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"
47 static void RemoveFromVector(std::vector<T*> &V, T *N) {
48 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
49 assert(I != V.end() && "N is not in this list!");
59 template<class N> class LoopInfoBase;
60 template<class N> class LoopBase;
62 typedef LoopBase<BasicBlock> Loop;
64 //===----------------------------------------------------------------------===//
65 /// LoopBase class - Instances of this class are used to represent loops that
66 /// are detected in the flow graph
68 template<class BlockT>
70 LoopBase<BlockT> *ParentLoop;
71 // SubLoops - Loops contained entirely within this one.
72 std::vector<LoopBase<BlockT>*> SubLoops;
74 // Blocks - The list of blocks in this loop. First entry is the header node.
75 std::vector<BlockT*> Blocks;
77 LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT
78 const LoopBase<BlockT>&operator=(const LoopBase<BlockT> &);// DO NOT IMPLEMENT
80 /// Loop ctor - This creates an empty loop.
81 LoopBase() : ParentLoop(0) {}
83 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
87 /// getLoopDepth - Return the nesting level of this loop. An outer-most
88 /// loop has depth 1, for consistency with loop depth values used for basic
89 /// blocks, where depth 0 is used for blocks not inside any loops.
90 unsigned getLoopDepth() const {
92 for (const LoopBase<BlockT> *CurLoop = ParentLoop; CurLoop;
93 CurLoop = CurLoop->ParentLoop)
97 BlockT *getHeader() const { return Blocks.front(); }
98 LoopBase<BlockT> *getParentLoop() const { return ParentLoop; }
100 /// contains - Return true if the specified basic block is in this loop
102 bool contains(const BlockT *BB) const {
103 return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
106 /// iterator/begin/end - Return the loops contained entirely within this loop.
108 const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; }
109 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
110 iterator begin() const { return SubLoops.begin(); }
111 iterator end() const { return SubLoops.end(); }
112 bool empty() const { return SubLoops.empty(); }
114 /// getBlocks - Get a list of the basic blocks which make up this loop.
116 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
117 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
118 block_iterator block_begin() const { return Blocks.begin(); }
119 block_iterator block_end() const { return Blocks.end(); }
121 /// isLoopExit - True if terminator in the block can branch to another block
122 /// that is outside of the current loop.
124 bool isLoopExit(const BlockT *BB) const {
125 typedef GraphTraits<BlockT*> BlockTraits;
126 for (typename BlockTraits::ChildIteratorType SI =
127 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
128 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
135 /// getNumBackEdges - Calculate the number of back edges to the loop header
137 unsigned getNumBackEdges() const {
138 unsigned NumBackEdges = 0;
139 BlockT *H = getHeader();
141 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
142 for (typename InvBlockTraits::ChildIteratorType I =
143 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
144 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
151 /// isLoopInvariant - Return true if the specified value is loop invariant
153 inline bool isLoopInvariant(Value *V) const {
154 if (Instruction *I = dyn_cast<Instruction>(V))
155 return !contains(I->getParent());
156 return true; // All non-instructions are loop invariant
159 //===--------------------------------------------------------------------===//
160 // APIs for simple analysis of the loop.
162 // Note that all of these methods can fail on general loops (ie, there may not
163 // be a preheader, etc). For best success, the loop simplification and
164 // induction variable canonicalization pass should be used to normalize loops
165 // for easy analysis. These methods assume canonical loops.
167 /// getExitingBlocks - Return all blocks inside the loop that have successors
168 /// outside of the loop. These are the blocks _inside of the current loop_
169 /// which branch out. The returned list is always unique.
171 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
172 // Sort the blocks vector so that we can use binary search to do quick
174 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
175 std::sort(LoopBBs.begin(), LoopBBs.end());
177 typedef GraphTraits<BlockT*> BlockTraits;
178 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
179 BE = Blocks.end(); BI != BE; ++BI)
180 for (typename BlockTraits::ChildIteratorType I =
181 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
183 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
184 // Not in current loop? It must be an exit block.
