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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 
62 #include "llvm/ADT/SmallVector.h"
63 #include "llvm/ADT/StringRef.h"
68 #include "llvm/Analysis/LoopInfo.h"
69 #include "llvm/Analysis/LoopPass.h"
72 #include "llvm/IR/CallSite.h"
73 #include "llvm/IR/Constants.h"
74 #include "llvm/IR/Dominators.h"
75 #include "llvm/IR/Instruction.h"
76 #include "llvm/IR/Instructions.h"
77 #include "llvm/IR/LLVMContext.h"
78 #include "llvm/IR/MDBuilder.h"
79 #include "llvm/IR/Metadata.h"
80 #include "llvm/IR/Type.h"
81 #include "llvm/IR/Value.h"
82 #include "llvm/Pass.h"
83 #include "llvm/Support/Casting.h"
85 #include "llvm/Support/Debug.h"
87 #include "llvm/Transforms/Scalar.h"
88 #include "llvm/Transforms/Utils.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 namespace {
116 
117 struct LoopVersioningLICM : public LoopPass {
118  static char ID;
119 
120  LoopVersioningLICM()
121  : LoopPass(ID), LoopDepthThreshold(LVLoopDepthThreshold),
122  InvariantThreshold(LVInvarThreshold) {
124  }
125 
126  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
127 
128  void getAnalysisUsage(AnalysisUsage &AU) const override {
129  AU.setPreservesCFG();
140  }
141 
142  StringRef getPassName() const override { return "Loop Versioning for LICM"; }
143 
144  void reset() {
145  AA = nullptr;
146  SE = nullptr;
147  LAA = nullptr;
148  CurLoop = nullptr;
149  LoadAndStoreCounter = 0;
150  InvariantCounter = 0;
151  IsReadOnlyLoop = true;
152  ORE = nullptr;
153  CurAST.reset();
154  }
155 
156  class AutoResetter {
157  public:
158  AutoResetter(LoopVersioningLICM &LVLICM) : LVLICM(LVLICM) {}
159  ~AutoResetter() { LVLICM.reset(); }
160 
161  private:
162  LoopVersioningLICM &LVLICM;
163  };
164 
165 private:
166  // Current AliasAnalysis information
167  AliasAnalysis *AA = nullptr;
168 
169  // Current ScalarEvolution
170  ScalarEvolution *SE = nullptr;
171 
172  // Current LoopAccessAnalysis
173  LoopAccessLegacyAnalysis *LAA = nullptr;
174 
175  // Current Loop's LoopAccessInfo
176  const LoopAccessInfo *LAI = nullptr;
177 
178  // The current loop we are working on.
179  Loop *CurLoop = nullptr;
180 
181  // AliasSet information for the current loop.
182  std::unique_ptr<AliasSetTracker> CurAST;
183 
184  // Maximum loop nest threshold
185  unsigned LoopDepthThreshold;
186 
187  // Minimum invariant threshold
188  float InvariantThreshold;
189 
190  // Counter to track num of load & store
191  unsigned LoadAndStoreCounter = 0;
192 
193  // Counter to track num of invariant
194  unsigned InvariantCounter = 0;
195 
196  // Read only loop marker.
197  bool IsReadOnlyLoop = true;
198 
199  // OptimizationRemarkEmitter
201 
202  bool isLegalForVersioning();
203  bool legalLoopStructure();
204  bool legalLoopInstructions();
205  bool legalLoopMemoryAccesses();
206  bool isLoopAlreadyVisited();
207  void setNoAliasToLoop(Loop *VerLoop);
208  bool instructionSafeForVersioning(Instruction *I);
209 };
210 
211 } // end anonymous namespace
212 
213 /// Check loop structure and confirms it's good for LoopVersioningLICM.
214 bool LoopVersioningLICM::legalLoopStructure() {
215  // Loop must be in loop simplify form.
