X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FAnalysis%2FLoopInfoImpl.h;h=dcd9a0f4cbcf2bfd763a235557263994c3d31c44;hb=00552e3875ee5f382db6c98286a241a7d0efe1b8;hp=ab83bb12fecf59e755c454a754b20faae98b5e8a;hpb=cbf24b4e58c2f621f480883c5bb1f2f2b2b8d497;p=oota-llvm.git diff --git a/include/llvm/Analysis/LoopInfoImpl.h b/include/llvm/Analysis/LoopInfoImpl.h index ab83bb12fec..dcd9a0f4cbc 100644 --- a/include/llvm/Analysis/LoopInfoImpl.h +++ b/include/llvm/Analysis/LoopInfoImpl.h @@ -12,10 +12,14 @@ // //===----------------------------------------------------------------------===// -#ifndef LLVM_ANALYSIS_LOOP_INFO_IMPL_H -#define LLVM_ANALYSIS_LOOP_INFO_IMPL_H +#ifndef LLVM_ANALYSIS_LOOPINFOIMPL_H +#define LLVM_ANALYSIS_LOOPINFOIMPL_H +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/PostOrderIterator.h" +#include "llvm/ADT/STLExtras.h" #include "llvm/Analysis/LoopInfo.h" +#include "llvm/IR/Dominators.h" namespace llvm { @@ -29,17 +33,12 @@ namespace llvm { template void LoopBase:: getExitingBlocks(SmallVectorImpl &ExitingBlocks) const { - // 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()); - typedef GraphTraits BlockTraits; for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) for (typename BlockTraits::ChildIteratorType I = BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); I != E; ++I) - if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { + if (!contains(*I)) { // Not in current loop? It must be an exit block. ExitingBlocks.push_back(*BI); break; @@ -54,7 +53,7 @@ BlockT *LoopBase::getExitingBlock() const { getExitingBlocks(ExitingBlocks); if (ExitingBlocks.size() == 1) return ExitingBlocks[0]; - return 0; + return nullptr; } /// getExitBlocks - Return all of the successor blocks of this loop. These @@ -63,17 +62,12 @@ BlockT *LoopBase::getExitingBlock() const { template void LoopBase:: getExitBlocks(SmallVectorImpl &ExitBlocks) const { - // 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()); - typedef GraphTraits BlockTraits; for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) for (typename BlockTraits::ChildIteratorType I = BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); I != E; ++I) - if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) + if (!contains(*I)) // Not in current loop? It must be an exit block. ExitBlocks.push_back(*I); } @@ -86,24 +80,19 @@ BlockT *LoopBase::getExitBlock() const { getExitBlocks(ExitBlocks); if (ExitBlocks.size() == 1) return ExitBlocks[0]; - return 0; + return nullptr; } /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). template void LoopBase:: getExitEdges(SmallVectorImpl &ExitEdges) const { - // Sort the blocks vector so that we can use binary search to do quick - // lookups. - SmallVector LoopBBs(block_begin(), block_end()); - array_pod_sort(LoopBBs.begin(), LoopBBs.end()); - typedef GraphTraits BlockTraits; for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) for (typename BlockTraits::ChildIteratorType I = BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); I != E; ++I) - if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) + if (!contains(*I)) // Not in current loop? It must be an exit block. ExitEdges.push_back(Edge(*BI, *I)); } @@ -119,14 +108,14 @@ template BlockT *LoopBase::getLoopPreheader() const { // Keep track of nodes outside the loop branching to the header... BlockT *Out = getLoopPredecessor(); - if (!Out) return 0; + if (!Out) return nullptr; // Make sure there is only one exit out of the preheader. typedef GraphTraits BlockTraits; typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); ++SI; if (SI != BlockTraits::child_end(Out)) - return 0; // Multiple exits from the block, must not be a preheader. + return nullptr; // Multiple exits from the block, must not be a preheader. // The predecessor has exactly one successor, so it is a preheader. return Out; @@ -140,11 +129,10 @@ BlockT *LoopBase::getLoopPreheader() const { template BlockT *LoopBase::getLoopPredecessor() const { // Keep track of nodes outside the loop branching to the header... - BlockT *Out = 0; + BlockT *Out = nullptr; // Loop over the predecessors of the header node... BlockT *Header = getHeader(); - typedef GraphTraits BlockTraits; typedef GraphTraits > InvBlockTraits; for (typename