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_LOOP_INFO_H
31 #define LLVM_ANALYSIS_LOOP_INFO_H
33 #include "llvm/Pass.h"
34 #include "llvm/ADT/DenseMap.h"
35 #include "llvm/ADT/DenseSet.h"
36 #include "llvm/ADT/DepthFirstIterator.h"
37 #include "llvm/ADT/GraphTraits.h"
38 #include "llvm/ADT/SmallVector.h"
39 #include "llvm/ADT/STLExtras.h"
40 #include "llvm/Analysis/Dominators.h"
41 #include "llvm/Support/CFG.h"
42 #include "llvm/Support/raw_ostream.h"
49 static void RemoveFromVector(std::vector<T*> &V, T *N) {
50 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
51 assert(I != V.end() && "N is not in this list!");
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;
76 LoopBase(const LoopBase<BlockT, LoopT> &);
78 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
80 /// Loop ctor - This creates an empty loop.
81 LoopBase() : ParentLoop(0) {}
83 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
87 /// getLoopDepth - Return the nesting level of this loop. An outer-most
88 /// loop has depth 1, for consistency with loop depth values used for basic
89 /// blocks, where depth 0 is used for blocks not inside any loops.
90 unsigned getLoopDepth() const {
92 for (const LoopT *CurLoop = ParentLoop; CurLoop;
93 CurLoop = CurLoop->ParentLoop)
97 BlockT *getHeader() const { return Blocks.front(); }
98 LoopT *getParentLoop() const { return ParentLoop; }
100 /// contains - Return true if the specified loop is contained within in
103 bool contains(const LoopT *L) const {
104 if (L == this) return true;
105 if (L == 0) return false;
106 return contains(L->getParentLoop());
109 /// contains - Return true if the specified basic block is in this loop.
111 bool contains(const BlockT *BB) const {
112 return std::find(block_begin(), block_end(), BB) != block_end();
115 /// contains - Return true if the specified instruction is in this loop.
117 template<class InstT>
118 bool contains(const InstT *Inst) const {
119 return contains(Inst->getParent());
122 /// iterator/begin/end - Return the loops contained entirely within this loop.
124 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
125 typedef typename std::vector<LoopT *>::const_iterator iterator;
126 iterator begin() const { return SubLoops.begin(); }
127 iterator end() const { return SubLoops.end(); }
128 bool empty() const { return SubLoops.empty(); }
130 /// getBlocks - Get a list of the basic blocks which make up this loop.
132 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
133 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
134 block_iterator block_begin() const { return Blocks.begin(); }
135 block_iterator block_end() const { return Blocks.end(); }
137 /// getNumBlocks - Get the number of blocks in this loop in constant time.
138 unsigned getNumBlocks() const {
139 return Blocks.size();
142 /// isLoopExiting - True if terminator in the block can branch to another
143 /// block that is outside of the current loop.
145 bool isLoopExiting(const BlockT *BB) const {
146 typedef GraphTraits<BlockT*> BlockTraits;
147 for (typename BlockTraits::ChildIteratorType SI =
148 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
149 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
156 /// getNumBackEdges - Calculate the number of back edges to the loop header
158 unsigned getNumBackEdges() const {
159 unsigned NumBackEdges = 0;
160 BlockT *H = getHeader();
162 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
163 for (typename InvBlockTraits::ChildIteratorType I =
164 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
165 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
172 //===--------------------------------------------------------------------===//
173 // APIs for simple analysis of the loop.
175 // Note that all of these methods can fail on general loops (ie, there may not
176 // be a preheader, etc). For best success, the loop simplification and
177 // induction variable canonicalization pass should be used to normalize loops
178 // for easy analysis. These methods assume canonical loops.
180 /// getExitingBlocks - Return all blocks inside the loop that have successors
181 /// outside of the loop. These are the blocks _inside of the current loop_
182 /// which branch out. The returned list is always unique.
