1 //===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG. A natural loop
12 // has exactly one entry-point, which is called the header. Note that natural
13 // loops may actually be several loops that share the same header node.
15 // This analysis calculates the nesting structure of loops in a function. For
16 // each natural loop identified, this analysis identifies natural loops
17 // contained entirely within the loop and the basic blocks the make up the loop.
19 // It can calculate on the fly various bits of information, for example:
21 // * whether there is a preheader for the loop
22 // * the number of back edges to the header
23 // * whether or not a particular block branches out of the loop
24 // * the successor blocks of the loop
29 //===----------------------------------------------------------------------===//
31 #ifndef LLVM_ANALYSIS_LOOP_INFO_H
32 #define LLVM_ANALYSIS_LOOP_INFO_H
34 #include "llvm/Pass.h"
35 #include "llvm/ADT/DepthFirstIterator.h"
36 #include "llvm/ADT/GraphTraits.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/Analysis/Dominators.h"
39 #include "llvm/Support/CFG.h"
40 #include "llvm/Support/raw_ostream.h"
46 static void RemoveFromVector(std::vector<T*> &V, T *N) {
47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
48 assert(I != V.end() && "N is not in this list!");
55 template<class N, class M> class LoopInfoBase;
56 template<class N, class M> class LoopBase;
58 //===----------------------------------------------------------------------===//
59 /// LoopBase class - Instances of this class are used to represent loops that
60 /// are detected in the flow graph
62 template<class BlockT, class LoopT>
65 // SubLoops - Loops contained entirely within this one.
66 std::vector<LoopT *> SubLoops;
68 // Blocks - The list of blocks in this loop. First entry is the header node.
69 std::vector<BlockT*> Blocks;
72 LoopBase(const LoopBase<BlockT, LoopT> &);
74 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
76 /// Loop ctor - This creates an empty loop.
77 LoopBase() : ParentLoop(0) {}
79 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
83 /// getLoopDepth - Return the nesting level of this loop. An outer-most
84 /// loop has depth 1, for consistency with loop depth values used for basic
85 /// blocks, where depth 0 is used for blocks not inside any loops.
86 unsigned getLoopDepth() const {
88 for (const LoopT *CurLoop = ParentLoop; CurLoop;
89 CurLoop = CurLoop->ParentLoop)
93 BlockT *getHeader() const { return Blocks.front(); }
94 LoopT *getParentLoop() const { return ParentLoop; }
96 /// contains - Return true if the specified loop is contained within in
99 bool contains(const LoopT *L) const {
100 if (L == this) return true;
101 if (L == 0) return false;
102 return contains(L->getParentLoop());
105 /// contains - Return true if the specified basic block is in this loop.
107 bool contains(const BlockT *BB) const {
108 return std::find(block_begin(), block_end(), BB) != block_end();
111 /// contains - Return true if the specified instruction is in this loop.
113 template<class InstT>
114 bool contains(const InstT *Inst) const {
115 return contains(Inst->getParent());
118 /// iterator/begin/end - Return the loops contained entirely within this loop.
120 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
121 typedef typename std::vector<LoopT *>::const_iterator iterator;
122 iterator begin() const { return SubLoops.begin(); }
123 iterator end() const { return SubLoops.end(); }
124 bool empty() const { return SubLoops.empty(); }
126 /// getBlocks - Get a list of the basic blocks which make up this loop.
128 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
129 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
130 block_iterator block_begin() const { return Blocks.begin(); }
131 block_iterator block_end() const { return Blocks.end(); }
133 /// isLoopExiting - True if terminator in the block can branch to another
134 /// block that is outside of the current loop.
136 bool isLoopExiting(const BlockT *BB) const {
137 typedef GraphTraits<BlockT*> BlockTraits;
138 for (typename BlockTraits::ChildIteratorType SI =
139 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
140 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
147 /// getNumBackEdges - Calculate the number of back edges to the loop header
149 unsigned getNumBackEdges() const {
150 unsigned NumBackEdges = 0;
151 BlockT *H = getHeader();
153 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
154 for (typename InvBlockTraits::ChildIteratorType I =
155 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
156 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
163 //===--------------------------------------------------------------------===//
164 // APIs for simple analysis of the loop.
166 // Note that all of these methods can fail on general loops (ie, there may not
167 // be a preheader, etc). For best success, the loop simplification and
168 // induction variable canonicalization pass should be used to normalize loops
169 // for easy analysis. These methods assume canonical loops.
