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1 //===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
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 the
12 // loops identified may actually be several natural loops that share the same
13 // header node... not just a single natural loop.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/ADT/DepthFirstIterator.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/Analysis/LoopInfoImpl.h"
21 #include "llvm/Analysis/LoopIterator.h"
22 #include "llvm/Analysis/ValueTracking.h"
23 #include "llvm/IR/CFG.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/Dominators.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/Metadata.h"
28 #include "llvm/Support/CommandLine.h"
29 #include "llvm/Support/Debug.h"
33 // Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
34 template class llvm::LoopBase
<BasicBlock
, Loop
>;
35 template class llvm::LoopInfoBase
<BasicBlock
, Loop
>;
37 // Always verify loopinfo if expensive checking is enabled.
39 static bool VerifyLoopInfo
= true;
41 static bool VerifyLoopInfo
= false;
43 static cl::opt
<bool,true>
44 VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo
),
45 cl::desc("Verify loop info (time consuming)"));
47 char LoopInfo::ID
= 0;
48 INITIALIZE_PASS_BEGIN(LoopInfo
, "loops", "Natural Loop Information", true, true)
49 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass
)
50 INITIALIZE_PASS_END(LoopInfo
, "loops", "Natural Loop Information", true, true)
52 // Loop identifier metadata name.
53 static const char *const LoopMDName
= "llvm.loop";
55 //===----------------------------------------------------------------------===//
56 // Loop implementation
59 /// isLoopInvariant - Return true if the specified value is loop invariant
61 bool Loop::isLoopInvariant(Value
*V
) const {
62 if (Instruction
*I
= dyn_cast
<Instruction
>(V
))
64 return true; // All non-instructions are loop invariant
67 /// hasLoopInvariantOperands - Return true if all the operands of the
68 /// specified instruction are loop invariant.
69 bool Loop::hasLoopInvariantOperands(Instruction
*I
) const {
70 for (unsigned i
= 0, e
= I
->getNumOperands(); i
!= e
; ++i
)
71 if (!isLoopInvariant(I
->getOperand(i
)))
77 /// makeLoopInvariant - If the given value is an instruciton inside of the
78 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
79 /// Return true if the value after any hoisting is loop invariant. This
80 /// function can be used as a slightly more aggressive replacement for
83 /// If InsertPt is specified, it is the point to hoist instructions to.
84 /// If null, the terminator of the loop preheader is used.
86 bool Loop::makeLoopInvariant(Value
*V
, bool &Changed
,
87 Instruction
*InsertPt
) const {
88 if (Instruction
*I
= dyn_cast
<Instruction
>(V
))
89 return makeLoopInvariant(I
, Changed
, InsertPt
);
90 return true; // All non-instructions are loop-invariant.
93 /// makeLoopInvariant - If the given instruction is inside of the
94 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
95 /// Return true if the instruction after any hoisting is loop invariant. This
96 /// function can be used as a slightly more aggressive replacement for
99 /// If InsertPt is specified, it is the point to hoist instructions to.
100 /// If null, the terminator of the loop preheader is used.
102 bool Loop::makeLoopInvariant(Instruction
*I
, bool &Changed
,
103 Instruction
*InsertPt
) const {
104 // Test if the value is already loop-invariant.
105 if (isLoopInvariant(I
))
107 if (!isSafeToSpeculativelyExecute(I
))
109 if (I
->mayReadFromMemory())
111 // The landingpad instruction is immobile.
112 if (isa
<LandingPadInst
>(I
))
114 // Determine the insertion point, unless one was given.
116 BasicBlock
*Preheader
= getLoopPreheader();
117 // Without a preheader, hoisting is not feasible.
120 InsertPt
= Preheader
->getTerminator();
122 // Don't hoist instructions with loop-variant operands.
123 for (unsigned i
= 0, e
= I
->getNumOperands(); i
!= e
; ++i
)
124 if (!makeLoopInvariant(I
->getOperand(i
), Changed
, InsertPt
))
128 I
->moveBefore(InsertPt
);
133 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
134 /// induction variable: an integer recurrence that starts at 0 and increments
135 /// by one each time through the loop. If so, return the phi node that
136 /// corresponds to it.
