X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FLoopRotation.cpp;h=1e4bfa94be56946c08d2c6c7108f72531bda44b2;hb=9ccaf53ada99c63737547c0235baeb8454b04e80;hp=783056d0790e1d441dfce54eb057d29fc663d52f;hpb=6c36157f3d0b27c05f5fbb599de0d992ea2f04ef;p=oota-llvm.git diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp index 783056d0790..1e4bfa94be5 100644 --- a/lib/Transforms/Scalar/LoopRotation.cpp +++ b/lib/Transforms/Scalar/LoopRotation.cpp @@ -2,8 +2,8 @@ // // The LLVM Compiler Infrastructure // -// This file was developed by Devang Patel and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // @@ -12,18 +12,19 @@ //===----------------------------------------------------------------------===// #define DEBUG_TYPE "loop-rotate" - #include "llvm/Transforms/Scalar.h" #include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/Analysis/LoopInfo.h" +#include "llvm/IntrinsicInst.h" #include "llvm/Analysis/LoopPass.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Analysis/ScalarEvolution.h" #include "llvm/Transforms/Utils/Local.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/SSAUpdater.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/SmallVector.h" - using namespace llvm; #define MAX_HEADER_SIZE 16 @@ -31,28 +32,26 @@ using namespace llvm; STATISTIC(NumRotated, "Number of loops rotated"); namespace { - class VISIBILITY_HIDDEN RenameData { + class LoopRotate : public LoopPass { public: - RenameData(Instruction *O, Value *P, Instruction *H) - : Original(O), PreHeader(P), Header(H) { } - public: - Instruction *Original; // Original instruction - Value *PreHeader; // Original pre-header replacement - Instruction *Header; // New header replacement - }; - - class VISIBILITY_HIDDEN LoopRotate : public LoopPass { + static char ID; // Pass ID, replacement for typeid + LoopRotate() : LoopPass(ID) {} - public: - // Rotate Loop L as many times as possible. Return true if // loop is rotated at least once. bool runOnLoop(Loop *L, LPPassManager &LPM); // LCSSA form makes instruction renaming easier. virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addPreserved(); + AU.addPreserved(); + AU.addRequired(); + AU.addPreserved(); + AU.addRequiredID(LoopSimplifyID); + AU.addPreservedID(LoopSimplifyID); AU.addRequiredID(LCSSAID); AU.addPreservedID(LCSSAID); + AU.addPreserved(); } // Helper functions @@ -63,46 +62,34 @@ namespace { /// Initialize local data void initialize(); - /// Make sure all Exit block PHINodes have required incoming values. - /// If incoming value is constant or defined outside the loop then - /// PHINode may not have an entry for original pre-header. - void updateExitBlock(); - - /// Return true if this instruction is used outside original header. - bool usedOutsideOriginalHeader(Instruction *In); - - /// Find Replacement information for instruction. Return NULL if it is - /// not available. - const RenameData *findReplacementData(Instruction *I); - /// After loop rotation, loop pre-header has multiple sucessors. /// Insert one forwarding basic block to ensure that loop pre-header /// has only one successor. void preserveCanonicalLoopForm(LPPassManager &LPM); private: - Loop *L; BasicBlock *OrigHeader; BasicBlock *OrigPreHeader; BasicBlock *OrigLatch; BasicBlock *NewHeader; BasicBlock *Exit; - - SmallVector LoopHeaderInfo; + LPPassManager *LPM_Ptr; }; - - RegisterPass X ("loop-rotate", "Rotate Loops"); } + +char LoopRotate::ID = 0; +INITIALIZE_PASS(LoopRotate, "loop-rotate", "Rotate Loops", false, false); -LoopPass *llvm::createLoopRotatePass() { return new LoopRotate(); } +Pass *llvm::createLoopRotatePass() { return new LoopRotate(); } /// Rotate Loop L as many times as possible. Return true if -/// loop is rotated at least once. +/// the loop is rotated at least once. bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) { - + bool RotatedOneLoop = false; initialize(); + LPM_Ptr = &LPM; // One loop can be rotated multiple times. while (rotateLoop(Lp,LPM)) { @@ -113,273 +100,173 @@ bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) { return RotatedOneLoop; } -/// Rotate loop LP. Return true if it loop is rotated. +/// Rotate loop LP. Return true if the loop is rotated. bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) { - L = Lp; - OrigHeader = L->getHeader(); OrigPreHeader = L->getLoopPreheader(); + if (!OrigPreHeader) return false; + OrigLatch = L->getLoopLatch(); + if (!OrigLatch) return false; - // If loop has only one block then there is not much to rotate. + OrigHeader = L->getHeader(); + + // If the loop has only one block then there is not much to rotate. if (L->getBlocks().size() == 1) return false; - assert (OrigHeader && OrigLatch && OrigPreHeader && - "Loop is not in cannocial form"); - - // If loop header is not one of the loop exit block then - // either this loop is already rotated or it is not + // If the loop header is not one of the loop exiting blocks then + // either this loop is already rotated or it is not // suitable for loop rotation transformations. - if (!L->isLoopExit(OrigHeader)) + if (!L->isLoopExiting(OrigHeader)) return false; BranchInst *BI = dyn_cast(OrigHeader->getTerminator()); if (!BI) return false; - assert (BI->isConditional() && "Branch Instruction is not condiitional"); + assert(BI->isConditional() && "Branch Instruction is not conditional"); // Updating PHInodes in loops with multiple exits adds complexity. // Keep it simple, and restrict loop rotation to loops with one exit only. // In future, lift this restriction and support for multiple exits if // required. - std::vector ExitBlocks; + SmallVector ExitBlocks; L->getExitBlocks(ExitBlocks); if (ExitBlocks.size() > 1) return false; + // Check size of original header and reject + // loop if it is very big. + unsigned Size = 0; + + // FIXME: Use common api to estimate size. + for (BasicBlock::const_iterator OI = OrigHeader->begin(), + OE = OrigHeader->end(); OI != OE; ++OI) { + if (isa(OI)) + continue; // PHI nodes don't count. + if (isa(OI)) + continue; // Debug intrinsics don't count as size. + ++Size; + } + + if (Size > MAX_HEADER_SIZE) + return false; + + // Now, this loop is suitable for rotation. + + // Anything ScalarEvolution may know about this loop or the PHI nodes + // in its header will soon be invalidated. + if (ScalarEvolution *SE = getAnalysisIfAvailable()) + SE->forgetLoop(L); + // Find new Loop header. NewHeader is a Header's one and only successor - // that is inside loop. Header's other successor is out side the - // loop. Otherwise loop is not suitable for rotation. + // that is inside loop. Header's other successor is outside the + // loop. Otherwise loop is not suitable for rotation. Exit = BI->getSuccessor(0); NewHeader = BI->getSuccessor(1); if (L->contains(Exit)) std::swap(Exit, NewHeader); - assert (NewHeader && "Unable to determine new loop header"); + assert(NewHeader && "Unable to determine new loop header"); assert(L->contains(NewHeader) && !L->contains(Exit) && "Unable to determine loop header and exit blocks"); - - // Check size of original header and reject - // loop if it is very big. - if (OrigHeader->getInstList().size() > MAX_HEADER_SIZE) - return false; - - // Now, this loop is suitable for rotation. - - // Copy PHI nodes and other instructions from original header - // into original pre-header. Unlike original header, original pre-header is - // not a member of loop. - // - // New loop header is one and only successor of original header that - // is inside the loop. All other original header successors are outside - // the loop. Copy PHI Nodes from original header into new loop header. - // Add second incoming value, from original loop pre-header into these phi - // nodes. If a value defined in original header is used outside original - // header then new loop header will need new phi nodes with two incoming - // values, one definition from original header and second definition is - // from original loop pre-header. - - // Remove terminator from Original pre-header. Original pre-header will - // receive a clone of original header terminator as a new terminator. - OrigPreHeader->getInstList().pop_back(); + + // This code assumes that the new header has exactly one predecessor. + // Remove any single-entry PHI nodes in it. + assert(NewHeader->getSinglePredecessor() && + "New header doesn't have one pred!"); + FoldSingleEntryPHINodes(NewHeader); + + // Begin by walking OrigHeader and populating ValueMap with an entry for + // each Instruction. BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end(); - PHINode *PN = NULL; - for (; (PN = dyn_cast(I)); ++I) { - Instruction *In = I; - - // PHI nodes are not copied into original pre-header. Instead their values - // are directly propagated. - Value * NPV = PN->getIncomingValueForBlock(OrigPreHeader); - - // Create new PHI node with two incoming values for NewHeader. - // One incoming value is from OrigLatch (through OrigHeader) and - // second incoming value is from original pre-header. - PHINode *NH = new PHINode(In->getType(), In->getName()); - NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader); - NH->addIncoming(NPV, OrigPreHeader); - NewHeader->getInstList().push_front(NH); - - // "In" can be replaced by NH at various places. - LoopHeaderInfo.push_back(RenameData(In, NPV, NH)); - } - - // Now, handle non-phi instructions. - for (; I != E; ++I) { - Instruction *In = I; - - assert (!isa(In) && "PHINode is not expected here"); - // This is not a PHI instruction. Insert its clone into original pre-header. - // If this instruction is using a value from same basic block then - // update it to use value from cloned instruction. - Instruction *C = In->clone(); - C->setName(In->getName()); - OrigPreHeader->getInstList().push_back(C); - - for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) { - if (Instruction *OpPhi = dyn_cast(In->getOperand(opi))) { - if (const RenameData *D = findReplacementData(OpPhi)) { - // This is using values from original header PHI node. - // Here, directly used incoming value from original pre-header. - C->setOperand(opi, D->PreHeader); - } - } - else if (Instruction *OpInsn = - dyn_cast(In->getOperand(opi))) { - if (const RenameData *D = findReplacementData(OpInsn)) - C->setOperand(opi, D->PreHeader); - } - } + DenseMap ValueMap; + // For PHI nodes, the value available in OldPreHeader is just the + // incoming value from OldPreHeader. + for (; PHINode *PN = dyn_cast(I); ++I) + ValueMap[PN] = PN->getIncomingValue(PN->getBasicBlockIndex(OrigPreHeader)); - // If this instruction is used outside this basic block then - // create new PHINode for this instruction. - Instruction *NewHeaderReplacement = NULL; - if (usedOutsideOriginalHeader(In)) { - PHINode *PN = new PHINode(In->getType(), In->getName()); - PN->addIncoming(In, OrigHeader); - PN->addIncoming(C, OrigPreHeader); - NewHeader->getInstList().push_front(PN); - NewHeaderReplacement = PN; - } - - // "In" can be replaced by NPH or NH at various places. - LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement)); + // For the rest of the instructions, create a clone in the OldPreHeader. + TerminatorInst *LoopEntryBranch = OrigPreHeader->getTerminator(); + for (; I != E; ++I) { + Instruction *C = I->clone(); + C->setName(I->getName()); + C->insertBefore(LoopEntryBranch); + ValueMap[I] = C; } - // Rename uses of original header instructions to reflect their new - // definitions (either from original pre-header node or from newly created - // new header PHINodes. - // - // Original header instructions are used in - // 1) Original header: - // - // If instruction is used in non-phi instructions then it is using - // defintion from original heder iteself. Do not replace this use - // with definition from new header or original pre-header. - // - // If instruction is used in phi node then it is an incoming - // value. Rename its use to reflect new definition from new-preheader - // or new header. - // - // 2) Inside loop but not in original header - // - // Replace this use to reflect definition from new header. - for(unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) { - const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI]; - - if (!ILoopHeaderInfo.Header) - continue; - - Instruction *OldPhi = ILoopHeaderInfo.Original; - Instruction *NewPhi = ILoopHeaderInfo.Header; - - // Before replacing uses, collect them first, so that iterator is - // not invalidated. - SmallVector AllUses; - for (Value::use_iterator UI = OldPhi->use_begin(), UE = OldPhi->use_end(); - UI != UE; ++UI) { - Instruction *U = cast(UI); - AllUses.push_back(U); - } - - for (SmallVector::iterator UI = AllUses.begin(), - UE = AllUses.end(); UI != UE; ++UI) { - Instruction *U = *UI; - BasicBlock *Parent = U->getParent(); - - // Used inside original header - if (Parent == OrigHeader) { - // Do not rename uses inside original header non-phi instructions. - PHINode *PU = dyn_cast(U); - if (!PU) + // Along with all the other instructions, we just cloned OrigHeader's + // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's + // successors by duplicating their incoming values for OrigHeader. + TerminatorInst *TI = OrigHeader->getTerminator(); + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + for (BasicBlock::iterator BI = TI->getSuccessor(i)->begin(); + PHINode *PN = dyn_cast(BI); ++BI) + PN->addIncoming(PN->getIncomingValueForBlock(OrigHeader), OrigPreHeader); + + // Now that OrigPreHeader has a clone of OrigHeader's terminator, remove + // OrigPreHeader's old terminator (the original branch into the loop), and + // remove the corresponding incoming values from the PHI nodes in OrigHeader. + LoopEntryBranch->eraseFromParent(); + for (I = OrigHeader->begin(); PHINode *PN = dyn_cast(I); ++I) + PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreHeader)); + + // Now fix up users of the instructions in OrigHeader, inserting PHI nodes + // as necessary. + SSAUpdater SSA; + for (I = OrigHeader->begin(); I != E; ++I) { + Value *OrigHeaderVal = I; + Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal]; + + // The value now exits in two versions: the initial value in the preheader + // and the loop "next" value in the original header. + SSA.Initialize(OrigHeaderVal); + SSA.AddAvailableValue(OrigHeader, OrigHeaderVal); + SSA.AddAvailableValue(OrigPreHeader, OrigPreHeaderVal); + + // Visit each use of the OrigHeader instruction. + for (Value::use_iterator UI = OrigHeaderVal->use_begin(), + UE = OrigHeaderVal->use_end(); UI != UE; ) { + // Grab the use before incrementing the iterator. + Use &U = UI.getUse(); + + // Increment the iterator before removing the use from the list. + ++UI; + + // SSAUpdater can't handle a non-PHI use in the same block as an + // earlier def. We can easily handle those cases manually. + Instruction *UserInst = cast(U.getUser()); + if (!isa(UserInst)) { + BasicBlock *UserBB = UserInst->getParent(); + + // The original users in the OrigHeader are already using the + // original definitions. + if (UserBB == OrigHeader) continue; - // Do not rename uses inside original header phi nodes, if the - // incoming value is for new header. - if (PU->getBasicBlockIndex(NewHeader) != -1 - && PU->getIncomingValueForBlock(NewHeader) == U) + // Users in the OrigPreHeader need to use the value to which the + // original definitions are mapped. + if (UserBB == OrigPreHeader) { + U = OrigPreHeaderVal; continue; - - U->replaceUsesOfWith(OldPhi, NewPhi); - continue; - } - - // Used inside loop, but not in original header. - if (L->contains(U->getParent())) { - if (U != NewPhi) - U->replaceUsesOfWith(OldPhi, NewPhi); - continue; + } } - // Used inside Exit Block. Since we are in LCSSA form, U must be PHINode. - assert (U->getParent() == Exit - && "Need to propagate new PHI into Exit blocks"); - assert (isa(U) && "Use in Exit Block that is not PHINode"); - - PHINode *UPhi = cast(U); - - // UPhi already has one incoming argument from original header. - // Add second incoming argument from new Pre header. - - UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader); + // Anything else can be handled by SSAUpdater. + SSA.RewriteUse(U); } } - - /// Make sure all Exit block PHINodes have required incoming values. - updateExitBlock(); - - // Update CFG - - // Removing incoming branch from loop preheader to original header. - // Now original header is inside the loop. - for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end(); - I != E; ++I) { - Instruction *In = I; - PHINode *PN = dyn_cast(In); - if (!PN) - break; - - PN->removeIncomingValue(OrigPreHeader); - } - // Make NewHeader as the new header for the loop. + // NewHeader is now the header of the loop. L->moveToHeader(NewHeader); preserveCanonicalLoopForm(LPM); - NumRotated++; + ++NumRotated; return true; } -/// Make sure all Exit block PHINodes have required incoming values. -/// If incoming value is constant or defined outside the loop then -/// PHINode may not have an entry for original pre-header. -void LoopRotate::updateExitBlock() { - - for (BasicBlock::iterator I = Exit->begin(), E = Exit->end(); - I != E; ++I) { - - PHINode *PN = dyn_cast(I); - if (!PN) - break; - - // There is already one incoming value from original pre-header block. - if (PN->getBasicBlockIndex(OrigPreHeader) != -1) - continue; - - const RenameData *ILoopHeaderInfo; - Value *V = PN->getIncomingValueForBlock(OrigHeader); - if (isa(V) && - (ILoopHeaderInfo = findReplacementData(cast(V)))) { - assert (ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction"); - PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader); - } else { - PN->addIncoming(V, OrigPreHeader); - } - } -} - /// Initialize local data void LoopRotate::initialize() { L = NULL; @@ -387,37 +274,6 @@ void LoopRotate::initialize() { OrigPreHeader = NULL; NewHeader = NULL; Exit = NULL; - - LoopHeaderInfo.clear(); -} - -/// Return true if this instruction is used by any instructions in the loop that -/// aren't in original header. -bool LoopRotate::usedOutsideOriginalHeader(Instruction *In) { - - for (Value::use_iterator UI = In->use_begin(), UE = In->use_end(); - UI != UE; ++UI) { - Instruction *U = cast(UI); - if (U->getParent() != OrigHeader) { - if (L->contains(U->getParent())) - return true; - } - } - - return false; -} - -/// Find Replacement information for instruction. Return NULL if it is -/// not available. -const RenameData *LoopRotate::findReplacementData(Instruction *In) { - - // Since LoopHeaderInfo is small, linear walk is OK. - for(unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) { - const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI]; - if (ILoopHeaderInfo.Original == In) - return &ILoopHeaderInfo; - } - return NULL; } /// After loop rotation, loop pre-header has multiple sucessors. @@ -428,40 +284,120 @@ void LoopRotate::preserveCanonicalLoopForm(LPPassManager &LPM) { // Right now original pre-header has two successors, new header and // exit block. Insert new block between original pre-header and // new header such that loop's new pre-header has only one successor. - BasicBlock *NewPreHeader = new BasicBlock("bb.nph", OrigHeader->getParent(), - NewHeader); - LoopInfo &LI = LPM.getAnalysis(); + BasicBlock *NewPreHeader = BasicBlock::Create(OrigHeader->getContext(), + "bb.nph", + OrigHeader->getParent(), + NewHeader); + LoopInfo &LI = getAnalysis(); if (Loop *PL = LI.getLoopFor(OrigPreHeader)) - PL->addBasicBlockToLoop(NewPreHeader, LI); - new BranchInst(NewHeader, NewPreHeader); + PL->addBasicBlockToLoop(NewPreHeader, LI.getBase()); + BranchInst::Create(NewHeader, NewPreHeader); BranchInst *OrigPH_BI = cast(OrigPreHeader->getTerminator()); if (OrigPH_BI->getSuccessor(0) == NewHeader) OrigPH_BI->setSuccessor(0, NewPreHeader); else { - assert (OrigPH_BI->getSuccessor(1) == NewHeader && - "Unexpected original pre-header terminator"); + assert(OrigPH_BI->getSuccessor(1) == NewHeader && + "Unexpected original pre-header terminator"); OrigPH_BI->setSuccessor(1, NewPreHeader); } - - for (BasicBlock::iterator I = NewHeader->begin(), E = NewHeader->end(); - I != E; ++I) { - Instruction *In = I; - PHINode *PN = dyn_cast(In); - if (!PN) - break; + PHINode *PN; + for (BasicBlock::iterator I = NewHeader->begin(); + (PN = dyn_cast(I)); ++I) { int index = PN->getBasicBlockIndex(OrigPreHeader); - assert (index != -1 && "Expected incoming value from Original PreHeader"); + assert(index != -1 && "Expected incoming value from Original PreHeader"); PN->setIncomingBlock(index, NewPreHeader); - assert (PN->getBasicBlockIndex(OrigPreHeader) == -1 && - "Expected only one incoming value from Original PreHeader"); + assert(PN->getBasicBlockIndex(OrigPreHeader) == -1 && + "Expected only one incoming value from Original PreHeader"); + } + + if (DominatorTree *DT = getAnalysisIfAvailable()) { + DT->addNewBlock(NewPreHeader, OrigPreHeader); + DT->changeImmediateDominator(L->getHeader(), NewPreHeader); + DT->changeImmediateDominator(Exit, OrigPreHeader); + for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end(); + BI != BE; ++BI) { + BasicBlock *B = *BI; + if (L->getHeader() != B) { + DomTreeNode *Node = DT->getNode(B); + if (Node && Node->getBlock() == OrigHeader) + DT->changeImmediateDominator(*BI, L->getHeader()); + } + } + DT->changeImmediateDominator(OrigHeader, OrigLatch); } - 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"); + if (DominanceFrontier *DF = getAnalysisIfAvailable()) { + // 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()) { + 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"); }