| //===- GenericLoopInfo - Generic Loop Info for graphs -----------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the LoopInfoBase class that is used to identify natural |
| // loops and determine the loop depth of various nodes in a generic graph of |
| // blocks. A natural loop has exactly one entry-point, which is called the |
| // header. Note that natural loops may actually be several loops that share the |
| // same header node. |
| // |
| // This analysis calculates the nesting structure of loops in a function. For |
| // each natural loop identified, this analysis identifies natural loops |
| // contained entirely within the loop and the basic blocks that make up the |
| // loop. |
| // |
| // It can calculate on the fly various bits of information, for example: |
| // |
| // * whether there is a preheader for the loop |
| // * the number of back edges to the header |
| // * whether or not a particular block branches out of the loop |
| // * the successor blocks of the loop |
| // * the loop depth |
| // * etc... |
| // |
| // Note that this analysis specifically identifies *Loops* not cycles or SCCs |
| // in the graph. There can be strongly connected components in the graph which |
| // this analysis will not recognize and that will not be represented by a Loop |
| // instance. In particular, a Loop might be inside such a non-loop SCC, or a |
| // non-loop SCC might contain a sub-SCC which is a Loop. |
| // |
| // For an overview of terminology used in this API (and thus all of our loop |
| // analyses or transforms), see docs/LoopTerminology.rst. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_GENERICLOOPINFO_H |
| #define LLVM_SUPPORT_GENERICLOOPINFO_H |
| |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/PostOrderIterator.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SetOperations.h" |
| #include "llvm/Support/Allocator.h" |
| #include "llvm/Support/GenericDomTree.h" |
| |
| namespace llvm { |
| |
| template <class N, class M> class LoopInfoBase; |
| template <class N, class M> class LoopBase; |
| |
| //===----------------------------------------------------------------------===// |
| /// Instances of this class are used to represent loops that are detected in the |
| /// flow graph. |
| /// |
| template <class BlockT, class LoopT> class LoopBase { |
| LoopT *ParentLoop; |
| // Loops contained entirely within this one. |
| std::vector<LoopT *> SubLoops; |
| |
| // The list of blocks in this loop. First entry is the header node. |
| std::vector<BlockT *> Blocks; |
| |
| SmallPtrSet<const BlockT *, 8> DenseBlockSet; |
| |
| #if LLVM_ENABLE_ABI_BREAKING_CHECKS |
| /// Indicator that this loop is no longer a valid loop. |
| bool IsInvalid = false; |
| #endif |
| |
| LoopBase(const LoopBase<BlockT, LoopT> &) = delete; |
| const LoopBase<BlockT, LoopT> & |
| operator=(const LoopBase<BlockT, LoopT> &) = delete; |
| |
| public: |
| /// Return the nesting level of this loop. An outer-most loop has depth 1, |
| /// for consistency with loop depth values used for basic blocks, where depth |
| /// 0 is used for blocks not inside any loops. |
| unsigned getLoopDepth() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| unsigned D = 1; |
| for (const LoopT *CurLoop = ParentLoop; CurLoop; |
| CurLoop = CurLoop->ParentLoop) |
| ++D; |
| return D; |
| } |
| BlockT *getHeader() const { return getBlocks().front(); } |
| /// Return the parent loop if it exists or nullptr for top |
| /// level loops. |
| |
| /// A loop is either top-level in a function (that is, it is not |
| /// contained in any other loop) or it is entirely enclosed in |
| /// some other loop. |
| /// If a loop is top-level, it has no parent, otherwise its |
| /// parent is the innermost loop in which it is enclosed. |
| LoopT *getParentLoop() const { return ParentLoop; } |
| |
| /// Get the outermost loop in which this loop is contained. |
