text: //===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This pass munges the code in the input function to better prepare it for
  // SelectionDAG-based code generation. This works around limitations in it's
  // basic-block-at-a-time approach. It should eventually be removed.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/CodeGen/Passes.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/SmallSet.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/Analysis/InstructionSimplify.h"
  #include "llvm/Analysis/TargetTransformInfo.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Dominators.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GetElementPtrTypeIterator.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/InlineAsm.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/MDBuilder.h"
  #include "llvm/IR/PatternMatch.h"
  #include "llvm/IR/ValueHandle.h"
  #include "llvm/IR/ValueMap.h"
  #include "llvm/Pass.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Target/TargetLibraryInfo.h"
  #include "llvm/Target/TargetLowering.h"
  #include "llvm/Target/TargetSubtargetInfo.h"
  #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  #include "llvm/Transforms/Utils/BuildLibCalls.h"
  #include "llvm/Transforms/Utils/BypassSlowDivision.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
  using namespace llvm;
  using namespace llvm::PatternMatch;
  
  #define DEBUG_TYPE "codegenprepare"
  
  STATISTIC(NumBlocksElim, "Number of blocks eliminated");
  STATISTIC(NumPHIsElim,   "Number of trivial PHIs eliminated");
  STATISTIC(NumGEPsElim,   "Number of GEPs converted to casts");
  STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
                        "sunken Cmps");
  STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
                         "of sunken Casts");
  STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
                            "computations were sunk");
  STATISTIC(NumExtsMoved,  "Number of [s|z]ext instructions combined with loads");
  STATISTIC(NumExtUses,    "Number of uses of [s|z]ext instructions optimized");
  STATISTIC(NumRetsDup,    "Number of return instructions duplicated");
  STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
  STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
  STATISTIC(NumAndCmpsMoved, "Number of and/cmp's pushed into branches");
  STATISTIC(NumStoreExtractExposed, "Number of store(extractelement) exposed");
  
  static cl::opt<bool> DisableBranchOpts(
    "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
    cl::desc("Disable branch optimizations in CodeGenPrepare"));
  
  static cl::opt<bool> DisableSelectToBranch(
    "disable-cgp-select2branch", cl::Hidden, cl::init(false),
    cl::desc("Disable select to branch conversion."));
  
  static cl::opt<bool> AddrSinkUsingGEPs(
    "addr-sink-using-gep", cl::Hidden, cl::init(false),
    cl::desc("Address sinking in CGP using GEPs."));
  
  static cl::opt<bool> EnableAndCmpSinking(
     "enable-andcmp-sinking", cl::Hidden, cl::init(true),
     cl::desc("Enable sinkinig and/cmp into branches."));
  
  static cl::opt<bool> DisableStoreExtract(
      "disable-cgp-store-extract", cl::Hidden, cl::init(false),
      cl::desc("Disable store(extract) optimizations in CodeGenPrepare"));
  
  static cl::opt<bool> StressStoreExtract(
      "stress-cgp-store-extract", cl::Hidden, cl::init(false),
      cl::desc("Stress test store(extract) optimizations in CodeGenPrepare"));
  
  static cl::opt<bool> DisableExtLdPromotion(
      "disable-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
      cl::desc("Disable ext(promotable(ld)) -> promoted(ext(ld)) optimization in "
               "CodeGenPrepare"));
  
  static cl::opt<bool> StressExtLdPromotion(
      "stress-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
      cl::desc("Stress test ext(promotable(ld)) -> promoted(ext(ld)) "
               "optimization in CodeGenPrepare"));
  
  namespace {
  typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
  struct TypeIsSExt {
    Type *Ty;
    bool IsSExt;
    TypeIsSExt(Type *Ty, bool IsSExt) : Ty(Ty), IsSExt(IsSExt) {}
  };
  typedef DenseMap<Instruction *, TypeIsSExt> InstrToOrigTy;
  class TypePromotionTransaction;
  
    class CodeGenPrepare : public FunctionPass {
      /// TLI - Keep a pointer of a TargetLowering to consult for determining
      /// transformation profitability.
      const TargetMachine *TM;
      const TargetLowering *TLI;
      const TargetTransformInfo *TTI;
      const TargetLibraryInfo *TLInfo;
      DominatorTree *DT;
  
      /// CurInstIterator - As we scan instructions optimizing them, this is the
      /// next instruction to optimize.  Xforms that can invalidate this should
      /// update it.
      BasicBlock::iterator CurInstIterator;
  
      /// Keeps track of non-local addresses that have been sunk into a block.
      /// This allows us to avoid inserting duplicate code for blocks with
      /// multiple load/stores of the same address.
      ValueMap<Value*, Value*> SunkAddrs;
  
      /// Keeps track of all truncates inserted for the current function.
      SetOfInstrs InsertedTruncsSet;
      /// Keeps track of the type of the related instruction before their
      /// promotion for the current function.
      InstrToOrigTy PromotedInsts;
  
      /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
      /// be updated.
      bool ModifiedDT;
  
      /// OptSize - True if optimizing for size.
      bool OptSize;
  
    public:
      static char ID; // Pass identification, replacement for typeid
      explicit CodeGenPrepare(const TargetMachine *TM = nullptr)
          : FunctionPass(ID), TM(TM), TLI(nullptr), TTI(nullptr) {
          initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
        }
      bool runOnFunction(Function &F) override;
  
      const char *getPassName() const override { return "CodeGen Prepare"; }
  
      void getAnalysisUsage(AnalysisUsage &AU) const override {
        AU.addPreserved<DominatorTreeWrapperPass>();
        AU.addRequired<TargetLibraryInfo>();
        AU.addRequired<TargetTransformInfo>();
      }
  
    private:
      bool EliminateFallThrough(Function &F);
      bool EliminateMostlyEmptyBlocks(Function &F);
      bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
      void EliminateMostlyEmptyBlock(BasicBlock *BB);
      bool OptimizeBlock(BasicBlock &BB, bool& ModifiedDT);
      bool OptimizeInst(Instruction *I, bool& ModifiedDT);
      bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy);
      bool OptimizeInlineAsmInst(CallInst *CS);
      bool OptimizeCallInst(CallInst *CI, bool& ModifiedDT);
      bool MoveExtToFormExtLoad(Instruction *&I);
      bool OptimizeExtUses(Instruction *I);
      bool OptimizeSelectInst(SelectInst *SI);
      bool OptimizeShuffleVectorInst(ShuffleVectorInst *SI);
      bool OptimizeExtractElementInst(Instruction *Inst);
      bool DupRetToEnableTailCallOpts(BasicBlock *BB);
      bool PlaceDbgValues(Function &F);
      bool sinkAndCmp(Function &F);
      bool ExtLdPromotion(TypePromotionTransaction &TPT, LoadInst *&LI,
                          Instruction *&Inst,
                          const SmallVectorImpl<Instruction *> &Exts,
                          unsigned CreatedInst);
      bool splitBranchCondition(Function &F);
    };
  }
  
  char CodeGenPrepare::ID = 0;
  INITIALIZE_TM_PASS(CodeGenPrepare, "codegenprepare",
                     "Optimize for code generation", false, false)
  
  FunctionPass *llvm::createCodeGenPreparePass(const TargetMachine *TM) {
    return new CodeGenPrepare(TM);
  }
  
  bool CodeGenPrepare::runOnFunction(Function &F) {
    if (skipOptnoneFunction(F))
      return false;
  
    bool EverMadeChange = false;
    // Clear per function information.
    InsertedTruncsSet.clear();
    PromotedInsts.clear();
  
    ModifiedDT = false;
    if (TM)
      TLI = TM->getSubtargetImpl()->getTargetLowering();
    TLInfo = &getAnalysis<TargetLibraryInfo>();
    TTI = &getAnalysis<TargetTransformInfo>();
    DominatorTreeWrapperPass *DTWP =
        getAnalysisIfAvailable<DominatorTreeWrapperPass>();
    DT = DTWP ? &DTWP->getDomTree() : nullptr;
    OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
                                             Attribute::OptimizeForSize);
  
    /// This optimization identifies DIV instructions that can be
    /// profitably bypassed and carried out with a shorter, faster divide.
    if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
      const DenseMap<unsigned int, unsigned int> &BypassWidths =
         TLI->getBypassSlowDivWidths();
      for (Function::iterator I = F.begin(); I != F.end(); I++)
        EverMadeChange |= bypassSlowDivision(F, I, BypassWidths);
    }
  
    // Eliminate blocks that contain only PHI nodes and an
    // unconditional branch.
    EverMadeChange |= EliminateMostlyEmptyBlocks(F);
  
    // llvm.dbg.value is far away from the value then iSel may not be able
    // handle it properly. iSel will drop llvm.dbg.value if it can not
    // find a node corresponding to the value.
    EverMadeChange |= PlaceDbgValues(F);
  
    // If there is a mask, compare against zero, and branch that can be combined
    // into a single target instruction, push the mask and compare into branch
    // users. Do this before OptimizeBlock -> OptimizeInst ->
    // OptimizeCmpExpression, which perturbs the pattern being searched for.
    if (!DisableBranchOpts) {
      EverMadeChange |= sinkAndCmp(F);
      EverMadeChange |= splitBranchCondition(F);
    }
  
    bool MadeChange = true;
    while (MadeChange) {
      MadeChange = false;
      for (Function::iterator I = F.begin(); I != F.end(); ) {
        BasicBlock *BB = I++;
        bool ModifiedDTOnIteration = false;
        MadeChange |= OptimizeBlock(*BB, ModifiedDTOnIteration);
        
        // Restart BB iteration if the dominator tree of the Function was changed
        ModifiedDT |= ModifiedDTOnIteration;
        if (ModifiedDTOnIteration)
          break;
      }
      EverMadeChange |= MadeChange;
    }
  
    SunkAddrs.clear();
  
    if (!DisableBranchOpts) {
      MadeChange = false;
      SmallPtrSet<BasicBlock*, 8> WorkList;
      for (BasicBlock &BB : F) {
        SmallVector<BasicBlock *, 2> Successors(succ_begin(&BB), succ_end(&BB));
        MadeChange |= ConstantFoldTerminator(&BB, true);
        if (!MadeChange) continue;
  
        for (SmallVectorImpl<BasicBlock*>::iterator
               II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
          if (pred_begin(*II) == pred_end(*II))
            WorkList.insert(*II);
      }
  
      // Delete the dead blocks and any of their dead successors.
      MadeChange |= !WorkList.empty();
      while (!WorkList.empty()) {
        BasicBlock *BB = *WorkList.begin();
        WorkList.erase(BB);
        SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
  
        DeleteDeadBlock(BB);
  
        for (SmallVectorImpl<BasicBlock*>::iterator
               II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
          if (pred_begin(*II) == pred_end(*II))
            WorkList.insert(*II);
      }
  
      // Merge pairs of basic blocks with unconditional branches, connected by
      // a single edge.
      if (EverMadeChange || MadeChange)
        MadeChange |= EliminateFallThrough(F);
  
      if (MadeChange)
        ModifiedDT = true;
      EverMadeChange |= MadeChange;
    }
  
    if (ModifiedDT && DT)
      DT->recalculate(F);
  
    return EverMadeChange;
  }
  
  /// EliminateFallThrough - Merge basic blocks which are connected
  /// by a single edge, where one of the basic blocks has a single successor
  /// pointing to the other basic block, which has a single predecessor.
  bool CodeGenPrepare::EliminateFallThrough(Function &F) {
    bool Changed = false;
    // Scan all of the blocks in the function, except for the entry block.
    for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
      BasicBlock *BB = I++;
      // If the destination block has a single pred, then this is a trivial
      // edge, just collapse it.
      BasicBlock *SinglePred = BB->getSinglePredecessor();
  
      // Don't merge if BB's address is taken.
      if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue;
  
      BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
      if (Term && !Term->isConditional()) {
        Changed = true;
        DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
        // Remember if SinglePred was the entry block of the function.
        // If so, we will need to move BB back to the entry position.
        bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
        MergeBasicBlockIntoOnlyPred(BB, this);
  
        if (isEntry && BB != &BB->getParent()->getEntryBlock())
          BB->moveBefore(&BB->getParent()->getEntryBlock());
  
        // We have erased a block. Update the iterator.
        I = BB;
      }
    }
    return Changed;
  }
  
  /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
  /// debug info directives, and an unconditional branch.  Passes before isel
  /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
  /// isel.  Start by eliminating these blocks so we can split them the way we
  /// want them.
  bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
    bool MadeChange = false;
    // Note that this intentionally skips the entry block.
    for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
      BasicBlock *BB = I++;
  
      // If this block doesn't end with an uncond branch, ignore it.
      BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
      if (!BI || !BI->isUnconditional())
        continue;
  
      // If the instruction before the branch (skipping debug info) isn't a phi
      // node, then other stuff is happening here.
      BasicBlock::iterator BBI = BI;
      if (BBI != BB->begin()) {
        --BBI;
        while (isa<DbgInfoIntrinsic>(BBI)) {
          if (BBI == BB->begin())
            break;
          --BBI;
        }
        if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
          continue;
      }
  
      // Do not break infinite loops.
      BasicBlock *DestBB = BI->getSuccessor(0);
      if (DestBB == BB)
        continue;
  
      if (!CanMergeBlocks(BB, DestBB))
        continue;
  
      EliminateMostlyEmptyBlock(BB);
      MadeChange = true;
    }
    return MadeChange;
  }
  
  /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
  /// single uncond branch between them, and BB contains no other non-phi
  /// instructions.
  bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
                                      const BasicBlock *DestBB) const {
    // We only want to eliminate blocks whose phi nodes are used by phi nodes in
    // the successor.  If there are more complex condition (e.g. preheaders),
    // don't mess around with them.
    BasicBlock::const_iterator BBI = BB->begin();
    while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
      for (const User *U : PN->users()) {
        const Instruction *UI = cast<Instruction>(U);
        if (UI->getParent() != DestBB || !isa<PHINode>(UI))
          return false;
        // If User is inside DestBB block and it is a PHINode then check
        // incoming value. If incoming value is not from BB then this is
        // a complex condition (e.g. preheaders) we want to avoid here.
        if (UI->getParent() == DestBB) {
          if (const PHINode *UPN = dyn_cast<PHINode>(UI))
            for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
              Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
              if (Insn && Insn->getParent() == BB &&
                  Insn->getParent() != UPN->getIncomingBlock(I))
                return false;
            }
        }
      }
    }
  
    // If BB and DestBB contain any common predecessors, then the phi nodes in BB
    // and DestBB may have conflicting incoming values for the block.  If so, we
    // can't merge the block.
    const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
    if (!DestBBPN) return true;  // no conflict.
  
    // Collect the preds of BB.
    SmallPtrSet<const BasicBlock*, 16> BBPreds;
    if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
      // It is faster to get preds from a PHI than with pred_iterator.
      for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
        BBPreds.insert(BBPN->getIncomingBlock(i));
    } else {
      BBPreds.insert(pred_begin(BB), pred_end(BB));
    }
  
    // Walk the preds of DestBB.
    for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
      BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
      if (BBPreds.count(Pred)) {   // Common predecessor?
        BBI = DestBB->begin();
        while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
          const Value *V1 = PN->getIncomingValueForBlock(Pred);
          const Value *V2 = PN->getIncomingValueForBlock(BB);
  
          // If V2 is a phi node in BB, look up what the mapped value will be.
          if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
            if (V2PN->getParent() == BB)
              V2 = V2PN->getIncomingValueForBlock(Pred);
  
          // If there is a conflict, bail out.
          if (V1 != V2) return false;
        }
      }
    }
  
    return true;
  }
  
  
  /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
  /// an unconditional branch in it.
  void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
    BranchInst *BI = cast<BranchInst>(BB->getTerminator());
    BasicBlock *DestBB = BI->getSuccessor(0);
  
    DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
  
    // If the destination block has a single pred, then this is a trivial edge,
    // just collapse it.
    if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
      if (SinglePred != DestBB) {
        // Remember if SinglePred was the entry block of the function.  If so, we
        // will need to move BB back to the entry position.
        bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
        MergeBasicBlockIntoOnlyPred(DestBB, this);
  
        if (isEntry && BB != &BB->getParent()->getEntryBlock())
          BB->moveBefore(&BB->getParent()->getEntryBlock());
  
        DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
        return;
      }
    }
  
    // Otherwise, we have multiple predecessors of BB.  Update the PHIs in DestBB
    // to handle the new incoming edges it is about to have.
    PHINode *PN;
    for (BasicBlock::iterator BBI = DestBB->begin();
         (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
      // Remove the incoming value for BB, and remember it.
      Value *InVal = PN->removeIncomingValue(BB, false);
  
      // Two options: either the InVal is a phi node defined in BB or it is some
      // value that dominates BB.
      PHINode *InValPhi = dyn_cast<PHINode>(InVal);
      if (InValPhi && InValPhi->getParent() == BB) {
        // Add all of the input values of the input PHI as inputs of this phi.
        for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
          PN->addIncoming(InValPhi->getIncomingValue(i),
                          InValPhi->getIncomingBlock(i));
      } else {
        // Otherwise, add one instance of the dominating value for each edge that
        // we will be adding.
        if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
          for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
            PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
        } else {
          for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
            PN->addIncoming(InVal, *PI);
        }
      }
    }
  
    // The PHIs are now updated, change everything that refers to BB to use
    // DestBB and remove BB.
    BB->replaceAllUsesWith(DestBB);
    if (DT && !ModifiedDT) {
      BasicBlock *BBIDom  = DT->getNode(BB)->getIDom()->getBlock();
      BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
      BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
      DT->changeImmediateDominator(DestBB, NewIDom);
      DT->eraseNode(BB);
    }
    BB->eraseFromParent();
    ++NumBlocksElim;
  
    DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
  }
  
  /// SinkCast - Sink the specified cast instruction into its user blocks
  static bool SinkCast(CastInst *CI) {
    BasicBlock *DefBB = CI->getParent();
  
    /// InsertedCasts - Only insert a cast in each block once.
    DenseMap<BasicBlock*, CastInst*> InsertedCasts;
  
    bool MadeChange = false;
    for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
         UI != E; ) {
      Use &TheUse = UI.getUse();
      Instruction *User = cast<Instruction>(*UI);
  
      // Figure out which BB this cast is used in.  For PHI's this is the
      // appropriate predecessor block.
      BasicBlock *UserBB = User->getParent();
      if (PHINode *PN = dyn_cast<PHINode>(User)) {
        UserBB = PN->getIncomingBlock(TheUse);
      }
  
      // Preincrement use iterator so we don't invalidate it.
      ++UI;
  
      // If this user is in the same block as the cast, don't change the cast.
      if (UserBB == DefBB) continue;
  
      // If we have already inserted a cast into this block, use it.
      CastInst *&InsertedCast = InsertedCasts[UserBB];
  
      if (!InsertedCast) {
        BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
        InsertedCast =
          CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
                           InsertPt);
        MadeChange = true;
      }
  
      // Replace a use of the cast with a use of the new cast.
      TheUse = InsertedCast;
      ++NumCastUses;
    }
  
    // If we removed all uses, nuke the cast.
    if (CI->use_empty()) {
      CI->eraseFromParent();
      MadeChange = true;
    }
  
    return MadeChange;
  }
  
  /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
  /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
  /// sink it into user blocks to reduce the number of virtual
  /// registers that must be created and coalesced.
  ///
  /// Return true if any changes are made.
  ///
  static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
    // If this is a noop copy,
    EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
    EVT DstVT = TLI.getValueType(CI->getType());
  
    // This is an fp<->int conversion?
    if (SrcVT.isInteger() != DstVT.isInteger())
      return false;
  
    // If this is an extension, it will be a zero or sign extension, which
    // isn't a noop.
    if (SrcVT.bitsLT(DstVT)) return false;
  
    // If these values will be promoted, find out what they will be promoted
    // to.  This helps us consider truncates on PPC as noop copies when they
    // are.
    if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
        TargetLowering::TypePromoteInteger)
      SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
    if (TLI.getTypeAction(CI->getContext(), DstVT) ==
        TargetLowering::TypePromoteInteger)
      DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
  
    // If, after promotion, these are the same types, this is a noop copy.
    if (SrcVT != DstVT)
      return false;
  
    return SinkCast(CI);
  }
  
  /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
  /// the number of virtual registers that must be created and coalesced.  This is
  /// a clear win except on targets with multiple condition code registers
  ///  (PowerPC), where it might lose; some adjustment may be wanted there.
  ///
  /// Return true if any changes are made.
  static bool OptimizeCmpExpression(CmpInst *CI) {
    BasicBlock *DefBB = CI->getParent();
  
    /// InsertedCmp - Only insert a cmp in each block once.
    DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
  
    bool MadeChange = false;
    for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
         UI != E; ) {
      Use &TheUse = UI.getUse();
      Instruction *User = cast<Instruction>(*UI);
  
      // Preincrement use iterator so we don't invalidate it.
      ++UI;
  
      // Don't bother for PHI nodes.
      if (isa<PHINode>(User))
        continue;
  
      // Figure out which BB this cmp is used in.
      BasicBlock *UserBB = User->getParent();
  
      // If this user is in the same block as the cmp, don't change the cmp.
      if (UserBB == DefBB) continue;
  
      // If we have already inserted a cmp into this block, use it.
      CmpInst *&InsertedCmp = InsertedCmps[UserBB];
  
      if (!InsertedCmp) {
        BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
        InsertedCmp =
          CmpInst::Create(CI->getOpcode(),
                          CI->getPredicate(),  CI->getOperand(0),
                          CI->getOperand(1), "", InsertPt);
        MadeChange = true;
      }
  
      // Replace a use of the cmp with a use of the new cmp.
      TheUse = InsertedCmp;
      ++NumCmpUses;
    }
  
    // If we removed all uses, nuke the cmp.
    if (CI->use_empty())
      CI->eraseFromParent();
  
    return MadeChange;
  }
  
  /// isExtractBitsCandidateUse - Check if the candidates could
  /// be combined with shift instruction, which includes:
  /// 1. Truncate instruction
  /// 2. And instruction and the imm is a mask of the low bits:
  /// imm & (imm+1) == 0
  static bool isExtractBitsCandidateUse(Instruction *User) {
    if (!isa<TruncInst>(User)) {
      if (User->getOpcode() != Instruction::And ||
          !isa<ConstantInt>(User->getOperand(1)))
        return false;
  
      const APInt &Cimm = cast<ConstantInt>(User->getOperand(1))->getValue();
  
      if ((Cimm & (Cimm + 1)).getBoolValue())
        return false;
    }
    return true;
  }
  
  /// SinkShiftAndTruncate - sink both shift and truncate instruction
  /// to the use of truncate's BB.
  static bool
  SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
                       DenseMap<BasicBlock *, BinaryOperator *> &InsertedShifts,
                       const TargetLowering &TLI) {
    BasicBlock *UserBB = User->getParent();
    DenseMap<BasicBlock *, CastInst *> InsertedTruncs;
    TruncInst *TruncI = dyn_cast<TruncInst>(User);
    bool MadeChange = false;
  
    for (Value::user_iterator TruncUI = TruncI->user_begin(),
                              TruncE = TruncI->user_end();
         TruncUI != TruncE;) {
  
      Use &TruncTheUse = TruncUI.getUse();
      Instruction *TruncUser = cast<Instruction>(*TruncUI);
      // Preincrement use iterator so we don't invalidate it.
  
