Revert LoopStrengthReduce.cpp to pre-r94061 for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94123 91177308-0d34-0410-b5e6-96231b3b80d8

17 files changed, 2308 insertions, 2601 deletions

diff --git a/include/llvm/Analysis/ScalarEvolutionExpander.h b/include/llvm/Analysis/ScalarEvolutionExpander.h
index 5bec8e445a..01df503a5e 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpander.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpander.h
@@ -27,7 +27,10 @@ namespace llvm {
   /// and destroy it when finished to allow the release of the associated
   /// memory.
   class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
+  public:
     ScalarEvolution &SE;
+
+  private:
     std::map<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> >
       InsertedExpressions;
     std::set<Value*> InsertedValues;
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index acc66246c3..fa820ed8e4 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -17,45 +17,6 @@
 // available on the target, and it performs a variety of other optimizations
 // related to loop induction variables.
 //
-// Terminology note: this code has a lot of handling for "post-increment" or
-// "post-inc" users. This is not talking about post-increment addressing modes;
-// it is instead talking about code like this:
-//
-//   %i = phi [ 0, %entry ], [ %i.next, %latch ]
-//   ...
-//   %i.next = add %i, 1
-//   %c = icmp eq %i.next, %n
-//
-// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
-// it's useful to think about these as the same register, with some uses using
-// the value of the register before the add and some using // it after. In this
-// example, the icmp is a post-increment user, since it uses %i.next, which is
-// the value of the induction variable after the increment. The other common
-// case of post-increment users is users outside the loop.
-//
-// TODO: More sophistication in the way Formulae are generated.
-//
-// TODO: Handle multiple loops at a time.
-//
-// TODO: test/CodeGen/X86/full-lsr.ll should get full lsr. The problem is
-//       that {0,+,1}<%bb> is getting picked first because all 7 uses can
-//       use it, and while it's a pretty good solution, it means that LSR
-//       doesn't look further to find an even better solution.
-//
-// TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr
-//       instead of a GlobalValue?
-//
-// TODO: When truncation is free, truncate ICmp users' operands to make it a
-//       smaller encoding (on x86 at least).
-//
-// TODO: When a negated register is used by an add (such as in a list of
-//       multiple base registers, or as the increment expression in an addrec),
-//       we may not actually need both reg and (-1 * reg) in registers; the
-//       negation can be implemented by using a sub instead of an add. The
-//       lack of support for taking this into consideration when making
-//       register pressure decisions is partly worked around by the "Special"
-//       use kind.
-//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "loop-reduce"
@@ -65,1549 +26,2025 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Analysis/IVUsers.h"
-#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Transforms/Utils/AddrModeMatcher.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/SmallBitVector.h"
-#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ValueHandle.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetLowering.h"
 #include <algorithm>
 using namespace llvm;
 
-namespace {
-
-// Constant strides come first which in turns are sorted by their absolute
-// values. If absolute values are the same, then positive strides comes first.
-// e.g.
-// 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
-struct StrideCompare {
-  const ScalarEvolution &SE;
-  explicit StrideCompare(const ScalarEvolution &se) : SE(se) {}
-
-  bool operator()(const SCEV *const &LHS, const SCEV *const &RHS) const {
-    const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
-    const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
-    if (LHSC && RHSC) {
-      unsigned BitWidth = std::max(SE.getTypeSizeInBits(LHS->getType()),
-                                   SE.getTypeSizeInBits(RHS->getType()));
-      APInt  LV = LHSC->getValue()->getValue();
-      APInt  RV = RHSC->getValue()->getValue();
-      LV.sextOrTrunc(BitWidth);
-      RV.sextOrTrunc(BitWidth);
-      APInt ALV = LV.abs();
-      APInt ARV = RV.abs();
-      if (ALV == ARV) {
-        if (LV != RV)
-          return LV.sgt(RV);
-      } else {
-        return ALV.ult(ARV);
-      }
-
-      // If it's the same value but different type, sort by bit width so
-      // that we emit larger induction variables before smaller
-      // ones, letting the smaller be re-written in terms of larger ones.
-      return SE.getTypeSizeInBits(RHS->getType()) <
-             SE.getTypeSizeInBits(LHS->getType());
-    }
-    return LHSC && !RHSC;
-  }
-};
-
-/// RegSortData - This class holds data which is used to order reuse
-/// candidates.
-class RegSortData {
-public:
-  /// Bits - This represents the set of LSRUses (by index) which reference a
-  /// particular register.
-  SmallBitVector Bits;
-
-  /// MaxComplexity - This represents the greatest complexity (see the comments
-  /// on Formula::getComplexity) seen with a particular register.
-  uint32_t MaxComplexity;
-
-  /// Index - This holds an arbitrary value used as a last-resort tie breaker
-  /// to ensure deterministic behavior.
-  unsigned Index;
-
-  RegSortData() {}
-
-  void print(raw_ostream &OS) const;
-  void dump() const;
-};
+STATISTIC(NumReduced ,    "Number of IV uses strength reduced");
+STATISTIC(NumInserted,    "Number of PHIs inserted");
+STATISTIC(NumVariable,    "Number of PHIs with variable strides");
+STATISTIC(NumEliminated,  "Number of strides eliminated");
+STATISTIC(NumShadow,      "Number of Shadow IVs optimized");
+STATISTIC(NumImmSunk,     "Number of common expr immediates sunk into uses");
+STATISTIC(NumLoopCond,    "Number of loop terminating conds optimized");
+STATISTIC(NumCountZero,   "Number of count iv optimized to count toward zero");
 
-}
-
-void RegSortData::print(raw_ostream &OS) const {
-  OS << "[NumUses=" << Bits.count()
-     << ", MaxComplexity=";
-  OS.write_hex(MaxComplexity);
-  OS << ", Index=" << Index << ']';
-}
-
-void RegSortData::dump() const {
-  print(errs()); errs() << '\n';
-}
+static cl::opt<bool> EnableFullLSRMode("enable-full-lsr",
+                                       cl::init(false),
+                                       cl::Hidden);
 
 namespace {
 
-/// RegCount - This is a helper class to sort a given set of registers
-/// according to associated RegSortData values.
-class RegCount {
-public:
-  const SCEV *Reg;
-  RegSortData Sort;
-
-  RegCount(const SCEV *R, const RegSortData &RSD)
-    : Reg(R), Sort(RSD) {}
-
-  // Sort by count. Returning true means the register is preferred.
-  bool operator<(const RegCount &Other) const {
-    // Sort by the number of unique uses of this register.
-    unsigned A = Sort.Bits.count();
-    unsigned B = Other.Sort.Bits.count();
-    if (A != B) return A > B;
-
-    if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
-      const SCEVAddRecExpr *BR = dyn_cast<SCEVAddRecExpr>(Other.Reg);
-      // AddRecs have higher priority than other things.
-      if (!BR) return true;
-
-      // Prefer affine values.
-      if (AR->isAffine() != BR->isAffine())
-        return AR->isAffine();
-
-      const Loop *AL = AR->getLoop();
-      const Loop *BL = BR->getLoop();
-      if (AL != BL) {
-        unsigned ADepth = AL->getLoopDepth();
-        unsigned BDepth = BL->getLoopDepth();
-        // Prefer a less deeply nested addrec.
-        if (ADepth != BDepth)
-          return ADepth < BDepth;
-
-        // Different loops at the same depth; do something arbitrary.
-        BasicBlock *AH = AL->getHeader();
-        BasicBlock *BH = BL->getHeader();
-        for (Function::iterator I = AH, E = AH->getParent()->end(); I != E; ++I)
-          if (&*I == BH) return true;
-        return false;
-      }
+  struct BasedUser;
 
-      // Sort addrecs by stride.
-      const SCEV *AStep = AR->getOperand(1);
-      const SCEV *BStep = BR->getOperand(1);
-      if (AStep != BStep) {
-        if (const SCEVConstant *AC = dyn_cast<SCEVConstant>(AStep)) {
-          const SCEVConstant *BC = dyn_cast<SCEVConstant>(BStep);
-          if (!BC) return true;
-          // Arbitrarily prefer wider registers.
-          if (AC->getValue()->getValue().getBitWidth() !=
-              BC->getValue()->getValue().getBitWidth())
-            return AC->getValue()->getValue().getBitWidth() >
-                   BC->getValue()->getValue().getBitWidth();
-          // Ignore the sign bit, assuming that striding by a negative value
-          // is just as easy as by a positive value.
-          // Prefer the addrec with the lesser absolute value stride, as it
-          // will allow uses to have simpler addressing modes.
-          return AC->getValue()->getValue().abs()
-            .ult(BC->getValue()->getValue().abs());
-        }
-      }
+  /// IVInfo - This structure keeps track of one IV expression inserted during
+  /// StrengthReduceStridedIVUsers. It contains the stride, the common base, as
+  /// well as the PHI node and increment value created for rewrite.
+  struct IVExpr {
+    const SCEV *Stride;
+    const SCEV *Base;
+    PHINode    *PHI;
 
-      // Then sort by the register which will permit the simplest uses.
-      // This is a heuristic; currently we only track the most complex use as a
-      // representative.
-      if (Sort.MaxComplexity != Other.Sort.MaxComplexity)
-        return Sort.MaxComplexity < Other.Sort.MaxComplexity;
-
-      // Then sort them by their start values.
-      const SCEV *AStart = AR->getStart();
-      const SCEV *BStart = BR->getStart();
-      if (AStart != BStart) {
-        if (const SCEVConstant *AC = dyn_cast<SCEVConstant>(AStart)) {
-          const SCEVConstant *BC = dyn_cast<SCEVConstant>(BStart);
-          if (!BC) return true;
-          // Arbitrarily prefer wider registers.
-          if (AC->getValue()->getValue().getBitWidth() !=
-              BC->getValue()->getValue().getBitWidth())
-            return AC->getValue()->getValue().getBitWidth() >
-                   BC->getValue()->getValue().getBitWidth();
-          // Prefer positive over negative if the absolute values are the same.
-          if (AC->getValue()->getValue().abs() ==
-              BC->getValue()->getValue().abs())
-            return AC->getValue()->getValue().isStrictlyPositive();
-          // Prefer the addrec with the lesser absolute value start.
-          return AC->getValue()->getValue().abs()
-            .ult(BC->getValue()->getValue().abs());
-        }
-      }
-    } else {
-      // AddRecs have higher priority than other things.
-      if (isa<SCEVAddRecExpr>(Other.Reg)) return false;
-      // Sort by the register which will permit the simplest uses.
-      // This is a heuristic; currently we only track the most complex use as a
-      // representative.
-      if (Sort.MaxComplexity != Other.Sort.MaxComplexity)
-        return Sort.MaxComplexity < Other.Sort.MaxComplexity;
-    }
+    IVExpr(const SCEV *const stride, const SCEV *const base, PHINode *phi)
+      : Stride(stride), Base(base), PHI(phi) {}
+  };
 
+  /// IVsOfOneStride - This structure keeps track of all IV expression inserted
+  /// during StrengthReduceStridedIVUsers for a particular stride of the IV.
+  struct IVsOfOneStride {
+    std::vector<IVExpr> IVs;
 
-    // Tie-breaker: the arbitrary index, to ensure a reliable ordering.
-    return Sort.Index < Other.Sort.Index;
-  }
+    void addIV(const SCEV *const Stride, const SCEV *const Base, PHINode *PHI) {
+      IVs.push_back(IVExpr(Stride, Base, PHI));
+    }
+  };
 
-  void print(raw_ostream &OS) const;
-  void dump() const;
-};
+  class LoopStrengthReduce : public LoopPass {
+    IVUsers *IU;
+    ScalarEvolution *SE;
+    bool Changed;
+
+    /// IVsByStride - Keep track of all IVs that have been inserted for a
+    /// particular stride.
+    std::map<const SCEV *, IVsOfOneStride> IVsByStride;
+
+    /// DeadInsts - Keep track of instructions we may have made dead, so that
+    /// we can remove them after we are done working.
+    SmallVector<WeakVH, 16> DeadInsts;
+
+    /// TLI - Keep a pointer of a TargetLowering to consult for determining
+    /// transformation profitability.
+    const TargetLowering *TLI;
+
+  public:
+    static char ID; // Pass ID, replacement for typeid
+    explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
+      LoopPass(&ID), TLI(tli) {}
+
+    bool runOnLoop(Loop *L, LPPassManager &LPM);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      // We split critical edges, so we change the CFG.  However, we do update
+      // many analyses if they are around.
+      AU.addPreservedID(LoopSimplifyID);
+      AU.addPreserved("loops");
+      AU.addPreserved("domfrontier");
+      AU.addPreserved("domtree");
+
+      AU.addRequiredID(LoopSimplifyID);
+      AU.addRequired<ScalarEvolution>();
+      AU.addPreserved<ScalarEvolution>();
+      AU.addRequired<IVUsers>();
+      AU.addPreserved<IVUsers>();
+    }
 
+  private:
+    void OptimizeIndvars(Loop *L);
+
+    /// OptimizeLoopTermCond - Change loop terminating condition to use the
+    /// postinc iv when possible.
+    void OptimizeLoopTermCond(Loop *L);
+
+    /// OptimizeShadowIV - If IV is used in a int-to-float cast
+    /// inside the loop then try to eliminate the cast opeation.
+    void OptimizeShadowIV(Loop *L);
+
+    /// OptimizeMax - Rewrite the loop's terminating condition
+    /// if it uses a max computation.
+    ICmpInst *OptimizeMax(Loop *L, ICmpInst *Cond,
+                          IVStrideUse* &CondUse);
+
+    /// OptimizeLoopCountIV - If, after all sharing of IVs, the IV used for
+    /// deciding when to exit the loop is used only for that purpose, try to
+    /// rearrange things so it counts down to a test against zero.
+    bool OptimizeLoopCountIV(Loop *L);
+    bool OptimizeLoopCountIVOfStride(const SCEV* &Stride,
+                                     IVStrideUse* &CondUse, Loop *L);
+
+    /// StrengthReduceIVUsersOfStride - Strength reduce all of the users of a
+    /// single stride of IV.  All of the users may have different starting
+    /// values, and this may not be the only stride.
+    void StrengthReduceIVUsersOfStride(const SCEV *Stride,
+                                      IVUsersOfOneStride &Uses,
+                                      Loop *L);
+    void StrengthReduceIVUsers(Loop *L);
+
+    ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
+                                  IVStrideUse* &CondUse,
+                                  const SCEV* &CondStride,
+                                  bool PostPass = false);
+
+    bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
+                           const SCEV* &CondStride);
+    bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
+    const SCEV *CheckForIVReuse(bool, bool, bool, const SCEV *,
+                             IVExpr&, const Type*,
+                             const std::vector<BasedUser>& UsersToProcess);
+    bool ValidScale(bool, int64_t,
+                    const std::vector<BasedUser>& UsersToProcess);
+    bool ValidOffset(bool, int64_t, int64_t,
+                     const std::vector<BasedUser>& UsersToProcess);
+    const SCEV *CollectIVUsers(const SCEV *Stride,
+                              IVUsersOfOneStride &Uses,
+                              Loop *L,
+                              bool &AllUsesAreAddresses,
+                              bool &AllUsesAreOutsideLoop,
+                              std::vector<BasedUser> &UsersToProcess);
+    bool StrideMightBeShared(const SCEV *Stride, Loop *L, bool CheckPreInc);
+    bool ShouldUseFullStrengthReductionMode(
+                                const std::vector<BasedUser> &UsersToProcess,
+                                const Loop *L,
+                                bool AllUsesAreAddresses,
+                                const SCEV *Stride);
+    void PrepareToStrengthReduceFully(
+                             std::vector<BasedUser> &UsersToProcess,
+                             const SCEV *Stride,
+                             const SCEV *CommonExprs,
+                             const Loop *L,
+                             SCEVExpander &PreheaderRewriter);
+    void PrepareToStrengthReduceFromSmallerStride(
+                                         std::vector<BasedUser> &UsersToProcess,
+                                         Value *CommonBaseV,
+                                         const IVExpr &ReuseIV,
+                                         Instruction *PreInsertPt);
+    void PrepareToStrengthReduceWithNewPhi(
+                                  std::vector<BasedUser> &UsersToProcess,
+                                  const SCEV *Stride,
+                                  const SCEV *CommonExprs,
+                                  Value *CommonBaseV,
+                                  Instruction *IVIncInsertPt,
+                                  const Loop *L,
+                                  SCEVExpander &PreheaderRewriter);
+
+    void DeleteTriviallyDeadInstructions();
+  };
 }
 
-void RegCount::print(raw_ostream &OS) const {
-  OS << *Reg << ':';
-  Sort.print(OS);
-}
+char LoopStrengthReduce::ID = 0;
+static RegisterPass<LoopStrengthReduce>
+X("loop-reduce", "Loop Strength Reduction");
 
-void RegCount::dump() const {
-  print(errs()); errs() << '\n';
+Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
+  return new LoopStrengthReduce(TLI);
 }
 
-namespace {
-
-/// Formula - This class holds information that describes a formula for
-/// satisfying a use. It may include broken-out immediates and scaled registers.
-struct Formula {
-  /// AM - This is used to represent complex addressing, as well as other kinds
-  /// of interesting uses.
-  TargetLowering::AddrMode AM;
-
-  /// BaseRegs - The list of "base" registers for this use. When this is
-  /// non-empty, AM.HasBaseReg should be set to true.
-  SmallVector<const SCEV *, 2> BaseRegs;
-
-  /// ScaledReg - The 'scaled' register for this use. This should be non-null
-  /// when AM.Scale is not zero.
-  const SCEV *ScaledReg;
-
-  Formula() : ScaledReg(0) {}
-
-  unsigned getNumRegs() const;
-  uint32_t getComplexity() const;
-  const Type *getType() const;
+/// DeleteTriviallyDeadInstructions - If any of the instructions is the
+/// specified set are trivially dead, delete them and see if this makes any of
+/// their operands subsequently dead.
+void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
+  while (!DeadInsts.empty()) {
+    Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
 
-  void InitialMatch(const SCEV *S, Loop *L,
-                    ScalarEvolution &SE, DominatorTree &DT);
+    if (I == 0 || !isInstructionTriviallyDead(I))
+      continue;
 
-  /// referencesReg - Test if this formula references the given register.
-  bool referencesReg(const SCEV *S) const {
-    return S == ScaledReg ||
-           std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
-  }
+    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+      if (Instruction *U = dyn_cast<Instruction>(*OI)) {
+        *OI = 0;
+        if (U->use_empty())
+          DeadInsts.push_back(U);
+      }
 
-  bool operator==(const Formula &Other) const {
-    return BaseRegs == Other.BaseRegs &&
-           ScaledReg == Other.ScaledReg &&
-           AM.Scale == Other.AM.Scale &&
-           AM.BaseOffs == Other.AM.BaseOffs &&
-           AM.BaseGV == Other.AM.BaseGV;
+    I->eraseFromParent();
+    Changed = true;
   }
+}
 
-  // This sorts at least partially based on host pointer values which are
-  // not deterministic, so it is only usable for uniqification.
-  bool operator<(const Formula &Other) const {
-    if (BaseRegs != Other.BaseRegs)
-      return BaseRegs < Other.BaseRegs;
-    if (ScaledReg != Other.ScaledReg)
-      return ScaledReg < Other.ScaledReg;
-    if (AM.Scale != Other.AM.Scale)
-      return AM.Scale < Other.AM.Scale;
-    if (AM.BaseOffs != Other.AM.BaseOffs)
-      return AM.BaseOffs < Other.AM.BaseOffs;
-    if (AM.BaseGV != Other.AM.BaseGV)
-      return AM.BaseGV < Other.AM.BaseGV;
-    return false;
+/// isAddressUse - Returns true if the specified instruction is using the
+/// specified value as an address.
+static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
+  bool isAddress = isa<LoadInst>(Inst);
+  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+    if (SI->getOperand(1) == OperandVal)
+      isAddress = true;
+  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+    // Addressing modes can also be folded into prefetches and a variety
+    // of intrinsics.
+    switch (II->getIntrinsicID()) {
+      default: break;
+      case Intrinsic::prefetch:
+      case Intrinsic::x86_sse2_loadu_dq:
+      case Intrinsic::x86_sse2_loadu_pd:
+      case Intrinsic::x86_sse_loadu_ps:
+      case Intrinsic::x86_sse_storeu_ps:
+      case Intrinsic::x86_sse2_storeu_pd:
+      case Intrinsic::x86_sse2_storeu_dq:
+      case Intrinsic::x86_sse2_storel_dq:
+        if (II->getOperand(1) == OperandVal)
+          isAddress = true;
+        break;
+    }
   }
-
-  void print(raw_ostream &OS) const;
-  void dump() const;
-};
-
+  return isAddress;
 }
 
-/// getNumRegs - Return the total number of register operands used by this
-/// formula. This does not include register uses implied by non-constant
-/// addrec strides.
-unsigned Formula::getNumRegs() const {
-  return !!ScaledReg + BaseRegs.size();
+/// getAccessType - Return the type of the memory being accessed.
+static const Type *getAccessType(const Instruction *Inst) {
+  const Type *AccessTy = Inst->getType();
+  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
+    AccessTy = SI->getOperand(0)->getType();
+  else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+    // Addressing modes can also be folded into prefetches and a variety
+    // of intrinsics.
+    switch (II->getIntrinsicID()) {
+    default: break;
+    case Intrinsic::x86_sse_storeu_ps:
+    case Intrinsic::x86_sse2_storeu_pd:
+    case Intrinsic::x86_sse2_storeu_dq:
+    case Intrinsic::x86_sse2_storel_dq:
+      AccessTy = II->getOperand(1)->getType();
+      break;
+    }
+  }
+  return AccessTy;
 }
 
-/// getComplexity - Return an oversimplified value indicating the complexity
-/// of this formula. This is used as a tie-breaker in choosing register
-/// preferences.
-uint32_t Formula::getComplexity() const {
-  // Encode the information in a uint32_t so that comparing with operator<
-  // will be interesting.
-  return
-    // Most significant, the number of registers. This saturates because we
-    // need the bits, and because beyond a few hundred it doesn't really matter.
-    (std::min(getNumRegs(), (1u<<15)-1) << 17) |
-    // Having multiple base regs is worse than having a base reg and a scale.
-    ((BaseRegs.size() > 1) << 16) |
-    // Scale absolute value.
-    ((AM.Scale != 0 ? (Log2_64(abs64(AM.Scale)) + 1) : 0u) << 9) |
-    // Scale sign, which is less significant than the absolute value.
-    ((AM.Scale < 0) << 8) |
-    // Offset absolute value.
-    ((AM.BaseOffs != 0 ? (Log2_64(abs64(AM.BaseOffs)) + 1) : 0u) << 1) |
-    // If a GV is present, treat it like a maximal offset.
-    ((AM.BaseGV ? ((1u<<7)-1) : 0) << 1) |
-    // Offset sign, which is less significant than the absolute offset.
-    ((AM.BaseOffs < 0) << 0);
+namespace {
+  /// BasedUser - For a particular base value, keep information about how we've
+  /// partitioned the expression so far.
+  struct BasedUser {
+    /// Base - The Base value for the PHI node that needs to be inserted for
+    /// this use.  As the use is processed, information gets moved from this
+    /// field to the Imm field (below).  BasedUser values are sorted by this
+    /// field.
+    const SCEV *Base;
+
+    /// Inst - The instruction using the induction variable.
+    Instruction *Inst;
+
+    /// OperandValToReplace - The operand value of Inst to replace with the
+    /// EmittedBase.
+    Value *OperandValToReplace;
+
+    /// Imm - The immediate value that should be added to the base immediately
+    /// before Inst, because it will be folded into the imm field of the
+    /// instruction.  This is also sometimes used for loop-variant values that
+    /// must be added inside the loop.
+    const SCEV *Imm;
+
+    /// Phi - The induction variable that performs the striding that
+    /// should be used for this user.
+    PHINode *Phi;
+
+    // isUseOfPostIncrementedValue - True if this should use the
+    // post-incremented version of this IV, not the preincremented version.
+    // This can only be set in special cases, such as the terminating setcc
+    // instruction for a loop and uses outside the loop that are dominated by
+    // the loop.
+    bool isUseOfPostIncrementedValue;
+
+    BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
+      : Base(IVSU.getOffset()), Inst(IVSU.getUser()),
+        OperandValToReplace(IVSU.getOperandValToReplace()),
+        Imm(se->getIntegerSCEV(0, Base->getType())),
+        isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue()) {}
+
+    // Once we rewrite the code to insert the new IVs we want, update the
+    // operands of Inst to use the new expression 'NewBase', with 'Imm' added
+    // to it.
+    void RewriteInstructionToUseNewBase(const SCEV *NewBase,
+                                        Instruction *InsertPt,
+                                       SCEVExpander &Rewriter, Loop *L, Pass *P,
+                                        SmallVectorImpl<WeakVH> &DeadInsts,
+                                        ScalarEvolution *SE);
+
+    Value *InsertCodeForBaseAtPosition(const SCEV *NewBase,
+                                       const Type *Ty,
+                                       SCEVExpander &Rewriter,
+                                       Instruction *IP,
+                                       ScalarEvolution *SE);
+    void dump() const;
+  };
 }
 
-/// getType - Return the type of this formula, if it has one, or null
-/// otherwise. This type is meaningless except for the bit size.
-const Type *Formula::getType() const {
-  return !BaseRegs.empty() ? BaseRegs.front()->getType() :
-         ScaledReg ? ScaledReg->getType() :
-         AM.BaseGV ? AM.BaseGV->getType() :
-         0;
+void BasedUser::dump() const {
+  dbgs() << " Base=" << *Base;
+  dbgs() << " Imm=" << *Imm;
+  dbgs() << "   Inst: " << *Inst;
 }
 
-namespace {
+Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *NewBase,
+                                              const Type *Ty,
+                                              SCEVExpander &Rewriter,
+                                              Instruction *IP,
+                                              ScalarEvolution *SE) {
+  Value *Base = Rewriter.expandCodeFor(NewBase, 0, IP);
 
-/// ComplexitySorter - A predicate which orders Formulae by the number of
-/// registers they contain.
-struct ComplexitySorter {
-  bool operator()(const Formula &LHS, const Formula &RHS) const {
-    unsigned L = LHS.getNumRegs();
-    unsigned R = RHS.getNumRegs();
-    if (L != R) return L < R;
+  // Wrap the base in a SCEVUnknown so that ScalarEvolution doesn't try to
+  // re-analyze it.
+  const SCEV *NewValSCEV = SE->getUnknown(Base);
 
-    return LHS.getComplexity() < RHS.getComplexity();
-  }
-};
+  // Always emit the immediate into the same block as the user.
+  NewValSCEV = SE->getAddExpr(NewValSCEV, Imm);
 
+  return Rewriter.expandCodeFor(NewValSCEV, Ty, IP);
 }
 
-/// DoInitialMatch - Recurrsion helper for InitialMatch.
-static void DoInitialMatch(const SCEV *S, Loop *L,
-                           SmallVectorImpl<const SCEV *> &Good,
-                           SmallVectorImpl<const SCEV *> &Bad,
-                           ScalarEvolution &SE, DominatorTree &DT) {
-  // Collect expressions which properly dominate the loop header.
-  if (S->properlyDominates(L->getHeader(), &DT)) {
-    Good.push_back(S);
-    return;
-  }
-
-  // Look at add operands.
-  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
-    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
-         I != E; ++I)
-      DoInitialMatch(*I, L, Good, Bad, SE, DT);
-    return;
-  }
 
