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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"
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"
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 /// \brief Create MDNode for input string.
115 static MDNode *createStringMetadata(Loop *TheLoop, StringRef Name, unsigned V) {
116  LLVMContext &Context = TheLoop->getHeader()->getContext();
117  Metadata *MDs[] = {
118  MDString::get(Context, Name),
120  return MDNode::get(Context, MDs);
121 }
122 
123 /// \brief Set input string into loop metadata by keeping other values intact.
124 void llvm::addStringMetadataToLoop(Loop *TheLoop, const char *MDString,
125  unsigned V) {
127  // If the loop already has metadata, retain it.
128  MDNode *LoopID = TheLoop->getLoopID();
129  if (LoopID) {
130  for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
131  MDNode *Node = cast<MDNode>(LoopID->getOperand(i));
132  MDs.push_back(Node);
133  }
134  }
135  // Add new metadata.
136  MDs.push_back(createStringMetadata(TheLoop, MDString, V));
137  // Replace current metadata node with new one.
138  LLVMContext &Context = TheLoop->getHeader()->getContext();
139  MDNode *NewLoopID = MDNode::get(Context, MDs);
140  // Set operand 0 to refer to the loop id itself.
141  NewLoopID->replaceOperandWith(0, NewLoopID);
142  TheLoop->setLoopID(NewLoopID);
143 }
144 
145 namespace {
146 
147 struct LoopVersioningLICM : public LoopPass {
148  static char ID;
149 
150  LoopVersioningLICM()
151  : LoopPass(ID), LoopDepthThreshold(LVLoopDepthThreshold),
152  InvariantThreshold(LVInvarThreshold) {
154  }
155 
156  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
157 
158  void getAnalysisUsage(AnalysisUsage &AU) const override {
159  AU.setPreservesCFG();
169  }
170 
171  StringRef getPassName() const override { return "Loop Versioning for LICM"; }
172 
173  void reset() {
174  AA = nullptr;
175  SE = nullptr;
176  LAA = nullptr;
177  CurLoop = nullptr;
178  LoadAndStoreCounter = 0;
179  InvariantCounter = 0;
180  IsReadOnlyLoop = true;
181  CurAST.reset();
182  }
183 
184  class AutoResetter {
185  public:
186  AutoResetter(LoopVersioningLICM &LVLICM) : LVLICM(LVLICM) {}
187  ~AutoResetter() { LVLICM.reset(); }
188 
189  private:
190  LoopVersioningLICM &LVLICM;
191  };
192 
193 private:
194  // Current AliasAnalysis information
195  AliasAnalysis *AA = nullptr;
196 
197  // Current ScalarEvolution
198  ScalarEvolution *SE = nullptr;
199 
200  // Current LoopAccessAnalysis
201  LoopAccessLegacyAnalysis *LAA = nullptr;
202 
203  // Current Loop's LoopAccessInfo
204  const LoopAccessInfo *LAI = nullptr;
205 
206  // The current loop we are working on.
207  Loop *CurLoop = nullptr;
208 
209  // AliasSet information for the current loop.
210  std::unique_ptr<AliasSetTracker> CurAST;
211 
212  // Maximum loop nest threshold
213  unsigned LoopDepthThreshold;
214 
215  // Minimum invariant threshold
216  float InvariantThreshold;
217 
218  // Counter to track num of load & store
219  unsigned LoadAndStoreCounter = 0;
220 
221  // Counter to track num of invariant
222  unsigned InvariantCounter = 0;
223 
224  // Read only loop marker.
225  bool IsReadOnlyLoop = true;
226 
227  bool isLegalForVersioning();
228  bool legalLoopStructure();
229  bool legalLoopInstructions();
230  bool legalLoopMemoryAccesses();
231  bool isLoopAlreadyVisited();
232  void setNoAliasToLoop(Loop *VerLoop);
233  bool instructionSafeForVersioning(Instruction *I);
234 };
235 
236 } // end anonymous namespace
237 
238 /// \brief Check loop structure and confirms it's good for LoopVersioningLICM.
239 bool LoopVersioningLICM::legalLoopStructure() {
240  // Loop must be in loop simplify form.
241  if (!CurLoop->isLoopSimplifyForm()) {
242  DEBUG(
243  dbgs() << " loop is not in loop-simplify form.\n");
244  return false;
245  }
246  // Loop should be innermost loop, if not return false.
247  if (!CurLoop->getSubLoops().empty()) {
248  DEBUG(dbgs() << " loop is not innermost\n");
249  return false;
250  }
251  // Loop should have a single backedge, if not return false.
