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 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
285 /// block, return that block. Otherwise return null.
286 BlockT *getUniqueExitBlock() const {
287 SmallVector<BlockT*, 8> UniqueExitBlocks;
288 getUniqueExitBlocks(UniqueExitBlocks);
289 if (UniqueExitBlocks.size() == 1)
290 return UniqueExitBlocks[0];
294 /// getLoopPreheader - If there is a preheader for this loop, return it. A
295 /// loop has a preheader if there is only one edge to the header of the loop
296 /// from outside of the loop. If this is the case, the block branching to the
297 /// header of the loop is the preheader node.
299 /// This method returns null if there is no preheader for the loop.
301 BlockT *getLoopPreheader() const {
302 // Keep track of nodes outside the loop branching to the header...
305 // Loop over the predecessors of the header node...
306 BlockT *Header = getHeader();
307 typedef GraphTraits<BlockT*> BlockTraits;
308 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
309 for (typename InvBlockTraits::ChildIteratorType PI =
310 InvBlockTraits::child_begin(Header),
311 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
312 if (!contains(*PI)) { // If the block is not in the loop...
313 if (Out && Out != *PI)
314 return 0; // Multiple predecessors outside the loop
318 // Make sure there is only one exit out of the preheader.
319 assert(Out && "Header of loop has no predecessors from outside loop?");
320 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
322 if (SI != BlockTraits::child_end(Out))
323 return 0; // Multiple exits from the block, must not be a preheader.
325 // If there is exactly one preheader, return it. If there was zero, then
326 // Out is still null.
330 /// getLoopLatch - If there is a single latch block for this loop, return it.
331 /// A latch block is a block that contains a branch back to the header.
332 /// A loop header in normal form has two edges into it: one from a preheader
333 /// and one from a latch block.
334 BlockT *getLoopLatch() const {
335 BlockT *Header = getHeader();
336 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
337 typename InvBlockTraits::ChildIteratorType PI =
338 InvBlockTraits::child_begin(Header);
339 typename InvBlockTraits::ChildIteratorType PE =
340 InvBlockTraits::child_end(Header);
341 if (PI == PE) return 0; // no preds?
347 if (PI == PE) return 0; // only one pred?
350 if (Latch) return 0; // multiple backedges
354 if (PI != PE) return 0; // more than two preds
359 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
360 /// induction variable: an integer recurrence that starts at 0 and increments
361 /// by one each time through the loop. If so, return the phi node that
362 /// corresponds to it.
364 /// The IndVarSimplify pass transforms loops to have a canonical induction
367 inline PHINode *getCanonicalInductionVariable() const {
368 BlockT *H = getHeader();
370 BlockT *Incoming = 0, *Backedge = 0;
371 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
372 typename InvBlockTraits::ChildIteratorType PI =
373 InvBlockTraits::child_begin(H);
374 assert(PI != InvBlockTraits::child_end(H) &&
375 "Loop must have at least one backedge!");
377 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop
379 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges?
381 if (contains(Incoming)) {
382 if (contains(Backedge))
384 std::swap(Incoming, Backedge);
385 } else if (!contains(Backedge))
388 // Loop over all of the PHI nodes, looking for a canonical indvar.
389 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) {
390 PHINode *PN = cast<PHINode>(I);
391 if (ConstantInt *CI =
392 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
393 if (CI->isNullValue())
394 if (Instruction *Inc =
395 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
396 if (Inc->getOpcode() == Instruction::Add &&
397 Inc->getOperand(0) == PN)
398 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
399 if (CI->equalsInt(1))
405 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
406 /// the canonical induction variable value for the "next" iteration of the
407 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
409 inline Instruction *getCanonicalInductionVariableIncrement() const {
410 if (PHINode *PN = getCanonicalInductionVariable()) {
411 bool P1InLoop = contains(PN->getIncomingBlock(1));
412 return cast<Instruction>(PN->getIncomingValue(P1InLoop));
417 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
418 /// times the loop will be executed. Note that this means that the backedge
419 /// of the loop executes N-1 times. If the trip-count cannot be determined,
420 /// this returns null.
