LLVM  15.0.0git
LoopVersioningLICM.cpp
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1 //===- LoopVersioningLICM.cpp - LICM Loop Versioning ----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // When alias analysis is uncertain about the aliasing between any two accesses,
10 // it will return MayAlias. This uncertainty from alias analysis restricts LICM
11 // from proceeding further. In cases where alias analysis is uncertain we might
12 // use loop versioning as an alternative.
13 //
14 // Loop Versioning will create a version of the loop with aggressive aliasing
15 // assumptions in addition to the original with conservative (default) aliasing
16 // assumptions. The version of the loop making aggressive aliasing assumptions
17 // will have all the memory accesses marked as no-alias. These two versions of
18 // loop will be preceded by a memory runtime check. This runtime check consists
19 // of bound checks for all unique memory accessed in loop, and it ensures the
20 // lack of memory aliasing. The result of the runtime check determines which of
21 // the loop versions is executed: If the runtime check detects any memory
22 // aliasing, then the original loop is executed. Otherwise, the version with
23 // aggressive aliasing assumptions is used.
24 //
25 // Following are the top level steps:
26 //
27 // a) Perform LoopVersioningLICM's feasibility check.
28 // b) If loop is a candidate for versioning then create a memory bound check,
29 // by considering all the memory accesses in loop body.
30 // c) Clone original loop and set all memory accesses as no-alias in new loop.
31 // d) Set original loop & versioned loop as a branch target of the runtime check
32 // result.
33 //
34 // It transforms loop as shown below:
35 //
36 // +----------------+
37 // |Runtime Memcheck|
38 // +----------------+
39 // |
40 // +----------+----------------+----------+
41 // | |
42 // +---------+----------+ +-----------+----------+
43 // |Orig Loop Preheader | |Cloned Loop Preheader |
44 // +--------------------+ +----------------------+
45 // | |
46 // +--------------------+ +----------------------+
47 // |Orig Loop Body | |Cloned Loop Body |
48 // +--------------------+ +----------------------+
49 // | |
50 // +--------------------+ +----------------------+
51 // |Orig Loop Exit Block| |Cloned Loop Exit Block|
52 // +--------------------+ +-----------+----------+
53 // | |
54 // +----------+--------------+-----------+
55 // |
56 // +-----+----+
57 // |Join Block|
58 // +----------+
59 //
60 //===----------------------------------------------------------------------===//
61 
63 #include "llvm/ADT/SmallVector.h"
64 #include "llvm/ADT/StringRef.h"
69 #include "llvm/Analysis/LoopInfo.h"
70 #include "llvm/Analysis/LoopPass.h"
73 #include "llvm/IR/Dominators.h"
74 #include "llvm/IR/Instruction.h"
75 #include "llvm/IR/Instructions.h"
76 #include "llvm/IR/LLVMContext.h"
77 #include "llvm/IR/MDBuilder.h"
78 #include "llvm/IR/Metadata.h"
79 #include "llvm/IR/Value.h"
80 #include "llvm/InitializePasses.h"
81 #include "llvm/Pass.h"
82 #include "llvm/Support/Casting.h"
84 #include "llvm/Support/Debug.h"
86 #include "llvm/Transforms/Scalar.h"
87 #include "llvm/Transforms/Utils.h"
90 #include <cassert>
91 #include <memory>
92 
93 using namespace llvm;
94 
95 #define DEBUG_TYPE "loop-versioning-licm"
96 
97 static const char *LICMVersioningMetaData = "llvm.loop.licm_versioning.disable";
98 
99 /// Threshold minimum allowed percentage for possible
100 /// invariant instructions in a loop.
101 static cl::opt<float>
102  LVInvarThreshold("licm-versioning-invariant-threshold",
103  cl::desc("LoopVersioningLICM's minimum allowed percentage"
104  "of possible invariant instructions per loop"),
105  cl::init(25), cl::Hidden);
106 
107 /// Threshold for maximum allowed loop nest/depth
109  "licm-versioning-max-depth-threshold",
110  cl::desc(
111  "LoopVersioningLICM's threshold for maximum allowed loop nest/depth"),
112  cl::init(2), cl::Hidden);
113 
114 namespace {
115 
116 struct LoopVersioningLICMLegacyPass : public LoopPass {
117  static char ID;
118 
119  LoopVersioningLICMLegacyPass() : LoopPass(ID) {
122  }
123 
124  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
125 
126  StringRef getPassName() const override { return "Loop Versioning for LICM"; }
127 
128  void getAnalysisUsage(AnalysisUsage &AU) const override {
129  AU.setPreservesCFG();
140  }
141 };
142 
143 struct LoopVersioningLICM {
144  // We don't explicitly pass in LoopAccessInfo to the constructor since the
145  // loop versioning might return early due to instructions that are not safe
146  // for versioning. By passing the proxy instead the construction of
147  // LoopAccessInfo will take place only when it's necessary.
