X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=3d30c3a06e2850cd895f2ad89e228f6a4ddb9fab;hb=ba3f3a65e64fe2cf1f492d90499928270fc1a426;hp=244db3064967b7069c78b35bcb948dcd589613e2;hpb=1b7f7dc4b45a900fae2e9b062d588a995935727a;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index 244db306496..3d30c3a06e2 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -1,4 +1,11 @@ -//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=// +//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// // // This file defines the LoopInfo class that is used to identify natural loops // and determine the loop depth of various nodes of the CFG. Note that the @@ -8,103 +15,727 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/LoopInfo.h" -#include "llvm/Analysis/Dominators.h" -#include "llvm/Support/CFG.h" -#include "Support/DepthFirstIterator.h" +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/Analysis/LoopInfoImpl.h" +#include "llvm/Analysis/LoopIterator.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Metadata.h" +#include "llvm/IR/PassManager.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" #include +using namespace llvm; + +// Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops. +template class llvm::LoopBase; +template class llvm::LoopInfoBase; -AnalysisID LoopInfo::ID(AnalysisID::create()); +// Always verify loopinfo if expensive checking is enabled. +#ifdef XDEBUG +static bool VerifyLoopInfo = true; +#else +static bool VerifyLoopInfo = false; +#endif +static cl::opt +VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo), + cl::desc("Verify loop info (time consuming)")); + +// Loop identifier metadata name. +static const char *const LoopMDName = "llvm.loop"; //===----------------------------------------------------------------------===// // Loop implementation // -bool Loop::contains(BasicBlock *BB) const { - return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); + +/// isLoopInvariant - Return true if the specified value is loop invariant +/// +bool Loop::isLoopInvariant(const Value *V) const { + if (const Instruction *I = dyn_cast(V)) + return !contains(I); + return true; // All non-instructions are loop invariant } -void LoopInfo::releaseMemory() { - for (std::vector::iterator I = TopLevelLoops.begin(), - E = TopLevelLoops.end(); I != E; ++I) - delete *I; // Delete all of the loops... +/// hasLoopInvariantOperands - Return true if all the operands of the +/// specified instruction are loop invariant. +bool Loop::hasLoopInvariantOperands(const Instruction *I) const { + return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); }); +} + +/// makeLoopInvariant - If the given value is an instruciton inside of the +/// loop and it can be hoisted, do so to make it trivially loop-invariant. +/// Return true if the value after any hoisting is loop invariant. This +/// function can be used as a slightly more aggressive replacement for +/// isLoopInvariant. +/// +/// If InsertPt is specified, it is the point to hoist instructions to. +/// If null, the terminator of the loop preheader is used. +/// +bool Loop::makeLoopInvariant(Value *V, bool &Changed, + Instruction *InsertPt) const { + if (Instruction *I = dyn_cast(V)) + return makeLoopInvariant(I, Changed, InsertPt); + return true; // All non-instructions are loop-invariant. +} - BBMap.clear(); // Reset internal state of analysis - TopLevelLoops.clear(); +/// makeLoopInvariant - If the given instruction is inside of the +/// loop and it can be hoisted, do so to make it trivially loop-invariant. +/// Return true if the instruction after any hoisting is loop invariant. This +/// function can be used as a slightly more aggressive replacement for +/// isLoopInvariant. +/// +/// If InsertPt is specified, it is the point to hoist instructions to. +/// If null, the terminator of the loop preheader is used. +/// +bool Loop::makeLoopInvariant(Instruction *I, bool &Changed, + Instruction *InsertPt) const { + // Test if the value is already loop-invariant. + if (isLoopInvariant(I)) + return true; + if (!isSafeToSpeculativelyExecute(I)) + return false; + if (I->mayReadFromMemory()) + return false; + // EH block instructions are immobile. + if (I->isEHPad()) + return false; + // Determine the insertion point, unless one was given. + if (!InsertPt) { + BasicBlock *Preheader = getLoopPreheader(); + // Without a preheader, hoisting is not feasible. + if (!Preheader) + return false; + InsertPt = Preheader->getTerminator(); + } + // Don't