422 /// The IndVarSimplify pass transforms loops to have a form that this
423 /// function easily understands.
425 inline Value *getTripCount() const {
426 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented
427 // canonical induction variable and V is the trip count of the loop.
428 Instruction *Inc = getCanonicalInductionVariableIncrement();
429 if (Inc == 0) return 0;
430 PHINode *IV = cast<PHINode>(Inc->getOperand(0));
432 BlockT *BackedgeBlock =
433 IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
435 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
436 if (BI->isConditional()) {
437 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
438 if (ICI->getOperand(0) == Inc) {
439 if (BI->getSuccessor(0) == getHeader()) {
440 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
441 return ICI->getOperand(1);
442 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
443 return ICI->getOperand(1);
452 /// getSmallConstantTripCount - Returns the trip count of this loop as a
453 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
454 /// of not constant. Will also return 0 if the trip count is very large
456 inline unsigned getSmallConstantTripCount() const {
457 Value* TripCount = this->getTripCount();
459 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
460 // Guard against huge trip counts.
461 if (TripCountC->getValue().getActiveBits() <= 32) {
462 return (unsigned)TripCountC->getZExtValue();
469 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
470 /// trip count of this loop as a normal unsigned value, if possible. This
471 /// means that the actual trip count is always a multiple of the returned
472 /// value (don't forget the trip count could very well be zero as well!).
474 /// Returns 1 if the trip count is unknown or not guaranteed to be the
475 /// multiple of a constant (which is also the case if the trip count is simply
476 /// constant, use getSmallConstantTripCount for that case), Will also return 1
477 /// if the trip count is very large (>= 2^32).
478 inline unsigned getSmallConstantTripMultiple() const {
479 Value* TripCount = this->getTripCount();
480 // This will hold the ConstantInt result, if any
481 ConstantInt *Result = NULL;
483 // See if the trip count is constant itself
484 Result = dyn_cast<ConstantInt>(TripCount);
485 // if not, see if it is a multiplication
487 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
488 switch (BO->getOpcode()) {
489 case BinaryOperator::Mul:
490 Result = dyn_cast<ConstantInt>(BO->getOperand(1));
497 // Guard against huge trip counts.
498 if (Result && Result->getValue().getActiveBits() <= 32) {
499 return (unsigned)Result->getZExtValue();
505 /// isLCSSAForm - Return true if the Loop is in LCSSA form
506 inline bool isLCSSAForm() const {
507 // Sort the blocks vector so that we can use binary search to do quick
509 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end());
511 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
513 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I)
514 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
516 BlockT *UserBB = cast<Instruction>(*UI)->getParent();
517 if (PHINode *P = dyn_cast<PHINode>(*UI)) {
518 UserBB = P->getIncomingBlock(UI);
521 // Check the current block, as a fast-path. Most values are used in
522 // the same block they are defined in.
523 if (UserBB != BB && !LoopBBs.count(UserBB))
531 //===--------------------------------------------------------------------===//
532 // APIs for updating loop information after changing the CFG
535 /// addBasicBlockToLoop - This method is used by other analyses to update loop
536 /// information. NewBB is set to be a new member of the current loop.
537 /// Because of this, it is added as a member of all parent loops, and is added
538 /// to the specified LoopInfo object as being in the current basic block. It
539 /// is not valid to replace the loop header with this method.
541 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI);
543 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
544 /// the OldChild entry in our children list with NewChild, and updates the
545 /// parent pointer of OldChild to be null and the NewChild to be this loop.
546 /// This updates the loop depth of the new child.
547 void replaceChildLoopWith(LoopBase<BlockT> *OldChild,
548 LoopBase<BlockT> *NewChild) {
549 assert(OldChild->ParentLoop == this && "This loop is already broken!");
550 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
551 typename std::vector<LoopBase<BlockT>*>::iterator I =
552 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
553 assert(I != SubLoops.end() && "OldChild not in loop!");
555 OldChild->ParentLoop = 0;
556 NewChild->ParentLoop = this;
559 /// addChildLoop - Add the specified loop to be a child of this loop. This
560 /// updates the loop depth of the new child.
