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
28 //===----------------------------------------------------------------------===//
30 #ifndef LLVM_ANALYSIS_LOOPINFO_H
31 #define LLVM_ANALYSIS_LOOPINFO_H
33 #include "llvm/ADT/DenseMap.h"
34 #include "llvm/ADT/DenseSet.h"
35 #include "llvm/ADT/GraphTraits.h"
36 #include "llvm/ADT/SmallPtrSet.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/IR/CFG.h"
39 #include "llvm/IR/Instruction.h"
40 #include "llvm/Pass.h"
46 inline 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!");
58 template<class N> class DominatorTreeBase;
59 template<class N, class M> class LoopInfoBase;
60 template<class N, class M> class LoopBase;
62 //===----------------------------------------------------------------------===//
63 /// LoopBase class - Instances of this class are used to represent loops that
64 /// are detected in the flow graph
66 template<class BlockT, class LoopT>
69 // SubLoops - Loops contained entirely within this one.
70 std::vector<LoopT *> SubLoops;
72 // Blocks - The list of blocks in this loop. First entry is the header node.
73 std::vector<BlockT*> Blocks;
75 SmallPtrSet<const BlockT*, 8> DenseBlockSet;
77 LoopBase(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION;
78 const LoopBase<BlockT, LoopT>&
79 operator=(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION;
81 /// Loop ctor - This creates an empty loop.
82 LoopBase() : ParentLoop(nullptr) {}
84 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
88 /// getLoopDepth - Return the nesting level of this loop. An outer-most
89 /// loop has depth 1, for consistency with loop depth values used for basic
90 /// blocks, where depth 0 is used for blocks not inside any loops.
91 unsigned getLoopDepth() const {
93 for (const LoopT *CurLoop = ParentLoop; CurLoop;
94 CurLoop = CurLoop->ParentLoop)
98 BlockT *getHeader() const { return Blocks.front(); }
99 LoopT *getParentLoop() const { return ParentLoop; }
101 /// setParentLoop is a raw interface for bypassing addChildLoop.
102 void setParentLoop(LoopT *L) { ParentLoop = L; }
104 /// contains - Return true if the specified loop is contained within in
107 bool contains(const LoopT *L) const {
108 if (L == this) return true;
109 if (!L) return false;
110 return contains(L->getParentLoop());
113 /// contains - Return true if the specified basic block is in this loop.
115 bool contains(const BlockT *BB) const {
116 return DenseBlockSet.count(BB);
119 /// contains - Return true if the specified instruction is in this loop.
121 template<class InstT>
122 bool contains(const InstT *Inst) const {
123 return contains(Inst->getParent());
126 /// iterator/begin/end - Return the loops contained entirely within this loop.
128 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
129 std::vector<LoopT *> &getSubLoopsVector() { return SubLoops; }
130 typedef typename std::vector<LoopT *>::const_iterator iterator;
131 typedef typename std::vector<LoopT *>::const_reverse_iterator
133 iterator begin() const { return SubLoops.begin(); }
134 iterator end() const { return SubLoops.end(); }
135 reverse_iterator rbegin() const { return SubLoops.rbegin(); }
136 reverse_iterator rend() const { return SubLoops.rend(); }
137 bool empty() const { return SubLoops.empty(); }
139 /// getBlocks - Get a list of the basic blocks which make up this loop.
141 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
142 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
143 block_iterator block_begin() const { return Blocks.begin(); }
144 block_iterator block_end() const { return Blocks.end(); }
146 /// getNumBlocks - Get the number of blocks in this loop in constant time.
147 unsigned getNumBlocks() const {
148 return Blocks.size();
151 /// isLoopExiting - True if terminator in the block can branch to another
152 /// block that is outside of the current loop.
