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 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
217 /// These are the blocks _outside of the current loop_ which are branched to.
218 /// This assumes that loop is in canonical form.
220 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
221 // Sort the blocks vector so that we can use binary search to do quick
223 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
224 std::sort(LoopBBs.begin(), LoopBBs.end());
226 std::vector<BlockT*> switchExitBlocks;
228 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
230 BlockT *current = *BI;
231 switchExitBlocks.clear();
233 typedef GraphTraits<BlockT*> BlockTraits;
234 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
235 for (typename BlockTraits::ChildIteratorType I =
236 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
238 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
239 // If block is inside the loop then it is not a exit block.
242 typename InvBlockTraits::ChildIteratorType PI =
243 InvBlockTraits::child_begin(*I);
244 BlockT *firstPred = *PI;
246 // If current basic block is this exit block's first predecessor
247 // then only insert exit block in to the output ExitBlocks vector.
248 // This ensures that same exit block is not inserted twice into
249 // ExitBlocks vector.
250 if (current != firstPred)
253 // If a terminator has more then two successors, for example SwitchInst,
254 // then it is possible that there are multiple edges from current block
255 // to one exit block.
256 if (std::distance(BlockTraits::child_begin(current),
257 BlockTraits::child_end(current)) <= 2) {
258 ExitBlocks.push_back(*I);
262 // In case of multiple edges from current block to exit block, collect
263 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
265 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
266 == switchExitBlocks.end()) {
267 switchExitBlocks.push_back(*I);
268 ExitBlocks.push_back(*I);
274 /// getLoopPreheader - If there is a preheader for this loop, return it. A
275 /// loop has a preheader if there is only one edge to the header of the loop
276 /// from outside of the loop. If this is the case, the block branching to the
277 /// header of the loop is the preheader node.
279 /// This method returns null if there is no preheader for the loop.
281 BlockT *getLoopPreheader() const {
282 // Keep track of nodes outside the loop branching to the header...
285 // Loop over the predecessors of the header node...
286 BlockT *Header = getHeader();
287 typedef GraphTraits<BlockT*> BlockTraits;
288 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
289 for (typename InvBlockTraits::ChildIteratorType PI =
290 InvBlockTraits::child_begin(Header),
291 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
292 if (!contains(*PI)) { // If the block is not in the loop...
293 if (Out && Out != *PI)
294 return 0; // Multiple predecessors outside the loop
298 // Make sure there is only one exit out of the preheader.
299 assert(Out && "Header of loop has no predecessors from outside loop?");
300 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
302 if (SI != BlockTraits::child_end(Out))
303 return 0; // Multiple exits from the block, must not be a preheader.
305 // If there is exactly one preheader, return it. If there was zero, then
306 // Out is still null.
310 /// getLoopLatch - If there is a single latch block for this loop, return it.
311 /// A latch block is a block that contains a branch back to the header.
312 /// A loop header in normal form has two edges into it: one from a preheader
313 /// and one from a latch block.
314 BlockT *getLoopLatch() const {
315 BlockT *Header = getHeader();
316 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
317 typename InvBlockTraits::ChildIteratorType PI =
318 InvBlockTraits::child_begin(Header);
319 typename InvBlockTraits::ChildIteratorType PE =
320 InvBlockTraits::child_end(Header);
321 if (PI == PE) return 0; // no preds?
327 if (PI == PE) return 0; // only one pred?
330 if (Latch) return 0; // multiple backedges
334 if (PI != PE) return 0; // more than two preds
339 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
340 /// induction variable: an integer recurrence that starts at 0 and increments
341 /// by one each time through the loop. If so, return the phi node that
342 /// corresponds to it.
344 inline PHINode *getCanonicalInductionVariable() const {
345 BlockT *H = getHeader();
347 BlockT *Incoming = 0, *Backedge = 0;
348 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
349 typename InvBlockTraits::ChildIteratorType PI =
350 InvBlockTraits::child_begin(H);
351 assert(PI != InvBlockTraits::child_end(H) &&
352 "Loop must have at least one backedge!");
354 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop
356 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges?
358 if (contains(Incoming)) {
359 if (contains(Backedge))
361 std::swap(Incoming, Backedge);
362 } else if (!contains(Backedge))
365 // Loop over all of the PHI nodes, looking for a canonical indvar.
