Nuke the old JIT.

I am sure we will be finding bits and pieces of dead code for years to
come, but this is a good start.

Thanks to Lang Hames for making MCJIT a good replacement!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215111 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 909 insertions, 22 deletions

diff --git a/lib/ExecutionEngine/MCJIT/CMakeLists.txt b/lib/ExecutionEngine/MCJIT/CMakeLists.txt
index 088635a0e99..0f42c31060b 100644
--- a/lib/ExecutionEngine/MCJIT/CMakeLists.txt
+++ b/lib/ExecutionEngine/MCJIT/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_llvm_library(LLVMMCJIT
+  JITMemoryManager.cpp
   MCJIT.cpp
   SectionMemoryManager.cpp
   )
diff --git a/lib/ExecutionEngine/MCJIT/JITMemoryManager.cpp b/lib/ExecutionEngine/MCJIT/JITMemoryManager.cpp
new file mode 100644
index 00000000000..584b93f8150
--- /dev/null
+++ b/lib/ExecutionEngine/MCJIT/JITMemoryManager.cpp
@@ -0,0 +1,904 @@
+//===-- JITMemoryManager.cpp - Memory Allocator for JIT'd code ------------===//
+//
+//                     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 DefaultJITMemoryManager class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITMemoryManager.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Config/config.h"
+#include "llvm/IR/GlobalValue.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Memory.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <climits>
+#include <cstring>
+#include <vector>
+
+#if defined(__linux__)
+#if defined(HAVE_SYS_STAT_H)
+#include <sys/stat.h>
+#endif
+#include <fcntl.h>
+#include <unistd.h>
+#endif
+
+using namespace llvm;
+
+#define DEBUG_TYPE "jit"
+
+STATISTIC(NumSlabs, "Number of slabs of memory allocated by the JIT");
+
+JITMemoryManager::~JITMemoryManager() {}
+
+//===----------------------------------------------------------------------===//
+// Memory Block Implementation.
+//===----------------------------------------------------------------------===//
+
+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.
+    unsigned 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.
+    unsigned PrevAllocated : 1;
+
+    /// BlockSize - This is the size in bytes of this memory block,
+    /// including this header.
+    uintptr_t BlockSize : (sizeof(intptr_t)*CHAR_BIT - 2);
+
+
+    /// getBlockAfter - Return the memory block immediately after this one.
+    ///
+    MemoryRangeHeader &getBlockAfter() const {
+      return *reinterpret_cast<MemoryRangeHeader *>(
+                reinterpret_cast<char*>(
+                  const_cast<MemoryRangeHeader *>(this))+BlockSize);
+    }
+
+    /// getFreeBlockBefore - If the block before this one is free, return it,
+    /// otherwise return null.
+    FreeRangeHeader *getFreeBlockBefore() const {
+      if (PrevAllocated) return nullptr;
+      intptr_t PrevSize = reinterpret_cast<intptr_t *>(
+                            const_cast<MemoryRangeHeader *>(this))[-1];
+      return reinterpret_cast<FreeRangeHeader *>(
+               reinterpret_cast<char*>(
+                 const_cast<MemoryRangeHeader *>(this))-PrevSize);
+    }
+
+    /// FreeBlock - Turn an allocated block into a free block, adjusting
+    /// bits in the object headers, and adding an end of region memory block.
+    FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
+
+    /// TrimAllocationToSize - If this allocated block is significantly larger
+    /// than NewSize, split it into two pieces (where the former is NewSize
+    /// bytes, including the header), and add the new block to the free list.
+    FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList,
+                                          uint64_t NewSize);
+  };
+
+  /// FreeRangeHeader - For a memory block that isn't already allocated, this
+  /// keeps track of the current block and has a pointer to the next free block.
+  /// Free blocks are kept on a circularly linked list.
+  struct FreeRangeHeader : public MemoryRangeHeader {
+    FreeRangeHeader *Prev;
+    FreeRangeHeader *Next;
+
+    /// getMinBlockSize - Get the minimum size for a memory block.  Blocks
+    /// smaller than this size cannot be created.
+    static unsigned getMinBlockSize() {
+      return sizeof(FreeRangeHeader)+sizeof(intptr_t);
+    }
+
+    /// SetEndOfBlockSizeMarker - The word at the end of every free block is
+    /// known to be the size of the free block.  Set it for this block.
