| //===- 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... |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_ANALYSIS_LOOP_INFO_H |
| #define LLVM_ANALYSIS_LOOP_INFO_H |
| |
| #include "llvm/Pass.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/GraphTraits.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <algorithm> |
| #include <map> |
| |
| namespace llvm { |
| |
| template<typename T> |
| static void RemoveFromVector(std::vector<T*> &V, T *N) { |
| typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); |
| assert(I != V.end() && "N is not in this list!"); |
| V.erase(I); |
| } |
| |
| class DominatorTree; |
| class LoopInfo; |
| class Loop; |
| class PHINode; |
| template<class N, class M> class LoopInfoBase; |
| template<class N, class M> class LoopBase; |
| |
| //===----------------------------------------------------------------------===// |
| /// LoopBase class - 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; |
| // SubLoops - Loops contained entirely within this one. |
| std::vector<LoopT *> SubLoops; |
| |
| // Blocks - The list of blocks in this loop. First entry is the header node. |
| std::vector<BlockT*> Blocks; |
| |
| // DO NOT IMPLEMENT |
| LoopBase(const LoopBase<BlockT, LoopT> &); |
| // DO NOT IMPLEMENT |
| const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); |
| public: |
| /// Loop ctor - This creates an empty loop. |
| LoopBase() : ParentLoop(0) {} |
| ~LoopBase() { |
| for (size_t i = 0, e = SubLoops.size(); i != e; ++i) |
| delete SubLoops[i]; |
| } |
| |
| /// getLoopDepth - 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 { |
| unsigned D = 1; |
| for (const LoopT *CurLoop = ParentLoop; CurLoop; |
| CurLoop = CurLoop->ParentLoop) |
| ++D; |
| return D; |
| } |
| BlockT *getHeader() const { return Blocks.front(); } |
| LoopT *getParentLoop() const { return ParentLoop; } |
| |
| /// contains - Return true if the specified loop is contained within in |
| /// this loop. |
| /// |
| bool contains(const LoopT *L) const { |
| if (L == this) return true; |
| if (L == 0) return false; |
| return contains(L->getParentLoop()); |
| } |
| |
| /// contains - Return true if the specified basic block is in this loop. |
| /// |
| bool contains(const BlockT *BB) const { |
| return std::find(block_begin(), block_end(), BB) != block_end(); |
| } |
| |
| /// contains - Return true if the specified instruction is in this loop. |
| /// |
| template<class InstT> |
| bool contains(const InstT *Inst) const { |
| return contains(Inst->getParent()); |
| } |
| |
| /// iterator/begin/end - Return the loops contained entirely within this loop. |
| /// |
| const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } |
| typedef typename std::vector<LoopT *>::const_iterator iterator; |
| iterator begin() const { return SubLoops.begin(); } |
| iterator end() const { return SubLoops.end(); } |
| bool empty() const { return SubLoops.empty(); } |
| |
| /// getBlocks - Get a list of the basic blocks which make up this loop. |
| /// |
| const std::vector<BlockT*> &getBlocks() const { return Blocks; } |
| typedef typename std::vector<BlockT*>::const_iterator block_iterator; |
| block_iterator block_begin() const { return Blocks.begin(); } |
| block_iterator block_end() const { return Blocks.end(); } |
| |
| /// getNumBlocks - Get the number of blocks in this loop in constant time. |
| unsigned getNumBlocks() const { |
| return Blocks.size(); |
| } |
| |
| /// isLoopExiting - True if terminator in the block can branch to another |
| /// block that is outside of the current loop. |
| /// |
| bool isLoopExiting(const BlockT *BB) const { |
| typedef GraphTraits<BlockT*> BlockTraits; |
| for (typename BlockTraits::ChildIteratorType SI = |
| BlockTraits::child_begin(const_cast<BlockT*>(BB)), |
| SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { |
| if (!contains(*SI)) |
| return true; |
| } |
| return false; |
| } |
| |
| /// getNumBackEdges - Calculate the number of back edges to the loop header |
