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. Returns true
259 /// if unrolling was successful, or false if the loop was unmodified. Unrolling
260 /// can only fail when the loop's latch block is not terminated by a conditional
261 /// branch instruction. However, if the trip count (and multiple) are not known,
262 /// loop unrolling will mostly produce more code that is no faster.
263 ///
264 /// TripCount is the upper bound of the iteration on which control exits
265 /// LatchBlock. Control may exit the loop prior to TripCount iterations either
266 /// via an early branch in other loop block or via LatchBlock terminator. This
267 /// is relaxed from the general definition of trip count which is the number of
268 /// times the loop header executes. Note that UnrollLoop assumes that the loop
269 /// counter test is in LatchBlock in order to remove unnecesssary instances of
270 /// the test. If control can exit the loop from the LatchBlock's terminator
271 /// prior to TripCount iterations, flag PreserveCondBr needs to be set.
272 ///
273 /// PreserveCondBr indicates whether the conditional branch of the LatchBlock
274 /// needs to be preserved. It is needed when we use trip count upper bound to
275 /// fully unroll the loop. If PreserveOnlyFirst is also set then only the first
276 /// conditional branch needs to be preserved.
277 ///
278 /// Similarly, TripMultiple divides the number of times that the LatchBlock may
279 /// execute without exiting the loop.
280 ///
281 /// If AllowRuntime is true then UnrollLoop will consider unrolling loops that
282 /// have a runtime (i.e. not compile time constant) trip count. Unrolling these
283 /// loops require a unroll "prologue" that runs "RuntimeTripCount % Count"
284 /// iterations before branching into the unrolled loop. UnrollLoop will not
285 /// runtime-unroll the loop if computing RuntimeTripCount will be expensive and
286 /// AllowExpensiveTripCount is false.
287 ///
288 /// If we want to perform PGO-based loop peeling, PeelCount is set to the
289 /// number of iterations we want to peel off.
290 ///
291 /// The LoopInfo Analysis that is passed will be kept consistent.
292 ///
293 /// This utility preserves LoopInfo. It will also preserve ScalarEvolution and
294 /// DominatorTree if they are non-null.
295 bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
296  bool AllowRuntime, bool AllowExpensiveTripCount,
297  bool PreserveCondBr, bool PreserveOnlyFirst,
298  unsigned TripMultiple, unsigned PeelCount, LoopInfo *LI,
301  bool PreserveLCSSA) {
302 
303  BasicBlock *Preheader = L->getLoopPreheader();
304  if (!Preheader) {
305  DEBUG(dbgs() << " Can't unroll; loop preheader-insertion failed.\n");
306  return false;
307  }
308 
309  BasicBlock *LatchBlock = L->getLoopLatch();
310  if (!LatchBlock) {
311  DEBUG(dbgs() << " Can't unroll; loop exit-block-insertion failed.\n");
312  return false;
313  }
314 
315  // Loops with indirectbr cannot be cloned.
316  if (!L->isSafeToClone()) {
317  DEBUG(dbgs() << " Can't unroll; Loop body cannot be cloned.\n");
318  return false;
319  }
320 
321  // The current loop unroll pass can only unroll loops with a single latch
322  // that's a conditional branch exiting the loop.
323  // FIXME: The implementation can be extended to work with more complicated
324  // cases, e.g. loops with multiple latches.
325  BasicBlock *Header = L->getHeader();
326  BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator());
327 
328  if (!BI || BI->isUnconditional()) {
329  // The loop-rotate pass can be helpful to avoid this in many cases.
330  DEBUG(dbgs() <<
331  " Can't unroll; loop not terminated by a conditional branch.\n");
332  return false;
333  }
334 
335  auto CheckSuccessors = [&](unsigned S1, unsigned S2) {
336  return BI->getSuccessor(S1) == Header && !L->contains(BI->getSuccessor(S2));
337  };
338 
339  if (!CheckSuccessors(0, 1) && !CheckSuccessors(1, 0)) {
340  DEBUG(dbgs() << "Can't unroll; only loops with one conditional latch"
341  " exiting the loop can be unrolled\n");
342  return false;
343  }
344 
345  if (Header->hasAddressTaken()) {
346  // The loop-rotate pass can be helpful to avoid this in many cases.
