LLVM  8.0.0svn
LoopIdiomRecognize.cpp
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1 //===- LoopIdiomRecognize.cpp - Loop idiom recognition --------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass implements an idiom recognizer that transforms simple loops into a
11 // non-loop form. In cases that this kicks in, it can be a significant
12 // performance win.
13 //
14 // If compiling for code size we avoid idiom recognition if the resulting
15 // code could be larger than the code for the original loop. One way this could
16 // happen is if the loop is not removable after idiom recognition due to the
17 // presence of non-idiom instructions. The initial implementation of the
18 // heuristics applies to idioms in multi-block loops.
19 //
20 //===----------------------------------------------------------------------===//
21 //
22 // TODO List:
23 //
24 // Future loop memory idioms to recognize:
25 // memcmp, memmove, strlen, etc.
26 // Future floating point idioms to recognize in -ffast-math mode:
27 // fpowi
28 // Future integer operation idioms to recognize:
29 // ctpop, ctlz, cttz
30 //
31 // Beware that isel's default lowering for ctpop is highly inefficient for
32 // i64 and larger types when i64 is legal and the value has few bits set. It
33 // would be good to enhance isel to emit a loop for ctpop in this case.
34 //
35 // This could recognize common matrix multiplies and dot product idioms and
36 // replace them with calls to BLAS (if linked in??).
37 //
38 //===----------------------------------------------------------------------===//
39 
40 #include "llvm/ADT/APInt.h"
41 #include "llvm/ADT/ArrayRef.h"
42 #include "llvm/ADT/DenseMap.h"
43 #include "llvm/ADT/MapVector.h"
44 #include "llvm/ADT/SetVector.h"
45 #include "llvm/ADT/SmallPtrSet.h"
46 #include "llvm/ADT/SmallVector.h"
47 #include "llvm/ADT/Statistic.h"
48 #include "llvm/ADT/StringRef.h"
51 #include "llvm/Analysis/LoopInfo.h"
52 #include "llvm/Analysis/LoopPass.h"
61 #include "llvm/IR/Attributes.h"
62 #include "llvm/IR/BasicBlock.h"
63 #include "llvm/IR/Constant.h"
64 #include "llvm/IR/Constants.h"
65 #include "llvm/IR/DataLayout.h"
66 #include "llvm/IR/DebugLoc.h"
67 #include "llvm/IR/DerivedTypes.h"
68 #include "llvm/IR/Dominators.h"
69 #include "llvm/IR/GlobalValue.h"
70 #include "llvm/IR/GlobalVariable.h"
71 #include "llvm/IR/IRBuilder.h"
72 #include "llvm/IR/InstrTypes.h"
73 #include "llvm/IR/Instruction.h"
74 #include "llvm/IR/Instructions.h"
75 #include "llvm/IR/IntrinsicInst.h"
76 #include "llvm/IR/Intrinsics.h"
77 #include "llvm/IR/LLVMContext.h"
78 #include "llvm/IR/Module.h"
79 #include "llvm/IR/PassManager.h"
80 #include "llvm/IR/Type.h"
81 #include "llvm/IR/User.h"
82 #include "llvm/IR/Value.h"
83 #include "llvm/IR/ValueHandle.h"
84 #include "llvm/Pass.h"
85 #include "llvm/Support/Casting.h"
87 #include "llvm/Support/Debug.h"
89 #include "llvm/Transforms/Scalar.h"
93 #include <algorithm>
94 #include <cassert>
95 #include <cstdint>
96 #include <utility>
97 #include <vector>
98 
99 using namespace llvm;
100 
101 #define DEBUG_TYPE "loop-idiom"
102 
103 STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
104 STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
105 
107  "use-lir-code-size-heurs",
108  cl::desc("Use loop idiom recognition code size heuristics when compiling"
109  "with -Os/-Oz"),
110  cl::init(true), cl::Hidden);
111 
112 namespace {
113 
114 class LoopIdiomRecognize {
115  Loop *CurLoop = nullptr;
116  AliasAnalysis *AA;
117  DominatorTree *DT;
118  LoopInfo *LI;
119  ScalarEvolution *SE;
120  TargetLibraryInfo *TLI;
121  const TargetTransformInfo *TTI;
122  const DataLayout *DL;
123  bool ApplyCodeSizeHeuristics;
124 
125 public:
126  explicit LoopIdiomRecognize(AliasAnalysis *AA, DominatorTree *DT,
127  LoopInfo *LI, ScalarEvolution *SE,
128  TargetLibraryInfo *TLI,
129  const TargetTransformInfo *TTI,
130  const DataLayout *DL)
131  : AA(AA), DT(DT), LI(LI), SE(SE), TLI(TLI), TTI(TTI), DL(DL) {}
132 
133  bool runOnLoop(Loop *L);
134 
135 private:
136  using StoreList = SmallVector<StoreInst *, 8>;
137  using StoreListMap = MapVector<Value *, StoreList>;
138 
139  StoreListMap StoreRefsForMemset;
140  StoreListMap StoreRefsForMemsetPattern;
141  StoreList StoreRefsForMemcpy;
142  bool HasMemset;
143  bool HasMemsetPattern;
144  bool HasMemcpy;
145 
146  /// Return code for isLegalStore()
147  enum LegalStoreKind {
148  None = 0,
149  Memset,
150  MemsetPattern,
151  Memcpy,
152  UnorderedAtomicMemcpy,
153  DontUse // Dummy retval never to be used. Allows catching errors in retval
154  // handling.
155  };
156 
157  /// \name Countable Loop Idiom Handling
158  /// @{
159 
160  bool runOnCountableLoop();
161  bool runOnLoopBlock(BasicBlock *BB, const SCEV *BECount,
162  SmallVectorImpl<BasicBlock *> &ExitBlocks);
163 
164  void collectStores(BasicBlock *BB);
165  LegalStoreKind isLegalStore(StoreInst *SI);
166  enum class ForMemset { No, Yes };
167  bool processLoopStores(SmallVectorImpl<StoreInst *> &SL, const SCEV *BECount,
168  ForMemset For);
169  bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount);
170 
171  bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
172  unsigned StoreAlignment, Value *StoredVal,
173  Instruction *TheStore,
175  const SCEVAddRecExpr *Ev, const SCEV *BECount,
176  bool NegStride, bool IsLoopMemset = false);
177  bool processLoopStoreOfLoopLoad(StoreInst *SI, const SCEV *BECount);
178  bool avoidLIRForMultiBlockLoop(bool IsMemset = false,
179  bool IsLoopMemset = false);
180 
181  /// @}
182  /// \name Noncountable Loop Idiom Handling
183  /// @{
184 
185  bool runOnNoncountableLoop();
186 
187  bool recognizePopcount();
188  void transformLoopToPopcount(BasicBlock *PreCondBB, Instruction *CntInst,
189  PHINode *CntPhi, Value *Var);
190  bool recognizeAndInsertCTLZ();
191  void transformLoopToCountable(BasicBlock *PreCondBB, Instruction *CntInst,
192  PHINode *CntPhi, Value *Var, Instruction *DefX,
193  const DebugLoc &DL, bool ZeroCheck,
194  bool IsCntPhiUsedOutsideLoop);
195 
196  /// @}
197 };
198 
199 class LoopIdiomRecognizeLegacyPass : public LoopPass {
200 public:
201  static char ID;
202 
203  explicit LoopIdiomRecognizeLegacyPass() : LoopPass(ID) {
206  }
207 
208  bool runOnLoop(Loop *L, LPPassManager &LPM) override {
209  if (skipLoop(L))
210  return false;
211 
212  AliasAnalysis *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
213  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
214  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
215  ScalarEvolution *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
216  TargetLibraryInfo *TLI =
217  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
218  const TargetTransformInfo *TTI =
219  &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
220  *L->getHeader()->getParent());
221  const DataLayout *DL = &L->getHeader()->getModule()->getDataLayout();
222 
223  LoopIdiomRecognize LIR(AA, DT, LI, SE, TLI, TTI, DL);
224  return LIR.runOnLoop(L);
225  }
226 
227  /// This transformation requires natural loop information & requires that
228  /// loop preheaders be inserted into the CFG.
229  void getAnalysisUsage(AnalysisUsage &AU) const override {
233  }
234 };
235 
236 } // end anonymous namespace
237 
239 
242  LPMUpdater &) {
243  const auto *DL = &L.getHeader()->getModule()->getDataLayout();
244 
245  LoopIdiomRecognize LIR(&AR.AA, &AR.DT, &AR.LI, &AR.SE, &AR.TLI, &AR.TTI, DL);
246  if (!LIR.runOnLoop(&L))
247  return PreservedAnalyses::all();
248 
250 }
251 
252 INITIALIZE_PASS_BEGIN(LoopIdiomRecognizeLegacyPass, "loop-idiom",
253  "Recognize loop idioms", false, false)
257 INITIALIZE_PASS_END(LoopIdiomRecognizeLegacyPass, "loop-idiom",
258  "Recognize loop idioms", false, false)
259 
260 Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognizeLegacyPass(); }
261 
264  I->eraseFromParent();
265 }
266 
267 //===----------------------------------------------------------------------===//
268 //
269 // Implementation of LoopIdiomRecognize
270 //
271 //===----------------------------------------------------------------------===//
272 
273 bool LoopIdiomRecognize::runOnLoop(Loop *L) {
274  CurLoop = L;
275  // If the loop could not be converted to canonical form, it must have an
276  // indirectbr in it, just give up.
277  if (!L->getLoopPreheader())
278  return false;
279 
280  // Disable loop idiom recognition if the function's name is a common idiom.
282  if (Name == "memset" || Name == "memcpy")
283  return false;
284 
285  // Determine if code size heuristics need to be applied.
286  ApplyCodeSizeHeuristics =
288 
289  HasMemset = TLI->has(LibFunc_memset);
290  HasMemsetPattern = TLI->has(LibFunc_memset_pattern16);
291  HasMemcpy = TLI->has(LibFunc_memcpy);
292 
293  if (HasMemset || HasMemsetPattern || HasMemcpy)
295  return runOnCountableLoop();
296 
297  return runOnNoncountableLoop();
298 }
299 
300 bool LoopIdiomRecognize::runOnCountableLoop() {
301  const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop);
302  assert(!isa<SCEVCouldNotCompute>(BECount) &&
303  "runOnCountableLoop() called on a loop without a predictable"
304  "backedge-taken count");
305 
306  // If this loop executes exactly one time, then it should be peeled, not
307  // optimized by this pass.