| /// |
| unsigned getNumBackEdges() const { |
| unsigned NumBackEdges = 0; |
| BlockT *H = getHeader(); |
| |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| for (typename InvBlockTraits::ChildIteratorType I = |
| InvBlockTraits::child_begin(const_cast<BlockT*>(H)), |
| E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) |
| if (contains(*I)) |
| ++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. |
| |
| /// getExitingBlocks - 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 { |
| // Sort the blocks vector so that we can use binary search to do quick |
| // lookups. |
| SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); |
| std::sort(LoopBBs.begin(), LoopBBs.end()); |
| |
| typedef GraphTraits<BlockT*> BlockTraits; |
| for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) |
| for (typename BlockTraits::ChildIteratorType I = |
| BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); |
| I != E; ++I) |
| if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { |
| // Not in current loop? It must be an exit block. |
| ExitingBlocks.push_back(*BI); |
| break; |
| } |
| } |
| |
| /// getExitingBlock - If getExitingBlocks would return exactly one block, |
| /// return that block. Otherwise return null. |
| BlockT *getExitingBlock() const { |
| SmallVector<BlockT*, 8> ExitingBlocks; |
| getExitingBlocks(ExitingBlocks); |
| if (ExitingBlocks.size() == 1) |
| return ExitingBlocks[0]; |
| return 0; |
| } |
| |
| /// getExitBlocks - 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 { |
| // Sort the blocks vector so that we can use binary search to do quick |
| // lookups. |
| SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); |
| std::sort(LoopBBs.begin(), LoopBBs.end()); |
| |
| typedef GraphTraits<BlockT*> BlockTraits; |
| for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) |
| for (typename BlockTraits::ChildIteratorType I = |
| BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); |
| I != E; ++I) |
| if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) |
| // Not in current loop? It must be an exit block. |
| ExitBlocks.push_back(*I); |
| } |
| |
| /// getExitBlock - If getExitBlocks would return exactly one block, |
| /// return that block. Otherwise return null. |
| BlockT *getExitBlock() const { |
| SmallVector<BlockT*, 8> ExitBlocks; |
| getExitBlocks(ExitBlocks); |
| if (ExitBlocks.size() == 1) |
| return ExitBlocks[0]; |
| return 0; |
| } |
| |
| /// Edge type. |
| typedef std::pair<BlockT*, BlockT*> Edge; |
| |
| /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). |
| template <typename EdgeT> |
| void getExitEdges(SmallVectorImpl<EdgeT> &ExitEdges) const { |
| // Sort the blocks vector so that we can use binary search to do quick |
| // lookups. |
| SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); |
| array_pod_sort(LoopBBs.begin(), LoopBBs.end()); |
| |
| typedef GraphTraits<BlockT*> BlockTraits; |
| for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) |
| for (typename BlockTraits::ChildIteratorType I = |
| BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); |
| I != E; ++I) |
| if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) |
| // Not in current loop? It must be an exit block. |
| ExitEdges.push_back(EdgeT(*BI, *I)); |
| } |
| |
| /// getLoopPreheader - 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 { |
| // Keep track of nodes outside the loop branching to the header... |
| BlockT *Out = getLoopPredecessor(); |
| if (!Out) return 0; |
| |
| // Make sure there is only one exit out of the preheader. |
| typedef GraphTraits<BlockT*> BlockTraits; |
| typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); |
| ++SI; |
| if (SI != BlockTraits::child_end(Out)) |
| return 0; // Multiple exits from the block, must not be a preheader. |
| |
| // The predecessor has exactly one successor, so it is a preheader. |
| return Out; |
| } |
| |
| /// getLoopPredecessor - 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 { |