252  if (CurLoop->getNumBackEdges() != 1) {
253  DEBUG(dbgs() << " loop has multiple backedges\n");
254  return false;
255  }
256  // Loop must have a single exiting block, if not return false.
257  if (!CurLoop->getExitingBlock()) {
258  DEBUG(dbgs() << " loop has multiple exiting block\n");
259  return false;
260  }
261  // We only handle bottom-tested loop, i.e. loop in which the condition is
262  // checked at the end of each iteration. With that we can assume that all
263  // instructions in the loop are executed the same number of times.
264  if (CurLoop->getExitingBlock() != CurLoop->getLoopLatch()) {
265  DEBUG(dbgs() << " loop is not bottom tested\n");
266  return false;
267  }
268  // Parallel loops must not have aliasing loop-invariant memory accesses.
269  // Hence we don't need to version anything in this case.
270  if (CurLoop->isAnnotatedParallel()) {
271  DEBUG(dbgs() << " Parallel loop is not worth versioning\n");
272  return false;
273  }
274  // Loop depth more then LoopDepthThreshold are not allowed
275  if (CurLoop->getLoopDepth() > LoopDepthThreshold) {
276  DEBUG(dbgs() << " loop depth is more then threshold\n");
277  return false;
278  }
279  // We need to be able to compute the loop trip count in order
280  // to generate the bound checks.
281  const SCEV *ExitCount = SE->getBackedgeTakenCount(CurLoop);
282  if (ExitCount == SE->getCouldNotCompute()) {
283  DEBUG(dbgs() << " loop does not has trip count\n");
284  return false;
285  }
286  return true;
287 }
288 
289 /// \brief Check memory accesses in loop and confirms it's good for
290 /// LoopVersioningLICM.
291 bool LoopVersioningLICM::legalLoopMemoryAccesses() {
292  bool HasMayAlias = false;
293  bool TypeSafety = false;
294  bool HasMod = false;
295  // Memory check:
296  // Transform phase will generate a versioned loop and also a runtime check to
297  // ensure the pointers are independent and they don’t alias.
298  // In version variant of loop, alias meta data asserts that all access are
299  // mutually independent.
300  //
301  // Pointers aliasing in alias domain are avoided because with multiple
302  // aliasing domains we may not be able to hoist potential loop invariant
303  // access out of the loop.
304  //
305  // Iterate over alias tracker sets, and confirm AliasSets doesn't have any
306  // must alias set.
307  for (const auto &I : *CurAST) {
308  const AliasSet &AS = I;
309  // Skip Forward Alias Sets, as this should be ignored as part of
310  // the AliasSetTracker object.
311  if (AS.isForwardingAliasSet())
312  continue;
313  // With MustAlias its not worth adding runtime bound check.
314  if (AS.isMustAlias())
315  return false;
316  Value *SomePtr = AS.begin()->getValue();
317  bool TypeCheck = true;
318  // Check for Mod & MayAlias
319  HasMayAlias |= AS.isMayAlias();
320  HasMod |= AS.isMod();
321  for (const auto &A : AS) {
322  Value *Ptr = A.getValue();
323  // Alias tracker should have pointers of same data type.
324  TypeCheck = (TypeCheck && (SomePtr->getType() == Ptr->getType()));
325  }
326  // At least one alias tracker should have pointers of same data type.
327  TypeSafety |= TypeCheck;
328  }
329  // Ensure types should be of same type.
330  if (!TypeSafety) {
331  DEBUG(dbgs() << " Alias tracker type safety failed!\n");
332  return false;
333  }
334  // Ensure loop body shouldn't be read only.
335  if (!HasMod) {
336  DEBUG(dbgs() << " No memory modified in loop body\n");
337  return false;
338  }
339  // Make sure alias set has may alias case.
340  // If there no alias memory ambiguity, return false.
341  if (!HasMayAlias) {
342  DEBUG(dbgs() << " No ambiguity in memory access.\n");
343  return false;
344  }
345  return true;
346 }
347 
348 /// \brief Check loop instructions safe for Loop versioning.
349 /// It returns true if it's safe else returns false.
350 /// Consider following:
351 /// 1) Check all load store in loop body are non atomic & non volatile.
352 /// 2) Check function call safety, by ensuring its not accessing memory.
353 /// 3) Loop body shouldn't have any may throw instruction.
