LLVM  7.0.0svn
LoopUnroll.cpp
Go to the documentation of this file.
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"
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"
41 using namespace llvm;
42 
43 #define DEBUG_TYPE "loop-unroll"
44 
45 // TODO: Should these be here or in LoopUnroll?
46 STATISTIC(NumCompletelyUnrolled, "Number of loops completely unrolled");
47 STATISTIC(NumUnrolled, "Number of loops unrolled (completely or otherwise)");
48 
49 static cl::opt<bool>
50 UnrollRuntimeEpilog("unroll-runtime-epilog", cl::init(false), cl::Hidden,
51  cl::desc("Allow runtime unrolled loops to be unrolled "
52  "with epilog instead of prolog."));
53 
54 static cl::opt<bool>
55 UnrollVerifyDomtree("unroll-verify-domtree", cl::Hidden,
56  cl::desc("Verify domtree after unrolling"),
57 #ifdef NDEBUG
58  cl::init(false)
59 #else
60  cl::init(true)
61 #endif
62  );
63 
64 /// Convert the instruction operands from referencing the current values into
65 /// those specified by VMap.
67  for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
68  Value *Op = I->getOperand(op);
69 
70  // Unwrap arguments of dbg.value intrinsics.
71  bool Wrapped = false;
72  if (auto *V = dyn_cast<MetadataAsValue>(Op))
73  if (auto *Unwrapped = dyn_cast<ValueAsMetadata>(V->getMetadata())) {
74  Op = Unwrapped->getValue();
75  Wrapped = true;
76  }
77 
78  auto wrap = [&](Value *V) {
79  auto &C = I->getContext();
80  return Wrapped ? MetadataAsValue::get(C, ValueAsMetadata::get(V)) : V;
81  };
82 
83  ValueToValueMapTy::iterator It = VMap.find(Op);
84  if (It != VMap.end())
85  I->setOperand(op, wrap(It->second));
86  }
87 
88  if (PHINode *PN = dyn_cast<PHINode>(I)) {
89  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
90  ValueToValueMapTy::iterator It = VMap.find(PN->getIncomingBlock(i));
91  if (It != VMap.end())
92  PN->setIncomingBlock(i, cast<BasicBlock>(It->second));
93  }
94  }
95 }
96 
97 /// Folds a basic block into its predecessor if it only has one predecessor, and
98 /// that predecessor only has one successor.
99 /// The LoopInfo Analysis that is passed will be kept consistent.
101  ScalarEvolution *SE,
102  DominatorTree *DT) {
103  // Merge basic blocks into their predecessor if there is only one distinct
104  // pred, and if there is only one distinct successor of the predecessor, and
105  // if there are no PHI nodes.
106  BasicBlock *OnlyPred = BB->getSinglePredecessor();
107  if (!OnlyPred) return nullptr;
108 
109  if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
110  return nullptr;
111 
112  LLVM_DEBUG(dbgs() << "Merging: " << BB->getName() << " into "
113  << OnlyPred->getName() << "\n");
114 
115  // Resolve any PHI nodes at the start of the block. They are all
116  // guaranteed to have exactly one entry if they exist, unless there are
117  // multiple duplicate (but guaranteed to be equal) entries for the
118  // incoming edges. This occurs when there are multiple edges from
119  // OnlyPred to OnlySucc.
121 
122  // Delete the unconditional branch from the predecessor...
123  OnlyPred->getInstList().pop_back();
124 
125  // Make all PHI nodes that referred to BB now refer to Pred as their
126  // source...
127  BB->replaceAllUsesWith(OnlyPred);
128 
129  // Move all definitions in the successor to the predecessor...
130  OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
131 
132  // OldName will be valid until erased.
133  StringRef OldName = BB->getName();
134 
135  // Erase the old block and update dominator info.
136  if (DT)
137  if (DomTreeNode *DTN = DT->getNode(BB)) {
138  DomTreeNode *PredDTN = DT->getNode(OnlyPred);
139  SmallVector<DomTreeNode *, 8> Children(DTN->begin(), DTN->end());
140  for (auto *DI : Children)
141  DT->changeImmediateDominator(DI, PredDTN);
142 
143  DT->eraseNode(BB);
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 = LI->AllocateLoop();
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 (const PHINode &PN : Header->phis()) {
249  if (isa<ConstantInt>(PN.getIncomingValueForBlock(PreHeader)))
250  return true;
251  }
252  return false;
253 }
254 
255 /// Perform some cleanup and simplifications on loops after unrolling. It is
256 /// useful to simplify the IV's in the new loop, as well as do a quick
257 /// simplify/dce pass of the instructions.
258 void llvm::simplifyLoopAfterUnroll(Loop *L, bool SimplifyIVs, LoopInfo *LI,
260  AssumptionCache *AC) {
261  // Simplify any new induction variables in the partially unrolled loop.
