Remove LoopIndexSplit pass. It is neither maintained nor used by anyone.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116004 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 1270 deletions

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
deleted file mode 100644
index f091a94bdd..0000000000
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ /dev/null
@@ -1,1270 +0,0 @@
-//===- LoopIndexSplit.cpp - Loop Index Splitting Pass ---------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements Loop Index Splitting Pass. This pass handles three
-// kinds of loops.
-//
-// [1] A loop may be eliminated if the body is executed exactly once.
-//     For example,
-//
-// for (i = 0; i < N; ++i) {
-//   if (i == X) {
-//     body;
-//   }
-// }
-//
-// is transformed to
-//
-// i = X;
-// body;
-//
-// [2] A loop's iteration space may be shrunk if the loop body is executed
-//     for a proper sub-range of the loop's iteration space. For example,
-//
-// for (i = 0; i < N; ++i) {
-//   if (i > A && i < B) {
-//     ...
-//   }
-// }
-//
-// is transformed to iterators from A to B, if A > 0 and B < N.
-//
-// [3] A loop may be split if the loop body is dominated by a branch.
-//     For example,
-//
-// for (i = LB; i < UB; ++i) { if (i < SV) A; else B; }
-//
-// is transformed into
-//
-// AEV = BSV = SV
-// for (i = LB; i < min(UB, AEV); ++i)
-//    A;
-// for (i = max(LB, BSV); i < UB; ++i);
-//    B;
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "loop-index-split"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Analysis/ScalarEvolution.h"
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Cloning.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/Statistic.h"
-
-using namespace llvm;
-
-STATISTIC(NumIndexSplit, "Number of loop index split");
-STATISTIC(NumIndexSplitRemoved, "Number of loops eliminated by loop index split");
-STATISTIC(NumRestrictBounds, "Number of loop iteration space restricted");
-
-namespace {
-
-  class LoopIndexSplit : public LoopPass {
-  public:
-    static char ID; // Pass ID, replacement for typeid
-    LoopIndexSplit() : LoopPass(ID) {}
-
-    // Index split Loop L. Return true if loop is split.
-    bool runOnLoop(Loop *L, LPPassManager &LPM);
-
-    void getAnalysisUsage(AnalysisUsage &AU) const {
-      AU.addPreserved<ScalarEvolution>();
-      AU.addRequiredID(LCSSAID);
-      AU.addPreservedID(LCSSAID);
-      AU.addRequired<LoopInfo>();
-      AU.addPreserved<LoopInfo>();
-      AU.addRequiredID(LoopSimplifyID);
-      AU.addPreservedID(LoopSimplifyID);
-      AU.addRequired<DominatorTree>();
-      AU.addRequired<DominanceFrontier>();
-      AU.addPreserved<DominatorTree>();
-      AU.addPreserved<DominanceFrontier>();
-    }
-
-  private:
-    /// processOneIterationLoop -- Eliminate loop if loop body is executed 
-    /// only once. For example,
-    /// for (i = 0; i < N; ++i) {
-    ///   if ( i == X) {
-    ///     ...
-    ///   }
-    /// }
-    ///
-    bool processOneIterationLoop();
-
-    // -- Routines used by updateLoopIterationSpace();
-
-    /// updateLoopIterationSpace -- Update loop's iteration space if loop 
-    /// body is executed for certain IV range only. For example,
-    /// 
-    /// for (i = 0; i < N; ++i) {
-    ///   if ( i > A && i < B) {
-    ///     ...
-    ///   }
-    /// }
-    /// is transformed to iterators from A to B, if A > 0 and B < N.
-    ///
-    bool updateLoopIterationSpace();
-
-    /// restrictLoopBound - Op dominates loop body. Op compares an IV based value
-    /// with a loop invariant value. Update loop's lower and upper bound based on
-    /// the loop invariant value.
-    bool restrictLoopBound(ICmpInst &Op);
-
-    // --- Routines used by splitLoop(). --- /
-
-    bool splitLoop();
-
-    /// removeBlocks - Remove basic block DeadBB and all blocks dominated by 
-    /// DeadBB. This routine is used to remove split condition's dead branch, 
-    /// dominated by DeadBB. LiveBB dominates split conidition's other branch.
-    void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
-    
-    /// moveExitCondition - Move exit condition EC into split condition block.
-    void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
-                           BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
-                           PHINode *IV, Instruction *IVAdd, Loop *LP,
-                           unsigned);
-    
-    /// updatePHINodes - CFG has been changed. 