354 bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
355  assert(I != nullptr && "Null instruction found!");
356  // Check function call safety
357  if (isa<CallInst>(I) && !AA->doesNotAccessMemory(CallSite(I))) {
358  DEBUG(dbgs() << " Unsafe call site found.\n");
359  return false;
360  }
361  // Avoid loops with possiblity of throw
362  if (I->mayThrow()) {
363  DEBUG(dbgs() << " May throw instruction found in loop body\n");
364  return false;
365  }
366  // If current instruction is load instructions
367  // make sure it's a simple load (non atomic & non volatile)
368  if (I->mayReadFromMemory()) {
369  LoadInst *Ld = dyn_cast<LoadInst>(I);
370  if (!Ld || !Ld->isSimple()) {
371  DEBUG(dbgs() << " Found a non-simple load.\n");
372  return false;
373  }
374  LoadAndStoreCounter++;
375  Value *Ptr = Ld->getPointerOperand();
376  // Check loop invariant.
377  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
378  InvariantCounter++;
379  }
380  // If current instruction is store instruction
381  // make sure it's a simple store (non atomic & non volatile)
382  else if (I->mayWriteToMemory()) {
383  StoreInst *St = dyn_cast<StoreInst>(I);
384  if (!St || !St->isSimple()) {
385  DEBUG(dbgs() << " Found a non-simple store.\n");
386  return false;
387  }
388  LoadAndStoreCounter++;
389  Value *Ptr = St->getPointerOperand();
390  // Check loop invariant.
391  if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
392  InvariantCounter++;
393 
394  IsReadOnlyLoop = false;
395  }
396  return true;
397 }
398 
399 /// \brief Check loop instructions and confirms it's good for
400 /// LoopVersioningLICM.
401 bool LoopVersioningLICM::legalLoopInstructions() {
402  // Resetting counters.
403  LoadAndStoreCounter = 0;
404  InvariantCounter = 0;
405  IsReadOnlyLoop = true;
406  // Iterate over loop blocks and instructions of each block and check
407  // instruction safety.
408  for (auto *Block : CurLoop->getBlocks())
409  for (auto &Inst : *Block) {
410  // If instruction is unsafe just return false.
411  if (!instructionSafeForVersioning(&Inst))
412  return false;
413  }
414  // Get LoopAccessInfo from current loop.
415  LAI = &LAA->getInfo(CurLoop);
416  // Check LoopAccessInfo for need of runtime check.
417  if (LAI->getRuntimePointerChecking()->getChecks().empty()) {
418  DEBUG(dbgs() << " LAA: Runtime check not found !!\n");
419  return false;
420  }
421  // Number of runtime-checks should be less then RuntimeMemoryCheckThreshold
422  if (LAI->getNumRuntimePointerChecks() >
424  DEBUG(dbgs() << " LAA: Runtime checks are more than threshold !!\n");
425  return false;
426  }
427  // Loop should have at least one invariant load or store instruction.
428  if (!InvariantCounter) {
429  DEBUG(dbgs() << " Invariant not found !!\n");
430  return false;
431  }
432  // Read only loop not allowed.
433  if (IsReadOnlyLoop) {
434  DEBUG(dbgs() << " Found a read-only loop!\n");
435  return false;
436  }
437  // Profitablity check:
438  // Check invariant threshold, should be in limit.
439  if (InvariantCounter * 100 < InvariantThreshold * LoadAndStoreCounter) {
440  DEBUG(dbgs()
441  << " Invariant load & store are less then defined threshold\n");
442  DEBUG(dbgs() << " Invariant loads & stores: "
443  << ((InvariantCounter * 100) / LoadAndStoreCounter) << "%\n");
444  DEBUG(dbgs() << " Invariant loads & store threshold: "
445  << InvariantThreshold << "%\n");
446  return false;
447  }
448  return true;
449 }
450 
451 /// \brief It checks loop is already visited or not.
452 /// check loop meta data, if loop revisited return true
453 /// else false.
454 bool LoopVersioningLICM::isLoopAlreadyVisited() {
455  // Check LoopVersioningLICM metadata into loop
456  if (findStringMetadataForLoop(CurLoop, LICMVersioningMetaData)) {
457  return true;
458  }
459  return false;
460 }
461 
462 /// \brief Checks legality for LoopVersioningLICM by considering following:
463 /// a) loop structure legality b) loop instruction legality
464 /// c) loop memory access legality.
465 /// Return true if legal else returns false.
466 bool LoopVersioningLICM::isLegalForVersioning() {
467  DEBUG(dbgs() << "Loop: " << *CurLoop);
468  // Make sure not re-visiting same loop again.
469  if (isLoopAlreadyVisited()) {
470  DEBUG(
471  dbgs() << " Revisiting loop in LoopVersioningLICM not allowed.\n\n");
472  return false;
473  }
474  // Check loop structure leagality.
475  if (!legalLoopStructure()) {
476  DEBUG(
477  dbgs() << " Loop structure not suitable for LoopVersioningLICM\n\n");
478  return false;
479  }
480  // Check loop instruction leagality.
