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. A natural loop
12 // has exactly one entry-point, which is called the header. Note that natural
13 // loops may actually be several loops that share the same header node.
15 // This analysis calculates the nesting structure of loops in a function. For
16 // each natural loop identified, this analysis identifies natural loops
17 // contained entirely within the loop and the basic blocks the make up the loop.
19 // It can calculate on the fly various bits of information, for example:
21 // * whether there is a preheader for the loop
22 // * the number of back edges to the header
23 // * whether or not a particular block branches out of the loop
24 // * the successor blocks of the loop
29 //===----------------------------------------------------------------------===//
31 #ifndef LLVM_ANALYSIS_LOOP_INFO_H
32 #define LLVM_ANALYSIS_LOOP_INFO_H
34 #include "llvm/Pass.h"
35 #include "llvm/ADT/DepthFirstIterator.h"
36 #include "llvm/ADT/GraphTraits.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/Analysis/Dominators.h"
39 #include "llvm/Support/CFG.h"
40 #include "llvm/Support/raw_ostream.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 loop is contained within in
99 bool contains(const LoopT *L) const {
100 if (L == this) return true;
101 if (L == 0) return false;
102 return contains(L->getParentLoop());
105 /// contains - Return true if the specified basic block is in this loop.
107 bool contains(const BlockT *BB) const {
108 return std::find(block_begin(), block_end(), BB) != block_end();
111 /// contains - Return true if the specified instruction is in this loop.
113 template<class InstT>
114 bool contains(const InstT *Inst) const {
115 return contains(Inst->getParent());
118 /// iterator/begin/end - Return the loops contained entirely within this loop.
120 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
121 typedef typename std::vector<LoopT *>::const_iterator iterator;
122 iterator begin() const { return SubLoops.begin(); }
123 iterator end() const { return SubLoops.end(); }
124 bool empty() const { return SubLoops.empty(); }
126 /// getBlocks - Get a list of the basic blocks which make up this loop.
128 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
129 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
130 block_iterator block_begin() const { return Blocks.begin(); }
131 block_iterator block_end() const { return Blocks.end(); }
133 /// isLoopExiting - True if terminator in the block can branch to another
134 /// block that is outside of the current loop.
136 bool isLoopExiting(const BlockT *BB) const {
137 typedef GraphTraits<BlockT*> BlockTraits;
138 for (typename BlockTraits::ChildIteratorType SI =
139 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
140 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
147 /// getNumBackEdges - Calculate the number of back edges to the loop header
149 unsigned getNumBackEdges() const {
150 unsigned NumBackEdges = 0;
151 BlockT *H = getHeader();
153 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
154 for (typename InvBlockTraits::ChildIteratorType I =
155 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
156 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
163 //===--------------------------------------------------------------------===//
164 // APIs for simple analysis of the loop.
166 // Note that all of these methods can fail on general loops (ie, there may not
167 // be a preheader, etc). For best success, the loop simplification and
168 // induction variable canonicalization pass should be used to normalize loops
169 // for easy analysis. These methods assume canonical loops.
171 /// getExitingBlocks - Return all blocks inside the loop that have successors
172 /// outside of the loop. These are the blocks _inside of the current loop_
173 /// which branch out. The returned list is always unique.
175 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
176 // Sort the blocks vector so that we can use binary search to do quick
178 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
179 std::sort(LoopBBs.begin(), LoopBBs.end());
181 typedef GraphTraits<BlockT*> BlockTraits;
182 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
183 for (typename BlockTraits::ChildIteratorType I =
184 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
186 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
187 // Not in current loop? It must be an exit block.
188 ExitingBlocks.push_back(*BI);
193 /// getExitingBlock - If getExitingBlocks would return exactly one block,
194 /// return that block. Otherwise return null.
195 BlockT *getExitingBlock() const {
196 SmallVector<BlockT*, 8> ExitingBlocks;
197 getExitingBlocks(ExitingBlocks);
198 if (ExitingBlocks.size() == 1)
199 return ExitingBlocks[0];
203 /// getExitBlocks - Return all of the successor blocks of this loop. These
204 /// are the blocks _outside of the current loop_ which are branched to.