InvBlockTraits::ChildIteratorType PI = InvBlockTraits::child_begin(Header), @@ -152,7 +140,7 @@ BlockT *LoopBase::getLoopPredecessor() const { typename InvBlockTraits::NodeType *N = *PI; if (!contains(N)) { // If the block is not in the loop... if (Out && Out != N) - return 0; // Multiple predecessors outside the loop + return nullptr; // Multiple predecessors outside the loop Out = N; } } @@ -172,11 +160,11 @@ BlockT *LoopBase::getLoopLatch() const { InvBlockTraits::child_begin(Header); typename InvBlockTraits::ChildIteratorType PE = InvBlockTraits::child_end(Header); - BlockT *Latch = 0; + BlockT *Latch = nullptr; for (; PI != PE; ++PI) { typename InvBlockTraits::NodeType *N = *PI; if (contains(N)) { - if (Latch) return 0; + if (Latch) return nullptr; Latch = N; } } @@ -200,7 +188,7 @@ addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase &LIB) { assert((Blocks.empty() || LIB[getHeader()] == this) && "Incorrect LI specified for this loop!"); assert(NewBB && "Cannot add a null basic block to the loop!"); - assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); + assert(!LIB[NewBB] && "BasicBlock already in the loop!"); LoopT *L = static_cast(this); @@ -209,7 +197,7 @@ addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase &LIB) { // Add the basic block to this loop and all parent loops... while (L) { - L->Blocks.push_back(NewBB); + L->addBlockEntry(NewBB); L = L->getParentLoop(); } } @@ -222,12 +210,12 @@ template void LoopBase:: replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild) { assert(OldChild->ParentLoop == this && "This loop is already broken!"); - assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + assert(!NewChild->ParentLoop && "NewChild already has a parent!"); typename std::vector::iterator I = std::find(SubLoops.begin(), SubLoops.end(), OldChild); assert(I != SubLoops.end() && "OldChild not in loop!"); *I = NewChild; - OldChild->ParentLoop = 0; + OldChild->ParentLoop = nullptr; NewChild->ParentLoop = static_cast(this); } @@ -249,11 +237,6 @@ void LoopBase::verifyLoop() const { // Keep track of the number of BBs visited. unsigned NumVisited = 0; - // 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()); - // Check the individual blocks. for ( ; BI != BE; ++BI) { BlockT *BB = *BI; @@ -265,7 +248,7 @@ void LoopBase::verifyLoop() const { for (typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); SI != SE; ++SI) - if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { + if (contains(*SI)) { HasInsideLoopSuccs = true; break; } @@ -274,7 +257,7 @@ void LoopBase::verifyLoop() const { InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); PI != PE; ++PI) { BlockT *N = *PI; - if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N)) + if (contains(N)) HasInsideLoopPreds = true; else OutsideLoopPreds.push_back(N); @@ -287,11 +270,10 @@ void LoopBase::verifyLoop() const { // though it is permitted if the predecessor is not itself actually // reachable. BlockT *EntryBB = BB->getParent()->begin(); - for (df_iterator NI = df_begin(EntryBB), - NE = df_end(EntryBB); NI != NE; ++NI) - for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) - assert(*NI != OutsideLoopPreds[i] && - "Loop has multiple entry points!"); + for (BlockT *CB : depth_first(EntryBB)) + for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) + assert(CB != OutsideLoopPreds[i] && + "Loop has multiple entry points!"); } assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); @@ -308,7 +290,7 @@ void LoopBase::verifyLoop() const { // Each block in each subloop should be contained within this loop. for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); BI != BE; ++BI) { - assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && + assert(contains(*BI) && "Loop does not contain all the blocks of a subloop!"); } @@ -341,7 +323,7 @@ void LoopBase::print(raw_ostream &OS, unsigned Depth) const { for (unsigned i = 0; i < getBlocks().size(); ++i) { if (i) OS << ","; BlockT *BB = getBlocks()[i]; - WriteAsOperand(OS, BB, false); + BB->printAsOperand(OS, false); if (BB == getHeader()) OS << "
