Line data Source code
1 : //===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
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 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.
14 : //
15 : //===----------------------------------------------------------------------===//
16 :
17 : #include "llvm/Analysis/LoopInfo.h"
18 : #include "llvm/ADT/DepthFirstIterator.h"
19 : #include "llvm/ADT/ScopeExit.h"
20 : #include "llvm/ADT/SmallPtrSet.h"
21 : #include "llvm/Analysis/LoopInfoImpl.h"
22 : #include "llvm/Analysis/LoopIterator.h"
23 : #include "llvm/Analysis/ValueTracking.h"
24 : #include "llvm/Config/llvm-config.h"
25 : #include "llvm/IR/CFG.h"
26 : #include "llvm/IR/Constants.h"
27 : #include "llvm/IR/DebugLoc.h"
28 : #include "llvm/IR/Dominators.h"
29 : #include "llvm/IR/IRPrintingPasses.h"
30 : #include "llvm/IR/Instructions.h"
31 : #include "llvm/IR/LLVMContext.h"
32 : #include "llvm/IR/Metadata.h"
33 : #include "llvm/IR/PassManager.h"
34 : #include "llvm/Support/CommandLine.h"
35 : #include "llvm/Support/Debug.h"
36 : #include "llvm/Support/raw_ostream.h"
37 : #include <algorithm>
38 : using namespace llvm;
39 :
40 : // Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
41 : template class llvm::LoopBase<BasicBlock, Loop>;
42 : template class llvm::LoopInfoBase<BasicBlock, Loop>;
43 :
44 : // Always verify loopinfo if expensive checking is enabled.
45 : #ifdef EXPENSIVE_CHECKS
46 : bool llvm::VerifyLoopInfo = true;
47 : #else
48 : bool llvm::VerifyLoopInfo = false;
49 : #endif
50 : static cl::opt<bool, true>
51 : VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
52 : cl::Hidden, cl::desc("Verify loop info (time consuming)"));
53 :
54 : //===----------------------------------------------------------------------===//
55 : // Loop implementation
56 : //
57 :
58 1959098 : bool Loop::isLoopInvariant(const Value *V) const {
59 : if (const Instruction *I = dyn_cast<Instruction>(V))
60 877993 : return !contains(I);
61 : return true; // All non-instructions are loop invariant
62 : }
63 :
64 1097723 : bool Loop::hasLoopInvariantOperands(const Instruction *I) const {
65 1097723 : return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); });
66 : }
67 :
68 12151 : bool Loop::makeLoopInvariant(Value *V, bool &Changed,
69 : Instruction *InsertPt) const {
70 : if (Instruction *I = dyn_cast<Instruction>(V))
71 11664 : return makeLoopInvariant(I, Changed, InsertPt);
72 : return true; // All non-instructions are loop-invariant.
73 : }
74 :
75 16120 : bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
76 : Instruction *InsertPt) const {
77 : // Test if the value is already loop-invariant.
78 16120 : if (isLoopInvariant(I))
79 : return true;
80 15629 : if (!isSafeToSpeculativelyExecute(I))
81 : return false;
82 9394 : if (I->mayReadFromMemory())
83 : return false;
84 : // EH block instructions are immobile.
85 : if (I->isEHPad())
86 : return false;
87 : // Determine the insertion point, unless one was given.
88 8872 : if (!InsertPt) {
89 2423 : BasicBlock *Preheader = getLoopPreheader();
90 : // Without a preheader, hoisting is not feasible.
91 2423 : if (!Preheader)
92 : return false;
93 : InsertPt = Preheader->getTerminator();
94 : }
95 : // Don't hoist instructions with loop-variant operands.
96 18445 : for (Value *Operand : I->operands())
97 9424 : if (!makeLoopInvariant(Operand, Changed, InsertPt))
98 : return false;
99 :
100 : // Hoist.
101 149 : I->moveBefore(InsertPt);
102 :
103 : // There is possibility of hoisting this instruction above some arbitrary
104 : // condition. Any metadata defined on it can be control dependent on this
105 : // condition. Conservatively strip it here so that we don't give any wrong
106 : // information to the optimizer.
