1 //===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG. Note that natural
12 // loops may actually be several loops that share the same header node.
14 // This analysis calculates the nesting structure of loops in a function. For
15 // each natural loop identified, this analysis identifies natural loops
16 // contained entirely within the loop and the basic blocks the make up the loop.
18 // It can calculate on the fly various bits of information, for example:
20 // * whether there is a preheader for the loop
21 // * the number of back edges to the header
22 // * whether or not a particular block branches out of the loop
23 // * the successor blocks of the loop
28 //===----------------------------------------------------------------------===//
30 #ifndef LLVM_ANALYSIS_LOOP_INFO_H
31 #define LLVM_ANALYSIS_LOOP_INFO_H
33 #include "llvm/Pass.h"
34 #include "llvm/ADT/DepthFirstIterator.h"
35 #include "llvm/ADT/GraphTraits.h"
36 #include "llvm/ADT/SmallVector.h"
37 #include "llvm/Analysis/Dominators.h"
38 #include "llvm/Support/CFG.h"
39 #include "llvm/Support/raw_ostream.h"
45 static void RemoveFromVector(std::vector<T*> &V, T *N) {
46 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
47 assert(I != V.end() && "N is not in this list!");
54 template<class N, class M> class LoopInfoBase;
55 template<class N, class M> class LoopBase;
57 //===----------------------------------------------------------------------===//
58 /// LoopBase class - Instances of this class are used to represent loops that
59 /// are detected in the flow graph
61 template<class BlockT, class LoopT>
64 // SubLoops - Loops contained entirely within this one.
65 std::vector<LoopT *> SubLoops;
67 // Blocks - The list of blocks in this loop. First entry is the header node.
68 std::vector<BlockT*> Blocks;
71 LoopBase(const LoopBase<BlockT, LoopT> &);
73 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
75 /// Loop ctor - This creates an empty loop.
76 LoopBase() : ParentLoop(0) {}
78 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
82 /// getLoopDepth - Return the nesting level of this loop. An outer-most
83 /// loop has depth 1, for consistency with loop depth values used for basic
84 /// blocks, where depth 0 is used for blocks not inside any loops.
85 unsigned getLoopDepth() const {
87 for (const LoopT *CurLoop = ParentLoop; CurLoop;
88 CurLoop = CurLoop->ParentLoop)
92 BlockT *getHeader() const { return Blocks.front(); }
93 LoopT *getParentLoop() const { return ParentLoop; }
95 /// contains - Return true if the specified basic block is in this loop
97 bool contains(const BlockT *BB) const {
98 return std::find(block_begin(), block_end(), BB) != block_end();
101 /// iterator/begin/end - Return the loops contained entirely within this loop.
103 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
104 typedef typename std::vector<LoopT *>::const_iterator iterator;
105 iterator begin() const { return SubLoops.begin(); }
106 iterator end() const { return SubLoops.end(); }
107 bool empty() const { return SubLoops.empty(); }
109 /// getBlocks - Get a list of the basic blocks which make up this loop.
111 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
112 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
113 block_iterator block_begin() const { return Blocks.begin(); }
114 block_iterator block_end() const { return Blocks.end(); }
116 /// isLoopExit - True if terminator in the block can branch to another block
117 /// that is outside of the current loop.
119 bool isLoopExit(const BlockT *BB) const {
120 typedef GraphTraits<BlockT*> BlockTraits;
121 for (typename BlockTraits::ChildIteratorType SI =
122 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
123 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
130 /// getNumBackEdges - Calculate the number of back edges to the loop header
132 unsigned getNumBackEdges() const {
133 unsigned NumBackEdges = 0;
134 BlockT *H = getHeader();
136 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
137 for (typename InvBlockTraits::ChildIteratorType I =
138 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
139 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
146 //===--------------------------------------------------------------------===//
147 // APIs for simple analysis of the loop.
149 // Note that all of these methods can fail on general loops (ie, there may not
150 // be a preheader, etc). For best success, the loop simplification and
151 // induction variable canonicalization pass should be used to normalize loops
152 // for easy analysis. These methods assume canonical loops.