138 /// The IndVarSimplify pass transforms loops to have a canonical induction
141 PHINode
*Loop::getCanonicalInductionVariable() const {
142 BasicBlock
*H
= getHeader();
144 BasicBlock
*Incoming
= nullptr, *Backedge
= nullptr;
145 pred_iterator PI
= pred_begin(H
);
146 assert(PI
!= pred_end(H
) &&
147 "Loop must have at least one backedge!");
149 if (PI
== pred_end(H
)) return nullptr; // dead loop
151 if (PI
!= pred_end(H
)) return nullptr; // multiple backedges?
153 if (contains(Incoming
)) {
154 if (contains(Backedge
))
156 std::swap(Incoming
, Backedge
);
157 } else if (!contains(Backedge
))
160 // Loop over all of the PHI nodes, looking for a canonical indvar.
161 for (BasicBlock::iterator I
= H
->begin(); isa
<PHINode
>(I
); ++I
) {
162 PHINode
*PN
= cast
<PHINode
>(I
);
163 if (ConstantInt
*CI
=
164 dyn_cast
<ConstantInt
>(PN
->getIncomingValueForBlock(Incoming
)))
165 if (CI
->isNullValue())
166 if (Instruction
*Inc
=
167 dyn_cast
<Instruction
>(PN
->getIncomingValueForBlock(Backedge
)))
168 if (Inc
->getOpcode() == Instruction::Add
&&
169 Inc
->getOperand(0) == PN
)
170 if (ConstantInt
*CI
= dyn_cast
<ConstantInt
>(Inc
->getOperand(1)))
171 if (CI
->equalsInt(1))
177 /// isLCSSAForm - Return true if the Loop is in LCSSA form
178 bool Loop::isLCSSAForm(DominatorTree
&DT
) const {
179 for (block_iterator BI
= block_begin(), E
= block_end(); BI
!= E
; ++BI
) {
180 BasicBlock
*BB
= *BI
;
181 for (BasicBlock::iterator I
= BB
->begin(), E
= BB
->end(); I
!= E
;++I
)
182 for (Use
&U
: I
->uses()) {
183 Instruction
*UI
= cast
<Instruction
>(U
.getUser());
184 BasicBlock
*UserBB
= UI
->getParent();
185 if (PHINode
*P
= dyn_cast
<PHINode
>(UI
))
186 UserBB
= P
->getIncomingBlock(U
);
188 // Check the current block, as a fast-path, before checking whether
189 // the use is anywhere in the loop. Most values are used in the same
190 // block they are defined in. Also, blocks not reachable from the
191 // entry are special; uses in them don't need to go through PHIs.
194 DT
.isReachableFromEntry(UserBB
))
202 /// isLoopSimplifyForm - Return true if the Loop is in the form that
203 /// the LoopSimplify form transforms loops to, which is sometimes called
205 bool Loop::isLoopSimplifyForm() const {
206 // Normal-form loops have a preheader, a single backedge, and all of their
207 // exits have all their predecessors inside the loop.
208 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
211 /// isSafeToClone - Return true if the loop body is safe to clone in practice.
212 /// Routines that reform the loop CFG and split edges often fail on indirectbr.
213 bool Loop::isSafeToClone() const {
214 // Return false if any loop blocks contain indirectbrs, or there are any calls
215 // to noduplicate functions.
216 for (Loop::block_iterator I
= block_begin(), E
= block_end(); I
!= E
; ++I
) {
217 if (isa
<IndirectBrInst
>((*I
)->getTerminator()))
220 if (const InvokeInst
*II
= dyn_cast
<InvokeInst
>((*I
)->getTerminator()))
221 if (II
->cannotDuplicate())
224 for (BasicBlock::iterator BI
= (*I
)->begin(), BE
= (*I
)->end(); BI
!= BE
; ++BI
) {
225 if (const CallInst
*CI
= dyn_cast
<CallInst
>(BI
)) {
226 if (CI
->cannotDuplicate())
234 MDNode
*Loop::getLoopID() const {
235 MDNode
*LoopID
= nullptr;
236 if (isLoopSimplifyForm()) {
237 LoopID
= getLoopLatch()->getTerminator()->getMetadata(LoopMDName
);
239 // Go through each predecessor of the loop header and check the
240 // terminator for the metadata.
241 BasicBlock
*H
= getHeader();
242 for (block_iterator I
= block_begin(), IE
= block_end(); I
!= IE
; ++I
) {
243 TerminatorInst
*TI
= (*I
)->getTerminator();
244 MDNode
*MD
= nullptr;
246 // Check if this terminator branches to the loop header.
