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Diffstat (limited to 'include/llvm/Analysis/LoopInfo.h')
| -rw-r--r-- | include/llvm/Analysis/LoopInfo.h | 1095 |
1 files changed, 1095 insertions, 0 deletions
diff --git a/include/llvm/Analysis/LoopInfo.h b/include/llvm/Analysis/LoopInfo.h new file mode 100644 index 0000000..fb0b584 --- /dev/null +++ b/include/llvm/Analysis/LoopInfo.h @@ -0,0 +1,1095 @@ +//===- 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. 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 +// * the trip count +// * etc... +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_ANALYSIS_LOOP_INFO_H +#define LLVM_ANALYSIS_LOOP_INFO_H + +#include "llvm/Pass.h" +#include "llvm/Constants.h" +#include "llvm/Instructions.h" +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/GraphTraits.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Support/CFG.h" +#include "llvm/Support/Streams.h" +#include <algorithm> +#include <ostream> + +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; +template<class N> class LoopInfoBase; +template<class N> class LoopBase; + +typedef LoopBase<BasicBlock> Loop; + +//===----------------------------------------------------------------------===// +/// LoopBase class - Instances of this class are used to represent loops that +/// are detected in the flow graph +/// +template<class BlockT> +class LoopBase { + LoopBase<BlockT> *ParentLoop; + // SubLoops - Loops contained entirely within this one. + std::vector<LoopBase<BlockT>*> SubLoops; + + // Blocks - The list of blocks in this loop. First entry is the header node. + std::vector<BlockT*> Blocks; + + LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT + const LoopBase<BlockT>&operator=(const LoopBase<BlockT> &);// DO NOT IMPLEMENT +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 LoopBase<BlockT> *CurLoop = ParentLoop; CurLoop; + CurLoop = CurLoop->ParentLoop) + ++D; + return D; + } + BlockT *getHeader() const { return Blocks.front(); } + LoopBase<BlockT> *getParentLoop() const { return ParentLoop; } + + /// 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(); + } + + /// iterator/begin/end - Return the loops contained entirely within this loop. + /// + const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; } + typedef typename std::vector<LoopBase<BlockT>*>::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(); } + + /// isLoopExit - True if terminator in the block can branch to another block + /// that is outside of the current loop. + /// + bool isLoopExit(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; + } + + /// isLoopInvariant - Return true if the specified value is loop invariant + /// + inline bool isLoopInvariant(Value *V) const { + if (Instruction *I = dyn_cast<Instruction>(V)) + return !contains(I->getParent()); + return true; // All non-instructions are loop invariant + } + + //===--------------------------------------------------------------------===// + // 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; + } + + /// 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 is in canonical form. + /// + void getUniqueExitBlocks(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()); + + std::vector<BlockT*> switchExitBlocks; + + for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { + + BlockT *current = *BI; + switchExitBlocks.clear(); + + typedef GraphTraits<BlockT*> BlockTraits; + typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; + 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)) + // If block is inside the loop then it is not a exit block. + continue; + + typename InvBlockTraits::ChildIteratorType PI = + InvBlockTraits::child_begin(*I); + BlockT *firstPred = *PI; + + // If current basic block is this exit block's first predecessor + // then only insert exit block in to the output ExitBlocks vector. + // This ensures that same exit block is not inserted twice into + // ExitBlocks vector. + if (current != firstPred) + continue; + + // If a terminator has more then two successors, for example SwitchInst, + // then it is possible that there are multiple edges from current block + // to one exit block. + if (std::distance(BlockTraits::child_begin(current), + BlockTraits::child_end(current)) <= 2) { + ExitBlocks.push_back(*I); + continue; + } + + // In case of multiple edges from current block to exit block, collect + // only one edge in ExitBlocks. Use switchExitBlocks to keep track of + // duplicate edges. + if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) + == switchExitBlocks.end()) { + switchExitBlocks.push_back(*I); + ExitBlocks.push_back(*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 = 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) + if (!contains(*PI)) { // If the block is not in the loop... + if (Out && Out != *PI) + return 0; // Multiple predecessors outside the loop + Out = *PI; + } + + // Make sure there is only one exit out of the preheader. + assert(Out && "Header of loop has no predecessors from outside loop?"); + 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. + + // If there is exactly one preheader, return it. If there was zero, then + // Out is still null. + 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. + /// A loop header in normal form has two edges into it: one from a preheader + /// and one from a latch block. + 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); + if (PI == PE) return 0; // no preds? + + BlockT *Latch = 0; + if (contains(*PI)) + Latch = *PI; + ++PI; + if (PI == PE) return 0; // only one pred? + + if (contains(*PI)) { + if (Latch) return 0; // multiple backedges + Latch = *PI; + } + ++PI; + if (PI != PE) return 0; // more than two preds + + return Latch; + } + + /// 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. + /// + inline PHINode *getCanonicalInductionVariable() const { + BlockT *H = getHeader(); + + BlockT *Incoming = 0, *Backedge = 0; + typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; + typename InvBlockTraits::ChildIteratorType PI = + InvBlockTraits::child_begin(H); + assert(PI != InvBlockTraits::child_end(H) && + "Loop must have at least one backedge!"); + Backedge = *PI++; + if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop + Incoming = *PI++; + if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? + + if (contains(Incoming)) { + if (contains(Backedge)) + return 0; + std::swap(Incoming, Backedge); + } else if (!contains(Backedge)) + return 0; + + // Loop over all of the PHI nodes, looking for a canonical indvar. + for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) { + PHINode *PN = cast<PHINode>(I); + if (ConstantInt *CI = + dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming))) + if (CI->isNullValue()) + if (Instruction *Inc = + dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) + if (Inc->getOpcode() == Instruction::Add && + Inc->getOperand(0) == PN) + if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) + if (CI->equalsInt(1)) + return PN; + } + return 0; + } + + /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds + /// the canonical induction variable value for the "next" iteration of the + /// loop. This always succeeds if getCanonicalInductionVariable succeeds. + /// + inline Instruction *getCanonicalInductionVariableIncrement() const { + if (PHINode *PN = getCanonicalInductionVariable()) { + bool P1InLoop = contains(PN->getIncomingBlock(1)); + return cast<Instruction>(PN->getIncomingValue(P1InLoop)); + } + return 0; + } + + /// getTripCount - Return a loop-invariant LLVM value indicating the number of + /// times the loop will be executed. Note that this means that the backedge + /// of the loop executes N-1 times. If the trip-count cannot be determined, + /// this returns null. + /// + /// The IndVarSimplify pass transforms loops to have a form that this + /// function easily understands. + /// + inline Value *getTripCount() const { + // Canonical loops will end with a 'cmp ne I, V', where I is the incremented + // canonical induction variable and V is the trip count of the loop. + Instruction *Inc = getCanonicalInductionVariableIncrement(); + if (Inc == 0) return 0; + PHINode *IV = cast<PHINode>(Inc->getOperand(0)); + + BlockT *BackedgeBlock = + IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); + + if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) + if (BI->isConditional()) { + if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) { + if (ICI->getOperand(0) == Inc) { + if (BI->getSuccessor(0) == getHeader()) { + if (ICI->getPredicate() == ICmpInst::ICMP_NE) + return ICI->getOperand(1); + } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { + return ICI->getOperand(1); + } + } + } + } + + return 0; + } + + /// getSmallConstantTripCount - Returns the trip count of this loop as a + /// normal unsigned value, if possible. Returns 0 if the trip count is unknown + /// of not constant. Will also return 0 if the trip count is very large + /// (>= 2^32) + inline unsigned getSmallConstantTripCount() const { + Value* TripCount = this->getTripCount(); + if (TripCount) { + if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) { + // Guard against huge trip counts. + if (TripCountC->getValue().getActiveBits() <= 32) { + return (unsigned)TripCountC->getZExtValue(); + } + } + } + return 0; + } + + /// getSmallConstantTripMultiple - Returns the largest constant divisor of the + /// trip count of this loop as a normal unsigned value, if possible. This + /// means that the actual trip count is always a multiple of the returned + /// value (don't forget the trip count could very well be zero as well!). + /// + /// Returns 1 if the trip count is unknown or not guaranteed to be the + /// multiple of a constant (which is also the case if the trip count is simply + /// constant, use getSmallConstantTripCount for that case), Will also return 1 + /// if the trip count is very large (>= 