+    void SetEndOfBlockSizeMarker() {
+      void *EndOfBlock = (char*)this + BlockSize;
+      ((intptr_t *)EndOfBlock)[-1] = BlockSize;
+    }
+
+    FreeRangeHeader *RemoveFromFreeList() {
+      assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
+      Next->Prev = Prev;
+      return Prev->Next = Next;
+    }
+
+    void AddToFreeList(FreeRangeHeader *FreeList) {
+      Next = FreeList;
+      Prev = FreeList->Prev;
+      Prev->Next = this;
+      Next->Prev = this;
+    }
+
+    /// GrowBlock - The block after this block just got deallocated.  Merge it
+    /// into the current block.
+    void GrowBlock(uintptr_t NewSize);
+
+    /// AllocateBlock - Mark this entire block allocated, updating freelists
+    /// etc.  This returns a pointer to the circular free-list.
+    FreeRangeHeader *AllocateBlock();
+  };
+}
+
+
+/// AllocateBlock - Mark this entire block allocated, updating freelists
+/// etc.  This returns a pointer to the circular free-list.
+FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
+  assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
+         "Cannot allocate an allocated block!");
+  // Mark this block allocated.
+  ThisAllocated = 1;
+  getBlockAfter().PrevAllocated = 1;
+
+  // Remove it from the free list.
+  return RemoveFromFreeList();
+}
+
+/// FreeBlock - Turn an allocated block into a free block, adjusting
+/// bits in the object headers, and adding an end of region memory block.
+/// If possible, coalesce this block with neighboring blocks.  Return the
+/// FreeRangeHeader to allocate from.
+FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
+  MemoryRangeHeader *FollowingBlock = &getBlockAfter();
+  assert(ThisAllocated && "This block is already free!");
+  assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
+
+  FreeRangeHeader *FreeListToReturn = FreeList;
+
+  // If the block after this one is free, merge it into this block.
+  if (!FollowingBlock->ThisAllocated) {
+    FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
+    // "FreeList" always needs to be a valid free block.  If we're about to
+    // coalesce with it, update our notion of what the free list is.
+    if (&FollowingFreeBlock == FreeList) {
+      FreeList = FollowingFreeBlock.Next;
+      FreeListToReturn = nullptr;
+      assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
+    }
+    FollowingFreeBlock.RemoveFromFreeList();
+
+    // Include the following block into this one.
+    BlockSize += FollowingFreeBlock.BlockSize;
+    FollowingBlock = &FollowingFreeBlock.getBlockAfter();
+
+    // Tell the block after the block we are coalescing that this block is
+    // allocated.
+    FollowingBlock->PrevAllocated = 1;
+  }
+
+  assert(FollowingBlock->ThisAllocated && "Missed coalescing?");
+
+  if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
+    PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
+    return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
+  }
+
+  // Otherwise, mark this block free.
+  FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
+  FollowingBlock->PrevAllocated = 0;
+  FreeBlock.ThisAllocated = 0;
+
+  // Link this into the linked list of free blocks.
+  FreeBlock.AddToFreeList(FreeList);
+
+  // Add a marker at the end of the block, indicating the size of this free
+  // block.
+  FreeBlock.SetEndOfBlockSizeMarker();
+  return FreeListToReturn ? FreeListToReturn : &FreeBlock;
+}
+
+/// GrowBlock - The block after this block just got deallocated.  Merge it
+/// into the current block.
+void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
+  assert(NewSize > BlockSize && "Not growing block?");
+  BlockSize = NewSize;
+  SetEndOfBlockSizeMarker();
+  getBlockAfter().PrevAllocated = 0;
+}
+
+/// TrimAllocationToSize - If this allocated block is significantly larger
+/// than NewSize, split it into two pieces (where the former is NewSize
+/// bytes, including the header), and add the new block to the free list.
+FreeRangeHeader *MemoryRangeHeader::
+TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
+  assert(ThisAllocated && getBlockAfter().PrevAllocated &&
+         "Cannot deallocate part of an allocated block!");
+
+  // Don't allow blocks to be trimmed below minimum required size
+  NewSize = std::max<uint64_t>(FreeRangeHeader::getMinBlockSize(), NewSize);
+
+  // Round up size for alignment of header.
+  unsigned HeaderAlign = __alignof(FreeRangeHeader);
+  NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
+
+  // Size is now the size of the block we will remove from the start of the
+  // current block.
+  assert(NewSize <= BlockSize &&
+         "Allocating more space from this block than exists!");
+
+  // If splitting this block will cause the remainder to be too small, do not
+  // split the block.
+  if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
+    return FreeList;
+
+  // Otherwise, we splice the required number of bytes out of this block, form
+  // a new block immediately after it, then mark this block allocated.
+  MemoryRangeHeader &FormerNextBlock = getBlockAfter();
+
+  // Change the size of this block.
+  BlockSize = NewSize;
+
+  // Get the new block we just sliced out and turn it into a free block.
