LLVM  6.0.0svn
LoopUnroll.cpp
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1 //===-- UnrollLoop.cpp - Loop unrolling utilities -------------------------===//
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 implements some loop unrolling utilities. It does not define any
11 // actual pass or policy, but provides a single function to perform loop
12 // unrolling.
13 //
14 // The process of unrolling can produce extraneous basic blocks linked with
15 // unconditional branches. This will be corrected in the future.
16 //
17 //===----------------------------------------------------------------------===//
18 
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/ADT/Statistic.h"
24 #include "llvm/Analysis/LoopPass.h"
27 #include "llvm/IR/BasicBlock.h"
28 #include "llvm/IR/DataLayout.h"
30 #include "llvm/IR/Dominators.h"
31 #include "llvm/IR/IntrinsicInst.h"
32 #include "llvm/IR/LLVMContext.h"
33 #include "llvm/Support/Debug.h"
42 using namespace llvm;
43 
44 #define DEBUG_TYPE "loop-unroll"
45 
46 // TODO: Should these be here or in LoopUnroll?
47 STATISTIC(NumCompletelyUnrolled, "Number of loops completely unrolled");
48 STATISTIC(NumUnrolled, "Number of loops unrolled (completely or otherwise)");
49 
50 static cl::opt<bool>
51 UnrollRuntimeEpilog("unroll-runtime-epilog", cl::init(false), cl::Hidden,
52  cl::desc("Allow runtime unrolled loops to be unrolled "
53  "with epilog instead of prolog."));
54 
55 static cl::opt<bool>
56 UnrollVerifyDomtree("unroll-verify-domtree", cl::Hidden,
57  cl::desc("Verify domtree after unrolling"),
58 #ifdef NDEBUG
59  cl::init(false)
60 #else
61  cl::init(true)
62 #endif
63  );
64 
65 /// Convert the instruction operands from referencing the current values into
66 /// those specified by VMap.
67 static inline void remapInstruction(Instruction *I,
68  ValueToValueMapTy &VMap) {
69  for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
70  Value *Op = I->getOperand(op);
71  ValueToValueMapTy::iterator It = VMap.find(Op);
72  if (It != VMap.end())
73  I->setOperand(op, It->second);
74  }
75 
76  if (PHINode *PN = dyn_cast<PHINode>(I)) {
77  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
78  ValueToValueMapTy::iterator It = VMap.find(PN->getIncomingBlock(i));
79  if (It != VMap.end())
80  PN->setIncomingBlock(i, cast<BasicBlock>(It->second));
81  }
82  }
83 }
84 
85 /// Folds a basic block into its predecessor if it only has one predecessor, and
86 /// that predecessor only has one successor.
87 /// The LoopInfo Analysis that is passed will be kept consistent. If folding is
88 /// successful references to the containing loop must be removed from
89 /// ScalarEvolution by calling ScalarEvolution::forgetLoop because SE may have
90 /// references to the eliminated BB. The argument ForgottenLoops contains a set
91 /// of loops that have already been forgotten to prevent redundant, expensive
92 /// calls to ScalarEvolution::forgetLoop. Returns the new combined block.
93 static BasicBlock *
95  SmallPtrSetImpl<Loop *> &ForgottenLoops,
96  DominatorTree *DT) {
97  // Merge basic blocks into their predecessor if there is only one distinct
98  // pred, and if there is only one distinct successor of the predecessor, and
99  // if there are no PHI nodes.
100  BasicBlock *OnlyPred = BB->getSinglePredecessor();
101  if (!OnlyPred) return nullptr;
102 
103  if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
104  return nullptr;
105 
106  DEBUG(dbgs() << "Merging: " << *BB << "into: " << *OnlyPred);
107 
108  // Resolve any PHI nodes at the start of the block. They are all
109  // guaranteed to have exactly one entry if they exist, unless there are
110  // multiple duplicate (but guaranteed to be equal) entries for the
111  // incoming edges. This occurs when there are multiple edges from
112  // OnlyPred to OnlySucc.
114 
115  // Delete the unconditional branch from the predecessor...
116  OnlyPred->getInstList().pop_back();
117 
118  // Make all PHI nodes that referred to BB now refer to Pred as their
119  // source...
120  BB->replaceAllUsesWith(OnlyPred);
121 
122  // Move all definitions in the successor to the predecessor...
123  OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
124 
125  // OldName will be valid until erased.
126  StringRef OldName = BB->getName();
127 
128  // Erase the old block and update dominator info.
129  if (DT)
130  if (DomTreeNode *DTN = DT->getNode(BB)) {
131  DomTreeNode *PredDTN = DT->getNode(OnlyPred);
132  SmallVector<DomTreeNode *, 8> Children(DTN->begin(), DTN->end());
133  for (auto *DI : Children)
134  DT->changeImmediateDominator(DI, PredDTN);
135 
136  DT->eraseNode(BB);
137  }
138 
139  // ScalarEvolution holds references to loop exit blocks.
140  if (SE) {
141  if (Loop *L = LI->getLoopFor(BB)) {
142  if (ForgottenLoops.insert(L).second)
143  SE->forgetLoop(L);
144  }
145  }
146  LI->removeBlock(BB);
147 
148  // Inherit predecessor's name if it exists...
149  if (!OldName.empty() && !OnlyPred->hasName())
150  OnlyPred->setName(OldName);
151 
152  BB->eraseFromParent();
153 
154  return OnlyPred;
155 }
156 
157 /// Check if unrolling created a situation where we need to insert phi nodes to
158 /// preserve LCSSA form.
159 /// \param Blocks is a vector of basic blocks representing unrolled loop.
160 /// \param L is the outer loop.
161 /// It's possible that some of the blocks are in L, and some are not. In this
162 /// case, if there is a use is outside L, and definition is inside L, we need to
163 /// insert a phi-node, otherwise LCSSA will be broken.
164 /// The function is just a helper function for llvm::UnrollLoop that returns
165 /// true if this situation occurs, indicating that LCSSA needs to be fixed.
