C++ TerminatorInst::successors方法代码示例

MDNode *Loop::getLoopID() const {
  MDNode *LoopID = nullptr;
  if (isLoopSimplifyForm()) {
    LoopID = getLoopLatch()->getTerminator()->getMetadata(LLVMContext::MD_loop);
  } else {
    // Go through each predecessor of the loop header and check the
    // terminator for the metadata.
    BasicBlock *H = getHeader();
    for (BasicBlock *BB : this->blocks()) {
      TerminatorInst *TI = BB->getTerminator();
      MDNode *MD = nullptr;

      // Check if this terminator branches to the loop header.
      for (BasicBlock *Successor : TI->successors()) {
        if (Successor == H) {
          MD = TI->getMetadata(LLVMContext::MD_loop);
          break;
        }
      }
      if (!MD)
        return nullptr;

      if (!LoopID)
        LoopID = MD;
      else if (MD != LoopID)
        return nullptr;
    }
  }
  if (!LoopID || LoopID->getNumOperands() == 0 ||
      LoopID->getOperand(0) != LoopID)
    return nullptr;
  return LoopID;
}

void MemorySSAUpdater::removeBlocks(
    const SmallPtrSetImpl<BasicBlock *> &DeadBlocks) {
  // First delete all uses of BB in MemoryPhis.
  for (BasicBlock *BB : DeadBlocks) {
    TerminatorInst *TI = BB->getTerminator();
    assert(TI && "Basic block expected to have a terminator instruction");
    for (BasicBlock *Succ : TI->successors())
      if (!DeadBlocks.count(Succ))
        if (MemoryPhi *MP = MSSA->getMemoryAccess(Succ)) {
          MP->unorderedDeleteIncomingBlock(BB);
          if (MP->getNumIncomingValues() == 1)
            removeMemoryAccess(MP);
        }
    // Drop all references of all accesses in BB
    if (MemorySSA::AccessList *Acc = MSSA->getWritableBlockAccesses(BB))
      for (MemoryAccess &MA : *Acc)
        MA.dropAllReferences();
  }

  // Next, delete all memory accesses in each block
  for (BasicBlock *BB : DeadBlocks) {
    MemorySSA::AccessList *Acc = MSSA->getWritableBlockAccesses(BB);
    if (!Acc)
      continue;
    for (auto AB = Acc->begin(), AE = Acc->end(); AB != AE;) {
      MemoryAccess *MA = &*AB;
      ++AB;
      MSSA->removeFromLookups(MA);
      MSSA->removeFromLists(MA);
    }
  }
}

void Loop::setLoopID(MDNode *LoopID) const {
  assert(LoopID && "Loop ID should not be null");
  assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
  assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");

  if (isLoopSimplifyForm()) {
    getLoopLatch()->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
    return;
  }

  BasicBlock *H = getHeader();
  for (BasicBlock *BB : this->blocks()) {
    TerminatorInst *TI = BB->getTerminator();
    for (BasicBlock *Successor : TI->successors()) {
      if (Successor == H)
        TI->setMetadata(LLVMContext::MD_loop, LoopID);
    }
  }
}

void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
  TerminatorInst *TI = getTerminator();
  if (!TI)
    // Cope with being called on a BasicBlock that doesn't have a terminator
    // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
    return;
  for (BasicBlock *Succ : TI->successors()) {
    // N.B. Succ might not be a complete BasicBlock, so don't assume
    // that it ends with a non-phi instruction.
    for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) {
      PHINode *PN = dyn_cast<PHINode>(II);
      if (!PN)
        break;
      int i;
      while ((i = PN->getBasicBlockIndex(this)) >= 0)
        PN->setIncomingBlock(i, New);
    }
  }
}

void llvm::DeleteDeadBlock(BasicBlock *BB, DeferredDominance *DDT) {
  assert((pred_begin(BB) == pred_end(BB) ||
         // Can delete self loop.
         BB->getSinglePredecessor() == BB) && "Block is not dead!");
  TerminatorInst *BBTerm = BB->getTerminator();
  std::vector<DominatorTree::UpdateType> Updates;

  // Loop through all of our successors and make sure they know that one
  // of their predecessors is going away.
  if (DDT)
    Updates.reserve(BBTerm->getNumSuccessors());
  for (BasicBlock *Succ : BBTerm->successors()) {
    Succ->removePredecessor(BB);
    if (DDT)
      Updates.push_back({DominatorTree::Delete, BB, Succ});
  }

  // Zap all the instructions in the block.
  while (!BB->empty()) {
    Instruction &I = BB->back();
    // If this instruction is used, replace uses with an arbitrary value.
    // Because control flow can't get here, we don't care what we replace the
    // value with.  Note that since this block is unreachable, and all values
    // contained within it must dominate their uses, that all uses will
    // eventually be removed (they are themselves dead).
    if (!I.use_empty())
      I.replaceAllUsesWith(UndefValue::get(I.getType()));
    BB->getInstList().pop_back();
  }

  if (DDT) {
    DDT->applyUpdates(Updates);
    DDT->deleteBB(BB); // Deferred deletion of BB.
  } else {
    BB->eraseFromParent(); // Zap the block!
  }
}