C++ iterator::use_begin方法代码示例

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (const auto &BB : ParentRegion->blocks())
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {

      bool Initialized = false;
      for (auto I = II->use_begin(), E = II->use_end(); I != E;) {
        Use &U = *I++;
        Instruction *User = cast<Instruction>(U.getUser());
        if (User->getParent() == BB) {
          continue;

        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(U) == BB)
            continue;
        }

        if (DT->dominates(II, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(II->getType());
          Updater.Initialize(II->getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, II);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(U);
      }
    }
}

/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool Loop::isLCSSAForm(DominatorTree &DT) const {
  // Sort the blocks vector so that we can use binary search to do quick
  // lookups.
  SmallPtrSet<BasicBlock*, 16> LoopBBs(block_begin(), block_end());

  for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
    BasicBlock *BB = *BI;
    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
      for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
           ++UI) {
        User *U = *UI;
        BasicBlock *UserBB = cast<Instruction>(U)->getParent();
        if (PHINode *P = dyn_cast<PHINode>(U))
          UserBB = P->getIncomingBlock(UI);

        // Check the current block, as a fast-path, before checking whether
        // the use is anywhere in the loop.  Most values are used in the same
        // block they are defined in.  Also, blocks not reachable from the
        // entry are special; uses in them don't need to go through PHIs.
        if (UserBB != BB &&
            !LoopBBs.count(UserBB) &&
            DT.isReachableFromEntry(UserBB))
          return false;
      }
  }

  return true;
}

/// If there's a single exit block, sink any loop-invariant values that
/// were defined in the preheader but not used inside the loop into the
/// exit block to reduce register pressure in the loop.
void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
  BasicBlock *ExitBlock = L->getExitBlock();
  if (!ExitBlock) return;

  BasicBlock *Preheader = L->getLoopPreheader();
  if (!Preheader) return;

  Instruction *InsertPt = ExitBlock->getFirstNonPHI();
  BasicBlock::iterator I = Preheader->getTerminator();
  while (I != Preheader->begin()) {
    --I;
    // New instructions were inserted at the end of the preheader.
    if (isa<PHINode>(I))
      break;
    // Don't move instructions which might have side effects, since the side
    // effects need to complete before instructions inside the loop.  Also
    // don't move instructions which might read memory, since the loop may
    // modify memory. Note that it's okay if the instruction might have
    // undefined behavior: LoopSimplify guarantees that the preheader
    // dominates the exit block.
    if (I->mayHaveSideEffects() || I->mayReadFromMemory())
      continue;
    // Don't sink static AllocaInsts out of the entry block, which would
    // turn them into dynamic allocas!
    if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
      if (AI->isStaticAlloca())
        continue;
    // Determine if there is a use in or before the loop (direct or
    // otherwise).
    bool UsedInLoop = false;
    for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
         UI != UE; ++UI) {
      BasicBlock *UseBB = cast<Instruction>(UI)->getParent();
      if (PHINode *P = dyn_cast<PHINode>(UI)) {
        unsigned i =
          PHINode::getIncomingValueNumForOperand(UI.getOperandNo());
        UseBB = P->getIncomingBlock(i);
      }
      if (UseBB == Preheader || L->contains(UseBB)) {
        UsedInLoop = true;
        break;
      }
    }
    // If there is, the def must remain in the preheader.
    if (UsedInLoop)
      continue;
    // Otherwise, sink it to the exit block.
    Instruction *ToMove = I;
    bool Done = false;
    if (I != Preheader->begin())
      --I;
    else
      Done = true;
    ToMove->moveBefore(InsertPt);
    if (Done)
      break;
    InsertPt = ToMove;
  }
}

bool RemoveExtendsPass::runOnFunction(Function& f)
{
  CurrentFile::set(__FILE__);
  bool changed = false ;
  
  //see if there are any ROCCCNames or ROCCCSizes that caused the extend
  for(Function::iterator BB = f.begin(); BB != f.end(); ++BB)
  {
    begin:
    for(BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
    {
      if( dynamic_cast<FPExtInst*>(&*II) or
          dynamic_cast<ZExtInst*>(&*II) or 
          dynamic_cast<SExtInst*>(&*II) or
          dynamic_cast<BitCastInst*>(&*II) )
      {
        INTERNAL_MESSAGE("Attempting to remove uses of " << II->getName() << "\n");
        for(Value::use_iterator UI = II->use_begin(); UI != II->use_end(); ++UI)
        {
          dynamic_cast<Instruction*>(*UI)->replaceUsesOfWith(II, II->getOperand(0));
          goto begin;
        }
        if( II->use_begin() == II->use_end() )
        {
          II->eraseFromParent();
          II = BB->begin();
        }
        else
        {
          INTERNAL_ERROR("Extend " << *II << " is still used in " << **II->use_begin() << "!");
          assert(0 and "Extend operation still exists!");
        }
      }
    }
  }

  return changed ;
}

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (Region::block_iterator I = ParentRegion->block_begin(),
                              E = ParentRegion->block_end();
       I != E; ++I) {

