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 typename InvBlockTraits::NodeType *N = *PI;
290 if (!contains(N)) { // If the block is not in the loop...
292 return 0; // Multiple predecessors outside the loop
297 // Make sure there is only one exit out of the preheader.
298 assert(Out && "Header of loop has no predecessors from outside loop?");
302 /// getLoopLatch - If there is a single latch block for this loop, return it.
303 /// A latch block is a block that contains a branch back to the header.
304 BlockT *getLoopLatch() const {
305 BlockT *Header = getHeader();
306 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
307 typename InvBlockTraits::ChildIteratorType PI =
308 InvBlockTraits::child_begin(Header);
309 typename InvBlockTraits::ChildIteratorType PE =
310 InvBlockTraits::child_end(Header);
312 for (; PI != PE; ++PI)
321 //===--------------------------------------------------------------------===//
322 // APIs for updating loop information after changing the CFG
325 /// addBasicBlockToLoop - This method is used by other analyses to update loop
326 /// information. NewBB is set to be a new member of the current loop.
327 /// Because of this, it is added as a member of all parent loops, and is added
328 /// to the specified LoopInfo object as being in the current basic block. It
329 /// is not valid to replace the loop header with this method.
331 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
333 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
334 /// the OldChild entry in our children list with NewChild, and updates the
335 /// parent pointer of OldChild to be null and the NewChild to be this loop.
336 /// This updates the loop depth of the new child.
337 void replaceChildLoopWith(LoopT *OldChild,
339 assert(OldChild->ParentLoop == this && "This loop is already broken!");
340 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
341 typename std::vector<LoopT *>::iterator I =
342 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
343 assert(I != SubLoops.end() && "OldChild not in loop!");
345 OldChild->ParentLoop = 0;
346 NewChild->ParentLoop = static_cast<LoopT *>(this);
349 /// addChildLoop - Add the specified loop to be a child of this loop. This
350 /// updates the loop depth of the new child.
352 void addChildLoop(LoopT *NewChild) {
353 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
354 NewChild->ParentLoop = static_cast<LoopT *>(this);
355 SubLoops.push_back(NewChild);
358 /// removeChildLoop - This removes the specified child from being a subloop of
359 /// this loop. The loop is not deleted, as it will presumably be inserted
360 /// into another loop.
361 LoopT *removeChildLoop(iterator I) {
362 assert(I != SubLoops.end() && "Cannot remove end iterator!");
364 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
365 SubLoops.erase(SubLoops.begin()+(I-begin()));
366 Child->ParentLoop = 0;
370 /// addBlockEntry - This adds a basic block directly to the basic block list.
371 /// This should only be used by transformations that create new loops. Other
372 /// transformations should use addBasicBlockToLoop.
373 void addBlockEntry(BlockT *BB) {
374 Blocks.push_back(BB);
377 /// moveToHeader - This method is used to move BB (which must be part of this
378 /// loop) to be the loop header of the loop (the block that dominates all
380 void moveToHeader(BlockT *BB) {
381 if (Blocks[0] == BB) return;
382 for (unsigned i = 0; ; ++i) {
383 assert(i != Blocks.size() && "Loop does not contain BB!");
384 if (Blocks[i] == BB) {
385 Blocks[i] = Blocks[0];
392 /// removeBlockFromLoop - This removes the specified basic block from the
393 /// current loop, updating the Blocks as appropriate. This does not update
394 /// the mapping in the LoopInfo class.
395 void removeBlockFromLoop(BlockT *BB) {
396 RemoveFromVector(Blocks, BB);
399 /// verifyLoop - Verify loop structure
400 void verifyLoop() const {
402 assert(!Blocks.empty() && "Loop header is missing");
404 // Sort the blocks vector so that we can use binary search to do quick
406 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
407 std::sort(LoopBBs.begin(), LoopBBs.end());
409 // Check the individual blocks.
