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1 : //===- llvm/Analysis/LoopInfoImpl.h - Natural Loop Calculator ---*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This is the generic implementation of LoopInfo used for both Loops and
11 : // MachineLoops.
12 : //
13 : //===----------------------------------------------------------------------===//
14 :
15 : #ifndef LLVM_ANALYSIS_LOOPINFOIMPL_H
16 : #define LLVM_ANALYSIS_LOOPINFOIMPL_H
17 :
18 : #include "llvm/ADT/DepthFirstIterator.h"
19 : #include "llvm/ADT/PostOrderIterator.h"
20 : #include "llvm/ADT/STLExtras.h"
21 : #include "llvm/ADT/SetVector.h"
22 : #include "llvm/Analysis/LoopInfo.h"
23 : #include "llvm/IR/Dominators.h"
24 :
25 : namespace llvm {
26 :
27 : //===----------------------------------------------------------------------===//
28 : // APIs for simple analysis of the loop. See header notes.
29 :
30 : /// getExitingBlocks - Return all blocks inside the loop that have successors
31 : /// outside of the loop. These are the blocks _inside of the current loop_
32 : /// which branch out. The returned list is always unique.
33 : ///
34 : template <class BlockT, class LoopT>
35 504389 : void LoopBase<BlockT, LoopT>::getExitingBlocks(
36 : SmallVectorImpl<BlockT *> &ExitingBlocks) const {
37 : assert(!isInvalid() && "Loop not in a valid state!");
38 3444653 : for (const auto BB : blocks())
39 9168626 : for (const auto &Succ : children<BlockT *>(BB))
40 4449871 : if (!contains(Succ)) {
41 : // Not in current loop? It must be an exit block.
42 1076297 : ExitingBlocks.push_back(BB);
43 1076297 : break;
44 : }
45 504389 : }
46 :
47 : /// getExitingBlock - If getExitingBlocks would return exactly one block,
48 : /// return that block. Otherwise return null.
49 : template <class BlockT, class LoopT>
50 129750 : BlockT *LoopBase<BlockT, LoopT>::getExitingBlock() const {
51 : assert(!isInvalid() && "Loop not in a valid state!");
52 : SmallVector<BlockT *, 8> ExitingBlocks;
53 129750 : getExitingBlocks(ExitingBlocks);
54 129750 : if (ExitingBlocks.size() == 1)
55 90412 : return ExitingBlocks[0];
56 : return nullptr;
57 : }
58 :
59 : /// getExitBlocks - Return all of the successor blocks of this loop. These
60 : /// are the blocks _outside of the current loop_ which are branched to.
61 : ///
62 : template <class BlockT, class LoopT>
63 271187 : void LoopBase<BlockT, LoopT>::getExitBlocks(
64 : SmallVectorImpl<BlockT *> &ExitBlocks) const {
65 : assert(!isInvalid() && "Loop not in a valid state!");
66 2300179 : for (const auto BB : blocks())
67 10731963 : for (const auto &Succ : children<BlockT *>(BB))
68 3441407 : if (!contains(Succ))
69 : // Not in current loop? It must be an exit block.
70 810864 : ExitBlocks.push_back(Succ);
71 271187 : }
72 :
73 : /// getExitBlock - If getExitBlocks would return exactly one block,
74 : /// return that block. Otherwise return null.
75 : template <class BlockT, class LoopT>
76 7674 : BlockT *LoopBase<BlockT, LoopT>::getExitBlock() const {
77 : assert(!isInvalid() && "Loop not in a valid state!");
78 : SmallVector<BlockT *, 8> ExitBlocks;
79 7674 : getExitBlocks(ExitBlocks);
80 7674 : if (ExitBlocks.size() == 1)
81 5094 : return ExitBlocks[0];
82 : return nullptr;
83 : }
84 :
85 : template <class BlockT, class LoopT>
86 127445 : bool LoopBase<BlockT, LoopT>::hasDedicatedExits() const {
87 : // Each predecessor of each exit block of a normal loop is contained
88 : // within the loop.
89 : SmallVector<BlockT *, 4> ExitBlocks;
90 127445 : getExitBlocks(ExitBlocks);
91 519478 : for (BlockT *EB : ExitBlocks)
92 2098892 : for (BlockT *Predecessor : children<Inverse<BlockT *>>(EB))
93 1706859 : if (!contains(Predecessor))
94 59 : return false;
95 : // All the requirements are met.
