1 //===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG. Note that natural
12 // loops may actually be several loops that share the same header node.
14 // This analysis calculates the nesting structure of loops in a function. For
15 // each natural loop identified, this analysis identifies natural loops
16 // contained entirely within the loop and the basic blocks the make up the loop.
18 // It can calculate on the fly various bits of information, for example:
20 // * whether there is a preheader for the loop
21 // * the number of back edges to the header
22 // * whether or not a particular block branches out of the loop
23 // * the successor blocks of the loop
28 //===----------------------------------------------------------------------===//
30 #ifndef LLVM_ANALYSIS_LOOP_INFO_H
31 #define LLVM_ANALYSIS_LOOP_INFO_H
33 #include "llvm/Pass.h"
34 #include "llvm/Constants.h"
35 #include "llvm/Instructions.h"
36 #include "llvm/ADT/DepthFirstIterator.h"
37 #include "llvm/ADT/GraphTraits.h"
38 #include "llvm/ADT/SmallPtrSet.h"
39 #include "llvm/ADT/SmallVector.h"
40 #include "llvm/Analysis/Dominators.h"
41 #include "llvm/Support/CFG.h"
42 #include "llvm/Support/Streams.h"
49 static void RemoveFromVector(std::vector<T*> &V, T *N) {
50 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
51 assert(I != V.end() && "N is not in this list!");
57 template<class N> class LoopInfoBase;
58 template<class N> class LoopBase;
60 typedef LoopBase<BasicBlock> Loop;
62 //===----------------------------------------------------------------------===//
63 /// LoopBase class - Instances of this class are used to represent loops that
64 /// are detected in the flow graph
66 template<class BlockT>
68 LoopBase<BlockT> *ParentLoop;
69 // SubLoops - Loops contained entirely within this one.
70 std::vector<LoopBase<BlockT>*> SubLoops;
72 // Blocks - The list of blocks in this loop. First entry is the header node.
73 std::vector<BlockT*> Blocks;
75 LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT
76 const LoopBase<BlockT>&operator=(const LoopBase<BlockT> &);// DO NOT IMPLEMENT
78 /// Loop ctor - This creates an empty loop.
79 LoopBase() : ParentLoop(0) {}
81 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
85 /// getLoopDepth - Return the nesting level of this loop. An outer-most
86 /// loop has depth 1, for consistency with loop depth values used for basic
87 /// blocks, where depth 0 is used for blocks not inside any loops.
88 unsigned getLoopDepth() const {
90 for (const LoopBase<BlockT> *CurLoop = ParentLoop; CurLoop;
91 CurLoop = CurLoop->ParentLoop)
95 BlockT *getHeader() const { return Blocks.front(); }
96 LoopBase<BlockT> *getParentLoop() const { return ParentLoop; }
98 /// contains - Return true if the specified basic block is in this loop
100 bool contains(const BlockT *BB) const {
101 return std::find(block_begin(), block_end(), BB) != block_end();
104 /// iterator/begin/end - Return the loops contained entirely within this loop.
106 const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; }
107 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
108 iterator begin() const { return SubLoops.begin(); }
109 iterator end() const { return SubLoops.end(); }
110 bool empty() const { return SubLoops.empty(); }
112 /// getBlocks - Get a list of the basic blocks which make up this loop.
114 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
115 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
116 block_iterator block_begin() const { return Blocks.begin(); }
117 block_iterator block_end() const { return Blocks.end(); }
119 /// isLoopExit - True if terminator in the block can branch to another block
120 /// that is outside of the current loop.
122 bool isLoopExit(const BlockT *BB) const {
123 typedef GraphTraits<BlockT*> BlockTraits;
124 for (typename BlockTraits::ChildIteratorType SI =
125 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
126 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
133 /// getNumBackEdges - Calculate the number of back edges to the loop header
135 unsigned getNumBackEdges() const {
136 unsigned NumBackEdges = 0;
137 BlockT *H = getHeader();
139 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
140 for (typename InvBlockTraits::ChildIteratorType I =
141 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
142 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
149 /// isLoopInvariant - Return true if the specified value is loop invariant
151 inline bool isLoopInvariant(Value *V) const {
152 if (Instruction *I = dyn_cast<Instruction>(V))
153 return !contains(I->getParent());
154 return true; // All non-instructions are loop invariant
157 //===--------------------------------------------------------------------===//
158 // APIs for simple analysis of the loop.
