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LoopVersioningLICM.cpp
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1 //===- LoopVersioningLICM.cpp - LICM Loop Versioning ----------------------===//
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 // When alias analysis is uncertain about the aliasing between any two accesses,
11 // it will return MayAlias. This uncertainty from alias analysis restricts LICM
12 // from proceeding further. In cases where alias analysis is uncertain we might
13 // use loop versioning as an alternative.
14 //
15 // Loop Versioning will create a version of the loop with aggressive aliasing
16 // assumptions in addition to the original with conservative (default) aliasing
17 // assumptions. The version of the loop making aggressive aliasing assumptions
18 // will have all the memory accesses marked as no-alias. These two versions of
19 // loop will be preceded by a memory runtime check. This runtime check consists
20 // of bound checks for all unique memory accessed in loop, and it ensures the
21 // lack of memory aliasing. The result of the runtime check determines which of
22 // the loop versions is executed: If the runtime check detects any memory
23 // aliasing, then the original loop is executed. Otherwise, the version with
24 // aggressive aliasing assumptions is used.
25 //
26 // Following are the top level steps:
27 //
28 // a) Perform LoopVersioningLICM's feasibility check.
29 // b) If loop is a candidate for versioning then create a memory bound check,
30 // by considering all the memory accesses in loop body.
31 // c) Clone original loop and set all memory accesses as no-alias in new loop.
32 // d) Set original loop & versioned loop as a branch target of the runtime check
33 // result.
34 //
35 // It transforms loop as shown below:
36 //
37 // +----------------+
38 // |Runtime Memcheck|
39 // +----------------+
40 // |
41 // +----------+----------------+----------+
42 // | |
43 // +---------+----------+ +-----------+----------+
44 // |Orig Loop Preheader | |Cloned Loop Preheader |
45 // +--------------------+ +----------------------+
46 // | |
47 // +--------------------+ +----------------------+
48 // |Orig Loop Body | |Cloned Loop Body |
49 // +--------------------+ +----------------------+
50 // | |
51 // +--------------------+ +----------------------+
52 // |Orig Loop Exit Block| |Cloned Loop Exit Block|
53 // +--------------------+ +-----------+----------+
54 // | |
55 // +----------+--------------+-----------+
56 // |
57 // +-----+----+
58 // |Join Block|
59 // +----------+
60 //
61 //===----------------------------------------------------------------------===//
62 
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/CallSite.h"
74 #include "llvm/IR/Constants.h"
75 #include "llvm/IR/Dominators.h"
76 #include "llvm/IR/Instruction.h"
77 #include "llvm/IR/Instructions.h"
78 #include "llvm/IR/LLVMContext.h"
79 #include "llvm/IR/MDBuilder.h"
80 #include "llvm/IR/Metadata.h"
81 #include "llvm/IR/Type.h"
82 #include "llvm/IR/Value.h"
83 #include "llvm/Pass.h"
84 #include "llvm/Support/Casting.h"
86 #include "llvm/Support/Debug.h"
88 #include "llvm/Transforms/Scalar.h"
91 #include <cassert>
92 #include <memory>
93 
94 using namespace llvm;
95 
96 #define DEBUG_TYPE "loop-versioning-licm"
97 
98 static const char *LICMVersioningMetaData = "llvm.loop.licm_versioning.disable";
99 
100 /// Threshold minimum allowed percentage for possible
101 /// invariant instructions in a loop.
102 static cl::opt<float>
103  LVInvarThreshold("licm-versioning-invariant-threshold",
104  cl::desc("LoopVersioningLICM's minimum allowed percentage"
105  "of possible invariant instructions per loop"),
106  cl::init(25), cl::Hidden);
107 
108 /// Threshold for maximum allowed loop nest/depth
110  "licm-versioning-max-depth-threshold",
111  cl::desc(
112  "LoopVersioningLICM's threshold for maximum allowed loop nest/depth"),
113  cl::init(2), cl::Hidden);
114 
115 /// \brief Create MDNode for input string.
