void PromoteMem2Reg::run() {
  Function &F = *DF.getRoot()->getParent();

  if (AST) PointerAllocaValues.resize(Allocas.size());
  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    assert(isAllocaPromotable(AI) &&
           "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      if (AST) AST->deleteValue(AI);
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }
    
    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    Info.AnalyzeAlloca(AI);

    // If there is only a single store to this value, replace any loads of
    // it that are directly dominated by the definition with the value stored.
    if (Info.DefiningBlocks.size() == 1) {
      RewriteSingleStoreAlloca(AI, Info, LBI);

      // Finally, after the scan, check to see if the store is all that is left.
      if (Info.UsingBlocks.empty()) {
        // Record debuginfo for the store and remove the declaration's debuginfo.
        if (DbgDeclareInst *DDI = Info.DbgDeclare) {
          ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore);
          DDI->eraseFromParent();
        }
        // Remove the (now dead) store and alloca.
        Info.OnlyStore->eraseFromParent();
        LBI.deleteValue(Info.OnlyStore);

        if (AST) AST->deleteValue(AI);
        AI->eraseFromParent();
        LBI.deleteValue(AI);
        
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        
        ++NumSingleStore;
        continue;
      }
    }
    
    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock) {
      PromoteSingleBlockAlloca(AI, Info, LBI);
      
      // Finally, after the scan, check to see if the stores are all that is
      // left.
      if (Info.UsingBlocks.empty()) {
        
        // Remove the (now dead) stores and alloca.
        while (!AI->use_empty()) {
          StoreInst *SI = cast<StoreInst>(AI->use_back());
          // Record debuginfo for the store before removing it.
          if (DbgDeclareInst *DDI = Info.DbgDeclare)
            ConvertDebugDeclareToDebugValue(DDI, SI);
          SI->eraseFromParent();
          LBI.deleteValue(SI);
        }
        
        if (AST) AST->deleteValue(AI);
        AI->eraseFromParent();
        LBI.deleteValue(AI);
        
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        
        // The alloca's debuginfo can be removed as well.
        if (DbgDeclareInst *DDI = Info.DbgDeclare)
          DDI->eraseFromParent();

        ++NumLocalPromoted;
        continue;
      }
    }
    
    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
        BBNumbers[I] = ID++;
    }

    // If we have an AST to keep updated, remember some pointer value that is
    // stored into the alloca.
    if (AST)
      PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal;
      
    // Remember the dbg.declare intrinsic describing this alloca, if any.
    if (Info.DbgDeclare) AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;
    
    // Keep the reverse mapping of the 'Allocas' array for the rename pass.
    AllocaLookup[Allocas[AllocaNum]] = AllocaNum;

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need PHI
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.
    DetermineInsertionPoint(AI, AllocaNum, Info);
  }

  if (Allocas.empty())
    return; // All of the allocas must have been trivial!

  LBI.clear();
  
  
  // Set the incoming values for the basic block to be null values for all of
  // the alloca's.  We do this in case there is a load of a value that has not
  // been stored yet.  In this case, it will get this null value.
  //
  RenamePassData::ValVector Values(Allocas.size());
  for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
    Values[i] = UndefValue::get(Allocas[i]->getAllocatedType());

  // Walks all basic blocks in the function performing the SSA rename algorithm
  // and inserting the phi nodes we marked as necessary
  //
  std::vector<RenamePassData> RenamePassWorkList;
  RenamePassWorkList.push_back(RenamePassData(F.begin(), 0, Values));
  do {
    RenamePassData RPD;
    RPD.swap(RenamePassWorkList.back());
    RenamePassWorkList.pop_back();
    // RenamePass may add new worklist entries.
    RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList);
  } while (!RenamePassWorkList.empty());
  
  // The renamer uses the Visited set to avoid infinite loops.  Clear it now.
  Visited.clear();

  // Remove the allocas themselves from the function.
  for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
    Instruction *A = Allocas[i];

    // If there are any uses of the alloca instructions left, they must be in
    // sections of dead code that were not processed on the dominance frontier.
    // Just delete the users now.
    //
    if (!A->use_empty())
      A->replaceAllUsesWith(UndefValue::get(A->getType()));
    if (AST) AST->deleteValue(A);
    A->eraseFromParent();
  }

  // Remove alloca's dbg.declare instrinsics from the function.
  for (unsigned i = 0, e = AllocaDbgDeclares.size(); i != e; ++i)
    if (DbgDeclareInst *DDI = AllocaDbgDeclares[i])
      DDI->eraseFromParent();

  // Loop over all of the PHI nodes and see if there are any that we can get
  // rid of because they merge all of the same incoming values.  This can
  // happen due to undef values coming into the PHI nodes.  This process is
  // iterative, because eliminating one PHI node can cause others to be removed.
  bool EliminatedAPHI = true;
  while (EliminatedAPHI) {
    EliminatedAPHI = false;
    
    for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I =
           NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E;) {
      PHINode *PN = I->second;
      
