C++ PHINode::replaceAllUsesWith方法代码示例

/// getInnerResumeDest - Get or create a target for the branch from ResumeInsts.
BasicBlock *InvokeInliningInfo::getInnerResumeDest() {
  if (InnerResumeDest) return InnerResumeDest;

  // Split the landing pad.
  BasicBlock::iterator SplitPoint = CallerLPad; ++SplitPoint;
  InnerResumeDest =
    OuterResumeDest->splitBasicBlock(SplitPoint,
                                     OuterResumeDest->getName() + ".body");

  // The number of incoming edges we expect to the inner landing pad.
  const unsigned PHICapacity = 2;

  // Create corresponding new PHIs for all the PHIs in the outer landing pad.
  BasicBlock::iterator InsertPoint = InnerResumeDest->begin();
  BasicBlock::iterator I = OuterResumeDest->begin();
  for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) {
    PHINode *OuterPHI = cast<PHINode>(I);
    PHINode *InnerPHI = PHINode::Create(OuterPHI->getType(), PHICapacity,
                                        OuterPHI->getName() + ".lpad-body",
                                        InsertPoint);
    OuterPHI->replaceAllUsesWith(InnerPHI);
    InnerPHI->addIncoming(OuterPHI, OuterResumeDest);
  }

  // Create a PHI for the exception values.
  InnerEHValuesPHI = PHINode::Create(CallerLPad->getType(), PHICapacity,
                                     "eh.lpad-body", InsertPoint);
  CallerLPad->replaceAllUsesWith(InnerEHValuesPHI);
  InnerEHValuesPHI->addIncoming(CallerLPad, OuterResumeDest);

  // All done.
  return InnerResumeDest;
}

/// Removes phis that have no predecessor
void ABCD::removePhis() {
  for (unsigned i = 0, e = phis_to_remove.size(); i != e; ++i) {
    PHINode *PN = phis_to_remove[i];
    PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
    PN->eraseFromParent();
  }
}

void LoopInterchangeTransform::splitInnerLoopHeader() {

  // Split the inner loop header out. Here make sure that the reduction PHI's
  // stay in the innerloop body.
  BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
  BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
  if (InnerLoopHasReduction) {
    // FIXME: Check if the induction PHI will always be the first PHI.
    BasicBlock *New = InnerLoopHeader->splitBasicBlock(
        ++(InnerLoopHeader->begin()), InnerLoopHeader->getName() + ".split");
    if (LI)
      if (Loop *L = LI->getLoopFor(InnerLoopHeader))
        L->addBasicBlockToLoop(New, *LI);

    // Adjust Reduction PHI's in the block.
    SmallVector<PHINode *, 8> PHIVec;
    for (auto I = New->begin(); isa<PHINode>(I); ++I) {
      PHINode *PHI = dyn_cast<PHINode>(I);
      Value *V = PHI->getIncomingValueForBlock(InnerLoopPreHeader);
      PHI->replaceAllUsesWith(V);
      PHIVec.push_back((PHI));
    }
    for (auto I = PHIVec.begin(), E = PHIVec.end(); I != E; ++I) {
      PHINode *P = *I;
      P->eraseFromParent();
    }
  } else {
    SplitBlock(InnerLoopHeader, InnerLoopHeader->getFirstNonPHI(), DT, LI);
  }

  DEBUG(dbgs() << "Output of splitInnerLoopHeader InnerLoopHeaderSucc & "
                  "InnerLoopHeader \n");
}

bool TailCallElim::runTRE(Function &F) {
  // If this function is a varargs function, we won't be able to PHI the args
  // right, so don't even try to convert it...
  if (F.getFunctionType()->isVarArg()) return false;

  TTI = &getAnalysis<TargetTransformInfo>();
  BasicBlock *OldEntry = nullptr;
  bool TailCallsAreMarkedTail = false;
  SmallVector<PHINode*, 8> ArgumentPHIs;
  bool MadeChange = false;

  // CanTRETailMarkedCall - If false, we cannot perform TRE on tail calls
  // marked with the 'tail' attribute, because doing so would cause the stack
  // size to increase (real TRE would deallocate variable sized allocas, TRE
  // doesn't).
  bool CanTRETailMarkedCall = CanTRE(F);

