Updating branches/google/testing to r169803

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/google/testing@169870 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1178 insertions, 1091 deletions

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 3f1d82cf5b..feeececedb 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6,392 +6,50 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
-// and generates target-independent LLVM-IR. Legalization of the IR is done
-// in the codegen. However, the vectorizes uses (will use) the codegen
-// interfaces to generate IR that is likely to result in an optimal binary.
-//
-// The loop vectorizer combines consecutive loop iteration into a single
-// 'wide' iteration. After this transformation the index is incremented
-// by the SIMD vector width, and not by one.
-//
-// This pass has three parts:
-// 1. The main loop pass that drives the different parts.
-// 2. LoopVectorizationLegality - A unit that checks for the legality
-//    of the vectorization.
-// 3. SingleBlockLoopVectorizer - A unit that performs the actual
-//    widening of instructions.
-// 4. LoopVectorizationCostModel - A unit that checks for the profitability
-//    of vectorization. It decides on the optimal vector width, which
-//    can be one, if vectorization is not profitable.
-//===----------------------------------------------------------------------===//
-//
-// The reduction-variable vectorization is based on the paper:
-//  D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
-//
-// Variable uniformity checks are inspired by:
-// Karrenberg, R. and Hack, S. Whole Function Vectorization.
-//
-// Other ideas/concepts are from:
-//  A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
-//
-//===----------------------------------------------------------------------===//
-#define LV_NAME "loop-vectorize"
-#define DEBUG_TYPE LV_NAME
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Pass.h"
-#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Value.h"
-#include "llvm/Function.h"
-#include "llvm/Analysis/Verifier.h"
-#include "llvm/Module.h"
-#include "llvm/Type.h"
-#include "llvm/ADT/SmallVector.h"
+#include "LoopVectorize.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AliasSetTracker.h"
-#include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/ScalarEvolutionExpressions.h"
-#include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopIterator.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/TargetTransformInfo.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Constants.h"
+#include "llvm/DataLayout.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/DataLayout.h"
+#include "llvm/TargetTransformInfo.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
-#include <algorithm>
-using namespace llvm;
+#include "llvm/Transforms/Vectorize.h"
+#include "llvm/Type.h"
+#include "llvm/Value.h"
 
 static cl::opt<unsigned>
 VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden,
-          cl::desc("Set the default vectorization width. Zero is autoselect."));
-
-/// We don't vectorize loops with a known constant trip count below this number.
-const unsigned TinyTripCountThreshold = 16;
+                    cl::desc("Sets the SIMD width. Zero is autoselect."));
 
-/// When performing a runtime memory check, do not check more than this
-/// number of pointers. Notice that the check is quadratic!
-const unsigned RuntimeMemoryCheckThreshold = 2;
+static cl::opt<bool>
+EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
+                   cl::desc("Enable if-conversion during vectorization."));
 