171 /// getExitingBlocks - Return all blocks inside the loop that have successors
172 /// outside of the loop. These are the blocks _inside of the current loop_
173 /// which branch out. The returned list is always unique.
175 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
176 // Sort the blocks vector so that we can use binary search to do quick
178 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
179 std::sort(LoopBBs.begin(), LoopBBs.end());
181 typedef GraphTraits<BlockT*> BlockTraits;
182 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
183 for (typename BlockTraits::ChildIteratorType I =
184 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
186 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
187 // Not in current loop? It must be an exit block.
188 ExitingBlocks.push_back(*BI);
193 /// getExitingBlock - If getExitingBlocks would return exactly one block,
194 /// return that block. Otherwise return null.
195 BlockT *getExitingBlock() const {
196 SmallVector<BlockT*, 8> ExitingBlocks;
197 getExitingBlocks(ExitingBlocks);
198 if (ExitingBlocks.size() == 1)
199 return ExitingBlocks[0];
203 /// getExitBlocks - Return all of the successor blocks of this loop. These
204 /// are the blocks _outside of the current loop_ which are branched to.
206 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
207 // Sort the blocks vector so that we can use binary search to do quick
209 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
210 std::sort(LoopBBs.begin(), LoopBBs.end());
212 typedef GraphTraits<BlockT*> BlockTraits;
213 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
214 for (typename BlockTraits::ChildIteratorType I =
215 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
217 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
218 // Not in current loop? It must be an exit block.
219 ExitBlocks.push_back(*I);
222 /// getExitBlock - If getExitBlocks would return exactly one block,
223 /// return that block. Otherwise return null.
224 BlockT *getExitBlock() const {
225 SmallVector<BlockT*, 8> ExitBlocks;
226 getExitBlocks(ExitBlocks);
227 if (ExitBlocks.size() == 1)
228 return ExitBlocks[0];
232 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
233 typedef std::pair<const BlockT*,const BlockT*> Edge;
234 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
235 // Sort the blocks vector so that we can use binary search to do quick
237 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
238 std::sort(LoopBBs.begin(), LoopBBs.end());
240 typedef GraphTraits<BlockT*> BlockTraits;
241 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
242 for (typename BlockTraits::ChildIteratorType I =
243 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
245 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
246 // Not in current loop? It must be an exit block.
247 ExitEdges.push_back(std::make_pair(*BI, *I));
250 /// getLoopPreheader - If there is a preheader for this loop, return it. A
251 /// loop has a preheader if there is only one edge to the header of the loop
252 /// from outside of the loop. If this is the case, the block branching to the
253 /// header of the loop is the preheader node.
255 /// This method returns null if there is no preheader for the loop.
257 BlockT *getLoopPreheader() const {
258 // Keep track of nodes outside the loop branching to the header...
261 // Loop over the predecessors of the header node...
262 BlockT *Header = getHeader();
263 typedef GraphTraits<BlockT*> BlockTraits;
264 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
265 for (typename InvBlockTraits::ChildIteratorType PI =
266 InvBlockTraits::child_begin(Header),
267 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
268 if (!contains(*PI)) { // If the block is not in the loop...
269 if (Out && Out != *PI)
270 return 0; // Multiple predecessors outside the loop
274 // Make sure there is only one exit out of the preheader.
275 assert(Out && "Header of loop has no predecessors from outside loop?");
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 // If there is exactly one preheader, return it. If there was zero, then
282 // Out is still null.
286 /// getLoopLatch - If there is a single latch block for this loop, return it.
287 /// A latch block is a block that contains a branch back to the header.
288 BlockT *getLoopLatch() const {
289 BlockT *Header = getHeader();
290 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
291 typename InvBlockTraits::ChildIteratorType PI =
292 InvBlockTraits::child_begin(Header);
293 typename InvBlockTraits::ChildIteratorType PE =
294 InvBlockTraits::child_end(Header);
296 for (; PI != PE; ++PI)
305 //===--------------------------------------------------------------------===//
306 // APIs for updating loop information after changing the CFG
309 /// addBasicBlockToLoop - This method is used by other analyses to update loop
310 /// information. NewBB is set to be a new member of the current loop.
311 /// Because of this, it is added as a member of all parent loops, and is added
312 /// to the specified LoopInfo object as being in the current basic block. It
313 /// is not valid to replace the loop header with this method.