410 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
412 bool HasInsideLoopSuccs = false;
413 bool HasInsideLoopPreds = false;
414 SmallVector<BlockT *, 2> OutsideLoopPreds;
416 typedef GraphTraits<BlockT*> BlockTraits;
417 for (typename BlockTraits::ChildIteratorType SI =
418 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
420 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
421 HasInsideLoopSuccs = true;
424 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
425 for (typename InvBlockTraits::ChildIteratorType PI =
426 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
428 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI))
429 HasInsideLoopPreds = true;
431 OutsideLoopPreds.push_back(*PI);
434 if (BB == getHeader()) {
435 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
436 } else if (!OutsideLoopPreds.empty()) {
437 // A non-header loop shouldn't be reachable from outside the loop,
438 // though it is permitted if the predecessor is not itself actually
440 BlockT *EntryBB = BB->getParent()->begin();
441 for (df_iterator<BlockT *> NI = df_begin(EntryBB),
442 NE = df_end(EntryBB); NI != NE; ++NI)
443 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
444 assert(*NI != OutsideLoopPreds[i] &&
445 "Loop has multiple entry points!");
447 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
448 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
449 assert(BB != getHeader()->getParent()->begin() &&
450 "Loop contains function entry block!");
453 // Check the subloops.
454 for (iterator I = begin(), E = end(); I != E; ++I)
455 // Each block in each subloop should be contained within this loop.
456 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
458 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
459 "Loop does not contain all the blocks of a subloop!");
462 // Check the parent loop pointer.
464 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
466 "Loop is not a subloop of its parent!");
471 /// verifyLoop - Verify loop structure of this loop and all nested loops.
472 void verifyLoopNest() const {
475 // Verify the subloops.
476 for (iterator I = begin(), E = end(); I != E; ++I)
477 (*I)->verifyLoopNest();
480 void print(raw_ostream &OS, unsigned Depth = 0) const {
481 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
484 for (unsigned i = 0; i < getBlocks().size(); ++i) {
486 BlockT *BB = getBlocks()[i];
487 WriteAsOperand(OS, BB, false);
488 if (BB == getHeader()) OS << "<header>";
489 if (BB == getLoopLatch()) OS << "<latch>";
490 if (isLoopExiting(BB)) OS << "<exiting>";
494 for (iterator I = begin(), E = end(); I != E; ++I)
495 (*I)->print(OS, Depth+2);
499 friend class LoopInfoBase<BlockT, LoopT>;
500 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
501 Blocks.push_back(BB);
505 class Loop : public LoopBase<BasicBlock, Loop> {
509 /// isLoopInvariant - Return true if the specified value is loop invariant
511 bool isLoopInvariant(Value *V) const;
513 /// isLoopInvariant - Return true if the specified instruction is
516 bool isLoopInvariant(Instruction *I) const;
518 /// makeLoopInvariant - If the given value is an instruction inside of the
519 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
520 /// Return true if the value after any hoisting is loop invariant. This
521 /// function can be used as a slightly more aggressive replacement for
524 /// If InsertPt is specified, it is the point to hoist instructions to.
525 /// If null, the terminator of the loop preheader is used.
527 bool makeLoopInvariant(Value *V, bool &Changed,
528 Instruction *InsertPt = 0) const;
530 /// makeLoopInvariant - If the given instruction is inside of the
531 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
532 /// Return true if the instruction after any hoisting is loop invariant. This
533 /// function can be used as a slightly more aggressive replacement for
536 /// If InsertPt is specified, it is the point to hoist instructions to.
537 /// If null, the terminator of the loop preheader is used.
539 bool makeLoopInvariant(Instruction *I, bool &Changed,
540 Instruction *InsertPt = 0) const;
542 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
543 /// induction variable: an integer recurrence that starts at 0 and increments
544 /// by one each time through the loop. If so, return the phi node that
545 /// corresponds to it.