154 bool isLoopExiting(const BlockT *BB) const {
155 typedef GraphTraits<const BlockT*> BlockTraits;
156 for (typename BlockTraits::ChildIteratorType SI =
157 BlockTraits::child_begin(BB),
158 SE = BlockTraits::child_end(BB); SI != SE; ++SI) {
165 /// getNumBackEdges - Calculate the number of back edges to the loop header
167 unsigned getNumBackEdges() const {
168 unsigned NumBackEdges = 0;
169 BlockT *H = getHeader();
171 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
172 for (typename InvBlockTraits::ChildIteratorType I =
173 InvBlockTraits::child_begin(H),
174 E = InvBlockTraits::child_end(H); I != E; ++I)
181 //===--------------------------------------------------------------------===//
182 // APIs for simple analysis of the loop.
184 // Note that all of these methods can fail on general loops (ie, there may not
185 // be a preheader, etc). For best success, the loop simplification and
186 // induction variable canonicalization pass should be used to normalize loops
187 // for easy analysis. These methods assume canonical loops.
189 /// getExitingBlocks - Return all blocks inside the loop that have successors
190 /// outside of the loop. These are the blocks _inside of the current loop_
191 /// which branch out. The returned list is always unique.
193 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const;
195 /// getExitingBlock - If getExitingBlocks would return exactly one block,
196 /// return that block. Otherwise return null.
197 BlockT *getExitingBlock() const;
199 /// getExitBlocks - Return all of the successor blocks of this loop. These
200 /// are the blocks _outside of the current loop_ which are branched to.
202 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const;
204 /// getExitBlock - If getExitBlocks would return exactly one block,
205 /// return that block. Otherwise return null.
206 BlockT *getExitBlock() const;
209 typedef std::pair<const BlockT*, const BlockT*> Edge;
211 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
212 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const;
214 /// getLoopPreheader - If there is a preheader for this loop, return it. A
215 /// loop has a preheader if there is only one edge to the header of the loop
216 /// from outside of the loop. If this is the case, the block branching to the
217 /// header of the loop is the preheader node.
219 /// This method returns null if there is no preheader for the loop.
221 BlockT *getLoopPreheader() const;
223 /// getLoopPredecessor - If the given loop's header has exactly one unique
224 /// predecessor outside the loop, return it. Otherwise return null.
225 /// This is less strict that the loop "preheader" concept, which requires
226 /// the predecessor to have exactly one successor.
228 BlockT *getLoopPredecessor() const;
230 /// getLoopLatch - If there is a single latch block for this loop, return it.
231 /// A latch block is a block that contains a branch back to the header.
232 BlockT *getLoopLatch() const;
234 /// getLoopLatches - Return all loop latch blocks of this loop. A latch block
235 /// is a block that contains a branch back to the header.
236 void getLoopLatches(SmallVectorImpl<BlockT *> &LoopLatches) const {
237 BlockT *H = getHeader();
238 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
239 for (typename InvBlockTraits::ChildIteratorType I =
240 InvBlockTraits::child_begin(H),
241 E = InvBlockTraits::child_end(H); I != E; ++I)
243 LoopLatches.push_back(*I);
246 //===--------------------------------------------------------------------===//
247 // APIs for updating loop information after changing the CFG
250 /// addBasicBlockToLoop - This method is used by other analyses to update loop
251 /// information. NewBB is set to be a new member of the current loop.
252 /// Because of this, it is added as a member of all parent loops, and is added
253 /// to the specified LoopInfo object as being in the current basic block. It
254 /// is not valid to replace the loop header with this method.
256 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
258 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
259 /// the OldChild entry in our children list with NewChild, and updates the
260 /// parent pointer of OldChild to be null and the NewChild to be this loop.
261 /// This updates the loop depth of the new child.
262 void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild);
264 /// addChildLoop - Add the specified loop to be a child of this loop. This
265 /// updates the loop depth of the new child.