262  if (SE && SimplifyIVs) {
264  simplifyLoopIVs(L, SE, DT, LI, DeadInsts);
265 
266  // Aggressively clean up dead instructions that simplifyLoopIVs already
267  // identified. Any remaining should be cleaned up below.
268  while (!DeadInsts.empty())
269  if (Instruction *Inst =
270  dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val()))
272  }
273 
274  // At this point, the code is well formed. We now do a quick sweep over the
275  // inserted code, doing constant propagation and dead code elimination as we
276  // go.
277  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
278  const std::vector<BasicBlock *> &NewLoopBlocks = L->getBlocks();
279  for (BasicBlock *BB : NewLoopBlocks) {
280  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
281  Instruction *Inst = &*I++;
282 
283  if (Value *V = SimplifyInstruction(Inst, {DL, nullptr, DT, AC}))
284  if (LI->replacementPreservesLCSSAForm(Inst, V))
285  Inst->replaceAllUsesWith(V);
286  if (isInstructionTriviallyDead(Inst))
287  BB->getInstList().erase(Inst);
288  }
289  }
290 
291  // TODO: after peeling or unrolling, previously loop variant conditions are
292  // likely to fold to constants, eagerly propagating those here will require
293  // fewer cleanup passes to be run. Alternatively, a LoopEarlyCSE might be
294  // appropriate.
295 }
296 
297 /// Unroll the given loop by Count. The loop must be in LCSSA form. Unrolling
298 /// can only fail when the loop's latch block is not terminated by a conditional
299 /// branch instruction. However, if the trip count (and multiple) are not known,
300 /// loop unrolling will mostly produce more code that is no faster.
301 ///
302 /// TripCount is the upper bound of the iteration on which control exits
303 /// LatchBlock. Control may exit the loop prior to TripCount iterations either
304 /// via an early branch in other loop block or via LatchBlock terminator. This
305 /// is relaxed from the general definition of trip count which is the number of
306 /// times the loop header executes. Note that UnrollLoop assumes that the loop
307 /// counter test is in LatchBlock in order to remove unnecesssary instances of
308 /// the test. If control can exit the loop from the LatchBlock's terminator
309 /// prior to TripCount iterations, flag PreserveCondBr needs to be set.
310 ///
311 /// PreserveCondBr indicates whether the conditional branch of the LatchBlock
312 /// needs to be preserved. It is needed when we use trip count upper bound to
313 /// fully unroll the loop. If PreserveOnlyFirst is also set then only the first
314 /// conditional branch needs to be preserved.
315 ///
316 /// Similarly, TripMultiple divides the number of times that the LatchBlock may
317 /// execute without exiting the loop.
318 ///
319 /// If AllowRuntime is true then UnrollLoop will consider unrolling loops that
320 /// have a runtime (i.e. not compile time constant) trip count. Unrolling these
321 /// loops require a unroll "prologue" that runs "RuntimeTripCount % Count"
322 /// iterations before branching into the unrolled loop. UnrollLoop will not
323 /// runtime-unroll the loop if computing RuntimeTripCount will be expensive and
324 /// AllowExpensiveTripCount is false.
325 ///
326 /// If we want to perform PGO-based loop peeling, PeelCount is set to the
327 /// number of iterations we want to peel off.
328 ///
329 /// The LoopInfo Analysis that is passed will be kept consistent.
330 ///
331 /// This utility preserves LoopInfo. It will also preserve ScalarEvolution and
332 /// DominatorTree if they are non-null.
334  Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime,
335  bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst,
336  unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder,
338  OptimizationRemarkEmitter *ORE, bool PreserveLCSSA) {
339 
340  BasicBlock *Preheader = L->getLoopPreheader();
341  if (!Preheader) {
342  LLVM_DEBUG(dbgs() << " Can't unroll; loop preheader-insertion failed.\n");
344  }
345 
346  BasicBlock *LatchBlock = L->getLoopLatch();
347  if (!LatchBlock) {
348  LLVM_DEBUG(dbgs() << " Can't unroll; loop exit-block-insertion failed.\n");
350  }
351 
352  // Loops with indirectbr cannot be cloned.
353  if (!L->isSafeToClone()) {
354  LLVM_DEBUG(dbgs() << " Can't unroll; Loop body cannot be cloned.\n");
356  }
357 
358  // The current loop unroll pass can only unroll loops with a single latch
359  // that's a conditional branch exiting the loop.
360  // FIXME: The implementation can be extended to work with more complicated
361  // cases, e.g. loops with multiple latches.
362  BasicBlock *Header = L->getHeader();
363  BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator());
364 
365  if (!BI || BI->isUnconditional()) {
366  // The loop-rotate pass can be helpful to avoid this in many cases.