315 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
317 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
318 /// the OldChild entry in our children list with NewChild, and updates the
319 /// parent pointer of OldChild to be null and the NewChild to be this loop.
320 /// This updates the loop depth of the new child.
321 void replaceChildLoopWith(LoopT *OldChild,
323 assert(OldChild->ParentLoop == this && "This loop is already broken!");
324 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
325 typename std::vector<LoopT *>::iterator I =
326 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
327 assert(I != SubLoops.end() && "OldChild not in loop!");
329 OldChild->ParentLoop = 0;
330 NewChild->ParentLoop = static_cast<LoopT *>(this);
333 /// addChildLoop - Add the specified loop to be a child of this loop. This
334 /// updates the loop depth of the new child.
336 void addChildLoop(LoopT *NewChild) {
337 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
338 NewChild->ParentLoop = static_cast<LoopT *>(this);
339 SubLoops.push_back(NewChild);
342 /// removeChildLoop - This removes the specified child from being a subloop of
343 /// this loop. The loop is not deleted, as it will presumably be inserted
344 /// into another loop.
345 LoopT *removeChildLoop(iterator I) {
346 assert(I != SubLoops.end() && "Cannot remove end iterator!");
348 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
349 SubLoops.erase(SubLoops.begin()+(I-begin()));
350 Child->ParentLoop = 0;
354 /// addBlockEntry - This adds a basic block directly to the basic block list.
355 /// This should only be used by transformations that create new loops. Other
356 /// transformations should use addBasicBlockToLoop.
357 void addBlockEntry(BlockT *BB) {
358 Blocks.push_back(BB);
361 /// moveToHeader - This method is used to move BB (which must be part of this
362 /// loop) to be the loop header of the loop (the block that dominates all
364 void moveToHeader(BlockT *BB) {
365 if (Blocks[0] == BB) return;
366 for (unsigned i = 0; ; ++i) {
367 assert(i != Blocks.size() && "Loop does not contain BB!");
368 if (Blocks[i] == BB) {
369 Blocks[i] = Blocks[0];
376 /// removeBlockFromLoop - This removes the specified basic block from the
377 /// current loop, updating the Blocks as appropriate. This does not update
378 /// the mapping in the LoopInfo class.
379 void removeBlockFromLoop(BlockT *BB) {
380 RemoveFromVector(Blocks, BB);
383 /// verifyLoop - Verify loop structure
384 void verifyLoop() const {
386 assert(!Blocks.empty() && "Loop header is missing");
388 // Sort the blocks vector so that we can use binary search to do quick
390 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
391 std::sort(LoopBBs.begin(), LoopBBs.end());
393 // Check the individual blocks.
394 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
396 bool HasInsideLoopSuccs = false;
397 bool HasInsideLoopPreds = false;
398 SmallVector<BlockT *, 2> OutsideLoopPreds;
400 typedef GraphTraits<BlockT*> BlockTraits;
401 for (typename BlockTraits::ChildIteratorType SI =
402 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
404 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
405 HasInsideLoopSuccs = true;
408 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
409 for (typename InvBlockTraits::ChildIteratorType PI =
410 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
412 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI))
413 HasInsideLoopPreds = true;
415 OutsideLoopPreds.push_back(*PI);
418 if (BB == getHeader()) {
419 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
420 } else if (!OutsideLoopPreds.empty()) {
421 // A non-header loop shouldn't be reachable from outside the loop,
422 // though it is permitted if the predecessor is not itself actually
424 BlockT *EntryBB = BB->getParent()->begin();
425 for (df_iterator<BlockT *> NI = df_begin(EntryBB),
426 NE = df_end(EntryBB); NI != NE; ++NI)
427 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
428 assert(*NI != OutsideLoopPreds[i] &&
429 "Loop has multiple entry points!");
431 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
432 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
433 assert(BB != getHeader()->getParent()->begin() &&
434 "Loop contains function entry block!");
437 // Check the subloops.
438 for (iterator I = begin(), E = end(); I != E; ++I)
439 // Each block in each subloop should be contained within this loop.
440 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
442 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
443 "Loop does not contain all the blocks of a subloop!");
446 // Check the parent loop pointer.
448 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
450 "Loop is not a subloop of its parent!");
455 /// verifyLoop - Verify loop structure of this loop and all nested loops.
456 void verifyLoopNest() const {
459 // Verify the subloops.