216  if (!CurLoop->isLoopSimplifyForm()) {
217  LLVM_DEBUG(dbgs() << " loop is not in loop-simplify form.\n");
218  return false;
219  }
220  // Loop should be innermost loop, if not return false.
221  if (!CurLoop->getSubLoops().empty()) {
222  LLVM_DEBUG(dbgs() << " loop is not innermost\n");
223  return false;
224  }
225  // Loop should have a single backedge, if not return false.
226  if (CurLoop->getNumBackEdges() != 1) {
227  LLVM_DEBUG(dbgs() << " loop has multiple backedges\n");
228  return false;
229  }
230  // Loop must have a single exiting block, if not return false.
231  if (!CurLoop->getExitingBlock()) {
232  LLVM_DEBUG(dbgs() << " loop has multiple exiting block\n");
233  return false;
234  }
235  // We only handle bottom-tested loop, i.e. loop in which the condition is
236  // checked at the end of each iteration. With that we can assume that all
237  // instructions in the loop are executed the same number of times.
238  if (CurLoop->getExitingBlock() != CurLoop->getLoopLatch()) {
239  LLVM_DEBUG(dbgs() << " loop is not bottom tested\n");
240  return false;
241  }
242  // Parallel loops must not have aliasing loop-invariant memory accesses.
243  // Hence we don't need to version anything in this case.
244  if (CurLoop->isAnnotatedParallel()) {
245  LLVM_DEBUG(dbgs() << " Parallel loop is not worth versioning\n");
246  return false;
247  }
248  // Loop depth more then LoopDepthThreshold are not allowed
249  if (CurLoop->getLoopDepth() > LoopDepthThreshold) {
250  LLVM_DEBUG(dbgs() << " loop depth is more then threshold\n");
251  return false;
252  }
253  // We need to be able to compute the loop trip count in order
254  // to generate the bound checks.
255  const SCEV *ExitCount = SE->getBackedgeTakenCount(CurLoop);
256  if (ExitCount == SE->getCouldNotCompute()) {
257  LLVM_DEBUG(dbgs() << " loop does not has trip count\n");
258  return false;
259  }
260  return true;
261 }
262 
263 /// Check memory accesses in loop and confirms it's good for
264 /// LoopVersioningLICM.
265 bool LoopVersioningLICM::legalLoopMemoryAccesses() {
266  bool HasMayAlias = false;
267  bool TypeSafety = false;
268  bool HasMod = false;
269  // Memory check:
270  // Transform phase will generate a versioned loop and also a runtime check to
271  // ensure the pointers are independent and they don’t alias.
272  // In version variant of loop, alias meta data asserts that all access are
273  // mutually independent.
274  //
275  // Pointers aliasing in alias domain are avoided because with multiple
276  // aliasing domains we may not be able to hoist potential loop invariant
277  // access out of the loop.
278  //
279  // Iterate over alias tracker sets, and confirm AliasSets doesn't have any
280  // must alias set.
281  for (const auto &I : *CurAST) {
282  const AliasSet &AS = I;
283  // Skip Forward Alias Sets, as this should be ignored as part of
284  // the AliasSetTracker object.
285  if (AS.isForwardingAliasSet())
286  continue;
287  // With MustAlias its not worth adding runtime bound check.
288  if (AS.isMustAlias())
289  return false;
290  Value *SomePtr = AS.begin()->getValue();
291  bool TypeCheck = true;
292  // Check for Mod & MayAlias
293  HasMayAlias |= AS.isMayAlias();
294  HasMod |= AS.isMod();
295  for (const auto &A : AS) {
296  Value *Ptr = A.getValue();
297  // Alias tracker should have pointers of same data type.
298  TypeCheck = (TypeCheck && (SomePtr->getType() == Ptr->getType()));
299  }
300  // At least one alias tracker should have pointers of same data type.
301  TypeSafety |= TypeCheck;
302  }
303  // Ensure types should be of same type.