116 static MDNode *createStringMetadata(Loop *TheLoop, StringRef Name, unsigned V) {
117  LLVMContext &Context = TheLoop->getHeader()->getContext();
118  Metadata *MDs[] = {
119  MDString::get(Context, Name),
121  return MDNode::get(Context, MDs);
122 }
123 
124 /// \brief Set input string into loop metadata by keeping other values intact.
125 void llvm::addStringMetadataToLoop(Loop *TheLoop, const char *MDString,
126  unsigned V) {
128  // If the loop already has metadata, retain it.
129  MDNode *LoopID = TheLoop->getLoopID();
130  if (LoopID) {
131  for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
132  MDNode *Node = cast<MDNode>(LoopID->getOperand(i));
133  MDs.push_back(Node);
134  }
135  }
136  // Add new metadata.
137  MDs.push_back(createStringMetadata(TheLoop, MDString, V));
138  // Replace current metadata node with new one.
139  LLVMContext &Context = TheLoop->getHeader()->getContext();
140  MDNode *NewLoopID = MDNode::get(Context, MDs);
141  // Set operand 0 to refer to the loop id itself.
142  NewLoopID->replaceOperandWith(0, NewLoopID);
143  TheLoop->setLoopID(NewLoopID);
144 }
145 
146 namespace {
147 
148 struct LoopVersioningLICM : public LoopPass {
149  static char ID;
150 
151  LoopVersioningLICM()
152  : LoopPass(ID), LoopDepthThreshold(LVLoopDepthThreshold),
153  InvariantThreshold(LVInvarThreshold) {
155  }
156 
157  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
158 
159  void getAnalysisUsage(AnalysisUsage &AU) const override {
160  AU.setPreservesCFG();
171  }
172 
173  StringRef getPassName() const override { return "Loop Versioning for LICM"; }
174 
175  void reset() {
176  AA = nullptr;
177  SE = nullptr;
178  LAA = nullptr;
179  CurLoop = nullptr;
180  LoadAndStoreCounter = 0;
181  InvariantCounter = 0;
182  IsReadOnlyLoop = true;
183  ORE = nullptr;
184  CurAST.reset();
185  }
186 
187  class AutoResetter {
188  public:
189  AutoResetter(LoopVersioningLICM &LVLICM) : LVLICM(LVLICM) {}
190  ~AutoResetter() { LVLICM.reset(); }
191 
192  private:
193  LoopVersioningLICM &LVLICM;
194  };
195 
196 private:
197  // Current AliasAnalysis information
198  AliasAnalysis *AA = nullptr;
199 
200  // Current ScalarEvolution
201  ScalarEvolution *SE = nullptr;
202 
203  // Current LoopAccessAnalysis
204  LoopAccessLegacyAnalysis *LAA = nullptr;
205 
206  // Current Loop's LoopAccessInfo
207  const LoopAccessInfo *LAI = nullptr;
208 
209  // The current loop we are working on.
210  Loop *CurLoop = nullptr;
211 
212  // AliasSet information for the current loop.
213  std::unique_ptr<AliasSetTracker> CurAST;
214 
215  // Maximum loop nest threshold
216  unsigned LoopDepthThreshold;
217 
218  // Minimum invariant threshold
219  float InvariantThreshold;
220 
221  // Counter to track num of load & store
222  unsigned LoadAndStoreCounter = 0;
223 
224  // Counter to track num of invariant
225  unsigned InvariantCounter = 0;
226 
227  // Read only loop marker.
228  bool IsReadOnlyLoop = true;
229 
230  // OptimizationRemarkEmitter
232 
233  bool isLegalForVersioning();
234  bool legalLoopStructure();
235  bool legalLoopInstructions();
236  bool legalLoopMemoryAccesses();
237  bool isLoopAlreadyVisited();
238  void setNoAliasToLoop(Loop *VerLoop);
239  bool instructionSafeForVersioning(Instruction *I);
240 };
241 
242 } // end anonymous namespace
243 
244 /// \brief Check loop structure and confirms it's good for LoopVersioningLICM.
245 bool LoopVersioningLICM::legalLoopStructure() {
246  // Loop must be in loop simplify form.
