diff --git a/lib/Transforms/InstCombine/InstCombinePHI.cpp b/lib/Transforms/InstCombine/InstCombinePHI.cpp
new file mode 100644
index 0000000..e650bf9
--- /dev/null
+++ b/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -0,0 +1,841 @@
+//===- InstCombinePHI.cpp -------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the visitPHINode function.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InstCombine.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
+using namespace llvm;
+
+/// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(a,c)]
+/// and if a/b/c and the add's all have a single use, turn this into a phi
+/// and a single binop.
+Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
+  Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
+  assert(isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst));
+  unsigned Opc = FirstInst->getOpcode();
+  Value *LHSVal = FirstInst->getOperand(0);
+  Value *RHSVal = FirstInst->getOperand(1);
+    
+  const Type *LHSType = LHSVal->getType();
+  const Type *RHSType = RHSVal->getType();
+  
+  // Scan to see if all operands are the same opcode, and all have one use.
+  for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
+    Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
+    if (!I || I->getOpcode() != Opc || !I->hasOneUse() ||
+        // Verify type of the LHS matches so we don't fold cmp's of different
+        // types or GEP's with different index types.
+        I->getOperand(0)->getType() != LHSType ||
+        I->getOperand(1)->getType() != RHSType)
+      return 0;
+
+    // If they are CmpInst instructions, check their predicates
+    if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
+      if (cast<CmpInst>(I)->getPredicate() !=
+          cast<CmpInst>(FirstInst)->getPredicate())
+        return 0;
+    
+    // Keep track of which operand needs a phi node.
+    if (I->getOperand(0) != LHSVal) LHSVal = 0;
+    if (I->getOperand(1) != RHSVal) RHSVal = 0;
+  }
+
+  // If both LHS and RHS would need a PHI, don't do this transformation,
+  // because it would increase the number of PHIs entering the block,
+  // which leads to higher register pressure. This is especially
+  // bad when the PHIs are in the header of a loop.
+  if (!LHSVal && !RHSVal)
+    return 0;
+  
+  // Otherwise, this is safe to transform!
+  
+  Value *InLHS = FirstInst->getOperand(0);
+  Value *InRHS = FirstInst->getOperand(1);
+  PHINode *NewLHS = 0, *NewRHS = 0;
+  if (LHSVal == 0) {
+    NewLHS = PHINode::Create(LHSType,
+                             FirstInst->getOperand(0)->getName() + ".pn");
+    NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
+    NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
+    InsertNewInstBefore(NewLHS, PN);
+    LHSVal = NewLHS;
+  }
+  
+  if (RHSVal == 0) {
+    NewRHS = PHINode::Create(RHSType,
+                             FirstInst->getOperand(1)->getName() + ".pn");
+    NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
+    NewRHS->addIncoming(InRHS, PN.getIncomingBlock(0));
+    InsertNewInstBefore(NewRHS, PN);
+    RHSVal = NewRHS;
+  }
+  
+  // Add all operands to the new PHIs.
+  if (NewLHS || NewRHS) {
+    for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+      Instruction *InInst = cast<Instruction>(PN.getIncomingValue(i));
+      if (NewLHS) {
+        Value *NewInLHS = InInst->getOperand(0);
+        NewLHS->addIncoming(NewInLHS, PN.getIncomingBlock(i));
+      }
+      if (NewRHS) {
+        Value *NewInRHS = InInst->getOperand(1);
+        NewRHS->addIncoming(NewInRHS, PN.getIncomingBlock(i));
+      }
+    }
+  }
+    
+  if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
+    return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
+  CmpInst *CIOp = cast<CmpInst>(FirstInst);
+  return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
+                         LHSVal, RHSVal);
+}
+
+Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
+  GetElementPtrInst *FirstInst =cast<GetElementPtrInst>(PN.getIncomingValue(0));
+  
+  SmallVector<Value*, 16> FixedOperands(FirstInst->op_begin(), 
+                                        FirstInst->op_end());
+  // This is true if all GEP bases are allocas and if all indices into them are
+  // constants.
+  bool AllBasePointersAreAllocas = true;
+
+  // We don't want to replace this phi if the replacement would require
+  // more than one phi, which leads to higher register pressure. This is
+  // especially bad when the PHIs are in the header of a loop.
+  bool NeededPhi = false;
+  
+  // Scan to see if all operands are the same opcode, and all have one use.