304  if (!TypeSafety) {
305  LLVM_DEBUG(dbgs() << " Alias tracker type safety failed!\n");
306  return false;
307  }
308  // Ensure loop body shouldn't be read only.
309  if (!HasMod) {
310  LLVM_DEBUG(dbgs() << " No memory modified in loop body\n");
311  return false;
312  }
313  // Make sure alias set has may alias case.
314  // If there no alias memory ambiguity, return false.
315  if (!HasMayAlias) {
316  LLVM_DEBUG(dbgs() << " No ambiguity in memory access.\n");
317  return false;
318  }
319  return true;
320 }
321 
322 /// Check loop instructions safe for Loop versioning.
323 /// It returns true if it's safe else returns false.
324 /// Consider following:
325 /// 1) Check all load store in loop body are non atomic & non volatile.
326 /// 2) Check function call safety, by ensuring its not accessing memory.
327 /// 3) Loop body shouldn't have any may throw instruction.
328 /// 4) Loop body shouldn't have any convergent or noduplicate instructions.
329 bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
330  assert(I != nullptr && "Null instruction found!");
331  // Check function call safety
332  if (auto *Call = dyn_cast<CallBase>(I)) {
333  if (Call->isConvergent() || Call->cannotDuplicate()) {
334  LLVM_DEBUG(dbgs() << " Convergent call site found.\n");
335  return false;
336  }
337 
338  if (!AA->doesNotAccessMemory(Call)) {
339  LLVM_DEBUG(dbgs() << " Unsafe call site found.\n");
340  return false;
341  }
342  }
343 
344  // Avoid loops with possiblity of throw
345  if (I->mayThrow()) {
346  LLVM_DEBUG(dbgs() << " May throw instruction found in loop body\n");
347  return false;
348  }
349  // If current instruction is load instructions
350  // make sure it's a simple load (non atomic & non volatile)
351  if (I->mayReadFromMemory()) {
352  LoadInst *Ld = dyn_cast<LoadInst>(I);
353  if (!Ld || !Ld->isSimple()) {
354  LLVM_DEBUG(dbgs() << " Found a non-simple load.\n");
355  return false;
356  }
357  LoadAndStoreCounter++;
358  Value *Ptr = Ld->getPointerOperand();
359  // Check loop invariant.
360  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
361  InvariantCounter++;
362  }
363  // If current instruction is store instruction
364  // make sure it's a simple store (non atomic & non volatile)
365  else if (I->mayWriteToMemory()) {
366  StoreInst *St = dyn_cast<StoreInst>(I);
367  if (!St || !St->isSimple()) {
368  LLVM_DEBUG(dbgs() << " Found a non-simple store.\n");
369  return false;
370  }
371  LoadAndStoreCounter++;
372  Value *Ptr = St->getPointerOperand();
373  // Check loop invariant.
374  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
375  InvariantCounter++;
376 
377  IsReadOnlyLoop = false;
378  }
379  return true;
380 }
381 
382 /// Check loop instructions and confirms it's good for
383 /// LoopVersioningLICM.
384 bool LoopVersioningLICM::legalLoopInstructions() {
385  // Resetting counters.
386  LoadAndStoreCounter = 0;
387  InvariantCounter = 0;
388  IsReadOnlyLoop = true;
389  using namespace ore;
390  // Iterate over loop blocks and instructions of each block and check
391  // instruction safety.
392  for (auto *Block : CurLoop->getBlocks())
393  for (auto &Inst : *Block) {
394  // If instruction is unsafe just return false.
395  if (!instructionSafeForVersioning(&Inst)) {
396  ORE->emit([&]() {
397  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopInst", &Inst)
398  << " Unsafe Loop Instruction";
399  });
400  return false;
401  }
402  }
403  // Get LoopAccessInfo from current loop.
404  LAI = &LAA->getInfo(CurLoop);
405  // Check LoopAccessInfo for need of runtime check.