206 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
207 // Sort the blocks vector so that we can use binary search to do quick
209 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
210 std::sort(LoopBBs.begin(), LoopBBs.end());
212 typedef GraphTraits<BlockT*> BlockTraits;
213 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
214 for (typename BlockTraits::ChildIteratorType I =
215 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
217 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
218 // Not in current loop? It must be an exit block.
219 ExitBlocks.push_back(*I);
222 /// getExitBlock - If getExitBlocks would return exactly one block,
223 /// return that block. Otherwise return null.
224 BlockT *getExitBlock() const {
225 SmallVector<BlockT*, 8> ExitBlocks;
226 getExitBlocks(ExitBlocks);
227 if (ExitBlocks.size() == 1)
228 return ExitBlocks[0];
232 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
233 typedef std::pair<const BlockT*,const BlockT*> Edge;
234 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
235 // Sort the blocks vector so that we can use binary search to do quick
237 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
238 std::sort(LoopBBs.begin(), LoopBBs.end());
240 typedef GraphTraits<BlockT*> BlockTraits;
241 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
242 for (typename BlockTraits::ChildIteratorType I =
243 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
245 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
246 // Not in current loop? It must be an exit block.
247 ExitEdges.push_back(std::make_pair(*BI, *I));
250 /// getLoopPreheader - If there is a preheader for this loop, return it. A
251 /// loop has a preheader if there is only one edge to the header of the loop
252 /// from outside of the loop. If this is the case, the block branching to the
253 /// header of the loop is the preheader node.
255 /// This method returns null if there is no preheader for the loop.
257 BlockT *getLoopPreheader() const {
258 // Keep track of nodes outside the loop branching to the header...
259 BlockT *Out = getLoopPredecessor();
262 // Make sure there is only one exit out of the preheader.
263 typedef GraphTraits<BlockT*> BlockTraits;
264 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
266 if (SI != BlockTraits::child_end(Out))
267 return 0; // Multiple exits from the block, must not be a preheader.
269 // The predecessor has exactly one successor, so it is a preheader.
273 /// getLoopPredecessor - If the given loop's header has exactly one unique
274 /// predecessor outside the loop, return it. Otherwise return null.
275 /// This is less strict that the loop "preheader" concept, which requires
276 /// the predecessor to have exactly one successor.
278 BlockT *getLoopPredecessor() const {
279 // Keep track of nodes outside the loop branching to the header...
282 // Loop over the predecessors of the header node...
283 BlockT *Header = getHeader();
284 typedef GraphTraits<BlockT*> BlockTraits;
285 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
286 for (typename InvBlockTraits::ChildIteratorType PI =
287 InvBlockTraits::child_begin(Header),
288 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
289 if (!contains(*PI)) { // If the block is not in the loop...
290 if (Out && Out != *PI)
291 return 0; // Multiple predecessors outside the loop
295 // Make sure there is only one exit out of the preheader.
296 assert(Out && "Header of loop has no predecessors from outside loop?");
300 /// getLoopLatch - If there is a single latch block for this loop, return it.
301 /// A latch block is a block that contains a branch back to the header.
302 BlockT *getLoopLatch() const {
303 BlockT *Header = getHeader();
304 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
305 typename InvBlockTraits::ChildIteratorType PI =
306 InvBlockTraits::child_begin(Header);
307 typename InvBlockTraits::ChildIteratorType PE =
308 InvBlockTraits::child_end(Header);
310 for (; PI != PE; ++PI)
319 //===--------------------------------------------------------------------===//
320 // APIs for updating loop information after changing the CFG
323 /// addBasicBlockToLoop - This method is used by other analyses to update loop
324 /// information. NewBB is set to be a new member of the current loop.
325 /// Because of this, it is added as a member of all parent loops, and is added
326 /// to the specified LoopInfo object as being in the current basic block. It
327 /// is not valid to replace the loop header with this method.
329 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
331 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
332 /// the OldChild entry in our children list with NewChild, and updates the
333 /// parent pointer of OldChild to be null and the NewChild to be this loop.
334 /// This updates the loop depth of the new child.
335 void replaceChildLoopWith(LoopT *OldChild,
337 assert(OldChild->ParentLoop == this && "This loop is already broken!");
338 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
339 typename std::vector<LoopT *>::iterator I =
340 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
341 assert(I != SubLoops.end() && "OldChild not in loop!");
343 OldChild->ParentLoop = 0;
344 NewChild->ParentLoop = static_cast<LoopT *>(this);
347 /// addChildLoop - Add the specified loop to be a child of this loop. This
348 /// updates the loop depth of the new child.