hoist instructions with loop-variant operands. + for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) + if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt)) + return false; + + // Hoist. + I->moveBefore(InsertPt); + Changed = true; + return true; +} + +/// getCanonicalInductionVariable - Check to see if the loop has a canonical +/// induction variable: an integer recurrence that starts at 0 and increments +/// by one each time through the loop. If so, return the phi node that +/// corresponds to it. +/// +/// The IndVarSimplify pass transforms loops to have a canonical induction +/// variable. +/// +PHINode *Loop::getCanonicalInductionVariable() const { + BasicBlock *H = getHeader(); + + BasicBlock *Incoming = nullptr, *Backedge = nullptr; + pred_iterator PI = pred_begin(H); + assert(PI != pred_end(H) && + "Loop must have at least one backedge!"); + Backedge = *PI++; + if (PI == pred_end(H)) return nullptr; // dead loop + Incoming = *PI++; + if (PI != pred_end(H)) return nullptr; // multiple backedges? + + if (contains(Incoming)) { + if (contains(Backedge)) + return nullptr; + std::swap(Incoming, Backedge); + } else if (!contains(Backedge)) + return nullptr; + + // Loop over all of the PHI nodes, looking for a canonical indvar. + for (BasicBlock::iterator I = H->begin(); isa(I); ++I) { + PHINode *PN = cast(I); + if (ConstantInt *CI = + dyn_cast(PN->getIncomingValueForBlock(Incoming))) + if (CI->isNullValue()) + if (Instruction *Inc = + dyn_cast(PN->getIncomingValueForBlock(Backedge))) + if (Inc->getOpcode() == Instruction::Add && + Inc->getOperand(0) == PN) + if (ConstantInt *CI = dyn_cast(Inc->getOperand(1))) + if (CI->equalsInt(1)) + return PN; + } + return nullptr; +} + +/// isLCSSAForm - Return true if the Loop is in LCSSA form +bool Loop::isLCSSAForm(DominatorTree &DT) const { + for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { + BasicBlock *BB = *BI; + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I) + for (Use &U : I->uses()) { + Instruction *UI = cast(U.getUser()); + BasicBlock *UserBB = UI->getParent(); + if (PHINode *P = dyn_cast(UI)) + UserBB = P->getIncomingBlock(U); + + // Check the current block, as a fast-path, before checking whether + // the use is anywhere in the loop. Most values are used in the same + // block they are defined in. Also, blocks not reachable from the + // entry are special; uses in them don't need to go through PHIs. + if (UserBB != BB && + !contains(UserBB) && + DT.isReachableFromEntry(UserBB)) + return false; + } + } + + return true; +} + +/// isLoopSimplifyForm - Return true if the Loop is in the form that +/// the LoopSimplify form transforms loops to, which is sometimes called +/// normal form. +bool Loop::isLoopSimplifyForm() const { + // Normal-form loops have a preheader, a single backedge, and all of their + // exits have all their predecessors inside the loop. + return getLoopPreheader() && getLoopLatch() && hasDedicatedExits(); +} + +/// isSafeToClone - Return true if the loop body is safe to clone in practice. +/// Routines that reform the loop CFG and split edges often fail on indirectbr. +bool Loop::isSafeToClone() const { + // Return false if any loop blocks contain indirectbrs, or there are any calls + // to noduplicate functions. + for (Loop::block_iterator I = block_begin(), E = block_end(); I != E; ++I) { + if (isa((*I)->getTerminator())) + return false; + + if (const InvokeInst *II = dyn_cast((*I)->getTerminator())) + if (II->cannotDuplicate()) + return false; + + for (BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end(); BI != BE; ++BI) { + if (const CallInst *CI = dyn_cast(BI)) { + if (CI->cannotDuplicate()) + return false; + } + if (BI->getType()->isTokenTy() && BI->isUsedOutsideOfBlock(*I)) + return false; + } + } + return true; +} + +MDNode *Loop::getLoopID() const { + MDNode *LoopID = nullptr; + if (isLoopSimplifyForm()) { + LoopID = getLoopLatch()->getTerminator()->getMetadata(LoopMDName); + } else { + // Go through each predecessor of the loop header and check the + // terminator for the metadata. + BasicBlock *H = getHeader(); + for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) { + TerminatorInst *TI = (*I)->getTerminator(); + MDNode *MD = nullptr; + + // Check if this terminator branches to the loop header. + for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) { + if (TI->getSuccessor(i) == H) { + MD = TI->getMetadata(LoopMDName); + break; + } + } + if (!MD) + return