367  LLVM_DEBUG(
368  dbgs()
369  << " Can't unroll; loop not terminated by a conditional branch.\n");
371  }
372 
373  auto CheckSuccessors = [&](unsigned S1, unsigned S2) {
374  return BI->getSuccessor(S1) == Header && !L->contains(BI->getSuccessor(S2));
375  };
376 
377  if (!CheckSuccessors(0, 1) && !CheckSuccessors(1, 0)) {
378  LLVM_DEBUG(dbgs() << "Can't unroll; only loops with one conditional latch"
379  " exiting the loop can be unrolled\n");
381  }
382 
383  if (Header->hasAddressTaken()) {
384  // The loop-rotate pass can be helpful to avoid this in many cases.
385  LLVM_DEBUG(
386  dbgs() << " Won't unroll loop: address of header block is taken.\n");
388  }
389 
390  if (TripCount != 0)
391  LLVM_DEBUG(dbgs() << " Trip Count = " << TripCount << "\n");
392  if (TripMultiple != 1)
393  LLVM_DEBUG(dbgs() << " Trip Multiple = " << TripMultiple << "\n");
394 
395  // Effectively "DCE" unrolled iterations that are beyond the tripcount
396  // and will never be executed.
397  if (TripCount != 0 && Count > TripCount)
398  Count = TripCount;
399 
400  // Don't enter the unroll code if there is nothing to do.
401  if (TripCount == 0 && Count < 2 && PeelCount == 0) {
402  LLVM_DEBUG(dbgs() << "Won't unroll; almost nothing to do\n");
404  }
405 
406  assert(Count > 0);
407  assert(TripMultiple > 0);
408  assert(TripCount == 0 || TripCount % TripMultiple == 0);
409 
410  // Are we eliminating the loop control altogether?
411  bool CompletelyUnroll = Count == TripCount;
412  SmallVector<BasicBlock *, 4> ExitBlocks;
413  L->getExitBlocks(ExitBlocks);
414  std::vector<BasicBlock*> OriginalLoopBlocks = L->getBlocks();
415 
416  // Go through all exits of L and see if there are any phi-nodes there. We just
417  // conservatively assume that they're inserted to preserve LCSSA form, which
418  // means that complete unrolling might break this form. We need to either fix
419  // it in-place after the transformation, or entirely rebuild LCSSA. TODO: For
420  // now we just recompute LCSSA for the outer loop, but it should be possible
421  // to fix it in-place.
422  bool NeedToFixLCSSA = PreserveLCSSA && CompletelyUnroll &&
423  any_of(ExitBlocks, [](const BasicBlock *BB) {
424  return isa<PHINode>(BB->begin());
425  });
426 
427  // We assume a run-time trip count if the compiler cannot
428  // figure out the loop trip count and the unroll-runtime
429  // flag is specified.
430  bool RuntimeTripCount = (TripCount == 0 && Count > 0 && AllowRuntime);
431 
432  assert((!RuntimeTripCount || !PeelCount) &&
433  "Did not expect runtime trip-count unrolling "
434  "and peeling for the same loop");
435 
436  bool Peeled = false;
437  if (PeelCount) {
438  Peeled = peelLoop(L, PeelCount, LI, SE, DT, AC, PreserveLCSSA);
439 
440  // Successful peeling may result in a change in the loop preheader/trip
441  // counts. If we later unroll the loop, we want these to be updated.
442  if (Peeled) {
443  BasicBlock *ExitingBlock = L->getExitingBlock();
444  assert(ExitingBlock && "Loop without exiting block?");
445  Preheader = L->getLoopPreheader();
446  TripCount = SE->getSmallConstantTripCount(L, ExitingBlock);
447  TripMultiple = SE->getSmallConstantTripMultiple(L, ExitingBlock);
448  }
449  }
450 
451  // Loops containing convergent instructions must have a count that divides
452  // their TripMultiple.
453  LLVM_DEBUG(
454  {
455  bool HasConvergent = false;
456  for (auto &BB : L->blocks())
457  for (auto &I : *BB)
458  if (auto CS = CallSite(&I))
459  HasConvergent |= CS.isConvergent();
460  assert((!HasConvergent || TripMultiple % Count == 0) &&
461  "Unroll count must divide trip multiple if loop contains a "
462  "convergent operation.");
463  });
464 
465  bool EpilogProfitability =
466  UnrollRuntimeEpilog.getNumOccurrences() ? UnrollRuntimeEpilog
467  : isEpilogProfitable(L);
468 
469  if (RuntimeTripCount && TripMultiple % Count != 0 &&
470  !UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
471  EpilogProfitability, UnrollRemainder, LI, SE,
472  DT, AC, PreserveLCSSA)) {
473  if (Force)
474  RuntimeTripCount = false;
475  else {
476  LLVM_DEBUG(dbgs() << "Won't unroll; remainder loop could not be "
477  "generated when assuming runtime trip count\n");
479  }
480  }
481 
482  // If we know the trip count, we know the multiple...