-    /// Before 
-    ///   - ExitBB's single predecessor was Latch
-    ///   - Latch's second successor was Header
-    /// Now
-    ///   - ExitBB's single predecessor was Header
-    ///   - Latch's one and only successor was Header
-    ///
-    /// Update ExitBB PHINodes' to reflect this change.
-    void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, 
-                        BasicBlock *Header,
-                        PHINode *IV, Instruction *IVIncrement, Loop *LP);
-
-    // --- Utility routines --- /
-
-    /// cleanBlock - A block is considered clean if all non terminal 
-    /// instructions are either PHINodes or IV based values.
-    bool cleanBlock(BasicBlock *BB);
-
-    /// IVisLT - If Op is comparing IV based value with an loop invariant and 
-    /// IV based value is less than  the loop invariant then return the loop 
-    /// invariant. Otherwise return NULL.
-    Value * IVisLT(ICmpInst &Op);
-
-    /// IVisLE - If Op is comparing IV based value with an loop invariant and 
-    /// IV based value is less than or equal to the loop invariant then 
-    /// return the loop invariant. Otherwise return NULL.
-    Value * IVisLE(ICmpInst &Op);
-
-    /// IVisGT - If Op is comparing IV based value with an loop invariant and 
-    /// IV based value is greater than  the loop invariant then return the loop 
-    /// invariant. Otherwise return NULL.
-    Value * IVisGT(ICmpInst &Op);
-
-    /// IVisGE - If Op is comparing IV based value with an loop invariant and 
-    /// IV based value is greater than or equal to the loop invariant then 
-    /// return the loop invariant. Otherwise return NULL.
-    Value * IVisGE(ICmpInst &Op);
-
-  private:
-
-    // Current Loop information.
-    Loop *L;
-    LPPassManager *LPM;
-    LoopInfo *LI;
-    DominatorTree *DT;
-    DominanceFrontier *DF;
-
-    PHINode *IndVar;
-    ICmpInst *ExitCondition;
-    ICmpInst *SplitCondition;
-    Value *IVStartValue;
-    Value *IVExitValue;
-    Instruction *IVIncrement;
-    SmallPtrSet<Value *, 4> IVBasedValues;
-  };
-}
-
-char LoopIndexSplit::ID = 0;
-INITIALIZE_PASS(LoopIndexSplit, "loop-index-split",
-                "Index Split Loops", false, false)
-
-Pass *llvm::createLoopIndexSplitPass() {
-  return new LoopIndexSplit();
-}
-
-// Index split Loop L. Return true if loop is split.
-bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
-  L = IncomingLoop;
-  LPM = &LPM_Ref;
-
-  // If LoopSimplify form is not available, stay out of trouble.
-  if (!L->isLoopSimplifyForm())
-    return false;
-
-  // FIXME - Nested loops make dominator info updates tricky. 
-  if (!L->getSubLoops().empty())
-    return false;
-
-  DT = &getAnalysis<DominatorTree>();
-  LI = &getAnalysis<LoopInfo>();
-  DF = &getAnalysis<DominanceFrontier>();
-
-  // Initialize loop data.
-  IndVar = L->getCanonicalInductionVariable();
-  if (!IndVar) return false;
-
-  bool P1InLoop = L->contains(IndVar->getIncomingBlock(1));
-  IVStartValue = IndVar->getIncomingValue(!P1InLoop);
-  IVIncrement = dyn_cast<Instruction>(IndVar->getIncomingValue(P1InLoop));
-  if (!IVIncrement) return false;
-  
-  IVBasedValues.clear();
-  IVBasedValues.insert(IndVar);
-  IVBasedValues.insert(IVIncrement);
-  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
-       I != E; ++I) 
-    for(BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end(); 
-        BI != BE; ++BI) {
-      if (BinaryOperator *BO = dyn_cast<BinaryOperator>(BI)) 
-        if (BO != IVIncrement 
-            && (BO->getOpcode() == Instruction::Add
-                || BO->getOpcode() == Instruction::Sub))
-          if (IVBasedValues.count(BO->getOperand(0))
-              && L->isLoopInvariant(BO->getOperand(1)))
-            IVBasedValues.insert(BO);
-    }
-
-  // Reject loop if loop exit condition is not suitable.
