| //===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- 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 LoopInfo class that is used to identify natural loops |
| // and determine the loop depth of various nodes of the CFG. 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 the 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 CFG. There can be strongly connected components in the CFG 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_ANALYSIS_LOOPINFO_H |
| #define LLVM_ANALYSIS_LOOPINFO_H |
| |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/GraphTraits.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/PassManager.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/Allocator.h" |
| #include <algorithm> |
| #include <utility> |
| |
| namespace llvm { |
| |
| class DominatorTree; |
| class LoopInfo; |
| class Loop; |
| class MDNode; |
| class PHINode; |
| class raw_ostream; |
| template <class N, bool IsPostDom> class DominatorTreeBase; |
| 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(); } |
| LoopT *getParentLoop() const { return ParentLoop; } |
| |
| /// 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(); } |
| bool empty() const { return getSubLoops().empty(); } |
| |
| /// 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. |
| bool isLoopExiting(const BlockT *BB) const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| 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"); |
| |
| BlockT *Header = getHeader(); |
| auto PredBegin = GraphTraits<Inverse<BlockT *>>::child_begin(Header); |
| auto PredEnd = GraphTraits<Inverse<BlockT *>>::child_end(Header); |
| return std::find(PredBegin, PredEnd, BB) != PredEnd; |
| } |
| |
| /// Calculate the number of back edges to the loop header. |
| unsigned getNumBackEdges() const { |
| assert(!isInvalid() && "Loop not in a valid state!"); |
| unsigned NumBackEdges = 0; |
| BlockT *H = getHeader(); |
| |
| for (const auto Pred : children<Inverse<BlockT *>>(H)) |
| if (contains(Pred)) |
| ++NumBackEdges; |
| |
| return NumBackEdges; |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // 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. |
| /// This assumes that loop exits are in canonical form, i.e. all exits are |
| /// dedicated exits. |
| void getUniqueExitBlocks(SmallVectorImpl<BlockT *> &ExitBlocks) const; |
| |
| /// If getUniqueExitBlocks would return exactly one block, return that block. |
| /// Otherwise return null. |
| BlockT *getUniqueExitBlock() const; |
| |
| /// Edge type. |
| typedef std::pair<const BlockT *, const 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 : children<Inverse<BlockT *>>(H)) |
| if (contains(Pred)) |
| LoopLatches.push_back(Pred); |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // 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, unsigned Depth = 0, bool Verbose = false) 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; |
| } |
| |
| // Implementation in LoopInfoImpl.h |
| extern template class LoopBase<BasicBlock, Loop>; |
| |
| /// Represents a single loop in the control flow graph. Note that not all SCCs |
| /// in the CFG are necessarily loops. |
| class Loop : public LoopBase<BasicBlock, Loop> { |
| public: |
| /// A range representing the start and end location of a loop. |
| class LocRange { |
| DebugLoc Start; |
| DebugLoc End; |
| |
| public: |
| LocRange() {} |
| LocRange(DebugLoc Start) : Start(std::move(Start)), End(std::move(Start)) {} |
| LocRange(DebugLoc Start, DebugLoc End) |
| : Start(std::move(Start)), End(std::move(End)) {} |
| |
| const DebugLoc &getStart() const { return Start; } |
| const DebugLoc &getEnd() const { return End; } |
| |
| /// Check for null. |
| /// |
| explicit operator bool() const { return Start && End; } |
| }; |
| |
| /// Return true if the specified value is loop invariant. |
| bool isLoopInvariant(const Value *V) const; |
| |
| /// Return true if all the operands of the specified instruction are loop |
| /// invariant. |
| bool hasLoopInvariantOperands(const Instruction *I) const; |
| |
| /// If the given value is an instruction 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 makeLoopInvariant(Value *V, bool &Changed, |
| Instruction *InsertPt = nullptr) const; |
| |
| /// 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 makeLoopInvariant(Instruction *I, bool &Changed, |
| Instruction *InsertPt = nullptr) const; |
| |