-  // Look at addrec operands.
-  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
-    if (!AR->getStart()->isZero()) {
-      DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
-      DoInitialMatch(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()),
-                                      AR->getStepRecurrence(SE),
-                                      AR->getLoop()),
-                     L, Good, Bad, SE, DT);
-      return;
+// Once we rewrite the code to insert the new IVs we want, update the
+// operands of Inst to use the new expression 'NewBase', with 'Imm' added
+// to it. NewBasePt is the last instruction which contributes to the
+// value of NewBase in the case that it's a diffferent instruction from
+// the PHI that NewBase is computed from, or null otherwise.
+//
+void BasedUser::RewriteInstructionToUseNewBase(const SCEV *NewBase,
+                                               Instruction *NewBasePt,
+                                      SCEVExpander &Rewriter, Loop *L, Pass *P,
+                                      SmallVectorImpl<WeakVH> &DeadInsts,
+                                      ScalarEvolution *SE) {
+  if (!isa<PHINode>(Inst)) {
+    // By default, insert code at the user instruction.
+    BasicBlock::iterator InsertPt = Inst;
+
+    // However, if the Operand is itself an instruction, the (potentially
+    // complex) inserted code may be shared by many users.  Because of this, we
+    // want to emit code for the computation of the operand right before its old
+    // computation.  This is usually safe, because we obviously used to use the
+    // computation when it was computed in its current block.  However, in some
+    // cases (e.g. use of a post-incremented induction variable) the NewBase
+    // value will be pinned to live somewhere after the original computation.
+    // In this case, we have to back off.
+    //
+    // If this is a use outside the loop (which means after, since it is based
+    // on a loop indvar) we use the post-incremented value, so that we don't
+    // artificially make the preinc value live out the bottom of the loop.
+    if (!isUseOfPostIncrementedValue && L->contains(Inst)) {
+      if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
+        InsertPt = NewBasePt;
+        ++InsertPt;
+      } else if (Instruction *OpInst
+                 = dyn_cast<Instruction>(OperandValToReplace)) {
+        InsertPt = OpInst;
+        while (isa<PHINode>(InsertPt)) ++InsertPt;
+      }
     }
+    Value *NewVal = InsertCodeForBaseAtPosition(NewBase,
+                                                OperandValToReplace->getType(),
+                                                Rewriter, InsertPt, SE);
+    // Replace the use of the operand Value with the new Phi we just created.
+    Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
+
+    DEBUG(dbgs() << "      Replacing with ");
+    DEBUG(WriteAsOperand(dbgs(), NewVal, /*PrintType=*/false));
+    DEBUG(dbgs() << ", which has value " << *NewBase << " plus IMM "
+                 << *Imm << "\n");
+    return;
   }
 
-  // Handle a multiplication by -1 (negation) if it didn't fold.
-  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
-    if (Mul->getOperand(0)->isAllOnesValue()) {
-      SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
-      const SCEV *NewMul = SE.getMulExpr(Ops);
-
-      SmallVector<const SCEV *, 4> MyGood;
-      SmallVector<const SCEV *, 4> MyBad;
-      DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
-      const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
-        SE.getEffectiveSCEVType(NewMul->getType())));
-      for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
-           E = MyGood.end(); I != E; ++I)
-        Good.push_back(SE.getMulExpr(NegOne, *I));
-      for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
-           E = MyBad.end(); I != E; ++I)
-        Bad.push_back(SE.getMulExpr(NegOne, *I));
-      return;
-    }
-
-  // Ok, we can't do anything interesting. Just stuff the whole thing into a
-  // register and hope for the best.
-  Bad.push_back(S);
-}
+  // PHI nodes are more complex.  We have to insert one copy of the NewBase+Imm
+  // expression into each operand block that uses it.  Note that PHI nodes can
+  // have multiple entries for the same predecessor.  We use a map to make sure
+  // that a PHI node only has a single Value* for each predecessor (which also
+  // prevents us from inserting duplicate code in some blocks).
+  DenseMap<BasicBlock*, Value*> InsertedCode;
+  PHINode *PN = cast<PHINode>(Inst);
+  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+    if (PN->getIncomingValue(i) == OperandValToReplace) {
+      // If the original expression is outside the loop, put the replacement
+      // code in the same place as the original expression,
+      // which need not be an immediate predecessor of this PHI.  This way we
+      // need only one copy of it even if it is referenced multiple times in
+      // the PHI.  We don't do this when the original expression is inside the
+      // loop because multiple copies sometimes do useful sinking of code in
+      // that case(?).
+      Instruction *OldLoc = dyn_cast<Instruction>(OperandValToReplace);
+      BasicBlock *PHIPred = PN->getIncomingBlock(i);
+      if (L->contains(OldLoc)) {
+        // If this is a critical edge, split the edge so that we do not insert
+        // the code on all predecessor/successor paths.  We do this unless this
+        // is the canonical backedge for this loop, as this can make some
+        // inserted code be in an illegal position.
+        if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
+            !isa<IndirectBrInst>(PHIPred->getTerminator()) &&
+            (PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
+
+          // First step, split the critical edge.
+          BasicBlock *NewBB = SplitCriticalEdge(PHIPred, PN->getParent(),
+                                                P, false);
+
+          // Next step: move the basic block.  In particular, if the PHI node
+          // is outside of the loop, and PredTI is in the loop, we want to
+          // move the block to be immediately before the PHI block, not
+          // immediately after PredTI.
+          if (L->contains(PHIPred) && !L->contains(PN))
+            NewBB->moveBefore(PN->getParent());
 
-/// InitialMatch - Incorporate loop-variant parts of S into this Formula,
-/// attempting to keep all loop-invariant and loop-computable values in a
-/// single base register.
-void Formula::InitialMatch(const SCEV *S, Loop *L,
-                           ScalarEvolution &SE, DominatorTree &DT) {
-  SmallVector<const SCEV *, 4> Good;
-  SmallVector<const SCEV *, 4> Bad;
-  DoInitialMatch(S, L, Good, Bad, SE, DT);
-  if (!Good.empty()) {
-    BaseRegs.push_back(SE.getAddExpr(Good));
-    AM.HasBaseReg = true;
-  }
-  if (!Bad.empty()) {
-    BaseRegs.push_back(SE.getAddExpr(Bad));
-    AM.HasBaseReg = true;
-  }
-}
+          // Splitting the edge can reduce the number of PHI entries we have.
+          e = PN->getNumIncomingValues();
+          PHIPred = NewBB;
+          i = PN->getBasicBlockIndex(PHIPred);
+        }
+      }
+      Value *&Code = InsertedCode[PHIPred];
+      if (!Code) {
+        // Insert the code into the end of the predecessor block.
+        Instruction *InsertPt = (L->contains(OldLoc)) ?
+                                PHIPred->getTerminator() :
+                                OldLoc->getParent()->getTerminator();
+        Code = InsertCodeForBaseAtPosition(NewBase, PN->getType(),
+                                           Rewriter, InsertPt, SE);
+
+        DEBUG(dbgs() << "      Changing PHI use to ");
+        DEBUG(WriteAsOperand(dbgs(), Code, /*PrintType=*/false));
+        DEBUG(dbgs() << ", which has value " << *NewBase << " plus IMM "
+                     << *Imm << "\n");
+      }
 
-void Formula::print(raw_ostream &OS) const {
-  bool First = true;
-  if (AM.BaseGV) {
-    if (!First) OS << " + "; else First = false;
-    WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
-  }
-  if (AM.BaseOffs != 0) {
-    if (!First) OS << " + "; else First = false;
-    OS << AM.BaseOffs;
-  }
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
-       E = BaseRegs.end(); I != E; ++I) {
-    if (!First) OS << " + "; else First = false;
-    OS << "reg(";
-    OS << **I;
-    OS << ")";
-  }
-  if (AM.Scale != 0) {
-    if (!First) OS << " + "; else First = false;
-    OS << AM.Scale << "*reg(";
-    if (ScaledReg)
-      OS << *ScaledReg;
-    else
-      OS << "<unknown>";
-    OS << ")";
+      // Replace the use of the operand Value with the new Phi we just created.
+      PN->setIncomingValue(i, Code);
+      Rewriter.clear();
+    }
   }
-}
 
-void Formula::dump() const {
-  print(errs()); errs() << '\n';
+  // PHI node might have become a constant value after SplitCriticalEdge.
+  DeadInsts.push_back(Inst);
 }
 
-/// getSDiv - Return an expression for LHS /s RHS, if it can be determined,
-/// or null otherwise. If IgnoreSignificantBits is true, expressions like
-/// (X * Y) /s Y are simplified to Y, ignoring that the multiplication may
-/// overflow, which is useful when the result will be used in a context where
-/// the most significant bits are ignored.
-static const SCEV *getSDiv(const SCEV *LHS, const SCEV *RHS,
-                           ScalarEvolution &SE,
-                           bool IgnoreSignificantBits = false) {
-  // Handle the trivial case, which works for any SCEV type.
-  if (LHS == RHS)
-    return SE.getIntegerSCEV(1, LHS->getType());
-
-  // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some
-  // folding.
-  if (RHS->isAllOnesValue())
-    return SE.getMulExpr(LHS, RHS);
-
-  // Check for a division of a constant by a constant.
-  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
-    const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
-    if (!RC)
-      return 0;
-    if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0)
-      return 0;
-    return SE.getConstant(C->getValue()->getValue()
-               .sdiv(RC->getValue()->getValue()));
-  }
 
-  // Distribute the sdiv over addrec operands.
-  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
-    const SCEV *Start = getSDiv(AR->getStart(), RHS, SE,
-                                IgnoreSignificantBits);
-    if (!Start) return 0;
-    const SCEV *Step = getSDiv(AR->getStepRecurrence(SE), RHS, SE,
-                               IgnoreSignificantBits);
-    if (!Step) return 0;
-    return SE.getAddRecExpr(Start, Step, AR->getLoop());
-  }
-
-  // Distribute the sdiv over add operands.
-  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
-    SmallVector<const SCEV *, 8> Ops;
-    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
-         I != E; ++I) {
-      const SCEV *Op = getSDiv(*I, RHS, SE,
-                               IgnoreSignificantBits);
-      if (!Op) return 0;
-      Ops.push_back(Op);
+/// fitsInAddressMode - Return true if V can be subsumed within an addressing
+/// mode, and does not need to be put in a register first.
+static bool fitsInAddressMode(const SCEV *V, const Type *AccessTy,
+                             const TargetLowering *TLI, bool HasBaseReg) {
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
+    int64_t VC = SC->getValue()->getSExtValue();
+    if (TLI) {
+      TargetLowering::AddrMode AM;
+      AM.BaseOffs = VC;
+      AM.HasBaseReg = HasBaseReg;
+      return TLI->isLegalAddressingMode(AM, AccessTy);
+    } else {
+      // Defaults to PPC. PPC allows a sign-extended 16-bit immediate field.
+      return (VC > -(1 << 16) && VC < (1 << 16)-1);
     }
-    return SE.getAddExpr(Ops);
   }
 
-  // Check for a multiply operand that we can pull RHS out of.
-  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS))
-    if (IgnoreSignificantBits || Mul->hasNoSignedWrap()) {
-      SmallVector<const SCEV *, 4> Ops;
-      bool Found = false;
-      for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
-           I != E; ++I) {
-        if (!Found)
-          if (const SCEV *Q = getSDiv(*I, RHS, SE, IgnoreSignificantBits)) {
-            Ops.push_back(Q);
-            Found = true;
-            continue;
-          }
-        Ops.push_back(*I);
+  if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
+    if (GlobalValue *GV = dyn_cast<GlobalValue>(SU->getValue())) {
+      if (TLI) {
+        TargetLowering::AddrMode AM;
+        AM.BaseGV = GV;
+        AM.HasBaseReg = HasBaseReg;
+        return TLI->isLegalAddressingMode(AM, AccessTy);
+      } else {
+        // Default: assume global addresses are not legal.
       }
-      return Found ? SE.getMulExpr(Ops) : 0;
     }
 
-  // Otherwise we don't know.
-  return 0;
+  return false;
 }
 
-namespace {
+/// MoveLoopVariantsToImmediateField - Move any subexpressions from Val that are
+/// loop varying to the Imm operand.
+static void MoveLoopVariantsToImmediateField(const SCEV *&Val, const SCEV *&Imm,
+                                             Loop *L, ScalarEvolution *SE) {
+  if (Val->isLoopInvariant(L)) return;  // Nothing to do.
 
-/// LSRUse - This class holds the state that LSR keeps for each use in
-/// IVUsers, as well as uses invented by LSR itself. It includes information
-/// about what kinds of things can be folded into the user, information
-/// about the user itself, and information about how the use may be satisfied.
-/// TODO: Represent multiple users of the same expression in common?
-class LSRUse {
-  SmallSet<Formula, 8> FormulaeUniquifier;
-
-public:
-  /// KindType - An enum for a kind of use, indicating what types of
-  /// scaled and immediate operands it might support.
-  enum KindType {
-    Basic,   ///< A normal use, with no folding.
-    Special, ///< A special case of basic, allowing -1 scales.
-    Address, ///< An address use; folding according to TargetLowering
-    ICmpZero ///< An equality icmp with both operands folded into one.
-    // TODO: Add a generic icmp too?
-  };
+  if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
+    SmallVector<const SCEV *, 4> NewOps;
+    NewOps.reserve(SAE->getNumOperands());
 
-  KindType Kind;
-  const Type *AccessTy;
-  Instruction *UserInst;
-  Value *OperandValToReplace;
+    for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
+      if (!SAE->getOperand(i)->isLoopInvariant(L)) {
+        // If this is a loop-variant expression, it must stay in the immediate
+        // field of the expression.
+        Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
+      } else {
+        NewOps.push_back(SAE->getOperand(i));
+      }
 
-  /// PostIncLoop - If this user is to use the post-incremented value of an
-  /// induction variable, this variable is non-null and holds the loop
-  /// associated with the induction variable.
-  const Loop *PostIncLoop;
+    if (NewOps.empty())
+      Val = SE->getIntegerSCEV(0, Val->getType());
+    else
+      Val = SE->getAddExpr(NewOps);
+  } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+    // Try to pull immediates out of the start value of nested addrec's.
+    const SCEV *Start = SARE->getStart();
+    MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
+
+    SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
+    Ops[0] = Start;
+    Val = SE->getAddRecExpr(Ops, SARE->getLoop());
+  } else {
+    // Otherwise, all of Val is variant, move the whole thing over.
+    Imm = SE->getAddExpr(Imm, Val);
+    Val = SE->getIntegerSCEV(0, Val->getType());
+  }
+}
 
-  /// Formulae - A list of ways to build a value that can satisfy this user.
-  /// After the list is populated, one of these is selected heuristically and
-  /// used to formulate a replacement for OperandValToReplace in UserInst.
-  SmallVector<Formula, 12> Formulae;
 
-  LSRUse() : Kind(Basic), AccessTy(0),
-             UserInst(0), OperandValToReplace(0), PostIncLoop(0) {}
+/// MoveImmediateValues - Look at Val, and pull out any additions of constants
+/// that can fit into the immediate field of instructions in the target.
+/// Accumulate these immediate values into the Imm value.
+static void MoveImmediateValues(const TargetLowering *TLI,
+                                const Type *AccessTy,
+                                const SCEV *&Val, const SCEV *&Imm,
+                                bool isAddress, Loop *L,
+                                ScalarEvolution *SE) {
+  if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
+    SmallVector<const SCEV *, 4> NewOps;
+    NewOps.reserve(SAE->getNumOperands());
 
-  void InsertInitialFormula(const SCEV *S, Loop *L,
-                            ScalarEvolution &SE, DominatorTree &DT);
-  void InsertSupplementalFormula(const SCEV *S);
+    for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
+      const SCEV *NewOp = SAE->getOperand(i);
+      MoveImmediateValues(TLI, AccessTy, NewOp, Imm, isAddress, L, SE);
 
-  bool InsertFormula(const Formula &F);
+      if (!NewOp->isLoopInvariant(L)) {
+        // If this is a loop-variant expression, it must stay in the immediate
+        // field of the expression.
+        Imm = SE->getAddExpr(Imm, NewOp);
+      } else {
+        NewOps.push_back(NewOp);
+      }
+    }
 
-  void Rewrite(Loop *L, Instruction *IVIncInsertPos,
-               SCEVExpander &Rewriter,
-               SmallVectorImpl<WeakVH> &DeadInsts,
-               ScalarEvolution &SE, DominatorTree &DT,
-               Pass *P) const;
+    if (NewOps.empty())
+      Val = SE->getIntegerSCEV(0, Val->getType());
+    else
+      Val = SE->getAddExpr(NewOps);
+    return;
+  } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+    // Try to pull immediates out of the start value of nested addrec's.
+    const SCEV *Start = SARE->getStart();
+    MoveImmediateValues(TLI, AccessTy, Start, Imm, isAddress, L, SE);
+
+    if (Start != SARE->getStart()) {
+      SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
+      Ops[0] = Start;
+      Val = SE->getAddRecExpr(Ops, SARE->getLoop());
+    }
+    return;
+  } else if (const SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
+    // Transform "8 * (4 + v)" -> "32 + 8*V" if "32" fits in the immed field.
+    if (isAddress &&
+        fitsInAddressMode(SME->getOperand(0), AccessTy, TLI, false) &&
+        SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
+
+      const SCEV *SubImm = SE->getIntegerSCEV(0, Val->getType());
+      const SCEV *NewOp = SME->getOperand(1);
+      MoveImmediateValues(TLI, AccessTy, NewOp, SubImm, isAddress, L, SE);
+
+      // If we extracted something out of the subexpressions, see if we can
+      // simplify this!
+      if (NewOp != SME->getOperand(1)) {
+        // Scale SubImm up by "8".  If the result is a target constant, we are
+        // good.
+        SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
+        if (fitsInAddressMode(SubImm, AccessTy, TLI, false)) {
+          // Accumulate the immediate.
+          Imm = SE->getAddExpr(Imm, SubImm);
+
+          // Update what is left of 'Val'.
+          Val = SE->getMulExpr(SME->getOperand(0), NewOp);
+          return;
+        }
+      }
+    }
+  }
 
-  void print(raw_ostream &OS) const;
-  void dump() const;
+  // Loop-variant expressions must stay in the immediate field of the
+  // expression.
+  if ((isAddress && fitsInAddressMode(Val, AccessTy, TLI, false)) ||
+      !Val->isLoopInvariant(L)) {
+    Imm = SE->getAddExpr(Imm, Val);
+    Val = SE->getIntegerSCEV(0, Val->getType());
+    return;
+  }
 
-private:
-  Value *Expand(BasicBlock::iterator IP, Loop *L, Instruction *IVIncInsertPos,
-                SCEVExpander &Rewriter,
-                SmallVectorImpl<WeakVH> &DeadInsts,
-                ScalarEvolution &SE, DominatorTree &DT) const;
-};
+  // Otherwise, no immediates to move.
+}
+
+static void MoveImmediateValues(const TargetLowering *TLI,
+                                Instruction *User,
+                                const SCEV *&Val, const SCEV *&Imm,
+                                bool isAddress, Loop *L,
+                                ScalarEvolution *SE) {
+  const Type *AccessTy = getAccessType(User);
+  MoveImmediateValues(TLI, AccessTy, Val, Imm, isAddress, L, SE);
+}
+
+/// SeparateSubExprs - Decompose Expr into all of the subexpressions that are
+/// added together.  This is used to reassociate common addition subexprs
+/// together for maximal sharing when rewriting bases.
+static void SeparateSubExprs(SmallVector<const SCEV *, 16> &SubExprs,
+                             const SCEV *Expr,
+                             ScalarEvolution *SE) {
+  if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
+    for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
+      SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
+  } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
+    const SCEV *Zero = SE->getIntegerSCEV(0, Expr->getType());
+    if (SARE->getOperand(0) == Zero) {
+      SubExprs.push_back(Expr);
+    } else {
+      // Compute the addrec with zero as its base.
+      SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
+      Ops[0] = Zero;   // Start with zero base.
+      SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
 
-}
 
-/// ExtractImmediate - If S involves the addition of a constant integer value,
-/// return that integer value, and mutate S to point to a new SCEV with that
-/// value excluded.
-static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
-  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
-    if (C->getValue()->getValue().getMinSignedBits() <= 64) {
-      S = SE.getIntegerSCEV(0, C->getType());
-      return C->getValue()->getSExtValue();
+      SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
     }
-  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
-    SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
-    int64_t Result = ExtractImmediate(NewOps.front(), SE);
-    S = SE.getAddExpr(NewOps);
-    return Result;
-  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
-    SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
-    int64_t Result = ExtractImmediate(NewOps.front(), SE);
-    S = SE.getAddRecExpr(NewOps, AR->getLoop());
-    return Result;
+  } else if (!Expr->isZero()) {
+    // Do not add zero.
+    SubExprs.push_back(Expr);
   }
-  return 0;
 }
 
-/// ExtractSymbol - If S involves the addition of a GlobalValue address,
-/// return that symbol, and mutate S to point to a new SCEV with that
-/// value excluded.
-static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
-  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
-    if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
-      S = SE.getIntegerSCEV(0, GV->getType());
-      return GV;
-    }
-  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
-    SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
-    GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
-    S = SE.getAddExpr(NewOps);
-    return Result;
-  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
-    SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
-    GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
-    S = SE.getAddRecExpr(NewOps, AR->getLoop());
+// This is logically local to the following function, but C++ says we have
+// to make it file scope.
+struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
+
+/// RemoveCommonExpressionsFromUseBases - Look through all of the Bases of all
+/// the Uses, removing any common subexpressions, except that if all such
+/// subexpressions can be folded into an addressing mode for all uses inside
+/// the loop (this case is referred to as "free" in comments herein) we do
+/// not remove anything.  This looks for things like (a+b+c) and
+/// (a+c+d) and computes the common (a+c) subexpression.  The common expression
+/// is *removed* from the Bases and returned.
+static const SCEV *
+RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
+                                    ScalarEvolution *SE, Loop *L,
+                                    const TargetLowering *TLI) {
+  unsigned NumUses = Uses.size();
+
+  // Only one use?  This is a very common case, so we handle it specially and
+  // cheaply.
+  const SCEV *Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
+  const SCEV *Result = Zero;
+  const SCEV *FreeResult = Zero;
+  if (NumUses == 1) {
+    // If the use is inside the loop, use its base, regardless of what it is:
+    // it is clearly shared across all the IV's.  If the use is outside the loop
+    // (which means after it) we don't want to factor anything *into* the loop,
+    // so just use 0 as the base.
+    if (L->contains(Uses[0].Inst))
+      std::swap(Result, Uses[0].Base);
     return Result;
   }
-  return 0;
-}
 
-/// isLegalUse - Test whether the use described by AM is "legal", meaning
-/// it can be completely folded into the user instruction at isel time.
-/// This includes address-mode folding and special icmp tricks.
-static bool isLegalUse(const TargetLowering::AddrMode &AM,
-                       LSRUse::KindType Kind, const Type *AccessTy,
-                       const TargetLowering *TLI) {
-  switch (Kind) {
-  case LSRUse::Address:
-    // If we have low-level target information, ask the target if it can
-    // completely fold this address.
-    if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
-
-    // Otherwise, just guess that reg+reg addressing is legal.
-    return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
-
-  case LSRUse::ICmpZero:
-    // There's not even a target hook for querying whether it would be legal
-    // to fold a GV into an ICmp.
-    if (AM.BaseGV)
-      return false;
+  // To find common subexpressions, count how many of Uses use each expression.
+  // If any subexpressions are used Uses.size() times, they are common.
+  // Also track whether all uses of each expression can be moved into an
+  // an addressing mode "for free"; such expressions are left within the loop.
+  // struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
+  std::map<const SCEV *, SubExprUseData> SubExpressionUseData;
+
+  // UniqueSubExprs - Keep track of all of the subexpressions we see in the
+  // order we see them.
+  SmallVector<const SCEV *, 16> UniqueSubExprs;
+
+  SmallVector<const SCEV *, 16> SubExprs;
+  unsigned NumUsesInsideLoop = 0;
+  for (unsigned i = 0; i != NumUses; ++i) {
+    // If the user is outside the loop, just ignore it for base computation.
+    // Since the user is outside the loop, it must be *after* the loop (if it
+    // were before, it could not be based on the loop IV).  We don't want users
+    // after the loop to affect base computation of values *inside* the loop,
+    // because we can always add their offsets to the result IV after the loop
+    // is done, ensuring we get good code inside the loop.
+    if (!L->contains(Uses[i].Inst))
+      continue;
+    NumUsesInsideLoop++;
+
+    // If the base is zero (which is common), return zero now, there are no
+    // CSEs we can find.
+    if (Uses[i].Base == Zero) return Zero;
+
+    // If this use is as an address we may be able to put CSEs in the addressing
+    // mode rather than hoisting them.
+    bool isAddrUse = isAddressUse(Uses[i].Inst, Uses[i].OperandValToReplace);
+    // We may need the AccessTy below, but only when isAddrUse, so compute it
+    // only in that case.
+    const Type *AccessTy = 0;
+    if (isAddrUse)
+      AccessTy = getAccessType(Uses[i].Inst);
+
+    // Split the expression into subexprs.
+    SeparateSubExprs(SubExprs, Uses[i].Base, SE);
+    // Add one to SubExpressionUseData.Count for each subexpr present, and
+    // if the subexpr is not a valid immediate within an addressing mode use,
+    // set SubExpressionUseData.notAllUsesAreFree.  We definitely want to
+    // hoist these out of the loop (if they are common to all uses).
+    for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
+      if (++SubExpressionUseData[SubExprs[j]].Count == 1)
+        UniqueSubExprs.push_back(SubExprs[j]);
+      if (!isAddrUse || !fitsInAddressMode(SubExprs[j], AccessTy, TLI, false))
+        SubExpressionUseData[SubExprs[j]].notAllUsesAreFree = true;
+    }
+    SubExprs.clear();
+  }
 
-    // ICmp only has two operands; don't allow more than two non-trivial parts.
-    if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
-      return false;
+  // Now that we know how many times each is used, build Result.  Iterate over
+  // UniqueSubexprs so that we have a stable ordering.
+  for (unsigned i = 0, e = UniqueSubExprs.size(); i != e; ++i) {
+    std::map<const SCEV *, SubExprUseData>::iterator I =
+       SubExpressionUseData.find(UniqueSubExprs[i]);
+    assert(I != SubExpressionUseData.end() && "Entry not found?");
+    if (I->second.Count == NumUsesInsideLoop) { // Found CSE!
+      if (I->second.notAllUsesAreFree)
+        Result = SE->getAddExpr(Result, I->first);
+      else
+        FreeResult = SE->getAddExpr(FreeResult, I->first);
+    } else
+      // Remove non-cse's from SubExpressionUseData.
+      SubExpressionUseData.erase(I);
+  }
 
-    // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale
-    // by putting the scaled register in the other operand of the icmp.
-    if (AM.Scale != 0 && AM.Scale != -1)
-      return false;
+  if (FreeResult != Zero) {
+    // We have some subexpressions that can be subsumed into addressing
+    // modes in every use inside the loop.  However, it's possible that
+    // there are so many of them that the combined FreeResult cannot
+    // be subsumed, or that the target cannot handle both a FreeResult
+    // and a Result in the same instruction (for example because it would
+    // require too many registers).  Check this.
+    for (unsigned i=0; i<NumUses; ++i) {
+      if (!L->contains(Uses[i].Inst))
+        continue;
+      // We know this is an addressing mode use; if there are any uses that
+      // are not, FreeResult would be Zero.
+      const Type *AccessTy = getAccessType(Uses[i].Inst);
+      if (!fitsInAddressMode(FreeResult, AccessTy, TLI, Result!=Zero)) {
+        // FIXME:  could split up FreeResult into pieces here, some hoisted
+        // and some not.  There is no obvious advantage to this.
+        Result = SE->getAddExpr(Result, FreeResult);
+        FreeResult = Zero;
+        break;
+      }
+    }
+  }
 
-    // If we have low-level target information, ask the target if it can
-    // fold an integer immediate on an icmp.
-    if (AM.BaseOffs != 0) {
-      if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
-      return false;
+  // If we found no CSE's, return now.
+  if (Result == Zero) return Result;
+
+  // If we still have a FreeResult, remove its subexpressions from
+  // SubExpressionUseData.  This means they will remain in the use Bases.
+  if (FreeResult != Zero) {
+    SeparateSubExprs(SubExprs, FreeResult, SE);
+    for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
+      std::map<const SCEV *, SubExprUseData>::iterator I =
+         SubExpressionUseData.find(SubExprs[j]);
+      SubExpressionUseData.erase(I);
     }
+    SubExprs.clear();
+  }
 
-    return true;
+  // Otherwise, remove all of the CSE's we found from each of the base values.
+  for (unsigned i = 0; i != NumUses; ++i) {
+    // Uses outside the loop don't necessarily include the common base, but
+    // the final IV value coming into those uses does.  Instead of trying to
+    // remove the pieces of the common base, which might not be there,
+    // subtract off the base to compensate for this.
+    if (!L->contains(Uses[i].Inst)) {
+      Uses[i].Base = SE->getMinusSCEV(Uses[i].Base, Result);
+      continue;
+    }
 