184 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
185 // Sort the blocks vector so that we can use binary search to do quick
187 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
188 std::sort(LoopBBs.begin(), LoopBBs.end());
190 typedef GraphTraits<BlockT*> BlockTraits;
191 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
192 for (typename BlockTraits::ChildIteratorType I =
193 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
195 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
196 // Not in current loop? It must be an exit block.
197 ExitingBlocks.push_back(*BI);
202 /// getExitingBlock - If getExitingBlocks would return exactly one block,
203 /// return that block. Otherwise return null.
204 BlockT *getExitingBlock() const {
205 SmallVector<BlockT*, 8> ExitingBlocks;
206 getExitingBlocks(ExitingBlocks);
207 if (ExitingBlocks.size() == 1)
208 return ExitingBlocks[0];
212 /// getExitBlocks - Return all of the successor blocks of this loop. These
213 /// are the blocks _outside of the current loop_ which are branched to.
215 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
216 // Sort the blocks vector so that we can use binary search to do quick
218 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
219 std::sort(LoopBBs.begin(), LoopBBs.end());
221 typedef GraphTraits<BlockT*> BlockTraits;
222 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
223 for (typename BlockTraits::ChildIteratorType I =
224 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
226 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
227 // Not in current loop? It must be an exit block.
228 ExitBlocks.push_back(*I);
231 /// getExitBlock - If getExitBlocks would return exactly one block,
232 /// return that block. Otherwise return null.
233 BlockT *getExitBlock() const {
234 SmallVector<BlockT*, 8> ExitBlocks;
235 getExitBlocks(ExitBlocks);
236 if (ExitBlocks.size() == 1)
237 return ExitBlocks[0];
242 typedef std::pair<BlockT*, BlockT*> Edge;
244 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
245 template <typename EdgeT>
246 void getExitEdges(SmallVectorImpl<EdgeT> &ExitEdges) const {
247 // Sort the blocks vector so that we can use binary search to do quick
249 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
250 array_pod_sort(LoopBBs.begin(), LoopBBs.end());
252 typedef GraphTraits<BlockT*> BlockTraits;
253 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
254 for (typename BlockTraits::ChildIteratorType I =
255 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
257 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
258 // Not in current loop? It must be an exit block.
259 ExitEdges.push_back(EdgeT(*BI, *I));
262 /// getLoopPreheader - If there is a preheader for this loop, return it. A
263 /// loop has a preheader if there is only one edge to the header of the loop
264 /// from outside of the loop. If this is the case, the block branching to the
265 /// header of the loop is the preheader node.
267 /// This method returns null if there is no preheader for the loop.
269 BlockT *getLoopPreheader() const {
270 // Keep track of nodes outside the loop branching to the header...
271 BlockT *Out = getLoopPredecessor();
274 // Make sure there is only one exit out of the preheader.
275 typedef GraphTraits<BlockT*> BlockTraits;
276 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
278 if (SI != BlockTraits::child_end(Out))
279 return 0; // Multiple exits from the block, must not be a preheader.
281 // The predecessor has exactly one successor, so it is a preheader.
285 /// getLoopPredecessor - If the given loop's header has exactly one unique
286 /// predecessor outside the loop, return it. Otherwise return null.
287 /// This is less strict that the loop "preheader" concept, which requires
288 /// the predecessor to have exactly one successor.
290 BlockT *getLoopPredecessor() const {
291 // Keep track of nodes outside the loop branching to the header...
294 // Loop over the predecessors of the header node...
295 BlockT *Header = getHeader();
296 typedef GraphTraits<BlockT*> BlockTraits;
297 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
298 for (typename InvBlockTraits::ChildIteratorType PI =
299 InvBlockTraits::child_begin(Header),
300 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) {
301 typename InvBlockTraits::NodeType *N = *PI;
302 if (!contains(N)) { // If the block is not in the loop...
304 return 0; // Multiple predecessors outside the loop
309 // Make sure there is only one exit out of the preheader.