| // Keep track of nodes outside the loop branching to the header... |
| BlockT *Out = 0; |
| |
| // Loop over the predecessors of the header node... |
| BlockT *Header = getHeader(); |
| typedef GraphTraits<BlockT*> BlockTraits; |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| for (typename InvBlockTraits::ChildIteratorType PI = |
| InvBlockTraits::child_begin(Header), |
| PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { |
| typename InvBlockTraits::NodeType *N = *PI; |
| if (!contains(N)) { // If the block is not in the loop... |
| if (Out && Out != N) |
| return 0; // Multiple predecessors outside the loop |
| Out = N; |
| } |
| } |
| |
| // Make sure there is only one exit out of the preheader. |
| assert(Out && "Header of loop has no predecessors from outside loop?"); |
| return Out; |
| } |
| |
| /// getLoopLatch - 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 { |
| BlockT *Header = getHeader(); |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| typename InvBlockTraits::ChildIteratorType PI = |
| InvBlockTraits::child_begin(Header); |
| typename InvBlockTraits::ChildIteratorType PE = |
| InvBlockTraits::child_end(Header); |
| BlockT *Latch = 0; |
| for (; PI != PE; ++PI) { |
| typename InvBlockTraits::NodeType *N = *PI; |
| if (contains(N)) { |
| if (Latch) return 0; |
| Latch = N; |
| } |
| } |
| |
| return Latch; |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // APIs for updating loop information after changing the CFG |
| // |
| |
| /// addBasicBlockToLoop - 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); |
| |
| /// replaceChildLoopWith - 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) { |
| assert(OldChild->ParentLoop == this && "This loop is already broken!"); |
| assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); |
| typename std::vector<LoopT *>::iterator I = |
| std::find(SubLoops.begin(), SubLoops.end(), OldChild); |
| assert(I != SubLoops.end() && "OldChild not in loop!"); |
| *I = NewChild; |
| OldChild->ParentLoop = 0; |
| NewChild->ParentLoop = static_cast<LoopT *>(this); |
| } |
| |
| /// addChildLoop - 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(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); |
| NewChild->ParentLoop = static_cast<LoopT *>(this); |
| SubLoops.push_back(NewChild); |
| } |
| |
| /// removeChildLoop - 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(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 = 0; |
| return Child; |
| } |
| |
| /// addBlockEntry - 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) { |
| Blocks.push_back(BB); |
| } |
| |
| /// moveToHeader - 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) { |
| 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; |
| } |
| } |
| } |
| |
| /// removeBlockFromLoop - 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) { |
| RemoveFromVector(Blocks, BB); |
| } |
| |
| /// verifyLoop - Verify loop structure |
| void verifyLoop() const { |
| #ifndef NDEBUG |
| assert(!Blocks.empty() && "Loop header is missing"); |
| |
| // Setup for using a depth-first iterator to visit every block in the loop. |
| SmallVector<BlockT*, 8> ExitBBs; |
| getExitBlocks(ExitBBs); |
| llvm::SmallPtrSet<BlockT*, 8> VisitSet; |
| VisitSet.insert(ExitBBs.begin(), ExitBBs.end()); |
| df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> > |
| BI = df_ext_begin(getHeader(), VisitSet), |
| BE = df_ext_end(getHeader(), VisitSet); |
| |
| // Keep track of the number of BBs visited. |
| unsigned NumVisited = 0; |
| |
| // Sort the blocks vector so that we can use binary search to do quick |
| // lookups. |
| SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); |
| std::sort(LoopBBs.begin(), LoopBBs.end()); |
| |
| // Check the individual blocks. |
| for ( ; BI != BE; ++BI) { |
| BlockT *BB = *BI; |
| bool HasInsideLoopSuccs = false; |
| bool HasInsideLoopPreds = false; |
| SmallVector<BlockT *, 2> OutsideLoopPreds; |
| |
| typedef GraphTraits<BlockT*> BlockTraits; |