    BasicBlock *BB = *I;
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {

      bool Initialized = false;
      for (Use *I = &II->use_begin().getUse(), *Next; I; I = Next) {

        Next = I->getNext();

        Instruction *User = cast<Instruction>(I->getUser());
        if (User->getParent() == BB) {
          continue;

        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(*I) == BB)
            continue;
        }

        if (DT->dominates(II, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(II->getType());
          Updater.Initialize(II->getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, II);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(*I);
      }
    }
  }
}

bool UnregisteredFanoutAnalysisPass::runOnFunction(Function& f)
{
  CurrentFile::set(__FILE__);
  bool changed = false ;
  if (f.isDeclaration() || f.getDFFunction() == NULL)
  {
    return changed ;
  }
  unsigned int MAX_FANOUT = 50;
  std::ifstream file(".ROCCC/.timingInfo");
  if (!file)
  {
    INTERNAL_SERIOUS_WARNING("Could not open timing information file for max fanout!\n");
  }
  else
  {
    while( !file.eof() )
    {
      std::string name;
      int value = -1;
      file >> name;
      //allow comments
      if( name.find("#") == 0 or name.find("//") == 0 or name.find("--") == 0 )
      {
        std::string temp;
        std::getline(file, temp);
      }
      else
      {
        file >> value;
      }
      if( name == "MaxFanoutRegistered" and value >= 0 )
      {
        MAX_FANOUT = value;
      }
    }
  }
  LOG_MESSAGE2("Pipelining", "Fanout Analysis", "In order to reduce the negative effect on frequency that a high unregistered fanout can have, operations with a fanout greater than " << MAX_FANOUT << " will be registered.\n");
  
  
  std::map<DFBasicBlock*, bool> allBlocks = getPipelineBlocks(f);
  for(std::map<DFBasicBlock*,bool>::iterator BBI = allBlocks.begin(); BBI != allBlocks.end(); ++BBI)
  {
    if( BBI->second )
    {
      for( BasicBlock::iterator II = BBI->first->begin(); II != BBI->first->end(); ++II )
      {
        unsigned int realFanout = 0;
        for(Instruction::use_iterator UI = II->use_begin(); UI != II->use_end(); ++UI)
        {
          if( dynamic_cast<Instruction*>(*UI) and
              allBlocks.find(dynamic_cast<Instruction*>(*UI)->getParent()->getDFBasicBlock()) != allBlocks.end() and
              allBlocks.find(dynamic_cast<Instruction*>(*UI)->getParent()->getDFBasicBlock())->second != false and
              !isDefinition(dynamic_cast<Instruction*>(*UI), II) )
          {
            ++realFanout;
          }
        }
        if( realFanout > MAX_FANOUT )
        {
          LOG_MESSAGE2("Pipelining", "Fanout Analysis", getValueName(II) << " has fanout of " << realFanout << "; "
                                                        "Putting " << getValueName(II) << " into own pipeline stage.\n");
          Pipelining::TimingRequirements* timing = Pipelining::TimingRequirements::getCurrentRequirements(&f);
          timing->setBasicBlockDelay(BBI->first, timing->getDesiredDelay());
        }
      }
    }
  }
  
  return changed ;
}

void DSWP::buildPDG(Loop *L) {
    //Initialize PDG
	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
			Instruction *inst = &(*ui);

			//standardlize the name for all expr
			if (util.hasNewDef(inst)) {
				inst->setName(util.genId());
				dname[inst] = inst->getNameStr();
			} else {
				dname[inst] = util.genId();
			}

			pdg[inst] = new vector<Edge>();
			rev[inst] = new vector<Edge>();
		}
	}

	//LoopInfo &li = getAnalysis<LoopInfo>();

	/*
	 * Memory dependency analysis
	 */
	MemoryDependenceAnalysis &mda = getAnalysis<MemoryDependenceAnalysis>();

	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
			Instruction *inst = &(*ii);

			//data dependence = register dependence + memory dependence

			//begin register dependence
			for (Value::use_iterator ui = ii->use_begin(); ui != ii->use_end(); ui++) {
				if (Instruction *user = dyn_cast<Instruction>(*ui)) {
					addEdge(inst, user, REG);
				}
			}
			//finish register dependence