148  LoopVersioningLICM(AliasAnalysis *AA, ScalarEvolution *SE,
150  function_ref<const LoopAccessInfo &(Loop *)> GetLAI)
151  : AA(AA), SE(SE), GetLAI(GetLAI),
152  LoopDepthThreshold(LVLoopDepthThreshold),
153  InvariantThreshold(LVInvarThreshold), ORE(ORE) {}
154 
155  bool runOnLoop(Loop *L, LoopInfo *LI, DominatorTree *DT);
156 
157  void reset() {
158  AA = nullptr;
159  SE = nullptr;
160  CurLoop = nullptr;
161  LoadAndStoreCounter = 0;
162  InvariantCounter = 0;
163  IsReadOnlyLoop = true;
164  ORE = nullptr;
165  CurAST.reset();
166  }
167 
168  class AutoResetter {
169  public:
170  AutoResetter(LoopVersioningLICM &LVLICM) : LVLICM(LVLICM) {}
171  ~AutoResetter() { LVLICM.reset(); }
172 
173  private:
174  LoopVersioningLICM &LVLICM;
175  };
176 
177 private:
178  // Current AliasAnalysis information
179  AliasAnalysis *AA = nullptr;
180 
181  // Current ScalarEvolution
182  ScalarEvolution *SE = nullptr;
183 
184  // Current Loop's LoopAccessInfo
185  const LoopAccessInfo *LAI = nullptr;
186 
187  // Proxy for retrieving LoopAccessInfo.
188  function_ref<const LoopAccessInfo &(Loop *)> GetLAI;
189 
190  // The current loop we are working on.
191  Loop *CurLoop = nullptr;
192 
193  // AliasSet information for the current loop.
194  std::unique_ptr<AliasSetTracker> CurAST;
195 
196  // Maximum loop nest threshold
197  unsigned LoopDepthThreshold;
198 
199  // Minimum invariant threshold
200  float InvariantThreshold;
201 
202  // Counter to track num of load & store
203  unsigned LoadAndStoreCounter = 0;
204 
205  // Counter to track num of invariant
206  unsigned InvariantCounter = 0;
207 
208  // Read only loop marker.
209  bool IsReadOnlyLoop = true;
210 
211  // OptimizationRemarkEmitter
213 
214  bool isLegalForVersioning();
215  bool legalLoopStructure();
216  bool legalLoopInstructions();
217  bool legalLoopMemoryAccesses();
218  bool isLoopAlreadyVisited();
219  void setNoAliasToLoop(Loop *VerLoop);
220  bool instructionSafeForVersioning(Instruction *I);
221 };
222 
223 } // end anonymous namespace
224 
225 /// Check loop structure and confirms it's good for LoopVersioningLICM.
226 bool LoopVersioningLICM::legalLoopStructure() {
227  // Loop must be in loop simplify form.
228  if (!CurLoop->isLoopSimplifyForm()) {
229  LLVM_DEBUG(dbgs() << " loop is not in loop-simplify form.\n");
230  return false;
231  }
232  // Loop should be innermost loop, if not return false.
233  if (!CurLoop->getSubLoops().empty()) {
234  LLVM_DEBUG(dbgs() << " loop is not innermost\n");
235  return false;
236  }
237  // Loop should have a single backedge, if not return false.
238  if (CurLoop->getNumBackEdges() != 1) {
239  LLVM_DEBUG(dbgs() << " loop has multiple backedges\n");
240  return false;
241  }
242  // Loop must have a single exiting block, if not return false.
243  if (!CurLoop->getExitingBlock()) {
244  LLVM_DEBUG(dbgs() << " loop has multiple exiting block\n");
245  return false;
246  }
247  // We only handle bottom-tested loop, i.e. loop in which the condition is
248  // checked at the end of each iteration. With that we can assume that all
249  // instructions in the loop are executed the same number of times.
250  if (CurLoop->getExitingBlock() != CurLoop->getLoopLatch()) {
251  LLVM_DEBUG(dbgs() << " loop is not bottom tested\n");
252  return false;
253  }
254  // Parallel loops must not have aliasing loop-invariant memory accesses.
255  // Hence we don't need to version anything in this case.
256  if (CurLoop->isAnnotatedParallel()) {
257  LLVM_DEBUG(dbgs() << " Parallel loop is not worth versioning\n");
258  return false;
259  }
260  // Loop depth more then LoopDepthThreshold are not allowed
261  if (CurLoop->getLoopDepth() > LoopDepthThreshold) {
262  LLVM_DEBUG(dbgs() << " loop depth is more then threshold\n");
263  return false;
264  }
265  // We need to be able to compute the loop trip count in order
266  // to generate the bound checks.