+  FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
+  NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
+  NewNextBlock.ThisAllocated = 0;
+  NewNextBlock.PrevAllocated = 1;
+  NewNextBlock.SetEndOfBlockSizeMarker();
+  FormerNextBlock.PrevAllocated = 0;
+  NewNextBlock.AddToFreeList(FreeList);
+  return &NewNextBlock;
+}
+
+//===----------------------------------------------------------------------===//
+// Memory Block Implementation.
+//===----------------------------------------------------------------------===//
+
+namespace {
+
+  class DefaultJITMemoryManager;
+
+  class JITAllocator {
+    DefaultJITMemoryManager &JMM;
+  public:
+    JITAllocator(DefaultJITMemoryManager &jmm) : JMM(jmm) { }
+    void *Allocate(size_t Size, size_t /*Alignment*/);
+    void Deallocate(void *Slab, size_t Size);
+  };
+
+  /// DefaultJITMemoryManager - Manage memory for the JIT code generation.
+  /// This splits a large block of MAP_NORESERVE'd memory into two
+  /// sections, one for function stubs, one for the functions themselves.  We
+  /// have to do this because we may need to emit a function stub while in the
+  /// middle of emitting a function, and we don't know how large the function we
+  /// are emitting is.
+  class DefaultJITMemoryManager : public JITMemoryManager {
+  public:
+    /// DefaultCodeSlabSize - When we have to go map more memory, we allocate at
+    /// least this much unless more is requested. Currently, in 512k slabs.
+    static const size_t DefaultCodeSlabSize = 512 * 1024;
+
+    /// DefaultSlabSize - Allocate globals and stubs into slabs of 64K (probably
+    /// 16 pages) unless we get an allocation above SizeThreshold.
+    static const size_t DefaultSlabSize = 64 * 1024;
+
+    /// DefaultSizeThreshold - For any allocation larger than 16K (probably
+    /// 4 pages), we should allocate a separate slab to avoid wasted space at
+    /// the end of a normal slab.
+    static const size_t DefaultSizeThreshold = 16 * 1024;
+
+  private:
+    // Whether to poison freed memory.
+    bool PoisonMemory;
+
+    /// LastSlab - This points to the last slab allocated and is used as the
+    /// NearBlock parameter to AllocateRWX so that we can attempt to lay out all
+    /// stubs, data, and code contiguously in memory.  In general, however, this
+    /// is not possible because the NearBlock parameter is ignored on Windows
+    /// platforms and even on Unix it works on a best-effort pasis.
+    sys::MemoryBlock LastSlab;
+
+    // Memory slabs allocated by the JIT.  We refer to them as slabs so we don't
+    // confuse them with the blocks of memory described above.
+    std::vector<sys::MemoryBlock> CodeSlabs;
+    BumpPtrAllocatorImpl<JITAllocator, DefaultSlabSize,
+                         DefaultSizeThreshold> StubAllocator;
+    BumpPtrAllocatorImpl<JITAllocator, DefaultSlabSize,
+                         DefaultSizeThreshold> DataAllocator;
+
+    // Circular list of free blocks.
+    FreeRangeHeader *FreeMemoryList;
+
+    // When emitting code into a memory block, this is the block.
+    MemoryRangeHeader *CurBlock;
+
+    uint8_t *GOTBase;     // Target Specific reserved memory
+  public:
+    DefaultJITMemoryManager();
+    ~DefaultJITMemoryManager();
+
+    /// allocateNewSlab - Allocates a new MemoryBlock and remembers it as the
+    /// last slab it allocated, so that subsequent allocations follow it.
+    sys::MemoryBlock allocateNewSlab(size_t size);
+
+    /// getPointerToNamedFunction - This method returns the address of the
+    /// specified function by using the dlsym function call.
+    void *getPointerToNamedFunction(const std::string &Name,
+                                    bool AbortOnFailure = true) override;
+
+    void AllocateGOT() override;
+
+    // Testing methods.
+    bool CheckInvariants(std::string &ErrorStr) override;
+    size_t GetDefaultCodeSlabSize() override { return DefaultCodeSlabSize; }
+    size_t GetDefaultDataSlabSize() override { return DefaultSlabSize; }
+    size_t GetDefaultStubSlabSize() override { return DefaultSlabSize; }
+    unsigned GetNumCodeSlabs() override { return CodeSlabs.size(); }
+    unsigned GetNumDataSlabs() override { return DataAllocator.GetNumSlabs(); }
+    unsigned GetNumStubSlabs() override { return StubAllocator.GetNumSlabs(); }
+
+    /// startFunctionBody - When a function starts, allocate a block of free
+    /// executable memory, returning a pointer to it and its actual size.