  // Change any tail recursive calls to loops.
  //
  // FIXME: The code generator produces really bad code when an 'escaping
  // alloca' is changed from being a static alloca to being a dynamic alloca.
  // Until this is resolved, disable this transformation if that would ever
  // happen.  This bug is PR962.
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
    if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
      bool Change = ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
                                          ArgumentPHIs, !CanTRETailMarkedCall);
      if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
        Change = FoldReturnAndProcessPred(BB, Ret, OldEntry,
                                          TailCallsAreMarkedTail, ArgumentPHIs,
                                          !CanTRETailMarkedCall);
      MadeChange |= Change;
    }
  }

  // If we eliminated any tail recursions, it's possible that we inserted some
  // silly PHI nodes which just merge an initial value (the incoming operand)
  // with themselves.  Check to see if we did and clean up our mess if so.  This
  // occurs when a function passes an argument straight through to its tail
  // call.
  for (unsigned i = 0, e = ArgumentPHIs.size(); i != e; ++i) {
    PHINode *PN = ArgumentPHIs[i];

    // If the PHI Node is a dynamic constant, replace it with the value it is.
    if (Value *PNV = SimplifyInstruction(PN)) {
      PN->replaceAllUsesWith(PNV);
      PN->eraseFromParent();
    }
  }

  return MadeChange;
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
  // create 2 PHIs: one for size and another for offset
  PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
  PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());

  // insert right away in the cache to handle recursive PHIs
  CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);

  // compute offset/size for each PHI incoming pointer
  for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
    Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt());
    SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));

    if (!bothKnown(EdgeData)) {
      OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
      OffsetPHI->eraseFromParent();
      SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
      SizePHI->eraseFromParent();
      return unknown();
    }
    SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
    OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
  }

  Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
  if ((Tmp = SizePHI->hasConstantValue())) {
    Size = Tmp;
    SizePHI->replaceAllUsesWith(Size);
    SizePHI->eraseFromParent();
  }
  if ((Tmp = OffsetPHI->hasConstantValue())) {
    Offset = Tmp;
    OffsetPHI->replaceAllUsesWith(Offset);
    OffsetPHI->eraseFromParent();
  }
  return std::make_pair(Size, Offset);
}

/// \brief The first part of loop-nestification is to find a PHI node that tells
/// us how to partition the loops.
static PHINode *findPHIToPartitionLoops(Loop *L, DominatorTree *DT,
                                        AssumptionCache *AC) {
  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
  for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
    PHINode *PN = cast<PHINode>(I);
    ++I;
    if (Value *V = SimplifyInstruction(PN, DL, nullptr, DT, AC)) {
      // This is a degenerate PHI already, don't modify it!
      PN->replaceAllUsesWith(V);
      PN->eraseFromParent();
      continue;
    }

    // Scan this PHI node looking for a use of the PHI node by itself.
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (PN->getIncomingValue(i) == PN &&
          L->contains(PN->getIncomingBlock(i)))
        // We found something tasty to remove.
        return PN;
  }
  return nullptr;
}

/// FindPHIToPartitionLoops - The first part of loop-nestification is to find a
/// PHI node that tells us how to partition the loops.
static PHINode *FindPHIToPartitionLoops(Loop *L, DominatorTree *DT,
                                        AliasAnalysis *AA, LoopInfo *LI) {
    for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
        PHINode *PN = cast<PHINode>(I);
        ++I;
        if (Value *V = SimplifyInstruction(PN, 0, DT)) {
            // This is a degenerate PHI already, don't modify it!
            PN->replaceAllUsesWith(V);
            if (AA) AA->deleteValue(PN);
            PN->eraseFromParent();
            continue;
        }

        // Scan this PHI node looking for a use of the PHI node by itself.
        for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
            if (PN->getIncomingValue(i) == PN &&
                    L->contains(PN->getIncomingBlock(i)))
                // We found something tasty to remove.
                return PN;
    }
    return 0;
}

/// 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 CodeExtractor::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 *NewBB = llvm::SplitBlock(Header, Header->getFirstNonPHI(), DT);

  // 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, 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.
    BasicBlock::iterator AfterPHIs;
    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->front());
      PN->replaceAllUsesWith(NewPN);
      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) {
        if (Blocks.count(PN->getIncomingBlock(i))) {
          NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i));
          PN->removeIncomingValue(i);
          --i;
        }
      }
    }
  }
}

Function *PartialInlinerImpl::unswitchFunction(Function *F) {
  // First, verify that this function is an unswitching candidate...
  BasicBlock *EntryBlock = &F->front();
  BranchInst *BR = dyn_cast<BranchInst>(EntryBlock->getTerminator());
  if (!BR || BR->isUnconditional())
    return nullptr;