267  const SCEV *ExitCount = SE->getBackedgeTakenCount(CurLoop);
268  if (isa<SCEVCouldNotCompute>(ExitCount)) {
269  LLVM_DEBUG(dbgs() << " loop does not has trip count\n");
270  return false;
271  }
272  return true;
273 }
274 
275 /// Check memory accesses in loop and confirms it's good for
276 /// LoopVersioningLICM.
277 bool LoopVersioningLICM::legalLoopMemoryAccesses() {
278  bool HasMayAlias = false;
279  bool TypeSafety = false;
280  bool HasMod = false;
281  // Memory check:
282  // Transform phase will generate a versioned loop and also a runtime check to
283  // ensure the pointers are independent and they don’t alias.
284  // In version variant of loop, alias meta data asserts that all access are
285  // mutually independent.
286  //
287  // Pointers aliasing in alias domain are avoided because with multiple
288  // aliasing domains we may not be able to hoist potential loop invariant
289  // access out of the loop.
290  //
291  // Iterate over alias tracker sets, and confirm AliasSets doesn't have any
292  // must alias set.
293  for (const auto &I : *CurAST) {
294  const AliasSet &AS = I;
295  // Skip Forward Alias Sets, as this should be ignored as part of
296  // the AliasSetTracker object.
297  if (AS.isForwardingAliasSet())
298  continue;
299  // With MustAlias its not worth adding runtime bound check.
300  if (AS.isMustAlias())
301  return false;
302  Value *SomePtr = AS.begin()->getValue();
303  bool TypeCheck = true;
304  // Check for Mod & MayAlias
305  HasMayAlias |= AS.isMayAlias();
306  HasMod |= AS.isMod();
307  for (const auto &A : AS) {
308  Value *Ptr = A.getValue();
309  // Alias tracker should have pointers of same data type.
310  TypeCheck = (TypeCheck && (SomePtr->getType() == Ptr->getType()));
311  }
312  // At least one alias tracker should have pointers of same data type.
313  TypeSafety |= TypeCheck;
314  }
315  // Ensure types should be of same type.
316  if (!TypeSafety) {
317  LLVM_DEBUG(dbgs() << " Alias tracker type safety failed!\n");
318  return false;
319  }
320  // Ensure loop body shouldn't be read only.
321  if (!HasMod) {
322  LLVM_DEBUG(dbgs() << " No memory modified in loop body\n");
323  return false;
324  }
325  // Make sure alias set has may alias case.
326  // If there no alias memory ambiguity, return false.
327  if (!HasMayAlias) {
328  LLVM_DEBUG(dbgs() << " No ambiguity in memory access.\n");
329  return false;
330  }
331  return true;
332 }
333 
334 /// Check loop instructions safe for Loop versioning.
335 /// It returns true if it's safe else returns false.
336 /// Consider following:
337 /// 1) Check all load store in loop body are non atomic & non volatile.
338 /// 2) Check function call safety, by ensuring its not accessing memory.
339 /// 3) Loop body shouldn't have any may throw instruction.
340 /// 4) Loop body shouldn't have any convergent or noduplicate instructions.
341 bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
342  assert(I != nullptr && "Null instruction found!");
343  // Check function call safety
344  if (auto *Call = dyn_cast<CallBase>(I)) {
345  if (Call->isConvergent() || Call->cannotDuplicate()) {
346  LLVM_DEBUG(dbgs() << " Convergent call site found.\n");
347  return false;
348  }
349 
350  if (!AA->doesNotAccessMemory(Call)) {
351  LLVM_DEBUG(dbgs() << " Unsafe call site found.\n");
352  return false;
353  }
354  }
355 
356  // Avoid loops with possiblity of throw
357  if (I->mayThrow()) {
358  LLVM_DEBUG(dbgs() << " May throw instruction found in loop body\n");
359  return false;
360  }
361  // If current instruction is load instructions
362  // make sure it's a simple load (non atomic & non volatile)
363  if (I->mayReadFromMemory()) {
364  LoadInst *Ld = dyn_cast<LoadInst>(I);
365  if (!Ld || !Ld->isSimple()) {
366  LLVM_DEBUG(dbgs() << " Found a non-simple load.\n");
367  return false;
368  }
369  LoadAndStoreCounter++;
370  Value *Ptr = Ld->getPointerOperand();
371  // Check loop invariant.
372  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
373  InvariantCounter++;
374  }
375  // If current instruction is store instruction
376  // make sure it's a simple store (non atomic & non volatile)
377  else if (I->mayWriteToMemory()) {
378  StoreInst *St = dyn_cast<StoreInst>(I);
379  if (!St || !St->isSimple()) {
380  LLVM_DEBUG(dbgs() << " Found a non-simple store.\n");
381  return false;
382  }
383  LoadAndStoreCounter++;
384  Value *Ptr = St->getPointerOperand();
385  // Check loop invariant.
