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+//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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 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;
+
+ /// 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;
+
+ /// 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:
+ /// \brief 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; }
+
+ /// \brief 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 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();
+
+ /// 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<BasicBlock *> &ExitBlocks) const;
+
+ /// If getUniqueExitBlocks would return exactly one block, return that block.
+ /// Otherwise return null.
+ BasicBlock *getUniqueExitBlock() const;
+
+ 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(); }
+};
+
+/// \brief 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);
+};
+
+/// \brief 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);
+};
+
+/// \brief Verifier pass for the \c LoopAnalysis results.
+struct LoopVerifierPass : public PassInfoMixin<LoopVerifierPass> {
+ PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
+/// \brief 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; }
+
+ /// \brief 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 = "");
+
+} // End llvm namespace
+
+#endif