  BasicBlock *ReturnBlock = nullptr;
  BasicBlock *NonReturnBlock = nullptr;
  unsigned ReturnCount = 0;
  for (BasicBlock *BB : successors(EntryBlock)) {
    if (isa<ReturnInst>(BB->getTerminator())) {
      ReturnBlock = BB;
      ReturnCount++;
    } else
      NonReturnBlock = BB;
  }

  if (ReturnCount != 1)
    return nullptr;

  // Clone the function, so that we can hack away on it.
  ValueToValueMapTy VMap;
  Function *DuplicateFunction = CloneFunction(F, VMap);
  DuplicateFunction->setLinkage(GlobalValue::InternalLinkage);
  BasicBlock *NewEntryBlock = cast<BasicBlock>(VMap[EntryBlock]);
  BasicBlock *NewReturnBlock = cast<BasicBlock>(VMap[ReturnBlock]);
  BasicBlock *NewNonReturnBlock = cast<BasicBlock>(VMap[NonReturnBlock]);

  // Go ahead and update all uses to the duplicate, so that we can just
  // use the inliner functionality when we're done hacking.
  F->replaceAllUsesWith(DuplicateFunction);

  // Special hackery is needed with PHI nodes that have inputs from more than
  // one extracted block.  For simplicity, just split the PHIs into a two-level
  // sequence of PHIs, some of which will go in the extracted region, and some
  // of which will go outside.
  BasicBlock *PreReturn = NewReturnBlock;
  NewReturnBlock = NewReturnBlock->splitBasicBlock(
      NewReturnBlock->getFirstNonPHI()->getIterator());
  BasicBlock::iterator I = PreReturn->begin();
  Instruction *Ins = &NewReturnBlock->front();
  while (I != PreReturn->end()) {
    PHINode *OldPhi = dyn_cast<PHINode>(I);
    if (!OldPhi)
      break;

    PHINode *RetPhi = PHINode::Create(OldPhi->getType(), 2, "", Ins);
    OldPhi->replaceAllUsesWith(RetPhi);
    Ins = NewReturnBlock->getFirstNonPHI();

    RetPhi->addIncoming(&*I, PreReturn);
    RetPhi->addIncoming(OldPhi->getIncomingValueForBlock(NewEntryBlock),
                        NewEntryBlock);
    OldPhi->removeIncomingValue(NewEntryBlock);

    ++I;
  }
  NewEntryBlock->getTerminator()->replaceUsesOfWith(PreReturn, NewReturnBlock);

  // Gather up the blocks that we're going to extract.
  std::vector<BasicBlock *> ToExtract;
  ToExtract.push_back(NewNonReturnBlock);
  for (BasicBlock &BB : *DuplicateFunction)
    if (&BB != NewEntryBlock && &BB != NewReturnBlock &&
        &BB != NewNonReturnBlock)
      ToExtract.push_back(&BB);

  // The CodeExtractor needs a dominator tree.
  DominatorTree DT;
  DT.recalculate(*DuplicateFunction);

  // Manually calculate a BlockFrequencyInfo and BranchProbabilityInfo.
  LoopInfo LI(DT);
  BranchProbabilityInfo BPI(*DuplicateFunction, LI);
  BlockFrequencyInfo BFI(*DuplicateFunction, BPI, LI);

  // Extract the body of the if.
  Function *ExtractedFunction =
      CodeExtractor(ToExtract, &DT, /*AggregateArgs*/ false, &BFI, &BPI)
          .extractCodeRegion();

  // Inline the top-level if test into all callers.
  std::vector<User *> Users(DuplicateFunction->user_begin(),
                            DuplicateFunction->user_end());
  for (User *User : Users)
    if (CallInst *CI = dyn_cast<CallInst>(User))
      InlineFunction(CI, IFI);
    else if (InvokeInst *II = dyn_cast<InvokeInst>(User))
      InlineFunction(II, IFI);

  // Ditch the duplicate, since we're done with it, and rewrite all remaining
  // users (function pointers, etc.) back to the original function.
  DuplicateFunction->replaceAllUsesWith(F);
  DuplicateFunction->eraseFromParent();

