path: root/lib/ExecutionEngine/JIT/JIT.cpp

//===-- JIT.cpp - LLVM Just in Time Compiler ------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This tool implements a just-in-time compiler for LLVM, allowing direct
// execution of LLVM bitcode in an efficient manner.
//
//===----------------------------------------------------------------------===//

#include "JIT.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/JITCodeEmitter.h"
#include "llvm/CodeGen/MachineCodeInfo.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/ExecutionEngine/JITEventListener.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MutexGuard.h"
#include "llvm/System/DynamicLibrary.h"
#include "llvm/Config/config.h"

using namespace llvm;

#ifdef __APPLE__ 
// Apple gcc defaults to -fuse-cxa-atexit (i.e. calls __cxa_atexit instead
// of atexit). It passes the address of linker generated symbol __dso_handle
// to the function.
// This configuration change happened at version 5330.
# include <AvailabilityMacros.h>
# if defined(MAC_OS_X_VERSION_10_4) && \
     ((MAC_OS_X_VERSION_MIN_REQUIRED > MAC_OS_X_VERSION_10_4) || \
      (MAC_OS_X_VERSION_MIN_REQUIRED == MAC_OS_X_VERSION_10_4 && \
       __APPLE_CC__ >= 5330))
#  ifndef HAVE___DSO_HANDLE
#   define HAVE___DSO_HANDLE 1
#  endif
# endif
#endif

#if HAVE___DSO_HANDLE
extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
#endif

namespace {

static struct RegisterJIT {
  RegisterJIT() { JIT::Register(); }
} JITRegistrator;

}

extern "C" void LLVMLinkInJIT() {
}

// Determine whether we can register EH tables.
#if (defined(__GNUC__) && !defined(__ARM_EABI__) && \
     !defined(__USING_SJLJ_EXCEPTIONS__))
#define HAVE_EHTABLE_SUPPORT 1
#else
#define HAVE_EHTABLE_SUPPORT 0
#endif

#if HAVE_EHTABLE_SUPPORT
 
// libgcc defines the __register_frame function to dynamically register new
// dwarf frames for exception handling. This functionality is not portable
// across compilers and is only provided by GCC. We use the __register_frame
// function here so that code generated by the JIT cooperates with the unwinding
// runtime of libgcc. When JITting with exception handling enable, LLVM
// generates dwarf frames and registers it to libgcc with __register_frame.
//
// The __register_frame function works with Linux.
//
// Unfortunately, this functionality seems to be in libgcc after the unwinding
// library of libgcc for darwin was written. The code for darwin overwrites the
// value updated by __register_frame with a value fetched with "keymgr".
// "keymgr" is an obsolete functionality, which should be rewritten some day.
// In the meantime, since "keymgr" is on all libgccs shipped with apple-gcc, we
// need a workaround in LLVM which uses the "keymgr" to dynamically modify the
// values of an opaque key, used by libgcc to find dwarf tables.

extern "C" void __register_frame(void*);
extern "C" void __deregister_frame(void*);

#if defined(__APPLE__) && MAC_OS_X_VERSION_MAX_ALLOWED <= 1050
# define USE_KEYMGR 1
#else
# define USE_KEYMGR 0
#endif

#if USE_KEYMGR

namespace {

// LibgccObject - This is the structure defined in libgcc. There is no #include
// provided for this structure, so we also define it here. libgcc calls it
// "struct object". The structure is undocumented in libgcc.
struct LibgccObject {
  void *unused1;
  void *unused2;
  void *unused3;
  
  /// frame - Pointer to the exception table.
  void *frame;
  
  /// encoding -  The encoding of the object?
  union {
    struct {
      unsigned long sorted : 1;
      unsigned long from_array : 1;
      unsigned long mixed_encoding : 1;
      unsigned long encoding : 8;
      unsigned long count : 21; 
    } b;
    size_t i;
  } encoding;
  
  /// fde_end - libgcc defines this field only if some macro is defined. We
  /// include this field even if it may not there, to make libgcc happy.
  char *fde_end;
  
  /// next - At least we know it's a chained list!
  struct LibgccObject *next;
};

// "kemgr" stuff. Apparently, all frame tables are stored there.
extern "C" void _keymgr_set_and_unlock_processwide_ptr(int, void *);
extern "C" void *_keymgr_get_and_lock_processwide_ptr(int);
#define KEYMGR_GCC3_DW2_OBJ_LIST        302     /* Dwarf2 object list  */

/// LibgccObjectInfo - libgcc defines this struct as km_object_info. It
/// probably contains all dwarf tables that are loaded.
struct LibgccObjectInfo {

  /// seenObjects - LibgccObjects already parsed by the unwinding runtime.
  ///
  struct LibgccObject* seenObjects;

  /// unseenObjects - LibgccObjects not parsed yet by the unwinding runtime.
  ///
  struct LibgccObject* unseenObjects;
  
  unsigned unused[2];
};

/// darwin_register_frame - Since __register_frame does not work with darwin's
/// libgcc,we provide our own function, which "tricks" libgcc by modifying the
/// "Dwarf2 object list" key.
void DarwinRegisterFrame(void* FrameBegin) {
  // Get the key.
  LibgccObjectInfo* LOI = (struct LibgccObjectInfo*)
    _keymgr_get_and_lock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST);
  assert(LOI && "This should be preallocated by the runtime");
  
  // Allocate a new LibgccObject to represent this frame. Deallocation of this
  // object may be impossible: since darwin code in libgcc was written after
  // the ability to dynamically register frames, things may crash if we
  // deallocate it.
  struct LibgccObject* ob = (struct LibgccObject*)
    malloc(sizeof(struct LibgccObject));
  
  // Do like libgcc for the values of the field.
  ob->unused1 = (void *)-1;
  ob->unused2 = 0;
  ob->unused3 = 0;
  ob->frame = FrameBegin;
  ob->encoding.i = 0; 
  ob->encoding.b.encoding = llvm::dwarf::DW_EH_PE_omit;
  
  // Put the info on both places, as libgcc uses the first or the second
  // field. Note that we rely on having two pointers here. If fde_end was a
  // char, things would get complicated.
  ob->fde_end = (char*)LOI->unseenObjects;
  ob->next = LOI->unseenObjects;
  
  // Update the key's unseenObjects list.
  LOI->unseenObjects = ob;
  
  // Finally update the "key". Apparently, libgcc requires it. 
  _keymgr_set_and_unlock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST,
                                         LOI);

}

}
#endif // __APPLE__
#endif // HAVE_EHTABLE_SUPPORT

/// 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 module.
ExecutionEngine *ExecutionEngine::createJIT(Module *M,
                                            std::string *ErrorStr,
                                            JITMemoryManager *JMM,
                                            CodeGenOpt::Level OptLevel,
                                            bool GVsWithCode,
                                            CodeModel::Model CMM) {
  // Use the defaults for extra parameters.  Users can use EngineBuilder to
  // set them.
  StringRef MArch = "";
  StringRef MCPU = "";
  SmallVector<std::string, 1> MAttrs;
  return JIT::createJIT(M, ErrorStr, JMM, OptLevel, GVsWithCode, CMM,
                        MArch, MCPU, MAttrs);
}

ExecutionEngine *JIT::createJIT(Module *M,
                                std::string *ErrorStr,
                                JITMemoryManager *JMM,
                                CodeGenOpt::Level OptLevel,
                                bool GVsWithCode,