+/// ReplaceLoopExternalDFMember -
+/// If BB's dominance frontier has a member that is not part of loop L then
+/// remove it. Add NewDFMember in BB's dominance frontier.
+void LoopUnswitch::ReplaceLoopExternalDFMember(Loop *L, BasicBlock *BB,
+ BasicBlock *NewDFMember) {
+
+ DominanceFrontier::iterator DFI = DF->find(BB);
+ if (DFI == DF->end())
+ return;
+
+ DominanceFrontier::DomSetType &DFSet = DFI->second;
+ for (DominanceFrontier::DomSetType::iterator DI = DFSet.begin(),
+ DE = DFSet.end(); DI != DE;) {
+ BasicBlock *B = *DI++;
+ if (L->contains(B))
+ continue;
+
+ DF->removeFromFrontier(DFI, B);
+ LoopDF.insert(B);
+ }
+
+ DF->addToFrontier(DFI, NewDFMember);
+}
+
+/// SplitExitEdges -
+/// Split all of the edges from inside the loop to their exit blocks. Update
+/// the appropriate Phi nodes as we do so.
+void LoopUnswitch::SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks,
+ SmallVector<BasicBlock *, 8> &MiddleBlocks) {
+
+ for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
+ BasicBlock *ExitBlock = ExitBlocks[i];
+ std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock));
+
+ for (unsigned j = 0, e = Preds.size(); j != e; ++j) {
+ BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock, this);
+ MiddleBlocks.push_back(MiddleBlock);
+ BasicBlock* StartBlock = Preds[j];
+ BasicBlock* EndBlock;
+ if (MiddleBlock->getSinglePredecessor() == ExitBlock) {
+ EndBlock = MiddleBlock;
+ MiddleBlock = EndBlock->getSinglePredecessor();;
+ } else {
+ EndBlock = ExitBlock;
+ }
+
+ OrigLoopExitMap[StartBlock] = EndBlock;
+
+ std::set<PHINode*> InsertedPHIs;
+ PHINode* OldLCSSA = 0;
+ for (BasicBlock::iterator I = EndBlock->begin();
+ (OldLCSSA = dyn_cast<PHINode>(I)); ++I) {
+ Value* OldValue = OldLCSSA->getIncomingValueForBlock(MiddleBlock);
+ PHINode* NewLCSSA = new PHINode(OldLCSSA->getType(),
+ OldLCSSA->getName() + ".us-lcssa",
+ MiddleBlock->getTerminator());
+ NewLCSSA->addIncoming(OldValue, StartBlock);
+ OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(MiddleBlock),
+ NewLCSSA);
+ InsertedPHIs.insert(NewLCSSA);
+ }
+
+ BasicBlock::iterator InsertPt = EndBlock->begin();
+ while (dyn_cast<PHINode>(InsertPt)) ++InsertPt;
+ for (BasicBlock::iterator I = MiddleBlock->begin();
+ (OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0;
+ ++I) {
+ PHINode *NewLCSSA = new PHINode(OldLCSSA->getType(),
+ OldLCSSA->getName() + ".us-lcssa",
+ InsertPt);
+ OldLCSSA->replaceAllUsesWith(NewLCSSA);
+ NewLCSSA->addIncoming(OldLCSSA, MiddleBlock);
+ }
+
+ if (DF && DT) {
+ // StartBlock -- > MiddleBlock -- > EndBlock
+ // StartBlock is loop exiting block. EndBlock will become merge point
+ // of two loop exits after loop unswitch.
+
+ // If StartBlock's DF member includes a block that is not loop member
+ // then replace that DF member with EndBlock.
+
+ // If MiddleBlock's DF member includes a block that is not loop member
+ // tnen replace that DF member with EndBlock.
+
+ ReplaceLoopExternalDFMember(L, StartBlock, EndBlock);
+ ReplaceLoopExternalDFMember(L, MiddleBlock, EndBlock);
+ }
+ }
+ }
+
+}