  ++NumPartialInlined;

  return ExtractedFunction;
}

/// RewriteLoopExitValues - Check to see if this loop has a computable
/// loop-invariant execution count.  If so, this means that we can compute the
/// final value of any expressions that are recurrent in the loop, and
/// substitute the exit values from the loop into any instructions outside of
/// the loop that use the final values of the current expressions.
///
/// This is mostly redundant with the regular IndVarSimplify activities that
/// happen later, except that it's more powerful in some cases, because it's
/// able to brute-force evaluate arbitrary instructions as long as they have
/// constant operands at the beginning of the loop.
void IndVarSimplify::RewriteLoopExitValues(Loop *L,
                                           SCEVExpander &Rewriter) {
  // Verify the input to the pass in already in LCSSA form.
  assert(L->isLCSSAForm(*DT));

  SmallVector<BasicBlock*, 8> ExitBlocks;
  L->getUniqueExitBlocks(ExitBlocks);

  // Find all values that are computed inside the loop, but used outside of it.
  // Because of LCSSA, these values will only occur in LCSSA PHI Nodes.  Scan
  // the exit blocks of the loop to find them.
  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *ExitBB = ExitBlocks[i];

    // If there are no PHI nodes in this exit block, then no values defined
    // inside the loop are used on this path, skip it.
    PHINode *PN = dyn_cast<PHINode>(ExitBB->begin());
    if (!PN) continue;

    unsigned NumPreds = PN->getNumIncomingValues();

    // Iterate over all of the PHI nodes.
    BasicBlock::iterator BBI = ExitBB->begin();
    while ((PN = dyn_cast<PHINode>(BBI++))) {
      if (PN->use_empty())
        continue; // dead use, don't replace it

      // SCEV only supports integer expressions for now.
      if (!PN->getType()->isIntegerTy() && !PN->getType()->isPointerTy())
        continue;

      // It's necessary to tell ScalarEvolution about this explicitly so that
      // it can walk the def-use list and forget all SCEVs, as it may not be
      // watching the PHI itself. Once the new exit value is in place, there
      // may not be a def-use connection between the loop and every instruction
      // which got a SCEVAddRecExpr for that loop.
      SE->forgetValue(PN);

      // Iterate over all of the values in all the PHI nodes.
      for (unsigned i = 0; i != NumPreds; ++i) {
        // If the value being merged in is not integer or is not defined
        // in the loop, skip it.
        Value *InVal = PN->getIncomingValue(i);
        if (!isa<Instruction>(InVal))
          continue;

        // If this pred is for a subloop, not L itself, skip it.
        if (LI->getLoopFor(PN->getIncomingBlock(i)) != L)
          continue; // The Block is in a subloop, skip it.

        // Check that InVal is defined in the loop.
        Instruction *Inst = cast<Instruction>(InVal);
        if (!L->contains(Inst))
          continue;

        // Okay, this instruction has a user outside of the current loop
        // and varies predictably *inside* the loop.  Evaluate the value it
        // contains when the loop exits, if possible.
        const SCEV *ExitValue = SE->getSCEVAtScope(Inst, L->getParentLoop());
        if (!ExitValue->isLoopInvariant(L))
          continue;

        Changed = true;
        ++NumReplaced;

        Value *ExitVal = Rewriter.expandCodeFor(ExitValue, PN->getType(), Inst);

        DEBUG(dbgs() << "INDVARS: RLEV: AfterLoopVal = " << *ExitVal << '\n'
                     << "  LoopVal = " << *Inst << "\n");

        PN->setIncomingValue(i, ExitVal);

        // If this instruction is dead now, delete it.
        RecursivelyDeleteTriviallyDeadInstructions(Inst);

        if (NumPreds == 1) {
          // Completely replace a single-pred PHI. This is safe, because the
          // NewVal won't be variant in the loop, so we don't need an LCSSA phi
          // node anymore.
          PN->replaceAllUsesWith(ExitVal);
          RecursivelyDeleteTriviallyDeadInstructions(PN);
        }
      }
      if (NumPreds != 1) {
        // Clone the PHI and delete the original one. This lets IVUsers and
        // any other maps purge the original user from their records.
        PHINode *NewPN = cast<PHINode>(PN->clone());
        NewPN->takeName(PN);
        NewPN->insertBefore(PN);
        PN->replaceAllUsesWith(NewPN);
//.........这里部分代码省略.........