166 static bool needToInsertPhisForLCSSA(Loop *L, std::vector<BasicBlock *> Blocks,
167  LoopInfo *LI) {
168  for (BasicBlock *BB : Blocks) {
169  if (LI->getLoopFor(BB) == L)
170  continue;
171  for (Instruction &I : *BB) {
172  for (Use &U : I.operands()) {
173  if (auto Def = dyn_cast<Instruction>(U)) {
174  Loop *DefLoop = LI->getLoopFor(Def->getParent());
175  if (!DefLoop)
176  continue;
177  if (DefLoop->contains(L))
178  return true;
179  }
180  }
181  }
182  }
183  return false;
184 }
185 
186 /// Adds ClonedBB to LoopInfo, creates a new loop for ClonedBB if necessary
187 /// and adds a mapping from the original loop to the new loop to NewLoops.
188 /// Returns nullptr if no new loop was created and a pointer to the
189 /// original loop OriginalBB was part of otherwise.
191  BasicBlock *ClonedBB, LoopInfo *LI,
192  NewLoopsMap &NewLoops) {
193  // Figure out which loop New is in.
194  const Loop *OldLoop = LI->getLoopFor(OriginalBB);
195  assert(OldLoop && "Should (at least) be in the loop being unrolled!");
196 
197  Loop *&NewLoop = NewLoops[OldLoop];
198  if (!NewLoop) {
199  // Found a new sub-loop.
200  assert(OriginalBB == OldLoop->getHeader() &&
201  "Header should be first in RPO");
202 
203  NewLoop = new Loop();
204  Loop *NewLoopParent = NewLoops.lookup(OldLoop->getParentLoop());
205 
206  if (NewLoopParent)
207  NewLoopParent->addChildLoop(NewLoop);
208  else
209  LI->addTopLevelLoop(NewLoop);
210 
211  NewLoop->addBasicBlockToLoop(ClonedBB, *LI);
212  return OldLoop;
213  } else {
214  NewLoop->addBasicBlockToLoop(ClonedBB, *LI);
215  return nullptr;
216  }
217 }
218 
219 /// The function chooses which type of unroll (epilog or prolog) is more
220 /// profitabale.
221 /// Epilog unroll is more profitable when there is PHI that starts from
222 /// constant. In this case epilog will leave PHI start from constant,
223 /// but prolog will convert it to non-constant.
224 ///
225 /// loop:
226 /// PN = PHI [I, Latch], [CI, PreHeader]
227 /// I = foo(PN)
228 /// ...
229 ///
230 /// Epilog unroll case.
231 /// loop:
232 /// PN = PHI [I2, Latch], [CI, PreHeader]
233 /// I1 = foo(PN)
234 /// I2 = foo(I1)
235 /// ...
236 /// Prolog unroll case.
237 /// NewPN = PHI [PrologI, Prolog], [CI, PreHeader]
238 /// loop:
239 /// PN = PHI [I2, Latch], [NewPN, PreHeader]
240 /// I1 = foo(PN)
241 /// I2 = foo(I1)
242 /// ...
243 ///
244 static bool isEpilogProfitable(Loop *L) {
245  BasicBlock *PreHeader = L->getLoopPreheader();
246  BasicBlock *Header = L->getHeader();
247  assert(PreHeader && Header);
248  for (Instruction &BBI : *Header) {
249  PHINode *PN = dyn_cast<PHINode>(&BBI);
250  if (!PN)
251  break;
252  if (isa<ConstantInt>(PN->getIncomingValueForBlock(PreHeader)))
253  return true;
254  }
255  return false;
256 }
257 
258 /// Unroll the given loop by Count. The loop must be in LCSSA form. Unrolling
259 /// can only fail when the loop's latch block is not terminated by a conditional
260 /// branch instruction. However, if the trip count (and multiple) are not known,
261 /// loop unrolling will mostly produce more code that is no faster.
262 ///
263 /// TripCount is the upper bound of the iteration on which control exits
264 /// LatchBlock. Control may exit the loop prior to TripCount iterations either
265 /// via an early branch in other loop block or via LatchBlock terminator. This
266 /// is relaxed from the general definition of trip count which is the number of
267 /// times the loop header executes. Note that UnrollLoop assumes that the loop
268 /// counter test is in LatchBlock in order to remove unnecesssary instances of
269 /// the test. If control can exit the loop from the LatchBlock's terminator
270 /// prior to TripCount iterations, flag PreserveCondBr needs to be set.
271 ///
272 /// PreserveCondBr indicates whether the conditional branch of the LatchBlock
273 /// needs to be preserved. It is needed when we use trip count upper bound to
274 /// fully unroll the loop. If PreserveOnlyFirst is also set then only the first
275 /// conditional branch needs to be preserved.
276 ///
277 /// Similarly, TripMultiple divides the number of times that the LatchBlock may
278 /// execute without exiting the loop.
279 ///
280 /// If AllowRuntime is true then UnrollLoop will consider unrolling loops that
281 /// have a runtime (i.e. not compile time constant) trip count. Unrolling these
282 /// loops require a unroll "prologue" that runs "RuntimeTripCount % Count"
283 /// iterations before branching into the unrolled loop. UnrollLoop will not
284 /// runtime-unroll the loop if computing RuntimeTripCount will be expensive and
285 /// AllowExpensiveTripCount is false.
286 ///
287 /// If we want to perform PGO-based loop peeling, PeelCount is set to the
288 /// number of iterations we want to peel off.
289 ///
290 /// The LoopInfo Analysis that is passed will be kept consistent.
291 ///
292 /// This utility preserves LoopInfo. It will also preserve ScalarEvolution and
293 /// DominatorTree if they are non-null.
295  Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime,
296  bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst,
297  unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder,
299  OptimizationRemarkEmitter *ORE, bool PreserveLCSSA) {
300 
301  BasicBlock *Preheader = L->getLoopPreheader();
302  if (!Preheader) {
303  DEBUG(dbgs() << " Can't unroll; loop preheader-insertion failed.\n");
305  }
306 
307  BasicBlock *LatchBlock = L->getLoopLatch();
308  if (!LatchBlock) {
309  DEBUG(dbgs() << " Can't unroll; loop exit-block-insertion failed.\n");
311  }
312 
313  // Loops with indirectbr cannot be cloned.