483  unsigned BreakoutTrip = 0;
484  if (TripCount != 0) {
485  BreakoutTrip = TripCount % Count;
486  TripMultiple = 0;
487  } else {
488  // Figure out what multiple to use.
489  BreakoutTrip = TripMultiple =
490  (unsigned)GreatestCommonDivisor64(Count, TripMultiple);
491  }
492 
493  using namespace ore;
494  // Report the unrolling decision.
495  if (CompletelyUnroll) {
496  LLVM_DEBUG(dbgs() << "COMPLETELY UNROLLING loop %" << Header->getName()
497  << " with trip count " << TripCount << "!\n");
498  if (ORE)
499  ORE->emit([&]() {
500  return OptimizationRemark(DEBUG_TYPE, "FullyUnrolled", L->getStartLoc(),
501  L->getHeader())
502  << "completely unrolled loop with "
503  << NV("UnrollCount", TripCount) << " iterations";
504  });
505  } else if (PeelCount) {
506  LLVM_DEBUG(dbgs() << "PEELING loop %" << Header->getName()
507  << " with iteration count " << PeelCount << "!\n");
508  if (ORE)
509  ORE->emit([&]() {
510  return OptimizationRemark(DEBUG_TYPE, "Peeled", L->getStartLoc(),
511  L->getHeader())
512  << " peeled loop by " << NV("PeelCount", PeelCount)
513  << " iterations";
514  });
515  } else {
516  auto DiagBuilder = [&]() {
517  OptimizationRemark Diag(DEBUG_TYPE, "PartialUnrolled", L->getStartLoc(),
518  L->getHeader());
519  return Diag << "unrolled loop by a factor of "
520  << NV("UnrollCount", Count);
521  };
522 
523  LLVM_DEBUG(dbgs() << "UNROLLING loop %" << Header->getName() << " by "
524  << Count);
525  if (TripMultiple == 0 || BreakoutTrip != TripMultiple) {
526  LLVM_DEBUG(dbgs() << " with a breakout at trip " << BreakoutTrip);
527  if (ORE)
528  ORE->emit([&]() {
529  return DiagBuilder() << " with a breakout at trip "
530  << NV("BreakoutTrip", BreakoutTrip);
531  });
532  } else if (TripMultiple != 1) {
533  LLVM_DEBUG(dbgs() << " with " << TripMultiple << " trips per branch");
534  if (ORE)
535  ORE->emit([&]() {
536  return DiagBuilder() << " with " << NV("TripMultiple", TripMultiple)
537  << " trips per branch";
538  });
539  } else if (RuntimeTripCount) {
540  LLVM_DEBUG(dbgs() << " with run-time trip count");
541  if (ORE)
542  ORE->emit(
543  [&]() { return DiagBuilder() << " with run-time trip count"; });
544  }
545  LLVM_DEBUG(dbgs() << "!\n");
546  }
547 
548  // We are going to make changes to this loop. SCEV may be keeping cached info
549  // about it, in particular about backedge taken count. The changes we make
550  // are guaranteed to invalidate this information for our loop. It is tempting
551  // to only invalidate the loop being unrolled, but it is incorrect as long as
552  // all exiting branches from all inner loops have impact on the outer loops,
553  // and if something changes inside them then any of outer loops may also
554  // change. When we forget outermost loop, we also forget all contained loops
555  // and this is what we need here.
556  if (SE)
557  SE->forgetTopmostLoop(L);
558 
559  bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
560  BasicBlock *LoopExit = BI->getSuccessor(ContinueOnTrue);
561 
562  // For the first iteration of the loop, we should use the precloned values for
563  // PHI nodes. Insert associations now.
564  ValueToValueMapTy LastValueMap;
565  std::vector<PHINode*> OrigPHINode;
566  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
567  OrigPHINode.push_back(cast<PHINode>(I));
568  }
569 
570  std::vector<BasicBlock*> Headers;
571  std::vector<BasicBlock*> Latches;
572  Headers.push_back(Header);
573  Latches.push_back(LatchBlock);
574 
575  // The current on-the-fly SSA update requires blocks to be processed in
576  // reverse postorder so that LastValueMap contains the correct value at each
577  // exit.
578  LoopBlocksDFS DFS(L);
579  DFS.perform(LI);
580 
581  // Stash the DFS iterators before adding blocks to the loop.
582  LoopBlocksDFS::RPOIterator BlockBegin = DFS.beginRPO();
583  LoopBlocksDFS::RPOIterator BlockEnd = DFS.endRPO();
584 
585  std::vector<BasicBlock*> UnrolledLoopBlocks = L->getBlocks();
586 
587  // Loop Unrolling might create new loops. While we do preserve LoopInfo, we
588  // might break loop-simplified form for these loops (as they, e.g., would
589  // share the same exit blocks). We'll keep track of loops for which we can
590  // break this so that later we can re-simplify them.