96 : return true;
97 : }
98 :
99 : template <class BlockT, class LoopT>
100 35587 : void LoopBase<BlockT, LoopT>::getUniqueExitBlocks(
101 : SmallVectorImpl<BlockT *> &ExitBlocks) const {
102 : typedef GraphTraits<BlockT *> BlockTraits;
103 : typedef GraphTraits<Inverse<BlockT *>> InvBlockTraits;
104 :
105 : assert(hasDedicatedExits() &&
106 : "getUniqueExitBlocks assumes the loop has canonical form exits!");
107 :
108 : SmallVector<BlockT *, 32> SwitchExitBlocks;
109 248067 : for (BlockT *Block : this->blocks()) {
110 : SwitchExitBlocks.clear();
111 1156290 : for (BlockT *Successor : children<BlockT *>(Block)) {
112 : // If block is inside the loop then it is not an exit block.
113 365665 : if (contains(Successor))
114 : continue;
115 :
116 90906 : BlockT *FirstPred = *InvBlockTraits::child_begin(Successor);
117 :
118 : // If current basic block is this exit block's first predecessor then only
119 : // insert exit block in to the output ExitBlocks vector. This ensures that
120 : // same exit block is not inserted twice into ExitBlocks vector.
121 90906 : if (Block != FirstPred)
122 : continue;
123 :
124 : // If a terminator has more then two successors, for example SwitchInst,
125 : // then it is possible that there are multiple edges from current block to
126 : // one exit block.
127 78015 : if (std::distance(BlockTraits::child_begin(Block),
128 : BlockTraits::child_end(Block)) <= 2) {
129 76539 : ExitBlocks.push_back(Successor);
130 76539 : continue;
131 : }
132 :
133 : // In case of multiple edges from current block to exit block, collect
134 : // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
135 : // duplicate edges.
136 1476 : if (!is_contained(SwitchExitBlocks, Successor)) {
137 1081 : SwitchExitBlocks.push_back(Successor);
138 1081 : ExitBlocks.push_back(Successor);
139 : }
140 : }
141 : }
142 35587 : }
143 :
144 : template <class BlockT, class LoopT>
145 8892 : BlockT *LoopBase<BlockT, LoopT>::getUniqueExitBlock() const {
146 : SmallVector<BlockT *, 8> UniqueExitBlocks;
147 8892 : getUniqueExitBlocks(UniqueExitBlocks);
148 8892 : if (UniqueExitBlocks.size() == 1)
149 7129 : return UniqueExitBlocks[0];
150 : return nullptr;
151 : }
152 :
153 : /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
154 : template <class BlockT, class LoopT>
155 48 : void LoopBase<BlockT, LoopT>::getExitEdges(
156 : SmallVectorImpl<Edge> &ExitEdges) const {
157 : assert(!isInvalid() && "Loop not in a valid state!");
158 118 : for (const auto BB : blocks())
159 404 : for (const auto &Succ : children<BlockT *>(BB))
160 132 : if (!contains(Succ))
161 : // Not in current loop? It must be an exit block.
162 54 : ExitEdges.emplace_back(BB, Succ);
163 48 : }
164 :
165 : /// getLoopPreheader - If there is a preheader for this loop, return it. A
166 : /// loop has a preheader if there is only one edge to the header of the loop
167 : /// from outside of the loop and it is legal to hoist instructions into the
168 : /// predecessor. If this is the case, the block branching to the header of the
169 : /// loop is the preheader node.
170 : ///
171 : /// This method returns null if there is no preheader for the loop.
172 : ///
173 : template <class BlockT, class LoopT>
174 340913 : BlockT *LoopBase<BlockT, LoopT>::getLoopPreheader() const {
175 : assert(!isInvalid() && "Loop not in a valid state!");
176 : // Keep track of nodes outside the loop branching to the header...
177 340913 : BlockT *Out = getLoopPredecessor();
178 340913 : if (!Out)
179 : return nullptr;
180 :
181 : // Make sure we are allowed to hoist instructions into the predecessor.
182 340612 : if (!Out->isLegalToHoistInto())
183 : return nullptr;
184 :
185 : // Make sure there is only one exit out of the preheader.
186 : typedef GraphTraits<BlockT *> BlockTraits;
187 : typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
188 1 : ++SI;
189 340564 : if (SI != BlockTraits::child_end(Out))
190 8730 : return nullptr; // Multiple exits from the block, must not be a preheader.
191 :
192 : // The predecessor has exactly one successor, so it is a preheader.
193 : return Out;
194 : }
195 :
196 : /// getLoopPredecessor - If the given loop's header has exactly one unique
197 : /// predecessor outside the loop, return it. Otherwise return null.