460 for (iterator I = begin(), E = end(); I != E; ++I)
461 (*I)->verifyLoopNest();
464 void print(raw_ostream &OS, unsigned Depth = 0) const {
465 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
468 for (unsigned i = 0; i < getBlocks().size(); ++i) {
470 BlockT *BB = getBlocks()[i];
471 WriteAsOperand(OS, BB, false);
472 if (BB == getHeader()) OS << "<header>";
473 if (BB == getLoopLatch()) OS << "<latch>";
474 if (isLoopExiting(BB)) OS << "<exiting>";
478 for (iterator I = begin(), E = end(); I != E; ++I)
479 (*I)->print(OS, Depth+2);
483 friend class LoopInfoBase<BlockT, LoopT>;
484 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
485 Blocks.push_back(BB);
489 class Loop : public LoopBase<BasicBlock, Loop> {
493 /// isLoopInvariant - Return true if the specified value is loop invariant
495 bool isLoopInvariant(Value *V) const;
497 /// isLoopInvariant - Return true if the specified instruction is
500 bool isLoopInvariant(Instruction *I) const;
502 /// makeLoopInvariant - If the given value is an instruction inside of the
503 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
504 /// Return true if the value after any hoisting is loop invariant. This
505 /// function can be used as a slightly more aggressive replacement for
508 /// If InsertPt is specified, it is the point to hoist instructions to.
509 /// If null, the terminator of the loop preheader is used.
511 bool makeLoopInvariant(Value *V, bool &Changed,
512 Instruction *InsertPt = 0) const;
514 /// makeLoopInvariant - If the given instruction is inside of the
515 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
516 /// Return true if the instruction after any hoisting is loop invariant. This
517 /// function can be used as a slightly more aggressive replacement for
520 /// If InsertPt is specified, it is the point to hoist instructions to.
521 /// If null, the terminator of the loop preheader is used.
523 bool makeLoopInvariant(Instruction *I, bool &Changed,
524 Instruction *InsertPt = 0) const;
526 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
527 /// induction variable: an integer recurrence that starts at 0 and increments
528 /// by one each time through the loop. If so, return the phi node that
529 /// corresponds to it.
531 /// The IndVarSimplify pass transforms loops to have a canonical induction
534 PHINode *getCanonicalInductionVariable() const;
536 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
537 /// the canonical induction variable value for the "next" iteration of the
538 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
540 Instruction *getCanonicalInductionVariableIncrement() const;
542 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
543 /// times the loop will be executed. Note that this means that the backedge
544 /// of the loop executes N-1 times. If the trip-count cannot be determined,
545 /// this returns null.
547 /// The IndVarSimplify pass transforms loops to have a form that this
548 /// function easily understands.
550 Value *getTripCount() const;
552 /// getSmallConstantTripCount - Returns the trip count of this loop as a
553 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
554 /// of not constant. Will also return 0 if the trip count is very large
557 /// The IndVarSimplify pass transforms loops to have a form that this
558 /// function easily understands.
560 unsigned getSmallConstantTripCount() const;
562 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
563 /// trip count of this loop as a normal unsigned value, if possible. This
564 /// means that the actual trip count is always a multiple of the returned
565 /// value (don't forget the trip count could very well be zero as well!).
567 /// Returns 1 if the trip count is unknown or not guaranteed to be the
568 /// multiple of a constant (which is also the case if the trip count is simply
569 /// constant, use getSmallConstantTripCount for that case), Will also return 1
570 /// if the trip count is very large (>= 2^32).
571 unsigned getSmallConstantTripMultiple() const;
573 /// isLCSSAForm - Return true if the Loop is in LCSSA form
574 bool isLCSSAForm(DominatorTree &DT) const;
576 /// isLoopSimplifyForm - Return true if the Loop is in the form that
577 /// the LoopSimplify form transforms loops to, which is sometimes called
579 bool isLoopSimplifyForm() const;
581 /// hasDedicatedExits - Return true if no exit block for the loop
582 /// has a predecessor that is outside the loop.
583 bool hasDedicatedExits() const;
585 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
586 /// These are the blocks _outside of the current loop_ which are branched to.
587 /// This assumes that loop exits are in canonical form.
589 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
591 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
592 /// block, return that block. Otherwise return null.
593 BasicBlock *getUniqueExitBlock() const;
598 friend class LoopInfoBase<BasicBlock, Loop>;
599 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
602 //===----------------------------------------------------------------------===//
603 /// LoopInfo - This class builds and contains all of the top level loop
604 /// structures in the specified function.