-  BasicBlock *ExitingBlock = L->getExitingBlock();
-  if (!ExitingBlock)
-    return false;
-  BranchInst *EBR = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
-  if (!EBR) return false;
-  ExitCondition = dyn_cast<ICmpInst>(EBR->getCondition());
-  if (!ExitCondition) return false;
-  if (ExitingBlock != L->getLoopLatch()) return false;
-  IVExitValue = ExitCondition->getOperand(1);
-  if (!L->isLoopInvariant(IVExitValue))
-    IVExitValue = ExitCondition->getOperand(0);
-  if (!L->isLoopInvariant(IVExitValue))
-    return false;
-  if (!IVBasedValues.count(
-        ExitCondition->getOperand(IVExitValue == ExitCondition->getOperand(0))))
-    return false;
-
-  // If start value is more then exit value where induction variable
-  // increments by 1 then we are potentially dealing with an infinite loop.
-  // Do not index split this loop.
-  if (ConstantInt *SV = dyn_cast<ConstantInt>(IVStartValue))
-    if (ConstantInt *EV = dyn_cast<ConstantInt>(IVExitValue))
-      if (SV->getSExtValue() > EV->getSExtValue())
-        return false;
-
-  if (processOneIterationLoop())
-    return true;
-
-  if (updateLoopIterationSpace())
-    return true;
-
-  if (splitLoop())
-    return true;
-
-  return false;
-}
-
-// --- Helper routines --- 
-// isUsedOutsideLoop - Returns true iff V is used outside the loop L.
-static bool isUsedOutsideLoop(Value *V, Loop *L) {
-  for(Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
-    if (!L->contains(cast<Instruction>(*UI)))
-      return true;
-  return false;
-}
-
-// Return V+1
-static Value *getPlusOne(Value *V, bool Sign, Instruction *InsertPt, 
-                         LLVMContext &Context) {
-  Constant *One = ConstantInt::get(V->getType(), 1, Sign);
-  return BinaryOperator::CreateAdd(V, One, "lsp", InsertPt);
-}
-
-// Return V-1
-static Value *getMinusOne(Value *V, bool Sign, Instruction *InsertPt,
-                          LLVMContext &Context) {
-  Constant *One = ConstantInt::get(V->getType(), 1, Sign);
-  return BinaryOperator::CreateSub(V, One, "lsp", InsertPt);
-}
-
-// Return min(V1, V1)
-static Value *getMin(Value *V1, Value *V2, bool Sign, Instruction *InsertPt) {
- 
-  Value *C = new ICmpInst(InsertPt,
-                          Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
-                          V1, V2, "lsp");
-  return SelectInst::Create(C, V1, V2, "lsp", InsertPt);
-}
-
-// Return max(V1, V2)
-static Value *getMax(Value *V1, Value *V2, bool Sign, Instruction *InsertPt) {
- 
-  Value *C = new ICmpInst(InsertPt, 
-                          Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
-                          V1, V2, "lsp");
-  return SelectInst::Create(C, V2, V1, "lsp", InsertPt);
-}
-
-/// processOneIterationLoop -- Eliminate loop if loop body is executed 
-/// only once. For example,
-/// for (i = 0; i < N; ++i) {
-///   if ( i == X) {
-///     ...
-///   }
-/// }
-///
-bool LoopIndexSplit::processOneIterationLoop() {
-  SplitCondition = NULL;
-  BasicBlock *Latch = L->getLoopLatch();
-  BasicBlock *Header = L->getHeader();
-  BranchInst *BR = dyn_cast<BranchInst>(Header->getTerminator());
-  if (!BR) return false;
-  if (!isa<BranchInst>(Latch->getTerminator())) return false;
-  if (BR->isUnconditional()) return false;
-  SplitCondition = dyn_cast<ICmpInst>(BR->getCondition());
-  if (!SplitCondition) return false;
-  if (SplitCondition == ExitCondition) return false;
-  if (SplitCondition->getPredicate() != ICmpInst::ICMP_EQ) return false;
-  if (BR->getOperand(1) != Latch) return false;
-  if (!IVBasedValues.count(SplitCondition->getOperand(0))
-      && !IVBasedValues.count(SplitCondition->getOperand(1)))
-    return false;
-
-  // If IV is used outside the loop then this loop traversal is required.
-  // FIXME: Calculate and use last IV value. 
-  if (isUsedOutsideLoop(IVIncrement, L))
-    return false;
-
-  // If BR operands are not IV or not loop invariants then skip this loop.
-  Value *OPV = SplitCondition->getOperand(0);
-  Value *SplitValue = SplitCondition->getOperand(1);
-  if (!L->isLoopInvariant(SplitValue))
-    std::swap(OPV, SplitValue);
-  if (!L->isLoopInvariant(SplitValue))
-    return false;
-  Instruction *OPI = dyn_cast<Instruction>(OPV);
-  if (!OPI) 
-    return false;
-  if (OPI->getParent() != Header || isUsedOutsideLoop(OPI, L))
-    return false;
-  Value *StartValue = IVStartValue;
-  Value *ExitValue = IVExitValue;;
-
-  if (OPV != IndVar) {
-    // If BR operand is IV based then use this operand to calculate
-    // effective conditions for loop body.