| /// This may be the loop itself, if it already is the outermost loop. |
| const LoopT *getOutermostLoop() const { |
| const LoopT *L = static_cast<const LoopT *>(this); |
| while (L->ParentLoop) |
| L = L->ParentLoop; |
| return L; |
| } |
| |
| LoopT *getOutermostLoop() { |
| LoopT *L = static_cast<LoopT *>(this); |
| while (L->ParentLoop) |
| L = L->ParentLoop; |
| return L; |
| } |
| |
| /// This is a raw interface for bypassing addChildLoop. |
| void setParentLoop(LoopT *L) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| ParentLoop = L; |
| } |
| |
| /// Return true if the specified loop is contained within in this loop. |
| bool contains(const LoopT *L) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| if (L == this) |
| return true; |
| if (!L) |
| return false; |
| return contains(L->getParentLoop()); |
| } |
| |
| /// Return true if the specified basic block is in this loop. |
| bool contains(const BlockT *BB) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return DenseBlockSet.count(BB); |
| } |
| |
| /// Return true if the specified instruction is in this loop. |
| template <class InstT> bool contains(const InstT *Inst) const { |
| return contains(Inst->getParent()); |
| } |
| |
| /// Return the loops contained entirely within this loop. |
| const std::vector<LoopT *> &getSubLoops() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return SubLoops; |
| } |
| std::vector<LoopT *> &getSubLoopsVector() { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return SubLoops; |
| } |
| typedef typename std::vector<LoopT *>::const_iterator iterator; |
| typedef |
| typename std::vector<LoopT *>::const_reverse_iterator reverse_iterator; |
| iterator begin() const { return getSubLoops().begin(); } |
| iterator end() const { return getSubLoops().end(); } |
| reverse_iterator rbegin() const { return getSubLoops().rbegin(); } |
| reverse_iterator rend() const { return getSubLoops().rend(); } |
| |
| // LoopInfo does not detect irreducible control flow, just natural |
| // loops. That is, it is possible that there is cyclic control |
| // flow within the "innermost loop" or around the "outermost |
| // loop". |
| |
| /// Return true if the loop does not contain any (natural) loops. |
| bool isInnermost() const { return getSubLoops().empty(); } |
| /// Return true if the loop does not have a parent (natural) loop |
| // (i.e. it is outermost, which is the same as top-level). |
| bool isOutermost() const { return getParentLoop() == nullptr; } |
| |
| /// Get a list of the basic blocks which make up this loop. |
| ArrayRef<BlockT *> getBlocks() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return Blocks; |
| } |
| typedef typename ArrayRef<BlockT *>::const_iterator block_iterator; |
| block_iterator block_begin() const { return getBlocks().begin(); } |
| block_iterator block_end() const { return getBlocks().end(); } |
| inline iterator_range<block_iterator> blocks() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return make_range(block_begin(), block_end()); |
| } |
| |
| /// Get the number of blocks in this loop in constant time. |
| /// Invalidate the loop, indicating that it is no longer a loop. |
| unsigned getNumBlocks() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return Blocks.size(); |
| } |
| |
| /// Return a direct, mutable handle to the blocks vector so that we can |
| /// mutate it efficiently with techniques like `std::remove`. |
| std::vector<BlockT *> &getBlocksVector() { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return Blocks; |
| } |
| /// Return a direct, mutable handle to the blocks set so that we can |
| /// mutate it efficiently. |
| SmallPtrSetImpl<const BlockT *> &getBlocksSet() { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return DenseBlockSet; |
| } |
| |
| /// Return a direct, immutable handle to the blocks set. |
| const SmallPtrSetImpl<const BlockT *> &getBlocksSet() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return DenseBlockSet; |