198 : /// This is less strict that the loop "preheader" concept, which requires
199 : /// the predecessor to have exactly one successor.
200 : ///
201 : template <class BlockT, class LoopT>
202 389334 : BlockT *LoopBase<BlockT, LoopT>::getLoopPredecessor() const {
203 : assert(!isInvalid() && "Loop not in a valid state!");
204 : // Keep track of nodes outside the loop branching to the header...
205 : BlockT *Out = nullptr;
206 :
207 : // Loop over the predecessors of the header node...
208 : BlockT *Header = getHeader();
209 1162976 : for (const auto Pred : children<Inverse<BlockT *>>(Header)) {
210 774082 : if (!contains(Pred)) { // If the block is not in the loop...
211 389778 : if (Out && Out != Pred)
212 237 : return nullptr; // Multiple predecessors outside the loop
213 : Out = Pred;
214 : }
215 : }
216 :
217 : // Make sure there is only one exit out of the preheader.
218 : assert(Out && "Header of loop has no predecessors from outside loop?");
219 364110 : return Out;
220 : }
221 :
222 : /// getLoopLatch - If there is a single latch block for this loop, return it.
223 : /// A latch block is a block that contains a branch back to the header.
224 : template <class BlockT, class LoopT>
225 516693 : BlockT *LoopBase<BlockT, LoopT>::getLoopLatch() const {
226 : assert(!isInvalid() && "Loop not in a valid state!");
227 : BlockT *Header = getHeader();
228 : BlockT *Latch = nullptr;
229 1548762 : for (const auto Pred : children<Inverse<BlockT *>>(Header)) {
230 1033082 : if (contains(Pred)) {
231 516798 : if (Latch)
232 1009 : return nullptr;
233 : Latch = Pred;
234 : }
235 : }
236 :
237 512672 : return Latch;
238 : }
239 :
240 : //===----------------------------------------------------------------------===//
241 : // APIs for updating loop information after changing the CFG
242 : //
243 :
244 : /// addBasicBlockToLoop - This method is used by other analyses to update loop
245 : /// information. NewBB is set to be a new member of the current loop.
246 : /// Because of this, it is added as a member of all parent loops, and is added
247 : /// to the specified LoopInfo object as being in the current basic block. It
248 : /// is not valid to replace the loop header with this method.
249 : ///
250 : template <class BlockT, class LoopT>
251 31399 : void LoopBase<BlockT, LoopT>::addBasicBlockToLoop(
252 : BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LIB) {
253 : assert(!isInvalid() && "Loop not in a valid state!");
254 : #ifndef NDEBUG
255 : if (!Blocks.empty()) {
256 : auto SameHeader = LIB[getHeader()];
257 : assert(contains(SameHeader) && getHeader() == SameHeader->getHeader() &&
258 : "Incorrect LI specified for this loop!");
259 : }
260 : #endif
261 : assert(NewBB && "Cannot add a null basic block to the loop!");
262 : assert(!LIB[NewBB] && "BasicBlock already in the loop!");
263 :
264 : LoopT *L = static_cast<LoopT *>(this);
265 :
266 : // Add the loop mapping to the LoopInfo object...
267 31399 : LIB.BBMap[NewBB] = L;
268 :
269 : // Add the basic block to this loop and all parent loops...
270 67741 : while (L) {
271 36342 : L->addBlockEntry(NewBB);
272 : L = L->getParentLoop();
273 : }
274 31399 : }
275 :
276 : /// replaceChildLoopWith - This is used when splitting loops up. It replaces
277 : /// the OldChild entry in our children list with NewChild, and updates the
278 : /// parent pointer of OldChild to be null and the NewChild to be this loop.
279 : /// This updates the loop depth of the new child.
280 : template <class BlockT, class LoopT>
281 6 : void LoopBase<BlockT, LoopT>::replaceChildLoopWith(LoopT *OldChild,
282 : LoopT *NewChild) {
283 : assert(!isInvalid() && "Loop not in a valid state!");
284 : assert(OldChild->ParentLoop == this && "This loop is already broken!");
285 : assert(!NewChild->ParentLoop && "NewChild already has a parent!");
286 : typename std::vector<LoopT *>::iterator I = find(SubLoops, OldChild);
287 : assert(I != SubLoops.end() && "OldChild not in loop!");
288 6 : *I = NewChild;
289 6 : OldChild->ParentLoop = nullptr;
290 6 : NewChild->ParentLoop = static_cast<LoopT *>(this);
291 6 : }
292 :
293 : /// verifyLoop - Verify loop structure
294 : template <class BlockT, class LoopT>
295 73777 : void LoopBase<BlockT, LoopT>::verifyLoop() const {
296 : assert(!isInvalid() && "Loop not in a valid state!");
297 : #ifndef NDEBUG
298 : assert(!Blocks.empty() && "Loop header is missing");
299 :
300 : // Setup for using a depth-first iterator to visit every block in the loop.