406  if (LAI->getRuntimePointerChecking()->getChecks().empty()) {
407  LLVM_DEBUG(dbgs() << " LAA: Runtime check not found !!\n");
408  return false;
409  }
410  // Number of runtime-checks should be less then RuntimeMemoryCheckThreshold
411  if (LAI->getNumRuntimePointerChecks() >
413  LLVM_DEBUG(
414  dbgs() << " LAA: Runtime checks are more than threshold !!\n");
415  ORE->emit([&]() {
416  return OptimizationRemarkMissed(DEBUG_TYPE, "RuntimeCheck",
417  CurLoop->getStartLoc(),
418  CurLoop->getHeader())
419  << "Number of runtime checks "
420  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks())
421  << " exceeds threshold "
423  });
424  return false;
425  }
426  // Loop should have at least one invariant load or store instruction.
427  if (!InvariantCounter) {
428  LLVM_DEBUG(dbgs() << " Invariant not found !!\n");
429  return false;
430  }
431  // Read only loop not allowed.
432  if (IsReadOnlyLoop) {
433  LLVM_DEBUG(dbgs() << " Found a read-only loop!\n");
434  return false;
435  }
436  // Profitablity check:
437  // Check invariant threshold, should be in limit.
438  if (InvariantCounter * 100 < InvariantThreshold * LoadAndStoreCounter) {
439  LLVM_DEBUG(
440  dbgs()
441  << " Invariant load & store are less then defined threshold\n");
442  LLVM_DEBUG(dbgs() << " Invariant loads & stores: "
443  << ((InvariantCounter * 100) / LoadAndStoreCounter)
444  << "%\n");
445  LLVM_DEBUG(dbgs() << " Invariant loads & store threshold: "
446  << InvariantThreshold << "%\n");
447  ORE->emit([&]() {
448  return OptimizationRemarkMissed(DEBUG_TYPE, "InvariantThreshold",
449  CurLoop->getStartLoc(),
450  CurLoop->getHeader())
451  << "Invariant load & store "
452  << NV("LoadAndStoreCounter",
453  ((InvariantCounter * 100) / LoadAndStoreCounter))
454  << " are less then defined threshold "
455  << NV("Threshold", InvariantThreshold);
456  });
457  return false;
458  }
459  return true;
460 }
461 
462 /// It checks loop is already visited or not.
463 /// check loop meta data, if loop revisited return true
464 /// else false.
465 bool LoopVersioningLICM::isLoopAlreadyVisited() {
466  // Check LoopVersioningLICM metadata into loop
467  if (findStringMetadataForLoop(CurLoop, LICMVersioningMetaData)) {
468  return true;
469  }
470  return false;
471 }
472 
473 /// Checks legality for LoopVersioningLICM by considering following:
474 /// a) loop structure legality b) loop instruction legality
475 /// c) loop memory access legality.
476 /// Return true if legal else returns false.
477 bool LoopVersioningLICM::isLegalForVersioning() {
478  using namespace ore;
479  LLVM_DEBUG(dbgs() << "Loop: " << *CurLoop);
480  // Make sure not re-visiting same loop again.
481  if (isLoopAlreadyVisited()) {
482  LLVM_DEBUG(
483  dbgs() << " Revisiting loop in LoopVersioningLICM not allowed.\n\n");
484  return false;
485  }
486  // Check loop structure leagality.
487  if (!legalLoopStructure()) {
488  LLVM_DEBUG(
489  dbgs() << " Loop structure not suitable for LoopVersioningLICM\n\n");
490  ORE->emit([&]() {
491  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopStruct",
492  CurLoop->getStartLoc(),
493  CurLoop->getHeader())
494  << " Unsafe Loop structure";
495  });
496  return false;
497  }
498  // Check loop instruction leagality.
499  if (!legalLoopInstructions()) {
500  LLVM_DEBUG(
501  dbgs()
502  << " Loop instructions not suitable for LoopVersioningLICM\n\n");
503  return false;
504  }
505  // Check loop memory access leagality.