| } |
| |
| /// Return true if this loop is no longer valid. The only valid use of this |
| /// helper is "assert(L.isInvalid())" or equivalent, since IsInvalid is set to |
| /// true by the destructor. In other words, if this accessor returns true, |
| /// the caller has already triggered UB by calling this accessor; and so it |
| /// can only be called in a context where a return value of true indicates a |
| /// programmer error. |
| bool isInvalid() const { |
| #if LLVM_ENABLE_ABI_BREAKING_CHECKS |
| return IsInvalid; |
| #else |
| return false; |
| #endif |
| } |
| |
| /// True if terminator in the block can branch to another block that is |
| /// outside of the current loop. \p BB must be inside the loop. |
| bool isLoopExiting(const BlockT *BB) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| assert(contains(BB) && "Exiting block must be part of the loop"); |
| for (const auto *Succ : children<const BlockT *>(BB)) { |
| if (!contains(Succ)) |
| return true; |
| } |
| return false; |
| } |
| |
| /// Returns true if \p BB is a loop-latch. |
| /// A latch block is a block that contains a branch back to the header. |
| /// This function is useful when there are multiple latches in a loop |
| /// because \fn getLoopLatch will return nullptr in that case. |
| bool isLoopLatch(const BlockT *BB) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| assert(contains(BB) && "block does not belong to the loop"); |
| return llvm::is_contained(inverse_children<BlockT *>(getHeader()), BB); |
| } |
| |
| /// Calculate the number of back edges to the loop header. |
| unsigned getNumBackEdges() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| return llvm::count_if(inverse_children<BlockT *>(getHeader()), |
| [&](BlockT *Pred) { return contains(Pred); }); |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // APIs for simple analysis of the loop. |
| // |
| // Note that all of these methods can fail on general loops (ie, there may not |
| // be a preheader, etc). For best success, the loop simplification and |
| // induction variable canonicalization pass should be used to normalize loops |
| // for easy analysis. These methods assume canonical loops. |
| |
| /// Return all blocks inside the loop that have successors outside of the |
| /// loop. These are the blocks _inside of the current loop_ which branch out. |
| /// The returned list is always unique. |
| void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const; |
| |
| /// If getExitingBlocks would return exactly one block, return that block. |
| /// Otherwise return null. |
| BlockT *getExitingBlock() const; |
| |
| /// Return all of the successor blocks of this loop. These are the blocks |
| /// _outside of the current loop_ which are branched to. |
| void getExitBlocks(SmallVectorImpl<BlockT *> &ExitBlocks) const; |
| |
| /// If getExitBlocks would return exactly one block, return that block. |
| /// Otherwise return null. |
| BlockT *getExitBlock() const; |
| |
| /// Return true if no exit block for the loop has a predecessor that is |
| /// outside the loop. |
| bool hasDedicatedExits() const; |
| |
| /// Return all unique successor blocks of this loop. |
| /// These are the blocks _outside of the current loop_ which are branched to. |
| void getUniqueExitBlocks(SmallVectorImpl<BlockT *> &ExitBlocks) const; |
| |
| /// Return all unique successor blocks of this loop except successors from |
| /// Latch block are not considered. If the exit comes from Latch has also |
| /// non Latch predecessor in a loop it will be added to ExitBlocks. |
| /// These are the blocks _outside of the current loop_ which are branched to. |
| void getUniqueNonLatchExitBlocks(SmallVectorImpl<BlockT *> &ExitBlocks) const; |
| |
| /// If getUniqueExitBlocks would return exactly one block, return that block. |
| /// Otherwise return null. |