| for (typename BlockTraits::ChildIteratorType SI = |
| BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); |
| SI != SE; ++SI) |
| if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { |
| HasInsideLoopSuccs = true; |
| break; |
| } |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| for (typename InvBlockTraits::ChildIteratorType PI = |
| InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); |
| PI != PE; ++PI) { |
| BlockT *N = *PI; |
| if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N)) |
| HasInsideLoopPreds = true; |
| else |
| OutsideLoopPreds.push_back(N); |
| } |
| |
| if (BB == getHeader()) { |
| assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); |
| } else if (!OutsideLoopPreds.empty()) { |
| // A non-header loop shouldn't be reachable from outside the loop, |
| // though it is permitted if the predecessor is not itself actually |
| // reachable. |
| BlockT *EntryBB = BB->getParent()->begin(); |
| for (df_iterator<BlockT *> NI = df_begin(EntryBB), |
| NE = df_end(EntryBB); NI != NE; ++NI) |
| for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) |
| assert(*NI != OutsideLoopPreds[i] && |
| "Loop has multiple entry points!"); |
| } |
| assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); |
| assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); |
| assert(BB != getHeader()->getParent()->begin() && |
| "Loop contains function entry block!"); |
| |
| NumVisited++; |
| } |
| |
| assert(NumVisited == getNumBlocks() && "Unreachable block in loop"); |
| |
| // Check the subloops. |
| for (iterator I = begin(), E = end(); I != E; ++I) |
| // Each block in each subloop should be contained within this loop. |
| for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); |
| BI != BE; ++BI) { |
| assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && |
| "Loop does not contain all the blocks of a subloop!"); |
| } |
| |
| // Check the parent loop pointer. |
| if (ParentLoop) { |
| assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != |
| ParentLoop->end() && |
| "Loop is not a subloop of its parent!"); |
| } |
| #endif |
| } |
| |
| /// verifyLoop - Verify loop structure of this loop and all nested loops. |
| void verifyLoopNest(DenseSet<const LoopT*> *Loops) const { |
| Loops->insert(static_cast<const LoopT *>(this)); |
| // Verify this loop. |
| verifyLoop(); |
| // Verify the subloops. |
| for (iterator I = begin(), E = end(); I != E; ++I) |
| (*I)->verifyLoopNest(Loops); |
| } |
| |
| void print(raw_ostream &OS, unsigned Depth = 0) const { |
| OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() |
| << " containing: "; |
| |
| for (unsigned i = 0; i < getBlocks().size(); ++i) { |
| if (i) OS << ","; |
| BlockT *BB = getBlocks()[i]; |
| WriteAsOperand(OS, BB, false); |
| if (BB == getHeader()) OS << "<header>"; |
| if (BB == getLoopLatch()) OS << "<latch>"; |
| if (isLoopExiting(BB)) OS << "<exiting>"; |
| } |
| OS << "\n"; |
| |
| for (iterator I = begin(), E = end(); I != E; ++I) |
| (*I)->print(OS, Depth+2); |
| } |
| |
| protected: |
| friend class LoopInfoBase<BlockT, LoopT>; |
| explicit LoopBase(BlockT *BB) : ParentLoop(0) { |
| Blocks.push_back(BB); |
| } |
| }; |
| |
| template<class BlockT, class LoopT> |
| raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { |
| Loop.print(OS); |
| return OS; |
| } |
| |
| class Loop : public LoopBase<BasicBlock, Loop> { |
| public: |
| Loop() {} |
| |
| /// isLoopInvariant - Return true if the specified value is loop invariant |
| /// |
| bool isLoopInvariant(Value *V) const; |
| |
| /// hasLoopInvariantOperands - Return true if all the operands of the |
| /// specified instruction are loop invariant. |
| bool hasLoopInvariantOperands(Instruction *I) const; |
| |
| /// makeLoopInvariant - 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 = 0) const; |
| |
| /// makeLoopInvariant - 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 = 0) const; |
| |
| /// getCanonicalInductionVariable - 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; |