247  if (!CurLoop->isLoopSimplifyForm()) {
248  DEBUG(
249  dbgs() << " loop is not in loop-simplify form.\n");
250  return false;
251  }
252  // Loop should be innermost loop, if not return false.
253  if (!CurLoop->getSubLoops().empty()) {
254  DEBUG(dbgs() << " loop is not innermost\n");
255  return false;
256  }
257  // Loop should have a single backedge, if not return false.
258  if (CurLoop->getNumBackEdges() != 1) {
259  DEBUG(dbgs() << " loop has multiple backedges\n");
260  return false;
261  }
262  // Loop must have a single exiting block, if not return false.
263  if (!CurLoop->getExitingBlock()) {
264  DEBUG(dbgs() << " loop has multiple exiting block\n");
265  return false;
266  }
267  // We only handle bottom-tested loop, i.e. loop in which the condition is
268  // checked at the end of each iteration. With that we can assume that all
269  // instructions in the loop are executed the same number of times.
270  if (CurLoop->getExitingBlock() != CurLoop->getLoopLatch()) {
271  DEBUG(dbgs() << " loop is not bottom tested\n");
272  return false;
273  }
274  // Parallel loops must not have aliasing loop-invariant memory accesses.
275  // Hence we don't need to version anything in this case.
276  if (CurLoop->isAnnotatedParallel()) {
277  DEBUG(dbgs() << " Parallel loop is not worth versioning\n");
278  return false;
279  }
280  // Loop depth more then LoopDepthThreshold are not allowed
281  if (CurLoop->getLoopDepth() > LoopDepthThreshold) {
282  DEBUG(dbgs() << " loop depth is more then threshold\n");
283  return false;
284  }
285  // We need to be able to compute the loop trip count in order
286  // to generate the bound checks.
287  const SCEV *ExitCount = SE->getBackedgeTakenCount(CurLoop);
288  if (ExitCount == SE->getCouldNotCompute()) {
289  DEBUG(dbgs() << " loop does not has trip count\n");
290  return false;
291  }
292  return true;
293 }
294 
295 /// \brief Check memory accesses in loop and confirms it's good for
296 /// LoopVersioningLICM.
297 bool LoopVersioningLICM::legalLoopMemoryAccesses() {
298  bool HasMayAlias = false;
299  bool TypeSafety = false;
300  bool HasMod = false;
301  // Memory check:
302  // Transform phase will generate a versioned loop and also a runtime check to
303  // ensure the pointers are independent and they don’t alias.
304  // In version variant of loop, alias meta data asserts that all access are
305  // mutually independent.
306  //
307  // Pointers aliasing in alias domain are avoided because with multiple
308  // aliasing domains we may not be able to hoist potential loop invariant
309  // access out of the loop.
310  //
311  // Iterate over alias tracker sets, and confirm AliasSets doesn't have any
312  // must alias set.
313  for (const auto &I : *CurAST) {
314  const AliasSet &AS = I;
315  // Skip Forward Alias Sets, as this should be ignored as part of
316  // the AliasSetTracker object.
317  if (AS.isForwardingAliasSet())
318  continue;
319  // With MustAlias its not worth adding runtime bound check.
320  if (AS.isMustAlias())
321  return false;
322  Value *SomePtr = AS.begin()->getValue();
323  bool TypeCheck = true;
324  // Check for Mod & MayAlias
325  HasMayAlias |= AS.isMayAlias();
326  HasMod |= AS.isMod();
327  for (const auto &A : AS) {
328  Value *Ptr = A.getValue();
329  // Alias tracker should have pointers of same data type.
330  TypeCheck = (TypeCheck && (SomePtr->getType() == Ptr->getType()));
331  }
332  // At least one alias tracker should have pointers of same data type.
333  TypeSafety |= TypeCheck;
334  }
335  // Ensure types should be of same type.
336  if (!TypeSafety) {
337  DEBUG(dbgs() << " Alias tracker type safety failed!\n");
338  return false;
339  }
340  // Ensure loop body shouldn't be read only.
341  if (!HasMod) {
342  DEBUG(dbgs() << " No memory modified in loop body\n");
343  return false;
344  }
345  // Make sure alias set has may alias case.