2^32). + inline unsigned getSmallConstantTripMultiple() const { + Value* TripCount = this->getTripCount(); + // This will hold the ConstantInt result, if any + ConstantInt *Result = NULL; + if (TripCount) { + // See if the trip count is constant itself + Result = dyn_cast<ConstantInt>(TripCount); + // if not, see if it is a multiplication + if (!Result) + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) { + switch (BO->getOpcode()) { + case BinaryOperator::Mul: + Result = dyn_cast<ConstantInt>(BO->getOperand(1)); + break; + default: + break; + } + } + } + // Guard against huge trip counts. + if (Result && Result->getValue().getActiveBits() <= 32) { + return (unsigned)Result->getZExtValue(); + } else { + return 1; + } + } + + /// isLCSSAForm - Return true if the Loop is in LCSSA form + inline bool isLCSSAForm() const { + // Sort the blocks vector so that we can use binary search to do quick + // lookups. + SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end()); + + for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { + BlockT *BB = *BI; + for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I) + for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; + ++UI) { + BlockT *UserBB = cast<Instruction>(*UI)->getParent(); + if (PHINode *P = dyn_cast<PHINode>(*UI)) { + UserBB = P->getIncomingBlock(UI); + } + + // Check the current block, as a fast-path. Most values are used in + // the same block they are defined in. + if (UserBB != BB && !LoopBBs.count(UserBB)) + return false; + } + } + + return true; + } + + //===--------------------------------------------------------------------===// + // 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> &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(LoopBase<BlockT> *OldChild, + LoopBase<BlockT> *NewChild) { + assert(OldChild->ParentLoop == this && "This loop is already broken!"); + assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + typename std::vector<LoopBase<BlockT>*>::iterator I = + std::find(SubLoops.begin(), SubLoops.end(), OldChild); + assert(I != SubLoops.end() && "OldChild not in loop!"); + *I = NewChild; + OldChild->ParentLoop = 0; + NewChild->ParentLoop = this; + } + + /// addChildLoop - Add the specified loop to be a child of this loop. This + /// updates the loop depth of the new child. + /// + void addChildLoop(LoopBase<BlockT> *NewChild) { + assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + NewChild->ParentLoop = 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. + LoopBase<BlockT> *removeChildLoop(iterator I) { + assert(I != SubLoops.end() && "Cannot remove end iterator!"); + LoopBase<BlockT> *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 (getHeader() && "Loop header is missing"); + assert (getLoopPreheader() && "Loop preheader is missing"); + assert (getLoopLatch() && "Loop latch is missing"); + for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) + (*I)->verifyLoop(); +#endif + } + + void print(std::ostream &OS, unsigned Depth = 0) const { + OS << std::string(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 (isLoopExit(BB)) OS << "<exit>"; + } + OS << "\n"; + + for (iterator I = begin(), E = end(); I != E; ++I) + (*I)->print(OS, Depth+2); + } + + void print(std::ostream *O, unsigned Depth = 0) const { + if (O) print(*O, Depth); + } + + void dump() const { + print(cerr); + } + +private: + friend class LoopInfoBase<BlockT>; + explicit LoopBase(BlockT *BB) : ParentLoop(0) { + Blocks.push_back(BB); + } +}; + + +//===----------------------------------------------------------------------===// +/// LoopInfo - This class builds and contains all of the top level loop +/// structures in the specified function. +/// + +template<class BlockT> +class LoopInfoBase { + // BBMap - Mapping of basic blocks to the inner most loop they occur in + std::map<BlockT*, LoopBase<BlockT>*> BBMap; + std::vector<LoopBase<BlockT>*> TopLevelLoops; + friend class LoopBase<BlockT>; + +public: + LoopInfoBase() { } + ~LoopInfoBase() { releaseMemory(); } + + void releaseMemory() { + for (typename std::vector<LoopBase<BlockT>* >::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<LoopBase<BlockT>*>::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. + /// + LoopBase<BlockT> *getLoopFor(const BlockT *BB) const { + typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I= + BBMap.find(const_cast<BlockT*>(BB)); + return I != BBMap.end() ? I->second : 0; + } + + /// operator[] - same as getLoopFor... + /// + const LoopBase<BlockT> *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 LoopBase<BlockT> *L = getLoopFor(BB); + return L ? L->getLoopDepth() : 0; + } + + // isLoopHeader - True if the block is a loop header node + bool isLoopHeader(BlockT *BB) const { + const LoopBase<BlockT> *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. + LoopBase<BlockT> *removeLoop(iterator I) { + assert(I != end() && "Cannot remove end