-    BinaryOperator *BOPV = dyn_cast<BinaryOperator>(OPV);
-    if (!BOPV) 
-      return false;
-    if (BOPV->getOpcode() != Instruction::Add) 
-      return false;
-    StartValue = BinaryOperator::CreateAdd(OPV, StartValue, "" , BR);
-    ExitValue = BinaryOperator::CreateAdd(OPV, ExitValue, "" , BR);
-  }
-
-  if (!cleanBlock(Header))
-    return false;
-
-  if (!cleanBlock(Latch))
-    return false;
-    
-  // If the merge point for BR is not loop latch then skip this loop.
-  if (BR->getSuccessor(0) != Latch) {
-    DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
-    assert (DF0 != DF->end() && "Unable to find dominance frontier");
-    if (!DF0->second.count(Latch))
-      return false;
-  }
-  
-  if (BR->getSuccessor(1) != Latch) {
-    DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
-    assert (DF1 != DF->end() && "Unable to find dominance frontier");
-    if (!DF1->second.count(Latch))
-      return false;
-  }
-    
-  // Now, Current loop L contains compare instruction
-  // that compares induction variable, IndVar, against loop invariant. And
-  // entire (i.e. meaningful) loop body is dominated by this compare
-  // instruction. In such case eliminate 
-  // loop structure surrounding this loop body. For example,
-  //     for (int i = start; i < end; ++i) {
-  //         if ( i == somevalue) {
-  //           loop_body
-  //         }
-  //     }
-  // can be transformed into
-  //     if (somevalue >= start && somevalue < end) {
-  //        i = somevalue;
-  //        loop_body
-  //     }
-
-  // Replace index variable with split value in loop body. Loop body is executed
-  // only when index variable is equal to split value.
-  IndVar->replaceAllUsesWith(SplitValue);
-
-  // Replace split condition in header.
-  // Transform 
-  //      SplitCondition : icmp eq i32 IndVar, SplitValue
-  // into
-  //      c1 = icmp uge i32 SplitValue, StartValue
-  //      c2 = icmp ult i32 SplitValue, ExitValue
-  //      and i32 c1, c2 
-  Instruction *C1 = new ICmpInst(BR, ExitCondition->isSigned() ? 
-                                 ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
-                                 SplitValue, StartValue, "lisplit");
-
-  CmpInst::Predicate C2P  = ExitCondition->getPredicate();
-  BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
-  if (LatchBR->getOperand(1) != Header)
-    C2P = CmpInst::getInversePredicate(C2P);
-  Instruction *C2 = new ICmpInst(BR, C2P, SplitValue, ExitValue, "lisplit");
-  Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit", BR);
-
-  SplitCondition->replaceAllUsesWith(NSplitCond);
-  SplitCondition->eraseFromParent();
-
-  // Remove Latch to Header edge.
-  BasicBlock *LatchSucc = NULL;
-  Header->removePredecessor(Latch);
-  for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
-       SI != E; ++SI) {
-    if (Header != *SI)
-      LatchSucc = *SI;
-  }
-
-  // Clean up latch block.
-  Value *LatchBRCond = LatchBR->getCondition();
-  LatchBR->setUnconditionalDest(LatchSucc);
-  RecursivelyDeleteTriviallyDeadInstructions(LatchBRCond);
-  
-  LPM->deleteLoopFromQueue(L);
-
-  // Update Dominator Info.
-  // Only CFG change done is to remove Latch to Header edge. This
-  // does not change dominator tree because Latch did not dominate
-  // Header.
-  if (DF) {
-    DominanceFrontier::iterator HeaderDF = DF->find(Header);
-    if (HeaderDF != DF->end()) 
-      DF->removeFromFrontier(HeaderDF, Header);
-
-    DominanceFrontier::iterator LatchDF = DF->find(Latch);
-    if (LatchDF != DF->end()) 
-      DF->removeFromFrontier(LatchDF, Header);
-  }
-
-  ++NumIndexSplitRemoved;
-  return true;
-}
-
-/// restrictLoopBound - Op dominates loop body. Op compares an IV based value 
-/// with a loop invariant value. Update loop's lower and upper bound based on 
-/// the loop invariant value.