 namespace {
 
-// Forward declarations.
-class LoopVectorizationLegality;
-class LoopVectorizationCostModel;
-
-/// SingleBlockLoopVectorizer vectorizes loops which contain only one basic
-/// block to a specified vectorization factor (VF).
-/// This class performs the widening of scalars into vectors, or multiple
-/// scalars. This class also implements the following features:
-/// * It inserts an epilogue loop for handling loops that don't have iteration
-///   counts that are known to be a multiple of the vectorization factor.
-/// * It handles the code generation for reduction variables.
-/// * Scalarization (implementation using scalars) of un-vectorizable
-///   instructions.
-/// SingleBlockLoopVectorizer does not perform any vectorization-legality
-/// checks, and relies on the caller to check for the different legality
-/// aspects. The SingleBlockLoopVectorizer relies on the
-/// LoopVectorizationLegality class to provide information about the induction
-/// and reduction variables that were found to a given vectorization factor.
-class SingleBlockLoopVectorizer {
-public:
-  /// Ctor.
-  SingleBlockLoopVectorizer(Loop *Orig, ScalarEvolution *Se, LoopInfo *Li,
-                            DominatorTree *dt, LPPassManager *Lpm,
-                            unsigned VecWidth):
-  OrigLoop(Orig), SE(Se), LI(Li), DT(dt), LPM(Lpm), VF(VecWidth),
-  Builder(Se->getContext()), Induction(0), OldInduction(0) { }
-
-  // Perform the actual loop widening (vectorization).
-  void vectorize(LoopVectorizationLegality *Legal) {
-    ///Create a new empty loop. Unlink the old loop and connect the new one.
-    createEmptyLoop(Legal);
-    /// Widen each instruction in the old loop to a new one in the new loop.
-    /// Use the Legality module to find the induction and reduction variables.
-    vectorizeLoop(Legal);
-    // Register the new loop and update the analysis passes.
-    updateAnalysis();
- }
-
-private:
-  /// Create an empty loop, based on the loop ranges of the old loop.
-  void createEmptyLoop(LoopVectorizationLegality *Legal);
-  /// Copy and widen the instructions from the old loop.
-  void vectorizeLoop(LoopVectorizationLegality *Legal);
-  /// Insert the new loop to the loop hierarchy and pass manager
-  /// and update the analysis passes.
-  void updateAnalysis();
-
-  /// This instruction is un-vectorizable. Implement it as a sequence
-  /// of scalars.
-  void scalarizeInstruction(Instruction *Instr);
-
-  /// Create a broadcast instruction. This method generates a broadcast
-  /// instruction (shuffle) for loop invariant values and for the induction
-  /// value. If this is the induction variable then we extend it to N, N+1, ...
-  /// this is needed because each iteration in the loop corresponds to a SIMD
-  /// element.
-  Value *getBroadcastInstrs(Value *V);
-
-  /// This is a helper function used by getBroadcastInstrs. It adds 0, 1, 2 ..
-  /// for each element in the vector. Starting from zero.
-  Value *getConsecutiveVector(Value* Val);
-
-  /// When we go over instructions in the basic block we rely on previous
-  /// values within the current basic block or on loop invariant values.
-  /// When we widen (vectorize) values we place them in the map. If the values
-  /// are not within the map, they have to be loop invariant, so we simply
-  /// broadcast them into a vector.
-  Value *getVectorValue(Value *V);
-
-  /// Get a uniform vector of constant integers. We use this to get
-  /// vectors of ones and zeros for the reduction code.
-  Constant* getUniformVector(unsigned Val, Type* ScalarTy);
-
-  typedef DenseMap<Value*, Value*> ValueMap;
-
-  /// The original loop.
-  Loop *OrigLoop;
-  // Scev analysis to use.
-  ScalarEvolution *SE;
-  // Loop Info.
-  LoopInfo *LI;
-  // Dominator Tree.
-  DominatorTree *DT;
-  // Loop Pass Manager;
-  LPPassManager *LPM;
-  // The vectorization factor to use.
-  unsigned VF;
-
-  // The builder that we use
-  IRBuilder<> Builder;
-
-  // --- Vectorization state ---
-
-  /// The vector-loop preheader.
-  BasicBlock *LoopVectorPreHeader;
-  /// The scalar-loop preheader.
-  BasicBlock *LoopScalarPreHeader;
-  /// Middle Block between the vector and the scalar.
-  BasicBlock *LoopMiddleBlock;
-  ///The ExitBlock of the scalar loop.
-  BasicBlock *LoopExitBlock;