185 ExitingBlocks.push_back(*BI);
190 /// getExitBlocks - Return all of the successor blocks of this loop. These
191 /// are the blocks _outside of the current loop_ which are branched to.
193 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
194 // Sort the blocks vector so that we can use binary search to do quick
196 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
197 std::sort(LoopBBs.begin(), LoopBBs.end());
199 typedef GraphTraits<BlockT*> BlockTraits;
200 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
201 BE = Blocks.end(); BI != BE; ++BI)
202 for (typename BlockTraits::ChildIteratorType I =
203 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
205 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
206 // Not in current loop? It must be an exit block.
207 ExitBlocks.push_back(*I);
210 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
211 /// These are the blocks _outside of the current loop_ which are branched to.
212 /// This assumes that loop is in canonical form.
214 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
215 // Sort the blocks vector so that we can use binary search to do quick
217 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
218 std::sort(LoopBBs.begin(), LoopBBs.end());
220 std::vector<BlockT*> switchExitBlocks;
222 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
223 BE = Blocks.end(); BI != BE; ++BI) {
225 BlockT *current = *BI;
226 switchExitBlocks.clear();
228 typedef GraphTraits<BlockT*> BlockTraits;
229 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
230 for (typename BlockTraits::ChildIteratorType I =
231 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
233 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
234 // If block is inside the loop then it is not a exit block.
237 typename InvBlockTraits::ChildIteratorType PI =
238 InvBlockTraits::child_begin(*I);
239 BlockT *firstPred = *PI;
241 // If current basic block is this exit block's first predecessor
242 // then only insert exit block in to the output ExitBlocks vector.
243 // This ensures that same exit block is not inserted twice into
244 // ExitBlocks vector.
245 if (current != firstPred)
248 // If a terminator has more then two successors, for example SwitchInst,
249 // then it is possible that there are multiple edges from current block
250 // to one exit block.
251 if (std::distance(BlockTraits::child_begin(current),
252 BlockTraits::child_end(current)) <= 2) {
253 ExitBlocks.push_back(*I);
257 // In case of multiple edges from current block to exit block, collect
258 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
260 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
261 == switchExitBlocks.end()) {
262 switchExitBlocks.push_back(*I);
263 ExitBlocks.push_back(*I);
269 /// getLoopPreheader - If there is a preheader for this loop, return it. A
270 /// loop has a preheader if there is only one edge to the header of the loop
271 /// from outside of the loop. If this is the case, the block branching to the
272 /// header of the loop is the preheader node.
274 /// This method returns null if there is no preheader for the loop.
276 BlockT *getLoopPreheader() const {
277 // Keep track of nodes outside the loop branching to the header...
280 // Loop over the predecessors of the header node...
281 BlockT *Header = getHeader();
282 typedef GraphTraits<BlockT*> BlockTraits;
283 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
284 for (typename InvBlockTraits::ChildIteratorType PI =
285 InvBlockTraits::child_begin(Header),
286 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
287 if (!contains(*PI)) { // If the block is not in the loop...
288 if (Out && Out != *PI)
289 return 0; // Multiple predecessors outside the loop
293 // Make sure there is only one exit out of the preheader.
294 assert(Out && "Header of loop has no predecessors from outside loop?");
295 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
297 if (SI != BlockTraits::child_end(Out))
298 return 0; // Multiple exits from the block, must not be a preheader.
300 // If there is exactly one preheader, return it. If there was zero, then
301 // Out is still null.
305 /// getLoopLatch - If there is a latch block for this loop, return it. A
306 /// latch block is the canonical backedge for a loop. A loop header in normal
307 /// form has two edges into it: one from a preheader and one from a latch
309 BlockT *getLoopLatch() const {
310 BlockT *Header = getHeader();
311 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
312 typename InvBlockTraits::ChildIteratorType PI =
313 InvBlockTraits::child_begin(Header);
314 typename InvBlockTraits::ChildIteratorType PE =
315 InvBlockTraits::child_end(Header);
316 if (PI == PE) return 0; // no preds?
322 if (PI == PE) return 0; // only one pred?