346  // If there no alias memory ambiguity, return false.
347  if (!HasMayAlias) {
348  DEBUG(dbgs() << " No ambiguity in memory access.\n");
349  return false;
350  }
351  return true;
352 }
353 
354 /// \brief Check loop instructions safe for Loop versioning.
355 /// It returns true if it's safe else returns false.
356 /// Consider following:
357 /// 1) Check all load store in loop body are non atomic & non volatile.
358 /// 2) Check function call safety, by ensuring its not accessing memory.
359 /// 3) Loop body shouldn't have any may throw instruction.
360 bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
361  assert(I != nullptr && "Null instruction found!");
362  // Check function call safety
363  if (isa<CallInst>(I) && !AA->doesNotAccessMemory(CallSite(I))) {
364  DEBUG(dbgs() << " Unsafe call site found.\n");
365  return false;
366  }
367  // Avoid loops with possiblity of throw
368  if (I->mayThrow()) {
369  DEBUG(dbgs() << " May throw instruction found in loop body\n");
370  return false;
371  }
372  // If current instruction is load instructions
373  // make sure it's a simple load (non atomic & non volatile)
374  if (I->mayReadFromMemory()) {
375  LoadInst *Ld = dyn_cast<LoadInst>(I);
376  if (!Ld || !Ld->isSimple()) {
377  DEBUG(dbgs() << " Found a non-simple load.\n");
378  return false;
379  }
380  LoadAndStoreCounter++;
381  Value *Ptr = Ld->getPointerOperand();
382  // Check loop invariant.
383  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
384  InvariantCounter++;
385  }
386  // If current instruction is store instruction
387  // make sure it's a simple store (non atomic & non volatile)
388  else if (I->mayWriteToMemory()) {
389  StoreInst *St = dyn_cast<StoreInst>(I);
390  if (!St || !St->isSimple()) {
391  DEBUG(dbgs() << " Found a non-simple store.\n");
392  return false;
393  }
394  LoadAndStoreCounter++;
395  Value *Ptr = St->getPointerOperand();
396  // Check loop invariant.
397  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
398  InvariantCounter++;
399 
400  IsReadOnlyLoop = false;
401  }
402  return true;
403 }
404 
405 /// \brief Check loop instructions and confirms it's good for
406 /// LoopVersioningLICM.
407 bool LoopVersioningLICM::legalLoopInstructions() {
408  // Resetting counters.
409  LoadAndStoreCounter = 0;
410  InvariantCounter = 0;
411  IsReadOnlyLoop = true;
412  using namespace ore;
413  // Iterate over loop blocks and instructions of each block and check
414  // instruction safety.
415  for (auto *Block : CurLoop->getBlocks())
416  for (auto &Inst : *Block) {
417  // If instruction is unsafe just return false.
418  if (!instructionSafeForVersioning(&Inst)) {
419  ORE->emit([&]() {
420  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopInst", &Inst)
421  << " Unsafe Loop Instruction";
422  });
423  return false;
424  }
425  }
426  // Get LoopAccessInfo from current loop.
427  LAI = &LAA->getInfo(CurLoop);
428  // Check LoopAccessInfo for need of runtime check.
429  if (LAI->getRuntimePointerChecking()->getChecks().empty()) {
430  DEBUG(dbgs() << " LAA: Runtime check not found !!\n");
431  return false;
432  }
433  // Number of runtime-checks should be less then RuntimeMemoryCheckThreshold
434  if (LAI->getNumRuntimePointerChecks() >
436  DEBUG(dbgs() << " LAA: Runtime checks are more than threshold !!\n");
437  ORE->emit([&]() {
438  return OptimizationRemarkMissed(DEBUG_TYPE, "RuntimeCheck",
439  CurLoop->getStartLoc(),
440  CurLoop->getHeader())
441  << "Number of runtime checks "
442  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks())
443  << " exceeds threshold "
445  });
446  return false;
447  }
448  // Loop should have at least one invariant load or store instruction.
449  if (!InvariantCounter) {
450  DEBUG(dbgs() << " Invariant not found !!\n");
451  return false;
452  }
453  // Read only loop not allowed.