247 for (unsigned i
= 0, ie
= TI
->getNumSuccessors(); i
!= ie
; ++i
) {
248 if (TI
->getSuccessor(i
) == H
) {
249 MD
= TI
->getMetadata(LoopMDName
);
258 else if (MD
!= LoopID
)
262 if (!LoopID
|| LoopID
->getNumOperands() == 0 ||
263 LoopID
->getOperand(0) != LoopID
)
268 void Loop::setLoopID(MDNode
*LoopID
) const {
269 assert(LoopID
&& "Loop ID should not be null");
270 assert(LoopID
->getNumOperands() > 0 && "Loop ID needs at least one operand");
271 assert(LoopID
->getOperand(0) == LoopID
&& "Loop ID should refer to itself");
273 if (isLoopSimplifyForm()) {
274 getLoopLatch()->getTerminator()->setMetadata(LoopMDName
, LoopID
);
278 BasicBlock
*H
= getHeader();
279 for (block_iterator I
= block_begin(), IE
= block_end(); I
!= IE
; ++I
) {
280 TerminatorInst
*TI
= (*I
)->getTerminator();
281 for (unsigned i
= 0, ie
= TI
->getNumSuccessors(); i
!= ie
; ++i
) {
282 if (TI
->getSuccessor(i
) == H
)
283 TI
->setMetadata(LoopMDName
, LoopID
);
288 bool Loop::isAnnotatedParallel() const {
289 MDNode
*desiredLoopIdMetadata
= getLoopID();
291 if (!desiredLoopIdMetadata
)
294 // The loop branch contains the parallel loop metadata. In order to ensure
295 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
296 // dependencies (thus converted the loop back to a sequential loop), check
297 // that all the memory instructions in the loop contain parallelism metadata
298 // that point to the same unique "loop id metadata" the loop branch does.
299 for (block_iterator BB
= block_begin(), BE
= block_end(); BB
!= BE
; ++BB
) {
300 for (BasicBlock::iterator II
= (*BB
)->begin(), EE
= (*BB
)->end();
303 if (!II
->mayReadOrWriteMemory())
306 // The memory instruction can refer to the loop identifier metadata
307 // directly or indirectly through another list metadata (in case of
308 // nested parallel loops). The loop identifier metadata refers to
309 // itself so we can check both cases with the same routine.
310 MDNode
*loopIdMD
= II
->getMetadata("llvm.mem.parallel_loop_access");
315 bool loopIdMDFound
= false;
316 for (unsigned i
= 0, e
= loopIdMD
->getNumOperands(); i
< e
; ++i
) {
317 if (loopIdMD
->getOperand(i
) == desiredLoopIdMetadata
) {
318 loopIdMDFound
= true;
331 /// hasDedicatedExits - Return true if no exit block for the loop
332 /// has a predecessor that is outside the loop.
333 bool Loop::hasDedicatedExits() const {
334 // Each predecessor of each exit block of a normal loop is contained
336 SmallVector
<BasicBlock
*, 4> ExitBlocks
;
337 getExitBlocks(ExitBlocks
);
338 for (unsigned i
= 0, e
= ExitBlocks
.size(); i
!= e
; ++i
)
339 for (pred_iterator PI
= pred_begin(ExitBlocks
[i
]),
340 PE
= pred_end(ExitBlocks
[i
]); PI
!= PE
; ++PI
)
343 // All the requirements are met.
347 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
348 /// These are the blocks _outside of the current loop_ which are branched to.
349 /// This assumes that loop exits are in canonical form.
352 Loop::getUniqueExitBlocks(SmallVectorImpl
<BasicBlock
*> &ExitBlocks
) const {
353 assert(hasDedicatedExits() &&
354 "getUniqueExitBlocks assumes the loop has canonical form exits!");
356 SmallVector
<BasicBlock
*, 32> switchExitBlocks
;
358 for (block_iterator BI
= block_begin(), BE
= block_end(); BI
!= BE
; ++BI
) {
360 BasicBlock
*current
= *BI
;
361 switchExitBlocks
.clear();
363 for (succ_iterator I
= succ_begin(*BI
), E
= succ_end(*BI
); I
!= E
; ++I
) {
364 // If block is inside the loop then it is not a exit block.