-  ///The vector loop body.
-  BasicBlock *LoopVectorBody;
-  ///The scalar loop body.
-  BasicBlock *LoopScalarBody;
-  ///The first bypass block.
-  BasicBlock *LoopBypassBlock;
-
-  /// The new Induction variable which was added to the new block.
-  PHINode *Induction;
-  /// The induction variable of the old basic block.
-  PHINode *OldInduction;
-  // Maps scalars to widened vectors.
-  ValueMap WidenMap;
-};
-
-/// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
-/// to what vectorization factor.
-/// This class does not look at the profitability of vectorization, only the
-/// legality. This class has two main kinds of checks:
-/// * Memory checks - The code in canVectorizeMemory checks if vectorization
-///   will change the order of memory accesses in a way that will change the
-///   correctness of the program.
-/// * Scalars checks - The code in canVectorizeBlock checks for a number
-///   of different conditions, such as the availability of a single induction
-///   variable, that all types are supported and vectorize-able, etc.
-/// This code reflects the capabilities of SingleBlockLoopVectorizer.
-/// This class is also used by SingleBlockLoopVectorizer for identifying
-/// induction variable and the different reduction variables.
-class LoopVectorizationLegality {
-public:
-  LoopVectorizationLegality(Loop *Lp, ScalarEvolution *Se, DataLayout *Dl):
-  TheLoop(Lp), SE(Se), DL(Dl), Induction(0) { }
-
-  /// This represents the kinds of reductions that we support.
-  enum ReductionKind {
-    NoReduction, /// Not a reduction.
-    IntegerAdd,  /// Sum of numbers.
-    IntegerMult, /// Product of numbers.
-    IntegerOr,   /// Bitwise or logical OR of numbers.
-    IntegerAnd,  /// Bitwise or logical AND of numbers.
-    IntegerXor   /// Bitwise or logical XOR of numbers.
-  };
-
-  /// This POD struct holds information about reduction variables.
-  struct ReductionDescriptor {
-    // Default C'tor
-    ReductionDescriptor():
-    StartValue(0), LoopExitInstr(0), Kind(NoReduction) {}
-
-    // C'tor.
-    ReductionDescriptor(Value *Start, Instruction *Exit, ReductionKind K):
-    StartValue(Start), LoopExitInstr(Exit), Kind(K) {}
-
-    // The starting value of the reduction.
-    // It does not have to be zero!
-    Value *StartValue;
-    // The instruction who's value is used outside the loop.
-    Instruction *LoopExitInstr;
-    // The kind of the reduction.
-    ReductionKind Kind;
-  };
-
-  // This POD struct holds information about the memory runtime legality
-  // check that a group of pointers do not overlap.
-  struct RuntimePointerCheck {
-    /// This flag indicates if we need to add the runtime check.
-    bool Need;
-    /// Holds the pointers that we need to check.
-    SmallVector<Value*, 2> Pointers;
-  };
-
-  /// ReductionList contains the reduction descriptors for all
-  /// of the reductions that were found in the loop.
-  typedef DenseMap<PHINode*, ReductionDescriptor> ReductionList;
-
-  /// InductionList saves induction variables and maps them to the initial
-  /// value entring the loop.
-  typedef DenseMap<PHINode*, Value*> InductionList;
-
-  /// Returns true if it is legal to vectorize this loop.
-  /// This does not mean that it is profitable to vectorize this
-  /// loop, only that it is legal to do so.
-  bool canVectorize();
-
-  /// Returns the Induction variable.
-  PHINode *getInduction() {return Induction;}
-
-  /// Returns the reduction variables found in the loop.
-  ReductionList *getReductionVars() { return &Reductions; }
-
-  /// Returns the induction variables found in the loop.
-  InductionList *getInductionVars() { return &Inductions; }
-
-  /// Check if the pointer returned by this GEP is consecutive
-  /// when the index is vectorized. This happens when the last
-  /// index of the GEP is consecutive, like the induction variable.
-  /// This check allows us to vectorize A[idx] into a wide load/store.
-  bool isConsecutiveGep(Value *Ptr);
-
-  /// Returns true if the value V is uniform within the loop.
-  bool isUniform(Value *V);
-
-  /// Returns true if this instruction will remain scalar after vectorization.
-  bool isUniformAfterVectorization(Instruction* I) {return Uniforms.count(I);}
-
-  /// Returns the information that we collected about runtime memory check.