| |
| /// isLCSSAForm - Return true if the Loop is in LCSSA form |
| bool isLCSSAForm(DominatorTree &DT) const; |
| |
| /// isLoopSimplifyForm - 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; |
| |
| /// hasDedicatedExits - Return true if no exit block for the loop |
| /// has a predecessor that is outside the loop. |
| bool hasDedicatedExits() const; |
| |
| /// getUniqueExitBlocks - 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. |
| /// |
| void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; |
| |
| /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one |
| /// block, return that block. Otherwise return null. |
| BasicBlock *getUniqueExitBlock() const; |
| |
| void dump() const; |
| |
| private: |
| friend class LoopInfoBase<BasicBlock, Loop>; |
| explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} |
| }; |
| |
| //===----------------------------------------------------------------------===// |
| /// LoopInfo - 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<BlockT *, LoopT *> BBMap; |
| std::vector<LoopT *> TopLevelLoops; |
| friend class LoopBase<BlockT, LoopT>; |
| friend class LoopInfo; |
| |
| void operator=(const LoopInfoBase &); // do not implement |
| LoopInfoBase(const LoopInfo &); // do not implement |
| public: |
| LoopInfoBase() { } |
| ~LoopInfoBase() { releaseMemory(); } |
| |
| void releaseMemory() { |
| for (typename std::vector<LoopT *>::iterator I = |
| TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) |
| delete *I; // Delete all of the loops... |
| |
| BBMap.clear(); // Reset internal state of analysis |
| TopLevelLoops.clear(); |
| } |
| |
| /// iterator/begin/end - The interface to the top-level loops in the current |
| /// function. |
| /// |
| typedef typename std::vector<LoopT *>::const_iterator iterator; |
| iterator begin() const { return TopLevelLoops.begin(); } |
| iterator end() const { return TopLevelLoops.end(); } |
| bool empty() const { return TopLevelLoops.empty(); } |
| |
| /// getLoopFor - 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 { |
| typename DenseMap<BlockT *, LoopT *>::const_iterator I= |
| BBMap.find(const_cast<BlockT*>(BB)); |
| return I != BBMap.end() ? I->second : 0; |
| } |
| |
| /// operator[] - same as getLoopFor... |
| /// |
| const LoopT *operator[](const BlockT *BB) const { |
| return getLoopFor(BB); |
| } |
| |
| /// getLoopDepth - 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; |
| } |
| |
| // isLoopHeader - True if the block is a loop header node |
| bool isLoopHeader(BlockT *BB) const { |
| const LoopT *L = getLoopFor(BB); |
| return L && L->getHeader() == BB; |
| } |
| |
| /// removeLoop - 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() == 0 && "Not a top-level loop!"); |
| TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); |
| return L; |
| } |
| |
| /// changeLoopFor - 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) { |
| typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB); |
| if (I != BBMap.end()) |
| BBMap.erase(I); |
| return; |
| } |
| BBMap[BB] = L; |
| } |
| |
| /// changeTopLevelLoop - Replace the specified loop in the top-level loops |
| /// list with the indicated loop. |
| void changeTopLevelLoop(LoopT *OldLoop, |
| LoopT *NewLoop) { |
| typename std::vector<LoopT *>::iterator I = |
| std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); |
| assert(I != TopLevelLoops.end() && "Old loop not at top level!"); |
| *I = NewLoop; |
| assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && |
| "Loops already embedded into a subloop!"); |
| } |
| |
| /// addTopLevelLoop - This adds the specified loop to the collection of |
| /// top-level loops. |
| void addTopLevelLoop(LoopT *New) { |
| assert(New->getParentLoop() == 0 && "Loop already in subloop!"); |
| TopLevelLoops.push_back(New); |
| } |
| |
| /// removeBlock - 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) { |
| typename DenseMap<BlockT *, LoopT *>::iterator 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 == 0) return true; |