//.........这里部分代码省略.........
    exn = findExceptionInBlock(exnBlock);
  } while (!exn);

  // Look for a selector call for the exception we found.
  EHSelectorInst *selector = findSelectorForException(exn);
  if (!selector) return 0;

  // The easy case is when the landing pad still dominates the
  // exception call, in which case we can just move both calls back to
  // the landing pad.
  if (dominates) {
    selector->moveBefore(lpad->getFirstNonPHI());
    exn->moveBefore(selector);
    return selector;
  }

  // Otherwise, we have to split at the first non-dominating block.
  // The CFG looks basically like this:
  //    lpad:
  //      phis_0
  //      insnsAndBranches_1
  //      br label %nonDominated
  //    nonDominated:
  //      phis_2
  //      insns_3
  //      %exn = call i8* @llvm.eh.exception()
  //      insnsAndBranches_4
  //      %selector = call @llvm.eh.selector(i8* %exn, ...
  // We need to turn this into:
  //    lpad:
  //      phis_0
  //      %exn0 = call i8* @llvm.eh.exception()
  //      %selector0 = call @llvm.eh.selector(i8* %exn0, ...
  //      insnsAndBranches_1
  //      br label %split // from lastDominated
  //    nonDominated:
  //      phis_2 (without edge from lastDominated)
  //      %exn1 = call i8* @llvm.eh.exception()
  //      %selector1 = call i8* @llvm.eh.selector(i8* %exn1, ...
  //      br label %split
  //    split:
  //      phis_2 (edge from lastDominated, edge from split)
  //      %exn = phi ...
  //      %selector = phi ...
  //      insns_3
  //      insnsAndBranches_4

  assert(nonDominated);
  assert(lastDominated);

  // First, make clones of the intrinsics to go in lpad.
  EHExceptionInst *lpadExn = cast<EHExceptionInst>(exn->clone());
  EHSelectorInst *lpadSelector = cast<EHSelectorInst>(selector->clone());
  lpadSelector->setArgOperand(0, lpadExn);
  lpadSelector->insertBefore(lpad->getFirstNonPHI());
  lpadExn->insertBefore(lpadSelector);

  // Split the non-dominated block.
  BasicBlock *split =
    nonDominated->splitBasicBlock(nonDominated->getFirstNonPHI(),
                                  nonDominated->getName() + ".lpad-fix");

  // Redirect the last dominated branch there.
  cast<BranchInst>(lastDominated->back()).setSuccessor(0, split);

  // Move the existing intrinsics to the end of the old block.
  selector->moveBefore(&nonDominated->back());
  exn->moveBefore(selector);

  Instruction *splitIP = &split->front();

  // For all the phis in nonDominated, make a new phi in split to join
  // that phi with the edge from lastDominated.
  for (BasicBlock::iterator
         i = nonDominated->begin(), e = nonDominated->end(); i != e; ++i) {
    PHINode *phi = dyn_cast<PHINode>(i);
    if (!phi) break;

    PHINode *splitPhi = PHINode::Create(phi->getType(), 2, phi->getName(),
                                        splitIP);
    phi->replaceAllUsesWith(splitPhi);
    splitPhi->addIncoming(phi, nonDominated);
    splitPhi->addIncoming(phi->removeIncomingValue(lastDominated),
                          lastDominated);
  }

  // Make new phis for the exception and selector.
  PHINode *exnPhi = PHINode::Create(exn->getType(), 2, "", splitIP);
  exn->replaceAllUsesWith(exnPhi);
  selector->setArgOperand(0, exn); // except for this use
  exnPhi->addIncoming(exn, nonDominated);
  exnPhi->addIncoming(lpadExn, lastDominated);

  PHINode *selectorPhi = PHINode::Create(selector->getType(), 2, "", splitIP);
  selector->replaceAllUsesWith(selectorPhi);
  selectorPhi->addIncoming(selector, nonDominated);
  selectorPhi->addIncoming(lpadSelector, lastDominated);

  return lpadSelector;
}

Function* PartialInliner::unswitchFunction(Function* F) {
  // First, verify that this function is an unswitching candidate...
  BasicBlock* entryBlock = F->begin();
  BranchInst *BR = dyn_cast<BranchInst>(entryBlock->getTerminator());
  if (!BR || BR->isUnconditional())
    return 0;
  
  BasicBlock* returnBlock = 0;
  BasicBlock* nonReturnBlock = 0;
  unsigned returnCount = 0;
  for (succ_iterator SI = succ_begin(entryBlock), SE = succ_end(entryBlock);
       SI != SE; ++SI)
    if (isa<ReturnInst>((*SI)->getTerminator())) {
      returnBlock = *SI;
      returnCount++;
    } else
      nonReturnBlock = *SI;
  
  if (returnCount != 1)
    return 0;
  