350 void addChildLoop(LoopT *NewChild) {
351 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
352 NewChild->ParentLoop = static_cast<LoopT *>(this);
353 SubLoops.push_back(NewChild);
356 /// removeChildLoop - This removes the specified child from being a subloop of
357 /// this loop. The loop is not deleted, as it will presumably be inserted
358 /// into another loop.
359 LoopT *removeChildLoop(iterator I) {
360 assert(I != SubLoops.end() && "Cannot remove end iterator!");
362 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
363 SubLoops.erase(SubLoops.begin()+(I-begin()));
364 Child->ParentLoop = 0;
368 /// addBlockEntry - This adds a basic block directly to the basic block list.
369 /// This should only be used by transformations that create new loops. Other
370 /// transformations should use addBasicBlockToLoop.
371 void addBlockEntry(BlockT *BB) {
372 Blocks.push_back(BB);
375 /// moveToHeader - This method is used to move BB (which must be part of this
376 /// loop) to be the loop header of the loop (the block that dominates all
378 void moveToHeader(BlockT *BB) {
379 if (Blocks[0] == BB) return;
380 for (unsigned i = 0; ; ++i) {
381 assert(i != Blocks.size() && "Loop does not contain BB!");
382 if (Blocks[i] == BB) {
383 Blocks[i] = Blocks[0];
390 /// removeBlockFromLoop - This removes the specified basic block from the
391 /// current loop, updating the Blocks as appropriate. This does not update
392 /// the mapping in the LoopInfo class.
393 void removeBlockFromLoop(BlockT *BB) {
394 RemoveFromVector(Blocks, BB);
397 /// verifyLoop - Verify loop structure
398 void verifyLoop() const {
400 assert(!Blocks.empty() && "Loop header is missing");
402 // Sort the blocks vector so that we can use binary search to do quick
404 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
405 std::sort(LoopBBs.begin(), LoopBBs.end());
407 // Check the individual blocks.
408 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
410 bool HasInsideLoopSuccs = false;
411 bool HasInsideLoopPreds = false;
412 SmallVector<BlockT *, 2> OutsideLoopPreds;
414 typedef GraphTraits<BlockT*> BlockTraits;
415 for (typename BlockTraits::ChildIteratorType SI =
416 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
418 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
419 HasInsideLoopSuccs = true;
422 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
423 for (typename InvBlockTraits::ChildIteratorType PI =
424 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
426 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI))
427 HasInsideLoopPreds = true;
429 OutsideLoopPreds.push_back(*PI);
432 if (BB == getHeader()) {
433 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
434 } else if (!OutsideLoopPreds.empty()) {
435 // A non-header loop shouldn't be reachable from outside the loop,
436 // though it is permitted if the predecessor is not itself actually
438 BlockT *EntryBB = BB->getParent()->begin();
439 for (df_iterator<BlockT *> NI = df_begin(EntryBB),
440 NE = df_end(EntryBB); NI != NE; ++NI)
441 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
442 assert(*NI != OutsideLoopPreds[i] &&
443 "Loop has multiple entry points!");
445 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
446 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
447 assert(BB != getHeader()->getParent()->begin() &&
448 "Loop contains function entry block!");
451 // Check the subloops.
452 for (iterator I = begin(), E = end(); I != E; ++I)
453 // Each block in each subloop should be contained within this loop.
454 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
456 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
457 "Loop does not contain all the blocks of a subloop!");
460 // Check the parent loop pointer.
462 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
464 "Loop is not a subloop of its parent!");
469 /// verifyLoop - Verify loop structure of this loop and all nested loops.
470 void verifyLoopNest() const {
473 // Verify the subloops.