-  case LSRUse::Basic:
-    // Only handle single-register values.
-    return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
+    // Split the expression into subexprs.
+    SeparateSubExprs(SubExprs, Uses[i].Base, SE);
+
+    // Remove any common subexpressions.
+    for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
+      if (SubExpressionUseData.count(SubExprs[j])) {
+        SubExprs.erase(SubExprs.begin()+j);
+        --j; --e;
+      }
 
-  case LSRUse::Special:
-    // Only handle -1 scales, or no scale.
-    return AM.Scale == 0 || AM.Scale == -1;
+    // Finally, add the non-shared expressions together.
+    if (SubExprs.empty())
+      Uses[i].Base = Zero;
+    else
+      Uses[i].Base = SE->getAddExpr(SubExprs);
+    SubExprs.clear();
   }
 
-  return false;
+  return Result;
 }
 
-static bool isAlwaysFoldable(const SCEV *S,
-                             bool HasBaseReg,
-                             LSRUse::KindType Kind, const Type *AccessTy,
-                             const TargetLowering *TLI,
-                             ScalarEvolution &SE) {
-  // Fast-path: zero is always foldable.
-  if (S->isZero()) return true;
-
-  // Conservatively, create an address with an immediate and a
-  // base and a scale.
-  TargetLowering::AddrMode AM;
-  AM.BaseOffs = ExtractImmediate(S, SE);
-  AM.BaseGV = ExtractSymbol(S, SE);
-  AM.HasBaseReg = HasBaseReg;
-  AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
-
-  // If there's anything else involved, it's not foldable.
-  if (!S->isZero()) return false;
-
-  return isLegalUse(AM, Kind, AccessTy, TLI);
-}
+/// ValidScale - Check whether the given Scale is valid for all loads and
+/// stores in UsersToProcess.
+///
+bool LoopStrengthReduce::ValidScale(bool HasBaseReg, int64_t Scale,
+                               const std::vector<BasedUser>& UsersToProcess) {
+  if (!TLI)
+    return true;
 
-/// InsertFormula - If the given formula has not yet been inserted, add it
-/// to the list, and return true. Return false otherwise.
-bool LSRUse::InsertFormula(const Formula &F) {
-  Formula Copy = F;
+  for (unsigned i = 0, e = UsersToProcess.size(); i!=e; ++i) {
+    // If this is a load or other access, pass the type of the access in.
+    const Type *AccessTy =
+        Type::getVoidTy(UsersToProcess[i].Inst->getContext());
+    if (isAddressUse(UsersToProcess[i].Inst,
+                     UsersToProcess[i].OperandValToReplace))
+      AccessTy = getAccessType(UsersToProcess[i].Inst);
+    else if (isa<PHINode>(UsersToProcess[i].Inst))
+      continue;
 
-  // Sort the base regs, to avoid adding the same solution twice with
-  // the base regs in different orders. This uses host pointer values, but
-  // it doesn't matter since it's only used for uniquifying.
-  std::sort(Copy.BaseRegs.begin(), Copy.BaseRegs.end());
+    TargetLowering::AddrMode AM;
+    if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
+      AM.BaseOffs = SC->getValue()->getSExtValue();
+    AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
+    AM.Scale = Scale;
 
-  DEBUG(for (SmallVectorImpl<const SCEV *>::const_iterator I =
-             F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
-          assert(!(*I)->isZero() && "Zero allocated in a base register!");
-        assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
-               "Zero allocated in a scaled register!"));
+    // If load[imm+r*scale] is illegal, bail out.
+    if (!TLI->isLegalAddressingMode(AM, AccessTy))
+      return false;
+  }
+  return true;
+}
 
-  if (FormulaeUniquifier.insert(Copy)) {
-    Formulae.push_back(F);
+/// ValidOffset - Check whether the given Offset is valid for all loads and
+/// stores in UsersToProcess.
+///
+bool LoopStrengthReduce::ValidOffset(bool HasBaseReg,
+                               int64_t Offset,
+                               int64_t Scale,
+                               const std::vector<BasedUser>& UsersToProcess) {
+  if (!TLI)
     return true;
-  }
 
-  return false;
-}
+  for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
+    // If this is a load or other access, pass the type of the access in.
+    const Type *AccessTy =
+        Type::getVoidTy(UsersToProcess[i].Inst->getContext());
+    if (isAddressUse(UsersToProcess[i].Inst,
+                     UsersToProcess[i].OperandValToReplace))
+      AccessTy = getAccessType(UsersToProcess[i].Inst);
+    else if (isa<PHINode>(UsersToProcess[i].Inst))
+      continue;
 
-void
-LSRUse::InsertInitialFormula(const SCEV *S, Loop *L,
-                             ScalarEvolution &SE, DominatorTree &DT) {
-  Formula F;
-  F.InitialMatch(S, L, SE, DT);
-  bool Inserted = InsertFormula(F);
-  assert(Inserted && "Initial formula already exists!"); (void)Inserted;
-}
+    TargetLowering::AddrMode AM;
+    if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
+      AM.BaseOffs = SC->getValue()->getSExtValue();
+    AM.BaseOffs = (uint64_t)AM.BaseOffs + (uint64_t)Offset;
+    AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
+    AM.Scale = Scale;
 
-void
-LSRUse::InsertSupplementalFormula(const SCEV *S) {
-  Formula F;
-  F.BaseRegs.push_back(S);
-  F.AM.HasBaseReg = true;
-  bool Inserted = InsertFormula(F);
-  assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
+    // If load[imm+r*scale] is illegal, bail out.
+    if (!TLI->isLegalAddressingMode(AM, AccessTy))
+      return false;
+  }
+  return true;
 }
 
-/// getImmediateDominator - A handy utility for the specific DominatorTree
-/// query that we need here.
-///
-static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) {
-  DomTreeNode *Node = DT.getNode(BB);
-  if (!Node) return 0;
-  Node = Node->getIDom();
-  if (!Node) return 0;
-  return Node->getBlock();
+/// RequiresTypeConversion - Returns true if converting Ty1 to Ty2 is not
+/// a nop.
+bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
+                                                const Type *Ty2) {
+  if (Ty1 == Ty2)
+    return false;
+  Ty1 = SE->getEffectiveSCEVType(Ty1);
+  Ty2 = SE->getEffectiveSCEVType(Ty2);
+  if (Ty1 == Ty2)
+    return false;
+  if (Ty1->canLosslesslyBitCastTo(Ty2))
+    return false;
+  if (TLI && TLI->isTruncateFree(Ty1, Ty2))
+    return false;
+  return true;
 }
 
-Value *LSRUse::Expand(BasicBlock::iterator IP,
-                      Loop *L, Instruction *IVIncInsertPos,
-                      SCEVExpander &Rewriter,
-                      SmallVectorImpl<WeakVH> &DeadInsts,
-                      ScalarEvolution &SE, DominatorTree &DT) const {
-  // Then, collect some instructions which we will remain dominated by when
-  // expanding the replacement. These must be dominated by any operands that
-  // will be required in the expansion.
-  SmallVector<Instruction *, 4> Inputs;
-  if (Instruction *I = dyn_cast<Instruction>(OperandValToReplace))
-    Inputs.push_back(I);
-  if (Kind == ICmpZero)
-    if (Instruction *I =
-          dyn_cast<Instruction>(cast<ICmpInst>(UserInst)->getOperand(1)))
-      Inputs.push_back(I);
-  if (PostIncLoop && !L->contains(UserInst))
-    Inputs.push_back(L->getLoopLatch()->getTerminator());
-
-  // Then, climb up the immediate dominator tree as far as we can go while
-  // still being dominated by the input positions.
-  for (;;) {
-    bool AllDominate = true;
-    Instruction *BetterPos = 0;
-    BasicBlock *IDom = getImmediateDominator(IP->getParent(), DT);
-    if (!IDom) break;
-    Instruction *Tentative = IDom->getTerminator();
-    for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
-         E = Inputs.end(); I != E; ++I) {
-      Instruction *Inst = *I;
-      if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
-        AllDominate = false;
-        break;
+/// CheckForIVReuse - Returns the multiple if the stride is the multiple
+/// of a previous stride and it is a legal value for the target addressing
+/// mode scale component and optional base reg. This allows the users of
+/// this stride to be rewritten as prev iv * factor. It returns 0 if no
+/// reuse is possible.  Factors can be negative on same targets, e.g. ARM.
+///
+/// If all uses are outside the loop, we don't require that all multiplies
+/// be folded into the addressing mode, nor even that the factor be constant;
+/// a multiply (executed once) outside the loop is better than another IV
+/// within.  Well, usually.
+const SCEV *LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
+                                bool AllUsesAreAddresses,
+                                bool AllUsesAreOutsideLoop,
+                                const SCEV *Stride,
+                                IVExpr &IV, const Type *Ty,
+                                const std::vector<BasedUser>& UsersToProcess) {
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
+    int64_t SInt = SC->getValue()->getSExtValue();
+    for (unsigned NewStride = 0, e = IU->StrideOrder.size();
+         NewStride != e; ++NewStride) {
+      std::map<const SCEV *, IVsOfOneStride>::iterator SI =
+                IVsByStride.find(IU->StrideOrder[NewStride]);
+      if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+        continue;
+      // The other stride has no uses, don't reuse it.
+      std::map<const SCEV *, IVUsersOfOneStride *>::iterator UI =
+        IU->IVUsesByStride.find(IU->StrideOrder[NewStride]);
+      if (UI->second->Users.empty())
+        continue;
+      int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+      if (SI->first != Stride &&
+          (unsigned(abs64(SInt)) < SSInt || (SInt % SSInt) != 0))
+        continue;
+      int64_t Scale = SInt / SSInt;
+      // Check that this stride is valid for all the types used for loads and
+      // stores; if it can be used for some and not others, we might as well use
+      // the original stride everywhere, since we have to create the IV for it
+      // anyway. If the scale is 1, then we don't need to worry about folding
+      // multiplications.
+      if (Scale == 1 ||
+          (AllUsesAreAddresses &&
+           ValidScale(HasBaseReg, Scale, UsersToProcess))) {
+        // Prefer to reuse an IV with a base of zero.
+        for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+               IE = SI->second.IVs.end(); II != IE; ++II)
+          // Only reuse previous IV if it would not require a type conversion
+          // and if the base difference can be folded.
+          if (II->Base->isZero() &&
+              !RequiresTypeConversion(II->Base->getType(), Ty)) {
+            IV = *II;
+            return SE->getIntegerSCEV(Scale, Stride->getType());
+          }
+        // Otherwise, settle for an IV with a foldable base.
+        if (AllUsesAreAddresses)
+          for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+                 IE = SI->second.IVs.end(); II != IE; ++II)
+            // Only reuse previous IV if it would not require a type conversion
+            // and if the base difference can be folded.
+            if (SE->getEffectiveSCEVType(II->Base->getType()) ==
+                SE->getEffectiveSCEVType(Ty) &&
+                isa<SCEVConstant>(II->Base)) {
+              int64_t Base =
+                cast<SCEVConstant>(II->Base)->getValue()->getSExtValue();
+              if (Base > INT32_MIN && Base <= INT32_MAX &&
+                  ValidOffset(HasBaseReg, -Base * Scale,
+                              Scale, UsersToProcess)) {
+                IV = *II;
+                return SE->getIntegerSCEV(Scale, Stride->getType());
+              }
+            }
       }
-      if (IDom == Inst->getParent() &&
-          (!BetterPos || DT.dominates(BetterPos, Inst)))
-        BetterPos = next(BasicBlock::iterator(Inst));
     }
-    if (!AllDominate)
-      break;
-    if (BetterPos)
-      IP = BetterPos;
-    else
-      IP = Tentative;
-  }
-  while (isa<PHINode>(IP)) ++IP;
-
-  // The first formula in the list is the winner.
-  const Formula &F = Formulae.front();
-
-  // Inform the Rewriter if we have a post-increment use, so that it can
-  // perform an advantageous expansion.
-  Rewriter.setPostInc(PostIncLoop);
-
-  // This is the type that the user actually needs.
-  const Type *OpTy = OperandValToReplace->getType();
-  // This will be the type that we'll initially expand to.
-  const Type *Ty = F.getType();
-  if (!Ty)
-    // No type known; just expand directly to the ultimate type.
-    Ty = OpTy;
-  else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
-    // Expand directly to the ultimate type if it's the right size.
-    Ty = OpTy;
-  // This is the type to do integer arithmetic in.
-  const Type *IntTy = SE.getEffectiveSCEVType(Ty);
-
-  // Build up a list of operands to add together to form the full base.
-  SmallVector<const SCEV *, 8> Ops;
-
-  // Expand the BaseRegs portion.
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
-       E = F.BaseRegs.end(); I != E; ++I) {
-    const SCEV *Reg = *I;
-    assert(!Reg->isZero() && "Zero allocated in a base register!");
-
-    // If we're expanding for a post-inc user for the add-rec's loop, make the
-    // post-inc adjustment.
-    if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg))
-      if (AR->getLoop() == PostIncLoop) {
-        Reg = SE.getAddExpr(Reg, AR->getStepRecurrence(SE));
-        // If the user is inside the loop, insert the code after the increment
-        // so that it is dominated by its operand.
-        if (L->contains(UserInst))
-          IP = IVIncInsertPos;
-      }
-
-    Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
-  }
-
-  // Expand the ScaledReg portion.
-  Value *ICmpScaledV = 0;
-  if (F.AM.Scale != 0) {
-    const SCEV *ScaledS = F.ScaledReg;
-
-    // If we're expanding for a post-inc user for the add-rec's loop, make the
-    // post-inc adjustment.
-    if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(ScaledS))
-      if (AR->getLoop() == PostIncLoop)
-        ScaledS = SE.getAddExpr(ScaledS, AR->getStepRecurrence(SE));
-
-    if (Kind == ICmpZero) {
-      // An interesting way of "folding" with an icmp is to use a negated
-      // scale, which we'll implement by inserting it into the other operand
-      // of the icmp.
-      assert(F.AM.Scale == -1 &&
-             "The only scale supported by ICmpZero uses is -1!");
-      ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
-    } else {
-      // Otherwise just expand the scaled register and an explicit scale,
-      // which is expected to be matched as part of the address.
-      ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
-      const Type *ScaledTy = SE.getEffectiveSCEVType(ScaledS->getType());
-      ScaledS = SE.getMulExpr(ScaledS,
-                              SE.getSCEV(ConstantInt::get(ScaledTy,
-                                                          F.AM.Scale)));
-      Ops.push_back(ScaledS);
+  } else if (AllUsesAreOutsideLoop) {
+    // Accept nonconstant strides here; it is really really right to substitute
+    // an existing IV if we can.
+    for (unsigned NewStride = 0, e = IU->StrideOrder.size();
+         NewStride != e; ++NewStride) {
+      std::map<const SCEV *, IVsOfOneStride>::iterator SI =
+                IVsByStride.find(IU->StrideOrder[NewStride]);
+      if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+        continue;
+      int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+      if (SI->first != Stride && SSInt != 1)
+        continue;
+      for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+             IE = SI->second.IVs.end(); II != IE; ++II)
+        // Accept nonzero base here.
+        // Only reuse previous IV if it would not require a type conversion.
+        if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
+          IV = *II;
+          return Stride;
+        }
     }
-  }
-
-  // Expand the immediate portions.
-  if (F.AM.BaseGV)
-    Ops.push_back(SE.getSCEV(F.AM.BaseGV));
-  if (F.AM.BaseOffs != 0) {
-    if (Kind == ICmpZero) {
-      // The other interesting way of "folding" with an ICmpZero is to use a
-      // negated immediate.
-      if (!ICmpScaledV)
-        ICmpScaledV = ConstantInt::get(IntTy, -F.AM.BaseOffs);
-      else {
-        Ops.push_back(SE.getUnknown(ICmpScaledV));
-        ICmpScaledV = ConstantInt::get(IntTy, F.AM.BaseOffs);
-      }
-    } else {
-      // Just add the immediate values. These again are expected to be matched
-      // as part of the address.
-      Ops.push_back(SE.getSCEV(ConstantInt::get(IntTy, F.AM.BaseOffs)));
+    // Special case, old IV is -1*x and this one is x.  Can treat this one as
+    // -1*old.
+    for (unsigned NewStride = 0, e = IU->StrideOrder.size();
+         NewStride != e; ++NewStride) {
+      std::map<const SCEV *, IVsOfOneStride>::iterator SI =
+                IVsByStride.find(IU->StrideOrder[NewStride]);
+      if (SI == IVsByStride.end())
+        continue;
+      if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(SI->first))
+        if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(ME->getOperand(0)))
+          if (Stride == ME->getOperand(1) &&
+              SC->getValue()->getSExtValue() == -1LL)
+            for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+                   IE = SI->second.IVs.end(); II != IE; ++II)
+              // Accept nonzero base here.
+              // Only reuse previous IV if it would not require type conversion.
+              if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
+                IV = *II;
+                return SE->getIntegerSCEV(-1LL, Stride->getType());
+              }
     }
   }
-
-  // Emit instructions summing all the operands.
-  const SCEV *FullS = Ops.empty() ?
-                      SE.getIntegerSCEV(0, IntTy) :
-                      SE.getAddExpr(Ops);
-  Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
-
-  // We're done expanding now, so reset the rewriter.
-  Rewriter.setPostInc(0);
-
-  // An ICmpZero Formula represents an ICmp which we're handling as a
-  // comparison against zero. Now that we've expanded an expression for that
-  // form, update the ICmp's other operand.
-  if (Kind == ICmpZero) {
-    ICmpInst *CI = cast<ICmpInst>(UserInst);
-    DeadInsts.push_back(CI->getOperand(1));
-    assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
-                           "a scale at the same time!");
-    if (F.AM.Scale == -1) {
-      if (ICmpScaledV->getType() != OpTy) {
-        Instruction *Cast =
-          CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
-                                                   OpTy, false),
-                           ICmpScaledV, OpTy, "tmp", CI);
-        ICmpScaledV = Cast;
-      }
-      CI->setOperand(1, ICmpScaledV);
-    } else {
-      assert(F.AM.Scale == 0 &&
-             "ICmp does not support folding a global value and "
-             "a scale at the same time!");
-      Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
-                                           -(uint64_t)F.AM.BaseOffs);
-      if (C->getType() != OpTy)
-        C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
-                                                          OpTy, false),
-                                  C, OpTy);
-
-      CI->setOperand(1, C);
-    }
+  return SE->getIntegerSCEV(0, Stride->getType());
+}
+
+/// PartitionByIsUseOfPostIncrementedValue - Simple boolean predicate that
+/// returns true if Val's isUseOfPostIncrementedValue is true.
+static bool PartitionByIsUseOfPostIncrementedValue(const BasedUser &Val) {
+  return Val.isUseOfPostIncrementedValue;
+}
+
+/// isNonConstantNegative - Return true if the specified scev is negated, but
+/// not a constant.
+static bool isNonConstantNegative(const SCEV *Expr) {
+  const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
+  if (!Mul) return false;
+
+  // If there is a constant factor, it will be first.
+  const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
+  if (!SC) return false;
+
+  // Return true if the value is negative, this matches things like (-42 * V).
+  return SC->getValue()->getValue().isNegative();
+}
+
+/// CollectIVUsers - Transform our list of users and offsets to a bit more
+/// complex table. In this new vector, each 'BasedUser' contains 'Base', the
+/// base of the strided accesses, as well as the old information from Uses. We
+/// progressively move information from the Base field to the Imm field, until
+/// we eventually have the full access expression to rewrite the use.
+const SCEV *LoopStrengthReduce::CollectIVUsers(const SCEV *Stride,
+                                              IVUsersOfOneStride &Uses,
+                                              Loop *L,
+                                              bool &AllUsesAreAddresses,
+                                              bool &AllUsesAreOutsideLoop,
+                                       std::vector<BasedUser> &UsersToProcess) {
+  // FIXME: Generalize to non-affine IV's.
+  if (!Stride->isLoopInvariant(L))
+    return SE->getIntegerSCEV(0, Stride->getType());
+
+  UsersToProcess.reserve(Uses.Users.size());
+  for (ilist<IVStrideUse>::iterator I = Uses.Users.begin(),
+       E = Uses.Users.end(); I != E; ++I) {
+    UsersToProcess.push_back(BasedUser(*I, SE));
+
+    // Move any loop variant operands from the offset field to the immediate
+    // field of the use, so that we don't try to use something before it is
+    // computed.
+    MoveLoopVariantsToImmediateField(UsersToProcess.back().Base,
+                                     UsersToProcess.back().Imm, L, SE);
+    assert(UsersToProcess.back().Base->isLoopInvariant(L) &&
+           "Base value is not loop invariant!");
   }
 
-  return FullV;
-}
-
-/// Rewrite - Emit instructions for the leading candidate expression for this
-/// LSRUse (this is called "expanding"), and update the UserInst to reference
-/// the newly expanded value.
-void LSRUse::Rewrite(Loop *L, Instruction *IVIncInsertPos,
-                     SCEVExpander &Rewriter,
-                     SmallVectorImpl<WeakVH> &DeadInsts,
-                     ScalarEvolution &SE, DominatorTree &DT,
-                     Pass *P) const {
-  const Type *OpTy = OperandValToReplace->getType();
-
-  // First, find an insertion point that dominates UserInst. For PHI nodes,
-  // find the nearest block which dominates all the relevant uses.
-  if (PHINode *PN = dyn_cast<PHINode>(UserInst)) {
-    DenseMap<BasicBlock *, Value *> Inserted;
-    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
-      if (PN->getIncomingValue(i) == OperandValToReplace) {
-        BasicBlock *BB = PN->getIncomingBlock(i);
+  // We now have a whole bunch of uses of like-strided induction variables, but
+  // they might all have different bases.  We want to emit one PHI node for this
+  // stride which we fold as many common expressions (between the IVs) into as
+  // possible.  Start by identifying the common expressions in the base values
+  // for the strides (e.g. if we have "A+C+B" and "A+B+D" as our bases, find
+  // "A+B"), emit it to the preheader, then remove the expression from the
+  // UsersToProcess base values.
+  const SCEV *CommonExprs =
+    RemoveCommonExpressionsFromUseBases(UsersToProcess, SE, L, TLI);
+
+  // Next, figure out what we can represent in the immediate fields of
+  // instructions.  If we can represent anything there, move it to the imm
+  // fields of the BasedUsers.  We do this so that it increases the commonality
+  // of the remaining uses.
+  unsigned NumPHI = 0;
+  bool HasAddress = false;
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
+    // If the user is not in the current loop, this means it is using the exit
+    // value of the IV.  Do not put anything in the base, make sure it's all in
+    // the immediate field to allow as much factoring as possible.
+    if (!L->contains(UsersToProcess[i].Inst)) {
+      UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
+                                             UsersToProcess[i].Base);
+      UsersToProcess[i].Base =
+        SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
+    } else {
+      // Not all uses are outside the loop.
+      AllUsesAreOutsideLoop = false;
+
+      // Addressing modes can be folded into loads and stores.  Be careful that
+      // the store is through the expression, not of the expression though.
+      bool isPHI = false;
+      bool isAddress = isAddressUse(UsersToProcess[i].Inst,
+                                    UsersToProcess[i].OperandValToReplace);
+      if (isa<PHINode>(UsersToProcess[i].Inst)) {
+        isPHI = true;
+        ++NumPHI;
+      }
 
-        // If this is a critical edge, split the edge so that we do not insert
-        // the code on all predecessor/successor paths.  We do this unless this
-        // is the canonical backedge for this loop, which complicates post-inc
-        // users.
-        if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
-            !isa<IndirectBrInst>(BB->getTerminator()) &&
-            (PN->getParent() != L->getHeader() || !L->contains(BB))) {
-          // Split the critical edge.
-          BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
-
-          // If PN is outside of the loop and BB is in the loop, we want to
-          // move the block to be immediately before the PHI block, not
-          // immediately after BB.
-          if (L->contains(BB) && !L->contains(PN))
-            NewBB->moveBefore(PN->getParent());
+      if (isAddress)
+        HasAddress = true;
 
-          // Splitting the edge can reduce the number of PHI entries we have.
-          e = PN->getNumIncomingValues();
-          BB = NewBB;
-          i = PN->getBasicBlockIndex(BB);
-        }
+      // If this use isn't an address, then not all uses are addresses.
+      if (!isAddress && !isPHI)
+        AllUsesAreAddresses = false;
 
-        std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
-          Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
-        if (!Pair.second)
-          PN->setIncomingValue(i, Pair.first->second);
-        else {
-          Value *FullV = Expand(BB->getTerminator(), L, IVIncInsertPos,
-                                Rewriter, DeadInsts, SE, DT);
-
-          // If this is reuse-by-noop-cast, insert the noop cast.
-          if (FullV->getType() != OpTy)
-            FullV =
-              CastInst::Create(CastInst::getCastOpcode(FullV, false,
-                                                       OpTy, false),
-                               FullV, OperandValToReplace->getType(),
-                               "tmp", BB->getTerminator());
-
-          PN->setIncomingValue(i, FullV);
-          Pair.first->second = FullV;
-        }
-      }
-  } else {
-    Value *FullV = Expand(UserInst, L, IVIncInsertPos,
-                          Rewriter, DeadInsts, SE, DT);
-
-    // If this is reuse-by-noop-cast, insert the noop cast.
-    if (FullV->getType() != OpTy) {
-      Instruction *Cast =
-        CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
-                         FullV, OpTy, "tmp", UserInst);
-      FullV = Cast;
+      MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
+                          UsersToProcess[i].Imm, isAddress, L, SE);
     }
-
-    // Update the user.
-    UserInst->replaceUsesOfWith(OperandValToReplace, FullV);
   }
 
-  DeadInsts.push_back(OperandValToReplace);
-}
+  // If one of the use is a PHI node and all other uses are addresses, still
+  // allow iv reuse. Essentially we are trading one constant multiplication
+  // for one fewer iv.
+  if (NumPHI > 1)
+    AllUsesAreAddresses = false;
 
-void LSRUse::print(raw_ostream &OS) const {
-  OS << "LSR Use: Kind=";
-  switch (Kind) {
-  case Basic:    OS << "Basic"; break;
-  case Special:  OS << "Special"; break;
-  case ICmpZero: OS << "ICmpZero"; break;
-  case Address:
-    OS << "Address of ";
-    if (isa<PointerType>(AccessTy))
-      OS << "pointer"; // the full pointer type could be really verbose
-    else
-      OS << *AccessTy;
-  }
-
-  OS << ", UserInst=";
-  // Store is common and interesting enough to be worth special-casing.
-  if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
-    OS << "store ";
-    WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
-  } else if (UserInst->getType()->isVoidTy())
-    OS << UserInst->getOpcodeName();
-  else
-    WriteAsOperand(OS, UserInst, /*PrintType=*/false);
-
-  OS << ", OperandValToReplace=";
-  WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
-
-  if (PostIncLoop) {
-    OS << ", PostIncLoop=";
-    WriteAsOperand(OS, PostIncLoop->getHeader(), /*PrintType=*/false);
-  }
-}
+  // There are no in-loop address uses.
+  if (AllUsesAreAddresses && (!HasAddress && !AllUsesAreOutsideLoop))
+    AllUsesAreAddresses = false;
 
-void LSRUse::dump() const {
-  print(errs()); errs() << '\n';
+  return CommonExprs;
 }
 
-namespace {
-
-/// Score - This class is used to measure and compare candidate formulae.
-class Score {
-  unsigned NumRegs;
-  unsigned NumPhis;
-  unsigned NumIVMuls;
-  unsigned NumBaseAdds;
-  unsigned NumImms;
-
-public:
-  Score()
-    : NumRegs(0), NumPhis(0), NumIVMuls(0), NumBaseAdds(0), NumImms(0) {}
-
-  void RateInitial(SmallVector<LSRUse, 16> const &Uses, const Loop *L,
-                   ScalarEvolution &SE);
-
-  void Rate(const SCEV *Reg, const SmallBitVector &Bits,
-            const SmallVector<LSRUse, 16> &Uses, const Loop *L,
-            ScalarEvolution &SE);
-
-  unsigned getNumRegs() const { return NumRegs; }
+/// ShouldUseFullStrengthReductionMode - Test whether full strength-reduction
+/// is valid and profitable for the given set of users of a stride. In
+/// full strength-reduction mode, all addresses at the current stride are
+/// strength-reduced all the way down to pointer arithmetic.
+///
+bool LoopStrengthReduce::ShouldUseFullStrengthReductionMode(
+                                   const std::vector<BasedUser> &UsersToProcess,
+                                   const Loop *L,
+                                   bool AllUsesAreAddresses,
+                                   const SCEV *Stride) {
+  if (!EnableFullLSRMode)
+    return false;
 
