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/ADT/DepthFirstIterator.h"
35 #include "llvm/ADT/GraphTraits.h"
36 #include "llvm/ADT/SmallVector.h"
37 #include "llvm/Analysis/Dominators.h"
38 #include "llvm/Support/CFG.h"
39 #include "llvm/Support/Streams.h"
46 static void RemoveFromVector(std::vector<T*> &V, T *N) {
47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
48 assert(I != V.end() && "N is not in this list!");
55 template<class N, class M> class LoopInfoBase;
56 template<class N, class M> class LoopBase;
58 //===----------------------------------------------------------------------===//
59 /// LoopBase class - Instances of this class are used to represent loops that
60 /// are detected in the flow graph
62 template<class BlockT, class LoopT>
65 // SubLoops - Loops contained entirely within this one.
66 std::vector<LoopT *> SubLoops;
68 // Blocks - The list of blocks in this loop. First entry is the header node.
69 std::vector<BlockT*> Blocks;
72 LoopBase(const LoopBase<BlockT, LoopT> &);
74 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
76 /// Loop ctor - This creates an empty loop.
77 LoopBase() : ParentLoop(0) {}
79 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
83 /// getLoopDepth - Return the nesting level of this loop. An outer-most
84 /// loop has depth 1, for consistency with loop depth values used for basic
85 /// blocks, where depth 0 is used for blocks not inside any loops.
86 unsigned getLoopDepth() const {
88 for (const LoopT *CurLoop = ParentLoop; CurLoop;
89 CurLoop = CurLoop->ParentLoop)
93 BlockT *getHeader() const { return Blocks.front(); }
94 LoopT *getParentLoop() const { return ParentLoop; }
96 /// contains - Return true if the specified basic block is in this loop
98 bool contains(const BlockT *BB) const {
99 return std::find(block_begin(), block_end(), BB) != block_end();
102 /// iterator/begin/end - Return the loops contained entirely within this loop.
104 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
105 typedef typename std::vector<LoopT *>::const_iterator iterator;
106 iterator begin() const { return SubLoops.begin(); }
107 iterator end() const { return SubLoops.end(); }
108 bool empty() const { return SubLoops.empty(); }
110 /// getBlocks - Get a list of the basic blocks which make up this loop.
112 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
113 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
114 block_iterator block_begin() const { return Blocks.begin(); }
115 block_iterator block_end() const { return Blocks.end(); }
117 /// isLoopExit - True if terminator in the block can branch to another block
118 /// that is outside of the current loop.
120 bool isLoopExit(const BlockT *BB) const {
121 typedef GraphTraits<BlockT*> BlockTraits;
122 for (typename BlockTraits::ChildIteratorType SI =
123 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
124 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
131 /// getNumBackEdges - Calculate the number of back edges to the loop header
133 unsigned getNumBackEdges() const {
134 unsigned NumBackEdges = 0;
135 BlockT *H = getHeader();
137 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
138 for (typename InvBlockTraits::ChildIteratorType I =
139 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
140 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
147 //===--------------------------------------------------------------------===//
148 // APIs for simple analysis of the loop.
150 // Note that all of these methods can fail on general loops (ie, there may not
151 // be a preheader, etc). For best success, the loop simplification and
152 // induction variable canonicalization pass should be used to normalize loops
153 // for easy analysis. These methods assume canonical loops.
155 /// getExitingBlocks - Return all blocks inside the loop that have successors
156 /// outside of the loop. These are the blocks _inside of the current loop_
157 /// which branch out. The returned list is always unique.
159 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
160 // Sort the blocks vector so that we can use binary search to do quick
162 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
163 std::sort(LoopBBs.begin(), LoopBBs.end());
165 typedef GraphTraits<BlockT*> BlockTraits;
166 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
167 for (typename BlockTraits::ChildIteratorType I =
168 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
170 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
171 // Not in current loop? It must be an exit block.
