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//===- ExecutionEngine.h - Abstract Execution Engine Interface --*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the abstract interface that implements execution support
// for LLVM.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_EXECUTION_ENGINE_H
#define LLVM_EXECUTION_ENGINE_H

#include <vector>
#include <map>
#include <string>
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/System/Mutex.h"
#include "llvm/Target/TargetMachine.h"

namespace llvm {

struct GenericValue;
class Constant;
class ExecutionEngine;
class Function;
class GlobalVariable;
class GlobalValue;
class JITEventListener;
class JITMemoryManager;
class MachineCodeInfo;
class Module;
class ModuleProvider;
class MutexGuard;
class TargetData;
class Type;

class ExecutionEngineState {
public:
  class MapUpdatingCVH : public CallbackVH {
    ExecutionEngineState &EES;

  public:
    MapUpdatingCVH(ExecutionEngineState &EES, const GlobalValue *GV);

    operator const GlobalValue*() const {
      return cast<GlobalValue>(getValPtr());
    }

    virtual void deleted();
    virtual void allUsesReplacedWith(Value *new_value);
  };

private:
  ExecutionEngine &EE;

  /// GlobalAddressMap - A mapping between LLVM global values and their
  /// actualized version...
  std::map<MapUpdatingCVH, void *> GlobalAddressMap;

  /// GlobalAddressReverseMap - This is the reverse mapping of GlobalAddressMap,
  /// used to convert raw addresses into the LLVM global value that is emitted
  /// at the address.  This map is not computed unless getGlobalValueAtAddress
  /// is called at some point.
  std::map<void *, AssertingVH<const GlobalValue> > GlobalAddressReverseMap;

public:
  ExecutionEngineState(ExecutionEngine &EE) : EE(EE) {}

  MapUpdatingCVH getVH(const GlobalValue *GV) {
    return MapUpdatingCVH(*this, GV);
  }

  std::map<MapUpdatingCVH, void *> &
  getGlobalAddressMap(const MutexGuard &) {
    return GlobalAddressMap;
  }

  std::map<void*, AssertingVH<const GlobalValue> > &
  getGlobalAddressReverseMap(const MutexGuard &) {
    return GlobalAddressReverseMap;
  }

  // Returns the address ToUnmap was mapped to.
  void *RemoveMapping(const MutexGuard &, const GlobalValue *ToUnmap);
};


class ExecutionEngine {
  const TargetData *TD;
  ExecutionEngineState EEState;
  bool LazyCompilationDisabled;
  bool GVCompilationDisabled;
  bool SymbolSearchingDisabled;
  bool DlsymStubsEnabled;

  friend class EngineBuilder;  // To allow access to JITCtor and InterpCtor.

protected:
  /// Modules - This is a list of ModuleProvider's that we are JIT'ing from.  We
  /// use a smallvector to optimize for the case where there is only one module.
  SmallVector<ModuleProvider*, 1> Modules;
  
  void setTargetData(const TargetData *td) {
    TD = td;
  }
  
  /// getMemoryforGV - Allocate memory for a global variable.
  virtual char* getMemoryForGV(const GlobalVariable* GV);

  // To avoid having libexecutionengine depend on the JIT and interpreter
  // libraries, the JIT and Interpreter set these functions to ctor pointers
  // at startup time if they are linked in.
  static ExecutionEngine *(*JITCtor)(ModuleProvider *MP,
                                     std::string *ErrorStr,
                                     JITMemoryManager *JMM,
                                     CodeGenOpt::Level OptLevel,
                                     bool GVsWithCode);
  static ExecutionEngine *(*InterpCtor)(ModuleProvider *MP,
                                        std::string *ErrorStr);

  /// LazyFunctionCreator - If an unknown function is needed, this function
  /// pointer is invoked to create it. If this returns null, the JIT will abort.
  void* (*LazyFunctionCreator)(const std::string &);
  
  /// ExceptionTableRegister - If Exception Handling is set, the JIT will 
  /// register dwarf tables with this function
  typedef void (*EERegisterFn)(void*);
  static EERegisterFn ExceptionTableRegister;

public:
  /// lock - This lock is protects the ExecutionEngine, JIT, JITResolver and
  /// JITEmitter classes.  It must be held while changing the internal state of
  /// any of those classes.
  sys::Mutex lock; // Used to make this class and subclasses thread-safe

  //===--------------------------------------------------------------------===//
  //  ExecutionEngine Startup
  //===--------------------------------------------------------------------===//

  virtual ~ExecutionEngine();