562 void addChildLoop(LoopBase<BlockT> *NewChild) {
563 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
564 NewChild->ParentLoop = this;
565 SubLoops.push_back(NewChild);
568 /// removeChildLoop - This removes the specified child from being a subloop of
569 /// this loop. The loop is not deleted, as it will presumably be inserted
570 /// into another loop.
571 LoopBase<BlockT> *removeChildLoop(iterator I) {
572 assert(I != SubLoops.end() && "Cannot remove end iterator!");
573 LoopBase<BlockT> *Child = *I;
574 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
575 SubLoops.erase(SubLoops.begin()+(I-begin()));
576 Child->ParentLoop = 0;
580 /// addBlockEntry - This adds a basic block directly to the basic block list.
581 /// This should only be used by transformations that create new loops. Other
582 /// transformations should use addBasicBlockToLoop.
583 void addBlockEntry(BlockT *BB) {
584 Blocks.push_back(BB);
587 /// moveToHeader - This method is used to move BB (which must be part of this
588 /// loop) to be the loop header of the loop (the block that dominates all
590 void moveToHeader(BlockT *BB) {
591 if (Blocks[0] == BB) return;
592 for (unsigned i = 0; ; ++i) {
593 assert(i != Blocks.size() && "Loop does not contain BB!");
594 if (Blocks[i] == BB) {
595 Blocks[i] = Blocks[0];
602 /// removeBlockFromLoop - This removes the specified basic block from the
603 /// current loop, updating the Blocks as appropriate. This does not update
604 /// the mapping in the LoopInfo class.
605 void removeBlockFromLoop(BlockT *BB) {
606 RemoveFromVector(Blocks, BB);
609 /// verifyLoop - Verify loop structure
610 void verifyLoop() const {
612 assert (getHeader() && "Loop header is missing");
613 assert (getLoopPreheader() && "Loop preheader is missing");
614 assert (getLoopLatch() && "Loop latch is missing");
615 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
620 void print(std::ostream &OS, unsigned Depth = 0) const {
621 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth()
624 for (unsigned i = 0; i < getBlocks().size(); ++i) {
626 BlockT *BB = getBlocks()[i];
627 WriteAsOperand(OS, BB, false);
628 if (BB == getHeader()) OS << "<header>";
629 if (BB == getLoopLatch()) OS << "<latch>";
630 if (isLoopExit(BB)) OS << "<exit>";
634 for (iterator I = begin(), E = end(); I != E; ++I)
635 (*I)->print(OS, Depth+2);
638 void print(std::ostream *O, unsigned Depth = 0) const {
639 if (O) print(*O, Depth);
647 friend class LoopInfoBase<BlockT>;
648 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
649 Blocks.push_back(BB);
654 //===----------------------------------------------------------------------===//
655 /// LoopInfo - This class builds and contains all of the top level loop
656 /// structures in the specified function.
659 template<class BlockT>
661 // BBMap - Mapping of basic blocks to the inner most loop they occur in
662 std::map<BlockT*, LoopBase<BlockT>*> BBMap;
663 std::vector<LoopBase<BlockT>*> TopLevelLoops;
664 friend class LoopBase<BlockT>;
666 void operator=(const LoopInfoBase &); // do not implement
667 LoopInfoBase(const LoopInfo &); // do not implement
670 ~LoopInfoBase() { releaseMemory(); }
672 void releaseMemory() {
673 for (typename std::vector<LoopBase<BlockT>* >::iterator I =
674 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
675 delete *I; // Delete all of the loops...
677 BBMap.clear(); // Reset internal state of analysis
678 TopLevelLoops.clear();
681 /// iterator/begin/end - The interface to the top-level loops in the current
684 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
685 iterator begin() const { return TopLevelLoops.begin(); }
686 iterator end() const { return TopLevelLoops.end(); }
687 bool empty() const { return TopLevelLoops.empty(); }
689 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
690 /// block is in no loop (for example the entry node), null is returned.