      ++TruncUI;
  
      int ISDOpcode = TLI.InstructionOpcodeToISD(TruncUser->getOpcode());
      if (!ISDOpcode)
        continue;
  
      // If the use is actually a legal node, there will not be an
      // implicit truncate.
      // FIXME: always querying the result type is just an
      // approximation; some nodes' legality is determined by the
      // operand or other means. There's no good way to find out though.
      if (TLI.isOperationLegalOrCustom(
              ISDOpcode, TLI.getValueType(TruncUser->getType(), true)))
        continue;
  
      // Don't bother for PHI nodes.
      if (isa<PHINode>(TruncUser))
        continue;
  
      BasicBlock *TruncUserBB = TruncUser->getParent();
  
      if (UserBB == TruncUserBB)
        continue;
  
      BinaryOperator *&InsertedShift = InsertedShifts[TruncUserBB];
      CastInst *&InsertedTrunc = InsertedTruncs[TruncUserBB];
  
      if (!InsertedShift && !InsertedTrunc) {
        BasicBlock::iterator InsertPt = TruncUserBB->getFirstInsertionPt();
        // Sink the shift
        if (ShiftI->getOpcode() == Instruction::AShr)
          InsertedShift =
              BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt);
        else
          InsertedShift =
              BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt);
  
        // Sink the trunc
        BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
        TruncInsertPt++;
  
        InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
                                         TruncI->getType(), "", TruncInsertPt);
  
        MadeChange = true;
  
        TruncTheUse = InsertedTrunc;
      }
    }
    return MadeChange;
  }
  
  /// OptimizeExtractBits - sink the shift *right* instruction into user blocks if
  /// the uses could potentially be combined with this shift instruction and
  /// generate BitExtract instruction. It will only be applied if the architecture
  /// supports BitExtract instruction. Here is an example:
  /// BB1:
  ///   %x.extract.shift = lshr i64 %arg1, 32
  /// BB2:
  ///   %x.extract.trunc = trunc i64 %x.extract.shift to i16
  /// ==>
  ///
  /// BB2:
  ///   %x.extract.shift.1 = lshr i64 %arg1, 32
  ///   %x.extract.trunc = trunc i64 %x.extract.shift.1 to i16
  ///
  /// CodeGen will recoginze the pattern in BB2 and generate BitExtract
  /// instruction.
  /// Return true if any changes are made.
  static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
                                  const TargetLowering &TLI) {
    BasicBlock *DefBB = ShiftI->getParent();
  
    /// Only insert instructions in each block once.
    DenseMap<BasicBlock *, BinaryOperator *> InsertedShifts;
  
    bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(ShiftI->getType()));
  
    bool MadeChange = false;
    for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end();
         UI != E;) {
      Use &TheUse = UI.getUse();
      Instruction *User = cast<Instruction>(*UI);
      // Preincrement use iterator so we don't invalidate it.
      ++UI;
  
      // Don't bother for PHI nodes.
      if (isa<PHINode>(User))
        continue;
  
      if (!isExtractBitsCandidateUse(User))
        continue;
  
      BasicBlock *UserBB = User->getParent();
  
      if (UserBB == DefBB) {
        // If the shift and truncate instruction are in the same BB. The use of
        // the truncate(TruncUse) may still introduce another truncate if not
        // legal. In this case, we would like to sink both shift and truncate
        // instruction to the BB of TruncUse.
        // for example:
        // BB1:
        // i64 shift.result = lshr i64 opnd, imm
        // trunc.result = trunc shift.result to i16
        //
        // BB2:
        //   ----> We will have an implicit truncate here if the architecture does
        //   not have i16 compare.
        // cmp i16 trunc.result, opnd2
        //
        if (isa<TruncInst>(User) && shiftIsLegal
            // If the type of the truncate is legal, no trucate will be
            // introduced in other basic blocks.
            && (!TLI.isTypeLegal(TLI.getValueType(User->getType()))))
          MadeChange =
              SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI);
  
        continue;
      }
      // If we have already inserted a shift into this block, use it.
      BinaryOperator *&InsertedShift = InsertedShifts[UserBB];
  
      if (!InsertedShift) {
        BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
  
        if (ShiftI->getOpcode() == Instruction::AShr)
          InsertedShift =
              BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt);
        else
          InsertedShift =
              BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt);
  
        MadeChange = true;
      }
  
      // Replace a use of the shift with a use of the new shift.
      TheUse = InsertedShift;
    }
  
    // If we removed all uses, nuke the shift.
    if (ShiftI->use_empty())
      ShiftI->eraseFromParent();
  
    return MadeChange;
  }
  
  //  ScalarizeMaskedLoad() translates masked load intrinsic, like 
  // <16 x i32 > @llvm.masked.load( <16 x i32>* %addr, i32 align,
  //                               <16 x i1> %mask, <16 x i32> %passthru)
  // to a chain of basic blocks, whith loading element one-by-one if
  // the appropriate mask bit is set
  // 
  //  %1 = bitcast i8* %addr to i32*
  //  %2 = extractelement <16 x i1> %mask, i32 0
  //  %3 = icmp eq i1 %2, true
  //  br i1 %3, label %cond.load, label %else
  //
  //cond.load:                                        ; preds = %0
  //  %4 = getelementptr i32* %1, i32 0
  //  %5 = load i32* %4
  //  %6 = insertelement <16 x i32> undef, i32 %5, i32 0
  //  br label %else
  //
  //else:                                             ; preds = %0, %cond.load
  //  %res.phi.else = phi <16 x i32> [ %6, %cond.load ], [ undef, %0 ]
  //  %7 = extractelement <16 x i1> %mask, i32 1
  //  %8 = icmp eq i1 %7, true
  //  br i1 %8, label %cond.load1, label %else2
  //
  //cond.load1:                                       ; preds = %else
  //  %9 = getelementptr i32* %1, i32 1
  //  %10 = load i32* %9
  //  %11 = insertelement <16 x i32> %res.phi.else, i32 %10, i32 1
  //  br label %else2
  //
  //else2:                                            ; preds = %else, %cond.load1
  //  %res.phi.else3 = phi <16 x i32> [ %11, %cond.load1 ], [ %res.phi.else, %else ]
  //  %12 = extractelement <16 x i1> %mask, i32 2
  //  %13 = icmp eq i1 %12, true
  //  br i1 %13, label %cond.load4, label %else5
  //
  static void ScalarizeMaskedLoad(CallInst *CI) {
    Value *Ptr  = CI->getArgOperand(0);
    Value *Src0 = CI->getArgOperand(3);
    Value *Mask = CI->getArgOperand(2);
    VectorType *VecType = dyn_cast<VectorType>(CI->getType());
    Type *EltTy = VecType->getElementType();
  
    assert(VecType && "Unexpected return type of masked load intrinsic");
  
    IRBuilder<> Builder(CI->getContext());
    Instruction *InsertPt = CI;
    BasicBlock *IfBlock = CI->getParent();
    BasicBlock *CondBlock = nullptr;
    BasicBlock *PrevIfBlock = CI->getParent();
    Builder.SetInsertPoint(InsertPt);
  
    Builder.SetCurrentDebugLocation(CI->getDebugLoc());
  
    // Bitcast %addr fron i8* to EltTy*
    Type *NewPtrType =
      EltTy->getPointerTo(cast<PointerType>(Ptr->getType())->getAddressSpace());
    Value *FirstEltPtr = Builder.CreateBitCast(Ptr, NewPtrType);
    Value *UndefVal = UndefValue::get(VecType);
  
    // The result vector
    Value *VResult = UndefVal;
  
    PHINode *Phi = nullptr;
    Value *PrevPhi = UndefVal;
  
    unsigned VectorWidth = VecType->getNumElements();
    for (unsigned Idx = 0; Idx < VectorWidth; ++Idx) {
  
      // Fill the "else" block, created in the previous iteration
      //
      //  %res.phi.else3 = phi <16 x i32> [ %11, %cond.load1 ], [ %res.phi.else, %else ]
      //  %mask_1 = extractelement <16 x i1> %mask, i32 Idx
      //  %to_load = icmp eq i1 %mask_1, true
      //  br i1 %to_load, label %cond.load, label %else
      //
      if (Idx > 0) {
        Phi = Builder.CreatePHI(VecType, 2, "res.phi.else");
        Phi->addIncoming(VResult, CondBlock);
        Phi->addIncoming(PrevPhi, PrevIfBlock);
        PrevPhi = Phi;
        VResult = Phi;
      }
  
      Value *Predicate = Builder.CreateExtractElement(Mask, Builder.getInt32(Idx));
      Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_EQ, Predicate,
                                      ConstantInt::get(Predicate->getType(), 1));
  
      // Create "cond" block
      //
      //  %EltAddr = getelementptr i32* %1, i32 0
      //  %Elt = load i32* %EltAddr
      //  VResult = insertelement <16 x i32> VResult, i32 %Elt, i32 Idx
      //
      CondBlock = IfBlock->splitBasicBlock(InsertPt, "cond.load");
      Builder.SetInsertPoint(InsertPt);
      
      Value* Gep = Builder.CreateInBoundsGEP(FirstEltPtr, Builder.getInt32(Idx));
      LoadInst* Load = Builder.CreateLoad(Gep, false);
      VResult = Builder.CreateInsertElement(VResult, Load, Builder.getInt32(Idx));
  
      // Create "else" block, fill it in the next iteration
      BasicBlock *NewIfBlock = CondBlock->splitBasicBlock(InsertPt, "else");
      Builder.SetInsertPoint(InsertPt);
      Instruction *OldBr = IfBlock->getTerminator();
      BranchInst::Create(CondBlock, NewIfBlock, Cmp, OldBr);
      OldBr->eraseFromParent();
      PrevIfBlock = IfBlock;
      IfBlock = NewIfBlock;
    }
  
    Phi = Builder.CreatePHI(VecType, 2, "res.phi.select");
    Phi->addIncoming(VResult, CondBlock);
    Phi->addIncoming(PrevPhi, PrevIfBlock);
    Value *NewI = Builder.CreateSelect(Mask, Phi, Src0);
    CI->replaceAllUsesWith(NewI);
    CI->eraseFromParent();
  }
  
  //  ScalarizeMaskedStore() translates masked store intrinsic, like
  // void @llvm.masked.store(<16 x i32> %src, <16 x i32>* %addr, i32 align,
  //                               <16 x i1> %mask)
  // to a chain of basic blocks, that stores element one-by-one if
  // the appropriate mask bit is set
  //
  //   %1 = bitcast i8* %addr to i32*
  //   %2 = extractelement <16 x i1> %mask, i32 0
  //   %3 = icmp eq i1 %2, true
  //   br i1 %3, label %cond.store, label %else
  //
  // cond.store:                                       ; preds = %0
  //   %4 = extractelement <16 x i32> %val, i32 0
  //   %5 = getelementptr i32* %1, i32 0
  //   store i32 %4, i32* %5
  //   br label %else
  // 
  // else:                                             ; preds = %0, %cond.store
  //   %6 = extractelement <16 x i1> %mask, i32 1
  //   %7 = icmp eq i1 %6, true
  //   br i1 %7, label %cond.store1, label %else2
  // 
  // cond.store1:                                      ; preds = %else
  //   %8 = extractelement <16 x i32> %val, i32 1
  //   %9 = getelementptr i32* %1, i32 1
  //   store i32 %8, i32* %9
  //   br label %else2
  //   . . .
  static void ScalarizeMaskedStore(CallInst *CI) {
    Value *Ptr  = CI->getArgOperand(1);
    Value *Src = CI->getArgOperand(0);
    Value *Mask = CI->getArgOperand(3);
  
    VectorType *VecType = dyn_cast<VectorType>(Src->getType());
    Type *EltTy = VecType->getElementType();
  
    assert(VecType && "Unexpected data type in masked store intrinsic");
  
    IRBuilder<> Builder(CI->getContext());
    Instruction *InsertPt = CI;
    BasicBlock *IfBlock = CI->getParent();
    Builder.SetInsertPoint(InsertPt);
    Builder.SetCurrentDebugLocation(CI->getDebugLoc());
  
    // Bitcast %addr fron i8* to EltTy*
    Type *NewPtrType =
      EltTy->getPointerTo(cast<PointerType>(Ptr->getType())->getAddressSpace());
    Value *FirstEltPtr = Builder.CreateBitCast(Ptr, NewPtrType);
  
    unsigned VectorWidth = VecType->getNumElements();
    for (unsigned Idx = 0; Idx < VectorWidth; ++Idx) {
  
      // Fill the "else" block, created in the previous iteration
      //
      //  %mask_1 = extractelement <16 x i1> %mask, i32 Idx
      //  %to_store = icmp eq i1 %mask_1, true
      //  br i1 %to_load, label %cond.store, label %else
      //
      Value *Predicate = Builder.CreateExtractElement(Mask, Builder.getInt32(Idx));
      Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_EQ, Predicate,
                                      ConstantInt::get(Predicate->getType(), 1));
  
      // Create "cond" block
      //
      //  %OneElt = extractelement <16 x i32> %Src, i32 Idx
      //  %EltAddr = getelementptr i32* %1, i32 0
      //  %store i32 %OneElt, i32* %EltAddr
      //
      BasicBlock *CondBlock = IfBlock->splitBasicBlock(InsertPt, "cond.store");
      Builder.SetInsertPoint(InsertPt);
      
      Value *OneElt = Builder.CreateExtractElement(Src, Builder.getInt32(Idx));
      Value* Gep = Builder.CreateInBoundsGEP(FirstEltPtr, Builder.getInt32(Idx));
      Builder.CreateStore(OneElt, Gep);
  
      // Create "else" block, fill it in the next iteration
      BasicBlock *NewIfBlock = CondBlock->splitBasicBlock(InsertPt, "else");
      Builder.SetInsertPoint(InsertPt);
      Instruction *OldBr = IfBlock->getTerminator();
      BranchInst::Create(CondBlock, NewIfBlock, Cmp, OldBr);
      OldBr->eraseFromParent();
      IfBlock = NewIfBlock;
    }
    CI->eraseFromParent();
  }
  
  bool CodeGenPrepare::OptimizeCallInst(CallInst *CI, bool& ModifiedDT) {
    BasicBlock *BB = CI->getParent();
  
    // Lower inline assembly if we can.
    // If we found an inline asm expession, and if the target knows how to
    // lower it to normal LLVM code, do so now.
    if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
      if (TLI->ExpandInlineAsm(CI)) {
        // Avoid invalidating the iterator.
        CurInstIterator = BB->begin();
        // Avoid processing instructions out of order, which could cause
        // reuse before a value is defined.
        SunkAddrs.clear();
        return true;
      }
      // Sink address computing for memory operands into the block.
      if (OptimizeInlineAsmInst(CI))
        return true;
    }
  
    IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
    if (II) {
      switch (II->getIntrinsicID()) {
      default: break;
      case Intrinsic::objectsize: {
        // Lower all uses of llvm.objectsize.*
        bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
        Type *ReturnTy = CI->getType();
        Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
  
        // Substituting this can cause recursive simplifications, which can
        // invalidate our iterator.  Use a WeakVH to hold onto it in case this
        // happens.
        WeakVH IterHandle(CurInstIterator);
  
        replaceAndRecursivelySimplify(CI, RetVal,
                                      TLI ? TLI->getDataLayout() : nullptr,
                                      TLInfo, ModifiedDT ? nullptr : DT);
  
        // If the iterator instruction was recursively deleted, start over at the
        // start of the block.
        if (IterHandle != CurInstIterator) {
          CurInstIterator = BB->begin();
          SunkAddrs.clear();
        }
        return true;
      }
      case Intrinsic::masked_load: {
        // Scalarize unsupported vector masked load
        if (!TTI->isLegalMaskedLoad(CI->getType(), 1)) {
          ScalarizeMaskedLoad(CI);
          ModifiedDT = true;
          return true;
        }
        return false;
      }
      case Intrinsic::masked_store: {
        if (!TTI->isLegalMaskedStore(CI->getArgOperand(0)->getType(), 1)) {
          ScalarizeMaskedStore(CI);
          ModifiedDT = true;
          return true;
        }
        return false;
      }
      }
  
      if (TLI) {
        SmallVector<Value*, 2> PtrOps;
        Type *AccessTy;
        if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy))
          while (!PtrOps.empty())
            if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy))
              return true;
      }
    }
  
    // From here on out we're working with named functions.
    if (!CI->getCalledFunction()) return false;
  
    // We'll need DataLayout from here on out.
    const DataLayout *TD = TLI ? TLI->getDataLayout() : nullptr;
    if (!TD) return false;
  
    // Lower all default uses of _chk calls.  This is very similar
    // to what InstCombineCalls does, but here we are only lowering calls
    // to fortified library functions (e.g. __memcpy_chk) that have the default
    // "don't know" as the objectsize.  Anything else should be left alone.
    FortifiedLibCallSimplifier Simplifier(TD, TLInfo, true);
    if (Value *V = Simplifier.optimizeCall(CI)) {
      CI->replaceAllUsesWith(V);
      CI->eraseFromParent();
      return true;
    }
    return false;
  }
  
  /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
  /// instructions to the predecessor to enable tail call optimizations. The
  /// case it is currently looking for is:
  /// @code
  /// bb0:
  ///   %tmp0 = tail call i32 @f0()
  ///   br label %return
  /// bb1:
  ///   %tmp1 = tail call i32 @f1()
  ///   br label %return
  /// bb2:
  ///   %tmp2 = tail call i32 @f2()
  ///   br label %return
  /// return:
  ///   %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
  ///   ret i32 %retval
  /// @endcode
  ///
  /// =>
  ///
  /// @code
  /// bb0:
  ///   %tmp0 = tail call i32 @f0()
  ///   ret i32 %tmp0
  /// bb1:
  ///   %tmp1 = tail call i32 @f1()
  ///   ret i32 %tmp1
  /// bb2:
  ///   %tmp2 = tail call i32 @f2()
  ///   ret i32 %tmp2
  /// @endcode
  bool CodeGenPrepare::DupRetToEnableTailCallOpts(BasicBlock *BB) {
    if (!TLI)
      return false;
  
    ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
    if (!RI)
      return false;
  
    PHINode *PN = nullptr;
    BitCastInst *BCI = nullptr;
    Value *V = RI->getReturnValue();
    if (V) {
      BCI = dyn_cast<BitCastInst>(V);
      if (BCI)
        V = BCI->getOperand(0);
  
      PN = dyn_cast<PHINode>(V);
      if (!PN)
        return false;
    }
  
    if (PN && PN->getParent() != BB)
      return false;
  