591  SmallSetVector<Loop *, 4> LoopsToSimplify;
592  for (Loop *SubLoop : *L)
593  LoopsToSimplify.insert(SubLoop);
594 
595  if (Header->getParent()->isDebugInfoForProfiling())
596  for (BasicBlock *BB : L->getBlocks())
597  for (Instruction &I : *BB)
598  if (!isa<DbgInfoIntrinsic>(&I))
599  if (const DILocation *DIL = I.getDebugLoc())
600  I.setDebugLoc(DIL->cloneWithDuplicationFactor(Count));
601 
602  for (unsigned It = 1; It != Count; ++It) {
603  std::vector<BasicBlock*> NewBlocks;
605  NewLoops[L] = L;
606 
607  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
608  ValueToValueMapTy VMap;
609  BasicBlock *New = CloneBasicBlock(*BB, VMap, "." + Twine(It));
610  Header->getParent()->getBasicBlockList().push_back(New);
611 
612  assert((*BB != Header || LI->getLoopFor(*BB) == L) &&
613  "Header should not be in a sub-loop");
614  // Tell LI about New.
615  const Loop *OldLoop = addClonedBlockToLoopInfo(*BB, New, LI, NewLoops);
616  if (OldLoop)
617  LoopsToSimplify.insert(NewLoops[OldLoop]);
618 
619  if (*BB == Header)
620  // Loop over all of the PHI nodes in the block, changing them to use
621  // the incoming values from the previous block.
622  for (PHINode *OrigPHI : OrigPHINode) {
623  PHINode *NewPHI = cast<PHINode>(VMap[OrigPHI]);
624  Value *InVal = NewPHI->getIncomingValueForBlock(LatchBlock);
625  if (Instruction *InValI = dyn_cast<Instruction>(InVal))
626  if (It > 1 && L->contains(InValI))
627  InVal = LastValueMap[InValI];
628  VMap[OrigPHI] = InVal;
629  New->getInstList().erase(NewPHI);
630  }
631 
632  // Update our running map of newest clones
633  LastValueMap[*BB] = New;
634  for (ValueToValueMapTy::iterator VI = VMap.begin(), VE = VMap.end();
635  VI != VE; ++VI)
636  LastValueMap[VI->first] = VI->second;
637 
638  // Add phi entries for newly created values to all exit blocks.
639  for (BasicBlock *Succ : successors(*BB)) {
640  if (L->contains(Succ))
641  continue;
642  for (PHINode &PHI : Succ->phis()) {
643  Value *Incoming = PHI.getIncomingValueForBlock(*BB);
644  ValueToValueMapTy::iterator It = LastValueMap.find(Incoming);
645  if (It != LastValueMap.end())
646  Incoming = It->second;
647  PHI.addIncoming(Incoming, New);
648  }
649  }
650  // Keep track of new headers and latches as we create them, so that
651  // we can insert the proper branches later.
652  if (*BB == Header)
653  Headers.push_back(New);
654  if (*BB == LatchBlock)
655  Latches.push_back(New);
656 
657  NewBlocks.push_back(New);
658  UnrolledLoopBlocks.push_back(New);
659 
660  // Update DomTree: since we just copy the loop body, and each copy has a
661  // dedicated entry block (copy of the header block), this header's copy
662  // dominates all copied blocks. That means, dominance relations in the
663  // copied body are the same as in the original body.
664  if (DT) {
665  if (*BB == Header)
666  DT->addNewBlock(New, Latches[It - 1]);
667  else {
668  auto BBDomNode = DT->getNode(*BB);
669  auto BBIDom = BBDomNode->getIDom();
670  BasicBlock *OriginalBBIDom = BBIDom->getBlock();
671  DT->addNewBlock(
672  New, cast<BasicBlock>(LastValueMap[cast<Value>(OriginalBBIDom)]));
673  }
674  }
675  }
676 
677  // Remap all instructions in the most recent iteration
678  for (BasicBlock *NewBlock : NewBlocks) {
679  for (Instruction &I : *NewBlock) {
680  ::remapInstruction(&I, LastValueMap);
681  if (auto *II = dyn_cast<IntrinsicInst>(&I))
682  if (II->getIntrinsicID() == Intrinsic::assume)
683  AC->registerAssumption(II);
684  }
685  }
686  }
687 
688  // Loop over the PHI nodes in the original block, setting incoming values.
689  for (PHINode *PN : OrigPHINode) {
690  if (CompletelyUnroll) {
691  PN->replaceAllUsesWith(PN->getIncomingValueForBlock(Preheader));
692  Header->getInstList().erase(PN);
693  }
694  else if (Count > 1) {
695  Value *InVal = PN->removeIncomingValue(LatchBlock, false);
696  // If this value was defined in the loop, take the value defined by the
697  // last iteration of the loop.