325 if (Latch) return 0; // multiple backedges
329 if (PI != PE) return 0; // more than two preds
334 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
335 /// induction variable: an integer recurrence that starts at 0 and increments
336 /// by one each time through the loop. If so, return the phi node that
337 /// corresponds to it.
339 inline PHINode *getCanonicalInductionVariable() const {
340 BlockT *H = getHeader();
342 BlockT *Incoming = 0, *Backedge = 0;
343 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
344 typename InvBlockTraits::ChildIteratorType PI =
345 InvBlockTraits::child_begin(H);
346 assert(PI != InvBlockTraits::child_end(H) &&
347 "Loop must have at least one backedge!");
349 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop
351 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges?
353 if (contains(Incoming)) {
354 if (contains(Backedge))
356 std::swap(Incoming, Backedge);
357 } else if (!contains(Backedge))
360 // Loop over all of the PHI nodes, looking for a canonical indvar.
361 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) {
362 PHINode *PN = cast<PHINode>(I);
363 if (Instruction *Inc =
364 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
365 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
366 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
367 if (CI->equalsInt(1))
373 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
374 /// the canonical induction variable value for the "next" iteration of the
375 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
377 inline Instruction *getCanonicalInductionVariableIncrement() const {
378 if (PHINode *PN = getCanonicalInductionVariable()) {
379 bool P1InLoop = contains(PN->getIncomingBlock(1));
380 return cast<Instruction>(PN->getIncomingValue(P1InLoop));
385 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
386 /// times the loop will be executed. Note that this means that the backedge
387 /// of the loop executes N-1 times. If the trip-count cannot be determined,
388 /// this returns null.
390 inline Value *getTripCount() const {
391 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented
392 // canonical induction variable and V is the trip count of the loop.
393 Instruction *Inc = getCanonicalInductionVariableIncrement();
394 if (Inc == 0) return 0;
395 PHINode *IV = cast<PHINode>(Inc->getOperand(0));
397 BlockT *BackedgeBlock =
398 IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
400 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
401 if (BI->isConditional()) {
402 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
403 if (ICI->getOperand(0) == Inc)
404 if (BI->getSuccessor(0) == getHeader()) {
405 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
406 return ICI->getOperand(1);
407 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
408 return ICI->getOperand(1);
416 /// isLCSSAForm - Return true if the Loop is in LCSSA form
417 inline bool isLCSSAForm() const {
418 // Sort the blocks vector so that we can use binary search to do quick
420 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end());
422 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
424 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I)
425 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
427 BlockT *UserBB = cast<Instruction>(*UI)->getParent();
428 if (PHINode *P = dyn_cast<PHINode>(*UI)) {
429 unsigned OperandNo = UI.getOperandNo();
430 UserBB = P->getIncomingBlock(OperandNo/2);
433 // Check the current block, as a fast-path. Most values are used in
434 // the same block they are defined in.
435 if (UserBB != BB && !LoopBBs.count(UserBB))
443 //===--------------------------------------------------------------------===//
444 // APIs for updating loop information after changing the CFG
447 /// addBasicBlockToLoop - This method is used by other analyses to update loop
448 /// information. NewBB is set to be a new member of the current loop.
449 /// Because of this, it is added as a member of all parent loops, and is added
450 /// to the specified LoopInfo object as being in the current basic block. It
451 /// is not valid to replace the loop header with this method.
453 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI);
455 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
456 /// the OldChild entry in our children list with NewChild, and updates the
457 /// parent pointer of OldChild to be null and the NewChild to be this loop.
458 /// This updates the loop depth of the new child.
459 void replaceChildLoopWith(LoopBase<BlockT> *OldChild,
460 LoopBase<BlockT> *NewChild) {
461 assert(OldChild->ParentLoop == this && "This loop is already broken!");
462 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
463 typename std::vector<LoopBase<BlockT>*>::iterator I =
464 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
465 assert(I != SubLoops.end() && "OldChild not in loop!");
467 OldChild->ParentLoop = 0;
468 NewChild->ParentLoop = this;
471 /// addChildLoop - Add the specified loop to be a child of this loop. This
472 /// updates the loop depth of the new child.
