emitter is very simple and is conforming to the
   * design decisions of Android RenderScript's Exection Environment:
   *   The code, data, and symbol sizes are limited (currently 100KB.)
   *
   * It's very different from typical compiler, which has no limitation
   * on the code size. How does code emitter know the size of the code
   * it is about to emit? It does not know beforehand. We want to solve
   * this without complicating the code emitter too much.
   *
   * We solve this by pre-allocating a certain amount of memory,
   * and then start the code emission. Once the buffer overflows, the emitter
   * simply discards all the subsequent emission but still has a counter
   * on how many bytes have been emitted.

   * So once the whole emission is done, if there's a buffer overflow,
   * it re-allocates the buffer with enough size (based on the
   *  counter from previous emission) and re-emit again.
   */
  class CodeMemoryManager : public llvm::JITMemoryManager {
    /* {{{ */
   private:
    static const unsigned int MaxCodeSize = 100 * 1024; /* 100 KiB for code */
    static const unsigned int MaxGOTSize = 1 * 1024;    /* 1 KiB for global
                                                           offset table (GOT) */

    /*
     * Our memory layout is as follows:
     *
     *  The direction of arrows (-> and <-) shows memory's growth direction
     *  when more space is needed.
     *
     * @mpCodeMem:
     *  +--------------------------------------------------------------+
     *  | Function Memory ... ->                <- ... Global/Stub/GOT |
     *  +--------------------------------------------------------------+
     *  |<------------------ Total: @MaxCodeSize KiB ----------------->|
     *
     *  Where size of GOT is @MaxGOTSize KiB.
     *
     * @mCurFuncMemIdx: The current index (starting from 0) of the last byte
     *                    of function code's memoey usage
     * @mCurGSGMemIdx: The current index (starting from 0) of the last byte
     *                    of Global Stub/GOT's memory usage
     *
     */

    intptr_t mCurFuncMemIdx;
    intptr_t mCurGSGMemIdx;
    llvm::sys::MemoryBlock* mpCodeMem;

    /* GOT Base */
    uint8_t* mpGOTBase;

    typedef std::map<const llvm::Function*, pair<void* /* start address */,
                                                 void* /* end address */>
                     > FunctionMapTy;
    FunctionMapTy mFunctionMap;

    inline intptr_t getFreeMemSize() const {
      return mCurGSGMemIdx - mCurFuncMemIdx;
    }
    inline uint8_t* getCodeMemBase() const {
      return static_cast<uint8_t*>(mpCodeMem->base());
    }

    uint8_t* allocateGSGMemory(uintptr_t Size,
                               unsigned Alignment = 1 /* no alignment */)
    {
      if(getFreeMemSize() < Size)
        /* The code size excesses our limit */
        return NULL;

      if(Alignment == 0)
        Alignment = 1;

      uint8_t* result = getCodeMemBase() + mCurGSGMemIdx - Size;
      result = (uint8_t*) (((intptr_t) result) & ~(intptr_t) (Alignment - 1));

      mCurGSGMemIdx = result - getCodeMemBase();

      return result;
    }

   public:
    CodeMemoryManager() : mpCodeMem(NULL), mpGOTBase(NULL) {
      reset();
      std::string ErrMsg;
      llvm::sys::MemoryBlock B = llvm::sys::Memory::
          AllocateRWX(MaxCodeSize, NULL, &ErrMsg);
      if(B.base() == 0)
        llvm::llvm_report_error(
            "Failed to allocate Memory for code emitter\n" + ErrMsg
                                );
      mpCodeMem = new llvm::sys::MemoryBlock(B.base(), B.size());

      return;
    }

    /*
     * setMemoryWritable - When code generation is in progress,
     *  the code pages may need permissions changed.
     */
    void setMemoryWritable() {
      llvm::sys::Memory::setWritable(*mpCodeMem);
      return;
    }

    /*
     * setMemoryExecutable - When code generation is done and we're ready to
     *  start execution, the code pages may need permissions changed.
     */
    void setMemoryExecutable() {
      llvm::sys::Memory::setExecutable(*mpCodeMem);
      return;
    }

    /*
     * setPoisonMemory - Setting this flag to true makes the memory manager
     *  garbage values over freed memory.  This is useful for testing and
     *  debugging, and is to be turned on by default in debug mode.
     */
    void setPoisonMemory(bool poison) {
      /* no effect */
      return;
    }

    /* Global Offset Table Management */

    /*
     * AllocateGOT - If the current table requires a Global Offset Table, this
     *  method is invoked to allocate it.  This method is required to set HasGOT
     *  to true.
     */
    void AllocateGOT() {
      assert(mpGOTBase != NULL && "Cannot allocate the GOT multiple times");
      mpGOTBase = allocateGSGMemory(MaxGOTSize);
      HasGOT = true;
      return;
    }

    /*
     * getGOTBase - If this is managing a Global Offset Table, this method
     *  should return a pointer to its base.
     */
    uint8_t* getGOTBase() const {
      return mpGOTBase;
    }

    /* Main Allocation Functions */

    /*
     * startFunctionBody - When we start JITing a function, the JIT calls this
     *  method to allocate a block of free RWX memory, which returns a pointer to
     *  it.  If the JIT wants to request a block of memory of at least a certain
     *  size, it passes that value as ActualSize, and this method returns a block
     *  with at least that much space.  If the JIT doesn't know ahead of time how
     *  much space it will need to emit the function, it passes 0 for the
     *  ActualSize.  In either case, this method is required to pass back the size
     *  of the allocated block through ActualSize.  The JIT will be careful to
     *  not write more than the returned ActualSize bytes of memory.
     */
    uint8_t* startFunctionBody(const llvm::Function *F, uintptr_t &ActualSize) {
      if(getFreeMemSize() < ActualSize)
        /* The code size excesses our limit */
        return NULL;

      ActualSize = getFreeMemSize();
      return (getCodeMemBase() + mCurFuncMemIdx);
    }

    /*
     * allocateStub - This method is called by the JIT to allocate space for a
     *  function stub (used to handle limited branch displacements) while it is
     *  JIT compiling a function.  For example, if foo calls bar, and if bar
     *  either needs to be lazily compiled or is a native function that exists
     *  too
     *  far away from the call site to work, this method will be used to make a
     *  thunk for it.  The stub should be "close" to the current function body,
     *  but should not be included in the 'actualsize' returned by
     *  startFunctionBody.
     */
    uint8_t* allocateStub(const llvm::GlobalValue* F, unsigned StubSize,
                          unsigned Alignment) {
      return allocateGSGMemory(StubSize, Alignment);
    }

    /*
     * endFunctionBody - This method is called when the JIT is done codegen'ing
     *  the specified function.  At this point we know the size of the JIT
     *  compiled function.  This passes in FunctionStart (which was returned by
     *  the startFunctionBody method) and FunctionEnd which is a pointer to the
     *  actual end of the function.  This method should mark the space allocated
     *  and remember where it is in case the client wants to deallocate it.
     */
    void endFunctionBody(const llvm::Function* F, uint8_t* FunctionStart,
                         uint8_t* FunctionEnd) {
      assert(FunctionEnd > FunctionStart);
      assert(FunctionStart == (getCodeMemBase() + mCurFuncMemIdx) &&
             "Mismatched function start/end!");

      /* Advance the pointer */
      intptr_t FunctionCodeSize = FunctionEnd - FunctionStart;
      assert(FunctionCodeSize <= getFreeMemSize() &&
             "Code size excess the limitation!");
      mCurFuncMemIdx += FunctionCodeSize;

      /* Record there's a function in our memory start from @FunctionStart */
      assert(mFunctionMap.find(F) == mFunctionMap.end() &&
             "Function already emitted!");
      mFunctionMap.insert( make_pair<const llvm::Function*, pair<void*, void*>
                                    >(F, make_pair(FunctionStart, FunctionEnd))
                           );

      return;
    }

    /*
     * allocateSpace - Allocate a (function code) memory block of the
     *  given size.  This method cannot be called between
     *  calls to startFunctionBody and endFunctionBody.
     */
    uint8_t* allocateSpace(intptr_t Size, unsigned Alignment) {
      if(getFreeMemSize() < Size)
        /* The code size excesses our limit */
        return NULL;

      if(Alignment == 0)
        Alignment = 1;

      uint8_t* result = getCodeMemBase() + mCurFuncMemIdx;
      result = (uint8_t*) (((intptr_t) result + Alignment - 1) &
                           ~(intptr_t) (Alignment - 1)
                           );

      mCurFuncMemIdx = (result + Size) - getCodeMemBase();

      return result;
    }

    /* allocateGlobal - Allocate memory for a global. */
    uint8_t* allocateGlobal(uintptr_t Size, unsigned Alignment) {
      return allocateGSGMemory(Size, Alignment);
    }

    /*
     * deallocateFunctionBody - Free the specified function body.  The argument
     *  must be the return value from a call to startFunctionBody() that hasn't
     *  been deallocated yet.  This is never called when the JIT is currently
     *  emitting a function.
     */
    void deallocateFunctionBody(void *Body) {
      /* linear search */
      FunctionMapTy::iterator I;
      for(I = mFunctionMap.begin();
          I != mFunctionMap.end();
          I++)
        if(I->second.first == Body)
          break;

      assert(I != mFunctionMap.end() && "Memory is never allocated!");

      /* free the memory */
      uint8_t* FunctionStart = (uint8_t*) I->second.first;
      uint8_t* FunctionEnd = (uint8_t*) I->second.second;
      intptr_t SizeNeedMove = (getCodeMemBase() + mCurFuncMemIdx) - FunctionEnd;

      assert(SizeNeedMove >= 0 &&
             "Internal error: CodeMemoryManager::mCurFuncMemIdx may not"
             " be correctly calculated!");

      if(SizeNeedMove > 0)
        /* there's data behind deallocating function */
        ::memmove(FunctionStart, FunctionEnd, SizeNeedMove);
      mCurFuncMemIdx -= (FunctionEnd - FunctionStart);

      return;
    }

    /*
     * startExceptionTable - When we finished JITing the function, if exception
     *  handling is set, we emit the exception table.
     */
    uint8_t* startExceptionTable(const llvm::Function* F, uintptr_t &ActualSize)
    {
      assert(false && "Exception is not allowed in our language specification");
      return NULL;
    }