160 // Note that all of these methods can fail on general loops (ie, there may not
161 // be a preheader, etc). For best success, the loop simplification and
162 // induction variable canonicalization pass should be used to normalize loops
163 // for easy analysis. These methods assume canonical loops.
165 /// getExitingBlocks - Return all blocks inside the loop that have successors
166 /// outside of the loop. These are the blocks _inside of the current loop_
167 /// which branch out. The returned list is always unique.
169 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
170 // Sort the blocks vector so that we can use binary search to do quick
172 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
173 std::sort(LoopBBs.begin(), LoopBBs.end());
175 typedef GraphTraits<BlockT*> BlockTraits;
176 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
177 for (typename BlockTraits::ChildIteratorType I =
178 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
180 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
181 // Not in current loop? It must be an exit block.
182 ExitingBlocks.push_back(*BI);
187 /// getExitingBlock - If getExitingBlocks would return exactly one block,
188 /// return that block. Otherwise return null.
189 BlockT *getExitingBlock() const {
190 SmallVector<BlockT*, 8> ExitingBlocks;
191 getExitingBlocks(ExitingBlocks);
192 if (ExitingBlocks.size() == 1)
193 return ExitingBlocks[0];
197 /// getExitBlocks - Return all of the successor blocks of this loop. These
198 /// are the blocks _outside of the current loop_ which are branched to.
200 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
201 // Sort the blocks vector so that we can use binary search to do quick
203 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
204 std::sort(LoopBBs.begin(), LoopBBs.end());
206 typedef GraphTraits<BlockT*> BlockTraits;
207 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
208 for (typename BlockTraits::ChildIteratorType I =
209 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
211 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
212 // Not in current loop? It must be an exit block.
213 ExitBlocks.push_back(*I);
216 /// getExitBlock - If getExitBlocks would return exactly one block,
217 /// return that block. Otherwise return null.
218 BlockT *getExitBlock() const {
219 SmallVector<BlockT*, 8> ExitBlocks;
220 getExitBlocks(ExitBlocks);
221 if (ExitBlocks.size() == 1)
222 return ExitBlocks[0];
226 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
227 /// These are the blocks _outside of the current loop_ which are branched to.
228 /// This assumes that loop is in canonical form.
230 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
231 // Sort the blocks vector so that we can use binary search to do quick
233 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
234 std::sort(LoopBBs.begin(), LoopBBs.end());
236 std::vector<BlockT*> switchExitBlocks;
238 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
240 BlockT *current = *BI;
241 switchExitBlocks.clear();
243 typedef GraphTraits<BlockT*> BlockTraits;
244 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
245 for (typename BlockTraits::ChildIteratorType I =
246 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
248 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
249 // If block is inside the loop then it is not a exit block.
252 typename InvBlockTraits::ChildIteratorType PI =
253 InvBlockTraits::child_begin(*I);
254 BlockT *firstPred = *PI;
256 // If current basic block is this exit block's first predecessor
257 // then only insert exit block in to the output ExitBlocks vector.
258 // This ensures that same exit block is not inserted twice into
259 // ExitBlocks vector.
260 if (current != firstPred)
263 // If a terminator has more then two successors, for example SwitchInst,
264 // then it is possible that there are multiple edges from current block
265 // to one exit block.