"; if (BB == getLoopLatch()) OS << ""; if (isLoopExiting(BB)) OS << ""; @@ -353,182 +335,172 @@ void LoopBase::print(raw_ostream &OS, unsigned Depth) const { } //===----------------------------------------------------------------------===// -/// LoopInfo - This class builds and contains all of the top level loop -/// structures in the specified function. +/// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the +/// result does / not depend on use list (block predecessor) order. /// +/// Discover a subloop with the specified backedges such that: All blocks within +/// this loop are mapped to this loop or a subloop. And all subloops within this +/// loop have their parent loop set to this loop or a subloop. template -void LoopInfoBase::Calculate(DominatorTreeBase &DT) { - BlockT *RootNode = DT.getRootNode()->getBlock(); +static void discoverAndMapSubloop(LoopT *L, ArrayRef Backedges, + LoopInfoBase *LI, + const DominatorTreeBase &DomTree) { + typedef GraphTraits > InvBlockTraits; - for (df_iterator NI = df_begin(RootNode), - NE = df_end(RootNode); NI != NE; ++NI) - if (LoopT *L = ConsiderForLoop(*NI, DT)) - TopLevelLoops.push_back(L); + unsigned NumBlocks = 0; + unsigned NumSubloops = 0; + + // Perform a backward CFG traversal using a worklist. + std::vector ReverseCFGWorklist(Backedges.begin(), Backedges.end()); + while (!ReverseCFGWorklist.empty()) { + BlockT *PredBB = ReverseCFGWorklist.back(); + ReverseCFGWorklist.pop_back(); + + LoopT *Subloop = LI->getLoopFor(PredBB); + if (!Subloop) { + if (!DomTree.isReachableFromEntry(PredBB)) + continue; + + // This is an undiscovered block. Map it to the current loop. + LI->changeLoopFor(PredBB, L); + ++NumBlocks; + if (PredBB == L->getHeader()) + continue; + // Push all block predecessors on the worklist. + ReverseCFGWorklist.insert(ReverseCFGWorklist.end(), + InvBlockTraits::child_begin(PredBB), + InvBlockTraits::child_end(PredBB)); + } + else { + // This is a discovered block. Find its outermost discovered loop. + while (LoopT *Parent = Subloop->getParentLoop()) + Subloop = Parent; + + // If it is already discovered to be a subloop of this loop, continue. + if (Subloop == L) + continue; + + // Discover a subloop of this loop. + Subloop->setParentLoop(L); + ++NumSubloops; + NumBlocks += Subloop->getBlocks().capacity(); + PredBB = Subloop->getHeader(); + // Continue traversal along predecessors that are not loop-back edges from + // within this subloop tree itself. Note that a predecessor may directly + // reach another subloop that is not yet discovered to be a subloop of + // this loop, which we must traverse. + for (typename InvBlockTraits::ChildIteratorType PI = + InvBlockTraits::child_begin(PredBB), + PE = InvBlockTraits::child_end(PredBB); PI != PE; ++PI) { + if (LI->getLoopFor(*PI) != Subloop) + ReverseCFGWorklist.push_back(*PI); + } + } + } + L->getSubLoopsVector().reserve(NumSubloops); + L->reserveBlocks(NumBlocks); } +/// Populate all loop data in a stable order during a single forward DFS. template -LoopT *LoopInfoBase:: -ConsiderForLoop(BlockT *BB, DominatorTreeBase &DT) { - if (BBMap.count(BB)) return 0; // Haven't processed this node? +class PopulateLoopsDFS { + typedef GraphTraits BlockTraits; + typedef typename BlockTraits::ChildIteratorType SuccIterTy; - std::vector TodoStack; + LoopInfoBase *LI; +public: + PopulateLoopsDFS(LoopInfoBase *li): + LI(li) {} - // Scan the predecessors of BB, checking to see if BB dominates any of - // them. This identifies backedges which target this node... - typedef GraphTraits > InvBlockTraits; - for (typename InvBlockTraits::ChildIteratorType I = - InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); - I != E; ++I) { - typename InvBlockTraits::NodeType *N = *I; - // If BB dominates its predecessor... - if (DT.dominates(BB, N) && DT.isReachableFromEntry(N)) - TodoStack.push_back(N); - } + void traverse(BlockT *EntryBlock); - if (TodoStack.empty()) return 0; // No backedges to this block... - - // Create a new loop to represent this basic block... - LoopT *L = new LoopT(BB); - BBMap[BB] = L; - - while (!TodoStack.empty()) { // Process all the nodes in the loop - BlockT *X = TodoStack.back(); - TodoStack.pop_back(); - - if (!L->contains(X) && // As of yet unprocessed?? - DT.isReachableFromEntry(X)) { - // Check to see if this block already belongs to a loop. If this occurs - // then we have a case where a loop that is supposed to be a child of - // the current loop was