547 /// The IndVarSimplify pass transforms loops to have a canonical induction
550 PHINode *getCanonicalInductionVariable() const;
552 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
553 /// the canonical induction variable value for the "next" iteration of the
554 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
556 Instruction *getCanonicalInductionVariableIncrement() const;
558 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
559 /// times the loop will be executed. Note that this means that the backedge
560 /// of the loop executes N-1 times. If the trip-count cannot be determined,
561 /// this returns null.
563 /// The IndVarSimplify pass transforms loops to have a form that this
564 /// function easily understands.
566 Value *getTripCount() const;
568 /// getSmallConstantTripCount - Returns the trip count of this loop as a
569 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
570 /// of not constant. Will also return 0 if the trip count is very large
573 /// The IndVarSimplify pass transforms loops to have a form that this
574 /// function easily understands.
576 unsigned getSmallConstantTripCount() const;
578 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
579 /// trip count of this loop as a normal unsigned value, if possible. This
580 /// means that the actual trip count is always a multiple of the returned
581 /// value (don't forget the trip count could very well be zero as well!).
583 /// Returns 1 if the trip count is unknown or not guaranteed to be the
584 /// multiple of a constant (which is also the case if the trip count is simply
585 /// constant, use getSmallConstantTripCount for that case), Will also return 1
586 /// if the trip count is very large (>= 2^32).
587 unsigned getSmallConstantTripMultiple() const;
589 /// isLCSSAForm - Return true if the Loop is in LCSSA form
590 bool isLCSSAForm(DominatorTree &DT) const;
592 /// isLoopSimplifyForm - Return true if the Loop is in the form that
593 /// the LoopSimplify form transforms loops to, which is sometimes called
595 bool isLoopSimplifyForm() const;
597 /// hasDedicatedExits - Return true if no exit block for the loop
598 /// has a predecessor that is outside the loop.
599 bool hasDedicatedExits() const;
601 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
602 /// These are the blocks _outside of the current loop_ which are branched to.
603 /// This assumes that loop exits are in canonical form.
605 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
607 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
608 /// block, return that block. Otherwise return null.
609 BasicBlock *getUniqueExitBlock() const;
614 friend class LoopInfoBase<BasicBlock, Loop>;
615 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
618 //===----------------------------------------------------------------------===//
619 /// LoopInfo - This class builds and contains all of the top level loop
620 /// structures in the specified function.
623 template<class BlockT, class LoopT>
625 // BBMap - Mapping of basic blocks to the inner most loop they occur in
626 std::map<BlockT *, LoopT *> BBMap;
627 std::vector<LoopT *> TopLevelLoops;
628 friend class LoopBase<BlockT, LoopT>;
630 void operator=(const LoopInfoBase &); // do not implement
631 LoopInfoBase(const LoopInfo &); // do not implement
634 ~LoopInfoBase() { releaseMemory(); }
636 void releaseMemory() {
637 for (typename std::vector<LoopT *>::iterator I =
638 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
639 delete *I; // Delete all of the loops...
641 BBMap.clear(); // Reset internal state of analysis
642 TopLevelLoops.clear();
645 /// iterator/begin/end - The interface to the top-level loops in the current
648 typedef typename std::vector<LoopT *>::const_iterator iterator;
649 iterator begin() const { return TopLevelLoops.begin(); }
650 iterator end() const { return TopLevelLoops.end(); }
651 bool empty() const { return TopLevelLoops.empty(); }
653 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
654 /// block is in no loop (for example the entry node), null is returned.
656 LoopT *getLoopFor(const BlockT *BB) const {
657 typename std::map<BlockT *, LoopT *>::const_iterator I=
658 BBMap.find(const_cast<BlockT*>(BB));
659 return I != BBMap.end() ? I->second : 0;
662 /// operator[] - same as getLoopFor...
664 const LoopT *operator[](const BlockT *BB) const {
665 return getLoopFor(BB);
668 /// getLoopDepth - Return the loop nesting level of the specified block. A
669 /// depth of 0 means the block is not inside any loop.