-bool LoopIndexSplit::restrictLoopBound(ICmpInst &Op) {
-  bool Sign = Op.isSigned();
-  Instruction *PHTerm = L->getLoopPreheader()->getTerminator();
-
-  if (IVisGT(*ExitCondition) || IVisGE(*ExitCondition)) {
-    BranchInst *EBR = 
-      cast<BranchInst>(ExitCondition->getParent()->getTerminator());
-    ExitCondition->setPredicate(ExitCondition->getInversePredicate());
-    BasicBlock *T = EBR->getSuccessor(0);
-    EBR->setSuccessor(0, EBR->getSuccessor(1));
-    EBR->setSuccessor(1, T);
-  }
-
-  LLVMContext &Context = Op.getContext();
-
-  // New upper and lower bounds.
-  Value *NLB = NULL;
-  Value *NUB = NULL;
-  if (Value *V = IVisLT(Op)) {
-    // Restrict upper bound.
-    if (IVisLE(*ExitCondition)) 
-      V = getMinusOne(V, Sign, PHTerm, Context);
-    NUB = getMin(V, IVExitValue, Sign, PHTerm);
-  } else if (Value *V = IVisLE(Op)) {
-    // Restrict upper bound.
-    if (IVisLT(*ExitCondition)) 
-      V = getPlusOne(V, Sign, PHTerm, Context);
-    NUB = getMin(V, IVExitValue, Sign, PHTerm);
-  } else if (Value *V = IVisGT(Op)) {
-    // Restrict lower bound.
-    V = getPlusOne(V, Sign, PHTerm, Context);
-    NLB = getMax(V, IVStartValue, Sign, PHTerm);
-  } else if (Value *V = IVisGE(Op))
-    // Restrict lower bound.
-    NLB = getMax(V, IVStartValue, Sign, PHTerm);
-
-  if (!NLB && !NUB) 
-    return false;
-
-  if (NLB) {
-    unsigned i = IndVar->getBasicBlockIndex(L->getLoopPreheader());
-    IndVar->setIncomingValue(i, NLB);
-  }
-
-  if (NUB) {
-    unsigned i = (ExitCondition->getOperand(0) != IVExitValue);
-    ExitCondition->setOperand(i, NUB);
-  }
-  return true;
-}
-
-/// updateLoopIterationSpace -- Update loop's iteration space if loop 
-/// body is executed for certain IV range only. For example,
-/// 
-/// for (i = 0; i < N; ++i) {
-///   if ( i > A && i < B) {
-///     ...
-///   }
-/// }
-/// is transformed to iterators from A to B, if A > 0 and B < N.
-///
-bool LoopIndexSplit::updateLoopIterationSpace() {
-  SplitCondition = NULL;
-  if (ExitCondition->getPredicate() == ICmpInst::ICMP_NE
-      || ExitCondition->getPredicate() == ICmpInst::ICMP_EQ)
-    return false;
-  BasicBlock *Latch = L->getLoopLatch();
-  BasicBlock *Header = L->getHeader();
-  BranchInst *BR = dyn_cast<BranchInst>(Header->getTerminator());
-  if (!BR) return false;
-  if (!isa<BranchInst>(Latch->getTerminator())) return false;
-  if (BR->isUnconditional()) return false;
-  BinaryOperator *AND = dyn_cast<BinaryOperator>(BR->getCondition());
-  if (!AND) return false;
-  if (AND->getOpcode() != Instruction::And) return false;
-  ICmpInst *Op0 = dyn_cast<ICmpInst>(AND->getOperand(0));
-  ICmpInst *Op1 = dyn_cast<ICmpInst>(AND->getOperand(1));
-  if (!Op0 || !Op1)
-    return false;
-  IVBasedValues.insert(AND);
-  IVBasedValues.insert(Op0);
-  IVBasedValues.insert(Op1);
-  if (!cleanBlock(Header)) return false;
-  BasicBlock *ExitingBlock = ExitCondition->getParent();
-  if (!cleanBlock(ExitingBlock)) return false;
-
-  // If the merge point for BR is not loop latch then skip this loop.
-  if (BR->getSuccessor(0) != Latch) {
-    DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
-    assert (DF0 != DF->end() && "Unable to find dominance frontier");
-    if (!DF0->second.count(Latch))
-      return false;
-  }
-  
-  if (BR->getSuccessor(1) != Latch) {
-    DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
-    assert (DF1 != DF->end() && "Unable to find dominance frontier");
-    if (!DF1->second.count(Latch))
-      return false;
-  }
-    
-  // Verify that loop exiting block has only two predecessor, where one pred
-  // is split condition block. The other predecessor will become exiting block's
-  // dominator after CFG is updated. TODO : Handle CFG's where exiting block has
-  // more then two predecessors. This requires extra work in updating dominator
-  // information.
