- // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
- // DF(PredBlocks[0]) without the stuff that the new block does not dominate
- // a predecessor of.
- DominatorTree &DT = getAnalysis<DominatorTree>();
- if (DT.dominates(NewBB, NewBBSucc)) {
- DominanceFrontier::iterator DFI = find(PredBlocks[0]);
- if (DFI != end()) {
- DominanceFrontier::DomSetType Set = DFI->second;
- // Filter out stuff in Set that we do not dominate a predecessor of.
- for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
- E = Set.end(); SetI != E;) {
- bool DominatesPred = false;
- for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
- PI != E; ++PI)
- if (DT.dominates(NewBB, *PI))
- DominatesPred = true;
- if (!DominatesPred)
- Set.erase(SetI++);
- else
- ++SetI;
- }
-
- if (NewBBI != end()) {
- for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
- E = Set.end(); SetI != E; ++SetI) {
- BasicBlock *SB = *SetI;
- addToFrontier(NewBBI, SB);
- }
- } else
- addBasicBlock(NewBB, Set);
- }
-
- } else {
- // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
- // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
- // NewBBSucc)). NewBBSucc is the single successor of NewBB.
- DominanceFrontier::DomSetType NewDFSet;
- NewDFSet.insert(NewBBSucc);
- addBasicBlock(NewBB, NewDFSet);
- }
-
- // Now we must loop over all of the dominance frontiers in the function,
- // replacing occurrences of NewBBSucc with NewBB in some cases. All
- // blocks that dominate a block in PredBlocks and contained NewBBSucc in
- // their dominance frontier must be updated to contain NewBB instead.
- //
- for (Function::iterator FI = NewBB->getParent()->begin(),
- FE = NewBB->getParent()->end(); FI != FE; ++FI) {
- DominanceFrontier::iterator DFI = find(FI);
- if (DFI == end()) continue; // unreachable block.
-
- // Only consider nodes that have NewBBSucc in their dominator frontier.
- if (!DFI->second.count(NewBBSucc)) continue;
-
- // Verify whether this block dominates a block in predblocks. If not, do
- // not update it.
- bool BlockDominatesAny = false;
- for (SmallVectorImpl<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
- BE = PredBlocks.end(); BI != BE; ++BI) {
- if (DT.dominates(FI, *BI)) {
- BlockDominatesAny = true;
- break;
- }
- }
-
- // If NewBBSucc should not stay in our dominator frontier, remove it.
- // We remove it unless there is a predecessor of NewBBSucc that we
- // dominate, but we don't strictly dominate NewBBSucc.
- bool ShouldRemove = true;
- if ((BasicBlock*)FI == NewBBSucc || !DT.dominates(FI, NewBBSucc)) {
- // Okay, we know that PredDom does not strictly dominate NewBBSucc.
- // Check to see if it dominates any predecessors of NewBBSucc.
- for (pred_iterator PI = pred_begin(NewBBSucc),
- E = pred_end(NewBBSucc); PI != E; ++PI)
- if (DT.dominates(FI, *PI)) {
- ShouldRemove = false;
- break;
- }
- }
-
- if (ShouldRemove)
- removeFromFrontier(DFI, NewBBSucc);
- if (BlockDominatesAny && (&*FI == NewBB || !DT.dominates(FI, NewBB)))
- addToFrontier(DFI, NewBB);
- }