671 unsigned getLoopDepth(const BlockT *BB) const {
672 const LoopT *L = getLoopFor(BB);
673 return L ? L->getLoopDepth() : 0;
676 // isLoopHeader - True if the block is a loop header node
677 bool isLoopHeader(BlockT *BB) const {
678 const LoopT *L = getLoopFor(BB);
679 return L && L->getHeader() == BB;
682 /// removeLoop - This removes the specified top-level loop from this loop info
683 /// object. The loop is not deleted, as it will presumably be inserted into
685 LoopT *removeLoop(iterator I) {
686 assert(I != end() && "Cannot remove end iterator!");
688 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
689 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
693 /// changeLoopFor - Change the top-level loop that contains BB to the
694 /// specified loop. This should be used by transformations that restructure
695 /// the loop hierarchy tree.
696 void changeLoopFor(BlockT *BB, LoopT *L) {
697 LoopT *&OldLoop = BBMap[BB];
698 assert(OldLoop && "Block not in a loop yet!");
702 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
703 /// list with the indicated loop.
704 void changeTopLevelLoop(LoopT *OldLoop,
706 typename std::vector<LoopT *>::iterator I =
707 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
708 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
710 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
711 "Loops already embedded into a subloop!");
714 /// addTopLevelLoop - This adds the specified loop to the collection of
716 void addTopLevelLoop(LoopT *New) {
717 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
718 TopLevelLoops.push_back(New);
721 /// removeBlock - This method completely removes BB from all data structures,
722 /// including all of the Loop objects it is nested in and our mapping from
723 /// BasicBlocks to loops.
724 void removeBlock(BlockT *BB) {
725 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
726 if (I != BBMap.end()) {
727 for (LoopT *L = I->second; L; L = L->getParentLoop())
728 L->removeBlockFromLoop(BB);
736 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
737 const LoopT *ParentLoop) {
738 if (SubLoop == 0) return true;
739 if (SubLoop == ParentLoop) return false;
740 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
743 void Calculate(DominatorTreeBase<BlockT> &DT) {
744 BlockT *RootNode = DT.getRootNode()->getBlock();
746 for (df_iterator<BlockT*> NI = df_begin(RootNode),
747 NE = df_end(RootNode); NI != NE; ++NI)
748 if (LoopT *L = ConsiderForLoop(*NI, DT))
749 TopLevelLoops.push_back(L);
752 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
753 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
755 std::vector<BlockT *> TodoStack;
757 // Scan the predecessors of BB, checking to see if BB dominates any of
758 // them. This identifies backedges which target this node...
759 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
760 for (typename InvBlockTraits::ChildIteratorType I =
761 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
763 typename InvBlockTraits::NodeType *N = *I;
764 if (DT.dominates(BB, N)) // If BB dominates its predecessor...
765 TodoStack.push_back(N);
768 if (TodoStack.empty()) return 0; // No backedges to this block...
770 // Create a new loop to represent this basic block...
771 LoopT *L = new LoopT(BB);
774 BlockT *EntryBlock = BB->getParent()->begin();
776 while (!TodoStack.empty()) { // Process all the nodes in the loop
777 BlockT *X = TodoStack.back();
778 TodoStack.pop_back();
780 if (!L->contains(X) && // As of yet unprocessed??
781 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
782 // Check to see if this block already belongs to a loop. If this occurs
783 // then we have a case where a loop that is supposed to be a child of
784 // the current loop was processed before the current loop. When this
785 // occurs, this child loop gets added to a part of the current loop,
786 // making it a sibling to the current loop. We have to reparent this
789 const_cast<LoopT *>(getLoopFor(X)))
790 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
791 // Remove the subloop from its current parent...
792 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
793 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
794 typename std::vector<LoopT *>::iterator I =
795 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
796 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
797 SLP->SubLoops.erase(I); // Remove from parent...
799 // Add the subloop to THIS loop...
