X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=3d30c3a06e2850cd895f2ad89e228f6a4ddb9fab;hb=29f50e978353954afd7db22ef842edbea0066518;hp=735e31f2524db5889f7640bfcee04dc52769ef23;hpb=b35798347ea87b8b6d36155b211016a7769f01ab;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index 735e31f2524..3d30c3a06e2 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -15,18 +15,28 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/LoopInfo.h" -#include "llvm/Constants.h" -#include "llvm/Instructions.h" -#include "llvm/Analysis/Dominators.h" -#include "llvm/Assembly/Writer.h" -#include "llvm/Support/CFG.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Debug.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; + // Always verify loopinfo if expensive checking is enabled. #ifdef XDEBUG static bool VerifyLoopInfo = true; @@ -37,9 +47,8 @@ static cl::opt VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo), cl::desc("Verify loop info (time consuming)")); -char LoopInfo::ID = 0; -static RegisterPass -X("loops", "Natural Loop Information", true, true); +// Loop identifier metadata name. +static const char *const LoopMDName = "llvm.loop"; //===----------------------------------------------------------------------===// // Loop implementation @@ -47,17 +56,16 @@ X("loops", "Natural Loop Information", true, true); /// isLoopInvariant - Return true if the specified value is loop invariant /// -bool Loop::isLoopInvariant(Value *V) const { - if (Instruction *I = dyn_cast(V)) - return isLoopInvariant(I); +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 } -/// isLoopInvariant - Return true if the specified instruction is -/// loop-invariant. -/// -bool Loop::isLoopInvariant(Instruction *I) const { - return !contains(I); +/// 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 @@ -90,10 +98,13 @@ bool Loop::makeLoopInvariant(Instruction *I, bool &Changed, // Test if the value is already loop-invariant. if (isLoopInvariant(I)) return true; - if (!I->isSafeToSpeculativelyExecute()) + 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(); @@ -106,6 +117,7 @@ bool Loop::makeLoopInvariant(Instruction *I, bool &Changed, 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; @@ -123,22 +135,21 @@ bool Loop::makeLoopInvariant(Instruction *I, bool &Changed, PHINode *Loop::getCanonicalInductionVariable() const { BasicBlock *H = getHeader(); - BasicBlock *Incoming = 0, *Backedge = 0; - typedef GraphTraits > InvBlockTraits; - InvBlockTraits::ChildIteratorType PI = InvBlockTraits::child_begin(H); - assert(PI != InvBlockTraits::child_end(H) && + 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 == InvBlockTraits::child_end(H)) return 0; // dead loop + if (PI == pred_end(H)) return nullptr; // dead loop Incoming = *PI++; - if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? + if (PI != pred_end(H)) return nullptr; // multiple backedges? if (contains(Incoming)) { if (contains(Backedge)) - return 0; + return nullptr; std::swap(Incoming, Backedge); } else if (!contains(Backedge)) - return 0; + return nullptr; // Loop over all of the PHI nodes, looking for a canonical indvar. for (BasicBlock::iterator I = H->begin(); isa(I); ++I) { @@ -154,135 +165,26 @@ PHINode *Loop::getCanonicalInductionVariable() const { if (CI->equalsInt(1)) return PN; } - return 0; -} - -/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds -/// the canonical induction variable value for the "next" iteration of the -/// loop. This always succeeds if getCanonicalInductionVariable succeeds. -/// -Instruction *Loop::getCanonicalInductionVariableIncrement() const { - if (PHINode *PN = getCanonicalInductionVariable()) { - bool P1InLoop = contains(PN->getIncomingBlock(1)); - return cast(PN->getIncomingValue(P1InLoop)); - } - return 0; -} - -/// getTripCount - Return a loop-invariant LLVM value indicating the number of -/// times the loop will be executed. Note that this means that the backedge -/// of the loop executes N-1 times. If the trip-count cannot be determined, -/// this returns null. -/// -/// The IndVarSimplify pass transforms loops to have a form that this -/// function easily