386  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
387  InvariantCounter++;
388 
389  IsReadOnlyLoop = false;
390  }
391  return true;
392 }
393 
394 /// Check loop instructions and confirms it's good for
395 /// LoopVersioningLICM.
396 bool LoopVersioningLICM::legalLoopInstructions() {
397  // Resetting counters.
398  LoadAndStoreCounter = 0;
399  InvariantCounter = 0;
400  IsReadOnlyLoop = true;
401  using namespace ore;
402  // Iterate over loop blocks and instructions of each block and check
403  // instruction safety.
404  for (auto *Block : CurLoop->getBlocks())
405  for (auto &Inst : *Block) {
406  // If instruction is unsafe just return false.
407  if (!instructionSafeForVersioning(&Inst)) {
408  ORE->emit([&]() {
409  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopInst", &Inst)
410  << " Unsafe Loop Instruction";
411  });
412  return false;
413  }
414  }
415  // Get LoopAccessInfo from current loop via the proxy.
416  LAI = &GetLAI(CurLoop);
417  // Check LoopAccessInfo for need of runtime check.
418  if (LAI->getRuntimePointerChecking()->getChecks().empty()) {
419  LLVM_DEBUG(dbgs() << " LAA: Runtime check not found !!\n");
420  return false;
421  }
422  // Number of runtime-checks should be less then RuntimeMemoryCheckThreshold
423  if (LAI->getNumRuntimePointerChecks() >
425  LLVM_DEBUG(
426  dbgs() << " LAA: Runtime checks are more than threshold !!\n");
427  ORE->emit([&]() {
428  return OptimizationRemarkMissed(DEBUG_TYPE, "RuntimeCheck",
429  CurLoop->getStartLoc(),
430  CurLoop->getHeader())
431  << "Number of runtime checks "
432  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks())
433  << " exceeds threshold "
435  });
436  return false;
437  }
438  // Loop should have at least one invariant load or store instruction.
439  if (!InvariantCounter) {
440  LLVM_DEBUG(dbgs() << " Invariant not found !!\n");
441  return false;
442  }
443  // Read only loop not allowed.
444  if (IsReadOnlyLoop) {
445  LLVM_DEBUG(dbgs() << " Found a read-only loop!\n");
446  return false;
447  }
448  // Profitablity check:
449  // Check invariant threshold, should be in limit.
450  if (InvariantCounter * 100 < InvariantThreshold * LoadAndStoreCounter) {
451  LLVM_DEBUG(
452  dbgs()
453  << " Invariant load & store are less then defined threshold\n");
454  LLVM_DEBUG(dbgs() << " Invariant loads & stores: "
455  << ((InvariantCounter * 100) / LoadAndStoreCounter)
456  << "%\n");
457  LLVM_DEBUG(dbgs() << " Invariant loads & store threshold: "
458  << InvariantThreshold << "%\n");
459  ORE->emit([&]() {
460  return OptimizationRemarkMissed(DEBUG_TYPE, "InvariantThreshold",
461  CurLoop->getStartLoc(),
462  CurLoop->getHeader())
463  << "Invariant load & store "
464  << NV("LoadAndStoreCounter",
465  ((InvariantCounter * 100) / LoadAndStoreCounter))
466  << " are less then defined threshold "
467  << NV("Threshold", InvariantThreshold);
468  });
469  return false;
470  }
471  return true;
472 }
473 
474 /// It checks loop is already visited or not.
475 /// check loop meta data, if loop revisited return true
476 /// else false.
477 bool LoopVersioningLICM::isLoopAlreadyVisited() {
478  // Check LoopVersioningLICM metadata into loop
480  return true;
481  }
482  return false;
483 }
484 
485 /// Checks legality for LoopVersioningLICM by considering following:
486 /// a) loop structure legality b) loop instruction legality
487 /// c) loop memory access legality.
488 /// Return true if legal else returns false.
489 bool LoopVersioningLICM::isLegalForVersioning() {
490  using namespace ore;
491  LLVM_DEBUG(dbgs() << "Loop: " << *CurLoop);
492  // Make sure not re-visiting same loop again.
493  if (isLoopAlreadyVisited()) {
494  LLVM_DEBUG(
495  dbgs() << " Revisiting loop in LoopVersioningLICM not allowed.\n\n");
496  return false;
497  }
498  // Check loop structure leagality.
499  if (!legalLoopStructure()) {
500  LLVM_DEBUG(
501  dbgs() << " Loop structure not suitable for LoopVersioningLICM\n\n");
502  ORE->emit([&]() {
503  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopStruct",
504  CurLoop->getStartLoc(),
505  CurLoop->getHeader())
506  << " Unsafe Loop structure";
507  });
508  return false;
509  }
510  // Check loop instruction leagality.
511  if (!legalLoopInstructions()) {
512  LLVM_DEBUG(
513  dbgs()
514  << " Loop instructions not suitable for LoopVersioningLICM\n\n");
515  return false;
516  }
517  // Check loop memory access leagality.