    /*
     * endExceptionTable - This method is called when the JIT is done emitting
     *  the exception table.
     */
    void endExceptionTable(const llvm::Function *F, uint8_t *TableStart,
                           uint8_t *TableEnd, uint8_t* FrameRegister) {
      assert(false && "Exception is not allowed in our language specification");
      return;
    }

    /*
     * deallocateExceptionTable - Free the specified exception table's memory.
     *  The argument must be the return value from a call to
     *  startExceptionTable()
     *  that hasn't been deallocated yet.  This is never called when the JIT is
     *  currently emitting an exception table.
     */
    void deallocateExceptionTable(void *ET) {
      assert(false && "Exception is not allowed in our language specification");
      return;
    }

    /* Below are the methods we create */
    void reset() {
      mpGOTBase = NULL;
      HasGOT = false;

      mCurFuncMemIdx = 0;
      mCurGSGMemIdx = MaxCodeSize - 1;

      mFunctionMap.clear();

      return;
    }

    ~CodeMemoryManager() {
      if(mpCodeMem != NULL)
        llvm::sys::Memory::ReleaseRWX(*mpCodeMem);
      return;
    }
    /* }}} */
  };  /* End of class CodeMemoryManager */

  /* The memory manager for code emitter */
  llvm::OwningPtr<CodeMemoryManager> mCodeMemMgr;
  CodeMemoryManager* createCodeMemoryManager() {
    mCodeMemMgr.reset(new CodeMemoryManager());
    return mCodeMemMgr.get();
  }

  /* Code emitter */
  class CodeEmitter : public llvm::JITCodeEmitter {
    /* {{{ */
   public:
    typedef llvm::DenseMap<const llvm::GlobalValue*, void*> GlobalAddressMapTy;
    typedef GlobalAddressMapTy::const_iterator global_addresses_const_iterator;

   private:
    CodeMemoryManager* mpMemMgr;

    /* The JITInfo for the target we are compiling to */
    llvm::TargetJITInfo* mpTJI;

    const llvm::TargetData* mpTD;

    /*
     * 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<uintptr_t> mMBBLocations;

    /* ConstantPool - The constant pool for the current function. */
    llvm::MachineConstantPool* mpConstantPool;

    /* ConstantPoolBase - A pointer to the first entry in the constant pool. */
    void *mpConstantPoolBase;

    /* ConstPoolAddresses - Addresses of individual constant pool entries. */
    llvm::SmallVector<uintptr_t, 8> mConstPoolAddresses;

    /* JumpTable - The jump tables for the current function. */
    llvm::MachineJumpTableInfo *mpJumpTable;

    /* JumpTableBase - A pointer to the first entry in the jump table. */
    void *mpJumpTableBase;

    /*
     * When outputting a function stub in the context of some other function, we
     *  save BufferBegin/BufferEnd/CurBufferPtr here.
     */
    uint8_t *mpSavedBufferBegin, *mpSavedBufferEnd, *mpSavedCurBufferPtr;

    /* Relocations - These are the relocations that the function needs,
       as emitted. */
    std::vector<llvm::MachineRelocation> mRelocations;

    /* LabelLocations - This vector is a mapping from Label ID's to their
       address. */
    std::vector<uintptr_t> mLabelLocations;

    class EmittedFunctionCode {
     public:
      void* FunctionBody;  // Beginning of the function's allocation.
      void* Code;  // The address the function's code actually starts at.
      int Size; // The size of the function code

      EmittedFunctionCode() : FunctionBody(NULL), Code(NULL) { return; }
    };
    EmittedFunctionCode* mpCurEmitFunction;

    typedef std::map<const std::string, EmittedFunctionCode*
                     > EmittedFunctionsMapTy;
    EmittedFunctionsMapTy mEmittedFunctions;

    /* MMI - Machine module info for exception informations */
    llvm::MachineModuleInfo* mpMMI;

    GlobalAddressMapTy mGlobalAddressMap;

    /*
     * UpdateGlobalMapping - Replace an existing mapping for GV with a new
     *  address.  This updates both maps as required.  If "Addr" is null, the
     *  entry for the global is removed from the mappings.
     */
    void* UpdateGlobalMapping(const llvm::GlobalValue *GV, void *Addr) {
      if(Addr == NULL) {
        /* Removing mapping */
        GlobalAddressMapTy::iterator I = mGlobalAddressMap.find(GV);
        void *OldVal;

        if(I == mGlobalAddressMap.end())
          OldVal = NULL;
        else {
          OldVal = I->second;
          mGlobalAddressMap.erase(I);
        }

        return OldVal;
      }

      void*& CurVal = mGlobalAddressMap[GV];
      void* OldVal = CurVal;

      CurVal = Addr;

      return OldVal;
    }

    /*
     * AddGlobalMapping - Tell the execution engine that the specified global is
     *  at the specified location.  This is used internally as functions are
     *  JIT'd
     *  and as global variables are laid out in memory.
     */
    void AddGlobalMapping(const llvm::GlobalValue *GV, void *Addr) {
      void*& CurVal = mGlobalAddressMap[GV];
      assert((CurVal == 0 || Addr == 0) && "GlobalMapping already established!");
      CurVal = Addr;
      return;
    }

    /*
     * GetPointerToGlobalIfAvailable - This returns the address of the specified
     *  global value if it is has already been codegen'd,
     *  otherwise it returns null.
     */
    void* GetPointerToGlobalIfAvailable(const llvm::GlobalValue* GV) const {
      GlobalAddressMapTy::const_iterator I = mGlobalAddressMap.find(GV);
      return ((I != mGlobalAddressMap.end()) ? I->second : NULL);
    }

    unsigned int GetConstantPoolSizeInBytes(llvm::MachineConstantPool* MCP) {
      const std::vector<llvm::MachineConstantPoolEntry>& Constants =
          MCP->getConstants();

      if(Constants.empty())
        return 0;

      unsigned int Size = 0;
      for(int i=0;i<Constants.size();i++) {
        llvm::MachineConstantPoolEntry CPE = Constants[i];
        unsigned int AlignMask = CPE.getAlignment() - 1;
        Size = (Size + AlignMask) & ~AlignMask;
        const llvm::Type* Ty = CPE.getType();
        Size += mpTD->getTypeAllocSize(Ty);
      }

      return Size;
    }

    /*
     * This function converts a Constant* into a GenericValue. The interesting
     *  part is if C is a ConstantExpr.
     */
    void GetConstantValue(const llvm::Constant *C, llvm::GenericValue& Result) {
      if(C->getValueID() == llvm::Value::UndefValueVal)
        return;
      else if(C->getValueID() == llvm::Value::ConstantExprVal) {
        const llvm::ConstantExpr* CE = (llvm::ConstantExpr*) C;
        const llvm::Constant* Op0 = CE->getOperand(0);

        switch(CE->getOpcode()) {
          case llvm::Instruction::GetElementPtr:
            {
              /* Compute the index */
              llvm::SmallVector<llvm::Value*, 8> Indices(CE->op_begin() + 1,
                                                         CE->op_end());
              uint64_t Offset = mpTD->getIndexedOffset(Op0->getType(),
                                                       &Indices[0],
                                                       Indices.size());

              GetConstantValue(Op0, Result);
              Result.PointerVal = (char*) Result.PointerVal + Offset;

              return;
            }
            break;

          case llvm::Instruction::Trunc:
            {
              uint32_t BitWidth =
                  llvm::cast<llvm::IntegerType>(CE->getType())->getBitWidth();

              GetConstantValue(Op0, Result);
              Result.IntVal = Result.IntVal.trunc(BitWidth);

              return;
            }
            break;

          case llvm::Instruction::ZExt:
            {
              uint32_t BitWidth =
                  llvm::cast<llvm::IntegerType>(CE->getType())->getBitWidth();

              GetConstantValue(Op0, Result);
              Result.IntVal = Result.IntVal.zext(BitWidth);

              return;
            }
            break;

          case llvm::Instruction::SExt:
            {
              uint32_t BitWidth =
                  llvm::cast<llvm::IntegerType>(CE->getType())->getBitWidth();

              GetConstantValue(Op0, Result);
              Result.IntVal = Result.IntVal.sext(BitWidth);

              return;
            }
            break;


          case llvm::Instruction::FPTrunc:
            {
              /* FIXME long double */
              GetConstantValue(Op0, Result);
              Result.FloatVal = float(Result.DoubleVal);
              return;
            }
            break;


          case llvm::Instruction::FPExt:
            {
              /* FIXME long double */
              GetConstantValue(Op0, Result);
              Result.DoubleVal = double(Result.FloatVal);
              return;
            }
            break;


          case llvm::Instruction::UIToFP:
            {
              GetConstantValue(Op0, Result);
              if(CE->getType()->isFloatTy())
                Result.FloatVal = float(Result.IntVal.roundToDouble());
              else if(CE->getType()->isDoubleTy())
                Result.DoubleVal = Result.IntVal.roundToDouble();
              else if(CE->getType()->isX86_FP80Ty()) {
                const uint64_t zero[] = { 0, 0 };
                llvm::APFloat apf = llvm::APFloat(llvm::APInt(80, 2, zero));
                apf.convertFromAPInt(Result.IntVal,
                                     false,
                                     llvm::APFloat::rmNearestTiesToEven);
                Result.IntVal = apf.bitcastToAPInt();
              }
              return;
            }
            break;

          case llvm::Instruction::SIToFP:
            {
              GetConstantValue(Op0, Result);
              if(CE->getType()->isFloatTy())
                Result.FloatVal = float(Result.IntVal.signedRoundToDouble());
              else if(CE->getType()->isDoubleTy())
                Result.DoubleVal = Result.IntVal.signedRoundToDouble();
              else if(CE->getType()->isX86_FP80Ty()) {
                const uint64_t zero[] = { 0, 0 };
                llvm::APFloat apf = llvm::APFloat(llvm::APInt(80, 2, zero));
                apf.convertFromAPInt(Result.IntVal,
                                     true,
                                     llvm::APFloat::rmNearestTiesToEven);
                Result.IntVal = apf.bitcastToAPInt();
              }
              return;
            }
            break;

            /* double->APInt conversion handles sign */
          case llvm::Instruction::FPToUI:
          case llvm::Instruction::FPToSI:
            {
              uint32_t BitWidth =
                  llvm::cast<llvm::IntegerType>(CE->getType())->getBitWidth();