154 /// getExitingBlocks - Return all blocks inside the loop that have successors
155 /// outside of the loop. These are the blocks _inside of the current loop_
156 /// which branch out. The returned list is always unique.
158 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
159 // Sort the blocks vector so that we can use binary search to do quick
161 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
162 std::sort(LoopBBs.begin(), LoopBBs.end());
164 typedef GraphTraits<BlockT*> BlockTraits;
165 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
166 for (typename BlockTraits::ChildIteratorType I =
167 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
169 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
170 // Not in current loop? It must be an exit block.
171 ExitingBlocks.push_back(*BI);
176 /// getExitingBlock - If getExitingBlocks would return exactly one block,
177 /// return that block. Otherwise return null.
178 BlockT *getExitingBlock() const {
179 SmallVector<BlockT*, 8> ExitingBlocks;
180 getExitingBlocks(ExitingBlocks);
181 if (ExitingBlocks.size() == 1)
182 return ExitingBlocks[0];
186 /// getExitBlocks - Return all of the successor blocks of this loop. These
187 /// are the blocks _outside of the current loop_ which are branched to.
189 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
190 // Sort the blocks vector so that we can use binary search to do quick
192 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
193 std::sort(LoopBBs.begin(), LoopBBs.end());
195 typedef GraphTraits<BlockT*> BlockTraits;
196 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
197 for (typename BlockTraits::ChildIteratorType I =
198 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
200 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
201 // Not in current loop? It must be an exit block.
202 ExitBlocks.push_back(*I);
205 /// getExitBlock - If getExitBlocks would return exactly one block,
206 /// return that block. Otherwise return null.
207 BlockT *getExitBlock() const {
208 SmallVector<BlockT*, 8> ExitBlocks;
209 getExitBlocks(ExitBlocks);
210 if (ExitBlocks.size() == 1)
211 return ExitBlocks[0];
215 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
216 typedef std::pair<const BlockT*,const BlockT*> Edge;
217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
218 // Sort the blocks vector so that we can use binary search to do quick
220 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
221 std::sort(LoopBBs.begin(), LoopBBs.end());
223 typedef GraphTraits<BlockT*> BlockTraits;
224 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
225 for (typename BlockTraits::ChildIteratorType I =
226 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
228 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
229 // Not in current loop? It must be an exit block.
230 ExitEdges.push_back(std::make_pair(*BI, *I));
233 /// getLoopPreheader - If there is a preheader for this loop, return it. A
234 /// loop has a preheader if there is only one edge to the header of the loop
235 /// from outside of the loop. If this is the case, the block branching to the
236 /// header of the loop is the preheader node.
238 /// This method returns null if there is no preheader for the loop.
240 BlockT *getLoopPreheader() const {
241 // Keep track of nodes outside the loop branching to the header...
244 // Loop over the predecessors of the header node...
245 BlockT *Header = getHeader();
246 typedef GraphTraits<BlockT*> BlockTraits;
247 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
248 for (typename InvBlockTraits::ChildIteratorType PI =
249 InvBlockTraits::child_begin(Header),
250 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
251 if (!contains(*PI)) { // If the block is not in the loop...
252 if (Out && Out != *PI)
253 return 0; // Multiple predecessors outside the loop
257 // Make sure there is only one exit out of the preheader.
258 assert(Out && "Header of loop has no predecessors from outside loop?");
259 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
261 if (SI != BlockTraits::child_end(Out))
262 return 0; // Multiple exits from the block, must not be a preheader.
264 // If there is exactly one preheader, return it. If there was zero, then
265 // Out is still null.
269 /// getLoopLatch - If there is a single latch block for this loop, return it.
270 /// A latch block is a block that contains a branch back to the header.
271 /// A loop header in normal form has two edges into it: one from a preheader
272 /// and one from a latch block.
273 BlockT *getLoopLatch() const {
274 BlockT *Header = getHeader();
275 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
276 typename InvBlockTraits::ChildIteratorType PI =
277 InvBlockTraits::child_begin(Header);
278 typename InvBlockTraits::ChildIteratorType PE =
279 InvBlockTraits::child_end(Header);
280 if (PI == PE) return 0; // no preds?