607 template<class BlockT, class LoopT>
609 // BBMap - Mapping of basic blocks to the inner most loop they occur in
610 std::map<BlockT *, LoopT *> BBMap;
611 std::vector<LoopT *> TopLevelLoops;
612 friend class LoopBase<BlockT, LoopT>;
614 void operator=(const LoopInfoBase &); // do not implement
615 LoopInfoBase(const LoopInfo &); // do not implement
618 ~LoopInfoBase() { releaseMemory(); }
620 void releaseMemory() {
621 for (typename std::vector<LoopT *>::iterator I =
622 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
623 delete *I; // Delete all of the loops...
625 BBMap.clear(); // Reset internal state of analysis
626 TopLevelLoops.clear();
629 /// iterator/begin/end - The interface to the top-level loops in the current
632 typedef typename std::vector<LoopT *>::const_iterator iterator;
633 iterator begin() const { return TopLevelLoops.begin(); }
634 iterator end() const { return TopLevelLoops.end(); }
635 bool empty() const { return TopLevelLoops.empty(); }
637 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
638 /// block is in no loop (for example the entry node), null is returned.
640 LoopT *getLoopFor(const BlockT *BB) const {
641 typename std::map<BlockT *, LoopT *>::const_iterator I=
642 BBMap.find(const_cast<BlockT*>(BB));
643 return I != BBMap.end() ? I->second : 0;
646 /// operator[] - same as getLoopFor...
648 const LoopT *operator[](const BlockT *BB) const {
649 return getLoopFor(BB);
652 /// getLoopDepth - Return the loop nesting level of the specified block. A
653 /// depth of 0 means the block is not inside any loop.
655 unsigned getLoopDepth(const BlockT *BB) const {
656 const LoopT *L = getLoopFor(BB);
657 return L ? L->getLoopDepth() : 0;
660 // isLoopHeader - True if the block is a loop header node
661 bool isLoopHeader(BlockT *BB) const {
662 const LoopT *L = getLoopFor(BB);
663 return L && L->getHeader() == BB;
666 /// removeLoop - This removes the specified top-level loop from this loop info
667 /// object. The loop is not deleted, as it will presumably be inserted into
669 LoopT *removeLoop(iterator I) {
670 assert(I != end() && "Cannot remove end iterator!");
672 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
673 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
677 /// changeLoopFor - Change the top-level loop that contains BB to the
678 /// specified loop. This should be used by transformations that restructure
679 /// the loop hierarchy tree.
680 void changeLoopFor(BlockT *BB, LoopT *L) {
681 LoopT *&OldLoop = BBMap[BB];
682 assert(OldLoop && "Block not in a loop yet!");
686 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
687 /// list with the indicated loop.
688 void changeTopLevelLoop(LoopT *OldLoop,
690 typename std::vector<LoopT *>::iterator I =
691 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
692 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
694 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
695 "Loops already embedded into a subloop!");
698 /// addTopLevelLoop - This adds the specified loop to the collection of
700 void addTopLevelLoop(LoopT *New) {
701 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
702 TopLevelLoops.push_back(New);
705 /// removeBlock - This method completely removes BB from all data structures,
706 /// including all of the Loop objects it is nested in and our mapping from
707 /// BasicBlocks to loops.
708 void removeBlock(BlockT *BB) {
709 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
710 if (I != BBMap.end()) {
711 for (LoopT *L = I->second; L; L = L->getParentLoop())
712 L->removeBlockFromLoop(BB);
720 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
721 const LoopT *ParentLoop) {
722 if (SubLoop == 0) return true;
723 if (SubLoop == ParentLoop) return false;
724 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
727 void Calculate(DominatorTreeBase<BlockT> &DT) {
728 BlockT *RootNode = DT.getRootNode()->getBlock();
730 for (df_iterator<BlockT*> NI = df_begin(RootNode),
731 NE = df_end(RootNode); NI != NE; ++NI)
732 if (LoopT *L = ConsiderForLoop(*NI, DT))
733 TopLevelLoops.push_back(L);
736 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
737 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
739 std::vector<BlockT *> TodoStack;
741 // Scan the predecessors of BB, checking to see if BB dominates any of
742 // them. This identifies backedges which target this node...
743 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
744 for (typename InvBlockTraits::ChildIteratorType I =
745 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
747 if (DT.dominates(BB, *I)) // If BB dominates its predecessor...
