diff --git a/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index 374d6e5..7c98b36 100644
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/include/llvm/CodeGen/MachineFrameInfo.h
@@ -15,6 +15,7 @@
 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
 
 #include "llvm/ADT/SmallVector.h"
+//#include "llvm/ADT/IndexedMap.h"
 #include "llvm/System/DataTypes.h"
 #include <cassert>
 #include <vector>
@@ -103,10 +104,14 @@
     // protector.
     bool MayNeedSP;
 
+    // PreAllocated - If true, the object was mapped into the local frame
+    // block and doesn't need additional handling for allocation beyond that.
+    bool PreAllocated;
+
     StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
                 bool isSS, bool NSP)
       : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
-        isSpillSlot(isSS), MayNeedSP(NSP) {}
+        isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {}
   };
 
   /// Objects - The list of stack objects allocated...
@@ -195,8 +200,20 @@
   ///
   const TargetFrameInfo &TFI;
 
+  /// LocalFrameObjects - References to frame indices which are mapped
+  /// into the local frame allocation block. <FrameIdx, LocalOffset>
+  SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
+
+  /// LocalFrameSize - Size of the pre-allocated local frame block.
+  int64_t LocalFrameSize;
+
+  /// LocalFrameBaseOffset - The base offset from the stack pointer at
+  /// function entry of the local frame blob. Set by PEI for use by
+  /// target in eliminateFrameIndex().
+  int64_t LocalFrameBaseOffset;
+
 public:
-  explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
+    explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
     StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
     HasVarSizedObjects = false;
     FrameAddressTaken = false;
@@ -206,6 +223,8 @@
     StackProtectorIdx = -1;
     MaxCallFrameSize = 0;
     CSIValid = false;
+    LocalFrameSize = 0;
+    LocalFrameBaseOffset = 0;
   }
 
   /// hasStackObjects - Return true if there are any stack objects in this
@@ -252,6 +271,42 @@
   ///
   unsigned getNumObjects() const { return Objects.size(); }
 
+  /// mapLocalFrameObject - Map a frame index into the local object block
+  void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
+    LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
+    Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
+  }
+
+  /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
+  std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
+    assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
+            "Invalid local object reference!");
+    return LocalFrameObjects[i];
+  }
+
+  /// getLocalFrameObjectCount - Return the number of objects allocated into
+  /// the local object block.
+  int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
+
+  /// setLocalFrameBaseOffset - Set the base SP offset of the local frame
+  /// blob.
+  void setLocalFrameBaseOffset(int64_t o) { LocalFrameBaseOffset = o; }
+
+  /// getLocalFrameBaseOffset - Get the base SP offset of the local frame
+  /// blob.
+  int64_t getLocalFrameBaseOffset() const { return LocalFrameBaseOffset; }
+
+  /// getLocalFrameSize - Get the size of the local object blob.
+  int64_t getLocalFrameSize() const { return LocalFrameSize; }
+
+  /// isObjectPreAllocated - Return true if the object was pre-allocated into
+  /// the local block.
+  bool isObjectPreAllocated(int ObjectIdx) const {
+    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
+           "Invalid Object Idx!");
+    return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
+  }
+
   /// getObjectSize - Return the size of the specified object.
   ///
   int64_t getObjectSize(int ObjectIdx) const {
diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index 3e6b3e1..0fa498a 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/include/llvm/CodeGen/Passes.h
@@ -198,6 +198,13 @@
   /// the GCC-style builtin setjmp/longjmp (sjlj) to handling EH control flow.
   FunctionPass *createSjLjEHPass(const TargetLowering *tli);
 
+  /// createLocalStackSlotAllocationPass - This pass assigns local frame
+  /// indices to stack slots relative to one another and allocates
+  /// base registers to access them when it is estimated by the target to
+  /// be out of range of normal frame pointer or stack pointer index
+  /// addressing.
+  FunctionPass *createLocalStackSlotAllocationPass();
+
 } // End llvm namespace
 