      // If this PHI node merges one value and/or undefs, get the value.
      if (Value *V = PN->hasConstantValue(&DT)) {
        if (AST && PN->getType()->isPointerTy())
          AST->deleteValue(PN);
        PN->replaceAllUsesWith(V);
        PN->eraseFromParent();
        NewPhiNodes.erase(I++);
        EliminatedAPHI = true;
        continue;
      }
      ++I;
    }
  }
  
  // At this point, the renamer has added entries to PHI nodes for all reachable
  // code.  Unfortunately, there may be unreachable blocks which the renamer
  // hasn't traversed.  If this is the case, the PHI nodes may not
  // have incoming values for all predecessors.  Loop over all PHI nodes we have
  // created, inserting undef values if they are missing any incoming values.
  //
  for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I =
         NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) {
    // We want to do this once per basic block.  As such, only process a block
    // when we find the PHI that is the first entry in the block.
    PHINode *SomePHI = I->second;
    BasicBlock *BB = SomePHI->getParent();
    if (&BB->front() != SomePHI)
      continue;

    // Only do work here if there the PHI nodes are missing incoming values.  We
    // know that all PHI nodes that were inserted in a block will have the same
    // number of incoming values, so we can just check any of them.
    if (SomePHI->getNumIncomingValues() == getNumPreds(BB))
      continue;

    // Get the preds for BB.
    SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB));
    
    // Ok, now we know that all of the PHI nodes are missing entries for some
    // basic blocks.  Start by sorting the incoming predecessors for efficient
    // access.
    std::sort(Preds.begin(), Preds.end());
    
    // Now we loop through all BB's which have entries in SomePHI and remove
    // them from the Preds list.
    for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) {
      // Do a log(n) search of the Preds list for the entry we want.
      SmallVector<BasicBlock*, 16>::iterator EntIt =
        std::lower_bound(Preds.begin(), Preds.end(),
                         SomePHI->getIncomingBlock(i));
      assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i)&&
             "PHI node has entry for a block which is not a predecessor!");

      // Remove the entry
      Preds.erase(EntIt);
    }

    // At this point, the blocks left in the preds list must have dummy
    // entries inserted into every PHI nodes for the block.  Update all the phi
    // nodes in this block that we are inserting (there could be phis before
    // mem2reg runs).
    unsigned NumBadPreds = SomePHI->getNumIncomingValues();
    BasicBlock::iterator BBI = BB->begin();
    while ((SomePHI = dyn_cast<PHINode>(BBI++)) &&
           SomePHI->getNumIncomingValues() == NumBadPreds) {
      Value *UndefVal = UndefValue::get(SomePHI->getType());
      for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred)
        SomePHI->addIncoming(UndefVal, Preds[pred]);
    }
  }
        
  NewPhiNodes.clear();
}
void PromoteMem2Reg::run() {
  Function &F = *DT.getRoot()->getParent();

  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;
  ForwardIDFCalculator IDF(DT);

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    removeLifetimeIntrinsicUsers(AI);

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }

    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    Info.AnalyzeAlloca(AI);

    // If there is only a single store to this value, replace any loads of
    // it that are directly dominated by the definition with the value stored.
    if (Info.DefiningBlocks.size() == 1) {
      if (rewriteSingleStoreAlloca(AI, Info, LBI, SQ.DL, DT, AC)) {
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        ++NumSingleStore;
        continue;
      }
    }

    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock &&
        promoteSingleBlockAlloca(AI, Info, LBI, SQ.DL, DT, AC)) {
      // The alloca has been processed, move on.
      RemoveFromAllocasList(AllocaNum);
      continue;
    }

    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (auto &BB : F)
        BBNumbers[&BB] = ID++;
    }

    // Remember the dbg.declare intrinsic describing this alloca, if any.
    if (!Info.DbgDeclares.empty())
      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclares;

    // Keep the reverse mapping of the 'Allocas' array for the rename pass.
    AllocaLookup[Allocas[AllocaNum]] = AllocaNum;

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need PHI
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.

    // Unique the set of defining blocks for efficient lookup.
    SmallPtrSet<BasicBlock *, 32> DefBlocks;
    DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());

    // Determine which blocks the value is live in.  These are blocks which lead
    // to uses.
    SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
    ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need phi
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.
    IDF.setLiveInBlocks(LiveInBlocks);
    IDF.setDefiningBlocks(DefBlocks);
    SmallVector<BasicBlock *, 32> PHIBlocks;
    IDF.calculate(PHIBlocks);
    if (PHIBlocks.size() > 1)
      llvm::sort(PHIBlocks, [this](BasicBlock *A, BasicBlock *B) {
        return BBNumbers.lookup(A) < BBNumbers.lookup(B);
      });

    unsigned CurrentVersion = 0;
    for (BasicBlock *BB : PHIBlocks)
      QueuePhiNode(BB, AllocaNum, CurrentVersion);
  }

  if (Allocas.empty())
    return; // All of the allocas must have been trivial!