+    uint8_t *startFunctionBody(const Function *F,
+                               uintptr_t &ActualSize) override {
+
+      FreeRangeHeader* candidateBlock = FreeMemoryList;
+      FreeRangeHeader* head = FreeMemoryList;
+      FreeRangeHeader* iter = head->Next;
+
+      uintptr_t largest = candidateBlock->BlockSize;
+
+      // Search for the largest free block
+      while (iter != head) {
+        if (iter->BlockSize > largest) {
+          largest = iter->BlockSize;
+          candidateBlock = iter;
+        }
+        iter = iter->Next;
+      }
+
+      largest = largest - sizeof(MemoryRangeHeader);
+
+      // If this block isn't big enough for the allocation desired, allocate
+      // another block of memory and add it to the free list.
+      if (largest < ActualSize ||
+          largest <= FreeRangeHeader::getMinBlockSize()) {
+        DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
+        candidateBlock = allocateNewCodeSlab((size_t)ActualSize);
+      }
+
+      // Select this candidate block for allocation
+      CurBlock = candidateBlock;
+
+      // Allocate the entire memory block.
+      FreeMemoryList = candidateBlock->AllocateBlock();
+      ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader);
+      return (uint8_t *)(CurBlock + 1);
+    }
+
+    /// allocateNewCodeSlab - Helper method to allocate a new slab of code
+    /// memory from the OS and add it to the free list.  Returns the new
+    /// FreeRangeHeader at the base of the slab.
+    FreeRangeHeader *allocateNewCodeSlab(size_t MinSize) {
+      // If the user needs at least MinSize free memory, then we account for
+      // two MemoryRangeHeaders: the one in the user's block, and the one at the
+      // end of the slab.
+      size_t PaddedMin = MinSize + 2 * sizeof(MemoryRangeHeader);
+      size_t SlabSize = std::max(DefaultCodeSlabSize, PaddedMin);
+      sys::MemoryBlock B = allocateNewSlab(SlabSize);
+      CodeSlabs.push_back(B);
+      char *MemBase = (char*)(B.base());
+
+      // Put a tiny allocated block at the end of the memory chunk, so when
+      // FreeBlock calls getBlockAfter it doesn't fall off the end.
+      MemoryRangeHeader *EndBlock =
+          (MemoryRangeHeader*)(MemBase + B.size()) - 1;
+      EndBlock->ThisAllocated = 1;
+      EndBlock->PrevAllocated = 0;
+      EndBlock->BlockSize = sizeof(MemoryRangeHeader);
+
+      // Start out with a vast new block of free memory.
+      FreeRangeHeader *NewBlock = (FreeRangeHeader*)MemBase;
+      NewBlock->ThisAllocated = 0;
+      // Make sure getFreeBlockBefore doesn't look into unmapped memory.
+      NewBlock->PrevAllocated = 1;
+      NewBlock->BlockSize = (uintptr_t)EndBlock - (uintptr_t)NewBlock;
+      NewBlock->SetEndOfBlockSizeMarker();
+      NewBlock->AddToFreeList(FreeMemoryList);
+
+      assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize &&
+             "The block was too small!");
+      return NewBlock;
+    }
+
+    /// endFunctionBody - The function F is now allocated, and takes the memory
+    /// in the range [FunctionStart,FunctionEnd).
+    void endFunctionBody(const Function *F, uint8_t *FunctionStart,
+                         uint8_t *FunctionEnd) override {
+      assert(FunctionEnd > FunctionStart);
+      assert(FunctionStart == (uint8_t *)(CurBlock+1) &&
+             "Mismatched function start/end!");
+
+      uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock;
+
+      // Release the memory at the end of this block that isn't needed.
+      FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
+    }
+
+    /// allocateSpace - Allocate a 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) override {
+      CurBlock = FreeMemoryList;
+      FreeMemoryList = FreeMemoryList->AllocateBlock();
+
+      uint8_t *result = (uint8_t *)(CurBlock + 1);
+
+      if (Alignment == 0) Alignment = 1;
+      result = (uint8_t*)(((intptr_t)result+Alignment-1) &
+               ~(intptr_t)(Alignment-1));
+
+      uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock;
+      FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
+
+      return result;
+    }
+
+    /// allocateStub - Allocate memory for a function stub.
+    uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
+                          unsigned Alignment) override {
+      return (uint8_t*)StubAllocator.Allocate(StubSize, Alignment);
+    }
+
+    /// allocateGlobal - Allocate memory for a global.
+    uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) override {
+      return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
+    }
+
+    /// allocateCodeSection - Allocate memory for a code section.
+    uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
+                                 unsigned SectionID,
+                                 StringRef SectionName) override {
+      // Grow the required block size to account for the block header
+      Size += sizeof(*CurBlock);
+
+      // Alignment handling.