-  BasicBlock *ExitingBBPred = NULL;
-  for (pred_iterator PI = pred_begin(ExitingBlock), PE = pred_end(ExitingBlock);
-       PI != PE; ++PI) {
-    BasicBlock *BB = *PI;
-    if (Header == BB)
-      continue;
-    if (ExitingBBPred)
-      return false;
-    else
-      ExitingBBPred = BB;
-  }
-
-  if (!restrictLoopBound(*Op0))
-    return false;
-
-  if (!restrictLoopBound(*Op1))
-    return false;
-
-  // Update CFG.
-  if (BR->getSuccessor(0) == ExitingBlock)
-    BR->setUnconditionalDest(BR->getSuccessor(1));
-  else
-    BR->setUnconditionalDest(BR->getSuccessor(0));
-
-  AND->eraseFromParent();
-  if (Op0->use_empty())
-    Op0->eraseFromParent();
-  if (Op1->use_empty())
-    Op1->eraseFromParent();
-
-  // Update dominator info. Now, ExitingBlock has only one predecessor, 
-  // ExitingBBPred, and it is ExitingBlock's immediate dominator.
-  DT->changeImmediateDominator(ExitingBlock, ExitingBBPred);
-
-  BasicBlock *ExitBlock = ExitingBlock->getTerminator()->getSuccessor(1);
-  if (L->contains(ExitBlock))
-    ExitBlock = ExitingBlock->getTerminator()->getSuccessor(0);
-
-  // If ExitingBlock is a member of the loop basic blocks' DF list then
-  // replace ExitingBlock with header and exit block in the DF list
-  DominanceFrontier::iterator ExitingBlockDF = DF->find(ExitingBlock);
-  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
-       I != E; ++I) {
-    BasicBlock *BB = *I;
-    if (BB == Header || BB == ExitingBlock)
-      continue;
-    DominanceFrontier::iterator BBDF = DF->find(BB);
-    DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
-    DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
-    while (DomSetI != DomSetE) {
-      DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
-      ++DomSetI;
-      BasicBlock *DFBB = *CurrentItr;
-      if (DFBB == ExitingBlock) {
-        BBDF->second.erase(DFBB);
-        for (DominanceFrontier::DomSetType::iterator 
-               EBI = ExitingBlockDF->second.begin(),
-               EBE = ExitingBlockDF->second.end(); EBI != EBE; ++EBI) 
-          BBDF->second.insert(*EBI);
-      }
-    }
-  }
-  ++NumRestrictBounds;
-  return true;
-}
-
-/// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
-/// This routine is used to remove split condition's dead branch, dominated by
-/// DeadBB. LiveBB dominates split conidition's other branch.
-void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP, 
-                                  BasicBlock *LiveBB) {
-
-  // First update DeadBB's dominance frontier. 
-  SmallVector<BasicBlock *, 8> FrontierBBs;
-  DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB);
-  if (DeadBBDF != DF->end()) {
-    SmallVector<BasicBlock *, 8> PredBlocks;
-    
-    DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second;
-    for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
-           DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) 
-      {
-      BasicBlock *FrontierBB = *DeadBBSetI;
-      FrontierBBs.push_back(FrontierBB);
-
-      // Rremove any PHI incoming edge from blocks dominated by DeadBB.
-      PredBlocks.clear();
-      for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB);
-          PI != PE; ++PI) {
-        BasicBlock *P = *PI;
-        if (DT->dominates(DeadBB, P))
-          PredBlocks.push_back(P);
-      }
-
-      for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end();
-          FBI != FBE; ++FBI) {
-        if (PHINode *PN = dyn_cast<PHINode>(FBI)) {
-          for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(),
-                PE = PredBlocks.end(); PI != PE; ++PI) {
-            BasicBlock *P = *PI;
-            PN->removeIncomingValue(P);
-          }
-        }
-        else
-          break;
-      }      
-    }
-  }
-  
-  // Now remove DeadBB and all nodes dominated by DeadBB in df order.