474 void addChildLoop(LoopBase<BlockT> *NewChild) {
475 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
476 NewChild->ParentLoop = this;
477 SubLoops.push_back(NewChild);
480 /// removeChildLoop - This removes the specified child from being a subloop of
481 /// this loop. The loop is not deleted, as it will presumably be inserted
482 /// into another loop.
483 LoopBase<BlockT> *removeChildLoop(iterator I) {
484 assert(I != SubLoops.end() && "Cannot remove end iterator!");
485 LoopBase<BlockT> *Child = *I;
486 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
487 SubLoops.erase(SubLoops.begin()+(I-begin()));
488 Child->ParentLoop = 0;
492 /// addBlockEntry - This adds a basic block directly to the basic block list.
493 /// This should only be used by transformations that create new loops. Other
494 /// transformations should use addBasicBlockToLoop.
495 void addBlockEntry(BlockT *BB) {
496 Blocks.push_back(BB);
499 /// moveToHeader - This method is used to move BB (which must be part of this
500 /// loop) to be the loop header of the loop (the block that dominates all
502 void moveToHeader(BlockT *BB) {
503 if (Blocks[0] == BB) return;
504 for (unsigned i = 0; ; ++i) {
505 assert(i != Blocks.size() && "Loop does not contain BB!");
506 if (Blocks[i] == BB) {
507 Blocks[i] = Blocks[0];
514 /// removeBlockFromLoop - This removes the specified basic block from the
515 /// current loop, updating the Blocks as appropriate. This does not update
516 /// the mapping in the LoopInfo class.
517 void removeBlockFromLoop(BlockT *BB) {
518 RemoveFromVector(Blocks, BB);
521 /// verifyLoop - Verify loop structure
522 void verifyLoop() const {
524 assert (getHeader() && "Loop header is missing");
525 assert (getLoopPreheader() && "Loop preheader is missing");
526 assert (getLoopLatch() && "Loop latch is missing");
527 for (typename std::vector<LoopBase<BlockT>*>::const_iterator I =
528 SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
533 void print(std::ostream &OS, unsigned Depth = 0) const {
534 OS << std::string(Depth*2, ' ') << "Loop Containing: ";
536 for (unsigned i = 0; i < getBlocks().size(); ++i) {
538 WriteAsOperand(OS, getBlocks()[i], false);
542 for (iterator I = begin(), E = end(); I != E; ++I)
543 (*I)->print(OS, Depth+2);
546 void print(std::ostream *O, unsigned Depth = 0) const {
547 if (O) print(*O, Depth);
555 friend class LoopInfoBase<BlockT>;
556 LoopBase(BlockT *BB) : ParentLoop(0) {
557 Blocks.push_back(BB);
562 //===----------------------------------------------------------------------===//
563 /// LoopInfo - This class builds and contains all of the top level loop
564 /// structures in the specified function.
567 template<class BlockT>
569 // BBMap - Mapping of basic blocks to the inner most loop they occur in
570 std::map<BlockT*, LoopBase<BlockT>*> BBMap;
571 std::vector<LoopBase<BlockT>*> TopLevelLoops;
572 friend class LoopBase<BlockT>;
576 ~LoopInfoBase() { releaseMemory(); }
578 void releaseMemory() {
579 for (typename std::vector<LoopBase<BlockT>* >::iterator I =
580 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
581 delete *I; // Delete all of the loops...
583 BBMap.clear(); // Reset internal state of analysis
584 TopLevelLoops.clear();
587 /// iterator/begin/end - The interface to the top-level loops in the current
590 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator;
591 iterator begin() const { return TopLevelLoops.begin(); }
592 iterator end() const { return TopLevelLoops.end(); }
594 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
595 /// block is in no loop (for example the entry node), null is returned.
597 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const {
598 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I=
599 BBMap.find(const_cast<BlockT*>(BB));
600 return I != BBMap.end() ? I->second : 0;
603 /// operator[] - same as getLoopFor...