| BlockT *getUniqueExitBlock() const; |
| |
| /// Return true if this loop does not have any exit blocks. |
| bool hasNoExitBlocks() const; |
| |
| /// Edge type. |
| typedef std::pair<BlockT *, BlockT *> Edge; |
| |
| /// Return all pairs of (_inside_block_,_outside_block_). |
| void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const; |
| |
| /// If there is a preheader for this loop, return it. A loop has a preheader |
| /// if there is only one edge to the header of the loop from outside of the |
| /// loop. If this is the case, the block branching to the header of the loop |
| /// is the preheader node. |
| /// |
| /// This method returns null if there is no preheader for the loop. |
| BlockT *getLoopPreheader() const; |
| |
| /// If the given loop's header has exactly one unique predecessor outside the |
| /// loop, return it. Otherwise return null. |
| /// This is less strict that the loop "preheader" concept, which requires |
| /// the predecessor to have exactly one successor. |
| BlockT *getLoopPredecessor() const; |
| |
| /// If there is a single latch block for this loop, return it. |
| /// A latch block is a block that contains a branch back to the header. |
| BlockT *getLoopLatch() const; |
| |
| /// Return all loop latch blocks of this loop. A latch block is a block that |
| /// contains a branch back to the header. |
| void getLoopLatches(SmallVectorImpl<BlockT *> &LoopLatches) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| BlockT *H = getHeader(); |
| for (const auto Pred : inverse_children<BlockT *>(H)) |
| if (contains(Pred)) |
| LoopLatches.push_back(Pred); |
| } |
| |
| /// Return all inner loops in the loop nest rooted by the loop in preorder, |
| /// with siblings in forward program order. |
| template <class Type> |
| static void getInnerLoopsInPreorder(const LoopT &L, |
| SmallVectorImpl<Type> &PreOrderLoops) { |
| SmallVector<LoopT *, 4> PreOrderWorklist; |
| PreOrderWorklist.append(L.rbegin(), L.rend()); |
| |
| while (!PreOrderWorklist.empty()) { |
| LoopT *L = PreOrderWorklist.pop_back_val(); |
| // Sub-loops are stored in forward program order, but will process the |
| // worklist backwards so append them in reverse order. |
| PreOrderWorklist.append(L->rbegin(), L->rend()); |
| PreOrderLoops.push_back(L); |
| } |
| } |
| |
| /// Return all loops in the loop nest rooted by the loop in preorder, with |
| /// siblings in forward program order. |
| SmallVector<const LoopT *, 4> getLoopsInPreorder() const { |
| SmallVector<const LoopT *, 4> PreOrderLoops; |
| const LoopT *CurLoop = static_cast<const LoopT *>(this); |
| PreOrderLoops.push_back(CurLoop); |
| getInnerLoopsInPreorder(*CurLoop, PreOrderLoops); |
| return PreOrderLoops; |
| } |
| SmallVector<LoopT *, 4> getLoopsInPreorder() { |
| SmallVector<LoopT *, 4> PreOrderLoops; |
| LoopT *CurLoop = static_cast<LoopT *>(this); |
| PreOrderLoops.push_back(CurLoop); |
| getInnerLoopsInPreorder(*CurLoop, PreOrderLoops); |
| return PreOrderLoops; |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // APIs for updating loop information after changing the CFG |
| // |
| |
| /// This method is used by other analyses to update loop information. |
| /// NewBB is set to be a new member of the current loop. |
| /// Because of this, it is added as a member of all parent loops, and is added |
| /// to the specified LoopInfo object as being in the current basic block. It |
| /// is not valid to replace the loop header with this method. |
| void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); |
| |
| /// This is used when splitting loops up. It replaces the OldChild entry in |
| /// our children list with NewChild, and updates the parent pointer of |
| /// OldChild to be null and the NewChild to be this loop. |
| /// This updates the loop depth of the new child. |
| void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild); |
| |
| /// Add the specified loop to be a child of this loop. |