310 assert(Out && "Header of loop has no predecessors from outside loop?");
314 /// getLoopLatch - If there is a single latch block for this loop, return it.
315 /// A latch block is a block that contains a branch back to the header.
316 BlockT *getLoopLatch() const {
317 BlockT *Header = getHeader();
318 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
319 typename InvBlockTraits::ChildIteratorType PI =
320 InvBlockTraits::child_begin(Header);
321 typename InvBlockTraits::ChildIteratorType PE =
322 InvBlockTraits::child_end(Header);
324 for (; PI != PE; ++PI) {
325 typename InvBlockTraits::NodeType *N = *PI;
335 //===--------------------------------------------------------------------===//
336 // APIs for updating loop information after changing the CFG
339 /// addBasicBlockToLoop - This method is used by other analyses to update loop
340 /// information. NewBB is set to be a new member of the current loop.
341 /// Because of this, it is added as a member of all parent loops, and is added
342 /// to the specified LoopInfo object as being in the current basic block. It
343 /// is not valid to replace the loop header with this method.
345 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
347 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
348 /// the OldChild entry in our children list with NewChild, and updates the
349 /// parent pointer of OldChild to be null and the NewChild to be this loop.
350 /// This updates the loop depth of the new child.
351 void replaceChildLoopWith(LoopT *OldChild,
353 assert(OldChild->ParentLoop == this && "This loop is already broken!");
354 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
355 typename std::vector<LoopT *>::iterator I =
356 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
357 assert(I != SubLoops.end() && "OldChild not in loop!");
359 OldChild->ParentLoop = 0;
360 NewChild->ParentLoop = static_cast<LoopT *>(this);
363 /// addChildLoop - Add the specified loop to be a child of this loop. This
364 /// updates the loop depth of the new child.
366 void addChildLoop(LoopT *NewChild) {
367 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
368 NewChild->ParentLoop = static_cast<LoopT *>(this);
369 SubLoops.push_back(NewChild);
372 /// removeChildLoop - This removes the specified child from being a subloop of
373 /// this loop. The loop is not deleted, as it will presumably be inserted
374 /// into another loop.
375 LoopT *removeChildLoop(iterator I) {
376 assert(I != SubLoops.end() && "Cannot remove end iterator!");
378 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
379 SubLoops.erase(SubLoops.begin()+(I-begin()));
380 Child->ParentLoop = 0;
384 /// addBlockEntry - This adds a basic block directly to the basic block list.
385 /// This should only be used by transformations that create new loops. Other
386 /// transformations should use addBasicBlockToLoop.
387 void addBlockEntry(BlockT *BB) {
388 Blocks.push_back(BB);
391 /// moveToHeader - This method is used to move BB (which must be part of this
392 /// loop) to be the loop header of the loop (the block that dominates all
394 void moveToHeader(BlockT *BB) {
395 if (Blocks[0] == BB) return;
396 for (unsigned i = 0; ; ++i) {
397 assert(i != Blocks.size() && "Loop does not contain BB!");
398 if (Blocks[i] == BB) {
399 Blocks[i] = Blocks[0];
406 /// removeBlockFromLoop - This removes the specified basic block from the
407 /// current loop, updating the Blocks as appropriate. This does not update
408 /// the mapping in the LoopInfo class.
409 void removeBlockFromLoop(BlockT *BB) {
410 RemoveFromVector(Blocks, BB);
413 /// verifyLoop - Verify loop structure
414 void verifyLoop() const {
416 assert(!Blocks.empty() && "Loop header is missing");
418 // Setup for using a depth-first iterator to visit every block in the loop.
419 SmallVector<BlockT*, 8> ExitBBs;
420 getExitBlocks(ExitBBs);
421 llvm::SmallPtrSet<BlockT*, 8> VisitSet;
422 VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
423 df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> >
424 BI = df_ext_begin(getHeader(), VisitSet),
425 BE = df_ext_end(getHeader(), VisitSet);
427 // Keep track of the number of BBs visited.