368 pred_iterator PI
= pred_begin(*I
);
369 BasicBlock
*firstPred
= *PI
;
371 // If current basic block is this exit block's first predecessor
372 // then only insert exit block in to the output ExitBlocks vector.
373 // This ensures that same exit block is not inserted twice into
374 // ExitBlocks vector.
375 if (current
!= firstPred
)
378 // If a terminator has more then two successors, for example SwitchInst,
379 // then it is possible that there are multiple edges from current block
380 // to one exit block.
381 if (std::distance(succ_begin(current
), succ_end(current
)) <= 2) {
382 ExitBlocks
.push_back(*I
);
386 // In case of multiple edges from current block to exit block, collect
387 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
389 if (std::find(switchExitBlocks
.begin(), switchExitBlocks
.end(), *I
)
390 == switchExitBlocks
.end()) {
391 switchExitBlocks
.push_back(*I
);
392 ExitBlocks
.push_back(*I
);
398 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
399 /// block, return that block. Otherwise return null.
400 BasicBlock
*Loop::getUniqueExitBlock() const {
401 SmallVector
<BasicBlock
*, 8> UniqueExitBlocks
;
402 getUniqueExitBlocks(UniqueExitBlocks
);
403 if (UniqueExitBlocks
.size() == 1)
404 return UniqueExitBlocks
[0];
408 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
409 void Loop::dump() const {
414 //===----------------------------------------------------------------------===//
415 // UnloopUpdater implementation
419 /// Find the new parent loop for all blocks within the "unloop" whose last
420 /// backedges has just been removed.
421 class UnloopUpdater
{
427 // Map unloop's immediate subloops to their nearest reachable parents. Nested
428 // loops within these subloops will not change parents. However, an immediate
429 // subloop's new parent will be the nearest loop reachable from either its own
430 // exits *or* any of its nested loop's exits.
431 DenseMap
<Loop
*, Loop
*> SubloopParents
;
433 // Flag the presence of an irreducible backedge whose destination is a block
434 // directly contained by the original unloop.
438 UnloopUpdater(Loop
*UL
, LoopInfo
*LInfo
) :
439 Unloop(UL
), LI(LInfo
), DFS(UL
), FoundIB(false) {}
441 void updateBlockParents();
443 void removeBlocksFromAncestors();
445 void updateSubloopParents();
448 Loop
*getNearestLoop(BasicBlock
*BB
, Loop
*BBLoop
);
450 } // end anonymous namespace
452 /// updateBlockParents - Update the parent loop for all blocks that are directly
453 /// contained within the original "unloop".
454 void UnloopUpdater::updateBlockParents() {
455 if (Unloop
->getNumBlocks()) {
456 // Perform a post order CFG traversal of all blocks within this loop,
457 // propagating the nearest loop from sucessors to predecessors.
458 LoopBlocksTraversal
Traversal(DFS
, LI
);
459 for (LoopBlocksTraversal::POTIterator POI
= Traversal
.begin(),
460 POE
= Traversal
.end(); POI
!= POE
; ++POI
) {
462 Loop
*L
= LI
->getLoopFor(*POI
);
463 Loop
*NL
= getNearestLoop(*POI
, L
);
466 // For reducible loops, NL is now an ancestor of Unloop.
467 assert((NL
!= Unloop
&& (!NL
|| NL
->contains(Unloop
))) &&
468 "uninitialized successor");
469 LI
->changeLoopFor(*POI
, NL
);
472 // Or the current block is part of a subloop, in which case its parent
474 assert((FoundIB
|| Unloop
->contains(L
)) && "uninitialized successor");
478 // Each irreducible loop within the unloop induces a round of iteration using
479 // the DFS result cached by Traversal.
480 bool Changed
= FoundIB
;
481 for (unsigned NIters
= 0; Changed
; ++NIters
) {
482 assert(NIters
< Unloop
->getNumBlocks() && "runaway iterative algorithm");
484 // Iterate over the postorder list of blocks, propagating the nearest loop
485 // from successors to predecessors as before.
487 for (LoopBlocksDFS::POIterator POI
= DFS
.beginPostorder(),
488 POE
= DFS
.endPostorder(); POI
!= POE
; ++POI
) {
490 Loop
*L
= LI
->getLoopFor(*POI
);
491 Loop
*NL
= getNearestLoop(*POI
, L
);
493 assert(NL
!= Unloop
&& (!NL
|| NL
->contains(Unloop
)) &&
494 "uninitialized successor");
495 LI
->changeLoopFor(*POI
, NL
);
502 /// removeBlocksFromAncestors - Remove unloop's blocks from all ancestors below
503 /// their new parents.