366 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) {
367 PHINode *PN = cast<PHINode>(I);
368 if (ConstantInt *CI =
369 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
370 if (CI->isNullValue())
371 if (Instruction *Inc =
372 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
373 if (Inc->getOpcode() == Instruction::Add &&
374 Inc->getOperand(0) == PN)
375 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
376 if (CI->equalsInt(1))
382 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
383 /// the canonical induction variable value for the "next" iteration of the
384 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
386 inline Instruction *getCanonicalInductionVariableIncrement() const {
387 if (PHINode *PN = getCanonicalInductionVariable()) {
388 bool P1InLoop = contains(PN->getIncomingBlock(1));
389 return cast<Instruction>(PN->getIncomingValue(P1InLoop));
394 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
395 /// times the loop will be executed. Note that this means that the backedge
396 /// of the loop executes N-1 times. If the trip-count cannot be determined,
397 /// this returns null.
399 inline Value *getTripCount() const {
400 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented
401 // canonical induction variable and V is the trip count of the loop.
402 Instruction *Inc = getCanonicalInductionVariableIncrement();
403 if (Inc == 0) return 0;
404 PHINode *IV = cast<PHINode>(Inc->getOperand(0));
406 BlockT *BackedgeBlock =
407 IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
409 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
410 if (BI->isConditional()) {
411 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
412 if (ICI->getOperand(0) == Inc) {
413 if (BI->getSuccessor(0) == getHeader()) {
414 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
415 return ICI->getOperand(1);
416 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
417 return ICI->getOperand(1);
426 /// getSmallConstantTripCount - Returns the trip count of this loop as a
427 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
428 /// of not constant. Will also return 0 if the trip count is very large
430 inline unsigned getSmallConstantTripCount() const {
431 Value* TripCount = this->getTripCount();
433 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
434 // Guard against huge trip counts.
435 if (TripCountC->getValue().getActiveBits() <= 32) {
436 return (unsigned)TripCountC->getZExtValue();
443 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
444 /// trip count of this loop as a normal unsigned value, if possible. This
445 /// means that the actual trip count is always a multiple of the returned
446 /// value (don't forget the trip count could very well be zero as well!).
448 /// Returns 1 if the trip count is unknown or not guaranteed to be the
449 /// multiple of a constant (which is also the case if the trip count is simply
450 /// constant, use getSmallConstantTripCount for that case), Will also return 1
451 /// if the trip count is very large (>= 2^32).
452 inline unsigned getSmallConstantTripMultiple() const {
453 Value* TripCount = this->getTripCount();
454 // This will hold the ConstantInt result, if any
455 ConstantInt *Result = NULL;
457 // See if the trip count is constant itself
458 Result = dyn_cast<ConstantInt>(TripCount);
459 // if not, see if it is a multiplication
461 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
462 switch (BO->getOpcode()) {
463 case BinaryOperator::Mul:
464 Result = dyn_cast<ConstantInt>(BO->getOperand(1));
471 // Guard against huge trip counts.
472 if (Result && Result->getValue().getActiveBits() <= 32) {
473 return (unsigned)Result->getZExtValue();
479 /// isLCSSAForm - Return true if the Loop is in LCSSA form
480 inline bool isLCSSAForm() const {
481 // Sort the blocks vector so that we can use binary search to do quick
483 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end());
485 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
487 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I)
488 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
490 BlockT *UserBB = cast<Instruction>(*UI)->getParent();
491 if (PHINode *P = dyn_cast<PHINode>(*UI)) {
492 UserBB = P->getIncomingBlock(UI);
495 // Check the current block, as a fast-path. Most values are used in
496 // the same block they are defined in.
497 if (UserBB != BB && !LoopBBs.count(UserBB))
505 //===--------------------------------------------------------------------===//
506 // APIs for updating loop information after changing the CFG
509 /// addBasicBlockToLoop - This method is used by other analyses to update loop
510 /// information. NewBB is set to be a new member of the current loop.
511 /// Because of this, it is added as a member of all parent loops, and is added
512 /// to the specified LoopInfo object as being in the current basic block. It
513 /// is not valid to replace the loop header with this method.