    // It's not safe to eliminate the sign / zero extension of the return value.
    // See llvm::isInTailCallPosition().
    const Function *F = BB->getParent();
    AttributeSet CallerAttrs = F->getAttributes();
    if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
        CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
      return false;
  
    // Make sure there are no instructions between the PHI and return, or that the
    // return is the first instruction in the block.
    if (PN) {
      BasicBlock::iterator BI = BB->begin();
      do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
      if (&*BI == BCI)
        // Also skip over the bitcast.
        ++BI;
      if (&*BI != RI)
        return false;
    } else {
      BasicBlock::iterator BI = BB->begin();
      while (isa<DbgInfoIntrinsic>(BI)) ++BI;
      if (&*BI != RI)
        return false;
    }
  
    /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
    /// call.
    SmallVector<CallInst*, 4> TailCalls;
    if (PN) {
      for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
        CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
        // Make sure the phi value is indeed produced by the tail call.
        if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
            TLI->mayBeEmittedAsTailCall(CI))
          TailCalls.push_back(CI);
      }
    } else {
      SmallPtrSet<BasicBlock*, 4> VisitedBBs;
      for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
        if (!VisitedBBs.insert(*PI).second)
          continue;
  
        BasicBlock::InstListType &InstList = (*PI)->getInstList();
        BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
        BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
        do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
        if (RI == RE)
          continue;
  
        CallInst *CI = dyn_cast<CallInst>(&*RI);
        if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
          TailCalls.push_back(CI);
      }
    }
  
    bool Changed = false;
    for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
      CallInst *CI = TailCalls[i];
      CallSite CS(CI);
  
      // Conservatively require the attributes of the call to match those of the
      // return. Ignore noalias because it doesn't affect the call sequence.
      AttributeSet CalleeAttrs = CS.getAttributes();
      if (AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
            removeAttribute(Attribute::NoAlias) !=
          AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
            removeAttribute(Attribute::NoAlias))
        continue;
  
      // Make sure the call instruction is followed by an unconditional branch to
      // the return block.
      BasicBlock *CallBB = CI->getParent();
      BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
      if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
        continue;
  
      // Duplicate the return into CallBB.
      (void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
      ModifiedDT = Changed = true;
      ++NumRetsDup;
    }
  
    // If we eliminated all predecessors of the block, delete the block now.
    if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
      BB->eraseFromParent();
  
    return Changed;
  }
  
  //===----------------------------------------------------------------------===//
  // Memory Optimization
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  /// ExtAddrMode - This is an extended version of TargetLowering::AddrMode
  /// which holds actual Value*'s for register values.
  struct ExtAddrMode : public TargetLowering::AddrMode {
    Value *BaseReg;
    Value *ScaledReg;
    ExtAddrMode() : BaseReg(nullptr), ScaledReg(nullptr) {}
    void print(raw_ostream &OS) const;
    void dump() const;
  
    bool operator==(const ExtAddrMode& O) const {
      return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) &&
             (BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) &&
             (HasBaseReg == O.HasBaseReg) && (Scale == O.Scale);
    }
  };
  
  #ifndef NDEBUG
  static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
    AM.print(OS);
    return OS;
  }
  #endif
  
  void ExtAddrMode::print(raw_ostream &OS) const {
    bool NeedPlus = false;
    OS << "[";
    if (BaseGV) {
      OS << (NeedPlus ? " + " : "")
         << "GV:";
      BaseGV->printAsOperand(OS, /*PrintType=*/false);
      NeedPlus = true;
    }
  
    if (BaseOffs) {
      OS << (NeedPlus ? " + " : "")
         << BaseOffs;
      NeedPlus = true;
    }
  
    if (BaseReg) {
      OS << (NeedPlus ? " + " : "")
         << "Base:";
      BaseReg->printAsOperand(OS, /*PrintType=*/false);
      NeedPlus = true;
    }
    if (Scale) {
      OS << (NeedPlus ? " + " : "")
         << Scale << "*";
      ScaledReg->printAsOperand(OS, /*PrintType=*/false);
    }
  
    OS << ']';
  }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  void ExtAddrMode::dump() const {
    print(dbgs());
    dbgs() << '\n';
  }
  #endif
  
  /// \brief This class provides transaction based operation on the IR.
  /// Every change made through this class is recorded in the internal state and
  /// can be undone (rollback) until commit is called.
  class TypePromotionTransaction {
  
    /// \brief This represents the common interface of the individual transaction.
    /// Each class implements the logic for doing one specific modification on
    /// the IR via the TypePromotionTransaction.
    class TypePromotionAction {
    protected:
      /// The Instruction modified.
      Instruction *Inst;
  
    public:
      /// \brief Constructor of the action.
      /// The constructor performs the related action on the IR.
      TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
  
      virtual ~TypePromotionAction() {}
  
      /// \brief Undo the modification done by this action.
      /// When this method is called, the IR must be in the same state as it was
      /// before this action was applied.
      /// \pre Undoing the action works if and only if the IR is in the exact same
      /// state as it was directly after this action was applied.
      virtual void undo() = 0;
  
      /// \brief Advocate every change made by this action.
      /// When the results on the IR of the action are to be kept, it is important
      /// to call this function, otherwise hidden information may be kept forever.
      virtual void commit() {
        // Nothing to be done, this action is not doing anything.
      }
    };
  
    /// \brief Utility to remember the position of an instruction.
    class InsertionHandler {
      /// Position of an instruction.
      /// Either an instruction:
      /// - Is the first in a basic block: BB is used.
      /// - Has a previous instructon: PrevInst is used.
      union {
        Instruction *PrevInst;
        BasicBlock *BB;
      } Point;
      /// Remember whether or not the instruction had a previous instruction.
      bool HasPrevInstruction;
  
    public:
      /// \brief Record the position of \p Inst.
      InsertionHandler(Instruction *Inst) {
        BasicBlock::iterator It = Inst;
        HasPrevInstruction = (It != (Inst->getParent()->begin()));
        if (HasPrevInstruction)
          Point.PrevInst = --It;
        else
          Point.BB = Inst->getParent();
      }
  
      /// \brief Insert \p Inst at the recorded position.
      void insert(Instruction *Inst) {
        if (HasPrevInstruction) {
          if (Inst->getParent())
            Inst->removeFromParent();
          Inst->insertAfter(Point.PrevInst);
        } else {
          Instruction *Position = Point.BB->getFirstInsertionPt();
          if (Inst->getParent())
            Inst->moveBefore(Position);
          else
            Inst->insertBefore(Position);
        }
      }
    };
  
    /// \brief Move an instruction before another.
    class InstructionMoveBefore : public TypePromotionAction {
      /// Original position of the instruction.
      InsertionHandler Position;
  
    public:
      /// \brief Move \p Inst before \p Before.
      InstructionMoveBefore(Instruction *Inst, Instruction *Before)
          : TypePromotionAction(Inst), Position(Inst) {
        DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n");
        Inst->moveBefore(Before);
      }
  
      /// \brief Move the instruction back to its original position.
      void undo() override {
        DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
        Position.insert(Inst);
      }
    };
  
    /// \brief Set the operand of an instruction with a new value.
    class OperandSetter : public TypePromotionAction {
      /// Original operand of the instruction.
      Value *Origin;
      /// Index of the modified instruction.
      unsigned Idx;
  
    public:
      /// \brief Set \p Idx operand of \p Inst with \p NewVal.
      OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
          : TypePromotionAction(Inst), Idx(Idx) {
        DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
                     << "for:" << *Inst << "\n"
                     << "with:" << *NewVal << "\n");
        Origin = Inst->getOperand(Idx);
        Inst->setOperand(Idx, NewVal);
      }
  
      /// \brief Restore the original value of the instruction.
      void undo() override {
        DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
                     << "for: " << *Inst << "\n"
                     << "with: " << *Origin << "\n");
        Inst->setOperand(Idx, Origin);
      }
    };
  
    /// \brief Hide the operands of an instruction.
    /// Do as if this instruction was not using any of its operands.
    class OperandsHider : public TypePromotionAction {
      /// The list of original operands.
      SmallVector<Value *, 4> OriginalValues;
  
    public:
      /// \brief Remove \p Inst from the uses of the operands of \p Inst.
      OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
        DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n");
        unsigned NumOpnds = Inst->getNumOperands();
        OriginalValues.reserve(NumOpnds);
        for (unsigned It = 0; It < NumOpnds; ++It) {
          // Save the current operand.
          Value *Val = Inst->getOperand(It);
          OriginalValues.push_back(Val);
          // Set a dummy one.
          // We could use OperandSetter here, but that would implied an overhead
          // that we are not willing to pay.
          Inst->setOperand(It, UndefValue::get(Val->getType()));
        }
      }
  
      /// \brief Restore the original list of uses.
      void undo() override {
        DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
        for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
          Inst->setOperand(It, OriginalValues[It]);
      }
    };
  
    /// \brief Build a truncate instruction.
    class TruncBuilder : public TypePromotionAction {
      Value *Val;
    public:
      /// \brief Build a truncate instruction of \p Opnd producing a \p Ty
      /// result.
      /// trunc Opnd to Ty.
      TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) {
        IRBuilder<> Builder(Opnd);
        Val = Builder.CreateTrunc(Opnd, Ty, "promoted");
        DEBUG(dbgs() << "Do: TruncBuilder: " << *Val << "\n");
      }
  
      /// \brief Get the built value.
      Value *getBuiltValue() { return Val; }
  
      /// \brief Remove the built instruction.
      void undo() override {
        DEBUG(dbgs() << "Undo: TruncBuilder: " << *Val << "\n");
        if (Instruction *IVal = dyn_cast<Instruction>(Val))
          IVal->eraseFromParent();
      }
    };
  
    /// \brief Build a sign extension instruction.
    class SExtBuilder : public TypePromotionAction {
      Value *Val;
    public:
      /// \brief Build a sign extension instruction of \p Opnd producing a \p Ty
      /// result.
      /// sext Opnd to Ty.
      SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
          : TypePromotionAction(InsertPt) {
        IRBuilder<> Builder(InsertPt);
        Val = Builder.CreateSExt(Opnd, Ty, "promoted");
        DEBUG(dbgs() << "Do: SExtBuilder: " << *Val << "\n");
      }
  
      /// \brief Get the built value.
      Value *getBuiltValue() { return Val; }
  
      /// \brief Remove the built instruction.
      void undo() override {
        DEBUG(dbgs() << "Undo: SExtBuilder: " << *Val << "\n");
        if (Instruction *IVal = dyn_cast<Instruction>(Val))
          IVal->eraseFromParent();
      }
    };
  
    /// \brief Build a zero extension instruction.
    class ZExtBuilder : public TypePromotionAction {
      Value *Val;
    public:
      /// \brief Build a zero extension instruction of \p Opnd producing a \p Ty
      /// result.
      /// zext Opnd to Ty.
      ZExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
          : TypePromotionAction(InsertPt) {
        IRBuilder<> Builder(InsertPt);
        Val = Builder.CreateZExt(Opnd, Ty, "promoted");
        DEBUG(dbgs() << "Do: ZExtBuilder: " << *Val << "\n");
      }
  
      /// \brief Get the built value.
      Value *getBuiltValue() { return Val; }
  
      /// \brief Remove the built instruction.
      void undo() override {
        DEBUG(dbgs() << "Undo: ZExtBuilder: " << *Val << "\n");
        if (Instruction *IVal = dyn_cast<Instruction>(Val))
          IVal->eraseFromParent();
      }
    };
  
    /// \brief Mutate an instruction to another type.
    class TypeMutator : public TypePromotionAction {
      /// Record the original type.
      Type *OrigTy;
  
    public:
      /// \brief Mutate the type of \p Inst into \p NewTy.
      TypeMutator(Instruction *Inst, Type *NewTy)
          : TypePromotionAction(Inst), OrigTy(Inst->getType()) {
        DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
                     << "\n");
        Inst->mutateType(NewTy);
      }
  
      /// \brief Mutate the instruction back to its original type.
      void undo() override {
        DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
                     << "\n");
        Inst->mutateType(OrigTy);
      }
    };
  
    /// \brief Replace the uses of an instruction by another instruction.
    class UsesReplacer : public TypePromotionAction {
      /// Helper structure to keep track of the replaced uses.
      struct InstructionAndIdx {
        /// The instruction using the instruction.
        Instruction *Inst;
        /// The index where this instruction is used for Inst.
        unsigned Idx;
        InstructionAndIdx(Instruction *Inst, unsigned Idx)
            : Inst(Inst), Idx(Idx) {}
      };
  
      /// Keep track of the original uses (pair Instruction, Index).
      SmallVector<InstructionAndIdx, 4> OriginalUses;
      typedef SmallVectorImpl<InstructionAndIdx>::iterator use_iterator;
  
    public:
      /// \brief Replace all the use of \p Inst by \p New.
      UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) {
        DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New
                     << "\n");
        // Record the original uses.
        for (Use &U : Inst->uses()) {
          Instruction *UserI = cast<Instruction>(U.getUser());
          OriginalUses.push_back(InstructionAndIdx(UserI, U.getOperandNo()));
        }
        // Now, we can replace the uses.
        Inst->replaceAllUsesWith(New);
      }
  
      /// \brief Reassign the original uses of Inst to Inst.
      void undo() override {
        DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
        for (use_iterator UseIt = OriginalUses.begin(),
                          EndIt = OriginalUses.end();
             UseIt != EndIt; ++UseIt) {
          UseIt->Inst->setOperand(UseIt->Idx, Inst);
        }
      }
    };
  
    /// \brief Remove an instruction from the IR.
    class InstructionRemover : public TypePromotionAction {
      /// Original position of the instruction.
      InsertionHandler Inserter;
      /// Helper structure to hide all the link to the instruction. In other
      /// words, this helps to do as if the instruction was removed.
      OperandsHider Hider;
      /// Keep track of the uses replaced, if any.
      UsesReplacer *Replacer;
  
    public:
      /// \brief Remove all reference of \p Inst and optinally replace all its
      /// uses with New.
      /// \pre If !Inst->use_empty(), then New != nullptr
      InstructionRemover(Instruction *Inst, Value *New = nullptr)
          : TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
            Replacer(nullptr) {
        if (New)
          Replacer = new UsesReplacer(Inst, New);
        DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
        Inst->removeFromParent();
      }
  
      ~InstructionRemover() { delete Replacer; }
  
      /// \brief Really remove the instruction.
      void commit() override { delete Inst; }
  
      /// \brief Resurrect the instruction and reassign it to the proper uses if
      /// new value was provided when build this action.
      void undo() override {
        DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
        Inserter.insert(Inst);
        if (Replacer)
          Replacer->undo();
        Hider.undo();
      }
    };
  
  public:
    /// Restoration point.
    /// The restoration point is a pointer to an action instead of an iterator
    /// because the iterator may be invalidated but not the pointer.
    typedef const TypePromotionAction *ConstRestorationPt;
    /// Advocate every changes made in that transaction.
    void commit();
    /// Undo all the changes made after the given point.
    void rollback(ConstRestorationPt Point);
    /// Get the current restoration point.
    ConstRestorationPt getRestorationPoint() const;
  
    /// \name API for IR modification with state keeping to support rollback.
    /// @{
    /// Same as Instruction::setOperand.
    void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal);
    /// Same as Instruction::eraseFromParent.
    void eraseInstruction(Instruction *Inst, Value *NewVal = nullptr);
    /// Same as Value::replaceAllUsesWith.
    void replaceAllUsesWith(Instruction *Inst, Value *New);
    /// Same as Value::mutateType.
    void mutateType(Instruction *Inst, Type *NewTy);
    /// Same as IRBuilder::createTrunc.
    Value *createTrunc(Instruction *Opnd, Type *Ty);
    /// Same as IRBuilder::createSExt.
    Value *createSExt(Instruction *Inst, Value *Opnd, Type *Ty);
    /// Same as IRBuilder::createZExt.
    Value *createZExt(Instruction *Inst, Value *Opnd, Type *Ty);
    /// Same as Instruction::moveBefore.
    void moveBefore(Instruction *Inst, Instruction *Before);
    /// @}
  
  private:
    /// The ordered list of actions made so far.
    SmallVector<std::unique_ptr<TypePromotionAction>, 16> Actions;
    typedef SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator CommitPt;
  };
  
  void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
                                            Value *NewVal) {
    Actions.push_back(
        make_unique<TypePromotionTransaction::OperandSetter>(Inst, Idx, NewVal));
  }
  
  void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
                                                  Value *NewVal) {
    Actions.push_back(
        make_unique<TypePromotionTransaction::InstructionRemover>(Inst, NewVal));
  }
  
  void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
                                                    Value *New) {
    Actions.push_back(make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
  }
  
  void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
    Actions.push_back(make_unique<TypePromotionTransaction::TypeMutator>(Inst, NewTy));
  }
  
  Value *TypePromotionTransaction::createTrunc(Instruction *Opnd,
                                               Type *Ty) {
    std::unique_ptr<TruncBuilder> Ptr(new TruncBuilder(Opnd, Ty));
    Value *Val = Ptr->getBuiltValue();
    Actions.push_back(std::move(Ptr));
    return Val;
  }
  
  Value *TypePromotionTransaction::createSExt(Instruction *Inst,
                                              Value *Opnd, Type *Ty) {
    std::unique_ptr<SExtBuilder> Ptr(new SExtBuilder(Inst, Opnd, Ty));
    Value *Val = Ptr->getBuiltValue();
    Actions.push_back(std::move(Ptr));
    return Val;
  }
  
  Value *TypePromotionTransaction::createZExt(Instruction *Inst,
                                              Value *Opnd, Type *Ty) {
    std::unique_ptr<ZExtBuilder> Ptr(new ZExtBuilder(Inst, Opnd, Ty));
    Value *Val = Ptr->getBuiltValue();
    Actions.push_back(std::move(Ptr));
    return Val;
  }
  
  void TypePromotionTransaction::moveBefore(Instruction *Inst,
                                            Instruction *Before) {
    Actions.push_back(
        make_unique<TypePromotionTransaction::InstructionMoveBefore>(Inst, Before));
  }
  
  TypePromotionTransaction::ConstRestorationPt
  TypePromotionTransaction::getRestorationPoint() const {
    return !Actions.empty() ? Actions.back().get() : nullptr;
  }
  
  void TypePromotionTransaction::commit() {
    for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt;
         ++It)
      (*It)->commit();
    Actions.clear();
  }
  
  void TypePromotionTransaction::rollback(
      TypePromotionTransaction::ConstRestorationPt Point) {
    while (!Actions.empty() && Point != Actions.back().get()) {
      std::unique_ptr<TypePromotionAction> Curr = Actions.pop_back_val();
      Curr->undo();
    }
  }
  
  /// \brief A helper class for matching addressing modes.
  ///
  /// This encapsulates the logic for matching the target-legal addressing modes.
  class AddressingModeMatcher {
    SmallVectorImpl<Instruction*> &AddrModeInsts;
    const TargetLowering &TLI;
  
    /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
    /// the memory instruction that we're computing this address for.
    Type *AccessTy;
    Instruction *MemoryInst;
  
    /// AddrMode - This is the addressing mode that we're building up.  This is
    /// part of the return value of this addressing mode matching stuff.
    ExtAddrMode &AddrMode;
  
    /// The truncate instruction inserted by other CodeGenPrepare optimizations.
    const SetOfInstrs &InsertedTruncs;
    /// A map from the instructions to their type before promotion.
    InstrToOrigTy &PromotedInsts;
    /// The ongoing transaction where every action should be registered.
    TypePromotionTransaction &TPT;
  
    /// IgnoreProfitability - This is set to true when we should not do
    /// profitability checks.  When true, IsProfitableToFoldIntoAddressingMode
    /// always returns true.
    bool IgnoreProfitability;
  
    AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI,
                          const TargetLowering &T, Type *AT,
                          Instruction *MI, ExtAddrMode &AM,
                          const SetOfInstrs &InsertedTruncs,
                          InstrToOrigTy &PromotedInsts,
                          TypePromotionTransaction &TPT)
        : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM),
          InsertedTruncs(InsertedTruncs), PromotedInsts(PromotedInsts), TPT(TPT) {
      IgnoreProfitability = false;
    }
  public:
  
