diff options
Diffstat (limited to 'clang-r353983/include/llvm/Analysis/LoopInfo.h')
| -rw-r--r-- | clang-r353983/include/llvm/Analysis/LoopInfo.h | 1039 |
1 files changed, 1039 insertions, 0 deletions
diff --git a/clang-r353983/include/llvm/Analysis/LoopInfo.h b/clang-r353983/include/llvm/Analysis/LoopInfo.h new file mode 100644 index 00000000..0899630f --- /dev/null +++ b/clang-r353983/include/llvm/Analysis/LoopInfo.h @@ -0,0 +1,1039 @@ +//===- 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 |