308  if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
309  if (BECst->getAPInt() == 0)
310  return false;
311 
312  SmallVector<BasicBlock *, 8> ExitBlocks;
313  CurLoop->getUniqueExitBlocks(ExitBlocks);
314 
315  LLVM_DEBUG(dbgs() << "loop-idiom Scanning: F["
316  << CurLoop->getHeader()->getParent()->getName()
317  << "] Loop %" << CurLoop->getHeader()->getName() << "\n");
318 
319  bool MadeChange = false;
320 
321  // The following transforms hoist stores/memsets into the loop pre-header.
322  // Give up if the loop has instructions may throw.
323  SimpleLoopSafetyInfo SafetyInfo;
324  SafetyInfo.computeLoopSafetyInfo(CurLoop);
325  if (SafetyInfo.anyBlockMayThrow())
326  return MadeChange;
327 
328  // Scan all the blocks in the loop that are not in subloops.
329  for (auto *BB : CurLoop->getBlocks()) {
330  // Ignore blocks in subloops.
331  if (LI->getLoopFor(BB) != CurLoop)
332  continue;
333 
334  MadeChange |= runOnLoopBlock(BB, BECount, ExitBlocks);
335  }
336  return MadeChange;
337 }
338 
339 static APInt getStoreStride(const SCEVAddRecExpr *StoreEv) {
340  const SCEVConstant *ConstStride = cast<SCEVConstant>(StoreEv->getOperand(1));
341  return ConstStride->getAPInt();
342 }
343 
344 /// getMemSetPatternValue - If a strided store of the specified value is safe to
345 /// turn into a memset_pattern16, return a ConstantArray of 16 bytes that should
346 /// be passed in. Otherwise, return null.
347 ///
348 /// Note that we don't ever attempt to use memset_pattern8 or 4, because these
349 /// just replicate their input array and then pass on to memset_pattern16.
351  // FIXME: This could check for UndefValue because it can be merged into any
352  // other valid pattern.
353 
354  // If the value isn't a constant, we can't promote it to being in a constant
355  // array. We could theoretically do a store to an alloca or something, but
356  // that doesn't seem worthwhile.
357  Constant *C = dyn_cast<Constant>(V);
358  if (!C)
359  return nullptr;
360 
361  // Only handle simple values that are a power of two bytes in size.
362  uint64_t Size = DL->getTypeSizeInBits(V->getType());
363  if (Size == 0 || (Size & 7) || (Size & (Size - 1)))
364  return nullptr;
365 
366  // Don't care enough about darwin/ppc to implement this.
367  if (DL->isBigEndian())
368  return nullptr;
369 
370  // Convert to size in bytes.
371  Size /= 8;
372 
373  // TODO: If CI is larger than 16-bytes, we can try slicing it in half to see
374  // if the top and bottom are the same (e.g. for vectors and large integers).
375  if (Size > 16)
376  return nullptr;
377 
378  // If the constant is exactly 16 bytes, just use it.
379  if (Size == 16)
380  return C;
381 
382  // Otherwise, we'll use an array of the constants.
383  unsigned ArraySize = 16 / Size;
384  ArrayType *AT = ArrayType::get(V->getType(), ArraySize);
385  return ConstantArray::get(AT, std::vector<Constant *>(ArraySize, C));
386 }
387 
388 LoopIdiomRecognize::LegalStoreKind
389 LoopIdiomRecognize::isLegalStore(StoreInst *SI) {
390  // Don't touch volatile stores.
391  if (SI->isVolatile())
392  return LegalStoreKind::None;
393  // We only want simple or unordered-atomic stores.
394  if (!SI->isUnordered())
395  return LegalStoreKind::None;
396 
397  // Don't convert stores of non-integral pointer types to memsets (which stores
398  // integers).
399  if (DL->isNonIntegralPointerType(SI->getValueOperand()->getType()))
400  return LegalStoreKind::None;
401 
402  // Avoid merging nontemporal stores.
404  return LegalStoreKind::None;
405 
406  Value *StoredVal = SI->getValueOperand();
407  Value *StorePtr = SI->getPointerOperand();
408 
409  // Reject stores that are so large that they overflow an unsigned.
410  uint64_t SizeInBits = DL->getTypeSizeInBits(StoredVal->getType());
411  if ((SizeInBits & 7) || (SizeInBits >> 32) != 0)
412  return LegalStoreKind::None;
413 
414  // See if the pointer expression is an AddRec like {base,+,1} on the current
415  // loop, which indicates a strided store. If we have something else, it's a
416  // random store we can't handle.
417  const SCEVAddRecExpr *StoreEv =
418  dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
419  if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine())
420  return LegalStoreKind::None;
421 
422  // Check to see if we have a constant stride.
423  if (!isa<SCEVConstant>(StoreEv->getOperand(1)))
424  return LegalStoreKind::None;
425 
426  // See if the store can be turned into a memset.
427 
428  // If the stored value is a byte-wise value (like i32 -1), then it may be
429  // turned into a memset of i8 -1, assuming that all the consecutive bytes
430  // are stored. A store of i32 0x01020304 can never be turned into a memset,
431  // but it can be turned into memset_pattern if the target supports it.
432  Value *SplatValue = isBytewiseValue(StoredVal);
433  Constant *PatternValue = nullptr;
434 
435  // Note: memset and memset_pattern on unordered-atomic is yet not supported
436  bool UnorderedAtomic = SI->isUnordered() && !SI->isSimple();
437 
438  // If we're allowed to form a memset, and the stored value would be
439  // acceptable for memset, use it.
440  if (!UnorderedAtomic && HasMemset && SplatValue &&
441  // Verify that the stored value is loop invariant. If not, we can't
442  // promote the memset.
443  CurLoop->isLoopInvariant(SplatValue)) {
444  // It looks like we can use SplatValue.
445  return LegalStoreKind::Memset;
446  } else if (!UnorderedAtomic && HasMemsetPattern &&
447  // Don't create memset_pattern16s with address spaces.
448  StorePtr->getType()->getPointerAddressSpace() == 0 &&
449  (PatternValue = getMemSetPatternValue(StoredVal, DL))) {
450  // It looks like we can use PatternValue!
451  return LegalStoreKind::MemsetPattern;
452  }
453 
454  // Otherwise, see if the store can be turned into a memcpy.
455  if (HasMemcpy) {
456  // Check to see if the stride matches the size of the store. If so, then we
457  // know that every byte is touched in the loop.
458  APInt Stride = getStoreStride(StoreEv);
459  unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
460  if (StoreSize != Stride && StoreSize != -Stride)
461  return LegalStoreKind::None;
462 
463  // The store must be feeding a non-volatile load.
465 
466  // Only allow non-volatile loads
467  if (!LI || LI->isVolatile())
468  return LegalStoreKind::None;
469  // Only allow simple or unordered-atomic loads
470  if (!LI->isUnordered())
471  return LegalStoreKind::None;
472 
473  // See if the pointer expression is an AddRec like {base,+,1} on the current
474  // loop, which indicates a strided load. If we have something else, it's a
475  // random load we can't handle.
476  const SCEVAddRecExpr *LoadEv =
478  if (!LoadEv || LoadEv->getLoop() != CurLoop || !LoadEv->isAffine())
479  return LegalStoreKind::None;
480 
481  // The store and load must share the same stride.
482  if (StoreEv->getOperand(1) != LoadEv->getOperand(1))
483  return LegalStoreKind::None;
484 
485  // Success. This store can be converted into a memcpy.
486  UnorderedAtomic = UnorderedAtomic || LI->isAtomic();
487  return UnorderedAtomic ? LegalStoreKind::UnorderedAtomicMemcpy
488  : LegalStoreKind::Memcpy;
489  }
490  // This store can't be transformed into a memset/memcpy.
491  return LegalStoreKind::None;
492 }
493 
494 void LoopIdiomRecognize::collectStores(BasicBlock *BB) {
495  StoreRefsForMemset.clear();
496  StoreRefsForMemsetPattern.clear();
497  StoreRefsForMemcpy.clear();
498  for (Instruction &I : *BB) {
499  StoreInst *SI = dyn_cast<StoreInst>(&I);
500  if (!SI)
501  continue;
502 
503  // Make sure this is a strided store with a constant stride.
504  switch (isLegalStore(SI)) {
506  // Nothing to do
507  break;
508  case LegalStoreKind::Memset: {
509  // Find the base pointer.
510  Value *Ptr = GetUnderlyingObject(SI->getPointerOperand(), *DL);
511  StoreRefsForMemset[Ptr].push_back(SI);
512  } break;
513  case LegalStoreKind::MemsetPattern: {
514  // Find the base pointer.
515  Value *Ptr = GetUnderlyingObject(SI->getPointerOperand(), *DL);
516  StoreRefsForMemsetPattern[Ptr].push_back(SI);
517  } break;
518  case LegalStoreKind::Memcpy:
519  case LegalStoreKind::UnorderedAtomicMemcpy:
520  StoreRefsForMemcpy.push_back(SI);
521  break;
522  default:
523  assert(false && "unhandled return value");
524  break;
525  }
526  }
527 }
528 
529 /// runOnLoopBlock - Process the specified block, which lives in a counted loop
530 /// with the specified backedge count. This block is known to be in the current
531 /// loop and not in any subloops.
532 bool LoopIdiomRecognize::runOnLoopBlock(
533  BasicBlock *BB, const SCEV *BECount,
534  SmallVectorImpl<BasicBlock *> &ExitBlocks) {
535  // We can only promote stores in this block if they are unconditionally
536  // executed in the loop. For a block to be unconditionally executed, it has
537  // to dominate all the exit blocks of the loop. Verify this now.
538  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
539  if (!DT->dominates(BB, ExitBlocks[i]))
540  return false;
541 
542  bool MadeChange = false;
543  // Look for store instructions, which may be optimized to memset/memcpy.
544  collectStores(BB);
545 
546  // Look for a single store or sets of stores with a common base, which can be
547  // optimized into a memset (memset_pattern). The latter most commonly happens
548  // with structs and handunrolled loops.
549  for (auto &SL : StoreRefsForMemset)
550  MadeChange |= processLoopStores(SL.second, BECount, ForMemset::Yes);
551 
552  for (auto &SL : StoreRefsForMemsetPattern)
553  MadeChange |= processLoopStores(SL.second, BECount, ForMemset::No);
554 
555  // Optimize the store into a memcpy, if it feeds an similarly strided load.
556  for (auto &SI : StoreRefsForMemcpy)
557  MadeChange |= processLoopStoreOfLoopLoad(SI, BECount);
558 
559  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
560  Instruction *Inst = &*I++;
561  // Look for memset instructions, which may be optimized to a larger memset.
