C++ DominatorTree::addNewBlock方法代码示例

//.........这里部分代码省略.........

  // Now update analysis information.  Since the only predecessor of NewBB is
  // the TIBB, TIBB clearly dominates NewBB.  TIBB usually doesn't dominate
  // anything, as there are other successors of DestBB.  However, if all other
  // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a
  // loop header) then NewBB dominates DestBB.
  SmallVector<BasicBlock*, 8> OtherPreds;

  // If there is a PHI in the block, loop over predecessors with it, which is
  // faster than iterating pred_begin/end.
  if (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (PN->getIncomingBlock(i) != NewBB)
        OtherPreds.push_back(PN->getIncomingBlock(i));
  } else {
    for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB);
         I != E; ++I) {
      BasicBlock *P = *I;
      if (P != NewBB)
        OtherPreds.push_back(P);
    }
  }

  bool NewBBDominatesDestBB = true;

  // Should we update DominatorTree information?
  if (DT) {
    DomTreeNode *TINode = DT->getNode(TIBB);

    // The new block is not the immediate dominator for any other nodes, but
    // TINode is the immediate dominator for the new node.
    //
    if (TINode) {       // Don't break unreachable code!
      DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB);
      DomTreeNode *DestBBNode = 0;

      // If NewBBDominatesDestBB hasn't been computed yet, do so with DT.
      if (!OtherPreds.empty()) {
        DestBBNode = DT->getNode(DestBB);
        while (!OtherPreds.empty() && NewBBDominatesDestBB) {
          if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back()))
            NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode);
          OtherPreds.pop_back();
        }
        OtherPreds.clear();
      }

      // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it
      // doesn't dominate anything.
      if (NewBBDominatesDestBB) {
        if (!DestBBNode) DestBBNode = DT->getNode(DestBB);
        DT->changeImmediateDominator(DestBBNode, NewBBNode);
      }
    }
  }

  // Update LoopInfo if it is around.
  if (LI) {
    if (Loop *TIL = LI->getLoopFor(TIBB)) {
      // If one or the other blocks were not in a loop, the new block is not
      // either, and thus LI doesn't need to be updated.
      if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
        if (TIL == DestLoop) {
          // Both in the same loop, the NewBB joins loop.
          DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
        } else if (TIL->contains(DestLoop)) {

//.........这里部分代码省略.........
  if (DT == 0 && DF == 0 && LI == 0 && PI == 0)
    return NewBB;

  // Now update analysis information.  Since the only predecessor of NewBB is
  // the TIBB, TIBB clearly dominates NewBB.  TIBB usually doesn't dominate
  // anything, as there are other successors of DestBB.  However, if all other
  // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a
  // loop header) then NewBB dominates DestBB.
  SmallVector<BasicBlock*, 8> OtherPreds;

  // If there is a PHI in the block, loop over predecessors with it, which is
  // faster than iterating pred_begin/end.
  if (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (PN->getIncomingBlock(i) != NewBB)
        OtherPreds.push_back(PN->getIncomingBlock(i));
  } else {
    for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB);
         I != E; ++I)
      if (*I != NewBB)
        OtherPreds.push_back(*I);
  }
  
  bool NewBBDominatesDestBB = true;
  
  // Should we update DominatorTree information?
  if (DT) {
    DomTreeNode *TINode = DT->getNode(TIBB);

    // The new block is not the immediate dominator for any other nodes, but
    // TINode is the immediate dominator for the new node.
    //
    if (TINode) {       // Don't break unreachable code!
      DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB);
      DomTreeNode *DestBBNode = 0;
     
      // If NewBBDominatesDestBB hasn't been computed yet, do so with DT.
      if (!OtherPreds.empty()) {
        DestBBNode = DT->getNode(DestBB);
        while (!OtherPreds.empty() && NewBBDominatesDestBB) {
          if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back()))
            NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode);
          OtherPreds.pop_back();
        }
        OtherPreds.clear();
      }
      
      // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it
      // doesn't dominate anything.
      if (NewBBDominatesDestBB) {
        if (!DestBBNode) DestBBNode = DT->getNode(DestBB);
        DT->changeImmediateDominator(DestBBNode, NewBBNode);
      }
    }
  }