| /// 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 *getCanonicalInductionVariable() const; |
| |
| /// Return true if the Loop is in LCSSA form. |
| bool isLCSSAForm(DominatorTree &DT) const; |
| |
| /// Return true if this Loop and all inner subloops are in LCSSA form. |
| bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const; |
| |
| /// Return true if the Loop is in the form that the LoopSimplify form |
| /// transforms loops to, which is sometimes called normal form. |
| bool isLoopSimplifyForm() const; |
| |
| /// Return true if the loop body is safe to clone in practice. |
| bool isSafeToClone() const; |
| |
| /// Returns true if the loop is annotated parallel. |
| /// |
| /// A parallel loop can be assumed to not contain any dependencies between |
| /// iterations by the compiler. That is, any loop-carried dependency checking |
| /// can be skipped completely when parallelizing the loop on the target |
| /// machine. Thus, if the parallel loop information originates from the |
| /// programmer, e.g. via the OpenMP parallel for pragma, it is the |
| /// programmer's responsibility to ensure there are no loop-carried |
| /// dependencies. The final execution order of the instructions across |
| /// iterations is not guaranteed, thus, the end result might or might not |
| /// implement actual concurrent execution of instructions across multiple |
| /// iterations. |
| bool isAnnotatedParallel() const; |
| |
| /// Return the llvm.loop loop id metadata node for this loop if it is present. |
| /// |
| /// If this loop contains the same llvm.loop metadata on each branch to the |
| /// header then the node is returned. If any latch instruction does not |
| /// contain llvm.loop or if multiple latches contain different nodes then |
| /// 0 is returned. |
| MDNode *getLoopID() const; |
| /// Set the llvm.loop loop id metadata for this loop. |
| /// |
| /// The LoopID metadata node will be added to each terminator instruction in |
| /// the loop that branches to the loop header. |
| /// |
| /// The LoopID metadata node should have one or more operands and the first |
| /// operand should be the node itself. |
| void setLoopID(MDNode *LoopID) const; |
| |
| /// Add llvm.loop.unroll.disable to this loop's loop id metadata. |
| /// |
| /// Remove existing unroll metadata and add unroll disable metadata to |
| /// indicate the loop has already been unrolled. This prevents a loop |
| /// from being unrolled more than is directed by a pragma if the loop |
| /// unrolling pass is run more than once (which it generally is). |
| void setLoopAlreadyUnrolled(); |
| |
| void dump() const; |
| void dumpVerbose() const; |
| |
| /// Return the debug location of the start of this loop. |
| /// This looks for a BB terminating instruction with a known debug |
| /// location by looking at the preheader and header blocks. If it |
| /// cannot find a terminating instruction with location information, |
| /// it returns an unknown location. |
| DebugLoc getStartLoc() const; |
| |
| /// Return the source code span of the loop. |
| LocRange getLocRange() const; |
| |
| StringRef getName() const { |
| if (BasicBlock *Header = getHeader()) |
| if (Header->hasName()) |
| return Header->getName(); |
| return "<unnamed loop>"; |
| } |
| |
| private: |
| Loop() = default; |
| |
| friend class LoopInfoBase<BasicBlock, Loop>; |
| friend class LoopBase<BasicBlock, Loop>; |
| explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} |
| ~Loop() = default; |
| }; |
| |
| //===----------------------------------------------------------------------===// |
| /// 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() {} |
| ~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(); |
| |
| /// 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(); |
| |
| /// 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; |
| } |
| |
| /// 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->getParentLoop() && "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->getParentLoop() && "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); |
| } |
| }; |
| |
| // Implementation in LoopInfoImpl.h |
| extern template class LoopInfoBase<BasicBlock, Loop>; |
| |
| class LoopInfo : public LoopInfoBase<BasicBlock, Loop> { |
| typedef LoopInfoBase<BasicBlock, Loop> BaseT; |
| |
| friend class LoopBase<BasicBlock, Loop>; |
| |
| void operator=(const LoopInfo &) = delete; |
| LoopInfo(const LoopInfo &) = delete; |