428 unsigned NumVisited = 0;
430 // Sort the blocks vector so that we can use binary search to do quick
432 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
433 std::sort(LoopBBs.begin(), LoopBBs.end());
435 // Check the individual blocks.
436 for ( ; BI != BE; ++BI) {
438 bool HasInsideLoopSuccs = false;
439 bool HasInsideLoopPreds = false;
440 SmallVector<BlockT *, 2> OutsideLoopPreds;
442 typedef GraphTraits<BlockT*> BlockTraits;
443 for (typename BlockTraits::ChildIteratorType SI =
444 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
446 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
447 HasInsideLoopSuccs = true;
450 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
451 for (typename InvBlockTraits::ChildIteratorType PI =
452 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
455 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N))
456 HasInsideLoopPreds = true;
458 OutsideLoopPreds.push_back(N);
461 if (BB == getHeader()) {
462 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
463 } else if (!OutsideLoopPreds.empty()) {
464 // A non-header loop shouldn't be reachable from outside the loop,
465 // though it is permitted if the predecessor is not itself actually
467 BlockT *EntryBB = BB->getParent()->begin();
468 for (df_iterator<BlockT *> NI = df_begin(EntryBB),
469 NE = df_end(EntryBB); NI != NE; ++NI)
470 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
471 assert(*NI != OutsideLoopPreds[i] &&
472 "Loop has multiple entry points!");
474 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
475 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
476 assert(BB != getHeader()->getParent()->begin() &&
477 "Loop contains function entry block!");
482 assert(NumVisited == getNumBlocks() && "Unreachable block in loop");
484 // Check the subloops.
485 for (iterator I = begin(), E = end(); I != E; ++I)
486 // Each block in each subloop should be contained within this loop.
487 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
489 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
490 "Loop does not contain all the blocks of a subloop!");
493 // Check the parent loop pointer.
495 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
497 "Loop is not a subloop of its parent!");
502 /// verifyLoop - Verify loop structure of this loop and all nested loops.
503 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const {
504 Loops->insert(static_cast<const LoopT *>(this));
507 // Verify the subloops.
508 for (iterator I = begin(), E = end(); I != E; ++I)
509 (*I)->verifyLoopNest(Loops);
512 void print(raw_ostream &OS, unsigned Depth = 0) const {
513 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
516 for (unsigned i = 0; i < getBlocks().size(); ++i) {
518 BlockT *BB = getBlocks()[i];
519 WriteAsOperand(OS, BB, false);
520 if (BB == getHeader()) OS << "<header>";
521 if (BB == getLoopLatch()) OS << "<latch>";
522 if (isLoopExiting(BB)) OS << "<exiting>";
526 for (iterator I = begin(), E = end(); I != E; ++I)
527 (*I)->print(OS, Depth+2);
531 friend class LoopInfoBase<BlockT, LoopT>;
532 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
533 Blocks.push_back(BB);
537 template<class BlockT, class LoopT>
538 raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) {
543 class Loop : public LoopBase<BasicBlock, Loop> {
547 /// isLoopInvariant - Return true if the specified value is loop invariant
549 bool isLoopInvariant(Value *V) const;
551 /// hasLoopInvariantOperands - Return true if all the operands of the
552 /// specified instruction are loop invariant.
553 bool hasLoopInvariantOperands(Instruction *I) const;
555 /// makeLoopInvariant - If the given value is an instruction inside of the
556 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
557 /// Return true if the value after any hoisting is loop invariant. This
558 /// function can be used as a slightly more aggressive replacement for
561 /// If InsertPt is specified, it is the point to hoist instructions to.
562 /// If null, the terminator of the loop preheader is used.
564 bool makeLoopInvariant(Value *V, bool &Changed,
565 Instruction *InsertPt = 0) const;
567 /// makeLoopInvariant - If the given instruction is inside of the
568 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
569 /// Return true if the instruction after any hoisting is loop invariant. This
570 /// function can be used as a slightly more aggressive replacement for
573 /// If InsertPt is specified, it is the point to hoist instructions to.