107 : I->dropUnknownNonDebugMetadata();
108 :
109 149 : Changed = true;
110 149 : return true;
111 : }
112 :
113 393 : PHINode *Loop::getCanonicalInductionVariable() const {
114 : BasicBlock *H = getHeader();
115 :
116 : BasicBlock *Incoming = nullptr, *Backedge = nullptr;
117 : pred_iterator PI = pred_begin(H);
118 : assert(PI != pred_end(H) && "Loop must have at least one backedge!");
119 : Backedge = *PI++;
120 393 : if (PI == pred_end(H))
121 : return nullptr; // dead loop
122 : Incoming = *PI++;
123 393 : if (PI != pred_end(H))
124 : return nullptr; // multiple backedges?
125 :
126 385 : if (contains(Incoming)) {
127 55 : if (contains(Backedge))
128 : return nullptr;
129 : std::swap(Incoming, Backedge);
130 330 : } else if (!contains(Backedge))
131 : return nullptr;
132 :
133 : // Loop over all of the PHI nodes, looking for a canonical indvar.
134 558 : for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
135 : PHINode *PN = cast<PHINode>(I);
136 : if (ConstantInt *CI =
137 412 : dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
138 323 : if (CI->isZero())
139 : if (Instruction *Inc =
140 303 : dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
141 592 : if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
142 : if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
143 282 : if (CI->isOne())
144 : return PN;
145 : }
146 : return nullptr;
147 : }
148 :
149 : // Check that 'BB' doesn't have any uses outside of the 'L'
150 2 : static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
151 : DominatorTree &DT) {
152 14 : for (const Instruction &I : BB) {
153 : // Tokens can't be used in PHI nodes and live-out tokens prevent loop
154 : // optimizations, so for the purposes of considered LCSSA form, we
155 : // can ignore them.
156 24 : if (I.getType()->isTokenTy())
157 : continue;
158 :
159 25 : for (const Use &U : I.uses()) {
160 13 : const Instruction *UI = cast<Instruction>(U.getUser());
161 13 : const BasicBlock *UserBB = UI->getParent();
162 : if (const PHINode *P = dyn_cast<PHINode>(UI))
163 : UserBB = P->getIncomingBlock(U);
164 :
165 : // Check the current block, as a fast-path, before checking whether
166 : // the use is anywhere in the loop. Most values are used in the same
167 : // block they are defined in. Also, blocks not reachable from the
168 : // entry are special; uses in them don't need to go through PHIs.
169 17 : if (UserBB != &BB && !L.contains(UserBB) &&
170 0 : DT.isReachableFromEntry(UserBB))
171 : return false;
172 : }
173 : }
174 : return true;
175 : }
176 :
177 0 : bool Loop::isLCSSAForm(DominatorTree &DT) const {
178 : // For each block we check that it doesn't have any uses outside of this loop.
179 : return all_of(this->blocks(), [&](const BasicBlock *BB) {
180 0 : return isBlockInLCSSAForm(*this, *BB, DT);
181 0 : });
182 : }
183 :
184 1 : bool Loop::isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const {
185 : // For each block we check that it doesn't have any uses outside of its
186 : // innermost loop. This process will transitively guarantee that the current
187 : // loop and all of the nested loops are in LCSSA form.
188 : return all_of(this->blocks(), [&](const BasicBlock *BB) {
189 : return isBlockInLCSSAForm(*LI.getLoopFor(BB), *BB, DT);
190 1 : });
191 : }
192 :
193 85333 : bool Loop::isLoopSimplifyForm() const {
194 : // Normal-form loops have a preheader, a single backedge, and all of their
195 : // exits have all their predecessors inside the loop.
196 85333 : return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
197 : }
198 :
199 : // Routines that reform the loop CFG and split edges often fail on indirectbr.
200 6794 : bool Loop::isSafeToClone() const {
201 : // Return false if any loop blocks contain indirectbrs, or there are any calls
202 : // to noduplicate functions.
203 51993 : for (BasicBlock *BB : this->blocks()) {
204 45204 : if (isa<IndirectBrInst>(BB->getTerminator()))
205 : return false;
206 :
207 538659 : for (Instruction &I : *BB)
208 493460 : if (auto CS = CallSite(&I))
209 81590 : if (CS.cannotDuplicate())
210 3 : return false;
211 : }
212 : return true;
213 : }
214 :
215 71750 : MDNode *Loop::getLoopID() const {
216 : MDNode *LoopID = nullptr;
217 :
218 : // Go through the latch blocks and check the terminator for the metadata.