| /// This updates the loop depth of the new child. |
| void addChildLoop(LoopT *NewChild) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| assert(!NewChild->ParentLoop && "NewChild already has a parent!"); |
| NewChild->ParentLoop = static_cast<LoopT *>(this); |
| SubLoops.push_back(NewChild); |
| } |
| |
| /// This removes the specified child from being a subloop of this loop. The |
| /// loop is not deleted, as it will presumably be inserted into another loop. |
| LoopT *removeChildLoop(iterator I) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| assert(I != SubLoops.end() && "Cannot remove end iterator!"); |
| LoopT *Child = *I; |
| assert(Child->ParentLoop == this && "Child is not a child of this loop!"); |
| SubLoops.erase(SubLoops.begin() + (I - begin())); |
| Child->ParentLoop = nullptr; |
| return Child; |
| } |
| |
| /// This removes the specified child from being a subloop of this loop. The |
| /// loop is not deleted, as it will presumably be inserted into another loop. |
| LoopT *removeChildLoop(LoopT *Child) { |
| return removeChildLoop(llvm::find(*this, Child)); |
| } |
| |
| /// This adds a basic block directly to the basic block list. |
| /// This should only be used by transformations that create new loops. Other |
| /// transformations should use addBasicBlockToLoop. |
| void addBlockEntry(BlockT *BB) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| Blocks.push_back(BB); |
| DenseBlockSet.insert(BB); |
| } |
| |
| /// interface to reverse Blocks[from, end of loop] in this loop |
| void reverseBlock(unsigned from) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| std::reverse(Blocks.begin() + from, Blocks.end()); |
| } |
| |
| /// interface to do reserve() for Blocks |
| void reserveBlocks(unsigned size) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| Blocks.reserve(size); |
| } |
| |
| /// This method is used to move BB (which must be part of this loop) to be the |
| /// loop header of the loop (the block that dominates all others). |
| void moveToHeader(BlockT *BB) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| if (Blocks[0] == BB) |
| return; |
| for (unsigned i = 0;; ++i) { |
| assert(i != Blocks.size() && "Loop does not contain BB!"); |
| if (Blocks[i] == BB) { |
| Blocks[i] = Blocks[0]; |
| Blocks[0] = BB; |
| return; |
| } |
| } |
| } |
| |
| /// This removes the specified basic block from the current loop, updating the |
| /// Blocks as appropriate. This does not update the mapping in the LoopInfo |
| /// class. |
| void removeBlockFromLoop(BlockT *BB) { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| auto I = find(Blocks, BB); |
| assert(I != Blocks.end() && "N is not in this list!"); |
| Blocks.erase(I); |
| |
| DenseBlockSet.erase(BB); |
| } |
| |
| /// Verify loop structure |
| void verifyLoop() const; |
| |
| /// Verify loop structure of this loop and all nested loops. |
| void verifyLoopNest(DenseSet<const LoopT *> *Loops) const; |
| |
| /// Returns true if the loop is annotated parallel. |
| /// |
| /// Derived classes can override this method using static template |
| /// polymorphism. |
| bool isAnnotatedParallel() const { return false; } |
| |
| /// Print loop with all the BBs inside it. |
| void print(raw_ostream &OS, bool Verbose = false, bool PrintNested = true, |
| unsigned Depth = 0) const; |
| |
| protected: |
| friend class LoopInfoBase<BlockT, LoopT>; |
| |
| /// This creates an empty loop. |
| LoopBase() : ParentLoop(nullptr) {} |
| |
| explicit LoopBase(BlockT *BB) : ParentLoop(nullptr) { |
| Blocks.push_back(BB); |
| DenseBlockSet.insert(BB); |
| } |
| |
| // Since loop passes like SCEV are allowed to key analysis results off of |
| // `Loop` pointers, we cannot re-use pointers within a loop pass manager. |
| // This means loop passes should not be `delete` ing `Loop` objects directly |
| // (and risk a later `Loop` allocation re-using the address of a previous one) |