314  if (!L->isSafeToClone()) {
315  DEBUG(dbgs() << " Can't unroll; Loop body cannot be cloned.\n");
317  }
318 
319  // The current loop unroll pass can only unroll loops with a single latch
320  // that's a conditional branch exiting the loop.
321  // FIXME: The implementation can be extended to work with more complicated
322  // cases, e.g. loops with multiple latches.
323  BasicBlock *Header = L->getHeader();
324  BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator());
325 
326  if (!BI || BI->isUnconditional()) {
327  // The loop-rotate pass can be helpful to avoid this in many cases.
328  DEBUG(dbgs() <<
329  " Can't unroll; loop not terminated by a conditional branch.\n");
331  }
332 
333  auto CheckSuccessors = [&](unsigned S1, unsigned S2) {
334  return BI->getSuccessor(S1) == Header && !L->contains(BI->getSuccessor(S2));
335  };
336 
337  if (!CheckSuccessors(0, 1) && !CheckSuccessors(1, 0)) {
338  DEBUG(dbgs() << "Can't unroll; only loops with one conditional latch"
339  " exiting the loop can be unrolled\n");
341  }
342 
343  if (Header->hasAddressTaken()) {
344  // The loop-rotate pass can be helpful to avoid this in many cases.
345  DEBUG(dbgs() <<
346  " Won't unroll loop: address of header block is taken.\n");
348  }
349 
350  if (TripCount != 0)
351  DEBUG(dbgs() << " Trip Count = " << TripCount << "\n");
352  if (TripMultiple != 1)
353  DEBUG(dbgs() << " Trip Multiple = " << TripMultiple << "\n");
354 
355  // Effectively "DCE" unrolled iterations that are beyond the tripcount
356  // and will never be executed.
357  if (TripCount != 0 && Count > TripCount)
358  Count = TripCount;
359 
360  // Don't enter the unroll code if there is nothing to do.
361  if (TripCount == 0 && Count < 2 && PeelCount == 0) {
362  DEBUG(dbgs() << "Won't unroll; almost nothing to do\n");
364  }
365 
366  assert(Count > 0);
367  assert(TripMultiple > 0);
368  assert(TripCount == 0 || TripCount % TripMultiple == 0);
369 
370  // Are we eliminating the loop control altogether?
371  bool CompletelyUnroll = Count == TripCount;
372  SmallVector<BasicBlock *, 4> ExitBlocks;
373  L->getExitBlocks(ExitBlocks);
374  std::vector<BasicBlock*> OriginalLoopBlocks = L->getBlocks();
375 
376  // Go through all exits of L and see if there are any phi-nodes there. We just
377  // conservatively assume that they're inserted to preserve LCSSA form, which
378  // means that complete unrolling might break this form. We need to either fix
379  // it in-place after the transformation, or entirely rebuild LCSSA. TODO: For
380  // now we just recompute LCSSA for the outer loop, but it should be possible
381  // to fix it in-place.
382  bool NeedToFixLCSSA = PreserveLCSSA && CompletelyUnroll &&
383  any_of(ExitBlocks, [](const BasicBlock *BB) {
384  return isa<PHINode>(BB->begin());
385  });
386 
387  // We assume a run-time trip count if the compiler cannot
388  // figure out the loop trip count and the unroll-runtime
389  // flag is specified.
390  bool RuntimeTripCount = (TripCount == 0 && Count > 0 && AllowRuntime);
391 
392  assert((!RuntimeTripCount || !PeelCount) &&
393  "Did not expect runtime trip-count unrolling "
394  "and peeling for the same loop");
395 
396  if (PeelCount) {
397  bool Peeled = peelLoop(L, PeelCount, LI, SE, DT, AC, PreserveLCSSA);
398 
399  // Successful peeling may result in a change in the loop preheader/trip
400  // counts. If we later unroll the loop, we want these to be updated.
401  if (Peeled) {
402  BasicBlock *ExitingBlock = L->getExitingBlock();
403  assert(ExitingBlock && "Loop without exiting block?");
404  Preheader = L->getLoopPreheader();
405  TripCount = SE->getSmallConstantTripCount(L, ExitingBlock);
406  TripMultiple = SE->getSmallConstantTripMultiple(L, ExitingBlock);
407  }
408  }
409 
410  // Loops containing convergent instructions must have a count that divides
411  // their TripMultiple.
412  DEBUG(
413  {
414  bool HasConvergent = false;
415  for (auto &BB : L->blocks())
416  for (auto &I : *BB)
417  if (auto CS = CallSite(&I))
418  HasConvergent |= CS.isConvergent();
419  assert((!HasConvergent || TripMultiple % Count == 0) &&
420  "Unroll count must divide trip multiple if loop contains a "
421  "convergent operation.");
422  });
423 
424  bool EpilogProfitability =
425  UnrollRuntimeEpilog.getNumOccurrences() ? UnrollRuntimeEpilog
426  : isEpilogProfitable(L);
427 
428  if (RuntimeTripCount && TripMultiple % Count != 0 &&
429  !UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
430  EpilogProfitability, UnrollRemainder,
431  LI, SE, DT, AC, ORE,
432  PreserveLCSSA)) {
433  if (Force)
434  RuntimeTripCount = false;
435  else {
436  DEBUG(
437  dbgs() << "Wont unroll; remainder loop could not be generated"
438  "when assuming runtime trip count\n");
440  }
441  }
442 
443  // Notify ScalarEvolution that the loop will be substantially changed,
444  // if not outright eliminated.
445  if (SE)
446  SE->forgetLoop(L);
447 
448  // If we know the trip count, we know the multiple...
449  unsigned BreakoutTrip = 0;
450  if (TripCount != 0) {
451  BreakoutTrip = TripCount % Count;
452  TripMultiple = 0;
453  } else {
454  // Figure out what multiple to use.