172 ExitingBlocks.push_back(*BI);
177 /// getExitingBlock - If getExitingBlocks would return exactly one block,
178 /// return that block. Otherwise return null.
179 BlockT *getExitingBlock() const {
180 SmallVector<BlockT*, 8> ExitingBlocks;
181 getExitingBlocks(ExitingBlocks);
182 if (ExitingBlocks.size() == 1)
183 return ExitingBlocks[0];
187 /// getExitBlocks - Return all of the successor blocks of this loop. These
188 /// are the blocks _outside of the current loop_ which are branched to.
190 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
191 // Sort the blocks vector so that we can use binary search to do quick
193 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
194 std::sort(LoopBBs.begin(), LoopBBs.end());
196 typedef GraphTraits<BlockT*> BlockTraits;
197 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
198 for (typename BlockTraits::ChildIteratorType I =
199 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
201 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
202 // Not in current loop? It must be an exit block.
203 ExitBlocks.push_back(*I);
206 /// getExitBlock - If getExitBlocks would return exactly one block,
207 /// return that block. Otherwise return null.
208 BlockT *getExitBlock() const {
209 SmallVector<BlockT*, 8> ExitBlocks;
210 getExitBlocks(ExitBlocks);
211 if (ExitBlocks.size() == 1)
212 return ExitBlocks[0];
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 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
275 /// block, return that block. Otherwise return null.
276 BlockT *getUniqueExitBlock() const {
277 SmallVector<BlockT*, 8> UniqueExitBlocks;
278 getUniqueExitBlocks(UniqueExitBlocks);
279 if (UniqueExitBlocks.size() == 1)
280 return UniqueExitBlocks[0];
284 /// getLoopPreheader - If there is a preheader for this loop, return it. A
285 /// loop has a preheader if there is only one edge to the header of the loop
286 /// from outside of the loop. If this is the case, the block branching to the
287 /// header of the loop is the preheader node.
289 /// This method returns null if there is no preheader for the loop.
291 BlockT *getLoopPreheader() const {
292 // Keep track of nodes outside the loop branching to the header...
295 // Loop over the predecessors of the header node...
296 BlockT *Header = getHeader();
297 typedef GraphTraits<BlockT*> BlockTraits;
298 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
299 for (typename InvBlockTraits::ChildIteratorType PI =
300 InvBlockTraits::child_begin(Header),
301 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
302 if (!contains(*PI)) { // If the block is not in the loop...
303 if (Out && Out != *PI)
304 return 0; // Multiple predecessors outside the loop
308 // Make sure there is only one exit out of the preheader.
309 assert(Out && "Header of loop has no predecessors from outside loop?");
310 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
312 if (SI != BlockTraits::child_end(Out))
313 return 0; // Multiple exits from the block, must not be a preheader.
315 // If there is exactly one preheader, return it. If there was zero, then
316 // Out is still null.
320 /// getLoopLatch - If there is a single latch block for this loop, return it.
321 /// A latch block is a block that contains a branch back to the header.
322 /// A loop header in normal form has two edges into it: one from a preheader
323 /// and one from a latch block.
324 BlockT *getLoopLatch() const {
325 BlockT *Header = getHeader();
326 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
327 typename InvBlockTraits::ChildIteratorType PI =
328 InvBlockTraits::child_begin(Header);
329 typename InvBlockTraits::ChildIteratorType PE =
330 InvBlockTraits::child_end(Header);
331 if (PI == PE) return 0; // no preds?
337 if (PI == PE) return 0; // only one pred?
340 if (Latch) return 0; // multiple backedges
344 if (PI != PE) return 0; // more than two preds
349 //===--------------------------------------------------------------------===//
350 // APIs for updating loop information after changing the CFG
353 /// addBasicBlockToLoop - This method is used by other analyses to update loop
354 /// information. NewBB is set to be a new member of the current loop.
355 /// Because of this, it is added as a member of all parent loops, and is added
356 /// to the specified LoopInfo object as being in the current basic block. It
357 /// is not valid to replace the loop header with this method.