 #endif
diff --git a/lib/CodeGen/CMakeLists.txt b/lib/CodeGen/CMakeLists.txt
index a1e270e..a8b9419 100644
--- a/lib/CodeGen/CMakeLists.txt
+++ b/lib/CodeGen/CMakeLists.txt
@@ -22,6 +22,7 @@
   LiveIntervalAnalysis.cpp
   LiveStackAnalysis.cpp
   LiveVariables.cpp
+  LocalStackAllocation.cpp
   LowerSubregs.cpp
   MachineBasicBlock.cpp
   MachineCSE.cpp
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index 20df99e..b856d90 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -74,6 +74,16 @@
 static cl::opt<bool> VerifyMachineCode("verify-machineinstrs", cl::Hidden,
     cl::desc("Verify generated machine code"),
     cl::init(getenv("LLVM_VERIFY_MACHINEINSTRS")!=NULL));
+// Enabled or disable local stack object block allocation. This is an
+// experimental pass that allocates locals relative to one another before
+// register allocation and then assigns them to actual stack slots as a block
+// later in PEI. This will eventually allow targets with limited index offset
+// range to allocate additional base registers (not just FP and SP) to
+// more efficiently reference locals, as well as handle situations where
+// locals cannot be referenced via SP or FP at all (dynamic stack realignment
+// together with variable sized objects, for example).
+cl::opt<bool> EnableLocalStackAlloc("enable-local-stack-alloc", cl::init(false),
+    cl::Hidden, cl::desc("Enable pre-regalloc stack frame index allocation"));
 
 static cl::opt<cl::boolOrDefault>
 AsmVerbose("asm-verbose", cl::desc("Add comments to directives."),
@@ -344,6 +354,12 @@
   if (OptLevel != CodeGenOpt::None)
     PM.add(createOptimizePHIsPass());
 
+  // Assign local variables to stack slots relative to one another and simplify
+  // frame index references where possible. Final stack slot locations will be
+  // assigned in PEI.
+  if (EnableLocalStackAlloc)
+    PM.add(createLocalStackSlotAllocationPass());
+
   if (OptLevel != CodeGenOpt::None) {
     // With optimization, dead code should already be eliminated. However
     // there is one known exception: lowered code for arguments that are only
diff --git a/lib/CodeGen/LocalStackSlotAllocation.cpp b/lib/CodeGen/LocalStackSlotAllocation.cpp
new file mode 100644
index 0000000..dabfb46
--- /dev/null
+++ b/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -0,0 +1,169 @@
+//===- LocalStackSlotAllocation.cpp - Pre-allocate locals to stack slots --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass assigns local frame indices to stack slots relative to one another
+// and allocates additional base registers to access them when the target
+// estimates the are likely to be out of range of stack pointer and frame
+// pointer relative addressing.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "localstackalloc"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetFrameInfo.h"
+
+using namespace llvm;
+
+STATISTIC(NumAllocations, "Number of frame indices processed");
+
+namespace {
+  class LocalStackSlotPass: public MachineFunctionPass {
+    int64_t LocalStackSize;
+
+    void calculateFrameObjectOffsets(MachineFunction &Fn);
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    explicit LocalStackSlotPass() : MachineFunctionPass(ID) { }
+    bool runOnMachineFunction(MachineFunction &MF);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+    const char *getPassName() const {
+      return "Local Stack Slot Allocation";
+    }
+
+  private:
+  };
+} // end anonymous namespace
+
+char LocalStackSlotPass::ID = 0;
+
+FunctionPass *llvm::createLocalStackSlotAllocationPass() {
+  return new LocalStackSlotPass();
+}
+
+bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
+  calculateFrameObjectOffsets(MF);
+  DEBUG(dbgs() << LocalStackSize << " bytes of local storage pre-allocated\n");
+  return true;
+}
+
+/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
+static inline void
+AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
+                  unsigned &MaxAlign) {
+  unsigned Align = MFI->getObjectAlignment(FrameIdx);
+
+  // If the alignment of this object is greater than that of the stack, then
+  // increase the stack alignment to match.
+  MaxAlign = std::max(MaxAlign, Align);
+
+  // Adjust to alignment boundary.
+  Offset = (Offset + Align - 1) / Align * Align;
+
+  DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
+        << Offset << "\n");
+  MFI->mapLocalFrameObject(FrameIdx, Offset);
+  Offset += MFI->getObjectSize(FrameIdx);
+
+  ++NumAllocations;
+}
+
+/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
+/// abstract stack objects.
+///
+void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
+  const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
+
+  // Loop over all of the stack objects, assigning sequential addresses...
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+  int64_t Offset = 0;
+  unsigned MaxAlign = MFI->getMaxAlignment();
+
+  // Make sure that the stack protector comes before the local variables on the
+  // stack.
+  SmallSet<int, 16> LargeStackObjs;
+  if (MFI->getStackProtectorIndex() >= 0) {
+    AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset, MaxAlign);
+
+    // Assign large stack objects first.
+    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+      if (MFI->isDeadObjectIndex(i))
+        continue;
+      if (MFI->getStackProtectorIndex() == (int)i)
+        continue;
+      if (!MFI->MayNeedStackProtector(i))
+        continue;
+
+      AdjustStackOffset(MFI, i, Offset, MaxAlign);
+      LargeStackObjs.insert(i);
+    }
+  }
+
+  // Then assign frame offsets to stack objects that are not used to spill
+  // callee saved registers.
+  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+    if (MFI->isDeadObjectIndex(i))
+      continue;
+    if (MFI->getStackProtectorIndex() == (int)i)
+      continue;
+    if (LargeStackObjs.count(i))
+      continue;
+
+    AdjustStackOffset(MFI, i, Offset, MaxAlign);
+  }
+
+  const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
+  if (!RegInfo->targetHandlesStackFrameRounding()) {
+    // If we have reserved argument space for call sites in the function
+    // immediately on entry to the current function, count it as part of the
+    // overall stack size.
+    if (MFI->adjustsStack() && RegInfo->hasReservedCallFrame(Fn))
+      Offset += MFI->getMaxCallFrameSize();
+
+    // Round up the size to a multiple of the alignment.  If the function has
+    // any calls or alloca's, align to the target's StackAlignment value to
+    // ensure that the callee's frame or the alloca data is suitably aligned;
+    // otherwise, for leaf functions, align to the TransientStackAlignment
+    // value.
+    unsigned StackAlign;
+    if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
+        (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
+      StackAlign = TFI.getStackAlignment();
+    else
+      StackAlign = TFI.getTransientStackAlignment();
+
+    // If the frame pointer is eliminated, all frame offsets will be relative to
+    // SP not FP. Align to MaxAlign so this works.
+    StackAlign = std::max(StackAlign, MaxAlign);
+    unsigned AlignMask = StackAlign - 1;
+    Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
+  }
+
+  // Remember how big this blob of stack space is
+  LocalStackSize = Offset;
+}
diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index cba92fa..8f1d3a6 100644
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -19,6 +19,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define DEBUG_TYPE "pei"
 #include "PrologEpilogInserter.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
@@ -32,6 +33,7 @@
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/STLExtras.h"
@@ -39,6 +41,10 @@
 