692 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const {
693 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I=
694 BBMap.find(const_cast<BlockT*>(BB));
695 return I != BBMap.end() ? I->second : 0;
698 /// operator[] - same as getLoopFor...
700 const LoopBase<BlockT> *operator[](const BlockT *BB) const {
701 return getLoopFor(BB);
704 /// getLoopDepth - Return the loop nesting level of the specified block. A
705 /// depth of 0 means the block is not inside any loop.
707 unsigned getLoopDepth(const BlockT *BB) const {
708 const LoopBase<BlockT> *L = getLoopFor(BB);
709 return L ? L->getLoopDepth() : 0;
712 // isLoopHeader - True if the block is a loop header node
713 bool isLoopHeader(BlockT *BB) const {
714 const LoopBase<BlockT> *L = getLoopFor(BB);
715 return L && L->getHeader() == BB;
718 /// removeLoop - This removes the specified top-level loop from this loop info
719 /// object. The loop is not deleted, as it will presumably be inserted into
721 LoopBase<BlockT> *removeLoop(iterator I) {
722 assert(I != end() && "Cannot remove end iterator!");
723 LoopBase<BlockT> *L = *I;
724 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
725 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
729 /// changeLoopFor - Change the top-level loop that contains BB to the
730 /// specified loop. This should be used by transformations that restructure
731 /// the loop hierarchy tree.
732 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) {
733 LoopBase<BlockT> *&OldLoop = BBMap[BB];
734 assert(OldLoop && "Block not in a loop yet!");
738 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
739 /// list with the indicated loop.
740 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop,
741 LoopBase<BlockT> *NewLoop) {
742 typename std::vector<LoopBase<BlockT>*>::iterator I =
743 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
744 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
746 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
747 "Loops already embedded into a subloop!");
750 /// addTopLevelLoop - This adds the specified loop to the collection of
752 void addTopLevelLoop(LoopBase<BlockT> *New) {
753 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
754 TopLevelLoops.push_back(New);
757 /// removeBlock - This method completely removes BB from all data structures,
758 /// including all of the Loop objects it is nested in and our mapping from
759 /// BasicBlocks to loops.
760 void removeBlock(BlockT *BB) {
761 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB);
762 if (I != BBMap.end()) {
763 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop())
764 L->removeBlockFromLoop(BB);
772 static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop,
773 const LoopBase<BlockT> *ParentLoop) {
774 if (SubLoop == 0) return true;
775 if (SubLoop == ParentLoop) return false;
776 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
779 void Calculate(DominatorTreeBase<BlockT> &DT) {
780 BlockT *RootNode = DT.getRootNode()->getBlock();
782 for (df_iterator<BlockT*> NI = df_begin(RootNode),
783 NE = df_end(RootNode); NI != NE; ++NI)
784 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT))
785 TopLevelLoops.push_back(L);
788 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
789 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
791 std::vector<BlockT *> TodoStack;
793 // Scan the predecessors of BB, checking to see if BB dominates any of
794 // them. This identifies backedges which target this node...
795 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
796 for (typename InvBlockTraits::ChildIteratorType I =
797 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
799 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
800 TodoStack.push_back(*I);
802 if (TodoStack.empty()) return 0; // No backedges to this block...
804 // Create a new loop to represent this basic block...
805 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB);
808 BlockT *EntryBlock = BB->getParent()->begin();
810 while (!TodoStack.empty()) { // Process all the nodes in the loop
811 BlockT *X = TodoStack.back();
812 TodoStack.pop_back();
814 if (!L->contains(X) && // As of yet unprocessed??
815 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
816 // Check to see if this block already belongs to a loop. If this occurs
817 // then we have a case where a loop that is supposed to be a child of
818 // the current loop was processed before the current loop. When this
819 // occurs, this child loop gets added to a part of the current loop,
820 // making it a sibling to the current loop. We have to reparent this
822 if (LoopBase<BlockT> *SubLoop =
823 const_cast<LoopBase<BlockT>*>(getLoopFor(X)))
824 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
825 // Remove the subloop from it's current parent...