800 SubLoop->ParentLoop = L;
801 L->SubLoops.push_back(SubLoop);
804 // Normal case, add the block to our loop...
805 L->Blocks.push_back(X);
807 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
809 // Add all of the predecessors of X to the end of the work stack...
810 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
811 InvBlockTraits::child_end(X));
815 // If there are any loops nested within this loop, create them now!
816 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
817 E = L->Blocks.end(); I != E; ++I)
818 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
819 L->SubLoops.push_back(NewLoop);
820 NewLoop->ParentLoop = L;
823 // Add the basic blocks that comprise this loop to the BBMap so that this
824 // loop can be found for them.
826 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
827 E = L->Blocks.end(); I != E; ++I)
828 BBMap.insert(std::make_pair(*I, L));
830 // Now that we have a list of all of the child loops of this loop, check to
831 // see if any of them should actually be nested inside of each other. We
832 // can accidentally pull loops our of their parents, so we must make sure to
833 // organize the loop nests correctly now.
835 std::map<BlockT *, LoopT *> ContainingLoops;
836 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
837 LoopT *Child = L->SubLoops[i];
838 assert(Child->getParentLoop() == L && "Not proper child loop?");
840 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
841 // If there is already a loop which contains this loop, move this loop
842 // into the containing loop.
843 MoveSiblingLoopInto(Child, ContainingLoop);
844 --i; // The loop got removed from the SubLoops list.
846 // This is currently considered to be a top-level loop. Check to see
847 // if any of the contained blocks are loop headers for subloops we
848 // have already processed.
849 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
850 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
851 if (BlockLoop == 0) { // Child block not processed yet...
853 } else if (BlockLoop != Child) {
854 LoopT *SubLoop = BlockLoop;
855 // Reparent all of the blocks which used to belong to BlockLoops
856 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
857 ContainingLoops[SubLoop->Blocks[j]] = Child;
859 // There is already a loop which contains this block, that means
860 // that we should reparent the loop which the block is currently
861 // considered to belong to to be a child of this loop.
862 MoveSiblingLoopInto(SubLoop, Child);
863 --i; // We just shrunk the SubLoops list.
873 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
874 /// of the NewParent Loop, instead of being a sibling of it.
875 void MoveSiblingLoopInto(LoopT *NewChild,
877 LoopT *OldParent = NewChild->getParentLoop();
878 assert(OldParent && OldParent == NewParent->getParentLoop() &&
879 NewChild != NewParent && "Not sibling loops!");
881 // Remove NewChild from being a child of OldParent
882 typename std::vector<LoopT *>::iterator I =
883 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
885 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
886 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
887 NewChild->ParentLoop = 0;
889 InsertLoopInto(NewChild, NewParent);
892 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
893 /// the parent loop contains a loop which should contain L, the loop gets
894 /// inserted into L instead.
895 void InsertLoopInto(LoopT *L, LoopT *Parent) {
896 BlockT *LHeader = L->getHeader();
897 assert(Parent->contains(LHeader) &&
898 "This loop should not be inserted here!");
900 // Check to see if it belongs in a child loop...
901 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
903 if (Parent->SubLoops[i]->contains(LHeader)) {
904 InsertLoopInto(L, Parent->SubLoops[i]);
908 // If not, insert it here!
909 Parent->SubLoops.push_back(L);
910 L->ParentLoop = Parent;
915 void print(raw_ostream &OS) const {
916 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
917 TopLevelLoops[i]->print(OS);
919 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
920 E = BBMap.end(); I != E; ++I)
921 OS << "BB '" << I->first->getName() << "' level = "
922 << I->second->getLoopDepth() << "\n";
927 class LoopInfo : public FunctionPass {
928 LoopInfoBase<BasicBlock, Loop> LI;
929 friend class LoopBase<BasicBlock, Loop>;
931 void operator=(const LoopInfo &); // do not implement
932 LoopInfo(const LoopInfo &); // do not implement
934 static char ID; // Pass identification, replacement for typeid
936 LoopInfo() : FunctionPass(&ID) {}
938 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
940 /// iterator/begin/end - The interface to the top-level loops in the current
943 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
944 inline iterator begin() const { return LI.begin(); }
945 inline iterator end() const { return LI.end(); }
946 bool empty() const { return LI.empty(); }
948 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
949 /// block is in no loop (for example the entry node), null is returned.