359 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
361 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
362 /// the OldChild entry in our children list with NewChild, and updates the
363 /// parent pointer of OldChild to be null and the NewChild to be this loop.
364 /// This updates the loop depth of the new child.
365 void replaceChildLoopWith(LoopT *OldChild,
367 assert(OldChild->ParentLoop == this && "This loop is already broken!");
368 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
369 typename std::vector<LoopT *>::iterator I =
370 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
371 assert(I != SubLoops.end() && "OldChild not in loop!");
373 OldChild->ParentLoop = 0;
374 NewChild->ParentLoop = static_cast<LoopT *>(this);
377 /// addChildLoop - Add the specified loop to be a child of this loop. This
378 /// updates the loop depth of the new child.
380 void addChildLoop(LoopT *NewChild) {
381 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
382 NewChild->ParentLoop = static_cast<LoopT *>(this);
383 SubLoops.push_back(NewChild);
386 /// removeChildLoop - This removes the specified child from being a subloop of
387 /// this loop. The loop is not deleted, as it will presumably be inserted
388 /// into another loop.
389 LoopT *removeChildLoop(iterator I) {
390 assert(I != SubLoops.end() && "Cannot remove end iterator!");
392 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
393 SubLoops.erase(SubLoops.begin()+(I-begin()));
394 Child->ParentLoop = 0;
398 /// addBlockEntry - This adds a basic block directly to the basic block list.
399 /// This should only be used by transformations that create new loops. Other
400 /// transformations should use addBasicBlockToLoop.
401 void addBlockEntry(BlockT *BB) {
402 Blocks.push_back(BB);
405 /// moveToHeader - This method is used to move BB (which must be part of this
406 /// loop) to be the loop header of the loop (the block that dominates all
408 void moveToHeader(BlockT *BB) {
409 if (Blocks[0] == BB) return;
410 for (unsigned i = 0; ; ++i) {
411 assert(i != Blocks.size() && "Loop does not contain BB!");
412 if (Blocks[i] == BB) {
413 Blocks[i] = Blocks[0];
420 /// removeBlockFromLoop - This removes the specified basic block from the
421 /// current loop, updating the Blocks as appropriate. This does not update
422 /// the mapping in the LoopInfo class.
423 void removeBlockFromLoop(BlockT *BB) {
424 RemoveFromVector(Blocks, BB);
427 /// verifyLoop - Verify loop structure
428 void verifyLoop() const {
430 assert (getHeader() && "Loop header is missing");
431 assert (getLoopPreheader() && "Loop preheader is missing");
432 assert (getLoopLatch() && "Loop latch is missing");
433 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
438 void print(std::ostream &OS, unsigned Depth = 0) const {
439 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth()
442 for (unsigned i = 0; i < getBlocks().size(); ++i) {
444 BlockT *BB = getBlocks()[i];
445 WriteAsOperand(OS, BB, false);
446 if (BB == getHeader()) OS << "<header>";
447 if (BB == getLoopLatch()) OS << "<latch>";
448 if (isLoopExit(BB)) OS << "<exit>";
452 for (iterator I = begin(), E = end(); I != E; ++I)
453 (*I)->print(OS, Depth+2);
456 void print(std::ostream *O, unsigned Depth = 0) const {
457 if (O) print(*O, Depth);
465 friend class LoopInfoBase<BlockT, LoopT>;
466 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
467 Blocks.push_back(BB);
471 class Loop : public LoopBase<BasicBlock, Loop> {
475 /// isLoopInvariant - Return true if the specified value is loop invariant
477 bool isLoopInvariant(Value *V) const;
479 /// isLoopInvariant - Return true if the specified instruction is
482 bool isLoopInvariant(Instruction *I) const;
484 /// makeLoopInvariant - If the given value is an instruction inside of the
485 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
486 /// Return true if the value after any hoisting is loop invariant. This
487 /// function can be used as a slightly more aggressive replacement for
490 /// If InsertPt is specified, it is the point to hoist instructions to.
