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/DenseMap.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 /// isLoopExiting - True if terminator in the block can branch to another
138 /// block that is outside of the current loop.
140 bool isLoopExiting(const BlockT *BB) const {
141 typedef GraphTraits<BlockT*> BlockTraits;
142 for (typename BlockTraits::ChildIteratorType SI =
143 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
144 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
151 /// getNumBackEdges - Calculate the number of back edges to the loop header
153 unsigned getNumBackEdges() const {
154 unsigned NumBackEdges = 0;
155 BlockT *H = getHeader();
157 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
158 for (typename InvBlockTraits::ChildIteratorType I =
159 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
160 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
167 //===--------------------------------------------------------------------===//
168 // APIs for simple analysis of the loop.
170 // Note that all of these methods can fail on general loops (ie, there may not
171 // be a preheader, etc). For best success, the loop simplification and
172 // induction variable canonicalization pass should be used to normalize loops
173 // for easy analysis. These methods assume canonical loops.
175 /// getExitingBlocks - Return all blocks inside the loop that have successors
176 /// outside of the loop. These are the blocks _inside of the current loop_
177 /// which branch out. The returned list is always unique.
179 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
180 // Sort the blocks vector so that we can use binary search to do quick
182 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
183 std::sort(LoopBBs.begin(), LoopBBs.end());
185 typedef GraphTraits<BlockT*> BlockTraits;
186 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
187 for (typename BlockTraits::ChildIteratorType I =
188 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
190 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
191 // Not in current loop? It must be an exit block.
192 ExitingBlocks.push_back(*BI);
197 /// getExitingBlock - If getExitingBlocks would return exactly one block,
198 /// return that block. Otherwise return null.
199 BlockT *getExitingBlock() const {
200 SmallVector<BlockT*, 8> ExitingBlocks;
201 getExitingBlocks(ExitingBlocks);
202 if (ExitingBlocks.size() == 1)
203 return ExitingBlocks[0];
207 /// getExitBlocks - Return all of the successor blocks of this loop. These
208 /// are the blocks _outside of the current loop_ which are branched to.
210 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
211 // Sort the blocks vector so that we can use binary search to do quick
213 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
214 std::sort(LoopBBs.begin(), LoopBBs.end());
216 typedef GraphTraits<BlockT*> BlockTraits;
217 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
218 for (typename BlockTraits::ChildIteratorType I =
219 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
221 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
222 // Not in current loop? It must be an exit block.
223 ExitBlocks.push_back(*I);
226 /// getExitBlock - If getExitBlocks would return exactly one block,
227 /// return that block. Otherwise return null.
228 BlockT *getExitBlock() const {
229 SmallVector<BlockT*, 8> ExitBlocks;
230 getExitBlocks(ExitBlocks);
231 if (ExitBlocks.size() == 1)
232 return ExitBlocks[0];
237 typedef std::pair<BlockT*, BlockT*> Edge;
239 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
240 template <typename EdgeT>
241 void getExitEdges(SmallVectorImpl<EdgeT> &ExitEdges) const {
242 // Sort the blocks vector so that we can use binary search to do quick
244 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
245 array_pod_sort(LoopBBs.begin(), LoopBBs.end());
247 typedef GraphTraits<BlockT*> BlockTraits;
248 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
249 for (typename BlockTraits::ChildIteratorType I =
250 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
252 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
253 // Not in current loop? It must be an exit block.
254 ExitEdges.push_back(EdgeT(*BI, *I));
257 /// getLoopPreheader - If there is a preheader for this loop, return it. A
258 /// loop has a preheader if there is only one edge to the header of the loop
259 /// from outside of the loop. If this is the case, the block branching to the
260 /// header of the loop is the preheader node.
262 /// This method returns null if there is no preheader for the loop.
264 BlockT *getLoopPreheader() const {
265 // Keep track of nodes outside the loop branching to the header...
266 BlockT *Out = getLoopPredecessor();
269 // Make sure there is only one exit out of the preheader.
270 typedef GraphTraits<BlockT*> BlockTraits;
271 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
273 if (SI != BlockTraits::child_end(Out))
274 return 0; // Multiple exits from the block, must not be a preheader.
276 // The predecessor has exactly one successor, so it is a preheader.
280 /// getLoopPredecessor - If the given loop's header has exactly one unique
281 /// predecessor outside the loop, return it. Otherwise return null.
282 /// This is less strict that the loop "preheader" concept, which requires
283 /// the predecessor to have exactly one successor.