-  bool operator<(const Score &Other) const;
+  // The heuristics below aim to avoid increasing register pressure, but
+  // fully strength-reducing all the addresses increases the number of
+  // add instructions, so don't do this when optimizing for size.
+  // TODO: If the loop is large, the savings due to simpler addresses
+  // may oughtweight the costs of the extra increment instructions.
+  if (L->getHeader()->getParent()->hasFnAttr(Attribute::OptimizeForSize))
+    return false;
 
-  void print_details(raw_ostream &OS, const SCEV *Reg,
-                     const SmallPtrSet<const SCEV *, 8> &Regs) const;
+  // TODO: For now, don't do full strength reduction if there could
+  // potentially be greater-stride multiples of the current stride
+  // which could reuse the current stride IV.
+  if (IU->StrideOrder.back() != Stride)
+    return false;
 
-  void print(raw_ostream &OS) const;
-  void dump() const;
+  // Iterate through the uses to find conditions that automatically rule out
+  // full-lsr mode.
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
+    const SCEV *Base = UsersToProcess[i].Base;
+    const SCEV *Imm = UsersToProcess[i].Imm;
+    // If any users have a loop-variant component, they can't be fully
+    // strength-reduced.
+    if (Imm && !Imm->isLoopInvariant(L))
+      return false;
+    // If there are to users with the same base and the difference between
+    // the two Imm values can't be folded into the address, full
+    // strength reduction would increase register pressure.
+    do {
+      const SCEV *CurImm = UsersToProcess[i].Imm;
+      if ((CurImm || Imm) && CurImm != Imm) {
+        if (!CurImm) CurImm = SE->getIntegerSCEV(0, Stride->getType());
+        if (!Imm)       Imm = SE->getIntegerSCEV(0, Stride->getType());
+        const Instruction *Inst = UsersToProcess[i].Inst;
+        const Type *AccessTy = getAccessType(Inst);
+        const SCEV *Diff = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
+        if (!Diff->isZero() &&
+            (!AllUsesAreAddresses ||
+             !fitsInAddressMode(Diff, AccessTy, TLI, /*HasBaseReg=*/true)))
+          return false;
+      }
+    } while (++i != e && Base == UsersToProcess[i].Base);
+  }
 
-private:
-  void RateRegister(const SCEV *Reg, SmallPtrSet<const SCEV *, 8> &Regs,
-                    const Loop *L);
-  void RateFormula(const Formula &F, SmallPtrSet<const SCEV *, 8> &Regs,
-                   const Loop *L);
+  // If there's exactly one user in this stride, fully strength-reducing it
+  // won't increase register pressure. If it's starting from a non-zero base,
+  // it'll be simpler this way.
+  if (UsersToProcess.size() == 1 && !UsersToProcess[0].Base->isZero())
+    return true;
 
-  void Loose();
-};
+  // Otherwise, if there are any users in this stride that don't require
+  // a register for their base, full strength-reduction will increase
+  // register pressure.
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+    if (UsersToProcess[i].Base->isZero())
+      return false;
 
+  // Otherwise, go for it.
+  return true;
 }
 
-/// RateRegister - Tally up interesting quantities from the given register.
-void Score::RateRegister(const SCEV *Reg,
-                         SmallPtrSet<const SCEV *, 8> &Regs,
-                         const Loop *L) {
-  if (Regs.insert(Reg))
-    if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
-      NumPhis += AR->getLoop() == L;
-
-      // Add the step value register, if it needs one.
-      if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
-        RateRegister(AR->getOperand(1), Regs, L);
+/// InsertAffinePhi Create and insert a PHI node for an induction variable
+/// with the specified start and step values in the specified loop.
+///
+/// If NegateStride is true, the stride should be negated by using a
+/// subtract instead of an add.
+///
+/// Return the created phi node.
+///
+static PHINode *InsertAffinePhi(const SCEV *Start, const SCEV *Step,
+                                Instruction *IVIncInsertPt,
+                                const Loop *L,
+                                SCEVExpander &Rewriter) {
+  assert(Start->isLoopInvariant(L) && "New PHI start is not loop invariant!");
+  assert(Step->isLoopInvariant(L) && "New PHI stride is not loop invariant!");
+
+  BasicBlock *Header = L->getHeader();
+  BasicBlock *Preheader = L->getLoopPreheader();
+  BasicBlock *LatchBlock = L->getLoopLatch();
+  const Type *Ty = Start->getType();
+  Ty = Rewriter.SE.getEffectiveSCEVType(Ty);
+
+  PHINode *PN = PHINode::Create(Ty, "lsr.iv", Header->begin());
+  PN->addIncoming(Rewriter.expandCodeFor(Start, Ty, Preheader->getTerminator()),
+                  Preheader);
+
+  // If the stride is negative, insert a sub instead of an add for the
+  // increment.
+  bool isNegative = isNonConstantNegative(Step);
+  const SCEV *IncAmount = Step;
+  if (isNegative)
+    IncAmount = Rewriter.SE.getNegativeSCEV(Step);
+
+  // Insert an add instruction right before the terminator corresponding
+  // to the back-edge or just before the only use. The location is determined
+  // by the caller and passed in as IVIncInsertPt.
+  Value *StepV = Rewriter.expandCodeFor(IncAmount, Ty,
+                                        Preheader->getTerminator());
+  Instruction *IncV;
+  if (isNegative) {
+    IncV = BinaryOperator::CreateSub(PN, StepV, "lsr.iv.next",
+                                     IVIncInsertPt);
+  } else {
+    IncV = BinaryOperator::CreateAdd(PN, StepV, "lsr.iv.next",
+                                     IVIncInsertPt);
+  }
+  if (!isa<ConstantInt>(StepV)) ++NumVariable;
+
+  PN->addIncoming(IncV, LatchBlock);
+
+  ++NumInserted;
+  return PN;
+}
+
+static void SortUsersToProcess(std::vector<BasedUser> &UsersToProcess) {
+  // We want to emit code for users inside the loop first.  To do this, we
+  // rearrange BasedUser so that the entries at the end have
+  // isUseOfPostIncrementedValue = false, because we pop off the end of the
+  // vector (so we handle them first).
+  std::partition(UsersToProcess.begin(), UsersToProcess.end(),
+                 PartitionByIsUseOfPostIncrementedValue);
+
+  // Sort this by base, so that things with the same base are handled
+  // together.  By partitioning first and stable-sorting later, we are
+  // guaranteed that within each base we will pop off users from within the
+  // loop before users outside of the loop with a particular base.
+  //
+  // We would like to use stable_sort here, but we can't.  The problem is that
+  // const SCEV *'s don't have a deterministic ordering w.r.t to each other, so
+  // we don't have anything to do a '<' comparison on.  Because we think the
+  // number of uses is small, do a horrible bubble sort which just relies on
+  // ==.
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
+    // Get a base value.
+    const SCEV *Base = UsersToProcess[i].Base;
+
+    // Compact everything with this base to be consecutive with this one.
+    for (unsigned j = i+1; j != e; ++j) {
+      if (UsersToProcess[j].Base == Base) {
+        std::swap(UsersToProcess[i+1], UsersToProcess[j]);
+        ++i;
+      }
     }
+  }
 }
 
-void Score::RateFormula(const Formula &F,
-                        SmallPtrSet<const SCEV *, 8> &Regs,
-                        const Loop *L) {
-  // Tally up the registers.
-  if (F.ScaledReg)
-    RateRegister(F.ScaledReg, Regs, L);
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
-       E = F.BaseRegs.end(); I != E; ++I) {
-    const SCEV *BaseReg = *I;
-    RateRegister(BaseReg, Regs, L);
-
-    NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
-                 BaseReg->hasComputableLoopEvolution(L);
+/// PrepareToStrengthReduceFully - Prepare to fully strength-reduce
+/// UsersToProcess, meaning lowering addresses all the way down to direct
+/// pointer arithmetic.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceFully(
+                                        std::vector<BasedUser> &UsersToProcess,
+                                        const SCEV *Stride,
+                                        const SCEV *CommonExprs,
+                                        const Loop *L,
+                                        SCEVExpander &PreheaderRewriter) {
+  DEBUG(dbgs() << "  Fully reducing all users\n");
+
+  // Rewrite the UsersToProcess records, creating a separate PHI for each
+  // unique Base value.
+  Instruction *IVIncInsertPt = L->getLoopLatch()->getTerminator();
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
+    // TODO: The uses are grouped by base, but not sorted. We arbitrarily
+    // pick the first Imm value here to start with, and adjust it for the
+    // other uses.
+    const SCEV *Imm = UsersToProcess[i].Imm;
+    const SCEV *Base = UsersToProcess[i].Base;
+    const SCEV *Start = SE->getAddExpr(CommonExprs, Base, Imm);
+    PHINode *Phi = InsertAffinePhi(Start, Stride, IVIncInsertPt, L,
+                                   PreheaderRewriter);
+    // Loop over all the users with the same base.
+    do {
+      UsersToProcess[i].Base = SE->getIntegerSCEV(0, Stride->getType());
+      UsersToProcess[i].Imm = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
+      UsersToProcess[i].Phi = Phi;
+      assert(UsersToProcess[i].Imm->isLoopInvariant(L) &&
+             "ShouldUseFullStrengthReductionMode should reject this!");
+    } while (++i != e && Base == UsersToProcess[i].Base);
   }
-
-  if (F.BaseRegs.size() > 1)
-    NumBaseAdds += F.BaseRegs.size() - 1;
-
-  // Tally up the non-zero immediates.
-  if (F.AM.BaseGV || F.AM.BaseOffs != 0)
-    ++NumImms;
 }
 
-/// Loose - Set this score to a loosing value.
-void Score::Loose() {
-  NumRegs = ~0u;
-  NumPhis = ~0u;
-  NumIVMuls = ~0u;
-  NumBaseAdds = ~0u;
-  NumImms = ~0u;
+/// FindIVIncInsertPt - Return the location to insert the increment instruction.
+/// If the only use if a use of postinc value, (must be the loop termination
+/// condition), then insert it just before the use.
+static Instruction *FindIVIncInsertPt(std::vector<BasedUser> &UsersToProcess,
+                                      const Loop *L) {
+  if (UsersToProcess.size() == 1 &&
+      UsersToProcess[0].isUseOfPostIncrementedValue &&
+      L->contains(UsersToProcess[0].Inst))
+    return UsersToProcess[0].Inst;
+  return L->getLoopLatch()->getTerminator();
 }
 
-/// RateInitial - Compute a score for the initial "fully reduced" solution.
-void Score::RateInitial(SmallVector<LSRUse, 16> const &Uses, const Loop *L,
-                        ScalarEvolution &SE) {
-  SmallPtrSet<const SCEV *, 8> Regs;
-  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
-       E = Uses.end(); I != E; ++I)
-    RateFormula(I->Formulae.front(), Regs, L);
-  NumRegs += Regs.size();
-
-  DEBUG(print_details(dbgs(), 0, Regs));
+/// PrepareToStrengthReduceWithNewPhi - Insert a new induction variable for the
+/// given users to share.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceWithNewPhi(
+                                         std::vector<BasedUser> &UsersToProcess,
+                                         const SCEV *Stride,
+                                         const SCEV *CommonExprs,
+                                         Value *CommonBaseV,
+                                         Instruction *IVIncInsertPt,
+                                         const Loop *L,
+                                         SCEVExpander &PreheaderRewriter) {
+  DEBUG(dbgs() << "  Inserting new PHI:\n");
+
+  PHINode *Phi = InsertAffinePhi(SE->getUnknown(CommonBaseV),
+                                 Stride, IVIncInsertPt, L,
+                                 PreheaderRewriter);
+
+  // Remember this in case a later stride is multiple of this.
+  IVsByStride[Stride].addIV(Stride, CommonExprs, Phi);
+
+  // All the users will share this new IV.
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+    UsersToProcess[i].Phi = Phi;
+
+  DEBUG(dbgs() << "    IV=");
+  DEBUG(WriteAsOperand(dbgs(), Phi, /*PrintType=*/false));
+  DEBUG(dbgs() << "\n");
+}
+
+/// PrepareToStrengthReduceFromSmallerStride - Prepare for the given users to
+/// reuse an induction variable with a stride that is a factor of the current
+/// induction variable.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceFromSmallerStride(
+                                         std::vector<BasedUser> &UsersToProcess,
+                                         Value *CommonBaseV,
+                                         const IVExpr &ReuseIV,
+                                         Instruction *PreInsertPt) {
+  DEBUG(dbgs() << "  Rewriting in terms of existing IV of STRIDE "
+               << *ReuseIV.Stride << " and BASE " << *ReuseIV.Base << "\n");
+
+  // All the users will share the reused IV.
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+    UsersToProcess[i].Phi = ReuseIV.PHI;
+
+  Constant *C = dyn_cast<Constant>(CommonBaseV);
+  if (C &&
+      (!C->isNullValue() &&
+       !fitsInAddressMode(SE->getUnknown(CommonBaseV), CommonBaseV->getType(),
+                         TLI, false)))
+    // We want the common base emitted into the preheader! This is just
+    // using cast as a copy so BitCast (no-op cast) is appropriate
+    CommonBaseV = new BitCastInst(CommonBaseV, CommonBaseV->getType(),
+                                  "commonbase", PreInsertPt);
+}
+
+static bool IsImmFoldedIntoAddrMode(GlobalValue *GV, int64_t Offset,
+                                    const Type *AccessTy,
+                                   std::vector<BasedUser> &UsersToProcess,
+                                   const TargetLowering *TLI) {
+  SmallVector<Instruction*, 16> AddrModeInsts;
+  for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
+    if (UsersToProcess[i].isUseOfPostIncrementedValue)
+      continue;
+    ExtAddrMode AddrMode =
+      AddressingModeMatcher::Match(UsersToProcess[i].OperandValToReplace,
+                                   AccessTy, UsersToProcess[i].Inst,
+                                   AddrModeInsts, *TLI);
+    if (GV && GV != AddrMode.BaseGV)
+      return false;
+    if (Offset && !AddrMode.BaseOffs)
+      // FIXME: How to accurate check it's immediate offset is folded.
+      return false;
+    AddrModeInsts.clear();
+  }
+  return true;
 }
 
-/// Rate - Compute a score for the solution where the reuse associated with
-/// putting Reg in a register is selected.
-void Score::Rate(const SCEV *Reg, const SmallBitVector &Bits,
-                 const SmallVector<LSRUse, 16> &Uses, const Loop *L,
-                 ScalarEvolution &SE) {
-  SmallPtrSet<const SCEV *, 8> Regs;
-  for (size_t i = 0, e = Uses.size(); i != e; ++i) {
-    const LSRUse &LU = Uses[i];
-
-    const Formula *BestFormula = 0;
-    if (i >= Bits.size() || !Bits.test(i))
-      // This use doesn't use the current register. Just go with the current
-      // leading candidate formula.
-      BestFormula = &LU.Formulae.front();
-    else
-      // Find the best formula for this use that uses the current register.
-      for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
-           E = LU.Formulae.end(); I != E; ++I) {
-        const Formula &F = *I;
-        if (F.referencesReg(Reg) &&
-            (!BestFormula || ComplexitySorter()(F, *BestFormula)))
-          BestFormula = &F;
-      }
-
-    // If we didn't find *any* forumlae, because earlier we eliminated some
-    // in greedy fashion, skip the current register's reuse opportunity.
-    if (!BestFormula) {
-      DEBUG(dbgs() << "Reuse with reg " << *Reg
-                   << " wouldn't help any users.\n");
-      Loose();
-      return;
-    }
+/// StrengthReduceIVUsersOfStride - Strength reduce all of the users of a single
+/// stride of IV.  All of the users may have different starting values, and this
+/// may not be the only stride.
+void
+LoopStrengthReduce::StrengthReduceIVUsersOfStride(const SCEV *Stride,
+                                                  IVUsersOfOneStride &Uses,
+                                                  Loop *L) {
+  // If all the users are moved to another stride, then there is nothing to do.
+  if (Uses.Users.empty())
+    return;
 
-    // For an in-loop post-inc user, don't allow multiple base registers,
-    // because that would require an awkward in-loop add after the increment.
-    if (LU.PostIncLoop && LU.PostIncLoop->contains(LU.UserInst) &&
-        BestFormula->BaseRegs.size() > 1) {
-      DEBUG(dbgs() << "Reuse with reg " << *Reg
-                   << " would require an in-loop post-inc add: ";
-            BestFormula->dump());
-      Loose();
-      return;
+  // Keep track if every use in UsersToProcess is an address. If they all are,
+  // we may be able to rewrite the entire collection of them in terms of a
+  // smaller-stride IV.
+  bool AllUsesAreAddresses = true;
+
+  // Keep track if every use of a single stride is outside the loop.  If so,
+  // we want to be more aggressive about reusing a smaller-stride IV; a
+  // multiply outside the loop is better than another IV inside.  Well, usually.
+  bool AllUsesAreOutsideLoop = true;
+
+  // Transform our list of users and offsets to a bit more complex table.  In
+  // this new vector, each 'BasedUser' contains 'Base' the base of the
+  // strided accessas well as the old information from Uses.  We progressively
+  // move information from the Base field to the Imm field, until we eventually
+  // have the full access expression to rewrite the use.
+  std::vector<BasedUser> UsersToProcess;
+  const SCEV *CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
+                                           AllUsesAreOutsideLoop,
+                                           UsersToProcess);
+
+  // Sort the UsersToProcess array so that users with common bases are
+  // next to each other.
+  SortUsersToProcess(UsersToProcess);
+
+  // If we managed to find some expressions in common, we'll need to carry
+  // their value in a register and add it in for each use. This will take up
+  // a register operand, which potentially restricts what stride values are
+  // valid.
+  bool HaveCommonExprs = !CommonExprs->isZero();
+  const Type *ReplacedTy = CommonExprs->getType();
+
+  // If all uses are addresses, consider sinking the immediate part of the
+  // common expression back into uses if they can fit in the immediate fields.
+  if (TLI && HaveCommonExprs && AllUsesAreAddresses) {
+    const SCEV *NewCommon = CommonExprs;
+    const SCEV *Imm = SE->getIntegerSCEV(0, ReplacedTy);
+    MoveImmediateValues(TLI, Type::getVoidTy(
+                        L->getLoopPreheader()->getContext()),
+                        NewCommon, Imm, true, L, SE);
+    if (!Imm->isZero()) {
+      bool DoSink = true;
+
+      // If the immediate part of the common expression is a GV, check if it's
+      // possible to fold it into the target addressing mode.
+      GlobalValue *GV = 0;
+      if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(Imm))
+        GV = dyn_cast<GlobalValue>(SU->getValue());
+      int64_t Offset = 0;
+      if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
+        Offset = SC->getValue()->getSExtValue();
+      if (GV || Offset)
+        // Pass VoidTy as the AccessTy to be conservative, because
+        // there could be multiple access types among all the uses.
+        DoSink = IsImmFoldedIntoAddrMode(GV, Offset,
+                          Type::getVoidTy(L->getLoopPreheader()->getContext()),
+                                         UsersToProcess, TLI);
+
+      if (DoSink) {
+        DEBUG(dbgs() << "  Sinking " << *Imm << " back down into uses\n");
+        for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+          UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm, Imm);
+        CommonExprs = NewCommon;
+        HaveCommonExprs = !CommonExprs->isZero();
+        ++NumImmSunk;
+      }
     }
-
-    RateFormula(*BestFormula, Regs, L);
   }
-  NumRegs += Regs.size();
 
-  DEBUG(print_details(dbgs(), Reg, Regs));
-}
+  // Now that we know what we need to do, insert the PHI node itself.
+  //
+  DEBUG(dbgs() << "LSR: Examining IVs of TYPE " << *ReplacedTy << " of STRIDE "
+               << *Stride << ":\n"
+               << "  Common base: " << *CommonExprs << "\n");
 
-/// operator< - Choose the better score.
-bool Score::operator<(const Score &Other) const {
-  if (NumRegs != Other.NumRegs)
-    return NumRegs < Other.NumRegs;
-  if (NumPhis != Other.NumPhis)
-    return NumPhis < Other.NumPhis;
-  if (NumIVMuls != Other.NumIVMuls)
-    return NumIVMuls < Other.NumIVMuls;
-  if (NumBaseAdds != Other.NumBaseAdds)
-    return NumBaseAdds < Other.NumBaseAdds;
-  return NumImms < Other.NumImms;
-}
+  SCEVExpander Rewriter(*SE);
+  SCEVExpander PreheaderRewriter(*SE);
 
-void Score::print_details(raw_ostream &OS,
-                          const SCEV *Reg,
-                          const SmallPtrSet<const SCEV *, 8> &Regs) const {
-  if (Reg) OS << "Reuse with reg " << *Reg << " would require ";
-  else     OS << "The initial solution would require ";
-  print(OS);
-  OS << ". Regs:";
-  for (SmallPtrSet<const SCEV *, 8>::const_iterator I = Regs.begin(),
-       E = Regs.end(); I != E; ++I)
-    OS << ' ' << **I;
-  OS << '\n';
-}
-
-void Score::print(raw_ostream &OS) const {
-  OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
-  if (NumPhis != 0)
-    OS << ", including " << NumPhis << " PHI" << (NumPhis == 1 ? "" : "s");
-  if (NumIVMuls != 0)
-    OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
-  if (NumBaseAdds != 0)
-    OS << ", plus " << NumBaseAdds << " base add"
-       << (NumBaseAdds == 1 ? "" : "s");
-  if (NumImms != 0)
-    OS << ", plus " << NumImms << " imm" << (NumImms == 1 ? "" : "s");
-}
-
-void Score::dump() const {
-  print(errs()); errs() << '\n';
-}
-
-/// isAddressUse - Returns true if the specified instruction is using the
-/// specified value as an address.
-static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
-  bool isAddress = isa<LoadInst>(Inst);
-  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
-    if (SI->getOperand(1) == OperandVal)
-      isAddress = true;
-  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
-    // Addressing modes can also be folded into prefetches and a variety
-    // of intrinsics.
-    switch (II->getIntrinsicID()) {
-      default: break;
-      case Intrinsic::prefetch:
-      case Intrinsic::x86_sse2_loadu_dq:
-      case Intrinsic::x86_sse2_loadu_pd:
-      case Intrinsic::x86_sse_loadu_ps:
-      case Intrinsic::x86_sse_storeu_ps:
-      case Intrinsic::x86_sse2_storeu_pd:
-      case Intrinsic::x86_sse2_storeu_dq:
-      case Intrinsic::x86_sse2_storel_dq:
-        if (II->getOperand(1) == OperandVal)
-          isAddress = true;
-        break;
+  BasicBlock  *Preheader = L->getLoopPreheader();
+  Instruction *PreInsertPt = Preheader->getTerminator();
+  BasicBlock *LatchBlock = L->getLoopLatch();
+  Instruction *IVIncInsertPt = LatchBlock->getTerminator();
+
+  Value *CommonBaseV = Constant::getNullValue(ReplacedTy);
+
+  const SCEV *RewriteFactor = SE->getIntegerSCEV(0, ReplacedTy);
+  IVExpr   ReuseIV(SE->getIntegerSCEV(0,
+                                    Type::getInt32Ty(Preheader->getContext())),
+                   SE->getIntegerSCEV(0,
+                                    Type::getInt32Ty(Preheader->getContext())),
+                   0);
+
+  // Choose a strength-reduction strategy and prepare for it by creating
+  // the necessary PHIs and adjusting the bookkeeping.
+  if (ShouldUseFullStrengthReductionMode(UsersToProcess, L,
+                                         AllUsesAreAddresses, Stride)) {
+    PrepareToStrengthReduceFully(UsersToProcess, Stride, CommonExprs, L,
+                                 PreheaderRewriter);
+  } else {
+    // Emit the initial base value into the loop preheader.
+    CommonBaseV = PreheaderRewriter.expandCodeFor(CommonExprs, ReplacedTy,
+                                                  PreInsertPt);
+
+    // If all uses are addresses, check if it is possible to reuse an IV.  The
+    // new IV must have a stride that is a multiple of the old stride; the
+    // multiple must be a number that can be encoded in the scale field of the
+    // target addressing mode; and we must have a valid instruction after this
+    // substitution, including the immediate field, if any.
+    RewriteFactor = CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
+                                    AllUsesAreOutsideLoop,
+                                    Stride, ReuseIV, ReplacedTy,
+                                    UsersToProcess);
+    if (!RewriteFactor->isZero())
+      PrepareToStrengthReduceFromSmallerStride(UsersToProcess, CommonBaseV,
+                                               ReuseIV, PreInsertPt);
+    else {
+      IVIncInsertPt = FindIVIncInsertPt(UsersToProcess, L);
+      PrepareToStrengthReduceWithNewPhi(UsersToProcess, Stride, CommonExprs,
+                                        CommonBaseV, IVIncInsertPt,
+                                        L, PreheaderRewriter);
     }
   }
-  return isAddress;
-}
 
-/// getAccessType - Return the type of the memory being accessed.
-static const Type *getAccessType(const Instruction *Inst) {
-  const Type *AccessTy = Inst->getType();
-  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
-    AccessTy = SI->getOperand(0)->getType();
-  else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
-    // Addressing modes can also be folded into prefetches and a variety
-    // of intrinsics.
-    switch (II->getIntrinsicID()) {
-    default: break;
-    case Intrinsic::x86_sse_storeu_ps:
-    case Intrinsic::x86_sse2_storeu_pd:
-    case Intrinsic::x86_sse2_storeu_dq:
-    case Intrinsic::x86_sse2_storel_dq:
-      AccessTy = II->getOperand(1)->getType();
-      break;
+  // Process all the users now, replacing their strided uses with
+  // strength-reduced forms.  This outer loop handles all bases, the inner
+  // loop handles all users of a particular base.
+  while (!UsersToProcess.empty()) {
+    const SCEV *Base = UsersToProcess.back().Base;
+    Instruction *Inst = UsersToProcess.back().Inst;
+
+    // Emit the code for Base into the preheader.
+    Value *BaseV = 0;
+    if (!Base->isZero()) {
+      BaseV = PreheaderRewriter.expandCodeFor(Base, 0, PreInsertPt);
+
+      DEBUG(dbgs() << "  INSERTING code for BASE = " << *Base << ":");
+      if (BaseV->hasName())
+        DEBUG(dbgs() << " Result value name = %" << BaseV->getName());
+      DEBUG(dbgs() << "\n");
+
+      // If BaseV is a non-zero constant, make sure that it gets inserted into
+      // the preheader, instead of being forward substituted into the uses.  We
+      // do this by forcing a BitCast (noop cast) to be inserted into the
+      // preheader in this case.
+      if (!fitsInAddressMode(Base, getAccessType(Inst), TLI, false) &&
+          isa<Constant>(BaseV)) {
+        // We want this constant emitted into the preheader! This is just
+        // using cast as a copy so BitCast (no-op cast) is appropriate
+        BaseV = new BitCastInst(BaseV, BaseV->getType(), "preheaderinsert",
+                                PreInsertPt);
+      }
     }
-  }
-  return AccessTy;
-}
-
-/// DeleteTriviallyDeadInstructions - If any of the instructions is the
-/// specified set are trivially dead, delete them and see if this makes any of
-/// their operands subsequently dead.
-static bool
-DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
-  bool Changed = false;
 
-  while (!DeadInsts.empty()) {
-    Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
-
-    if (I == 0 || !isInstructionTriviallyDead(I))
-      continue;
+    // Emit the code to add the immediate offset to the Phi value, just before
+    // the instructions that we identified as using this stride and base.
+    do {
+      // FIXME: Use emitted users to emit other users.
+      BasedUser &User = UsersToProcess.back();
 