301 : SmallVector<BlockT *, 8> ExitBBs;
302 : getExitBlocks(ExitBBs);
303 : df_iterator_default_set<BlockT *> VisitSet;
304 : VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
305 : df_ext_iterator<BlockT *, df_iterator_default_set<BlockT *>>
306 : BI = df_ext_begin(getHeader(), VisitSet),
307 : BE = df_ext_end(getHeader(), VisitSet);
308 :
309 : // Keep track of the BBs visited.
310 : SmallPtrSet<BlockT *, 8> VisitedBBs;
311 :
312 : // Check the individual blocks.
313 : for (; BI != BE; ++BI) {
314 : BlockT *BB = *BI;
315 :
316 : assert(std::any_of(GraphTraits<BlockT *>::child_begin(BB),
317 : GraphTraits<BlockT *>::child_end(BB),
318 : [&](BlockT *B) { return contains(B); }) &&
319 : "Loop block has no in-loop successors!");
320 :
321 : assert(std::any_of(GraphTraits<Inverse<BlockT *>>::child_begin(BB),
322 : GraphTraits<Inverse<BlockT *>>::child_end(BB),
323 : [&](BlockT *B) { return contains(B); }) &&
324 : "Loop block has no in-loop predecessors!");
325 :
326 : SmallVector<BlockT *, 2> OutsideLoopPreds;
327 : std::for_each(GraphTraits<Inverse<BlockT *>>::child_begin(BB),
328 : GraphTraits<Inverse<BlockT *>>::child_end(BB),
329 : [&](BlockT *B) {
330 : if (!contains(B))
331 : OutsideLoopPreds.push_back(B);
332 : });
333 :
334 : if (BB == getHeader()) {
335 : assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
336 : } else if (!OutsideLoopPreds.empty()) {
337 : // A non-header loop shouldn't be reachable from outside the loop,
338 : // though it is permitted if the predecessor is not itself actually
339 : // reachable.
340 : BlockT *EntryBB = &BB->getParent()->front();
341 : for (BlockT *CB : depth_first(EntryBB))
342 : for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
343 : assert(CB != OutsideLoopPreds[i] &&
344 : "Loop has multiple entry points!");
345 : }
346 : assert(BB != &getHeader()->getParent()->front() &&
347 : "Loop contains function entry block!");
348 :
349 : VisitedBBs.insert(BB);
350 : }
351 :
352 : if (VisitedBBs.size() != getNumBlocks()) {
353 : dbgs() << "The following blocks are unreachable in the loop: ";
354 : for (auto BB : Blocks) {
355 : if (!VisitedBBs.count(BB)) {
356 : dbgs() << *BB << "\n";
357 : }
358 : }
359 : assert(false && "Unreachable block in loop");
360 : }
361 :
362 : // Check the subloops.
363 : for (iterator I = begin(), E = end(); I != E; ++I)
364 : // Each block in each subloop should be contained within this loop.
365 : for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
366 : BI != BE; ++BI) {
367 : assert(contains(*BI) &&
368 : "Loop does not contain all the blocks of a subloop!");
369 : }
370 :
371 : // Check the parent loop pointer.
372 : if (ParentLoop) {
373 : assert(is_contained(*ParentLoop, this) &&
374 : "Loop is not a subloop of its parent!");
375 : }
376 : #endif
377 73777 : }
378 :
379 : /// verifyLoop - Verify loop structure of this loop and all nested loops.
380 : template <class BlockT, class LoopT>
381 217 : void LoopBase<BlockT, LoopT>::verifyLoopNest(
382 : DenseSet<const LoopT *> *Loops) const {
383 : assert(!isInvalid() && "Loop not in a valid state!");
384 217 : Loops->insert(static_cast<const LoopT *>(this));
385 : // Verify this loop.
386 217 : verifyLoop();
387 : // Verify the subloops.