347  DEBUG(dbgs() <<
348  " Won't unroll loop: address of header block is taken.\n");
349  return false;
350  }
351 
352  if (TripCount != 0)
353  DEBUG(dbgs() << " Trip Count = " << TripCount << "\n");
354  if (TripMultiple != 1)
355  DEBUG(dbgs() << " Trip Multiple = " << TripMultiple << "\n");
356 
357  // Effectively "DCE" unrolled iterations that are beyond the tripcount
358  // and will never be executed.
359  if (TripCount != 0 && Count > TripCount)
360  Count = TripCount;
361 
362  // Don't enter the unroll code if there is nothing to do.
363  if (TripCount == 0 && Count < 2 && PeelCount == 0) {
364  DEBUG(dbgs() << "Won't unroll; almost nothing to do\n");
365  return false;
366  }
367 
368  assert(Count > 0);
369  assert(TripMultiple > 0);
370  assert(TripCount == 0 || TripCount % TripMultiple == 0);
371 
372  // Are we eliminating the loop control altogether?
373  bool CompletelyUnroll = Count == TripCount;
374  SmallVector<BasicBlock *, 4> ExitBlocks;
375  L->getExitBlocks(ExitBlocks);
376  std::vector<BasicBlock*> OriginalLoopBlocks = L->getBlocks();
377 
378  // Go through all exits of L and see if there are any phi-nodes there. We just
379  // conservatively assume that they're inserted to preserve LCSSA form, which
380  // means that complete unrolling might break this form. We need to either fix
381  // it in-place after the transformation, or entirely rebuild LCSSA. TODO: For
382  // now we just recompute LCSSA for the outer loop, but it should be possible
383  // to fix it in-place.
384  bool NeedToFixLCSSA = PreserveLCSSA && CompletelyUnroll &&
385  any_of(ExitBlocks, [](const BasicBlock *BB) {
386  return isa<PHINode>(BB->begin());
387  });
388 
389  // We assume a run-time trip count if the compiler cannot
390  // figure out the loop trip count and the unroll-runtime
391  // flag is specified.
392  bool RuntimeTripCount = (TripCount == 0 && Count > 0 && AllowRuntime);
393 
394  assert((!RuntimeTripCount || !PeelCount) &&
395  "Did not expect runtime trip-count unrolling "
396  "and peeling for the same loop");
397 
398  if (PeelCount)
399  peelLoop(L, PeelCount, LI, SE, DT, AC, PreserveLCSSA);
400 
401  // Loops containing convergent instructions must have a count that divides
402  // their TripMultiple.
403  DEBUG(
404  {
405  bool HasConvergent = false;
406  for (auto &BB : L->blocks())
407  for (auto &I : *BB)
408  if (auto CS = CallSite(&I))
409  HasConvergent |= CS.isConvergent();
410  assert((!HasConvergent || TripMultiple % Count == 0) &&
411  "Unroll count must divide trip multiple if loop contains a "
412  "convergent operation.");
413  });
414 
415  bool EpilogProfitability =
416  UnrollRuntimeEpilog.getNumOccurrences() ? UnrollRuntimeEpilog
417  : isEpilogProfitable(L);
418 
419  if (RuntimeTripCount && TripMultiple % Count != 0 &&
420  !UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
421  EpilogProfitability, LI, SE, DT,
422  PreserveLCSSA)) {
423  if (Force)
424  RuntimeTripCount = false;
425  else {
426  DEBUG(
427  dbgs() << "Wont unroll; remainder loop could not be generated"
428  "when assuming runtime trip count\n");
429  return false;
430  }
431  }
432 
433  // Notify ScalarEvolution that the loop will be substantially changed,
434  // if not outright eliminated.
435  if (SE)
436  SE->forgetLoop(L);
437 
438  // If we know the trip count, we know the multiple...
439  unsigned BreakoutTrip = 0;
440  if (TripCount != 0) {
441  BreakoutTrip = TripCount % Count;
442  TripMultiple = 0;
443  } else {
444  // Figure out what multiple to use.