			//begin memory dependence
			MemDepResult mdr = mda.getDependency(inst);
			//TODO not sure clobbers mean!!

			if (mdr.isDef()) {
				Instruction *dep = mdr.getInst();

				if (isa<LoadInst>(inst)) {
					if (isa<StoreInst>(dep)) {
						addEdge(dep, inst, DTRUE);	//READ AFTER WRITE
					}
				}
				if (isa<StoreInst>(inst)) {
					if (isa<LoadInst>(dep)) {
						addEdge(dep, inst, DANTI);	//WRITE AFTER READ
					}
					if (isa<StoreInst>(dep)) {
						addEdge(dep, inst, DOUT);	//WRITE AFTER WRITE
					}
				}
				//READ AFTER READ IS INSERT AFTER PDG BUILD
			}
			//end memory dependence
		}//for ii
	}//for bi

	/*
	 * begin control dependence
	 */
	PostDominatorTree &pdt = getAnalysis<PostDominatorTree>();
	//cout << pdt.getRootNode()->getBlock()->getNameStr() << endl;

	/*
	 * alien code part 1
	 */
	LoopInfo *LI = &getAnalysis<LoopInfo>();
	std::set<BranchInst*> backedgeParents;
	for (Loop::block_iterator bi = L->getBlocks().begin(); bi
			!= L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
			Instruction *inst = ii;
			if (BranchInst *brInst = dyn_cast<BranchInst>(inst)) {
				// get the loop this instruction (and therefore basic block) belongs to
				Loop *instLoop = LI->getLoopFor(BB);
				bool branchesToHeader = false;
				for (int i = brInst->getNumSuccessors() - 1; i >= 0
						&& !branchesToHeader; i--) {
					// if the branch could exit, store it
					if (LI->getLoopFor(brInst->getSuccessor(i)) != instLoop) {
						branchesToHeader = true;
					}
				}
				if (branchesToHeader) {
					backedgeParents.insert(brInst);
				}
			}
		}
//.........这里部分代码省略.........

bool LoopUnroll::visitLoop(Loop *L) {
  bool Changed = false;

  // Recurse through all subloops before we process this loop.  Copy the loop
  // list so that the child can update the loop tree if it needs to delete the
  // loop.
  std::vector<Loop*> SubLoops(L->begin(), L->end());
  for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
    Changed |= visitLoop(SubLoops[i]);

  // We only handle single basic block loops right now.
  if (L->getBlocks().size() != 1)
    return Changed;

  BasicBlock *BB = L->getHeader();
  BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
  if (BI == 0) return Changed;  // Must end in a conditional branch

  ConstantInt *TripCountC = dyn_cast_or_null<ConstantInt>(L->getTripCount());
  if (!TripCountC) return Changed;  // Must have constant trip count!

  unsigned TripCount = TripCountC->getRawValue();
  if (TripCount != TripCountC->getRawValue() || TripCount == 0)
    return Changed; // More than 2^32 iterations???

  unsigned LoopSize = ApproximateLoopSize(L);
  DEBUG(std::cerr << "Loop Unroll: F[" << BB->getParent()->getName()
        << "] Loop %" << BB->getName() << " Loop Size = " << LoopSize
        << " Trip Count = " << TripCount << " - ");
  uint64_t Size = (uint64_t)LoopSize*(uint64_t)TripCount;
  if (Size > UnrollThreshold) {
    DEBUG(std::cerr << "TOO LARGE: " << Size << ">" << UnrollThreshold << "\n");
    return Changed;
  }
  DEBUG(std::cerr << "UNROLLING!\n");
  
  BasicBlock *LoopExit = BI->getSuccessor(L->contains(BI->getSuccessor(0)));

  // Create a new basic block to temporarily hold all of the cloned code.
  BasicBlock *NewBlock = new BasicBlock();

  // For the first iteration of the loop, we should use the precloned values for
  // PHI nodes.  Insert associations now.
  std::map<const Value*, Value*> LastValueMap;
  std::vector<PHINode*> OrigPHINode;
  for (BasicBlock::iterator I = BB->begin();
       PHINode *PN = dyn_cast<PHINode>(I); ++I) {
    OrigPHINode.push_back(PN);
    if (Instruction *I =dyn_cast<Instruction>(PN->getIncomingValueForBlock(BB)))
      if (I->getParent() == BB)
        LastValueMap[I] = I;
  }