574 /// If null, the terminator of the loop preheader is used.
576 bool makeLoopInvariant(Instruction *I, bool &Changed,
577 Instruction *InsertPt = 0) const;
579 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
580 /// induction variable: an integer recurrence that starts at 0 and increments
581 /// by one each time through the loop. If so, return the phi node that
582 /// corresponds to it.
584 /// The IndVarSimplify pass transforms loops to have a canonical induction
587 PHINode *getCanonicalInductionVariable() 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 /// isSafeToClone - Return true if the loop body is safe to clone in practice.
598 bool isSafeToClone() const;
600 /// hasDedicatedExits - Return true if no exit block for the loop
601 /// has a predecessor that is outside the loop.
602 bool hasDedicatedExits() const;
604 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
605 /// These are the blocks _outside of the current loop_ which are branched to.
606 /// This assumes that loop exits are in canonical form.
608 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
610 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
611 /// block, return that block. Otherwise return null.
612 BasicBlock *getUniqueExitBlock() const;
617 friend class LoopInfoBase<BasicBlock, Loop>;
618 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
621 //===----------------------------------------------------------------------===//
622 /// LoopInfo - This class builds and contains all of the top level loop
623 /// structures in the specified function.
626 template<class BlockT, class LoopT>
628 // BBMap - Mapping of basic blocks to the inner most loop they occur in
629 DenseMap<BlockT *, LoopT *> BBMap;
630 std::vector<LoopT *> TopLevelLoops;
631 friend class LoopBase<BlockT, LoopT>;
632 friend class LoopInfo;
634 void operator=(const LoopInfoBase &); // do not implement
635 LoopInfoBase(const LoopInfo &); // do not implement
638 ~LoopInfoBase() { releaseMemory(); }
640 void releaseMemory() {
641 for (typename std::vector<LoopT *>::iterator I =
642 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
643 delete *I; // Delete all of the loops...
645 BBMap.clear(); // Reset internal state of analysis
646 TopLevelLoops.clear();
649 /// iterator/begin/end - The interface to the top-level loops in the current
652 typedef typename std::vector<LoopT *>::const_iterator iterator;
653 iterator begin() const { return TopLevelLoops.begin(); }
654 iterator end() const { return TopLevelLoops.end(); }
655 bool empty() const { return TopLevelLoops.empty(); }
657 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
658 /// block is in no loop (for example the entry node), null is returned.
660 LoopT *getLoopFor(const BlockT *BB) const {
661 return BBMap.lookup(const_cast<BlockT*>(BB));
664 /// operator[] - same as getLoopFor...
666 const LoopT *operator[](const BlockT *BB) const {
667 return getLoopFor(BB);
670 /// getLoopDepth - Return the loop nesting level of the specified block. A
671 /// depth of 0 means the block is not inside any loop.
673 unsigned getLoopDepth(const BlockT *BB) const {
674 const LoopT *L = getLoopFor(BB);
675 return L ? L->getLoopDepth() : 0;
678 // isLoopHeader - True if the block is a loop header node
679 bool isLoopHeader(BlockT *BB) const {
680 const LoopT *L = getLoopFor(BB);
681 return L && L->getHeader() == BB;
684 /// removeLoop - This removes the specified top-level loop from this loop info
685 /// object. The loop is not deleted, as it will presumably be inserted into
687 LoopT *removeLoop(iterator I) {
688 assert(I != end() && "Cannot remove end iterator!");
690 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
691 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
695 /// changeLoopFor - Change the top-level loop that contains BB to the
696 /// specified loop. This should be used by transformations that restructure
697 /// the loop hierarchy tree.
698 void changeLoopFor(BlockT *BB, LoopT *L) {
706 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
707 /// list with the indicated loop.