+      if (!Alignment)
+        Alignment = 16;
+      Size += Alignment - 1;
+
+      FreeRangeHeader* candidateBlock = FreeMemoryList;
+      FreeRangeHeader* head = FreeMemoryList;
+      FreeRangeHeader* iter = head->Next;
+
+      uintptr_t largest = candidateBlock->BlockSize;
+
+      // Search for the largest free block.
+      while (iter != head) {
+        if (iter->BlockSize > largest) {
+          largest = iter->BlockSize;
+          candidateBlock = iter;
+        }
+        iter = iter->Next;
+      }
+
+      largest = largest - sizeof(MemoryRangeHeader);
+
+      // If this block isn't big enough for the allocation desired, allocate
+      // another block of memory and add it to the free list.
+      if (largest < Size || largest <= FreeRangeHeader::getMinBlockSize()) {
+        DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
+        candidateBlock = allocateNewCodeSlab((size_t)Size);
+      }
+
+      // Select this candidate block for allocation
+      CurBlock = candidateBlock;
+
+      // Allocate the entire memory block.
+      FreeMemoryList = candidateBlock->AllocateBlock();
+      // Release the memory at the end of this block that isn't needed.
+      FreeMemoryList = CurBlock->TrimAllocationToSize(FreeMemoryList, Size);
+      uintptr_t unalignedAddr = (uintptr_t)CurBlock + sizeof(*CurBlock);
+      return (uint8_t*)RoundUpToAlignment((uint64_t)unalignedAddr, Alignment);
+    }
+
+    /// allocateDataSection - Allocate memory for a data section.
+    uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
+                                 unsigned SectionID, StringRef SectionName,
+                                 bool IsReadOnly) override {
+      return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
+    }
+
+    bool finalizeMemory(std::string *ErrMsg) override {
+      return false;
+    }
+
+    uint8_t *getGOTBase() const override {
+      return GOTBase;
+    }
+
+    void deallocateBlock(void *Block) {
+      // Find the block that is allocated for this function.
+      MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1;
+      assert(MemRange->ThisAllocated && "Block isn't allocated!");
+
+      // Fill the buffer with garbage!
+      if (PoisonMemory) {
+        memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange));
+      }
+
+      // Free the memory.
+      FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
+    }
+
+    /// deallocateFunctionBody - Deallocate all memory for the specified
+    /// function body.
+    void deallocateFunctionBody(void *Body) override {
+      if (Body) deallocateBlock(Body);
+    }
+
+    /// setMemoryWritable - When code generation is in progress,
+    /// the code pages may need permissions changed.
+    void setMemoryWritable() override {
+      for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
+        sys::Memory::setWritable(CodeSlabs[i]);
+    }
+    /// setMemoryExecutable - When code generation is done and we're ready to
+    /// start execution, the code pages may need permissions changed.
+    void setMemoryExecutable() override {
+      for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
+        sys::Memory::setExecutable(CodeSlabs[i]);
+    }
+
+    /// setPoisonMemory - Controls whether we write garbage over freed memory.
+    ///
+    void setPoisonMemory(bool poison) override {
+      PoisonMemory = poison;
+    }
+  };
+}
+
+void *JITAllocator::Allocate(size_t Size, size_t /*Alignment*/) {
+  sys::MemoryBlock B = JMM.allocateNewSlab(Size);
+  return B.base();
+}
+
+void JITAllocator::Deallocate(void *Slab, size_t Size) {
+  sys::MemoryBlock B(Slab, Size);
+  sys::Memory::ReleaseRWX(B);
+}
+
+DefaultJITMemoryManager::DefaultJITMemoryManager()
+    :
+#ifdef NDEBUG
+      PoisonMemory(false),
+#else
+      PoisonMemory(true),
+#endif
+      LastSlab(nullptr, 0), StubAllocator(*this), DataAllocator(*this) {
+
+  // Allocate space for code.
+  sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize);
+  CodeSlabs.push_back(MemBlock);
+  uint8_t *MemBase = (uint8_t*)MemBlock.base();
+
+  // We set up the memory chunk with 4 mem regions, like this:
+  //  [ START
+  //    [ Free      #0 ] -> Large space to allocate functions from.
+  //    [ Allocated #1 ] -> Tiny space to separate regions.
+  //    [ Free      #2 ] -> Tiny space so there is always at least 1 free block.
+  //    [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
+  //  END ]
+  //
+  // The last three blocks are never deallocated or touched.
+
+  // Add MemoryRangeHeader to the end of the memory region, indicating that
+  // the space after the block of memory is allocated.  This is block #3.