748 TodoStack.push_back(*I);
750 if (TodoStack.empty()) return 0; // No backedges to this block...
752 // Create a new loop to represent this basic block...
753 LoopT *L = new LoopT(BB);
756 BlockT *EntryBlock = BB->getParent()->begin();
758 while (!TodoStack.empty()) { // Process all the nodes in the loop
759 BlockT *X = TodoStack.back();
760 TodoStack.pop_back();
762 if (!L->contains(X) && // As of yet unprocessed??
763 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
764 // Check to see if this block already belongs to a loop. If this occurs
765 // then we have a case where a loop that is supposed to be a child of
766 // the current loop was processed before the current loop. When this
767 // occurs, this child loop gets added to a part of the current loop,
768 // making it a sibling to the current loop. We have to reparent this
771 const_cast<LoopT *>(getLoopFor(X)))
772 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
773 // Remove the subloop from its current parent...
774 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
775 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
776 typename std::vector<LoopT *>::iterator I =
777 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
778 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
779 SLP->SubLoops.erase(I); // Remove from parent...
781 // Add the subloop to THIS loop...
782 SubLoop->ParentLoop = L;
783 L->SubLoops.push_back(SubLoop);
786 // Normal case, add the block to our loop...
787 L->Blocks.push_back(X);
789 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
791 // Add all of the predecessors of X to the end of the work stack...
792 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
793 InvBlockTraits::child_end(X));
797 // If there are any loops nested within this loop, create them now!
798 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
799 E = L->Blocks.end(); I != E; ++I)
800 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
801 L->SubLoops.push_back(NewLoop);
802 NewLoop->ParentLoop = L;
805 // Add the basic blocks that comprise this loop to the BBMap so that this
806 // loop can be found for them.
808 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
809 E = L->Blocks.end(); I != E; ++I)
810 BBMap.insert(std::make_pair(*I, L));
812 // Now that we have a list of all of the child loops of this loop, check to
813 // see if any of them should actually be nested inside of each other. We
814 // can accidentally pull loops our of their parents, so we must make sure to
815 // organize the loop nests correctly now.
817 std::map<BlockT *, LoopT *> ContainingLoops;
818 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
819 LoopT *Child = L->SubLoops[i];
820 assert(Child->getParentLoop() == L && "Not proper child loop?");
822 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
823 // If there is already a loop which contains this loop, move this loop
824 // into the containing loop.
825 MoveSiblingLoopInto(Child, ContainingLoop);
826 --i; // The loop got removed from the SubLoops list.
828 // This is currently considered to be a top-level loop. Check to see
829 // if any of the contained blocks are loop headers for subloops we
830 // have already processed.
831 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
832 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
833 if (BlockLoop == 0) { // Child block not processed yet...
835 } else if (BlockLoop != Child) {
836 LoopT *SubLoop = BlockLoop;
837 // Reparent all of the blocks which used to belong to BlockLoops
838 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
839 ContainingLoops[SubLoop->Blocks[j]] = Child;
841 // There is already a loop which contains this block, that means
842 // that we should reparent the loop which the block is currently
843 // considered to belong to to be a child of this loop.
844 MoveSiblingLoopInto(SubLoop, Child);
845 --i; // We just shrunk the SubLoops list.
855 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
856 /// of the NewParent Loop, instead of being a sibling of it.
857 void MoveSiblingLoopInto(LoopT *NewChild,
859 LoopT *OldParent = NewChild->getParentLoop();
860 assert(OldParent && OldParent == NewParent->getParentLoop() &&
861 NewChild != NewParent && "Not sibling loops!");
863 // Remove NewChild from being a child of OldParent
864 typename std::vector<LoopT *>::iterator I =
865 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
867 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
868 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
869 NewChild->ParentLoop = 0;
871 InsertLoopInto(NewChild, NewParent);
874 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
875 /// the parent loop contains a loop which should contain L, the loop gets
876 /// inserted into L instead.
877 void InsertLoopInto(LoopT *L, LoopT *Parent) {
878 BlockT *LHeader = L->getHeader();
879 assert(Parent->contains(LHeader) &&
880 "This loop should not be inserted here!");
882 // Check to see if it belongs in a child loop...
883 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
885 if (Parent->SubLoops[i]->contains(LHeader)) {
886 InsertLoopInto(L, Parent->SubLoops[i]);
890 // If not, insert it here!