506  if (!legalLoopMemoryAccesses()) {
507  LLVM_DEBUG(
508  dbgs()
509  << " Loop memory access not suitable for LoopVersioningLICM\n\n");
510  ORE->emit([&]() {
511  return OptimizationRemarkMissed(DEBUG_TYPE, "IllegalLoopMemoryAccess",
512  CurLoop->getStartLoc(),
513  CurLoop->getHeader())
514  << " Unsafe Loop memory access";
515  });
516  return false;
517  }
518  // Loop versioning is feasible, return true.
519  LLVM_DEBUG(dbgs() << " Loop Versioning found to be beneficial\n\n");
520  ORE->emit([&]() {
521  return OptimizationRemark(DEBUG_TYPE, "IsLegalForVersioning",
522  CurLoop->getStartLoc(), CurLoop->getHeader())
523  << " Versioned loop for LICM."
524  << " Number of runtime checks we had to insert "
525  << NV("RuntimeChecks", LAI->getNumRuntimePointerChecks());
526  });
527  return true;
528 }
529 
530 /// Update loop with aggressive aliasing assumptions.
531 /// It marks no-alias to any pairs of memory operations by assuming
532 /// loop should not have any must-alias memory accesses pairs.
533 /// During LoopVersioningLICM legality we ignore loops having must
534 /// aliasing memory accesses.
535 void LoopVersioningLICM::setNoAliasToLoop(Loop *VerLoop) {
536  // Get latch terminator instruction.
537  Instruction *I = VerLoop->getLoopLatch()->getTerminator();
538  // Create alias scope domain.
539  MDBuilder MDB(I->getContext());
540  MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("LVDomain");
541  StringRef Name = "LVAliasScope";
543  MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
544  // Iterate over each instruction of loop.
545  // set no-alias for all load & store instructions.
546  for (auto *Block : CurLoop->getBlocks()) {
547  for (auto &Inst : *Block) {
548  // Only interested in instruction that may modify or read memory.
549  if (!Inst.mayReadFromMemory() && !Inst.mayWriteToMemory())
550  continue;
551  Scopes.push_back(NewScope);
552  NoAliases.push_back(NewScope);
553  // Set no-alias for current instruction.
554  Inst.setMetadata(
555  LLVMContext::MD_noalias,
556  MDNode::concatenate(Inst.getMetadata(LLVMContext::MD_noalias),
557  MDNode::get(Inst.getContext(), NoAliases)));
558  // set alias-scope for current instruction.
559  Inst.setMetadata(
560  LLVMContext::MD_alias_scope,
561  MDNode::concatenate(Inst.getMetadata(LLVMContext::MD_alias_scope),
562  MDNode::get(Inst.getContext(), Scopes)));
563  }
564  }
565 }
566 
567 bool LoopVersioningLICM::runOnLoop(Loop *L, LPPassManager &LPM) {
568  // This will automatically release all resources hold by the current
569  // LoopVersioningLICM object.
570  AutoResetter Resetter(*this);
571 
572  if (skipLoop(L))
573  return false;
574 
575  // Do not do the transformation if disabled by metadata.
577  return false;
578 
579  // Get Analysis information.
580  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
581  SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
582  LAA = &getAnalysis<LoopAccessLegacyAnalysis>();
583  ORE = &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
584  LAI = nullptr;
585  // Set Current Loop
586  CurLoop = L;
587  CurAST.reset(new AliasSetTracker(*AA));
588 
589  // Loop over the body of this loop, construct AST.
590  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
591  for (auto *Block : L->getBlocks()) {
592  if (LI->getLoopFor(Block) == L) // Ignore blocks in subloop.
593  CurAST->add(*Block); // Incorporate the specified basic block
594  }
595 
596  bool Changed = false;
597 
598  // Check feasiblity of LoopVersioningLICM.
599  // If versioning found to be feasible and beneficial then proceed
600  // else simply return, by cleaning up memory.
601  if (isLegalForVersioning()) {
602  // Do loop versioning.