504 void UnloopUpdater::removeBlocksFromAncestors() {
505 // Remove all unloop's blocks (including those in nested subloops) from
506 // ancestors below the new parent loop.
507 for (Loop::block_iterator BI
= Unloop
->block_begin(),
508 BE
= Unloop
->block_end(); BI
!= BE
; ++BI
) {
509 Loop
*OuterParent
= LI
->getLoopFor(*BI
);
510 if (Unloop
->contains(OuterParent
)) {
511 while (OuterParent
->getParentLoop() != Unloop
)
512 OuterParent
= OuterParent
->getParentLoop();
513 OuterParent
= SubloopParents
[OuterParent
];
515 // Remove blocks from former Ancestors except Unloop itself which will be
517 for (Loop
*OldParent
= Unloop
->getParentLoop(); OldParent
!= OuterParent
;
518 OldParent
= OldParent
->getParentLoop()) {
519 assert(OldParent
&& "new loop is not an ancestor of the original");
520 OldParent
->removeBlockFromLoop(*BI
);
525 /// updateSubloopParents - Update the parent loop for all subloops directly
526 /// nested within unloop.
527 void UnloopUpdater::updateSubloopParents() {
528 while (!Unloop
->empty()) {
529 Loop
*Subloop
= *std::prev(Unloop
->end());
530 Unloop
->removeChildLoop(std::prev(Unloop
->end()));
532 assert(SubloopParents
.count(Subloop
) && "DFS failed to visit subloop");
533 if (Loop
*Parent
= SubloopParents
[Subloop
])
534 Parent
->addChildLoop(Subloop
);
536 LI
->addTopLevelLoop(Subloop
);
540 /// getNearestLoop - Return the nearest parent loop among this block's
541 /// successors. If a successor is a subloop header, consider its parent to be
542 /// the nearest parent of the subloop's exits.
544 /// For subloop blocks, simply update SubloopParents and return NULL.
545 Loop
*UnloopUpdater::getNearestLoop(BasicBlock
*BB
, Loop
*BBLoop
) {
547 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
548 // is considered uninitialized.
549 Loop
*NearLoop
= BBLoop
;
551 Loop
*Subloop
= nullptr;
552 if (NearLoop
!= Unloop
&& Unloop
->contains(NearLoop
)) {
554 // Find the subloop ancestor that is directly contained within Unloop.
555 while (Subloop
->getParentLoop() != Unloop
) {
556 Subloop
= Subloop
->getParentLoop();
557 assert(Subloop
&& "subloop is not an ancestor of the original loop");
559 // Get the current nearest parent of the Subloop exits, initially Unloop.
561 SubloopParents
.insert(std::make_pair(Subloop
, Unloop
)).first
->second
;
564 succ_iterator I
= succ_begin(BB
), E
= succ_end(BB
);
566 assert(!Subloop
&& "subloop blocks must have a successor");
567 NearLoop
= nullptr; // unloop blocks may now exit the function.
569 for (; I
!= E
; ++I
) {
571 continue; // self loops are uninteresting
573 Loop
*L
= LI
->getLoopFor(*I
);
575 // This successor has not been processed. This path must lead to an
576 // irreducible backedge.
577 assert((FoundIB
|| !DFS
.hasPostorder(*I
)) && "should have seen IB");
580 if (L
!= Unloop
&& Unloop
->contains(L
)) {
581 // Successor is in a subloop.
583 continue; // Branching within subloops. Ignore it.
585 // BB branches from the original into a subloop header.
586 assert(L
->getParentLoop() == Unloop
&& "cannot skip into nested loops");
588 // Get the current nearest parent of the Subloop's exits.
589 L
= SubloopParents
[L
];
590 // L could be Unloop if the only exit was an irreducible backedge.
595 // Handle critical edges from Unloop into a sibling loop.
596 if (L
&& !L
->contains(Unloop
)) {
597 L
= L
->getParentLoop();
599 // Remember the nearest parent loop among successors or subloop exits.