              GetConstantValue(Op0, Result);
              if(Op0->getType()->isFloatTy())
                Result.IntVal =
                 llvm::APIntOps::RoundFloatToAPInt(Result.FloatVal, BitWidth);
              else if(Op0->getType()->isDoubleTy())
                Result.IntVal =
                 llvm::APIntOps::RoundDoubleToAPInt(Result.DoubleVal, BitWidth);
              else if(Op0->getType()->isX86_FP80Ty()) {
                llvm::APFloat apf = llvm::APFloat(Result.IntVal);
                uint64_t v;
                bool ignored;
                apf.convertToInteger(&v,
                                     BitWidth,
                                     CE->getOpcode()
                                      == llvm::Instruction::FPToSI,
                                     llvm::APFloat::rmTowardZero,
                                     &ignored);
                Result.IntVal = v; // endian?
              }
              return;
            }
            break;

          case llvm::Instruction::PtrToInt:
            {
              uint32_t PtrWidth = mpTD->getPointerSizeInBits();

              GetConstantValue(Op0, Result);
              Result.IntVal = llvm::APInt(PtrWidth, uintptr_t
                                          (Result.PointerVal));

              return;
            }
            break;

          case llvm::Instruction::IntToPtr:
            {
              uint32_t PtrWidth = mpTD->getPointerSizeInBits();

              GetConstantValue(Op0, Result);
              if(PtrWidth != Result.IntVal.getBitWidth())
                Result.IntVal = Result.IntVal.zextOrTrunc(PtrWidth);
              assert(Result.IntVal.getBitWidth() <= 64 && "Bad pointer width");

              Result.PointerVal = llvm::PointerTy
                  (uintptr_t(Result.IntVal.getZExtValue()));

              return;
            }
            break;

          case llvm::Instruction::BitCast:
            {
              GetConstantValue(Op0, Result);
              const llvm::Type* DestTy = CE->getType();

              switch(Op0->getType()->getTypeID()) {
                case llvm::Type::IntegerTyID:
                  assert(DestTy->isFloatingPointTy() && "invalid bitcast");
                  if(DestTy->isFloatTy())
                    Result.FloatVal = Result.IntVal.bitsToFloat();
                  else if(DestTy->isDoubleTy())
                    Result.DoubleVal = Result.IntVal.bitsToDouble();
                  break;

                case llvm::Type::FloatTyID:
                  assert(DestTy->isIntegerTy(32) && "Invalid bitcast");
                  Result.IntVal.floatToBits(Result.FloatVal);
                  break;

                case llvm::Type::DoubleTyID:
                  assert(DestTy->isIntegerTy(64) && "Invalid bitcast");
                  Result.IntVal.doubleToBits(Result.DoubleVal);
                  break;

                case llvm::Type::PointerTyID:
                  assert(DestTy->isPointerTy() && "Invalid bitcast");
                  break; // getConstantValue(Op0) above already converted it

                default:
                  llvm_unreachable("Invalid bitcast operand");
                  break;
              }

              return;
            }
            break;

          case llvm::Instruction::Add:
          case llvm::Instruction::FAdd:
          case llvm::Instruction::Sub:
          case llvm::Instruction::FSub:
          case llvm::Instruction::Mul:
          case llvm::Instruction::FMul:
          case llvm::Instruction::UDiv:
          case llvm::Instruction::SDiv:
          case llvm::Instruction::URem:
          case llvm::Instruction::SRem:
          case llvm::Instruction::And:
          case llvm::Instruction::Or:
          case llvm::Instruction::Xor:
            {
              llvm::GenericValue LHS, RHS;
              GetConstantValue(Op0, LHS);
              GetConstantValue(CE->getOperand(1), RHS);

              switch(Op0->getType()->getTypeID()) {
                case llvm::Type::IntegerTyID:
                  switch (CE->getOpcode()) {
                    case llvm::Instruction::Add:
                      Result.IntVal = LHS.IntVal + RHS.IntVal;
                      break;
                    case llvm::Instruction::Sub:
                      Result.IntVal = LHS.IntVal - RHS.IntVal;
                      break;
                    case llvm::Instruction::Mul:
                      Result.IntVal = LHS.IntVal * RHS.IntVal;
                      break;
                    case llvm::Instruction::UDiv:
                      Result.IntVal = LHS.IntVal.udiv(RHS.IntVal);
                      break;
                    case llvm::Instruction::SDiv:
                      Result.IntVal = LHS.IntVal.sdiv(RHS.IntVal);
                      break;
                    case llvm::Instruction::URem:
                      Result.IntVal = LHS.IntVal.urem(RHS.IntVal);
                      break;
                    case llvm::Instruction::SRem:
                      Result.IntVal = LHS.IntVal.srem(RHS.IntVal);
                      break;
                    case llvm::Instruction::And:
                      Result.IntVal = LHS.IntVal & RHS.IntVal;
                      break;
                    case llvm::Instruction::Or:
                      Result.IntVal = LHS.IntVal | RHS.IntVal;
                      break;
                    case llvm::Instruction::Xor:
                      Result.IntVal = LHS.IntVal ^ RHS.IntVal;
                      break;
                    default:
                      llvm_unreachable("Invalid integer opcode");
                      break;
                  }
                  break;

                case llvm::Type::FloatTyID:
                  switch (CE->getOpcode()) {
                    case llvm::Instruction::FAdd:
                      Result.FloatVal = LHS.FloatVal + RHS.FloatVal;
                      break;
                    case llvm::Instruction::FSub:
                      Result.FloatVal = LHS.FloatVal - RHS.FloatVal;
                      break;
                    case llvm::Instruction::FMul:
                      Result.FloatVal = LHS.FloatVal * RHS.FloatVal;
                      break;
                    case llvm::Instruction::FDiv:
                      Result.FloatVal = LHS.FloatVal / RHS.FloatVal;
                      break;
                    case llvm::Instruction::FRem:
                      Result.FloatVal = ::fmodf(LHS.FloatVal, RHS.FloatVal);
                      break;
                    default:
                      llvm_unreachable("Invalid float opcode");
                      break;
                  }
                  break;

                case llvm::Type::DoubleTyID:
                  switch (CE->getOpcode()) {
                    case llvm::Instruction::FAdd:
                      Result.DoubleVal = LHS.DoubleVal + RHS.DoubleVal;
                      break;
                    case llvm::Instruction::FSub:
                      Result.DoubleVal = LHS.DoubleVal - RHS.DoubleVal;
                      break;
                    case llvm::Instruction::FMul:
                      Result.DoubleVal = LHS.DoubleVal * RHS.DoubleVal;
                      break;
                    case llvm::Instruction::FDiv:
                      Result.DoubleVal = LHS.DoubleVal / RHS.DoubleVal;
                      break;
                    case llvm::Instruction::FRem:
                      Result.DoubleVal = ::fmod(LHS.DoubleVal, RHS.DoubleVal);
                      break;
                    default:
                      llvm_unreachable("Invalid double opcode");
                      break;
                  }
                  break;

                case llvm::Type::X86_FP80TyID:
                case llvm::Type::PPC_FP128TyID:
                case llvm::Type::FP128TyID:
                  {
                    llvm::APFloat apfLHS = llvm::APFloat(LHS.IntVal);
                    switch (CE->getOpcode()) {
                      case llvm::Instruction::FAdd:
                        apfLHS.add(llvm::APFloat(RHS.IntVal),
                                   llvm::APFloat::rmNearestTiesToEven);
                        break;
                      case llvm::Instruction::FSub:
                        apfLHS.subtract(llvm::APFloat(RHS.IntVal),
                                        llvm::APFloat::rmNearestTiesToEven);
                        break;
                      case llvm::Instruction::FMul:
                        apfLHS.multiply(llvm::APFloat(RHS.IntVal),
                                        llvm::APFloat::rmNearestTiesToEven);
                        break;
                      case llvm::Instruction::FDiv:
                        apfLHS.divide(llvm::APFloat(RHS.IntVal),
                                      llvm::APFloat::rmNearestTiesToEven);
                        break;
                      case llvm::Instruction::FRem:
                        apfLHS.mod(llvm::APFloat(RHS.IntVal),
                                   llvm::APFloat::rmNearestTiesToEven);
                        break;
                      default:
                        llvm_unreachable("Invalid long double opcode");
                        llvm_unreachable(0);
                        break;
                    }

                    Result.IntVal = apfLHS.bitcastToAPInt();
                  }
                  break;

                default:
                  llvm_unreachable("Bad add type!");
                  break;
              } /* End switch(Op0->getType()->getTypeID()) */

              return;
            }

          default:
            break;
        }   /* End switch(CE->getOpcode()) */

        std::string msg;
        llvm::raw_string_ostream Msg(msg);
        Msg << "ConstantExpr not handled: " << *CE;
        llvm::llvm_report_error(Msg.str());
      } /* C->getValueID() == llvm::Value::ConstantExprVal */

      switch (C->getType()->getTypeID()) {
        case llvm::Type::FloatTyID:
          Result.FloatVal = llvm::cast<llvm::ConstantFP>(C)
              ->getValueAPF().convertToFloat();
          break;

        case llvm::Type::DoubleTyID:
          Result.DoubleVal = llvm::cast<llvm::ConstantFP>(C)
              ->getValueAPF().convertToDouble();
          break;

        case llvm::Type::X86_FP80TyID:
        case llvm::Type::FP128TyID:
        case llvm::Type::PPC_FP128TyID:
          Result.IntVal = llvm::cast <llvm::ConstantFP>(C)
              ->getValueAPF().bitcastToAPInt();
          break;

        case llvm::Type::IntegerTyID:
          Result.IntVal = llvm::cast<llvm::ConstantInt>(C)
              ->getValue();
          break;

        case llvm::Type::PointerTyID:
          switch(C->getValueID()) {
            case llvm::Value::ConstantPointerNullVal:
              Result.PointerVal = NULL;
              break;

            case llvm::Value::FunctionVal:
              {
                const llvm::Function* F = (llvm::Function*) C;
                Result.PointerVal = GetPointerToFunctionOrStub
                    (const_cast<llvm::Function*>(F)
                     );
              }
              break;