445  BreakoutTrip = TripMultiple =
446  (unsigned)GreatestCommonDivisor64(Count, TripMultiple);
447  }
448 
449  using namespace ore;
450  // Report the unrolling decision.
451  if (CompletelyUnroll) {
452  DEBUG(dbgs() << "COMPLETELY UNROLLING loop %" << Header->getName()
453  << " with trip count " << TripCount << "!\n");
454  ORE->emit(OptimizationRemark(DEBUG_TYPE, "FullyUnrolled", L->getStartLoc(),
455  L->getHeader())
456  << "completely unrolled loop with "
457  << NV("UnrollCount", TripCount) << " iterations");
458  } else if (PeelCount) {
459  DEBUG(dbgs() << "PEELING loop %" << Header->getName()
460  << " with iteration count " << PeelCount << "!\n");
461  ORE->emit(OptimizationRemark(DEBUG_TYPE, "Peeled", L->getStartLoc(),
462  L->getHeader())
463  << " peeled loop by " << NV("PeelCount", PeelCount)
464  << " iterations");
465  } else {
466  OptimizationRemark Diag(DEBUG_TYPE, "PartialUnrolled", L->getStartLoc(),
467  L->getHeader());
468  Diag << "unrolled loop by a factor of " << NV("UnrollCount", Count);
469 
470  DEBUG(dbgs() << "UNROLLING loop %" << Header->getName()
471  << " by " << Count);
472  if (TripMultiple == 0 || BreakoutTrip != TripMultiple) {
473  DEBUG(dbgs() << " with a breakout at trip " << BreakoutTrip);
474  ORE->emit(Diag << " with a breakout at trip "
475  << NV("BreakoutTrip", BreakoutTrip));
476  } else if (TripMultiple != 1) {
477  DEBUG(dbgs() << " with " << TripMultiple << " trips per branch");
478  ORE->emit(Diag << " with " << NV("TripMultiple", TripMultiple)
479  << " trips per branch");
480  } else if (RuntimeTripCount) {
481  DEBUG(dbgs() << " with run-time trip count");
482  ORE->emit(Diag << " with run-time trip count");
483  }
484  DEBUG(dbgs() << "!\n");
485  }
486 
487  bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
488  BasicBlock *LoopExit = BI->getSuccessor(ContinueOnTrue);
489 
490  // For the first iteration of the loop, we should use the precloned values for
491  // PHI nodes. Insert associations now.
492  ValueToValueMapTy LastValueMap;
493  std::vector<PHINode*> OrigPHINode;
494  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
495  OrigPHINode.push_back(cast<PHINode>(I));
496  }
497 
498  std::vector<BasicBlock*> Headers;
499  std::vector<BasicBlock*> Latches;
500  Headers.push_back(Header);
501  Latches.push_back(LatchBlock);
502 
503  // The current on-the-fly SSA update requires blocks to be processed in
504  // reverse postorder so that LastValueMap contains the correct value at each
505  // exit.
506  LoopBlocksDFS DFS(L);
507  DFS.perform(LI);
508 
509  // Stash the DFS iterators before adding blocks to the loop.
510  LoopBlocksDFS::RPOIterator BlockBegin = DFS.beginRPO();
511  LoopBlocksDFS::RPOIterator BlockEnd = DFS.endRPO();
512 
513  std::vector<BasicBlock*> UnrolledLoopBlocks = L->getBlocks();
514 
515  // Loop Unrolling might create new loops. While we do preserve LoopInfo, we
516  // might break loop-simplified form for these loops (as they, e.g., would
517  // share the same exit blocks). We'll keep track of loops for which we can
518  // break this so that later we can re-simplify them.