285 BlockT *getLoopPredecessor() const {
286 // Keep track of nodes outside the loop branching to the header...
289 // Loop over the predecessors of the header node...
290 BlockT *Header = getHeader();
291 typedef GraphTraits<BlockT*> BlockTraits;
292 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
293 for (typename InvBlockTraits::ChildIteratorType PI =
294 InvBlockTraits::child_begin(Header),
295 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) {
296 typename InvBlockTraits::NodeType *N = *PI;
297 if (!contains(N)) { // If the block is not in the loop...
299 return 0; // Multiple predecessors outside the loop
304 // Make sure there is only one exit out of the preheader.
305 assert(Out && "Header of loop has no predecessors from outside loop?");
309 /// getLoopLatch - If there is a single latch block for this loop, return it.
310 /// A latch block is a block that contains a branch back to the header.
311 BlockT *getLoopLatch() const {
312 BlockT *Header = getHeader();
313 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
314 typename InvBlockTraits::ChildIteratorType PI =
315 InvBlockTraits::child_begin(Header);
316 typename InvBlockTraits::ChildIteratorType PE =
317 InvBlockTraits::child_end(Header);
319 for (; PI != PE; ++PI) {
320 typename InvBlockTraits::NodeType *N = *PI;
330 //===--------------------------------------------------------------------===//
331 // APIs for updating loop information after changing the CFG
334 /// addBasicBlockToLoop - This method is used by other analyses to update loop
335 /// information. NewBB is set to be a new member of the current loop.
336 /// Because of this, it is added as a member of all parent loops, and is added
337 /// to the specified LoopInfo object as being in the current basic block. It
338 /// is not valid to replace the loop header with this method.
340 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
342 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
343 /// the OldChild entry in our children list with NewChild, and updates the
344 /// parent pointer of OldChild to be null and the NewChild to be this loop.
345 /// This updates the loop depth of the new child.
346 void replaceChildLoopWith(LoopT *OldChild,
348 assert(OldChild->ParentLoop == this && "This loop is already broken!");
349 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
350 typename std::vector<LoopT *>::iterator I =
351 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
352 assert(I != SubLoops.end() && "OldChild not in loop!");
354 OldChild->ParentLoop = 0;
355 NewChild->ParentLoop = static_cast<LoopT *>(this);
358 /// addChildLoop - Add the specified loop to be a child of this loop. This
359 /// updates the loop depth of the new child.
361 void addChildLoop(LoopT *NewChild) {
362 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
363 NewChild->ParentLoop = static_cast<LoopT *>(this);
364 SubLoops.push_back(NewChild);
367 /// removeChildLoop - This removes the specified child from being a subloop of
368 /// this loop. The loop is not deleted, as it will presumably be inserted
369 /// into another loop.
370 LoopT *removeChildLoop(iterator I) {
371 assert(I != SubLoops.end() && "Cannot remove end iterator!");
373 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
374 SubLoops.erase(SubLoops.begin()+(I-begin()));
375 Child->ParentLoop = 0;
379 /// addBlockEntry - This adds a basic block directly to the basic block list.
380 /// This should only be used by transformations that create new loops. Other
381 /// transformations should use addBasicBlockToLoop.
382 void addBlockEntry(BlockT *BB) {
383 Blocks.push_back(BB);
386 /// moveToHeader - This method is used to move BB (which must be part of this
387 /// loop) to be the loop header of the loop (the block that dominates all
389 void moveToHeader(BlockT *BB) {
390 if (Blocks[0] == BB) return;
391 for (unsigned i = 0; ; ++i) {
392 assert(i != Blocks.size() && "Loop does not contain BB!");
393 if (Blocks[i] == BB) {
394 Blocks[i] = Blocks[0];
401 /// removeBlockFromLoop - This removes the specified basic block from the
402 /// current loop, updating the Blocks as appropriate. This does not update
403 /// the mapping in the LoopInfo class.
404 void removeBlockFromLoop(BlockT *BB) {
405 RemoveFromVector(Blocks, BB);
408 /// verifyLoop - Verify loop structure
409 void verifyLoop() const {
411 assert(!Blocks.empty() && "Loop header is missing");
413 // Sort the blocks vector so that we can use binary search to do quick
415 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
416 std::sort(LoopBBs.begin(), LoopBBs.end());
418 // Check the individual blocks.