605 const LoopBase<BlockT> *operator[](const BlockT *BB) const {
606 return getLoopFor(BB);
609 /// getLoopDepth - Return the loop nesting level of the specified block. A
610 /// depth of 0 means the block is not inside any loop.
612 unsigned getLoopDepth(const BlockT *BB) const {
613 const LoopBase<BlockT> *L = getLoopFor(BB);
614 return L ? L->getLoopDepth() : 0;
617 // isLoopHeader - True if the block is a loop header node
618 bool isLoopHeader(BlockT *BB) const {
619 const LoopBase<BlockT> *L = getLoopFor(BB);
620 return L && L->getHeader() == BB;
623 /// removeLoop - This removes the specified top-level loop from this loop info
624 /// object. The loop is not deleted, as it will presumably be inserted into
626 LoopBase<BlockT> *removeLoop(iterator I) {
627 assert(I != end() && "Cannot remove end iterator!");
628 LoopBase<BlockT> *L = *I;
629 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
630 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
634 /// changeLoopFor - Change the top-level loop that contains BB to the
635 /// specified loop. This should be used by transformations that restructure
636 /// the loop hierarchy tree.
637 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) {
638 LoopBase<BlockT> *&OldLoop = BBMap[BB];
639 assert(OldLoop && "Block not in a loop yet!");
643 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
644 /// list with the indicated loop.
645 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop,
646 LoopBase<BlockT> *NewLoop) {
647 typename std::vector<LoopBase<BlockT>*>::iterator I =
648 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
649 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
651 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
652 "Loops already embedded into a subloop!");
655 /// addTopLevelLoop - This adds the specified loop to the collection of
657 void addTopLevelLoop(LoopBase<BlockT> *New) {
658 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
659 TopLevelLoops.push_back(New);
662 /// removeBlock - This method completely removes BB from all data structures,
663 /// including all of the Loop objects it is nested in and our mapping from
664 /// BasicBlocks to loops.
665 void removeBlock(BlockT *BB) {
666 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB);
667 if (I != BBMap.end()) {
668 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop())
669 L->removeBlockFromLoop(BB);
677 static bool isNotAlreadyContainedIn(LoopBase<BlockT> *SubLoop,
678 LoopBase<BlockT> *ParentLoop) {
679 if (SubLoop == 0) return true;
680 if (SubLoop == ParentLoop) return false;
681 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
684 void Calculate(DominatorTreeBase<BlockT> &DT) {
685 BlockT *RootNode = DT.getRootNode()->getBlock();
687 for (df_iterator<BlockT*> NI = df_begin(RootNode),
688 NE = df_end(RootNode); NI != NE; ++NI)
689 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT))
690 TopLevelLoops.push_back(L);
693 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
694 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
696 std::vector<BlockT *> TodoStack;
698 // Scan the predecessors of BB, checking to see if BB dominates any of
699 // them. This identifies backedges which target this node...
700 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
701 for (typename InvBlockTraits::ChildIteratorType I =
702 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
704 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
705 TodoStack.push_back(*I);
707 if (TodoStack.empty()) return 0; // No backedges to this block...
709 // Create a new loop to represent this basic block...
710 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB);
713 BlockT *EntryBlock = BB->getParent()->begin();
715 while (!TodoStack.empty()) { // Process all the nodes in the loop
716 BlockT *X = TodoStack.back();
717 TodoStack.pop_back();
719 if (!L->contains(X) && // As of yet unprocessed??
720 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
721 // Check to see if this block already belongs to a loop. If this occurs
722 // then we have a case where a loop that is supposed to be a child of
723 // the current loop was processed before the current loop. When this
724 // occurs, this child loop gets added to a part of the current loop,
725 // making it a sibling to the current loop. We have to reparent this
727 if (LoopBase<BlockT> *SubLoop =
728 const_cast<LoopBase<BlockT>*>(getLoopFor(X)))
729 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
730 // Remove the subloop from it's current parent...