| // but should be using LoopInfo::markAsRemoved, which keeps around the `Loop` |
| // pointer till the end of the lifetime of the `LoopInfo` object. |
| // |
| // To make it easier to follow this rule, we mark the destructor as |
| // non-public. |
| ~LoopBase() { |
| for (auto *SubLoop : SubLoops) |
| SubLoop->~LoopT(); |
| |
| #if LLVM_ENABLE_ABI_BREAKING_CHECKS |
| IsInvalid = true; |
| #endif |
| SubLoops.clear(); |
| Blocks.clear(); |
| DenseBlockSet.clear(); |
| ParentLoop = nullptr; |
| } |
| }; |
| |
| template <class BlockT, class LoopT> |
| raw_ostream &operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { |
| Loop.print(OS); |
| return OS; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| /// This class builds and contains all of the top-level loop |
| /// structures in the specified function. |
| /// |
| |
| template <class BlockT, class LoopT> class LoopInfoBase { |
| // BBMap - Mapping of basic blocks to the inner most loop they occur in |
| DenseMap<const BlockT *, LoopT *> BBMap; |
| std::vector<LoopT *> TopLevelLoops; |
| BumpPtrAllocator LoopAllocator; |
| |
| friend class LoopBase<BlockT, LoopT>; |
| friend class LoopInfo; |
| |
| void operator=(const LoopInfoBase &) = delete; |
| LoopInfoBase(const LoopInfoBase &) = delete; |
| |
| public: |
| LoopInfoBase() = default; |
| ~LoopInfoBase() { releaseMemory(); } |
| |
| LoopInfoBase(LoopInfoBase &&Arg) |
| : BBMap(std::move(Arg.BBMap)), |
| TopLevelLoops(std::move(Arg.TopLevelLoops)), |
| LoopAllocator(std::move(Arg.LoopAllocator)) { |
| // We have to clear the arguments top level loops as we've taken ownership. |
| Arg.TopLevelLoops.clear(); |
| } |
| LoopInfoBase &operator=(LoopInfoBase &&RHS) { |
| BBMap = std::move(RHS.BBMap); |
| |
| for (auto *L : TopLevelLoops) |
| L->~LoopT(); |
| |
| TopLevelLoops = std::move(RHS.TopLevelLoops); |
| LoopAllocator = std::move(RHS.LoopAllocator); |
| RHS.TopLevelLoops.clear(); |
| return *this; |
| } |
| |
| void releaseMemory() { |
| BBMap.clear(); |
| |
| for (auto *L : TopLevelLoops) |
| L->~LoopT(); |
| TopLevelLoops.clear(); |
| LoopAllocator.Reset(); |
| } |
| |
| template <typename... ArgsTy> LoopT *AllocateLoop(ArgsTy &&...Args) { |
| LoopT *Storage = LoopAllocator.Allocate<LoopT>(); |
| return new (Storage) LoopT(std::forward<ArgsTy>(Args)...); |
| } |
| |
| /// iterator/begin/end - The interface to the top-level loops in the current |
| /// function. |
| /// |
| typedef typename std::vector<LoopT *>::const_iterator iterator; |
| typedef |
| typename std::vector<LoopT *>::const_reverse_iterator reverse_iterator; |
| iterator begin() const { return TopLevelLoops.begin(); } |
| iterator end() const { return TopLevelLoops.end(); } |
| reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); } |
| reverse_iterator rend() const { return TopLevelLoops.rend(); } |
| bool empty() const { return TopLevelLoops.empty(); } |
| |
| /// Return all of the loops in the function in preorder across the loop |
| /// nests, with siblings in forward program order. |
| /// |
| /// Note that because loops form a forest of trees, preorder is equivalent to |
| /// reverse postorder. |
| SmallVector<LoopT *, 4> getLoopsInPreorder() const; |
| |
| /// Return all of the loops in the function in preorder across the loop |
| /// nests, with siblings in *reverse* program order. |
| /// |
| /// Note that because loops form a forest of trees, preorder is equivalent to |
| /// reverse postorder. |
| /// |
| /// Also note that this is *not* a reverse preorder. Only the siblings are in |
| /// reverse program order. |
| SmallVector<LoopT *, 4> getLoopsInReverseSiblingPreorder() const; |
| |
| /// Return the inner most loop that BB lives in. If a basic block is in no |
| /// loop (for example the entry node), null is returned. |
| LoopT *getLoopFor(const BlockT *BB) const { return BBMap.lookup(BB); } |
| |
| /// Same as getLoopFor. |