562  if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst)) {
563  WeakTrackingVH InstPtr(&*I);
564  if (!processLoopMemSet(MSI, BECount))
565  continue;
566  MadeChange = true;
567 
568  // If processing the memset invalidated our iterator, start over from the
569  // top of the block.
570  if (!InstPtr)
571  I = BB->begin();
572  continue;
573  }
574  }
575 
576  return MadeChange;
577 }
578 
579 /// See if this store(s) can be promoted to a memset.
580 bool LoopIdiomRecognize::processLoopStores(SmallVectorImpl<StoreInst *> &SL,
581  const SCEV *BECount, ForMemset For) {
582  // Try to find consecutive stores that can be transformed into memsets.
583  SetVector<StoreInst *> Heads, Tails;
585 
586  // Do a quadratic search on all of the given stores and find
587  // all of the pairs of stores that follow each other.
588  SmallVector<unsigned, 16> IndexQueue;
589  for (unsigned i = 0, e = SL.size(); i < e; ++i) {
590  assert(SL[i]->isSimple() && "Expected only non-volatile stores.");
591 
592  Value *FirstStoredVal = SL[i]->getValueOperand();
593  Value *FirstStorePtr = SL[i]->getPointerOperand();
594  const SCEVAddRecExpr *FirstStoreEv =
595  cast<SCEVAddRecExpr>(SE->getSCEV(FirstStorePtr));
596  APInt FirstStride = getStoreStride(FirstStoreEv);
597  unsigned FirstStoreSize = DL->getTypeStoreSize(SL[i]->getValueOperand()->getType());
598 
599  // See if we can optimize just this store in isolation.
600  if (FirstStride == FirstStoreSize || -FirstStride == FirstStoreSize) {
601  Heads.insert(SL[i]);
602  continue;
603  }
604 
605  Value *FirstSplatValue = nullptr;
606  Constant *FirstPatternValue = nullptr;
607 
608  if (For == ForMemset::Yes)
609  FirstSplatValue = isBytewiseValue(FirstStoredVal);
610  else
611  FirstPatternValue = getMemSetPatternValue(FirstStoredVal, DL);
612 
613  assert((FirstSplatValue || FirstPatternValue) &&
614  "Expected either splat value or pattern value.");
615 
616  IndexQueue.clear();
617  // If a store has multiple consecutive store candidates, search Stores
618  // array according to the sequence: from i+1 to e, then from i-1 to 0.
619  // This is because usually pairing with immediate succeeding or preceding
620  // candidate create the best chance to find memset opportunity.
621  unsigned j = 0;
622  for (j = i + 1; j < e; ++j)
623  IndexQueue.push_back(j);
624  for (j = i; j > 0; --j)
625  IndexQueue.push_back(j - 1);
626 
627  for (auto &k : IndexQueue) {
628  assert(SL[k]->isSimple() && "Expected only non-volatile stores.");
629  Value *SecondStorePtr = SL[k]->getPointerOperand();
630  const SCEVAddRecExpr *SecondStoreEv =
631  cast<SCEVAddRecExpr>(SE->getSCEV(SecondStorePtr));
632  APInt SecondStride = getStoreStride(SecondStoreEv);
633 
634  if (FirstStride != SecondStride)
635  continue;
636 
637  Value *SecondStoredVal = SL[k]->getValueOperand();
638  Value *SecondSplatValue = nullptr;
639  Constant *SecondPatternValue = nullptr;
640 
641  if (For == ForMemset::Yes)
642  SecondSplatValue = isBytewiseValue(SecondStoredVal);
643  else
644  SecondPatternValue = getMemSetPatternValue(SecondStoredVal, DL);
645 
646  assert((SecondSplatValue || SecondPatternValue) &&
647  "Expected either splat value or pattern value.");
648 
649  if (isConsecutiveAccess(SL[i], SL[k], *DL, *SE, false)) {
650  if (For == ForMemset::Yes) {
651  if (isa<UndefValue>(FirstSplatValue))
652  FirstSplatValue = SecondSplatValue;
653  if (FirstSplatValue != SecondSplatValue)
654  continue;
655  } else {
656  if (isa<UndefValue>(FirstPatternValue))
657  FirstPatternValue = SecondPatternValue;
658  if (FirstPatternValue != SecondPatternValue)
659  continue;
660  }
661  Tails.insert(SL[k]);
662  Heads.insert(SL[i]);
663  ConsecutiveChain[SL[i]] = SL[k];
664  break;
665  }
666  }
667  }
668 
669  // We may run into multiple chains that merge into a single chain. We mark the
670  // stores that we transformed so that we don't visit the same store twice.
671  SmallPtrSet<Value *, 16> TransformedStores;
672  bool Changed = false;
673 
674  // For stores that start but don't end a link in the chain:
675  for (SetVector<StoreInst *>::iterator it = Heads.begin(), e = Heads.end();
676  it != e; ++it) {
677  if (Tails.count(*it))
678  continue;
679 
680  // We found a store instr that starts a chain. Now follow the chain and try
681  // to transform it.
682  SmallPtrSet<Instruction *, 8> AdjacentStores;
683  StoreInst *I = *it;
684 
685  StoreInst *HeadStore = I;
686  unsigned StoreSize = 0;
687 
688  // Collect the chain into a list.
689  while (Tails.count(I) || Heads.count(I)) {
690  if (TransformedStores.count(I))
691  break;
692  AdjacentStores.insert(I);
693 
694  StoreSize += DL->getTypeStoreSize(I->getValueOperand()->getType());
695  // Move to the next value in the chain.
696  I = ConsecutiveChain[I];
697  }
698 
699  Value *StoredVal = HeadStore->getValueOperand();
700  Value *StorePtr = HeadStore->getPointerOperand();
701  const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
702  APInt Stride = getStoreStride(StoreEv);
703 
704  // Check to see if the stride matches the size of the stores. If so, then
705  // we know that every byte is touched in the loop.
706  if (StoreSize != Stride && StoreSize != -Stride)
707  continue;
708 
709  bool NegStride = StoreSize == -Stride;
710 
711  if (processLoopStridedStore(StorePtr, StoreSize, HeadStore->getAlignment(),
712  StoredVal, HeadStore, AdjacentStores, StoreEv,
713  BECount, NegStride)) {
714  TransformedStores.insert(AdjacentStores.begin(), AdjacentStores.end());
715  Changed = true;
716  }
717  }
718 
719  return Changed;
720 }
721 
722 /// processLoopMemSet - See if this memset can be promoted to a large memset.
723 bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
724  const SCEV *BECount) {
725  // We can only handle non-volatile memsets with a constant size.
726  if (MSI->isVolatile() || !isa<ConstantInt>(MSI->getLength()))
727  return false;
728 
729  // If we're not allowed to hack on memset, we fail.
730  if (!HasMemset)
731  return false;
732 
733  Value *Pointer = MSI->getDest();
734 
735  // See if the pointer expression is an AddRec like {base,+,1} on the current
736  // loop, which indicates a strided store. If we have something else, it's a
737  // random store we can't handle.
738  const SCEVAddRecExpr *Ev = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Pointer));
739  if (!Ev || Ev->getLoop() != CurLoop || !Ev->isAffine())
740  return false;
741 
742  // Reject memsets that are so large that they overflow an unsigned.
743  uint64_t SizeInBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
744  if ((SizeInBytes >> 32) != 0)
745  return false;
746 
747  // Check to see if the stride matches the size of the memset. If so, then we
748  // know that every byte is touched in the loop.
749  const SCEVConstant *ConstStride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
750  if (!ConstStride)
751  return false;
752 
753  APInt Stride = ConstStride->getAPInt();
754  if (SizeInBytes != Stride && SizeInBytes != -Stride)
755  return false;
756 
757  // Verify that the memset value is loop invariant. If not, we can't promote
758  // the memset.
759  Value *SplatValue = MSI->getValue();
760  if (!SplatValue || !CurLoop->isLoopInvariant(SplatValue))
761  return false;
762 
764  MSIs.insert(MSI);
765  bool NegStride = SizeInBytes == -Stride;
766  return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
767  MSI->getDestAlignment(), SplatValue, MSI, MSIs,
768  Ev, BECount, NegStride, /*IsLoopMemset=*/true);
769 }
770 
771 /// mayLoopAccessLocation - Return true if the specified loop might access the
772 /// specified pointer location, which is a loop-strided access. The 'Access'
773 /// argument specifies what the verboten forms of access are (read or write).
774 static bool
776  const SCEV *BECount, unsigned StoreSize,
777  AliasAnalysis &AA,
778  SmallPtrSetImpl<Instruction *> &IgnoredStores) {
779  // Get the location that may be stored across the loop. Since the access is
780  // strided positively through memory, we say that the modified location starts
781  // at the pointer and has infinite size.
782  uint64_t AccessSize = MemoryLocation::UnknownSize;
783 
784  // If the loop iterates a fixed number of times, we can refine the access size
785  // to be exactly the size of the memset, which is (BECount+1)*StoreSize
786  if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
787  AccessSize = (BECst->getValue()->getZExtValue() + 1) * StoreSize;
788 
789  // TODO: For this to be really effective, we have to dive into the pointer
790  // operand in the store. Store to &A[i] of 100 will always return may alias
791  // with store of &A[100], we need to StoreLoc to be "A" with size of 100,
792  // which will then no-alias a store to &A[100].
793  MemoryLocation StoreLoc(Ptr, AccessSize);
794 
795  for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
796  ++BI)
797  for (Instruction &I : **BI)
798  if (IgnoredStores.count(&I) == 0 &&
800  intersectModRef(AA.getModRefInfo(&I, StoreLoc), Access)))
801  return true;
802 
803  return false;
804 }
805 
806 // If we have a negative stride, Start refers to the end of the memory location
807 // we're trying to memset. Therefore, we need to recompute the base pointer,
808 // which is just Start - BECount*Size.
809 static const SCEV *getStartForNegStride(const SCEV *Start, const SCEV *BECount,
810  Type *IntPtr, unsigned StoreSize,
811  ScalarEvolution *SE) {
812  const SCEV *Index = SE->getTruncateOrZeroExtend(BECount, IntPtr);
813  if (StoreSize != 1)
814  Index = SE->getMulExpr(Index, SE->getConstant(IntPtr, StoreSize),
815  SCEV::FlagNUW);
816  return SE->getMinusSCEV(Start, Index);
817 }
818 
819 /// Compute the number of bytes as a SCEV from the backedge taken count.
820 ///
821 /// This also maps the SCEV into the provided type and tries to handle the
822 /// computation in a way that will fold cleanly.