| if (SubLoop == ParentLoop) return false; |
| return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); |
| } |
| |
| void Calculate(DominatorTreeBase<BlockT> &DT) { |
| BlockT *RootNode = DT.getRootNode()->getBlock(); |
| |
| for (df_iterator<BlockT*> NI = df_begin(RootNode), |
| NE = df_end(RootNode); NI != NE; ++NI) |
| if (LoopT *L = ConsiderForLoop(*NI, DT)) |
| TopLevelLoops.push_back(L); |
| } |
| |
| LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { |
| if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? |
| |
| std::vector<BlockT *> TodoStack; |
| |
| // Scan the predecessors of BB, checking to see if BB dominates any of |
| // them. This identifies backedges which target this node... |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| for (typename InvBlockTraits::ChildIteratorType I = |
| InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); |
| I != E; ++I) { |
| typename InvBlockTraits::NodeType *N = *I; |
| if (DT.dominates(BB, N)) // If BB dominates its predecessor... |
| TodoStack.push_back(N); |
| } |
| |
| if (TodoStack.empty()) return 0; // No backedges to this block... |
| |
| // Create a new loop to represent this basic block... |
| LoopT *L = new LoopT(BB); |
| BBMap[BB] = L; |
| |
| BlockT *EntryBlock = BB->getParent()->begin(); |
| |
| while (!TodoStack.empty()) { // Process all the nodes in the loop |
| BlockT *X = TodoStack.back(); |
| TodoStack.pop_back(); |
| |
| if (!L->contains(X) && // As of yet unprocessed?? |
| DT.dominates(EntryBlock, X)) { // X is reachable from entry block? |
| // Check to see if this block already belongs to a loop. If this occurs |
| // then we have a case where a loop that is supposed to be a child of |
| // the current loop was processed before the current loop. When this |
| // occurs, this child loop gets added to a part of the current loop, |
| // making it a sibling to the current loop. We have to reparent this |
| // loop. |
| if (LoopT *SubLoop = |
| const_cast<LoopT *>(getLoopFor(X))) |
| if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ |
| // Remove the subloop from its current parent... |
| assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); |
| LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent |
| typename std::vector<LoopT *>::iterator I = |
| std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); |
| assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); |
| SLP->SubLoops.erase(I); // Remove from parent... |
| |
| // Add the subloop to THIS loop... |
| SubLoop->ParentLoop = L; |
| L->SubLoops.push_back(SubLoop); |
| } |
| |
| // Normal case, add the block to our loop... |
| L->Blocks.push_back(X); |
| |
| typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; |
| |
| // Add all of the predecessors of X to the end of the work stack... |
| TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), |
| InvBlockTraits::child_end(X)); |
| } |
| } |
| |
| // If there are any loops nested within this loop, create them now! |
| for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), |
| E = L->Blocks.end(); I != E; ++I) |
| if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { |
| L->SubLoops.push_back(NewLoop); |
| NewLoop->ParentLoop = L; |
| } |
| |
| // Add the basic blocks that comprise this loop to the BBMap so that this |
| // loop can be found for them. |
| // |
| for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), |
| E = L->Blocks.end(); I != E; ++I) |
| BBMap.insert(std::make_pair(*I, L)); |
| |
| // Now that we have a list of all of the child loops of this loop, check to |
| // see if any of them should actually be nested inside of each other. We |
| // can accidentally pull loops our of their parents, so we must make sure to |
| // organize the loop nests correctly now. |
| { |
| std::map<BlockT *, LoopT *> ContainingLoops; |
| for (unsigned i = 0; i != L->SubLoops.size(); ++i) { |
| LoopT *Child = L->SubLoops[i]; |