454  if (IsReadOnlyLoop) {
455  DEBUG(dbgs() << " Found a read-only loop!\n");
456  return false;
457  }
458  // Profitablity check:
459  // Check invariant threshold, should be in limit.
460  if (InvariantCounter * 100 < InvariantThreshold * LoadAndStoreCounter) {
461  DEBUG(dbgs()
462  << " Invariant load & store are less then defined threshold\n");
463  DEBUG(dbgs() << " Invariant loads & stores: "
464  << ((InvariantCounter * 100) / LoadAndStoreCounter) << "%\n");
465  DEBUG(dbgs() << " Invariant loads & store threshold: "
466  << InvariantThreshold << "%\n");
467  ORE->emit([&]() {
468  return OptimizationRemarkMissed(DEBUG_TYPE, "InvariantThreshold",
469  CurLoop->getStartLoc(),
470  CurLoop->getHeader())
471  << "Invariant load & store "
472  << NV("LoadAndStoreCounter",
473  ((InvariantCounter * 100) / LoadAndStoreCounter))
474  << " are less then defined threshold "
475  << NV("Threshold", InvariantThreshold);
476  });
477  return false;
478  }
479  return true;
480 }
481 
482 /// \brief It checks loop is already visited or not.
483 /// check loop meta data, if loop revisited return true
484 /// else false.
485 bool LoopVersioningLICM::isLoopAlreadyVisited() {
486  // Check LoopVersioningLICM metadata into loop
487  if (findStringMetadataForLoop(CurLoop, LICMVersioningMetaData)) {
488  return true;
489  }
490  return false;
491 }
492 
493 /// \brief Checks legality for LoopVersioningLICM by considering following:
494 /// a) loop structure legality b) loop instruction legality
495 /// c) loop memory access legality.
496 /// Return true if legal else returns false.
497 bool LoopVersioningLICM::isLegalForVersioning() {
498  using namespace ore;
499  DEBUG(dbgs() << "Loop: " << *CurLoop);
500  // Make sure not re-visiting same loop again.
501  if (isLoopAlreadyVisited()) {
502  DEBUG(
503  dbgs() << " Revisiting loop in LoopVersioningLICM not allowed.\n\n");
504  return false;
505  }
506  // Check loop structure leagality.
507  if (!legalLoopStructure()) {
508  DEBUG(
509  dbgs() << " Loop structure not suitable for LoopVersioningLICM\n\n");
510  ORE->emit([&]() {
511  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopStruct",
512  CurLoop->getStartLoc(),
513  CurLoop->getHeader())
514  << " Unsafe Loop structure";
515  });
516  return false;
517  }
518  // Check loop instruction leagality.
519  if (!legalLoopInstructions()) {
520  DEBUG(dbgs()
521  << " Loop instructions not suitable for LoopVersioningLICM\n\n");
522  return false;
523  }
524  // Check loop memory access leagality.
525  if (!legalLoopMemoryAccesses()) {
526  DEBUG(dbgs()
527  << " Loop memory access not suitable for LoopVersioningLICM\n\n");
528  ORE->emit([&]() {
529  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopMemoryAccess",
530  CurLoop->getStartLoc(),
531  CurLoop->getHeader())
532  << " Unsafe Loop memory access";
533  });
534  return false;
535  }
536  // Loop versioning is feasible, return true.
537  DEBUG(dbgs() << " Loop Versioning found to be beneficial\n\n");
538  ORE->emit([&]() {
539  return OptimizationRemark(DEBUG_TYPE, "IsLegalForVersioning",
540  CurLoop->getStartLoc(), CurLoop->getHeader())
541  << " Versioned loop for LICM."
542  << " Number of runtime checks we had to insert "
543  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks());
544  });
545  return true;
546 }
547 
548 /// \brief Update loop with aggressive aliasing assumptions.
549 /// It marks no-alias to any pairs of memory operations by assuming
550 /// loop should not have any must-alias memory accesses pairs.
551 /// During LoopVersioningLICM legality we ignore loops having must
552 /// aliasing memory accesses.