+  MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
+  Mem3->ThisAllocated = 1;
+  Mem3->PrevAllocated = 0;
+  Mem3->BlockSize     = sizeof(MemoryRangeHeader);
+
+  /// Add a tiny free region so that the free list always has one entry.
+  FreeRangeHeader *Mem2 =
+    (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
+  Mem2->ThisAllocated = 0;
+  Mem2->PrevAllocated = 1;
+  Mem2->BlockSize     = FreeRangeHeader::getMinBlockSize();
+  Mem2->SetEndOfBlockSizeMarker();
+  Mem2->Prev = Mem2;   // Mem2 *is* the free list for now.
+  Mem2->Next = Mem2;
+
+  /// Add a tiny allocated region so that Mem2 is never coalesced away.
+  MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
+  Mem1->ThisAllocated = 1;
+  Mem1->PrevAllocated = 0;
+  Mem1->BlockSize     = sizeof(MemoryRangeHeader);
+
+  // Add a FreeRangeHeader to the start of the function body region, indicating
+  // that the space is free.  Mark the previous block allocated so we never look
+  // at it.
+  FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase;
+  Mem0->ThisAllocated = 0;
+  Mem0->PrevAllocated = 1;
+  Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
+  Mem0->SetEndOfBlockSizeMarker();
+  Mem0->AddToFreeList(Mem2);
+
+  // Start out with the freelist pointing to Mem0.
+  FreeMemoryList = Mem0;
+
+  GOTBase = nullptr;
+}
+
+void DefaultJITMemoryManager::AllocateGOT() {
+  assert(!GOTBase && "Cannot allocate the got multiple times");
+  GOTBase = new uint8_t[sizeof(void*) * 8192];
+  HasGOT = true;
+}
+
+DefaultJITMemoryManager::~DefaultJITMemoryManager() {
+  for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
+    sys::Memory::ReleaseRWX(CodeSlabs[i]);
+
+  delete[] GOTBase;
+}
+
+sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
+  // Allocate a new block close to the last one.
+  std::string ErrMsg;
+  sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : nullptr;
+  sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg);
+  if (!B.base()) {
+    report_fatal_error("Allocation failed when allocating new memory in the"
+                       " JIT\n" + Twine(ErrMsg));
+  }
+  LastSlab = B;
+  ++NumSlabs;
+  // Initialize the slab to garbage when debugging.
+  if (PoisonMemory) {
+    memset(B.base(), 0xCD, B.size());
+  }
+  return B;
+}
+
+/// CheckInvariants - For testing only.  Return "" if all internal invariants
+/// are preserved, and a helpful error message otherwise.  For free and
+/// allocated blocks, make sure that adding BlockSize gives a valid block.
+/// For free blocks, make sure they're in the free list and that their end of
+/// block size marker is correct.  This function should return an error before
+/// accessing bad memory.  This function is defined here instead of in
+/// JITMemoryManagerTest.cpp so that we don't have to expose all of the
+/// implementation details of DefaultJITMemoryManager.
+bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) {
+  raw_string_ostream Err(ErrorStr);
+
+  // Construct a the set of FreeRangeHeader pointers so we can query it
+  // efficiently.
+  llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet;
+  FreeRangeHeader* FreeHead = FreeMemoryList;
+  FreeRangeHeader* FreeRange = FreeHead;
+
+  do {
+    // Check that the free range pointer is in the blocks we've allocated.
+    bool Found = false;
+    for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
+         E = CodeSlabs.end(); I != E && !Found; ++I) {
+      char *Start = (char*)I->base();
+      char *End = Start + I->size();
+      Found = (Start <= (char*)FreeRange && (char*)FreeRange < End);
+    }
+    if (!Found) {
+      Err << "Corrupt free list; points to " << FreeRange;
+      return false;
+    }
+
+    if (FreeRange->Next->Prev != FreeRange) {
+      Err << "Next and Prev pointers do not match.";
+      return false;
+    }
+
+    // Otherwise, add it to the set.
+    FreeHdrSet.insert(FreeRange);
+    FreeRange = FreeRange->Next;
+  } while (FreeRange != FreeHead);
+
+  // Go over each block, and look at each MemoryRangeHeader.
+  for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
+       E = CodeSlabs.end(); I != E; ++I) {
+    char *Start = (char*)I->base();
+    char *End = Start + I->size();
+
+    // Check each memory range.
+    for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = nullptr;
+         Start <= (char*)Hdr && (char*)Hdr < End;
+         Hdr = &Hdr->getBlockAfter()) {
+      if (Hdr->ThisAllocated == 0) {
+        // Check that this range is in the free list.