515 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI);
517 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
518 /// the OldChild entry in our children list with NewChild, and updates the
519 /// parent pointer of OldChild to be null and the NewChild to be this loop.
520 /// This updates the loop depth of the new child.
521 void replaceChildLoopWith(LoopBase<BlockT> *OldChild,
522 LoopBase<BlockT> *NewChild) {
523 assert(OldChild->ParentLoop == this && "This loop is already broken!");
524 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
525 typename std::vector<LoopBase<BlockT>*>::iterator I =
526 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
527 assert(I != SubLoops.end() && "OldChild not in loop!");
529 OldChild->ParentLoop = 0;
530 NewChild->ParentLoop = this;
533 /// addChildLoop - Add the specified loop to be a child of this loop. This
534 /// updates the loop depth of the new child.
536 void addChildLoop(LoopBase<BlockT> *NewChild) {
537 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
538 NewChild->ParentLoop = this;
539 SubLoops.push_back(NewChild);
542 /// removeChildLoop - This removes the specified child from being a subloop of
543 /// this loop. The loop is not deleted, as it will presumably be inserted
544 /// into another loop.
545 LoopBase<BlockT> *removeChildLoop(iterator I) {
546 assert(I != SubLoops.end() && "Cannot remove end iterator!");
547 LoopBase<BlockT> *Child = *I;
548 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
549 SubLoops.erase(SubLoops.begin()+(I-begin()));
550 Child->ParentLoop = 0;
554 /// addBlockEntry - This adds a basic block directly to the basic block list.
555 /// This should only be used by transformations that create new loops. Other
556 /// transformations should use addBasicBlockToLoop.
557 void addBlockEntry(BlockT *BB) {
558 Blocks.push_back(BB);
561 /// moveToHeader - This method is used to move BB (which must be part of this
562 /// loop) to be the loop header of the loop (the block that dominates all
564 void moveToHeader(BlockT *BB) {
565 if (Blocks[0] == BB) return;
566 for (unsigned i = 0; ; ++i) {
567 assert(i != Blocks.size() && "Loop does not contain BB!");
568 if (Blocks[i] == BB) {
569 Blocks[i] = Blocks[0];
576 /// removeBlockFromLoop - This removes the specified basic block from the
577 /// current loop, updating the Blocks as appropriate. This does not update
578 /// the mapping in the LoopInfo class.
579 void removeBlockFromLoop(BlockT *BB) {
580 RemoveFromVector(Blocks, BB);
583 /// verifyLoop - Verify loop structure
584 void verifyLoop() const {
586 assert (getHeader() && "Loop header is missing");
587 assert (getLoopPreheader() && "Loop preheader is missing");
588 assert (getLoopLatch() && "Loop latch is missing");
589 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
594 void print(std::ostream &OS, unsigned Depth = 0) const {
595 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth()
598 for (unsigned i = 0; i < getBlocks().size(); ++i) {
600 BlockT *BB = getBlocks()[i];
601 WriteAsOperand(OS, BB, false);
602 if (BB == getHeader()) OS << "<header>";
603 if (BB == getLoopLatch()) OS << "<latch>";
604 if (isLoopExit(BB)) OS << "<exit>";
608 for (iterator I = begin(), E = end(); I != E; ++I)
609 (*I)->print(OS, Depth+2);
612 void print(std::ostream *O, unsigned Depth = 0) const {
613 if (O) print(*O, Depth);
621 friend class LoopInfoBase<BlockT>;
622 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
623 Blocks.push_back(BB);
628 //===----------------------------------------------------------------------===//
629 /// LoopInfo - This class builds and contains all of the top level loop
630 /// structures in the specified function.
633 template<class BlockT>
635 // BBMap - Mapping of basic blocks to the inner most loop they occur in
636 std::map<BlockT*, LoopBase<BlockT>*> BBMap;
637 std::vector<LoopBase<BlockT>*> TopLevelLoops;
638 friend class LoopBase<BlockT>;
642 ~LoopInfoBase() { releaseMemory(); }
644 void releaseMemory() {
645 for (typename std::vector<LoopBase<BlockT>* >::iterator I =
646 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
647 delete *I; // Delete all of the loops...