| const LoopT *operator[](const BlockT *BB) const { return getLoopFor(BB); } |
| |
| /// Return the loop nesting level of the specified block. A depth of 0 means |
| /// the block is not inside any loop. |
| unsigned getLoopDepth(const BlockT *BB) const { |
| const LoopT *L = getLoopFor(BB); |
| return L ? L->getLoopDepth() : 0; |
| } |
| |
| // True if the block is a loop header node |
| bool isLoopHeader(const BlockT *BB) const { |
| const LoopT *L = getLoopFor(BB); |
| return L && L->getHeader() == BB; |
| } |
| |
| /// Return the top-level loops. |
| const std::vector<LoopT *> &getTopLevelLoops() const { return TopLevelLoops; } |
| |
| /// Return the top-level loops. |
| std::vector<LoopT *> &getTopLevelLoopsVector() { return TopLevelLoops; } |
| |
| /// This removes the specified top-level loop from this loop info object. |
| /// The loop is not deleted, as it will presumably be inserted into |
| /// another loop. |
| LoopT *removeLoop(iterator I) { |
| assert(I != end() && "Cannot remove end iterator!"); |
| LoopT *L = *I; |
| assert(L->isOutermost() && "Not a top-level loop!"); |
| TopLevelLoops.erase(TopLevelLoops.begin() + (I - begin())); |
| return L; |
| } |
| |
| /// Change the top-level loop that contains BB to the specified loop. |
| /// This should be used by transformations that restructure the loop hierarchy |
| /// tree. |
| void changeLoopFor(BlockT *BB, LoopT *L) { |
| if (!L) { |
| BBMap.erase(BB); |
| return; |
| } |
| BBMap[BB] = L; |
| } |
| |
| /// Replace the specified loop in the top-level loops list with the indicated |
| /// loop. |
| void changeTopLevelLoop(LoopT *OldLoop, LoopT *NewLoop) { |
| auto I = find(TopLevelLoops, OldLoop); |
| assert(I != TopLevelLoops.end() && "Old loop not at top level!"); |
| *I = NewLoop; |
| assert(!NewLoop->ParentLoop && !OldLoop->ParentLoop && |
| "Loops already embedded into a subloop!"); |
| } |
| |
| /// This adds the specified loop to the collection of top-level loops. |
| void addTopLevelLoop(LoopT *New) { |
| assert(New->isOutermost() && "Loop already in subloop!"); |
| TopLevelLoops.push_back(New); |
| } |
| |
| /// This method completely removes BB from all data structures, |
| /// including all of the Loop objects it is nested in and our mapping from |
| /// BasicBlocks to loops. |
| void removeBlock(BlockT *BB) { |
| auto I = BBMap.find(BB); |
| if (I != BBMap.end()) { |
| for (LoopT *L = I->second; L; L = L->getParentLoop()) |
| L->removeBlockFromLoop(BB); |
| |
| BBMap.erase(I); |
| } |
| } |
| |
| // Internals |
| |
| static bool isNotAlreadyContainedIn(const LoopT *SubLoop, |
| const LoopT *ParentLoop) { |
| if (!SubLoop) |
| return true; |
| if (SubLoop == ParentLoop) |
| return false; |
| return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); |
| } |
| |
| /// Create the loop forest using a stable algorithm. |
| void analyze(const DominatorTreeBase<BlockT, false> &DomTree); |
| |
| // Debugging |
| void print(raw_ostream &OS) const; |
| |
| void verify(const DominatorTreeBase<BlockT, false> &DomTree) const; |
| |
| /// Destroy a loop that has been removed from the `LoopInfo` nest. |
| /// |
| /// This runs the destructor of the loop object making it invalid to |
| /// reference afterward. The memory is retained so that the *pointer* to the |
| /// loop remains valid. |
| /// |
| /// The caller is responsible for removing this loop from the loop nest and |
| /// otherwise disconnecting it from the broader `LoopInfo` data structures. |
| /// Callers that don't naturally handle this themselves should probably call |
| /// `erase' instead. |
| void destroy(LoopT *L) { |
| L->~LoopT(); |
| |
| // Since LoopAllocator is a BumpPtrAllocator, this Deallocate only poisons |
| // \c L, but the pointer remains valid for non-dereferencing uses. |
| LoopAllocator.Deallocate(L); |
| } |
| }; |
| |
| } // namespace llvm |
| |
| #endif // LLVM_SUPPORT_GENERICLOOPINFO_H |