  /// create - This is the factory method for creating an execution engine which
  /// is appropriate for the current machine.  This takes ownership of the
  /// module provider.
  static ExecutionEngine *create(ModuleProvider *MP,
                                 bool ForceInterpreter = false,
                                 std::string *ErrorStr = 0,
                                 CodeGenOpt::Level OptLevel =
                                   CodeGenOpt::Default,
                                 // Allocating globals with code breaks
                                 // freeMachineCodeForFunction and is probably
                                 // unsafe and bad for performance.  However,
                                 // we have clients who depend on this
                                 // behavior, so we must support it.
                                 // Eventually, when we're willing to break
                                 // some backwards compatability, this flag
                                 // should be flipped to false, so that by
                                 // default freeMachineCodeForFunction works.
                                 bool GVsWithCode = true);

  /// create - This is the factory method for creating an execution engine which
  /// is appropriate for the current machine.  This takes ownership of the
  /// module.
  static ExecutionEngine *create(Module *M);

  /// createJIT - This is the factory method for creating a JIT for the current
  /// machine, it does not fall back to the interpreter.  This takes ownership
  /// of the ModuleProvider and JITMemoryManager if successful.
  ///
  /// Clients should make sure to initialize targets prior to calling this
  /// function.
  static ExecutionEngine *createJIT(ModuleProvider *MP,
                                    std::string *ErrorStr = 0,
                                    JITMemoryManager *JMM = 0,
                                    CodeGenOpt::Level OptLevel =
                                      CodeGenOpt::Default,
                                    bool GVsWithCode = true);

  /// addModuleProvider - Add a ModuleProvider to the list of modules that we
  /// can JIT from.  Note that this takes ownership of the ModuleProvider: when
  /// the ExecutionEngine is destroyed, it destroys the MP as well.
  virtual void addModuleProvider(ModuleProvider *P) {
    Modules.push_back(P);
  }
  
  //===----------------------------------------------------------------------===//

  const TargetData *getTargetData() const { return TD; }


  /// removeModuleProvider - Remove a ModuleProvider from the list of modules.
  /// Relases the Module from the ModuleProvider, materializing it in the
  /// process, and returns the materialized Module.
  virtual Module* removeModuleProvider(ModuleProvider *P,
                                       std::string *ErrInfo = 0);

  /// deleteModuleProvider - Remove a ModuleProvider from the list of modules,
  /// and deletes the ModuleProvider and owned Module.  Avoids materializing 
  /// the underlying module.
  virtual void deleteModuleProvider(ModuleProvider *P,std::string *ErrInfo = 0);

  /// FindFunctionNamed - Search all of the active modules to find the one that
  /// defines FnName.  This is very slow operation and shouldn't be used for
  /// general code.
  Function *FindFunctionNamed(const char *FnName);
  
  /// runFunction - Execute the specified function with the specified arguments,
  /// and return the result.
  ///
  virtual GenericValue runFunction(Function *F,
                                const std::vector<GenericValue> &ArgValues) = 0;

  /// runStaticConstructorsDestructors - This method is used to execute all of
  /// the static constructors or destructors for a program, depending on the
  /// value of isDtors.
  void runStaticConstructorsDestructors(bool isDtors);
  /// runStaticConstructorsDestructors - This method is used to execute all of
  /// the static constructors or destructors for a module, depending on the
  /// value of isDtors.
  void runStaticConstructorsDestructors(Module *module, bool isDtors);
  
  
  /// runFunctionAsMain - This is a helper function which wraps runFunction to
  /// handle the common task of starting up main with the specified argc, argv,
  /// and envp parameters.
  int runFunctionAsMain(Function *Fn, const std::vector<std::string> &argv,
                        const char * const * envp);


  /// 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.  It can and should also be
  /// used by clients of the EE that want to have an LLVM global overlay
  /// existing data in memory.  Mappings are automatically removed when their
  /// GlobalValue is destroyed.
  void addGlobalMapping(const GlobalValue *GV, void *Addr);
  
  /// clearAllGlobalMappings - Clear all global mappings and start over again
  /// use in dynamic compilation scenarios when you want to move globals
  void clearAllGlobalMappings();
  
  /// clearGlobalMappingsFromModule - Clear all global mappings that came from a
  /// particular module, because it has been removed from the JIT.
  void clearGlobalMappingsFromModule(Module *M);
  