491 /// If null, the terminator of the loop preheader is used.
493 bool makeLoopInvariant(Value *V, bool &Changed,
494 Instruction *InsertPt = 0) const;
496 /// makeLoopInvariant - If the given instruction is inside of the
497 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
498 /// Return true if the instruction after any hoisting is loop invariant. This
499 /// function can be used as a slightly more aggressive replacement for
502 /// If InsertPt is specified, it is the point to hoist instructions to.
503 /// If null, the terminator of the loop preheader is used.
505 bool makeLoopInvariant(Instruction *I, bool &Changed,
506 Instruction *InsertPt = 0) const;
508 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
509 /// induction variable: an integer recurrence that starts at 0 and increments
510 /// by one each time through the loop. If so, return the phi node that
511 /// corresponds to it.
513 /// The IndVarSimplify pass transforms loops to have a canonical induction
516 PHINode *getCanonicalInductionVariable() const;
518 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
519 /// the canonical induction variable value for the "next" iteration of the
520 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
522 Instruction *getCanonicalInductionVariableIncrement() const;
524 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
525 /// times the loop will be executed. Note that this means that the backedge
526 /// of the loop executes N-1 times. If the trip-count cannot be determined,
527 /// this returns null.
529 /// The IndVarSimplify pass transforms loops to have a form that this
530 /// function easily understands.
532 Value *getTripCount() const;
534 /// getSmallConstantTripCount - Returns the trip count of this loop as a
535 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
536 /// of not constant. Will also return 0 if the trip count is very large
538 unsigned getSmallConstantTripCount() const;
540 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
541 /// trip count of this loop as a normal unsigned value, if possible. This
542 /// means that the actual trip count is always a multiple of the returned
543 /// value (don't forget the trip count could very well be zero as well!).
545 /// Returns 1 if the trip count is unknown or not guaranteed to be the
546 /// multiple of a constant (which is also the case if the trip count is simply
547 /// constant, use getSmallConstantTripCount for that case), Will also return 1
548 /// if the trip count is very large (>= 2^32).
549 unsigned getSmallConstantTripMultiple() const;
551 /// isLCSSAForm - Return true if the Loop is in LCSSA form
552 bool isLCSSAForm() const;
554 /// isLoopSimplifyForm - Return true if the Loop is in the form that
555 /// the LoopSimplify form transforms loops to, which is sometimes called
557 bool isLoopSimplifyForm() const;
560 friend class LoopInfoBase<BasicBlock, Loop>;
561 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
564 //===----------------------------------------------------------------------===//
565 /// LoopInfo - This class builds and contains all of the top level loop
566 /// structures in the specified function.
569 template<class BlockT, class LoopT>
571 // BBMap - Mapping of basic blocks to the inner most loop they occur in
572 std::map<BlockT *, LoopT *> BBMap;
573 std::vector<LoopT *> TopLevelLoops;
574 friend class LoopBase<BlockT, LoopT>;
576 void operator=(const LoopInfoBase &); // do not implement
577 LoopInfoBase(const LoopInfo &); // do not implement
580 ~LoopInfoBase() { releaseMemory(); }
582 void releaseMemory() {
583 for (typename std::vector<LoopT *>::iterator I =
584 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
585 delete *I; // Delete all of the loops...
587 BBMap.clear(); // Reset internal state of analysis
588 TopLevelLoops.clear();
591 /// iterator/begin/end - The interface to the top-level loops in the current
594 typedef typename std::vector<LoopT *>::const_iterator iterator;
595 iterator begin() const { return TopLevelLoops.begin(); }
596 iterator end() const { return TopLevelLoops.end(); }
597 bool empty() const { return TopLevelLoops.empty(); }
599 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
600 /// block is in no loop (for example the entry node), null is returned.
602 LoopT *getLoopFor(const BlockT *BB) const {
603 typename std::map<BlockT *, LoopT *>::const_iterator I=
604 BBMap.find(const_cast<BlockT*>(BB));
605 return I != BBMap.end() ? I->second : 0;
608 /// operator[] - same as getLoopFor...