-    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
-      if (Instruction *U = dyn_cast<Instruction>(*OI)) {
-        *OI = 0;
-        if (U->use_empty())
-          DeadInsts.push_back(U);
+      DEBUG(dbgs() << "    Examining ");
+      if (User.isUseOfPostIncrementedValue)
+        DEBUG(dbgs() << "postinc");
+      else
+        DEBUG(dbgs() << "preinc");
+      DEBUG(dbgs() << " use ");
+      DEBUG(WriteAsOperand(dbgs(), UsersToProcess.back().OperandValToReplace,
+                           /*PrintType=*/false));
+      DEBUG(dbgs() << " in Inst: " << *User.Inst);
+
+      // If this instruction wants to use the post-incremented value, move it
+      // after the post-inc and use its value instead of the PHI.
+      Value *RewriteOp = User.Phi;
+      if (User.isUseOfPostIncrementedValue) {
+        RewriteOp = User.Phi->getIncomingValueForBlock(LatchBlock);
+        // If this user is in the loop, make sure it is the last thing in the
+        // loop to ensure it is dominated by the increment. In case it's the
+        // only use of the iv, the increment instruction is already before the
+        // use.
+        if (L->contains(User.Inst) && User.Inst != IVIncInsertPt)
+          User.Inst->moveBefore(IVIncInsertPt);
       }
 
-    I->eraseFromParent();
-    Changed = true;
-  }
-
-  return Changed;
-}
-
-namespace {
-
-/// LSRInstance - This class holds state for the main loop strength
-/// reduction logic.
-class LSRInstance {
-  IVUsers &IU;
-  ScalarEvolution &SE;
-  DominatorTree &DT;
-  const TargetLowering *const TLI;
-  Loop *const L;
-  bool Changed;
-
-  /// IVIncInsertPos - This is the insert position that the current loop's
-  /// induction variable increment should be placed. In simple loops, this is
-  /// the latch block's terminator. But in more complicated cases, this is
-  /// a position which will dominate all the in-loop post-increment users.
-  Instruction *IVIncInsertPos;
-
-  /// CurrentArbitraryRegIndex - To ensure a deterministic ordering, assign an
-  /// arbitrary index value to each register as a sort tie breaker.
-  unsigned CurrentArbitraryRegIndex;
-
-  /// MaxNumRegs - To help prune the search for solutions, identify the number
-  /// of registers needed by the initial solution. No formula should require
-  /// more than this.
-  unsigned MaxNumRegs;
-
-  /// Factors - Interesting factors between use strides.
-  SmallSetVector<int64_t, 4> Factors;
-
-  /// Types - Interesting use types, to facilitate truncation reuse.
-  SmallSetVector<const Type *, 4> Types;
-
-  /// Uses - The list of interesting uses.
-  SmallVector<LSRUse, 16> Uses;
-
-  // TODO: Reorganize these data structures.
-  typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
-  RegUsesTy RegUses;
-  SmallVector<const SCEV *, 16> RegSequence;
-
-  void OptimizeShadowIV();
-  bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
-                         const SCEV* &CondStride);
-  ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
-  bool StrideMightBeShared(const SCEV* Stride);
-  bool OptimizeLoopTermCond();
-
-  LSRUse &getNewUse() {
-    Uses.push_back(LSRUse());
-    return Uses.back();
-  }
-
-  void CountRegister(const SCEV *Reg, uint32_t Complexity, size_t LUIdx);
-  void CountRegisters(const Formula &F, size_t LUIdx);
+      const SCEV *RewriteExpr = SE->getUnknown(RewriteOp);
 
-  bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
+      if (SE->getEffectiveSCEVType(RewriteOp->getType()) !=
+          SE->getEffectiveSCEVType(ReplacedTy)) {
+        assert(SE->getTypeSizeInBits(RewriteOp->getType()) >
+               SE->getTypeSizeInBits(ReplacedTy) &&
+               "Unexpected widening cast!");
+        RewriteExpr = SE->getTruncateExpr(RewriteExpr, ReplacedTy);
+      }
 
-  void GenerateSymbolicOffsetReuse(LSRUse &LU, unsigned LUIdx,
-                                   Formula Base);
-  void GenerateICmpZeroScaledReuse(LSRUse &LU, unsigned LUIdx,
-                                   Formula Base);
-  void GenerateFormulaeFromReplacedBaseReg(LSRUse &LU,
-                                           unsigned LUIdx,
-                                           const Formula &Base, unsigned i,
-                                           const SmallVectorImpl<const SCEV *>
-                                             &AddOps);
-  void GenerateReassociationReuse(LSRUse &LU, unsigned LUIdx,
-                                  Formula Base);
-  void GenerateCombinationReuse(LSRUse &LU, unsigned LUIdx,
-                                Formula Base);
-  void GenerateScaledReuse(LSRUse &LU, unsigned LUIdx,
-                           Formula Base);
-  void GenerateTruncateReuse(LSRUse &LU, unsigned LUIdx,
-                             Formula Base);
+      // If we had to insert new instructions for RewriteOp, we have to
+      // consider that they may not have been able to end up immediately
+      // next to RewriteOp, because non-PHI instructions may never precede
+      // PHI instructions in a block. In this case, remember where the last
+      // instruction was inserted so that if we're replacing a different
+      // PHI node, we can use the later point to expand the final
+      // RewriteExpr.
+      Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
+      if (RewriteOp == User.Phi) NewBasePt = 0;
+
+      // Clear the SCEVExpander's expression map so that we are guaranteed
+      // to have the code emitted where we expect it.
+      Rewriter.clear();
+
+      // If we are reusing the iv, then it must be multiplied by a constant
+      // factor to take advantage of the addressing mode scale component.
+      if (!RewriteFactor->isZero()) {
+        // If we're reusing an IV with a nonzero base (currently this happens
+        // only when all reuses are outside the loop) subtract that base here.
+        // The base has been used to initialize the PHI node but we don't want
+        // it here.
+        if (!ReuseIV.Base->isZero()) {
+          const SCEV *typedBase = ReuseIV.Base;
+          if (SE->getEffectiveSCEVType(RewriteExpr->getType()) !=
+              SE->getEffectiveSCEVType(ReuseIV.Base->getType())) {
+            // It's possible the original IV is a larger type than the new IV,
+            // in which case we have to truncate the Base.  We checked in
+            // RequiresTypeConversion that this is valid.
+            assert(SE->getTypeSizeInBits(RewriteExpr->getType()) <
+                   SE->getTypeSizeInBits(ReuseIV.Base->getType()) &&
+                   "Unexpected lengthening conversion!");
+            typedBase = SE->getTruncateExpr(ReuseIV.Base,
+                                            RewriteExpr->getType());
+          }
+          RewriteExpr = SE->getMinusSCEV(RewriteExpr, typedBase);
+        }
 
-  void GenerateConstantOffsetReuse();
+        // Multiply old variable, with base removed, by new scale factor.
+        RewriteExpr = SE->getMulExpr(RewriteFactor,
+                                     RewriteExpr);
+
+        // The common base is emitted in the loop preheader. But since we
+        // are reusing an IV, it has not been used to initialize the PHI node.
+        // Add it to the expression used to rewrite the uses.
+        // When this use is outside the loop, we earlier subtracted the
+        // common base, and are adding it back here.  Use the same expression
+        // as before, rather than CommonBaseV, so DAGCombiner will zap it.
+        if (!CommonExprs->isZero()) {
+          if (L->contains(User.Inst))
+            RewriteExpr = SE->getAddExpr(RewriteExpr,
+                                       SE->getUnknown(CommonBaseV));
+          else
+            RewriteExpr = SE->getAddExpr(RewriteExpr, CommonExprs);
+        }
+      }
 
-  void GenerateAllReuseFormulae();
+      // Now that we know what we need to do, insert code before User for the
+      // immediate and any loop-variant expressions.
+      if (BaseV)
+        // Add BaseV to the PHI value if needed.
+        RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
 
-  void GenerateLoopInvariantRegisterUses();
+      User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
+                                          Rewriter, L, this,
+                                          DeadInsts, SE);
 
-public:
-  LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
+      // Mark old value we replaced as possibly dead, so that it is eliminated
+      // if we just replaced the last use of that value.
+      DeadInsts.push_back(User.OperandValToReplace);
 
-  bool getChanged() const { return Changed; }
+      UsersToProcess.pop_back();
+      ++NumReduced;
 
-  void print(raw_ostream &OS) const;
-  void dump() const;
-};
+      // If there are any more users to process with the same base, process them
+      // now.  We sorted by base above, so we just have to check the last elt.
+    } while (!UsersToProcess.empty() && UsersToProcess.back().Base == Base);
+    // TODO: Next, find out which base index is the most common, pull it out.
+  }
 
+  // IMPORTANT TODO: Figure out how to partition the IV's with this stride, but
+  // different starting values, into different PHIs.
 }
 
-/// OptimizeShadowIV - If IV is used in a int-to-float cast
-/// inside the loop then try to eliminate the cast opeation.
-void LSRInstance::OptimizeShadowIV() {
-  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
-  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
-    return;
-
-  for (size_t StrideIdx = 0, e = IU.StrideOrder.size();
-       StrideIdx != e; ++StrideIdx) {
+void LoopStrengthReduce::StrengthReduceIVUsers(Loop *L) {
+  // Note: this processes each stride/type pair individually.  All users
+  // passed into StrengthReduceIVUsersOfStride have the same type AND stride.
+  // Also, note that we iterate over IVUsesByStride indirectly by using
+  // StrideOrder. This extra layer of indirection makes the ordering of
+  // strides deterministic - not dependent on map order.
+  for (unsigned Stride = 0, e = IU->StrideOrder.size(); Stride != e; ++Stride) {
     std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
-      IU.IVUsesByStride.find(IU.StrideOrder[StrideIdx]);
-    assert(SI != IU.IVUsesByStride.end() && "Stride doesn't exist!");
-    if (!isa<SCEVConstant>(SI->first))
+      IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
+    assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
+    // FIXME: Generalize to non-affine IV's.
+    if (!SI->first->isLoopInvariant(L))
       continue;
+    StrengthReduceIVUsersOfStride(SI->first, *SI->second, L);
+  }
+}
 
-    for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
-           E = SI->second->Users.end(); UI != E; /* empty */) {
-      ilist<IVStrideUse>::iterator CandidateUI = UI;
-      ++UI;
-      Instruction *ShadowUse = CandidateUI->getUser();
-      const Type *DestTy = NULL;
-
-      /* If shadow use is a int->float cast then insert a second IV
-         to eliminate this cast.
-
-           for (unsigned i = 0; i < n; ++i)
-             foo((double)i);
+/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
+/// set the IV user and stride information and return true, otherwise return
+/// false.
+bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond,
+                                           IVStrideUse *&CondUse,
+                                           const SCEV* &CondStride) {
+  for (unsigned Stride = 0, e = IU->StrideOrder.size();
+       Stride != e && !CondUse; ++Stride) {
+    std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
+      IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
+    assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
 
-         is transformed into
+    for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
+         E = SI->second->Users.end(); UI != E; ++UI)
+      if (UI->getUser() == Cond) {
+        // NOTE: we could handle setcc instructions with multiple uses here, but
+        // InstCombine does it as well for simple uses, it's not clear that it
+        // occurs enough in real life to handle.
+        CondUse = UI;
+        CondStride = SI->first;
+        return true;
+      }
+  }
+  return false;
+}
 
-           double d = 0.0;
-           for (unsigned i = 0; i < n; ++i, ++d)
-             foo(d);
-      */
-      if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
-        DestTy = UCast->getDestTy();
-      else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
-        DestTy = SCast->getDestTy();
-      if (!DestTy) continue;
+namespace {
+  // Constant strides come first which in turns are sorted by their absolute
+  // values. If absolute values are the same, then positive strides comes first.
+  // e.g.
+  // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
+  struct StrideCompare {
+    const ScalarEvolution *SE;
+    explicit StrideCompare(const ScalarEvolution *se) : SE(se) {}
+
+    bool operator()(const SCEV *LHS, const SCEV *RHS) {
+      const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
+      const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
+      if (LHSC && RHSC) {
+        int64_t  LV = LHSC->getValue()->getSExtValue();
+        int64_t  RV = RHSC->getValue()->getSExtValue();
+        uint64_t ALV = (LV < 0) ? -LV : LV;
+        uint64_t ARV = (RV < 0) ? -RV : RV;
+        if (ALV == ARV) {
+          if (LV != RV)
+            return LV > RV;
+        } else {
+          return ALV < ARV;
+        }
 
-      if (TLI) {
-        // If target does not support DestTy natively then do not apply
-        // this transformation.
-        EVT DVT = TLI->getValueType(DestTy);
-        if (!TLI->isTypeLegal(DVT)) continue;
+        // If it's the same value but different type, sort by bit width so
+        // that we emit larger induction variables before smaller
+        // ones, letting the smaller be re-written in terms of larger ones.
+        return SE->getTypeSizeInBits(RHS->getType()) <
+               SE->getTypeSizeInBits(LHS->getType());
       }
+      return LHSC && !RHSC;
+    }
+  };
+}
 
-      PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
-      if (!PH) continue;
-      if (PH->getNumIncomingValues() != 2) continue;
+/// ChangeCompareStride - If a loop termination compare instruction is the
+/// only use of its stride, and the compaison is against a constant value,
+/// try eliminate the stride by moving the compare instruction to another
+/// stride and change its constant operand accordingly. e.g.
+///
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// v2 = v2 + 1
+/// if (v2 < 10) goto loop
+/// =>
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// if (v1 < 30) goto loop
+ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
+                                                  IVStrideUse* &CondUse,
+                                                  const SCEV* &CondStride,
+                                                  bool PostPass) {
+  // If there's only one stride in the loop, there's nothing to do here.
+  if (IU->StrideOrder.size() < 2)
+    return Cond;
+  // If there are other users of the condition's stride, don't bother
+  // trying to change the condition because the stride will still
+  // remain.
+  std::map<const SCEV *, IVUsersOfOneStride *>::iterator I =
+    IU->IVUsesByStride.find(CondStride);
+  if (I == IU->IVUsesByStride.end())
+    return Cond;
+  if (I->second->Users.size() > 1) {
+    for (ilist<IVStrideUse>::iterator II = I->second->Users.begin(),
+           EE = I->second->Users.end(); II != EE; ++II) {
+      if (II->getUser() == Cond)
+        continue;
+      if (!isInstructionTriviallyDead(II->getUser()))
+        return Cond;
+    }
+  }
+  // Only handle constant strides for now.
+  const SCEVConstant *SC = dyn_cast<SCEVConstant>(CondStride);
+  if (!SC) return Cond;
+
+  ICmpInst::Predicate Predicate = Cond->getPredicate();
+  int64_t CmpSSInt = SC->getValue()->getSExtValue();
+  unsigned BitWidth = SE->getTypeSizeInBits(CondStride->getType());
+  uint64_t SignBit = 1ULL << (BitWidth-1);
+  const Type *CmpTy = Cond->getOperand(0)->getType();
+  const Type *NewCmpTy = NULL;
+  unsigned TyBits = SE->getTypeSizeInBits(CmpTy);
+  unsigned NewTyBits = 0;
+  const SCEV *NewStride = NULL;
+  Value *NewCmpLHS = NULL;
+  Value *NewCmpRHS = NULL;
+  int64_t Scale = 1;
+  const SCEV *NewOffset = SE->getIntegerSCEV(0, CmpTy);
+
+  if (ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1))) {
+    int64_t CmpVal = C->getValue().getSExtValue();
+
+    // Check the relevant induction variable for conformance to
+    // the pattern.
+    const SCEV *IV = SE->getSCEV(Cond->getOperand(0));
+    const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
+    if (!AR || !AR->isAffine())
+      return Cond;
+
+    const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
+    // Check stride constant and the comparision constant signs to detect
+    // overflow.
+    if (StartC) {
+      if ((StartC->getValue()->getSExtValue() < CmpVal && CmpSSInt < 0) ||
+          (StartC->getValue()->getSExtValue() > CmpVal && CmpSSInt > 0))
+        return Cond;
+    } else {
+      // More restrictive check for the other cases.
+      if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
+        return Cond;
+    }
 
-      const Type *SrcTy = PH->getType();
-      int Mantissa = DestTy->getFPMantissaWidth();
-      if (Mantissa == -1) continue;
-      if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
+    // Look for a suitable stride / iv as replacement.
+    for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
+      std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
+        IU->IVUsesByStride.find(IU->StrideOrder[i]);
+      if (!isa<SCEVConstant>(SI->first) || SI->second->Users.empty())
+        continue;
+      int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+      if (SSInt == CmpSSInt ||
+          abs64(SSInt) < abs64(CmpSSInt) ||
+          (SSInt % CmpSSInt) != 0)
         continue;
 
-      unsigned Entry, Latch;
-      if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
-        Entry = 0;
-        Latch = 1;
-      } else {
-        Entry = 1;
-        Latch = 0;
-      }
+      Scale = SSInt / CmpSSInt;
+      int64_t NewCmpVal = CmpVal * Scale;
 
-      ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
-      if (!Init) continue;
-      Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+      // If old icmp value fits in icmp immediate field, but the new one doesn't
+      // try something else.
+      if (TLI &&
+          TLI->isLegalICmpImmediate(CmpVal) &&
+          !TLI->isLegalICmpImmediate(NewCmpVal))
+        continue;
 
-      BinaryOperator *Incr =
-        dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
-      if (!Incr) continue;
-      if (Incr->getOpcode() != Instruction::Add
-          && Incr->getOpcode() != Instruction::Sub)
+      APInt Mul = APInt(BitWidth*2, CmpVal, true);
+      Mul = Mul * APInt(BitWidth*2, Scale, true);
+      // Check for overflow.
+      if (!Mul.isSignedIntN(BitWidth))
+        continue;
+      // Check for overflow in the stride's type too.
+      if (!Mul.isSignedIntN(SE->getTypeSizeInBits(SI->first->getType())))
         continue;
 
-      /* Initialize new IV, double d = 0.0 in above example. */
-      ConstantInt *C = NULL;
-      if (Incr->getOperand(0) == PH)
-        C = dyn_cast<ConstantInt>(Incr->getOperand(1));
-      else if (Incr->getOperand(1) == PH)
-        C = dyn_cast<ConstantInt>(Incr->getOperand(0));
-      else
+      // Watch out for overflow.
+      if (ICmpInst::isSigned(Predicate) &&
+          (CmpVal & SignBit) != (NewCmpVal & SignBit))
         continue;
 
-      if (!C) continue;
+      // Pick the best iv to use trying to avoid a cast.
+      NewCmpLHS = NULL;
+      for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
+             E = SI->second->Users.end(); UI != E; ++UI) {
+        Value *Op = UI->getOperandValToReplace();
+
+        // If the IVStrideUse implies a cast, check for an actual cast which
+        // can be used to find the original IV expression.
+        if (SE->getEffectiveSCEVType(Op->getType()) !=
+            SE->getEffectiveSCEVType(SI->first->getType())) {
+          CastInst *CI = dyn_cast<CastInst>(Op);
+          // If it's not a simple cast, it's complicated.
+          if (!CI)
+            continue;
+          // If it's a cast from a type other than the stride type,
+          // it's complicated.
+          if (CI->getOperand(0)->getType() != SI->first->getType())
+            continue;
+          // Ok, we found the IV expression in the stride's type.
+          Op = CI->getOperand(0);
+        }
 
-      // Ignore negative constants, as the code below doesn't handle them
-      // correctly. TODO: Remove this restriction.
-      if (!C->getValue().isStrictlyPositive()) continue;
+        NewCmpLHS = Op;
+        if (NewCmpLHS->getType() == CmpTy)
+          break;
+      }
+      if (!NewCmpLHS)
+        continue;
 
-      /* Add new PHINode. */
-      PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+      NewCmpTy = NewCmpLHS->getType();
+      NewTyBits = SE->getTypeSizeInBits(NewCmpTy);
+      const Type *NewCmpIntTy = IntegerType::get(Cond->getContext(), NewTyBits);
+      if (RequiresTypeConversion(NewCmpTy, CmpTy)) {
+        // Check if it is possible to rewrite it using
+        // an iv / stride of a smaller integer type.
+        unsigned Bits = NewTyBits;
+        if (ICmpInst::isSigned(Predicate))
+          --Bits;
+        uint64_t Mask = (1ULL << Bits) - 1;
+        if (((uint64_t)NewCmpVal & Mask) != (uint64_t)NewCmpVal)
+          continue;
+      }
 
-      /* create new increment. '++d' in above example. */
-      Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
-      BinaryOperator *NewIncr =
-        BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
-                                 Instruction::FAdd : Instruction::FSub,
-                               NewPH, CFP, "IV.S.next.", Incr);
+      // Don't rewrite if use offset is non-constant and the new type is
+      // of a different type.
+      // FIXME: too conservative?
+      if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->getOffset()))
+        continue;
 
-      NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
-      NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+      if (!PostPass) {
+        bool AllUsesAreAddresses = true;
+        bool AllUsesAreOutsideLoop = true;
+        std::vector<BasedUser> UsersToProcess;
+        const SCEV *CommonExprs = CollectIVUsers(SI->first, *SI->second, L,
+                                                 AllUsesAreAddresses,
+                                                 AllUsesAreOutsideLoop,
+                                                 UsersToProcess);
+        // Avoid rewriting the compare instruction with an iv of new stride
+        // if it's likely the new stride uses will be rewritten using the
+        // stride of the compare instruction.
+        if (AllUsesAreAddresses &&
+            ValidScale(!CommonExprs->isZero(), Scale, UsersToProcess))
+          continue;
+      }
 
-      /* Remove cast operation */
-      ShadowUse->replaceAllUsesWith(NewPH);
-      ShadowUse->eraseFromParent();
+      // Avoid rewriting the compare instruction with an iv which has
+      // implicit extension or truncation built into it.
+      // TODO: This is over-conservative.
+      if (SE->getTypeSizeInBits(CondUse->getOffset()->getType()) != TyBits)
+        continue;
+
+      // If scale is negative, use swapped predicate unless it's testing
+      // for equality.
+      if (Scale < 0 && !Cond->isEquality())
+        Predicate = ICmpInst::getSwappedPredicate(Predicate);
+
+      NewStride = IU->StrideOrder[i];
+      if (!isa<PointerType>(NewCmpTy))
+        NewCmpRHS = ConstantInt::get(NewCmpTy, NewCmpVal);
+      else {
+        Constant *CI = ConstantInt::get(NewCmpIntTy, NewCmpVal);
+        NewCmpRHS = ConstantExpr::getIntToPtr(CI, NewCmpTy);
+      }
+      NewOffset = TyBits == NewTyBits
+        ? SE->getMulExpr(CondUse->getOffset(),
+                         SE->getConstant(CmpTy, Scale))
+        : SE->getConstant(NewCmpIntTy,
+          cast<SCEVConstant>(CondUse->getOffset())->getValue()
+            ->getSExtValue()*Scale);
       break;
     }
   }
-}
 
-/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
-/// set the IV user and stride information and return true, otherwise return
-/// false.
-bool LSRInstance::FindIVUserForCond(ICmpInst *Cond,
-                                    IVStrideUse *&CondUse,
-                                    const SCEV* &CondStride) {
-  for (unsigned StrideIdx = 0, e = IU.StrideOrder.size();
-       StrideIdx != e && !CondUse; ++StrideIdx) {
-    std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
-      IU.IVUsesByStride.find(IU.StrideOrder[StrideIdx]);
-    assert(SI != IU.IVUsesByStride.end() && "Stride doesn't exist!");
+  // Forgo this transformation if it the increment happens to be
+  // unfortunately positioned after the condition, and the condition
+  // has multiple uses which prevent it from being moved immediately
+  // before the branch. See
+  // test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
+  // for an example of this situation.
+  if (!Cond->hasOneUse()) {
+    for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
+         I != E; ++I)
+      if (I == NewCmpLHS)
+        return Cond;
+  }
 
-    for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
-         E = SI->second->Users.end(); UI != E; ++UI)
-      if (UI->getUser() == Cond) {
-        // NOTE: we could handle setcc instructions with multiple uses here, but
-        // InstCombine does it as well for simple uses, it's not clear that it
-        // occurs enough in real life to handle.
-        CondUse = UI;
-        CondStride = SI->first;
-        return true;
-      }
+  if (NewCmpRHS) {
+    // Create a new compare instruction using new stride / iv.
+    ICmpInst *OldCond = Cond;
+    // Insert new compare instruction.
+    Cond = new ICmpInst(OldCond, Predicate, NewCmpLHS, NewCmpRHS,
+                        L->getHeader()->getName() + ".termcond");
+
+    DEBUG(dbgs() << "    Change compare stride in Inst " << *OldCond);
+    DEBUG(dbgs() << " to " << *Cond << '\n');
+
+    // Remove the old compare instruction. The old indvar is probably dead too.
+    DeadInsts.push_back(CondUse->getOperandValToReplace());
+    OldCond->replaceAllUsesWith(Cond);
+    OldCond->eraseFromParent();
+
+    IU->IVUsesByStride[NewStride]->addUser(NewOffset, Cond, NewCmpLHS);
+    CondUse = &IU->IVUsesByStride[NewStride]->Users.back();
+    CondStride = NewStride;
+    ++NumEliminated;
+    Changed = true;
   }
-  return false;
+
+  return Cond;
 }
 
 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
@@ -1650,7 +2087,7 @@ bool LSRInstance::FindIVUserForCond(ICmpInst *Cond,
 /// are designed around them. The most obvious example of this is the
 /// LoopInfo analysis, which doesn't remember trip count values. It
 /// expects to be able to rediscover the trip count each time it is
-/// needed, and it does this using a simple analysis that only succeeds if
+/// needed, and it does this using a simple analyis that only succeeds if
 /// the loop has a canonical induction variable.
 ///
 /// However, when it comes time to generate code, the maximum operation
@@ -1660,7 +2097,8 @@ bool LSRInstance::FindIVUserForCond(ICmpInst *Cond,
 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
 /// the instructions for the maximum computation.
 ///
-ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
+ICmpInst *LoopStrengthReduce::OptimizeMax(Loop *L, ICmpInst *Cond,
+                                          IVStrideUse* &CondUse) {
   // Check that the loop matches the pattern we're looking for.
   if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
       Cond->getPredicate() != CmpInst::ICMP_NE)
@@ -1669,19 +2107,19 @@ ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
   SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
   if (!Sel || !Sel->hasOneUse()) return Cond;
 
-  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
+  const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
   if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
     return Cond;
-  const SCEV *One = SE.getIntegerSCEV(1, BackedgeTakenCount->getType());
+  const SCEV *One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType());
 
   // Add one to the backedge-taken count to get the trip count.
-  const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One);
+  const SCEV *IterationCount = SE->getAddExpr(BackedgeTakenCount, One);
 
   // Check for a max calculation that matches the pattern.
   if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount))
     return Cond;
   const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount);
-  if (Max != SE.getSCEV(Sel)) return Cond;
+  if (Max != SE->getSCEV(Sel)) return Cond;
 
   // To handle a max with more than two operands, this optimization would
   // require additional checking and setup.
@@ -1691,13 +2129,14 @@ ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
   const SCEV *MaxLHS = Max->getOperand(0);
   const SCEV *MaxRHS = Max->getOperand(1);
   if (!MaxLHS || MaxLHS != One) return Cond;
+
   // Check the relevant induction variable for conformance to
   // the pattern.
-  const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
+  const SCEV *IV = SE->getSCEV(Cond->getOperand(0));
   const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
   if (!AR || !AR->isAffine() ||
       AR->getStart() != One ||
-      AR->getStepRecurrence(SE) != One)
+      AR->getStepRecurrence(*SE) != One)
     return Cond;
 
   assert(AR->getLoop() == L &&
@@ -1706,9 +2145,9 @@ ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
   // Check the right operand of the select, and remember it, as it will
   // be used in the new comparison instruction.
   Value *NewRHS = 0;
-  if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
+  if (SE->getSCEV(Sel->getOperand(1)) == MaxRHS)
     NewRHS = Sel->getOperand(1);
-  else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
+  else if (SE->getSCEV(Sel->getOperand(2)) == MaxRHS)
     NewRHS = Sel->getOperand(2);
   if (!NewRHS) return Cond;
 
@@ -1735,11 +2174,136 @@ ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
   return NewCond;
 }
 