455  BreakoutTrip = TripMultiple =
456  (unsigned)GreatestCommonDivisor64(Count, TripMultiple);
457  }
458 
459  using namespace ore;
460  // Report the unrolling decision.
461  if (CompletelyUnroll) {
462  DEBUG(dbgs() << "COMPLETELY UNROLLING loop %" << Header->getName()
463  << " with trip count " << TripCount << "!\n");
464  ORE->emit(OptimizationRemark(DEBUG_TYPE, "FullyUnrolled", L->getStartLoc(),
465  L->getHeader())
466  << "completely unrolled loop with "
467  << NV("UnrollCount", TripCount) << " iterations");
468  } else if (PeelCount) {
469  DEBUG(dbgs() << "PEELING loop %" << Header->getName()
470  << " with iteration count " << PeelCount << "!\n");
471  ORE->emit(OptimizationRemark(DEBUG_TYPE, "Peeled", L->getStartLoc(),
472  L->getHeader())
473  << " peeled loop by " << NV("PeelCount", PeelCount)
474  << " iterations");
475  } else {
476  auto DiagBuilder = [&]() {
477  OptimizationRemark Diag(DEBUG_TYPE, "PartialUnrolled", L->getStartLoc(),
478  L->getHeader());
479  return Diag << "unrolled loop by a factor of "
480  << NV("UnrollCount", Count);
481  };
482 
483  DEBUG(dbgs() << "UNROLLING loop %" << Header->getName()
484  << " by " << Count);
485  if (TripMultiple == 0 || BreakoutTrip != TripMultiple) {
486  DEBUG(dbgs() << " with a breakout at trip " << BreakoutTrip);
487  ORE->emit([&]() {
488  return DiagBuilder() << " with a breakout at trip "
489  << NV("BreakoutTrip", BreakoutTrip);
490  });
491  } else if (TripMultiple != 1) {
492  DEBUG(dbgs() << " with " << TripMultiple << " trips per branch");
493  ORE->emit([&]() {
494  return DiagBuilder() << " with " << NV("TripMultiple", TripMultiple)
495  << " trips per branch";
496  });
497  } else if (RuntimeTripCount) {
498  DEBUG(dbgs() << " with run-time trip count");
499  ORE->emit([&]() { return DiagBuilder() << " with run-time trip count"; });
500  }
501  DEBUG(dbgs() << "!\n");
502  }
503 
504  bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
505  BasicBlock *LoopExit = BI->getSuccessor(ContinueOnTrue);
506 
507  // For the first iteration of the loop, we should use the precloned values for
508  // PHI nodes. Insert associations now.
509  ValueToValueMapTy LastValueMap;
510  std::vector<PHINode*> OrigPHINode;
511  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
512  OrigPHINode.push_back(cast<PHINode>(I));
513  }
514 
515  std::vector<BasicBlock*> Headers;
516  std::vector<BasicBlock*> Latches;
517  Headers.push_back(Header);
518  Latches.push_back(LatchBlock);
519 
520  // The current on-the-fly SSA update requires blocks to be processed in
521  // reverse postorder so that LastValueMap contains the correct value at each
522  // exit.
523  LoopBlocksDFS DFS(L);
524  DFS.perform(LI);
525 
526  // Stash the DFS iterators before adding blocks to the loop.
527  LoopBlocksDFS::RPOIterator BlockBegin = DFS.beginRPO();
528  LoopBlocksDFS::RPOIterator BlockEnd = DFS.endRPO();
529 
530  std::vector<BasicBlock*> UnrolledLoopBlocks = L->getBlocks();
531 
532  // Loop Unrolling might create new loops. While we do preserve LoopInfo, we
533  // might break loop-simplified form for these loops (as they, e.g., would
534  // share the same exit blocks). We'll keep track of loops for which we can
535  // break this so that later we can re-simplify them.
536  SmallSetVector<Loop *, 4> LoopsToSimplify;
537  for (Loop *SubLoop : *L)
538  LoopsToSimplify.insert(SubLoop);
539 
540  if (Header->getParent()->isDebugInfoForProfiling())
541  for (BasicBlock *BB : L->getBlocks())
542  for (Instruction &I : *BB)
543  if (const DILocation *DIL = I.getDebugLoc())
544  I.setDebugLoc(DIL->cloneWithDuplicationFactor(Count));
545 
546  for (unsigned It = 1; It != Count; ++It) {
547  std::vector<BasicBlock*> NewBlocks;
549  NewLoops[L] = L;
550 
551  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
552  ValueToValueMapTy VMap;
553  BasicBlock *New = CloneBasicBlock(*BB, VMap, "." + Twine(It));
554  Header->getParent()->getBasicBlockList().push_back(New);
555 
556  assert((*BB != Header || LI->getLoopFor(*BB) == L) &&
557  "Header should not be in a sub-loop");
558  // Tell LI about New.
559  const Loop *OldLoop = addClonedBlockToLoopInfo(*BB, New, LI, NewLoops);
560  if (OldLoop) {
561  LoopsToSimplify.insert(NewLoops[OldLoop]);
562 
563  // Forget the old loop, since its inputs may have changed.
564  if (SE)
565  SE->forgetLoop(OldLoop);
566  }
567 
568  if (*BB == Header)
569  // Loop over all of the PHI nodes in the block, changing them to use
570  // the incoming values from the previous block.
571  for (PHINode *OrigPHI : OrigPHINode) {
572  PHINode *NewPHI = cast<PHINode>(VMap[OrigPHI]);
573  Value *InVal = NewPHI->getIncomingValueForBlock(LatchBlock);
574  if (Instruction *InValI = dyn_cast<Instruction>(InVal))
575  if (It > 1 && L->contains(InValI))
576  InVal = LastValueMap[InValI];
577  VMap[OrigPHI] = InVal;
578  New->getInstList().erase(NewPHI);
579  }
580 
581  // Update our running map of newest clones
582  LastValueMap[*BB] = New;
583  for (ValueToValueMapTy::iterator VI = VMap.begin(), VE = VMap.end();
584  VI != VE; ++VI)
585  LastValueMap[VI->first] = VI->second;
586 
587  // Add phi entries for newly created values to all exit blocks.