698  if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
699  if (L->contains(InValI))
700  InVal = LastValueMap[InVal];
701  }
702  assert(Latches.back() == LastValueMap[LatchBlock] && "bad last latch");
703  PN->addIncoming(InVal, Latches.back());
704  }
705  }
706 
707  // Now that all the basic blocks for the unrolled iterations are in place,
708  // set up the branches to connect them.
709  for (unsigned i = 0, e = Latches.size(); i != e; ++i) {
710  // The original branch was replicated in each unrolled iteration.
711  BranchInst *Term = cast<BranchInst>(Latches[i]->getTerminator());
712 
713  // The branch destination.
714  unsigned j = (i + 1) % e;
715  BasicBlock *Dest = Headers[j];
716  bool NeedConditional = true;
717 
718  if (RuntimeTripCount && j != 0) {
719  NeedConditional = false;
720  }
721 
722  // For a complete unroll, make the last iteration end with a branch
723  // to the exit block.
724  if (CompletelyUnroll) {
725  if (j == 0)
726  Dest = LoopExit;
727  // If using trip count upper bound to completely unroll, we need to keep
728  // the conditional branch except the last one because the loop may exit
729  // after any iteration.
730  assert(NeedConditional &&
731  "NeedCondition cannot be modified by both complete "
732  "unrolling and runtime unrolling");
733  NeedConditional = (PreserveCondBr && j && !(PreserveOnlyFirst && i != 0));
734  } else if (j != BreakoutTrip && (TripMultiple == 0 || j % TripMultiple != 0)) {
735  // If we know the trip count or a multiple of it, we can safely use an
736  // unconditional branch for some iterations.
737  NeedConditional = false;
738  }
739 
740  if (NeedConditional) {
741  // Update the conditional branch's successor for the following
742  // iteration.
743  Term->setSuccessor(!ContinueOnTrue, Dest);
744  } else {
745  // Remove phi operands at this loop exit
746  if (Dest != LoopExit) {
747  BasicBlock *BB = Latches[i];
748  for (BasicBlock *Succ: successors(BB)) {
749  if (Succ == Headers[i])
750  continue;
751  for (PHINode &Phi : Succ->phis())
752  Phi.removeIncomingValue(BB, false);
753  }
754  }
755  // Replace the conditional branch with an unconditional one.
756  BranchInst::Create(Dest, Term);
757  Term->eraseFromParent();
758  }
759  }
760 
761  // Update dominators of blocks we might reach through exits.
762  // Immediate dominator of such block might change, because we add more
763  // routes which can lead to the exit: we can now reach it from the copied
764  // iterations too.
765  if (DT && Count > 1) {
766  for (auto *BB : OriginalLoopBlocks) {
767  auto *BBDomNode = DT->getNode(BB);
768  SmallVector<BasicBlock *, 16> ChildrenToUpdate;
769  for (auto *ChildDomNode : BBDomNode->getChildren()) {
770  auto *ChildBB = ChildDomNode->getBlock();
771  if (!L->contains(ChildBB))
772  ChildrenToUpdate.push_back(ChildBB);
773  }
774  BasicBlock *NewIDom;
775  if (BB == LatchBlock) {
776  // The latch is special because we emit unconditional branches in
777  // some cases where the original loop contained a conditional branch.
778  // Since the latch is always at the bottom of the loop, if the latch
779  // dominated an exit before unrolling, the new dominator of that exit
780  // must also be a latch. Specifically, the dominator is the first
781  // latch which ends in a conditional branch, or the last latch if
782  // there is no such latch.
783  NewIDom = Latches.back();
784  for (BasicBlock *IterLatch : Latches) {
785  TerminatorInst *Term = IterLatch->getTerminator();
786  if (isa<BranchInst>(Term) && cast<BranchInst>(Term)->isConditional()) {
787  NewIDom = IterLatch;
788  break;
789  }
790  }
791  } else {
792  // The new idom of the block will be the nearest common dominator
793  // of all copies of the previous idom. This is equivalent to the
794  // nearest common dominator of the previous idom and the first latch,
795  // which dominates all copies of the previous idom.
796  NewIDom = DT->findNearestCommonDominator(BB, LatchBlock);
797  }
798  for (auto *ChildBB : ChildrenToUpdate)
799  DT->changeImmediateDominator(ChildBB, NewIDom);
800  }
801  }
802 
803  assert(!DT || !UnrollVerifyDomtree ||
805 
806  // Merge adjacent basic blocks, if possible.