266 if (std::distance(BlockTraits::child_begin(current),
267 BlockTraits::child_end(current)) <= 2) {
268 ExitBlocks.push_back(*I);
272 // In case of multiple edges from current block to exit block, collect
273 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
275 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
276 == switchExitBlocks.end()) {
277 switchExitBlocks.push_back(*I);
278 ExitBlocks.push_back(*I);
284 /// getLoopPreheader - If there is a preheader for this loop, return it. A
285 /// loop has a preheader if there is only one edge to the header of the loop
286 /// from outside of the loop. If this is the case, the block branching to the
287 /// header of the loop is the preheader node.
289 /// This method returns null if there is no preheader for the loop.
291 BlockT *getLoopPreheader() const {
292 // Keep track of nodes outside the loop branching to the header...
295 // Loop over the predecessors of the header node...
296 BlockT *Header = getHeader();
297 typedef GraphTraits<BlockT*> BlockTraits;
298 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
299 for (typename InvBlockTraits::ChildIteratorType PI =
300 InvBlockTraits::child_begin(Header),
301 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
302 if (!contains(*PI)) { // If the block is not in the loop...
303 if (Out && Out != *PI)
304 return 0; // Multiple predecessors outside the loop
308 // Make sure there is only one exit out of the preheader.
309 assert(Out && "Header of loop has no predecessors from outside loop?");
310 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
312 if (SI != BlockTraits::child_end(Out))
313 return 0; // Multiple exits from the block, must not be a preheader.
315 // If there is exactly one preheader, return it. If there was zero, then
316 // Out is still null.
320 /// getLoopLatch - If there is a single latch block for this loop, return it.
321 /// A latch block is a block that contains a branch back to the header.
322 /// A loop header in normal form has two edges into it: one from a preheader
323 /// and one from a latch block.
324 BlockT *getLoopLatch() const {
325 BlockT *Header = getHeader();
326 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
327 typename InvBlockTraits::ChildIteratorType PI =
328 InvBlockTraits::child_begin(Header);
329 typename InvBlockTraits::ChildIteratorType PE =
330 InvBlockTraits::child_end(Header);
331 if (PI == PE) return 0; // no preds?
337 if (PI == PE) return 0; // only one pred?
340 if (Latch) return 0; // multiple backedges
344 if (PI != PE) return 0; // more than two preds
349 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
350 /// induction variable: an integer recurrence that starts at 0 and increments
351 /// by one each time through the loop. If so, return the phi node that
352 /// corresponds to it.
354 /// The IndVarSimplify pass transforms loops to have a canonical induction
357 inline PHINode *getCanonicalInductionVariable() const {
358 BlockT *H = getHeader();
360 BlockT *Incoming = 0, *Backedge = 0;
361 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
362 typename InvBlockTraits::ChildIteratorType PI =
363 InvBlockTraits::child_begin(H);
364 assert(PI != InvBlockTraits::child_end(H) &&
365 "Loop must have at least one backedge!");
367 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop
369 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges?
371 if (contains(Incoming)) {
372 if (contains(Backedge))
374 std::swap(Incoming, Backedge);
375 } else if (!contains(Backedge))
378 // Loop over all of the PHI nodes, looking for a canonical indvar.
379 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) {
380 PHINode *PN = cast<PHINode>(I);
381 if (ConstantInt *CI =
382 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
383 if (CI->isNullValue())
384 if (Instruction *Inc =
385 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
386 if (Inc->getOpcode() == Instruction::Add &&
387 Inc->getOperand(0) == PN)
388 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
389 if (CI->equalsInt(1))
395 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
396 /// the canonical induction variable value for the "next" iteration of the
397 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
399 inline Instruction *getCanonicalInductionVariableIncrement() const {
400 if (PHINode *PN = getCanonicalInductionVariable()) {
401 bool P1InLoop = contains(PN->getIncomingBlock(1));
402 return cast<Instruction>(PN->getIncomingValue(P1InLoop));
407 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
408 /// times the loop will be executed. Note that this means that the backedge
409 /// of the loop executes N-1 times. If the trip-count cannot be determined,
410 /// this returns null.
412 /// The IndVarSimplify pass transforms loops to have a form that this
413 /// function easily understands.
415 inline Value *getTripCount() const {
416 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented
417 // canonical induction variable and V is the trip count of the loop.