891 Parent->SubLoops.push_back(L);
892 L->ParentLoop = Parent;
897 void print(raw_ostream &OS) const {
898 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
899 TopLevelLoops[i]->print(OS);
901 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
902 E = BBMap.end(); I != E; ++I)
903 OS << "BB '" << I->first->getName() << "' level = "
904 << I->second->getLoopDepth() << "\n";
909 class LoopInfo : public FunctionPass {
910 LoopInfoBase<BasicBlock, Loop> LI;
911 friend class LoopBase<BasicBlock, Loop>;
913 void operator=(const LoopInfo &); // do not implement
914 LoopInfo(const LoopInfo &); // do not implement
916 static char ID; // Pass identification, replacement for typeid
918 LoopInfo() : FunctionPass(&ID) {}
920 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
922 /// iterator/begin/end - The interface to the top-level loops in the current
925 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
926 inline iterator begin() const { return LI.begin(); }
927 inline iterator end() const { return LI.end(); }
928 bool empty() const { return LI.empty(); }
930 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
931 /// block is in no loop (for example the entry node), null is returned.
933 inline Loop *getLoopFor(const BasicBlock *BB) const {
934 return LI.getLoopFor(BB);
937 /// operator[] - same as getLoopFor...
939 inline const Loop *operator[](const BasicBlock *BB) const {
940 return LI.getLoopFor(BB);
943 /// getLoopDepth - Return the loop nesting level of the specified block. A
944 /// depth of 0 means the block is not inside any loop.
946 inline unsigned getLoopDepth(const BasicBlock *BB) const {
947 return LI.getLoopDepth(BB);
950 // isLoopHeader - True if the block is a loop header node
951 inline bool isLoopHeader(BasicBlock *BB) const {
952 return LI.isLoopHeader(BB);
955 /// runOnFunction - Calculate the natural loop information.
957 virtual bool runOnFunction(Function &F);
959 virtual void verifyAnalysis() const;
961 virtual void releaseMemory() { LI.releaseMemory(); }
963 virtual void print(raw_ostream &O, const Module* M = 0) const;
965 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
967 /// removeLoop - This removes the specified top-level loop from this loop info
968 /// object. The loop is not deleted, as it will presumably be inserted into
970 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
972 /// changeLoopFor - Change the top-level loop that contains BB to the
973 /// specified loop. This should be used by transformations that restructure
974 /// the loop hierarchy tree.
975 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
976 LI.changeLoopFor(BB, L);
979 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
980 /// list with the indicated loop.
981 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
982 LI.changeTopLevelLoop(OldLoop, NewLoop);
985 /// addTopLevelLoop - This adds the specified loop to the collection of
987 inline void addTopLevelLoop(Loop *New) {
988 LI.addTopLevelLoop(New);
991 /// removeBlock - This method completely removes BB from all data structures,
992 /// including all of the Loop objects it is nested in and our mapping from
993 /// BasicBlocks to loops.
994 void removeBlock(BasicBlock *BB) {
1000 // Allow clients to walk the list of nested loops...
1001 template <> struct GraphTraits<const Loop*> {
1002 typedef const Loop NodeType;
1003 typedef LoopInfo::iterator ChildIteratorType;
1005 static NodeType *getEntryNode(const Loop *L) { return L; }
1006 static inline ChildIteratorType child_begin(NodeType *N) {
1009 static inline ChildIteratorType child_end(NodeType *N) {
1014 template <> struct GraphTraits<Loop*> {
1015 typedef Loop NodeType;
1016 typedef LoopInfo::iterator ChildIteratorType;
1018 static NodeType *getEntryNode(Loop *L) { return L; }
1019 static inline ChildIteratorType child_begin(NodeType *N) {
1022 static inline ChildIteratorType child_end(NodeType *N) {
1027 template<class BlockT, class LoopT>
1029 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1030 LoopInfoBase<BlockT, LoopT> &LIB) {
1031 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1032 "Incorrect LI specified for this loop!");
1033 assert(NewBB && "Cannot add a null basic block to the loop!");
1034 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1036 LoopT *L = static_cast<LoopT *>(this);
1038 // Add the loop mapping to the LoopInfo object...
1039 LIB.BBMap[NewBB] = L;
1041 // Add the basic block to this loop and all parent loops...
1043 L->Blocks.push_back(NewBB);
1044 L = L->getParentLoop();
1048 } // End llvm namespace