            case llvm::Value::GlobalVariableVal:
              {
                const llvm::GlobalVariable* GV = (llvm::GlobalVariable*) C;
                Result.PointerVal = GetOrEmitGlobalVariable
                    (const_cast<llvm::GlobalVariable*>(GV)
                     );
              }
              break;

            case llvm::Value::BlockAddressVal:
              {
                // const llvm::BlockAddress* BA = (llvm::BlockAddress*) C;
                // Result.PointerVal = getPointerToBasicBlock
                //    (const_cast<llvm::BasicBlock*>(BA->getBasicBlock()));
                assert(false && "JIT does not support address-of-label yet!");
              }
              break;

            default:
              llvm_unreachable("Unknown constant pointer type!");
              break;
          }
          break;

        default:
          std::string msg;
          llvm::raw_string_ostream Msg(msg);
          Msg << "ERROR: Constant unimplemented for type: " << *C->getType();
          llvm::llvm_report_error(Msg.str());
          break;
      }

      return;
    }

    /*
     * StoreValueToMemory -
     *   Stores the data in @Val of type @Ty at address @Addr.
     */
    void StoreValueToMemory(const llvm::GenericValue& Val, void* Addr,
                            const llvm::Type *Ty) {
      const unsigned int StoreBytes = mpTD->getTypeStoreSize(Ty);

      switch(Ty->getTypeID()) {
        case llvm::Type::IntegerTyID:
          {
            const llvm::APInt& IntVal = Val.IntVal;
            assert((IntVal.getBitWidth() + 7) / 8 >= StoreBytes &&
                   "Integer too small!");

            uint8_t *Src = (uint8_t*) IntVal.getRawData();

            if(llvm::sys::isLittleEndianHost()) {
              /*
               * Little-endian host - the source is ordered from LSB to MSB.
               * Order the destination from LSB to MSB: Do a straight copy.
               */
              memcpy(Addr, Src, StoreBytes);
            } else {
              /*
               * Big-endian host - the source is an array of 64 bit words
               * ordered from LSW to MSW.
               *
               * Each word is ordered from MSB to LSB.
               *
               * Order the destination from MSB to LSB:
               *  Reverse the word order, but not the bytes in a word.
               */
              unsigned int i = StoreBytes;
              while(i > sizeof(uint64_t)) {
                i -= sizeof(uint64_t);
                memcpy((uint8_t*) Addr + i, Src, sizeof(uint64_t));
                Src += sizeof(uint64_t);
              }

              memcpy(Addr, Src + sizeof(uint64_t) - i, i);
            }
          }
          break;

        case llvm::Type::FloatTyID:
          {
            *((float*) Addr) = Val.FloatVal;
          }
          break;

        case llvm::Type::DoubleTyID:
          {
            *((double*) Addr) = Val.DoubleVal;
          }
          break;

        case llvm::Type::X86_FP80TyID:
          {
            memcpy(Addr, Val.IntVal.getRawData(), 10);
          }
          break;

        case llvm::Type::PointerTyID:
          {
            /*
             * Ensure 64 bit target pointers are fully
             * initialized on 32 bit hosts.
             */
            if(StoreBytes != sizeof(llvm::PointerTy))
              memset(Addr, 0, StoreBytes);
            *((llvm::PointerTy*) Addr) = Val.PointerVal;
          }
          break;

        default:
          break;
      }

      if(llvm::sys::isLittleEndianHost() != mpTD->isLittleEndian())
        std::reverse((uint8_t*) Addr, (uint8_t*) Addr + StoreBytes);

      return;
    }

    /*
     * InitializeConstantToMemory -
     *   Recursive function to apply a @Constant value into the
     *   specified memory location @Addr.
     */
    void InitializeConstantToMemory(const llvm::Constant *C, void *Addr) {
      switch(C->getValueID()) {
        case llvm::Value::UndefValueVal:
          // Nothing to do
          break;

        case llvm::Value::ConstantVectorVal:
          {
            // dynamic cast may hurt performance
            const llvm::ConstantVector* CP = (llvm::ConstantVector*) C;

            unsigned int ElementSize = mpTD->getTypeAllocSize
                (CP->getType()->getElementType());

            for(int i=0;i<CP->getNumOperands();i++)
              InitializeConstantToMemory(CP->getOperand(i),
                                         (char*) Addr + i * ElementSize);
          }
          break;

        case llvm::Value::ConstantAggregateZeroVal:
          memset(Addr, 0, (size_t) mpTD->getTypeAllocSize(C->getType()));
          break;

        case llvm::Value::ConstantArrayVal:
          {
            const llvm::ConstantArray* CPA = (llvm::ConstantArray*) C;
            unsigned int ElementSize = mpTD->getTypeAllocSize
                (CPA->getType()->getElementType());

            for(int i=0;i<CPA->getNumOperands();i++)
              InitializeConstantToMemory(CPA->getOperand(i),
                                         (char*) Addr + i * ElementSize);
          }
          break;

        case llvm::Value::ConstantStructVal:
          {
            const llvm::ConstantStruct* CPS = (llvm::ConstantStruct*) C;
            const llvm::StructLayout* SL = mpTD->getStructLayout
                (llvm::cast<llvm::StructType>(CPS->getType()));

            for(int i=0;i<CPS->getNumOperands();i++)
              InitializeConstantToMemory(CPS->getOperand(i),
                                         (char*) Addr +
                                         SL->getElementOffset(i));
          }
          break;

        default:
          {
            if(C->getType()->isFirstClassType()) {
              llvm::GenericValue Val;
              GetConstantValue(C, Val);
              StoreValueToMemory(Val, Addr, C->getType());
            } else
              llvm_unreachable
                  ("Unknown constant type to initialize memory with!");
          }
          break;
      }

      return;
    }

    void emitConstantPool(llvm::MachineConstantPool *MCP) {
      if(mpTJI->hasCustomConstantPool())
        return;

      /*
       * Constant pool address resolution is handled by the target itself in ARM
       * (TargetJITInfo::hasCustomConstantPool() return true).
       */
#if !defined(PROVIDE_ARM_CODEGEN)
      const std::vector<llvm::MachineConstantPoolEntry>& Constants =
          MCP->getConstants();

      if(Constants.empty())
        return;

      unsigned Size = GetConstantPoolSizeInBytes(MCP);
      unsigned Align = MCP->getConstantPoolAlignment();

      mpConstantPoolBase = allocateSpace(Size, Align);
      mpConstantPool = MCP;

      if(mpConstantPoolBase == NULL)
        return; /* out of memory */

      unsigned Offset = 0;
      for(int i=0;i<Constants.size();i++) {
        llvm::MachineConstantPoolEntry CPE = Constants[i];
        unsigned AlignMask = CPE.getAlignment() - 1;
        Offset = (Offset + AlignMask) & ~AlignMask;

        uintptr_t CAddr = (uintptr_t) mpConstantPoolBase + Offset;
        mConstPoolAddresses.push_back(CAddr);

        if(CPE.isMachineConstantPoolEntry())
          llvm::llvm_report_error
              ("Initialize memory with machine specific constant pool"
               " entry has not been implemented!");

        InitializeConstantToMemory(CPE.Val.ConstVal, (void*) CAddr);

        const llvm::Type *Ty = CPE.Val.ConstVal->getType();
        Offset += mpTD->getTypeAllocSize(Ty);
      }
#endif
      return;
    }

    void initJumpTableInfo(llvm::MachineJumpTableInfo *MJTI) {
      if(mpTJI->hasCustomJumpTables())
        return;

      const std::vector<llvm::MachineJumpTableEntry>& JT =
          MJTI->getJumpTables();
      if(JT.empty())
        return;

      unsigned NumEntries = 0;
      for(int i=0;i<JT.size();i++)
        NumEntries += JT[i].MBBs.size();

      unsigned EntrySize = MJTI->getEntrySize(*mpTD);

      mpJumpTable = MJTI;;
      mpJumpTableBase = allocateSpace(NumEntries * EntrySize,
                                      MJTI->getEntryAlignment(*mpTD));

      return;
    }

    void emitJumpTableInfo(llvm::MachineJumpTableInfo *MJTI) {
      if(mpTJI->hasCustomJumpTables())
        return;

      const std::vector<llvm::MachineJumpTableEntry>& JT =
          MJTI->getJumpTables();
      if(JT.empty() || mpJumpTableBase == 0)
        return;

      assert((llvm::TargetMachine::getRelocationModel() == llvm::Reloc::Static)
             && "Cross JIT'ing?");
      assert(MJTI->getEntrySize(*mpTD) == 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*) mpJumpTableBase;
      for(int i=0;i<JT.size();i++) {
        const std::vector<llvm::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(int j=0;j<MBBs.size();j++)
          *SlotPtr++ = getMachineBasicBlockAddress(MBBs[j]);
      }
    }

    void* GetPointerToGlobal(llvm::GlobalValue* V, void* Reference,
                             bool MayNeedFarStub) {
      switch(V->getValueID()) {
        case llvm::Value::FunctionVal:
          {
            llvm::Function* F = (llvm::Function*) V;
            void* FnStub = GetLazyFunctionStubIfAvailable(F);

            if(FnStub)
              /*
               * Return the function stub if it's already created.
               * We do this first so that:
               *   we're returning the same address for the function
               *   as any previous call.
               *
               *  TODO: Yes, this is wrong. The lazy stub isn't guaranteed
               *  to be close enough to call.
               */
              return FnStub;

            /*
             * If we know the target can handle arbitrary-distance calls, try to
             *  return a direct pointer.
             */
            if(!MayNeedFarStub) {
              /* If we have code, go ahead and return that. */
              if(void* ResultPtr = GetPointerToGlobalIfAvailable(F))
                return ResultPtr;

              /*
               * x86_64 architecture may encounter the bug
               *  http://hlvm.llvm.org/bugs/show_bug.cgi?id=5201
               *  which generate instruction "call" instead of "callq".
               *
               * And once the real address of stub is
               *  greater than 64-bit long, the replacement will truncate
               *  to 32-bit resulting a serious problem.
               */
#if !defined(__x86_64__)
              /*
               * If this is an external function pointer,
               * we can force the JIT to
               *  'compile' it, which really just adds it to the map.
               */
              if(F->isDeclaration() || F->hasAvailableExternallyLinkage())
                return GetPointerToFunction(F, /* AbortOnFailure */true);
#endif
            }