    /// Match - Find the maximal addressing mode that a load/store of V can fold,
    /// give an access type of AccessTy.  This returns a list of involved
    /// instructions in AddrModeInsts.
    /// \p InsertedTruncs The truncate instruction inserted by other
    /// CodeGenPrepare
    /// optimizations.
    /// \p PromotedInsts maps the instructions to their type before promotion.
    /// \p The ongoing transaction where every action should be registered.
    static ExtAddrMode Match(Value *V, Type *AccessTy,
                             Instruction *MemoryInst,
                             SmallVectorImpl<Instruction*> &AddrModeInsts,
                             const TargetLowering &TLI,
                             const SetOfInstrs &InsertedTruncs,
                             InstrToOrigTy &PromotedInsts,
                             TypePromotionTransaction &TPT) {
      ExtAddrMode Result;
  
      bool Success = AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
                                           MemoryInst, Result, InsertedTruncs,
                                           PromotedInsts, TPT).MatchAddr(V, 0);
      (void)Success; assert(Success && "Couldn't select *anything*?");
      return Result;
    }
  private:
    bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
    bool MatchAddr(Value *V, unsigned Depth);
    bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth,
                            bool *MovedAway = nullptr);
    bool IsProfitableToFoldIntoAddressingMode(Instruction *I,
                                              ExtAddrMode &AMBefore,
                                              ExtAddrMode &AMAfter);
    bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
    bool IsPromotionProfitable(unsigned MatchedSize, unsigned SizeWithPromotion,
                               Value *PromotedOperand) const;
  };
  
  /// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode.
  /// Return true and update AddrMode if this addr mode is legal for the target,
  /// false if not.
  bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale,
                                               unsigned Depth) {
    // If Scale is 1, then this is the same as adding ScaleReg to the addressing
    // mode.  Just process that directly.
    if (Scale == 1)
      return MatchAddr(ScaleReg, Depth);
  
    // If the scale is 0, it takes nothing to add this.
    if (Scale == 0)
      return true;
  
    // If we already have a scale of this value, we can add to it, otherwise, we
    // need an available scale field.
    if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
      return false;
  
    ExtAddrMode TestAddrMode = AddrMode;
  
    // Add scale to turn X*4+X*3 -> X*7.  This could also do things like
    // [A+B + A*7] -> [B+A*8].
    TestAddrMode.Scale += Scale;
    TestAddrMode.ScaledReg = ScaleReg;
  
    // If the new address isn't legal, bail out.
    if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy))
      return false;
  
    // It was legal, so commit it.
    AddrMode = TestAddrMode;
  
    // Okay, we decided that we can add ScaleReg+Scale to AddrMode.  Check now
    // to see if ScaleReg is actually X+C.  If so, we can turn this into adding
    // X*Scale + C*Scale to addr mode.
    ConstantInt *CI = nullptr; Value *AddLHS = nullptr;
    if (isa<Instruction>(ScaleReg) &&  // not a constant expr.
        match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
      TestAddrMode.ScaledReg = AddLHS;
      TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
  
      // If this addressing mode is legal, commit it and remember that we folded
      // this instruction.
      if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) {
        AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
        AddrMode = TestAddrMode;
        return true;
      }
    }
  
    // Otherwise, not (x+c)*scale, just return what we have.
    return true;
  }
  
  /// MightBeFoldableInst - This is a little filter, which returns true if an
  /// addressing computation involving I might be folded into a load/store
  /// accessing it.  This doesn't need to be perfect, but needs to accept at least
  /// the set of instructions that MatchOperationAddr can.
  static bool MightBeFoldableInst(Instruction *I) {
    switch (I->getOpcode()) {
    case Instruction::BitCast:
    case Instruction::AddrSpaceCast:
      // Don't touch identity bitcasts.
      if (I->getType() == I->getOperand(0)->getType())
        return false;
      return I->getType()->isPointerTy() || I->getType()->isIntegerTy();
    case Instruction::PtrToInt:
      // PtrToInt is always a noop, as we know that the int type is pointer sized.
      return true;
    case Instruction::IntToPtr:
      // We know the input is intptr_t, so this is foldable.
      return true;
    case Instruction::Add:
      return true;
    case Instruction::Mul:
    case Instruction::Shl:
      // Can only handle X*C and X << C.
      return isa<ConstantInt>(I->getOperand(1));
    case Instruction::GetElementPtr:
      return true;
    default:
      return false;
    }
  }
  
  /// \brief Check whether or not \p Val is a legal instruction for \p TLI.
  /// \note \p Val is assumed to be the product of some type promotion.
  /// Therefore if \p Val has an undefined state in \p TLI, this is assumed
  /// to be legal, as the non-promoted value would have had the same state.
  static bool isPromotedInstructionLegal(const TargetLowering &TLI, Value *Val) {
    Instruction *PromotedInst = dyn_cast<Instruction>(Val);
    if (!PromotedInst)
      return false;
    int ISDOpcode = TLI.InstructionOpcodeToISD(PromotedInst->getOpcode());
    // If the ISDOpcode is undefined, it was undefined before the promotion.
    if (!ISDOpcode)
      return true;
    // Otherwise, check if the promoted instruction is legal or not.
    return TLI.isOperationLegalOrCustom(
        ISDOpcode, TLI.getValueType(PromotedInst->getType()));
  }
  
  /// \brief Hepler class to perform type promotion.
  class TypePromotionHelper {
    /// \brief Utility function to check whether or not a sign or zero extension
    /// of \p Inst with \p ConsideredExtType can be moved through \p Inst by
    /// either using the operands of \p Inst or promoting \p Inst.
    /// The type of the extension is defined by \p IsSExt.
    /// In other words, check if:
    /// ext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredExtType.
    /// #1 Promotion applies:
    /// ConsideredExtType Inst (ext opnd1 to ConsideredExtType, ...).
    /// #2 Operand reuses:
    /// ext opnd1 to ConsideredExtType.
    /// \p PromotedInsts maps the instructions to their type before promotion.
    static bool canGetThrough(const Instruction *Inst, Type *ConsideredExtType,
                              const InstrToOrigTy &PromotedInsts, bool IsSExt);
  
    /// \brief Utility function to determine if \p OpIdx should be promoted when
    /// promoting \p Inst.
    static bool shouldExtOperand(const Instruction *Inst, int OpIdx) {
      if (isa<SelectInst>(Inst) && OpIdx == 0)
        return false;
      return true;
    }
  
    /// \brief Utility function to promote the operand of \p Ext when this
    /// operand is a promotable trunc or sext or zext.
    /// \p PromotedInsts maps the instructions to their type before promotion.
    /// \p CreatedInsts[out] contains how many non-free instructions have been
    /// created to promote the operand of Ext.
    /// Newly added extensions are inserted in \p Exts.
    /// Newly added truncates are inserted in \p Truncs.
    /// Should never be called directly.
    /// \return The promoted value which is used instead of Ext.
    static Value *promoteOperandForTruncAndAnyExt(
        Instruction *Ext, TypePromotionTransaction &TPT,
        InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
        SmallVectorImpl<Instruction *> *Exts,
        SmallVectorImpl<Instruction *> *Truncs);
  
    /// \brief Utility function to promote the operand of \p Ext when this
    /// operand is promotable and is not a supported trunc or sext.
    /// \p PromotedInsts maps the instructions to their type before promotion.
    /// \p CreatedInsts[out] contains how many non-free instructions have been
    /// created to promote the operand of Ext.
    /// Newly added extensions are inserted in \p Exts.
    /// Newly added truncates are inserted in \p Truncs.
    /// Should never be called directly.
    /// \return The promoted value which is used instead of Ext.
    static Value *
    promoteOperandForOther(Instruction *Ext, TypePromotionTransaction &TPT,
                           InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
                           SmallVectorImpl<Instruction *> *Exts,
                           SmallVectorImpl<Instruction *> *Truncs, bool IsSExt);
  
    /// \see promoteOperandForOther.
    static Value *
    signExtendOperandForOther(Instruction *Ext, TypePromotionTransaction &TPT,
                              InstrToOrigTy &PromotedInsts,
                              unsigned &CreatedInsts,
                              SmallVectorImpl<Instruction *> *Exts,
                              SmallVectorImpl<Instruction *> *Truncs) {
      return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInsts, Exts,
                                    Truncs, true);
    }
  
    /// \see promoteOperandForOther.
    static Value *
    zeroExtendOperandForOther(Instruction *Ext, TypePromotionTransaction &TPT,
                              InstrToOrigTy &PromotedInsts,
                              unsigned &CreatedInsts,
                              SmallVectorImpl<Instruction *> *Exts,
                              SmallVectorImpl<Instruction *> *Truncs) {
      return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInsts, Exts,
                                    Truncs, false);
    }
  
  public:
    /// Type for the utility function that promotes the operand of Ext.
    typedef Value *(*Action)(Instruction *Ext, TypePromotionTransaction &TPT,
                             InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
                             SmallVectorImpl<Instruction *> *Exts,
                             SmallVectorImpl<Instruction *> *Truncs);
    /// \brief Given a sign/zero extend instruction \p Ext, return the approriate
    /// action to promote the operand of \p Ext instead of using Ext.
    /// \return NULL if no promotable action is possible with the current
    /// sign extension.
    /// \p InsertedTruncs keeps track of all the truncate instructions inserted by
    /// the others CodeGenPrepare optimizations. This information is important
    /// because we do not want to promote these instructions as CodeGenPrepare
    /// will reinsert them later. Thus creating an infinite loop: create/remove.
    /// \p PromotedInsts maps the instructions to their type before promotion.
    static Action getAction(Instruction *Ext, const SetOfInstrs &InsertedTruncs,
                            const TargetLowering &TLI,
                            const InstrToOrigTy &PromotedInsts);
  };
  
  bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
                                          Type *ConsideredExtType,
                                          const InstrToOrigTy &PromotedInsts,
                                          bool IsSExt) {
    // The promotion helper does not know how to deal with vector types yet.
    // To be able to fix that, we would need to fix the places where we
    // statically extend, e.g., constants and such.
    if (Inst->getType()->isVectorTy())
      return false;
  
    // We can always get through zext.
    if (isa<ZExtInst>(Inst))
      return true;
  
    // sext(sext) is ok too.
    if (IsSExt && isa<SExtInst>(Inst))
      return true;
  
    // We can get through binary operator, if it is legal. In other words, the
    // binary operator must have a nuw or nsw flag.
    const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst);
    if (BinOp && isa<OverflowingBinaryOperator>(BinOp) &&
        ((!IsSExt && BinOp->hasNoUnsignedWrap()) ||
         (IsSExt && BinOp->hasNoSignedWrap())))
      return true;
  
    // Check if we can do the following simplification.
    // ext(trunc(opnd)) --> ext(opnd)
    if (!isa<TruncInst>(Inst))
      return false;
  
    Value *OpndVal = Inst->getOperand(0);
    // Check if we can use this operand in the extension.
    // If the type is larger than the result type of the extension,
    // we cannot.
    if (!OpndVal->getType()->isIntegerTy() ||
        OpndVal->getType()->getIntegerBitWidth() >
            ConsideredExtType->getIntegerBitWidth())
      return false;
  
    // If the operand of the truncate is not an instruction, we will not have
    // any information on the dropped bits.
    // (Actually we could for constant but it is not worth the extra logic).
    Instruction *Opnd = dyn_cast<Instruction>(OpndVal);
    if (!Opnd)
      return false;
  
    // Check if the source of the type is narrow enough.
    // I.e., check that trunc just drops extended bits of the same kind of
    // the extension.
    // #1 get the type of the operand and check the kind of the extended bits.
    const Type *OpndType;
    InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
    if (It != PromotedInsts.end() && It->second.IsSExt == IsSExt)
      OpndType = It->second.Ty;
    else if ((IsSExt && isa<SExtInst>(Opnd)) || (!IsSExt && isa<ZExtInst>(Opnd)))
      OpndType = Opnd->getOperand(0)->getType();
    else
      return false;
  
    // #2 check that the truncate just drop extended bits.
    if (Inst->getType()->getIntegerBitWidth() >= OpndType->getIntegerBitWidth())
      return true;
  
    return false;
  }
  
  TypePromotionHelper::Action TypePromotionHelper::getAction(
      Instruction *Ext, const SetOfInstrs &InsertedTruncs,
      const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) {
    assert((isa<SExtInst>(Ext) || isa<ZExtInst>(Ext)) &&
           "Unexpected instruction type");
    Instruction *ExtOpnd = dyn_cast<Instruction>(Ext->getOperand(0));
    Type *ExtTy = Ext->getType();
    bool IsSExt = isa<SExtInst>(Ext);
    // If the operand of the extension is not an instruction, we cannot
    // get through.
    // If it, check we can get through.
    if (!ExtOpnd || !canGetThrough(ExtOpnd, ExtTy, PromotedInsts, IsSExt))
      return nullptr;
  
    // Do not promote if the operand has been added by codegenprepare.
    // Otherwise, it means we are undoing an optimization that is likely to be
    // redone, thus causing potential infinite loop.
    if (isa<TruncInst>(ExtOpnd) && InsertedTruncs.count(ExtOpnd))
      return nullptr;
  
    // SExt or Trunc instructions.
    // Return the related handler.
    if (isa<SExtInst>(ExtOpnd) || isa<TruncInst>(ExtOpnd) ||
        isa<ZExtInst>(ExtOpnd))
      return promoteOperandForTruncAndAnyExt;
  
    // Regular instruction.
    // Abort early if we will have to insert non-free instructions.
    if (!ExtOpnd->hasOneUse() && !TLI.isTruncateFree(ExtTy, ExtOpnd->getType()))
      return nullptr;
    return IsSExt ? signExtendOperandForOther : zeroExtendOperandForOther;
  }
  
  Value *TypePromotionHelper::promoteOperandForTruncAndAnyExt(
      llvm::Instruction *SExt, TypePromotionTransaction &TPT,
      InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
      SmallVectorImpl<Instruction *> *Exts,
      SmallVectorImpl<Instruction *> *Truncs) {
    // By construction, the operand of SExt is an instruction. Otherwise we cannot
    // get through it and this method should not be called.
    Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
    Value *ExtVal = SExt;
    if (isa<ZExtInst>(SExtOpnd)) {
      // Replace s|zext(zext(opnd))
      // => zext(opnd).
      Value *ZExt =
          TPT.createZExt(SExt, SExtOpnd->getOperand(0), SExt->getType());
      TPT.replaceAllUsesWith(SExt, ZExt);
      TPT.eraseInstruction(SExt);
      ExtVal = ZExt;
    } else {
      // Replace z|sext(trunc(opnd)) or sext(sext(opnd))
      // => z|sext(opnd).
      TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0));
    }
    CreatedInsts = 0;
  
    // Remove dead code.
    if (SExtOpnd->use_empty())
      TPT.eraseInstruction(SExtOpnd);
  
    // Check if the extension is still needed.
    Instruction *ExtInst = dyn_cast<Instruction>(ExtVal);
    if (!ExtInst || ExtInst->getType() != ExtInst->getOperand(0)->getType()) {
      if (ExtInst && Exts)
        Exts->push_back(ExtInst);
      return ExtVal;
    }
  
    // At this point we have: ext ty opnd to ty.
    // Reassign the uses of ExtInst to the opnd and remove ExtInst.
    Value *NextVal = ExtInst->getOperand(0);
    TPT.eraseInstruction(ExtInst, NextVal);
    return NextVal;
  }
  
  Value *TypePromotionHelper::promoteOperandForOther(
      Instruction *Ext, TypePromotionTransaction &TPT,
      InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
      SmallVectorImpl<Instruction *> *Exts,
      SmallVectorImpl<Instruction *> *Truncs, bool IsSExt) {
    // By construction, the operand of Ext is an instruction. Otherwise we cannot
    // get through it and this method should not be called.
    Instruction *ExtOpnd = cast<Instruction>(Ext->getOperand(0));
    CreatedInsts = 0;
    if (!ExtOpnd->hasOneUse()) {
      // ExtOpnd will be promoted.
      // All its uses, but Ext, will need to use a truncated value of the
      // promoted version.
      // Create the truncate now.
      Value *Trunc = TPT.createTrunc(Ext, ExtOpnd->getType());
      if (Instruction *ITrunc = dyn_cast<Instruction>(Trunc)) {
        ITrunc->removeFromParent();
        // Insert it just after the definition.
        ITrunc->insertAfter(ExtOpnd);
        if (Truncs)
          Truncs->push_back(ITrunc);
      }
  
      TPT.replaceAllUsesWith(ExtOpnd, Trunc);
      // Restore the operand of Ext (which has been replace by the previous call
      // to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext.
      TPT.setOperand(Ext, 0, ExtOpnd);
    }
  
    // Get through the Instruction:
    // 1. Update its type.
    // 2. Replace the uses of Ext by Inst.
    // 3. Extend each operand that needs to be extended.
  
    // Remember the original type of the instruction before promotion.
    // This is useful to know that the high bits are sign extended bits.
    PromotedInsts.insert(std::pair<Instruction *, TypeIsSExt>(
        ExtOpnd, TypeIsSExt(ExtOpnd->getType(), IsSExt)));
    // Step #1.
    TPT.mutateType(ExtOpnd, Ext->getType());
    // Step #2.
    TPT.replaceAllUsesWith(Ext, ExtOpnd);
    // Step #3.
    Instruction *ExtForOpnd = Ext;
  
    DEBUG(dbgs() << "Propagate Ext to operands\n");
    for (int OpIdx = 0, EndOpIdx = ExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
         ++OpIdx) {
      DEBUG(dbgs() << "Operand:\n" << *(ExtOpnd->getOperand(OpIdx)) << '\n');
      if (ExtOpnd->getOperand(OpIdx)->getType() == Ext->getType() ||
          !shouldExtOperand(ExtOpnd, OpIdx)) {
        DEBUG(dbgs() << "No need to propagate\n");
        continue;
      }
      // Check if we can statically extend the operand.
      Value *Opnd = ExtOpnd->getOperand(OpIdx);
      if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) {
        DEBUG(dbgs() << "Statically extend\n");
        unsigned BitWidth = Ext->getType()->getIntegerBitWidth();
        APInt CstVal = IsSExt ? Cst->getValue().sext(BitWidth)
                              : Cst->getValue().zext(BitWidth);
        TPT.setOperand(ExtOpnd, OpIdx, ConstantInt::get(Ext->getType(), CstVal));
        continue;
      }
      // UndefValue are typed, so we have to statically sign extend them.
      if (isa<UndefValue>(Opnd)) {
        DEBUG(dbgs() << "Statically extend\n");
        TPT.setOperand(ExtOpnd, OpIdx, UndefValue::get(Ext->getType()));
        continue;
      }
  
      // Otherwise we have to explicity sign extend the operand.
      // Check if Ext was reused to extend an operand.
      if (!ExtForOpnd) {
        // If yes, create a new one.
        DEBUG(dbgs() << "More operands to ext\n");
        Value *ValForExtOpnd = IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
          : TPT.createZExt(Ext, Opnd, Ext->getType());
        if (!isa<Instruction>(ValForExtOpnd)) {
          TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
          continue;
        }
        ExtForOpnd = cast<Instruction>(ValForExtOpnd);
        ++CreatedInsts;
      }
      if (Exts)
        Exts->push_back(ExtForOpnd);
      TPT.setOperand(ExtForOpnd, 0, Opnd);
  
      // Move the sign extension before the insertion point.
      TPT.moveBefore(ExtForOpnd, ExtOpnd);
      TPT.setOperand(ExtOpnd, OpIdx, ExtForOpnd);
      // If more sext are required, new instructions will have to be created.
      ExtForOpnd = nullptr;
    }
    if (ExtForOpnd == Ext) {
      DEBUG(dbgs() << "Extension is useless now\n");
      TPT.eraseInstruction(Ext);
    }
    return ExtOpnd;
  }
  
  /// IsPromotionProfitable - Check whether or not promoting an instruction
  /// to a wider type was profitable.
  /// \p MatchedSize gives the number of instructions that have been matched
  /// in the addressing mode after the promotion was applied.
  /// \p SizeWithPromotion gives the number of created instructions for
  /// the promotion plus the number of instructions that have been
  /// matched in the addressing mode before the promotion.
  /// \p PromotedOperand is the value that has been promoted.
  /// \return True if the promotion is profitable, false otherwise.
  bool
  AddressingModeMatcher::IsPromotionProfitable(unsigned MatchedSize,
                                               unsigned SizeWithPromotion,
                                               Value *PromotedOperand) const {
    // We folded less instructions than what we created to promote the operand.
    // This is not profitable.
    if (MatchedSize < SizeWithPromotion)
      return false;
    if (MatchedSize > SizeWithPromotion)
      return true;
    // The promotion is neutral but it may help folding the sign extension in
    // loads for instance.
    // Check that we did not create an illegal instruction.
    return isPromotedInstructionLegal(TLI, PromotedOperand);
  }
  
  /// MatchOperationAddr - Given an instruction or constant expr, see if we can
  /// fold the operation into the addressing mode.  If so, update the addressing
  /// mode and return true, otherwise return false without modifying AddrMode.
  /// If \p MovedAway is not NULL, it contains the information of whether or
  /// not AddrInst has to be folded into the addressing mode on success.
  /// If \p MovedAway == true, \p AddrInst will not be part of the addressing
  /// because it has been moved away.
  /// Thus AddrInst must not be added in the matched instructions.
  /// This state can happen when AddrInst is a sext, since it may be moved away.
  /// Therefore, AddrInst may not be valid when MovedAway is true and it must
  /// not be referenced anymore.
  bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
                                                 unsigned Depth,
                                                 bool *MovedAway) {
    // Avoid exponential behavior on extremely deep expression trees.
    if (Depth >= 5) return false;
  