-  SmallVector<BasicBlock *, 32> WorkList;
-  DomTreeNode *DN = DT->getNode(DeadBB);
-  for (df_iterator<DomTreeNode*> DI = df_begin(DN),
-         E = df_end(DN); DI != E; ++DI) {
-    BasicBlock *BB = DI->getBlock();
-    WorkList.push_back(BB);
-    BB->replaceAllUsesWith(UndefValue::get(
-                                       Type::getLabelTy(DeadBB->getContext())));
-  }
-
-  while (!WorkList.empty()) {
-    BasicBlock *BB = WorkList.pop_back_val();
-    LPM->deleteSimpleAnalysisValue(BB, LP);
-    for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end(); 
-        BBI != BBE; ) {
-      Instruction *I = BBI;
-      ++BBI;
-      I->replaceAllUsesWith(UndefValue::get(I->getType()));
-      LPM->deleteSimpleAnalysisValue(I, LP);
-      I->eraseFromParent();
-    }
-    DT->eraseNode(BB);
-    DF->removeBlock(BB);
-    LI->removeBlock(BB);
-    BB->eraseFromParent();
-  }
-
-  // Update Frontier BBs' dominator info.
-  while (!FrontierBBs.empty()) {
-    BasicBlock *FBB = FrontierBBs.pop_back_val();
-    BasicBlock *NewDominator = FBB->getSinglePredecessor();
-    if (!NewDominator) {
-      pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
-      NewDominator = *PI;
-      ++PI;
-      if (NewDominator != LiveBB) {
-        for(; PI != PE; ++PI) {
-          BasicBlock *P = *PI;
-          if (P == LiveBB) {
-            NewDominator = LiveBB;
-            break;
-          }
-          NewDominator = DT->findNearestCommonDominator(NewDominator, P);
-        }
-      }
-    }
-    assert (NewDominator && "Unable to fix dominator info.");
-    DT->changeImmediateDominator(FBB, NewDominator);
-    DF->changeImmediateDominator(FBB, NewDominator, DT);
-  }
-
-}
-
-// moveExitCondition - Move exit condition EC into split condition block CondBB.
-void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
-                                       BasicBlock *ExitBB, ICmpInst *EC, 
-                                       ICmpInst *SC, PHINode *IV, 
-                                       Instruction *IVAdd, Loop *LP,
-                                       unsigned ExitValueNum) {
-
-  BasicBlock *ExitingBB = EC->getParent();
-  Instruction *CurrentBR = CondBB->getTerminator();
-
-  // Move exit condition into split condition block.
-  EC->moveBefore(CurrentBR);
-  EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV);
-
-  // Move exiting block's branch into split condition block. Update its branch
-  // destination.
-  BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
-  ExitingBR->moveBefore(CurrentBR);
-  BasicBlock *OrigDestBB = NULL;
-  if (ExitingBR->getSuccessor(0) == ExitBB) {
-    OrigDestBB = ExitingBR->getSuccessor(1);
-    ExitingBR->setSuccessor(1, ActiveBB);
-  }
-  else {
-    OrigDestBB = ExitingBR->getSuccessor(0);
-    ExitingBR->setSuccessor(0, ActiveBB);
-  }
-    
-  // Remove split condition and current split condition branch.
-  SC->eraseFromParent();
-  CurrentBR->eraseFromParent();
-
-  // Connect exiting block to original destination.
-  BranchInst::Create(OrigDestBB, ExitingBB);
-
-  // Update PHINodes
-  updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
-
-  // Fix dominator info.
-  // ExitBB is now dominated by CondBB
-  DT->changeImmediateDominator(ExitBB, CondBB);
-  DF->changeImmediateDominator(ExitBB, CondBB, DT);
-
-  // Blocks outside the loop may have been in the dominance frontier of blocks
-  // inside the condition; this is now impossible because the blocks inside the
-  // condition no loger dominate the exit.  Remove the relevant blocks from
-  // the dominance frontiers.
-  for (Loop::block_iterator I = LP->block_begin(), E = LP->block_end();
-       I != E; ++I) {
-    if (!DT->properlyDominates(CondBB, *I)) continue;
-    DominanceFrontier::iterator BBDF = DF->find(*I);
-    DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
-    DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
-    while (DomSetI != DomSetE) {
-      DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
-      ++DomSetI;
-      BasicBlock *DFBB = *CurrentItr;
-      if (!LP->contains(DFBB))
-        BBDF->second.erase(DFBB);
-    }
-  }
-}
-
-/// updatePHINodes - CFG has been changed. 
-/// Before 
-///   - ExitBB's single predecessor was Latch
-///   - Latch's second successor was Header
-/// Now
-///   - ExitBB's single predecessor is Header
-///   - Latch's one and only successor is Header
-///
-/// Update ExitBB PHINodes' to reflect this change.
-void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, 
-                                    BasicBlock *Header,
-                                    PHINode *IV, Instruction *IVIncrement,
-                                    Loop *LP) {
-
-  for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end(); 
-       BI != BE; ) {
-    PHINode *PN = dyn_cast<PHINode>(BI);
-    ++BI;
-    if (!PN)
-      break;
-
-    Value *V = PN->getIncomingValueForBlock(Latch);
-    if (PHINode *PHV = dyn_cast<PHINode>(V)) {
-      // PHV is in Latch. PHV has one use is in ExitBB PHINode. And one use
-      // in Header which is new incoming value for PN.