| assert(Child->getParentLoop() == L && "Not proper child loop?"); |
| |
| if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { |
| // If there is already a loop which contains this loop, move this loop |
| // into the containing loop. |
| MoveSiblingLoopInto(Child, ContainingLoop); |
| --i; // The loop got removed from the SubLoops list. |
| } else { |
| // This is currently considered to be a top-level loop. Check to see |
| // if any of the contained blocks are loop headers for subloops we |
| // have already processed. |
| for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { |
| LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; |
| if (BlockLoop == 0) { // Child block not processed yet... |
| BlockLoop = Child; |
| } else if (BlockLoop != Child) { |
| LoopT *SubLoop = BlockLoop; |
| // Reparent all of the blocks which used to belong to BlockLoops |
| for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j) |
| ContainingLoops[SubLoop->Blocks[j]] = Child; |
| |
| // There is already a loop which contains this block, that means |
| // that we should reparent the loop which the block is currently |
| // considered to belong to to be a child of this loop. |
| MoveSiblingLoopInto(SubLoop, Child); |
| --i; // We just shrunk the SubLoops list. |
| } |
| } |
| } |
| } |
| } |
| |
| return L; |
| } |
| |
| /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside |
| /// of the NewParent Loop, instead of being a sibling of it. |
| void MoveSiblingLoopInto(LoopT *NewChild, |
| LoopT *NewParent) { |
| LoopT *OldParent = NewChild->getParentLoop(); |
| assert(OldParent && OldParent == NewParent->getParentLoop() && |
| NewChild != NewParent && "Not sibling loops!"); |
| |
| // Remove NewChild from being a child of OldParent |
| typename std::vector<LoopT *>::iterator I = |
| std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), |
| NewChild); |
| assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); |
| OldParent->SubLoops.erase(I); // Remove from parent's subloops list |
| NewChild->ParentLoop = 0; |
| |
| InsertLoopInto(NewChild, NewParent); |
| } |
| |
| /// InsertLoopInto - This inserts loop L into the specified parent loop. If |
| /// the parent loop contains a loop which should contain L, the loop gets |
| /// inserted into L instead. |
| void InsertLoopInto(LoopT *L, LoopT *Parent) { |
| BlockT *LHeader = L->getHeader(); |
| assert(Parent->contains(LHeader) && |
| "This loop should not be inserted here!"); |
| |
| // Check to see if it belongs in a child loop... |
| for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); |
| i != e; ++i) |
| if (Parent->SubLoops[i]->contains(LHeader)) { |
| InsertLoopInto(L, Parent->SubLoops[i]); |
| return; |
| } |
| |
| // If not, insert it here! |
| Parent->SubLoops.push_back(L); |
| L->ParentLoop = Parent; |
| } |
| |
| // Debugging |
| |
| void print(raw_ostream &OS) const { |
| for (unsigned i = 0; i < TopLevelLoops.size(); ++i) |
| TopLevelLoops[i]->print(OS); |
| #if 0 |
| for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), |
| E = BBMap.end(); I != E; ++I) |
| OS << "BB '" << I->first->getName() << "' level = " |
| << I->second->getLoopDepth() << "\n"; |
| #endif |
| } |
| }; |
| |
| class LoopInfo : public FunctionPass { |
| LoopInfoBase<BasicBlock, Loop> LI; |
| friend class LoopBase<BasicBlock, Loop>; |
| |
| void operator=(const LoopInfo &); // do not implement |
| LoopInfo(const LoopInfo &); // do not implement |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| |
| LoopInfo() : FunctionPass(ID) { |
| initializeLoopInfoPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } |
| |
| /// iterator/begin/end - The interface to the top-level loops in the current |
| /// function. |
| /// |
| typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; |
| inline iterator begin() const { return LI.begin(); } |
| inline iterator end() const { return LI.end(); } |
| bool empty() const { return LI.empty(); } |
| |
| /// getLoopFor - 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. |