518  if (!legalLoopMemoryAccesses()) {
519  LLVM_DEBUG(
520  dbgs()
521  << " Loop memory access not suitable for LoopVersioningLICM\n\n");
522  ORE->emit([&]() {
523  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopMemoryAccess",
524  CurLoop->getStartLoc(),
525  CurLoop->getHeader())
526  << " Unsafe Loop memory access";
527  });
528  return false;
529  }
530  // Loop versioning is feasible, return true.
531  LLVM_DEBUG(dbgs() << " Loop Versioning found to be beneficial\n\n");
532  ORE->emit([&]() {
533  return OptimizationRemark(DEBUG_TYPE, "IsLegalForVersioning",
534  CurLoop->getStartLoc(), CurLoop->getHeader())
535  << " Versioned loop for LICM."
536  << " Number of runtime checks we had to insert "
537  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks());
538  });
539  return true;
540 }
541 
542 /// Update loop with aggressive aliasing assumptions.
543 /// It marks no-alias to any pairs of memory operations by assuming
544 /// loop should not have any must-alias memory accesses pairs.
545 /// During LoopVersioningLICM legality we ignore loops having must
546 /// aliasing memory accesses.
547 void LoopVersioningLICM::setNoAliasToLoop(Loop *VerLoop) {
548  // Get latch terminator instruction.
549  Instruction *I = VerLoop->getLoopLatch()->getTerminator();
550  // Create alias scope domain.
551  MDBuilder MDB(I->getContext());
552  MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("LVDomain");
553  StringRef Name = "LVAliasScope";
554  MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
555  SmallVector<Metadata *, 4> Scopes{NewScope}, NoAliases{NewScope};
556  // Iterate over each instruction of loop.
557  // set no-alias for all load & store instructions.
558  for (auto *Block : CurLoop->getBlocks()) {
559  for (auto &Inst : *Block) {
560  // Only interested in instruction that may modify or read memory.
561  if (!Inst.mayReadFromMemory() && !Inst.mayWriteToMemory())
562  continue;
563  // Set no-alias for current instruction.
564  Inst.setMetadata(
565  LLVMContext::MD_noalias,
566  MDNode::concatenate(Inst.getMetadata(LLVMContext::MD_noalias),
567  MDNode::get(Inst.getContext(), NoAliases)));
568  // set alias-scope for current instruction.
569  Inst.setMetadata(
570  LLVMContext::MD_alias_scope,
571  MDNode::concatenate(Inst.getMetadata(LLVMContext::MD_alias_scope),
572  MDNode::get(Inst.getContext(), Scopes)));
573  }
574  }
575 }
576 
577 bool LoopVersioningLICMLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) {
578  if (skipLoop(L))
579  return false;
580 
581  AliasAnalysis *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
582  ScalarEvolution *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
584  &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
585  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
586  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
587 
588  auto GetLAI = [&](Loop *L) -> const LoopAccessInfo & {
589  return getAnalysis<LoopAccessLegacyAnalysis>().getInfo(L);
590  };
591 
592  return LoopVersioningLICM(AA, SE, ORE, GetLAI).runOnLoop(L, LI, DT);
593 }
594 
595 bool LoopVersioningLICM::runOnLoop(Loop *L, LoopInfo *LI, DominatorTree *DT) {
596  // This will automatically release all resources hold by the current
597  // LoopVersioningLICM object.
598  AutoResetter Resetter(*this);
599 
600  // Do not do the transformation if disabled by metadata.
602  return false;
603 
604  // Set Current Loop
605  CurLoop = L;
606  CurAST.reset(new AliasSetTracker(*AA));
607 
608  // Loop over the body of this loop, construct AST.
609  for (auto *Block : L->getBlocks()) {
610  if (LI->getLoopFor(Block) == L) // Ignore blocks in subloop.
611  CurAST->add(*Block); // Incorporate the specified basic block
612  }
613 
614  bool Changed = false;
615 
616  // Check feasiblity of LoopVersioningLICM.
617  // If versioning found to be feasible and beneficial then proceed
618  // else simply return, by cleaning up memory.
619  if (isLegalForVersioning()) {
620  // Do loop versioning.
621  // Create memcheck for memory accessed inside loop.
622  // Clone original loop, and set blocks properly.
623  LoopVersioning LVer(*LAI, LAI->getRuntimePointerChecking()->getChecks(),
624  CurLoop, LI, DT, SE);
625  LVer.versionLoop();
626  // Set Loop Versioning metaData for original loop.
627  addStringMetadataToLoop(LVer.getNonVersionedLoop(), LICMVersioningMetaData);
628  // Set Loop Versioning metaData for version loop.
629  addStringMetadataToLoop(LVer.getVersionedLoop(), LICMVersioningMetaData);
630  // Set "llvm.mem.parallel_loop_access" metaData to versioned loop.