    // By default, all matched instructions stay in place.
    if (MovedAway)
      *MovedAway = false;
  
    switch (Opcode) {
    case Instruction::PtrToInt:
      // PtrToInt is always a noop, as we know that the int type is pointer sized.
      return MatchAddr(AddrInst->getOperand(0), Depth);
    case Instruction::IntToPtr:
      // This inttoptr is a no-op if the integer type is pointer sized.
      if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
          TLI.getPointerTy(AddrInst->getType()->getPointerAddressSpace()))
        return MatchAddr(AddrInst->getOperand(0), Depth);
      return false;
    case Instruction::BitCast:
    case Instruction::AddrSpaceCast:
      // BitCast is always a noop, and we can handle it as long as it is
      // int->int or pointer->pointer (we don't want int<->fp or something).
      if ((AddrInst->getOperand(0)->getType()->isPointerTy() ||
           AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
          // Don't touch identity bitcasts.  These were probably put here by LSR,
          // and we don't want to mess around with them.  Assume it knows what it
          // is doing.
          AddrInst->getOperand(0)->getType() != AddrInst->getType())
        return MatchAddr(AddrInst->getOperand(0), Depth);
      return false;
    case Instruction::Add: {
      // Check to see if we can merge in the RHS then the LHS.  If so, we win.
      ExtAddrMode BackupAddrMode = AddrMode;
      unsigned OldSize = AddrModeInsts.size();
      // Start a transaction at this point.
      // The LHS may match but not the RHS.
      // Therefore, we need a higher level restoration point to undo partially
      // matched operation.
      TypePromotionTransaction::ConstRestorationPt LastKnownGood =
          TPT.getRestorationPoint();
  
      if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
          MatchAddr(AddrInst->getOperand(0), Depth+1))
        return true;
  
      // Restore the old addr mode info.
      AddrMode = BackupAddrMode;
      AddrModeInsts.resize(OldSize);
      TPT.rollback(LastKnownGood);
  
      // Otherwise this was over-aggressive.  Try merging in the LHS then the RHS.
      if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
          MatchAddr(AddrInst->getOperand(1), Depth+1))
        return true;
  
      // Otherwise we definitely can't merge the ADD in.
      AddrMode = BackupAddrMode;
      AddrModeInsts.resize(OldSize);
      TPT.rollback(LastKnownGood);
      break;
    }
    //case Instruction::Or:
    // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
    //break;
    case Instruction::Mul:
    case Instruction::Shl: {
      // Can only handle X*C and X << C.
      ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
      if (!RHS)
        return false;
      int64_t Scale = RHS->getSExtValue();
      if (Opcode == Instruction::Shl)
        Scale = 1LL << Scale;
  
      return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth);
    }
    case Instruction::GetElementPtr: {
      // Scan the GEP.  We check it if it contains constant offsets and at most
      // one variable offset.
      int VariableOperand = -1;
      unsigned VariableScale = 0;
  
      int64_t ConstantOffset = 0;
      const DataLayout *TD = TLI.getDataLayout();
      gep_type_iterator GTI = gep_type_begin(AddrInst);
      for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
          const StructLayout *SL = TD->getStructLayout(STy);
          unsigned Idx =
            cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
          ConstantOffset += SL->getElementOffset(Idx);
        } else {
          uint64_t TypeSize = TD->getTypeAllocSize(GTI.getIndexedType());
          if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
            ConstantOffset += CI->getSExtValue()*TypeSize;
          } else if (TypeSize) {  // Scales of zero don't do anything.
            // We only allow one variable index at the moment.
            if (VariableOperand != -1)
              return false;
  
            // Remember the variable index.
            VariableOperand = i;
            VariableScale = TypeSize;
          }
        }
      }
  
      // A common case is for the GEP to only do a constant offset.  In this case,
      // just add it to the disp field and check validity.
      if (VariableOperand == -1) {
        AddrMode.BaseOffs += ConstantOffset;
        if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
          // Check to see if we can fold the base pointer in too.
          if (MatchAddr(AddrInst->getOperand(0), Depth+1))
            return true;
        }
        AddrMode.BaseOffs -= ConstantOffset;
        return false;
      }
  
      // Save the valid addressing mode in case we can't match.
      ExtAddrMode BackupAddrMode = AddrMode;
      unsigned OldSize = AddrModeInsts.size();
  
      // See if the scale and offset amount is valid for this target.
      AddrMode.BaseOffs += ConstantOffset;
  
      // Match the base operand of the GEP.
      if (!MatchAddr(AddrInst->getOperand(0), Depth+1)) {
        // If it couldn't be matched, just stuff the value in a register.
        if (AddrMode.HasBaseReg) {
          AddrMode = BackupAddrMode;
          AddrModeInsts.resize(OldSize);
          return false;
        }
        AddrMode.HasBaseReg = true;
        AddrMode.BaseReg = AddrInst->getOperand(0);
      }
  
      // Match the remaining variable portion of the GEP.
      if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
                            Depth)) {
        // If it couldn't be matched, try stuffing the base into a register
        // instead of matching it, and retrying the match of the scale.
        AddrMode = BackupAddrMode;
        AddrModeInsts.resize(OldSize);
        if (AddrMode.HasBaseReg)
          return false;
        AddrMode.HasBaseReg = true;
        AddrMode.BaseReg = AddrInst->getOperand(0);
        AddrMode.BaseOffs += ConstantOffset;
        if (!MatchScaledValue(AddrInst->getOperand(VariableOperand),
                              VariableScale, Depth)) {
          // If even that didn't work, bail.
          AddrMode = BackupAddrMode;
          AddrModeInsts.resize(OldSize);
          return false;
        }
      }
  
      return true;
    }
    case Instruction::SExt:
    case Instruction::ZExt: {
      Instruction *Ext = dyn_cast<Instruction>(AddrInst);
      if (!Ext)
        return false;
  
      // Try to move this ext out of the way of the addressing mode.
      // Ask for a method for doing so.
      TypePromotionHelper::Action TPH =
          TypePromotionHelper::getAction(Ext, InsertedTruncs, TLI, PromotedInsts);
      if (!TPH)
        return false;
  
      TypePromotionTransaction::ConstRestorationPt LastKnownGood =
          TPT.getRestorationPoint();
      unsigned CreatedInsts = 0;
      Value *PromotedOperand =
          TPH(Ext, TPT, PromotedInsts, CreatedInsts, nullptr, nullptr);
      // SExt has been moved away.
      // Thus either it will be rematched later in the recursive calls or it is
      // gone. Anyway, we must not fold it into the addressing mode at this point.
      // E.g.,
      // op = add opnd, 1
      // idx = ext op
      // addr = gep base, idx
      // is now:
      // promotedOpnd = ext opnd            <- no match here
      // op = promoted_add promotedOpnd, 1  <- match (later in recursive calls)
      // addr = gep base, op                <- match
      if (MovedAway)
        *MovedAway = true;
  
      assert(PromotedOperand &&
             "TypePromotionHelper should have filtered out those cases");
  
      ExtAddrMode BackupAddrMode = AddrMode;
      unsigned OldSize = AddrModeInsts.size();
  
      if (!MatchAddr(PromotedOperand, Depth) ||
          !IsPromotionProfitable(AddrModeInsts.size(), OldSize + CreatedInsts,
                                 PromotedOperand)) {
        AddrMode = BackupAddrMode;
        AddrModeInsts.resize(OldSize);
        DEBUG(dbgs() << "Sign extension does not pay off: rollback\n");
        TPT.rollback(LastKnownGood);
        return false;
      }
      return true;
    }
    }
    return false;
  }
  
  /// MatchAddr - If we can, try to add the value of 'Addr' into the current
  /// addressing mode.  If Addr can't be added to AddrMode this returns false and
  /// leaves AddrMode unmodified.  This assumes that Addr is either a pointer type
  /// or intptr_t for the target.
  ///
  bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
    // Start a transaction at this point that we will rollback if the matching
    // fails.
    TypePromotionTransaction::ConstRestorationPt LastKnownGood =
        TPT.getRestorationPoint();
    if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
      // Fold in immediates if legal for the target.
      AddrMode.BaseOffs += CI->getSExtValue();
      if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
        return true;
      AddrMode.BaseOffs -= CI->getSExtValue();
    } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
      // If this is a global variable, try to fold it into the addressing mode.
      if (!AddrMode.BaseGV) {
        AddrMode.BaseGV = GV;
        if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
          return true;
        AddrMode.BaseGV = nullptr;
      }
    } else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
      ExtAddrMode BackupAddrMode = AddrMode;
      unsigned OldSize = AddrModeInsts.size();
  
      // Check to see if it is possible to fold this operation.
      bool MovedAway = false;
      if (MatchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) {
        // This instruction may have been move away. If so, there is nothing
        // to check here.
        if (MovedAway)
          return true;
        // Okay, it's possible to fold this.  Check to see if it is actually
        // *profitable* to do so.  We use a simple cost model to avoid increasing
        // register pressure too much.
        if (I->hasOneUse() ||
            IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
          AddrModeInsts.push_back(I);
          return true;
        }
  
        // It isn't profitable to do this, roll back.
        //cerr << "NOT FOLDING: " << *I;
        AddrMode = BackupAddrMode;
        AddrModeInsts.resize(OldSize);
        TPT.rollback(LastKnownGood);
      }
    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
      if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
        return true;
      TPT.rollback(LastKnownGood);
    } else if (isa<ConstantPointerNull>(Addr)) {
      // Null pointer gets folded without affecting the addressing mode.
      return true;
    }
  
    // Worse case, the target should support [reg] addressing modes. :)
    if (!AddrMode.HasBaseReg) {
      AddrMode.HasBaseReg = true;
      AddrMode.BaseReg = Addr;
      // Still check for legality in case the target supports [imm] but not [i+r].
      if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
        return true;
      AddrMode.HasBaseReg = false;
      AddrMode.BaseReg = nullptr;
    }
  
    // If the base register is already taken, see if we can do [r+r].
    if (AddrMode.Scale == 0) {
      AddrMode.Scale = 1;
      AddrMode.ScaledReg = Addr;
      if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
        return true;
      AddrMode.Scale = 0;
      AddrMode.ScaledReg = nullptr;
    }
    // Couldn't match.
    TPT.rollback(LastKnownGood);
    return false;
  }
  
  /// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified
  /// inline asm call are due to memory operands.  If so, return true, otherwise
  /// return false.
  static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
                                      const TargetLowering &TLI) {
    TargetLowering::AsmOperandInfoVector TargetConstraints = TLI.ParseConstraints(ImmutableCallSite(CI));
    for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
      TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
  
      // Compute the constraint code and ConstraintType to use.
      TLI.ComputeConstraintToUse(OpInfo, SDValue());
  
      // If this asm operand is our Value*, and if it isn't an indirect memory
      // operand, we can't fold it!
      if (OpInfo.CallOperandVal == OpVal &&
          (OpInfo.ConstraintType != TargetLowering::C_Memory ||
           !OpInfo.isIndirect))
        return false;
    }
  
    return true;
  }
  
  /// FindAllMemoryUses - Recursively walk all the uses of I until we find a
  /// memory use.  If we find an obviously non-foldable instruction, return true.
  /// Add the ultimately found memory instructions to MemoryUses.
  static bool FindAllMemoryUses(Instruction *I,
                  SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
                                SmallPtrSetImpl<Instruction*> &ConsideredInsts,
                                const TargetLowering &TLI) {
    // If we already considered this instruction, we're done.
    if (!ConsideredInsts.insert(I).second)
      return false;
  
    // If this is an obviously unfoldable instruction, bail out.
    if (!MightBeFoldableInst(I))
      return true;
  
    // Loop over all the uses, recursively processing them.
    for (Use &U : I->uses()) {
      Instruction *UserI = cast<Instruction>(U.getUser());
  
      if (LoadInst *LI = dyn_cast<LoadInst>(UserI)) {
        MemoryUses.push_back(std::make_pair(LI, U.getOperandNo()));
        continue;
      }
  
      if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) {
        unsigned opNo = U.getOperandNo();
        if (opNo == 0) return true; // Storing addr, not into addr.
        MemoryUses.push_back(std::make_pair(SI, opNo));
        continue;
      }
  
      if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
        InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
        if (!IA) return true;
  
        // If this is a memory operand, we're cool, otherwise bail out.
        if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
          return true;
        continue;
      }
  
      if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI))
        return true;
    }
  
    return false;
  }
  
  /// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at
  /// the use site that we're folding it into.  If so, there is no cost to
  /// include it in the addressing mode.  KnownLive1 and KnownLive2 are two values
  /// that we know are live at the instruction already.
  bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
                                                     Value *KnownLive2) {
    // If Val is either of the known-live values, we know it is live!
    if (Val == nullptr || Val == KnownLive1 || Val == KnownLive2)
      return true;
  
    // All values other than instructions and arguments (e.g. constants) are live.
    if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
  
    // If Val is a constant sized alloca in the entry block, it is live, this is
    // true because it is just a reference to the stack/frame pointer, which is
    // live for the whole function.
    if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
      if (AI->isStaticAlloca())
        return true;
  
    // Check to see if this value is already used in the memory instruction's
    // block.  If so, it's already live into the block at the very least, so we
    // can reasonably fold it.
    return Val->isUsedInBasicBlock(MemoryInst->getParent());
  }
  
  /// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing
  /// mode of the machine to fold the specified instruction into a load or store
  /// that ultimately uses it.  However, the specified instruction has multiple
  /// uses.  Given this, it may actually increase register pressure to fold it
  /// into the load.  For example, consider this code:
  ///
  ///     X = ...
  ///     Y = X+1
  ///     use(Y)   -> nonload/store
  ///     Z = Y+1
  ///     load Z
  ///
  /// In this case, Y has multiple uses, and can be folded into the load of Z
  /// (yielding load [X+2]).  However, doing this will cause both "X" and "X+1" to
  /// be live at the use(Y) line.  If we don't fold Y into load Z, we use one
  /// fewer register.  Since Y can't be folded into "use(Y)" we don't increase the
  /// number of computations either.
  ///
  /// Note that this (like most of CodeGenPrepare) is just a rough heuristic.  If
  /// X was live across 'load Z' for other reasons, we actually *would* want to
  /// fold the addressing mode in the Z case.  This would make Y die earlier.
  bool AddressingModeMatcher::
  IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
                                       ExtAddrMode &AMAfter) {
    if (IgnoreProfitability) return true;
  
    // AMBefore is the addressing mode before this instruction was folded into it,
    // and AMAfter is the addressing mode after the instruction was folded.  Get
    // the set of registers referenced by AMAfter and subtract out those
    // referenced by AMBefore: this is the set of values which folding in this
    // address extends the lifetime of.
    //
    // Note that there are only two potential values being referenced here,
    // BaseReg and ScaleReg (global addresses are always available, as are any
    // folded immediates).
    Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
  
    // If the BaseReg or ScaledReg was referenced by the previous addrmode, their
    // lifetime wasn't extended by adding this instruction.
    if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
      BaseReg = nullptr;
    if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
      ScaledReg = nullptr;
  
    // If folding this instruction (and it's subexprs) didn't extend any live
    // ranges, we're ok with it.
    if (!BaseReg && !ScaledReg)
      return true;
  
    // If all uses of this instruction are ultimately load/store/inlineasm's,
    // check to see if their addressing modes will include this instruction.  If
    // so, we can fold it into all uses, so it doesn't matter if it has multiple
    // uses.
    SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
    SmallPtrSet<Instruction*, 16> ConsideredInsts;
    if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
      return false;  // Has a non-memory, non-foldable use!
  
    // Now that we know that all uses of this instruction are part of a chain of
    // computation involving only operations that could theoretically be folded
    // into a memory use, loop over each of these uses and see if they could
    // *actually* fold the instruction.
    SmallVector<Instruction*, 32> MatchedAddrModeInsts;
    for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
      Instruction *User = MemoryUses[i].first;
      unsigned OpNo = MemoryUses[i].second;
  
      // Get the access type of this use.  If the use isn't a pointer, we don't
      // know what it accesses.
      Value *Address = User->getOperand(OpNo);
      if (!Address->getType()->isPointerTy())
        return false;
      Type *AddressAccessTy = Address->getType()->getPointerElementType();
  
      // Do a match against the root of this address, ignoring profitability. This
      // will tell us if the addressing mode for the memory operation will
      // *actually* cover the shared instruction.
      ExtAddrMode Result;
      TypePromotionTransaction::ConstRestorationPt LastKnownGood =
          TPT.getRestorationPoint();
      AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
                                    MemoryInst, Result, InsertedTruncs,
                                    PromotedInsts, TPT);
      Matcher.IgnoreProfitability = true;
      bool Success = Matcher.MatchAddr(Address, 0);
      (void)Success; assert(Success && "Couldn't select *anything*?");
  
      // The match was to check the profitability, the changes made are not
      // part of the original matcher. Therefore, they should be dropped
      // otherwise the original matcher will not present the right state.
      TPT.rollback(LastKnownGood);
  
      // If the match didn't cover I, then it won't be shared by it.
      if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
                    I) == MatchedAddrModeInsts.end())
        return false;
  
      MatchedAddrModeInsts.clear();
    }
  
    return true;
  }
  
  } // end anonymous namespace
  
  /// IsNonLocalValue - Return true if the specified values are defined in a
  /// different basic block than BB.
  static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
    if (Instruction *I = dyn_cast<Instruction>(V))
      return I->getParent() != BB;
    return false;
  }
  
  /// OptimizeMemoryInst - Load and Store Instructions often have
  /// addressing modes that can do significant amounts of computation.  As such,
  /// instruction selection will try to get the load or store to do as much
  /// computation as possible for the program.  The problem is that isel can only
  /// see within a single block.  As such, we sink as much legal addressing mode
  /// stuff into the block as possible.
  ///
  /// This method is used to optimize both load/store and inline asms with memory
  /// operands.
  bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
                                          Type *AccessTy) {
    Value *Repl = Addr;
  
    // Try to collapse single-value PHI nodes.  This is necessary to undo
    // unprofitable PRE transformations.
    SmallVector<Value*, 8> worklist;
    SmallPtrSet<Value*, 16> Visited;
    worklist.push_back(Addr);
  
    // Use a worklist to iteratively look through PHI nodes, and ensure that
    // the addressing mode obtained from the non-PHI roots of the graph
    // are equivalent.
    Value *Consensus = nullptr;
    unsigned NumUsesConsensus = 0;
    bool IsNumUsesConsensusValid = false;
    SmallVector<Instruction*, 16> AddrModeInsts;
    ExtAddrMode AddrMode;
    TypePromotionTransaction TPT;
    TypePromotionTransaction::ConstRestorationPt LastKnownGood =
        TPT.getRestorationPoint();
    while (!worklist.empty()) {
      Value *V = worklist.back();
      worklist.pop_back();
  
      // Break use-def graph loops.
      if (!Visited.insert(V).second) {
        Consensus = nullptr;
        break;
      }
  
      // For a PHI node, push all of its incoming values.
      if (PHINode *P = dyn_cast<PHINode>(V)) {
        for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
          worklist.push_back(P->getIncomingValue(i));
        continue;
      }
  
      // For non-PHIs, determine the addressing mode being computed.
      SmallVector<Instruction*, 16> NewAddrModeInsts;
      ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
          V, AccessTy, MemoryInst, NewAddrModeInsts, *TLI, InsertedTruncsSet,
          PromotedInsts, TPT);
  
      // This check is broken into two cases with very similar code to avoid using
      // getNumUses() as much as possible. Some values have a lot of uses, so
      // calling getNumUses() unconditionally caused a significant compile-time
      // regression.
      if (!Consensus) {
        Consensus = V;
        AddrMode = NewAddrMode;
        AddrModeInsts = NewAddrModeInsts;
        continue;
      } else if (NewAddrMode == AddrMode) {
        if (!IsNumUsesConsensusValid) {
          NumUsesConsensus = Consensus->getNumUses();
          IsNumUsesConsensusValid = true;
        }
  
        // Ensure that the obtained addressing mode is equivalent to that obtained
        // for all other roots of the PHI traversal.  Also, when choosing one
        // such root as representative, select the one with the most uses in order
        // to keep the cost modeling heuristics in AddressingModeMatcher
        // applicable.
        unsigned NumUses = V->getNumUses();
        if (NumUses > NumUsesConsensus) {
          Consensus = V;
          NumUsesConsensus = NumUses;
          AddrModeInsts = NewAddrModeInsts;
        }
        continue;
      }
  
      Consensus = nullptr;
      break;
    }
  
    // If the addressing mode couldn't be determined, or if multiple different
    // ones were determined, bail out now.
    if (!Consensus) {
      TPT.rollback(LastKnownGood);
      return false;
    }
    TPT.commit();
  
    // Check to see if any of the instructions supersumed by this addr mode are
    // non-local to I's BB.
    bool AnyNonLocal = false;
    for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
      if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
        AnyNonLocal = true;
        break;
      }
    }
  