            /*
             * Otherwise, we may need a to emit a stub, and, conservatively, we
             *  always do so.
             */
            return GetLazyFunctionStub(F);
          }
          break;

        case llvm::Value::GlobalVariableVal:
          return GetOrEmitGlobalVariable((llvm::GlobalVariable*) V);
          break;

        case llvm::Value::GlobalAliasVal:
          {
            llvm::GlobalAlias* GA = (llvm::GlobalAlias*) V;
            const llvm::GlobalValue* GV = GA->resolveAliasedGlobal(false);

            switch(GV->getValueID()) {
              case llvm::Value::FunctionVal:
                /* FIXME: is there's any possibility that the function
                   is not code-gen'd? */
                return GetPointerToFunction(
                    const_cast<llvm::Function*>((const llvm::Function*) GV),
                    /* AbortOnFailure */true
                                            );
                break;

              case llvm::Value::GlobalVariableVal:
                {
                  if(void* p = mGlobalAddressMap[GV])
                    return p;

                  llvm::GlobalVariable* GVar = (llvm::GlobalVariable*) GV;
                  EmitGlobalVariable(GVar);

                  return mGlobalAddressMap[GV];
                }
                break;

              case llvm::Value::GlobalAliasVal:
                assert(false && "Alias should be resolved ultimately!");
                break;
            }
          }
          break;

        default:
          break;
      }

      llvm_unreachable("Unknown type of global value!");

    }

    /*
     * 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(llvm::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. */
      return GetLazyFunctionStub(F);
    }

    typedef llvm::DenseMap<llvm::Function*, void*> FunctionToLazyStubMapTy;
    FunctionToLazyStubMapTy mFunctionToLazyStubMap;

    void* GetLazyFunctionStubIfAvailable(llvm::Function* F) {
      return mFunctionToLazyStubMap.lookup(F);
    }

    std::set<llvm::Function*> PendingFunctions;
    void* GetLazyFunctionStub(llvm::Function* F) {
      /* If we already have a lazy stub for this function, recycle it. */
      void*& Stub = mFunctionToLazyStubMap[F];
      if(Stub)
        return Stub;

      /*
       * In any cases, we should NOT resolve function at runtime
       *  (though we are able to).
       *  We resolve this right now.
       */
      void* Actual = NULL;
      if(F->isDeclaration() || F->hasAvailableExternallyLinkage())
        Actual = GetPointerToFunction(F, /* AbortOnFailure */true);

      /*
       * Codegen a new stub, calling the actual address of
       * the external function, if it was resolved.
       */
      llvm::TargetJITInfo::StubLayout SL = mpTJI->getStubLayout();
      startGVStub(F, SL.Size, SL.Alignment);
      Stub = mpTJI->emitFunctionStub(F, Actual, *this);
      finishGVStub();

      /*
       * We really want the address of the stub in the GlobalAddressMap
       * for the JIT, not the address of the external function.
       */
      UpdateGlobalMapping(F, Stub);

      if(!Actual)
        PendingFunctions.insert(F);
      else
        Disassembler(F->getNameStr() + " (stub)",
                     (uint8_t*) Stub, SL.Size, (uintptr_t) Stub);

      return Stub;
    }

    /* Our resolver to undefined symbol */
    BCCSymbolLookupFn mpSymbolLookupFn;
    void* mpSymbolLookupContext;

    void* GetPointerToFunction(llvm::Function* F, bool AbortOnFailure) {
      void* Addr = GetPointerToGlobalIfAvailable(F);
      if(Addr)
        return Addr;

      assert((F->isDeclaration() || F->hasAvailableExternallyLinkage()) &&
             "Internal error: only external defined function routes here!");

      /* Handle the failure resolution by ourselves. */
      Addr = GetPointerToNamedSymbol(F->getName().str().c_str(),
                                     /* AbortOnFailure */ false);

      /*
       * If we resolved the symbol to a null address (eg. a weak external)
       *  return a null pointer let the application handle it.
       */
      if(Addr == NULL)
        if(AbortOnFailure)
          llvm::llvm_report_error
              ("Could not resolve external function address: " + F->getName()
               );
        else
          return NULL;

      AddGlobalMapping(F, Addr);

      return Addr;
    }

    void* GetPointerToNamedSymbol(const std::string& Name,
                                  bool AbortOnFailure) {
      if(void* Addr = FindRuntimeFunction(Name.c_str()))
        return Addr;

      if(mpSymbolLookupFn)
        if(void* Addr = mpSymbolLookupFn(mpSymbolLookupContext, Name.c_str()))
          return Addr;

      if(AbortOnFailure)
        llvm::llvm_report_error("Program used external symbol '" + Name +
                                "' which could not be resolved!");

      return NULL;
    }

    /*
     * 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 llvm::GlobalVariable *GV) {
      void* Ptr = GetPointerToGlobalIfAvailable(GV);
      if(Ptr)
        return Ptr;

      if(GV->isDeclaration() || GV->hasAvailableExternallyLinkage()) {
        /* If the global is external, just remember the address. */
        Ptr = GetPointerToNamedSymbol(GV->getName().str(), true);
        AddGlobalMapping(GV, Ptr);
      } else {
        /* If the global hasn't been emitted to memory yet,
           allocate space and emit it into memory. */
        Ptr = GetMemoryForGV(GV);
        AddGlobalMapping(GV, Ptr);
        EmitGlobalVariable(GV);
      }

      return Ptr;
    }

    /*
     * GetMemoryForGV - This method abstracts memory allocation of global
     *  variable so that the JIT can allocate thread local variables depending
     *  on the target.
     */
    void* GetMemoryForGV(const llvm::GlobalVariable* GV) {
      char* Ptr;

      const llvm::Type* GlobalType = GV->getType()->getElementType();
      size_t S = mpTD->getTypeAllocSize(GlobalType);
      size_t A = mpTD->getPreferredAlignment(GV);

      if(GV->isThreadLocal()) {
        /*
         * We can support TLS by
         *
         *  Ptr = TJI.allocateThreadLocalMemory(S);
         *
         * But I tend not to .
         * (should we disable this in the front-end (i.e. slang)?).
         */
        llvm::llvm_report_error
            ("Compilation of Thread Local Storage (TLS) is disabled!");

      } else if(mpTJI->allocateSeparateGVMemory()) {
        /*
         * On the Apple's ARM target (such as iPhone),
         *  the global variable should be
         *  placed in separately allocated heap memory rather than in the same
         *  code memory.
         *  The question is, how about the Android?
         */
        if(A <= 8) {
          Ptr = (char*) malloc(S);
        } else {
          /*
           * Allocate (S + A) bytes of memory,
           * then use an aligned pointer within that space.
           */
          Ptr = (char*) malloc(S + A);
          unsigned int MisAligned = ((intptr_t) Ptr & (A - 1));
          Ptr = Ptr + (MisAligned ? (A - MisAligned) : 0);
        }
      } else {
        Ptr = (char*) allocateGlobal(S, A);
      }

      return Ptr;
    }

    void EmitGlobalVariable(const llvm::GlobalVariable *GV) {
      void* GA = GetPointerToGlobalIfAvailable(GV);

      if(GV->isThreadLocal())
        llvm::llvm_report_error("We don't support Thread Local Storage (TLS)!");

      if(GA == NULL) {
        /* If it's not already specified, allocate memory for the global. */
        GA = GetMemoryForGV(GV);
        AddGlobalMapping(GV, GA);
      }

      InitializeConstantToMemory(GV->getInitializer(), GA);

      /* You can do some statistics on global variable here */
      return;
    }

    typedef std::map<llvm::AssertingVH<llvm::GlobalValue>, void*
                     > GlobalToIndirectSymMapTy;
    GlobalToIndirectSymMapTy GlobalToIndirectSymMap;

    void* GetPointerToGVIndirectSym(llvm::GlobalValue *V, void *Reference) {
      /*
       * Make sure GV is emitted first, and create a stub containing the fully
       *  resolved address.
       */
      void* GVAddress = GetPointerToGlobal(V, Reference, false);

      /* If we already have a stub for this global variable, recycle it. */
      void*& IndirectSym = GlobalToIndirectSymMap[V];
      /* Otherwise, codegen a new indirect symbol. */
      if(!IndirectSym)
        IndirectSym = mpTJI->emitGlobalValueIndirectSym(V, GVAddress, *this);

      return IndirectSym;
    }

    /*
     * ExternalFnToStubMap - This is the equivalent of FunctionToLazyStubMap
     *  for external functions.
     *
     *  TODO: Of course, external functions don't need a lazy stub.
     *        It's actually
     *        here to make it more likely that far calls succeed, but no single
     *        stub can guarantee that. I'll remove this in a subsequent checkin
     *        when I actually fix far calls. (comment from LLVM source)
     */
    std::map<void*, void*> ExternalFnToStubMap;

    /*
     * GetExternalFunctionStub - Return a stub for the function at the
     *  specified address.
     */
    void* GetExternalFunctionStub(void* FnAddr) {
      void*& Stub = ExternalFnToStubMap[FnAddr];
      if(Stub)
        return Stub;

      llvm::TargetJITInfo::StubLayout SL = mpTJI->getStubLayout();
      startGVStub(0, SL.Size, SL.Alignment);
      Stub = mpTJI->emitFunctionStub(0, FnAddr, *this);
      finishGVStub();

      return Stub;
    }


    void Disassembler(const std::string& Name, uint8_t* Start,
                      size_t Length, uintptr_t PC) {
#if defined(USE_DISASSEMBLER)
      FILE* out = stdout;

      fprintf(out, "JIT: Disassembled code: %s\n", Name.c_str());

      disassemble_info disasm_info;
      int (*print_insn)(bfd_vma pc, disassemble_info *info);

      INIT_DISASSEMBLE_INFO(disasm_info, out, fprintf);

      disasm_info.buffer = Start;
      disasm_info.buffer_vma = (bfd_vma) (uintptr_t) Start;
      disasm_info.buffer_length = Length;
      disasm_info.endian = BFD_ENDIAN_LITTLE;

#if defined(DEFAULT_X86_CODEGEN)
      disasm_info.mach = bfd_mach_i386_i386;
      print_insn = print_insn_i386;
#elif defined(DEFAULT_ARM_CODEGEN)
      print_insn = print_insn_arm;
#elif defined(DEFAULT_X64_CODEGEN)
      disasm_info.mach = bfd_mach_x86_64;
      print_insn = print_insn_i386;
#else
#error "Unknown target for disassembler"
#endif