  // Remove the exit branch from the loop
  BB->getInstList().erase(BI);

  assert(TripCount != 0 && "Trip count of 0 is impossible!");
  for (unsigned It = 1; It != TripCount; ++It) {
    char SuffixBuffer[100];
    sprintf(SuffixBuffer, ".%d", It);
    std::map<const Value*, Value*> ValueMap;
    BasicBlock *New = CloneBasicBlock(BB, ValueMap, SuffixBuffer);

    // Loop over all of the PHI nodes in the block, changing them to use the
    // incoming values from the previous block.
    for (unsigned i = 0, e = OrigPHINode.size(); i != e; ++i) {
      PHINode *NewPHI = cast<PHINode>(ValueMap[OrigPHINode[i]]);
      Value *InVal = NewPHI->getIncomingValueForBlock(BB);
      if (Instruction *InValI = dyn_cast<Instruction>(InVal))
        if (InValI->getParent() == BB)
          InVal = LastValueMap[InValI];
      ValueMap[OrigPHINode[i]] = InVal;
      New->getInstList().erase(NewPHI);
    }

    for (BasicBlock::iterator I = New->begin(), E = New->end(); I != E; ++I)
      RemapInstruction(I, ValueMap);

    // Now that all of the instructions are remapped, splice them into the end
    // of the NewBlock.
    NewBlock->getInstList().splice(NewBlock->end(), New->getInstList());
    delete New;

    // LastValue map now contains values from this iteration.
    std::swap(LastValueMap, ValueMap);
  }

  // If there was more than one iteration, replace any uses of values computed
  // in the loop with values computed during the last iteration of the loop.
  if (TripCount != 1) {
    std::set<User*> Users;
    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
      Users.insert(I->use_begin(), I->use_end());

    // We don't want to reprocess entries with PHI nodes in them.  For this
    // reason, we look at each operand of each user exactly once, performing the
    // stubstitution exactly once.
    for (std::set<User*>::iterator UI = Users.begin(), E = Users.end(); UI != E;
         ++UI) {
      Instruction *I = cast<Instruction>(*UI);
//.........这里部分代码省略.........

// TransformSetJmpCall - The setjmp call is a bit trickier to transform.
// We're going to convert all setjmp calls to nops. Then all "call" and
// "invoke" instructions in the function are converted to "invoke" where
// the "except" branch is used when returning from a longjmp call.
void LowerSetJmp::TransformSetJmpCall(CallInst* Inst)
{
  BasicBlock* ABlock = Inst->getParent();
  Function* Func = ABlock->getParent();

  // Add this setjmp to the setjmp map.
  const Type* SBPTy = PointerType::getUnqual(Type::Int8Ty);
  CastInst* BufPtr = 
    new BitCastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst);
  std::vector<Value*> Args = 
    make_vector<Value*>(GetSetJmpMap(Func), BufPtr,
                        ConstantInt::get(Type::Int32Ty,
                                         SetJmpIDMap[Func]++), 0);
  CallInst::Create(AddSJToMap, Args.begin(), Args.end(), "", Inst);

  // We are guaranteed that there are no values live across basic blocks
  // (because we are "not in SSA form" yet), but there can still be values live
  // in basic blocks.  Because of this, splitting the setjmp block can cause
  // values above the setjmp to not dominate uses which are after the setjmp
  // call.  For all of these occasions, we must spill the value to the stack.
  //
  std::set<Instruction*> InstrsAfterCall;

  // The call is probably very close to the end of the basic block, for the
  // common usage pattern of: 'if (setjmp(...))', so keep track of the
  // instructions after the call.
  for (BasicBlock::iterator I = ++BasicBlock::iterator(Inst), E = ABlock->end();
       I != E; ++I)
    InstrsAfterCall.insert(I);

  for (BasicBlock::iterator II = ABlock->begin();
       II != BasicBlock::iterator(Inst); ++II)
    // Loop over all of the uses of instruction.  If any of them are after the
    // call, "spill" the value to the stack.
    for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
         UI != E; ++UI)
      if (cast<Instruction>(*UI)->getParent() != ABlock ||
          InstrsAfterCall.count(cast<Instruction>(*UI))) {
        DemoteRegToStack(*II);
        break;
      }
  InstrsAfterCall.clear();

  // Change the setjmp call into a branch statement. We'll remove the
  // setjmp call in a little bit. No worries.
  BasicBlock* SetJmpContBlock = ABlock->splitBasicBlock(Inst);
  assert(SetJmpContBlock && "Couldn't split setjmp BB!!");

  SetJmpContBlock->setName(ABlock->getName()+"SetJmpCont");

  // Add the SetJmpContBlock to the set of blocks reachable from a setjmp.
  DFSBlocks.insert(SetJmpContBlock);