+        if (!FreeHdrSet.count(Hdr)) {
+          Err << "Found free header at " << Hdr << " that is not in free list.";
+          return false;
+        }
+
+        // Now make sure the size marker at the end of the block is correct.
+        uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1;
+        if (!(Start <= (char*)Marker && (char*)Marker < End)) {
+          Err << "Block size in header points out of current MemoryBlock.";
+          return false;
+        }
+        if (Hdr->BlockSize != *Marker) {
+          Err << "End of block size marker (" << *Marker << ") "
+              << "and BlockSize (" << Hdr->BlockSize << ") don't match.";
+          return false;
+        }
+      }
+
+      if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) {
+        Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != "
+            << "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")";
+        return false;
+      } else if (!LastHdr && !Hdr->PrevAllocated) {
+        Err << "The first header should have PrevAllocated true.";
+        return false;
+      }
+
+      // Remember the last header.
+      LastHdr = Hdr;
+    }
+  }
+
+  // All invariants are preserved.
+  return true;
+}
+
+//===----------------------------------------------------------------------===//
+// getPointerToNamedFunction() implementation.
+//===----------------------------------------------------------------------===//
+
+// AtExitHandlers - List of functions to call when the program exits,
+// registered with the atexit() library function.
+static std::vector<void (*)()> AtExitHandlers;
+
+/// runAtExitHandlers - Run any functions registered by the program's
+/// calls to atexit(3), which we intercept and store in
+/// AtExitHandlers.
+///
+static void runAtExitHandlers() {
+  while (!AtExitHandlers.empty()) {
+    void (*Fn)() = AtExitHandlers.back();
+    AtExitHandlers.pop_back();
+    Fn();
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// Function stubs that are invoked instead of certain library calls
+//
+// Force the following functions to be linked in to anything that uses the
+// JIT. This is a hack designed to work around the all-too-clever Glibc
+// strategy of making these functions work differently when inlined vs. when
+// not inlined, and hiding their real definitions in a separate archive file
+// that the dynamic linker can't see. For more info, search for
+// 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
+#if defined(__linux__) && defined(__GLIBC__)
+/* stat functions are redirecting to __xstat with a version number.  On x86-64
+ * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
+ * available as an exported symbol, so we have to add it explicitly.
+ */
+namespace {
+class StatSymbols {
+public:
+  StatSymbols() {
+    sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
+    sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
+    sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
+    sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
+    sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
+    sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
+    sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
+    sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
+    sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
+    sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
+    sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
+  }
+};
+}
+static StatSymbols initStatSymbols;
+#endif // __linux__
+
+// jit_exit - Used to intercept the "exit" library call.
+static void jit_exit(int Status) {
+  runAtExitHandlers();   // Run atexit handlers...
+  exit(Status);
+}
+
+// jit_atexit - Used to intercept the "atexit" library call.
+static int jit_atexit(void (*Fn)()) {
+  AtExitHandlers.push_back(Fn);    // Take note of atexit handler...
+  return 0;  // Always successful
+}
+
+static int jit_noop() {
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+//
+/// getPointerToNamedFunction - This method returns the address of the specified
+/// function by using the dynamic loader interface.  As such it is only useful
+/// for resolving library symbols, not code generated symbols.
+///
+void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name,
+                                                         bool AbortOnFailure) {
+  // Check to see if this is one of the functions we want to intercept.  Note,
+  // we cast to intptr_t here to silence a -pedantic warning that complains
+  // about casting a function pointer to a normal pointer.
+  if (Name == "exit") return (void*)(intptr_t)&jit_exit;
+  if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
+
+  // We should not invoke parent's ctors/dtors from generated main()!
+  // On Mingw and Cygwin, the symbol __main is resolved to
+  // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
+  // (and register wrong callee's dtors with atexit(3)).
+  // We expect ExecutionEngine::runStaticConstructorsDestructors()
+  // is called before ExecutionEngine::runFunctionAsMain() is called.
+  if (Name == "__main") return (void*)(intptr_t)&jit_noop;
+
+  const char *NameStr = Name.c_str();
+  // If this is an asm specifier, skip the sentinal.
+  if (NameStr[0] == 1) ++NameStr;
+
+  // If it's an external function, look it up in the process image...
+  void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
+  if (Ptr) return Ptr;
+
+  // If it wasn't found and if it starts with an underscore ('_') character,
+  // try again without the underscore.
+  if (NameStr[0] == '_') {
+    Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
+    if (Ptr) return Ptr;
+  }
+
+  // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf.  These
+  // are references to hidden visibility symbols that dlsym cannot resolve.
+  // If we have one of these, strip off $LDBLStub and try again.
