C++ TerminatorInst::getMetadata方法代码示例

MDNode *Loop::getLoopID() const {
  MDNode *LoopID = nullptr;
  if (isLoopSimplifyForm()) {
    LoopID = getLoopLatch()->getTerminator()->getMetadata(LoopMDName);
  } else {
    // Go through each predecessor of the loop header and check the
    // terminator for the metadata.
    BasicBlock *H = getHeader();
    for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) {
      TerminatorInst *TI = (*I)->getTerminator();
      MDNode *MD = nullptr;

      // Check if this terminator branches to the loop header.
      for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) {
        if (TI->getSuccessor(i) == H) {
          MD = TI->getMetadata(LoopMDName);
          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;
}

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;
}

// Propagate existing explicit probabilities from either profile data or
// 'expect' intrinsic processing.
bool BranchProbabilityAnalysis::calcMetadataWeights(BasicBlock *BB) {
  TerminatorInst *TI = BB->getTerminator();
  if (TI->getNumSuccessors() == 1)
    return false;
  if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
    return false;

  MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
  if (!WeightsNode)
    return false;

  // Ensure there are weights for all of the successors. Note that the first
  // operand to the metadata node is a name, not a weight.
  if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1)
    return false;

  // Build up the final weights that will be used in a temporary buffer, but
  // don't add them until all weihts are present. Each weight value is clamped
  // to [1, getMaxWeightFor(BB)].
  uint32_t WeightLimit = getMaxWeightFor(BB);
  SmallVector<uint32_t, 2> Weights;
  Weights.reserve(TI->getNumSuccessors());
  for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
    ConstantInt *Weight = dyn_cast<ConstantInt>(WeightsNode->getOperand(i));
    if (!Weight)
      return false;
    Weights.push_back(
      std::max<uint32_t>(1, Weight->getLimitedValue(WeightLimit)));
  }
  assert(Weights.size() == TI->getNumSuccessors() && "Checked above");
  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
    BP->setEdgeWeight(BB, TI->getSuccessor(i), Weights[i]);

  return true;
}

// Propagate existing explicit probabilities from either profile data or
// 'expect' intrinsic processing.
bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) {
    TerminatorInst *TI = BB->getTerminator();
    if (TI->getNumSuccessors() == 1)
        return false;
    if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
        return false;

    MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
    if (!WeightsNode)
        return false;

    // Check that the number of successors is manageable.
    assert(TI->getNumSuccessors() < UINT32_MAX && "Too many successors");

    // Ensure there are weights for all of the successors. Note that the first
    // operand to the metadata node is a name, not a weight.
    if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1)
        return false;

    // Build up the final weights that will be used in a temporary buffer.
    // Compute the sum of all weights to later decide whether they need to
    // be scaled to fit in 32 bits.
    uint64_t WeightSum = 0;
    SmallVector<uint32_t, 2> Weights;
    Weights.reserve(TI->getNumSuccessors());
    for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
        ConstantInt *Weight =
            mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(i));
        if (!Weight)
            return false;
        assert(Weight->getValue().getActiveBits() <= 32 &&
               "Too many bits for uint32_t");
        Weights.push_back(Weight->getZExtValue());
        WeightSum += Weights.back();
    }
    assert(Weights.size() == TI->getNumSuccessors() && "Checked above");

    // If the sum of weights does not fit in 32 bits, scale every weight down
    // accordingly.
    uint64_t ScalingFactor =
        (WeightSum > UINT32_MAX) ? WeightSum / UINT32_MAX + 1 : 1;

    WeightSum = 0;
    for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
        uint32_t W = Weights[i] / ScalingFactor;
        WeightSum += W;
        setEdgeWeight(BB, i, W);
    }
    assert(WeightSum <= UINT32_MAX &&
           "Expected weights to scale down to 32 bits");

    return true;
}