diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index 2aceeb3..c9072a7 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -38,6 +38,7 @@
 add_subdirectory(llvm-diff)
 add_subdirectory(macho-dump)
 add_subdirectory(llvm-objdump)
+add_subdirectory(llvm-rtdyld)
 
 add_subdirectory(bugpoint)
 add_subdirectory(bugpoint-passes)
diff --git a/tools/Makefile b/tools/Makefile
index 7310247..5960433 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -13,19 +13,20 @@
 OPTIONAL_PARALLEL_DIRS := clang
 
 # Build LLDB if present. Note LLDB must be built last as it depends on the
-# wider LLVM infrastructure (including Clang). 
+# wider LLVM infrastructure (including Clang).
 OPTIONAL_DIRS := lldb
 
 # NOTE: The tools are organized into five groups of four consisting of one
 # large and three small executables. This is done to minimize memory load
 # in parallel builds.  Please retain this ordering.
-DIRS := llvm-config 
+DIRS := llvm-config
 PARALLEL_DIRS := opt llvm-as llvm-dis \
                  llc llvm-ranlib llvm-ar llvm-nm \
                  llvm-ld llvm-prof llvm-link \
                  lli llvm-extract llvm-mc \
                  bugpoint llvm-bcanalyzer llvm-stub \
-                 llvmc llvm-diff macho-dump llvm-objdump
+                 llvmc llvm-diff macho-dump llvm-objdump \
+	         llvm-rtdyld
 