 using namespace llvm;
 
+// FIXME: For testing purposes only. Remove once the pre-allocation pass
+// is done.
+extern cl::opt<bool> EnableLocalStackAlloc;
+
 char PEI::ID = 0;
 
 INITIALIZE_PASS(PEI, "prologepilog",
@@ -462,8 +468,10 @@
   Offset = (Offset + Align - 1) / Align * Align;
 
   if (StackGrowsDown) {
+    DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
     MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
   } else {
+    DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
     MFI->setObjectOffset(FrameIdx, Offset);
     Offset += MFI->getObjectSize(FrameIdx);
   }
@@ -548,6 +556,26 @@
       AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
   }
 
+  // Store the offset of the start of the local allocation block. This
+  // will be used later when resolving frame base virtual register pseudos.
+  MFI->setLocalFrameBaseOffset(Offset);
+  if (EnableLocalStackAlloc) {
+    // Allocate the local block
+    Offset += MFI->getLocalFrameSize();
+
+    // Resolve offsets for objects in the local block.
+    for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
+      std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
+      int64_t FIOffset = MFI->getLocalFrameBaseOffset() + Entry.second;
+
+      AdjustStackOffset(MFI, Entry.first, StackGrowsDown, FIOffset, MaxAlign);
+    }
+  }
+  // FIXME: Allocate locals. Once the block allocation pass is turned on,
+  // this simplifies to just the second loop, since all of the large objects
+  // will have already been handled. The second loop can also simplify a
+  // bit, as the conditionals inside aren't all necessary.
+
   // Make sure that the stack protector comes before the local variables on the
   // stack.
   SmallSet<int, 16> LargeStackObjs;
@@ -557,6 +585,8 @@
 
     // Assign large stack objects first.
     for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+      if (MFI->isObjectPreAllocated(i))
+        continue;
       if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
         continue;
       if (RS && (int)i == RS->getScavengingFrameIndex())
@@ -576,6 +606,8 @@
   // Then assign frame offsets to stack objects that are not used to spill
   // callee saved registers.
   for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+    if (MFI->isObjectPreAllocated(i))
+      continue;
     if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
       continue;
     if (RS && (int)i == RS->getScavengingFrameIndex())