-  RuntimePointerCheck *getRuntimePointerCheck() {return &PtrRtCheck; }
-private:
-  /// Check if a single basic block loop is vectorizable.
-  /// At this point we know that this is a loop with a constant trip count
-  /// and we only need to check individual instructions.
-  bool canVectorizeBlock(BasicBlock &BB);
-
-  /// When we vectorize loops we may change the order in which
-  /// we read and write from memory. This method checks if it is
-  /// legal to vectorize the code, considering only memory constrains.
-  /// Returns true if BB is vectorizable
-  bool canVectorizeMemory(BasicBlock &BB);
-
-  /// Returns True, if 'Phi' is the kind of reduction variable for type
-  /// 'Kind'. If this is a reduction variable, it adds it to ReductionList.
-  bool AddReductionVar(PHINode *Phi, ReductionKind Kind);
-  /// Returns true if the instruction I can be a reduction variable of type
-  /// 'Kind'.
-  bool isReductionInstr(Instruction *I, ReductionKind Kind);
-  /// Returns True, if 'Phi' is an induction variable.
-  bool isInductionVariable(PHINode *Phi);
-  /// Return true if can compute the address bounds of Ptr within the loop.
-  bool hasComputableBounds(Value *Ptr);
-
-  /// The loop that we evaluate.
-  Loop *TheLoop;
-  /// Scev analysis.
-  ScalarEvolution *SE;
-  /// DataLayout analysis.
-  DataLayout *DL;
-
-  //  ---  vectorization state --- //
-
-  /// Holds the integer induction variable. This is the counter of the
-  /// loop.
-  PHINode *Induction;
-  /// Holds the reduction variables.
-  ReductionList Reductions;
-  /// Holds all of the induction variables that we found in the loop.
-  /// Notice that inductions don't need to start at zero and that induction
-  /// variables can be pointers.
-  InductionList Inductions;
-
-  /// Allowed outside users. This holds the reduction
-  /// vars which can be accessed from outside the loop.
-  SmallPtrSet<Value*, 4> AllowedExit;
-  /// This set holds the variables which are known to be uniform after
-  /// vectorization.
-  SmallPtrSet<Instruction*, 4> Uniforms;
-  /// We need to check that all of the pointers in this list are disjoint
-  /// at runtime.
-  RuntimePointerCheck PtrRtCheck;
-};
-
-/// LoopVectorizationCostModel - estimates the expected speedups due to
-/// vectorization.
-/// In many cases vectorization is not profitable. This can happen because
-/// of a number of reasons. In this class we mainly attempt to predict
-/// the expected speedup/slowdowns due to the supported instruction set.
-/// We use the VectorTargetTransformInfo to query the different backends
-/// for the cost of different operations.
-class LoopVectorizationCostModel {
-public:
-  /// C'tor.
-  LoopVectorizationCostModel(Loop *Lp, ScalarEvolution *Se,
-                             LoopVectorizationLegality *Leg,
-                             const VectorTargetTransformInfo *Vtti):
-  TheLoop(Lp), SE(Se), Legal(Leg), VTTI(Vtti) { }
-
-  /// Returns the most profitable vectorization factor for the loop that is
-  /// smaller or equal to the VF argument. This method checks every power
-  /// of two up to VF.
-  unsigned findBestVectorizationFactor(unsigned VF = 8);
-
-private:
-  /// Returns the expected execution cost. The unit of the cost does
-  /// not matter because we use the 'cost' units to compare different
-  /// vector widths. The cost that is returned is *not* normalized by
-  /// the factor width.
-  unsigned expectedCost(unsigned VF);
-
-  /// Returns the execution time cost of an instruction for a given vector
-  /// width. Vector width of one means scalar.
-  unsigned getInstructionCost(Instruction *I, unsigned VF);
-
-  /// A helper function for converting Scalar types to vector types.
-  /// If the incoming type is void, we return void. If the VF is 1, we return
-  /// the scalar type.
-  static Type* ToVectorTy(Type *Scalar, unsigned VF);
-
-  /// The loop that we evaluate.
-  Loop *TheLoop;
-  /// Scev analysis.
-  ScalarEvolution *SE;
-
-  /// Vectorization legality.
-  LoopVectorizationLegality *Legal;
-  /// Vector target information.
-  const VectorTargetTransformInfo *VTTI;
-};
-
+/// The LoopVectorize Pass.
 struct LoopVectorize : public LoopPass {
   static char ID; // Pass identification, replacement for typeid
 