#if defined(DEFAULT_X64_CODEGEN)
#   define TARGET_FMT_lx "%llx"
#else
#   define TARGET_FMT_lx "%08x"
#endif
      int Count;
      for( ; Length > 0; PC += Count, Length -= Count) {
        fprintf(out, "\t0x" TARGET_FMT_lx ": ", (bfd_vma) PC);
        Count = print_insn(PC, &disasm_info);
        fprintf(out, "\n");
      }

      fprintf(out, "\n");
#undef TARGET_FMT_lx

#endif  /* USE_DISASSEMBLER */
      return;
    }

   public:
    /* Will take the ownership of @MemMgr */
    CodeEmitter(CodeMemoryManager* pMemMgr) :
        mpMemMgr(pMemMgr),
        mpTJI(NULL),
        mpTD(NULL),
        mpCurEmitFunction(NULL),
        mpConstantPool(NULL),
        mpJumpTable(NULL),
        mpMMI(NULL),
        mpSymbolLookupFn(NULL),
        mpSymbolLookupContext(NULL)
    {
      return;
    }

    inline global_addresses_const_iterator global_address_begin() const {
      return mGlobalAddressMap.begin();
    }
    inline global_addresses_const_iterator global_address_end() const {
      return mGlobalAddressMap.end();
    }

    void registerSymbolCallback(BCCSymbolLookupFn pFn, BCCvoid* pContext) {
      mpSymbolLookupFn = pFn;
      mpSymbolLookupContext = pContext;
      return;
    }

    void setTargetMachine(llvm::TargetMachine& TM) {
      /* set TargetJITInfo */
      mpTJI = TM.getJITInfo();
      /* set TargetData */
      mpTD = TM.getTargetData();

      /*
        if(mpTJI->needsGOT())
        mpMemMgr->AllocateGOT();  // however,
        // both X86 and ARM target don't need GOT
        // (mpTJI->needsGOT() always returns false)
      */
      assert(!mpTJI->needsGOT() && "We don't support GOT needed target!");

      return;
    }

    /*
     * startFunction - This callback is invoked when the specified function is
     *  about to be code generated.  This initializes the BufferBegin/End/Ptr
     *  fields.
     */
    void startFunction(llvm::MachineFunction &F) {
      uintptr_t ActualSize = 0;

      mpMemMgr->setMemoryWritable();

      /*
       * BufferBegin, BufferEnd and CurBufferPtr
       *  are all inherited from class MachineCodeEmitter,
       *  which is the super class of the class JITCodeEmitter.
       *
       * BufferBegin/BufferEnd - Pointers to the start and end of the memory
       *  allocated for this code buffer.
       *
       * CurBufferPtr - Pointer to the next byte of memory to fill when emitting
       *  code.
       *  This is guranteed to be in the range [BufferBegin,BufferEnd].  If
       *  this pointer is at BufferEnd, it will never move due to code emission,
       *  and
       *  all code emission requests will be ignored (this is
       *  the buffer overflow condition).
       */
      BufferBegin = CurBufferPtr = mpMemMgr
          ->startFunctionBody(F.getFunction(), ActualSize);
      BufferEnd = BufferBegin + ActualSize;

      if(mpCurEmitFunction == NULL)
        mpCurEmitFunction = new EmittedFunctionCode();
      mpCurEmitFunction->FunctionBody = BufferBegin;

      /* Ensure the constant pool/jump table info is at least 4-byte aligned. */
      emitAlignment(16);

      emitConstantPool(F.getConstantPool());
      if(llvm::MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
        initJumpTableInfo(MJTI);

      /* About to start emitting the machine code for the function. */
      emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));

      UpdateGlobalMapping(F.getFunction(), CurBufferPtr);

      mpCurEmitFunction->Code = CurBufferPtr;

      mMBBLocations.clear();

      return;
    }

    /*
     * finishFunction - This callback is invoked
     *  when the specified function has
     *  finished code generation.
     *  If a buffer overflow has occurred, this method
     *  returns true (the callee is required to try again), otherwise it returns
     *  false.
     */
    bool finishFunction(llvm::MachineFunction &F) {
      if(CurBufferPtr == BufferEnd) {
        /* No enough memory */
        mpMemMgr->endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
        return false;
      }

      if(llvm::MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
        emitJumpTableInfo(MJTI);

      /*
       * FnStart is the start of the text,
       * not the start of the constant pool and other per-function data.
       */
      uint8_t* FnStart = (uint8_t*) GetPointerToGlobalIfAvailable
          (F.getFunction());

      /* FnEnd is the end of the function's machine code. */
      uint8_t* FnEnd = CurBufferPtr;

      if(!mRelocations.empty()) {
        /* Resolve the relocations to concrete pointers. */
        for(int i=0;i<mRelocations.size();i++) {
          llvm::MachineRelocation& MR = mRelocations[i];
          void* ResultPtr = NULL;

          if(!MR.letTargetResolve()) {
            if(MR.isExternalSymbol()) {
              ResultPtr = GetPointerToNamedSymbol(MR.getExternalSymbol(), true);
              if(MR.mayNeedFarStub())
                ResultPtr = GetExternalFunctionStub(ResultPtr);
            } else if(MR.isGlobalValue()) {
              ResultPtr = GetPointerToGlobal(MR.getGlobalValue(),
                                             BufferBegin
                                               + MR.getMachineCodeOffset(),
                                             MR.mayNeedFarStub());
            } else if(MR.isIndirectSymbol()) {
              ResultPtr = GetPointerToGVIndirectSym
                  (MR.getGlobalValue(),
                   BufferBegin + MR.getMachineCodeOffset()
                   );
            } else if(MR.isBasicBlock()) {
              ResultPtr =
                  (void*) getMachineBasicBlockAddress(MR.getBasicBlock());
            } else if(MR.isConstantPoolIndex()) {
              ResultPtr =
                  (void*) getConstantPoolEntryAddress
                    (MR.getConstantPoolIndex());
            } else {
              assert(MR.isJumpTableIndex() && "Unknown type of relocation");
              ResultPtr =
                  (void*) getJumpTableEntryAddress(MR.getJumpTableIndex());
            }

            MR.setResultPointer(ResultPtr);
          }
        }

        mpTJI->relocate(BufferBegin, &mRelocations[0], mRelocations.size(),
                        mpMemMgr->getGOTBase());
      }

      mpMemMgr->endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
      /*
       * CurBufferPtr may have moved beyond FnEnd, due to memory allocation for
       *  global variables that were referenced in the relocations.
       */
      if(CurBufferPtr == BufferEnd)
        return false;

      /* Now that we've succeeded in emitting the function */
      mpCurEmitFunction->Size = CurBufferPtr - BufferBegin;
      BufferBegin = CurBufferPtr = 0;

      if(F.getFunction()->hasName())
        mEmittedFunctions[F.getFunction()->getNameStr()] = mpCurEmitFunction;
      mpCurEmitFunction = NULL;

      mRelocations.clear();
      mConstPoolAddresses.clear();

      /* Mark code region readable and executable if it's not so already. */
      mpMemMgr->setMemoryExecutable();

      Disassembler(F.getFunction()->getNameStr(),
                   FnStart, FnEnd - FnStart, (uintptr_t) FnStart);

      if(mpMMI)
        mpMMI->EndFunction();

      return false;
    }

    void startGVStub(const llvm::GlobalValue* GV, unsigned StubSize,
                     unsigned Alignment) {
      mpSavedBufferBegin = BufferBegin;
      mpSavedBufferEnd = BufferEnd;
      mpSavedCurBufferPtr = CurBufferPtr;

      BufferBegin = CurBufferPtr = mpMemMgr->allocateStub(GV, StubSize,
                                                          Alignment);
      BufferEnd = BufferBegin + StubSize + 1;

      return;
    }

    void startGVStub(void* Buffer, unsigned StubSize) {
      mpSavedBufferBegin = BufferBegin;
      mpSavedBufferEnd = BufferEnd;
      mpSavedCurBufferPtr = CurBufferPtr;

      BufferBegin = CurBufferPtr = (uint8_t *) Buffer;
      BufferEnd = BufferBegin + StubSize + 1;

      return;
    }

    void finishGVStub() {
      assert(CurBufferPtr != BufferEnd && "Stub overflowed allocated space.");

      /* restore */
      BufferBegin = mpSavedBufferBegin;
      BufferEnd = mpSavedBufferEnd;
      CurBufferPtr = mpSavedCurBufferPtr;

      return;
    }

    /*
     * allocIndirectGV - Allocates and fills storage for an indirect
     *  GlobalValue, and returns the address.
     */
    void* allocIndirectGV(const llvm::GlobalValue *GV,
                          const uint8_t *Buffer, size_t Size,
                          unsigned Alignment) {
      uint8_t* IndGV = mpMemMgr->allocateStub(GV, Size, Alignment);
      memcpy(IndGV, Buffer, Size);
      return IndGV;
    }

    /* emitLabel - Emits a label */
    void emitLabel(uint64_t LabelID) {
      if(mLabelLocations.size() <= LabelID)
        mLabelLocations.resize((LabelID + 1) * 2);
      mLabelLocations[LabelID] = getCurrentPCValue();
      return;
    }

    /*
     * allocateGlobal - Allocate memory for a global.  Unlike allocateSpace,
     *  this method does not allocate memory in the current output buffer,
     *  because a global may live longer than the current function.
     */
    void* allocateGlobal(uintptr_t Size, unsigned Alignment) {
      /* Delegate this call through the memory manager. */
      return mpMemMgr->allocateGlobal(Size, Alignment);
    }

    /*
     * StartMachineBasicBlock - This should be called by the target when a new
     *  basic block is about to be emitted.  This way the MCE knows where the
     *  start of the block is, and can implement getMachineBasicBlockAddress.
     */
    void StartMachineBasicBlock(llvm::MachineBasicBlock *MBB) {
      if(mMBBLocations.size() <= (unsigned) MBB->getNumber())
        mMBBLocations.resize((MBB->getNumber() + 1) * 2);
      mMBBLocations[MBB->getNumber()] = getCurrentPCValue();
      return;
    }