388 298 : for (iterator I = begin(), E = end(); I != E; ++I)
389 81 : (*I)->verifyLoopNest(Loops);
390 217 : }
391 :
392 : template <class BlockT, class LoopT>
393 735 : void LoopBase<BlockT, LoopT>::print(raw_ostream &OS, unsigned Depth,
394 : bool Verbose) const {
395 1470 : OS.indent(Depth * 2) << "Loop at depth " << getLoopDepth() << " containing: ";
396 :
397 : BlockT *H = getHeader();
398 2889 : for (unsigned i = 0; i < getBlocks().size(); ++i) {
399 1419 : BlockT *BB = getBlocks()[i];
400 1419 : if (!Verbose) {
401 1419 : if (i)
402 684 : OS << ",";
403 1419 : BB->printAsOperand(OS, false);
404 : } else
405 0 : OS << "\n";
406 :
407 1419 : if (BB == H)
408 735 : OS << "<header>";
409 1419 : if (isLoopLatch(BB))
410 735 : OS << "<latch>";
411 1419 : if (isLoopExiting(BB))
412 896 : OS << "<exiting>";
413 1419 : if (Verbose)
414 0 : BB->print(OS);
415 : }
416 735 : OS << "\n";
417 :
418 873 : for (iterator I = begin(), E = end(); I != E; ++I)
419 138 : (*I)->print(OS, Depth + 2);
420 735 : }
421 :
422 : //===----------------------------------------------------------------------===//
423 : /// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the
424 : /// result does / not depend on use list (block predecessor) order.
425 : ///
426 :
427 : /// Discover a subloop with the specified backedges such that: All blocks within
428 : /// this loop are mapped to this loop or a subloop. And all subloops within this
429 : /// loop have their parent loop set to this loop or a subloop.
430 : template <class BlockT, class LoopT>
431 146630 : static void discoverAndMapSubloop(LoopT *L, ArrayRef<BlockT *> Backedges,
432 : LoopInfoBase<BlockT, LoopT> *LI,
433 : const DomTreeBase<BlockT> &DomTree) {
434 : typedef GraphTraits<Inverse<BlockT *>> InvBlockTraits;
435 :
436 : unsigned NumBlocks = 0;
437 : unsigned NumSubloops = 0;
438 :
439 : // Perform a backward CFG traversal using a worklist.
440 146630 : std::vector<BlockT *> ReverseCFGWorklist(Backedges.begin(), Backedges.end());
441 1113249 : while (!ReverseCFGWorklist.empty()) {
442 966619 : BlockT *PredBB = ReverseCFGWorklist.back();
443 : ReverseCFGWorklist.pop_back();
444 :
445 : LoopT *Subloop = LI->getLoopFor(PredBB);
446 217464 : if (!Subloop) {
447 749155 : if (!DomTree.isReachableFromEntry(PredBB))
448 : continue;
449 :
450 : // This is an undiscovered block. Map it to the current loop.
451 749131 : LI->changeLoopFor(PredBB, L);
452 749131 : ++NumBlocks;
453 749131 : if (PredBB == L->getHeader())
454 : continue;
455 : // Push all block predecessors on the worklist.
456 602491 : ReverseCFGWorklist.insert(ReverseCFGWorklist.end(),
457 : InvBlockTraits::child_begin(PredBB),
458 : InvBlockTraits::child_end(PredBB));
459 : } else {
460 : // This is a discovered block. Find its outermost discovered loop.
461 224233 : while (LoopT *Parent = Subloop->getParentLoop())
462 : Subloop = Parent;
463 :
464 : // If it is already discovered to be a subloop of this loop, continue.
465 217464 : if (Subloop == L)
466 : continue;
467 :
468 : // Discover a subloop of this loop.
469 : Subloop->setParentLoop(L);
470 25212 : ++NumSubloops;
471 50424 : NumBlocks += Subloop->getBlocksVector().capacity();
472 : PredBB = Subloop->getHeader();
473 : // Continue traversal along predecessors that are not loop-back edges from
474 : // within this subloop tree itself. Note that a predecessor may directly
475 : // reach another subloop that is not yet discovered to be a subloop of
476 : // this loop, which we must traverse.
477 76231 : for (const auto Pred : children<Inverse<BlockT *>>(PredBB)) {
478 51019 : if (LI->getLoopFor(Pred) != Subloop)
479 25411 : ReverseCFGWorklist.push_back(Pred);
480 : }
481 : }
482 : }
483 146630 : L->getSubLoopsVector().reserve(NumSubloops);
484 : L->reserveBlocks(NumBlocks);
485 146630 : }
486 :
487 : /// Populate all loop data in a stable order during a single forward DFS.