418 Instruction *Inc = getCanonicalInductionVariableIncrement();
419 if (Inc == 0) return 0;
420 PHINode *IV = cast<PHINode>(Inc->getOperand(0));
422 BlockT *BackedgeBlock =
423 IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
425 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
426 if (BI->isConditional()) {
427 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
428 if (ICI->getOperand(0) == Inc) {
429 if (BI->getSuccessor(0) == getHeader()) {
430 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
431 return ICI->getOperand(1);
432 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
433 return ICI->getOperand(1);
442 /// getSmallConstantTripCount - Returns the trip count of this loop as a
443 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
444 /// of not constant. Will also return 0 if the trip count is very large
446 inline unsigned getSmallConstantTripCount() const {
447 Value* TripCount = this->getTripCount();
449 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
450 // Guard against huge trip counts.
451 if (TripCountC->getValue().getActiveBits() <= 32) {
452 return (unsigned)TripCountC->getZExtValue();
459 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
460 /// trip count of this loop as a normal unsigned value, if possible. This
461 /// means that the actual trip count is always a multiple of the returned
462 /// value (don't forget the trip count could very well be zero as well!).
464 /// Returns 1 if the trip count is unknown or not guaranteed to be the
465 /// multiple of a constant (which is also the case if the trip count is simply
466 /// constant, use getSmallConstantTripCount for that case), Will also return 1
467 /// if the trip count is very large (>= 2^32).
468 inline unsigned getSmallConstantTripMultiple() const {
469 Value* TripCount = this->getTripCount();
470 // This will hold the ConstantInt result, if any
471 ConstantInt *Result = NULL;
473 // See if the trip count is constant itself
474 Result = dyn_cast<ConstantInt>(TripCount);
475 // if not, see if it is a multiplication
477 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
478 switch (BO->getOpcode()) {
479 case BinaryOperator::Mul:
480 Result = dyn_cast<ConstantInt>(BO->getOperand(1));
487 // Guard against huge trip counts.
488 if (Result && Result->getValue().getActiveBits() <= 32) {
489 return (unsigned)Result->getZExtValue();
495 /// isLCSSAForm - Return true if the Loop is in LCSSA form
496 inline bool isLCSSAForm() const {
497 // Sort the blocks vector so that we can use binary search to do quick
499 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end());
501 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
503 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I)
504 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
506 BlockT *UserBB = cast<Instruction>(*UI)->getParent();
507 if (PHINode *P = dyn_cast<PHINode>(*UI)) {
508 UserBB = P->getIncomingBlock(UI);
511 // Check the current block, as a fast-path. Most values are used in
512 // the same block they are defined in.
513 if (UserBB != BB && !LoopBBs.count(UserBB))
521 //===--------------------------------------------------------------------===//
522 // APIs for updating loop information after changing the CFG
525 /// addBasicBlockToLoop - This method is used by other analyses to update loop
526 /// information. NewBB is set to be a new member of the current loop.
527 /// Because of this, it is added as a member of all parent loops, and is added
528 /// to the specified LoopInfo object as being in the current basic block. It
529 /// is not valid to replace the loop header with this method.
531 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI);
533 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
534 /// the OldChild entry in our children list with NewChild, and updates the
535 /// parent pointer of OldChild to be null and the NewChild to be this loop.
536 /// This updates the loop depth of the new child.
537 void replaceChildLoopWith(LoopBase<BlockT> *OldChild,
538 LoopBase<BlockT> *NewChild) {
539 assert(OldChild->ParentLoop == this && "This loop is already broken!");
540 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
541 typename std::vector<LoopBase<BlockT>*>::iterator I =
542 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
543 assert(I != SubLoops.end() && "OldChild not in loop!");
545 OldChild->ParentLoop = 0;
546 NewChild->ParentLoop = this;
549 /// addChildLoop - Add the specified loop to be a child of this loop. This
550 /// updates the loop depth of the new child.