  /// 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.  This returns the old
  /// value of the pointer, or null if it was not in the map.
  void *updateGlobalMapping(const GlobalValue *GV, void *Addr);
  
  /// 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 GlobalValue *GV);

  /// getPointerToGlobal - This returns the address of the specified global
  /// value.  This may involve code generation if it's a function.
  ///
  void *getPointerToGlobal(const GlobalValue *GV);

  /// getPointerToFunction - The different EE's represent function bodies in
  /// different ways.  They should each implement this to say what a function
  /// pointer should look like.  When F is destroyed, the ExecutionEngine will
  /// remove its global mapping but will not yet free its machine code.  Call
  /// freeMachineCodeForFunction(F) explicitly to do that.  Note that global
  /// optimizations can destroy Functions without notifying the ExecutionEngine.
  ///
  virtual void *getPointerToFunction(Function *F) = 0;

  /// 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.  See
  /// getPointerToFunction for the requirements on destroying F.
  ///
  virtual void *getPointerToFunctionOrStub(Function *F) {
    // Default implementation, just codegen the function.
    return getPointerToFunction(F);
  }

  // The JIT overrides a version that actually does this.
  virtual void runJITOnFunction(Function *, MachineCodeInfo * = 0) { }

  /// getGlobalValueAtAddress - Return the LLVM global value object that starts
  /// at the specified address.
  ///
  const GlobalValue *getGlobalValueAtAddress(void *Addr);


  void StoreValueToMemory(const GenericValue &Val, GenericValue *Ptr,
                          const Type *Ty);
  void InitializeMemory(const Constant *Init, void *Addr);

  /// recompileAndRelinkFunction - This method is used to force a function
  /// which has already been compiled to be compiled again, possibly
  /// after it has been modified. Then the entry to the old copy is overwritten
  /// with a branch to the new copy. If there was no old copy, this acts
  /// just like VM::getPointerToFunction().
  ///
  virtual void *recompileAndRelinkFunction(Function *F) = 0;

  /// freeMachineCodeForFunction - Release memory in the ExecutionEngine
  /// corresponding to the machine code emitted to execute this function, useful
  /// for garbage-collecting generated code.
  ///
  virtual void freeMachineCodeForFunction(Function *F) = 0;

  /// getOrEmitGlobalVariable - Return the address of the specified global
  /// variable, possibly emitting it to memory if needed.  This is used by the
  /// Emitter.
  virtual void *getOrEmitGlobalVariable(const GlobalVariable *GV) {
    return getPointerToGlobal((GlobalValue*)GV);
  }

  /// Registers a listener to be called back on various events within
  /// the JIT.  See JITEventListener.h for more details.  Does not
  /// take ownership of the argument.  The argument may be NULL, in
  /// which case these functions do nothing.
  virtual void RegisterJITEventListener(JITEventListener *) {}
  virtual void UnregisterJITEventListener(JITEventListener *) {}

  /// DisableLazyCompilation - If called, the JIT will abort if lazy compilation
  /// is ever attempted.
  void DisableLazyCompilation(bool Disabled = true) {
    LazyCompilationDisabled = Disabled;
  }
  bool isLazyCompilationDisabled() const {
    return LazyCompilationDisabled;
  }

  /// DisableGVCompilation - If called, the JIT will abort if it's asked to
  /// allocate space and populate a GlobalVariable that is not internal to
  /// the module.
  void DisableGVCompilation(bool Disabled = true) {
    GVCompilationDisabled = Disabled;
  }
  bool isGVCompilationDisabled() const {
    return GVCompilationDisabled;
  }

  /// DisableSymbolSearching - If called, the JIT will not try to lookup unknown
  /// symbols with dlsym.  A client can still use InstallLazyFunctionCreator to
  /// resolve symbols in a custom way.
  void DisableSymbolSearching(bool Disabled = true) {
    SymbolSearchingDisabled = Disabled;
  }
  bool isSymbolSearchingDisabled() const {
    return SymbolSearchingDisabled;
  }
  
  /// EnableDlsymStubs - 
  void EnableDlsymStubs(bool Enabled = true) {
    DlsymStubsEnabled = Enabled;
  }
  bool areDlsymStubsEnabled() const {
    return DlsymStubsEnabled;
  }
  
  /// InstallLazyFunctionCreator - If an unknown function is needed, the
  /// specified function pointer is invoked to create it.  If it returns null,
  /// the JIT will abort.
  void InstallLazyFunctionCreator(void* (*P)(const std::string &)) {
    LazyFunctionCreator = P;
  }
  