267 void addChildLoop(LoopT *NewChild) {
268 assert(!NewChild->ParentLoop && "NewChild already has a parent!");
269 NewChild->ParentLoop = static_cast<LoopT *>(this);
270 SubLoops.push_back(NewChild);
273 /// removeChildLoop - This removes the specified child from being a subloop of
274 /// this loop. The loop is not deleted, as it will presumably be inserted
275 /// into another loop.
276 LoopT *removeChildLoop(iterator I) {
277 assert(I != SubLoops.end() && "Cannot remove end iterator!");
279 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
280 SubLoops.erase(SubLoops.begin()+(I-begin()));
281 Child->ParentLoop = nullptr;
285 /// addBlockEntry - This adds a basic block directly to the basic block list.
286 /// This should only be used by transformations that create new loops. Other
287 /// transformations should use addBasicBlockToLoop.
288 void addBlockEntry(BlockT *BB) {
289 Blocks.push_back(BB);
290 DenseBlockSet.insert(BB);
293 /// reverseBlocks - interface to reverse Blocks[from, end of loop] in this loop
294 void reverseBlock(unsigned from) {
295 std::reverse(Blocks.begin() + from, Blocks.end());
298 /// reserveBlocks- interface to do reserve() for Blocks
299 void reserveBlocks(unsigned size) {
300 Blocks.reserve(size);
303 /// moveToHeader - This method is used to move BB (which must be part of this
304 /// loop) to be the loop header of the loop (the block that dominates all
306 void moveToHeader(BlockT *BB) {
307 if (Blocks[0] == BB) return;
308 for (unsigned i = 0; ; ++i) {
309 assert(i != Blocks.size() && "Loop does not contain BB!");
310 if (Blocks[i] == BB) {
311 Blocks[i] = Blocks[0];
318 /// removeBlockFromLoop - This removes the specified basic block from the
319 /// current loop, updating the Blocks as appropriate. This does not update
320 /// the mapping in the LoopInfo class.
321 void removeBlockFromLoop(BlockT *BB) {
322 RemoveFromVector(Blocks, BB);
323 DenseBlockSet.erase(BB);
326 /// verifyLoop - Verify loop structure
327 void verifyLoop() const;
329 /// verifyLoop - Verify loop structure of this loop and all nested loops.
330 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const;
332 void print(raw_ostream &OS, unsigned Depth = 0) const;
335 friend class LoopInfoBase<BlockT, LoopT>;
336 explicit LoopBase(BlockT *BB) : ParentLoop(nullptr) {
337 Blocks.push_back(BB);
338 DenseBlockSet.insert(BB);
342 template<class BlockT, class LoopT>
343 raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) {
348 // Implementation in LoopInfoImpl.h
350 __extension__ extern template class LoopBase<BasicBlock, Loop>;
353 class Loop : public LoopBase<BasicBlock, Loop> {
357 /// isLoopInvariant - Return true if the specified value is loop invariant
359 bool isLoopInvariant(Value *V) const;
361 /// hasLoopInvariantOperands - Return true if all the operands of the
362 /// specified instruction are loop invariant.
363 bool hasLoopInvariantOperands(Instruction *I) const;
365 /// makeLoopInvariant - If the given value is an instruction inside of the
366 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
367 /// Return true if the value after any hoisting is loop invariant. This
368 /// function can be used as a slightly more aggressive replacement for
371 /// If InsertPt is specified, it is the point to hoist instructions to.
372 /// If null, the terminator of the loop preheader is used.
374 bool makeLoopInvariant(Value *V, bool &Changed,
375 Instruction *InsertPt = nullptr) const;
377 /// makeLoopInvariant - If the given instruction is inside of the
378 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
379 /// Return true if the instruction after any hoisting is loop invariant. This
380 /// function can be used as a slightly more aggressive replacement for
383 /// If InsertPt is specified, it is the point to hoist instructions to.
384 /// If null, the terminator of the loop preheader is used.
386 bool makeLoopInvariant(Instruction *I, bool &Changed,
387 Instruction *InsertPt = nullptr) const;
389 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
390 /// induction variable: an integer recurrence that starts at 0 and increments
391 /// by one each time through the loop. If so, return the phi node that
392 /// corresponds to it.