+#if defined(__APPLE__) && defined(__ppc__)
+  if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
+      memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
+    // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
+    // This mirrors logic in libSystemStubs.a.
+    std::string Prefix = std::string(Name.begin(), Name.end()-9);
+    if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
+      return Ptr;
+    if (void *Ptr = getPointerToNamedFunction(Prefix, false))
+      return Ptr;
+  }
+#endif
+
+  if (AbortOnFailure) {
+    report_fatal_error("Program used external function '"+Name+
+                      "' which could not be resolved!");
+  }
+  return nullptr;
+}
+
+
+
+JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() {
+  return new DefaultJITMemoryManager();
+}
+
+const size_t DefaultJITMemoryManager::DefaultCodeSlabSize;
+const size_t DefaultJITMemoryManager::DefaultSlabSize;
+const size_t DefaultJITMemoryManager::DefaultSizeThreshold;
diff --git a/lib/ExecutionEngine/MCJIT/MCJIT.cpp b/lib/ExecutionEngine/MCJIT/MCJIT.cpp
index 53630d5a5e8..5f1fac7eff1 100644
--- a/lib/ExecutionEngine/MCJIT/MCJIT.cpp
+++ b/lib/ExecutionEngine/MCJIT/MCJIT.cpp
@@ -247,10 +247,6 @@ void MCJIT::finalizeModule(Module *M) {
   finalizeLoadedModules();
 }
 
-void *MCJIT::getPointerToBasicBlock(BasicBlock *BB) {
-  report_fatal_error("not yet implemented");
-}
-
 uint64_t MCJIT::getExistingSymbolAddress(const std::string &Name) {
   Mangler Mang(TM->getSubtargetImpl()->getDataLayout());
   SmallString<128> FullName;
@@ -372,14 +368,6 @@ void *MCJIT::getPointerToFunction(Function *F) {
   return (void*)Dyld.getSymbolLoadAddress(Name);
 }
 
-void *MCJIT::recompileAndRelinkFunction(Function *F) {
-  report_fatal_error("not yet implemented");
-}
-
-void MCJIT::freeMachineCodeForFunction(Function *F) {
-  report_fatal_error("not yet implemented");
-}
-
 void MCJIT::runStaticConstructorsDestructorsInModulePtrSet(
     bool isDtors, ModulePtrSet::iterator I, ModulePtrSet::iterator E) {
   for (; I != E; ++I) {
@@ -549,8 +537,7 @@ void MCJIT::UnregisterJITEventListener(JITEventListener *L) {
   if (!L)
     return;
   MutexGuard locked(lock);
-  SmallVector<JITEventListener*, 2>::reverse_iterator I=
-      std::find(EventListeners.rbegin(), EventListeners.rend(), L);
+  auto I = std::find(EventListeners.rbegin(), EventListeners.rend(), L);
   if (I != EventListeners.rend()) {
     std::swap(*I, EventListeners.back());
     EventListeners.pop_back();
@@ -566,7 +553,8 @@ void MCJIT::NotifyObjectEmitted(const ObjectImage& Obj) {
 void MCJIT::NotifyFreeingObject(const ObjectImage& Obj) {
   MutexGuard locked(lock);
   for (unsigned I = 0, S = EventListeners.size(); I < S; ++I) {
-    EventListeners[I]->NotifyFreeingObject(Obj);
+    JITEventListener *L = EventListeners[I];
+    L->NotifyFreeingObject(Obj);
   }
 }
 
diff --git a/lib/ExecutionEngine/MCJIT/MCJIT.h b/lib/ExecutionEngine/MCJIT/MCJIT.h
index 83e3321db92..247de7c90b8 100644
--- a/lib/ExecutionEngine/MCJIT/MCJIT.h
+++ b/lib/ExecutionEngine/MCJIT/MCJIT.h
@@ -211,7 +211,7 @@ class MCJIT : public ExecutionEngine {
   MCContext *Ctx;
   LinkingMemoryManager MemMgr;
   RuntimeDyld Dyld;
-  SmallVector<JITEventListener*, 2> EventListeners;
+  std::vector<JITEventListener*> EventListeners;
 
   OwningModuleContainer OwnedModules;
 
@@ -275,14 +275,8 @@ public:
   /// \param isDtors - Run the destructors instead of constructors.
   void runStaticConstructorsDestructors(bool isDtors) override;
 
-  void *getPointerToBasicBlock(BasicBlock *BB) override;
-
   void *getPointerToFunction(Function *F) override;
 
-  void *recompileAndRelinkFunction(Function *F) override;
-
-  void freeMachineCodeForFunction(Function *F) override;
-
   GenericValue runFunction(Function *F,
                            const std::vector<GenericValue> &ArgValues) override;