649 BBMap.clear(); // Reset internal state of analysis
650 TopLevelLoops.clear();
653 /// iterator/begin/end - The interface to the top-level loops in the current
656 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
657 iterator begin() const { return TopLevelLoops.begin(); }
658 iterator end() const { return TopLevelLoops.end(); }
659 bool empty() const { return TopLevelLoops.empty(); }
661 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
662 /// block is in no loop (for example the entry node), null is returned.
664 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const {
665 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I=
666 BBMap.find(const_cast<BlockT*>(BB));
667 return I != BBMap.end() ? I->second : 0;
670 /// operator[] - same as getLoopFor...
672 const LoopBase<BlockT> *operator[](const BlockT *BB) const {
673 return getLoopFor(BB);
676 /// getLoopDepth - Return the loop nesting level of the specified block. A
677 /// depth of 0 means the block is not inside any loop.
679 unsigned getLoopDepth(const BlockT *BB) const {
680 const LoopBase<BlockT> *L = getLoopFor(BB);
681 return L ? L->getLoopDepth() : 0;
684 // isLoopHeader - True if the block is a loop header node
685 bool isLoopHeader(BlockT *BB) const {
686 const LoopBase<BlockT> *L = getLoopFor(BB);
687 return L && L->getHeader() == BB;
690 /// removeLoop - This removes the specified top-level loop from this loop info
691 /// object. The loop is not deleted, as it will presumably be inserted into
693 LoopBase<BlockT> *removeLoop(iterator I) {
694 assert(I != end() && "Cannot remove end iterator!");
695 LoopBase<BlockT> *L = *I;
696 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
697 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
701 /// changeLoopFor - Change the top-level loop that contains BB to the
702 /// specified loop. This should be used by transformations that restructure
703 /// the loop hierarchy tree.
704 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) {
705 LoopBase<BlockT> *&OldLoop = BBMap[BB];
706 assert(OldLoop && "Block not in a loop yet!");
710 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
711 /// list with the indicated loop.
712 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop,
713 LoopBase<BlockT> *NewLoop) {
714 typename std::vector<LoopBase<BlockT>*>::iterator I =
715 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
716 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
718 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
719 "Loops already embedded into a subloop!");
722 /// addTopLevelLoop - This adds the specified loop to the collection of
724 void addTopLevelLoop(LoopBase<BlockT> *New) {
725 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
726 TopLevelLoops.push_back(New);
729 /// removeBlock - This method completely removes BB from all data structures,
730 /// including all of the Loop objects it is nested in and our mapping from
731 /// BasicBlocks to loops.
732 void removeBlock(BlockT *BB) {
733 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB);
734 if (I != BBMap.end()) {
735 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop())
736 L->removeBlockFromLoop(BB);
744 static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop,
745 const LoopBase<BlockT> *ParentLoop) {
746 if (SubLoop == 0) return true;
747 if (SubLoop == ParentLoop) return false;
748 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
751 void Calculate(DominatorTreeBase<BlockT> &DT) {
752 BlockT *RootNode = DT.getRootNode()->getBlock();
754 for (df_iterator<BlockT*> NI = df_begin(RootNode),
755 NE = df_end(RootNode); NI != NE; ++NI)
756 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT))
757 TopLevelLoops.push_back(L);
760 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
761 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
763 std::vector<BlockT *> TodoStack;
765 // Scan the predecessors of BB, checking to see if BB dominates any of
766 // them. This identifies backedges which target this node...
767 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
768 for (typename InvBlockTraits::ChildIteratorType I =
769 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
771 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
772 TodoStack.push_back(*I);
774 if (TodoStack.empty()) return 0; // No backedges to this block...
776 // Create a new loop to represent this basic block...
777 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB);
780 BlockT *EntryBlock = BB->getParent()->begin();
782 while (!TodoStack.empty()) { // Process all the nodes in the loop
783 BlockT *X = TodoStack.back();
784 TodoStack.pop_back();
786 if (!L->contains(X) && // As of yet unprocessed??