488 : template <class BlockT, class LoopT> class PopulateLoopsDFS {
489 : typedef GraphTraits<BlockT *> BlockTraits;
490 : typedef typename BlockTraits::ChildIteratorType SuccIterTy;
491 :
492 : LoopInfoBase<BlockT, LoopT> *LI;
493 :
494 : public:
495 2456032 : PopulateLoopsDFS(LoopInfoBase<BlockT, LoopT> *li) : LI(li) {}
496 :
497 : void traverse(BlockT *EntryBlock);
498 :
499 : protected:
500 : void insertIntoLoop(BlockT *Block);
501 : };
502 :
503 : /// Top-level driver for the forward DFS within the loop.
504 : template <class BlockT, class LoopT>
505 2456032 : void PopulateLoopsDFS<BlockT, LoopT>::traverse(BlockT *EntryBlock) {
506 12145798 : for (BlockT *BB : post_order(EntryBlock))
507 7233734 : insertIntoLoop(BB);
508 2456032 : }
509 :
510 : /// Add a single Block to its ancestor loops in PostOrder. If the block is a
511 : /// subloop header, add the subloop to its parent in PostOrder, then reverse the
512 : /// Block and Subloop vectors of the now complete subloop to achieve RPO.
513 : template <class BlockT, class LoopT>
514 7233734 : void PopulateLoopsDFS<BlockT, LoopT>::insertIntoLoop(BlockT *Block) {
515 7233734 : LoopT *Subloop = LI->getLoopFor(Block);
516 7233734 : if (Subloop && Block == Subloop->getHeader()) {
517 : // We reach this point once per subloop after processing all the blocks in
518 : // the subloop.
519 146630 : if (Subloop->getParentLoop())
520 25212 : Subloop->getParentLoop()->getSubLoopsVector().push_back(Subloop);
521 : else
522 121418 : LI->addTopLevelLoop(Subloop);
523 :
524 : // For convenience, Blocks and Subloops are inserted in postorder. Reverse
525 : // the lists, except for the loop header, which is always at the beginning.
526 146630 : Subloop->reverseBlock(1);
527 : std::reverse(Subloop->getSubLoopsVector().begin(),
528 : Subloop->getSubLoopsVector().end());
529 :
530 293252 : Subloop = Subloop->getParentLoop();
531 : }
532 8761144 : for (; Subloop; Subloop = Subloop->getParentLoop())
533 763711 : Subloop->addBlockEntry(Block);
534 7233734 : }
535 :
536 : /// Analyze LoopInfo discovers loops during a postorder DominatorTree traversal
537 : /// interleaved with backward CFG traversals within each subloop
538 : /// (discoverAndMapSubloop). The backward traversal skips inner subloops, so
539 : /// this part of the algorithm is linear in the number of CFG edges. Subloop and
540 : /// Block vectors are then populated during a single forward CFG traversal
541 : /// (PopulateLoopDFS).
542 : ///
543 : /// During the two CFG traversals each block is seen three times:
544 : /// 1) Discovered and mapped by a reverse CFG traversal.
545 : /// 2) Visited during a forward DFS CFG traversal.
546 : /// 3) Reverse-inserted in the loop in postorder following forward DFS.
547 : ///
548 : /// The Block vectors are inclusive, so step 3 requires loop-depth number of
549 : /// insertions per block.
550 : template <class BlockT, class LoopT>
551 2456032 : void LoopInfoBase<BlockT, LoopT>::analyze(const DomTreeBase<BlockT> &DomTree) {
552 : // Postorder traversal of the dominator tree.
553 2456032 : const DomTreeNodeBase<BlockT> *DomRoot = DomTree.getRootNode();
554 12145798 : for (auto DomNode : post_order(DomRoot)) {
555 :
556 7233734 : BlockT *Header = DomNode->getBlock();
557 : SmallVector<BlockT *, 4> Backedges;
558 :
559 : // Check each predecessor of the potential loop header.
560 13827367 : for (const auto Backedge : children<Inverse<BlockT *>>(Header)) {
561 : // If Header dominates predBB, this is a new loop. Collect the backedges.
562 6593633 : if (DomTree.dominates(Header, Backedge) &&
563 : DomTree.isReachableFromEntry(Backedge)) {
564 150351 : Backedges.push_back(Backedge);
565 : }
566 : }
567 : // Perform a backward CFG traversal to discover and map blocks in this loop.
568 7233734 : if (!Backedges.empty()) {
569 146630 : LoopT *L = AllocateLoop(Header);
570 146630 : discoverAndMapSubloop(L, ArrayRef<BlockT *>(Backedges), this, DomTree);
571 : }
572 : }
573 : // Perform a single forward CFG traversal to populate block and subloop
574 : // vectors for all loops.