708 void changeTopLevelLoop(LoopT *OldLoop,
710 typename std::vector<LoopT *>::iterator I =
711 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
712 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
714 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
715 "Loops already embedded into a subloop!");
718 /// addTopLevelLoop - This adds the specified loop to the collection of
720 void addTopLevelLoop(LoopT *New) {
721 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
722 TopLevelLoops.push_back(New);
725 /// removeBlock - This method completely removes BB from all data structures,
726 /// including all of the Loop objects it is nested in and our mapping from
727 /// BasicBlocks to loops.
728 void removeBlock(BlockT *BB) {
729 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
730 if (I != BBMap.end()) {
731 for (LoopT *L = I->second; L; L = L->getParentLoop())
732 L->removeBlockFromLoop(BB);
740 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
741 const LoopT *ParentLoop) {
742 if (SubLoop == 0) return true;
743 if (SubLoop == ParentLoop) return false;
744 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
747 void Calculate(DominatorTreeBase<BlockT> &DT) {
748 BlockT *RootNode = DT.getRootNode()->getBlock();
750 for (df_iterator<BlockT*> NI = df_begin(RootNode),
751 NE = df_end(RootNode); NI != NE; ++NI)
752 if (LoopT *L = ConsiderForLoop(*NI, DT))
753 TopLevelLoops.push_back(L);
756 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
757 if (BBMap.count(BB)) return 0; // Haven't processed this node?
759 std::vector<BlockT *> TodoStack;
761 // Scan the predecessors of BB, checking to see if BB dominates any of
762 // them. This identifies backedges which target this node...
763 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
764 for (typename InvBlockTraits::ChildIteratorType I =
765 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
767 typename InvBlockTraits::NodeType *N = *I;
768 // If BB dominates its predecessor...
769 if (DT.dominates(BB, N) && DT.isReachableFromEntry(N))
770 TodoStack.push_back(N);
773 if (TodoStack.empty()) return 0; // No backedges to this block...
775 // Create a new loop to represent this basic block...
776 LoopT *L = new LoopT(BB);
779 while (!TodoStack.empty()) { // Process all the nodes in the loop
780 BlockT *X = TodoStack.back();
781 TodoStack.pop_back();
783 if (!L->contains(X) && // As of yet unprocessed??
784 DT.isReachableFromEntry(X)) {
785 // Check to see if this block already belongs to a loop. If this occurs
786 // then we have a case where a loop that is supposed to be a child of
787 // the current loop was processed before the current loop. When this
788 // occurs, this child loop gets added to a part of the current loop,
789 // making it a sibling to the current loop. We have to reparent this
792 const_cast<LoopT *>(getLoopFor(X)))
793 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
794 // Remove the subloop from its current parent...
795 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
796 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
797 typename std::vector<LoopT *>::iterator I =
798 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
799 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
800 SLP->SubLoops.erase(I); // Remove from parent...
802 // Add the subloop to THIS loop...
803 SubLoop->ParentLoop = L;
804 L->SubLoops.push_back(SubLoop);
807 // Normal case, add the block to our loop...
808 L->Blocks.push_back(X);
810 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
812 // Add all of the predecessors of X to the end of the work stack...
813 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
814 InvBlockTraits::child_end(X));
818 // If there are any loops nested within this loop, create them now!
819 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
820 E = L->Blocks.end(); I != E; ++I)
821 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
822 L->SubLoops.push_back(NewLoop);
823 NewLoop->ParentLoop = L;
826 // Add the basic blocks that comprise this loop to the BBMap so that this
827 // loop can be found for them.
829 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
830 E = L->Blocks.end(); I != E; ++I)
831 BBMap.insert(std::make_pair(*I, L));
833 // Now that we have a list of all of the child loops of this loop, check to
834 // see if any of them should actually be nested inside of each other. We
835 // can accidentally pull loops our of their parents, so we must make sure to
836 // organize the loop nests correctly now.