519  SmallSetVector<Loop *, 4> LoopsToSimplify;
520  for (Loop *SubLoop : *L)
521  LoopsToSimplify.insert(SubLoop);
522 
523  if (Header->getParent()->isDebugInfoForProfiling())
524  for (BasicBlock *BB : L->getBlocks())
525  for (Instruction &I : *BB)
526  if (const DILocation *DIL = I.getDebugLoc())
527  I.setDebugLoc(DIL->cloneWithDuplicationFactor(Count));
528 
529  for (unsigned It = 1; It != Count; ++It) {
530  std::vector<BasicBlock*> NewBlocks;
532  NewLoops[L] = L;
533 
534  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
535  ValueToValueMapTy VMap;
536  BasicBlock *New = CloneBasicBlock(*BB, VMap, "." + Twine(It));
537  Header->getParent()->getBasicBlockList().push_back(New);
538 
539  assert((*BB != Header || LI->getLoopFor(*BB) == L) &&
540  "Header should not be in a sub-loop");
541  // Tell LI about New.
542  const Loop *OldLoop = addClonedBlockToLoopInfo(*BB, New, LI, NewLoops);
543  if (OldLoop) {
544  LoopsToSimplify.insert(NewLoops[OldLoop]);
545 
546  // Forget the old loop, since its inputs may have changed.
547  if (SE)
548  SE->forgetLoop(OldLoop);
549  }
550 
551  if (*BB == Header)
552  // Loop over all of the PHI nodes in the block, changing them to use
553  // the incoming values from the previous block.
554  for (PHINode *OrigPHI : OrigPHINode) {
555  PHINode *NewPHI = cast<PHINode>(VMap[OrigPHI]);
556  Value *InVal = NewPHI->getIncomingValueForBlock(LatchBlock);
557  if (Instruction *InValI = dyn_cast<Instruction>(InVal))
558  if (It > 1 && L->contains(InValI))
559  InVal = LastValueMap[InValI];
560  VMap[OrigPHI] = InVal;
561  New->getInstList().erase(NewPHI);
562  }
563 
564  // Update our running map of newest clones
565  LastValueMap[*BB] = New;
566  for (ValueToValueMapTy::iterator VI = VMap.begin(), VE = VMap.end();
567  VI != VE; ++VI)
568  LastValueMap[VI->first] = VI->second;
569 
570  // Add phi entries for newly created values to all exit blocks.
571  for (BasicBlock *Succ : successors(*BB)) {
572  if (L->contains(Succ))
573  continue;
574  for (BasicBlock::iterator BBI = Succ->begin();
575  PHINode *phi = dyn_cast<PHINode>(BBI); ++BBI) {
576  Value *Incoming = phi->getIncomingValueForBlock(*BB);
577  ValueToValueMapTy::iterator It = LastValueMap.find(Incoming);
578  if (It != LastValueMap.end())
579  Incoming = It->second;
580  phi->addIncoming(Incoming, New);
581  }
582  }
583  // Keep track of new headers and latches as we create them, so that
584  // we can insert the proper branches later.
585  if (*BB == Header)
586  Headers.push_back(New);
587  if (*BB == LatchBlock)
588  Latches.push_back(New);
589 
590  NewBlocks.push_back(New);
591  UnrolledLoopBlocks.push_back(New);
592 
593  // Update DomTree: since we just copy the loop body, and each copy has a
594  // dedicated entry block (copy of the header block), this header's copy
595  // dominates all copied blocks. That means, dominance relations in the
596  // copied body are the same as in the original body.
597  if (DT) {
598  if (*BB == Header)
599  DT->addNewBlock(New, Latches[It - 1]);
600  else {
601  auto BBDomNode = DT->getNode(*BB);
602  auto BBIDom = BBDomNode->getIDom();
603  BasicBlock *OriginalBBIDom = BBIDom->getBlock();
604  DT->addNewBlock(
605  New, cast<BasicBlock>(LastValueMap[cast<Value>(OriginalBBIDom)]));
606  }
607  }
608  }
609 
610  // Remap all instructions in the most recent iteration
611  for (BasicBlock *NewBlock : NewBlocks) {
612  for (Instruction &I : *NewBlock) {
613  ::remapInstruction(&I, LastValueMap);
614  if (auto *II = dyn_cast<IntrinsicInst>(&I))
615  if (II->getIntrinsicID() == Intrinsic::assume)
616  AC->registerAssumption(II);
617  }
618  }
619  }
620 
621  // Loop over the PHI nodes in the original block, setting incoming values.