474 for (iterator I = begin(), E = end(); I != E; ++I)
475 (*I)->verifyLoopNest();
478 void print(raw_ostream &OS, unsigned Depth = 0) const {
479 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
482 for (unsigned i = 0; i < getBlocks().size(); ++i) {
484 BlockT *BB = getBlocks()[i];
485 WriteAsOperand(OS, BB, false);
486 if (BB == getHeader()) OS << "<header>";
487 if (BB == getLoopLatch()) OS << "<latch>";
488 if (isLoopExiting(BB)) OS << "<exiting>";
492 for (iterator I = begin(), E = end(); I != E; ++I)
493 (*I)->print(OS, Depth+2);
497 friend class LoopInfoBase<BlockT, LoopT>;
498 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
499 Blocks.push_back(BB);
503 class Loop : public LoopBase<BasicBlock, Loop> {
507 /// isLoopInvariant - Return true if the specified value is loop invariant
509 bool isLoopInvariant(Value *V) const;
511 /// isLoopInvariant - Return true if the specified instruction is
514 bool isLoopInvariant(Instruction *I) const;
516 /// makeLoopInvariant - If the given value is an instruction inside of the
517 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
518 /// Return true if the value after any hoisting is loop invariant. This
519 /// function can be used as a slightly more aggressive replacement for
522 /// If InsertPt is specified, it is the point to hoist instructions to.
523 /// If null, the terminator of the loop preheader is used.
525 bool makeLoopInvariant(Value *V, bool &Changed,
526 Instruction *InsertPt = 0) const;
528 /// makeLoopInvariant - If the given instruction is inside of the
529 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
530 /// Return true if the instruction after any hoisting is loop invariant. This
531 /// function can be used as a slightly more aggressive replacement for
534 /// If InsertPt is specified, it is the point to hoist instructions to.
535 /// If null, the terminator of the loop preheader is used.
537 bool makeLoopInvariant(Instruction *I, bool &Changed,
538 Instruction *InsertPt = 0) const;
540 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
541 /// induction variable: an integer recurrence that starts at 0 and increments
542 /// by one each time through the loop. If so, return the phi node that
543 /// corresponds to it.
545 /// The IndVarSimplify pass transforms loops to have a canonical induction
548 PHINode *getCanonicalInductionVariable() const;
550 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
551 /// the canonical induction variable value for the "next" iteration of the
552 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
554 Instruction *getCanonicalInductionVariableIncrement() const;
556 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
557 /// times the loop will be executed. Note that this means that the backedge
558 /// of the loop executes N-1 times. If the trip-count cannot be determined,
559 /// this returns null.
561 /// The IndVarSimplify pass transforms loops to have a form that this
562 /// function easily understands.
564 Value *getTripCount() const;
566 /// getSmallConstantTripCount - Returns the trip count of this loop as a
567 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
568 /// of not constant. Will also return 0 if the trip count is very large
571 /// The IndVarSimplify pass transforms loops to have a form that this
572 /// function easily understands.
574 unsigned getSmallConstantTripCount() const;
576 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
577 /// trip count of this loop as a normal unsigned value, if possible. This
578 /// means that the actual trip count is always a multiple of the returned
579 /// value (don't forget the trip count could very well be zero as well!).
581 /// Returns 1 if the trip count is unknown or not guaranteed to be the
582 /// multiple of a constant (which is also the case if the trip count is simply
583 /// constant, use getSmallConstantTripCount for that case), Will also return 1
584 /// if the trip count is very large (>= 2^32).
585 unsigned getSmallConstantTripMultiple() const;
587 /// isLCSSAForm - Return true if the Loop is in LCSSA form
588 bool isLCSSAForm(DominatorTree &DT) const;
590 /// isLoopSimplifyForm - Return true if the Loop is in the form that
591 /// the LoopSimplify form transforms loops to, which is sometimes called
593 bool isLoopSimplifyForm() const;
595 /// hasDedicatedExits - Return true if no exit block for the loop
596 /// has a predecessor that is outside the loop.
597 bool hasDedicatedExits() const;
599 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
600 /// These are the blocks _outside of the current loop_ which are branched to.
601 /// This assumes that loop exits are in canonical form.
603 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
605 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
606 /// block, return that block. Otherwise return null.
607 BasicBlock *getUniqueExitBlock() const;
612 friend class LoopInfoBase<BasicBlock, Loop>;
613 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
616 //===----------------------------------------------------------------------===//
617 /// LoopInfo - This class builds and contains all of the top level loop
618 /// structures in the specified function.