838 std::map<BlockT *, LoopT *> ContainingLoops;
839 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
840 LoopT *Child = L->SubLoops[i];
841 assert(Child->getParentLoop() == L && "Not proper child loop?");
843 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
844 // If there is already a loop which contains this loop, move this loop
845 // into the containing loop.
846 MoveSiblingLoopInto(Child, ContainingLoop);
847 --i; // The loop got removed from the SubLoops list.
849 // This is currently considered to be a top-level loop. Check to see
850 // if any of the contained blocks are loop headers for subloops we
851 // have already processed.
852 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
853 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
854 if (BlockLoop == 0) { // Child block not processed yet...
856 } else if (BlockLoop != Child) {
857 LoopT *SubLoop = BlockLoop;
858 // Reparent all of the blocks which used to belong to BlockLoops
859 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
860 ContainingLoops[SubLoop->Blocks[j]] = Child;
862 // There is already a loop which contains this block, that means
863 // that we should reparent the loop which the block is currently
864 // considered to belong to to be a child of this loop.
865 MoveSiblingLoopInto(SubLoop, Child);
866 --i; // We just shrunk the SubLoops list.
876 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
877 /// of the NewParent Loop, instead of being a sibling of it.
878 void MoveSiblingLoopInto(LoopT *NewChild,
880 LoopT *OldParent = NewChild->getParentLoop();
881 assert(OldParent && OldParent == NewParent->getParentLoop() &&
882 NewChild != NewParent && "Not sibling loops!");
884 // Remove NewChild from being a child of OldParent
885 typename std::vector<LoopT *>::iterator I =
886 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
888 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
889 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
890 NewChild->ParentLoop = 0;
892 InsertLoopInto(NewChild, NewParent);
895 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
896 /// the parent loop contains a loop which should contain L, the loop gets
897 /// inserted into L instead.
898 void InsertLoopInto(LoopT *L, LoopT *Parent) {
899 BlockT *LHeader = L->getHeader();
900 assert(Parent->contains(LHeader) &&
901 "This loop should not be inserted here!");
903 // Check to see if it belongs in a child loop...
904 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
906 if (Parent->SubLoops[i]->contains(LHeader)) {
907 InsertLoopInto(L, Parent->SubLoops[i]);
911 // If not, insert it here!
912 Parent->SubLoops.push_back(L);
913 L->ParentLoop = Parent;
918 void print(raw_ostream &OS) const {
919 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
920 TopLevelLoops[i]->print(OS);
922 for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
923 E = BBMap.end(); I != E; ++I)
924 OS << "BB '" << I->first->getName() << "' level = "
925 << I->second->getLoopDepth() << "\n";
930 class LoopInfo : public FunctionPass {
931 LoopInfoBase<BasicBlock, Loop> LI;
932 friend class LoopBase<BasicBlock, Loop>;
934 void operator=(const LoopInfo &); // do not implement
935 LoopInfo(const LoopInfo &); // do not implement
937 static char ID; // Pass identification, replacement for typeid
939 LoopInfo() : FunctionPass(ID) {
940 initializeLoopInfoPass(*PassRegistry::getPassRegistry());
943 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
945 /// iterator/begin/end - The interface to the top-level loops in the current
948 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
949 inline iterator begin() const { return LI.begin(); }
950 inline iterator end() const { return LI.end(); }
951 bool empty() const { return LI.empty(); }
953 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
954 /// block is in no loop (for example the entry node), null is returned.
956 inline Loop *getLoopFor(const BasicBlock *BB) const {
957 return LI.getLoopFor(BB);
960 /// operator[] - same as getLoopFor...
962 inline const Loop *operator[](const BasicBlock *BB) const {
963 return LI.getLoopFor(BB);
966 /// getLoopDepth - Return the loop nesting level of the specified block. A
967 /// depth of 0 means the block is not inside any loop.
969 inline unsigned getLoopDepth(const BasicBlock *BB) const {
970 return LI.getLoopDepth(BB);
973 // isLoopHeader - True if the block is a loop header node
974 inline bool isLoopHeader(BasicBlock *BB) const {
975 return LI.isLoopHeader(BB);
978 /// runOnFunction - Calculate the natural loop information.