622  for (PHINode *PN : OrigPHINode) {
623  if (CompletelyUnroll) {
624  PN->replaceAllUsesWith(PN->getIncomingValueForBlock(Preheader));
625  Header->getInstList().erase(PN);
626  }
627  else if (Count > 1) {
628  Value *InVal = PN->removeIncomingValue(LatchBlock, false);
629  // If this value was defined in the loop, take the value defined by the
630  // last iteration of the loop.
631  if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
632  if (L->contains(InValI))
633  InVal = LastValueMap[InVal];
634  }
635  assert(Latches.back() == LastValueMap[LatchBlock] && "bad last latch");
636  PN->addIncoming(InVal, Latches.back());
637  }
638  }
639 
640  // Now that all the basic blocks for the unrolled iterations are in place,
641  // set up the branches to connect them.
642  for (unsigned i = 0, e = Latches.size(); i != e; ++i) {
643  // The original branch was replicated in each unrolled iteration.
644  BranchInst *Term = cast<BranchInst>(Latches[i]->getTerminator());
645 
646  // The branch destination.
647  unsigned j = (i + 1) % e;
648  BasicBlock *Dest = Headers[j];
649  bool NeedConditional = true;
650 
651  if (RuntimeTripCount && j != 0) {
652  NeedConditional = false;
653  }
654 
655  // For a complete unroll, make the last iteration end with a branch
656  // to the exit block.
657  if (CompletelyUnroll) {
658  if (j == 0)
659  Dest = LoopExit;
660  // If using trip count upper bound to completely unroll, we need to keep
661  // the conditional branch except the last one because the loop may exit
662  // after any iteration.
663  assert(NeedConditional &&
664  "NeedCondition cannot be modified by both complete "
665  "unrolling and runtime unrolling");
666  NeedConditional = (PreserveCondBr && j && !(PreserveOnlyFirst && i != 0));
667  } else if (j != BreakoutTrip && (TripMultiple == 0 || j % TripMultiple != 0)) {
668  // If we know the trip count or a multiple of it, we can safely use an
669  // unconditional branch for some iterations.
670  NeedConditional = false;
671  }
672 
673  if (NeedConditional) {
674  // Update the conditional branch's successor for the following
675  // iteration.
676  Term->setSuccessor(!ContinueOnTrue, Dest);
677  } else {
678  // Remove phi operands at this loop exit
679  if (Dest != LoopExit) {
680  BasicBlock *BB = Latches[i];
681  for (BasicBlock *Succ: successors(BB)) {
682  if (Succ == Headers[i])
683  continue;
684  for (BasicBlock::iterator BBI = Succ->begin();
685  PHINode *Phi = dyn_cast<PHINode>(BBI); ++BBI) {
686  Phi->removeIncomingValue(BB, false);
687  }
688  }
689  }
690  // Replace the conditional branch with an unconditional one.
691  BranchInst::Create(Dest, Term);
692  Term->eraseFromParent();
693  }
694  }
695 
696  // Update dominators of blocks we might reach through exits.
697  // Immediate dominator of such block might change, because we add more
698  // routes which can lead to the exit: we can now reach it from the copied
699  // iterations too.
700  if (DT && Count > 1) {
701  for (auto *BB : OriginalLoopBlocks) {
702  auto *BBDomNode = DT->getNode(BB);
703  SmallVector<BasicBlock *, 16> ChildrenToUpdate;
704  for (auto *ChildDomNode : BBDomNode->getChildren()) {
705  auto *ChildBB = ChildDomNode->getBlock();
706  if (!L->contains(ChildBB))
707  ChildrenToUpdate.push_back(ChildBB);
708  }
709  BasicBlock *NewIDom;
710  if (BB == LatchBlock) {
711  // The latch is special because we emit unconditional branches in
712  // some cases where the original loop contained a conditional branch.
713  // Since the latch is always at the bottom of the loop, if the latch
714  // dominated an exit before unrolling, the new dominator of that exit
715  // must also be a latch. Specifically, the dominator is the first
716  // latch which ends in a conditional branch, or the last latch if
717  // there is no such latch.