600 if (NearLoop
== Unloop
|| !NearLoop
|| NearLoop
->contains(L
))
604 SubloopParents
[Subloop
] = NearLoop
;
610 //===----------------------------------------------------------------------===//
611 // LoopInfo implementation
613 bool LoopInfo::runOnFunction(Function
&) {
615 LI
.Analyze(getAnalysis
<DominatorTreeWrapperPass
>().getDomTree());
619 /// updateUnloop - The last backedge has been removed from a loop--now the
620 /// "unloop". Find a new parent for the blocks contained within unloop and
621 /// update the loop tree. We don't necessarily have valid dominators at this
622 /// point, but LoopInfo is still valid except for the removal of this loop.
624 /// Note that Unloop may now be an empty loop. Calling Loop::getHeader without
625 /// checking first is illegal.
626 void LoopInfo::updateUnloop(Loop
*Unloop
) {
628 // First handle the special case of no parent loop to simplify the algorithm.
629 if (!Unloop
->getParentLoop()) {
630 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
631 for (Loop::block_iterator I
= Unloop
->block_begin(),
632 E
= Unloop
->block_end(); I
!= E
; ++I
) {
634 // Don't reparent blocks in subloops.
635 if (getLoopFor(*I
) != Unloop
)
638 // Blocks no longer have a parent but are still referenced by Unloop until
639 // the Unloop object is deleted.
640 LI
.changeLoopFor(*I
, nullptr);
643 // Remove the loop from the top-level LoopInfo object.
644 for (LoopInfo::iterator I
= LI
.begin();; ++I
) {
645 assert(I
!= LI
.end() && "Couldn't find loop");
652 // Move all of the subloops to the top-level.
653 while (!Unloop
->empty())
654 LI
.addTopLevelLoop(Unloop
->removeChildLoop(std::prev(Unloop
->end())));
659 // Update the parent loop for all blocks within the loop. Blocks within
660 // subloops will not change parents.
661 UnloopUpdater
Updater(Unloop
, this);
662 Updater
.updateBlockParents();
664 // Remove blocks from former ancestor loops.
665 Updater
.removeBlocksFromAncestors();
667 // Add direct subloops as children in their new parent loop.
668 Updater
.updateSubloopParents();
670 // Remove unloop from its parent loop.
671 Loop
*ParentLoop
= Unloop
->getParentLoop();
672 for (Loop::iterator I
= ParentLoop
->begin();; ++I
) {
673 assert(I
!= ParentLoop
->end() && "Couldn't find loop");
675 ParentLoop
->removeChildLoop(I
);
681 void LoopInfo::verifyAnalysis() const {
682 // LoopInfo is a FunctionPass, but verifying every loop in the function
683 // each time verifyAnalysis is called is very expensive. The
684 // -verify-loop-info option can enable this. In order to perform some
685 // checking by default, LoopPass has been taught to call verifyLoop
686 // manually during loop pass sequences.
688 if (!VerifyLoopInfo
) return;
690 DenseSet
<const Loop
*> Loops
;
691 for (iterator I
= begin(), E
= end(); I
!= E
; ++I
) {
692 assert(!(*I
)->getParentLoop() && "Top-level loop has a parent!");
693 (*I
)->verifyLoopNest(&Loops
);
696 // Verify that blocks are mapped to valid loops.
697 for (DenseMap
<BasicBlock
*, Loop
*>::const_iterator I
= LI
.BBMap
.begin(),
698 E
= LI
.BBMap
.end(); I
!= E
; ++I
) {
699 assert(Loops
.count(I
->second
) && "orphaned loop");
700 assert(I
->second
->contains(I
->first
) && "orphaned block");
704 void LoopInfo::getAnalysisUsage(AnalysisUsage
&AU
) const {
705 AU
.setPreservesAll();
706 AU
.addRequired
<DominatorTreeWrapperPass
>();
709 void LoopInfo::print(raw_ostream
&OS
, const Module
*) const {
713 //===----------------------------------------------------------------------===//
714 // LoopBlocksDFS implementation
717 /// Traverse the loop blocks and store the DFS result.
718 /// Useful for clients that just want the final DFS result and don't need to
719 /// visit blocks during the initial traversal.
720 void LoopBlocksDFS::perform(LoopInfo
*LI
) {
721 LoopBlocksTraversal
Traversal(*this, LI
);
722 for (LoopBlocksTraversal::POTIterator POI
= Traversal
.begin(),
723 POE
= Traversal
.end(); POI
!= POE
; ++POI
) ;