394 /// The IndVarSimplify pass transforms loops to have a canonical induction
397 PHINode *getCanonicalInductionVariable() const;
399 /// isLCSSAForm - Return true if the Loop is in LCSSA form
400 bool isLCSSAForm(DominatorTree &DT) const;
402 /// isLoopSimplifyForm - Return true if the Loop is in the form that
403 /// the LoopSimplify form transforms loops to, which is sometimes called
405 bool isLoopSimplifyForm() const;
407 /// isSafeToClone - Return true if the loop body is safe to clone in practice.
408 bool isSafeToClone() const;
410 /// Returns true if the loop is annotated parallel.
412 /// A parallel loop can be assumed to not contain any dependencies between
413 /// iterations by the compiler. That is, any loop-carried dependency checking
414 /// can be skipped completely when parallelizing the loop on the target
415 /// machine. Thus, if the parallel loop information originates from the
416 /// programmer, e.g. via the OpenMP parallel for pragma, it is the
417 /// programmer's responsibility to ensure there are no loop-carried
418 /// dependencies. The final execution order of the instructions across
419 /// iterations is not guaranteed, thus, the end result might or might not
420 /// implement actual concurrent execution of instructions across multiple
422 bool isAnnotatedParallel() const;
424 /// Return the llvm.loop loop id metadata node for this loop if it is present.
426 /// If this loop contains the same llvm.loop metadata on each branch to the
427 /// header then the node is returned. If any latch instruction does not
428 /// contain llvm.loop or or if multiple latches contain different nodes then
430 MDNode *getLoopID() const;
431 /// Set the llvm.loop loop id metadata for this loop.
433 /// The LoopID metadata node will be added to each terminator instruction in
434 /// the loop that branches to the loop header.
436 /// The LoopID metadata node should have one or more operands and the first
437 /// operand should should be the node itself.
438 void setLoopID(MDNode *LoopID) const;
440 /// hasDedicatedExits - Return true if no exit block for the loop
441 /// has a predecessor that is outside the loop.
442 bool hasDedicatedExits() const;
444 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
445 /// These are the blocks _outside of the current loop_ which are branched to.
446 /// This assumes that loop exits are in canonical form.
448 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
450 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
451 /// block, return that block. Otherwise return null.
452 BasicBlock *getUniqueExitBlock() const;
457 friend class LoopInfoBase<BasicBlock, Loop>;
458 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
461 //===----------------------------------------------------------------------===//
462 /// LoopInfo - This class builds and contains all of the top level loop
463 /// structures in the specified function.
466 template<class BlockT, class LoopT>
468 // BBMap - Mapping of basic blocks to the inner most loop they occur in
469 DenseMap<BlockT *, LoopT *> BBMap;
470 std::vector<LoopT *> TopLevelLoops;
471 friend class LoopBase<BlockT, LoopT>;
472 friend class LoopInfo;
474 void operator=(const LoopInfoBase &) LLVM_DELETED_FUNCTION;
475 LoopInfoBase(const LoopInfo &) LLVM_DELETED_FUNCTION;
478 ~LoopInfoBase() { releaseMemory(); }
480 void releaseMemory() {
481 for (typename std::vector<LoopT *>::iterator I =
482 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
483 delete *I; // Delete all of the loops...
485 BBMap.clear(); // Reset internal state of analysis
486 TopLevelLoops.clear();
489 /// iterator/begin/end - The interface to the top-level loops in the current
492 typedef typename std::vector<LoopT *>::const_iterator iterator;
493 typedef typename std::vector<LoopT *>::const_reverse_iterator
495 iterator begin() const { return TopLevelLoops.begin(); }
496 iterator end() const { return TopLevelLoops.end(); }
497 reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); }
498 reverse_iterator rend() const { return TopLevelLoops.rend(); }
499 bool empty() const { return TopLevelLoops.empty(); }
501 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
502 /// block is in no loop (for example the entry node), null is returned.