718  NewIDom = Latches.back();
719  for (BasicBlock *IterLatch : Latches) {
720  TerminatorInst *Term = IterLatch->getTerminator();
721  if (isa<BranchInst>(Term) && cast<BranchInst>(Term)->isConditional()) {
722  NewIDom = IterLatch;
723  break;
724  }
725  }
726  } else {
727  // The new idom of the block will be the nearest common dominator
728  // of all copies of the previous idom. This is equivalent to the
729  // nearest common dominator of the previous idom and the first latch,
730  // which dominates all copies of the previous idom.
731  NewIDom = DT->findNearestCommonDominator(BB, LatchBlock);
732  }
733  for (auto *ChildBB : ChildrenToUpdate)
734  DT->changeImmediateDominator(ChildBB, NewIDom);
735  }
736  }
737 
738  if (DT && UnrollVerifyDomtree)
739  DT->verifyDomTree();
740 
741  // Merge adjacent basic blocks, if possible.
742  SmallPtrSet<Loop *, 4> ForgottenLoops;
743  for (BasicBlock *Latch : Latches) {
744  BranchInst *Term = cast<BranchInst>(Latch->getTerminator());
745  if (Term->isUnconditional()) {
746  BasicBlock *Dest = Term->getSuccessor(0);
747  if (BasicBlock *Fold =
748  foldBlockIntoPredecessor(Dest, LI, SE, ForgottenLoops, DT)) {
749  // Dest has been folded into Fold. Update our worklists accordingly.
750  std::replace(Latches.begin(), Latches.end(), Dest, Fold);
751  UnrolledLoopBlocks.erase(std::remove(UnrolledLoopBlocks.begin(),
752  UnrolledLoopBlocks.end(), Dest),
753  UnrolledLoopBlocks.end());
754  }
755  }
756  }
757 
758  // Simplify any new induction variables in the partially unrolled loop.
759  if (SE && !CompletelyUnroll && Count > 1) {
761  simplifyLoopIVs(L, SE, DT, LI, DeadInsts);
762 
763  // Aggressively clean up dead instructions that simplifyLoopIVs already
764  // identified. Any remaining should be cleaned up below.
765  while (!DeadInsts.empty())
766  if (Instruction *Inst =
767  dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val()))
769  }
770 
771  // At this point, the code is well formed. We now do a quick sweep over the
772  // inserted code, doing constant propagation and dead code elimination as we
773  // go.
774  const DataLayout &DL = Header->getModule()->getDataLayout();
775  const std::vector<BasicBlock*> &NewLoopBlocks = L->getBlocks();
776  for (BasicBlock *BB : NewLoopBlocks) {
777  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
778  Instruction *Inst = &*I++;
779 
780  if (Value *V = SimplifyInstruction(Inst, {DL, nullptr, DT, AC}))
781  if (LI->replacementPreservesLCSSAForm(Inst, V))
782  Inst->replaceAllUsesWith(V);
783  if (isInstructionTriviallyDead(Inst))
784  BB->getInstList().erase(Inst);
785  }
786  }
787 
788  // TODO: after peeling or unrolling, previously loop variant conditions are
789  // likely to fold to constants, eagerly propagating those here will require
790  // fewer cleanup passes to be run. Alternatively, a LoopEarlyCSE might be
791  // appropriate.
792 
793  NumCompletelyUnrolled += CompletelyUnroll;
794  ++NumUnrolled;
795 
796  Loop *OuterL = L->getParentLoop();
797  // Update LoopInfo if the loop is completely removed.
798  if (CompletelyUnroll)
799  LI->markAsRemoved(L);
800 
801  // After complete unrolling most of the blocks should be contained in OuterL.
802  // However, some of them might happen to be out of OuterL (e.g. if they
803  // precede a loop exit). In this case we might need to insert PHI nodes in
804  // order to preserve LCSSA form.
805  // We don't need to check this if we already know that we need to fix LCSSA
806  // form.
807  // TODO: For now we just recompute LCSSA for the outer loop in this case, but
808  // it should be possible to fix it in-place.
809  if (PreserveLCSSA && OuterL && CompletelyUnroll && !NeedToFixLCSSA)
810  NeedToFixLCSSA |= ::needToInsertPhisForLCSSA(OuterL, UnrolledLoopBlocks, LI);
811 
812  // If we have a pass and a DominatorTree we should re-simplify impacted loops
813  // to ensure subsequent analyses can rely on this form. We want to simplify
814  // at least one layer outside of the loop that was unrolled so that any
815  // changes to the parent loop exposed by the unrolling are considered.