951 inline Loop *getLoopFor(const BasicBlock *BB) const {
952 return LI.getLoopFor(BB);
955 /// operator[] - same as getLoopFor...
957 inline const Loop *operator[](const BasicBlock *BB) const {
958 return LI.getLoopFor(BB);
961 /// getLoopDepth - Return the loop nesting level of the specified block. A
962 /// depth of 0 means the block is not inside any loop.
964 inline unsigned getLoopDepth(const BasicBlock *BB) const {
965 return LI.getLoopDepth(BB);
968 // isLoopHeader - True if the block is a loop header node
969 inline bool isLoopHeader(BasicBlock *BB) const {
970 return LI.isLoopHeader(BB);
973 /// runOnFunction - Calculate the natural loop information.
975 virtual bool runOnFunction(Function &F);
977 virtual void verifyAnalysis() const;
979 virtual void releaseMemory() { LI.releaseMemory(); }
981 virtual void print(raw_ostream &O, const Module* M = 0) const;
983 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
985 /// removeLoop - This removes the specified top-level loop from this loop info
986 /// object. The loop is not deleted, as it will presumably be inserted into
988 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
990 /// changeLoopFor - Change the top-level loop that contains BB to the
991 /// specified loop. This should be used by transformations that restructure
992 /// the loop hierarchy tree.
993 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
994 LI.changeLoopFor(BB, L);
997 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
998 /// list with the indicated loop.
999 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1000 LI.changeTopLevelLoop(OldLoop, NewLoop);
1003 /// addTopLevelLoop - This adds the specified loop to the collection of
1004 /// top-level loops.
1005 inline void addTopLevelLoop(Loop *New) {
1006 LI.addTopLevelLoop(New);
1009 /// removeBlock - This method completely removes BB from all data structures,
1010 /// including all of the Loop objects it is nested in and our mapping from
1011 /// BasicBlocks to loops.
1012 void removeBlock(BasicBlock *BB) {
1018 // Allow clients to walk the list of nested loops...
1019 template <> struct GraphTraits<const Loop*> {
1020 typedef const Loop NodeType;
1021 typedef LoopInfo::iterator ChildIteratorType;
1023 static NodeType *getEntryNode(const Loop *L) { return L; }
1024 static inline ChildIteratorType child_begin(NodeType *N) {
1027 static inline ChildIteratorType child_end(NodeType *N) {
1032 template <> struct GraphTraits<Loop*> {
1033 typedef Loop NodeType;
1034 typedef LoopInfo::iterator ChildIteratorType;
1036 static NodeType *getEntryNode(Loop *L) { return L; }
1037 static inline ChildIteratorType child_begin(NodeType *N) {
1040 static inline ChildIteratorType child_end(NodeType *N) {
1045 template<class BlockT, class LoopT>
1047 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1048 LoopInfoBase<BlockT, LoopT> &LIB) {
1049 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1050 "Incorrect LI specified for this loop!");
1051 assert(NewBB && "Cannot add a null basic block to the loop!");
1052 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1054 LoopT *L = static_cast<LoopT *>(this);
1056 // Add the loop mapping to the LoopInfo object...
1057 LIB.BBMap[NewBB] = L;
1059 // Add the basic block to this loop and all parent loops...
1061 L->Blocks.push_back(NewBB);
1062 L = L->getParentLoop();
1066 } // End llvm namespace