| |
| public: |
| LoopInfo() {} |
| explicit LoopInfo(const DominatorTreeBase<BasicBlock, false> &DomTree); |
| |
| LoopInfo(LoopInfo &&Arg) : BaseT(std::move(static_cast<BaseT &>(Arg))) {} |
| LoopInfo &operator=(LoopInfo &&RHS) { |
| BaseT::operator=(std::move(static_cast<BaseT &>(RHS))); |
| return *this; |
| } |
| |
| /// Handle invalidation explicitly. |
| bool invalidate(Function &F, const PreservedAnalyses &PA, |
| FunctionAnalysisManager::Invalidator &); |
| |
| // Most of the public interface is provided via LoopInfoBase. |
| |
| /// Update LoopInfo after removing the last backedge from a loop. This updates |
| /// the loop forest and parent loops for each block so that \c L is no longer |
| /// referenced, but does not actually delete \c L immediately. The pointer |
| /// will remain valid until this LoopInfo's memory is released. |
| void erase(Loop *L); |
| |
| /// Returns true if replacing From with To everywhere is guaranteed to |
| /// preserve LCSSA form. |
| bool replacementPreservesLCSSAForm(Instruction *From, Value *To) { |
| // Preserving LCSSA form is only problematic if the replacing value is an |
| // instruction. |
| Instruction *I = dyn_cast<Instruction>(To); |
| if (!I) |
| return true; |
| // If both instructions are defined in the same basic block then replacement |
| // cannot break LCSSA form. |
| if (I->getParent() == From->getParent()) |
| return true; |
| // If the instruction is not defined in a loop then it can safely replace |
| // anything. |
| Loop *ToLoop = getLoopFor(I->getParent()); |
| if (!ToLoop) |
| return true; |
| // If the replacing instruction is defined in the same loop as the original |
| // instruction, or in a loop that contains it as an inner loop, then using |
| // it as a replacement will not break LCSSA form. |
| return ToLoop->contains(getLoopFor(From->getParent())); |
| } |
| |
| /// Checks if moving a specific instruction can break LCSSA in any loop. |
| /// |
| /// Return true if moving \p Inst to before \p NewLoc will break LCSSA, |
| /// assuming that the function containing \p Inst and \p NewLoc is currently |
| /// in LCSSA form. |
| bool movementPreservesLCSSAForm(Instruction *Inst, Instruction *NewLoc) { |
| assert(Inst->getFunction() == NewLoc->getFunction() && |
| "Can't reason about IPO!"); |
| |
| auto *OldBB = Inst->getParent(); |
| auto *NewBB = NewLoc->getParent(); |
| |
| // Movement within the same loop does not break LCSSA (the equality check is |
| // to avoid doing a hashtable lookup in case of intra-block movement). |
| if (OldBB == NewBB) |
| return true; |
| |
| auto *OldLoop = getLoopFor(OldBB); |
| auto *NewLoop = getLoopFor(NewBB); |
| |
| if (OldLoop == NewLoop) |
| return true; |
| |
| // Check if Outer contains Inner; with the null loop counting as the |
| // "outermost" loop. |
| auto Contains = [](const Loop *Outer, const Loop *Inner) { |
| return !Outer || Outer->contains(Inner); |
| }; |
| |
| // To check that the movement of Inst to before NewLoc does not break LCSSA, |
| // we need to check two sets of uses for possible LCSSA violations at |
| // NewLoc: the users of NewInst, and the operands of NewInst. |
| |
| // If we know we're hoisting Inst out of an inner loop to an outer loop, |
| // then the uses *of* Inst don't need to be checked. |
| |
| if (!Contains(NewLoop, OldLoop)) { |
| for (Use &U : Inst->uses()) { |
| auto *UI = cast<Instruction>(U.getUser()); |
| auto *UBB = isa<PHINode>(UI) ? cast<PHINode>(UI)->getIncomingBlock(U) |
| : UI->getParent(); |
| if (UBB != NewBB && getLoopFor(UBB) != NewLoop) |
| return false; |
| } |
| } |
| |
| // If we know we're sinking Inst from an outer loop into an inner loop, then |
| // the *operands* of Inst don't need to be checked. |
| |
| if (!Contains(OldLoop, NewLoop)) { |
| // See below on why we can't handle phi nodes here. |
| if (isa<PHINode>(Inst)) |
| return false; |
| |
| for (Use &U : Inst->operands()) { |
| auto *DefI = dyn_cast<Instruction>(U.get()); |
| if (!DefI) |
| return false; |
| |
| // This would need adjustment if we allow Inst to be a phi node -- the |
| // new use block won't simply be NewBB. |
| |
| auto *DefBlock = DefI->getParent(); |
| if (DefBlock != NewBB && getLoopFor(DefBlock) != NewLoop) |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| }; |
| |
| // Allow clients to walk the list of nested loops... |
| template <> struct GraphTraits<const Loop *> { |