  // Clone the function, so that we can hack away on it.
  ValueToValueMapTy VMap;
  Function* duplicateFunction = CloneFunction(F, VMap,
                                              /*ModuleLevelChanges=*/false);
  duplicateFunction->setLinkage(GlobalValue::InternalLinkage);
  F->getParent()->getFunctionList().push_back(duplicateFunction);
  BasicBlock* newEntryBlock = cast<BasicBlock>(VMap[entryBlock]);
  BasicBlock* newReturnBlock = cast<BasicBlock>(VMap[returnBlock]);
  BasicBlock* newNonReturnBlock = cast<BasicBlock>(VMap[nonReturnBlock]);
  
  // Go ahead and update all uses to the duplicate, so that we can just
  // use the inliner functionality when we're done hacking.
  F->replaceAllUsesWith(duplicateFunction);
  
  // Special hackery is needed with PHI nodes that have inputs from more than
  // one extracted block.  For simplicity, just split the PHIs into a two-level
  // sequence of PHIs, some of which will go in the extracted region, and some
  // of which will go outside.
  BasicBlock* preReturn = newReturnBlock;
  newReturnBlock = newReturnBlock->splitBasicBlock(
                                              newReturnBlock->getFirstNonPHI());
  BasicBlock::iterator I = preReturn->begin();
  BasicBlock::iterator Ins = newReturnBlock->begin();
  while (I != preReturn->end()) {
    PHINode* OldPhi = dyn_cast<PHINode>(I);
    if (!OldPhi) break;
    
    PHINode* retPhi = PHINode::Create(OldPhi->getType(), 2, "", Ins);
    OldPhi->replaceAllUsesWith(retPhi);
    Ins = newReturnBlock->getFirstNonPHI();
    
    retPhi->addIncoming(I, preReturn);
    retPhi->addIncoming(OldPhi->getIncomingValueForBlock(newEntryBlock),
                        newEntryBlock);
    OldPhi->removeIncomingValue(newEntryBlock);
    
    ++I;
  }
  newEntryBlock->getTerminator()->replaceUsesOfWith(preReturn, newReturnBlock);
  
  // Gather up the blocks that we're going to extract.
  std::vector<BasicBlock*> toExtract;
  toExtract.push_back(newNonReturnBlock);
  for (Function::iterator FI = duplicateFunction->begin(),
       FE = duplicateFunction->end(); FI != FE; ++FI)
    if (&*FI != newEntryBlock && &*FI != newReturnBlock &&
        &*FI != newNonReturnBlock)
      toExtract.push_back(FI);
      
  // The CodeExtractor needs a dominator tree.
  DominatorTree DT;
  DT.runOnFunction(*duplicateFunction);
  
  // Extract the body of the if.
  Function* extractedFunction
    = CodeExtractor(toExtract, &DT).extractCodeRegion();
  
  InlineFunctionInfo IFI;
  
  // Inline the top-level if test into all callers.
  std::vector<User*> Users(duplicateFunction->use_begin(), 
                           duplicateFunction->use_end());
  for (std::vector<User*>::iterator UI = Users.begin(), UE = Users.end();
       UI != UE; ++UI)
    if (CallInst *CI = dyn_cast<CallInst>(*UI))
      InlineFunction(CI, IFI);
    else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI))
      InlineFunction(II, IFI);
  
  // Ditch the duplicate, since we're done with it, and rewrite all remaining
  // users (function pointers, etc.) back to the original function.
  duplicateFunction->replaceAllUsesWith(F);
  duplicateFunction->eraseFromParent();
  
  ++NumPartialInlined;
  
  return extractedFunction;
}

/// Get or create a target for the branch out of rewritten calls to
/// llvm.eh.resume.
BasicBlock *InvokeInliningInfo::getInnerUnwindDest() {
  if (InnerUnwindDest) return InnerUnwindDest;

  // Find and hoist the llvm.eh.exception and llvm.eh.selector calls
  // in the outer landing pad to immediately following the phis.
  EHSelectorInst *selector = getOuterSelector();
  if (!selector) return 0;

  // The call to llvm.eh.exception *must* be in the landing pad.
  Instruction *exn = cast<Instruction>(selector->getArgOperand(0));
  assert(exn->getParent() == OuterUnwindDest);

  // TODO: recognize when we've already done this, so that we don't
  // get a linear number of these when inlining calls into lots of
  // invokes with the same landing pad.