826 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
827 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent
828 typename std::vector<LoopBase<BlockT>*>::iterator I =
829 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
830 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
831 SLP->SubLoops.erase(I); // Remove from parent...
833 // Add the subloop to THIS loop...
834 SubLoop->ParentLoop = L;
835 L->SubLoops.push_back(SubLoop);
838 // Normal case, add the block to our loop...
839 L->Blocks.push_back(X);
841 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
843 // Add all of the predecessors of X to the end of the work stack...
844 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
845 InvBlockTraits::child_end(X));
849 // If there are any loops nested within this loop, create them now!
850 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
851 E = L->Blocks.end(); I != E; ++I)
852 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) {
853 L->SubLoops.push_back(NewLoop);
854 NewLoop->ParentLoop = L;
857 // Add the basic blocks that comprise this loop to the BBMap so that this
858 // loop can be found for them.
860 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
861 E = L->Blocks.end(); I != E; ++I) {
862 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI =
864 if (BBMI == BBMap.end()) // Not in map yet...
865 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
868 // Now that we have a list of all of the child loops of this loop, check to
869 // see if any of them should actually be nested inside of each other. We
870 // can accidentally pull loops our of their parents, so we must make sure to
871 // organize the loop nests correctly now.
873 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops;
874 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
875 LoopBase<BlockT> *Child = L->SubLoops[i];
876 assert(Child->getParentLoop() == L && "Not proper child loop?");
878 if (LoopBase<BlockT> *ContainingLoop =
879 ContainingLoops[Child->getHeader()]) {
880 // If there is already a loop which contains this loop, move this loop
881 // into the containing loop.
882 MoveSiblingLoopInto(Child, ContainingLoop);
883 --i; // The loop got removed from the SubLoops list.
885 // This is currently considered to be a top-level loop. Check to see
886 // if any of the contained blocks are loop headers for subloops we
887 // have already processed.
888 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
889 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]];
890 if (BlockLoop == 0) { // Child block not processed yet...
892 } else if (BlockLoop != Child) {
893 LoopBase<BlockT> *SubLoop = BlockLoop;
894 // Reparent all of the blocks which used to belong to BlockLoops
895 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
896 ContainingLoops[SubLoop->Blocks[j]] = Child;
898 // There is already a loop which contains this block, that means
899 // that we should reparent the loop which the block is currently
900 // considered to belong to to be a child of this loop.
901 MoveSiblingLoopInto(SubLoop, Child);
902 --i; // We just shrunk the SubLoops list.
912 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
913 /// of the NewParent Loop, instead of being a sibling of it.
914 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild,
915 LoopBase<BlockT> *NewParent) {
916 LoopBase<BlockT> *OldParent = NewChild->getParentLoop();
917 assert(OldParent && OldParent == NewParent->getParentLoop() &&
918 NewChild != NewParent && "Not sibling loops!");
920 // Remove NewChild from being a child of OldParent
921 typename std::vector<LoopBase<BlockT>*>::iterator I =
922 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
924 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
925 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
926 NewChild->ParentLoop = 0;
928 InsertLoopInto(NewChild, NewParent);
931 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
932 /// the parent loop contains a loop which should contain L, the loop gets
933 /// inserted into L instead.
934 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) {
935 BlockT *LHeader = L->getHeader();
936 assert(Parent->contains(LHeader) &&
937 "This loop should not be inserted here!");
939 // Check to see if it belongs in a child loop...
940 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
942 if (Parent->SubLoops[i]->contains(LHeader)) {
943 InsertLoopInto(L, Parent->SubLoops[i]);
947 // If not, insert it here!