+  for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
+    GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i));
+    if (!GEP || !GEP->hasOneUse() || GEP->getType() != FirstInst->getType() ||
+      GEP->getNumOperands() != FirstInst->getNumOperands())
+      return 0;
+
+    // Keep track of whether or not all GEPs are of alloca pointers.
+    if (AllBasePointersAreAllocas &&
+        (!isa<AllocaInst>(GEP->getOperand(0)) ||
+         !GEP->hasAllConstantIndices()))
+      AllBasePointersAreAllocas = false;
+    
+    // Compare the operand lists.
+    for (unsigned op = 0, e = FirstInst->getNumOperands(); op != e; ++op) {
+      if (FirstInst->getOperand(op) == GEP->getOperand(op))
+        continue;
+      
+      // Don't merge two GEPs when two operands differ (introducing phi nodes)
+      // if one of the PHIs has a constant for the index.  The index may be
+      // substantially cheaper to compute for the constants, so making it a
+      // variable index could pessimize the path.  This also handles the case
+      // for struct indices, which must always be constant.
+      if (isa<ConstantInt>(FirstInst->getOperand(op)) ||
+          isa<ConstantInt>(GEP->getOperand(op)))
+        return 0;
+      
+      if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType())
+        return 0;
+
+      // If we already needed a PHI for an earlier operand, and another operand
+      // also requires a PHI, we'd be introducing more PHIs than we're
+      // eliminating, which increases register pressure on entry to the PHI's
+      // block.
+      if (NeededPhi)
+        return 0;
+
+      FixedOperands[op] = 0;  // Needs a PHI.
+      NeededPhi = true;
+    }
+  }
+  
+  // If all of the base pointers of the PHI'd GEPs are from allocas, don't
+  // bother doing this transformation.  At best, this will just save a bit of
+  // offset calculation, but all the predecessors will have to materialize the
+  // stack address into a register anyway.  We'd actually rather *clone* the
+  // load up into the predecessors so that we have a load of a gep of an alloca,
+  // which can usually all be folded into the load.
+  if (AllBasePointersAreAllocas)
+    return 0;
+  
+  // Otherwise, this is safe to transform.  Insert PHI nodes for each operand
+  // that is variable.
+  SmallVector<PHINode*, 16> OperandPhis(FixedOperands.size());
+  
+  bool HasAnyPHIs = false;
+  for (unsigned i = 0, e = FixedOperands.size(); i != e; ++i) {
+    if (FixedOperands[i]) continue;  // operand doesn't need a phi.
+    Value *FirstOp = FirstInst->getOperand(i);
+    PHINode *NewPN = PHINode::Create(FirstOp->getType(),
+                                     FirstOp->getName()+".pn");
+    InsertNewInstBefore(NewPN, PN);
+    
+    NewPN->reserveOperandSpace(e);
+    NewPN->addIncoming(FirstOp, PN.getIncomingBlock(0));
+    OperandPhis[i] = NewPN;
+    FixedOperands[i] = NewPN;
+    HasAnyPHIs = true;
+  }
+
+  
+  // Add all operands to the new PHIs.
+  if (HasAnyPHIs) {
+    for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+      GetElementPtrInst *InGEP =cast<GetElementPtrInst>(PN.getIncomingValue(i));
+      BasicBlock *InBB = PN.getIncomingBlock(i);
+      
+      for (unsigned op = 0, e = OperandPhis.size(); op != e; ++op)
+        if (PHINode *OpPhi = OperandPhis[op])
+          OpPhi->addIncoming(InGEP->getOperand(op), InBB);
+    }
+  }
+  
+  Value *Base = FixedOperands[0];
+  return cast<GEPOperator>(FirstInst)->isInBounds() ?
+    GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
+                                      FixedOperands.end()) :
+    GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
+                              FixedOperands.end());
+}
+
+
+/// isSafeAndProfitableToSinkLoad - Return true if we know that it is safe to
+/// sink the load out of the block that defines it.  This means that it must be
+/// obvious the value of the load is not changed from the point of the load to
+/// the end of the block it is in.
+///
+/// Finally, it is safe, but not profitable, to sink a load targetting a
+/// non-address-taken alloca.  Doing so will cause us to not promote the alloca
+/// to a register.