787 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
788 // Check to see if this block already belongs to a loop. If this occurs
789 // then we have a case where a loop that is supposed to be a child of
790 // the current loop was processed before the current loop. When this
791 // occurs, this child loop gets added to a part of the current loop,
792 // making it a sibling to the current loop. We have to reparent this
794 if (LoopBase<BlockT> *SubLoop =
795 const_cast<LoopBase<BlockT>*>(getLoopFor(X)))
796 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
797 // Remove the subloop from it's current parent...
798 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
799 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent
800 typename std::vector<LoopBase<BlockT>*>::iterator I =
801 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
802 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
803 SLP->SubLoops.erase(I); // Remove from parent...
805 // Add the subloop to THIS loop...
806 SubLoop->ParentLoop = L;
807 L->SubLoops.push_back(SubLoop);
810 // Normal case, add the block to our loop...
811 L->Blocks.push_back(X);
813 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
815 // Add all of the predecessors of X to the end of the work stack...
816 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
817 InvBlockTraits::child_end(X));
821 // If there are any loops nested within this loop, create them now!
822 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
823 E = L->Blocks.end(); I != E; ++I)
824 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) {
825 L->SubLoops.push_back(NewLoop);
826 NewLoop->ParentLoop = L;
829 // Add the basic blocks that comprise this loop to the BBMap so that this
830 // loop can be found for them.
832 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
833 E = L->Blocks.end(); I != E; ++I) {
834 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI =
836 if (BBMI == BBMap.end()) // Not in map yet...
837 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
840 // Now that we have a list of all of the child loops of this loop, check to
841 // see if any of them should actually be nested inside of each other. We
842 // can accidentally pull loops our of their parents, so we must make sure to
843 // organize the loop nests correctly now.
845 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops;
846 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
847 LoopBase<BlockT> *Child = L->SubLoops[i];
848 assert(Child->getParentLoop() == L && "Not proper child loop?");
850 if (LoopBase<BlockT> *ContainingLoop =
851 ContainingLoops[Child->getHeader()]) {
852 // If there is already a loop which contains this loop, move this loop
853 // into the containing loop.
854 MoveSiblingLoopInto(Child, ContainingLoop);
855 --i; // The loop got removed from the SubLoops list.
857 // This is currently considered to be a top-level loop. Check to see
858 // if any of the contained blocks are loop headers for subloops we
859 // have already processed.
860 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
861 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]];
862 if (BlockLoop == 0) { // Child block not processed yet...
864 } else if (BlockLoop != Child) {
865 LoopBase<BlockT> *SubLoop = BlockLoop;
866 // Reparent all of the blocks which used to belong to BlockLoops
867 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
868 ContainingLoops[SubLoop->Blocks[j]] = Child;
870 // There is already a loop which contains this block, that means
871 // that we should reparent the loop which the block is currently
872 // considered to belong to to be a child of this loop.
873 MoveSiblingLoopInto(SubLoop, Child);
874 --i; // We just shrunk the SubLoops list.
884 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
885 /// of the NewParent Loop, instead of being a sibling of it.
886 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild,
887 LoopBase<BlockT> *NewParent) {
888 LoopBase<BlockT> *OldParent = NewChild->getParentLoop();
889 assert(OldParent && OldParent == NewParent->getParentLoop() &&
890 NewChild != NewParent && "Not sibling loops!");
892 // Remove NewChild from being a child of OldParent
893 typename std::vector<LoopBase<BlockT>*>::iterator I =
894 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
896 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
897 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
898 NewChild->ParentLoop = 0;
900 InsertLoopInto(NewChild, NewParent);
903 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
904 /// the parent loop contains a loop which should contain L, the loop gets
905 /// inserted into L instead.
906 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) {
907 BlockT *LHeader = L->getHeader();
908 assert(Parent->contains(LHeader) &&
909 "This loop should not be inserted here!");
911 // Check to see if it belongs in a child loop...
912 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
914 if (Parent->SubLoops[i]->contains(LHeader)) {
915 InsertLoopInto(L, Parent->SubLoops[i]);
919 // If not, insert it here!
