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

//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a MachineCodeEmitter object that is used by the JIT to
// write machine code to memory and remember where relocatable values are.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "jit"
#include "JIT.h"
#include "llvm/Constant.h"
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineRelocation.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MutexGuard.h"
#include "llvm/System/Disassembler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/System/Memory.h"
#include <algorithm>
using namespace llvm;

STATISTIC(NumBytes, "Number of bytes of machine code compiled");
STATISTIC(NumRelos, "Number of relocations applied");
static JIT *TheJIT = 0;

//===----------------------------------------------------------------------===//
// JITMemoryManager code.
//
namespace {
  /// MemoryRangeHeader - For a range of memory, this is the header that we put
  /// on the block of memory.  It is carefully crafted to be one word of memory.
  /// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
  /// which starts with this.
  struct FreeRangeHeader;
  struct MemoryRangeHeader {
    /// ThisAllocated - This is true if this block is currently allocated.  If
    /// not, this can be converted to a FreeRangeHeader.
    intptr_t ThisAllocated : 1;
    
    /// PrevAllocated - Keep track of whether the block immediately before us is
    /// allocated.  If not, the word immediately before this header is the size
    /// of the previous block.
    intptr_t PrevAllocated : 1;
    
    /// BlockSize - This is the size in bytes of this memory block,
    /// including this header.
    uintptr_t BlockSize : (sizeof(intptr_t)*8 - 2);
    

    /// getBlockAfter - Return the memory block immediately after this one.
    ///
    MemoryRangeHeader &getBlockAfter() const {
      return *(MemoryRangeHeader*)((char*)this+BlockSize);
    }
    
    /// getFreeBlockBefore - If the block before this one is free, return it,
    /// otherwise return null.
    FreeRangeHeader *getFreeBlockBefore() const {
      if (PrevAllocated) return 0;
      intptr_t PrevSize = ((intptr_t *)this)[-1];
      return (FreeRangeHeader*)((char*)this-PrevSize);
    }
    
    /// FreeBlock - Turn an allocated block into a free block, adjusting
    /// bits in the object headers, and adding an end of region memory block.
    FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
    
    /// TrimAllocationToSize - If this allocated block is significantly larger
    /// than NewSize, split it into two pieces (where the former is NewSize
    /// bytes, including the header), and add the new block to the free list.
    FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList, 
                                          uint64_t NewSize);
  };

  /// FreeRangeHeader - For a memory block that isn't already allocated, this
  /// keeps track of the current block and has a pointer to the next free block.
  /// Free blocks are kept on a circularly linked list.
  struct FreeRangeHeader : public MemoryRangeHeader {
    FreeRangeHeader *Prev;
    FreeRangeHeader *Next;
    
    /// getMinBlockSize - Get the minimum size for a memory block.  Blocks
    /// smaller than this size cannot be created.
    static unsigned getMinBlockSize() {
      return sizeof(FreeRangeHeader)+sizeof(intptr_t);
    }
    
    /// SetEndOfBlockSizeMarker - The word at the end of every free block is
    /// known to be the size of the free block.  Set it for this block.
    void SetEndOfBlockSizeMarker() {
      void *EndOfBlock = (char*)this + BlockSize;
      ((intptr_t *)EndOfBlock)[-1] = BlockSize;
    }

    FreeRangeHeader *RemoveFromFreeList() {
      assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
      Next->Prev = Prev;
      return Prev->Next = Next;
    }
    
    void AddToFreeList(FreeRangeHeader *FreeList) {
      Next = FreeList;
      Prev = FreeList->Prev;
      Prev->Next = this;
      Next->Prev = this;
    }

    /// GrowBlock - The block after this block just got deallocated.  Merge it
    /// into the current block.
    void GrowBlock(uintptr_t NewSize);
    
    /// AllocateBlock - Mark this entire block allocated, updating freelists
    /// etc.  This returns a pointer to the circular free-list.
    FreeRangeHeader *AllocateBlock();
  };
}


/// AllocateBlock - Mark this entire block allocated, updating freelists
/// etc.  This returns a pointer to the circular free-list.
FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
  assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
         "Cannot allocate an allocated block!");
  // Mark this block allocated.
  ThisAllocated = 1