+ if (DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>()) {
+ // New Preheader's dominance frontier is Exit block.
+ DominanceFrontier::DomSetType NewPHSet;
+ NewPHSet.insert(Exit);
+ DF->addBasicBlock(NewPreHeader, NewPHSet);
+
+ // New Header's dominance frontier now includes itself and Exit block
+ DominanceFrontier::iterator HeadI = DF->find(L->getHeader());
+ if (HeadI != DF->end()) {
+ DominanceFrontier::DomSetType & HeaderSet = HeadI->second;
+ HeaderSet.clear();
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType HeaderSet;
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), HeaderSet);
+ }
+
+ // Original header (new Loop Latch)'s dominance frontier is Exit.
+ DominanceFrontier::iterator LatchI = DF->find(L->getLoopLatch());
+ if (LatchI != DF->end()) {
+ DominanceFrontier::DomSetType &LatchSet = LatchI->second;
+ LatchSet = LatchI->second;
+ LatchSet.clear();
+ LatchSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType LatchSet;
+ LatchSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), LatchSet);
+ }
+
+ // If a loop block dominates new loop latch then add to its frontiers
+ // new header and Exit and remove new latch (which is equal to original
+ // header).
+ BasicBlock *NewLatch = L->getLoopLatch();
+
+ assert(NewLatch == OrigHeader && "NewLatch is inequal to OrigHeader");
+
+ if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (DT->dominates(B, NewLatch)) {
+ DominanceFrontier::iterator BDFI = DF->find(B);
+ if (BDFI != DF->end()) {
+ DominanceFrontier::DomSetType &BSet = BDFI->second;
+ BSet.erase(NewLatch);
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType BSet;
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ DF->addBasicBlock(B, BSet);
+ }
+ }
+ }
+ }
+ }
+
+ // Preserve canonical loop form, which means Exit block should
+ // have only one predecessor.
+ SplitEdge(L->getLoopLatch(), Exit, this);
+
+ assert(NewHeader && L->getHeader() == NewHeader &&
+ "Invalid loop header after loop rotation");
+ assert(NewPreHeader && L->getLoopPreheader() == NewPreHeader &&
+ "Invalid loop preheader after loop rotation");
+ assert(L->getLoopLatch() &&
+ "Invalid loop latch after loop rotation");