219 : SmallVector<BasicBlock *, 4> LatchesBlocks;
220 71750 : getLoopLatches(LatchesBlocks);
221 126924 : for (BasicBlock *BB : LatchesBlocks) {
222 : Instruction *TI = BB->getTerminator();
223 : MDNode *MD = TI->getMetadata(LLVMContext::MD_loop);
224 :
225 58754 : if (!MD)
226 16581 : return nullptr;
227 :
228 55174 : if (!LoopID)
229 : LoopID = MD;
230 5 : else if (MD != LoopID)
231 : return nullptr;
232 : }
233 55169 : if (!LoopID || LoopID->getNumOperands() == 0 ||
234 : LoopID->getOperand(0) != LoopID)
235 0 : return nullptr;
236 : return LoopID;
237 : }
238 :
239 5338 : void Loop::setLoopID(MDNode *LoopID) const {
240 : assert(LoopID && "Loop ID should not be null");
241 : assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
242 : assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
243 :
244 5338 : if (BasicBlock *Latch = getLoopLatch()) {
245 5336 : Latch->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
246 5336 : return;
247 : }
248 :
249 : assert(!getLoopLatch() &&
250 : "The loop should have no single latch at this point");
251 : BasicBlock *H = getHeader();
252 8 : for (BasicBlock *BB : this->blocks()) {
253 : Instruction *TI = BB->getTerminator();
254 16 : for (BasicBlock *Successor : successors(TI)) {
255 10 : if (Successor == H)
256 4 : TI->setMetadata(LLVMContext::MD_loop, LoopID);
257 : }
258 : }
259 : }
260 :
261 321 : void Loop::setLoopAlreadyUnrolled() {
262 321 : MDNode *LoopID = getLoopID();
263 : // First remove any existing loop unrolling metadata.
264 : SmallVector<Metadata *, 4> MDs;
265 : // Reserve first location for self reference to the LoopID metadata node.
266 321 : MDs.push_back(nullptr);
267 :
268 321 : if (LoopID) {
269 106 : for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
270 : bool IsUnrollMetadata = false;
271 : MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
272 : if (MD) {
273 : const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
274 96 : IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
275 : }
276 58 : if (!IsUnrollMetadata)
277 32 : MDs.push_back(LoopID->getOperand(i));
278 : }
279 : }
280 :
281 : // Add unroll(disable) metadata to disable future unrolling.
282 321 : LLVMContext &Context = getHeader()->getContext();
283 : SmallVector<Metadata *, 1> DisableOperands;
284 321 : DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
285 : MDNode *DisableNode = MDNode::get(Context, DisableOperands);
286 321 : MDs.push_back(DisableNode);
287 :
288 : MDNode *NewLoopID = MDNode::get(Context, MDs);
289 : // Set operand 0 to refer to the loop id itself.
290 321 : NewLoopID->replaceOperandWith(0, NewLoopID);
291 321 : setLoopID(NewLoopID);
292 321 : }
293 :
294 3118 : bool Loop::isAnnotatedParallel() const {
295 3118 : MDNode *DesiredLoopIdMetadata = getLoopID();
296 :
297 3118 : if (!DesiredLoopIdMetadata)
298 : return false;
299 :
300 : // The loop branch contains the parallel loop metadata. In order to ensure
301 : // that any parallel-loop-unaware optimization pass hasn't added loop-carried
302 : // dependencies (thus converted the loop back to a sequential loop), check
303 : // that all the memory instructions in the loop contain parallelism metadata
304 : // that point to the same unique "loop id metadata" the loop branch does.
305 1685 : for (BasicBlock *BB : this->blocks()) {
306 10915 : for (Instruction &I : *BB) {
307 10827 : if (!I.mayReadOrWriteMemory())
308 : continue;
309 :
310 : // The memory instruction can refer to the loop identifier metadata
311 : // directly or indirectly through another list metadata (in case of
312 : // nested parallel loops). The loop identifier metadata refers to
313 : // itself so we can check both cases with the same routine.