-bool LSRInstance::StrideMightBeShared(const SCEV* Stride) {
+/// OptimizeShadowIV - If IV is used in a int-to-float cast
+/// inside the loop then try to eliminate the cast opeation.
+void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
+
+  const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
+    return;
+
+  for (unsigned Stride = 0, e = IU->StrideOrder.size(); Stride != e;
+       ++Stride) {
+    std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
+      IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
+    assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
+    if (!isa<SCEVConstant>(SI->first))
+      continue;
+
+    for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
+           E = SI->second->Users.end(); UI != E; /* empty */) {
+      ilist<IVStrideUse>::iterator CandidateUI = UI;
+      ++UI;
+      Instruction *ShadowUse = CandidateUI->getUser();
+      const Type *DestTy = NULL;
+
+      /* If shadow use is a int->float cast then insert a second IV
+         to eliminate this cast.
+
+           for (unsigned i = 0; i < n; ++i)
+             foo((double)i);
+
+         is transformed into
+
+           double d = 0.0;
+           for (unsigned i = 0; i < n; ++i, ++d)
+             foo(d);
+      */
+      if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
+        DestTy = UCast->getDestTy();
+      else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
+        DestTy = SCast->getDestTy();
+      if (!DestTy) continue;
+
+      if (TLI) {
+        // If target does not support DestTy natively then do not apply
+        // this transformation.
+        EVT DVT = TLI->getValueType(DestTy);
+        if (!TLI->isTypeLegal(DVT)) continue;
+      }
+
+      PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
+      if (!PH) continue;
+      if (PH->getNumIncomingValues() != 2) continue;
+
+      const Type *SrcTy = PH->getType();
+      int Mantissa = DestTy->getFPMantissaWidth();
+      if (Mantissa == -1) continue;
+      if ((int)SE->getTypeSizeInBits(SrcTy) > Mantissa)
+        continue;
+
+      unsigned Entry, Latch;
+      if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
+        Entry = 0;
+        Latch = 1;
+      } else {
+        Entry = 1;
+        Latch = 0;
+      }
+
+      ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
+      if (!Init) continue;
+      Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+
+      BinaryOperator *Incr =
+        dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
+      if (!Incr) continue;
+      if (Incr->getOpcode() != Instruction::Add
+          && Incr->getOpcode() != Instruction::Sub)
+        continue;
+
+      /* Initialize new IV, double d = 0.0 in above example. */
+      ConstantInt *C = NULL;
+      if (Incr->getOperand(0) == PH)
+        C = dyn_cast<ConstantInt>(Incr->getOperand(1));
+      else if (Incr->getOperand(1) == PH)
+        C = dyn_cast<ConstantInt>(Incr->getOperand(0));
+      else
+        continue;
+
+      if (!C) continue;
+
+      // Ignore negative constants, as the code below doesn't handle them
+      // correctly. TODO: Remove this restriction.
+      if (!C->getValue().isStrictlyPositive()) continue;
+
+      /* Add new PHINode. */
+      PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+
+      /* create new increment. '++d' in above example. */
+      Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+      BinaryOperator *NewIncr =
+        BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
+                                 Instruction::FAdd : Instruction::FSub,
+                               NewPH, CFP, "IV.S.next.", Incr);
+
+      NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
+      NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+
+      /* Remove cast operation */
+      ShadowUse->replaceAllUsesWith(NewPH);
+      ShadowUse->eraseFromParent();
+      NumShadow++;
+      break;
+    }
+  }
+}
+
+/// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
+/// uses in the loop, look to see if we can eliminate some, in favor of using
+/// common indvars for the different uses.
+void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
+  // TODO: implement optzns here.
+
+  OptimizeShadowIV(L);
+}
+
+bool LoopStrengthReduce::StrideMightBeShared(const SCEV* Stride, Loop *L,
+                                             bool CheckPreInc) {
   int64_t SInt = cast<SCEVConstant>(Stride)->getValue()->getSExtValue();
-  for (unsigned i = 0, e = IU.StrideOrder.size(); i != e; ++i) {
+  for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
     std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
-      IU.IVUsesByStride.find(IU.StrideOrder[i]);
+      IU->IVUsesByStride.find(IU->StrideOrder[i]);
     const SCEV *Share = SI->first;
     if (!isa<SCEVConstant>(SI->first) || Share == Stride)
       continue;
@@ -1749,44 +2313,110 @@ bool LSRInstance::StrideMightBeShared(const SCEV* Stride) {
     if (unsigned(abs64(SSInt)) < SInt || (SSInt % SInt) != 0)
       continue;
     int64_t Scale = SSInt / SInt;
-
-    // This AM will be used for conservative queries. At this point in the
-    // process we don't know which users will have a base reg, immediate,
-    // etc., so we conservatively assume that it may not, making more
-    // strides valid, thus erring on the side of assuming that there
-    // might be sharing.
-    TargetLowering::AddrMode AM;
-    AM.Scale = Scale;
-
-    // Any pre-inc iv use?
-    IVUsersOfOneStride &StrideUses = *IU.IVUsesByStride[Share];
-    for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
-           E = StrideUses.Users.end(); I != E; ++I) {
-      bool isAddress = isAddressUse(I->getUser(), I->getOperandValToReplace());
-      if (!I->isUseOfPostIncrementedValue() &&
-          isLegalUse(AM, isAddress ? LSRUse::Address : LSRUse::Basic,
-                     isAddress ? getAccessType(I->getUser()) : 0,
-                     TLI))
+    bool AllUsesAreAddresses = true;
+    bool AllUsesAreOutsideLoop = true;
+    std::vector<BasedUser> UsersToProcess;
+    const SCEV *CommonExprs = CollectIVUsers(SI->first, *SI->second, L,
+                                             AllUsesAreAddresses,
+                                             AllUsesAreOutsideLoop,
+                                             UsersToProcess);
+    if (AllUsesAreAddresses &&
+        ValidScale(!CommonExprs->isZero(), Scale, UsersToProcess)) {
+      if (!CheckPreInc)
         return true;
+      // Any pre-inc iv use?
+      IVUsersOfOneStride &StrideUses = *IU->IVUsesByStride[Share];
+      for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
+             E = StrideUses.Users.end(); I != E; ++I) {
+        if (!I->isUseOfPostIncrementedValue())
+          return true;
+      }
     }
   }
   return false;
 }
 
+/// isUsedByExitBranch - Return true if icmp is used by a loop terminating
+/// conditional branch or it's and / or with other conditions before being used
+/// as the condition.
+static bool isUsedByExitBranch(ICmpInst *Cond, Loop *L) {
+  BasicBlock *CondBB = Cond->getParent();
+  if (!L->isLoopExiting(CondBB))
+    return false;
+  BranchInst *TermBr = dyn_cast<BranchInst>(CondBB->getTerminator());
+  if (!TermBr || !TermBr->isConditional())
+    return false;
+
+  Value *User = *Cond->use_begin();
+  Instruction *UserInst = dyn_cast<Instruction>(User);
+  while (UserInst &&
+         (UserInst->getOpcode() == Instruction::And ||
+          UserInst->getOpcode() == Instruction::Or)) {
+    if (!UserInst->hasOneUse() || UserInst->getParent() != CondBB)
+      return false;
+    User = *User->use_begin();
+    UserInst = dyn_cast<Instruction>(User);
+  }
+  return User == TermBr;
+}
+
+static bool ShouldCountToZero(ICmpInst *Cond, IVStrideUse* &CondUse,
+                              ScalarEvolution *SE, Loop *L,
+                              const TargetLowering *TLI = 0) {
+  if (!L->contains(Cond))
+    return false;
+
+  if (!isa<SCEVConstant>(CondUse->getOffset()))
+    return false;
+
+  // Handle only tests for equality for the moment.
+  if (!Cond->isEquality() || !Cond->hasOneUse())
+    return false;
+  if (!isUsedByExitBranch(Cond, L))
+    return false;
+
+  Value *CondOp0 = Cond->getOperand(0);
+  const SCEV *IV = SE->getSCEV(CondOp0);
+  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
+  if (!AR || !AR->isAffine())
+    return false;
+
+  const SCEVConstant *SC = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE));
+  if (!SC || SC->getValue()->getSExtValue() < 0)
+    // If it's already counting down, don't do anything.
+    return false;
+
+  // If the RHS of the comparison is not an loop invariant, the rewrite
+  // cannot be done. Also bail out if it's already comparing against a zero.
+  // If we are checking this before cmp stride optimization, check if it's
+  // comparing against a already legal immediate.
+  Value *RHS = Cond->getOperand(1);
+  ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS);
+  if (!L->isLoopInvariant(RHS) ||
+      (RHSC && RHSC->isZero()) ||
+      (RHSC && TLI && TLI->isLegalICmpImmediate(RHSC->getSExtValue())))
+    return false;
+
+  // Make sure the IV is only used for counting.  Value may be preinc or
+  // postinc; 2 uses in either case.
+  if (!CondOp0->hasNUses(2))
+    return false;
+
+  return true;
+}
+
 /// OptimizeLoopTermCond - Change loop terminating condition to use the
 /// postinc iv when possible.
-bool
-LSRInstance::OptimizeLoopTermCond() {
-  SmallPtrSet<Instruction *, 4> PostIncs;
-
+void LoopStrengthReduce::OptimizeLoopTermCond(Loop *L) {
   BasicBlock *LatchBlock = L->getLoopLatch();
+  bool LatchExit = L->isLoopExiting(LatchBlock);
   SmallVector<BasicBlock*, 8> ExitingBlocks;
   L->getExitingBlocks(ExitingBlocks);
 
   for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
     BasicBlock *ExitingBlock = ExitingBlocks[i];
 
-    // Get the terminating condition for the loop if possible.  If we
+    // Finally, get the terminating condition for the loop if possible.  If we
     // can, we want to change it to use a post-incremented version of its
     // induction variable, to allow coalescing the live ranges for the IV into
     // one register value.
@@ -1805,1008 +2435,291 @@ LSRInstance::OptimizeLoopTermCond() {
     if (!FindIVUserForCond(Cond, CondUse, CondStride))
       continue;
 
-    // If the trip count is computed in terms of a max (due to ScalarEvolution
-    // being unable to find a sufficient guard, for example), change the loop
-    // comparison to use SLT or ULT instead of NE.
-    // One consequence of doing this now is that it disrupts the count-down
-    // optimization. That's not always a bad thing though, because in such
-    // cases it may still be worthwhile to avoid a max.
-    Cond = OptimizeMax(Cond, CondUse);
-
-    // If this exiting block is the latch block, and the condition has only
-    // one use inside the loop (the branch), use the post-incremented value
-    // of the induction variable
-    if (ExitingBlock != LatchBlock) {
-      // If this exiting block dominates the latch block, it may also use
-      // the post-inc value if it won't be shared with other uses.
-      // Check for dominance.
-      if (!DT.dominates(ExitingBlock, LatchBlock))
-        continue;
-      // Check for sharing within the same stride.
-      bool SameStrideSharing = false;
-      IVUsersOfOneStride &StrideUses = *IU.IVUsesByStride[CondStride];
-      for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
-             E = StrideUses.Users.end(); I != E; ++I) {
-        if (I->getUser() == Cond)
-          continue;
-        if (!I->isUseOfPostIncrementedValue()) {
-          SameStrideSharing = true;
-          break;
+    // If the latch block is exiting and it's not a single block loop, it's
+    // not safe to use postinc iv in other exiting blocks. FIXME: overly
+    // conservative? How about icmp stride optimization?
+    bool UsePostInc =  !(e > 1 && LatchExit && ExitingBlock != LatchBlock);
+    if (UsePostInc && ExitingBlock != LatchBlock) {
+      if (!Cond->hasOneUse())
+        // See below, we don't want the condition to be cloned.
+        UsePostInc = false;
+      else {
+        // If exiting block is the latch block, we know it's safe and profitable
+        // to transform the icmp to use post-inc iv. Otherwise do so only if it
+        // would not reuse another iv and its iv would be reused by other uses.
+        // We are optimizing for the case where the icmp is the only use of the
+        // iv.
+        IVUsersOfOneStride &StrideUses = *IU->IVUsesByStride[CondStride];
+        for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
+               E = StrideUses.Users.end(); I != E; ++I) {
+          if (I->getUser() == Cond)
+            continue;
+          if (!I->isUseOfPostIncrementedValue()) {
+            UsePostInc = false;
+            break;
+          }
         }
       }
-      if (SameStrideSharing)
-        continue;
-      // Check for sharing from a different stride.
-      if (isa<SCEVConstant>(CondStride) && StrideMightBeShared(CondStride))
-        continue;
+
+      // If iv for the stride might be shared and any of the users use pre-inc
+      // iv might be used, then it's not safe to use post-inc iv.
+      if (UsePostInc &&
+          isa<SCEVConstant>(CondStride) &&
+          StrideMightBeShared(CondStride, L, true))
+        UsePostInc = false;
     }
-    if (!Cond->hasOneUse()) {
-      bool HasOneUseInLoop = true;
-      for (Value::use_iterator UI = Cond->use_begin(), UE = Cond->use_end();
-           UI != UE; ++UI) {
-        Instruction *U = cast<Instruction>(*UI);
-        if (U == TermBr)
-          continue;
-        if (L->contains(U)) {
-          HasOneUseInLoop = false;
-          break;
-        }
-      }
-      if (!HasOneUseInLoop)
-        continue;
+
+    // If the trip count is computed in terms of a max (due to ScalarEvolution
+    // being unable to find a sufficient guard, for example), change the loop
+    // comparison to use SLT or ULT instead of NE.
+    Cond = OptimizeMax(L, Cond, CondUse);
+
+    // If possible, change stride and operands of the compare instruction to
+    // eliminate one stride. However, avoid rewriting the compare instruction
+    // with an iv of new stride if it's likely the new stride uses will be
+    // rewritten using the stride of the compare instruction.
+    if (ExitingBlock == LatchBlock && isa<SCEVConstant>(CondStride)) {
+      // If the condition stride is a constant and it's the only use, we might
+      // want to optimize it first by turning it to count toward zero.
+      if (!StrideMightBeShared(CondStride, L, false) &&
+          !ShouldCountToZero(Cond, CondUse, SE, L, TLI))
+        Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
     }
 
+    if (!UsePostInc)
+      continue;
+
     DEBUG(dbgs() << "  Change loop exiting icmp to use postinc iv: "
-                 << *Cond << '\n');
+          << *Cond << '\n');
 
     // It's possible for the setcc instruction to be anywhere in the loop, and
     // possible for it to have multiple users.  If it is not immediately before
     // the exiting block branch, move it.
-    if (&*++BasicBlock::iterator(Cond) != TermBr) {
+    if (&*++BasicBlock::iterator(Cond) != (Instruction*)TermBr) {
       if (Cond->hasOneUse()) {   // Condition has a single use, just move it.
         Cond->moveBefore(TermBr);
       } else {
         // Otherwise, clone the terminating condition and insert into the
         // loopend.
-        ICmpInst *OldCond = Cond;
         Cond = cast<ICmpInst>(Cond->clone());
         Cond->setName(L->getHeader()->getName() + ".termcond");
         ExitingBlock->getInstList().insert(TermBr, Cond);
 
         // Clone the IVUse, as the old use still exists!
-        IU.IVUsesByStride[CondStride]->addUser(CondUse->getOffset(), Cond,
+        IU->IVUsesByStride[CondStride]->addUser(CondUse->getOffset(), Cond,
                                              CondUse->getOperandValToReplace());
-        CondUse = &IU.IVUsesByStride[CondStride]->Users.back();
-        TermBr->replaceUsesOfWith(OldCond, Cond);
+        CondUse = &IU->IVUsesByStride[CondStride]->Users.back();
       }
     }
 
     // If we get to here, we know that we can transform the setcc instruction to
     // use the post-incremented version of the IV, allowing us to coalesce the
     // live ranges for the IV correctly.
-    CondUse->setOffset(SE.getMinusSCEV(CondUse->getOffset(), CondStride));
+    CondUse->setOffset(SE->getMinusSCEV(CondUse->getOffset(), CondStride));
     CondUse->setIsUseOfPostIncrementedValue(true);
     Changed = true;
 
-    PostIncs.insert(Cond);
-  }
-
-  // Determine an insertion point for the loop induction variable increment. It
-  // must dominate all the post-inc comparisons we just set up, and it must
-  // dominate the loop latch edge.
-  IVIncInsertPos = L->getLoopLatch()->getTerminator();
-  for (SmallPtrSet<Instruction *, 4>::iterator I = PostIncs.begin(),
-       E = PostIncs.end(); I != E; ++I) {
-    BasicBlock *BB =
-      DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
-                                    (*I)->getParent());
-    if (BB == (*I)->getParent())
-      IVIncInsertPos = *I;
-    else if (BB != IVIncInsertPos->getParent())
-      IVIncInsertPos = BB->getTerminator();
-  }
-
-  return Changed;
-}
-
-/// CountRegisters - Note the given register.
-void LSRInstance::CountRegister(const SCEV *Reg, uint32_t Complexity,
-                                size_t LUIdx) {
-  std::pair<RegUsesTy::iterator, bool> Pair =
-    RegUses.insert(std::make_pair(Reg, RegSortData()));
-  RegSortData &BV = Pair.first->second;
-  if (Pair.second) {
-    BV.Index = CurrentArbitraryRegIndex++;
-    BV.MaxComplexity = Complexity;
-    RegSequence.push_back(Reg);
-  } else {
-    BV.MaxComplexity = std::max(BV.MaxComplexity, Complexity);
+    ++NumLoopCond;
   }
-  BV.Bits.resize(std::max(BV.Bits.size(), LUIdx + 1));
-  BV.Bits.set(LUIdx);
 }
 
-/// CountRegisters - Note which registers are used by the given formula,
-/// updating RegUses.
-void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
-  uint32_t Complexity = F.getComplexity();
-  if (F.ScaledReg)
-    CountRegister(F.ScaledReg, Complexity, LUIdx);
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
-       E = F.BaseRegs.end(); I != E; ++I)
-    CountRegister(*I, Complexity, LUIdx);
-}
+bool LoopStrengthReduce::OptimizeLoopCountIVOfStride(const SCEV* &Stride,
+                                                     IVStrideUse* &CondUse,
+                                                     Loop *L) {
+  // If the only use is an icmp of a loop exiting conditional branch, then
+  // attempt the optimization.
+  BasedUser User = BasedUser(*CondUse, SE);
+  assert(isa<ICmpInst>(User.Inst) && "Expecting an ICMPInst!");
+  ICmpInst *Cond = cast<ICmpInst>(User.Inst);
 
-/// InsertFormula - If the given formula has not yet been inserted, add it
-/// to the list, and return true. Return false otherwise.
-bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
-  // If a formula by itself would require more registers than the base solution,
-  // discard it and stop searching from it, as it won't be profitable. This is
-  // actually more permissive than it could be, because it doesn't include
-  // registers used by non-constant strides in F.
-  if (F.getNumRegs() > MaxNumRegs)
+  // Less strict check now that compare stride optimization is done.
+  if (!ShouldCountToZero(Cond, CondUse, SE, L))
     return false;
 
-  if (!LU.InsertFormula(F))
-    return false;
-
-  CountRegisters(LU.Formulae.back(), LUIdx);
-  return true;
-}
-
-/// GenerateSymbolicOffsetReuse - Generate reuse formulae using symbolic
-/// offsets.
-void LSRInstance::GenerateSymbolicOffsetReuse(LSRUse &LU, unsigned LUIdx,
-                                              Formula Base) {
-  // We can't add a symbolic offset if the address already contains one.
-  if (Base.AM.BaseGV) return;
-
-  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
-    const SCEV *G = Base.BaseRegs[i];
-    GlobalValue *GV = ExtractSymbol(G, SE);
-    if (G->isZero())
-      continue;
-    Formula F = Base;
-    F.AM.BaseGV = GV;
-    if (!isLegalUse(F.AM, LU.Kind, LU.AccessTy, TLI))
-      continue;
-    F.BaseRegs[i] = G;
-    (void)InsertFormula(LU, LUIdx, F);
-  }
-}
-
-/// GenerateICmpZeroScaledReuse - For ICmpZero, check to see if we can scale up
-/// the comparison. For example, x == y -> x*c == y*c.
-void LSRInstance::GenerateICmpZeroScaledReuse(LSRUse &LU, unsigned LUIdx,
-                                              Formula Base) {
-  if (LU.Kind != LSRUse::ICmpZero) return;
-
-  // Determine the integer type for the base formula.
-  const Type *IntTy = Base.getType();
-  if (!IntTy) return;
-  if (SE.getTypeSizeInBits(IntTy) > 64) return;
-  IntTy = SE.getEffectiveSCEVType(IntTy);
-
-  assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
-
-  // Check each interesting stride.
-  for (SmallSetVector<int64_t, 4>::const_iterator
-       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
-    int64_t Factor = *I;
-    Formula F = Base;
-
-    // Check that the multiplication doesn't overflow.
-    F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs * Factor;
-    if ((int64_t)F.AM.BaseOffs / Factor != F.AM.BaseOffs)
-      continue;
-
-    // Check that this scale is legal.
-    if (!isLegalUse(F.AM, LU.Kind, LU.AccessTy, TLI))
-      continue;
-
-    const SCEV *FactorS = SE.getSCEV(ConstantInt::get(IntTy, Factor));
-
-    // Check that multiplying with each base register doesn't overflow.
-    for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
-      F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
-      if (getSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
-        goto next;
-    }
-
-    // Check that multiplying with the scaled register doesn't overflow.
-    if (F.ScaledReg) {
-      F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
-      if (getSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
-        continue;
-    }
-
-    // If we make it here and it's legal, add it.
-    (void)InsertFormula(LU, LUIdx, F);
-  next:;
-  }
-}
-
-/// GenerateFormulaeFromReplacedBaseReg - If removing base register with
-/// index i from the BaseRegs list and adding the registers in AddOps
-/// to the address forms an interesting formula, pursue it.
-void
-LSRInstance::GenerateFormulaeFromReplacedBaseReg(
-                                             LSRUse &LU,
-                                             unsigned LUIdx,
-                                             const Formula &Base, unsigned i,
-                                             const SmallVectorImpl<const SCEV *>
-                                               &AddOps) {
-  if (AddOps.empty()) return;
-
-  Formula F = Base;
-  std::swap(F.BaseRegs[i], F.BaseRegs.back());
-  F.BaseRegs.pop_back();
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = AddOps.begin(),
-       E = AddOps.end(); I != E; ++I)
-    F.BaseRegs.push_back(*I);
-  F.AM.HasBaseReg = !F.BaseRegs.empty();
-  if (InsertFormula(LU, LUIdx, F))
-    // If that formula hadn't been seen before, recurse to find more like it.
-    GenerateReassociationReuse(LU, LUIdx, LU.Formulae.back());
-}
+  Value *CondOp0 = Cond->getOperand(0);
+  PHINode *PHIExpr = dyn_cast<PHINode>(CondOp0);
+  Instruction *Incr;
+  if (!PHIExpr) {
+    // Value tested is postinc. Find the phi node.
+    Incr = dyn_cast<BinaryOperator>(CondOp0);
+    // FIXME: Just use User.OperandValToReplace here?
+    if (!Incr || Incr->getOpcode() != Instruction::Add)
+      return false;
 
-/// GenerateReassociationReuse - Split out subexpressions from adds and
-/// the bases of addrecs.
-void LSRInstance::GenerateReassociationReuse(LSRUse &LU, unsigned LUIdx,
-                                             Formula Base) {
-  SmallVector<const SCEV *, 8> AddOps;
-  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
-    const SCEV *BaseReg = Base.BaseRegs[i];
-    if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BaseReg)) {
-      for (SCEVAddExpr::op_iterator J = Add->op_begin(), JE = Add->op_end();
-           J != JE; ++J) {
-        // Don't pull a constant into a register if the constant could be
-        // folded into an immediate field.
-        if (isAlwaysFoldable(*J, true, LU.Kind, LU.AccessTy, TLI, SE)) continue;
-        SmallVector<const SCEV *, 8> InnerAddOps;
-        for (SCEVAddExpr::op_iterator K = Add->op_begin(); K != JE; ++K)
-          if (K != J)
-            InnerAddOps.push_back(*K);
-        // Splitting a 2-operand add both ways is redundant. Pruning this
-        // now saves compile time.
-        if (InnerAddOps.size() < 2 && next(J) == JE)
-          continue;
-        AddOps.push_back(*J);
-        const SCEV *InnerAdd = SE.getAddExpr(InnerAddOps);
-        AddOps.push_back(InnerAdd);
-        GenerateFormulaeFromReplacedBaseReg(LU, LUIdx, Base, i, AddOps);
-        AddOps.clear();
-      }
-    } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(BaseReg)) {
-      if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(AR->getStart())) {
-        for (SCEVAddExpr::op_iterator J = Add->op_begin(), JE = Add->op_end();
-             J != JE; ++J) {
-          // Don't pull a constant into a register if the constant could be
-          // folded into an immediate field.
-          if (isAlwaysFoldable(*J, true, LU.Kind, LU.AccessTy, TLI, SE))
-            continue;
-          SmallVector<const SCEV *, 8> InnerAddOps;
-          for (SCEVAddExpr::op_iterator K = Add->op_begin(); K != JE; ++K)
-            if (K != J)
-              InnerAddOps.push_back(*K);
-          AddOps.push_back(*J);
-          const SCEV *InnerAdd = SE.getAddExpr(InnerAddOps);
-          AddOps.push_back(SE.getAddRecExpr(InnerAdd,
-                                            AR->getStepRecurrence(SE),
-                                            AR->getLoop()));
-          GenerateFormulaeFromReplacedBaseReg(LU, LUIdx, Base, i, AddOps);
-          AddOps.clear();
-        }
-      } else if (!isAlwaysFoldable(AR->getStart(), Base.BaseRegs.size() > 1,
-                                   LU.Kind, LU.AccessTy,
-                                   TLI, SE)) {
-        AddOps.push_back(AR->getStart());
-        AddOps.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0,
-                                                            BaseReg->getType()),
-                                          AR->getStepRecurrence(SE),
-                                          AR->getLoop()));
-        GenerateFormulaeFromReplacedBaseReg(LU, LUIdx, Base, i, AddOps);
-        AddOps.clear();
-      }
-    }
+    PHIExpr = dyn_cast<PHINode>(Incr->getOperand(0));
+    if (!PHIExpr)
+      return false;
+    // 1 use for preinc value, the increment.
+    if (!PHIExpr->hasOneUse())
+      return false;
+  } else {
+    assert(isa<PHINode>(CondOp0) &&
+           "Unexpected loop exiting counting instruction sequence!");
+    PHIExpr = cast<PHINode>(CondOp0);
+    // Value tested is preinc.  Find the increment.
+    // A CmpInst is not a BinaryOperator; we depend on this.
+    Instruction::use_iterator UI = PHIExpr->use_begin();
+    Incr = dyn_cast<BinaryOperator>(UI);
+    if (!Incr)
+      Incr = dyn_cast<BinaryOperator>(++UI);
+    // One use for postinc value, the phi.  Unnecessarily conservative?
+    if (!Incr || !Incr->hasOneUse() || Incr->getOpcode() != Instruction::Add)
+      return false;
   }
-}
 
-/// GenerateCombinationReuse - Generate a formula consisting of all of the
-/// loop-dominating registers added into a single register.
-void LSRInstance::GenerateCombinationReuse(LSRUse &LU, unsigned LUIdx,
-                                           Formula Base) {
-  // This method is only intersting on a plurality of registers.
-  if (Base.BaseRegs.size() <= 1) return;
-
-  Formula F = Base;
-  F.BaseRegs.clear();
-  SmallVector<const SCEV *, 4> Ops;
-  for (SmallVectorImpl<const SCEV *>::const_iterator
-       I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
-    const SCEV *BaseReg = *I;
-    if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
-        !BaseReg->hasComputableLoopEvolution(L))
-      Ops.push_back(BaseReg);
-    else
-      F.BaseRegs.push_back(BaseReg);
-  }
-  if (Ops.size() > 1) {
-    F.BaseRegs.push_back(SE.getAddExpr(Ops));
-    (void)InsertFormula(LU, LUIdx, F);
-  }
-}
+  // Replace the increment with a decrement.
+  DEBUG(dbgs() << "LSR: Examining use ");
+  DEBUG(WriteAsOperand(dbgs(), CondOp0, /*PrintType=*/false));
+  DEBUG(dbgs() << " in Inst: " << *Cond << '\n');
+  BinaryOperator *Decr =  BinaryOperator::Create(Instruction::Sub,
+                         Incr->getOperand(0), Incr->getOperand(1), "tmp", Incr);
+  Incr->replaceAllUsesWith(Decr);
+  Incr->eraseFromParent();
+
+  // Substitute endval-startval for the original startval, and 0 for the
+  // original endval.  Since we're only testing for equality this is OK even
+  // if the computation wraps around.
+  BasicBlock  *Preheader = L->getLoopPreheader();
+  Instruction *PreInsertPt = Preheader->getTerminator();
+  unsigned InBlock = L->contains(PHIExpr->getIncomingBlock(0)) ? 1 : 0;
+  Value *StartVal = PHIExpr->getIncomingValue(InBlock);
+  Value *EndVal = Cond->getOperand(1);
+  DEBUG(dbgs() << "    Optimize loop counting iv to count down ["
+        << *EndVal << " .. " << *StartVal << "]\n");
+
+  // FIXME: check for case where both are constant.
+  Constant* Zero = ConstantInt::get(Cond->getOperand(1)->getType(), 0);
+  BinaryOperator *NewStartVal = BinaryOperator::Create(Instruction::Sub,
+                                          EndVal, StartVal, "tmp", PreInsertPt);
+  PHIExpr->setIncomingValue(InBlock, NewStartVal);
+  Cond->setOperand(1, Zero);
+  DEBUG(dbgs() << "    New icmp: " << *Cond << "\n");
 