588  for (BasicBlock *Succ : successors(*BB)) {
589  if (L->contains(Succ))
590  continue;
591  for (BasicBlock::iterator BBI = Succ->begin();
592  PHINode *phi = dyn_cast<PHINode>(BBI); ++BBI) {
593  Value *Incoming = phi->getIncomingValueForBlock(*BB);
594  ValueToValueMapTy::iterator It = LastValueMap.find(Incoming);
595  if (It != LastValueMap.end())
596  Incoming = It->second;
597  phi->addIncoming(Incoming, New);
598  }
599  }
600  // Keep track of new headers and latches as we create them, so that
601  // we can insert the proper branches later.
602  if (*BB == Header)
603  Headers.push_back(New);
604  if (*BB == LatchBlock)
605  Latches.push_back(New);
606 
607  NewBlocks.push_back(New);
608  UnrolledLoopBlocks.push_back(New);
609 
610  // Update DomTree: since we just copy the loop body, and each copy has a
611  // dedicated entry block (copy of the header block), this header's copy
612  // dominates all copied blocks. That means, dominance relations in the
613  // copied body are the same as in the original body.
614  if (DT) {
615  if (*BB == Header)
616  DT->addNewBlock(New, Latches[It - 1]);
617  else {
618  auto BBDomNode = DT->getNode(*BB);
619  auto BBIDom = BBDomNode->getIDom();
620  BasicBlock *OriginalBBIDom = BBIDom->getBlock();
621  DT->addNewBlock(
622  New, cast<BasicBlock>(LastValueMap[cast<Value>(OriginalBBIDom)]));
623  }
624  }
625  }
626 
627  // Remap all instructions in the most recent iteration
628  for (BasicBlock *NewBlock : NewBlocks) {
629  for (Instruction &I : *NewBlock) {
630  ::remapInstruction(&I, LastValueMap);
631  if (auto *II = dyn_cast<IntrinsicInst>(&I))
632  if (II->getIntrinsicID() == Intrinsic::assume)
633  AC->registerAssumption(II);
634  }
635  }
636  }
637 
638  // Loop over the PHI nodes in the original block, setting incoming values.
639  for (PHINode *PN : OrigPHINode) {
640  if (CompletelyUnroll) {
641  PN->replaceAllUsesWith(PN->getIncomingValueForBlock(Preheader));
642  Header->getInstList().erase(PN);
643  }
644  else if (Count > 1) {
645  Value *InVal = PN->removeIncomingValue(LatchBlock, false);
646  // If this value was defined in the loop, take the value defined by the
647  // last iteration of the loop.
648  if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
649  if (L->contains(InValI))
650  InVal = LastValueMap[InVal];
651  }
652  assert(Latches.back() == LastValueMap[LatchBlock] && "bad last latch");
653  PN->addIncoming(InVal, Latches.back());
654  }
655  }
656 
657  // Now that all the basic blocks for the unrolled iterations are in place,
658  // set up the branches to connect them.
659  for (unsigned i = 0, e = Latches.size(); i != e; ++i) {
660  // The original branch was replicated in each unrolled iteration.
661  BranchInst *Term = cast<BranchInst>(Latches[i]->getTerminator());
662 
663  // The branch destination.
664  unsigned j = (i + 1) % e;
665  BasicBlock *Dest = Headers[j];
666  bool NeedConditional = true;
667 
668  if (RuntimeTripCount && j != 0) {
669  NeedConditional = false;
670  }
671 
672  // For a complete unroll, make the last iteration end with a branch
673  // to the exit block.
674  if (CompletelyUnroll) {
675  if (j == 0)
676  Dest = LoopExit;
677  // If using trip count upper bound to completely unroll, we need to keep
678  // the conditional branch except the last one because the loop may exit
679  // after any iteration.
680  assert(NeedConditional &&
681  "NeedCondition cannot be modified by both complete "
682  "unrolling and runtime unrolling");
683  NeedConditional = (PreserveCondBr && j && !(PreserveOnlyFirst && i != 0));
684  } else if (j != BreakoutTrip && (TripMultiple == 0 || j % TripMultiple != 0)) {
685  // If we know the trip count or a multiple of it, we can safely use an
686  // unconditional branch for some iterations.
687  NeedConditional = false;
688  }
689 
690  if (NeedConditional) {
691  // Update the conditional branch's successor for the following
692  // iteration.
693  Term->setSuccessor(!ContinueOnTrue, Dest);
694  } else {
695  // Remove phi operands at this loop exit
696  if (Dest != LoopExit) {
697  BasicBlock *BB = Latches[i];
698  for (BasicBlock *Succ: successors(BB)) {
699  if (Succ == Headers[i])
700  continue;
701  for (BasicBlock::iterator BBI = Succ->begin();
702  PHINode *Phi = dyn_cast<PHINode>(BBI); ++BBI) {
703  Phi->removeIncomingValue(BB, false);
704  }
705  }
706  }
707  // Replace the conditional branch with an unconditional one.
708  BranchInst::Create(Dest, Term);
709  Term->eraseFromParent();
710  }
711  }
712 
713  // Update dominators of blocks we might reach through exits.
714  // Immediate dominator of such block might change, because we add more
715  // routes which can lead to the exit: we can now reach it from the copied
716  // iterations too.
717  if (DT && Count > 1) {
718  for (auto *BB : OriginalLoopBlocks) {
719  auto *BBDomNode = DT->getNode(BB);
720  SmallVector<BasicBlock *, 16> ChildrenToUpdate;
721  for (auto *ChildDomNode : BBDomNode->getChildren()) {
722  auto *ChildBB = ChildDomNode->getBlock();
723  if (!L->contains(ChildBB))
724  ChildrenToUpdate.push_back(ChildBB);
725  }
726  BasicBlock *NewIDom;
727  if (BB == LatchBlock) {
728  // The latch is special because we emit unconditional branches in
729  // some cases where the original loop contained a conditional branch.