419 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
421 bool HasInsideLoopSuccs = false;
422 bool HasInsideLoopPreds = false;
423 SmallVector<BlockT *, 2> OutsideLoopPreds;
425 typedef GraphTraits<BlockT*> BlockTraits;
426 for (typename BlockTraits::ChildIteratorType SI =
427 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
429 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
430 HasInsideLoopSuccs = true;
433 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
434 for (typename InvBlockTraits::ChildIteratorType PI =
435 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
437 typename InvBlockTraits::NodeType *N = *PI;
438 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N))
439 HasInsideLoopPreds = true;
441 OutsideLoopPreds.push_back(N);
444 if (BB == getHeader()) {
445 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
446 } else if (!OutsideLoopPreds.empty()) {
447 // A non-header loop shouldn't be reachable from outside the loop,
448 // though it is permitted if the predecessor is not itself actually
450 BlockT *EntryBB = BB->getParent()->begin();
451 for (df_iterator<BlockT *> NI = df_begin(EntryBB),
452 NE = df_end(EntryBB); NI != NE; ++NI)
453 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
454 assert(*NI != OutsideLoopPreds[i] &&
455 "Loop has multiple entry points!");
457 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
458 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
459 assert(BB != getHeader()->getParent()->begin() &&
460 "Loop contains function entry block!");
463 // Check the subloops.
464 for (iterator I = begin(), E = end(); I != E; ++I)
465 // Each block in each subloop should be contained within this loop.
466 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
468 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
469 "Loop does not contain all the blocks of a subloop!");
472 // Check the parent loop pointer.
474 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
476 "Loop is not a subloop of its parent!");
481 /// verifyLoop - Verify loop structure of this loop and all nested loops.
482 void verifyLoopNest() const {
485 // Verify the subloops.
486 for (iterator I = begin(), E = end(); I != E; ++I)
487 (*I)->verifyLoopNest();
490 void print(raw_ostream &OS, unsigned Depth = 0) const {
491 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
494 for (unsigned i = 0; i < getBlocks().size(); ++i) {
496 BlockT *BB = getBlocks()[i];
497 WriteAsOperand(OS, BB, false);
498 if (BB == getHeader()) OS << "<header>";
499 if (BB == getLoopLatch()) OS << "<latch>";
500 if (isLoopExiting(BB)) OS << "<exiting>";
504 for (iterator I = begin(), E = end(); I != E; ++I)
505 (*I)->print(OS, Depth+2);
509 friend class LoopInfoBase<BlockT, LoopT>;
510 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
511 Blocks.push_back(BB);
515 template<class BlockT, class LoopT>
516 raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) {
521 class Loop : public LoopBase<BasicBlock, Loop> {
525 /// isLoopInvariant - Return true if the specified value is loop invariant
527 bool isLoopInvariant(Value *V) const;
529 /// hasLoopInvariantOperands - Return true if all the operands of the
530 /// specified instruction are loop invariant.
531 bool hasLoopInvariantOperands(Instruction *I) const;
533 /// makeLoopInvariant - If the given value is an instruction inside of the
534 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
535 /// Return true if the value after any hoisting is loop invariant. This
536 /// function can be used as a slightly more aggressive replacement for
539 /// If InsertPt is specified, it is the point to hoist instructions to.
540 /// If null, the terminator of the loop preheader is used.
542 bool makeLoopInvariant(Value *V, bool &Changed,
543 Instruction *InsertPt = 0) const;
545 /// makeLoopInvariant - If the given instruction is inside of the
546 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
547 /// Return true if the instruction after any hoisting is loop invariant. This
548 /// function can be used as a slightly more aggressive replacement for
551 /// If InsertPt is specified, it is the point to hoist instructions to.
552 /// If null, the terminator of the loop preheader is used.
554 bool makeLoopInvariant(Instruction *I, bool &Changed,
555 Instruction *InsertPt = 0) const;
557 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
558 /// induction variable: an integer recurrence that starts at 0 and increments
559 /// by one each time through the loop. If so, return the phi node that
560 /// corresponds to it.
562 /// The IndVarSimplify pass transforms loops to have a canonical induction
565 PHINode *getCanonicalInductionVariable() const;
567 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
568 /// times the loop will be executed. Note that this means that the backedge
569 /// of the loop executes N-1 times. If the trip-count cannot be determined,
570 /// this returns null.
572 /// The IndVarSimplify pass transforms loops to have a form that this
573 /// function easily understands.
575 Value *getTripCount() const;
577 /// getSmallConstantTripCount - Returns the trip count of this loop as a
578 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
579 /// of not constant. Will also return 0 if the trip count is very large
582 /// The IndVarSimplify pass transforms loops to have a form that this
583 /// function easily understands.