823 static const SCEV *getNumBytes(const SCEV *BECount, Type *IntPtr,
824  unsigned StoreSize, Loop *CurLoop,
825  const DataLayout *DL, ScalarEvolution *SE) {
826  const SCEV *NumBytesS;
827  // The # stored bytes is (BECount+1)*Size. Expand the trip count out to
828  // pointer size if it isn't already.
829  //
830  // If we're going to need to zero extend the BE count, check if we can add
831  // one to it prior to zero extending without overflow. Provided this is safe,
832  // it allows better simplification of the +1.
833  if (DL->getTypeSizeInBits(BECount->getType()) <
834  DL->getTypeSizeInBits(IntPtr) &&
836  CurLoop, ICmpInst::ICMP_NE, BECount,
837  SE->getNegativeSCEV(SE->getOne(BECount->getType())))) {
838  NumBytesS = SE->getZeroExtendExpr(
839  SE->getAddExpr(BECount, SE->getOne(BECount->getType()), SCEV::FlagNUW),
840  IntPtr);
841  } else {
842  NumBytesS = SE->getAddExpr(SE->getTruncateOrZeroExtend(BECount, IntPtr),
843  SE->getOne(IntPtr), SCEV::FlagNUW);
844  }
845 
846  // And scale it based on the store size.
847  if (StoreSize != 1) {
848  NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
849  SCEV::FlagNUW);
850  }
851  return NumBytesS;
852 }
853 
854 /// processLoopStridedStore - We see a strided store of some value. If we can
855 /// transform this into a memset or memset_pattern in the loop preheader, do so.
856 bool LoopIdiomRecognize::processLoopStridedStore(
857  Value *DestPtr, unsigned StoreSize, unsigned StoreAlignment,
858  Value *StoredVal, Instruction *TheStore,
860  const SCEV *BECount, bool NegStride, bool IsLoopMemset) {
861  Value *SplatValue = isBytewiseValue(StoredVal);
862  Constant *PatternValue = nullptr;
863 
864  if (!SplatValue)
865  PatternValue = getMemSetPatternValue(StoredVal, DL);
866 
867  assert((SplatValue || PatternValue) &&
868  "Expected either splat value or pattern value.");
869 
870  // The trip count of the loop and the base pointer of the addrec SCEV is
871  // guaranteed to be loop invariant, which means that it should dominate the
872  // header. This allows us to insert code for it in the preheader.
873  unsigned DestAS = DestPtr->getType()->getPointerAddressSpace();
874  BasicBlock *Preheader = CurLoop->getLoopPreheader();
875  IRBuilder<> Builder(Preheader->getTerminator());
876  SCEVExpander Expander(*SE, *DL, "loop-idiom");
877 
878  Type *DestInt8PtrTy = Builder.getInt8PtrTy(DestAS);
879  Type *IntPtr = Builder.getIntPtrTy(*DL, DestAS);
880 
881  const SCEV *Start = Ev->getStart();
882  // Handle negative strided loops.
883  if (NegStride)
884  Start = getStartForNegStride(Start, BECount, IntPtr, StoreSize, SE);
885 
886  // TODO: ideally we should still be able to generate memset if SCEV expander
887  // is taught to generate the dependencies at the latest point.
888  if (!isSafeToExpand(Start, *SE))
889  return false;
890 
891  // Okay, we have a strided store "p[i]" of a splattable value. We can turn
892  // this into a memset in the loop preheader now if we want. However, this
893  // would be unsafe to do if there is anything else in the loop that may read
894  // or write to the aliased location. Check for any overlap by generating the
895  // base pointer and checking the region.
896  Value *BasePtr =
897  Expander.expandCodeFor(Start, DestInt8PtrTy, Preheader->getTerminator());
898  if (mayLoopAccessLocation(BasePtr, ModRefInfo::ModRef, CurLoop, BECount,
899  StoreSize, *AA, Stores)) {
900  Expander.clear();
901  // If we generated new code for the base pointer, clean up.
903  return false;
904  }
905 
906  if (avoidLIRForMultiBlockLoop(/*IsMemset=*/true, IsLoopMemset))
907  return false;
908 
909  // Okay, everything looks good, insert the memset.
910 
911  const SCEV *NumBytesS =
912  getNumBytes(BECount, IntPtr, StoreSize, CurLoop, DL, SE);
913 
914  // TODO: ideally we should still be able to generate memset if SCEV expander
915  // is taught to generate the dependencies at the latest point.
916  if (!isSafeToExpand(NumBytesS, *SE))
917  return false;
918 
919  Value *NumBytes =
920  Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
921 
922  CallInst *NewCall;
923  if (SplatValue) {
924  NewCall =
925  Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, StoreAlignment);
926  } else {
927  // Everything is emitted in default address space
928  Type *Int8PtrTy = DestInt8PtrTy;
929 
930  Module *M = TheStore->getModule();
931  StringRef FuncName = "memset_pattern16";
932  Value *MSP =
933  M->getOrInsertFunction(FuncName, Builder.getVoidTy(),
934  Int8PtrTy, Int8PtrTy, IntPtr);
935  inferLibFuncAttributes(M, FuncName, *TLI);
936 
937  // Otherwise we should form a memset_pattern16. PatternValue is known to be
938  // an constant array of 16-bytes. Plop the value into a mergable global.
939  GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true,
941  PatternValue, ".memset_pattern");
942  GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global); // Ok to merge these.
943  GV->setAlignment(16);
944  Value *PatternPtr = ConstantExpr::getBitCast(GV, Int8PtrTy);
945  NewCall = Builder.CreateCall(MSP, {BasePtr, PatternPtr, NumBytes});
946  }
947 
948  LLVM_DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n"
949  << " from store to: " << *Ev << " at: " << *TheStore
950  << "\n");
951  NewCall->setDebugLoc(TheStore->getDebugLoc());
952 
953  // Okay, the memset has been formed. Zap the original store and anything that
954  // feeds into it.
955  for (auto *I : Stores)
957  ++NumMemSet;
958  return true;
959 }
960 
961 /// If the stored value is a strided load in the same loop with the same stride
962 /// this may be transformable into a memcpy. This kicks in for stuff like
963 /// for (i) A[i] = B[i];
964 bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(StoreInst *SI,
965  const SCEV *BECount) {
966  assert(SI->isUnordered() && "Expected only non-volatile non-ordered stores.");
967 
968  Value *StorePtr = SI->getPointerOperand();
969  const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
970  APInt Stride = getStoreStride(StoreEv);
971  unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
972  bool NegStride = StoreSize == -Stride;
973 
974  // The store must be feeding a non-volatile load.
975  LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
976  assert(LI->isUnordered() && "Expected only non-volatile non-ordered loads.");
977 
978  // See if the pointer expression is an AddRec like {base,+,1} on the current
979  // loop, which indicates a strided load. If we have something else, it's a
980  // random load we can't handle.
981  const SCEVAddRecExpr *LoadEv =
982  cast<SCEVAddRecExpr>(SE->getSCEV(LI->getPointerOperand()));
983 
984  // The trip count of the loop and the base pointer of the addrec SCEV is
985  // guaranteed to be loop invariant, which means that it should dominate the
986  // header. This allows us to insert code for it in the preheader.
987  BasicBlock *Preheader = CurLoop->getLoopPreheader();
988  IRBuilder<> Builder(Preheader->getTerminator());
989  SCEVExpander Expander(*SE, *DL, "loop-idiom");
990 
991  const SCEV *StrStart = StoreEv->getStart();
992  unsigned StrAS = SI->getPointerAddressSpace();
993  Type *IntPtrTy = Builder.getIntPtrTy(*DL, StrAS);
994 
995  // Handle negative strided loops.
996  if (NegStride)
997  StrStart = getStartForNegStride(StrStart, BECount, IntPtrTy, StoreSize, SE);
998 
999  // Okay, we have a strided store "p[i]" of a loaded value. We can turn
1000  // this into a memcpy in the loop preheader now if we want. However, this
1001  // would be unsafe to do if there is anything else in the loop that may read
1002  // or write the memory region we're storing to. This includes the load that
1003  // feeds the stores. Check for an alias by generating the base address and
1004  // checking everything.
1005  Value *StoreBasePtr = Expander.expandCodeFor(
1006  StrStart, Builder.getInt8PtrTy(StrAS), Preheader->getTerminator());
1007 
1009  Stores.insert(SI);
1010  if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
1011  StoreSize, *AA, Stores)) {
1012  Expander.clear();
1013  // If we generated new code for the base pointer, clean up.
1014  RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
1015  return false;
1016  }
1017 
1018  const SCEV *LdStart = LoadEv->getStart();
1019  unsigned LdAS = LI->getPointerAddressSpace();
1020 
1021  // Handle negative strided loops.
1022  if (NegStride)
1023  LdStart = getStartForNegStride(LdStart, BECount, IntPtrTy, StoreSize, SE);
1024 
1025  // For a memcpy, we have to make sure that the input array is not being
1026  // mutated by the loop.
1027  Value *LoadBasePtr = Expander.expandCodeFor(
1028  LdStart, Builder.getInt8PtrTy(LdAS), Preheader->getTerminator());
1029 
1030  if (mayLoopAccessLocation(LoadBasePtr, ModRefInfo::Mod, CurLoop, BECount,
1031  StoreSize, *AA, Stores)) {
1032  Expander.clear();
1033  // If we generated new code for the base pointer, clean up.
1035  RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
1036  return false;
1037  }
1038 
1039  if (avoidLIRForMultiBlockLoop())
1040  return false;
1041 
1042  // Okay, everything is safe, we can transform this!
1043 
1044  const SCEV *NumBytesS =
1045  getNumBytes(BECount, IntPtrTy, StoreSize, CurLoop, DL, SE);
1046 
1047  Value *NumBytes =
1048  Expander.expandCodeFor(NumBytesS, IntPtrTy, Preheader->getTerminator());
1049 
1050  CallInst *NewCall = nullptr;
1051  // Check whether to generate an unordered atomic memcpy:
1052  // If the load or store are atomic, then they must necessarily be unordered
1053  // by previous checks.
1054  if (!SI->isAtomic() && !LI->isAtomic())
1055  NewCall = Builder.CreateMemCpy(StoreBasePtr, SI->getAlignment(),
1056  LoadBasePtr, LI->getAlignment(), NumBytes);
1057  else {
1058  // We cannot allow unaligned ops for unordered load/store, so reject
1059  // anything where the alignment isn't at least the element size.
1060  unsigned Align = std::min(SI->getAlignment(), LI->getAlignment());
1061  if (Align < StoreSize)
1062  return false;
1063 
1064  // If the element.atomic memcpy is not lowered into explicit
1065  // loads/stores later, then it will be lowered into an element-size
1066  // specific lib call. If the lib call doesn't exist for our store size, then
1067  // we shouldn't generate the memcpy.