552 void addChildLoop(LoopBase<BlockT> *NewChild) {
553 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
554 NewChild->ParentLoop = this;
555 SubLoops.push_back(NewChild);
558 /// removeChildLoop - This removes the specified child from being a subloop of
559 /// this loop. The loop is not deleted, as it will presumably be inserted
560 /// into another loop.
561 LoopBase<BlockT> *removeChildLoop(iterator I) {
562 assert(I != SubLoops.end() && "Cannot remove end iterator!");
563 LoopBase<BlockT> *Child = *I;
564 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
565 SubLoops.erase(SubLoops.begin()+(I-begin()));
566 Child->ParentLoop = 0;
570 /// addBlockEntry - This adds a basic block directly to the basic block list.
571 /// This should only be used by transformations that create new loops. Other
572 /// transformations should use addBasicBlockToLoop.
573 void addBlockEntry(BlockT *BB) {
574 Blocks.push_back(BB);
577 /// moveToHeader - This method is used to move BB (which must be part of this
578 /// loop) to be the loop header of the loop (the block that dominates all
580 void moveToHeader(BlockT *BB) {
581 if (Blocks[0] == BB) return;
582 for (unsigned i = 0; ; ++i) {
583 assert(i != Blocks.size() && "Loop does not contain BB!");
584 if (Blocks[i] == BB) {
585 Blocks[i] = Blocks[0];
592 /// removeBlockFromLoop - This removes the specified basic block from the
593 /// current loop, updating the Blocks as appropriate. This does not update
594 /// the mapping in the LoopInfo class.
595 void removeBlockFromLoop(BlockT *BB) {
596 RemoveFromVector(Blocks, BB);
599 /// verifyLoop - Verify loop structure
600 void verifyLoop() const {
602 assert (getHeader() && "Loop header is missing");
603 assert (getLoopPreheader() && "Loop preheader is missing");
604 assert (getLoopLatch() && "Loop latch is missing");
605 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
610 void print(std::ostream &OS, unsigned Depth = 0) const {
611 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth()
614 for (unsigned i = 0; i < getBlocks().size(); ++i) {
616 BlockT *BB = getBlocks()[i];
617 WriteAsOperand(OS, BB, false);
618 if (BB == getHeader()) OS << "<header>";
619 if (BB == getLoopLatch()) OS << "<latch>";
620 if (isLoopExit(BB)) OS << "<exit>";
624 for (iterator I = begin(), E = end(); I != E; ++I)
625 (*I)->print(OS, Depth+2);
628 void print(std::ostream *O, unsigned Depth = 0) const {
629 if (O) print(*O, Depth);
637 friend class LoopInfoBase<BlockT>;
638 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
639 Blocks.push_back(BB);
644 //===----------------------------------------------------------------------===//
645 /// LoopInfo - This class builds and contains all of the top level loop
646 /// structures in the specified function.
649 template<class BlockT>
651 // BBMap - Mapping of basic blocks to the inner most loop they occur in
652 std::map<BlockT*, LoopBase<BlockT>*> BBMap;
653 std::vector<LoopBase<BlockT>*> TopLevelLoops;
654 friend class LoopBase<BlockT>;
658 ~LoopInfoBase() { releaseMemory(); }
660 void releaseMemory() {
661 for (typename std::vector<LoopBase<BlockT>* >::iterator I =
662 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
663 delete *I; // Delete all of the loops...
665 BBMap.clear(); // Reset internal state of analysis
666 TopLevelLoops.clear();
669 /// iterator/begin/end - The interface to the top-level loops in the current
672 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
673 iterator begin() const { return TopLevelLoops.begin(); }
674 iterator end() const { return TopLevelLoops.end(); }
675 bool empty() const { return TopLevelLoops.empty(); }
677 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
678 /// block is in no loop (for example the entry node), null is returned.
680 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const {
681 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I=
682 BBMap.find(const_cast<BlockT*>(BB));
683 return I != BBMap.end() ? I->second : 0;
686 /// operator[] - same as getLoopFor...