-/// GenerateScaledReuse - Generate stride factor reuse formulae by making
-/// use of scaled-offset address modes, for example.
-void LSRInstance::GenerateScaledReuse(LSRUse &LU, unsigned LUIdx,
-                                      Formula Base) {
-  // Determine the integer type for the base formula.
-  const Type *IntTy = Base.getType();
-  if (!IntTy) return;
-  IntTy = SE.getEffectiveSCEVType(IntTy);
-
-  // Check each interesting stride.
-  for (SmallSetVector<int64_t, 4>::const_iterator
-       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
-    int64_t Factor = *I;
-
-    // If this Formula already has a scaled register, we can't add another one.
-    if (Base.AM.Scale != 0)
-      continue;
-    Formula F = Base;
-    F.AM.Scale = Factor;
-    // Check whether this scale is going to be legal.
-    if (!isLegalUse(F.AM, LU.Kind, LU.AccessTy, TLI)) {
-      // As a special-case, handle special out-of-loop Basic users specially.
-      // TODO: Reconsider this special case.
-      if (LU.Kind == LSRUse::Basic &&
-          isLegalUse(F.AM, LSRUse::Special, LU.AccessTy, TLI) &&
-          !L->contains(LU.UserInst))
-        LU.Kind = LSRUse::Special;
-      else
-        continue;
-    }
-    // For each addrec base reg, apply the scale, if possible.
-    for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
-      if (const SCEVAddRecExpr *AR =
-            dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
-        const SCEV *FactorS = SE.getSCEV(ConstantInt::get(IntTy, Factor));
-        // Divide out the factor, ignoring high bits, since we'll be
-        // scaling the value back up in the end.
-        if (const SCEV *Quotient = getSDiv(AR, FactorS, SE, true)) {
-          // TODO: This could be optimized to avoid all the copying.
-          Formula NewF = F;
-          NewF.ScaledReg = Quotient;
-          std::swap(NewF.BaseRegs[i], NewF.BaseRegs.back());
-          NewF.BaseRegs.pop_back();
-          NewF.AM.HasBaseReg = !NewF.BaseRegs.empty();
-          (void)InsertFormula(LU, LUIdx, NewF);
-        }
+  int64_t SInt = cast<SCEVConstant>(Stride)->getValue()->getSExtValue();
+  const SCEV *NewStride = 0;
+  bool Found = false;
+  for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
+    const SCEV *OldStride = IU->StrideOrder[i];
+    if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OldStride))
+      if (SC->getValue()->getSExtValue() == -SInt) {
+        Found = true;
+        NewStride = OldStride;
+        break;
       }
   }
-}
-
-/// GenerateTruncateReuse - Generate reuse formulae from different IV types.
-void LSRInstance::GenerateTruncateReuse(LSRUse &LU, unsigned LUIdx,
-                                        Formula Base) {
-  // This requires TargetLowering to tell us which truncates are free.
-  if (!TLI) return;
-
-  // Don't attempt to truncate symbolic values.
-  if (Base.AM.BaseGV) return;
-
-  // Determine the integer type for the base formula.
-  const Type *DstTy = Base.getType();
-  if (!DstTy) return;
-  DstTy = SE.getEffectiveSCEVType(DstTy);
-
-  for (SmallSetVector<const Type *, 4>::const_iterator
-       I = Types.begin(), E = Types.end(); I != E; ++I) {
-    const Type *SrcTy = *I;
-    if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
-      Formula F = Base;
-      if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
-      for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
-           JE = F.BaseRegs.end(); J != JE; ++J)
-        *J = SE.getAnyExtendExpr(*J, SrcTy);
-      (void)InsertFormula(LU, LUIdx, F);
-    }
-  }
-}
 
-namespace {
+  if (!Found)
+    NewStride = SE->getIntegerSCEV(-SInt, Stride->getType());
+  IU->AddUser(NewStride, CondUse->getOffset(), Cond, Cond->getOperand(0));
+  IU->IVUsesByStride[Stride]->removeUser(CondUse);
 
-/// WorkItem - Helper class for GenerateConstantOffsetReuse. It's used to
-/// defer modifications so that the search phase doesn't have to worry about
-/// the data structures moving underneath it.
-struct WorkItem {
-  LSRUse *LU;
-  size_t LUIdx;
-  int64_t Imm;
-  const SCEV *OrigReg;
-
-  WorkItem(LSRUse *U, size_t LI, int64_t I, const SCEV *R)
-    : LU(U), LUIdx(LI), Imm(I), OrigReg(R) {}
-
-  void print(raw_ostream &OS) const;
-  void dump() const;
-};
-
-void WorkItem::print(raw_ostream &OS) const {
-  OS << "in use ";
-  LU->print(OS);
-  OS << " (at index " << LUIdx << "), add offset " << Imm
-     << " and compensate by adjusting refences to " << *OrigReg << "\n";
-}
+  CondUse = &IU->IVUsesByStride[NewStride]->Users.back();
+  Stride = NewStride;
 
-void WorkItem::dump() const {
-  print(errs()); errs() << '\n';
-}
+  ++NumCountZero;
 
+  return true;
 }
 
-/// GenerateConstantOffsetReuse - Look for registers which are a constant
-/// distance apart and try to form reuse opportunities between them.
-void LSRInstance::GenerateConstantOffsetReuse() {
-  // Group the registers by their value without any added constant offset.
-  typedef std::map<int64_t, const SCEV *> ImmMapTy;
-  typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
-  RegMapTy Map;
-  SmallVector<const SCEV *, 8> Sequence;
-  for (SmallVectorImpl<const SCEV *>::iterator I = RegSequence.begin(),
-       E = RegSequence.end(); I != E; ++I) {
-    const SCEV *Reg = *I;
-    int64_t Imm = ExtractImmediate(Reg, SE);
-    std::pair<RegMapTy::iterator, bool> Pair =
-      Map.insert(std::make_pair(Reg, ImmMapTy()));
-    if (Pair.second)
-      Sequence.push_back(Reg);
-    Pair.first->second.insert(std::make_pair(Imm, *I));
-  }
-
-  // Insert an artificial expression at offset 0 (if there isn't one already),
-  // as this may lead to more reuse opportunities.
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
-       E = Sequence.end(); I != E; ++I)
-    Map.find(*I)->second.insert(ImmMapTy::value_type(0, 0));
-
-  // Now examine each set of registers with the same base value. Build up
-  // a list of work to do and do the work in a separate step so that we're
-  // not adding formulae and register counts while we're searching.
-  SmallVector<WorkItem, 32> WorkItems;
-  for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
-       E = Sequence.end(); I != E; ++I) {
-    const SCEV *Reg = *I;
-    const ImmMapTy &Imms = Map.find(Reg)->second;
-    // Examine each offset.
-    for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
-         J != JE; ++J) {
-      const SCEV *OrigReg = J->second;
-      // Skip the artifical register at offset 0.
-      if (!OrigReg) continue;
-
-      int64_t JImm = J->first;
-      const SmallBitVector &Bits = RegUses.find(OrigReg)->second.Bits;
-
-      // Examine each other offset associated with the same register. This is
-      // quadradic in the number of registers with the same base, but it's
-      // uncommon for this to be a large number.
-      for (ImmMapTy::const_iterator M = Imms.begin(); M != JE; ++M) {
-        if (M == J) continue;
-
-        // Compute the difference between the two.
-        int64_t Imm = (uint64_t)JImm - M->first;
-        for (int LUIdx = Bits.find_first(); LUIdx != -1;
-             LUIdx = Bits.find_next(LUIdx))
-          // Make a memo of this use, offset, and register tuple.
-          WorkItems.push_back(WorkItem(&Uses[LUIdx], LUIdx, Imm, OrigReg));
-      }
-    }
-  }
-
-  // Now iterate through the worklist and add new formulae.
-  for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
-       E = WorkItems.end(); I != E; ++I) {
-    const WorkItem &WI = *I;
-    LSRUse &LU = *WI.LU;
-    size_t LUIdx = WI.LUIdx;
-    int64_t Imm = WI.Imm;
-    const SCEV *OrigReg = WI.OrigReg;
-
-    const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
-    const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy,
-                                                      -(uint64_t)Imm));
-
-    for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
-      Formula F = LU.Formulae[L];
-      // Use the immediate in the scaled register.
-      if (F.ScaledReg == OrigReg) {
-        int64_t Offs = (uint64_t)F.AM.BaseOffs +
-                       Imm * (uint64_t)F.AM.Scale;
-        // Don't create 50 + reg(-50).
-        if (F.referencesReg(SE.getSCEV(
-                   ConstantInt::get(IntTy, -(uint64_t)Offs))))
-          continue;
-        Formula NewF = F;
-        NewF.AM.BaseOffs = Offs;
-        if (!isLegalUse(NewF.AM, LU.Kind, LU.AccessTy, TLI))
-          continue;
-        const SCEV *Diff = SE.getAddExpr(NegImmS, NewF.ScaledReg);
-        if (Diff->isZero()) continue;
-        NewF.ScaledReg = Diff;
-        (void)InsertFormula(LU, LUIdx, NewF);
-      }
-      // Use the immediate in a base register.
-      for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
-        const SCEV *BaseReg = F.BaseRegs[N];
-        if (BaseReg != OrigReg)
-          continue;
-        Formula NewF = F;
-        NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
-        if (!isLegalUse(NewF.AM, LU.Kind, LU.AccessTy, TLI))
-          continue;
-        const SCEV *Diff = SE.getAddExpr(NegImmS, BaseReg);
-        if (Diff->isZero()) continue;
-        // Don't create 50 + reg(-50).
-        if (Diff ==
-            SE.getSCEV(ConstantInt::get(IntTy,
-                                        -(uint64_t)NewF.AM.BaseOffs)))
-          continue;
-        NewF.BaseRegs[N] = Diff;
-        (void)InsertFormula(LU, LUIdx, NewF);
-      }
-    }
-  }
-}
-
-/// GenerateAllReuseFormulae - Generate formulae for each use.
-void
-LSRInstance::GenerateAllReuseFormulae() {
-  SmallVector<Formula, 12> Save;
-  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
-    LSRUse &LU = Uses[LUIdx];
-
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateSymbolicOffsetReuse(LU, LUIdx, LU.Formulae[i]);
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateICmpZeroScaledReuse(LU, LUIdx, LU.Formulae[i]);
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateReassociationReuse(LU, LUIdx, LU.Formulae[i]);
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateCombinationReuse(LU, LUIdx, LU.Formulae[i]);
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateScaledReuse(LU, LUIdx, LU.Formulae[i]);
-    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
-      GenerateTruncateReuse(LU, LUIdx, LU.Formulae[i]);
-  }
-
-  GenerateConstantOffsetReuse();
-}
+/// OptimizeLoopCountIV - If, after all sharing of IVs, the IV used for deciding
+/// when to exit the loop is used only for that purpose, try to rearrange things
+/// so it counts down to a test against zero.
+bool LoopStrengthReduce::OptimizeLoopCountIV(Loop *L) {
+  bool ThisChanged = false;
+  for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
+    const SCEV *Stride = IU->StrideOrder[i];
+    std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
+      IU->IVUsesByStride.find(Stride);
+    assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
+    // FIXME: Generalize to non-affine IV's.
+    if (!SI->first->isLoopInvariant(L))
+      continue;
+    // If stride is a constant and it has an icmpinst use, check if we can
+    // optimize the loop to count down.
+    if (isa<SCEVConstant>(Stride) && SI->second->Users.size() == 1) {
+      Instruction *User = SI->second->Users.begin()->getUser();
+      if (!isa<ICmpInst>(User))
+        continue;
+      const SCEV *CondStride = Stride;
+      IVStrideUse *Use = &*SI->second->Users.begin();
+      if (!OptimizeLoopCountIVOfStride(CondStride, Use, L))
+        continue;
+      ThisChanged = true;
 
-/// GenerateLoopInvariantRegisterUses - Check for other uses of loop-invariant
-/// values which we're tracking. These other uses will pin these values in
-/// registers, making them less profitable for elimination.
-/// TODO: This currently misses non-constant addrec step registers.
-/// TODO: Should this give more weight to users inside the loop?
-void
-LSRInstance::GenerateLoopInvariantRegisterUses() {
-  SmallVector<const SCEV *, 8> Worklist(RegSequence.begin(), RegSequence.end());
-
-  while (!Worklist.empty()) {
-    const SCEV *S = Worklist.pop_back_val();
-
-    if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
-      Worklist.insert(Worklist.end(), N->op_begin(), N->op_end());
-    else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
-      Worklist.push_back(C->getOperand());
-    else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
-      Worklist.push_back(D->getLHS());
-      Worklist.push_back(D->getRHS());
-    } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
-      const Value *V = U->getValue();
-      if (const Instruction *Inst = dyn_cast<Instruction>(V))
-        if (L->contains(Inst)) continue;
-      for (Value::use_const_iterator UI = V->use_begin(), UE = V->use_end();
-           UI != UE; ++UI) {
-        const Instruction *UserInst = dyn_cast<Instruction>(*UI);
-        // Ignore non-instructions.
-        if (!UserInst)
+      // Now check if it's possible to reuse this iv for other stride uses.
+      for (unsigned j = 0, ee = IU->StrideOrder.size(); j != ee; ++j) {
+        const SCEV *SStride = IU->StrideOrder[j];
+        if (SStride == CondStride)
           continue;
-        // Ignore instructions in other functions (as can happen with
-        // Constants).
-        if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
+        std::map<const SCEV *, IVUsersOfOneStride *>::iterator SII =
+          IU->IVUsesByStride.find(SStride);
+        assert(SII != IU->IVUsesByStride.end() && "Stride doesn't exist!");
+        // FIXME: Generalize to non-affine IV's.
+        if (!SII->first->isLoopInvariant(L))
           continue;
-        // Ignore instructions not dominated by the loop.
-        const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
-          UserInst->getParent() :
-          cast<PHINode>(UserInst)->getIncomingBlock(
-            PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
-        if (!DT.dominates(L->getHeader(), UseBB))
-          continue;
-        // Ignore uses which are part of other SCEV expressions, to avoid
-        // analyzing them multiple times.
-        if (SE.isSCEVable(UserInst->getType()) &&
-            !isa<SCEVUnknown>(SE.getSCEV(const_cast<Instruction *>(UserInst))))
-          continue;
-        // Ignore icmp instructions which are already being analyzed.
-        if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
-          unsigned OtherIdx = !UI.getOperandNo();
-          Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
-          if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
-            continue;
-        }
-
-        LSRUse &LU = getNewUse();
-        LU.UserInst = const_cast<Instruction *>(UserInst);
-        LU.OperandValToReplace = UI.getUse();
-        LU.InsertSupplementalFormula(U);
-        CountRegisters(LU.Formulae.back(), Uses.size() - 1);
+        // FIXME: Rewrite other stride using CondStride.
       }
     }
   }
-}
 
-#ifndef NDEBUG
-
-static void debug_winner(SmallVector<LSRUse, 16> const &Uses) {
-  dbgs() << "LSR has selected formulae for each use:\n";
-  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
-       E = Uses.end(); I != E; ++I) {
-    const LSRUse &LU = *I;
-    dbgs() << "  ";
-    LU.print(dbgs());
-    dbgs() << '\n';
-    dbgs() << "    ";
-    LU.Formulae.front().print(dbgs());
-    dbgs() << "\n";
-  }
+  Changed |= ThisChanged;
+  return ThisChanged;
 }
 
-#endif
-
-LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
-  : IU(P->getAnalysis<IVUsers>()),
-    SE(P->getAnalysis<ScalarEvolution>()),
-    DT(P->getAnalysis<DominatorTree>()),
-    TLI(tli), L(l), Changed(false), IVIncInsertPos(0),
-    CurrentArbitraryRegIndex(0), MaxNumRegs(0) {
+bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
+  IU = &getAnalysis<IVUsers>();
+  SE = &getAnalysis<ScalarEvolution>();
+  Changed = false;
 
   // If LoopSimplify form is not available, stay out of trouble.
-  if (!L->isLoopSimplifyForm()) return;
-
-  // If there's no interesting work to be done, bail early.
-  if (IU.IVUsesByStride.empty()) return;
-
-  DEBUG(dbgs() << "\nLSR on loop ";
-        WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
-        dbgs() << ":\n");
-
-  // Sort the StrideOrder so we process larger strides first.
-  std::stable_sort(IU.StrideOrder.begin(), IU.StrideOrder.end(),
-                   StrideCompare(SE));
-
-  /// OptimizeShadowIV - If IV is used in a int-to-float cast
-  /// inside the loop then try to eliminate the cast opeation.
-  OptimizeShadowIV();
-
-  // Change loop terminating condition to use the postinc iv when possible.
-  Changed |= OptimizeLoopTermCond();
-
-  for (SmallVectorImpl<const SCEV *>::const_iterator SIter =
-       IU.StrideOrder.begin(), SEnd = IU.StrideOrder.end();
-       SIter != SEnd; ++SIter) {
-    const SCEV *Stride = *SIter;
-
-    // Collect interesting types.
-    Types.insert(SE.getEffectiveSCEVType(Stride->getType()));
-
-    // Collect interesting factors.
-    for (SmallVectorImpl<const SCEV *>::const_iterator NewStrideIter =
-         SIter + 1; NewStrideIter != SEnd; ++NewStrideIter) {
-      const SCEV *OldStride = Stride;
-      const SCEV *NewStride = *NewStrideIter;
-
-      if (SE.getTypeSizeInBits(OldStride->getType()) !=
-          SE.getTypeSizeInBits(NewStride->getType())) {
-        if (SE.getTypeSizeInBits(OldStride->getType()) >
-            SE.getTypeSizeInBits(NewStride->getType()))
-          NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
-        else
-          OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
-      }
-      if (const SCEVConstant *Factor =
-            dyn_cast_or_null<SCEVConstant>(getSDiv(NewStride, OldStride,
-                                                   SE, true)))
-        if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
-          Factors.insert(Factor->getValue()->getValue().getSExtValue());
-    }
-
-    std::map<const SCEV *, IVUsersOfOneStride *>::const_iterator SI =
-      IU.IVUsesByStride.find(Stride);
-    assert(SI != IU.IVUsesByStride.end() && "Stride doesn't exist!");
-    for (ilist<IVStrideUse>::const_iterator UI = SI->second->Users.begin(),
-         E = SI->second->Users.end(); UI != E; ++UI) {
-      // Record the uses.
-      LSRUse &LU = getNewUse();
-      LU.UserInst = UI->getUser();
-      LU.OperandValToReplace = UI->getOperandValToReplace();
-      if (isAddressUse(LU.UserInst, LU.OperandValToReplace)) {
-        LU.Kind = LSRUse::Address;
-        LU.AccessTy = getAccessType(LU.UserInst);
-      }
-      if (UI->isUseOfPostIncrementedValue())
-        LU.PostIncLoop = L;
-
-      const SCEV *S = IU.getCanonicalExpr(*UI);
-
-      // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
-      // (N - i == 0), and this allows (N - i) to be the expression that we
-      // work with rather than just N or i, so we can consider the register
-      // requirements for both N and i at the same time. Limiting this code
-      // to equality icmps is not a problem because all interesting loops
-      // use equality icmps, thanks to IndVarSimplify.
-      if (ICmpInst *CI = dyn_cast<ICmpInst>(LU.UserInst))
-        if (CI->isEquality()) {
-          // Swap the operands if needed to put the OperandValToReplace on
-          // the left, for consistency.
-          Value *NV = CI->getOperand(1);
-          if (NV == LU.OperandValToReplace) {
-            CI->setOperand(1, CI->getOperand(0));
-            CI->setOperand(0, NV);
-          }
+  if (!L->getLoopPreheader() || !L->getLoopLatch())
+    return false;
 
-          // x == y  -->  x - y == 0
-          const SCEV *N = SE.getSCEV(NV);
-          if (N->isLoopInvariant(L)) {
-            LU.Kind = LSRUse::ICmpZero;
-            S = SE.getMinusSCEV(N, S);
-          }
+  if (!IU->IVUsesByStride.empty()) {
+    DEBUG(dbgs() << "\nLSR on \"" << L->getHeader()->getParent()->getName()
+          << "\" ";
+          L->print(dbgs()));
 
-          // -1 and the negations of all interesting strides (except the
-          // negation of -1) are now also interesting.
-          for (size_t i = 0, e = Factors.size(); i != e; ++i)
-            if (Factors[i] != -1)
-              Factors.insert(-(uint64_t)Factors[i]);
-          Factors.insert(-1);
-        }
+    // Sort the StrideOrder so we process larger strides first.
+    std::stable_sort(IU->StrideOrder.begin(), IU->StrideOrder.end(),
+                     StrideCompare(SE));
 
-      // Set up the initial formula for this use.
-      LU.InsertInitialFormula(S, L, SE, DT);
-      CountRegisters(LU.Formulae.back(), Uses.size() - 1);
-    }
-  }
+    // Optimize induction variables.  Some indvar uses can be transformed to use
+    // strides that will be needed for other purposes.  A common example of this
+    // is the exit test for the loop, which can often be rewritten to use the
+    // computation of some other indvar to decide when to terminate the loop.
+    OptimizeIndvars(L);
 
-  // If all uses use the same type, don't bother looking for truncation-based
-  // reuse.
-  if (Types.size() == 1)
-    Types.clear();
-
-  // If there are any uses of registers that we're tracking that have escaped
-  // IVUsers' attention, add trivial uses for them, so that the register
-  // voting process takes the into consideration.
-  GenerateLoopInvariantRegisterUses();
-
-  // Start by assuming we'll assign each use its own register. This is
-  // sometimes called "full" strength reduction, or "superhero" mode.
-  // Sometimes this is the best solution, but if there are opportunities for
-  // reuse we may find a better solution.
-  Score CurScore;
-  CurScore.RateInitial(Uses, L, SE);
-
-  MaxNumRegs = CurScore.getNumRegs();
-
-  // Now use the reuse data to generate a bunch of interesting ways
-  // to formulate the values needed for the uses.
-  GenerateAllReuseFormulae();
-
-  // Sort the formulae. TODO: This is redundantly sorted below.
-  for (SmallVectorImpl<LSRUse>::iterator I = Uses.begin(), E = Uses.end();
-       I != E; ++I) {
-    LSRUse &LU = *I;
-    std::stable_sort(LU.Formulae.begin(), LU.Formulae.end(),
-                     ComplexitySorter());
-  }
+    // Change loop terminating condition to use the postinc iv when possible
+    // and optimize loop terminating compare. FIXME: Move this after
+    // StrengthReduceIVUsersOfStride?
+    OptimizeLoopTermCond(L);
 
-  // Ok, we've now collected all the uses and noted their register uses. The
-  // next step is to start looking at register reuse possibilities.
-  DEBUG(print(dbgs()); dbgs() << '\n'; IU.dump());
-
-  // Create a sorted list of registers with those with the most uses appearing
-  // earlier in the list. We'll visit them first, as they're the most likely
-  // to represent profitable reuse opportunities.
-  SmallVector<RegCount, 8> RegOrder;
-  for (SmallVectorImpl<const SCEV *>::const_iterator I =
-       RegSequence.begin(), E = RegSequence.end(); I != E; ++I)
-    RegOrder.push_back(RegCount(*I, RegUses.find(*I)->second));
-  std::stable_sort(RegOrder.begin(), RegOrder.end());
-
-  // Visit each register. Determine which ones represent profitable reuse
-  // opportunities and remember them.
-  // TODO: Extract this code into a function.
-  for (SmallVectorImpl<RegCount>::const_iterator I = RegOrder.begin(),
-       E = RegOrder.end(); I != E; ++I) {
-    const SCEV *Reg = I->Reg;
-    const SmallBitVector &Bits = I->Sort.Bits;
-
-    // Registers with only one use don't represent reuse opportunities, so
-    // when we get there, we're done.
-    if (Bits.count() <= 1) break;
-
-    DEBUG(dbgs() << "Reg " << *Reg << ": ";
-          I->Sort.print(dbgs());
-          dbgs() << '\n');
-
-    // Determine the total number of registers will be needed if we make use
-    // of the reuse opportunity represented by the current register.
-    Score NewScore;
-    NewScore.Rate(Reg, Bits, Uses, L, SE);
-
-    // Now decide whether this register's reuse opportunity is an overall win.
-    // Currently the decision is heavily skewed for register pressure.
-    if (!(NewScore < CurScore)) {
-      continue;
-    }
+    // FIXME: We can shrink overlarge IV's here.  e.g. if the code has
+    // computation in i64 values and the target doesn't support i64, demote
+    // the computation to 32-bit if safe.
 
-    // Ok, use this opportunity.
-    DEBUG(dbgs() << "This candidate has been accepted.\n");
-    CurScore = NewScore;
-
-    // Now that we've selected a new reuse opportunity, delete formulae that
-    // do not participate in that opportunity.
-    for (int j = Bits.find_first(); j != -1; j = Bits.find_next(j)) {
-      LSRUse &LU = Uses[j];
-      for (unsigned k = 0, h = LU.Formulae.size(); k != h; ++k) {
-        Formula &F = LU.Formulae[k];
-        if (!F.referencesReg(Reg)) {
-          std::swap(LU.Formulae[k], LU.Formulae.back());
-          LU.Formulae.pop_back();
-          --k; --h;
-        }
-      }
-      // Also re-sort the list to put the formulae with the fewest registers
-      // at the front.
-      // TODO: Do this earlier, we don't need it each time.
-      std::stable_sort(LU.Formulae.begin(), LU.Formulae.end(),
-                       ComplexitySorter());
-    }
-  }
+    // FIXME: Attempt to reuse values across multiple IV's.  In particular, we
+    // could have something like "for(i) { foo(i*8); bar(i*16) }", which should
+    // be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
+    // Need to be careful that IV's are all the same type.  Only works for
+    // intptr_t indvars.
 