| /// |
| inline Loop *getLoopFor(const BasicBlock *BB) const { |
| return LI.getLoopFor(BB); |
| } |
| |
| /// operator[] - same as getLoopFor... |
| /// |
| inline const Loop *operator[](const BasicBlock *BB) const { |
| return LI.getLoopFor(BB); |
| } |
| |
| /// getLoopDepth - Return the loop nesting level of the specified block. A |
| /// depth of 0 means the block is not inside any loop. |
| /// |
| inline unsigned getLoopDepth(const BasicBlock *BB) const { |
| return LI.getLoopDepth(BB); |
| } |
| |
| // isLoopHeader - True if the block is a loop header node |
| inline bool isLoopHeader(BasicBlock *BB) const { |
| return LI.isLoopHeader(BB); |
| } |
| |
| /// runOnFunction - Calculate the natural loop information. |
| /// |
| virtual bool runOnFunction(Function &F); |
| |
| virtual void verifyAnalysis() const; |
| |
| virtual void releaseMemory() { LI.releaseMemory(); } |
| |
| virtual void print(raw_ostream &O, const Module* M = 0) const; |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| |
| /// removeLoop - 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. |
| inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } |
| |
| /// changeLoopFor - Change the top-level loop that contains BB to the |
| /// specified loop. This should be used by transformations that restructure |
| /// the loop hierarchy tree. |
| inline void changeLoopFor(BasicBlock *BB, Loop *L) { |
| LI.changeLoopFor(BB, L); |
| } |
| |
| /// changeTopLevelLoop - Replace the specified loop in the top-level loops |
| /// list with the indicated loop. |
| inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { |
| LI.changeTopLevelLoop(OldLoop, NewLoop); |
| } |
| |
| /// addTopLevelLoop - This adds the specified loop to the collection of |
| /// top-level loops. |
| inline void addTopLevelLoop(Loop *New) { |
| LI.addTopLevelLoop(New); |
| } |
| |
| /// removeBlock - 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(BasicBlock *BB) { |
| LI.removeBlock(BB); |
| } |
| |
| /// updateUnloop - Update LoopInfo after removing the last backedge from a |
| /// loop--now the "unloop". This updates the loop forest and parent loops for |
| /// each block so that Unloop is no longer referenced, but the caller must |
| /// actually delete the Unloop object. |
| void updateUnloop(Loop *Unloop); |
| |
| /// replacementPreservesLCSSAForm - 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())); |
| } |
| }; |
| |
| |
| // Allow clients to walk the list of nested loops... |
| template <> struct GraphTraits<const Loop*> { |
| typedef const Loop NodeType; |
| typedef LoopInfo::iterator ChildIteratorType; |
| |
| static NodeType *getEntryNode(const Loop *L) { return L; } |
| static inline ChildIteratorType child_begin(NodeType *N) { |
| return N->begin(); |
| } |
| static inline ChildIteratorType child_end(NodeType *N) { |
| return N->end(); |
| } |
| }; |
| |
| template <> struct GraphTraits<Loop*> { |
| typedef Loop NodeType; |
| typedef LoopInfo::iterator ChildIteratorType; |
| |
| static NodeType *getEntryNode(Loop *L) { return L; } |
| static inline ChildIteratorType child_begin(NodeType *N) { |
| return N->begin(); |
| } |
| static inline ChildIteratorType child_end(NodeType *N) { |
| return N->end(); |
| } |
| }; |
| |
| template<class BlockT, class LoopT> |
| void |
| LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, |
| LoopInfoBase<BlockT, LoopT> &LIB) { |
| assert((Blocks.empty() || LIB[getHeader()] == this) && |
| "Incorrect LI specified for this loop!"); |
| assert(NewBB && "Cannot add a null basic block to the loop!"); |
| assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); |
| |
| LoopT *L = static_cast<LoopT *>(this); |
| |
| // Add the loop mapping to the LoopInfo object... |
| LIB.BBMap[NewBB] = L; |
| |
| // Add the basic block to this loop and all parent loops... |
| while (L) { |
| L->Blocks.push_back(NewBB); |
| L = L->getParentLoop(); |
| } |
| } |
| |
| } // End llvm namespace |
| |
| #endif |