  /// InstallExceptionTableRegister - The JIT will use the given function
  /// to register the exception tables it generates.
  static void InstallExceptionTableRegister(void (*F)(void*)) {
    ExceptionTableRegister = F;
  }
  
  /// RegisterTable - Registers the given pointer as an exception table. It uses
  /// the ExceptionTableRegister function.
  static void RegisterTable(void* res) {
    if (ExceptionTableRegister)
      ExceptionTableRegister(res);
  }

protected:
  explicit ExecutionEngine(ModuleProvider *P);

  void emitGlobals();

  // EmitGlobalVariable - This method emits the specified global variable to the
  // address specified in GlobalAddresses, or allocates new memory if it's not
  // already in the map.
  void EmitGlobalVariable(const GlobalVariable *GV);

  GenericValue getConstantValue(const Constant *C);
  void LoadValueFromMemory(GenericValue &Result, GenericValue *Ptr, 
                           const Type *Ty);
};

namespace EngineKind {
  // These are actually bitmasks that get or-ed together.
  enum Kind {
    JIT         = 0x1,
    Interpreter = 0x2
  };
  const static Kind Either = (Kind)(JIT | Interpreter);
}

/// EngineBuilder - Builder class for ExecutionEngines.  Use this by
/// stack-allocating a builder, chaining the various set* methods, and
/// terminating it with a .create() call.
class EngineBuilder {

 private:
  ModuleProvider *MP;
  EngineKind::Kind WhichEngine;
  std::string *ErrorStr;
  CodeGenOpt::Level OptLevel;
  JITMemoryManager *JMM;
  bool AllocateGVsWithCode;

  /// InitEngine - Does the common initialization of default options.
  ///
  void InitEngine() {
    WhichEngine = EngineKind::Either;
    ErrorStr = NULL;
    OptLevel = CodeGenOpt::Default;
    JMM = NULL;
    AllocateGVsWithCode = false;
  }

 public:
  /// EngineBuilder - Constructor for EngineBuilder.  If create() is called and
  /// is successful, the created engine takes ownership of the module
  /// provider.
  EngineBuilder(ModuleProvider *mp) : MP(mp) {
    InitEngine();
  }

  /// EngineBuilder - Overloaded constructor that automatically creates an
  /// ExistingModuleProvider for an existing module.
  EngineBuilder(Module *m);

  /// setEngineKind - Controls whether the user wants the interpreter, the JIT,
  /// or whichever engine works.  This option defaults to EngineKind::Either.
  EngineBuilder &setEngineKind(EngineKind::Kind w) {
    WhichEngine = w;
    return *this;
  }

  /// setJITMemoryManager - Sets the memory manager to use.  This allows
  /// clients to customize their memory allocation policies.  If create() is
  /// called and is successful, the created engine takes ownership of the
  /// memory manager.  This option defaults to NULL.
  EngineBuilder &setJITMemoryManager(JITMemoryManager *jmm) {
    JMM = jmm;
    return *this;
  }

  /// setErrorStr - Set the error string to write to on error.  This option
  /// defaults to NULL.
  EngineBuilder &setErrorStr(std::string *e) {
    ErrorStr = e;
    return *this;
  }

  /// setOptLevel - Set the optimization level for the JIT.  This option
  /// defaults to CodeGenOpt::Default.
  EngineBuilder &setOptLevel(CodeGenOpt::Level l) {
    OptLevel = l;
    return *this;
  }

  /// setAllocateGVsWithCode - Sets whether global values should be allocated
  /// into the same buffer as code.  For most applications this should be set
  /// to false.  Allocating globals with code breaks freeMachineCodeForFunction
  /// and is probably unsafe and bad for performance.  However, we have clients
  /// who depend on this behavior, so we must support it.  This option defaults
  /// to false so that users of the new API can safely use the new memory
  /// manager and free machine code.
  EngineBuilder &setAllocateGVsWithCode(bool a) {
    AllocateGVsWithCode = a;
    return *this;
  }

  ExecutionEngine *create();

};

inline bool operator<(const ExecutionEngineState::MapUpdatingCVH& lhs,
                      const ExecutionEngineState::MapUpdatingCVH& rhs) {
    return static_cast<const GlobalValue*>(lhs) <
        static_cast<const GlobalValue*>(rhs);
}

} // End llvm namespace

#endif