504 LoopT *getLoopFor(const BlockT *BB) const {
505 return BBMap.lookup(const_cast<BlockT*>(BB));
508 /// operator[] - same as getLoopFor...
510 const LoopT *operator[](const BlockT *BB) const {
511 return getLoopFor(BB);
514 /// getLoopDepth - Return the loop nesting level of the specified block. A
515 /// depth of 0 means the block is not inside any loop.
517 unsigned getLoopDepth(const BlockT *BB) const {
518 const LoopT *L = getLoopFor(BB);
519 return L ? L->getLoopDepth() : 0;
522 // isLoopHeader - True if the block is a loop header node
523 bool isLoopHeader(BlockT *BB) const {
524 const LoopT *L = getLoopFor(BB);
525 return L && L->getHeader() == BB;
528 /// removeLoop - This removes the specified top-level loop from this loop info
529 /// object. The loop is not deleted, as it will presumably be inserted into
531 LoopT *removeLoop(iterator I) {
532 assert(I != end() && "Cannot remove end iterator!");
534 assert(!L->getParentLoop() && "Not a top-level loop!");
535 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
539 /// changeLoopFor - Change the top-level loop that contains BB to the
540 /// specified loop. This should be used by transformations that restructure
541 /// the loop hierarchy tree.
542 void changeLoopFor(BlockT *BB, LoopT *L) {
550 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
551 /// list with the indicated loop.
552 void changeTopLevelLoop(LoopT *OldLoop,
554 typename std::vector<LoopT *>::iterator I =
555 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
556 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
558 assert(!NewLoop->ParentLoop && !OldLoop->ParentLoop &&
559 "Loops already embedded into a subloop!");
562 /// addTopLevelLoop - This adds the specified loop to the collection of
564 void addTopLevelLoop(LoopT *New) {
565 assert(!New->getParentLoop() && "Loop already in subloop!");
566 TopLevelLoops.push_back(New);
569 /// removeBlock - This method completely removes BB from all data structures,
570 /// including all of the Loop objects it is nested in and our mapping from
571 /// BasicBlocks to loops.
572 void removeBlock(BlockT *BB) {
573 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
574 if (I != BBMap.end()) {
575 for (LoopT *L = I->second; L; L = L->getParentLoop())
576 L->removeBlockFromLoop(BB);
584 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
585 const LoopT *ParentLoop) {
586 if (!SubLoop) return true;
587 if (SubLoop == ParentLoop) return false;
588 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
591 /// Create the loop forest using a stable algorithm.
592 void Analyze(DominatorTreeBase<BlockT> &DomTree);
596 void print(raw_ostream &OS) const;
599 // Implementation in LoopInfoImpl.h
601 __extension__ extern template class LoopInfoBase<BasicBlock, Loop>;
604 class LoopInfo : public FunctionPass {
605 LoopInfoBase<BasicBlock, Loop> LI;
606 friend class LoopBase<BasicBlock, Loop>;
608 void operator=(const LoopInfo &) LLVM_DELETED_FUNCTION;
609 LoopInfo(const LoopInfo &) LLVM_DELETED_FUNCTION;
611 static char ID; // Pass identification, replacement for typeid
613 LoopInfo() : FunctionPass(ID) {
614 initializeLoopInfoPass(*PassRegistry::getPassRegistry());
617 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
619 /// iterator/begin/end - The interface to the top-level loops in the current
622 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
623 typedef LoopInfoBase<BasicBlock, Loop>::reverse_iterator reverse_iterator;
624 inline iterator begin() const { return LI.begin(); }
625 inline iterator end() const { return LI.end(); }
626 inline reverse_iterator rbegin() const { return LI.rbegin(); }
627 inline reverse_iterator rend() const { return LI.rend(); }
628 bool empty() const { return LI.empty(); }
630 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
631 /// block is in no loop (for example the entry node), null is returned.