    /*
     * addRelocation - Whenever a relocatable address is needed, it should be
     *  noted with this interface.
     */
    void addRelocation(const llvm::MachineRelocation &MR) {
      mRelocations.push_back(MR);
      return;
    }

    /*
     * getConstantPoolEntryAddress - Return the address of the 'Index' entry in
     *  the constant pool that was last emitted with
     *  the emitConstantPool method.
     */
    uintptr_t getConstantPoolEntryAddress(unsigned Index) const {
      assert(Index < mpConstantPool->getConstants().size() &&
             "Invalid constant pool index!");
      return mConstPoolAddresses[Index];
    }

    /*
     * getJumpTableEntryAddress - Return the address of the jump table
     *  with index
     *  'Index' in the function that last called initJumpTableInfo.
     */
    uintptr_t getJumpTableEntryAddress(unsigned Index) const {
      const std::vector<llvm::MachineJumpTableEntry>& JT =
          mpJumpTable->getJumpTables();

      assert(Index < JT.size() && "Invalid jump table index!");

      unsigned int Offset = 0;
      unsigned int EntrySize = mpJumpTable->getEntrySize(*mpTD);

      for(int i=0;i<Index;i++)
        Offset += JT[i].MBBs.size();
      Offset *= EntrySize;

      return (uintptr_t)((char *) mpJumpTableBase + Offset);
    }

    /*
     * getMachineBasicBlockAddress - Return the address of the specified
     *  MachineBasicBlock, only usable after the label for the MBB has been
     *  emitted.
     */
    uintptr_t getMachineBasicBlockAddress(llvm::MachineBasicBlock *MBB) const {
      assert(mMBBLocations.size() > (unsigned) MBB->getNumber() &&
             mMBBLocations[MBB->getNumber()] && "MBB not emitted!");
      return mMBBLocations[MBB->getNumber()];
    }

    /*
     * getLabelAddress - Return the address of the specified LabelID,
     *  only usable after the LabelID has been emitted.
     */
    uintptr_t getLabelAddress(uint64_t LabelID) const {
      assert(mLabelLocations.size() > (unsigned) LabelID &&
             mLabelLocations[LabelID] && "Label not emitted!");
      return mLabelLocations[LabelID];
    }

    /*
     * Specifies the MachineModuleInfo object.
     *  This is used for exception handling
     *  purposes.
     */
    void setModuleInfo(llvm::MachineModuleInfo* Info) {
      mpMMI = Info;
      return;
    }

    void updateFunctionStub(llvm::Function* F) {
      /* Get the empty stub we generated earlier. */
      void* Stub;
      std::set<llvm::Function*>::iterator I = PendingFunctions.find(F);
      if(I != PendingFunctions.end())
        Stub = *I;
      else
        return;

      void* Addr = GetPointerToGlobalIfAvailable(F);

      assert(Addr != Stub &&
             "Function must have non-stub address to be updated.");

      /*
       * Tell the target jit info to rewrite the stub at the specified address,
       *  rather than creating a new one.
       */
      llvm::TargetJITInfo::StubLayout SL = mpTJI->getStubLayout();
      startGVStub(Stub, SL.Size);
      mpTJI->emitFunctionStub(F, Addr, *this);
      finishGVStub();

      Disassembler(F->getNameStr() + " (stub)", (uint8_t*) Stub,
                   SL.Size, (uintptr_t) Stub);

      PendingFunctions.erase(I);

      return;
    }

    /*
     * Once you finish the compilation on a translation unit,
     *  you can call this function to recycle the memory
     *  (which is used at compilation time and not needed for runtime).
     *
     *  NOTE: You should not call this funtion until the code-gen passes
     *   for a given module is done.
     *   Otherwise, the results is undefined and may cause the system crash!
     */
    void releaseUnnecessary() {
      mMBBLocations.clear();
      mLabelLocations.clear();
      //sliao mGlobalAddressMap.clear();
      mFunctionToLazyStubMap.clear();
      GlobalToIndirectSymMap.clear();
      ExternalFnToStubMap.clear();
      PendingFunctions.clear();

      return;
    }

    void reset() {
      releaseUnnecessary();

      mpSymbolLookupFn = NULL;
      mpSymbolLookupContext = NULL;

      mpTJI = NULL;
      mpTD = NULL;

      for(EmittedFunctionsMapTy::iterator I = mEmittedFunctions.begin();
          I != mEmittedFunctions.end();
          I++)
        if(I->second != NULL)
          delete I->second;
      mEmittedFunctions.clear();

      mpMemMgr->reset();

      return;
    }

    void* lookup(const char* Name) {
      EmittedFunctionsMapTy::const_iterator I = mEmittedFunctions.find(Name);
      if(I == mEmittedFunctions.end())
        return NULL;
      else
        return I->second->Code;
    }

    void getVarNames(llvm::Module *M,
                     BCCsizei* actualVarCount,
                     BCCsizei maxVarCount,
                     void** vars) {
      int cnt = 0;
      for (llvm::Module::const_global_iterator c = M->global_begin(),
             e = M->global_end(); c != e; ++c) {
        llvm::GlobalVariable *g = (const_cast<llvm::GlobalVariable*> (&(*c)));
        if (!g->hasInternalLinkage()) {
          cnt++;
        }
      }

      if (actualVarCount)
        *actualVarCount = cnt;
      if (cnt > maxVarCount)
        cnt = maxVarCount;
      if (!vars)
        return;

      for (llvm::Module::const_global_iterator c = M->global_begin(),
               e = M->global_end();
           c != e && cnt > 0;
           ++c, --cnt) {
        llvm::GlobalVariable *g = (const_cast<llvm::GlobalVariable*> (&(*c)));
        if (!g->hasInternalLinkage()) {
          // A member function in CodeEmitter
          *vars++ = (void*) GetPointerToGlobalIfAvailable(g);
        }
      }
    }

    void getFunctionNames(BCCsizei* actualFunctionCount,
                          BCCsizei maxFunctionCount,
                          BCCchar** functions) {
      int functionCount = mEmittedFunctions.size();

      if(actualFunctionCount)
        *actualFunctionCount = functionCount;
      if(functionCount > maxFunctionCount)
        functionCount = maxFunctionCount;
      if(functions)
        for(EmittedFunctionsMapTy::const_iterator it =
              mEmittedFunctions.begin();
            functionCount > 0;
            functionCount--, it++)
          *functions++ = (BCCchar*) it->first.c_str();

      return;
    }

    void getFunctionBinary(BCCchar* label,
                           BCCvoid** base,
                           BCCsizei* length) {
      EmittedFunctionsMapTy::const_iterator I = mEmittedFunctions.find(label);
      if(I == mEmittedFunctions.end()) {
        *base = NULL;
        *length = 0;
      } else {
        *base = I->second->Code;
        *length = I->second->Size;
      }
      return;
    }

    ~CodeEmitter() {
      if(mpMemMgr)
        delete mpMemMgr;
      return;
    }
    /* }}} */
  };  /* End of Class CodeEmitter */

  /* The CodeEmitter */
  llvm::OwningPtr<CodeEmitter> mCodeEmitter;
  CodeEmitter* createCodeEmitter() {
    mCodeEmitter.reset(new CodeEmitter(mCodeMemMgr.take()));
    return mCodeEmitter.get();
  }

  BCCSymbolLookupFn mpSymbolLookupFn;
  void* mpSymbolLookupContext;

  llvm::Module* mModule;

  bool mTypeInformationPrepared;
  std::vector<const llvm::Type*> mTypes;

  typedef llvm::StringMap<void*> GlobalVarAddresseTy;
  GlobalVarAddresseTy mGlobalVarAddresses;

 public:
  Compiler() : mpSymbolLookupFn(NULL), mpSymbolLookupContext(NULL), mModule(NULL) {
    llvm::llvm_install_error_handler(LLVMErrorHandler, &mError);
    return;
  }

  /* interface for BCCscript::registerSymbolCallback() */
  void registerSymbolCallback(BCCSymbolLookupFn pFn, BCCvoid* pContext) {
    mpSymbolLookupFn = pFn;
    mpSymbolLookupContext = pContext;
    return;
  }

  int loadModule(const char* bitcode, size_t bitcodeSize) {
    llvm::MemoryBuffer* SB = NULL;

    if(bitcode == NULL || bitcodeSize <= 0)
      return 0;

    GlobalInitialization();

    /* Package input to object MemoryBuffer */
    SB = llvm::MemoryBuffer::getMemBuffer(bitcode, bitcode + bitcodeSize);
    if(SB == NULL) {
      setError("Error reading input Bitcode into memory");
      goto on_bcc_load_module_error;
    }

    /* Read the input Bitcode as a Module */
    mModule = llvm::ParseBitcodeFile(SB, llvm::getGlobalContext(), &mError);

on_bcc_load_module_error:
    if (SB)
      delete SB;

    return hasError();
  }

  /* interace for bccCompileScript() */
  int compile() {
    llvm::TargetData* TD = NULL;

    llvm::TargetMachine* TM = NULL;
    const llvm::Target* Target;
    std::string FeaturesStr;

    llvm::FunctionPassManager* CodeGenPasses = NULL;
    const llvm::NamedMDNode* PragmaMetadata;

    if(mModule == NULL) /* No module was loaded */
      return 0;

    /* Create TargetMachine */
    Target = llvm::TargetRegistry::lookupTarget(Triple, mError);
    if(hasError())
      goto on_bcc_compile_error;

    if(!CPU.empty() || !Features.empty()) {
      llvm::SubtargetFeatures F;
      F.setCPU(CPU);
      for(std::vector<std::string>::const_iterator it = Features.begin();
          it != Features.end();
          it++)
        F.AddFeature(*it);
      FeaturesStr = F.getString();
    }

    TM = Target->createTargetMachine(Triple, FeaturesStr);
    if(TM == NULL) {
      setError("Failed to create target machine implementation for the"
               " specified triple '" + Triple + "'");
      goto on_bcc_compile_error;
    }

    /* Create memory manager for creation of code emitter later */
    if(!mCodeMemMgr.get() && !createCodeMemoryManager()) {
      setError("Failed to startup memory management for further compilation");
      goto on_bcc_compile_error;
    }