948 Parent->SubLoops.push_back(L);
949 L->ParentLoop = Parent;
954 void print(std::ostream &OS, const Module* ) const {
955 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
956 TopLevelLoops[i]->print(OS);
958 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
959 E = BBMap.end(); I != E; ++I)
960 OS << "BB '" << I->first->getName() << "' level = "
961 << I->second->getLoopDepth() << "\n";
966 class LoopInfo : public FunctionPass {
967 LoopInfoBase<BasicBlock> LI;
968 friend class LoopBase<BasicBlock>;
970 void operator=(const LoopInfo &); // do not implement
971 LoopInfo(const LoopInfo &); // do not implement
973 static char ID; // Pass identification, replacement for typeid
975 LoopInfo() : FunctionPass(&ID) {}
977 LoopInfoBase<BasicBlock>& getBase() { return LI; }
979 /// iterator/begin/end - The interface to the top-level loops in the current
982 typedef LoopInfoBase<BasicBlock>::iterator iterator;
983 inline iterator begin() const { return LI.begin(); }
984 inline iterator end() const { return LI.end(); }
985 bool empty() const { return LI.empty(); }
987 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
988 /// block is in no loop (for example the entry node), null is returned.
990 inline Loop *getLoopFor(const BasicBlock *BB) const {
991 return LI.getLoopFor(BB);
994 /// operator[] - same as getLoopFor...
996 inline const Loop *operator[](const BasicBlock *BB) const {
997 return LI.getLoopFor(BB);
1000 /// getLoopDepth - Return the loop nesting level of the specified block. A
1001 /// depth of 0 means the block is not inside any loop.
1003 inline unsigned getLoopDepth(const BasicBlock *BB) const {
1004 return LI.getLoopDepth(BB);
1007 // isLoopHeader - True if the block is a loop header node
1008 inline bool isLoopHeader(BasicBlock *BB) const {
1009 return LI.isLoopHeader(BB);
1012 /// runOnFunction - Calculate the natural loop information.
1014 virtual bool runOnFunction(Function &F);
1016 virtual void releaseMemory() { LI.releaseMemory(); }
1018 virtual void print(std::ostream &O, const Module* M = 0) const {
1022 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
1024 /// removeLoop - This removes the specified top-level loop from this loop info
1025 /// object. The loop is not deleted, as it will presumably be inserted into
1027 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
1029 /// changeLoopFor - Change the top-level loop that contains BB to the
1030 /// specified loop. This should be used by transformations that restructure
1031 /// the loop hierarchy tree.
1032 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
1033 LI.changeLoopFor(BB, L);
1036 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
1037 /// list with the indicated loop.
1038 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1039 LI.changeTopLevelLoop(OldLoop, NewLoop);
1042 /// addTopLevelLoop - This adds the specified loop to the collection of
1043 /// top-level loops.
1044 inline void addTopLevelLoop(Loop *New) {
1045 LI.addTopLevelLoop(New);
1048 /// removeBlock - This method completely removes BB from all data structures,
1049 /// including all of the Loop objects it is nested in and our mapping from
1050 /// BasicBlocks to loops.
1051 void removeBlock(BasicBlock *BB) {
1057 // Allow clients to walk the list of nested loops...
1058 template <> struct GraphTraits<const Loop*> {
1059 typedef const Loop NodeType;
1060 typedef LoopInfo::iterator ChildIteratorType;
1062 static NodeType *getEntryNode(const Loop *L) { return L; }
1063 static inline ChildIteratorType child_begin(NodeType *N) {
1066 static inline ChildIteratorType child_end(NodeType *N) {
1071 template <> struct GraphTraits<Loop*> {
1072 typedef Loop NodeType;
1073 typedef LoopInfo::iterator ChildIteratorType;
1075 static NodeType *getEntryNode(Loop *L) { return L; }
1076 static inline ChildIteratorType child_begin(NodeType *N) {
1079 static inline ChildIteratorType child_end(NodeType *N) {
1084 template<class BlockT>
1085 void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB,
1086 LoopInfoBase<BlockT> &LIB) {
1087 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1088 "Incorrect LI specified for this loop!");
1089 assert(NewBB && "Cannot add a null basic block to the loop!");
1090 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1092 // Add the loop mapping to the LoopInfo object...
1093 LIB.BBMap[NewBB] = this;
1095 // Add the basic block to this loop and all parent loops...
1096 LoopBase<BlockT> *L = this;
1098 L->Blocks.push_back(NewBB);
1099 L = L->getParentLoop();
1103 } // End llvm namespace