286 if (PI == PE) return 0; // only one pred?
289 if (Latch) return 0; // multiple backedges
293 if (PI != PE) return 0; // more than two preds
298 //===--------------------------------------------------------------------===//
299 // APIs for updating loop information after changing the CFG
302 /// addBasicBlockToLoop - This method is used by other analyses to update loop
303 /// information. NewBB is set to be a new member of the current loop.
304 /// Because of this, it is added as a member of all parent loops, and is added
305 /// to the specified LoopInfo object as being in the current basic block. It
306 /// is not valid to replace the loop header with this method.
308 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
310 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
311 /// the OldChild entry in our children list with NewChild, and updates the
312 /// parent pointer of OldChild to be null and the NewChild to be this loop.
313 /// This updates the loop depth of the new child.
314 void replaceChildLoopWith(LoopT *OldChild,
316 assert(OldChild->ParentLoop == this && "This loop is already broken!");
317 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
318 typename std::vector<LoopT *>::iterator I =
319 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
320 assert(I != SubLoops.end() && "OldChild not in loop!");
322 OldChild->ParentLoop = 0;
323 NewChild->ParentLoop = static_cast<LoopT *>(this);
326 /// addChildLoop - Add the specified loop to be a child of this loop. This
327 /// updates the loop depth of the new child.
329 void addChildLoop(LoopT *NewChild) {
330 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
331 NewChild->ParentLoop = static_cast<LoopT *>(this);
332 SubLoops.push_back(NewChild);
335 /// removeChildLoop - This removes the specified child from being a subloop of
336 /// this loop. The loop is not deleted, as it will presumably be inserted
337 /// into another loop.
338 LoopT *removeChildLoop(iterator I) {
339 assert(I != SubLoops.end() && "Cannot remove end iterator!");
341 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
342 SubLoops.erase(SubLoops.begin()+(I-begin()));
343 Child->ParentLoop = 0;
347 /// addBlockEntry - This adds a basic block directly to the basic block list.
348 /// This should only be used by transformations that create new loops. Other
349 /// transformations should use addBasicBlockToLoop.
350 void addBlockEntry(BlockT *BB) {
351 Blocks.push_back(BB);
354 /// moveToHeader - This method is used to move BB (which must be part of this
355 /// loop) to be the loop header of the loop (the block that dominates all
357 void moveToHeader(BlockT *BB) {
358 if (Blocks[0] == BB) return;
359 for (unsigned i = 0; ; ++i) {
360 assert(i != Blocks.size() && "Loop does not contain BB!");
361 if (Blocks[i] == BB) {
362 Blocks[i] = Blocks[0];
369 /// removeBlockFromLoop - This removes the specified basic block from the
370 /// current loop, updating the Blocks as appropriate. This does not update
371 /// the mapping in the LoopInfo class.
372 void removeBlockFromLoop(BlockT *BB) {
373 RemoveFromVector(Blocks, BB);
376 /// verifyLoop - Verify loop structure
377 void verifyLoop() const {
379 assert (getHeader() && "Loop header is missing");
380 assert (getLoopPreheader() && "Loop preheader is missing");
381 assert (getLoopLatch() && "Loop latch is missing");
382 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
387 void print(raw_ostream &OS, unsigned Depth = 0) const {
388 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
391 for (unsigned i = 0; i < getBlocks().size(); ++i) {
393 BlockT *BB = getBlocks()[i];
394 WriteAsOperand(OS, BB, false);
395 if (BB == getHeader()) OS << "<header>";
396 if (BB == getLoopLatch()) OS << "<latch>";
397 if (isLoopExit(BB)) OS << "<exit>";
401 for (iterator I = begin(), E = end(); I != E; ++I)
402 (*I)->print(OS, Depth+2);
410 friend class LoopInfoBase<BlockT, LoopT>;
411 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
412 Blocks.push_back(BB);
416 class Loop : public LoopBase<BasicBlock, Loop> {
420 /// isLoopInvariant - Return true if the specified value is loop invariant
422 bool isLoopInvariant(Value *V) const;
424 /// isLoopInvariant - Return true if the specified instruction is
427 bool isLoopInvariant(Instruction *I) const;
429 /// makeLoopInvariant - If the given value is an instruction inside of the
430 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
431 /// Return true if the value after any hoisting is loop invariant. This
432 /// function can be used as a slightly more aggressive replacement for
435 /// If InsertPt is specified, it is the point to hoist instructions to.