  LBI.clear();

  // Set the incoming values for the basic block to be null values for all of
  // the alloca's.  We do this in case there is a load of a value that has not
  // been stored yet.  In this case, it will get this null value.
  RenamePassData::ValVector Values(Allocas.size());
  for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
    Values[i] = UndefValue::get(Allocas[i]->getAllocatedType());

  // When handling debug info, treat all incoming values as if they have unknown
  // locations until proven otherwise.
  RenamePassData::LocationVector Locations(Allocas.size());

  // Walks all basic blocks in the function performing the SSA rename algorithm
  // and inserting the phi nodes we marked as necessary
  std::vector<RenamePassData> RenamePassWorkList;
  RenamePassWorkList.emplace_back(&F.front(), nullptr, std::move(Values),
                                  std::move(Locations));
  do {
    RenamePassData RPD = std::move(RenamePassWorkList.back());
    RenamePassWorkList.pop_back();
    // RenamePass may add new worklist entries.
    RenamePass(RPD.BB, RPD.Pred, RPD.Values, RPD.Locations, RenamePassWorkList);
  } while (!RenamePassWorkList.empty());

  // The renamer uses the Visited set to avoid infinite loops.  Clear it now.
  Visited.clear();

  // Remove the allocas themselves from the function.
  for (Instruction *A : Allocas) {
    // If there are any uses of the alloca instructions left, they must be in
    // unreachable basic blocks that were not processed by walking the dominator
    // tree. Just delete the users now.
    if (!A->use_empty())
      A->replaceAllUsesWith(UndefValue::get(A->getType()));
    A->eraseFromParent();
  }

  // Remove alloca's dbg.declare instrinsics from the function.
  for (auto &Declares : AllocaDbgDeclares)
    for (auto *DII : Declares)
      DII->eraseFromParent();

  // Loop over all of the PHI nodes and see if there are any that we can get
  // rid of because they merge all of the same incoming values.  This can
  // happen due to undef values coming into the PHI nodes.  This process is
  // iterative, because eliminating one PHI node can cause others to be removed.
  bool EliminatedAPHI = true;
  while (EliminatedAPHI) {
    EliminatedAPHI = false;

    // Iterating over NewPhiNodes is deterministic, so it is safe to try to
    // simplify and RAUW them as we go.  If it was not, we could add uses to
    // the values we replace with in a non-deterministic order, thus creating
    // non-deterministic def->use chains.
    for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
             I = NewPhiNodes.begin(),
             E = NewPhiNodes.end();
         I != E;) {
      PHINode *PN = I->second;

      // If this PHI node merges one value and/or undefs, get the value.
      if (Value *V = SimplifyInstruction(PN, SQ)) {
        PN->replaceAllUsesWith(V);
        PN->eraseFromParent();
        NewPhiNodes.erase(I++);
        EliminatedAPHI = true;
        continue;
      }
      ++I;
    }
  }

  // At this point, the renamer has added entries to PHI nodes for all reachable
  // code.  Unfortunately, there may be unreachable blocks which the renamer
  // hasn't traversed.  If this is the case, the PHI nodes may not
  // have incoming values for all predecessors.  Loop over all PHI nodes we have
  // created, inserting undef values if they are missing any incoming values.
  for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
           I = NewPhiNodes.begin(),
           E = NewPhiNodes.end();
       I != E; ++I) {
    // We want to do this once per basic block.  As such, only process a block
    // when we find the PHI that is the first entry in the block.
    PHINode *SomePHI = I->second;
    BasicBlock *BB = SomePHI->getParent();
    if (&BB->front() != SomePHI)
      continue;

    // Only do work here if there the PHI nodes are missing incoming values.  We
    // know that all PHI nodes that were inserted in a block will have the same
    // number of incoming values, so we can just check any of them.
    if (SomePHI->getNumIncomingValues() == getNumPreds(BB))
      continue;

    // Get the preds for BB.
    SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));

    // Ok, now we know that all of the PHI nodes are missing entries for some
    // basic blocks.  Start by sorting the incoming predecessors for efficient
    // access.
    auto CompareBBNumbers = [this](BasicBlock *A, BasicBlock *B) {
      return BBNumbers.lookup(A) < BBNumbers.lookup(B);
    };
    llvm::sort(Preds, CompareBBNumbers);

    // Now we loop through all BB's which have entries in SomePHI and remove
    // them from the Preds list.
    for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) {
      // Do a log(n) search of the Preds list for the entry we want.
      SmallVectorImpl<BasicBlock *>::iterator EntIt = std::lower_bound(
          Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i),
          CompareBBNumbers);
      assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i) &&
             "PHI node has entry for a block which is not a predecessor!");

      // Remove the entry
      Preds.erase(EntIt);
    }

    // At this point, the blocks left in the preds list must have dummy
    // entries inserted into every PHI nodes for the block.  Update all the phi
    // nodes in this block that we are inserting (there could be phis before
    // mem2reg runs).
    unsigned NumBadPreds = SomePHI->getNumIncomingValues();
    BasicBlock::iterator BBI = BB->begin();
    while ((SomePHI = dyn_cast<PHINode>(BBI++)) &&
           SomePHI->getNumIncomingValues() == NumBadPreds) {
      Value *UndefVal = UndefValue::get(SomePHI->getType());
      for (BasicBlock *Pred : Preds)
        SomePHI->addIncoming(UndefVal, Pred);
    }
  }

  NewPhiNodes.clear();
}