585 unsigned getSmallConstantTripCount() const;
587 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
588 /// trip count of this loop as a normal unsigned value, if possible. This
589 /// means that the actual trip count is always a multiple of the returned
590 /// value (don't forget the trip count could very well be zero as well!).
592 /// Returns 1 if the trip count is unknown or not guaranteed to be the
593 /// multiple of a constant (which is also the case if the trip count is simply
594 /// constant, use getSmallConstantTripCount for that case), Will also return 1
595 /// if the trip count is very large (>= 2^32).
596 unsigned getSmallConstantTripMultiple() const;
598 /// isLCSSAForm - Return true if the Loop is in LCSSA form
599 bool isLCSSAForm(DominatorTree &DT) const;
601 /// isLoopSimplifyForm - Return true if the Loop is in the form that
602 /// the LoopSimplify form transforms loops to, which is sometimes called
604 bool isLoopSimplifyForm() const;
606 /// hasDedicatedExits - Return true if no exit block for the loop
607 /// has a predecessor that is outside the loop.
608 bool hasDedicatedExits() const;
610 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
611 /// These are the blocks _outside of the current loop_ which are branched to.
612 /// This assumes that loop exits are in canonical form.
614 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
616 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
617 /// block, return that block. Otherwise return null.
618 BasicBlock *getUniqueExitBlock() const;
623 friend class LoopInfoBase<BasicBlock, Loop>;
624 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
627 //===----------------------------------------------------------------------===//
628 /// LoopInfo - This class builds and contains all of the top level loop
629 /// structures in the specified function.
632 template<class BlockT, class LoopT>
634 // BBMap - Mapping of basic blocks to the inner most loop they occur in
635 DenseMap<BlockT *, LoopT *> BBMap;
636 std::vector<LoopT *> TopLevelLoops;
637 friend class LoopBase<BlockT, LoopT>;
639 void operator=(const LoopInfoBase &); // do not implement
640 LoopInfoBase(const LoopInfo &); // do not implement
643 ~LoopInfoBase() { releaseMemory(); }
645 void releaseMemory() {
646 for (typename std::vector<LoopT *>::iterator I =
647 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
648 delete *I; // Delete all of the loops...
650 BBMap.clear(); // Reset internal state of analysis
651 TopLevelLoops.clear();
654 /// iterator/begin/end - The interface to the top-level loops in the current
657 typedef typename std::vector<LoopT *>::const_iterator iterator;
658 iterator begin() const { return TopLevelLoops.begin(); }
659 iterator end() const { return TopLevelLoops.end(); }
660 bool empty() const { return TopLevelLoops.empty(); }
662 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
663 /// block is in no loop (for example the entry node), null is returned.
665 LoopT *getLoopFor(const BlockT *BB) const {
666 typename DenseMap<BlockT *, LoopT *>::const_iterator I=
667 BBMap.find(const_cast<BlockT*>(BB));
668 return I != BBMap.end() ? I->second : 0;
671 /// operator[] - same as getLoopFor...
673 const LoopT *operator[](const BlockT *BB) const {
674 return getLoopFor(BB);
677 /// getLoopDepth - Return the loop nesting level of the specified block. A
678 /// depth of 0 means the block is not inside any loop.
680 unsigned getLoopDepth(const BlockT *BB) const {
681 const LoopT *L = getLoopFor(BB);
682 return L ? L->getLoopDepth() : 0;
685 // isLoopHeader - True if the block is a loop header node
686 bool isLoopHeader(BlockT *BB) const {
687 const LoopT *L = getLoopFor(BB);
688 return L && L->getHeader() == BB;
691 /// removeLoop - This removes the specified top-level loop from this loop info
692 /// object. The loop is not deleted, as it will presumably be inserted into
694 LoopT *removeLoop(iterator I) {
695 assert(I != end() && "Cannot remove end iterator!");
697 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
698 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
702 /// changeLoopFor - Change the top-level loop that contains BB to the
703 /// specified loop. This should be used by transformations that restructure
704 /// the loop hierarchy tree.
705 void changeLoopFor(BlockT *BB, LoopT *L) {
706 LoopT *&OldLoop = BBMap[BB];
707 assert(OldLoop && "Block not in a loop yet!");
711 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
712 /// list with the indicated loop.