621 template<class BlockT, class LoopT>
623 // BBMap - Mapping of basic blocks to the inner most loop they occur in
624 std::map<BlockT *, LoopT *> BBMap;
625 std::vector<LoopT *> TopLevelLoops;
626 friend class LoopBase<BlockT, LoopT>;
628 void operator=(const LoopInfoBase &); // do not implement
629 LoopInfoBase(const LoopInfo &); // do not implement
632 ~LoopInfoBase() { releaseMemory(); }
634 void releaseMemory() {
635 for (typename std::vector<LoopT *>::iterator I =
636 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
637 delete *I; // Delete all of the loops...
639 BBMap.clear(); // Reset internal state of analysis
640 TopLevelLoops.clear();
643 /// iterator/begin/end - The interface to the top-level loops in the current
646 typedef typename std::vector<LoopT *>::const_iterator iterator;
647 iterator begin() const { return TopLevelLoops.begin(); }
648 iterator end() const { return TopLevelLoops.end(); }
649 bool empty() const { return TopLevelLoops.empty(); }
651 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
652 /// block is in no loop (for example the entry node), null is returned.
654 LoopT *getLoopFor(const BlockT *BB) const {
655 typename std::map<BlockT *, LoopT *>::const_iterator I=
656 BBMap.find(const_cast<BlockT*>(BB));
657 return I != BBMap.end() ? I->second : 0;
660 /// operator[] - same as getLoopFor...
662 const LoopT *operator[](const BlockT *BB) const {
663 return getLoopFor(BB);
666 /// getLoopDepth - Return the loop nesting level of the specified block. A
667 /// depth of 0 means the block is not inside any loop.
669 unsigned getLoopDepth(const BlockT *BB) const {
670 const LoopT *L = getLoopFor(BB);
671 return L ? L->getLoopDepth() : 0;
674 // isLoopHeader - True if the block is a loop header node
675 bool isLoopHeader(BlockT *BB) const {
676 const LoopT *L = getLoopFor(BB);
677 return L && L->getHeader() == BB;
680 /// removeLoop - This removes the specified top-level loop from this loop info
681 /// object. The loop is not deleted, as it will presumably be inserted into
683 LoopT *removeLoop(iterator I) {
684 assert(I != end() && "Cannot remove end iterator!");
686 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
687 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
691 /// changeLoopFor - Change the top-level loop that contains BB to the
692 /// specified loop. This should be used by transformations that restructure
693 /// the loop hierarchy tree.
694 void changeLoopFor(BlockT *BB, LoopT *L) {
695 LoopT *&OldLoop = BBMap[BB];
696 assert(OldLoop && "Block not in a loop yet!");
700 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
701 /// list with the indicated loop.
702 void changeTopLevelLoop(LoopT *OldLoop,
704 typename std::vector<LoopT *>::iterator I =
705 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
706 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
708 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
709 "Loops already embedded into a subloop!");
712 /// addTopLevelLoop - This adds the specified loop to the collection of
714 void addTopLevelLoop(LoopT *New) {
715 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
716 TopLevelLoops.push_back(New);
719 /// removeBlock - This method completely removes BB from all data structures,
720 /// including all of the Loop objects it is nested in and our mapping from
721 /// BasicBlocks to loops.
722 void removeBlock(BlockT *BB) {
723 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
724 if (I != BBMap.end()) {
725 for (LoopT *L = I->second; L; L = L->getParentLoop())
726 L->removeBlockFromLoop(BB);
734 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
735 const LoopT *ParentLoop) {
736 if (SubLoop == 0) return true;
737 if (SubLoop == ParentLoop) return false;
738 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
741 void Calculate(DominatorTreeBase<BlockT> &DT) {
742 BlockT *RootNode = DT.getRootNode()->getBlock();
744 for (df_iterator<BlockT*> NI = df_begin(RootNode),
745 NE = df_end(RootNode); NI != NE; ++NI)
746 if (LoopT *L = ConsiderForLoop(*NI, DT))
747 TopLevelLoops.push_back(L);
750 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
751 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
753 std::vector<BlockT *> TodoStack;
755 // Scan the predecessors of BB, checking to see if BB dominates any of
756 // them. This identifies backedges which target this node...
757 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
758 for (typename InvBlockTraits::ChildIteratorType I =
759 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
761 if (DT.dominates(BB, *I)) // If BB dominates its predecessor...
762 TodoStack.push_back(*I);
764 if (TodoStack.empty()) return 0; // No backedges to this block...
766 // Create a new loop to represent this basic block...