  // Do the hoisting.
  Instruction *splitPoint = exn->getParent()->getFirstNonPHI();
  assert(splitPoint != selector && "selector-on-exception dominance broken!");
  if (splitPoint == exn) {
    selector->removeFromParent();
    selector->insertAfter(exn);
    splitPoint = selector->getNextNode();
  } else {
    exn->moveBefore(splitPoint);
    selector->moveBefore(splitPoint);
  }

  // Split the landing pad.
  InnerUnwindDest = OuterUnwindDest->splitBasicBlock(splitPoint,
                                        OuterUnwindDest->getName() + ".body");

  // The number of incoming edges we expect to the inner landing pad.
  const unsigned phiCapacity = 2;

  // Create corresponding new phis for all the phis in the outer landing pad.
  BasicBlock::iterator insertPoint = InnerUnwindDest->begin();
  BasicBlock::iterator I = OuterUnwindDest->begin();
  for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) {
    PHINode *outerPhi = cast<PHINode>(I);
    PHINode *innerPhi = PHINode::Create(outerPhi->getType(), phiCapacity,
                                        outerPhi->getName() + ".lpad-body",
                                        insertPoint);
    outerPhi->replaceAllUsesWith(innerPhi);
    innerPhi->addIncoming(outerPhi, OuterUnwindDest);
  }

  // Create a phi for the exception value...
  InnerExceptionPHI = PHINode::Create(exn->getType(), phiCapacity,
                                      "exn.lpad-body", insertPoint);
  exn->replaceAllUsesWith(InnerExceptionPHI);
  selector->setArgOperand(0, exn); // restore this use
  InnerExceptionPHI->addIncoming(exn, OuterUnwindDest);

  // ...and the selector.
  InnerSelectorPHI = PHINode::Create(selector->getType(), phiCapacity,
                                     "selector.lpad-body", insertPoint);
  selector->replaceAllUsesWith(InnerSelectorPHI);
  InnerSelectorPHI->addIncoming(selector, OuterUnwindDest);

  // All done.
  return InnerUnwindDest;
}

/// \brief This method is called when the specified loop has more than one
/// backedge in it.
///
/// If this occurs, revector all of these backedges to target a new basic block
/// and have that block branch to the loop header.  This ensures that loops
/// have exactly one backedge.
static BasicBlock *insertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader,
                                             DominatorTree *DT, LoopInfo *LI) {
  assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");

  // Get information about the loop
  BasicBlock *Header = L->getHeader();
  Function *F = Header->getParent();

  // Unique backedge insertion currently depends on having a preheader.
  if (!Preheader)
    return nullptr;

  // The header is not a landing pad; preheader insertion should ensure this.
  assert(!Header->isLandingPad() && "Can't insert backedge to landing pad");

  // Figure out which basic blocks contain back-edges to the loop header.
  std::vector<BasicBlock*> BackedgeBlocks;
  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
    BasicBlock *P = *I;

    // Indirectbr edges cannot be split, so we must fail if we find one.
    if (isa<IndirectBrInst>(P->getTerminator()))
      return nullptr;

    if (P != Preheader) BackedgeBlocks.push_back(P);
  }

  // Create and insert the new backedge block...
  BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
                                           Header->getName() + ".backedge", F);
  BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
  BETerminator->setDebugLoc(Header->getFirstNonPHI()->getDebugLoc());

  DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
               << BEBlock->getName() << "\n");

  // Move the new backedge block to right after the last backedge block.
  Function::iterator InsertPos = BackedgeBlocks.back(); ++InsertPos;
  F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);

  // Now that the block has been inserted into the function, create PHI nodes in
  // the backedge block which correspond to any PHI nodes in the header block.
  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
                                     PN->getName()+".be", BETerminator);

    // Loop over the PHI node, moving all entries except the one for the
    // preheader over to the new PHI node.
    unsigned PreheaderIdx = ~0U;
    bool HasUniqueIncomingValue = true;
    Value *UniqueValue = nullptr;
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
      BasicBlock *IBB = PN->getIncomingBlock(i);
      Value *IV = PN->getIncomingValue(i);
      if (IBB == Preheader) {
        PreheaderIdx = i;
      } else {
        NewPN->addIncoming(IV, IBB);
        if (HasUniqueIncomingValue) {
          if (!UniqueValue)
            UniqueValue = IV;
          else if (UniqueValue != IV)
            HasUniqueIncomingValue = false;
        }
      }
    }