understands. -/// -Value *Loop::getTripCount() const { - // Canonical loops will end with a 'cmp ne I, V', where I is the incremented - // canonical induction variable and V is the trip count of the loop. - Instruction *Inc = getCanonicalInductionVariableIncrement(); - if (Inc == 0) return 0; - PHINode *IV = cast(Inc->getOperand(0)); - - BasicBlock *BackedgeBlock = - IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); - - if (BranchInst *BI = dyn_cast(BackedgeBlock->getTerminator())) - if (BI->isConditional()) { - if (ICmpInst *ICI = dyn_cast(BI->getCondition())) { - if (ICI->getOperand(0) == Inc) { - if (BI->getSuccessor(0) == getHeader()) { - if (ICI->getPredicate() == ICmpInst::ICMP_NE) - return ICI->getOperand(1); - } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { - return ICI->getOperand(1); - } - } - } - } - - return 0; -} - -/// getSmallConstantTripCount - Returns the trip count of this loop as a -/// normal unsigned value, if possible. Returns 0 if the trip count is unknown -/// of not constant. Will also return 0 if the trip count is very large -/// (>= 2^32) -unsigned Loop::getSmallConstantTripCount() const { - Value* TripCount = this->getTripCount(); - if (TripCount) { - if (ConstantInt *TripCountC = dyn_cast(TripCount)) { - // Guard against huge trip counts. - if (TripCountC->getValue().getActiveBits() <= 32) { - return (unsigned)TripCountC->getZExtValue(); - } - } - } - return 0; -} - -/// getSmallConstantTripMultiple - Returns the largest constant divisor of the -/// trip count of this loop as a normal unsigned value, if possible. This -/// means that the actual trip count is always a multiple of the returned -/// value (don't forget the trip count could very well be zero as well!). -/// -/// Returns 1 if the trip count is unknown or not guaranteed to be the -/// multiple of a constant (which is also the case if the trip count is simply -/// constant, use getSmallConstantTripCount for that case), Will also return 1 -/// if the trip count is very large (>= 2^32). -unsigned Loop::getSmallConstantTripMultiple() const { - Value* TripCount = this->getTripCount(); - // This will hold the ConstantInt result, if any - ConstantInt *Result = NULL; - if (TripCount) { - // See if the trip count is constant itself - Result = dyn_cast(TripCount); - // if not, see if it is a multiplication - if (!Result) - if (BinaryOperator *BO = dyn_cast(TripCount)) { - switch (BO->getOpcode()) { - case BinaryOperator::Mul: - Result = dyn_cast(BO->getOperand(1)); - break; - case BinaryOperator::Shl: - if (ConstantInt *CI = dyn_cast(BO->getOperand(1))) - if (CI->getValue().getActiveBits() <= 5) - return 1u << CI->getZExtValue(); - break; - default: - break; - } - } - } - // Guard against huge trip counts. - if (Result && Result->getValue().getActiveBits() <= 32) { - return (unsigned)Result->getZExtValue(); - } else { - return 1; - } + return nullptr; } /// isLCSSAForm - Return true if the Loop is in LCSSA form bool Loop::isLCSSAForm(DominatorTree &DT) const { - // Sort the blocks vector so that we can use binary search to do quick - // lookups. - SmallPtrSet LoopBBs(block_begin(), block_end()); - 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 (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; - ++UI) { - BasicBlock *UserBB = cast(*UI)->getParent(); - if (PHINode *P = dyn_cast(*UI)) - UserBB = P->getIncomingBlock(UI); + 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 && - !LoopBBs.count(UserBB) && + !contains(UserBB) && DT.isReachableFromEntry(UserBB)) return false; } @@ -300,12 +202,132 @@ bool Loop::isLoopSimplifyForm() const { 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 { - // Sort the blocks vector so that we can use binary search to do quick - // lookups. - SmallPtrSet LoopBBs(block_begin(), block_end()); // Each predecessor of each exit block of a normal loop is contained // within the loop. SmallVector ExitBlocks; @@ -313,7 +335,7 @@ bool Loop::hasDedicatedExits() const { 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 (!LoopBBs.count(*PI)) + if (!contains(*PI)) return false; // All the requirements are met. return true; @@ -328,11 +350,6 @@ Loop::getUniqueExitBlocks(SmallVectorImpl &ExitBlocks) const { assert(hasDedicatedExits() && "getUniqueExitBlocks assumes the loop has canonical form exits!"); - // Sort the blocks vector so that we can use binary search to do quick - // lookups. - SmallVector LoopBBs(block_begin(), block_end()); - std::sort(LoopBBs.begin(), LoopBBs.end()); - SmallVector switchExitBlocks; for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { @@ -340,16 +357,12 @@ Loop::getUniqueExitBlocks(SmallVectorImpl &ExitBlocks) const { BasicBlock *current = *BI; switchExitBlocks.clear(); - typedef GraphTraits BlockTraits; - typedef GraphTraits > InvBlockTraits; - for (BlockTraits::ChildIteratorType I = - BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); - I != E; ++I) { + 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 (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) + if (contains(*I)) continue; - InvBlockTraits::ChildIteratorType PI = InvBlockTraits::child_begin(*I); + pred_iterator PI = pred_begin(*I); BasicBlock *firstPred = *PI; // If current basic block is this exit block's first predecessor @@ -362,8 +375,7 @@ Loop::getUniqueExitBlocks(SmallVectorImpl &ExitBlocks) const { // 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(BlockTraits::child_begin(current), - BlockTraits::child_end(current)) <= 2) { + if (std::distance(succ_begin(current), succ_end(current)) <= 2) { ExitBlocks.push_back(*I); continue; } @@ -387,45 +399,343 @@ BasicBlock *Loop::getUniqueExitBlock() const { getUniqueExitBlocks(UniqueExitBlocks); if (UniqueExitBlocks.size() == 1) return UniqueExitBlocks[0]; - return 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 &) { - releaseMemory(); - LI.Calculate(getAnalysis().getBase()); // Update - return false; + +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) { + + 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; + } + } + } } -void LoopInfo::verifyAnalysis() const { - // LoopInfo 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. +/// 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); + } + } +} + +/// 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) { + + // Initially for blocks directly contained by Unloop, NearLoop == Unloop and + // is considered uninitialized. + Loop *NearLoop = BBLoop; + + 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; +} + +LoopInfo::LoopInfo(const DominatorTreeBase &DomTree) { + analyze(DomTree); +} + +/// 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) { + + // 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) { + + // Don't reparent blocks in subloops. + if (getLoopFor(*I) != Unloop) + continue; + + // Blocks no longer have a parent but are still referenced by Unloop until + // the Unloop object is deleted. + changeLoopFor(*I, nullptr); + } + + // 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; + } + + // Update the parent loop for all blocks within the loop. Blocks within + // subloops will not change parents. + UnloopUpdater Updater(Unloop, this); + Updater.updateBlockParents(); + + // Remove blocks from former ancestor loops. + Updater.removeBlocksFromAncestors(); - if (!VerifyLoopInfo) return; + // Add direct subloops as children in their new parent loop. + Updater.updateSubloopParents(); - for (iterator I = begin(), E = end(); I != E; ++I) { - assert(!(*I)->getParentLoop() && "Top-level loop has a parent!"); - (*I)->verifyLoopNest(); + // 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; + } } +} + +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 +// - // TODO: check BBMap consistency. +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 LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { +void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesAll(); - AU.addRequired(); + AU.addRequired(); } -void LoopInfo::print(raw_ostream &OS, const Module*) const { +void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const { LI.print(OS); } +//===----------------------------------------------------------------------===// +// LoopBlocksDFS implementation +// + +/// 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) ; +}