  // This PHI node will be in the new block created from the
  // splitBasicBlock call.
  PHINode* PHI = PHINode::Create(Type::Int32Ty, "SetJmpReturn", Inst);

  // Coming from a call to setjmp, the return is 0.
  PHI->addIncoming(ConstantInt::getNullValue(Type::Int32Ty), ABlock);

  // Add the case for this setjmp's number...
  SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func));
  SVP.first->addCase(ConstantInt::get(Type::Int32Ty, SetJmpIDMap[Func] - 1),
                     SetJmpContBlock);

  // Value coming from the handling of the exception.
  PHI->addIncoming(SVP.second, SVP.second->getParent());

  // Replace all uses of this instruction with the PHI node created by
  // the eradication of setjmp.
  Inst->replaceAllUsesWith(PHI);
  Inst->getParent()->getInstList().erase(Inst);

  ++SetJmpsTransformed;
}

void RegionExtractor::findInputsOutputs(ValueSet &Inputs,
                                      ValueSet &Outputs) const {
  for (SetVector<BasicBlock *>::const_iterator I = Blocks.begin(),
                                               E = Blocks.end();
       I != E; ++I) {
    BasicBlock *BB = *I;

    // If a used value is defined outside the region, it's an input.  If an
    // instruction is used outside the region, it's an output.
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {
      for (User::op_iterator OI = II->op_begin(), OE = II->op_end();
           OI != OE; ++OI)
        if (definedInCaller(Blocks, *OI))
          Inputs.insert(*OI);
#if LLVM_VERSION_MINOR == 5
      for (User *U : II->users())
        if (!definedInRegion(Blocks, U)) {
#else
      for (Value::use_iterator UI = II->use_begin(), UE = II->use_end();
           UI != UE; ++UI)
        if (!definedInRegion(Blocks, *UI)) {
#endif
          Outputs.insert(II);
          break;
        }
    }
  }
}

/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the
/// region, we need to split the entry block of the region so that the PHI node
/// is easier to deal with.
void RegionExtractor::severSplitPHINodes(BasicBlock *&Header) {
  unsigned NumPredsFromRegion = 0;
  unsigned NumPredsOutsideRegion = 0;

  if (Header != &Header->getParent()->getEntryBlock()) {
    PHINode *PN = dyn_cast<PHINode>(Header->begin());
    if (!PN) return; // No PHI nodes.

    // If the header node contains any PHI nodes, check to see if there is more
    // than one entry from outside the region.  If so, we need to sever the
    // header block into two.
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (Blocks.count(PN->getIncomingBlock(i)))
        ++NumPredsFromRegion;
      else
        ++NumPredsOutsideRegion;

    // If there is one (or fewer) predecessor from outside the region, we don't
    // need to do anything special.
    if (NumPredsOutsideRegion <= 1) return;
  }

  // Otherwise, we need to split the header block into two pieces: one
  // containing PHI nodes merging values from outside of the region, and a
  // second that contains all of the code for the block and merges back any
  // incoming values from inside of the region.
  BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI();
  BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs,
                                              Header->getName()+".ce");

  // We only want to code extract the second block now, and it becomes the new
  // header of the region.
  BasicBlock *OldPred = Header;
  Blocks.remove(OldPred);
  Blocks.insert(NewBB);
  Header = NewBB;

  // Okay, update dominator sets. The blocks that dominate the new one are the
  // blocks that dominate TIBB plus the new block itself.
  if (DT)
    DT->splitBlock(NewBB);

  // Okay, now we need to adjust the PHI nodes and any branches from within the
  // region to go to the new header block instead of the old header block.
  if (NumPredsFromRegion) {
    PHINode *PN = cast<PHINode>(OldPred->begin());
    // Loop over all of the predecessors of OldPred that are in the region,
    // changing them to branch to NewBB instead.
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (Blocks.count(PN->getIncomingBlock(i))) {
        TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator();
        TI->replaceUsesOfWith(OldPred, NewBB);
      }

    // Okay, everything within the region is now branching to the right block, we
    // just have to update the PHI nodes now, inserting PHI nodes into NewBB.
    for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) {
      PHINode *PN = cast<PHINode>(AfterPHIs);
      // Create a new PHI node in the new region, which has an incoming value
      // from OldPred of PN.
      PHINode *NewPN = PHINode::Create(PN->getType(), 1 + NumPredsFromRegion,
                                       PN->getName()+".ce", NewBB->begin());
      NewPN->addIncoming(PN, OldPred);

      // Loop over all of the incoming value in PN, moving them to NewPN if they
      // are from the extracted region.
      for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) {
//.........这里部分代码省略.........