731 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
732 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent
733 typename std::vector<LoopBase<BlockT>*>::iterator I =
734 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
735 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
736 SLP->SubLoops.erase(I); // Remove from parent...
738 // Add the subloop to THIS loop...
739 SubLoop->ParentLoop = L;
740 L->SubLoops.push_back(SubLoop);
743 // Normal case, add the block to our loop...
744 L->Blocks.push_back(X);
746 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
748 // Add all of the predecessors of X to the end of the work stack...
749 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
750 InvBlockTraits::child_end(X));
754 // If there are any loops nested within this loop, create them now!
755 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
756 E = L->Blocks.end(); I != E; ++I)
757 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) {
758 L->SubLoops.push_back(NewLoop);
759 NewLoop->ParentLoop = L;
762 // Add the basic blocks that comprise this loop to the BBMap so that this
763 // loop can be found for them.
765 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
766 E = L->Blocks.end(); I != E; ++I) {
767 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI =
768 BBMap.lower_bound(*I);
769 if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet...
770 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
773 // Now that we have a list of all of the child loops of this loop, check to
774 // see if any of them should actually be nested inside of each other. We
775 // can accidentally pull loops our of their parents, so we must make sure to
776 // organize the loop nests correctly now.
778 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops;
779 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
780 LoopBase<BlockT> *Child = L->SubLoops[i];
781 assert(Child->getParentLoop() == L && "Not proper child loop?");
783 if (LoopBase<BlockT> *ContainingLoop =
784 ContainingLoops[Child->getHeader()]) {
785 // If there is already a loop which contains this loop, move this loop
786 // into the containing loop.
787 MoveSiblingLoopInto(Child, ContainingLoop);
788 --i; // The loop got removed from the SubLoops list.
790 // This is currently considered to be a top-level loop. Check to see
791 // if any of the contained blocks are loop headers for subloops we
792 // have already processed.
793 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
794 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]];
795 if (BlockLoop == 0) { // Child block not processed yet...
797 } else if (BlockLoop != Child) {
798 LoopBase<BlockT> *SubLoop = BlockLoop;
799 // Reparent all of the blocks which used to belong to BlockLoops
800 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
801 ContainingLoops[SubLoop->Blocks[j]] = Child;
803 // There is already a loop which contains this block, that means
804 // that we should reparent the loop which the block is currently
805 // considered to belong to to be a child of this loop.
806 MoveSiblingLoopInto(SubLoop, Child);
807 --i; // We just shrunk the SubLoops list.
817 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
818 /// of the NewParent Loop, instead of being a sibling of it.
819 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild,
820 LoopBase<BlockT> *NewParent) {
821 LoopBase<BlockT> *OldParent = NewChild->getParentLoop();
822 assert(OldParent && OldParent == NewParent->getParentLoop() &&
823 NewChild != NewParent && "Not sibling loops!");
825 // Remove NewChild from being a child of OldParent
826 typename std::vector<LoopBase<BlockT>*>::iterator I =
827 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
829 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
830 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
831 NewChild->ParentLoop = 0;
833 InsertLoopInto(NewChild, NewParent);
836 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
837 /// the parent loop contains a loop which should contain L, the loop gets
838 /// inserted into L instead.
839 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) {
840 BlockT *LHeader = L->getHeader();
841 assert(Parent->contains(LHeader) &&
842 "This loop should not be inserted here!");
844 // Check to see if it belongs in a child loop...
845 for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i)
846 if (Parent->SubLoops[i]->contains(LHeader)) {
847 InsertLoopInto(L, Parent->SubLoops[i]);
851 // If not, insert it here!