processed before the current loop. When this - // occurs, this child loop gets added to a part of the current loop, - // making it a sibling to the current loop. We have to reparent this - // loop. - if (LoopT *SubLoop = - const_cast(getLoopFor(X))) - if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ - // Remove the subloop from its current parent... - assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); - LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent - typename std::vector::iterator I = - std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); - assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); - SLP->SubLoops.erase(I); // Remove from parent... - - // Add the subloop to THIS loop... - SubLoop->ParentLoop = L; - L->SubLoops.push_back(SubLoop); - } - - // Normal case, add the block to our loop... - L->Blocks.push_back(X); - - typedef GraphTraits > InvBlockTraits; - - // Add all of the predecessors of X to the end of the work stack... - TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), - InvBlockTraits::child_end(X)); - } - } +protected: + void insertIntoLoop(BlockT *Block); +}; - // If there are any loops nested within this loop, create them now! - for (typename std::vector::iterator I = L->Blocks.begin(), - E = L->Blocks.end(); I != E; ++I) - if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { - L->SubLoops.push_back(NewLoop); - NewLoop->ParentLoop = L; - } +/// Top-level driver for the forward DFS within the loop. +template +void PopulateLoopsDFS::traverse(BlockT *EntryBlock) { + for (BlockT *BB : post_order(EntryBlock)) + insertIntoLoop(BB); +} - // Add the basic blocks that comprise this loop to the BBMap so that this - // loop can be found for them. - // - for (typename std::vector::iterator I = L->Blocks.begin(), - E = L->Blocks.end(); I != E; ++I) - BBMap.insert(std::make_pair(*I, L)); - - // Now that we have a list of all of the child loops of this loop, check to - // see if any of them should actually be nested inside of each other. We - // can accidentally pull loops our of their parents, so we must make sure to - // organize the loop nests correctly now. - { - std::map ContainingLoops; - for (unsigned i = 0; i != L->SubLoops.size(); ++i) { - LoopT *Child = L->SubLoops[i]; - assert(Child->getParentLoop() == L && "Not proper child loop?"); - - if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { - // If there is already a loop which contains this loop, move this loop - // into the containing loop. - MoveSiblingLoopInto(Child, ContainingLoop); - --i; // The loop got removed from the SubLoops list. - } else { - // This is currently considered to be a top-level loop. Check to see - // if any of the contained blocks are loop headers for subloops we - // have already processed. - for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { - LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; - if (BlockLoop == 0) { // Child block not processed yet... - BlockLoop = Child; - } else if (BlockLoop != Child) { - LoopT *SubLoop = BlockLoop; - // Reparent all of the blocks which used to belong to BlockLoops - for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j) - ContainingLoops[SubLoop->Blocks[j]] = Child; - - // There is already a loop which contains this block, that means - // that we should reparent the loop which the block is currently - // considered to belong to to be a child of this loop. - MoveSiblingLoopInto(SubLoop, Child); - --i; // We just shrunk the SubLoops list. - } - } - } - } +/// Add a single Block to its ancestor loops in PostOrder. If the block is a +/// subloop header, add the subloop to its parent in PostOrder, then reverse the +/// Block and Subloop vectors of the now complete subloop to achieve RPO. +template +void PopulateLoopsDFS::insertIntoLoop(BlockT *Block) { + LoopT *Subloop = LI->getLoopFor(Block); + if (Subloop && Block == Subloop->getHeader()) { + // We reach this point once per subloop after processing all the blocks in + // the subloop. + if (Subloop->getParentLoop()) + Subloop->getParentLoop()->getSubLoopsVector().push_back(Subloop); + else + LI->addTopLevelLoop(Subloop); + + // For convenience, Blocks and Subloops are inserted in postorder. Reverse + // the lists, except for the loop header, which