920 Parent->SubLoops.push_back(L);
921 L->ParentLoop = Parent;
926 void print(std::ostream &OS, const Module* ) const {
927 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
928 TopLevelLoops[i]->print(OS);
930 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
931 E = BBMap.end(); I != E; ++I)
932 OS << "BB '" << I->first->getName() << "' level = "
933 << I->second->getLoopDepth() << "\n";
938 class LoopInfo : public FunctionPass {
939 LoopInfoBase<BasicBlock>* LI;
940 friend class LoopBase<BasicBlock>;
943 static char ID; // Pass identification, replacement for typeid
945 LoopInfo() : FunctionPass(&ID) {
946 LI = new LoopInfoBase<BasicBlock>();
949 ~LoopInfo() { delete LI; }
951 LoopInfoBase<BasicBlock>& getBase() { return *LI; }
953 /// iterator/begin/end - The interface to the top-level loops in the current
956 typedef std::vector<Loop*>::const_iterator iterator;
957 inline iterator begin() const { return LI->begin(); }
958 inline iterator end() const { return LI->end(); }
959 bool empty() const { return LI->empty(); }
961 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
962 /// block is in no loop (for example the entry node), null is returned.
964 inline Loop *getLoopFor(const BasicBlock *BB) const {
965 return LI->getLoopFor(BB);
968 /// operator[] - same as getLoopFor...
970 inline const Loop *operator[](const BasicBlock *BB) const {
971 return LI->getLoopFor(BB);
974 /// getLoopDepth - Return the loop nesting level of the specified block. A
975 /// depth of 0 means the block is not inside any loop.
977 inline unsigned getLoopDepth(const BasicBlock *BB) const {
978 return LI->getLoopDepth(BB);
981 // isLoopHeader - True if the block is a loop header node
982 inline bool isLoopHeader(BasicBlock *BB) const {
983 return LI->isLoopHeader(BB);
986 /// runOnFunction - Calculate the natural loop information.
988 virtual bool runOnFunction(Function &F);
990 virtual void releaseMemory() { LI->releaseMemory(); }
992 virtual void print(std::ostream &O, const Module* M = 0) const {
993 if (O) LI->print(O, M);
996 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
998 /// removeLoop - This removes the specified top-level loop from this loop info
999 /// object. The loop is not deleted, as it will presumably be inserted into
1001 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); }
1003 /// changeLoopFor - Change the top-level loop that contains BB to the
1004 /// specified loop. This should be used by transformations that restructure
1005 /// the loop hierarchy tree.
1006 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
1007 LI->changeLoopFor(BB, L);
1010 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
1011 /// list with the indicated loop.
1012 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1013 LI->changeTopLevelLoop(OldLoop, NewLoop);
1016 /// addTopLevelLoop - This adds the specified loop to the collection of
1017 /// top-level loops.
1018 inline void addTopLevelLoop(Loop *New) {
1019 LI->addTopLevelLoop(New);
1022 /// removeBlock - This method completely removes BB from all data structures,
1023 /// including all of the Loop objects it is nested in and our mapping from
1024 /// BasicBlocks to loops.
1025 void removeBlock(BasicBlock *BB) {
1026 LI->removeBlock(BB);
1031 // Allow clients to walk the list of nested loops...
1032 template <> struct GraphTraits<const Loop*> {
1033 typedef const Loop NodeType;
1034 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
1036 static NodeType *getEntryNode(const Loop *L) { return L; }
1037 static inline ChildIteratorType child_begin(NodeType *N) {
1040 static inline ChildIteratorType child_end(NodeType *N) {
1045 template <> struct GraphTraits<Loop*> {
1046 typedef Loop NodeType;
1047 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
1049 static NodeType *getEntryNode(Loop *L) { return L; }
1050 static inline ChildIteratorType child_begin(NodeType *N) {
1053 static inline ChildIteratorType child_end(NodeType *N) {
1058 template<class BlockT>
1059 void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB,
1060 LoopInfoBase<BlockT> &LIB) {
1061 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1062 "Incorrect LI specified for this loop!");
1063 assert(NewBB && "Cannot add a null basic block to the loop!");
1064 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1066 // Add the loop mapping to the LoopInfo object...
1067 LIB.BBMap[NewBB] = this;
1069 // Add the basic block to this loop and all parent loops...
1070 LoopBase<BlockT> *L = this;
1072 L->Blocks.push_back(NewBB);
1073 L = L->getParentLoop();
1077 } // End llvm namespace