iterator!"); + LoopBase<BlockT> *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, LoopBase<BlockT> *L) { + LoopBase<BlockT> *&OldLoop = BBMap[BB]; + assert(OldLoop && "Block not in a loop yet!"); + OldLoop = L; + } + + /// changeTopLevelLoop - Replace the specified loop in the top-level loops + /// list with the indicated loop. + void changeTopLevelLoop(LoopBase<BlockT> *OldLoop, + LoopBase<BlockT> *NewLoop) { + typename std::vector<LoopBase<BlockT>*>::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(LoopBase<BlockT> *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 std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB); + if (I != BBMap.end()) { + for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop()) + L->removeBlockFromLoop(BB); + + BBMap.erase(I); + } + } + + // Internals + + static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop, + const LoopBase<BlockT> *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 (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT)) + TopLevelLoops.push_back(L); + } + + LoopBase<BlockT> *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) + if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... + TodoStack.push_back(*I); + + if (TodoStack.empty()) return 0; // No backedges to this block... + + // Create a new loop to represent this basic block... + LoopBase<BlockT> *L = new LoopBase<BlockT>(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 (LoopBase<BlockT> *SubLoop = + const_cast<LoopBase<BlockT>*>(getLoopFor(X))) + if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ + // Remove the subloop from it's current parent... + assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); + LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent + typename std::vector<LoopBase<BlockT>*>::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 (LoopBase<BlockT> *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) { + typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI = + BBMap.find(*I); + if (BBMI == BBMap.end()) // Not in map yet... + BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level + } + + // 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*, LoopBase<BlockT>*> ContainingLoops; + for (unsigned i = 0; i != L->SubLoops.size(); ++i) { + LoopBase<BlockT> *Child = L->SubLoops[i]; + assert(Child->getParentLoop() == L && "Not proper child loop?"); + + if (LoopBase<BlockT> *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) { + LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]]; + if (BlockLoop == 0) { // Child block not processed yet... + BlockLoop = Child; + } else if (BlockLoop != Child) { + LoopBase<BlockT> *SubLoop = BlockLoop; + // Reparent all of the blocks which used to belong to BlockLoops + for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++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(LoopBase<BlockT> *NewChild, + LoopBase<BlockT> *NewParent) { + LoopBase<BlockT> *OldParent = NewChild->getParentLoop(); + assert(OldParent && OldParent == NewParent->getParentLoop() && + NewChild != NewParent && "Not sibling loops!"); + + // Remove NewChild from being a child of OldParent + typename std::vector<LoopBase<BlockT>*>::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(LoopBase<BlockT> *L, LoopBase<BlockT> *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(std::ostream &OS, const Module* ) const { + for (unsigned i = 0; i < TopLevelLoops.size(); ++i) + TopLevelLoops[i]->print(OS); + #if 0 + for (std::map<BasicBlock*, Loop*>::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>* LI; + friend class LoopBase<BasicBlock>; + +public: + static char ID; // Pass identification, replacement for typeid + + LoopInfo() : FunctionPass(&ID) { + LI = new LoopInfoBase<BasicBlock>(); + } + + ~LoopInfo() { delete LI; } + + LoopInfoBase<BasicBlock>& getBase() { return *LI; } + + /// iterator/begin/end - The interface to the top-level loops in the current + /// function. + /// + typedef std::vector<Loop*>::const_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 releaseMemory() { LI->releaseMemory(); } + + virtual void print(std::ostream &O, const Module* M = 0) const { + if (O) LI->print(O, M); + } + + 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); + } +}; + + +// Allow clients to walk the list of nested loops... +template <> struct GraphTraits<const Loop*> { + typedef const Loop NodeType; + typedef std::vector<Loop*>::const_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 std::vector<Loop*>::const_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> +void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB, + LoopInfoBase<BlockT> &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!"); + + // Add the loop mapping to the LoopInfo object... + LIB.BBMap[NewBB] = this; + + // Add the basic block to this loop and all parent loops... + LoopBase<BlockT> *L = this; + while (L) { + L->Blocks.push_back(NewBB); + L = L->getParentLoop(); + } +} + +} // End llvm namespace + +#endif |