+static bool isSafeAndProfitableToSinkLoad(LoadInst *L) {
+  BasicBlock::iterator BBI = L, E = L->getParent()->end();
+  
+  for (++BBI; BBI != E; ++BBI)
+    if (BBI->mayWriteToMemory())
+      return false;
+  
+  // Check for non-address taken alloca.  If not address-taken already, it isn't
+  // profitable to do this xform.
+  if (AllocaInst *AI = dyn_cast<AllocaInst>(L->getOperand(0))) {
+    bool isAddressTaken = false;
+    for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+         UI != E; ++UI) {
+      if (isa<LoadInst>(UI)) continue;
+      if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+        // If storing TO the alloca, then the address isn't taken.
+        if (SI->getOperand(1) == AI) continue;
+      }
+      isAddressTaken = true;
+      break;
+    }
+    
+    if (!isAddressTaken && AI->isStaticAlloca())
+      return false;
+  }
+  
+  // If this load is a load from a GEP with a constant offset from an alloca,
+  // then we don't want to sink it.  In its present form, it will be
+  // load [constant stack offset].  Sinking it will cause us to have to
+  // materialize the stack addresses in each predecessor in a register only to
+  // do a shared load from register in the successor.
+  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(L->getOperand(0)))
+    if (AllocaInst *AI = dyn_cast<AllocaInst>(GEP->getOperand(0)))
+      if (AI->isStaticAlloca() && GEP->hasAllConstantIndices())
+        return false;
+  
+  return true;
+}
+
+Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
+  LoadInst *FirstLI = cast<LoadInst>(PN.getIncomingValue(0));
+  
+  // When processing loads, we need to propagate two bits of information to the
+  // sunk load: whether it is volatile, and what its alignment is.  We currently
+  // don't sink loads when some have their alignment specified and some don't.
+  // visitLoadInst will propagate an alignment onto the load when TD is around,
+  // and if TD isn't around, we can't handle the mixed case.
+  bool isVolatile = FirstLI->isVolatile();
+  unsigned LoadAlignment = FirstLI->getAlignment();
+  
+  // We can't sink the load if the loaded value could be modified between the
+  // load and the PHI.
+  if (FirstLI->getParent() != PN.getIncomingBlock(0) ||
+      !isSafeAndProfitableToSinkLoad(FirstLI))
+    return 0;
+  
+  // If the PHI is of volatile loads and the load block has multiple
+  // successors, sinking it would remove a load of the volatile value from
+  // the path through the other successor.
+  if (isVolatile && 
+      FirstLI->getParent()->getTerminator()->getNumSuccessors() != 1)
+    return 0;
+  
+  // Check to see if all arguments are the same operation.
+  for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+    LoadInst *LI = dyn_cast<LoadInst>(PN.getIncomingValue(i));
+    if (!LI || !LI->hasOneUse())
+      return 0;
+    
+    // We can't sink the load if the loaded value could be modified between 
+    // the load and the PHI.
+    if (LI->isVolatile() != isVolatile ||
+        LI->getParent() != PN.getIncomingBlock(i) ||
+        !isSafeAndProfitableToSinkLoad(LI))
+      return 0;
+      
+    // If some of the loads have an alignment specified but not all of them,
+    // we can't do the transformation.
+    if ((LoadAlignment != 0) != (LI->getAlignment() != 0))
+      return 0;
+    
+    LoadAlignment = std::min(LoadAlignment, LI->getAlignment());
+    
+    // If the PHI is of volatile loads and the load block has multiple
+    // successors, sinking it would remove a load of the volatile value from
+    // the path through the other successor.
+    if (isVolatile &&
+        LI->getParent()->getTerminator()->getNumSuccessors() != 1)
+      return 0;
+  }
+  
+  // Okay, they are all the same operation.  Create a new PHI node of the
+  // correct type, and PHI together all of the LHS's of the instructions.
+  PHINode *NewPN = PHINode::Create(FirstLI->getOperand(0)->getType(),
+                                   PN.getName()+".in");
+  NewPN->reserveOperandSpace(PN.getNumOperands()/2);
+  
+  Value *InVal = FirstLI->getOperand(0);
+  NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
+  
+  // Add all operands to the new PHI.
+  for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+    Value *NewInVal = cast<LoadInst>(PN.getIncomingValue(i))->getOperand(0);
+    if (NewInVal != InVal)
+      InVal = 0;
+    NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
+  }
+  
+  Value *PhiVal;
+  if (InVal) {
+    // The new PHI unions all of the same values together.  This is really
+    // common, so we handle it intelligently here for compile-time speed.