nullptr; + + if (!LoopID) + LoopID = MD; + else if (MD != LoopID) + return nullptr; + } + } + if (!LoopID || LoopID->getNumOperands() == 0 || + LoopID->getOperand(0) != LoopID) + return nullptr; + return LoopID; } +void Loop::setLoopID(MDNode *LoopID) const { + assert(LoopID && "Loop ID should not be null"); + assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand"); + assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself"); + + if (isLoopSimplifyForm()) { + getLoopLatch()->getTerminator()->setMetadata(LoopMDName, LoopID); + return; + } + + BasicBlock *H = getHeader(); + for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) { + TerminatorInst *TI = (*I)->getTerminator(); + for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) { + if (TI->getSuccessor(i) == H) + TI->setMetadata(LoopMDName, LoopID); + } + } +} + +bool Loop::isAnnotatedParallel() const { + MDNode *desiredLoopIdMetadata = getLoopID(); + + if (!desiredLoopIdMetadata) + return false; + + // The loop branch contains the parallel loop metadata. In order to ensure + // that any parallel-loop-unaware optimization pass hasn't added loop-carried + // dependencies (thus converted the loop back to a sequential loop), check + // that all the memory instructions in the loop contain parallelism metadata + // that point to the same unique "loop id metadata" the loop branch does. + for (block_iterator BB = block_begin(), BE = block_end(); BB != BE; ++BB) { + for (BasicBlock::iterator II = (*BB)->begin(), EE = (*BB)->end(); + II != EE; II++) { + + if (!II->mayReadOrWriteMemory()) + continue; + + // The memory instruction can refer to the loop identifier metadata + // directly or indirectly through another list metadata (in case of + // nested parallel loops). The loop identifier metadata refers to + // itself so we can check both cases with the same routine. + MDNode *loopIdMD = + II->getMetadata(LLVMContext::MD_mem_parallel_loop_access); + + if (!loopIdMD) + return false; + + bool loopIdMDFound = false; + for (unsigned i = 0, e = loopIdMD->getNumOperands(); i < e; ++i) { + if (loopIdMD->getOperand(i) == desiredLoopIdMetadata) { + loopIdMDFound = true; + break; + } + } + + if (!loopIdMDFound) + return false; + } + } + return true; +} + + +/// hasDedicatedExits - Return true if no exit block for the loop +/// has a predecessor that is outside the loop. +bool Loop::hasDedicatedExits() const { + // Each predecessor of each exit block of a normal loop is contained + // within the loop. + SmallVector ExitBlocks; + getExitBlocks(ExitBlocks); + for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) + for (pred_iterator PI = pred_begin(ExitBlocks[i]), + PE = pred_end(ExitBlocks[i]); PI != PE; ++PI) + if (!contains(*PI)) + return false; + // All the requirements are met. + return true; +} + +/// getUniqueExitBlocks - Return all unique successor blocks of this loop. +/// These are the blocks _outside of the current loop_ which are branched to. +/// This assumes that loop exits are in canonical form. +/// +void +Loop::getUniqueExitBlocks(SmallVectorImpl &ExitBlocks) const { + assert(hasDedicatedExits() && + "getUniqueExitBlocks assumes the loop has canonical form exits!"); + + SmallVector switchExitBlocks; + + for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { + + BasicBlock *current = *BI; + switchExitBlocks.clear(); + + for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) { + // If block is inside the loop then it is not a exit block. + if (contains(*I)) + continue; + + pred_iterator PI = pred_begin(*I); + BasicBlock *firstPred = *PI; + + // If current basic block is this exit block's first predecessor + // then only insert exit block in to the output ExitBlocks vector. + // This ensures that same exit block is not inserted twice into + // ExitBlocks vector. + if (current != firstPred) + continue; + + // If a terminator has more then two successors, for example SwitchInst, + // then it is possible that there are multiple edges from current block + // to one exit block. + if (std::distance(succ_begin(current), succ_end(current)) <= 2) { + ExitBlocks.push_back(*I); + continue; + } + + // In case of multiple edges from current block to exit block, collect + // only one edge in ExitBlocks. Use switchExitBlocks to keep track of + // duplicate edges. + if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) + == switchExitBlocks.end()) { + switchExitBlocks.push_back(*I); + ExitBlocks.push_back(*I); + } + } + } +} + +/// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one +/// block, return that block. Otherwise return null. +BasicBlock *Loop::getUniqueExitBlock() const { + SmallVector UniqueExitBlocks; + getUniqueExitBlocks(UniqueExitBlocks); + if (UniqueExitBlocks.size() == 1) + return UniqueExitBlocks[0]; + return nullptr; +} + +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) +void Loop::dump() const { + print(dbgs()); +} +#endif //===----------------------------------------------------------------------===// -// LoopInfo implementation +// UnloopUpdater implementation // -bool LoopInfo::runOnFunction(Function *F) { - releaseMemory(); - Calculate(getAnalysis()); // Update - return false; -} -void LoopInfo::Calculate(const DominatorSet &DS) { - BasicBlock *RootNode = DS.getRoot(); +namespace { +/// Find the new parent loop for all blocks within the "unloop" whose last +/// backedges has just been removed. +class UnloopUpdater { + Loop *Unloop; + LoopInfo *LI; + + LoopBlocksDFS DFS; + + // Map unloop's immediate subloops to their nearest reachable parents. Nested + // loops within these subloops will not change parents. However, an immediate + // subloop's new parent will be the nearest loop reachable from either its own + // exits *or* any of its nested loop's exits. + DenseMap SubloopParents; + + // Flag the presence of an irreducible backedge whose destination is a block + // directly contained by the original unloop. + bool FoundIB; + +public: + UnloopUpdater(Loop *UL, LoopInfo *LInfo) : + Unloop(UL), LI(LInfo), DFS(UL), FoundIB(false) {} + + void updateBlockParents(); + + void removeBlocksFromAncestors(); + + void updateSubloopParents(); + +protected: + Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop); +}; +} // end anonymous namespace + +/// updateBlockParents - Update the parent loop for all blocks that are directly +/// contained within the original "unloop". +void UnloopUpdater::updateBlockParents() { + if (Unloop->getNumBlocks()) { + // Perform a post order CFG traversal of all blocks within this loop, + // propagating the nearest loop from sucessors to predecessors. + LoopBlocksTraversal Traversal(DFS, LI); + for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(), + POE = Traversal.end(); POI != POE; ++POI) { + + Loop *L = LI->getLoopFor(*POI); + Loop *NL = getNearestLoop(*POI, L); + + if (NL != L) { + // For reducible loops, NL is now an ancestor of Unloop. + assert((NL != Unloop && (!NL || NL->contains(Unloop))) && + "uninitialized successor"); + LI->changeLoopFor(*POI, NL); + } + else { + // Or the current block is part of a subloop, in which case its parent + // is unchanged. + assert((FoundIB || Unloop->contains(L)) && "uninitialized successor"); + } + } + } + // Each irreducible loop within the unloop induces a round of iteration using + // the DFS result cached by Traversal. + bool Changed = FoundIB; + for (unsigned NIters = 0; Changed; ++NIters) { + assert(NIters < Unloop->getNumBlocks() && "runaway iterative algorithm"); + + // Iterate over the postorder list of blocks, propagating the nearest loop + // from successors to predecessors as before. + Changed = false; + for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(), + POE = DFS.endPostorder(); POI != POE; ++POI) { - for (df_iterator NI = df_begin(RootNode), - NE = df_end(RootNode); NI != NE; ++NI) - if (Loop *L = ConsiderForLoop(*NI, DS)) - TopLevelLoops.push_back(L); + Loop *L = LI->getLoopFor(*POI); + Loop *NL = getNearestLoop(*POI, L); + if (NL != L) { + assert(NL != Unloop && (!NL || NL->contains(Unloop)) && + "uninitialized successor"); + LI->changeLoopFor(*POI, NL); + Changed = true; + } + } + } +} - for (unsigned i = 0; i < TopLevelLoops.size(); ++i) - TopLevelLoops[i]->setLoopDepth(1); +/// removeBlocksFromAncestors - Remove unloop's blocks from all ancestors below +/// their new parents. +void UnloopUpdater::removeBlocksFromAncestors() { + // Remove all unloop's blocks (including those in nested subloops) from + // ancestors below the new parent loop. + for (Loop::block_iterator BI = Unloop->block_begin(), + BE = Unloop->block_end(); BI != BE; ++BI) { + Loop *OuterParent = LI->getLoopFor(*BI); + if (Unloop->contains(OuterParent)) { + while (OuterParent->getParentLoop() != Unloop) + OuterParent = OuterParent->getParentLoop(); + OuterParent = SubloopParents[OuterParent]; + } + // Remove blocks from former Ancestors except Unloop itself which will be + // deleted. + for (Loop *OldParent = Unloop->getParentLoop(); OldParent != OuterParent; + OldParent = OldParent->getParentLoop()) { + assert(OldParent && "new loop is not an ancestor of the original"); + OldParent->removeBlockFromLoop(*BI); + } + } } -void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { - AU.setPreservesAll(); - AU.addRequired(DominatorSet::ID); - AU.addProvided(ID); +/// updateSubloopParents - Update the parent loop for all subloops directly +/// nested within unloop. +void UnloopUpdater::updateSubloopParents() { + while (!Unloop->empty()) { + Loop *Subloop = *std::prev(Unloop->end()); + Unloop->removeChildLoop(std::prev(Unloop->end())); + + assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop"); + if (Loop *Parent = SubloopParents[Subloop]) + Parent->addChildLoop(Subloop); + else + LI->addTopLevelLoop(Subloop); + } } +/// getNearestLoop - Return the nearest parent loop among this block's +/// successors. If a successor is a subloop header, consider its parent to be +/// the nearest parent of the subloop's exits. +/// +/// For subloop blocks, simply update SubloopParents and return NULL. +Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) { -Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { - if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node? + // Initially for blocks directly contained by Unloop, NearLoop == Unloop and + // is considered uninitialized. + Loop *NearLoop = BBLoop; - std::vector TodoStack; + Loop *Subloop = nullptr; + if (NearLoop != Unloop && Unloop->contains(NearLoop)) { + Subloop = NearLoop; + // Find the subloop ancestor that is directly contained within Unloop. + while (Subloop->getParentLoop() != Unloop) { + Subloop = Subloop->getParentLoop(); + assert(Subloop && "subloop is not an ancestor of the original loop"); + } + // Get the current nearest parent of the Subloop exits, initially Unloop. + NearLoop = + SubloopParents.insert(std::make_pair(Subloop, Unloop)).first->second; + } + + succ_iterator I = succ_begin(BB), E = succ_end(BB); + if (I == E) { + assert(!Subloop && "subloop blocks must have a successor"); + NearLoop = nullptr; // unloop blocks may now exit the function. + } + for (; I != E; ++I) { + if (*I == BB) + continue; // self loops are uninteresting + + Loop *L = LI->getLoopFor(*I); + if (L == Unloop) { + // This successor has not been processed. This path must lead to an + // irreducible backedge. + assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB"); + FoundIB = true; + } + if (L != Unloop && Unloop->contains(L)) { + // Successor is in a subloop. + if (Subloop) + continue; // Branching within subloops. Ignore it. + + // BB branches from the original into a subloop header. + assert(L->getParentLoop() == Unloop && "cannot skip into nested loops"); + + // Get the current nearest parent of the Subloop's exits. + L = SubloopParents[L]; + // L could be Unloop if the only exit was an irreducible backedge. + } + if (L == Unloop) { + continue; + } + // Handle critical edges from Unloop into a sibling loop. + if (L && !L->contains(Unloop)) { + L = L->getParentLoop(); + } + // Remember the nearest parent loop among successors or subloop exits. + if (NearLoop == Unloop || !NearLoop || NearLoop->contains(L)) + NearLoop = L; + } + if (Subloop) { + SubloopParents[Subloop] = NearLoop; + return BBLoop; + } + return NearLoop; +} - // Scan the predecessors of BB, checking to see if BB dominates any of - // them. - for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) - if (DS.dominates(BB, *I)) // If BB dominates it's predecessor... - TodoStack.push_back(*I); +LoopInfo::LoopInfo(const DominatorTreeBase &DomTree) { + analyze(DomTree); +} - if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors... +/// updateUnloop - The last backedge has been removed from a loop--now the +/// "unloop". Find a new parent for the blocks contained within unloop and +/// update the loop tree. We don't necessarily have valid dominators at this +/// point, but LoopInfo is still valid except for the removal of this loop. +/// +/// Note that Unloop may now be an empty loop. Calling Loop::getHeader without +/// checking first is illegal. +void LoopInfo::updateUnloop(Loop *Unloop) { - // Create a new loop to represent this basic block... - Loop *L = new Loop(BB); - BBMap[BB] = L; + // First handle the special case of no parent loop to simplify the algorithm. + if (!Unloop->getParentLoop()) { + // Since BBLoop had no parent, Unloop blocks are no longer in a