  // Should we update DominanceFrontier information?
  if (DF) {
    // If NewBBDominatesDestBB hasn't been computed yet, do so with DF.
    if (!OtherPreds.empty()) {
      // FIXME: IMPLEMENT THIS!
      llvm_unreachable("Requiring domfrontiers but not idom/domtree/domset."
                       " not implemented yet!");
    }
    
    // Since the new block is dominated by its only predecessor TIBB,

std::pair<polly::BBPair, BranchInst *>
polly::executeScopConditionally(Scop &S, Value *RTC, DominatorTree &DT,
                                RegionInfo &RI, LoopInfo &LI) {
  Region &R = S.getRegion();
  PollyIRBuilder Builder(S.getEntry());

  // Before:
  //
  //      \   /      //
  //    EnteringBB   //
  //   _____|_____   //
  //  /  EntryBB  \  //
  //  |  (region) |  //
  //  \_ExitingBB_/  //
  //        |        //
  //      ExitBB     //
  //      /    \     //

  // Create a fork block.
  BasicBlock *EnteringBB = S.getEnteringBlock();
  BasicBlock *EntryBB = S.getEntry();
  assert(EnteringBB && "Must be a simple region");
  BasicBlock *SplitBlock =
      splitEdge(EnteringBB, EntryBB, ".split_new_and_old", &DT, &LI, &RI);
  SplitBlock->setName("polly.split_new_and_old");

  // If EntryBB is the exit block of the region that includes Prev, exclude
  // SplitBlock from that region by making it itself the exit block. This is
  // trivially possible because there is just one edge to EnteringBB.
  // This is necessary because we will add an outgoing edge from SplitBlock,
  // which would violate the single exit block requirement of PrevRegion.
  Region *PrevRegion = RI.getRegionFor(EnteringBB);
  while (PrevRegion->getExit() == EntryBB) {
    PrevRegion->replaceExit(SplitBlock);
    PrevRegion = PrevRegion->getParent();
  }
  RI.setRegionFor(SplitBlock, PrevRegion);

  // Create a join block
  BasicBlock *ExitingBB = S.getExitingBlock();
  BasicBlock *ExitBB = S.getExit();
  assert(ExitingBB && "Must be a simple region");
  BasicBlock *MergeBlock =
      splitEdge(ExitingBB, ExitBB, ".merge_new_and_old", &DT, &LI, &RI);
  MergeBlock->setName("polly.merge_new_and_old");

  // Exclude the join block from the region.
  R.replaceExitRecursive(MergeBlock);
  RI.setRegionFor(MergeBlock, R.getParent());

  //      \   /      //
  //    EnteringBB   //
  //        |        //
  //    SplitBlock   //
  //   _____|_____   //
  //  /  EntryBB  \  //
  //  |  (region) |  //
  //  \_ExitingBB_/  //
  //        |        //
  //    MergeBlock   //
  //        |        //
  //      ExitBB     //
  //      /    \     //

  // Create the start and exiting block.
  Function *F = SplitBlock->getParent();
  BasicBlock *StartBlock =
      BasicBlock::Create(F->getContext(), "polly.start", F);
  BasicBlock *ExitingBlock =
      BasicBlock::Create(F->getContext(), "polly.exiting", F);
  SplitBlock->getTerminator()->eraseFromParent();
  Builder.SetInsertPoint(SplitBlock);
  BranchInst *CondBr = Builder.CreateCondBr(RTC, StartBlock, S.getEntry());

  if (Loop *L = LI.getLoopFor(SplitBlock)) {
    L->addBasicBlockToLoop(StartBlock, LI);
    L->addBasicBlockToLoop(ExitingBlock, LI);
  }
  DT.addNewBlock(StartBlock, SplitBlock);
  DT.addNewBlock(ExitingBlock, StartBlock);
  RI.setRegionFor(StartBlock, RI.getRegionFor(SplitBlock));
  RI.setRegionFor(ExitingBlock, RI.getRegionFor(SplitBlock));

  //      \   /                    //
  //    EnteringBB                 //
  //        |                      //
  //    SplitBlock---------\       //
  //   _____|_____         |       //
  //  /  EntryBB  \    StartBlock  //
  //  |  (region) |        |       //
  //  \_ExitingBB_/   ExitingBlock //
  //        |                      //
  //    MergeBlock                 //
  //        |                      //
  //      ExitBB                   //
  //      /    \                   //

  // Connect start block to exiting block.
  Builder.SetInsertPoint(StartBlock);
  Builder.CreateBr(ExitingBlock);
//.........这里部分代码省略.........