631  // FIXME: "llvm.mem.parallel_loop_access" annotates memory access
632  // instructions, not loops.
633  addStringMetadataToLoop(LVer.getVersionedLoop(),
634  "llvm.mem.parallel_loop_access");
635  // Update version loop with aggressive aliasing assumption.
636  setNoAliasToLoop(LVer.getVersionedLoop());
637  Changed = true;
638  }
639  return Changed;
640 }
641 
643 
644 INITIALIZE_PASS_BEGIN(LoopVersioningLICMLegacyPass, "loop-versioning-licm",
645  "Loop Versioning For LICM", false, false)
649 INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
652 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
655 INITIALIZE_PASS_END(LoopVersioningLICMLegacyPass, "loop-versioning-licm",
656  "Loop Versioning For LICM", false, false)
657 
659  return new LoopVersioningLICMLegacyPass();
660 }
661 
662 namespace llvm {
663 
666  LPMUpdater &U) {
667  AliasAnalysis *AA = &LAR.AA;
668  ScalarEvolution *SE = &LAR.SE;
669  DominatorTree *DT = &LAR.DT;
670  LoopInfo *LI = &LAR.LI;
671  const Function *F = L.getHeader()->getParent();
673 
674  auto GetLAI = [&](Loop *L) -> const LoopAccessInfo & {
675  return AM.getResult<LoopAccessAnalysis>(*L, LAR);
676  };
677 
678  if (!LoopVersioningLICM(AA, SE, &ORE, GetLAI).runOnLoop(&L, LI, DT))
679  return PreservedAnalyses::all();
681 }
682 } // namespace llvm
llvm::PreservedAnalyses
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:152
llvm::OptimizationRemarkMissed
Diagnostic information for missed-optimization remarks.
Definition: DiagnosticInfo.h:735
llvm::LoopAccessLegacyAnalysis
This analysis provides dependence information for the memory accesses of a loop.
Definition: LoopAccessAnalysis.h:771
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:17
INITIALIZE_PASS_BEGIN
INITIALIZE_PASS_BEGIN(LoopVersioningLICMLegacyPass, "loop-versioning-licm", "Loop Versioning For LICM", false, false) INITIALIZE_PASS_END(LoopVersioningLICMLegacyPass
Metadata.h
llvm::BasicBlock::getParent
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:104
llvm::AnalysisManager::getResult
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:780
Scalar.h
llvm::Function
Definition: Function.h:60
llvm::Loop
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:546
StringRef.h
Pass.h
llvm::SmallVector
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1185
llvm::AliasSet::isMod
bool isMod() const
Definition: AliasSetTracker.h:202
LoopAccessAnalysis.h
llvm::ScalarEvolution
The main scalar evolution driver.
Definition: ScalarEvolution.h:449
OptimizationRemarkEmitter.h
llvm::DominatorTree
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:166
GlobalsModRef.h
llvm::AliasSetTracker
Definition: AliasSetTracker.h:322
llvm::cl::Hidden
@ Hidden
Definition: CommandLine.h:139
llvm::LoopAccessAnalysis
This analysis provides dependence information for the memory accesses of a loop.
Definition: LoopAccessAnalysis.h:813
ScalarEvolution.h
llvm::LoopInfoWrapperPass
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:1287
llvm::LoopStandardAnalysisResults
The adaptor from a function pass to a loop pass computes these analyses and makes them available to t...
Definition: LoopAnalysisManager.h:51
llvm::ore::NV
DiagnosticInfoOptimizationBase::Argument NV
Definition: OptimizationRemarkEmitter.h:136
llvm::LoopVersioningLICMPass::run
PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &LAR, LPMUpdater &U)
Definition: LoopVersioningLICM.cpp:664
llvm::LoadInst::getPointerOperand
Value * getPointerOperand()
Definition: Instructions.h:260
llvm::LoopStandardAnalysisResults::DT
DominatorTree & DT
Definition: LoopAnalysisManager.h:54
LLVM_DEBUG
#define LLVM_DEBUG(X)
Definition: Debug.h:101
llvm::MDNode::get
static MDTuple * get(LLVMContext &Context, ArrayRef< Metadata * > MDs)
Definition: Metadata.h:1384
F
#define F(x, y, z)
Definition: MD5.cpp:55
loop
Analysis the ScalarEvolution expression for r is< loop > Outside the loop
Definition: README.txt:8
AliasAnalysis.h
llvm::dbgs
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
Instruction.h
CommandLine.h
llvm::PassRegistry::getPassRegistry
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
Definition: PassRegistry.cpp:31
llvm::AAResults
Definition: AliasAnalysis.h:511
llvm::ARM_PROC::A
@ A
Definition: ARMBaseInfo.h:34
llvm::createLoopVersioningLICMPass
Pass * createLoopVersioningLICMPass()
Definition: LoopVersioningLICM.cpp:658
LVLoopDepthThreshold
static cl::opt< unsigned > LVLoopDepthThreshold("licm-versioning-max-depth-threshold", cl::desc("LoopVersioningLICM's threshold for maximum allowed loop nest/depth"), cl::init(2), cl::Hidden)
Threshold for maximum allowed loop nest/depth.
llvm::AnalysisUsage
Represent the analysis usage information of a pass.