-  // Ok, we've now made all our decisions. The first formula for each use
-  // will be used.
-  DEBUG(dbgs() << "Concluding, we need "; CurScore.print(dbgs());
-        dbgs() << ".\n";
-        debug_winner(Uses));
-
-  // Free memory no longer needed.
-  RegOrder.clear();
-  Factors.clear();
-  Types.clear();
-  RegUses.clear();
-  RegSequence.clear();
-
-  // Keep track of instructions we may have made dead, so that
-  // we can remove them after we are done working.
-  SmallVector<WeakVH, 16> DeadInsts;
-
-  SCEVExpander Rewriter(SE);
-  Rewriter.disableCanonicalMode();
-  Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
-
-  // Expand the new value definitions and update the users.
-  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
-       E = Uses.end(); I != E; ++I) {
-    // Formulae should be legal.
-    DEBUG(for (SmallVectorImpl<Formula>::const_iterator J = I->Formulae.begin(),
-               JE = I->Formulae.end(); J != JE; ++J)
-            assert(isLegalUse(J->AM, I->Kind, I->AccessTy, TLI) &&
-                   "Illegal formula generated!"));
-
-    // Expand the new code and update the user.
-    I->Rewrite(L, IVIncInsertPos, Rewriter, DeadInsts, SE, DT, P);
-    Changed = true;
-  }
+    // IVsByStride keeps IVs for one particular loop.
+    assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
 
-  // Clean up after ourselves. This must be done before deleting any
-  // instructions.
-  Rewriter.clear();
+    StrengthReduceIVUsers(L);
 
-  Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
-}
+    // After all sharing is done, see if we can adjust the loop to test against
+    // zero instead of counting up to a maximum.  This is usually faster.
+    OptimizeLoopCountIV(L);
 
-void LSRInstance::print(raw_ostream &OS) const {
-  if (MaxNumRegs != 0)
-    OS << "LSR is considering " << MaxNumRegs << " to be the maximum "
-          "number of registers needed.\n";
+    // We're done analyzing this loop; release all the state we built up for it.
+    IVsByStride.clear();
 
-  OS << "LSR has identified the following interesting factors and types: ";
-  bool First = true;
-
-  for (SmallSetVector<int64_t, 4>::const_iterator
-       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
-    if (!First) OS << ", ";
-    First = false;
-    OS << '*' << *I;
-  }
-
-  for (SmallSetVector<const Type *, 4>::const_iterator
-       I = Types.begin(), E = Types.end(); I != E; ++I) {
-    if (!First) OS << ", ";
-    First = false;
-    OS << '(' << **I << ')';
+    // Clean up after ourselves
+    DeleteTriviallyDeadInstructions();
   }
-  OS << '\n';
-
-  OS << "LSR is examining the following uses, and candidate formulae:\n";
-  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
-       E = Uses.end(); I != E; ++I) {
-    const LSRUse &LU = *I;
-    dbgs() << "  ";
-    LU.print(OS);
-    OS << '\n';
-    for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
-         JE = LU.Formulae.end(); J != JE; ++J) {
-      OS << "    ";
-      J->print(OS);
-      OS << "\n";
-    }
-  }
-}
-
-void LSRInstance::dump() const {
-  print(errs()); errs() << '\n';
-}
-
-namespace {
-
-class LoopStrengthReduce : public LoopPass {
-  /// TLI - Keep a pointer of a TargetLowering to consult for determining
-  /// transformation profitability.
-  const TargetLowering *const TLI;
-
-public:
-  static char ID; // Pass ID, replacement for typeid
-  explicit LoopStrengthReduce(const TargetLowering *tli = NULL);
-
-private:
-  bool runOnLoop(Loop *L, LPPassManager &LPM);
-  void getAnalysisUsage(AnalysisUsage &AU) const;
-};
-
-}
-
-char LoopStrengthReduce::ID = 0;
-static RegisterPass<LoopStrengthReduce>
-X("loop-reduce", "Loop Strength Reduction");
-
-Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
-  return new LoopStrengthReduce(TLI);
-}
-
-LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
-  : LoopPass(&ID), TLI(tli) {}
-
-void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
-  // We split critical edges, so we change the CFG.  However, we do update
-  // many analyses if they are around.
-  AU.addPreservedID(LoopSimplifyID);
-  AU.addPreserved<LoopInfo>();
-  AU.addPreserved("domfrontier");
-
-  AU.addRequiredID(LoopSimplifyID);
-  AU.addRequired<DominatorTree>();
-  AU.addPreserved<DominatorTree>();
-  AU.addRequired<ScalarEvolution>();
-  AU.addPreserved<ScalarEvolution>();
-  AU.addRequired<IVUsers>();
-  AU.addPreserved<IVUsers>();
-}
-
-bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
-  bool Changed = false;
-
-  // Run the main LSR transformation.
-  Changed |= LSRInstance(TLI, L, this).getChanged();
 
   // At this point, it is worth checking to see if any recurrence PHIs are also
   // dead, so that we can remove them as well.
diff --git a/test/CodeGen/ARM/arm-negative-stride.ll b/test/CodeGen/ARM/arm-negative-stride.ll
index 52ab8717c1..72ec8efcc4 100644
--- a/test/CodeGen/ARM/arm-negative-stride.ll
+++ b/test/CodeGen/ARM/arm-negative-stride.ll
@@ -1,32 +1,7 @@
 ; RUN: llc < %s -march=arm | FileCheck %s
 
-; This loop is rewritten with an indvar which counts down, which
-; frees up a register from holding the trip count.
-
 define void @test(i32* %P, i32 %A, i32 %i) nounwind {
 entry:
-; CHECK: str r1, [{{r.*}}, +{{r.*}}, lsl #2]
-        icmp eq i32 %i, 0               ; <i1>:0 [#uses=1]
-        br i1 %0, label %return, label %bb
-
-bb:             ; preds = %bb, %entry
-        %indvar = phi i32 [ 0, %entry ], [ %indvar.next, %bb ]          ; <i32> [#uses=2]
-        %i_addr.09.0 = sub i32 %i, %indvar              ; <i32> [#uses=1]
-        %tmp2 = getelementptr i32* %P, i32 %i_addr.09.0         ; <i32*> [#uses=1]
-        store i32 %A, i32* %tmp2
-        %indvar.next = add i32 %indvar, 1               ; <i32> [#uses=2]
-        icmp eq i32 %indvar.next, %i            ; <i1>:1 [#uses=1]
-        br i1 %1, label %return, label %bb
-
-return:         ; preds = %bb, %entry
-        ret void
-}
-
-; This loop has a non-address use of the count-up indvar, so
-; it'll remain. Now the original store uses a negative-stride address.
-
-define void @test_with_forced_iv(i32* %P, i32 %A, i32 %i) nounwind {
-entry:
 ; CHECK: str r1, [{{r.*}}, -{{r.*}}, lsl #2]
         icmp eq i32 %i, 0               ; <i1>:0 [#uses=1]
         br i1 %0, label %return, label %bb
@@ -36,7 +11,6 @@ bb:             ; preds = %bb, %entry
         %i_addr.09.0 = sub i32 %i, %indvar              ; <i32> [#uses=1]
         %tmp2 = getelementptr i32* %P, i32 %i_addr.09.0         ; <i32*> [#uses=1]
         store i32 %A, i32* %tmp2
-        store i32 %indvar, i32* null
         %indvar.next = add i32 %indvar, 1               ; <i32> [#uses=2]
         icmp eq i32 %indvar.next, %i            ; <i1>:1 [#uses=1]
         br i1 %1, label %return, label %bb
diff --git a/test/CodeGen/ARM/lsr-code-insertion.ll b/test/CodeGen/ARM/lsr-code-insertion.ll
index 1bbb96deee..507ec2c7bd 100644
--- a/test/CodeGen/ARM/lsr-code-insertion.ll
+++ b/test/CodeGen/ARM/lsr-code-insertion.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -stats |& grep {39.*Number of machine instrs printed}
-; RUN: llc < %s -stats |& not grep {.*Number of re-materialization}
+; RUN: llc < %s -stats |& grep {40.*Number of machine instrs printed}
+; RUN: llc < %s -stats |& grep {.*Number of re-materialization}
 ; This test really wants to check that the resultant "cond_true" block only 
 ; has a single store in it, and that cond_true55 only has code to materialize 
 ; the constant and do a store.  We do *not* want something like this:
diff --git a/test/CodeGen/ARM/remat.ll b/test/CodeGen/ARM/remat.ll
index 9072bcb762..9565c8bca6 100644
--- a/test/CodeGen/ARM/remat.ll
+++ b/test/CodeGen/ARM/remat.ll
@@ -1,4 +1,5 @@
-; RUN: llc < %s -mtriple=arm-apple-darwin -stats -info-output-file - | not grep "Number of re-materialization"
+; RUN: llc < %s -mtriple=arm-apple-darwin 
+; RUN: llc < %s -mtriple=arm-apple-darwin -stats -info-output-file - | grep "Number of re-materialization" | grep 3
 
 	%struct.CONTENTBOX = type { i32, i32, i32, i32, i32 }
 	%struct.LOCBOX = type { i32, i32, i32, i32 }
diff --git a/test/CodeGen/Thumb2/lsr-deficiency.ll b/test/CodeGen/Thumb2/lsr-deficiency.ll
index ac2cd34e4b..7b1b57a786 100644
--- a/test/CodeGen/Thumb2/lsr-deficiency.ll
+++ b/test/CodeGen/Thumb2/lsr-deficiency.ll
@@ -1,29 +1,25 @@
 ; RUN: llc < %s -mtriple=thumbv7-apple-darwin10 -relocation-model=pic | FileCheck %s
 ; rdar://7387640
 
-; This now reduces to a single induction variable.
-
-; TODO: It still gets a GPR shuffle at the end of the loop
-; This is because something in instruction selection has decided
-; that comparing the pre-incremented value with zero is better
-; than comparing the post-incremented value with -4.
+; FIXME: We still need to rewrite array reference iv of stride -4 with loop
+; count iv of stride -1.
 
 @G = external global i32                          ; <i32*> [#uses=2]
 @array = external global i32*                     ; <i32**> [#uses=1]
 
 define arm_apcscc void @t() nounwind optsize {
 ; CHECK: t:
-; CHECK: mov.w r2, #1000
+; CHECK: mov.w r2, #4000
+; CHECK: movw r3, #1001
 entry:
   %.pre = load i32* @G, align 4                   ; <i32> [#uses=1]
   br label %bb
 
 bb:                                               ; preds = %bb, %entry
 ; CHECK: LBB1_1:
-; CHECK: cmp r2, #0
-; CHECK: sub.w r9, r2, #1
-; CHECK: mov r2, r9
-
+; CHECK: subs r3, #1
+; CHECK: cmp r3, #0
+; CHECK: sub.w r2, r2, #4
   %0 = phi i32 [ %.pre, %entry ], [ %3, %bb ]     ; <i32> [#uses=1]
   %indvar = phi i32 [ 0, %entry ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
   %tmp5 = sub i32 1000, %indvar                   ; <i32> [#uses=1]
diff --git a/test/CodeGen/Thumb2/thumb2-ifcvt1.ll b/test/CodeGen/Thumb2/thumb2-ifcvt1.ll
index 1d267565e0..71199abc57 100644
--- a/test/CodeGen/Thumb2/thumb2-ifcvt1.ll
+++ b/test/CodeGen/Thumb2/thumb2-ifcvt1.ll
@@ -1,6 +1,6 @@
 ; RUN: llc < %s -mtriple=thumbv7-apple-darwin | FileCheck %s
 
-define i32 @t1(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
+define i32 @t1(i32 %a, i32 %b, i32 %c, i32 %d) {
 ; CHECK: t1:
 ; CHECK: it ne
 ; CHECK: cmpne
@@ -20,12 +20,12 @@ cond_next:
 }
 
 ; FIXME: Check for # of unconditional branch after adding branch folding post ifcvt.
-define i32 @t2(i32 %a, i32 %b) nounwind {
+define i32 @t2(i32 %a, i32 %b) {
 entry:
 ; CHECK: t2:
-; CHECK: ite gt
-; CHECK: subgt
+; CHECK: ite le
 ; CHECK: suble
+; CHECK: subgt
 	%tmp1434 = icmp eq i32 %a, %b		; <i1> [#uses=1]
 	br i1 %tmp1434, label %bb17, label %bb.outer
 
@@ -60,14 +60,14 @@ bb17:		; preds = %cond_false, %cond_true, %entry
 
 @x = external global i32*		; <i32**> [#uses=1]
 
-define void @foo(i32 %a) nounwind {
+define void @foo(i32 %a) {
 entry:
 	%tmp = load i32** @x		; <i32*> [#uses=1]
 	store i32 %a, i32* %tmp
 	ret void
 }
 
-define void @t3(i32 %a, i32 %b) nounwind {
+define void @t3(i32 %a, i32 %b) {
 entry:
 ; CHECK: t3:
 ; CHECK: it lt
diff --git a/test/CodeGen/X86/2006-05-11-InstrSched.ll b/test/CodeGen/X86/2006-05-11-InstrSched.ll
index 56d6aa960e..bdbe713a29 100644
--- a/test/CodeGen/X86/2006-05-11-InstrSched.ll
+++ b/test/CodeGen/X86/2006-05-11-InstrSched.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -march=x86 -mattr=+sse2 -stats -realign-stack=0 |&\
-; RUN:     grep {asm-printer} | grep 34
+; RUN:     grep {asm-printer} | grep 31
 
 target datalayout = "e-p:32:32"
 define void @foo(i32* %mc, i32* %bp, i32* %ms, i32* %xmb, i32* %mpp, i32* %tpmm, i32* %ip, i32* %tpim, i32* %dpp, i32* %tpdm, i32* %bpi, i32 %M) nounwind {
@@ -40,7 +40,7 @@ cond_true:		; preds = %cond_true, %entry
 	%tmp137.upgrd.7 = bitcast i32* %tmp137 to <2 x i64>*		; <<2 x i64>*> [#uses=1]
 	store <2 x i64> %tmp131, <2 x i64>* %tmp137.upgrd.7
 	%tmp147 = add nsw i32 %tmp.10, 8		; <i32> [#uses=1]
-	%tmp.upgrd.8 = icmp ne i32 %tmp147, %M		; <i1> [#uses=1]
+	%tmp.upgrd.8 = icmp slt i32 %tmp147, %M		; <i1> [#uses=1]
 	%indvar.next = add i32 %indvar, 1		; <i32> [#uses=1]
 	br i1 %tmp.upgrd.8, label %cond_true, label %return
 
diff --git a/test/CodeGen/X86/2007-11-30-LoadFolding-Bug.ll b/test/CodeGen/X86/2007-11-30-LoadFolding-Bug.ll
index 8e315f4d80..721d4c945b 100644
--- a/test/CodeGen/X86/2007-11-30-LoadFolding-Bug.ll
+++ b/test/CodeGen/X86/2007-11-30-LoadFolding-Bug.ll
@@ -35,7 +35,7 @@ cond_next36.i:		; preds = %cond_next.i
 bb.i28.i:		; preds = %bb.i28.i, %cond_next36.i
 ; CHECK: %bb.i28.i
 ; CHECK: addl $2
-; CHECK: addl $-2
+; CHECK: addl $2
 	%j.0.reg2mem.0.i16.i = phi i32 [ 0, %cond_next36.i ], [ %indvar.next39.i, %bb.i28.i ]		; <i32> [#uses=2]
 	%din_addr.1.reg2mem.0.i17.i = phi double [ 0.000000e+00, %cond_next36.i ], [ %tmp16.i25.i, %bb.i28.i ]		; <double> [#uses=1]
 	%tmp1.i18.i = fptosi double %din_addr.1.reg2mem.0.i17.i to i32		; <i32> [#uses=2]
diff --git a/test/CodeGen/X86/iv-users-in-other-loops.ll b/test/CodeGen/X86/iv-users-in-other-loops.ll
index 0410bc0d9a..c695c29e06 100644
--- a/test/CodeGen/X86/iv-users-in-other-loops.ll
+++ b/test/CodeGen/X86/iv-users-in-other-loops.ll
@@ -1,11 +1,11 @@
 ; RUN: llc < %s -march=x86-64 -o %t
-; RUN: not grep inc %t
+; RUN: grep inc %t | count 1
 ; RUN: grep dec %t | count 2
-; RUN: grep addq %t | count 10
+; RUN: grep addq %t | count 13
 ; RUN: not grep addb %t
 ; RUN: grep leaq %t | count 9
-; RUN: grep leal %t | count 2
-; RUN: grep movq %t | count 10
+; RUN: grep leal %t | count 3
+; RUN: grep movq %t | count 5
 
 ; IV users in each of the loops from other loops shouldn't cause LSR
 ; to insert new induction variables. Previously it would create a
diff --git a/test/CodeGen/X86/loop-strength-reduce4.ll b/test/CodeGen/X86/loop-strength-reduce4.ll
index 6c0eb8c0df..07e46eca75 100644
--- a/test/CodeGen/X86/loop-strength-reduce4.ll
+++ b/test/CodeGen/X86/loop-strength-reduce4.ll
@@ -1,19 +1,5 @@
-; RUN: llc < %s -march=x86 -relocation-model=static -mtriple=i686-apple-darwin | FileCheck %s -check-prefix=STATIC
-; RUN: llc < %s -march=x86 -relocation-model=pic | FileCheck %s -check-prefix=PIC
-
-; By starting the IV at -64 instead of 0, a cmp is eliminated,
-; as the flags from the add can be used directly.
-
-; STATIC: movl    $-64, %ecx
-
-; STATIC: movl    %eax, _state+76(%ecx)
-; STATIC: addl    $16, %ecx
-; STATIC: jne
-
-; In PIC mode the symbol can't be folded, so the change-compare-stride
-; trick applies.
-
-; PIC: cmpl $64
+; RUN: llc < %s -march=x86 | grep cmp | grep 64
+; RUN: llc < %s -march=x86 | not grep inc
 
 @state = external global [0 x i32]		; <[0 x i32]*> [#uses=4]
 @S = external global [0 x i32]		; <[0 x i32]*> [#uses=4]
diff --git a/test/CodeGen/X86/loop-strength-reduce8.ll b/test/CodeGen/X86/loop-strength-reduce8.ll
index 6b2247d1d6..e14cd8a99e 100644
--- a/test/CodeGen/X86/loop-strength-reduce8.ll
+++ b/test/CodeGen/X86/loop-strength-reduce8.ll
@@ -1,10 +1,4 @@
-; RUN: llc < %s -mtriple=i386-apple-darwin | FileCheck %s
-
-; CHECK: leal 16(%eax), %edx
-; CHECK: align
-; CHECK: addl    $4, %edx
-; CHECK: decl    %ecx
-; CHECK: jne     LBB1_2
+; RUN: llc < %s -mtriple=i386-apple-darwin | grep leal | not grep 16
 
 	%struct.CUMULATIVE_ARGS = type { i32, i32, i32, i32, i32, i32, i32 }
 	%struct.bitmap_element = type { %struct.bitmap_element*, %struct.bitmap_element*, i32, [2 x i64] }
diff --git a/test/CodeGen/X86/lsr-reuse.ll b/test/CodeGen/X86/lsr-reuse.ll
deleted file mode 100644
index a1919bab38..0000000000
--- a/test/CodeGen/X86/lsr-reuse.ll
+++ /dev/null
@@ -1,159 +0,0 @@
-; RUN: llc < %s -march=x86-64 | FileCheck %s
-target datalayout = "e-p:64:64:64"
-target triple = "x86_64-unknown-unknown"
-
-; Full strength reduction reduces register pressure from 5 to 4 here.
-
-; CHECK: full_me:
-; CHECK: movsd   (%rsi), %xmm0
-; CHECK: mulsd   (%rdx), %xmm0
-; CHECK: movsd   %xmm0, (%rdi)
-; CHECK: addq    $8, %rsi
-; CHECK: addq    $8, %rdx
-; CHECK: addq    $8, %rdi
-; CHECK: decq    %rcx
-; CHECK: jne
-
-define void @full_me(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
-entry:
-  %t0 = icmp sgt i64 %n, 0
-  br i1 %t0, label %loop, label %return
-
-loop:
-  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
-  %Ai = getelementptr inbounds double* %A, i64 %i
-  %Bi = getelementptr inbounds double* %B, i64 %i
-  %Ci = getelementptr inbounds double* %C, i64 %i
-  %t1 = load double* %Bi
-  %t2 = load double* %Ci
-  %m = fmul double %t1, %t2
-  store double %m, double* %Ai
-  %i.next = add nsw i64 %i, 1
-  %exitcond = icmp eq i64 %i.next, %n
-  br i1 %exitcond, label %return, label %loop
-
-return:
-  ret void
-}
-
-; In this test, the counting IV exit value is used, so full strength reduction
-; would not reduce register pressure. IndVarSimplify ought to simplify such
-; cases away, but it's useful here to verify that LSR's register pressure
-; heuristics are working as expected.
-
-; CHECK: count_me_0:
-; CHECK: movsd   (%rsi,%rax,8), %xmm0
-; CHECK: mulsd   (%rdx,%rax,8), %xmm0
-; CHECK: movsd   %xmm0, (%rdi,%rax,8)
-; CHECK: incq    %rax
-; CHECK: cmpq    %rax, %rcx
-; CHECK: jne
-
-define i64 @count_me_0(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
-entry:
-  %t0 = icmp sgt i64 %n, 0
-  br i1 %t0, label %loop, label %return
-
-loop:
-  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
-  %Ai = getelementptr inbounds double* %A, i64 %i
-  %Bi = getelementptr inbounds double* %B, i64 %i
-  %Ci = getelementptr inbounds double* %C, i64 %i
-  %t1 = load double* %Bi
-  %t2 = load double* %Ci
-  %m = fmul double %t1, %t2
-  store double %m, double* %Ai
-  %i.next = add nsw i64 %i, 1
-  %exitcond = icmp eq i64 %i.next, %n
-  br i1 %exitcond, label %return, label %loop
-
-return:
-  %q = phi i64 [ 0, %entry ], [ %i.next, %loop ]
-  ret i64 %q
-}
-
-; In this test, the trip count value is used, so full strength reduction
-; would not reduce register pressure.
-; (though it would reduce register pressure inside the loop...)
-
-; CHECK: count_me_1:
-; CHECK: movsd   (%rsi,%rax,8), %xmm0
-; CHECK: mulsd   (%rdx,%rax,8), %xmm0
-; CHECK: movsd   %xmm0, (%rdi,%rax,8)
-; CHECK: incq    %rax
-; CHECK: cmpq    %rax, %rcx
-; CHECK: jne
-
-define i64 @count_me_1(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
-entry:
-  %t0 = icmp sgt i64 %n, 0
-  br i1 %t0, label %loop, label %return
-
-loop:
-  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
-  %Ai = getelementptr inbounds double* %A, i64 %i
-  %Bi = getelementptr inbounds double* %B, i64 %i
-  %Ci = getelementptr inbounds double* %C, i64 %i
-  %t1 = load double* %Bi
-  %t2 = load double* %Ci
-  %m = fmul double %t1, %t2
-  store double %m, double* %Ai
-  %i.next = add nsw i64 %i, 1
-  %exitcond = icmp eq i64 %i.next, %n
-  br i1 %exitcond, label %return, label %loop
-
-return:
-  %q = phi i64 [ 0, %entry ], [ %n, %loop ]
-  ret i64 %q
-}
-
-; This should be fully strength-reduced to reduce register pressure, however
-; the current heuristics get distracted by all the reuse with the stride-1
-; induction variable first.
-
-; But even so, be clever and start the stride-1 variable at a non-zero value
-; to eliminate an in-loop immediate value.
-
-; CHECK: count_me_2:
-; CHECK: movl    $5, %eax
-; CHECK: align
-; CHECK: BB4_1:
-; CHECK: movsd   (%rdi,%rax,8), %xmm0
-; CHECK: addsd   (%rsi,%rax,8), %xmm0
-; CHECK: movsd   %xmm0, (%rdx,%rax,8)
-; CHECK: movsd   40(%rdi,%rax,8), %xmm0
-; CHECK: addsd   40(%rsi,%rax,8), %xmm0
-; CHECK: movsd   %xmm0, 40(%rdx,%rax,8)
-; CHECK: incq    %rax
-; CHECK: cmpq    $5005, %rax
-; CHECK: jne
-
-define void @count_me_2(double* nocapture %A, double* nocapture %B, double* nocapture %C) nounwind {
-entry:
-  br label %loop
-
-loop:
-  %i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
-  %i5 = add i64 %i, 5
-  %Ai = getelementptr double* %A, i64 %i5
-  %t2 = load double* %Ai
-  %Bi = getelementptr double* %B, i64 %i5
-  %t4 = load double* %Bi
-  %t5 = fadd double %t2, %t4
-  %Ci = getelementptr double* %C, i64 %i5
-  store double %t5, double* %Ci
-  %i10 = add i64 %i, 10
-  %Ai10 = getelementptr double* %A, i64 %i10
-  %t9 = load double* %Ai10
-  %Bi10 = getelementptr double* %B, i64 %i10
-  %t11 = load double* %Bi10
-  %t12 = fadd double %t9, %t11
-  %Ci10 = getelementptr double* %C, i64 %i10
-  store double %t12, double* %Ci10
-  %i.next = add i64 %i, 1
-  %exitcond = icmp eq i64 %i.next, 5000
-  br i1 %exitcond, label %return, label %loop
-
-return:
-  ret void
-}
diff --git a/test/CodeGen/X86/masked-iv-safe.ll b/test/CodeGen/X86/masked-iv-safe.ll
index 7111d687ed..bc493bd8f7 100644
--- a/test/CodeGen/X86/masked-iv-safe.ll
+++ b/test/CodeGen/X86/masked-iv-safe.ll
@@ -4,9 +4,9 @@
 ; RUN: not grep sar %t
 ; RUN: not grep shl %t
 ; RUN: grep add %t | count 2
-; RUN: grep inc %t | count 3
+; RUN: grep inc %t | count 4
 ; RUN: grep dec %t | count 2
-; RUN: grep lea %t | count 3
+; RUN: grep lea %t | count 2
 
 ; Optimize away zext-inreg and sext-inreg on the loop induction
 ; variable using trip-count information.
@@ -127,9 +127,6 @@ return:
 	ret void
 }
 
-; TODO: If we could handle all the loads and stores as post-inc users, we could
-; use {-1,+,1} in the induction variable register, and we'd get another inc,
-; one fewer add, and a comparison with zero.
 define void @another_count_up(double* %d, i64 %n) nounwind {
 entry:
 	br label %loop
diff --git a/test/Transforms/LoopStrengthReduce/2008-08-06-CmpStride.ll b/test/Transforms/LoopStrengthReduce/2008-08-06-CmpStride.ll
index 99cb8569b3..7c7a21c013 100644
--- a/test/Transforms/LoopStrengthReduce/2008-08-06-CmpStride.ll
+++ b/test/Transforms/LoopStrengthReduce/2008-08-06-CmpStride.ll
@@ -1,4 +1,5 @@
-; RUN: llc -march=x86-64 < %s -o - | grep {cmpl	\\$\[1\], %}
+; RUN: opt < %s -loop-reduce -S | grep ugt
+; PR2535
 
 @.str = internal constant [4 x i8] c"%d\0A\00"
 
@@ -15,7 +16,7 @@ forbody:
         %add166 = or i32 %mul15, 1              ; <i32> [#uses=1] *
         call i32 (i8*, ...)* @printf( i8* noalias  getelementptr ([4 x i8]* @.str, i32 0, i32 0), i32 %add166 ) nounwind
         %inc = add i32 %i.0, 1          ; <i32> [#uses=3]
-        %cmp = icmp ne i32 %inc, 1027          ; <i1> [#uses=1]
+        %cmp = icmp ult i32 %inc, 1027          ; <i1> [#uses=1]
         br i1 %cmp, label %forbody, label %afterfor
 
 afterfor:               ; preds = %forcond
diff --git a/test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-0.ll b/test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-0.ll
index d9abc8ba66..36941ad6d3 100644
--- a/test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-0.ll
+++ b/test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-0.ll
@@ -1,9 +1,10 @@
-; RUN: llc < %s -o - | grep {testl	%ecx, %ecx}
+; RUN: llc %s -o - --x86-asm-syntax=att | grep {cmpl	\$4}
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
 target triple = "x86_64-apple-darwin9"
 
-; The comparison happens before the relevant use, but it can still be rewritten
-; to compare with zero.
+; This is like change-compare-stride-trickiness-1.ll except the comparison
+; happens before the relevant use, so the comparison stride can't be
+; easily changed.
 
 define void @foo() nounwind {
 entry:
diff --git a/test/Transforms/LoopStrengthReduce/count-to-zero.ll b/test/Transforms/LoopStrengthReduce/count-to-zero.ll
index feb79f8a0c..8cc3b5c103 100644
--- a/test/Transforms/LoopStrengthReduce/count-to-zero.ll
+++ b/test/Transforms/LoopStrengthReduce/count-to-zero.ll
@@ -19,7 +19,7 @@ bb3:                                              ; preds = %bb1
   %tmp4 = add i32 %c_addr.1, -1                   ; <i32> [#uses=1]
   %c_addr.1.be = select i1 %tmp2, i32 %tmp3, i32 %tmp4 ; <i32> [#uses=1]
   %indvar.next = add i32 %indvar, 1               ; <i32> [#uses=1]
-; CHECK: add i32 %lsr.iv, -1
+; CHECK: sub i32 %lsr.iv, 1
   br label %bb6
 
 bb6:                                              ; preds = %bb3, %entry