is always at the beginning. + Subloop->reverseBlock(1); + std::reverse(Subloop->getSubLoopsVector().begin(), + Subloop->getSubLoopsVector().end()); + + Subloop = Subloop->getParentLoop(); } - - return L; + for (; Subloop; Subloop = Subloop->getParentLoop()) + Subloop->addBlockEntry(Block); } -/// MoveSiblingLoopInto - This method moves the NewChild loop to live inside -/// of the NewParent Loop, instead of being a sibling of it. +/// Analyze LoopInfo discovers loops during a postorder DominatorTree traversal +/// interleaved with backward CFG traversals within each subloop +/// (discoverAndMapSubloop). The backward traversal skips inner subloops, so +/// this part of the algorithm is linear in the number of CFG edges. Subloop and +/// Block vectors are then populated during a single forward CFG traversal +/// (PopulateLoopDFS). +/// +/// During the two CFG traversals each block is seen three times: +/// 1) Discovered and mapped by a reverse CFG traversal. +/// 2) Visited during a forward DFS CFG traversal. +/// 3) Reverse-inserted in the loop in postorder following forward DFS. +/// +/// The Block vectors are inclusive, so step 3 requires loop-depth number of +/// insertions per block. template void LoopInfoBase:: -MoveSiblingLoopInto(LoopT *NewChild, LoopT *NewParent) { - LoopT *OldParent = NewChild->getParentLoop(); - assert(OldParent && OldParent == NewParent->getParentLoop() && - NewChild != NewParent && "Not sibling loops!"); +analyze(const DominatorTreeBase &DomTree) { - // Remove NewChild from being a child of OldParent - typename std::vector::iterator I = - std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), - NewChild); - assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); - OldParent->SubLoops.erase(I); // Remove from parent's subloops list - NewChild->ParentLoop = 0; + // Postorder traversal of the dominator tree. + const DomTreeNodeBase *DomRoot = DomTree.getRootNode(); + for (auto DomNode : post_order(DomRoot)) { - InsertLoopInto(NewChild, NewParent); -} + BlockT *Header = DomNode->getBlock(); + SmallVector Backedges; -/// InsertLoopInto - This inserts loop L into the specified parent loop. If -/// the parent loop contains a loop which should contain L, the loop gets -/// inserted into L instead. -template -void LoopInfoBase::InsertLoopInto(LoopT *L, LoopT *Parent) { - BlockT *LHeader = L->getHeader(); - assert(Parent->contains(LHeader) && - "This loop should not be inserted here!"); - - // Check to see if it belongs in a child loop... - for (unsigned i = 0, e = static_cast(Parent->SubLoops.size()); - i != e; ++i) - if (Parent->SubLoops[i]->contains(LHeader)) { - InsertLoopInto(L, Parent->SubLoops[i]); - return; - } + // Check each predecessor of the potential loop header. + typedef GraphTraits > InvBlockTraits; + for (typename InvBlockTraits::ChildIteratorType PI = + InvBlockTraits::child_begin(Header), + PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { + + BlockT *Backedge = *PI; - // If not, insert it here! - Parent->SubLoops.push_back(L); - L->ParentLoop = Parent; + // If Header dominates predBB, this is a new loop. Collect the backedges. + if (DomTree.dominates(Header, Backedge) + && DomTree.isReachableFromEntry(Backedge)) { + Backedges.push_back(Backedge); + } + } + // Perform a backward CFG traversal to discover and map blocks in this loop. + if (!Backedges.empty()) { + LoopT *L = new LoopT(Header); + discoverAndMapSubloop(L, ArrayRef(Backedges), this, DomTree); + } + } + // Perform a single forward CFG traversal to populate block and subloop + // vectors for all loops. + PopulateLoopsDFS DFS(this); + DFS.traverse(DomRoot->getBlock()); } // Debugging @@ -544,6 +516,25 @@ void LoopInfoBase::print(raw_ostream &OS) const { #endif } +template +void LoopInfoBase::verify() const { + DenseSet Loops; + for (iterator I = begin(), E = end(); I != E; ++I) { + assert(!(*I)->getParentLoop() && "Top-level loop has a parent!"); + (*I)->verifyLoopNest(&Loops); + } + + // Verify that blocks are mapped to valid loops. +#ifndef NDEBUG + for (auto &Entry : BBMap) { + const BlockT *BB = Entry.first; + LoopT *L = Entry.second; + assert(Loops.count(L) && "orphaned loop"); + assert(L->contains(BB) && "orphaned block"); + } +#endif +} + } // End llvm namespace #endif