1068  if (StoreSize > TTI->getAtomicMemIntrinsicMaxElementSize())
1069  return false;
1070 
1071  // Create the call.
1072  // Note that unordered atomic loads/stores are *required* by the spec to
1073  // have an alignment but non-atomic loads/stores may not.
1074  NewCall = Builder.CreateElementUnorderedAtomicMemCpy(
1075  StoreBasePtr, SI->getAlignment(), LoadBasePtr, LI->getAlignment(),
1076  NumBytes, StoreSize);
1077  }
1078  NewCall->setDebugLoc(SI->getDebugLoc());
1079 
1080  LLVM_DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n"
1081  << " from load ptr=" << *LoadEv << " at: " << *LI << "\n"
1082  << " from store ptr=" << *StoreEv << " at: " << *SI
1083  << "\n");
1084 
1085  // Okay, the memcpy has been formed. Zap the original store and anything that
1086  // feeds into it.
1088  ++NumMemCpy;
1089  return true;
1090 }
1091 
1092 // When compiling for codesize we avoid idiom recognition for a multi-block loop
1093 // unless it is a loop_memset idiom or a memset/memcpy idiom in a nested loop.
1094 //
1095 bool LoopIdiomRecognize::avoidLIRForMultiBlockLoop(bool IsMemset,
1096  bool IsLoopMemset) {
1097  if (ApplyCodeSizeHeuristics && CurLoop->getNumBlocks() > 1) {
1098  if (!CurLoop->getParentLoop() && (!IsMemset || !IsLoopMemset)) {
1099  LLVM_DEBUG(dbgs() << " " << CurLoop->getHeader()->getParent()->getName()
1100  << " : LIR " << (IsMemset ? "Memset" : "Memcpy")
1101  << " avoided: multi-block top-level loop\n");
1102  return true;
1103  }
1104  }
1105 
1106  return false;
1107 }
1108 
1109 bool LoopIdiomRecognize::runOnNoncountableLoop() {
1110  return recognizePopcount() || recognizeAndInsertCTLZ();
1111 }
1112 
1113 /// Check if the given conditional branch is based on the comparison between
1114 /// a variable and zero, and if the variable is non-zero, the control yields to
1115 /// the loop entry. If the branch matches the behavior, the variable involved
1116 /// in the comparison is returned. This function will be called to see if the
1117 /// precondition and postcondition of the loop are in desirable form.
1118 static Value *matchCondition(BranchInst *BI, BasicBlock *LoopEntry) {
1119  if (!BI || !BI->isConditional())
1120  return nullptr;
1121 
1122  ICmpInst *Cond = dyn_cast<ICmpInst>(BI->getCondition());
1123  if (!Cond)
1124  return nullptr;
1125 
1126  ConstantInt *CmpZero = dyn_cast<ConstantInt>(Cond->getOperand(1));
1127  if (!CmpZero || !CmpZero->isZero())
1128  return nullptr;
1129 
1130  ICmpInst::Predicate Pred = Cond->getPredicate();
1131  if ((Pred == ICmpInst::ICMP_NE && BI->getSuccessor(0) == LoopEntry) ||
1132  (Pred == ICmpInst::ICMP_EQ && BI->getSuccessor(1) == LoopEntry))
1133  return Cond->getOperand(0);
1134 
1135  return nullptr;
1136 }
1137 
1138 // Check if the recurrence variable `VarX` is in the right form to create
1139 // the idiom. Returns the value coerced to a PHINode if so.
1141  BasicBlock *LoopEntry) {
1142  auto *PhiX = dyn_cast<PHINode>(VarX);
1143  if (PhiX && PhiX->getParent() == LoopEntry &&
1144  (PhiX->getOperand(0) == DefX || PhiX->getOperand(1) == DefX))
1145  return PhiX;
1146  return nullptr;
1147 }
1148 
1149 /// Return true iff the idiom is detected in the loop.
1150 ///
1151 /// Additionally:
1152 /// 1) \p CntInst is set to the instruction counting the population bit.
1153 /// 2) \p CntPhi is set to the corresponding phi node.
1154 /// 3) \p Var is set to the value whose population bits are being counted.
1155 ///
1156 /// The core idiom we are trying to detect is:
1157 /// \code
1158 /// if (x0 != 0)
1159 /// goto loop-exit // the precondition of the loop
1160 /// cnt0 = init-val;
1161 /// do {
1162 /// x1 = phi (x0, x2);
1163 /// cnt1 = phi(cnt0, cnt2);
1164 ///
1165 /// cnt2 = cnt1 + 1;
1166 /// ...
1167 /// x2 = x1 & (x1 - 1);
1168 /// ...
1169 /// } while(x != 0);
1170 ///
1171 /// loop-exit:
1172 /// \endcode
1173 static bool detectPopcountIdiom(Loop *CurLoop, BasicBlock *PreCondBB,
1174  Instruction *&CntInst, PHINode *&CntPhi,
1175  Value *&Var) {
1176  // step 1: Check to see if the look-back branch match this pattern:
1177  // "if (a!=0) goto loop-entry".
1178  BasicBlock *LoopEntry;
1179  Instruction *DefX2, *CountInst;
1180  Value *VarX1, *VarX0;
1181  PHINode *PhiX, *CountPhi;
1182 
1183  DefX2 = CountInst = nullptr;
1184  VarX1 = VarX0 = nullptr;
1185  PhiX = CountPhi = nullptr;
1186  LoopEntry = *(CurLoop->block_begin());
1187 
1188  // step 1: Check if the loop-back branch is in desirable form.
1189  {
1190  if (Value *T = matchCondition(
1191  dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
1192  DefX2 = dyn_cast<Instruction>(T);
1193  else
1194  return false;
1195  }
1196 
1197  // step 2: detect instructions corresponding to "x2 = x1 & (x1 - 1)"
1198  {
1199  if (!DefX2 || DefX2->getOpcode() != Instruction::And)
1200  return false;
1201 
1202  BinaryOperator *SubOneOp;
1203 
1204  if ((SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(0))))
1205  VarX1 = DefX2->getOperand(1);
1206  else {
1207  VarX1 = DefX2->getOperand(0);
1208  SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(1));
1209  }
1210  if (!SubOneOp || SubOneOp->getOperand(0) != VarX1)
1211  return false;
1212 
1213  ConstantInt *Dec = dyn_cast<ConstantInt>(SubOneOp->getOperand(1));
1214  if (!Dec ||
1215  !((SubOneOp->getOpcode() == Instruction::Sub && Dec->isOne()) ||
1216  (SubOneOp->getOpcode() == Instruction::Add &&
1217  Dec->isMinusOne()))) {
1218  return false;
1219  }
1220  }
1221 
1222  // step 3: Check the recurrence of variable X
1223  PhiX = getRecurrenceVar(VarX1, DefX2, LoopEntry);
1224  if (!PhiX)
1225  return false;
1226 
1227  // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1
1228  {
1229  CountInst = nullptr;
1230  for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI()->getIterator(),
1231  IterE = LoopEntry->end();
1232  Iter != IterE; Iter++) {
1233  Instruction *Inst = &*Iter;
1234  if (Inst->getOpcode() != Instruction::Add)
1235  continue;
1236 
1237  ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
1238  if (!Inc || !Inc->isOne())
1239  continue;
1240 
1241  PHINode *Phi = getRecurrenceVar(Inst->getOperand(0), Inst, LoopEntry);
1242  if (!Phi)
1243  continue;
1244 
1245  // Check if the result of the instruction is live of the loop.
1246  bool LiveOutLoop = false;
1247  for (User *U : Inst->users()) {
1248  if ((cast<Instruction>(U))->getParent() != LoopEntry) {
1249  LiveOutLoop = true;
1250  break;
1251  }
1252  }
1253 
1254  if (LiveOutLoop) {
1255  CountInst = Inst;
1256  CountPhi = Phi;
1257  break;
1258  }
1259  }
1260 
1261  if (!CountInst)
1262  return false;
1263  }
1264 
1265  // step 5: check if the precondition is in this form:
1266  // "if (x != 0) goto loop-head ; else goto somewhere-we-don't-care;"
1267  {
1268  auto *PreCondBr = dyn_cast<BranchInst>(PreCondBB->getTerminator());
1269  Value *T = matchCondition(PreCondBr, CurLoop->getLoopPreheader());
1270  if (T != PhiX->getOperand(0) && T != PhiX->getOperand(1))
1271  return false;
1272 
1273  CntInst = CountInst;
1274  CntPhi = CountPhi;
1275  Var = T;
1276  }
1277 
1278  return true;
1279 }
1280 
1281 /// Return true if the idiom is detected in the loop.
1282 ///
1283 /// Additionally:
1284 /// 1) \p CntInst is set to the instruction Counting Leading Zeros (CTLZ)
1285 /// or nullptr if there is no such.
1286 /// 2) \p CntPhi is set to the corresponding phi node
1287 /// or nullptr if there is no such.
1288 /// 3) \p Var is set to the value whose CTLZ could be used.
1289 /// 4) \p DefX is set to the instruction calculating Loop exit condition.
1290 ///
1291 /// The core idiom we are trying to detect is:
1292 /// \code
1293 /// if (x0 == 0)
1294 /// goto loop-exit // the precondition of the loop
1295 /// cnt0 = init-val;
1296 /// do {
1297 /// x = phi (x0, x.next); //PhiX
1298 /// cnt = phi(cnt0, cnt.next);
1299 ///
1300 /// cnt.next = cnt + 1;
1301 /// ...
1302 /// x.next = x >> 1; // DefX
1303 /// ...
1304 /// } while(x.next != 0);
1305 ///
1306 /// loop-exit:
1307 /// \endcode
1308 static bool detectCTLZIdiom(Loop *CurLoop, PHINode *&PhiX,
1309  Instruction *&CntInst, PHINode *&CntPhi,
1310  Instruction *&DefX) {
1311  BasicBlock *LoopEntry;
1312  Value *VarX = nullptr;
1313 
1314  DefX = nullptr;
1315  PhiX = nullptr;
1316  CntInst = nullptr;
1317  CntPhi = nullptr;
1318  LoopEntry = *(CurLoop->block_begin());
1319 
1320  // step 1: Check if the loop-back branch is in desirable form.