Definition: PassAnalysisSupport.h:47
llvm::AliasSet
Definition: AliasSetTracker.h:46
llvm::StoreInst::isSimple
bool isSimple() const
Definition: Instructions.h:378
false
Definition: StackSlotColoring.cpp:141
llvm::AliasSet::isForwardingAliasSet
bool isForwardingAliasSet() const
Return true if this alias set should be ignored as part of the AliasSetTracker object.
Definition: AliasSetTracker.h:208
llvm::LoopBase::getBlocks
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:187
llvm::Instruction
Definition: Instruction.h:42
llvm::DominatorTreeWrapperPass
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:302
MDBuilder.h
llvm::initializeLoopVersioningLICMLegacyPassPass
void initializeLoopVersioningLICMLegacyPassPass(PassRegistry &)
LoopUtils.h
llvm::ScalarEvolutionWrapperPass
Definition: ScalarEvolution.h:2153
llvm::LPPassManager
Definition: LoopPass.h:76
llvm::hasLICMVersioningTransformation
TransformationMode hasLICMVersioningTransformation(const Loop *L)
Definition: LoopUtils.cpp:440
llvm::MCID::Call
@ Call
Definition: MCInstrDesc.h:155
Utils.h
llvm::CallingConv::ID
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
INITIALIZE_PASS_END
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:58
LoopInfo.h
llvm::ScalarEvolution::getSCEV
const SCEV * getSCEV(Value *V)
Return a SCEV expression for the full generality of the specified expression.
Definition: ScalarEvolution.cpp:4402
llvm::function_ref
An efficient, type-erasing, non-owning reference to a callable.
Definition: STLFunctionalExtras.h:36
llvm::getLoopPassPreservedAnalyses
PreservedAnalyses getLoopPassPreservedAnalyses()
Returns the minimum set of Analyses that all loop passes must preserve.
Definition: LoopAnalysisManager.cpp:137
llvm::findStringMetadataForLoop
Optional< const MDOperand * > findStringMetadataForLoop(const Loop *TheLoop, StringRef Name)
Find string metadata for loop.
Definition: LoopInfo.cpp:1051
llvm::cl::opt
Definition: CommandLine.h:1392
llvm::SCEV
This class represents an analyzed expression in the program.
Definition: ScalarEvolution.h:75
llvm::StoreInst
An instruction for storing to memory.
Definition: Instructions.h:297
LICM
loop versioning Loop Versioning For LICM
Definition: LoopVersioningLICM.cpp:656
llvm::LoopPass
Definition: LoopPass.h:28
llvm::LPMUpdater
This class provides an interface for updating the loop pass manager based on mutations to the loop ne...
Definition: LoopPassManager.h:262
INITIALIZE_PASS_DEPENDENCY
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
llvm::LoopVersioning
This class emits a version of the loop where run-time checks ensure that may-alias pointers can't ove...
Definition: LoopVersioning.h:41
llvm::addStringMetadataToLoop
void addStringMetadataToLoop(Loop *TheLoop, const char *MDString, unsigned V=0)
Set input string into loop metadata by keeping other values intact.
Definition: LoopUtils.cpp:217
llvm::LoopInfoBase::getLoopFor
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:986
I
#define I(x, y, z)
Definition: MD5.cpp:58
llvm::cl::init
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:432
llvm::LoopAccessInfo
Drive the analysis of memory accesses in the loop.
Definition: LoopAccessAnalysis.h:559
llvm::AliasSet::isMayAlias
bool isMayAlias() const
Definition: AliasSetTracker.h:204
llvm::LoopBase::getLoopLatch
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:215
llvm::TM_Disable
@ TM_Disable
The transformation should not be applied.
Definition: LoopUtils.h:277
assert
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
llvm::OptimizationRemarkEmitter::emit
void emit(DiagnosticInfoOptimizationBase &OptDiag)
Output the remark via the diagnostic handler and to the optimization record file.
Definition: OptimizationRemarkEmitter.cpp:77
llvm::VectorizerParams::RuntimeMemoryCheckThreshold
static unsigned RuntimeMemoryCheckThreshold
\When performing memory disambiguation checks at runtime do not make more than this number of compari...
Definition: LoopAccessAnalysis.h:49
llvm::MDNode
Metadata node.