767 LoopT *L = new LoopT(BB);
770 BlockT *EntryBlock = BB->getParent()->begin();
772 while (!TodoStack.empty()) { // Process all the nodes in the loop
773 BlockT *X = TodoStack.back();
774 TodoStack.pop_back();
776 if (!L->contains(X) && // As of yet unprocessed??
777 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
778 // Check to see if this block already belongs to a loop. If this occurs
779 // then we have a case where a loop that is supposed to be a child of
780 // the current loop was processed before the current loop. When this
781 // occurs, this child loop gets added to a part of the current loop,
782 // making it a sibling to the current loop. We have to reparent this
785 const_cast<LoopT *>(getLoopFor(X)))
786 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
787 // Remove the subloop from its current parent...
788 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
789 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
790 typename std::vector<LoopT *>::iterator I =
791 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
792 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
793 SLP->SubLoops.erase(I); // Remove from parent...
795 // Add the subloop to THIS loop...
796 SubLoop->ParentLoop = L;
797 L->SubLoops.push_back(SubLoop);
800 // Normal case, add the block to our loop...
801 L->Blocks.push_back(X);
803 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
805 // Add all of the predecessors of X to the end of the work stack...
806 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
807 InvBlockTraits::child_end(X));
811 // If there are any loops nested within this loop, create them now!
812 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
813 E = L->Blocks.end(); I != E; ++I)
814 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
815 L->SubLoops.push_back(NewLoop);
816 NewLoop->ParentLoop = L;
819 // Add the basic blocks that comprise this loop to the BBMap so that this
820 // loop can be found for them.
822 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
823 E = L->Blocks.end(); I != E; ++I)
824 BBMap.insert(std::make_pair(*I, L));
826 // Now that we have a list of all of the child loops of this loop, check to
827 // see if any of them should actually be nested inside of each other. We
828 // can accidentally pull loops our of their parents, so we must make sure to
829 // organize the loop nests correctly now.
831 std::map<BlockT *, LoopT *> ContainingLoops;
832 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
833 LoopT *Child = L->SubLoops[i];
834 assert(Child->getParentLoop() == L && "Not proper child loop?");
836 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
837 // If there is already a loop which contains this loop, move this loop
838 // into the containing loop.
839 MoveSiblingLoopInto(Child, ContainingLoop);
840 --i; // The loop got removed from the SubLoops list.
842 // This is currently considered to be a top-level loop. Check to see
843 // if any of the contained blocks are loop headers for subloops we
844 // have already processed.
845 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
846 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
847 if (BlockLoop == 0) { // Child block not processed yet...
849 } else if (BlockLoop != Child) {
850 LoopT *SubLoop = BlockLoop;
851 // Reparent all of the blocks which used to belong to BlockLoops
852 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
853 ContainingLoops[SubLoop->Blocks[j]] = Child;
855 // There is already a loop which contains this block, that means
856 // that we should reparent the loop which the block is currently
857 // considered to belong to to be a child of this loop.
858 MoveSiblingLoopInto(SubLoop, Child);
859 --i; // We just shrunk the SubLoops list.
869 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
870 /// of the NewParent Loop, instead of being a sibling of it.
871 void MoveSiblingLoopInto(LoopT *NewChild,
873 LoopT *OldParent = NewChild->getParentLoop();
874 assert(OldParent && OldParent == NewParent->getParentLoop() &&
875 NewChild != NewParent && "Not sibling loops!");
877 // Remove NewChild from being a child of OldParent
878 typename std::vector<LoopT *>::iterator I =
879 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
881 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
882 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
883 NewChild->ParentLoop = 0;
885 InsertLoopInto(NewChild, NewParent);
888 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
889 /// the parent loop contains a loop which should contain L, the loop gets
890 /// inserted into L instead.
891 void InsertLoopInto(LoopT *L, LoopT *Parent) {
892 BlockT *LHeader = L->getHeader();
893 assert(Parent->contains(LHeader) &&
894 "This loop should not be inserted here!");
896 // Check to see if it belongs in a child loop...
897 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
899 if (Parent->SubLoops[i]->contains(LHeader)) {
900 InsertLoopInto(L, Parent->SubLoops[i]);
904 // If not, insert it here!