610 const LoopT *operator[](const BlockT *BB) const {
611 return getLoopFor(BB);
614 /// getLoopDepth - Return the loop nesting level of the specified block. A
615 /// depth of 0 means the block is not inside any loop.
617 unsigned getLoopDepth(const BlockT *BB) const {
618 const LoopT *L = getLoopFor(BB);
619 return L ? L->getLoopDepth() : 0;
622 // isLoopHeader - True if the block is a loop header node
623 bool isLoopHeader(BlockT *BB) const {
624 const LoopT *L = getLoopFor(BB);
625 return L && L->getHeader() == BB;
628 /// removeLoop - This removes the specified top-level loop from this loop info
629 /// object. The loop is not deleted, as it will presumably be inserted into
631 LoopT *removeLoop(iterator I) {
632 assert(I != end() && "Cannot remove end iterator!");
634 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
635 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
639 /// changeLoopFor - Change the top-level loop that contains BB to the
640 /// specified loop. This should be used by transformations that restructure
641 /// the loop hierarchy tree.
642 void changeLoopFor(BlockT *BB, LoopT *L) {
643 LoopT *&OldLoop = BBMap[BB];
644 assert(OldLoop && "Block not in a loop yet!");
648 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
649 /// list with the indicated loop.
650 void changeTopLevelLoop(LoopT *OldLoop,
652 typename std::vector<LoopT *>::iterator I =
653 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
654 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
656 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
657 "Loops already embedded into a subloop!");
660 /// addTopLevelLoop - This adds the specified loop to the collection of
662 void addTopLevelLoop(LoopT *New) {
663 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
664 TopLevelLoops.push_back(New);
667 /// removeBlock - This method completely removes BB from all data structures,
668 /// including all of the Loop objects it is nested in and our mapping from
669 /// BasicBlocks to loops.
670 void removeBlock(BlockT *BB) {
671 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
672 if (I != BBMap.end()) {
673 for (LoopT *L = I->second; L; L = L->getParentLoop())
674 L->removeBlockFromLoop(BB);
682 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
683 const LoopT *ParentLoop) {
684 if (SubLoop == 0) return true;
685 if (SubLoop == ParentLoop) return false;
686 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
689 void Calculate(DominatorTreeBase<BlockT> &DT) {
690 BlockT *RootNode = DT.getRootNode()->getBlock();
692 for (df_iterator<BlockT*> NI = df_begin(RootNode),
693 NE = df_end(RootNode); NI != NE; ++NI)
694 if (LoopT *L = ConsiderForLoop(*NI, DT))
695 TopLevelLoops.push_back(L);
698 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
699 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
701 std::vector<BlockT *> TodoStack;
703 // Scan the predecessors of BB, checking to see if BB dominates any of
704 // them. This identifies backedges which target this node...
705 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
706 for (typename InvBlockTraits::ChildIteratorType I =
707 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
709 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
710 TodoStack.push_back(*I);
712 if (TodoStack.empty()) return 0; // No backedges to this block...
714 // Create a new loop to represent this basic block...
715 LoopT *L = new LoopT(BB);
718 BlockT *EntryBlock = BB->getParent()->begin();
720 while (!TodoStack.empty()) { // Process all the nodes in the loop
721 BlockT *X = TodoStack.back();
722 TodoStack.pop_back();
724 if (!L->contains(X) && // As of yet unprocessed??
725 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
726 // Check to see if this block already belongs to a loop. If this occurs
727 // then we have a case where a loop that is supposed to be a child of
728 // the current loop was processed before the current loop. When this
729 // occurs, this child loop gets added to a part of the current loop,
730 // making it a sibling to the current loop. We have to reparent this
733 const_cast<LoopT *>(getLoopFor(X)))
734 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
735 // Remove the subloop from it's current parent...