@@ -420,7 +78,7 @@ struct LoopVectorize : public LoopPass {
           L->getHeader()->getParent()->getName() << "\"\n");
 
     // Check if it is legal to vectorize the loop.
-    LoopVectorizationLegality LVL(L, SE, DL);
+    LoopVectorizationLegality LVL(L, SE, DL, DT);
     if (!LVL.canVectorize()) {
       DEBUG(dbgs() << "LV: Not vectorizing.\n");
       return false;
@@ -451,7 +109,7 @@ struct LoopVectorize : public LoopPass {
           "\n");
 
     // If we decided that it is *legal* to vectorizer the loop then do it.
-    SingleBlockLoopVectorizer LB(L, SE, LI, DT, &LPM, VF);
+    InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF);
     LB.vectorize(&LVL);
 
     DEBUG(verifyFunction(*L->getHeader()->getParent()));
@@ -471,15 +129,44 @@ struct LoopVectorize : public LoopPass {
 
 };
 
-Value *SingleBlockLoopVectorizer::getBroadcastInstrs(Value *V) {
-  // Instructions that access the old induction variable
-  // actually want to get the new one.
-  if (V == OldInduction)
-    V = Induction;
+}// namespace
+
+//===----------------------------------------------------------------------===//
+// Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
+// LoopVectorizationCostModel.
+//===----------------------------------------------------------------------===//
+
+void
+LoopVectorizationLegality::RuntimePointerCheck::insert(ScalarEvolution *SE,
+                                                       Loop *Lp, Value *Ptr) {
+  const SCEV *Sc = SE->getSCEV(Ptr);
+  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
+  assert(AR && "Invalid addrec expression");
+  const SCEV *Ex = SE->getExitCount(Lp, Lp->getLoopLatch());
+  const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
+  Pointers.push_back(Ptr);
+  Starts.push_back(AR->getStart());
+  Ends.push_back(ScEnd);
+}
+
+Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
   // Create the types.
   LLVMContext &C = V->getContext();
   Type *VTy = VectorType::get(V->getType(), VF);
   Type *I32 = IntegerType::getInt32Ty(C);
+
+  // Save the current insertion location.
+  Instruction *Loc = Builder.GetInsertPoint();
+
+  // We need to place the broadcast of invariant variables outside the loop.
+  Instruction *Instr = dyn_cast<Instruction>(V);
+  bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
+  bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
+
+  // Place the code for broadcasting invariant variables in the new preheader.
+  if (Invariant)
+    Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
+
   Constant *Zero = ConstantInt::get(I32, 0);
   Value *Zeros = ConstantAggregateZero::get(VectorType::get(I32, VF));
   Value *UndefVal = UndefValue::get(VTy);
@@ -487,27 +174,28 @@ Value *SingleBlockLoopVectorizer::getBroadcastInstrs(Value *V) {
   Value *SingleElem = Builder.CreateInsertElement(UndefVal, V, Zero);
   // Broadcast the scalar into all locations in the vector.
   Value *Shuf = Builder.CreateShuffleVector(SingleElem, UndefVal, Zeros,
-                                             "broadcast");
-  // We are accessing the induction variable. Make sure to promote the
-  // index for each consecutive SIMD lane. This adds 0,1,2 ... to all lanes.
-  if (V == Induction)
-    return getConsecutiveVector(Shuf);
+                                            "broadcast");
+
+  // Restore the builder insertion point.
+  if (Invariant)
+    Builder.SetInsertPoint(Loc);
+
   return Shuf;
 }
 
-Value *SingleBlockLoopVectorizer::getConsecutiveVector(Value* Val) {
+Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, bool Negate) {
   assert(Val->getType()->isVectorTy() && "Must be a vector");
   assert(Val->getType()->getScalarType()->isIntegerTy() &&
          "Elem must be an integer");
   // Create the types.
   Type *ITy = Val->getType()->getScalarType();
   VectorType *Ty = cast<VectorType>(Val->getType());
-  unsigned VLen = Ty->getNumElements();
+  int VLen = Ty->getNumElements();
   SmallVector<Constant*, 8> Indices;
 
   // Create a vector of consecutive numbers from zero to VF.
-  for (unsigned i = 0; i < VLen; ++i)
-    Indices.push_back(ConstantInt::get(ITy, i));
+  for (int i = 0; i < VLen; ++i)
+    Indices.push_back(ConstantInt::get(ITy, Negate ? (-i): i ));
 
   // Add the consecutive indices to the vector value.
   Constant *Cv = ConstantVector::get(Indices);
@@ -515,7 +203,17 @@ Value *SingleBlockLoopVectorizer::getConsecutiveVector(Value* Val) {
   return Builder.CreateAdd(Val, Cv, "induction");
 }
 
-bool LoopVectorizationLegality::isConsecutiveGep(Value *Ptr) {
+bool LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
+  assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr");
+
+  // If this value is a pointer induction variable we know it is consecutive.
+  PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
+  if (Phi && Inductions.count(Phi)) {
+    InductionInfo II = Inductions[Phi];
+    if (PtrInduction == II.IK)
+      return true;
+  }
+
   GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
   if (!Gep)
     return false;
@@ -528,7 +226,7 @@ bool LoopVectorizationLegality::isConsecutiveGep(Value *Ptr) {
     if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
       return false;
 