807  for (BasicBlock *Latch : Latches) {
808  BranchInst *Term = cast<BranchInst>(Latch->getTerminator());
809  if (Term->isUnconditional()) {
810  BasicBlock *Dest = Term->getSuccessor(0);
811  if (BasicBlock *Fold = foldBlockIntoPredecessor(Dest, LI, SE, DT)) {
812  // Dest has been folded into Fold. Update our worklists accordingly.
813  std::replace(Latches.begin(), Latches.end(), Dest, Fold);
814  UnrolledLoopBlocks.erase(std::remove(UnrolledLoopBlocks.begin(),
815  UnrolledLoopBlocks.end(), Dest),
816  UnrolledLoopBlocks.end());
817  }
818  }
819  }
820 
821  // At this point, the code is well formed. We now simplify the unrolled loop,
822  // doing constant propagation and dead code elimination as we go.
823  simplifyLoopAfterUnroll(L, !CompletelyUnroll && (Count > 1 || Peeled), LI, SE,
824  DT, AC);
825 
826  NumCompletelyUnrolled += CompletelyUnroll;
827  ++NumUnrolled;
828 
829  Loop *OuterL = L->getParentLoop();
830  // Update LoopInfo if the loop is completely removed.
831  if (CompletelyUnroll)
832  LI->erase(L);
833 
834  // After complete unrolling most of the blocks should be contained in OuterL.
835  // However, some of them might happen to be out of OuterL (e.g. if they
836  // precede a loop exit). In this case we might need to insert PHI nodes in
837  // order to preserve LCSSA form.
838  // We don't need to check this if we already know that we need to fix LCSSA
839  // form.
840  // TODO: For now we just recompute LCSSA for the outer loop in this case, but
841  // it should be possible to fix it in-place.
842  if (PreserveLCSSA && OuterL && CompletelyUnroll && !NeedToFixLCSSA)
843  NeedToFixLCSSA |= ::needToInsertPhisForLCSSA(OuterL, UnrolledLoopBlocks, LI);
844 
845  // If we have a pass and a DominatorTree we should re-simplify impacted loops
846  // to ensure subsequent analyses can rely on this form. We want to simplify
847  // at least one layer outside of the loop that was unrolled so that any
848  // changes to the parent loop exposed by the unrolling are considered.
849  if (DT) {
850  if (OuterL) {
851  // OuterL includes all loops for which we can break loop-simplify, so
852  // it's sufficient to simplify only it (it'll recursively simplify inner
853  // loops too).
854  if (NeedToFixLCSSA) {
855  // LCSSA must be performed on the outermost affected loop. The unrolled
856  // loop's last loop latch is guaranteed to be in the outermost loop
857  // after LoopInfo's been updated by LoopInfo::erase.
858  Loop *LatchLoop = LI->getLoopFor(Latches.back());
859  Loop *FixLCSSALoop = OuterL;
860  if (!FixLCSSALoop->contains(LatchLoop))
861  while (FixLCSSALoop->getParentLoop() != LatchLoop)
862  FixLCSSALoop = FixLCSSALoop->getParentLoop();
863 
864  formLCSSARecursively(*FixLCSSALoop, *DT, LI, SE);
865  } else if (PreserveLCSSA) {
866  assert(OuterL->isLCSSAForm(*DT) &&
867  "Loops should be in LCSSA form after loop-unroll.");
868  }
869 
870  // TODO: That potentially might be compile-time expensive. We should try
871  // to fix the loop-simplified form incrementally.
872  simplifyLoop(OuterL, DT, LI, SE, AC, PreserveLCSSA);
873  } else {
874  // Simplify loops for which we might've broken loop-simplify form.
875  for (Loop *SubLoop : LoopsToSimplify)
876  simplifyLoop(SubLoop, DT, LI, SE, AC, PreserveLCSSA);
877  }
878  }
879 
880  return CompletelyUnroll ? LoopUnrollResult::FullyUnrolled
882 }
883 
884 /// Given an llvm.loop loop id metadata node, returns the loop hint metadata
885 /// node with the given name (for example, "llvm.loop.unroll.count"). If no
886 /// such metadata node exists, then nullptr is returned.
888  // First operand should refer to the loop id itself.
889  assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
890  assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
891 
892  for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
893  MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
894  if (!MD)
895  continue;
896 
897  MDString *S = dyn_cast<MDString>(MD->getOperand(0));
898  if (!S)
899  continue;
900 
901  if (Name.equals(S->getString()))
902  return MD;
903  }
904  return nullptr;
905 }
uint64_t CallInst * C
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:68
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:225
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:563
iterator erase(iterator where)
Definition: ilist.h:267
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:176
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:174
A cache of @llvm.assume calls within a function.
BasicBlock * foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT)
Folds a basic block into its predecessor if it only has one predecessor, and that predecessor only ha...
Definition: LoopUnroll.cpp:100
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:714
NodeT * findNearestCommonDominator(NodeT *A, NodeT *B) const
findNearestCommonDominator - Find nearest common dominator basic block for basic block A and B...