736 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
737 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
738 typename std::vector<LoopT *>::iterator I =
739 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
740 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
741 SLP->SubLoops.erase(I); // Remove from parent...
743 // Add the subloop to THIS loop...
744 SubLoop->ParentLoop = L;
745 L->SubLoops.push_back(SubLoop);
748 // Normal case, add the block to our loop...
749 L->Blocks.push_back(X);
751 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
753 // Add all of the predecessors of X to the end of the work stack...
754 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
755 InvBlockTraits::child_end(X));
759 // If there are any loops nested within this loop, create them now!
760 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
761 E = L->Blocks.end(); I != E; ++I)
762 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
763 L->SubLoops.push_back(NewLoop);
764 NewLoop->ParentLoop = L;
767 // Add the basic blocks that comprise this loop to the BBMap so that this
768 // loop can be found for them.
770 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
771 E = L->Blocks.end(); I != E; ++I) {
772 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I);
773 if (BBMI == BBMap.end()) // Not in map yet...
774 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
777 // Now that we have a list of all of the child loops of this loop, check to
778 // see if any of them should actually be nested inside of each other. We
779 // can accidentally pull loops our of their parents, so we must make sure to
780 // organize the loop nests correctly now.
782 std::map<BlockT *, LoopT *> ContainingLoops;
783 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
784 LoopT *Child = L->SubLoops[i];
785 assert(Child->getParentLoop() == L && "Not proper child loop?");
787 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
788 // If there is already a loop which contains this loop, move this loop
789 // into the containing loop.
790 MoveSiblingLoopInto(Child, ContainingLoop);
791 --i; // The loop got removed from the SubLoops list.
793 // This is currently considered to be a top-level loop. Check to see
794 // if any of the contained blocks are loop headers for subloops we
795 // have already processed.
796 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
797 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
798 if (BlockLoop == 0) { // Child block not processed yet...
800 } else if (BlockLoop != Child) {
801 LoopT *SubLoop = BlockLoop;
802 // Reparent all of the blocks which used to belong to BlockLoops
803 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
804 ContainingLoops[SubLoop->Blocks[j]] = Child;
806 // There is already a loop which contains this block, that means
807 // that we should reparent the loop which the block is currently
808 // considered to belong to to be a child of this loop.
809 MoveSiblingLoopInto(SubLoop, Child);
810 --i; // We just shrunk the SubLoops list.
820 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
821 /// of the NewParent Loop, instead of being a sibling of it.
822 void MoveSiblingLoopInto(LoopT *NewChild,
824 LoopT *OldParent = NewChild->getParentLoop();
825 assert(OldParent && OldParent == NewParent->getParentLoop() &&
826 NewChild != NewParent && "Not sibling loops!");
828 // Remove NewChild from being a child of OldParent
829 typename std::vector<LoopT *>::iterator I =
830 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
832 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
833 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
834 NewChild->ParentLoop = 0;
836 InsertLoopInto(NewChild, NewParent);
839 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
840 /// the parent loop contains a loop which should contain L, the loop gets
841 /// inserted into L instead.
842 void InsertLoopInto(LoopT *L, LoopT *Parent) {
843 BlockT *LHeader = L->getHeader();
844 assert(Parent->contains(LHeader) &&
845 "This loop should not be inserted here!");
847 // Check to see if it belongs in a child loop...
848 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
850 if (Parent->SubLoops[i]->contains(LHeader)) {
851 InsertLoopInto(L, Parent->SubLoops[i]);
855 // If not, insert it here!
