C++ LandingPadInst::use_empty方法代码示例

void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
                                       ArrayRef<BasicBlock *> Preds,
                                       const char *Suffix1, const char *Suffix2,
                                       SmallVectorImpl<BasicBlock *> &NewBBs,
                                       DominatorTree *DT, LoopInfo *LI,
                                       bool PreserveLCSSA) {
  assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");

  // Create a new basic block for OrigBB's predecessors listed in Preds. Insert
  // it right before the original block.
  BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
                                          OrigBB->getName() + Suffix1,
                                          OrigBB->getParent(), OrigBB);
  NewBBs.push_back(NewBB1);

  // The new block unconditionally branches to the old block.
  BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);
  BI1->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());

  // Move the edges from Preds to point to NewBB1 instead of OrigBB.
  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
    // This is slightly more strict than necessary; the minimum requirement
    // is that there be no more than one indirectbr branching to BB. And
    // all BlockAddress uses would need to be updated.
    assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
  }

  bool HasLoopExit = false;
  UpdateAnalysisInformation(OrigBB, NewBB1, Preds, DT, LI, PreserveLCSSA,
                            HasLoopExit);

  // Update the PHI nodes in OrigBB with the values coming from NewBB1.
  UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, HasLoopExit);

  // Move the remaining edges from OrigBB to point to NewBB2.
  SmallVector<BasicBlock*, 8> NewBB2Preds;
  for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
       i != e; ) {
    BasicBlock *Pred = *i++;
    if (Pred == NewBB1) continue;
    assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    NewBB2Preds.push_back(Pred);
    e = pred_end(OrigBB);
  }

  BasicBlock *NewBB2 = nullptr;
  if (!NewBB2Preds.empty()) {
    // Create another basic block for the rest of OrigBB's predecessors.
    NewBB2 = BasicBlock::Create(OrigBB->getContext(),
                                OrigBB->getName() + Suffix2,
                                OrigBB->getParent(), OrigBB);
    NewBBs.push_back(NewBB2);

    // The new block unconditionally branches to the old block.
    BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);
    BI2->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());

    // Move the remaining edges from OrigBB to point to NewBB2.
    for (BasicBlock *NewBB2Pred : NewBB2Preds)
      NewBB2Pred->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);

    // Update DominatorTree, LoopInfo, and LCCSA analysis information.
    HasLoopExit = false;
    UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, DT, LI,
                              PreserveLCSSA, HasLoopExit);

    // Update the PHI nodes in OrigBB with the values coming from NewBB2.
    UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, HasLoopExit);
  }

  LandingPadInst *LPad = OrigBB->getLandingPadInst();
  Instruction *Clone1 = LPad->clone();
  Clone1->setName(Twine("lpad") + Suffix1);
  NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);

  if (NewBB2) {
    Instruction *Clone2 = LPad->clone();
    Clone2->setName(Twine("lpad") + Suffix2);
    NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);

    // Create a PHI node for the two cloned landingpad instructions only
    // if the original landingpad instruction has some uses.
    if (!LPad->use_empty()) {
      assert(!LPad->getType()->isTokenTy() &&
             "Split cannot be applied if LPad is token type. Otherwise an "
             "invalid PHINode of token type would be created.");
      PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
      PN->addIncoming(Clone1, NewBB1);
      PN->addIncoming(Clone2, NewBB2);
      LPad->replaceAllUsesWith(PN);
    }
    LPad->eraseFromParent();
  } else {
    // There is no second clone. Just replace the landing pad with the first
    // clone.
    LPad->replaceAllUsesWith(Clone1);
    LPad->eraseFromParent();
//.........这里部分代码省略.........