713 void changeTopLevelLoop(LoopT *OldLoop,
715 typename std::vector<LoopT *>::iterator I =
716 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
717 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
719 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
720 "Loops already embedded into a subloop!");
723 /// addTopLevelLoop - This adds the specified loop to the collection of
725 void addTopLevelLoop(LoopT *New) {
726 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
727 TopLevelLoops.push_back(New);
730 /// removeBlock - This method completely removes BB from all data structures,
731 /// including all of the Loop objects it is nested in and our mapping from
732 /// BasicBlocks to loops.
733 void removeBlock(BlockT *BB) {
734 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
735 if (I != BBMap.end()) {
736 for (LoopT *L = I->second; L; L = L->getParentLoop())
737 L->removeBlockFromLoop(BB);
745 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
746 const LoopT *ParentLoop) {
747 if (SubLoop == 0) return true;
748 if (SubLoop == ParentLoop) return false;
749 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
752 void Calculate(DominatorTreeBase<BlockT> &DT) {
753 BlockT *RootNode = DT.getRootNode()->getBlock();
755 for (df_iterator<BlockT*> NI = df_begin(RootNode),
756 NE = df_end(RootNode); NI != NE; ++NI)
757 if (LoopT *L = ConsiderForLoop(*NI, DT))
758 TopLevelLoops.push_back(L);
761 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
762 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
764 std::vector<BlockT *> TodoStack;
766 // Scan the predecessors of BB, checking to see if BB dominates any of
767 // them. This identifies backedges which target this node...
768 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
769 for (typename InvBlockTraits::ChildIteratorType I =
770 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
772 typename InvBlockTraits::NodeType *N = *I;
773 if (DT.dominates(BB, N)) // If BB dominates its predecessor...
774 TodoStack.push_back(N);
777 if (TodoStack.empty()) return 0; // No backedges to this block...
779 // Create a new loop to represent this basic block...
780 LoopT *L = new LoopT(BB);
783 BlockT *EntryBlock = BB->getParent()->begin();
785 while (!TodoStack.empty()) { // Process all the nodes in the loop
786 BlockT *X = TodoStack.back();
787 TodoStack.pop_back();
789 if (!L->contains(X) && // As of yet unprocessed??
790 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
791 // Check to see if this block already belongs to a loop. If this occurs
792 // then we have a case where a loop that is supposed to be a child of
793 // the current loop was processed before the current loop. When this
794 // occurs, this child loop gets added to a part of the current loop,
795 // making it a sibling to the current loop. We have to reparent this
798 const_cast<LoopT *>(getLoopFor(X)))
799 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
800 // Remove the subloop from its current parent...
801 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
802 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
803 typename std::vector<LoopT *>::iterator I =
804 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
805 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
806 SLP->SubLoops.erase(I); // Remove from parent...
808 // Add the subloop to THIS loop...
809 SubLoop->ParentLoop = L;
810 L->SubLoops.push_back(SubLoop);
813 // Normal case, add the block to our loop...
814 L->Blocks.push_back(X);
816 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
818 // Add all of the predecessors of X to the end of the work stack...
819 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
820 InvBlockTraits::child_end(X));
824 // If there are any loops nested within this loop, create them now!
825 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
826 E = L->Blocks.end(); I != E; ++I)
827 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
828 L->SubLoops.push_back(NewLoop);
829 NewLoop->ParentLoop = L;
832 // Add the basic blocks that comprise this loop to the BBMap so that this
833 // loop can be found for them.
835 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
836 E = L->Blocks.end(); I != E; ++I)
837 BBMap.insert(std::make_pair(*I, L));
839 // Now that we have a list of all of the child loops of this loop, check to
840 // see if any of them should actually be nested inside of each other. We
841 // can accidentally pull loops our of their parents, so we must make sure to
842 // organize the loop nests correctly now.
844 std::map<BlockT *, LoopT *> ContainingLoops;
845 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
846 LoopT *Child = L->SubLoops[i];
847 assert(Child->getParentLoop() == L && "Not proper child loop?");
849 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
850 // If there is already a loop which contains this loop, move this loop
851 // into the containing loop.
852 MoveSiblingLoopInto(Child, ContainingLoop);
853 --i; // The loop got removed from the SubLoops list.
855 // This is currently considered to be a top-level loop. Check to see
856 // if any of the contained blocks are loop headers for subloops we
857 // have already processed.
858 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
859 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
860 if (BlockLoop == 0) { // Child block not processed yet...
862 } else if (BlockLoop != Child) {
863 LoopT *SubLoop = BlockLoop;
864 // Reparent all of the blocks which used to belong to BlockLoops
865 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
866 ContainingLoops[SubLoop->Blocks[j]] = Child;
868 // There is already a loop which contains this block, that means
869 // that we should reparent the loop which the block is currently
870 // considered to belong to to be a child of this loop.