314 : MDNode *LoopIdMD =
315 : I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);
316 :
317 1497 : if (!LoopIdMD)
318 1571 : return false;
319 :
320 : bool LoopIdMDFound = false;
321 68 : for (const MDOperand &MDOp : LoopIdMD->operands()) {
322 62 : if (MDOp == DesiredLoopIdMetadata) {
323 : LoopIdMDFound = true;
324 : break;
325 : }
326 : }
327 :
328 56 : if (!LoopIdMDFound)
329 : return false;
330 : }
331 : }
332 : return true;
333 : }
334 :
335 13398 : DebugLoc Loop::getStartLoc() const { return getLocRange().getStart(); }
336 :
337 6699 : Loop::LocRange Loop::getLocRange() const {
338 : // If we have a debug location in the loop ID, then use it.
339 6699 : if (MDNode *LoopID = getLoopID()) {
340 4927 : DebugLoc Start;
341 : // We use the first DebugLoc in the header as the start location of the loop
342 : // and if there is a second DebugLoc in the header we use it as end location
343 : // of the loop.
344 9872 : for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
345 : if (DILocation *L = dyn_cast<DILocation>(LoopID->getOperand(i))) {
346 9583 : if (!Start)
347 9626 : Start = DebugLoc(L);
348 : else
349 14310 : return LocRange(Start, DebugLoc(L));
350 : }
351 : }
352 :
353 157 : if (Start)
354 86 : return LocRange(Start);
355 : }
356 :
357 : // Try the pre-header first.
358 1886 : if (BasicBlock *PHeadBB = getLoopPreheader())
359 1820 : if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
360 1072 : return LocRange(DL);
361 :
362 : // If we have no pre-header or there are no instructions with debug
363 : // info in it, try the header.
364 1350 : if (BasicBlock *HeadBB = getHeader())
365 2700 : return LocRange(HeadBB->getTerminator()->getDebugLoc());
366 :
367 : return LocRange();
368 : }
369 :
370 : #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
371 : LLVM_DUMP_METHOD void Loop::dump() const { print(dbgs()); }
372 :
373 : LLVM_DUMP_METHOD void Loop::dumpVerbose() const {
374 : print(dbgs(), /*Depth=*/0, /*Verbose=*/true);
375 : }
376 : #endif
377 :
378 : //===----------------------------------------------------------------------===//
379 : // UnloopUpdater implementation
380 : //
381 :
382 : namespace {
383 : /// Find the new parent loop for all blocks within the "unloop" whose last
384 : /// backedges has just been removed.
385 88 : class UnloopUpdater {
386 : Loop &Unloop;
387 : LoopInfo *LI;
388 :
389 : LoopBlocksDFS DFS;
390 :
391 : // Map unloop's immediate subloops to their nearest reachable parents. Nested
392 : // loops within these subloops will not change parents. However, an immediate
393 : // subloop's new parent will be the nearest loop reachable from either its own
394 : // exits *or* any of its nested loop's exits.
395 : DenseMap<Loop *, Loop *> SubloopParents;
396 :
397 : // Flag the presence of an irreducible backedge whose destination is a block
398 : // directly contained by the original unloop.
399 : bool FoundIB;
400 :
401 : public:
402 : UnloopUpdater(Loop *UL, LoopInfo *LInfo)
403 88 : : Unloop(*UL), LI(LInfo), DFS(UL), FoundIB(false) {}
404 :
405 : void updateBlockParents();
406 :
407 : void removeBlocksFromAncestors();
408 :
409 : void updateSubloopParents();
410 :
411 : protected:
412 : Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
413 : };
414 : } // end anonymous namespace
415 :
416 : /// Update the parent loop for all blocks that are directly contained within the
417 : /// original "unloop".
418 88 : void UnloopUpdater::updateBlockParents() {
419 176 : if (Unloop.getNumBlocks()) {
420 : // Perform a post order CFG traversal of all blocks within this loop,
421 : // propagating the nearest loop from successors to predecessors.
422 64 : LoopBlocksTraversal Traversal(DFS, LI);
423 852 : for (BasicBlock *POI : Traversal) {
424 :
425 362 : Loop *L = LI->getLoopFor(POI);
426 362 : Loop *NL = getNearestLoop(POI, L);
427 :
428 362 : if (NL != L) {
429 : // For reducible loops, NL is now an ancestor of Unloop.