    /* Create code emitter */
    if(!mCodeEmitter.get()) {
      if(!createCodeEmitter()) {
        setError("Failed to create machine code emitter to complete"
                 " the compilation");
        goto on_bcc_compile_error;
      }
    } else {
      /* reuse the code emitter */
      mCodeEmitter->reset();
    }

    mCodeEmitter->setTargetMachine(*TM);
    mCodeEmitter->registerSymbolCallback(mpSymbolLookupFn,
                                         mpSymbolLookupContext);

    /* Get target data from Module */
    TD = new llvm::TargetData(mModule);
    /* Create code-gen pass to run the code emitter */
    CodeGenPasses = new llvm::FunctionPassManager(mModule);
    CodeGenPasses->add(TD); // Will take the ownership of TD

    if(TM->addPassesToEmitMachineCode(*CodeGenPasses,
                                      *mCodeEmitter, CodeGenOptLevel)) {
      setError("The machine code emission is not supported by BCC on target '"
               + Triple + "'");
      goto on_bcc_compile_error;
    }

    /*
     * Run the pass (the code emitter) on every non-declaration function
     * in the module
     */
    CodeGenPasses->doInitialization();
    for(llvm::Module::iterator I = mModule->begin();
        I != mModule->end();
        I++)
      if(!I->isDeclaration())
        CodeGenPasses->run(*I);

    CodeGenPasses->doFinalization();

    /* Copy the global address mapping from code emitter and remapping */
    for(CodeEmitter::global_addresses_const_iterator I =
          mCodeEmitter->global_address_begin();
        I != mCodeEmitter->global_address_end();
        I++)
    {
      if(I->first->getValueID() != llvm::Value::GlobalVariableVal)
        continue;
      llvm::StringRef GlobalVarName = I->first->getName();
      GlobalVarAddresseTy::value_type* V =
          GlobalVarAddresseTy::value_type::Create(
              GlobalVarName.begin(),
              GlobalVarName.end(),
              mGlobalVarAddresses.getAllocator(),
              I->second
          );
      bool ret = mGlobalVarAddresses.insert(V);
      assert(ret && "The global variable name should be unique over the module");
    }

    /*
     * Tell code emitter now can release the memory using
     * during the JIT since we have done the code emission
     */
    mCodeEmitter->releaseUnnecessary();

    /*
     * Finally, read pragma information from the metadata node
     * of the @Module if any
     */
    PragmaMetadata = mModule->getNamedMetadata(PragmaMetadataName);
    if(PragmaMetadata)
      for(int i=0;i<PragmaMetadata->getNumOperands();i++) {
        llvm::MDNode* Pragma = PragmaMetadata->getOperand(i);
        if(Pragma != NULL &&
           Pragma->getNumOperands() == 2 /* should have exactly 2 operands */) {
          llvm::Value* PragmaNameMDS = Pragma->getOperand(0);
          llvm::Value* PragmaValueMDS = Pragma->getOperand(1);

          if((PragmaNameMDS->getValueID() == llvm::Value::MDStringVal) &&
             (PragmaValueMDS->getValueID() == llvm::Value::MDStringVal)) {
            llvm::StringRef PragmaName =
                static_cast<llvm::MDString*>(PragmaNameMDS)->getString();
            llvm::StringRef PragmaValue =
                static_cast<llvm::MDString*>(PragmaValueMDS)->getString();

            mPragmas.push_back( make_pair( std::string(PragmaName.data(),
                                                       PragmaName.size()),
                                           std::string(PragmaValue.data(),
                                                       PragmaValue.size())
                                           )
                                );
          }
        }
      }

 on_bcc_compile_error:
    if (CodeGenPasses) {
      delete CodeGenPasses;
    } else if (TD) {
      delete TD;
    }
    if (TM)
      delete TM;

    return hasError();
  }

  /* interface for bccGetScriptInfoLog() */
  char* getErrorMessage() {
    return const_cast<char*>(mError.c_str());
  }

  /* interface for bccGetScriptLabel() */
  void* lookup(const char* name) {
    void* addr = NULL;
    if(mCodeEmitter.get()) {
      /* Find function pointer */
      addr = mCodeEmitter->lookup(name);
      if(addr == NULL) {
        /*
         * No function labeled with given name.
         * Try searching the global variables.
         */
        GlobalVarAddresseTy::const_iterator I = mGlobalVarAddresses.find(name);
        if(I != mGlobalVarAddresses.end())
          addr = I->getValue();
      }
    }
    return addr;
  }

  /* Interface for bccGetPragmas() */
  void getPragmas(BCCsizei* actualStringCount,
                  BCCsizei maxStringCount,
                  BCCchar** strings) {
    int stringCount = mPragmas.size() * 2;

    if(actualStringCount)
      *actualStringCount = stringCount;
    if(stringCount > maxStringCount)
      stringCount = maxStringCount;
    if(strings)
      for(PragmaList::const_iterator it = mPragmas.begin();
          stringCount > 0;
          stringCount-=2, it++)
      {
        *strings++ = (BCCchar*) it->first.c_str();
        *strings++ = (BCCchar*) it->second.c_str();
      }

    return;
  }

  /* Interface for bccGetVars() */
  void getVars(BCCsizei* actualVarCount,
               BCCsizei maxVarCount,
               void** vars) {
    if(mCodeEmitter.get())
      mCodeEmitter->getVarNames(mModule,
                                actualVarCount,
                                maxVarCount,
                                vars);
    else
      *actualVarCount = 0;

    return;
  }

  /* Interface for bccGetFunctions() */
  void getFunctions(BCCsizei* actualFunctionCount,
                 BCCsizei maxFunctionCount,
                 BCCchar** functions) {
    if(mCodeEmitter.get())
      mCodeEmitter->getFunctionNames(actualFunctionCount,
                                     maxFunctionCount,
                                     functions);
    else
      *actualFunctionCount = 0;

    return;
  }

  /* Interface for bccGetFunctionBinary() */
  void getFunctionBinary(BCCchar* function,
                         BCCvoid** base,
                         BCCsizei* length) {
    if(mCodeEmitter.get()) {
      mCodeEmitter->getFunctionBinary(function, base, length);
    } else {
      *base = NULL;
      *length = 0;
    }
    return;
  }

  inline const llvm::Module* getModule() const {
    return mModule;
  }

  inline const std::vector<const llvm::Type*>& getTypes() const {
    return mTypes;
  }

  ~Compiler() {
    delete mModule;
    llvm::llvm_shutdown();
    return;
  }
};  /* End of Class Compiler */

bool Compiler::GlobalInitialized = false;

/* Code generation optimization level for the compiler */
llvm::CodeGenOpt::Level Compiler::CodeGenOptLevel;

std::string Compiler::Triple;

std::string Compiler::CPU;

std::vector<std::string> Compiler::Features;

/*
 * The named of metadata node that pragma resides
 * (should be synced with slang.cpp)
 */
const llvm::StringRef Compiler::PragmaMetadataName = "#pragma";

struct BCCscript {
  /*
   * Part I. Compiler
   */

  Compiler compiler;

  void registerSymbolCallback(BCCSymbolLookupFn pFn, BCCvoid* pContext) {
    compiler.registerSymbolCallback(pFn, pContext);
  }

  /*
   * Part II. Logistics & Error handling
   */

  BCCscript() {
    bccError = BCC_NO_ERROR;
  }

  ~BCCscript() {
  }

  void setError(BCCenum error) {
    if (bccError == BCC_NO_ERROR && error != BCC_NO_ERROR) {
      bccError = error;
    }
  }

  BCCenum getError() {
    BCCenum result = bccError;
    bccError = BCC_NO_ERROR;
    return result;
  }

  BCCenum bccError;
};


extern "C"
BCCscript* bccCreateScript()
{
  return new BCCscript();
}

extern "C"
BCCenum bccGetError( BCCscript* script )
{
  return script->getError();
}

extern "C"
void bccDeleteScript(BCCscript* script) {
  delete script;
}

extern "C"
void bccRegisterSymbolCallback(BCCscript* script,
                               BCCSymbolLookupFn pFn,
                               BCCvoid* pContext)
{
  script->registerSymbolCallback(pFn, pContext);
}

extern "C"
void bccScriptBitcode(BCCscript* script,
                      const BCCchar* bitcode,
                      BCCint size)
{
  script->compiler.loadModule(bitcode, size);
}

extern "C"
void bccCompileScript(BCCscript* script)
{
  int result = script->compiler.compile();
  if (result)
    script->setError(BCC_INVALID_OPERATION);
}

extern "C"
void bccGetScriptInfoLog(BCCscript* script,
                         BCCsizei maxLength,
                         BCCsizei* length,
                         BCCchar* infoLog)
{
  char* message = script->compiler.getErrorMessage();
  int messageLength = strlen(message) + 1;
  if (length)
    *length = messageLength;

  if (infoLog && maxLength > 0) {
    int trimmedLength = maxLength < messageLength ? maxLength : messageLength;
    memcpy(infoLog, message, trimmedLength);
    infoLog[trimmedLength] = 0;
  }
}

extern "C"
void bccGetScriptLabel(BCCscript* script,
                       const BCCchar * name,
                       BCCvoid ** address)
{
  void* value = script->compiler.lookup(name);
  if (value)
    *address = value;
  else
    script->setError(BCC_INVALID_VALUE);
}

extern "C"
void bccGetPragmas(BCCscript* script,
                   BCCsizei* actualStringCount,
                   BCCsizei maxStringCount,
                   BCCchar** strings)
{
  script->compiler.getPragmas(actualStringCount, maxStringCount, strings);
}

extern "C"
void bccGetVars(BCCscript* script,
                BCCsizei* actualVarCount,
                BCCsizei maxVarCount,
                void** vars)
{
  script->compiler.getVars(actualVarCount,
                           maxVarCount,
                           vars);
}

extern "C"
void bccGetFunctions(BCCscript* script,
                     BCCsizei* actualFunctionCount,
                     BCCsizei maxFunctionCount,
                     BCCchar** functions)
{
  script->compiler.getFunctions(actualFunctionCount,
                                maxFunctionCount,
                                functions);
}

extern "C"
void bccGetFunctionBinary(BCCscript* script,
                          BCCchar* function,
                          BCCvoid** base,
                          BCCsizei* length)
{
  script->compiler.getFunctionBinary(function, base, length);
}

struct BCCtype {
  const Compiler* compiler;
  const llvm::Type* t;
};

}  /* End of namespace bcc */