-  // We can emit wide load/stores only of the last index is the induction
+  // We can emit wide load/stores only if the last index is the induction
   // variable.
   const SCEV *Last = SE->getSCEV(LastIndex);
   if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) {
@@ -547,7 +245,8 @@ bool LoopVectorizationLegality::isUniform(Value *V) {
   return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
 }
 
-Value *SingleBlockLoopVectorizer::getVectorValue(Value *V) {
+Value *InnerLoopVectorizer::getVectorValue(Value *V) {
+  assert(V != Induction && "The new induction variable should not be used.");
   assert(!V->getType()->isVectorTy() && "Can't widen a vector");
   // If we saved a vectorized copy of V, use it.
   Value *&MapEntry = WidenMap[V];
@@ -561,11 +260,11 @@ Value *SingleBlockLoopVectorizer::getVectorValue(Value *V) {
 }
 
 Constant*
-SingleBlockLoopVectorizer::getUniformVector(unsigned Val, Type* ScalarTy) {
+InnerLoopVectorizer::getUniformVector(unsigned Val, Type* ScalarTy) {
   return ConstantVector::getSplat(VF, ConstantInt::get(ScalarTy, Val, true));
 }
 
-void SingleBlockLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
+void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
   assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
   // Holds vector parameters or scalars, in case of uniform vals.
   SmallVector<Value*, 8> Params;
@@ -576,7 +275,7 @@ void SingleBlockLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
 
     // If we are accessing the old induction variable, use the new one.
     if (SrcOp == OldInduction) {
-      Params.push_back(getBroadcastInstrs(Induction));
+      Params.push_back(getVectorValue(SrcOp));
       continue;
     }
 
@@ -635,77 +334,158 @@ void SingleBlockLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
     WidenMap[Instr] = VecResults;
 }
 
+Value*
+InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
+                                     Instruction *Loc) {
+  LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
+  Legal->getRuntimePointerCheck();
+
+  if (!PtrRtCheck->Need)
+    return NULL;
+
+  Value *MemoryRuntimeCheck = 0;
+  unsigned NumPointers = PtrRtCheck->Pointers.size();
+  SmallVector<Value* , 2> Starts;
+  SmallVector<Value* , 2> Ends;
+
+  SCEVExpander Exp(*SE, "induction");
+
+  // Use this type for pointer arithmetic.
+  Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0);
+
+  for (unsigned i = 0; i < NumPointers; ++i) {
+    Value *Ptr = PtrRtCheck->Pointers[i];
+    const SCEV *Sc = SE->getSCEV(Ptr);
+
+    if (SE->isLoopInvariant(Sc, OrigLoop)) {
+      DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
+            *Ptr <<"\n");
+      Starts.push_back(Ptr);
+      Ends.push_back(Ptr);
+    } else {
+      DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
+
+      Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
+      Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
+      Starts.push_back(Start);
+      Ends.push_back(End);
+    }
+  }
+
+  for (unsigned i = 0; i < NumPointers; ++i) {
+    for (unsigned j = i+1; j < NumPointers; ++j) {
+      Instruction::CastOps Op = Instruction::BitCast;
+      Value *Start0 = CastInst::Create(Op, Starts[i], PtrArithTy, "bc", Loc);
+      Value *Start1 = CastInst::Create(Op, Starts[j], PtrArithTy, "bc", Loc);
+      Value *End0 =   CastInst::Create(Op, Ends[i],   PtrArithTy, "bc", Loc);
+      Value *End1 =   CastInst::Create(Op, Ends[j],   PtrArithTy, "bc", Loc);
+
+      Value *Cmp0 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
+                                    Start0, End1, "bound0", Loc);
+      Value *Cmp1 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
+                                    Start1, End0, "bound1", Loc);
+      Value *IsConflict = BinaryOperator::Create(Instruction::And, Cmp0, Cmp1,
+                                                 "found.conflict", Loc);
+      if (MemoryRuntimeCheck)
+        MemoryRuntimeCheck = BinaryOperator::Create(Instruction::Or,
+                                                    MemoryRuntimeCheck,
+                                                    IsConflict,
+                                                    "conflict.rdx", Loc);
+      else
+        MemoryRuntimeCheck = IsConflict;
+
+    }
+  }
+
+  return MemoryRuntimeCheck;
+}
+
 void
-SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
+InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
   /*
    In this function we generate a new loop. The new loop will contain
    the vectorized instructions while the old loop will continue to run the
    scalar remainder.
 