1321  if (Value *T = matchCondition(
1322  dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
1323  DefX = dyn_cast<Instruction>(T);
1324  else
1325  return false;
1326 
1327  // step 2: detect instructions corresponding to "x.next = x >> 1"
1328  if (!DefX || (DefX->getOpcode() != Instruction::AShr &&
1329  DefX->getOpcode() != Instruction::LShr))
1330  return false;
1331  ConstantInt *Shft = dyn_cast<ConstantInt>(DefX->getOperand(1));
1332  if (!Shft || !Shft->isOne())
1333  return false;
1334  VarX = DefX->getOperand(0);
1335 
1336  // step 3: Check the recurrence of variable X
1337  PhiX = getRecurrenceVar(VarX, DefX, LoopEntry);
1338  if (!PhiX)
1339  return false;
1340 
1341  // step 4: Find the instruction which count the CTLZ: cnt.next = cnt + 1
1342  // TODO: We can skip the step. If loop trip count is known (CTLZ),
1343  // then all uses of "cnt.next" could be optimized to the trip count
1344  // plus "cnt0". Currently it is not optimized.
1345  // This step could be used to detect POPCNT instruction:
1346  // cnt.next = cnt + (x.next & 1)
1347  for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI()->getIterator(),
1348  IterE = LoopEntry->end();
1349  Iter != IterE; Iter++) {
1350  Instruction *Inst = &*Iter;
1351  if (Inst->getOpcode() != Instruction::Add)
1352  continue;
1353 
1354  ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
1355  if (!Inc || !Inc->isOne())
1356  continue;
1357 
1358  PHINode *Phi = getRecurrenceVar(Inst->getOperand(0), Inst, LoopEntry);
1359  if (!Phi)
1360  continue;
1361 
1362  CntInst = Inst;
1363  CntPhi = Phi;
1364  break;
1365  }
1366  if (!CntInst)
1367  return false;
1368 
1369  return true;
1370 }
1371 
1372 /// Recognize CTLZ idiom in a non-countable loop and convert the loop
1373 /// to countable (with CTLZ trip count).
1374 /// If CTLZ inserted as a new trip count returns true; otherwise, returns false.
1375 bool LoopIdiomRecognize::recognizeAndInsertCTLZ() {
1376  // Give up if the loop has multiple blocks or multiple backedges.
1377  if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
1378  return false;
1379 
1380  Instruction *CntInst, *DefX;
1381  PHINode *CntPhi, *PhiX;
1382  if (!detectCTLZIdiom(CurLoop, PhiX, CntInst, CntPhi, DefX))
1383  return false;
1384 
1385  bool IsCntPhiUsedOutsideLoop = false;
1386  for (User *U : CntPhi->users())
1387  if (!CurLoop->contains(cast<Instruction>(U))) {
1388  IsCntPhiUsedOutsideLoop = true;
1389  break;
1390  }
1391  bool IsCntInstUsedOutsideLoop = false;
1392  for (User *U : CntInst->users())
1393  if (!CurLoop->contains(cast<Instruction>(U))) {
1394  IsCntInstUsedOutsideLoop = true;
1395  break;
1396  }
1397  // If both CntInst and CntPhi are used outside the loop the profitability
1398  // is questionable.
1399  if (IsCntInstUsedOutsideLoop && IsCntPhiUsedOutsideLoop)
1400  return false;
1401 
1402  // For some CPUs result of CTLZ(X) intrinsic is undefined
1403  // when X is 0. If we can not guarantee X != 0, we need to check this
1404  // when expand.
1405  bool ZeroCheck = false;
1406  // It is safe to assume Preheader exist as it was checked in
1407  // parent function RunOnLoop.
1408  BasicBlock *PH = CurLoop->getLoopPreheader();
1409  Value *InitX = PhiX->getIncomingValueForBlock(PH);
1410 
1411  // Make sure the initial value can't be negative otherwise the ashr in the
1412  // loop might never reach zero which would make the loop infinite.
1413  if (DefX->getOpcode() == Instruction::AShr && !isKnownNonNegative(InitX, *DL))
1414  return false;
1415 
1416  // If we are using the count instruction outside the loop, make sure we
1417  // have a zero check as a precondition. Without the check the loop would run
1418  // one iteration for before any check of the input value. This means 0 and 1
1419  // would have identical behavior in the original loop and thus
1420  if (!IsCntPhiUsedOutsideLoop) {
1421  auto *PreCondBB = PH->getSinglePredecessor();
1422  if (!PreCondBB)
1423  return false;
1424  auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
1425  if (!PreCondBI)
1426  return false;
1427  if (matchCondition(PreCondBI, PH) != InitX)
1428  return false;
1429  ZeroCheck = true;
1430  }
1431 
1432  // Check if CTLZ intrinsic is profitable. Assume it is always profitable
1433  // if we delete the loop (the loop has only 6 instructions):
1434  // %n.addr.0 = phi [ %n, %entry ], [ %shr, %while.cond ]
1435  // %i.0 = phi [ %i0, %entry ], [ %inc, %while.cond ]
1436  // %shr = ashr %n.addr.0, 1
1437  // %tobool = icmp eq %shr, 0
1438  // %inc = add nsw %i.0, 1
1439  // br i1 %tobool
1440 
1441  const Value *Args[] =
1442  {InitX, ZeroCheck ? ConstantInt::getTrue(InitX->getContext())
1443  : ConstantInt::getFalse(InitX->getContext())};
1444  if (CurLoop->getHeader()->size() != 6 &&
1445  TTI->getIntrinsicCost(Intrinsic::ctlz, InitX->getType(), Args) >
1447  return false;
1448 
1449  transformLoopToCountable(PH, CntInst, CntPhi, InitX, DefX,
1450  DefX->getDebugLoc(), ZeroCheck,
1451  IsCntPhiUsedOutsideLoop);
1452  return true;
1453 }
1454 
1455 /// Recognizes a population count idiom in a non-countable loop.
1456 ///
1457 /// If detected, transforms the relevant code to issue the popcount intrinsic
1458 /// function call, and returns true; otherwise, returns false.
1459 bool LoopIdiomRecognize::recognizePopcount() {
1461  return false;
1462 
1463  // Counting population are usually conducted by few arithmetic instructions.
1464  // Such instructions can be easily "absorbed" by vacant slots in a
1465  // non-compact loop. Therefore, recognizing popcount idiom only makes sense
1466  // in a compact loop.
1467 
1468  // Give up if the loop has multiple blocks or multiple backedges.
1469  if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
1470  return false;
1471 
1472  BasicBlock *LoopBody = *(CurLoop->block_begin());
1473  if (LoopBody->size() >= 20) {
1474  // The loop is too big, bail out.
1475  return false;
1476  }
1477 
1478  // It should have a preheader containing nothing but an unconditional branch.
1479  BasicBlock *PH = CurLoop->getLoopPreheader();
1480  if (!PH || &PH->front() != PH->getTerminator())
1481  return false;
1482  auto *EntryBI = dyn_cast<BranchInst>(PH->getTerminator());
1483  if (!EntryBI || EntryBI->isConditional())
1484  return false;
1485 
1486  // It should have a precondition block where the generated popcount intrinsic
1487  // function can be inserted.
1488  auto *PreCondBB = PH->getSinglePredecessor();
1489  if (!PreCondBB)
1490  return false;
1491  auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
1492  if (!PreCondBI || PreCondBI->isUnconditional())
1493  return false;
1494 
1495  Instruction *CntInst;
1496  PHINode *CntPhi;
1497  Value *Val;
1498  if (!detectPopcountIdiom(CurLoop, PreCondBB, CntInst, CntPhi, Val))
1499  return false;
1500 
1501  transformLoopToPopcount(PreCondBB, CntInst, CntPhi, Val);
1502  return true;
1503 }
1504 
1506  const DebugLoc &DL) {
1507  Value *Ops[] = {Val};
1508  Type *Tys[] = {Val->getType()};
1509 
1510  Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
1511  Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys);
1512  CallInst *CI = IRBuilder.CreateCall(Func, Ops);
1513  CI->setDebugLoc(DL);
1514 
1515  return CI;
1516 }
1517 
1519  const DebugLoc &DL, bool ZeroCheck) {
1520  Value *Ops[] = {Val, ZeroCheck ? IRBuilder.getTrue() : IRBuilder.getFalse()};
1521  Type *Tys[] = {Val->getType()};
1522 
1523  Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
1524  Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctlz, Tys);
1525  CallInst *CI = IRBuilder.CreateCall(Func, Ops);
1526  CI->setDebugLoc(DL);
1527 
1528  return CI;
1529 }
1530 
1531 /// Transform the following loop:
1532 /// loop:
1533 /// CntPhi = PHI [Cnt0, CntInst]
1534 /// PhiX = PHI [InitX, DefX]
1535 /// CntInst = CntPhi + 1
1536 /// DefX = PhiX >> 1
1537 /// LOOP_BODY
1538 /// Br: loop if (DefX != 0)
1539 /// Use(CntPhi) or Use(CntInst)
1540 ///
1541 /// Into:
1542 /// If CntPhi used outside the loop:
1543 /// CountPrev = BitWidth(InitX) - CTLZ(InitX >> 1)
1544 /// Count = CountPrev + 1
1545 /// else
1546 /// Count = BitWidth(InitX) - CTLZ(InitX)
1547 /// loop:
1548 /// CntPhi = PHI [Cnt0, CntInst]
1549 /// PhiX = PHI [InitX, DefX]
1550 /// PhiCount = PHI [Count, Dec]
1551 /// CntInst = CntPhi + 1
1552 /// DefX = PhiX >> 1
1553 /// Dec = PhiCount - 1
1554 /// LOOP_BODY
1555 /// Br: loop if (Dec != 0)
1556 /// Use(CountPrev + Cnt0) // Use(CntPhi)
1557 /// or
1558 /// Use(Count + Cnt0) // Use(CntInst)
1559 ///
1560 /// If LOOP_BODY is empty the loop will be deleted.
1561 /// If CntInst and DefX are not used in LOOP_BODY they will be removed.