436 /// If null, the terminator of the loop preheader is used.
438 bool makeLoopInvariant(Value *V, bool &Changed,
439 Instruction *InsertPt = 0) const;
441 /// makeLoopInvariant - If the given instruction is inside of the
442 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
443 /// Return true if the instruction after any hoisting is loop invariant. This
444 /// function can be used as a slightly more aggressive replacement for
447 /// If InsertPt is specified, it is the point to hoist instructions to.
448 /// If null, the terminator of the loop preheader is used.
450 bool makeLoopInvariant(Instruction *I, bool &Changed,
451 Instruction *InsertPt = 0) const;
453 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
454 /// induction variable: an integer recurrence that starts at 0 and increments
455 /// by one each time through the loop. If so, return the phi node that
456 /// corresponds to it.
458 /// The IndVarSimplify pass transforms loops to have a canonical induction
461 PHINode *getCanonicalInductionVariable() const;
463 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
464 /// the canonical induction variable value for the "next" iteration of the
465 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
467 Instruction *getCanonicalInductionVariableIncrement() const;
469 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
470 /// times the loop will be executed. Note that this means that the backedge
471 /// of the loop executes N-1 times. If the trip-count cannot be determined,
472 /// this returns null.
474 /// The IndVarSimplify pass transforms loops to have a form that this
475 /// function easily understands.
477 Value *getTripCount() const;
479 /// getSmallConstantTripCount - Returns the trip count of this loop as a
480 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
481 /// of not constant. Will also return 0 if the trip count is very large
483 unsigned getSmallConstantTripCount() const;
485 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
486 /// trip count of this loop as a normal unsigned value, if possible. This
487 /// means that the actual trip count is always a multiple of the returned
488 /// value (don't forget the trip count could very well be zero as well!).
490 /// Returns 1 if the trip count is unknown or not guaranteed to be the
491 /// multiple of a constant (which is also the case if the trip count is simply
492 /// constant, use getSmallConstantTripCount for that case), Will also return 1
493 /// if the trip count is very large (>= 2^32).
494 unsigned getSmallConstantTripMultiple() const;
496 /// isLCSSAForm - Return true if the Loop is in LCSSA form
497 bool isLCSSAForm() const;
499 /// isLoopSimplifyForm - Return true if the Loop is in the form that
500 /// the LoopSimplify form transforms loops to, which is sometimes called
502 bool isLoopSimplifyForm() const;
504 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
505 /// These are the blocks _outside of the current loop_ which are branched to.
506 /// This assumes that loop is in canonical form.
508 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
510 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
511 /// block, return that block. Otherwise return null.
512 BasicBlock *getUniqueExitBlock() const;
515 friend class LoopInfoBase<BasicBlock, Loop>;
516 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
519 //===----------------------------------------------------------------------===//
520 /// LoopInfo - This class builds and contains all of the top level loop
521 /// structures in the specified function.
524 template<class BlockT, class LoopT>
526 // BBMap - Mapping of basic blocks to the inner most loop they occur in
527 std::map<BlockT *, LoopT *> BBMap;
528 std::vector<LoopT *> TopLevelLoops;
529 friend class LoopBase<BlockT, LoopT>;
531 void operator=(const LoopInfoBase &); // do not implement
532 LoopInfoBase(const LoopInfo &); // do not implement
535 ~LoopInfoBase() { releaseMemory(); }
537 void releaseMemory() {
538 for (typename std::vector<LoopT *>::iterator I =
539 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
540 delete *I; // Delete all of the loops...