603  // Create memcheck for memory accessed inside loop.
604  // Clone original loop, and set blocks properly.
605  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
606  LoopVersioning LVer(*LAI, CurLoop, LI, DT, SE, true);
607  LVer.versionLoop();
608  // Set Loop Versioning metaData for original loop.
609  addStringMetadataToLoop(LVer.getNonVersionedLoop(), LICMVersioningMetaData);
610  // Set Loop Versioning metaData for version loop.
611  addStringMetadataToLoop(LVer.getVersionedLoop(), LICMVersioningMetaData);
612  // Set "llvm.mem.parallel_loop_access" metaData to versioned loop.
613  // FIXME: "llvm.mem.parallel_loop_access" annotates memory access
614  // instructions, not loops.
615  addStringMetadataToLoop(LVer.getVersionedLoop(),
616  "llvm.mem.parallel_loop_access");
617  // Update version loop with aggressive aliasing assumption.
618  setNoAliasToLoop(LVer.getVersionedLoop());
619  Changed = true;
620  }
621  return Changed;
622 }
623 
624 char LoopVersioningLICM::ID = 0;
625 
626 INITIALIZE_PASS_BEGIN(LoopVersioningLICM, "loop-versioning-licm",
627  "Loop Versioning For LICM", false, false)
631 INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
634 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
637 INITIALIZE_PASS_END(LoopVersioningLICM, "loop-versioning-licm",
638  "Loop Versioning For LICM", false, false)
639 
640 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:80
static unsigned RuntimeMemoryCheckThreshold
performing memory disambiguation checks at runtime do not make more than this number of comparisons...
bool isSimple() const
Definition: Instructions.h:276
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:209
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
DiagnosticInfoOptimizationBase::Argument NV
This class represents lattice values for constants.
Definition: AllocatorList.h:23
bool isMayAlias() const
This is the interface for a simple mod/ref and alias analysis over globals.
amdgpu Simplify well known AMD library false FunctionCallee Value const Twine & Name
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:733
Metadata node.
Definition: Metadata.h:863
An instruction for reading from memory.
Definition: Instructions.h:167
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.cpp:144
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:928
static const char * LICMVersioningMetaData
bool isMustAlias() const
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
iterator begin() const
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:320
void addStringMetadataToLoop(Loop *TheLoop, const char *MDString, unsigned V=0)
Set input string into loop metadata by keeping other values intact.
Definition: LoopUtils.cpp:211
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
static MDTuple * get(LLVMContext &Context, ArrayRef< Metadata *> MDs)
Definition: Metadata.h:1165
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:432
#define DEBUG_TYPE
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:467
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:284
bool isMod() const
Pass * createLoopVersioningLICMPass()
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
char & LoopSimplifyID
The transformation should not be applied.
Definition: LoopUtils.h:231
void initializeLoopVersioningLICMPass(PassRegistry &)
AnalysisUsage & addRequiredID(const void *ID)
Definition: Pass.cpp:314
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
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)
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
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
This class represents an analyzed expression in the program.
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:509
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:154
static MDNode * concatenate(MDNode *A, MDNode *B)
Methods for metadata merging.
Definition: Metadata.cpp:895
#define I(x, y, z)
Definition: MD5.cpp:58
bool mayReadFromMemory() const
Return true if this instruction may read memory.
Optional< const MDOperand * > findStringMetadataForLoop(const Loop *TheLoop, StringRef Name)
Find string metadata for loop.
Definition: LoopUtils.cpp:251
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:332
TransformationMode hasLICMVersioningTransformation(Loop *L)
Definition: LoopUtils.cpp:475
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
OptimizationRemarkEmitter legacy analysis pass.
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:1208
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:259
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:401
#define LLVM_DEBUG(X)
Definition: Debug.h:122
Value * getPointerOperand()
Definition: Instructions.h:412
The optimization diagnostic interface.
loop versioning Loop Versioning For LICM