-      Value *NewV = NULL;
-      for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end(); 
-           UI != E; ++UI) 
-        if (PHINode *U = dyn_cast<PHINode>(*UI)) 
-          if (LP->contains(U)) {
-            NewV = U;
-            break;
-          }
-
-      // Add incoming value from header only if PN has any use inside the loop.
-      if (NewV)
-        PN->addIncoming(NewV, Header);
-
-    } else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
-      // If this instruction is IVIncrement then IV is new incoming value 
-      // from header otherwise this instruction must be incoming value from 
-      // header because loop is in LCSSA form.
-      if (PHI == IVIncrement)
-        PN->addIncoming(IV, Header);
-      else
-        PN->addIncoming(V, Header);
-    } else
-      // Otherwise this is an incoming value from header because loop is in 
-      // LCSSA form.
-      PN->addIncoming(V, Header);
-    
-    // Remove incoming value from Latch.
-    PN->removeIncomingValue(Latch);
-  }
-}
-
-bool LoopIndexSplit::splitLoop() {
-  SplitCondition = NULL;
-  if (ExitCondition->getPredicate() == ICmpInst::ICMP_NE
-      || ExitCondition->getPredicate() == ICmpInst::ICMP_EQ)
-    return false;
-  BasicBlock *Header = L->getHeader();
-  BasicBlock *Latch = L->getLoopLatch();
-  BranchInst *SBR = NULL; // Split Condition Branch
-  BranchInst *EBR = cast<BranchInst>(ExitCondition->getParent()->getTerminator());
-  // If Exiting block includes loop variant instructions then this
-  // loop may not be split safely.
-  BasicBlock *ExitingBlock = ExitCondition->getParent();
-  if (!cleanBlock(ExitingBlock)) return false;
-
-  LLVMContext &Context = Header->getContext();
-
-  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
-       I != E; ++I) {
-    BranchInst *BR = dyn_cast<BranchInst>((*I)->getTerminator());
-    if (!BR || BR->isUnconditional()) continue;
-    ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
-    if (!CI || CI == ExitCondition 
-        || CI->getPredicate() == ICmpInst::ICMP_NE
-        || CI->getPredicate() == ICmpInst::ICMP_EQ)
-      continue;
-
-    // Unable to handle triangle loops at the moment.
-    // In triangle loop, split condition is in header and one of the
-    // the split destination is loop latch. If split condition is EQ
-    // then such loops are already handle in processOneIterationLoop().
-    if (Header == (*I)
-        && (Latch == BR->getSuccessor(0) || Latch == BR->getSuccessor(1)))
-      continue;
-
-    // If the block does not dominate the latch then this is not a diamond.
-    // Such loop may not benefit from index split.
-    if (!DT->dominates((*I), Latch))
-      continue;
-
-    // If split condition branches heads do not have single predecessor, 
-    // SplitCondBlock, then is not possible to remove inactive branch.
-    if (!BR->getSuccessor(0)->getSinglePredecessor() 
-        || !BR->getSuccessor(1)->getSinglePredecessor())
-      return false;
-
-    // If the merge point for BR is not loop latch then skip this condition.
-    if (BR->getSuccessor(0) != Latch) {
-      DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
-      assert (DF0 != DF->end() && "Unable to find dominance frontier");
-      if (!DF0->second.count(Latch))
-        continue;
-    }
-    
-    if (BR->getSuccessor(1) != Latch) {
-      DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
-      assert (DF1 != DF->end() && "Unable to find dominance frontier");
-      if (!DF1->second.count(Latch))
-        continue;
-    }
-    SplitCondition = CI;
-    SBR = BR;
-    break;
-  }
-   
-  if (!SplitCondition)
-    return false;
-
-  // If the predicate sign does not match then skip.
-  if (ExitCondition->isSigned() != SplitCondition->isSigned())
-    return false;
-
-  unsigned EVOpNum = (ExitCondition->getOperand(1) == IVExitValue);
-  unsigned SVOpNum = IVBasedValues.count(SplitCondition->getOperand(0));
-  Value *SplitValue = SplitCondition->getOperand(SVOpNum);
-  if (!L->isLoopInvariant(SplitValue))
-    return false;
-  if (!IVBasedValues.count(SplitCondition->getOperand(!SVOpNum)))
-    return false;
-
-