688 const LoopBase<BlockT> *operator[](const BlockT *BB) const {
689 return getLoopFor(BB);
692 /// getLoopDepth - Return the loop nesting level of the specified block. A
693 /// depth of 0 means the block is not inside any loop.
695 unsigned getLoopDepth(const BlockT *BB) const {
696 const LoopBase<BlockT> *L = getLoopFor(BB);
697 return L ? L->getLoopDepth() : 0;
700 // isLoopHeader - True if the block is a loop header node
701 bool isLoopHeader(BlockT *BB) const {
702 const LoopBase<BlockT> *L = getLoopFor(BB);
703 return L && L->getHeader() == BB;
706 /// removeLoop - This removes the specified top-level loop from this loop info
707 /// object. The loop is not deleted, as it will presumably be inserted into
709 LoopBase<BlockT> *removeLoop(iterator I) {
710 assert(I != end() && "Cannot remove end iterator!");
711 LoopBase<BlockT> *L = *I;
712 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
713 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
717 /// changeLoopFor - Change the top-level loop that contains BB to the
718 /// specified loop. This should be used by transformations that restructure
719 /// the loop hierarchy tree.
720 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) {
721 LoopBase<BlockT> *&OldLoop = BBMap[BB];
722 assert(OldLoop && "Block not in a loop yet!");
726 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
727 /// list with the indicated loop.
728 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop,
729 LoopBase<BlockT> *NewLoop) {
730 typename std::vector<LoopBase<BlockT>*>::iterator I =
731 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
732 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
734 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
735 "Loops already embedded into a subloop!");
738 /// addTopLevelLoop - This adds the specified loop to the collection of
740 void addTopLevelLoop(LoopBase<BlockT> *New) {
741 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
742 TopLevelLoops.push_back(New);
745 /// removeBlock - This method completely removes BB from all data structures,
746 /// including all of the Loop objects it is nested in and our mapping from
747 /// BasicBlocks to loops.
748 void removeBlock(BlockT *BB) {
749 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB);
750 if (I != BBMap.end()) {
751 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop())
752 L->removeBlockFromLoop(BB);
760 static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop,
761 const LoopBase<BlockT> *ParentLoop) {
762 if (SubLoop == 0) return true;
763 if (SubLoop == ParentLoop) return false;
764 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
767 void Calculate(DominatorTreeBase<BlockT> &DT) {
768 BlockT *RootNode = DT.getRootNode()->getBlock();
770 for (df_iterator<BlockT*> NI = df_begin(RootNode),
771 NE = df_end(RootNode); NI != NE; ++NI)
772 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT))
773 TopLevelLoops.push_back(L);
776 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
777 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
779 std::vector<BlockT *> TodoStack;
781 // Scan the predecessors of BB, checking to see if BB dominates any of
782 // them. This identifies backedges which target this node...
783 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
784 for (typename InvBlockTraits::ChildIteratorType I =
785 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
787 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
788 TodoStack.push_back(*I);
790 if (TodoStack.empty()) return 0; // No backedges to this block...
792 // Create a new loop to represent this basic block...
793 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB);
796 BlockT *EntryBlock = BB->getParent()->begin();
798 while (!TodoStack.empty()) { // Process all the nodes in the loop
799 BlockT *X = TodoStack.back();
800 TodoStack.pop_back();
802 if (!L->contains(X) && // As of yet unprocessed??
803 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
804 // Check to see if this block already belongs to a loop. If this occurs
805 // then we have a case where a loop that is supposed to be a child of
806 // the current loop was processed before the current loop. When this
807 // occurs, this child loop gets added to a part of the current loop,
808 // making it a sibling to the current loop. We have to reparent this
810 if (LoopBase<BlockT> *SubLoop =
811 const_cast<LoopBase<BlockT>*>(getLoopFor(X)))
812 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
813 // Remove the subloop from it's current parent...
814 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
815 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent
816 typename std::vector<LoopBase<BlockT>*>::iterator I =
817 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
818 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
819 SLP->SubLoops.erase(I); // Remove from parent...
821 // Add the subloop to THIS loop...