+    PhiVal = InVal;
+    delete NewPN;
+  } else {
+    InsertNewInstBefore(NewPN, PN);
+    PhiVal = NewPN;
+  }
+  
+  // If this was a volatile load that we are merging, make sure to loop through
+  // and mark all the input loads as non-volatile.  If we don't do this, we will
+  // insert a new volatile load and the old ones will not be deletable.
+  if (isVolatile)
+    for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+      cast<LoadInst>(PN.getIncomingValue(i))->setVolatile(false);
+  
+  return new LoadInst(PhiVal, "", isVolatile, LoadAlignment);
+}
+
+
+
+/// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
+/// operator and they all are only used by the PHI, PHI together their
+/// inputs, and do the operation once, to the result of the PHI.
+Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
+  Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
+
+  if (isa<GetElementPtrInst>(FirstInst))
+    return FoldPHIArgGEPIntoPHI(PN);
+  if (isa<LoadInst>(FirstInst))
+    return FoldPHIArgLoadIntoPHI(PN);
+  
+  // Scan the instruction, looking for input operations that can be folded away.
+  // If all input operands to the phi are the same instruction (e.g. a cast from
+  // the same type or "+42") we can pull the operation through the PHI, reducing
+  // code size and simplifying code.
+  Constant *ConstantOp = 0;
+  const Type *CastSrcTy = 0;
+  
+  if (isa<CastInst>(FirstInst)) {
+    CastSrcTy = FirstInst->getOperand(0)->getType();
+
+    // Be careful about transforming integer PHIs.  We don't want to pessimize
+    // the code by turning an i32 into an i1293.
+    if (isa<IntegerType>(PN.getType()) && isa<IntegerType>(CastSrcTy)) {
+      if (!ShouldChangeType(PN.getType(), CastSrcTy))
+        return 0;
+    }
+  } else if (isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst)) {
+    // Can fold binop, compare or shift here if the RHS is a constant, 
+    // otherwise call FoldPHIArgBinOpIntoPHI.
+    ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
+    if (ConstantOp == 0)
+      return FoldPHIArgBinOpIntoPHI(PN);
+  } else {
+    return 0;  // Cannot fold this operation.
+  }
+
+  // Check to see if all arguments are the same operation.
+  for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+    Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
+    if (I == 0 || !I->hasOneUse() || !I->isSameOperationAs(FirstInst))
+      return 0;
+    if (CastSrcTy) {
+      if (I->getOperand(0)->getType() != CastSrcTy)
+        return 0;  // Cast operation must match.
+    } else if (I->getOperand(1) != ConstantOp) {
+      return 0;
+    }
+  }
+
+  // Okay, they are all the same operation.  Create a new PHI node of the
+  // correct type, and PHI together all of the LHS's of the instructions.
+  PHINode *NewPN = PHINode::Create(FirstInst->getOperand(0)->getType(),
+                                   PN.getName()+".in");
+  NewPN->reserveOperandSpace(PN.getNumOperands()/2);
+
+  Value *InVal = FirstInst->getOperand(0);
+  NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
+
+  // Add all operands to the new PHI.
+  for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
+    Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
+    if (NewInVal != InVal)
+      InVal = 0;
+    NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
+  }
+
+  Value *PhiVal;
+  if (InVal) {
+    // The new PHI unions all of the same values together.  This is really
+    // common, so we handle it intelligently here for compile-time speed.
+    PhiVal = InVal;
+    delete NewPN;
+  } else {
+    InsertNewInstBefore(NewPN, PN);
+    PhiVal = NewPN;
+  }
+
+  // Insert and return the new operation.
+  if (CastInst *FirstCI = dyn_cast<CastInst>(FirstInst))
+    return CastInst::Create(FirstCI->getOpcode(), PhiVal, PN.getType());
+  
+  if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
+    return BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
+  
+  CmpInst *CIOp = cast<CmpInst>(FirstInst);
+  return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
+                         PhiVal, ConstantOp);
+}
+
+/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
+/// that is dead.
+static bool DeadPHICycle(PHINode *PN,
+                         SmallPtrSet<PHINode*, 16> &PotentiallyDeadPHIs) {
+  if (PN->use_empty()) return true;
+  if (!PN->hasOneUse()) return false;
+
+  // Remember this node, and if we find the cycle, return.