-    [ ] <-- vector loop bypass.
-  /  |
- /   v
-|   [ ]     <-- vector pre header.
-|    |
-|    v
-|   [  ] \
-|   [  ]_|   <-- vector loop.
-|    |
- \   v
+   [ ] <-- vector loop bypass.
+   /  |
+   /   v
+   |   [ ]     <-- vector pre header.
+   |    |
+   |    v
+   |   [  ] \
+   |   [  ]_|   <-- vector loop.
+   |    |
+   \   v
    >[ ]   <--- middle-block.
-  /  |
- /   v
-|   [ ]     <--- new preheader.
-|    |
-|    v
-|   [ ] \
-|   [ ]_|   <-- old scalar loop to handle remainder.
- \   |
-  \  v
+   /  |
+   /   v
+   |   [ ]     <--- new preheader.
+   |    |
+   |    v
+   |   [ ] \
+   |   [ ]_|   <-- old scalar loop to handle remainder.
+   \   |
+   \  v
    >[ ]     <-- exit block.
    ...
    */
 
+  BasicBlock *OldBasicBlock = OrigLoop->getHeader();
+  BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
+  BasicBlock *ExitBlock = OrigLoop->getExitBlock();
+  assert(ExitBlock && "Must have an exit block");
+
+  // Some loops have a single integer induction variable, while other loops
+  // don't. One example is c++ iterators that often have multiple pointer
+  // induction variables. In the code below we also support a case where we
+  // don't have a single induction variable.
   OldInduction = Legal->getInduction();
-  assert(OldInduction && "We must have a single phi node.");
-  Type *IdxTy = OldInduction->getType();
+  Type *IdxTy = OldInduction ? OldInduction->getType() :
+  DL->getIntPtrType(SE->getContext());
 
   // Find the loop boundaries.
-  const SCEV *ExitCount = SE->getExitCount(OrigLoop, OrigLoop->getHeader());
+  const SCEV *ExitCount = SE->getExitCount(OrigLoop, OrigLoop->getLoopLatch());
   assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count");
 
   // Get the total trip count from the count by adding 1.
   ExitCount = SE->getAddExpr(ExitCount,
                              SE->getConstant(ExitCount->getType(), 1));
-  // We may need to extend the index in case there is a type mismatch.
-  // We know that the count starts at zero and does not overflow.
-  // We are using Zext because it should be less expensive.
-  if (ExitCount->getType() != IdxTy)
-    ExitCount = SE->getZeroExtendExpr(ExitCount, IdxTy);
 
-  // This is the original scalar-loop preheader.
-  BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
-  BasicBlock *ExitBlock = OrigLoop->getExitBlock();
-  assert(ExitBlock && "Must have an exit block");
+  // Expand the trip count and place the new instructions in the preheader.
+  // Notice that the pre-header does not change, only the loop body.
+  SCEVExpander Exp(*SE, "induction");
+
+  // Count holds the overall loop count (N).
+  Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
+                                   BypassBlock->getTerminator());
 
-  // The loop index does not have to start at Zero. It starts with this value.
-  Value *StartIdx = OldInduction->getIncomingValueForBlock(BypassBlock);
+  // The loop index does not have to start at Zero. Find the original start
+  // value from the induction PHI node. If we don't have an induction variable
+  // then we know that it starts at zero.
+  Value *StartIdx = OldInduction ?
+  OldInduction->getIncomingValueForBlock(BypassBlock):
+  ConstantInt::get(IdxTy, 0);
 
-  assert(OrigLoop->getNumBlocks() == 1 && "Invalid loop");
   assert(BypassBlock && "Invalid loop structure");
 
-  BasicBlock *VectorPH =
-      BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
-  BasicBlock *VecBody = VectorPH->splitBasicBlock(VectorPH->getTerminator(),
-                                                 "vector.body");
+  // Generate the code that checks in runtime if arrays overlap.
+  Value *MemoryRuntimeCheck = addRuntimeCheck(Legal,
+                                              BypassBlock->getTerminator());
 