    // If all the instructions matched are already in this BB, don't do anything.
    if (!AnyNonLocal) {
      DEBUG(dbgs() << "CGP: Found      local addrmode: " << AddrMode << "\n");
      return false;
    }
  
    // Insert this computation right after this user.  Since our caller is
    // scanning from the top of the BB to the bottom, reuse of the expr are
    // guaranteed to happen later.
    IRBuilder<> Builder(MemoryInst);
  
    // Now that we determined the addressing expression we want to use and know
    // that we have to sink it into this block.  Check to see if we have already
    // done this for some other load/store instr in this block.  If so, reuse the
    // computation.
    Value *&SunkAddr = SunkAddrs[Addr];
    if (SunkAddr) {
      DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
                   << *MemoryInst << "\n");
      if (SunkAddr->getType() != Addr->getType())
        SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
    } else if (AddrSinkUsingGEPs || (!AddrSinkUsingGEPs.getNumOccurrences() &&
                 TM && TM->getSubtarget<TargetSubtargetInfo>().useAA())) {
      // By default, we use the GEP-based method when AA is used later. This
      // prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
      DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
                   << *MemoryInst << "\n");
      Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType());
      Value *ResultPtr = nullptr, *ResultIndex = nullptr;
  
      // First, find the pointer.
      if (AddrMode.BaseReg && AddrMode.BaseReg->getType()->isPointerTy()) {
        ResultPtr = AddrMode.BaseReg;
        AddrMode.BaseReg = nullptr;
      }
  
      if (AddrMode.Scale && AddrMode.ScaledReg->getType()->isPointerTy()) {
        // We can't add more than one pointer together, nor can we scale a
        // pointer (both of which seem meaningless).
        if (ResultPtr || AddrMode.Scale != 1)
          return false;
  
        ResultPtr = AddrMode.ScaledReg;
        AddrMode.Scale = 0;
      }
  
      if (AddrMode.BaseGV) {
        if (ResultPtr)
          return false;
  
        ResultPtr = AddrMode.BaseGV;
      }
  
      // If the real base value actually came from an inttoptr, then the matcher
      // will look through it and provide only the integer value. In that case,
      // use it here.
      if (!ResultPtr && AddrMode.BaseReg) {
        ResultPtr =
          Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(), "sunkaddr");
        AddrMode.BaseReg = nullptr;
      } else if (!ResultPtr && AddrMode.Scale == 1) {
        ResultPtr =
          Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(), "sunkaddr");
        AddrMode.Scale = 0;
      }
  
      if (!ResultPtr &&
          !AddrMode.BaseReg && !AddrMode.Scale && !AddrMode.BaseOffs) {
        SunkAddr = Constant::getNullValue(Addr->getType());
      } else if (!ResultPtr) {
        return false;
      } else {
        Type *I8PtrTy =
          Builder.getInt8PtrTy(Addr->getType()->getPointerAddressSpace());
  
        // Start with the base register. Do this first so that subsequent address
        // matching finds it last, which will prevent it from trying to match it
        // as the scaled value in case it happens to be a mul. That would be
        // problematic if we've sunk a different mul for the scale, because then
        // we'd end up sinking both muls.
        if (AddrMode.BaseReg) {
          Value *V = AddrMode.BaseReg;
          if (V->getType() != IntPtrTy)
            V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
  
          ResultIndex = V;
        }
  
        // Add the scale value.
        if (AddrMode.Scale) {
          Value *V = AddrMode.ScaledReg;
          if (V->getType() == IntPtrTy) {
            // done.
          } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
                     cast<IntegerType>(V->getType())->getBitWidth()) {
            V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
          } else {
            // It is only safe to sign extend the BaseReg if we know that the math
            // required to create it did not overflow before we extend it. Since
            // the original IR value was tossed in favor of a constant back when
            // the AddrMode was created we need to bail out gracefully if widths
            // do not match instead of extending it.
            Instruction *I = dyn_cast_or_null<Instruction>(ResultIndex);
            if (I && (ResultIndex != AddrMode.BaseReg))
              I->eraseFromParent();
            return false;
          }
  
          if (AddrMode.Scale != 1)
            V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
                                  "sunkaddr");
          if (ResultIndex)
            ResultIndex = Builder.CreateAdd(ResultIndex, V, "sunkaddr");
          else
            ResultIndex = V;
        }
  
        // Add in the Base Offset if present.
        if (AddrMode.BaseOffs) {
          Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
          if (ResultIndex) {
            // We need to add this separately from the scale above to help with
            // SDAG consecutive load/store merging.
            if (ResultPtr->getType() != I8PtrTy)
              ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
            ResultPtr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
          }
  
          ResultIndex = V;
        }
  
        if (!ResultIndex) {
          SunkAddr = ResultPtr;
        } else {
          if (ResultPtr->getType() != I8PtrTy)
            ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
          SunkAddr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
        }
  
        if (SunkAddr->getType() != Addr->getType())
          SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
      }
    } else {
      DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
                   << *MemoryInst << "\n");
      Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType());
      Value *Result = nullptr;
  
      // Start with the base register. Do this first so that subsequent address
      // matching finds it last, which will prevent it from trying to match it
      // as the scaled value in case it happens to be a mul. That would be
      // problematic if we've sunk a different mul for the scale, because then
      // we'd end up sinking both muls.
      if (AddrMode.BaseReg) {
        Value *V = AddrMode.BaseReg;
        if (V->getType()->isPointerTy())
          V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
        if (V->getType() != IntPtrTy)
          V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
        Result = V;
      }
  
      // Add the scale value.
      if (AddrMode.Scale) {
        Value *V = AddrMode.ScaledReg;
        if (V->getType() == IntPtrTy) {
          // done.
        } else if (V->getType()->isPointerTy()) {
          V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
        } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
                   cast<IntegerType>(V->getType())->getBitWidth()) {
          V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
        } else {
          // It is only safe to sign extend the BaseReg if we know that the math
          // required to create it did not overflow before we extend it. Since
          // the original IR value was tossed in favor of a constant back when
          // the AddrMode was created we need to bail out gracefully if widths
          // do not match instead of extending it.
          Instruction *I = dyn_cast_or_null<Instruction>(Result);
          if (I && (Result != AddrMode.BaseReg))
            I->eraseFromParent();
          return false;
        }
        if (AddrMode.Scale != 1)
          V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
                                "sunkaddr");
        if (Result)
          Result = Builder.CreateAdd(Result, V, "sunkaddr");
        else
          Result = V;
      }
  
      // Add in the BaseGV if present.
      if (AddrMode.BaseGV) {
        Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr");
        if (Result)
          Result = Builder.CreateAdd(Result, V, "sunkaddr");
        else
          Result = V;
      }
  
      // Add in the Base Offset if present.
      if (AddrMode.BaseOffs) {
        Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
        if (Result)
          Result = Builder.CreateAdd(Result, V, "sunkaddr");
        else
          Result = V;
      }
  
      if (!Result)
        SunkAddr = Constant::getNullValue(Addr->getType());
      else
        SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr");
    }
  
    MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
  
    // If we have no uses, recursively delete the value and all dead instructions
    // using it.
    if (Repl->use_empty()) {
      // This can cause recursive deletion, which can invalidate our iterator.
      // Use a WeakVH to hold onto it in case this happens.
      WeakVH IterHandle(CurInstIterator);
      BasicBlock *BB = CurInstIterator->getParent();
  
      RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo);
  
      if (IterHandle != CurInstIterator) {
        // If the iterator instruction was recursively deleted, start over at the
        // start of the block.
        CurInstIterator = BB->begin();
        SunkAddrs.clear();
      }
    }
    ++NumMemoryInsts;
    return true;
  }
  
  /// OptimizeInlineAsmInst - If there are any memory operands, use
  /// OptimizeMemoryInst to sink their address computing into the block when
  /// possible / profitable.
  bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) {
    bool MadeChange = false;
  
    TargetLowering::AsmOperandInfoVector
      TargetConstraints = TLI->ParseConstraints(CS);
    unsigned ArgNo = 0;
    for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
      TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
  
      // Compute the constraint code and ConstraintType to use.
      TLI->ComputeConstraintToUse(OpInfo, SDValue());
  
      if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
          OpInfo.isIndirect) {
        Value *OpVal = CS->getArgOperand(ArgNo++);
        MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType());
      } else if (OpInfo.Type == InlineAsm::isInput)
        ArgNo++;
    }
  
    return MadeChange;
  }
  
  /// \brief Check if all the uses of \p Inst are equivalent (or free) zero or
  /// sign extensions.
  static bool hasSameExtUse(Instruction *Inst, const TargetLowering &TLI) {
    assert(!Inst->use_empty() && "Input must have at least one use");
    const Instruction *FirstUser = cast<Instruction>(*Inst->user_begin());
    bool IsSExt = isa<SExtInst>(FirstUser);
    Type *ExtTy = FirstUser->getType();
    for (const User *U : Inst->users()) {
      const Instruction *UI = cast<Instruction>(U);
      if ((IsSExt && !isa<SExtInst>(UI)) || (!IsSExt && !isa<ZExtInst>(UI)))
        return false;
      Type *CurTy = UI->getType();
      // Same input and output types: Same instruction after CSE.
      if (CurTy == ExtTy)
        continue;
  
      // If IsSExt is true, we are in this situation:
      // a = Inst
      // b = sext ty1 a to ty2
      // c = sext ty1 a to ty3
      // Assuming ty2 is shorter than ty3, this could be turned into:
      // a = Inst
      // b = sext ty1 a to ty2
      // c = sext ty2 b to ty3
      // However, the last sext is not free.
      if (IsSExt)
        return false;
  
      // This is a ZExt, maybe this is free to extend from one type to another.
      // In that case, we would not account for a different use.
      Type *NarrowTy;
      Type *LargeTy;
      if (ExtTy->getScalarType()->getIntegerBitWidth() >
          CurTy->getScalarType()->getIntegerBitWidth()) {
        NarrowTy = CurTy;
        LargeTy = ExtTy;
      } else {
        NarrowTy = ExtTy;
        LargeTy = CurTy;
      }
  
      if (!TLI.isZExtFree(NarrowTy, LargeTy))
        return false;
    }
    // All uses are the same or can be derived from one another for free.
    return true;
  }
  
  /// \brief Try to form ExtLd by promoting \p Exts until they reach a
  /// load instruction.
  /// If an ext(load) can be formed, it is returned via \p LI for the load
  /// and \p Inst for the extension.
  /// Otherwise LI == nullptr and Inst == nullptr.
  /// When some promotion happened, \p TPT contains the proper state to
  /// revert them.
  ///
  /// \return true when promoting was necessary to expose the ext(load)
  /// opportunity, false otherwise.
  ///
  /// Example:
  /// \code
  /// %ld = load i32* %addr
  /// %add = add nuw i32 %ld, 4
  /// %zext = zext i32 %add to i64
  /// \endcode
  /// =>
  /// \code
  /// %ld = load i32* %addr
  /// %zext = zext i32 %ld to i64
  /// %add = add nuw i64 %zext, 4
  /// \encode
  /// Thanks to the promotion, we can match zext(load i32*) to i64.
  bool CodeGenPrepare::ExtLdPromotion(TypePromotionTransaction &TPT,
                                      LoadInst *&LI, Instruction *&Inst,
                                      const SmallVectorImpl<Instruction *> &Exts,
                                      unsigned CreatedInsts = 0) {
    // Iterate over all the extensions to see if one form an ext(load).
    for (auto I : Exts) {
      // Check if we directly have ext(load).
      if ((LI = dyn_cast<LoadInst>(I->getOperand(0)))) {
        Inst = I;
        // No promotion happened here.
        return false;
      }
      // Check whether or not we want to do any promotion.
      if (!TLI || !TLI->enableExtLdPromotion() || DisableExtLdPromotion)
        continue;
      // Get the action to perform the promotion.
      TypePromotionHelper::Action TPH = TypePromotionHelper::getAction(
          I, InsertedTruncsSet, *TLI, PromotedInsts);
      // Check if we can promote.
      if (!TPH)
        continue;
      // Save the current state.
      TypePromotionTransaction::ConstRestorationPt LastKnownGood =
          TPT.getRestorationPoint();
      SmallVector<Instruction *, 4> NewExts;
      unsigned NewCreatedInsts = 0;
      // Promote.
      Value *PromotedVal =
          TPH(I, TPT, PromotedInsts, NewCreatedInsts, &NewExts, nullptr);
      assert(PromotedVal &&
             "TypePromotionHelper should have filtered out those cases");
  
      // We would be able to merge only one extension in a load.
      // Therefore, if we have more than 1 new extension we heuristically
      // cut this search path, because it means we degrade the code quality.
      // With exactly 2, the transformation is neutral, because we will merge
      // one extension but leave one. However, we optimistically keep going,
      // because the new extension may be removed too.
      unsigned TotalCreatedInsts = CreatedInsts + NewCreatedInsts;
      if (!StressExtLdPromotion &&
          (TotalCreatedInsts > 1 ||
           !isPromotedInstructionLegal(*TLI, PromotedVal))) {
        // The promotion is not profitable, rollback to the previous state.
        TPT.rollback(LastKnownGood);
        continue;
      }
      // The promotion is profitable.
      // Check if it exposes an ext(load).
      (void)ExtLdPromotion(TPT, LI, Inst, NewExts, TotalCreatedInsts);
      if (LI && (StressExtLdPromotion || NewCreatedInsts == 0 ||
                 // If we have created a new extension, i.e., now we have two
                 // extensions. We must make sure one of them is merged with
                 // the load, otherwise we may degrade the code quality.
                 (LI->hasOneUse() || hasSameExtUse(LI, *TLI))))
        // Promotion happened.
        return true;
      // If this does not help to expose an ext(load) then, rollback.
      TPT.rollback(LastKnownGood);
    }
    // None of the extension can form an ext(load).
    LI = nullptr;
    Inst = nullptr;
    return false;
  }
  
  /// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
  /// basic block as the load, unless conditions are unfavorable. This allows
  /// SelectionDAG to fold the extend into the load.
  /// \p I[in/out] the extension may be modified during the process if some
  /// promotions apply.
  ///
  bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *&I) {
    // Try to promote a chain of computation if it allows to form
    // an extended load.
    TypePromotionTransaction TPT;
    TypePromotionTransaction::ConstRestorationPt LastKnownGood =
      TPT.getRestorationPoint();
    SmallVector<Instruction *, 1> Exts;
    Exts.push_back(I);
    // Look for a load being extended.
    LoadInst *LI = nullptr;
    Instruction *OldExt = I;
    bool HasPromoted = ExtLdPromotion(TPT, LI, I, Exts);
    if (!LI || !I) {
      assert(!HasPromoted && !LI && "If we did not match any load instruction "
                                    "the code must remain the same");
      I = OldExt;
      return false;
    }
  
    // If they're already in the same block, there's nothing to do.
    // Make the cheap checks first if we did not promote.
    // If we promoted, we need to check if it is indeed profitable.
    if (!HasPromoted && LI->getParent() == I->getParent())
      return false;
  
    EVT VT = TLI->getValueType(I->getType());
    EVT LoadVT = TLI->getValueType(LI->getType());
  
    // If the load has other users and the truncate is not free, this probably
    // isn't worthwhile.
    if (!LI->hasOneUse() && TLI &&
        (TLI->isTypeLegal(LoadVT) || !TLI->isTypeLegal(VT)) &&
        !TLI->isTruncateFree(I->getType(), LI->getType())) {
      I = OldExt;
      TPT.rollback(LastKnownGood);
      return false;
    }
  
    // Check whether the target supports casts folded into loads.
    unsigned LType;
    if (isa<ZExtInst>(I))
      LType = ISD::ZEXTLOAD;
    else {
      assert(isa<SExtInst>(I) && "Unexpected ext type!");
      LType = ISD::SEXTLOAD;
    }
    if (TLI && !TLI->isLoadExtLegal(LType, VT, LoadVT)) {
      I = OldExt;
      TPT.rollback(LastKnownGood);
      return false;
    }
  
    // Move the extend into the same block as the load, so that SelectionDAG
    // can fold it.
    TPT.commit();
    I->removeFromParent();
    I->insertAfter(LI);
    ++NumExtsMoved;
    return true;
  }
  
  bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
    BasicBlock *DefBB = I->getParent();
  
    // If the result of a {s|z}ext and its source are both live out, rewrite all
    // other uses of the source with result of extension.
    Value *Src = I->getOperand(0);
    if (Src->hasOneUse())
      return false;
  
    // Only do this xform if truncating is free.
    if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
      return false;
  
    // Only safe to perform the optimization if the source is also defined in
    // this block.
    if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
      return false;
  
    bool DefIsLiveOut = false;
    for (User *U : I->users()) {
      Instruction *UI = cast<Instruction>(U);
  
      // Figure out which BB this ext is used in.
      BasicBlock *UserBB = UI->getParent();
      if (UserBB == DefBB) continue;
      DefIsLiveOut = true;
      break;
    }
    if (!DefIsLiveOut)
      return false;
  
    // Make sure none of the uses are PHI nodes.
    for (User *U : Src->users()) {
      Instruction *UI = cast<Instruction>(U);
      BasicBlock *UserBB = UI->getParent();
      if (UserBB == DefBB) continue;
      // Be conservative. We don't want this xform to end up introducing
      // reloads just before load / store instructions.
      if (isa<PHINode>(UI) || isa<LoadInst>(UI) || isa<StoreInst>(UI))
        return false;
    }
  
    // InsertedTruncs - Only insert one trunc in each block once.
    DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
  
    bool MadeChange = false;
    for (Use &U : Src->uses()) {
      Instruction *User = cast<Instruction>(U.getUser());
  
      // Figure out which BB this ext is used in.
      BasicBlock *UserBB = User->getParent();
      if (UserBB == DefBB) continue;
  
      // Both src and def are live in this block. Rewrite the use.
      Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
  
      if (!InsertedTrunc) {
        BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
        InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
        InsertedTruncsSet.insert(InsertedTrunc);
      }
  
      // Replace a use of the {s|z}ext source with a use of the result.
      U = InsertedTrunc;
      ++NumExtUses;
      MadeChange = true;
    }
  
    return MadeChange;
  }
  
  /// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be
  /// turned into an explicit branch.
  static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
    // FIXME: This should use the same heuristics as IfConversion to determine
    // whether a select is better represented as a branch.  This requires that
    // branch probability metadata is preserved for the select, which is not the
    // case currently.
  
    CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
  
    // If the branch is predicted right, an out of order CPU can avoid blocking on
    // the compare.  Emit cmovs on compares with a memory operand as branches to
    // avoid stalls on the load from memory.  If the compare has more than one use
    // there's probably another cmov or setcc around so it's not worth emitting a
    // branch.
    if (!Cmp)
      return false;
  
    Value *CmpOp0 = Cmp->getOperand(0);
    Value *CmpOp1 = Cmp->getOperand(1);
  
    // We check that the memory operand has one use to avoid uses of the loaded
    // value directly after the compare, making branches unprofitable.
    return Cmp->hasOneUse() &&
           ((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) ||
            (isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse()));
  }
  
  
  /// If we have a SelectInst that will likely profit from branch prediction,
  /// turn it into a branch.
  bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) {
    bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
  
    // Can we convert the 'select' to CF ?
    if (DisableSelectToBranch || OptSize || !TLI || VectorCond)
      return false;
  
    TargetLowering::SelectSupportKind SelectKind;
    if (VectorCond)
      SelectKind = TargetLowering::VectorMaskSelect;
    else if (SI->getType()->isVectorTy())
      SelectKind = TargetLowering::ScalarCondVectorVal;
    else
      SelectKind = TargetLowering::ScalarValSelect;
  
    // Do we have efficient codegen support for this kind of 'selects' ?
    if (TLI->isSelectSupported(SelectKind)) {
      // We have efficient codegen support for the select instruction.
      // Check if it is profitable to keep this 'select'.
      if (!TLI->isPredictableSelectExpensive() ||
          !isFormingBranchFromSelectProfitable(SI))
        return false;
    }
  
    ModifiedDT = true;
  
    // First, we split the block containing the select into 2 blocks.
    BasicBlock *StartBlock = SI->getParent();
    BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI));
    BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
  
    // Create a new block serving as the landing pad for the branch.
    BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid",
                                               NextBlock->getParent(), NextBlock);
  
    // Move the unconditional branch from the block with the select in it into our
    // landing pad block.
    StartBlock->getTerminator()->eraseFromParent();
    BranchInst::Create(NextBlock, SmallBlock);
  
    // Insert the real conditional branch based on the original condition.
    BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI);
  
    // The select itself is replaced with a PHI Node.
    PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin());
    PN->takeName(SI);
    PN->addIncoming(SI->getTrueValue(), StartBlock);
    PN->addIncoming(SI->getFalseValue(), SmallBlock);
    SI->replaceAllUsesWith(PN);
    SI->eraseFromParent();
  
    // Instruct OptimizeBlock to skip to the next block.
    CurInstIterator = StartBlock->end();
    ++NumSelectsExpanded;
    return true;
  }
  
  static bool isBroadcastShuffle(ShuffleVectorInst *SVI) {
    SmallVector<int, 16> Mask(SVI->getShuffleMask());
    int SplatElem = -1;
    for (unsigned i = 0; i < Mask.size(); ++i) {
      if (SplatElem != -1 && Mask[i] != -1 && Mask[i] != SplatElem)
        return false;
      SplatElem = Mask[i];
    }
  
    return true;
  }
  
  /// Some targets have expensive vector shifts if the lanes aren't all the same
  /// (e.g. x86 only introduced "vpsllvd" and friends with AVX2). In these cases
  /// it's often worth sinking a shufflevector splat down to its use so that
  /// codegen can spot all lanes are identical.
  bool CodeGenPrepare::OptimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
    BasicBlock *DefBB = SVI->getParent();
  
    // Only do this xform if variable vector shifts are particularly expensive.
    if (!TLI || !TLI->isVectorShiftByScalarCheap(SVI->getType()))
      return false;
  
    // We only expect better codegen by sinking a shuffle if we can recognise a
    // constant splat.
    if (!isBroadcastShuffle(SVI))
      return false;
  
    // InsertedShuffles - Only insert a shuffle in each block once.
    DenseMap<BasicBlock*, Instruction*> InsertedShuffles;
  
    bool MadeChange = false;
    for (User *U : SVI->users()) {
      Instruction *UI = cast<Instruction>(U);
  
      // Figure out which BB this ext is used in.
      BasicBlock *UserBB = UI->getParent();
      if (UserBB == DefBB) continue;
  
      // For now only apply this when the splat is used by a shift instruction.
      if (!UI->isShift()) continue;
  
      // Everything checks out, sink the shuffle if the user's block doesn't
      // already have a copy.
      Instruction *&InsertedShuffle = InsertedShuffles[UserBB];
  
      if (!InsertedShuffle) {
        BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
        InsertedShuffle = new ShuffleVectorInst(SVI->getOperand(0),
                                                SVI->getOperand(1),
                                                SVI->getOperand(2), "", InsertPt);
      }
  
      UI->replaceUsesOfWith(SVI, InsertedShuffle);
      MadeChange = true;
    }
  
    // If we removed all uses, nuke the shuffle.
    if (SVI->use_empty()) {
      SVI->eraseFromParent();
      MadeChange = true;
    }
  
    return MadeChange;
  }
  
  namespace {
  /// \brief Helper class to promote a scalar operation to a vector one.
  /// This class is used to move downward extractelement transition.
  /// E.g.,
  /// a = vector_op <2 x i32>
  /// b = extractelement <2 x i32> a, i32 0
  /// c = scalar_op b
  /// store c
  ///
  /// =>
  /// a = vector_op <2 x i32>
  /// c = vector_op a (equivalent to scalar_op on the related lane)
  /// * d = extractelement <2 x i32> c, i32 0
  /// * store d
  /// Assuming both extractelement and store can be combine, we get rid of the
  /// transition.
  class VectorPromoteHelper {
    /// Used to perform some checks on the legality of vector operations.
    const TargetLowering &TLI;
  
    /// Used to estimated the cost of the promoted chain.
    const TargetTransformInfo &TTI;
  
    /// The transition being moved downwards.
    Instruction *Transition;
    /// The sequence of instructions to be promoted.
    SmallVector<Instruction *, 4> InstsToBePromoted;
    /// Cost of combining a store and an extract.
    unsigned StoreExtractCombineCost;
    /// Instruction that will be combined with the transition.
    Instruction *CombineInst;
  
    /// \brief The instruction that represents the current end of the transition.
    /// Since we are faking the promotion until we reach the end of the chain
    /// of computation, we need a way to get the current end of the transition.
    Instruction *getEndOfTransition() const {
      if (InstsToBePromoted.empty())
        return Transition;
      return InstsToBePromoted.back();
    }
  
    /// \brief Return the index of the original value in the transition.
    /// E.g., for "extractelement <2 x i32> c, i32 1" the original value,
    /// c, is at index 0.
    unsigned getTransitionOriginalValueIdx() const {
      assert(isa<ExtractElementInst>(Transition) &&
             "Other kind of transitions are not supported yet");
      return 0;
    }
  
    /// \brief Return the index of the index in the transition.
    /// E.g., for "extractelement <2 x i32> c, i32 0" the index
    /// is at index 1.
    unsigned getTransitionIdx() const {
      assert(isa<ExtractElementInst>(Transition) &&
             "Other kind of transitions are not supported yet");
      return 1;
    }
  
    /// \brief Get the type of the transition.
    /// This is the type of the original value.
    /// E.g., for "extractelement <2 x i32> c, i32 1" the type of the
    /// transition is <2 x i32>.
    Type *getTransitionType() const {
      return Transition->getOperand(getTransitionOriginalValueIdx())->getType();
    }
  
    /// \brief Promote \p ToBePromoted by moving \p Def downward through.
    /// I.e., we have the following sequence:
    /// Def = Transition <ty1> a to <ty2>
    /// b = ToBePromoted <ty2> Def, ...
    /// =>
    /// b = ToBePromoted <ty1> a, ...
    /// Def = Transition <ty1> ToBePromoted to <ty2>
    void promoteImpl(Instruction *ToBePromoted);
  
    /// \brief Check whether or not it is profitable to promote all the
    /// instructions enqueued to be promoted.
    bool isProfitableToPromote() {
      Value *ValIdx = Transition->getOperand(getTransitionOriginalValueIdx());
      unsigned Index = isa<ConstantInt>(ValIdx)
                           ? cast<ConstantInt>(ValIdx)->getZExtValue()
                           : -1;
      Type *PromotedType = getTransitionType();
  
      StoreInst *ST = cast<StoreInst>(CombineInst);
      unsigned AS = ST->getPointerAddressSpace();
      unsigned Align = ST->getAlignment();
      // Check if this store is supported.
      if (!TLI.allowsMisalignedMemoryAccesses(
              TLI.getValueType(ST->getValueOperand()->getType()), AS, Align)) {
        // If this is not supported, there is no way we can combine
        // the extract with the store.
        return false;
      }
  
      // The scalar chain of computation has to pay for the transition
      // scalar to vector.
      // The vector chain has to account for the combining cost.
      uint64_t ScalarCost =
          TTI.getVectorInstrCost(Transition->getOpcode(), PromotedType, Index);
      uint64_t VectorCost = StoreExtractCombineCost;
      for (const auto &Inst : InstsToBePromoted) {
        // Compute the cost.
        // By construction, all instructions being promoted are arithmetic ones.
        // Moreover, one argument is a constant that can be viewed as a splat
        // constant.
        Value *Arg0 = Inst->getOperand(0);
        bool IsArg0Constant = isa<UndefValue>(Arg0) || isa<ConstantInt>(Arg0) ||
                              isa<ConstantFP>(Arg0);
        TargetTransformInfo::OperandValueKind Arg0OVK =
            IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
                           : TargetTransformInfo::OK_AnyValue;
        TargetTransformInfo::OperandValueKind Arg1OVK =
            !IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
                            : TargetTransformInfo::OK_AnyValue;
        ScalarCost += TTI.getArithmeticInstrCost(
            Inst->getOpcode(), Inst->getType(), Arg0OVK, Arg1OVK);
        VectorCost += TTI.getArithmeticInstrCost(Inst->getOpcode(), PromotedType,
                                                 Arg0OVK, Arg1OVK);
      }
      DEBUG(dbgs() << "Estimated cost of computation to be promoted:\nScalar: "
                   << ScalarCost << "\nVector: " << VectorCost << '\n');
      return ScalarCost > VectorCost;
    }
  
    /// \brief Generate a constant vector with \p Val with the same
    /// number of elements as the transition.
    /// \p UseSplat defines whether or not \p Val should be replicated
    /// accross the whole vector.
    /// In other words, if UseSplat == true, we generate <Val, Val, ..., Val>,
    /// otherwise we generate a vector with as many undef as possible:
    /// <undef, ..., undef, Val, undef, ..., undef> where \p Val is only
    /// used at the index of the extract.
    Value *getConstantVector(Constant *Val, bool UseSplat) const {
      unsigned ExtractIdx = UINT_MAX;
      if (!UseSplat) {
        // If we cannot determine where the constant must be, we have to
        // use a splat constant.
        Value *ValExtractIdx = Transition->getOperand(getTransitionIdx());
        if (ConstantInt *CstVal = dyn_cast<ConstantInt>(ValExtractIdx))
          ExtractIdx = CstVal->getSExtValue();
        else
          UseSplat = true;
      }
  
      unsigned End = getTransitionType()->getVectorNumElements();
      if (UseSplat)
        return ConstantVector::getSplat(End, Val);
  
      SmallVector<Constant *, 4> ConstVec;
      UndefValue *UndefVal = UndefValue::get(Val->getType());
      for (unsigned Idx = 0; Idx != End; ++Idx) {
        if (Idx == ExtractIdx)
          ConstVec.push_back(Val);
        else
          ConstVec.push_back(UndefVal);
      }
      return ConstantVector::get(ConstVec);
    }
  
    /// \brief Check if promoting to a vector type an operand at \p OperandIdx
    /// in \p Use can trigger undefined behavior.
    static bool canCauseUndefinedBehavior(const Instruction *Use,
                                          unsigned OperandIdx) {
      // This is not safe to introduce undef when the operand is on
      // the right hand side of a division-like instruction.
      if (OperandIdx != 1)
        return false;
      switch (Use->getOpcode()) {
      default:
        return false;
      case Instruction::SDiv:
      case Instruction::UDiv:
      case Instruction::SRem:
      case Instruction::URem:
        return true;
      case Instruction::FDiv:
      case Instruction::FRem:
        return !Use->hasNoNaNs();
      }
      llvm_unreachable(nullptr);
    }
  
  public:
    VectorPromoteHelper(const TargetLowering &TLI, const TargetTransformInfo &TTI,
                        Instruction *Transition, unsigned CombineCost)
        : TLI(TLI), TTI(TTI), Transition(Transition),
          StoreExtractCombineCost(CombineCost), CombineInst(nullptr) {
      assert(Transition && "Do not know how to promote null");
    }
  
    /// \brief Check if we can promote \p ToBePromoted to \p Type.
    bool canPromote(const Instruction *ToBePromoted) const {
      // We could support CastInst too.
      return isa<BinaryOperator>(ToBePromoted);
    }
  
    /// \brief Check if it is profitable to promote \p ToBePromoted
    /// by moving downward the transition through.
    bool shouldPromote(const Instruction *ToBePromoted) const {
      // Promote only if all the operands can be statically expanded.
      // Indeed, we do not want to introduce any new kind of transitions.
      for (const Use &U : ToBePromoted->operands()) {
        const Value *Val = U.get();
        if (Val == getEndOfTransition()) {
          // If the use is a division and the transition is on the rhs,
          // we cannot promote the operation, otherwise we may create a
          // division by zero.
          if (canCauseUndefinedBehavior(ToBePromoted, U.getOperandNo()))
            return false;
          continue;
        }
        if (!isa<ConstantInt>(Val) && !isa<UndefValue>(Val) &&
            !isa<ConstantFP>(Val))
          return false;
      }
      // Check that the resulting operation is legal.
      int ISDOpcode = TLI.InstructionOpcodeToISD(ToBePromoted->getOpcode());
      if (!ISDOpcode)
        return false;
      return StressStoreExtract ||
             TLI.isOperationLegalOrCustom(
                 ISDOpcode, TLI.getValueType(getTransitionType(), true));
    }
  
    /// \brief Check whether or not \p Use can be combined
    /// with the transition.
    /// I.e., is it possible to do Use(Transition) => AnotherUse?
    bool canCombine(const Instruction *Use) { return isa<StoreInst>(Use); }
  
    /// \brief Record \p ToBePromoted as part of the chain to be promoted.
    void enqueueForPromotion(Instruction *ToBePromoted) {
      InstsToBePromoted.push_back(ToBePromoted);
    }
  
    /// \brief Set the instruction that will be combined with the transition.
    void recordCombineInstruction(Instruction *ToBeCombined) {
      assert(canCombine(ToBeCombined) && "Unsupported instruction to combine");
      CombineInst = ToBeCombined;
    }
  
    /// \brief Promote all the instructions enqueued for promotion if it is
    /// is profitable.
    /// \return True if the promotion happened, false otherwise.
    bool promote() {
      // Check if there is something to promote.
      // Right now, if we do not have anything to combine with,
      // we assume the promotion is not profitable.
      if (InstsToBePromoted.empty() || !CombineInst)
        return false;
  
      // Check cost.
      if (!StressStoreExtract && !isProfitableToPromote())
        return false;
  
      // Promote.
      for (auto &ToBePromoted : InstsToBePromoted)
        promoteImpl(ToBePromoted);
      InstsToBePromoted.clear();
      return true;
    }
  };
  } // End of anonymous namespace.
  
  void VectorPromoteHelper::promoteImpl(Instruction *ToBePromoted) {
    // At this point, we know that all the operands of ToBePromoted but Def
    // can be statically promoted.
    // For Def, we need to use its parameter in ToBePromoted:
    // b = ToBePromoted ty1 a
    // Def = Transition ty1 b to ty2
    // Move the transition down.
    // 1. Replace all uses of the promoted operation by the transition.
    // = ... b => = ... Def.
    assert(ToBePromoted->getType() == Transition->getType() &&
           "The type of the result of the transition does not match "
           "the final type");
    ToBePromoted->replaceAllUsesWith(Transition);
    // 2. Update the type of the uses.
    // b = ToBePromoted ty2 Def => b = ToBePromoted ty1 Def.
    Type *TransitionTy = getTransitionType();
    ToBePromoted->mutateType(TransitionTy);
    // 3. Update all the operands of the promoted operation with promoted
    // operands.
    // b = ToBePromoted ty1 Def => b = ToBePromoted ty1 a.
    for (Use &U : ToBePromoted->operands()) {
      Value *Val = U.get();
      Value *NewVal = nullptr;
      if (Val == Transition)
        NewVal = Transition->getOperand(getTransitionOriginalValueIdx());
      else if (isa<UndefValue>(Val) || isa<ConstantInt>(Val) ||
               isa<ConstantFP>(Val)) {
        // Use a splat constant if it is not safe to use undef.
        NewVal = getConstantVector(
            cast<Constant>(Val),
            isa<UndefValue>(Val) ||
                canCauseUndefinedBehavior(ToBePromoted, U.getOperandNo()));
      } else
        llvm_unreachable("Did you modified shouldPromote and forgot to update "
                         "this?");
      ToBePromoted->setOperand(U.getOperandNo(), NewVal);
    }
    Transition->removeFromParent();
    Transition->insertAfter(ToBePromoted);
    Transition->setOperand(getTransitionOriginalValueIdx(), ToBePromoted);
  }
  
  // See if we can speculate calls to intrinsic cttz/ctlz.
  //
  // Example:
  // entry:
  //   ...
  //   %cmp = icmp eq i64 %val, 0
  //   br i1 %cmp, label %end.bb, label %then.bb
  //
  // then.bb:
  //   %c = tail call i64 @llvm.cttz.i64(i64 %val, i1 true)
  //   br label %EndBB
  //
  // end.bb:
  //   %cond = phi i64 [ %c, %then.bb ], [ 64, %entry ]
  //
  // ==>
  //
  // entry:
  //   ...
  //   %c = tail call i64 @llvm.cttz.i64(i64 %val, i1 false)
  //
  static bool OptimizeBranchInst(BranchInst *BrInst, const TargetLowering &TLI) {
    assert(BrInst->isConditional() && "Expected a conditional branch!");
    BasicBlock *ThenBB = BrInst->getSuccessor(1);
    BasicBlock *EndBB = BrInst->getSuccessor(0);
  
    // See if ThenBB contains only one instruction (excluding the
    // terminator and DbgInfoIntrinsic calls).
    IntrinsicInst *II = nullptr;
    CastInst *CI = nullptr;
    for (BasicBlock::iterator I = ThenBB->begin(),
                              E = std::prev(ThenBB->end()); I != E; ++I) {
      // Skip debug info.
      if (isa<DbgInfoIntrinsic>(I))
        continue;
  
      // Check if this is a zero extension or a truncate of a previously
      // matched call to intrinsic cttz/ctlz.
      if (II) {
        // Early exit if we already found a "free" zero extend/truncate.
        if (CI)
          return false;
  
        Type *SrcTy = II->getType();
        Type *DestTy = I->getType();
        Value *V;
   
        if (match(cast<Instruction>(I), m_ZExt(m_Value(V))) && V == II) {
          // Speculate this zero extend only if it is "free" for the target.
          if (TLI.isZExtFree(SrcTy, DestTy)) {
            CI = cast<CastInst>(I);
            continue;
          }
        } else if (match(cast<Instruction>(I), m_Trunc(m_Value(V))) && V == II) {
          // Speculate this truncate only if it is "free" for the target.
          if (TLI.isTruncateFree(SrcTy, DestTy)) {
            CI = cast<CastInst>(I);
            continue;
          }
        } else {
          // Avoid speculating more than one instruction.
          return false;
        }
      }
  
      // See if this is a call to intrinsic cttz/ctlz.
      if (match(cast<Instruction>(I), m_Intrinsic<Intrinsic::cttz>())) {
        // Avoid speculating expensive intrinsic calls.
        if (!TLI.isCheapToSpeculateCttz())
          return false;
      }
      else if (match(cast<Instruction>(I), m_Intrinsic<Intrinsic::ctlz>())) {
        // Avoid speculating expensive intrinsic calls.
        if (!TLI.isCheapToSpeculateCtlz())
          return false;
      } else
        return false;
      
      II = cast<IntrinsicInst>(I);
    }
  
    // Look for PHI nodes with 'II' as the incoming value from 'ThenBB'.
    BasicBlock *EntryBB = BrInst->getParent();
    for (BasicBlock::iterator I = EndBB->begin();
         PHINode *PN = dyn_cast<PHINode>(I); ++I) {
      Value *ThenV = PN->getIncomingValueForBlock(ThenBB);
      Value *OrigV = PN->getIncomingValueForBlock(EntryBB);
  
      if (!OrigV)
        return false;
  
      if (ThenV != II && (!CI || ThenV != CI))
        return false;
      
      if (ConstantInt *CInt = dyn_cast<ConstantInt>(OrigV)) {
        unsigned BitWidth = II->getType()->getIntegerBitWidth();
  
        // Don't try to simplify this phi node if 'ThenV' is a cttz/ctlz
        // intrinsic call, but 'OrigV' is not equal to the 'size-of' in bits
        // of the value in input to the cttz/ctlz.
        if (CInt->getValue() != BitWidth)
          return false;
  
        // Hoist the call to cttz/ctlz from ThenBB into EntryBB.
        EntryBB->getInstList().splice(BrInst, ThenBB->getInstList(),
                                      ThenBB->begin(), std::prev(ThenBB->end()));
   
        // Update PN setting ThenV as the incoming value from both 'EntryBB'
        // and 'ThenBB'. Eventually, method 'OptimizeInst' will fold this
        // phi node if all the incoming values are the same.
        PN->setIncomingValue(PN->getBasicBlockIndex(EntryBB), ThenV);
        PN->setIncomingValue(PN->getBasicBlockIndex(ThenBB), ThenV);
  
        // Clear the 'undef on zero' flag of the cttz/ctlz intrinsic call.
        if (cast<ConstantInt>(II->getArgOperand(1))->isOne()) {
          Type *Ty = II->getArgOperand(0)->getType();
          Value *Args[] = { II->getArgOperand(0),
                            ConstantInt::getFalse(II->getContext()) };
          Module *M = EntryBB->getParent()->getParent();
          Value *IF = Intrinsic::getDeclaration(M, II->getIntrinsicID(), Ty);
          IRBuilder<> Builder(II);
          Instruction *NewI = Builder.CreateCall(IF, Args);
  
          // Replace the old call to cttz/ctlz.
          II->replaceAllUsesWith(NewI);
          II->eraseFromParent();
        }
   
        // Update BrInst condition so that the branch to EndBB is always taken.
        // Later on, method 'ConstantFoldTerminator' will simplify this branch
        // replacing it with a direct branch to 'EndBB'.
        // As a side effect, CodeGenPrepare will attempt to simplify the control
        // flow graph by deleting basic block 'ThenBB' and merging 'EntryBB' into
        // 'EndBB' (calling method 'EliminateFallThrough').
        BrInst->setCondition(ConstantInt::getTrue(BrInst->getContext()));
        return true;
      }
    }
  
    return false;
  }
  
  /// Some targets can do store(extractelement) with one instruction.
  /// Try to push the extractelement towards the stores when the target
  /// has this feature and this is profitable.
  bool CodeGenPrepare::OptimizeExtractElementInst(Instruction *Inst) {
    unsigned CombineCost = UINT_MAX;
    if (DisableStoreExtract || !TLI ||
        (!StressStoreExtract &&
         !TLI->canCombineStoreAndExtract(Inst->getOperand(0)->getType(),
                                         Inst->getOperand(1), CombineCost)))
      return false;
  