542 BBMap.clear(); // Reset internal state of analysis
543 TopLevelLoops.clear();
546 /// iterator/begin/end - The interface to the top-level loops in the current
549 typedef typename std::vector<LoopT *>::const_iterator iterator;
550 iterator begin() const { return TopLevelLoops.begin(); }
551 iterator end() const { return TopLevelLoops.end(); }
552 bool empty() const { return TopLevelLoops.empty(); }
554 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
555 /// block is in no loop (for example the entry node), null is returned.
557 LoopT *getLoopFor(const BlockT *BB) const {
558 typename std::map<BlockT *, LoopT *>::const_iterator I=
559 BBMap.find(const_cast<BlockT*>(BB));
560 return I != BBMap.end() ? I->second : 0;
563 /// operator[] - same as getLoopFor...
565 const LoopT *operator[](const BlockT *BB) const {
566 return getLoopFor(BB);
569 /// getLoopDepth - Return the loop nesting level of the specified block. A
570 /// depth of 0 means the block is not inside any loop.
572 unsigned getLoopDepth(const BlockT *BB) const {
573 const LoopT *L = getLoopFor(BB);
574 return L ? L->getLoopDepth() : 0;
577 // isLoopHeader - True if the block is a loop header node
578 bool isLoopHeader(BlockT *BB) const {
579 const LoopT *L = getLoopFor(BB);
580 return L && L->getHeader() == BB;
583 /// removeLoop - This removes the specified top-level loop from this loop info
584 /// object. The loop is not deleted, as it will presumably be inserted into
586 LoopT *removeLoop(iterator I) {
587 assert(I != end() && "Cannot remove end iterator!");
589 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
590 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
594 /// changeLoopFor - Change the top-level loop that contains BB to the
595 /// specified loop. This should be used by transformations that restructure
596 /// the loop hierarchy tree.
597 void changeLoopFor(BlockT *BB, LoopT *L) {
598 LoopT *&OldLoop = BBMap[BB];
599 assert(OldLoop && "Block not in a loop yet!");
603 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
604 /// list with the indicated loop.
605 void changeTopLevelLoop(LoopT *OldLoop,
607 typename std::vector<LoopT *>::iterator I =
608 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
609 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
611 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
612 "Loops already embedded into a subloop!");
615 /// addTopLevelLoop - This adds the specified loop to the collection of
617 void addTopLevelLoop(LoopT *New) {
618 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
619 TopLevelLoops.push_back(New);
622 /// removeBlock - This method completely removes BB from all data structures,
623 /// including all of the Loop objects it is nested in and our mapping from
624 /// BasicBlocks to loops.
625 void removeBlock(BlockT *BB) {
626 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
627 if (I != BBMap.end()) {
628 for (LoopT *L = I->second; L; L = L->getParentLoop())
629 L->removeBlockFromLoop(BB);
637 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
638 const LoopT *ParentLoop) {
639 if (SubLoop == 0) return true;
640 if (SubLoop == ParentLoop) return false;
641 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
644 void Calculate(DominatorTreeBase<BlockT> &DT) {
645 BlockT *RootNode = DT.getRootNode()->getBlock();
647 for (df_iterator<BlockT*> NI = df_begin(RootNode),
648 NE = df_end(RootNode); NI != NE; ++NI)
649 if (LoopT *L = ConsiderForLoop(*NI, DT))
650 TopLevelLoops.push_back(L);
653 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
654 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
656 std::vector<BlockT *> TodoStack;
658 // Scan the predecessors of BB, checking to see if BB dominates any of
659 // them. This identifies backedges which target this node...
660 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
661 for (typename InvBlockTraits::ChildIteratorType I =
662 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
664 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
665 TodoStack.push_back(*I);
667 if (TodoStack.empty()) return 0; // No backedges to this block...
669 // Create a new loop to represent this basic block...
670 LoopT *L = new LoopT(BB);
673 BlockT *EntryBlock = BB->getParent()->begin();
675 while (!TodoStack.empty()) { // Process all the nodes in the loop
676 BlockT *X = TodoStack.back();
677 TodoStack.pop_back();
679 if (!L->contains(X) && // As of yet unprocessed??