730  // Since the latch is always at the bottom of the loop, if the latch
731  // dominated an exit before unrolling, the new dominator of that exit
732  // must also be a latch. Specifically, the dominator is the first
733  // latch which ends in a conditional branch, or the last latch if
734  // there is no such latch.
735  NewIDom = Latches.back();
736  for (BasicBlock *IterLatch : Latches) {
737  TerminatorInst *Term = IterLatch->getTerminator();
738  if (isa<BranchInst>(Term) && cast<BranchInst>(Term)->isConditional()) {
739  NewIDom = IterLatch;
740  break;
741  }
742  }
743  } else {
744  // The new idom of the block will be the nearest common dominator
745  // of all copies of the previous idom. This is equivalent to the
746  // nearest common dominator of the previous idom and the first latch,
747  // which dominates all copies of the previous idom.
748  NewIDom = DT->findNearestCommonDominator(BB, LatchBlock);
749  }
750  for (auto *ChildBB : ChildrenToUpdate)
751  DT->changeImmediateDominator(ChildBB, NewIDom);
752  }
753  }
754 
755  if (DT && UnrollVerifyDomtree)
756  DT->verifyDomTree();
757 
758  // Merge adjacent basic blocks, if possible.
759  SmallPtrSet<Loop *, 4> ForgottenLoops;
760  for (BasicBlock *Latch : Latches) {
761  BranchInst *Term = cast<BranchInst>(Latch->getTerminator());
762  if (Term->isUnconditional()) {
763  BasicBlock *Dest = Term->getSuccessor(0);
764  if (BasicBlock *Fold =
765  foldBlockIntoPredecessor(Dest, LI, SE, ForgottenLoops, DT)) {
766  // Dest has been folded into Fold. Update our worklists accordingly.
767  std::replace(Latches.begin(), Latches.end(), Dest, Fold);
768  UnrolledLoopBlocks.erase(std::remove(UnrolledLoopBlocks.begin(),
769  UnrolledLoopBlocks.end(), Dest),
770  UnrolledLoopBlocks.end());
771  }
772  }
773  }
774 
775  // Simplify any new induction variables in the partially unrolled loop.
776  if (SE && !CompletelyUnroll && Count > 1) {
778  simplifyLoopIVs(L, SE, DT, LI, DeadInsts);
779 
780  // Aggressively clean up dead instructions that simplifyLoopIVs already
781  // identified. Any remaining should be cleaned up below.
782  while (!DeadInsts.empty())
783  if (Instruction *Inst =
784  dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val()))
786  }
787 
788  // At this point, the code is well formed. We now do a quick sweep over the
789  // inserted code, doing constant propagation and dead code elimination as we
790  // go.
791  const DataLayout &DL = Header->getModule()->getDataLayout();
792  const std::vector<BasicBlock*> &NewLoopBlocks = L->getBlocks();
793  for (BasicBlock *BB : NewLoopBlocks) {
794  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
795  Instruction *Inst = &*I++;
796 
797  if (Value *V = SimplifyInstruction(Inst, {DL, nullptr, DT, AC}))
798  if (LI->replacementPreservesLCSSAForm(Inst, V))
799  Inst->replaceAllUsesWith(V);
800  if (isInstructionTriviallyDead(Inst))
801  BB->getInstList().erase(Inst);
802  }
803  }
804 
805  // TODO: after peeling or unrolling, previously loop variant conditions are
806  // likely to fold to constants, eagerly propagating those here will require
807  // fewer cleanup passes to be run. Alternatively, a LoopEarlyCSE might be
808  // appropriate.
809 
810  NumCompletelyUnrolled += CompletelyUnroll;
811  ++NumUnrolled;
812 
813  Loop *OuterL = L->getParentLoop();
814  // Update LoopInfo if the loop is completely removed.
815  if (CompletelyUnroll)
816  LI->erase(L);
817 
818  // After complete unrolling most of the blocks should be contained in OuterL.
819  // However, some of them might happen to be out of OuterL (e.g. if they
820  // precede a loop exit). In this case we might need to insert PHI nodes in
821  // order to preserve LCSSA form.
822  // We don't need to check this if we already know that we need to fix LCSSA
823  // form.
824  // TODO: For now we just recompute LCSSA for the outer loop in this case, but
825  // it should be possible to fix it in-place.
826  if (PreserveLCSSA && OuterL && CompletelyUnroll && !NeedToFixLCSSA)
827  NeedToFixLCSSA |= ::needToInsertPhisForLCSSA(OuterL, UnrolledLoopBlocks, LI);
828 
829  // If we have a pass and a DominatorTree we should re-simplify impacted loops
830  // to ensure subsequent analyses can rely on this form. We want to simplify
831  // at least one layer outside of the loop that was unrolled so that any
832  // changes to the parent loop exposed by the unrolling are considered.
833  if (DT) {
834  if (OuterL) {
835  // OuterL includes all loops for which we can break loop-simplify, so
836  // it's sufficient to simplify only it (it'll recursively simplify inner
837  // loops too).
838  if (NeedToFixLCSSA) {
839  // LCSSA must be performed on the outermost affected loop. The unrolled
840  // loop's last loop latch is guaranteed to be in the outermost loop
841  // after LoopInfo's been updated by LoopInfo::erase.
842  Loop *LatchLoop = LI->getLoopFor(Latches.back());
843  Loop *FixLCSSALoop = OuterL;
844  if (!FixLCSSALoop->contains(LatchLoop))
845  while (FixLCSSALoop->getParentLoop() != LatchLoop)
846  FixLCSSALoop = FixLCSSALoop->getParentLoop();
847 
848  formLCSSARecursively(*FixLCSSALoop, *DT, LI, SE);
849  } else if (PreserveLCSSA) {
850  assert(OuterL->isLCSSAForm(*DT) &&
851  "Loops should be in LCSSA form after loop-unroll.");
852  }
853 
854  // TODO: That potentially might be compile-time expensive. We should try
855  // to fix the loop-simplified form incrementally.
856  simplifyLoop(OuterL, DT, LI, SE, AC, PreserveLCSSA);
857  } else {
858  // Simplify loops for which we might've broken loop-simplify form.