430 : assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
431 : "uninitialized successor");
432 292 : LI->changeLoopFor(POI, NL);
433 : } else {
434 : // Or the current block is part of a subloop, in which case its parent
435 : // is unchanged.
436 : assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
437 : }
438 : }
439 : }
440 : // Each irreducible loop within the unloop induces a round of iteration using
441 : // the DFS result cached by Traversal.
442 88 : bool Changed = FoundIB;
443 92 : for (unsigned NIters = 0; Changed; ++NIters) {
444 : assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
445 :
446 : // Iterate over the postorder list of blocks, propagating the nearest loop
447 : // from successors to predecessors as before.
448 : Changed = false;
449 : for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
450 : POE = DFS.endPostorder();
451 56 : POI != POE; ++POI) {
452 :
453 52 : Loop *L = LI->getLoopFor(*POI);
454 52 : Loop *NL = getNearestLoop(*POI, L);
455 52 : if (NL != L) {
456 : assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
457 : "uninitialized successor");
458 6 : LI->changeLoopFor(*POI, NL);
459 : Changed = true;
460 : }
461 : }
462 : }
463 88 : }
464 :
465 : /// Remove unloop's blocks from all ancestors below their new parents.
466 88 : void UnloopUpdater::removeBlocksFromAncestors() {
467 : // Remove all unloop's blocks (including those in nested subloops) from
468 : // ancestors below the new parent loop.
469 450 : for (Loop::block_iterator BI = Unloop.block_begin(), BE = Unloop.block_end();
470 450 : BI != BE; ++BI) {
471 362 : Loop *OuterParent = LI->getLoopFor(*BI);
472 724 : if (Unloop.contains(OuterParent)) {
473 144 : while (OuterParent->getParentLoop() != &Unloop)
474 8 : OuterParent = OuterParent->getParentLoop();
475 64 : OuterParent = SubloopParents[OuterParent];
476 : }
477 : // Remove blocks from former Ancestors except Unloop itself which will be
478 : // deleted.
479 403 : for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
480 : OldParent = OldParent->getParentLoop()) {
481 : assert(OldParent && "new loop is not an ancestor of the original");
482 41 : OldParent->removeBlockFromLoop(*BI);
483 : }
484 : }
485 88 : }
486 :
487 : /// Update the parent loop for all subloops directly nested within unloop.
488 88 : void UnloopUpdater::updateSubloopParents() {
489 204 : while (!Unloop.empty()) {
490 28 : Loop *Subloop = *std::prev(Unloop.end());
491 : Unloop.removeChildLoop(std::prev(Unloop.end()));
492 :
493 : assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
494 28 : if (Loop *Parent = SubloopParents[Subloop])
495 24 : Parent->addChildLoop(Subloop);
496 : else
497 4 : LI->addTopLevelLoop(Subloop);
498 : }
499 88 : }
500 :
501 : /// Return the nearest parent loop among this block's successors. If a successor
502 : /// is a subloop header, consider its parent to be the nearest parent of the
503 : /// subloop's exits.
504 : ///
505 : /// For subloop blocks, simply update SubloopParents and return NULL.
506 414 : Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
507 :
508 : // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
509 : // is considered uninitialized.
510 : Loop *NearLoop = BBLoop;
511 :
512 414 : Loop *Subloop = nullptr;
513 524 : if (NearLoop != &Unloop && Unloop.contains(NearLoop)) {
514 64 : Subloop = NearLoop;
515 : // Find the subloop ancestor that is directly contained within Unloop.
516 144 : while (Subloop->getParentLoop() != &Unloop) {
517 8 : Subloop = Subloop->getParentLoop();
518 : assert(Subloop && "subloop is not an ancestor of the original loop");
519 : }
520 : // Get the current nearest parent of the Subloop exits, initially Unloop.
521 64 : NearLoop = SubloopParents.insert({Subloop, &Unloop}).first->second;
522 : }
523 :
524 414 : succ_iterator I = succ_begin(BB), E = succ_end(BB);
525 414 : if (I == E) {
526 : assert(!Subloop && "subloop blocks must have a successor");
527 : NearLoop = nullptr; // unloop blocks may now exit the function.