-  BasicBlock *MiddleBlock = VecBody->splitBasicBlock(VecBody->getTerminator(),
-                                                  "middle.block");
+  // Split the single block loop into the two loop structure described above.
+  BasicBlock *VectorPH =
+  BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
+  BasicBlock *VecBody =
+  VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
+  BasicBlock *MiddleBlock =
+  VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
   BasicBlock *ScalarPH =
-    MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(),
-                                 "scalar.preheader");
-  // Find the induction variable.
-  BasicBlock *OldBasicBlock = OrigLoop->getHeader();
+  MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
+
+  // This is the location in which we add all of the logic for bypassing
+  // the new vector loop.
+  Instruction *Loc = BypassBlock->getTerminator();
 
   // Use this IR builder to create the loop instructions (Phi, Br, Cmp)
   // inside the loop.
@@ -715,13 +495,16 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
   Induction = Builder.CreatePHI(IdxTy, 2, "index");
   Constant *Step = ConstantInt::get(IdxTy, VF);
 
-  // Expand the trip count and place the new instructions in the preheader.
-  // Notice that the pre-header does not change, only the loop body.
-  SCEVExpander Exp(*SE, "induction");
-  Instruction *Loc = BypassBlock->getTerminator();
-
-  // Count holds the overall loop count (N).
-  Value *Count = Exp.expandCodeFor(ExitCount, Induction->getType(), Loc);
+  // We may need to extend the index in case there is a type mismatch.
+  // We know that the count starts at zero and does not overflow.
+  if (Count->getType() != IdxTy) {
+    // The exit count can be of pointer type. Convert it to the correct
+    // integer type.
+    if (ExitCount->getType()->isPointerTy())
+      Count = CastInst::CreatePointerCast(Count, IdxTy, "ptrcnt.to.int", Loc);
+    else
+      Count = CastInst::CreateZExtOrBitCast(Count, IdxTy, "zext.cnt", Loc);
+  }
 
   // Add the start index to the loop count to get the new end index.
   Value *IdxEnd = BinaryOperator::CreateAdd(Count, StartIdx, "end.idx", Loc);
@@ -734,70 +517,17 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
   Value *IdxEndRoundDown = BinaryOperator::CreateAdd(CountRoundDown, StartIdx,
                                                      "end.idx.rnd.down", Loc);
 
-  // Now, compare the new count to zero. If it is zero, jump to the scalar part.
+  // Now, compare the new count to zero. If it is zero skip the vector loop and
+  // jump to the scalar loop.
   Value *Cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
                                IdxEndRoundDown,
                                StartIdx,
                                "cmp.zero", Loc);
 
-  LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
-    Legal->getRuntimePointerCheck();
-  Value *MemoryRuntimeCheck = 0;
-  if (PtrRtCheck->Need) {
-    unsigned NumPointers = PtrRtCheck->Pointers.size();
-    SmallVector<Value* , 2> Starts;
-    SmallVector<Value* , 2> Ends;
-
-    // Use this type for pointer arithmetic.
-    Type* PtrArithTy = PtrRtCheck->Pointers[0]->getType();
-
-    for (unsigned i=0; i < NumPointers; ++i) {
-      Value *Ptr = PtrRtCheck->Pointers[i];
-      const SCEV *Sc = SE->getSCEV(Ptr);
-
-      if (SE->isLoopInvariant(Sc, OrigLoop)) {
-        DEBUG(dbgs() << "LV1: Adding RT check for a loop invariant ptr:" <<
-              *Ptr <<"\n");
-        Starts.push_back(Ptr);
-        Ends.push_back(Ptr);
-      } else {
-        DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
-        const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
-        Value *Start = Exp.expandCodeFor(AR->getStart(), PtrArithTy, Loc);
-        const SCEV *Ex = SE->getExitCount(OrigLoop, OrigLoop->getHeader());
-        const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
-        assert(!isa<SCEVCouldNotCompute>(ScEnd) && "Invalid scev range.");
-        Value *End = Exp.expandCodeFor(ScEnd, PtrArithTy, Loc);
-        Starts.push_back(Start);
-        Ends.push_back(End);
-      }
-    }
-
-    for (unsigned i=0; i < NumPointers; ++i) {
-      for (unsigned j=i+1; j < NumPointers; ++j) {
-        Value *Cmp0 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
-                                      Starts[0], Ends[1], "bound0", Loc);
-        Value *Cmp1 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
-                                      Starts[1], Ends[0], "bound1", Loc);
-        Value *IsConflict = BinaryOperator::Create(Instruction::And, Cmp0, Cmp