1562 void LoopIdiomRecognize::transformLoopToCountable(
1563  BasicBlock *Preheader, Instruction *CntInst, PHINode *CntPhi, Value *InitX,
1564  Instruction *DefX, const DebugLoc &DL, bool ZeroCheck,
1565  bool IsCntPhiUsedOutsideLoop) {
1566  BranchInst *PreheaderBr = cast<BranchInst>(Preheader->getTerminator());
1567 
1568  // Step 1: Insert the CTLZ instruction at the end of the preheader block
1569  // Count = BitWidth - CTLZ(InitX);
1570  // If there are uses of CntPhi create:
1571  // CountPrev = BitWidth - CTLZ(InitX >> 1);
1572  IRBuilder<> Builder(PreheaderBr);
1573  Builder.SetCurrentDebugLocation(DL);
1574  Value *CTLZ, *Count, *CountPrev, *NewCount, *InitXNext;
1575 
1576  if (IsCntPhiUsedOutsideLoop) {
1577  if (DefX->getOpcode() == Instruction::AShr)
1578  InitXNext =
1579  Builder.CreateAShr(InitX, ConstantInt::get(InitX->getType(), 1));
1580  else if (DefX->getOpcode() == Instruction::LShr)
1581  InitXNext =
1582  Builder.CreateLShr(InitX, ConstantInt::get(InitX->getType(), 1));
1583  else
1584  llvm_unreachable("Unexpected opcode!");
1585  } else
1586  InitXNext = InitX;
1587  CTLZ = createCTLZIntrinsic(Builder, InitXNext, DL, ZeroCheck);
1588  Count = Builder.CreateSub(
1589  ConstantInt::get(CTLZ->getType(),
1590  CTLZ->getType()->getIntegerBitWidth()),
1591  CTLZ);
1592  if (IsCntPhiUsedOutsideLoop) {
1593  CountPrev = Count;
1594  Count = Builder.CreateAdd(
1595  CountPrev,
1596  ConstantInt::get(CountPrev->getType(), 1));
1597  }
1598  if (IsCntPhiUsedOutsideLoop)
1599  NewCount = Builder.CreateZExtOrTrunc(CountPrev,
1600  cast<IntegerType>(CntInst->getType()));
1601  else
1602  NewCount = Builder.CreateZExtOrTrunc(Count,
1603  cast<IntegerType>(CntInst->getType()));
1604 
1605  // If the CTLZ counter's initial value is not zero, insert Add Inst.
1606  Value *CntInitVal = CntPhi->getIncomingValueForBlock(Preheader);
1607  ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
1608  if (!InitConst || !InitConst->isZero())
1609  NewCount = Builder.CreateAdd(NewCount, CntInitVal);
1610 
1611  // Step 2: Insert new IV and loop condition:
1612  // loop:
1613  // ...
1614  // PhiCount = PHI [Count, Dec]
1615  // ...
1616  // Dec = PhiCount - 1
1617  // ...
1618  // Br: loop if (Dec != 0)
1619  BasicBlock *Body = *(CurLoop->block_begin());
1620  auto *LbBr = cast<BranchInst>(Body->getTerminator());
1621  ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
1622  Type *Ty = Count->getType();
1623 
1624  PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", &Body->front());
1625 
1626  Builder.SetInsertPoint(LbCond);
1627  Instruction *TcDec = cast<Instruction>(
1628  Builder.CreateSub(TcPhi, ConstantInt::get(Ty, 1),
1629  "tcdec", false, true));
1630 
1631  TcPhi->addIncoming(Count, Preheader);
1632  TcPhi->addIncoming(TcDec, Body);
1633 
1634  CmpInst::Predicate Pred =
1635  (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_NE : CmpInst::ICMP_EQ;
1636  LbCond->setPredicate(Pred);
1637  LbCond->setOperand(0, TcDec);
1638  LbCond->setOperand(1, ConstantInt::get(Ty, 0));
1639 
1640  // Step 3: All the references to the original counter outside
1641  // the loop are replaced with the NewCount -- the value returned from
1642  // __builtin_ctlz(x).
1643  if (IsCntPhiUsedOutsideLoop)
1644  CntPhi->replaceUsesOutsideBlock(NewCount, Body);
1645  else
1646  CntInst->replaceUsesOutsideBlock(NewCount, Body);
1647 
1648  // step 4: Forget the "non-computable" trip-count SCEV associated with the
1649  // loop. The loop would otherwise not be deleted even if it becomes empty.
1650  SE->forgetLoop(CurLoop);
1651 }
1652 
1653 void LoopIdiomRecognize::transformLoopToPopcount(BasicBlock *PreCondBB,
1654  Instruction *CntInst,
1655  PHINode *CntPhi, Value *Var) {
1656  BasicBlock *PreHead = CurLoop->getLoopPreheader();
1657  auto *PreCondBr = cast<BranchInst>(PreCondBB->getTerminator());
1658  const DebugLoc &DL = CntInst->getDebugLoc();
1659 
1660  // Assuming before transformation, the loop is following:
1661  // if (x) // the precondition
1662  // do { cnt++; x &= x - 1; } while(x);
1663 
1664  // Step 1: Insert the ctpop instruction at the end of the precondition block
1665  IRBuilder<> Builder(PreCondBr);
1666  Value *PopCnt, *PopCntZext, *NewCount, *TripCnt;
1667  {
1668  PopCnt = createPopcntIntrinsic(Builder, Var, DL);
1669  NewCount = PopCntZext =
1670  Builder.CreateZExtOrTrunc(PopCnt, cast<IntegerType>(CntPhi->getType()));
1671 
1672  if (NewCount != PopCnt)
1673  (cast<Instruction>(NewCount))->setDebugLoc(DL);
1674 
1675  // TripCnt is exactly the number of iterations the loop has
1676  TripCnt = NewCount;
1677 
1678  // If the population counter's initial value is not zero, insert Add Inst.
1679  Value *CntInitVal = CntPhi->getIncomingValueForBlock(PreHead);
1680  ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
1681  if (!InitConst || !InitConst->isZero()) {
1682  NewCount = Builder.CreateAdd(NewCount, CntInitVal);
1683  (cast<Instruction>(NewCount))->setDebugLoc(DL);
1684  }
1685  }
1686 
1687  // Step 2: Replace the precondition from "if (x == 0) goto loop-exit" to
1688  // "if (NewCount == 0) loop-exit". Without this change, the intrinsic
1689  // function would be partial dead code, and downstream passes will drag
1690  // it back from the precondition block to the preheader.
1691  {
1692  ICmpInst *PreCond = cast<ICmpInst>(PreCondBr->getCondition());
1693 
1694  Value *Opnd0 = PopCntZext;
1695  Value *Opnd1 = ConstantInt::get(PopCntZext->getType(), 0);
1696  if (PreCond->getOperand(0) != Var)
1697  std::swap(Opnd0, Opnd1);
1698 
1699  ICmpInst *NewPreCond = cast<ICmpInst>(
1700  Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1));
1701  PreCondBr->setCondition(NewPreCond);
1702 
1704  }
1705 
1706  // Step 3: Note that the population count is exactly the trip count of the
1707  // loop in question, which enable us to convert the loop from noncountable
1708  // loop into a countable one. The benefit is twofold:
1709  //
1710  // - If the loop only counts population, the entire loop becomes dead after
1711  // the transformation. It is a lot easier to prove a countable loop dead
1712  // than to prove a noncountable one. (In some C dialects, an infinite loop
1713  // isn't dead even if it computes nothing useful. In general, DCE needs
1714  // to prove a noncountable loop finite before safely delete it.)
1715  //
1716  // - If the loop also performs something else, it remains alive.
1717  // Since it is transformed to countable form, it can be aggressively
1718  // optimized by some optimizations which are in general not applicable
1719  // to a noncountable loop.
1720  //
1721  // After this step, this loop (conceptually) would look like following:
1722  // newcnt = __builtin_ctpop(x);
1723  // t = newcnt;
1724  // if (x)
1725  // do { cnt++; x &= x-1; t--) } while (t > 0);
1726  BasicBlock *Body = *(CurLoop->block_begin());
1727  {
1728  auto *LbBr = cast<BranchInst>(Body->getTerminator());
1729  ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
1730  Type *Ty = TripCnt->getType();
1731 
1732  PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", &Body->front());
1733 
1734  Builder.SetInsertPoint(LbCond);
1735  Instruction *TcDec = cast<Instruction>(
1736  Builder.CreateSub(TcPhi, ConstantInt::get(Ty, 1),
1737  "tcdec", false, true));
1738 
1739  TcPhi->addIncoming(TripCnt, PreHead);
1740  TcPhi->addIncoming(TcDec, Body);
1741 
1742  CmpInst::Predicate Pred =
1743  (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_UGT : CmpInst::ICMP_SLE;
1744  LbCond->setPredicate(Pred);
1745  LbCond->setOperand(0, TcDec);
1746  LbCond->setOperand(1, ConstantInt::get(Ty, 0));
1747  }
1748 
1749  // Step 4: All the references to the original population counter outside
1750  // the loop are replaced with the NewCount -- the value returned from
1751  // __builtin_ctpop().
1752  CntInst->replaceUsesOutsideBlock(NewCount, Body);
1753 
1754  // step 5: Forget the "non-computable" trip-count SCEV associated with the
1755  // loop. The loop would otherwise not be deleted even if it becomes empty.
1756  SE->forgetLoop(CurLoop);
1757 }
The access may reference and may modify the value stored in memory.
virtual void computeLoopSafetyInfo(const Loop *CurLoop)
Computes safety information for a loop checks loop body & header for the possibility of may throw exc...
Definition: MustExecute.cpp:45
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
uint64_t CallInst * C
Value * getValueOperand()
Definition: Instructions.h:399
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
void push_back(const T &Elt)
Definition: SmallVector.h:218
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:584
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
Value * CreateICmp(CmpInst::Predicate P, Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1858
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
static CallInst * createPopcntIntrinsic(IRBuilder<> &IRBuilder, Value *Val, const DebugLoc &DL)
PreservedAnalyses getLoopPassPreservedAnalyses()
Returns the minimum set of Analyses that all loop passes must preserve.
Value * CreateZExtOrTrunc(Value *V, Type *DestTy, const Twine &Name="")
Create a ZExt or Trunc from the integer value V to DestTy.
Definition: IRBuilder.h:1578
const SCEV * getConstant(ConstantInt *V)
Compute iterated dominance frontiers using a linear time algorithm.
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BinaryOps getOpcode() const
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Value * isBytewiseValue(Value *V)
If the specified value can be set by repeating the same byte in memory, return the i8 value that it i...
bool isAtomic() const
Return true if this instruction has an AtomicOrdering of unordered or higher.
Constant * getOrInsertFunction(StringRef Name, FunctionType *T, AttributeList AttributeList)
Look up the specified function in the module symbol table.
Definition: Module.cpp:143
ArrayRef< BasicBlock *>::const_iterator block_iterator
Definition: LoopInfo.h:153
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:64
bool isUnordered() const
Definition: Instructions.h:393
The main scalar evolution driver.
static bool detectCTLZIdiom(Loop *CurLoop, PHINode *&PhiX, Instruction *&CntInst, PHINode *&CntPhi, Instruction *&DefX)
Return true if the idiom is detected in the loop.
This class represents a function call, abstracting a target machine&#39;s calling convention.
static PHINode * getRecurrenceVar(Value *VarX, Instruction *DefX, BasicBlock *LoopEntry)
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:174
Value * getValue() const
Like Internal, but omit from symbol table.
Definition: GlobalValue.h:57
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:714
This class wraps the llvm.memset intrinsic.
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
A debug info location.