575 : PopulateLoopsDFS<BlockT, LoopT> DFS(this);
576 2456032 : DFS.traverse(DomRoot->getBlock());
577 2456032 : }
578 :
579 : template <class BlockT, class LoopT>
580 53 : SmallVector<LoopT *, 4> LoopInfoBase<BlockT, LoopT>::getLoopsInPreorder() {
581 : SmallVector<LoopT *, 4> PreOrderLoops, PreOrderWorklist;
582 : // The outer-most loop actually goes into the result in the same relative
583 : // order as we walk it. But LoopInfo stores the top level loops in reverse
584 : // program order so for here we reverse it to get forward program order.
585 : // FIXME: If we change the order of LoopInfo we will want to remove the
586 : // reverse here.
587 106 : for (LoopT *RootL : reverse(*this)) {
588 : assert(PreOrderWorklist.empty() &&
589 : "Must start with an empty preorder walk worklist.");
590 53 : PreOrderWorklist.push_back(RootL);
591 : do {
592 66 : LoopT *L = PreOrderWorklist.pop_back_val();
593 : // Sub-loops are stored in forward program order, but will process the
594 : // worklist backwards so append them in reverse order.
595 66 : PreOrderWorklist.append(L->rbegin(), L->rend());
596 66 : PreOrderLoops.push_back(L);
597 66 : } while (!PreOrderWorklist.empty());
598 : }
599 :
600 53 : return PreOrderLoops;
601 : }
602 :
603 : template <class BlockT, class LoopT>
604 : SmallVector<LoopT *, 4>
605 462 : LoopInfoBase<BlockT, LoopT>::getLoopsInReverseSiblingPreorder() {
606 : SmallVector<LoopT *, 4> PreOrderLoops, PreOrderWorklist;
607 : // The outer-most loop actually goes into the result in the same relative
608 : // order as we walk it. LoopInfo stores the top level loops in reverse
609 : // program order so we walk in order here.
610 : // FIXME: If we change the order of LoopInfo we will want to add a reverse
611 : // here.
612 1030 : for (LoopT *RootL : *this) {
613 : assert(PreOrderWorklist.empty() &&
614 : "Must start with an empty preorder walk worklist.");
615 568 : PreOrderWorklist.push_back(RootL);
616 : do {
617 740 : LoopT *L = PreOrderWorklist.pop_back_val();
618 : // Sub-loops are stored in forward program order, but will process the
619 : // worklist backwards so we can just append them in order.
620 740 : PreOrderWorklist.append(L->begin(), L->end());
621 740 : PreOrderLoops.push_back(L);
622 740 : } while (!PreOrderWorklist.empty());
623 : }
624 :
625 462 : return PreOrderLoops;
626 : }
627 :
628 : // Debugging
629 : template <class BlockT, class LoopT>
630 10 : void LoopInfoBase<BlockT, LoopT>::print(raw_ostream &OS) const {
631 35 : for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
632 15 : TopLevelLoops[i]->print(OS);
633 : #if 0
634 : for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
635 : E = BBMap.end(); I != E; ++I)
636 : OS << "BB '" << I->first->getName() << "' level = "
637 : << I->second->getLoopDepth() << "\n";
638 : #endif
639 10 : }
640 :
641 : template <typename T>
642 : bool compareVectors(std::vector<T> &BB1, std::vector<T> &BB2) {
643 : llvm::sort(BB1);
644 : llvm::sort(BB2);
645 : return BB1 == BB2;
646 : }
647 :
648 : template <class BlockT, class LoopT>
649 : void addInnerLoopsToHeadersMap(DenseMap<BlockT *, const LoopT *> &LoopHeaders,
650 : const LoopInfoBase<BlockT, LoopT> &LI,
651 : const LoopT &L) {
652 : LoopHeaders[L.getHeader()] = &L;
653 : for (LoopT *SL : L)
654 : addInnerLoopsToHeadersMap(LoopHeaders, LI, *SL);
655 : }
656 :
657 : #ifndef NDEBUG
658 : template <class BlockT, class LoopT>
659 : static void compareLoops(const LoopT *L, const LoopT *OtherL,
660 : DenseMap<BlockT *, const LoopT *> &OtherLoopHeaders) {
661 : BlockT *H = L->getHeader();
662 : BlockT *OtherH = OtherL->getHeader();
663 : assert(H == OtherH &&
664 : "Mismatched headers even though found in the same map entry!");
665 :