905 Parent->SubLoops.push_back(L);
906 L->ParentLoop = Parent;
911 void print(raw_ostream &OS) const {
912 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
913 TopLevelLoops[i]->print(OS);
915 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
916 E = BBMap.end(); I != E; ++I)
917 OS << "BB '" << I->first->getName() << "' level = "
918 << I->second->getLoopDepth() << "\n";
923 class LoopInfo : public FunctionPass {
924 LoopInfoBase<BasicBlock, Loop> LI;
925 friend class LoopBase<BasicBlock, Loop>;
927 void operator=(const LoopInfo &); // do not implement
928 LoopInfo(const LoopInfo &); // do not implement
930 static char ID; // Pass identification, replacement for typeid
932 LoopInfo() : FunctionPass(&ID) {}
934 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
936 /// iterator/begin/end - The interface to the top-level loops in the current
939 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
940 inline iterator begin() const { return LI.begin(); }
941 inline iterator end() const { return LI.end(); }
942 bool empty() const { return LI.empty(); }
944 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
945 /// block is in no loop (for example the entry node), null is returned.
947 inline Loop *getLoopFor(const BasicBlock *BB) const {
948 return LI.getLoopFor(BB);
951 /// operator[] - same as getLoopFor...
953 inline const Loop *operator[](const BasicBlock *BB) const {
954 return LI.getLoopFor(BB);
957 /// getLoopDepth - Return the loop nesting level of the specified block. A
958 /// depth of 0 means the block is not inside any loop.
960 inline unsigned getLoopDepth(const BasicBlock *BB) const {
961 return LI.getLoopDepth(BB);
964 // isLoopHeader - True if the block is a loop header node
965 inline bool isLoopHeader(BasicBlock *BB) const {
966 return LI.isLoopHeader(BB);
969 /// runOnFunction - Calculate the natural loop information.
971 virtual bool runOnFunction(Function &F);
973 virtual void verifyAnalysis() const;
975 virtual void releaseMemory() { LI.releaseMemory(); }
977 virtual void print(raw_ostream &O, const Module* M = 0) const;
979 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
981 /// removeLoop - This removes the specified top-level loop from this loop info
982 /// object. The loop is not deleted, as it will presumably be inserted into
984 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
986 /// changeLoopFor - Change the top-level loop that contains BB to the
987 /// specified loop. This should be used by transformations that restructure
988 /// the loop hierarchy tree.
989 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
990 LI.changeLoopFor(BB, L);
993 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
994 /// list with the indicated loop.
995 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
996 LI.changeTopLevelLoop(OldLoop, NewLoop);
999 /// addTopLevelLoop - This adds the specified loop to the collection of
1000 /// top-level loops.
1001 inline void addTopLevelLoop(Loop *New) {
1002 LI.addTopLevelLoop(New);
1005 /// removeBlock - This method completely removes BB from all data structures,
1006 /// including all of the Loop objects it is nested in and our mapping from
1007 /// BasicBlocks to loops.
1008 void removeBlock(BasicBlock *BB) {
1014 // Allow clients to walk the list of nested loops...
1015 template <> struct GraphTraits<const Loop*> {
1016 typedef const Loop NodeType;
1017 typedef LoopInfo::iterator ChildIteratorType;
1019 static NodeType *getEntryNode(const Loop *L) { return L; }
1020 static inline ChildIteratorType child_begin(NodeType *N) {
1023 static inline ChildIteratorType child_end(NodeType *N) {
1028 template <> struct GraphTraits<Loop*> {
1029 typedef Loop NodeType;
1030 typedef LoopInfo::iterator ChildIteratorType;
1032 static NodeType *getEntryNode(Loop *L) { return L; }
1033 static inline ChildIteratorType child_begin(NodeType *N) {
1036 static inline ChildIteratorType child_end(NodeType *N) {
1041 template<class BlockT, class LoopT>
1043 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1044 LoopInfoBase<BlockT, LoopT> &LIB) {
1045 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1046 "Incorrect LI specified for this loop!");
1047 assert(NewBB && "Cannot add a null basic block to the loop!");
1048 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1050 LoopT *L = static_cast<LoopT *>(this);
1052 // Add the loop mapping to the LoopInfo object...
1053 LIB.BBMap[NewBB] = L;
1055 // Add the basic block to this loop and all parent loops...
1057 L->Blocks.push_back(NewBB);
1058 L = L->getParentLoop();
1062 } // End llvm namespace