856 Parent->SubLoops.push_back(L);
857 L->ParentLoop = Parent;
862 void print(std::ostream &OS, const Module* ) const {
863 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
864 TopLevelLoops[i]->print(OS);
866 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
867 E = BBMap.end(); I != E; ++I)
868 OS << "BB '" << I->first->getName() << "' level = "
869 << I->second->getLoopDepth() << "\n";
874 class LoopInfo : public FunctionPass {
875 LoopInfoBase<BasicBlock, Loop> LI;
876 friend class LoopBase<BasicBlock, Loop>;
878 void operator=(const LoopInfo &); // do not implement
879 LoopInfo(const LoopInfo &); // do not implement
881 static char ID; // Pass identification, replacement for typeid
883 LoopInfo() : FunctionPass(&ID) {}
885 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
887 /// iterator/begin/end - The interface to the top-level loops in the current
890 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
891 inline iterator begin() const { return LI.begin(); }
892 inline iterator end() const { return LI.end(); }
893 bool empty() const { return LI.empty(); }
895 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
896 /// block is in no loop (for example the entry node), null is returned.
898 inline Loop *getLoopFor(const BasicBlock *BB) const {
899 return LI.getLoopFor(BB);
902 /// operator[] - same as getLoopFor...
904 inline const Loop *operator[](const BasicBlock *BB) const {
905 return LI.getLoopFor(BB);
908 /// getLoopDepth - Return the loop nesting level of the specified block. A
909 /// depth of 0 means the block is not inside any loop.
911 inline unsigned getLoopDepth(const BasicBlock *BB) const {
912 return LI.getLoopDepth(BB);
915 // isLoopHeader - True if the block is a loop header node
916 inline bool isLoopHeader(BasicBlock *BB) const {
917 return LI.isLoopHeader(BB);
920 /// runOnFunction - Calculate the natural loop information.
922 virtual bool runOnFunction(Function &F);
924 virtual void releaseMemory() { LI.releaseMemory(); }
926 virtual void print(std::ostream &O, const Module* M = 0) const {
930 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
932 /// removeLoop - This removes the specified top-level loop from this loop info
933 /// object. The loop is not deleted, as it will presumably be inserted into
935 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
937 /// changeLoopFor - Change the top-level loop that contains BB to the
938 /// specified loop. This should be used by transformations that restructure
939 /// the loop hierarchy tree.
940 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
941 LI.changeLoopFor(BB, L);
944 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
945 /// list with the indicated loop.
946 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
947 LI.changeTopLevelLoop(OldLoop, NewLoop);
950 /// addTopLevelLoop - This adds the specified loop to the collection of
952 inline void addTopLevelLoop(Loop *New) {
953 LI.addTopLevelLoop(New);
956 /// removeBlock - This method completely removes BB from all data structures,
957 /// including all of the Loop objects it is nested in and our mapping from
958 /// BasicBlocks to loops.
959 void removeBlock(BasicBlock *BB) {
963 static bool isNotAlreadyContainedIn(const Loop *SubLoop,
964 const Loop *ParentLoop) {
966 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop,
972 // Allow clients to walk the list of nested loops...
973 template <> struct GraphTraits<const Loop*> {
974 typedef const Loop NodeType;
975 typedef LoopInfo::iterator ChildIteratorType;
977 static NodeType *getEntryNode(const Loop *L) { return L; }
978 static inline ChildIteratorType child_begin(NodeType *N) {
981 static inline ChildIteratorType child_end(NodeType *N) {
986 template <> struct GraphTraits<Loop*> {
987 typedef Loop NodeType;
988 typedef LoopInfo::iterator ChildIteratorType;
990 static NodeType *getEntryNode(Loop *L) { return L; }
991 static inline ChildIteratorType child_begin(NodeType *N) {
994 static inline ChildIteratorType child_end(NodeType *N) {
999 template<class BlockT, class LoopT>
1001 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1002 LoopInfoBase<BlockT, LoopT> &LIB) {
1003 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1004 "Incorrect LI specified for this loop!");
1005 assert(NewBB && "Cannot add a null basic block to the loop!");
1006 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1008 LoopT *L = static_cast<LoopT *>(this);
1010 // Add the loop mapping to the LoopInfo object...
1011 LIB.BBMap[NewBB] = L;
1013 // Add the basic block to this loop and all parent loops...
1015 L->Blocks.push_back(NewBB);
1016 L = L->getParentLoop();
1020 } // End llvm namespace