553 void LoopVersioningLICM::setNoAliasToLoop(Loop *VerLoop) {
554  // Get latch terminator instruction.
555  Instruction *I = VerLoop->getLoopLatch()->getTerminator();
556  // Create alias scope domain.
557  MDBuilder MDB(I->getContext());
558  MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("LVDomain");
559  StringRef Name = "LVAliasScope";
561  MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
562  // Iterate over each instruction of loop.
563  // set no-alias for all load & store instructions.
564  for (auto *Block : CurLoop->getBlocks()) {
565  for (auto &Inst : *Block) {
566  // Only interested in instruction that may modify or read memory.
567  if (!Inst.mayReadFromMemory() && !Inst.mayWriteToMemory())
568  continue;
569  Scopes.push_back(NewScope);
570  NoAliases.push_back(NewScope);
571  // Set no-alias for current instruction.
572  Inst.setMetadata(
575  MDNode::get(Inst.getContext(), NoAliases)));
576  // set alias-scope for current instruction.
577  Inst.setMetadata(
580  MDNode::get(Inst.getContext(), Scopes)));
581  }
582  }
583 }
584 
585 bool LoopVersioningLICM::runOnLoop(Loop *L, LPPassManager &LPM) {
586  // This will automatically release all resources hold by the current
587  // LoopVersioningLICM object.
588  AutoResetter Resetter(*this);
589 
590  if (skipLoop(L))
591  return false;
592  // Get Analysis information.
593  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
594  SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
595  LAA = &getAnalysis<LoopAccessLegacyAnalysis>();
596  ORE = &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
597  LAI = nullptr;
598  // Set Current Loop
599  CurLoop = L;
600  CurAST.reset(new AliasSetTracker(*AA));
601 
602  // Loop over the body of this loop, construct AST.
603  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
604  for (auto *Block : L->getBlocks()) {
605  if (LI->getLoopFor(Block) == L) // Ignore blocks in subloop.
606  CurAST->add(*Block); // Incorporate the specified basic block
607  }
608 
609  bool Changed = false;
610 
611  // Check feasiblity of LoopVersioningLICM.
612  // If versioning found to be feasible and beneficial then proceed
613  // else simply return, by cleaning up memory.
614  if (isLegalForVersioning()) {
615  // Do loop versioning.
616  // Create memcheck for memory accessed inside loop.
617  // Clone original loop, and set blocks properly.
618  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
619  LoopVersioning LVer(*LAI, CurLoop, LI, DT, SE, true);
620  LVer.versionLoop();
621  // Set Loop Versioning metaData for original loop.
623  // Set Loop Versioning metaData for version loop.
625  // Set "llvm.mem.parallel_loop_access" metaData to versioned loop.
627  "llvm.mem.parallel_loop_access");
628  // Update version loop with aggressive aliasing assumption.
629  setNoAliasToLoop(LVer.getVersionedLoop());
630  Changed = true;
631  }
632  return Changed;
633 }
634 
635 char LoopVersioningLICM::ID = 0;
636 
637 INITIALIZE_PASS_BEGIN(LoopVersioningLICM, "loop-versioning-licm",
638  "Loop Versioning For LICM", false, false)
642 INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
645 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
648 INITIALIZE_PASS_END(LoopVersioningLICM, "loop-versioning-licm",
649  "Loop Versioning For LICM", false, false)
650 
651 Pass *llvm::createLoopVersioningLICMPass() { return new LoopVersioningLICM(); }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
static unsigned RuntimeMemoryCheckThreshold
\brief When performing memory disambiguation checks at runtime do not make more than this number of c...
bool isSimple() const
Definition: Instructions.h:262
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
Diagnostic information for missed-optimization remarks.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:157
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
LLVMContext & Context
DiagnosticInfoOptimizationBase::Argument NV
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
bool isMayAlias() const
This is the interface for a simple mod/ref and alias analysis over globals.
void replaceOperandWith(unsigned I, Metadata *New)
Replace a specific operand.
Definition: Metadata.cpp:859
static MDString * get(LLVMContext &Context, StringRef Str)
Definition: Metadata.cpp:454
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.
The main scalar evolution driver.