528 : }
529 1067 : for (; I != E; ++I) {
530 653 : if (*I == BB)
531 82 : continue; // self loops are uninteresting
532 :
533 637 : Loop *L = LI->getLoopFor(*I);
534 637 : if (L == &Unloop) {
535 : // This successor has not been processed. This path must lead to an
536 : // irreducible backedge.
537 : assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
538 10 : FoundIB = true;
539 : }
540 1264 : if (L != &Unloop && Unloop.contains(L)) {
541 : // Successor is in a subloop.
542 84 : if (Subloop)
543 : continue; // Branching within subloops. Ignore it.
544 :
545 : // BB branches from the original into a subloop header.
546 : assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
547 :
548 : // Get the current nearest parent of the Subloop's exits.
549 28 : L = SubloopParents[L];
550 : // L could be Unloop if the only exit was an irreducible backedge.
551 : }
552 581 : if (L == &Unloop) {
553 : continue;
554 : }
555 : // Handle critical edges from Unloop into a sibling loop.
556 992 : if (L && !L->contains(&Unloop)) {
557 3 : L = L->getParentLoop();
558 : }
559 : // Remember the nearest parent loop among successors or subloop exits.
560 782 : if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
561 477 : NearLoop = L;
562 : }
563 414 : if (Subloop) {
564 64 : SubloopParents[Subloop] = NearLoop;
565 64 : return BBLoop;
566 : }
567 : return NearLoop;
568 : }
569 :
570 433 : LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
571 :
572 1470 : bool LoopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
573 : FunctionAnalysisManager::Invalidator &) {
574 : // Check whether the analysis, all analyses on functions, or the function's
575 : // CFG have been preserved.
576 : auto PAC = PA.getChecker<LoopAnalysis>();
577 2306 : return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
578 836 : PAC.preservedSet<CFGAnalyses>());
579 : }
580 :
581 725 : void LoopInfo::erase(Loop *Unloop) {
582 : assert(!Unloop->isInvalid() && "Loop has already been erased!");
583 :
584 : auto InvalidateOnExit = make_scope_exit([&]() { destroy(Unloop); });
585 :
586 : // First handle the special case of no parent loop to simplify the algorithm.
587 1450 : if (!Unloop->getParentLoop()) {
588 : // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
589 2796 : for (Loop::block_iterator I = Unloop->block_begin(),
590 : E = Unloop->block_end();
591 3433 : I != E; ++I) {
592 :
593 : // Don't reparent blocks in subloops.
594 5592 : if (getLoopFor(*I) != Unloop)
595 : continue;
596 :
597 : // Blocks no longer have a parent but are still referenced by Unloop until
598 : // the Unloop object is deleted.
599 2567 : changeLoopFor(*I, nullptr);
600 : }
601 :
602 : // Remove the loop from the top-level LoopInfo object.
603 : for (iterator I = begin();; ++I) {
604 : assert(I != end() && "Couldn't find loop");
605 881 : if (*I == Unloop) {
606 : removeLoop(I);
607 : break;
608 : }
609 : }
610 :
611 : // Move all of the subloops to the top-level.
612 698 : while (!Unloop->empty())
613 61 : addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
614 :
615 : return;
616 : }
617 :
618 : // Update the parent loop for all blocks within the loop. Blocks within
619 : // subloops will not change parents.
620 : UnloopUpdater Updater(Unloop, this);
621 88 : Updater.updateBlockParents();
622 :
623 : // Remove blocks from former ancestor loops.
624 88 : Updater.removeBlocksFromAncestors();
625 :
626 : // Add direct subloops as children in their new parent loop.
627 88 : Updater.updateSubloopParents();
628 :
629 : // Remove unloop from its parent loop.
630 : Loop *ParentLoop = Unloop->getParentLoop();
631 : for (Loop::iterator I = ParentLoop->begin();; ++I) {
632 : assert(I != ParentLoop->end() && "Couldn't find loop");
633 98 : if (*I == Unloop) {
634 : ParentLoop->removeChildLoop(I);
635 : break;
636 : }
637 : }
638 : }
639 :
640 : AnalysisKey LoopAnalysis::Key;
641 :
642 1866 : LoopInfo LoopAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
643 : // FIXME: Currently we create a LoopInfo from scratch for every function.