680 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
681 // Check to see if this block already belongs to a loop. If this occurs
682 // then we have a case where a loop that is supposed to be a child of
683 // the current loop was processed before the current loop. When this
684 // occurs, this child loop gets added to a part of the current loop,
685 // making it a sibling to the current loop. We have to reparent this
688 const_cast<LoopT *>(getLoopFor(X)))
689 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
690 // Remove the subloop from it's current parent...
691 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
692 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
693 typename std::vector<LoopT *>::iterator I =
694 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
695 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
696 SLP->SubLoops.erase(I); // Remove from parent...
698 // Add the subloop to THIS loop...
699 SubLoop->ParentLoop = L;
700 L->SubLoops.push_back(SubLoop);
703 // Normal case, add the block to our loop...
704 L->Blocks.push_back(X);
706 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
708 // Add all of the predecessors of X to the end of the work stack...
709 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
710 InvBlockTraits::child_end(X));
714 // If there are any loops nested within this loop, create them now!
715 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
716 E = L->Blocks.end(); I != E; ++I)
717 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
718 L->SubLoops.push_back(NewLoop);
719 NewLoop->ParentLoop = L;
722 // Add the basic blocks that comprise this loop to the BBMap so that this
723 // loop can be found for them.
725 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
726 E = L->Blocks.end(); I != E; ++I)
727 BBMap.insert(std::make_pair(*I, L));
729 // Now that we have a list of all of the child loops of this loop, check to
730 // see if any of them should actually be nested inside of each other. We
731 // can accidentally pull loops our of their parents, so we must make sure to
732 // organize the loop nests correctly now.
734 std::map<BlockT *, LoopT *> ContainingLoops;
735 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
736 LoopT *Child = L->SubLoops[i];
737 assert(Child->getParentLoop() == L && "Not proper child loop?");
739 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
740 // If there is already a loop which contains this loop, move this loop
741 // into the containing loop.
742 MoveSiblingLoopInto(Child, ContainingLoop);
743 --i; // The loop got removed from the SubLoops list.
745 // This is currently considered to be a top-level loop. Check to see
746 // if any of the contained blocks are loop headers for subloops we
747 // have already processed.
748 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
749 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
750 if (BlockLoop == 0) { // Child block not processed yet...
752 } else if (BlockLoop != Child) {
753 LoopT *SubLoop = BlockLoop;
754 // Reparent all of the blocks which used to belong to BlockLoops
755 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
756 ContainingLoops[SubLoop->Blocks[j]] = Child;
758 // There is already a loop which contains this block, that means
759 // that we should reparent the loop which the block is currently
760 // considered to belong to to be a child of this loop.
761 MoveSiblingLoopInto(SubLoop, Child);
762 --i; // We just shrunk the SubLoops list.
772 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
773 /// of the NewParent Loop, instead of being a sibling of it.
774 void MoveSiblingLoopInto(LoopT *NewChild,
776 LoopT *OldParent = NewChild->getParentLoop();
777 assert(OldParent && OldParent == NewParent->getParentLoop() &&
778 NewChild != NewParent && "Not sibling loops!");
780 // Remove NewChild from being a child of OldParent
781 typename std::vector<LoopT *>::iterator I =
782 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
784 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
785 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
786 NewChild->ParentLoop = 0;
788 InsertLoopInto(NewChild, NewParent);
791 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
792 /// the parent loop contains a loop which should contain L, the loop gets
793 /// inserted into L instead.
794 void InsertLoopInto(LoopT *L, LoopT *Parent) {
795 BlockT *LHeader = L->getHeader();
796 assert(Parent->contains(LHeader) &&
797 "This loop should not be inserted here!");
799 // Check to see if it belongs in a child loop...
800 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
802 if (Parent->SubLoops[i]->contains(LHeader)) {
803 InsertLoopInto(L, Parent->SubLoops[i]);
807 // If not, insert it here!