859  for (Loop *SubLoop : LoopsToSimplify)
860  simplifyLoop(SubLoop, DT, LI, SE, AC, PreserveLCSSA);
861  }
862  }
863 
864  return CompletelyUnroll ? LoopUnrollStatus::FullyUnrolled
866 }
867 
868 /// Given an llvm.loop loop id metadata node, returns the loop hint metadata
869 /// node with the given name (for example, "llvm.loop.unroll.count"). If no
870 /// such metadata node exists, then nullptr is returned.
872  // First operand should refer to the loop id itself.
873  assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
874  assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
875 
876  for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
877  MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
878  if (!MD)
879  continue;
880 
881  MDString *S = dyn_cast<MDString>(MD->getOperand(0));
882  if (!S)
883  continue;
884 
885  if (Name.equals(S->getString()))
886  return MD;
887  }
888  return nullptr;
889 }
DomTreeNodeBase< NodeT > * getNode(NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
unsigned getSmallConstantTripCount(const Loop *L)
Returns the maximum trip count of the loop if it is a single-exit loop and we can compute a small max...
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:109
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:157
unsigned getSmallConstantTripMultiple(const Loop *L)
Returns the largest constant divisor of the trip count of the loop if it is a single-exit loop and we...
DiagnosticInfoOptimizationBase::Argument NV
uint64_t GreatestCommonDivisor64(uint64_t A, uint64_t B)
Return the greatest common divisor of the values using Euclid&#39;s algorithm.
Definition: MathExtras.h:555
iterator erase(iterator where)
Definition: ilist.h:280
static void remapInstruction(Instruction *I, ValueToValueMapTy &VMap)
Convert the instruction operands from referencing the current values into those specified by VMap...
Definition: LoopUnroll.cpp:67
static bool needToInsertPhisForLCSSA(Loop *L, std::vector< BasicBlock *> Blocks, LoopInfo *LI)
Check if unrolling created a situation where we need to insert phi nodes to preserve LCSSA form...
Definition: LoopUnroll.cpp:166
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
std::error_code remove(const Twine &path, bool IgnoreNonExisting=true)
Remove path.
bool isLCSSAForm(DominatorTree &DT) const
Return true if the Loop is in LCSSA form.
Definition: LoopInfo.cpp:175
The main scalar evolution driver.
static cl::opt< bool > UnrollVerifyDomtree("unroll-verify-domtree", cl::Hidden, cl::desc("Verify domtree after unrolling"), cl::init(true))
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:106
A cache of .assume calls within a function.
NodeT * findNearestCommonDominator(NodeT *A, NodeT *B) const
findNearestCommonDominator - Find nearest common dominator basic block for basic block A and B...
LoopUnrollStatus
Represents the result of a UnrollLoop invocation.
Definition: UnrollLoop.h:43
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
Metadata node.
Definition: Metadata.h:862
const MDOperand & getOperand(unsigned I) const
Definition: Metadata.h:1067
#define op(i)
void eraseNode(NodeT *BB)
eraseNode - Removes a node from the dominator tree.
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:336
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
static cl::opt< bool > UnrollRuntimeEpilog("unroll-runtime-epilog", cl::init(false), cl::Hidden, cl::desc("Allow runtime unrolled loops to be unrolled " "with epilog instead of prolog."))
bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put a loop nest into LCSSA form.
Definition: LCSSA.cpp:332
The loop was not modified.
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr it the function does no...
Definition: BasicBlock.cpp:116
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:631
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
void erase(Loop *L)
Update LoopInfo after removing the last backedge from a loop.
Definition: LoopInfo.cpp:621
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:284
RPOIterator endRPO() const
Definition: LoopIterator.h:141
BlockT * getHeader() const
Definition: LoopInfo.h:107
void getExitBlocks(SmallVectorImpl< BlockT *> &ExitBlocks) const
Return all of the successor blocks of this loop.
Definition: LoopInfoImpl.h:63
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:142
void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase< BlockT, LoopT > &LI)
This method is used by other analyses to update loop information.
Definition: LoopInfoImpl.h:183
bool simplifyLoopIVs(Loop *L, ScalarEvolution *SE, DominatorTree *DT, LoopInfo *LI, SmallVectorImpl< WeakTrackingVH > &Dead)
SimplifyLoopIVs - Simplify users of induction variables within this loop.
void addTopLevelLoop(LoopT *New)
This adds the specified loop to the collection of top-level loops.
Definition: LoopInfo.h:682
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:133
iterator find(const KeyT &Val)
Definition: ValueMap.h:158
static bool isEpilogProfitable(Loop *L)
The function chooses which type of unroll (epilog or prolog) is more profitabale. ...
Definition: LoopUnroll.cpp:244
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:428
Debug location.
void perform(LoopInfo *LI)
Traverse the loop blocks and store the DFS result.
Definition: LoopInfo.cpp:764
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:140
Value * getOperand(unsigned i) const
Definition: User.h:154
StringRef getString() const
Definition: Metadata.cpp:456
bool isDebugInfoForProfiling() const
Returns true if we should emit debug info for profiling.
Definition: Metadata.cpp:1502
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:406
LoopUnrollStatus UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime, bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst, unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, OptimizationRemarkEmitter *ORE, bool PreserveLCSSA)
Unroll the given loop by Count.
Definition: LoopUnroll.cpp:294
void verifyDomTree() const
Verify the correctness of the domtree by re-computing it.
Definition: Dominators.cpp:305
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:54
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:217
bool hasName() const
Definition: Value.h:251
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The loop was fully unrolled into straight-line code.
Conditional or Unconditional Branch instruction.
void changeImmediateDominator(DomTreeNodeBase< NodeT > *N, DomTreeNodeBase< NodeT > *NewIDom)
changeImmediateDominator - This method is used to update the dominator tree information when a node&#39;s...
DomTreeNodeBase * getIDom() const
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
Value * getIncomingValueForBlock(const BasicBlock *BB) const
bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA)
Peel off the first PeelCount iterations of loop L.