980 virtual bool runOnFunction(Function &F);
982 virtual void verifyAnalysis() const;
984 virtual void releaseMemory() { LI.releaseMemory(); }
986 virtual void print(raw_ostream &O, const Module* M = 0) const;
988 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
990 /// removeLoop - This removes the specified top-level loop from this loop info
991 /// object. The loop is not deleted, as it will presumably be inserted into
993 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
995 /// changeLoopFor - Change the top-level loop that contains BB to the
996 /// specified loop. This should be used by transformations that restructure
997 /// the loop hierarchy tree.
998 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
999 LI.changeLoopFor(BB, L);
1002 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
1003 /// list with the indicated loop.
1004 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1005 LI.changeTopLevelLoop(OldLoop, NewLoop);
1008 /// addTopLevelLoop - This adds the specified loop to the collection of
1009 /// top-level loops.
1010 inline void addTopLevelLoop(Loop *New) {
1011 LI.addTopLevelLoop(New);
1014 /// removeBlock - This method completely removes BB from all data structures,
1015 /// including all of the Loop objects it is nested in and our mapping from
1016 /// BasicBlocks to loops.
1017 void removeBlock(BasicBlock *BB) {
1021 /// updateUnloop - Update LoopInfo after removing the last backedge from a
1022 /// loop--now the "unloop". This updates the loop forest and parent loops for
1023 /// each block so that Unloop is no longer referenced, but the caller must
1024 /// actually delete the Unloop object.
1025 void updateUnloop(Loop *Unloop);
1027 /// replacementPreservesLCSSAForm - Returns true if replacing From with To
1028 /// everywhere is guaranteed to preserve LCSSA form.
1029 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) {
1030 // Preserving LCSSA form is only problematic if the replacing value is an
1032 Instruction *I = dyn_cast<Instruction>(To);
1033 if (!I) return true;
1034 // If both instructions are defined in the same basic block then replacement
1035 // cannot break LCSSA form.
1036 if (I->getParent() == From->getParent())
1038 // If the instruction is not defined in a loop then it can safely replace
1040 Loop *ToLoop = getLoopFor(I->getParent());
1041 if (!ToLoop) return true;
1042 // If the replacing instruction is defined in the same loop as the original
1043 // instruction, or in a loop that contains it as an inner loop, then using
1044 // it as a replacement will not break LCSSA form.
1045 return ToLoop->contains(getLoopFor(From->getParent()));
1050 // Allow clients to walk the list of nested loops...
1051 template <> struct GraphTraits<const Loop*> {
1052 typedef const Loop NodeType;
1053 typedef LoopInfo::iterator ChildIteratorType;
1055 static NodeType *getEntryNode(const Loop *L) { return L; }
1056 static inline ChildIteratorType child_begin(NodeType *N) {
1059 static inline ChildIteratorType child_end(NodeType *N) {
1064 template <> struct GraphTraits<Loop*> {
1065 typedef Loop NodeType;
1066 typedef LoopInfo::iterator ChildIteratorType;
1068 static NodeType *getEntryNode(Loop *L) { return L; }
1069 static inline ChildIteratorType child_begin(NodeType *N) {
1072 static inline ChildIteratorType child_end(NodeType *N) {
1077 template<class BlockT, class LoopT>
1079 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1080 LoopInfoBase<BlockT, LoopT> &LIB) {
1081 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1082 "Incorrect LI specified for this loop!");
1083 assert(NewBB && "Cannot add a null basic block to the loop!");
1084 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1086 LoopT *L = static_cast<LoopT *>(this);
1088 // Add the loop mapping to the LoopInfo object...
1089 LIB.BBMap[NewBB] = L;
1091 // Add the basic block to this loop and all parent loops...
1093 L->Blocks.push_back(NewBB);
1094 L = L->getParentLoop();
1098 } // End llvm namespace