Definition: Metadata.h:944
LICMVersioningMetaData
static const char * LICMVersioningMetaData
Definition: LoopVersioningLICM.cpp:97
llvm::LoopInfo
Definition: LoopInfo.h:1102
llvm::OptimizationRemarkEmitter
The optimization diagnostic interface.
Definition: OptimizationRemarkEmitter.h:33
llvm::AnalysisUsage::setPreservesCFG
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:263
llvm::StringRef
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:58
llvm::LoadInst::isSimple
bool isSimple() const
Definition: Instructions.h:252
DEBUG_TYPE
#define DEBUG_TYPE
Definition: LoopVersioningLICM.cpp:95
LoopPass.h
llvm::Value::getType
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
llvm::MDNode::concatenate
static MDNode * concatenate(MDNode *A, MDNode *B)
Methods for metadata merging.
Definition: Metadata.cpp:1012
llvm::AnalysisUsage::addPreserved
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
Definition: PassAnalysisSupport.h:98
llvm::LoopStandardAnalysisResults::LI
LoopInfo & LI
Definition: LoopAnalysisManager.h:55
llvm::LoadInst
An instruction for reading from memory.
Definition: Instructions.h:173
llvm::ScalarEvolution::isLoopInvariant
bool isLoopInvariant(const SCEV *S, const Loop *L)
Return true if the value of the given SCEV is unchanging in the specified loop.
Definition: ScalarEvolution.cpp:13404
LoopVersioningLICM.h
llvm::LCSSAID
char & LCSSAID
Definition: LCSSA.cpp:486
llvm::OptimizationRemarkEmitterWrapperPass
OptimizationRemarkEmitter legacy analysis pass.
Definition: OptimizationRemarkEmitter.h:146
llvm::LoopSimplifyID
char & LoopSimplifyID
Definition: LoopSimplify.cpp:794
llvm::GraphProgram::Name
Name
Definition: GraphWriter.h:50
llvm::PreservedAnalyses::all
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:158
Casting.h
llvm::LoopBase::getHeader
BlockT * getHeader() const
Definition: LoopInfo.h:104
LoopVersioning.h
llvm::LoopStandardAnalysisResults::SE
ScalarEvolution & SE
Definition: LoopAnalysisManager.h:56
llvm::LoopStandardAnalysisResults::AA
AAResults & AA
Definition: LoopAnalysisManager.h:52
llvm::MDBuilder
Definition: MDBuilder.h:35
AA
licm
loop versioning licm
Definition: LoopVersioningLICM.cpp:655
llvm::AliasSet::begin
iterator begin() const
Definition: AliasSetTracker.h:216
llvm::OptimizationRemark
Diagnostic information for applied optimization remarks.
Definition: DiagnosticInfo.h:690
llvm::Pass
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:91
Instructions.h
SmallVector.h
llvm::StoreInst::getPointerOperand
Value * getPointerOperand()
Definition: Instructions.h:389
Dominators.h
NoAliases
static cl::opt< bool > NoAliases("csky-no-aliases", cl::desc("Disable the emission of assembler pseudo instructions"), cl::init(false), cl::Hidden)
llvm::AliasSet::isMustAlias
bool isMustAlias() const
Definition: AliasSetTracker.h:203
llvm::AAResultsWrapperPass
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object.
Definition: AliasAnalysis.h:1351
llvm::GlobalsAAWrapperPass
Legacy wrapper pass to provide the GlobalsAAResult object.
Definition: GlobalsModRef.h:148
llvm::BasicBlock::getTerminator
const Instruction * 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.h:119
llvm::AnalysisManager
A container for analyses that lazily runs them and caches their results.
Definition: InstructionSimplify.h:42
AliasSetTracker.h
llvm::AnalysisUsage::addRequiredID
AnalysisUsage & addRequiredID(const void *ID)
Definition: Pass.cpp:277
llvm::AnalysisUsage::addRequired
AnalysisUsage & addRequired()
Definition: PassAnalysisSupport.h:75
LLVMContext.h
llvm::cl::desc
Definition: CommandLine.h:405
raw_ostream.h
llvm::ScalarEvolution::getBackedgeTakenCount
const SCEV * getBackedgeTakenCount(const Loop *L, ExitCountKind Kind=Exact)
If the specified loop has a predictable backedge-taken count, return it, otherwise return a SCEVCould...
Definition: ScalarEvolution.cpp:8096
Value.h
InitializePasses.h
llvm::Value
LLVM Value Representation.
Definition: Value.h:74
Debug.h
LVInvarThreshold
static cl::opt< float > LVInvarThreshold("licm-versioning-invariant-threshold", cl::desc("LoopVersioningLICM's minimum allowed percentage" "of possible invariant instructions per loop"), cl::init(25), cl::Hidden)
Threshold minimum allowed percentage for possible invariant instructions in a loop.
llvm::Intrinsic::ID
unsigned ID
Definition: TargetTransformInfo.h:38