808 Parent->SubLoops.push_back(L);
809 L->ParentLoop = Parent;
814 void print(raw_ostream &OS) const {
815 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
816 TopLevelLoops[i]->print(OS);
818 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
819 E = BBMap.end(); I != E; ++I)
820 OS << "BB '" << I->first->getName() << "' level = "
821 << I->second->getLoopDepth() << "\n";
826 class LoopInfo : public FunctionPass {
827 LoopInfoBase<BasicBlock, Loop> LI;
828 friend class LoopBase<BasicBlock, Loop>;
830 void operator=(const LoopInfo &); // do not implement
831 LoopInfo(const LoopInfo &); // do not implement
833 static char ID; // Pass identification, replacement for typeid
835 LoopInfo() : FunctionPass(&ID) {}
837 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
839 /// iterator/begin/end - The interface to the top-level loops in the current
842 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
843 inline iterator begin() const { return LI.begin(); }
844 inline iterator end() const { return LI.end(); }
845 bool empty() const { return LI.empty(); }
847 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
848 /// block is in no loop (for example the entry node), null is returned.
850 inline Loop *getLoopFor(const BasicBlock *BB) const {
851 return LI.getLoopFor(BB);
854 /// operator[] - same as getLoopFor...
856 inline const Loop *operator[](const BasicBlock *BB) const {
857 return LI.getLoopFor(BB);
860 /// getLoopDepth - Return the loop nesting level of the specified block. A
861 /// depth of 0 means the block is not inside any loop.
863 inline unsigned getLoopDepth(const BasicBlock *BB) const {
864 return LI.getLoopDepth(BB);
867 // isLoopHeader - True if the block is a loop header node
868 inline bool isLoopHeader(BasicBlock *BB) const {
869 return LI.isLoopHeader(BB);
872 /// runOnFunction - Calculate the natural loop information.
874 virtual bool runOnFunction(Function &F);
876 virtual void releaseMemory() { LI.releaseMemory(); }
878 virtual void print(raw_ostream &O, const Module* M = 0) const;
880 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
882 /// removeLoop - This removes the specified top-level loop from this loop info
883 /// object. The loop is not deleted, as it will presumably be inserted into
885 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
887 /// changeLoopFor - Change the top-level loop that contains BB to the
888 /// specified loop. This should be used by transformations that restructure
889 /// the loop hierarchy tree.
890 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
891 LI.changeLoopFor(BB, L);
894 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
895 /// list with the indicated loop.
896 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
897 LI.changeTopLevelLoop(OldLoop, NewLoop);
900 /// addTopLevelLoop - This adds the specified loop to the collection of
902 inline void addTopLevelLoop(Loop *New) {
903 LI.addTopLevelLoop(New);
906 /// removeBlock - This method completely removes BB from all data structures,
907 /// including all of the Loop objects it is nested in and our mapping from
908 /// BasicBlocks to loops.
909 void removeBlock(BasicBlock *BB) {
913 static bool isNotAlreadyContainedIn(const Loop *SubLoop,
914 const Loop *ParentLoop) {
916 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop,
922 // Allow clients to walk the list of nested loops...
923 template <> struct GraphTraits<const Loop*> {
924 typedef const Loop NodeType;
925 typedef LoopInfo::iterator ChildIteratorType;
927 static NodeType *getEntryNode(const Loop *L) { return L; }
928 static inline ChildIteratorType child_begin(NodeType *N) {
931 static inline ChildIteratorType child_end(NodeType *N) {
936 template <> struct GraphTraits<Loop*> {
937 typedef Loop NodeType;
938 typedef LoopInfo::iterator ChildIteratorType;
940 static NodeType *getEntryNode(Loop *L) { return L; }
941 static inline ChildIteratorType child_begin(NodeType *N) {
944 static inline ChildIteratorType child_end(NodeType *N) {
949 template<class BlockT, class LoopT>
951 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
952 LoopInfoBase<BlockT, LoopT> &LIB) {
953 assert((Blocks.empty() || LIB[getHeader()] == this) &&
954 "Incorrect LI specified for this loop!");
955 assert(NewBB && "Cannot add a null basic block to the loop!");
956 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
958 LoopT *L = static_cast<LoopT *>(this);
960 // Add the loop mapping to the LoopInfo object...
961 LIB.BBMap[NewBB] = L;
963 // Add the basic block to this loop and all parent loops...
965 L->Blocks.push_back(NewBB);
966 L = L->getParentLoop();
970 } // End llvm namespace