871 MoveSiblingLoopInto(SubLoop, Child);
872 --i; // We just shrunk the SubLoops list.
882 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
883 /// of the NewParent Loop, instead of being a sibling of it.
884 void MoveSiblingLoopInto(LoopT *NewChild,
886 LoopT *OldParent = NewChild->getParentLoop();
887 assert(OldParent && OldParent == NewParent->getParentLoop() &&
888 NewChild != NewParent && "Not sibling loops!");
890 // Remove NewChild from being a child of OldParent
891 typename std::vector<LoopT *>::iterator I =
892 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
894 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
895 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
896 NewChild->ParentLoop = 0;
898 InsertLoopInto(NewChild, NewParent);
901 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
902 /// the parent loop contains a loop which should contain L, the loop gets
903 /// inserted into L instead.
904 void InsertLoopInto(LoopT *L, LoopT *Parent) {
905 BlockT *LHeader = L->getHeader();
906 assert(Parent->contains(LHeader) &&
907 "This loop should not be inserted here!");
909 // Check to see if it belongs in a child loop...
910 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
912 if (Parent->SubLoops[i]->contains(LHeader)) {
913 InsertLoopInto(L, Parent->SubLoops[i]);
917 // If not, insert it here!
918 Parent->SubLoops.push_back(L);
919 L->ParentLoop = Parent;
924 void print(raw_ostream &OS) const {
925 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
926 TopLevelLoops[i]->print(OS);
928 for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
929 E = BBMap.end(); I != E; ++I)
930 OS << "BB '" << I->first->getName() << "' level = "
931 << I->second->getLoopDepth() << "\n";
936 class LoopInfo : public FunctionPass {
937 LoopInfoBase<BasicBlock, Loop> LI;
938 friend class LoopBase<BasicBlock, Loop>;
940 void operator=(const LoopInfo &); // do not implement
941 LoopInfo(const LoopInfo &); // do not implement
943 static char ID; // Pass identification, replacement for typeid
945 LoopInfo() : FunctionPass(ID) {
946 initializeLoopInfoPass(*PassRegistry::getPassRegistry());
949 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
951 /// iterator/begin/end - The interface to the top-level loops in the current
954 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
955 inline iterator begin() const { return LI.begin(); }
956 inline iterator end() const { return LI.end(); }
957 bool empty() const { return LI.empty(); }
959 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
960 /// block is in no loop (for example the entry node), null is returned.
962 inline Loop *getLoopFor(const BasicBlock *BB) const {
963 return LI.getLoopFor(BB);
966 /// operator[] - same as getLoopFor...
968 inline const Loop *operator[](const BasicBlock *BB) const {
969 return LI.getLoopFor(BB);
972 /// getLoopDepth - Return the loop nesting level of the specified block. A
973 /// depth of 0 means the block is not inside any loop.
975 inline unsigned getLoopDepth(const BasicBlock *BB) const {
976 return LI.getLoopDepth(BB);
979 // isLoopHeader - True if the block is a loop header node
980 inline bool isLoopHeader(BasicBlock *BB) const {
981 return LI.isLoopHeader(BB);
984 /// runOnFunction - Calculate the natural loop information.
986 virtual bool runOnFunction(Function &F);
988 virtual void verifyAnalysis() const;
990 virtual void releaseMemory() { LI.releaseMemory(); }
992 virtual void print(raw_ostream &O, const Module* M = 0) const;
994 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
996 /// removeLoop - This removes the specified top-level loop from this loop info
997 /// object. The loop is not deleted, as it will presumably be inserted into
999 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
1001 /// changeLoopFor - Change the top-level loop that contains BB to the
1002 /// specified loop. This should be used by transformations that restructure
1003 /// the loop hierarchy tree.
1004 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
1005 LI.changeLoopFor(BB, L);
1008 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
1009 /// list with the indicated loop.
1010 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
1011 LI.changeTopLevelLoop(OldLoop, NewLoop);
1014 /// addTopLevelLoop - This adds the specified loop to the collection of
1015 /// top-level loops.
1016 inline void addTopLevelLoop(Loop *New) {
1017 LI.addTopLevelLoop(New);
1020 /// removeBlock - This method completely removes BB from all data structures,
1021 /// including all of the Loop objects it is nested in and our mapping from
1022 /// BasicBlocks to loops.
1023 void removeBlock(BasicBlock *BB) {
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