+  if (!PotentiallyDeadPHIs.insert(PN))
+    return true;
+  
+  // Don't scan crazily complex things.
+  if (PotentiallyDeadPHIs.size() == 16)
+    return false;
+
+  if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
+    return DeadPHICycle(PU, PotentiallyDeadPHIs);
+
+  return false;
+}
+
+/// PHIsEqualValue - Return true if this phi node is always equal to
+/// NonPhiInVal.  This happens with mutually cyclic phi nodes like:
+///   z = some value; x = phi (y, z); y = phi (x, z)
+static bool PHIsEqualValue(PHINode *PN, Value *NonPhiInVal, 
+                           SmallPtrSet<PHINode*, 16> &ValueEqualPHIs) {
+  // See if we already saw this PHI node.
+  if (!ValueEqualPHIs.insert(PN))
+    return true;
+  
+  // Don't scan crazily complex things.
+  if (ValueEqualPHIs.size() == 16)
+    return false;
+ 
+  // Scan the operands to see if they are either phi nodes or are equal to
+  // the value.
+  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+    Value *Op = PN->getIncomingValue(i);
+    if (PHINode *OpPN = dyn_cast<PHINode>(Op)) {
+      if (!PHIsEqualValue(OpPN, NonPhiInVal, ValueEqualPHIs))
+        return false;
+    } else if (Op != NonPhiInVal)
+      return false;
+  }
+  
+  return true;
+}
+
+
+namespace {
+struct PHIUsageRecord {
+  unsigned PHIId;     // The ID # of the PHI (something determinstic to sort on)
+  unsigned Shift;     // The amount shifted.
+  Instruction *Inst;  // The trunc instruction.
+  
+  PHIUsageRecord(unsigned pn, unsigned Sh, Instruction *User)
+    : PHIId(pn), Shift(Sh), Inst(User) {}
+  
+  bool operator<(const PHIUsageRecord &RHS) const {
+    if (PHIId < RHS.PHIId) return true;
+    if (PHIId > RHS.PHIId) return false;
+    if (Shift < RHS.Shift) return true;
+    if (Shift > RHS.Shift) return false;
+    return Inst->getType()->getPrimitiveSizeInBits() <
+           RHS.Inst->getType()->getPrimitiveSizeInBits();
+  }
+};
+  
+struct LoweredPHIRecord {
+  PHINode *PN;        // The PHI that was lowered.
+  unsigned Shift;     // The amount shifted.
+  unsigned Width;     // The width extracted.
+  
+  LoweredPHIRecord(PHINode *pn, unsigned Sh, const Type *Ty)
+    : PN(pn), Shift(Sh), Width(Ty->getPrimitiveSizeInBits()) {}
+  
+  // Ctor form used by DenseMap.
+  LoweredPHIRecord(PHINode *pn, unsigned Sh)
+    : PN(pn), Shift(Sh), Width(0) {}
+};
+}
+
+namespace llvm {
+  template<>
+  struct DenseMapInfo<LoweredPHIRecord> {
+    static inline LoweredPHIRecord getEmptyKey() {
+      return LoweredPHIRecord(0, 0);
+    }
+    static inline LoweredPHIRecord getTombstoneKey() {
+      return LoweredPHIRecord(0, 1);
+    }
+    static unsigned getHashValue(const LoweredPHIRecord &Val) {
+      return DenseMapInfo<PHINode*>::getHashValue(Val.PN) ^ (Val.Shift>>3) ^
+             (Val.Width>>3);
+    }
+    static bool isEqual(const LoweredPHIRecord &LHS,
+                        const LoweredPHIRecord &RHS) {
+      return LHS.PN == RHS.PN && LHS.Shift == RHS.Shift &&
+             LHS.Width == RHS.Width;
+    }
+  };
+  template <>
+  struct isPodLike<LoweredPHIRecord> { static const bool value = true; };
+}
+
+
+/// SliceUpIllegalIntegerPHI - This is an integer PHI and we know that it has an
+/// illegal type: see if it is only used by trunc or trunc(lshr) operations.  If
+/// so, we split the PHI into the various pieces being extracted.  This sort of
+/// thing is introduced when SROA promotes an aggregate to large integer values.
+///
+/// TODO: The user of the trunc may be an bitcast to float/double/vector or an
+/// inttoptr.  We should produce new PHIs in the right type.