852 Parent->SubLoops.push_back(L);
853 L->ParentLoop = Parent;
858 void print(std::ostream &OS, const Module* ) const {
859 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
860 TopLevelLoops[i]->print(OS);
862 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
863 E = BBMap.end(); I != E; ++I)
864 OS << "BB '" << I->first->getName() << "' level = "
865 << I->second->getLoopDepth() << "\n";
870 class LoopInfo : public FunctionPass {
871 LoopInfoBase<BasicBlock>* LI;
872 friend class LoopBase<BasicBlock>;
875 static char ID; // Pass identification, replacement for typeid
877 LoopInfo() : FunctionPass(intptr_t(&ID)) {
878 LI = new LoopInfoBase<BasicBlock>();
881 ~LoopInfo() { delete LI; }
883 LoopInfoBase<BasicBlock>& getBase() { return *LI; }
885 /// iterator/begin/end - The interface to the top-level loops in the current
888 typedef std::vector<Loop*>::const_iterator iterator;
889 inline iterator begin() const { return LI->begin(); }
890 inline iterator end() const { return LI->end(); }
892 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
893 /// block is in no loop (for example the entry node), null is returned.
895 inline Loop *getLoopFor(const BasicBlock *BB) const {
896 return LI->getLoopFor(BB);
899 /// operator[] - same as getLoopFor...
901 inline const Loop *operator[](const BasicBlock *BB) const {
902 return LI->getLoopFor(BB);
905 /// getLoopDepth - Return the loop nesting level of the specified block. A
906 /// depth of 0 means the block is not inside any loop.
908 inline unsigned getLoopDepth(const BasicBlock *BB) const {
909 return LI->getLoopDepth(BB);
912 // isLoopHeader - True if the block is a loop header node
913 inline bool isLoopHeader(BasicBlock *BB) const {
914 return LI->isLoopHeader(BB);
917 /// runOnFunction - Calculate the natural loop information.
919 virtual bool runOnFunction(Function &F);
921 virtual void releaseMemory() { LI->releaseMemory(); }
923 virtual void print(std::ostream &O, const Module* M = 0) const {
924 if (O) LI->print(O, M);
927 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
929 /// removeLoop - This removes the specified top-level loop from this loop info
930 /// object. The loop is not deleted, as it will presumably be inserted into
932 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); }
934 /// changeLoopFor - Change the top-level loop that contains BB to the
935 /// specified loop. This should be used by transformations that restructure
936 /// the loop hierarchy tree.
937 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
938 LI->changeLoopFor(BB, L);
941 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
942 /// list with the indicated loop.
943 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
944 LI->changeTopLevelLoop(OldLoop, NewLoop);
947 /// addTopLevelLoop - This adds the specified loop to the collection of
949 inline void addTopLevelLoop(Loop *New) {
950 LI->addTopLevelLoop(New);
953 /// removeBlock - This method completely removes BB from all data structures,
954 /// including all of the Loop objects it is nested in and our mapping from
955 /// BasicBlocks to loops.
956 void removeBlock(BasicBlock *BB) {
962 // Allow clients to walk the list of nested loops...
963 template <> struct GraphTraits<const Loop*> {
964 typedef const Loop NodeType;
965 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
967 static NodeType *getEntryNode(const Loop *L) { return L; }
968 static inline ChildIteratorType child_begin(NodeType *N) {
971 static inline ChildIteratorType child_end(NodeType *N) {
976 template <> struct GraphTraits<Loop*> {
977 typedef Loop NodeType;
978 typedef std::vector<Loop*>::const_iterator ChildIteratorType;
980 static NodeType *getEntryNode(Loop *L) { return L; }
981 static inline ChildIteratorType child_begin(NodeType *N) {
984 static inline ChildIteratorType child_end(NodeType *N) {
989 template<class BlockT>
990 void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB,
991 LoopInfoBase<BlockT> &LIB) {
992 assert((Blocks.empty() || LIB[getHeader()] == this) &&
993 "Incorrect LI specified for this loop!");
994 assert(NewBB && "Cannot add a null basic block to the loop!");
995 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
997 // Add the loop mapping to the LoopInfo object...
998 LIB.BBMap[NewBB] = this;
1000 // Add the basic block to this loop and all parent loops...
1001 LoopBase<BlockT> *L = this;
1003 L->Blocks.push_back(NewBB);
1004 L = L->getParentLoop();
1008 } // End llvm namespace
1010 // Make sure that any clients of this file link in LoopInfo.cpp
1011 FORCE_DEFINING_FILE_TO_BE_LINKED(LoopInfo)