This file contains the declarations for metadata subclasses.
bool mayWriteToMemory() const
Return true if this instruction may modify memory.
INITIALIZE_PASS_BEGIN(LoopVersioningLICM, "loop-versioning-licm", "Loop Versioning For LICM", false, false) INITIALIZE_PASS_END(LoopVersioningLICM
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:738
Metadata node.
Definition: Metadata.h:862
const MDOperand & getOperand(unsigned I) const
Definition: Metadata.h:1067
An instruction for reading from memory.
Definition: Instructions.h:164
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:33
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:678
static const char * LICMVersioningMetaData
bool isMustAlias() const
BlockT * getHeader() const
Definition: LoopInfo.h:100
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
iterator begin() const
void setLoopID(MDNode *LoopID) const
Set the llvm.loop loop id metadata for this loop.
Definition: LoopInfo.cpp:249
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.
An instruction for storing to memory.
Definition: Instructions.h:306
void versionLoop()
Performs the CFG manipulation part of versioning the loop including the DominatorTree and LoopInfo up...
static ConstantAsMetadata * get(Constant *C)
Definition: Metadata.h:408
void addStringMetadataToLoop(Loop *TheLoop, const char *MDString, unsigned V=0)
Set input string into loop metadata by keeping other values intact.
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:142
Loop * getVersionedLoop()
Returns the versioned loop.
static MDTuple * get(LLVMContext &Context, ArrayRef< Metadata *> MDs)
Definition: Metadata.h:1164
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:406
#define DEBUG_TYPE
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
This analysis provides dependence information for the memory accesses of a loop.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
char & LCSSAID
Definition: LCSSA.cpp:418
bool mayThrow() const
Return true if this instruction may throw an exception.
Diagnostic information for applied optimization remarks.
Represent the analysis usage information of a pass.
Value * getPointerOperand()
Definition: Instructions.h:270
bool isMod() const
const AMDGPUAS & AS
Pass * createLoopVersioningLICMPass()
Optional< const MDOperand * > findStringMetadataForLoop(Loop *TheLoop, StringRef Name)
Find string metadata for loop.
Definition: LoopUtils.cpp:1284
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
char & LoopSimplifyID
void initializeLoopVersioningLICMPass(PassRegistry &)
AnalysisUsage & addRequiredID(const void *ID)
Definition: Pass.cpp:298
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:862
loop versioning licm
Drive the analysis of memory accesses in the loop.
static cl::opt< bool > NoAliases("riscv-no-aliases", cl::desc("Disable the emission of assembler pseudo instructions"), cl::init(false), cl::Hidden)
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:598
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:285
This class emits a version of the loop where run-time checks ensure that may-alias pointers can&#39;t ove...
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
MDNode * getLoopID() const
Return the llvm.loop loop id metadata node for this loop if it is present.
Definition: LoopInfo.cpp:213
This class represents an analyzed expression in the program.
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:176
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:439
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:149
static MDNode * concatenate(MDNode *A, MDNode *B)
Methods for metadata merging.
Definition: Metadata.cpp:896
#define I(x, y, z)
Definition: MD5.cpp:58
bool mayReadFromMemory() const
Return true if this instruction may read memory.
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
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static MDNode * createStringMetadata(Loop *TheLoop, StringRef Name, unsigned V)
Create MDNode for input string.
LLVM Value Representation.
Definition: Value.h:73
OptimizationRemarkEmitter legacy analysis pass.
#define DEBUG(X)
Definition: Debug.h:118
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:958
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
A single uniqued string.
Definition: Metadata.h:602
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:260
bool isForwardingAliasSet() const
Return true if this alias set should be ignored as part of the AliasSetTracker object.
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
bool isSimple() const
Definition: Instructions.h:387
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
unsigned getNumOperands() const
Return number of MDNode operands.
Definition: Metadata.h:1073
Root of the metadata hierarchy.
Definition: Metadata.h:58
Value * getPointerOperand()
Definition: Instructions.h:398
Loop * getNonVersionedLoop()
Returns the fall-back loop.
The optimization diagnostic interface.
loop versioning Loop Versioning For LICM