+///
+Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
+  // PHIUsers - Keep track of all of the truncated values extracted from a set
+  // of PHIs, along with their offset.  These are the things we want to rewrite.
+  SmallVector<PHIUsageRecord, 16> PHIUsers;
+  
+  // PHIs are often mutually cyclic, so we keep track of a whole set of PHI
+  // nodes which are extracted from. PHIsToSlice is a set we use to avoid
+  // revisiting PHIs, PHIsInspected is a ordered list of PHIs that we need to
+  // check the uses of (to ensure they are all extracts).
+  SmallVector<PHINode*, 8> PHIsToSlice;
+  SmallPtrSet<PHINode*, 8> PHIsInspected;
+  
+  PHIsToSlice.push_back(&FirstPhi);
+  PHIsInspected.insert(&FirstPhi);
+  
+  for (unsigned PHIId = 0; PHIId != PHIsToSlice.size(); ++PHIId) {
+    PHINode *PN = PHIsToSlice[PHIId];
+    
+    // Scan the input list of the PHI.  If any input is an invoke, and if the
+    // input is defined in the predecessor, then we won't be split the critical
+    // edge which is required to insert a truncate.  Because of this, we have to
+    // bail out.
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+      InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i));
+      if (II == 0) continue;
+      if (II->getParent() != PN->getIncomingBlock(i))
+        continue;
+     
+      // If we have a phi, and if it's directly in the predecessor, then we have
+      // a critical edge where we need to put the truncate.  Since we can't
+      // split the edge in instcombine, we have to bail out.
+      return 0;
+    }
+      
+    
+    for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
+         UI != E; ++UI) {
+      Instruction *User = cast<Instruction>(*UI);
+      
+      // If the user is a PHI, inspect its uses recursively.
+      if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+        if (PHIsInspected.insert(UserPN))
+          PHIsToSlice.push_back(UserPN);
+        continue;
+      }
+      
+      // Truncates are always ok.
+      if (isa<TruncInst>(User)) {
+        PHIUsers.push_back(PHIUsageRecord(PHIId, 0, User));
+        continue;
+      }
+      
+      // Otherwise it must be a lshr which can only be used by one trunc.
+      if (User->getOpcode() != Instruction::LShr ||
+          !User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
+          !isa<ConstantInt>(User->getOperand(1)))
+        return 0;
+      
+      unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
+      PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, User->use_back()));
+    }
+  }
+  
+  // If we have no users, they must be all self uses, just nuke the PHI.
+  if (PHIUsers.empty())
+    return ReplaceInstUsesWith(FirstPhi, UndefValue::get(FirstPhi.getType()));
+  
+  // If this phi node is transformable, create new PHIs for all the pieces
+  // extracted out of it.  First, sort the users by their offset and size.
+  array_pod_sort(PHIUsers.begin(), PHIUsers.end());
+  
+  DEBUG(errs() << "SLICING UP PHI: " << FirstPhi << '\n';
+            for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
+              errs() << "AND USER PHI #" << i << ": " << *PHIsToSlice[i] <<'\n';
+        );
+  
+  // PredValues - This is a temporary used when rewriting PHI nodes.  It is
+  // hoisted out here to avoid construction/destruction thrashing.
+  DenseMap<BasicBlock*, Value*> PredValues;
+  
+  // ExtractedVals - Each new PHI we introduce is saved here so we don't
+  // introduce redundant PHIs.
+  DenseMap<LoweredPHIRecord, PHINode*> ExtractedVals;
+  
+  for (unsigned UserI = 0, UserE = PHIUsers.size(); UserI != UserE; ++UserI) {
+    unsigned PHIId = PHIUsers[UserI].PHIId;
+    PHINode *PN = PHIsToSlice[PHIId];
+    unsigned Offset = PHIUsers[UserI].Shift;
+    const Type *Ty = PHIUsers[UserI].Inst->getType();
+    
+    PHINode *EltPHI;
+    
+    // If we've already lowered a user like this, reuse the previously lowered
+    // value.
+    if ((EltPHI = ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)]) == 0) {
+      
+      // Otherwise, Create the new PHI node for this user.