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.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:264
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:343
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr if the function does no...
Definition: BasicBlock.cpp:134
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
bool verify(VerificationLevel VL=VerificationLevel::Full) const
verify - checks if the tree is correct.
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:684
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:592
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:295
RPOIterator endRPO() const
Definition: LoopIterator.h:141
BlockT * getHeader() const
Definition: LoopInfo.h:100
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:251
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:735
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:162
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:439
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:142
Value * getOperand(unsigned i) const
Definition: User.h:170
void remapInstruction(Instruction *I, ValueToValueMapTy &VMap)
Convert the instruction operands from referencing the current values into those specified by VMap...
Definition: LoopUnroll.cpp:66
static MetadataAsValue * get(LLVMContext &Context, Metadata *MD)
Definition: Metadata.cpp:106
StringRef getString() const
Definition: Metadata.cpp:464
The loop was fully unrolled into straight-line code.
bool isDebugInfoForProfiling() const
Returns true if we should emit debug info for profiling.
Definition: Metadata.cpp:1512
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:55
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:235
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
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.
Diagnostic information for applied optimization remarks.
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:329
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:915
const Instruction & back() const
Definition: BasicBlock.h:278
std::vector< BasicBlock * >::const_reverse_iterator RPOIterator
Definition: LoopIterator.h:102
The loop was partially unrolled – we still have a loop, but with a smaller trip count.
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, const TargetLibraryInfo *TLI=nullptr)
If the specified value is a trivially dead instruction, delete it.
Definition: Local.cpp:429
bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, bool AllowExpensiveTripCount, bool UseEpilogRemainder, bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA)
Insert code in the prolog/epilog code when unrolling a loop with a run-time trip-count.
DebugLoc getStartLoc() const
Return the debug location of the start of this loop.
Definition: LoopInfo.cpp:346
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
void setSuccessor(unsigned idx, BasicBlock *NewSucc)
iterator end()
Definition: ValueMap.h:142
bool hasAddressTaken() const
Returns true if there are any uses of this basic block other than direct branches, switches, etc.
Definition: BasicBlock.h:387
const InstListType & getInstList() const
Return the underlying instruction list container.
Definition: BasicBlock.h:329
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:192
void emit(DiagnosticInfoOptimizationBase &OptDiag)
Output the remark via the diagnostic handler and to the optimization record file. ...
iterator end()
Definition: BasicBlock.h:266
static ValueAsMetadata * get(Value *V)
Definition: Metadata.cpp:349
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
LoopT * AllocateLoop(ArgsTy &&... Args)
Definition: LoopInfo.h:648
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:382
static BranchInst * Create(BasicBlock *IfTrue, Instruction *InsertBefore=nullptr)
void setOperand(unsigned i, Value *Val)
Definition: User.h:175
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
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:313
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
Fast - This calling convention attempts to make calls as fast as possible (e.g.
Definition: CallingConv.h:43
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:887
LoopT * getParentLoop() const
Definition: LoopInfo.h:101
LLVMAttributeRef wrap(Attribute Attr)
Definition: Attributes.h:190
void registerAssumption(CallInst *CI)
Add an @llvm.assume intrinsic to this function&#39;s cache.
void addChildLoop(LoopT *NewChild)
Add the specified loop to be a child of this loop.
Definition: LoopInfo.h:331
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:62
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:459
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:149
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
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:115
#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:619
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:320
bool isSafeToClone() const
Return true if the loop body is safe to clone in practice.
Definition: LoopInfo.cpp:199
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:346
LLVM Value Representation.
Definition: Value.h:73
succ_range successors(BasicBlock *BB)
Definition: CFG.h:149
RPOIterator beginRPO() const
Reverse iterate over the cached postorder blocks.
Definition: LoopIterator.h:137
The loop was not modified.
#define DEBUG_TYPE
Definition: LoopUnroll.cpp:43
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:826
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:138
void pop_back()
Definition: ilist.h:318
unsigned getNumOperands() const
Return number of MDNode operands.
Definition: Metadata.h:1073
#define LLVM_DEBUG(X)
Definition: Debug.h:119
for(unsigned i=Desc.getNumOperands(), e=OldMI.getNumOperands();i !=e;++i)
iterator_range< block_iterator > blocks() const
Definition: LoopInfo.h:156
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
LoopUnrollResult 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:333
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:743
iterator begin()
Definition: ValueMap.h:141
void forgetTopmostLoop(const Loop *L)
LoopUnrollResult
Represents the result of a UnrollLoop invocation.
Definition: UnrollLoop.h:43
void simplifyLoopAfterUnroll(Loop *L, bool SimplifyIVs, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC)
Perform some cleanup and simplifications on loops after unrolling.
Definition: LoopUnroll.cpp:258