C++ LandingPadInst::eraseFromParent方法代码示例

/// SplitLandingPadPredecessors - This method transforms the landing pad,
/// OrigBB, by introducing two new basic blocks into the function. One of those
/// new basic blocks gets the predecessors listed in Preds. The other basic
/// block gets the remaining predecessors of OrigBB. The landingpad instruction
/// OrigBB is clone into both of the new basic blocks. The new blocks are given
/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
/// 
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
/// it does not preserve LoopSimplify (because it's complicated to handle the
/// case where one of the edges being split is an exit of a loop with other
/// exits).
/// 
void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
                                       ArrayRef<BasicBlock*> Preds,
                                       const char *Suffix1, const char *Suffix2,
                                       Pass *P,
                                       SmallVectorImpl<BasicBlock*> &NewBBs) {
  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);

  // 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);
  }

  // Update DominatorTree, LoopInfo, and LCCSA analysis information.
  bool HasLoopExit = false;
  UpdateAnalysisInformation(OrigBB, NewBB1, Preds, P, HasLoopExit);

  // Update the PHI nodes in OrigBB with the values coming from NewBB1.
  UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, P, 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 = 0;
  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);

    // Move the remaining edges from OrigBB to point to NewBB2.
    for (SmallVectorImpl<BasicBlock*>::iterator
           i = NewBB2Preds.begin(), e = NewBB2Preds.end(); i != e; ++i)
      (*i)->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);

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

    // Update the PHI nodes in OrigBB with the values coming from NewBB2.
    UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, P, 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.
    PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
    PN->addIncoming(Clone1, NewBB1);
    PN->addIncoming(Clone2, NewBB2);
    LPad->replaceAllUsesWith(PN);
    LPad->eraseFromParent();
  } else {
//.........这里部分代码省略.........