816  if (DT) {
817  if (OuterL) {
818  // OuterL includes all loops for which we can break loop-simplify, so
819  // it's sufficient to simplify only it (it'll recursively simplify inner
820  // loops too).
821  if (NeedToFixLCSSA) {
822  // LCSSA must be performed on the outermost affected loop. The unrolled
823  // loop's last loop latch is guaranteed to be in the outermost loop
824  // after LoopInfo's been updated by markAsRemoved.
825  Loop *LatchLoop = LI->getLoopFor(Latches.back());
826  Loop *FixLCSSALoop = OuterL;
827  if (!FixLCSSALoop->contains(LatchLoop))
828  while (FixLCSSALoop->getParentLoop() != LatchLoop)
829  FixLCSSALoop = FixLCSSALoop->getParentLoop();
830 
831  formLCSSARecursively(*FixLCSSALoop, *DT, LI, SE);
832  } else if (PreserveLCSSA) {
833  assert(OuterL->isLCSSAForm(*DT) &&
834  "Loops should be in LCSSA form after loop-unroll.");
835  }
836 
837  // TODO: That potentially might be compile-time expensive. We should try
838  // to fix the loop-simplified form incrementally.
839  simplifyLoop(OuterL, DT, LI, SE, AC, PreserveLCSSA);
840  } else {
841  // Simplify loops for which we might've broken loop-simplify form.
842  for (Loop *SubLoop : LoopsToSimplify)
843  simplifyLoop(SubLoop, DT, LI, SE, AC, PreserveLCSSA);
844  }
845  }
846 
847  return true;
848 }
849 
850 /// Given an llvm.loop loop id metadata node, returns the loop hint metadata
851 /// node with the given name (for example, "llvm.loop.unroll.count"). If no
852 /// such metadata node exists, then nullptr is returned.
854  // First operand should refer to the loop id itself.
855  assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
856  assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
857 
858  for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
859  MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
860  if (!MD)
861  continue;
862 
863  MDString *S = dyn_cast<MDString>(MD->getOperand(0));
864  if (!S)
865  continue;
866 
867  if (Name.equals(S->getString()))
868  return MD;
869  }
870  return nullptr;
871 }
DomTreeNodeBase< NodeT > * getNode(NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
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:149
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:174
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:101
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...
const std::vector< BlockT * > & getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:140
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
newgvn phi
Definition: NewGVN.cpp:122
#define op(i)
void eraseNode(NodeT *BB)
eraseNode - Removes a node from the dominator tree.
bool UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime, bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst, unsigned TripMultiple, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, OptimizationRemarkEmitter *ORE, bool PreserveLCSSA)
Unroll the given loop by Count.
Definition: LoopUnroll.cpp:295
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:345
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
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:585
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 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:103
void getExitBlocks(SmallVectorImpl< BlockT *> &ExitBlocks) const
Return all of the successor blocks of this loop.
Definition: LoopInfoImpl.h:62
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:174
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:639
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:766
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:134
const char * Name
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:404
void verifyDomTree() const
Verify the correctness of the domtree by re-computing it.
Definition: Dominators.cpp:300
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
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
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:372
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:825
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
void markAsRemoved(Loop *L)
Update LoopInfo after removing the last backedge from a loop.
Definition: LoopInfo.cpp:625
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:310
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:110
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:423
#define E
Definition: LargeTest.cpp:27
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
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:853
bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, bool AllowExpensiveTripCount, bool UseEpilogRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, bool PreserveLCSSA)
Insert code in the prolog/epilog code when unrolling a loop with a run-time trip-count.
LoopT * getParentLoop() const
Definition: LoopInfo.h:104
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:271
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:360
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:557
bool isSafeToClone() const
Return true if the loop body is safe to clone in practice.
Definition: LoopInfo.cpp:197
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:166
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:709
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:144
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
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:647
iterator begin()
Definition: ValueMap.h:137