    // At this point we know that Inst is a vector to scalar transition.
    // Try to move it down the def-use chain, until:
    // - We can combine the transition with its single use
    //   => we got rid of the transition.
    // - We escape the current basic block
    //   => we would need to check that we are moving it at a cheaper place and
    //      we do not do that for now.
    BasicBlock *Parent = Inst->getParent();
    DEBUG(dbgs() << "Found an interesting transition: " << *Inst << '\n');
    VectorPromoteHelper VPH(*TLI, *TTI, Inst, CombineCost);
    // If the transition has more than one use, assume this is not going to be
    // beneficial.
    while (Inst->hasOneUse()) {
      Instruction *ToBePromoted = cast<Instruction>(*Inst->user_begin());
      DEBUG(dbgs() << "Use: " << *ToBePromoted << '\n');
  
      if (ToBePromoted->getParent() != Parent) {
        DEBUG(dbgs() << "Instruction to promote is in a different block ("
                     << ToBePromoted->getParent()->getName()
                     << ") than the transition (" << Parent->getName() << ").\n");
        return false;
      }
  
      if (VPH.canCombine(ToBePromoted)) {
        DEBUG(dbgs() << "Assume " << *Inst << '\n'
                     << "will be combined with: " << *ToBePromoted << '\n');
        VPH.recordCombineInstruction(ToBePromoted);
        bool Changed = VPH.promote();
        NumStoreExtractExposed += Changed;
        return Changed;
      }
  
      DEBUG(dbgs() << "Try promoting.\n");
      if (!VPH.canPromote(ToBePromoted) || !VPH.shouldPromote(ToBePromoted))
        return false;
  
      DEBUG(dbgs() << "Promoting is possible... Enqueue for promotion!\n");
  
      VPH.enqueueForPromotion(ToBePromoted);
      Inst = ToBePromoted;
    }
    return false;
  }
  
  bool CodeGenPrepare::OptimizeInst(Instruction *I, bool& ModifiedDT) {
    if (PHINode *P = dyn_cast<PHINode>(I)) {
      // It is possible for very late stage optimizations (such as SimplifyCFG)
      // to introduce PHI nodes too late to be cleaned up.  If we detect such a
      // trivial PHI, go ahead and zap it here.
      if (Value *V = SimplifyInstruction(P, TLI ? TLI->getDataLayout() : nullptr,
                                         TLInfo, DT)) {
        P->replaceAllUsesWith(V);
        P->eraseFromParent();
        ++NumPHIsElim;
        return true;
      }
      return false;
    }
  
    if (CastInst *CI = dyn_cast<CastInst>(I)) {
      // If the source of the cast is a constant, then this should have
      // already been constant folded.  The only reason NOT to constant fold
      // it is if something (e.g. LSR) was careful to place the constant
      // evaluation in a block other than then one that uses it (e.g. to hoist
      // the address of globals out of a loop).  If this is the case, we don't
      // want to forward-subst the cast.
      if (isa<Constant>(CI->getOperand(0)))
        return false;
  
      if (TLI && OptimizeNoopCopyExpression(CI, *TLI))
        return true;
  
      if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
        /// Sink a zext or sext into its user blocks if the target type doesn't
        /// fit in one register
        if (TLI && TLI->getTypeAction(CI->getContext(),
                                      TLI->getValueType(CI->getType())) ==
                       TargetLowering::TypeExpandInteger) {
          return SinkCast(CI);
        } else {
          bool MadeChange = MoveExtToFormExtLoad(I);
          return MadeChange | OptimizeExtUses(I);
        }
      }
      return false;
    }
  
    if (CmpInst *CI = dyn_cast<CmpInst>(I))
      if (!TLI || !TLI->hasMultipleConditionRegisters())
        return OptimizeCmpExpression(CI);
  
    if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
      if (TLI)
        return OptimizeMemoryInst(I, I->getOperand(0), LI->getType());
      return false;
    }
  
    if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
      if (TLI)
        return OptimizeMemoryInst(I, SI->getOperand(1),
                                  SI->getOperand(0)->getType());
      return false;
    }
  
    BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I);
  
    if (BinOp && (BinOp->getOpcode() == Instruction::AShr ||
                  BinOp->getOpcode() == Instruction::LShr)) {
      ConstantInt *CI = dyn_cast<ConstantInt>(BinOp->getOperand(1));
      if (TLI && CI && TLI->hasExtractBitsInsn())
        return OptimizeExtractBits(BinOp, CI, *TLI);
  
      return false;
    }
  
    if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
      if (GEPI->hasAllZeroIndices()) {
        /// The GEP operand must be a pointer, so must its result -> BitCast
        Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
                                          GEPI->getName(), GEPI);
        GEPI->replaceAllUsesWith(NC);
        GEPI->eraseFromParent();
        ++NumGEPsElim;
        OptimizeInst(NC, ModifiedDT);
        return true;
      }
      return false;
    }
  
    if (CallInst *CI = dyn_cast<CallInst>(I))
      return OptimizeCallInst(CI, ModifiedDT);
  
    if (SelectInst *SI = dyn_cast<SelectInst>(I))
      return OptimizeSelectInst(SI);
  
    if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
      return OptimizeShuffleVectorInst(SVI);
  
    if (isa<ExtractElementInst>(I))
      return OptimizeExtractElementInst(I);
  
    if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
      if (TLI && BI->isConditional() && BI->getCondition()->hasOneUse()) {
        // Check if the branch condition compares a value agaist zero.
        if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
          if (ICI->getPredicate() == ICmpInst::ICMP_EQ &&
              match(ICI->getOperand(1), m_Zero())) {
            BasicBlock *ThenBB = BI->getSuccessor(1);
            BasicBlock *EndBB = BI->getSuccessor(0);
  
            // Check if ThenBB is only reachable from this basic block; also,
            // check if EndBB has more than one predecessor.
            if (ThenBB->getSinglePredecessor() &&
                !EndBB->getSinglePredecessor()) {
              TerminatorInst *TI = ThenBB->getTerminator();
  
              if (TI->getNumSuccessors() == 1 && TI->getSuccessor(0) == EndBB &&
                  // Try to speculate calls to intrinsic cttz/ctlz from 'ThenBB'.
                  OptimizeBranchInst(BI, *TLI)) {
                ModifiedDT = true;
                return true;
              }
            }
          }
        }
      }
      return false;
    }
  
    return false;
  }
  
  // In this pass we look for GEP and cast instructions that are used
  // across basic blocks and rewrite them to improve basic-block-at-a-time
  // selection.
  bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB, bool& ModifiedDT) {
    SunkAddrs.clear();
    bool MadeChange = false;
  
    CurInstIterator = BB.begin();
    while (CurInstIterator != BB.end()) {
      MadeChange |= OptimizeInst(CurInstIterator++, ModifiedDT);
      if (ModifiedDT)
        return true;
    }
    MadeChange |= DupRetToEnableTailCallOpts(&BB);
  
    return MadeChange;
  }
  
  // llvm.dbg.value is far away from the value then iSel may not be able
  // handle it properly. iSel will drop llvm.dbg.value if it can not
  // find a node corresponding to the value.
  bool CodeGenPrepare::PlaceDbgValues(Function &F) {
    bool MadeChange = false;
    for (BasicBlock &BB : F) {
      Instruction *PrevNonDbgInst = nullptr;
      for (BasicBlock::iterator BI = BB.begin(), BE = BB.end(); BI != BE;) {
        Instruction *Insn = BI++;
        DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn);
        // Leave dbg.values that refer to an alloca alone. These
        // instrinsics describe the address of a variable (= the alloca)
        // being taken.  They should not be moved next to the alloca
        // (and to the beginning of the scope), but rather stay close to
        // where said address is used.
        if (!DVI || (DVI->getValue() && isa<AllocaInst>(DVI->getValue()))) {
          PrevNonDbgInst = Insn;
          continue;
        }
  
        Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue());
        if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) {
          DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
          DVI->removeFromParent();
          if (isa<PHINode>(VI))
            DVI->insertBefore(VI->getParent()->getFirstInsertionPt());
          else
            DVI->insertAfter(VI);
          MadeChange = true;
          ++NumDbgValueMoved;
        }
      }
    }
    return MadeChange;
  }
  
  // If there is a sequence that branches based on comparing a single bit
  // against zero that can be combined into a single instruction, and the
  // target supports folding these into a single instruction, sink the
  // mask and compare into the branch uses. Do this before OptimizeBlock ->
  // OptimizeInst -> OptimizeCmpExpression, which perturbs the pattern being
  // searched for.
  bool CodeGenPrepare::sinkAndCmp(Function &F) {
    if (!EnableAndCmpSinking)
      return false;
    if (!TLI || !TLI->isMaskAndBranchFoldingLegal())
      return false;
    bool MadeChange = false;
    for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
      BasicBlock *BB = I++;
  
      // Does this BB end with the following?
      //   %andVal = and %val, #single-bit-set
      //   %icmpVal = icmp %andResult, 0
      //   br i1 %cmpVal label %dest1, label %dest2"
      BranchInst *Brcc = dyn_cast<BranchInst>(BB->getTerminator());
      if (!Brcc || !Brcc->isConditional())
        continue;
      ICmpInst *Cmp = dyn_cast<ICmpInst>(Brcc->getOperand(0));
      if (!Cmp || Cmp->getParent() != BB)
        continue;
      ConstantInt *Zero = dyn_cast<ConstantInt>(Cmp->getOperand(1));
      if (!Zero || !Zero->isZero())
        continue;
      Instruction *And = dyn_cast<Instruction>(Cmp->getOperand(0));
      if (!And || And->getOpcode() != Instruction::And || And->getParent() != BB)
        continue;
      ConstantInt* Mask = dyn_cast<ConstantInt>(And->getOperand(1));
      if (!Mask || !Mask->getUniqueInteger().isPowerOf2())
        continue;
      DEBUG(dbgs() << "found and; icmp ?,0; brcc\n"); DEBUG(BB->dump());
  
      // Push the "and; icmp" for any users that are conditional branches.
      // Since there can only be one branch use per BB, we don't need to keep
      // track of which BBs we insert into.
      for (Value::use_iterator UI = Cmp->use_begin(), E = Cmp->use_end();
           UI != E; ) {
        Use &TheUse = *UI;
        // Find brcc use.
        BranchInst *BrccUser = dyn_cast<BranchInst>(*UI);
        ++UI;
        if (!BrccUser || !BrccUser->isConditional())
          continue;
        BasicBlock *UserBB = BrccUser->getParent();
        if (UserBB == BB) continue;
        DEBUG(dbgs() << "found Brcc use\n");
  
        // Sink the "and; icmp" to use.
        MadeChange = true;
        BinaryOperator *NewAnd =
          BinaryOperator::CreateAnd(And->getOperand(0), And->getOperand(1), "",
                                    BrccUser);
        CmpInst *NewCmp =
          CmpInst::Create(Cmp->getOpcode(), Cmp->getPredicate(), NewAnd, Zero,
                          "", BrccUser);
        TheUse = NewCmp;
        ++NumAndCmpsMoved;
        DEBUG(BrccUser->getParent()->dump());
      }
    }
    return MadeChange;
  }
  
  /// \brief Retrieve the probabilities of a conditional branch. Returns true on
  /// success, or returns false if no or invalid metadata was found.
  static bool extractBranchMetadata(BranchInst *BI,
                                    uint64_t &ProbTrue, uint64_t &ProbFalse) {
    assert(BI->isConditional() &&
           "Looking for probabilities on unconditional branch?");
    auto *ProfileData = BI->getMetadata(LLVMContext::MD_prof);
    if (!ProfileData || ProfileData->getNumOperands() != 3)
      return false;
  
    const auto *CITrue =
        mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(1));
    const auto *CIFalse =
        mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2));
    if (!CITrue || !CIFalse)
      return false;
  
    ProbTrue = CITrue->getValue().getZExtValue();
    ProbFalse = CIFalse->getValue().getZExtValue();
  
    return true;
  }
  
  /// \brief Scale down both weights to fit into uint32_t.
  static void scaleWeights(uint64_t &NewTrue, uint64_t &NewFalse) {
    uint64_t NewMax = (NewTrue > NewFalse) ? NewTrue : NewFalse;
    uint32_t Scale = (NewMax / UINT32_MAX) + 1;
    NewTrue = NewTrue / Scale;
    NewFalse = NewFalse / Scale;
  }
  
  /// \brief Some targets prefer to split a conditional branch like:
  /// \code
  ///   %0 = icmp ne i32 %a, 0
  ///   %1 = icmp ne i32 %b, 0
  ///   %or.cond = or i1 %0, %1
  ///   br i1 %or.cond, label %TrueBB, label %FalseBB
  /// \endcode
  /// into multiple branch instructions like:
  /// \code
  ///   bb1:
  ///     %0 = icmp ne i32 %a, 0
  ///     br i1 %0, label %TrueBB, label %bb2
  ///   bb2:
  ///     %1 = icmp ne i32 %b, 0
  ///     br i1 %1, label %TrueBB, label %FalseBB
  /// \endcode
  /// This usually allows instruction selection to do even further optimizations
  /// and combine the compare with the branch instruction. Currently this is
  /// applied for targets which have "cheap" jump instructions.
  ///
  /// FIXME: Remove the (equivalent?) implementation in SelectionDAG.
  ///
  bool CodeGenPrepare::splitBranchCondition(Function &F) {
    if (!TM || TM->Options.EnableFastISel != true ||
        !TLI || TLI->isJumpExpensive())
      return false;
  
    bool MadeChange = false;
    for (auto &BB : F) {
      // Does this BB end with the following?
      //   %cond1 = icmp|fcmp|binary instruction ...
      //   %cond2 = icmp|fcmp|binary instruction ...
      //   %cond.or = or|and i1 %cond1, cond2
      //   br i1 %cond.or label %dest1, label %dest2"
      BinaryOperator *LogicOp;
      BasicBlock *TBB, *FBB;
      if (!match(BB.getTerminator(), m_Br(m_OneUse(m_BinOp(LogicOp)), TBB, FBB)))
        continue;
  
      unsigned Opc;
      Value *Cond1, *Cond2;
      if (match(LogicOp, m_And(m_OneUse(m_Value(Cond1)),
                               m_OneUse(m_Value(Cond2)))))
        Opc = Instruction::And;
      else if (match(LogicOp, m_Or(m_OneUse(m_Value(Cond1)),
                                   m_OneUse(m_Value(Cond2)))))
        Opc = Instruction::Or;
      else
        continue;
  
      if (!match(Cond1, m_CombineOr(m_Cmp(), m_BinOp())) ||
          !match(Cond2, m_CombineOr(m_Cmp(), m_BinOp()))   )
        continue;
  
      DEBUG(dbgs() << "Before branch condition splitting\n"; BB.dump());
  
      // Create a new BB.
      auto *InsertBefore = std::next(Function::iterator(BB))
          .getNodePtrUnchecked();
      auto TmpBB = BasicBlock::Create(BB.getContext(),
                                      BB.getName() + ".cond.split",
                                      BB.getParent(), InsertBefore);
  
      // Update original basic block by using the first condition directly by the
      // branch instruction and removing the no longer needed and/or instruction.
      auto *Br1 = cast<BranchInst>(BB.getTerminator());
      Br1->setCondition(Cond1);
      LogicOp->eraseFromParent();
  
      // Depending on the conditon we have to either replace the true or the false
      // successor of the original branch instruction.
      if (Opc == Instruction::And)
        Br1->setSuccessor(0, TmpBB);
      else
        Br1->setSuccessor(1, TmpBB);
  
      // Fill in the new basic block.
      auto *Br2 = IRBuilder<>(TmpBB).CreateCondBr(Cond2, TBB, FBB);
      if (auto *I = dyn_cast<Instruction>(Cond2)) {
        I->removeFromParent();
        I->insertBefore(Br2);
      }
  
      // Update PHI nodes in both successors. The original BB needs to be
      // replaced in one succesor's PHI nodes, because the branch comes now from
      // the newly generated BB (NewBB). In the other successor we need to add one
      // incoming edge to the PHI nodes, because both branch instructions target
      // now the same successor. Depending on the original branch condition
      // (and/or) we have to swap the successors (TrueDest, FalseDest), so that
      // we perfrom the correct update for the PHI nodes.
      // This doesn't change the successor order of the just created branch
      // instruction (or any other instruction).
      if (Opc == Instruction::Or)
        std::swap(TBB, FBB);
  
      // Replace the old BB with the new BB.
      for (auto &I : *TBB) {
        PHINode *PN = dyn_cast<PHINode>(&I);
        if (!PN)
          break;
        int i;
        while ((i = PN->getBasicBlockIndex(&BB)) >= 0)
          PN->setIncomingBlock(i, TmpBB);
      }
  
      // Add another incoming edge form the new BB.
      for (auto &I : *FBB) {
        PHINode *PN = dyn_cast<PHINode>(&I);
        if (!PN)
          break;
        auto *Val = PN->getIncomingValueForBlock(&BB);
        PN->addIncoming(Val, TmpBB);
      }
  
      // Update the branch weights (from SelectionDAGBuilder::
      // FindMergedConditions).
      if (Opc == Instruction::Or) {
        // Codegen X | Y as:
        // BB1:
        //   jmp_if_X TBB
        //   jmp TmpBB
        // TmpBB:
        //   jmp_if_Y TBB
        //   jmp FBB
        //
  
        // We have flexibility in setting Prob for BB1 and Prob for NewBB.
        // The requirement is that
        //   TrueProb for BB1 + (FalseProb for BB1 * TrueProb for TmpBB)
        //     = TrueProb for orignal BB.
        // Assuming the orignal weights are A and B, one choice is to set BB1's
        // weights to A and A+2B, and set TmpBB's weights to A and 2B. This choice
        // assumes that
        //   TrueProb for BB1 == FalseProb for BB1 * TrueProb for TmpBB.
        // Another choice is to assume TrueProb for BB1 equals to TrueProb for
        // TmpBB, but the math is more complicated.
        uint64_t TrueWeight, FalseWeight;
        if (extractBranchMetadata(Br1, TrueWeight, FalseWeight)) {
          uint64_t NewTrueWeight = TrueWeight;
          uint64_t NewFalseWeight = TrueWeight + 2 * FalseWeight;
          scaleWeights(NewTrueWeight, NewFalseWeight);
          Br1->setMetadata(LLVMContext::MD_prof, MDBuilder(Br1->getContext())
                           .createBranchWeights(TrueWeight, FalseWeight));
  
          NewTrueWeight = TrueWeight;
          NewFalseWeight = 2 * FalseWeight;
          scaleWeights(NewTrueWeight, NewFalseWeight);
          Br2->setMetadata(LLVMContext::MD_prof, MDBuilder(Br2->getContext())
                           .createBranchWeights(TrueWeight, FalseWeight));
        }
      } else {
        // Codegen X & Y as:
        // BB1:
        //   jmp_if_X TmpBB
        //   jmp FBB
        // TmpBB:
        //   jmp_if_Y TBB
        //   jmp FBB
        //
        //  This requires creation of TmpBB after CurBB.
  
        // We have flexibility in setting Prob for BB1 and Prob for TmpBB.
        // The requirement is that
        //   FalseProb for BB1 + (TrueProb for BB1 * FalseProb for TmpBB)
        //     = FalseProb for orignal BB.
        // Assuming the orignal weights are A and B, one choice is to set BB1's
        // weights to 2A+B and B, and set TmpBB's weights to 2A and B. This choice
        // assumes that
        //   FalseProb for BB1 == TrueProb for BB1 * FalseProb for TmpBB.
        uint64_t TrueWeight, FalseWeight;
        if (extractBranchMetadata(Br1, TrueWeight, FalseWeight)) {
          uint64_t NewTrueWeight = 2 * TrueWeight + FalseWeight;
          uint64_t NewFalseWeight = FalseWeight;
          scaleWeights(NewTrueWeight, NewFalseWeight);
          Br1->setMetadata(LLVMContext::MD_prof, MDBuilder(Br1->getContext())
                           .createBranchWeights(TrueWeight, FalseWeight));
  
          NewTrueWeight = 2 * TrueWeight;
          NewFalseWeight = FalseWeight;
          scaleWeights(NewTrueWeight, NewFalseWeight);
          Br2->setMetadata(LLVMContext::MD_prof, MDBuilder(Br2->getContext())
                           .createBranchWeights(TrueWeight, FalseWeight));
        }
      }
  
      // Request DOM Tree update.
      // Note: No point in getting fancy here, since the DT info is never
      // available to CodeGenPrepare and the existing update code is broken
      // anyways.
      ModifiedDT = true;
  
      MadeChange = true;
  
      DEBUG(dbgs() << "After branch condition splitting\n"; BB.dump();
            TmpBB->dump());
    }
    return MadeChange;
  }
  