666 : assert(L->getLoopDepth() == OtherL->getLoopDepth() &&
667 : "Mismatched loop depth!");
668 : const LoopT *ParentL = L, *OtherParentL = OtherL;
669 : do {
670 : assert(ParentL->getHeader() == OtherParentL->getHeader() &&
671 : "Mismatched parent loop headers!");
672 : ParentL = ParentL->getParentLoop();
673 : OtherParentL = OtherParentL->getParentLoop();
674 : } while (ParentL);
675 :
676 : for (const LoopT *SubL : *L) {
677 : BlockT *SubH = SubL->getHeader();
678 : const LoopT *OtherSubL = OtherLoopHeaders.lookup(SubH);
679 : assert(OtherSubL && "Inner loop is missing in computed loop info!");
680 : OtherLoopHeaders.erase(SubH);
681 : compareLoops(SubL, OtherSubL, OtherLoopHeaders);
682 : }
683 :
684 : std::vector<BlockT *> BBs = L->getBlocks();
685 : std::vector<BlockT *> OtherBBs = OtherL->getBlocks();
686 : assert(compareVectors(BBs, OtherBBs) &&
687 : "Mismatched basic blocks in the loops!");
688 :
689 : const SmallPtrSetImpl<const BlockT *> &BlocksSet = L->getBlocksSet();
690 : const SmallPtrSetImpl<const BlockT *> &OtherBlocksSet = L->getBlocksSet();
691 : assert(BlocksSet.size() == OtherBlocksSet.size() &&
692 : std::all_of(BlocksSet.begin(), BlocksSet.end(),
693 : [&OtherBlocksSet](const BlockT *BB) {
694 : return OtherBlocksSet.count(BB);
695 : }) &&
696 : "Mismatched basic blocks in BlocksSets!");
697 : }
698 : #endif
699 :
700 : template <class BlockT, class LoopT>
701 94 : void LoopInfoBase<BlockT, LoopT>::verify(
702 : const DomTreeBase<BlockT> &DomTree) const {
703 : DenseSet<const LoopT *> Loops;
704 230 : for (iterator I = begin(), E = end(); I != E; ++I) {
705 : assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
706 136 : (*I)->verifyLoopNest(&Loops);
707 : }
708 :
709 : // Verify that blocks are mapped to valid loops.
710 : #ifndef NDEBUG
711 : for (auto &Entry : BBMap) {
712 : const BlockT *BB = Entry.first;
713 : LoopT *L = Entry.second;
714 : assert(Loops.count(L) && "orphaned loop");
715 : assert(L->contains(BB) && "orphaned block");
716 : for (LoopT *ChildLoop : *L)
717 : assert(!ChildLoop->contains(BB) &&
718 : "BBMap should point to the innermost loop containing BB");
719 : }
720 :
721 : // Recompute LoopInfo to verify loops structure.
722 : LoopInfoBase<BlockT, LoopT> OtherLI;
723 : OtherLI.analyze(DomTree);
724 :
725 : // Build a map we can use to move from our LI to the computed one. This
726 : // allows us to ignore the particular order in any layer of the loop forest
727 : // while still comparing the structure.
728 : DenseMap<BlockT *, const LoopT *> OtherLoopHeaders;
729 : for (LoopT *L : OtherLI)
730 : addInnerLoopsToHeadersMap(OtherLoopHeaders, OtherLI, *L);
731 :
732 : // Walk the top level loops and ensure there is a corresponding top-level
733 : // loop in the computed version and then recursively compare those loop
734 : // nests.
735 : for (LoopT *L : *this) {
736 : BlockT *Header = L->getHeader();
737 : const LoopT *OtherL = OtherLoopHeaders.lookup(Header);
738 : assert(OtherL && "Top level loop is missing in computed loop info!");
739 : // Now that we've matched this loop, erase its header from the map.
740 : OtherLoopHeaders.erase(Header);
741 : // And recursively compare these loops.
742 : compareLoops(L, OtherL, OtherLoopHeaders);
743 : }
744 :
745 : // Any remaining entries in the map are loops which were found when computing
746 : // a fresh LoopInfo but not present in the current one.
747 : if (!OtherLoopHeaders.empty()) {
748 : for (const auto &HeaderAndLoop : OtherLoopHeaders)
749 : dbgs() << "Found new loop: " << *HeaderAndLoop.second << "\n";
750 : llvm_unreachable("Found new loops when recomputing LoopInfo!");
751 : }
752 : #endif
753 94 : }
754 :
755 : } // End llvm namespace
756 :
757 : #endif
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