 # Let users override the set of tools to build from the command line.
 ifdef ONLY_TOOLS
diff --git a/tools/llvm-rtdyld/CMakeLists.txt b/tools/llvm-rtdyld/CMakeLists.txt
new file mode 100644
index 0000000..320bb5f
--- /dev/null
+++ b/tools/llvm-rtdyld/CMakeLists.txt
@@ -0,0 +1,5 @@
+set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD} support MC)
+
+add_llvm_tool(llvm-rtdyld
+  llvm-rtdyld.cpp
+  )
diff --git a/tools/llvm-rtdyld/Makefile b/tools/llvm-rtdyld/Makefile
new file mode 100644
index 0000000..a30a85c
--- /dev/null
+++ b/tools/llvm-rtdyld/Makefile
@@ -0,0 +1,23 @@
+##===- tools/llvm-rtdyld/Makefile --------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+TOOLNAME = llvm-rtdyld
+
+# This tool has no plugins, optimize startup time.
+TOOL_NO_EXPORTS = 1
+
+# Include this here so we can get the configuration of the targets
+# that have been configured for construction. We have to do this
+# early so we can set up LINK_COMPONENTS before including Makefile.rules
+include $(LEVEL)/Makefile.config
+
+LINK_COMPONENTS := $(TARGETS_TO_BUILD) support MC object
+
+include $(LLVM_SRC_ROOT)/Makefile.rules
diff --git a/tools/llvm-rtdyld/llvm-rtdyld.cpp b/tools/llvm-rtdyld/llvm-rtdyld.cpp
new file mode 100644
index 0000000..01c3ead
--- /dev/null
+++ b/tools/llvm-rtdyld/llvm-rtdyld.cpp
@@ -0,0 +1,231 @@
+//===-- llvm-rtdyld.cpp - MCJIT Testing Tool ------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a testing tool for use with the MC-JIT LLVM components.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/Object/MachOObject.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Memory.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/system_error.h"
+using namespace llvm;
+using namespace llvm::object;
+
+static cl::opt<std::string>
+InputFile(cl::Positional, cl::desc("<input file>"), cl::init("-"));
+
+enum ActionType {
+  AC_Execute
+};
+
+static cl::opt<ActionType>
+Action(cl::desc("Action to perform:"),
+       cl::init(AC_Execute),
+       cl::values(clEnumValN(AC_Execute, "execute",
+                             "Load, link, and execute the inputs."),
+                  clEnumValEnd));
+
+/* *** */
+
+static const char *ProgramName;
+
+static void Message(const char *Type, const Twine &Msg) {
+  errs() << ProgramName << ": " << Type << ": " << Msg << "\n";
+}
+
+static int Error(const Twine &Msg) {
+  Message("error", Msg);
+  return 1;
+}
+
+/* *** */
+
+static int ExecuteInput() {
+  // Load the input memory buffer.
+  OwningPtr<MemoryBuffer> InputBuffer;
+  if (error_code ec = MemoryBuffer::getFileOrSTDIN(InputFile, InputBuffer))
+    return Error("unable to read input: '" + ec.message() + "'");
+
+  // Load the Mach-O wrapper object.
+  std::string ErrorStr;
+  OwningPtr<MachOObject> Obj(
+    MachOObject::LoadFromBuffer(InputBuffer.take(), &ErrorStr));
+  if (!Obj)
+    return Error("unable to load object: '" + ErrorStr + "'");
+
+  // Validate that the load commands match what we expect.
+  const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
+    *DysymtabLCI = 0;
+  for (unsigned i = 0; i != Obj->getHeader().NumLoadCommands; ++i) {
+    const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
+    switch (LCI.Command.Type) {
+    case macho::LCT_Segment:
+    case macho::LCT_Segment64:
+      if (SegmentLCI)
+        return Error("unexpected input object (multiple segments)");
+      SegmentLCI = &LCI;
+      break;
+    case macho::LCT_Symtab:
+      if (SymtabLCI)
+        return Error("unexpected input object (multiple symbol tables)");
+      SymtabLCI = &LCI;
+      break;
+    case macho::LCT_Dysymtab:
+      if (DysymtabLCI)
+        return Error("unexpected input object (multiple symbol tables)");
+      DysymtabLCI = &LCI;
+      break;
+    default:
+      return Error("unexpected input object (unexpected load command");
+    }
+  }
+
+  if (!SymtabLCI)
+    return Error("no symbol table found in object");
+  if (!SegmentLCI)
+    return Error("no symbol table found in object");
+
+  // Read and register the symbol table data.
+  InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
+  Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
+  if (!SymtabLC)
+    return Error("unable to load symbol table load command");
+  Obj->RegisterStringTable(*SymtabLC);
+
+  // Read the dynamic link-edit information, if present (not present in static
+  // objects).
+  if (DysymtabLCI) {
+    InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
+    Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
+    if (!DysymtabLC)
+      return Error("unable to load dynamic link-exit load command");
+
+    // FIXME: We don't support anything interesting yet.
+    if (DysymtabLC->LocalSymbolsIndex != 0)
+      return Error("NOT YET IMPLEMENTED: local symbol entries");
+    if (DysymtabLC->ExternalSymbolsIndex != 0)
+      return Error("NOT YET IMPLEMENTED: non-external symbol entries");
+    if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
+      return Error("NOT YET IMPLEMENTED: undefined symbol entries");
+  }
+
+  // Load the segment load command.
+  if (SegmentLCI->Command.Type != macho::LCT_Segment64)
+    return Error("Segment32 not yet implemented!");
+  InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
+  Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
+  if (!Segment64LC)
+    return Error("unable to load segment load command");
+
+  // Map the segment into memory.
+  sys::MemoryBlock Data = sys::Memory::AllocateRWX(Segment64LC->VMSize,
+                                                   0, &ErrorStr);
+  if (!Data.base())
+    return Error("unable to allocate memory block: '" + ErrorStr + "'");
+  memcpy(Data.base(), Obj->getData(Segment64LC->FileOffset,
+                                   Segment64LC->FileSize).data(),
+         Segment64LC->FileSize);
+  memset((char*)Data.base() + Segment64LC->FileSize, 0,
+         Segment64LC->VMSize - Segment64LC->FileSize);
+
+  // Bind the section indices to address.
+  void **SectionBases = new void*[Segment64LC->NumSections];
+  for (unsigned i = 0; i != Segment64LC->NumSections; ++i) {
+    InMemoryStruct<macho::Section64> Sect;
+    Obj->ReadSection64(*SegmentLCI, i, Sect);
+    if (!Sect)
+      return Error("unable to load section: '" + Twine(i) + "'");
+
+    // FIXME: We don't support relocations yet.
+    if (Sect->NumRelocationTableEntries != 0)
+      return Error("not yet implemented: relocations!");
+
+    // FIXME: Improve check.
+    if (Sect->Flags != 0x80000400)
+      return Error("unsupported section type!");
+
+    SectionBases[i] = (char*) Data.base() + Sect->Address;
+  }
+
+  // Bind all the symbols to address.
+  StringMap<void*> SymbolTable;
+  for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
+    InMemoryStruct<macho::Symbol64TableEntry> STE;
+    Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
+    if (!STE)
+      return Error("unable to read symbol: '" + Twine(i) + "'");
+    if (STE->SectionIndex == 0)
+      return Error("unexpected undefined symbol!");
+
+    unsigned Index = STE->SectionIndex - 1;
+    if (Index >= Segment64LC->NumSections)
+      return Error("invalid section index for symbol: '" + Twine() + "'");
+
+    // Get the symbol name.
+    StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
+
+    // Get the section base address.
+    void *SectionBase = SectionBases[Index];
+
+    // Get the symbol address.
+    void *Address = (char*) SectionBase + STE->Value;
+
+    // FIXME: Check the symbol type and flags.
+    if (STE->Type != 0xF)
+      return Error("unexpected symbol type!");
+    if (STE->Flags != 0x0)
+      return Error("unexpected symbol type!");
+
+    SymbolTable[Name] = Address;
+  }
+
+  // Get the address of "_main".
+  StringMap<void*>::iterator it = SymbolTable.find("_main");
+  if (it == SymbolTable.end())
+    return Error("no definition for '_main'");
+
+  // Invalidate the instruction cache.
+  sys::Memory::InvalidateInstructionCache(Data.base(), Data.size());
+
+  // Make sure the memory is executable.
+  if (!sys::Memory::setExecutable(Data, &ErrorStr))
+    return Error("unable to mark function executable: '" + ErrorStr + "'");
+
+  // Dispatch to _main().
+  void *MainAddress = it->second;
+  errs() << "loaded '_main' at: " << MainAddress << "\n";
+
+  int (*Main)(int, const char**) =
+    (int(*)(int,const char**)) uintptr_t(MainAddress);
+  const char **Argv = new const char*[2];
+  Argv[0] = InputFile.c_str();
+  Argv[1] = 0;
+  return Main(1, Argv);
+}
+
+int main(int argc, char **argv) {
+  ProgramName = argv[0];
+  llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.
+
+  cl::ParseCommandLineOptions(argc, argv, "llvm MC-JIT tool\n");
+
+  switch (Action) {
+  default:
+  case AC_Execute:
+    return ExecuteInput();
+  }
+
+  return 0;
+}