822 SubLoop->ParentLoop = L;
823 L->SubLoops.push_back(SubLoop);
826 // Normal case, add the block to our loop...
827 L->Blocks.push_back(X);
829 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
831 // Add all of the predecessors of X to the end of the work stack...
832 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
833 InvBlockTraits::child_end(X));
837 // If there are any loops nested within this loop, create them now!
838 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
839 E = L->Blocks.end(); I != E; ++I)
840 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) {
841 L->SubLoops.push_back(NewLoop);
842 NewLoop->ParentLoop = L;
845 // Add the basic blocks that comprise this loop to the BBMap so that this
846 // loop can be found for them.
848 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
849 E = L->Blocks.end(); I != E; ++I) {
850 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI =
852 if (BBMI == BBMap.end()) // Not in map yet...
853 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
856 // Now that we have a list of all of the child loops of this loop, check to
857 // see if any of them should actually be nested inside of each other. We
858 // can accidentally pull loops our of their parents, so we must make sure to
859 // organize the loop nests correctly now.
861 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops;
862 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
863 LoopBase<BlockT> *Child = L->SubLoops[i];
864 assert(Child->getParentLoop() == L && "Not proper child loop?");
866 if (LoopBase<BlockT> *ContainingLoop =
867 ContainingLoops[Child->getHeader()]) {
868 // If there is already a loop which contains this loop, move this loop
869 // into the containing loop.
870 MoveSiblingLoopInto(Child, ContainingLoop);
871 --i; // The loop got removed from the SubLoops list.
873 // This is currently considered to be a top-level loop. Check to see
874 // if any of the contained blocks are loop headers for subloops we
875 // have already processed.
876 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
877 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]];
878 if (BlockLoop == 0) { // Child block not processed yet...
880 } else if (BlockLoop != Child) {
881 LoopBase<BlockT> *SubLoop = BlockLoop;
882 // Reparent all of the blocks which used to belong to BlockLoops
883 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
884 ContainingLoops[SubLoop->Blocks[j]] = Child;
886 // There is already a loop which contains this block, that means
887 // that we should reparent the loop which the block is currently
888 // considered to belong to to be a child of this loop.
889 MoveSiblingLoopInto(SubLoop, Child);
890 --i; // We just shrunk the SubLoops list.
900 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
901 /// of the NewParent Loop, instead of being a sibling of it.
902 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild,
903 LoopBase<BlockT> *NewParent) {
904 LoopBase<BlockT> *OldParent = NewChild->getParentLoop();
905 assert(OldParent && OldParent == NewParent->getParentLoop() &&
906 NewChild != NewParent && "Not sibling loops!");
908 // Remove NewChild from being a child of OldParent
909 typename std::vector<LoopBase<BlockT>*>::iterator I =
910 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
912 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
913 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
914 NewChild->ParentLoop = 0;
916 InsertLoopInto(NewChild, NewParent);
919 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
920 /// the parent loop contains a loop which should contain L, the loop gets
921 /// inserted into L instead.
922 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) {
923 BlockT *LHeader = L->getHeader();
924 assert(Parent->contains(LHeader) &&
925 "This loop should not be inserted here!");
927 // Check to see if it belongs in a child loop...
928 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
930 if (Parent->SubLoops[i]->contains(LHeader)) {
931 InsertLoopInto(L, Parent->SubLoops[i]);
935 // If not, insert it here!