| typedef const Loop *NodeRef; |
| typedef LoopInfo::iterator ChildIteratorType; |
| |
| static NodeRef getEntryNode(const Loop *L) { return L; } |
| static ChildIteratorType child_begin(NodeRef N) { return N->begin(); } |
| static ChildIteratorType child_end(NodeRef N) { return N->end(); } |
| }; |
| |
| template <> struct GraphTraits<Loop *> { |
| typedef Loop *NodeRef; |
| typedef LoopInfo::iterator ChildIteratorType; |
| |
| static NodeRef getEntryNode(Loop *L) { return L; } |
| static ChildIteratorType child_begin(NodeRef N) { return N->begin(); } |
| static ChildIteratorType child_end(NodeRef N) { return N->end(); } |
| }; |
| |
| /// Analysis pass that exposes the \c LoopInfo for a function. |
| class LoopAnalysis : public AnalysisInfoMixin<LoopAnalysis> { |
| friend AnalysisInfoMixin<LoopAnalysis>; |
| static AnalysisKey Key; |
| |
| public: |
| typedef LoopInfo Result; |
| |
| LoopInfo run(Function &F, FunctionAnalysisManager &AM); |
| }; |
| |
| /// Printer pass for the \c LoopAnalysis results. |
| class LoopPrinterPass : public PassInfoMixin<LoopPrinterPass> { |
| raw_ostream &OS; |
| |
| public: |
| explicit LoopPrinterPass(raw_ostream &OS) : OS(OS) {} |
| PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); |
| }; |
| |
| /// Verifier pass for the \c LoopAnalysis results. |
| struct LoopVerifierPass : public PassInfoMixin<LoopVerifierPass> { |
| PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); |
| }; |
| |
| /// The legacy pass manager's analysis pass to compute loop information. |
| class LoopInfoWrapperPass : public FunctionPass { |
| LoopInfo LI; |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| |
| LoopInfoWrapperPass() : FunctionPass(ID) { |
| initializeLoopInfoWrapperPassPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| LoopInfo &getLoopInfo() { return LI; } |
| const LoopInfo &getLoopInfo() const { return LI; } |
| |
| /// Calculate the natural loop information for a given function. |
| bool runOnFunction(Function &F) override; |
| |
| void verifyAnalysis() const override; |
| |
| void releaseMemory() override { LI.releaseMemory(); } |
| |
| void print(raw_ostream &O, const Module *M = nullptr) const override; |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override; |
| }; |
| |
| /// Function to print a loop's contents as LLVM's text IR assembly. |
| void printLoop(Loop &L, raw_ostream &OS, const std::string &Banner = ""); |
| |
| /// Find and return the loop attribute node for the attribute @p Name in |
| /// @p LoopID. Return nullptr if there is no such attribute. |
| MDNode *findOptionMDForLoopID(MDNode *LoopID, StringRef Name); |
| |
| /// Find string metadata for a loop. |
| /// |
| /// Returns the MDNode where the first operand is the metadata's name. The |
| /// following operands are the metadata's values. If no metadata with @p Name is |
| /// found, return nullptr. |
| MDNode *findOptionMDForLoop(const Loop *TheLoop, StringRef Name); |
| |
| /// Return whether an MDNode might represent an access group. |
| /// |
| /// Access group metadata nodes have to be distinct and empty. Being |
| /// always-empty ensures that it never needs to be changed (which -- because |
| /// MDNodes are designed immutable -- would require creating a new MDNode). Note |
| /// that this is not a sufficient condition: not every distinct and empty NDNode |
| /// is representing an access group. |
| bool isValidAsAccessGroup(MDNode *AccGroup); |
| |
| /// Create a new LoopID after the loop has been transformed. |
| /// |
| /// This can be used when no follow-up loop attributes are defined |
| /// (llvm::makeFollowupLoopID returning None) to stop transformations to be |
| /// applied again. |
| /// |
| /// @param Context The LLVMContext in which to create the new LoopID. |
| /// @param OrigLoopID The original LoopID; can be nullptr if the original |
| /// loop has no LoopID. |
| /// @param RemovePrefixes Remove all loop attributes that have these prefixes. |
| /// Use to remove metadata of the transformation that has |
| /// been applied. |
| /// @param AddAttrs Add these loop attributes to the new LoopID. |
| /// |
| /// @return A new LoopID that can be applied using Loop::setLoopID(). |
| llvm::MDNode * |
| makePostTransformationMetadata(llvm::LLVMContext &Context, MDNode *OrigLoopID, |
| llvm::ArrayRef<llvm::StringRef> RemovePrefixes, |
| llvm::ArrayRef<llvm::MDNode *> AddAttrs); |
| |
| } // End llvm namespace |
| |
| #endif |