633 inline Loop *getLoopFor(const BasicBlock *BB) const {
634 return LI.getLoopFor(BB);
637 /// operator[] - same as getLoopFor...
639 inline const Loop *operator[](const BasicBlock *BB) const {
640 return LI.getLoopFor(BB);
643 /// getLoopDepth - Return the loop nesting level of the specified block. A
644 /// depth of 0 means the block is not inside any loop.
646 inline unsigned getLoopDepth(const BasicBlock *BB) const {
647 return LI.getLoopDepth(BB);
650 // isLoopHeader - True if the block is a loop header node
651 inline bool isLoopHeader(BasicBlock *BB) const {
652 return LI.isLoopHeader(BB);
655 /// runOnFunction - Calculate the natural loop information.
657 bool runOnFunction(Function &F) override;
659 void verifyAnalysis() const override;
661 void releaseMemory() override { LI.releaseMemory(); }
663 void print(raw_ostream &O, const Module* M = nullptr) const override;
665 void getAnalysisUsage(AnalysisUsage &AU) const override;
667 /// removeLoop - This removes the specified top-level loop from this loop info
668 /// object. The loop is not deleted, as it will presumably be inserted into
670 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
672 /// changeLoopFor - Change the top-level loop that contains BB to the
673 /// specified loop. This should be used by transformations that restructure
674 /// the loop hierarchy tree.
675 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
676 LI.changeLoopFor(BB, L);
679 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
680 /// list with the indicated loop.
681 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
682 LI.changeTopLevelLoop(OldLoop, NewLoop);
685 /// addTopLevelLoop - This adds the specified loop to the collection of
687 inline void addTopLevelLoop(Loop *New) {
688 LI.addTopLevelLoop(New);
691 /// removeBlock - This method completely removes BB from all data structures,
692 /// including all of the Loop objects it is nested in and our mapping from
693 /// BasicBlocks to loops.
694 void removeBlock(BasicBlock *BB) {
698 /// updateUnloop - Update LoopInfo after removing the last backedge from a
699 /// loop--now the "unloop". This updates the loop forest and parent loops for
700 /// each block so that Unloop is no longer referenced, but the caller must
701 /// actually delete the Unloop object.
702 void updateUnloop(Loop *Unloop);
704 /// replacementPreservesLCSSAForm - Returns true if replacing From with To
705 /// everywhere is guaranteed to preserve LCSSA form.
706 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) {
707 // Preserving LCSSA form is only problematic if the replacing value is an
709 Instruction *I = dyn_cast<Instruction>(To);
711 // If both instructions are defined in the same basic block then replacement
712 // cannot break LCSSA form.
713 if (I->getParent() == From->getParent())
715 // If the instruction is not defined in a loop then it can safely replace
717 Loop *ToLoop = getLoopFor(I->getParent());
718 if (!ToLoop) return true;
719 // If the replacing instruction is defined in the same loop as the original
720 // instruction, or in a loop that contains it as an inner loop, then using
721 // it as a replacement will not break LCSSA form.
722 return ToLoop->contains(getLoopFor(From->getParent()));
727 // Allow clients to walk the list of nested loops...
728 template <> struct GraphTraits<const Loop*> {
729 typedef const Loop NodeType;
730 typedef LoopInfo::iterator ChildIteratorType;
732 static NodeType *getEntryNode(const Loop *L) { return L; }
733 static inline ChildIteratorType child_begin(NodeType *N) {
736 static inline ChildIteratorType child_end(NodeType *N) {
741 template <> struct GraphTraits<Loop*> {
742 typedef Loop NodeType;
743 typedef LoopInfo::iterator ChildIteratorType;
745 static NodeType *getEntryNode(Loop *L) { return L; }
746 static inline ChildIteratorType child_begin(NodeType *N) {
749 static inline ChildIteratorType child_end(NodeType *N) {
754 } // End llvm namespace