644 : // This may prove to be too wasteful due to deallocating and re-allocating
645 : // memory each time for the underlying map and vector datastructures. At some
646 : // point it may prove worthwhile to use a freelist and recycle LoopInfo
647 : // objects. I don't want to add that kind of complexity until the scope of
648 : // the problem is better understood.
649 : LoopInfo LI;
650 1866 : LI.analyze(AM.getResult<DominatorTreeAnalysis>(F));
651 1866 : return LI;
652 : }
653 :
654 1 : PreservedAnalyses LoopPrinterPass::run(Function &F,
655 : FunctionAnalysisManager &AM) {
656 1 : AM.getResult<LoopAnalysis>(F).print(OS);
657 1 : return PreservedAnalyses::all();
658 : }
659 :
660 7 : void llvm::printLoop(Loop &L, raw_ostream &OS, const std::string &Banner) {
661 :
662 7 : if (forcePrintModuleIR()) {
663 : // handling -print-module-scope
664 1 : OS << Banner << " (loop: ";
665 1 : L.getHeader()->printAsOperand(OS, false);
666 1 : OS << ")\n";
667 :
668 : // printing whole module
669 : OS << *L.getHeader()->getModule();
670 1 : return;
671 : }
672 :
673 : OS << Banner;
674 :
675 6 : auto *PreHeader = L.getLoopPreheader();
676 6 : if (PreHeader) {
677 6 : OS << "\n; Preheader:";
678 6 : PreHeader->print(OS);
679 6 : OS << "\n; Loop:";
680 : }
681 :
682 14 : for (auto *Block : L.blocks())
683 8 : if (Block)
684 8 : Block->print(OS);
685 : else
686 0 : OS << "Printing <null> block";
687 :
688 : SmallVector<BasicBlock *, 8> ExitBlocks;
689 6 : L.getExitBlocks(ExitBlocks);
690 6 : if (!ExitBlocks.empty()) {
691 6 : OS << "\n; Exit blocks";
692 12 : for (auto *Block : ExitBlocks)
693 6 : if (Block)
694 6 : Block->print(OS);
695 : else
696 0 : OS << "Printing <null> block";
697 : }
698 : }
699 :
700 : //===----------------------------------------------------------------------===//
701 : // LoopInfo implementation
702 : //
703 :
704 : char LoopInfoWrapperPass::ID = 0;
705 85428 : INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
706 : true, true)
707 85428 : INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
708 2614001 : INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
709 : true, true)
710 :
711 1341207 : bool LoopInfoWrapperPass::runOnFunction(Function &) {
712 1341207 : releaseMemory();
713 1341207 : LI.analyze(getAnalysis<DominatorTreeWrapperPass>().getDomTree());
714 1341207 : return false;
715 : }
716 :
717 0 : void LoopInfoWrapperPass::verifyAnalysis() const {
718 : // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
719 : // function each time verifyAnalysis is called is very expensive. The
720 : // -verify-loop-info option can enable this. In order to perform some
721 : // checking by default, LoopPass has been taught to call verifyLoop manually
722 : // during loop pass sequences.
723 0 : if (VerifyLoopInfo) {
724 0 : auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
725 0 : LI.verify(DT);
726 : }
727 0 : }
728 :
729 118671 : void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
730 : AU.setPreservesAll();
731 : AU.addRequired<DominatorTreeWrapperPass>();
732 118671 : }
733 :
734 9 : void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
735 9 : LI.print(OS);
736 9 : }
737 :
738 94 : PreservedAnalyses LoopVerifierPass::run(Function &F,
739 : FunctionAnalysisManager &AM) {
740 : LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
741 : auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
742 94 : LI.verify(DT);
743 94 : return PreservedAnalyses::all();
744 : }
745 :
746 : //===----------------------------------------------------------------------===//
747 : // LoopBlocksDFS implementation
748 : //
749 :
750 : /// Traverse the loop blocks and store the DFS result.
751 : /// Useful for clients that just want the final DFS result and don't need to
752 : /// visit blocks during the initial traversal.
753 8394 : void LoopBlocksDFS::perform(LoopInfo *LI) {
754 : LoopBlocksTraversal Traversal(*this, LI);
755 37941 : for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
756 : POE = Traversal.end();
757 37941 : POI != POE; ++POI)
758 : ;
759 8394 : }
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