936 Parent->SubLoops.push_back(L);
937 L->ParentLoop = Parent;
942 void print(std::ostream &OS, const Module* ) const {
943 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
944 TopLevelLoops[i]->print(OS);
946 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
947 E = BBMap.end(); I != E; ++I)
948 OS << "BB '" << I->first->getName() << "' level = "
949 << I->second->getLoopDepth() << "\n";
954 class LoopInfo : public FunctionPass {
955 LoopInfoBase<BasicBlock>* LI;
956 friend class LoopBase<BasicBlock>;
959 static char ID; // Pass identification, replacement for typeid
961 LoopInfo() : FunctionPass(&ID) {
962 LI = new LoopInfoBase<BasicBlock>();
965 ~LoopInfo() { delete LI; }
967 LoopInfoBase<BasicBlock>& getBase() { return *LI; }
969 /// iterator/begin/end - The interface to the top-level loops in the current
972 typedef std::vector<Loop*>::const_iterator iterator;
973 inline iterator begin() const { return LI->begin(); }
974 inline iterator end() const { return LI->end(); }
975 bool empty() const { return LI->empty(); }
977 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
978 /// block is in no loop (for example the entry node), null is returned.
980 inline Loop *getLoopFor(const BasicBlock *BB) const {
981 return LI->getLoopFor(BB);
984 /// operator[] - same as getLoopFor...
986 inline const Loop *operator[](const BasicBlock *BB) const {
987 return LI->getLoopFor(BB);
990 /// getLoopDepth - Return the loop nesting level of the specified block. A
991 /// depth of 0 means the block is not inside any loop.
993 inline unsigned getLoopDepth(const BasicBlock *BB) const {
994 return LI->getLoopDepth(BB);
997 // isLoopHeader - True if the block is a loop header node
998 inline bool isLoopHeader(BasicBlock *BB) const {
999 return LI->isLoopHeader(BB);
1002 /// runOnFunction - Calculate the natural loop information.
1004 virtual bool runOnFunction(Function &F);
1006 virtual void releaseMemory() { LI->releaseMemory(); }
1008 virtual void print(std::ostream &O, const Module* M = 0) const {
1009 if (O) LI->print(O, M);
1012 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
1014 /// removeLoop - This removes the specified top-level loop from this loop info
1015 /// object. The loop is not deleted, as it will presumably be inserted into
1017 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); }
1019 /// changeLoopFor - Change the top-level loop that contains BB to the
1020 /// specified loop. This should be used by transformations that restructure
1021 /// the loop hierarchy tree.
1022 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
1023 LI->changeLoopFor(BB, L);
1026 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
1027 /// list with the indicated loop.
1028 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1029 LI->changeTopLevelLoop(OldLoop, NewLoop);
1032 /// addTopLevelLoop - This adds the specified loop to the collection of
1033 /// top-level loops.
1034 inline void addTopLevelLoop(Loop *New) {
1035 LI->addTopLevelLoop(New);
1038 /// removeBlock - This method completely removes BB from all data structures,
1039 /// including all of the Loop objects it is nested in and our mapping from
1040 /// BasicBlocks to loops.
1041 void removeBlock(BasicBlock *BB) {
1042 LI->removeBlock(BB);
1047 // Allow clients to walk the list of nested loops...
1048 template <> struct GraphTraits<const Loop*> {
1049 typedef const Loop NodeType;
1050 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
1052 static NodeType *getEntryNode(const Loop *L) { return L; }
1053 static inline ChildIteratorType child_begin(NodeType *N) {
1056 static inline ChildIteratorType child_end(NodeType *N) {
1061 template <> struct GraphTraits<Loop*> {
1062 typedef Loop NodeType;
1063 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
1065 static NodeType *getEntryNode(Loop *L) { return L; }
1066 static inline ChildIteratorType child_begin(NodeType *N) {
1069 static inline ChildIteratorType child_end(NodeType *N) {
1074 template<class BlockT>
1075 void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB,
1076 LoopInfoBase<BlockT> &LIB) {
1077 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1078 "Incorrect LI specified for this loop!");
1079 assert(NewBB && "Cannot add a null basic block to the loop!");
1080 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1082 // Add the loop mapping to the LoopInfo object...
1083 LIB.BBMap[NewBB] = this;
1085 // Add the basic block to this loop and all parent loops...
1086 LoopBase<BlockT> *L = this;
1088 L->Blocks.push_back(NewBB);
1089 L = L->getParentLoop();
1093 } // End llvm namespace