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:363
const std::vector< BlockT * > & getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:156
Diagnostic information for applied optimization remarks.
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:342
bool any_of(R &&Range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:823
const Instruction & back() const
Definition: BasicBlock.h:266
std::vector< BasicBlock * >::const_reverse_iterator RPOIterator
Definition: LoopIterator.h:102
static BasicBlock * foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI, ScalarEvolution *SE, SmallPtrSetImpl< Loop *> &ForgottenLoops, DominatorTree *DT)
Folds a basic block into its predecessor if it only has one predecessor, and that predecessor only ha...
Definition: LoopUnroll.cpp:94
bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, bool AllowExpensiveTripCount, bool UseEpilogRemainder, bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, OptimizationRemarkEmitter *ORE, bool PreserveLCSSA)
Insert code in the prolog/epilog code when unrolling a loop with a run-time trip-count.
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, const TargetLibraryInfo *TLI=nullptr)
If the specified value is a trivially dead instruction, delete it.
Definition: Local.cpp:370
DebugLoc getStartLoc() const
Return the debug location of the start of this loop.
Definition: LoopInfo.cpp:312
void setSuccessor(unsigned idx, BasicBlock *NewSucc)
iterator end()
Definition: ValueMap.h:138
bool hasAddressTaken() const
Returns true if there are any uses of this basic block other than direct branches, switches, etc.
Definition: BasicBlock.h:376
const InstListType & getInstList() const
Return the underlying instruction list container.
Definition: BasicBlock.h:317
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:117
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:298
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:176
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:410
void emit(DiagnosticInfoOptimizationBase &OptDiag)
Output the remark via the diagnostic handler and to the optimization record file. ...
iterator end()
Definition: BasicBlock.h:254
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:385
static BranchInst * Create(BasicBlock *IfTrue, Instruction *InsertBefore=nullptr)
void setOperand(unsigned i, Value *Val)
Definition: User.h:159
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
The loop was partially unrolled – we still have a loop, but with a smaller trip count.
const Loop * addClonedBlockToLoopInfo(BasicBlock *OriginalBB, BasicBlock *ClonedBB, LoopInfo *LI, NewLoopsMap &NewLoops)
Adds ClonedBB to LoopInfo, creates a new loop for ClonedBB if necessary and adds a mapping from the o...
Definition: LoopUnroll.cpp:190
Store the result of a depth first search within basic blocks contained by a single loop...
Definition: LoopIterator.h:98
void push_back(pointer val)
Definition: ilist.h:326
BasicBlock * CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, const Twine &NameSuffix="", Function *F=nullptr, ClonedCodeInfo *CodeInfo=nullptr, DebugInfoFinder *DIFinder=nullptr)
CloneBasicBlock - Return a copy of the specified basic block, but without embedding the block into a ...
static void DFS(BasicBlock *Root, SetVector< BasicBlock *> &Set)
#define NDEBUG
Definition: regutils.h:48
void FoldSingleEntryPHINodes(BasicBlock *BB, MemoryDependenceResults *MemDep=nullptr)
We know that BB has one predecessor.
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool equals(StringRef RHS) const
equals - Check for string equality, this is more efficient than compare() when the relative ordering ...
Definition: StringRef.h:169
MDNode * GetUnrollMetadata(MDNode *LoopID, StringRef Name)
Given an llvm.loop loop id metadata node, returns the loop hint metadata node with the given name (fo...
Definition: LoopUnroll.cpp:871
LoopT * getParentLoop() const
Definition: LoopInfo.h:108
void registerAssumption(CallInst *CI)
Add an .assume intrinsic to this function&#39;s cache.
void forgetLoop(const Loop *L)
This method should be called by the client when it has changed a loop in a way that may effect Scalar...
void addChildLoop(LoopT *NewChild)
Add the specified loop to be a child of this loop.
Definition: LoopInfo.h:294
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:404
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:218
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:108
SymbolTableList< BasicBlock >::iterator eraseFromParent()
Unlink &#39;this&#39; from the containing function and delete it.
Definition: BasicBlock.cpp:97
#define I(x, y, z)
Definition: MD5.cpp:58
DomTreeNodeBase< NodeT > * addNewBlock(NodeT *BB, NodeT *DomBB)
Add a new node to the dominator tree information.
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:565
bool isSafeToClone() const
Return true if the loop body is safe to clone in practice.
Definition: LoopInfo.cpp:198
bool isUnconditional() const
ValueT lookup(const_arg_type_t< KeyT > Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: DenseMap.h:181
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
unsigned getNumSuccessors() const
Return the number of successors that this terminator has.
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction is not used, and the instruction has no side ef...
Definition: Local.cpp:293
LLVM Value Representation.
Definition: Value.h:73
succ_range successors(BasicBlock *BB)
Definition: CFG.h:143
RPOIterator beginRPO() const
Reverse iterate over the cached postorder blocks.
Definition: LoopIterator.h:137
#define DEBUG_TYPE
Definition: LoopUnroll.cpp:44
#define DEBUG(X)
Definition: Debug.h:118
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
static Expected< std::string > replace(StringRef S, StringRef From, StringRef To)
A single uniqued string.
Definition: Metadata.h:602
bool replacementPreservesLCSSAForm(Instruction *From, Value *To)
Returns true if replacing From with To everywhere is guaranteed to preserve LCSSA form...
Definition: LoopInfo.h:758
const TerminatorInst * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:120
void pop_back()
Definition: ilist.h:331
unsigned getNumOperands() const
Return number of MDNode operands.
Definition: Metadata.h:1073
for(unsigned i=Desc.getNumOperands(), e=OldMI.getNumOperands();i !=e;++i)
iterator_range< block_iterator > blocks() const
Definition: LoopInfo.h:163
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
BlockT * getExitingBlock() const
If getExitingBlocks would return exactly one block, return that block.
Definition: LoopInfoImpl.h:50
The optimization diagnostic interface.
void removeBlock(BlockT *BB)
This method completely removes BB from all data structures, including all of the Loop objects it is n...
Definition: LoopInfo.h:690
iterator begin()
Definition: ValueMap.h:137