481  if (!legalLoopInstructions()) {
482  DEBUG(dbgs()
483  << " Loop instructions not suitable for LoopVersioningLICM\n\n");
484  return false;
485  }
486  // Check loop memory access leagality.
487  if (!legalLoopMemoryAccesses()) {
488  DEBUG(dbgs()
489  << " Loop memory access not suitable for LoopVersioningLICM\n\n");
490  return false;
491  }
492  // Loop versioning is feasible, return true.
493  DEBUG(dbgs() << " Loop Versioning found to be beneficial\n\n");
494  return true;
495 }
496 
497 /// \brief Update loop with aggressive aliasing assumptions.
498 /// It marks no-alias to any pairs of memory operations by assuming
499 /// loop should not have any must-alias memory accesses pairs.
500 /// During LoopVersioningLICM legality we ignore loops having must
501 /// aliasing memory accesses.
502 void LoopVersioningLICM::setNoAliasToLoop(Loop *VerLoop) {
503  // Get latch terminator instruction.
504  Instruction *I = VerLoop->getLoopLatch()->getTerminator();
505  // Create alias scope domain.
506  MDBuilder MDB(I->getContext());
507  MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("LVDomain");
508  StringRef Name = "LVAliasScope";
509  SmallVector<Metadata *, 4> Scopes, NoAliases;
510  MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
511  // Iterate over each instruction of loop.
512  // set no-alias for all load & store instructions.
513  for (auto *Block : CurLoop->getBlocks()) {
514  for (auto &Inst : *Block) {
515  // Only interested in instruction that may modify or read memory.
516  if (!Inst.mayReadFromMemory() && !Inst.mayWriteToMemory())
517  continue;
518  Scopes.push_back(NewScope);
519  NoAliases.push_back(NewScope);
520  // Set no-alias for current instruction.
521  Inst.setMetadata(
524  MDNode::get(Inst.getContext(), NoAliases)));
525  // set alias-scope for current instruction.
526  Inst.setMetadata(
529  MDNode::get(Inst.getContext(), Scopes)));
530  }
531  }
532 }
533 
534 bool LoopVersioningLICM::runOnLoop(Loop *L, LPPassManager &LPM) {
535  // This will automatically release all resources hold by the current
536  // LoopVersioningLICM object.
537  AutoResetter Resetter(*this);
538 
539  if (skipLoop(L))
540  return false;
541  // Get Analysis information.
542  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
543  SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
544  LAA = &getAnalysis<LoopAccessLegacyAnalysis>();
545  LAI = nullptr;
546  // Set Current Loop
547  CurLoop = L;
548  CurAST.reset(new AliasSetTracker(*AA));
549 
550  // Loop over the body of this loop, construct AST.
551  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
552  for (auto *Block : L->getBlocks()) {
553  if (LI->getLoopFor(Block) == L) // Ignore blocks in subloop.
554  CurAST->add(*Block); // Incorporate the specified basic block
555  }
556 
557  bool Changed = false;
558 
559  // Check feasiblity of LoopVersioningLICM.
560  // If versioning found to be feasible and beneficial then proceed
561  // else simply return, by cleaning up memory.
562  if (isLegalForVersioning()) {
563  // Do loop versioning.
564  // Create memcheck for memory accessed inside loop.
565  // Clone original loop, and set blocks properly.
566  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
567  LoopVersioning LVer(*LAI, CurLoop, LI, DT, SE, true);
568  LVer.versionLoop();
569  // Set Loop Versioning metaData for original loop.
571  // Set Loop Versioning metaData for version loop.
573  // Set "llvm.mem.parallel_loop_access" metaData to versioned loop.
575  "llvm.mem.parallel_loop_access");
576  // Update version loop with aggressive aliasing assumption.
577  setNoAliasToLoop(LVer.getVersionedLoop());
578  Changed = true;
579  }
580  return Changed;
581 }
582 
583 char LoopVersioningLICM::ID = 0;
584 
585 INITIALIZE_PASS_BEGIN(LoopVersioningLICM, "loop-versioning-licm",
586  "Loop Versioning For LICM", false, false)
590 INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
593 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
595 INITIALIZE_PASS_END(LoopVersioningLICM, "loop-versioning-licm",
596  "Loop Versioning For LICM", false, false)
597 
598 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.
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
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:851
static MDString * get(LLVMContext &Context, StringRef Str)
Definition: Metadata.cpp:446
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:728
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:140
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
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:412
bool mayThrow() const
Return true if this instruction may throw an exception.
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:1086
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:864
loop versioning licm
Drive the analysis of memory accesses in the loop.
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:560
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:888
#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
#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:267
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.
loop versioning Loop Versioning For LICM