+      EltPHI = PHINode::Create(Ty, PN->getName()+".off"+Twine(Offset), PN);
+      assert(EltPHI->getType() != PN->getType() &&
+             "Truncate didn't shrink phi?");
+    
+      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+        BasicBlock *Pred = PN->getIncomingBlock(i);
+        Value *&PredVal = PredValues[Pred];
+        
+        // If we already have a value for this predecessor, reuse it.
+        if (PredVal) {
+          EltPHI->addIncoming(PredVal, Pred);
+          continue;
+        }
+
+        // Handle the PHI self-reuse case.
+        Value *InVal = PN->getIncomingValue(i);
+        if (InVal == PN) {
+          PredVal = EltPHI;
+          EltPHI->addIncoming(PredVal, Pred);
+          continue;
+        }
+        
+        if (PHINode *InPHI = dyn_cast<PHINode>(PN)) {
+          // If the incoming value was a PHI, and if it was one of the PHIs we
+          // already rewrote it, just use the lowered value.
+          if (Value *Res = ExtractedVals[LoweredPHIRecord(InPHI, Offset, Ty)]) {
+            PredVal = Res;
+            EltPHI->addIncoming(PredVal, Pred);
+            continue;
+          }
+        }
+        
+        // Otherwise, do an extract in the predecessor.
+        Builder->SetInsertPoint(Pred, Pred->getTerminator());
+        Value *Res = InVal;
+        if (Offset)
+          Res = Builder->CreateLShr(Res, ConstantInt::get(InVal->getType(),
+                                                          Offset), "extract");
+        Res = Builder->CreateTrunc(Res, Ty, "extract.t");
+        PredVal = Res;
+        EltPHI->addIncoming(Res, Pred);
+        
+        // If the incoming value was a PHI, and if it was one of the PHIs we are
+        // rewriting, we will ultimately delete the code we inserted.  This
+        // means we need to revisit that PHI to make sure we extract out the
+        // needed piece.
+        if (PHINode *OldInVal = dyn_cast<PHINode>(PN->getIncomingValue(i)))
+          if (PHIsInspected.count(OldInVal)) {
+            unsigned RefPHIId = std::find(PHIsToSlice.begin(),PHIsToSlice.end(),
+                                          OldInVal)-PHIsToSlice.begin();
+            PHIUsers.push_back(PHIUsageRecord(RefPHIId, Offset, 
+                                              cast<Instruction>(Res)));
+            ++UserE;
+          }
+      }
+      PredValues.clear();
+      
+      DEBUG(errs() << "  Made element PHI for offset " << Offset << ": "
+                   << *EltPHI << '\n');
+      ExtractedVals[LoweredPHIRecord(PN, Offset, Ty)] = EltPHI;
+    }
+    
+    // Replace the use of this piece with the PHI node.
+    ReplaceInstUsesWith(*PHIUsers[UserI].Inst, EltPHI);
+  }
+  
+  // Replace all the remaining uses of the PHI nodes (self uses and the lshrs)
+  // with undefs.
+  Value *Undef = UndefValue::get(FirstPhi.getType());
+  for (unsigned i = 1, e = PHIsToSlice.size(); i != e; ++i)
+    ReplaceInstUsesWith(*PHIsToSlice[i], Undef);
+  return ReplaceInstUsesWith(FirstPhi, Undef);
+}
+
+// PHINode simplification
+//
+Instruction *InstCombiner::visitPHINode(PHINode &PN) {
+  // If LCSSA is around, don't mess with Phi nodes
+  if (MustPreserveLCSSA) return 0;
+  
+  if (Value *V = PN.hasConstantValue())
+    return ReplaceInstUsesWith(PN, V);
+
+  // If all PHI operands are the same operation, pull them through the PHI,
+  // reducing code size.
+  if (isa<Instruction>(PN.getIncomingValue(0)) &&
+      isa<Instruction>(PN.getIncomingValue(1)) &&
+      cast<Instruction>(PN.getIncomingValue(0))->getOpcode() ==
+      cast<Instruction>(PN.getIncomingValue(1))->getOpcode() &&
+      // FIXME: The hasOneUse check will fail for PHIs that use the value more
+      // than themselves more than once.
+      PN.getIncomingValue(0)->hasOneUse())
+    if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
+      return Result;
+
+  // If this is a trivial cycle in the PHI node graph, remove it.  Basically, if
+  // this PHI only has a single use (a PHI), and if that PHI only has one use (a
+  // PHI)... break the cycle.