loop. + for (Loop::block_iterator I = Unloop->block_begin(), + E = Unloop->block_end(); + I != E; ++I) { - while (!TodoStack.empty()) { // Process all the nodes in the loop - BasicBlock *X = TodoStack.back(); - TodoStack.pop_back(); + // Don't reparent blocks in subloops. + if (getLoopFor(*I) != Unloop) + continue; - if (!L->contains(X)) { // As of yet unprocessed?? - L->Blocks.push_back(X); + // Blocks no longer have a parent but are still referenced by Unloop until + // the Unloop object is deleted. + changeLoopFor(*I, nullptr); + } - // Add all of the predecessors of X to the end of the work stack... - TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X)); + // Remove the loop from the top-level LoopInfo object. + for (iterator I = begin();; ++I) { + assert(I != end() && "Couldn't find loop"); + if (*I == Unloop) { + removeLoop(I); + break; + } } + + // Move all of the subloops to the top-level. + while (!Unloop->empty()) + addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end()))); + + return; } - // Add the basic blocks that comprise this loop to the BBMap so that this - // loop can be found for them. Also check subsidary basic blocks to see if - // they start subloops of their own. - // - for (std::vector::reverse_iterator I = L->Blocks.rbegin(), - E = L->Blocks.rend(); I != E; ++I) { + // Update the parent loop for all blocks within the loop. Blocks within + // subloops will not change parents. + UnloopUpdater Updater(Unloop, this); + Updater.updateBlockParents(); - // Check to see if this block starts a new loop - if (Loop *NewLoop = ConsiderForLoop(*I, DS)) { - L->SubLoops.push_back(NewLoop); - NewLoop->ParentLoop = L; + // Remove blocks from former ancestor loops. + Updater.removeBlocksFromAncestors(); + + // Add direct subloops as children in their new parent loop. + Updater.updateSubloopParents(); + + // Remove unloop from its parent loop. + Loop *ParentLoop = Unloop->getParentLoop(); + for (Loop::iterator I = ParentLoop->begin();; ++I) { + assert(I != ParentLoop->end() && "Couldn't find loop"); + if (*I == Unloop) { + ParentLoop->removeChildLoop(I); + break; } - - if (BBMap.find(*I) == BBMap.end()) - BBMap.insert(std::make_pair(*I, L)); } +} + +char LoopAnalysis::PassID; + +LoopInfo LoopAnalysis::run(Function &F, AnalysisManager *AM) { + // FIXME: Currently we create a LoopInfo from scratch for every function. + // This may prove to be too wasteful due to deallocating and re-allocating + // memory each time for the underlying map and vector datastructures. At some + // point it may prove worthwhile to use a freelist and recycle LoopInfo + // objects. I don't want to add that kind of complexity until the scope of + // the problem is better understood. + LoopInfo LI; + LI.analyze(AM->getResult(F)); + return LI; +} + +PreservedAnalyses LoopPrinterPass::run(Function &F, + AnalysisManager *AM) { + AM->getResult(F).print(OS); + return PreservedAnalyses::all(); +} + +//===----------------------------------------------------------------------===// +// LoopInfo implementation +// + +char LoopInfoWrapperPass::ID = 0; +INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information", + true, true) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information", + true, true) + +bool LoopInfoWrapperPass::runOnFunction(Function &) { + releaseMemory(); + LI.analyze(getAnalysis().getDomTree()); + return false; +} + +void LoopInfoWrapperPass::verifyAnalysis() const { + // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the + // function each time verifyAnalysis is called is very expensive. The + // -verify-loop-info option can enable this. In order to perform some + // checking by default, LoopPass has been taught to call verifyLoop manually + // during loop pass sequences. + if (VerifyLoopInfo) + LI.verify(); +} + +void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequired(); +} + +void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const { + LI.print(OS); +} + +//===----------------------------------------------------------------------===// +// LoopBlocksDFS implementation +// - return L; +/// Traverse the loop blocks and store the DFS result. +/// Useful for clients that just want the final DFS result and don't need to +/// visit blocks during the initial traversal. +void LoopBlocksDFS::perform(LoopInfo *LI) { + LoopBlocksTraversal Traversal(*this, LI); + for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(), + POE = Traversal.end(); POI != POE; ++POI) ; }