    // Delete all of the incoming values from the old PN except the preheader's
    assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
    if (PreheaderIdx != 0) {
      PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
      PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
    }
    // Nuke all entries except the zero'th.
    for (unsigned i = 0, e = PN->getNumIncomingValues()-1; i != e; ++i)
      PN->removeIncomingValue(e-i, false);

    // Finally, add the newly constructed PHI node as the entry for the BEBlock.
    PN->addIncoming(NewPN, BEBlock);

    // As an optimization, if all incoming values in the new PhiNode (which is a
    // subset of the incoming values of the old PHI node) have the same value,
    // eliminate the PHI Node.
    if (HasUniqueIncomingValue) {
      NewPN->replaceAllUsesWith(UniqueValue);
      BEBlock->getInstList().erase(NewPN);
    }
  }

  // Now that all of the PHI nodes have been inserted and adjusted, modify the
  // backedge blocks to just to the BEBlock instead of the header.
  for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
    TerminatorInst *TI = BackedgeBlocks[i]->getTerminator();
//.........这里部分代码省略.........

/// SplitBlockPredecessors - This method transforms BB by introducing a new
/// basic block into the function, and moving some of the predecessors of BB to
/// be predecessors of the new block.  The new predecessors are indicated by the
/// Preds array, which has NumPreds elements in it.  The new block is given a
/// suffix of 'Suffix'.
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
/// DominanceFrontier, but no other analyses.
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, 
                                         BasicBlock *const *Preds,
                                         unsigned NumPreds, const char *Suffix,
                                         Pass *P) {
  // Create new basic block, insert right before the original block.
  BasicBlock *NewBB =
    BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB);
  
  // The new block unconditionally branches to the old block.
  BranchInst *BI = BranchInst::Create(BB, NewBB);
  
  // Move the edges from Preds to point to NewBB instead of BB.
  for (unsigned i = 0; i != NumPreds; ++i)
    Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
  
  // Update dominator tree and dominator frontier if available.
  DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
  if (DT)
    DT->splitBlock(NewBB);
  if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
    DF->splitBlock(NewBB);
  AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
  
  
  // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
  // node becomes an incoming value for BB's phi node.  However, if the Preds
  // list is empty, we need to insert dummy entries into the PHI nodes in BB to
  // account for the newly created predecessor.
  if (NumPreds == 0) {
    // Insert dummy values as the incoming value.
    for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
      cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
    return NewBB;
  }
  
  // Otherwise, create a new PHI node in NewBB for each PHI node in BB.
  for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
    PHINode *PN = cast<PHINode>(I++);
    
    // Check to see if all of the values coming in are the same.  If so, we
    // don't need to create a new PHI node.
    Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
    for (unsigned i = 1; i != NumPreds; ++i)
      if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
        InVal = 0;
        break;
      }
    
    if (InVal) {
      // If all incoming values for the new PHI would be the same, just don't
      // make a new PHI.  Instead, just remove the incoming values from the old
      // PHI.
      for (unsigned i = 0; i != NumPreds; ++i)
        PN->removeIncomingValue(Preds[i], false);
    } else {
      // If the values coming into the block are not the same, we need a PHI.
      // Create the new PHI node, insert it into NewBB at the end of the block
      PHINode *NewPHI =
        PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
      if (AA) AA->copyValue(PN, NewPHI);
      
      // Move all of the PHI values for 'Preds' to the new PHI.
      for (unsigned i = 0; i != NumPreds; ++i) {
        Value *V = PN->removeIncomingValue(Preds[i], false);
        NewPHI->addIncoming(V, Preds[i]);
      }
      InVal = NewPHI;
    }
    
    // Add an incoming value to the PHI node in the loop for the preheader
    // edge.
    PN->addIncoming(InVal, NewBB);
    
    // Check to see if we can eliminate this phi node.
    if (Value *V = PN->hasConstantValue(DT != 0)) {
      Instruction *I = dyn_cast<Instruction>(V);
      if (!I || DT == 0 || DT->dominates(I, PN)) {
        PN->replaceAllUsesWith(V);
        if (AA) AA->deleteValue(PN);
        PN->eraseFromParent();
      }
    }
  }
  
  return NewBB;
}