+  if (PN.hasOneUse()) {
+    Instruction *PHIUser = cast<Instruction>(PN.use_back());
+    if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) {
+      SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs;
+      PotentiallyDeadPHIs.insert(&PN);
+      if (DeadPHICycle(PU, PotentiallyDeadPHIs))
+        return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
+    }
+   
+    // If this phi has a single use, and if that use just computes a value for
+    // the next iteration of a loop, delete the phi.  This occurs with unused
+    // induction variables, e.g. "for (int j = 0; ; ++j);".  Detecting this
+    // common case here is good because the only other things that catch this
+    // are induction variable analysis (sometimes) and ADCE, which is only run
+    // late.
+    if (PHIUser->hasOneUse() &&
+        (isa<BinaryOperator>(PHIUser) || isa<GetElementPtrInst>(PHIUser)) &&
+        PHIUser->use_back() == &PN) {
+      return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
+    }
+  }
+
+  // We sometimes end up with phi cycles that non-obviously end up being the
+  // same value, for example:
+  //   z = some value; x = phi (y, z); y = phi (x, z)
+  // where the phi nodes don't necessarily need to be in the same block.  Do a
+  // quick check to see if the PHI node only contains a single non-phi value, if
+  // so, scan to see if the phi cycle is actually equal to that value.
+  {
+    unsigned InValNo = 0, NumOperandVals = PN.getNumIncomingValues();
+    // Scan for the first non-phi operand.
+    while (InValNo != NumOperandVals && 
+           isa<PHINode>(PN.getIncomingValue(InValNo)))
+      ++InValNo;
+
+    if (InValNo != NumOperandVals) {
+      Value *NonPhiInVal = PN.getOperand(InValNo);
+      
+      // Scan the rest of the operands to see if there are any conflicts, if so
+      // there is no need to recursively scan other phis.
+      for (++InValNo; InValNo != NumOperandVals; ++InValNo) {
+        Value *OpVal = PN.getIncomingValue(InValNo);
+        if (OpVal != NonPhiInVal && !isa<PHINode>(OpVal))
+          break;
+      }
+      
+      // If we scanned over all operands, then we have one unique value plus
+      // phi values.  Scan PHI nodes to see if they all merge in each other or
+      // the value.
+      if (InValNo == NumOperandVals) {
+        SmallPtrSet<PHINode*, 16> ValueEqualPHIs;
+        if (PHIsEqualValue(&PN, NonPhiInVal, ValueEqualPHIs))
+          return ReplaceInstUsesWith(PN, NonPhiInVal);
+      }
+    }
+  }
+
+  // If there are multiple PHIs, sort their operands so that they all list
+  // the blocks in the same order. This will help identical PHIs be eliminated
+  // by other passes. Other passes shouldn't depend on this for correctness
+  // however.
+  PHINode *FirstPN = cast<PHINode>(PN.getParent()->begin());
+  if (&PN != FirstPN)
+    for (unsigned i = 0, e = FirstPN->getNumIncomingValues(); i != e; ++i) {
+      BasicBlock *BBA = PN.getIncomingBlock(i);
+      BasicBlock *BBB = FirstPN->getIncomingBlock(i);
+      if (BBA != BBB) {
+        Value *VA = PN.getIncomingValue(i);
+        unsigned j = PN.getBasicBlockIndex(BBB);
+        Value *VB = PN.getIncomingValue(j);
+        PN.setIncomingBlock(i, BBB);
+        PN.setIncomingValue(i, VB);
+        PN.setIncomingBlock(j, BBA);
+        PN.setIncomingValue(j, VA);
+        // NOTE: Instcombine normally would want us to "return &PN" if we
+        // modified any of the operands of an instruction.  However, since we
+        // aren't adding or removing uses (just rearranging them) we don't do
+        // this in this case.
+      }
+    }
+
+  // If this is an integer PHI and we know that it has an illegal type, see if
+  // it is only used by trunc or trunc(lshr) operations.  If so, we split the
+  // PHI into the various pieces being extracted.  This sort of thing is
+  // introduced when SROA promotes an aggregate to a single large integer type.
+  if (isa<IntegerType>(PN.getType()) && TD &&
+      !TD->isLegalInteger(PN.getType()->getPrimitiveSizeInBits()))
+    if (Instruction *Res = SliceUpIllegalIntegerPHI(PN))
+      return Res;
+  
+  return 0;
+}
\ No newline at end of file