Definition: DebugLoc.h:34
The adaptor from a function pass to a loop pass computes these analyses and makes them available to t...
unsigned getPointerAddressSpace() const
Get the address space of this pointer or pointer vector type.
Definition: DerivedTypes.h:503
An instruction for reading from memory.
Definition: Instructions.h:168
Value * getCondition() const
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:138
void setAlignment(unsigned Align)
Definition: Globals.cpp:116
Value * getLength() const
iterator end()
Get an iterator to the end of the SetVector.
Definition: SetVector.h:93
static Constant * get(ArrayType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:960
Value * getDest() const
This is just like getRawDest, but it strips off any cast instructions (including addrspacecast) that ...
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:263
PopcntSupportKind getPopcntSupport(unsigned IntTyWidthInBit) const
Return hardware support for population count.
Simple and conservative implementation of LoopSafetyInfo that can give false-positive answers to its ...
Definition: MustExecute.h:105
AnalysisUsage & addRequired()
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr if the function does no...
Definition: BasicBlock.cpp:134
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:221
amdgpu Simplify well known AMD library false Value Value const Twine & Name
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:364
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:684
static CallInst * createCTLZIntrinsic(IRBuilder<> &IRBuilder, Value *Val, const DebugLoc &DL, bool ZeroCheck)
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:743
This file contains the simple types necessary to represent the attributes associated with functions a...
Value * CreateAdd(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:974
unsigned getDestAlignment() const
This file implements a class to represent arbitrary precision integral constant values and operations...
const APInt & getAPInt() const
BlockT * getHeader() const
Definition: LoopInfo.h:100
static bool isSimple(Instruction *I)
bool isOne() const
This is just a convenience method to make client code smaller for a common case.
Definition: Constants.h:201
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:408
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
Value handle that is nullable, but tries to track the Value.
Definition: ValueHandle.h:182
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:142
This node represents a polynomial recurrence on the trip count of the specified loop.
static APInt getStoreStride(const SCEVAddRecExpr *StoreEv)
#define T
BasicBlock * GetInsertBlock() const
Definition: IRBuilder.h:121
Class to represent array types.
Definition: DerivedTypes.h:369
static cl::opt< bool > UseLIRCodeSizeHeurs("use-lir-code-size-heurs", cl::desc("Use loop idiom recognition code size heuristics when compiling" "with -Os/-Oz"), cl::init(true), cl::Hidden)
bool has(LibFunc F) const
Tests whether a library function is available.
iterator begin()
Get an iterator to the beginning of the SetVector.
Definition: SetVector.h:83
MDNode * getMetadata(unsigned KindID) const
Get the metadata of given kind attached to this Instruction.
Definition: Instruction.h:217
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:126
Value * CreateSub(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:991
void initializeLoopIdiomRecognizeLegacyPassPass(PassRegistry &)
An instruction for storing to memory.
Definition: Instructions.h:310
bool isMinusOne() const
This function will return true iff every bit in this constant is set to true.
Definition: Constants.h:209
bool isKnownNonNegative(const Value *V, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Returns true if the give value is known to be non-negative.
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
static void deleteDeadInstruction(Instruction *I)
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:145
Function * getDeclaration(Module *M, ID id, ArrayRef< Type *> Tys=None)
Create or insert an LLVM Function declaration for an intrinsic, and return it.
Definition: Function.cpp:1021
void SetInsertPoint(BasicBlock *TheBB)
This specifies that created instructions should be appended to the end of the specified block...
Definition: IRBuilder.h:127
Value * getOperand(unsigned i) const
Definition: User.h:170
size_type count(const key_type &key) const
Count the number of elements of a given key in the SetVector.
Definition: SetVector.h:211
bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS)
Test whether entry to the loop is protected by a conditional between LHS and RHS. ...
static Constant * getBitCast(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1750
bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL, ScalarEvolution &SE, bool CheckType=true)
Returns true if the memory operations A and B are consecutive.
bool inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI)
Analyze the name and prototype of the given function and set any applicable attributes.
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
const SCEV * getOperand(unsigned i) const
const Instruction * getFirstNonPHI() const
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:190
Wrapper pass for TargetTransformInfo.
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
const SCEV * getOne(Type *Ty)
Return a SCEV for the constant 1 of a specific type.
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:304
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:236
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
ConstantInt * getTrue()
Get the constant value for i1 true.
Definition: IRBuilder.h:287
Conditional or Unconditional Branch instruction.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
Value * getIncomingValueForBlock(const BasicBlock *BB) const
This file contains the declarations for the subclasses of Constant, which represent the different fla...
const Instruction & front() const
Definition: BasicBlock.h:275
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
const SCEV * getAddExpr(SmallVectorImpl< const SCEV *> &Ops, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Get a canonical add expression, or something simpler if possible.
size_t size() const
Definition: BasicBlock.h:273
bool isUnordered() const
Definition: Instructions.h:268
Represent the analysis usage information of a pass.
bool optForSize() const
Optimize this function for size (-Os) or minimum size (-Oz).
Definition: Function.h:598
static Value * matchCondition(BranchInst *BI, BasicBlock *LoopEntry)
Check if the given conditional branch is based on the comparison between a variable and zero...
This instruction compares its operands according to the predicate given to the constructor.
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:657
bool isAffine() const
Return true if this represents an expression A + B*x where A and B are loop invariant values...
Value * getPointerOperand()
Definition: Instructions.h:274
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
self_iterator getIterator()
Definition: ilist_node.h:82
const SCEV * getMinusSCEV(const SCEV *LHS, const SCEV *RHS, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, const TargetLibraryInfo *TLI=nullptr, MemorySSAUpdater *MSSAU=nullptr)
If the specified value is a trivially dead instruction, delete it.
Definition: Local.cpp:430
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1392
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
size_t size() const
Definition: SmallVector.h:53
static wasm::ValType getType(const TargetRegisterClass *RC)
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:220
bool isVolatile() const
const SCEV * getMulExpr(SmallVectorImpl< const SCEV *> &Ops, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Get a canonical multiply expression, or something simpler if possible.
Value * GetUnderlyingObject(Value *V, const DataLayout &DL, unsigned MaxLookup=6)
This method strips off any GEP address adjustments and pointer casts from the specified value...
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
Representation for a specific memory location.
This class provides an interface for updating the loop pass manager based on mutations to the loop ne...
typename vector_type::const_iterator iterator
Definition: SetVector.h:49
Iterator for intrusive lists based on ilist_node.
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
Type * getType() const
Return the LLVM type of this SCEV expression.
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
iterator end()
Definition: BasicBlock.h:265
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:249
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
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:621
bool isConditional() const
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
static Constant * getMemSetPatternValue(Value *V, const DataLayout *DL)
getMemSetPatternValue - If a strided store of the specified value is safe to turn into a memset_patte...
static const SCEV * getNumBytes(const SCEV *BECount, Type *IntPtr, unsigned StoreSize, Loop *CurLoop, const DataLayout *DL, ScalarEvolution *SE)
Compute the number of bytes as a SCEV from the backedge taken count.
static bool detectPopcountIdiom(Loop *CurLoop, BasicBlock *PreCondBB, Instruction *&CntInst, PHINode *&CntPhi, Value *&Var)
Return true iff the idiom is detected in the loop.
static ConstantInt * getTrue(LLVMContext &Context)
Definition: Constants.cpp:577
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
The access may modify the value stored in memory.
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:941
signed less or equal
Definition: InstrTypes.h:687
loop Recognize loop idioms
const Module * getModule() const
Return the module owning the function this instruction belongs to or nullptr it the function does not...
Definition: Instruction.cpp:56
Class for arbitrary precision integers.
Definition: APInt.h:70
loop idiom
ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc)
getModRefInfo (for call sites) - Return information about whether a particular call site modifies or ...
iterator_range< user_iterator > users()
Definition: Value.h:400
This class uses information about analyze scalars to rewrite expressions in canonical form...
Pass * createLoopIdiomPass()
ConstantInt * getFalse()
Get the constant value for i1 false.
Definition: IRBuilder.h:292
uint64_t getTypeSizeInBits(Type *Ty) const
Size examples:
Definition: DataLayout.h:560
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:731
bool isVolatile() const
Return true if this is a store to a volatile memory location.
Definition: Instructions.h:343
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:307
INITIALIZE_PASS_BEGIN(LoopIdiomRecognizeLegacyPass, "loop-idiom", "Recognize loop idioms", false, false) INITIALIZE_PASS_END(LoopIdiomRecognizeLegacyPass
void forgetLoop(const Loop *L)
This method should be called by the client when it has changed a loop in a way that may effect Scalar...
void setUnnamedAddr(UnnamedAddr Val)
Definition: GlobalValue.h:216
unsigned getAtomicMemIntrinsicMaxElementSize() const
unsigned getAlignment() const
Return the alignment of the access that is being performed.
Definition: Instructions.h:230
This class represents an analyzed expression in the program.
unsigned getIntegerBitWidth() const
Definition: DerivedTypes.h:97
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:459
This file provides utility analysis objects describing memory locations.
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
LLVM_NODISCARD ModRefInfo intersectModRef(const ModRefInfo MRI1, const ModRefInfo MRI2)
#define I(x, y, z)
Definition: MD5.cpp:58
bool isZero() const
This is just a convenience method to make client code smaller for a common code.
Definition: Constants.h:193
void getLoopAnalysisUsage(AnalysisUsage &AU)
Helper to consistently add the set of standard passes to a loop pass&#39;s AnalysisUsage.
Definition: LoopUtils.cpp:128
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:568
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
block_iterator block_end() const
Definition: LoopInfo.h:155
uint32_t Size
Definition: Profile.cpp:47
unsigned getAlignment() const
Return the alignment of the access that is being performed.
Definition: Instructions.h:355
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:280
static const SCEV * getStartForNegStride(const SCEV *Start, const SCEV *BECount, Type *IntPtr, unsigned StoreSize, ScalarEvolution *SE)
const SCEV * getBackedgeTakenCount(const Loop *L)
If the specified loop has a predictable backedge-taken count, return it, otherwise return a SCEVCould...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
The cost of a typical &#39;add&#39; instruction.
int getIntrinsicCost(Intrinsic::ID IID, Type *RetTy, ArrayRef< Type *> ParamTys) const
Estimate the cost of an intrinsic when lowered.
const SCEV * getNegativeSCEV(const SCEV *V, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap)
Return the SCEV object corresponding to -V.
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:566
LLVM Value Representation.
Definition: Value.h:73
const SCEV * getSCEV(Value *V)
Return a SCEV expression for the full generality of the specified expression.
A vector that has set insertion semantics.
Definition: SetVector.h:41
static bool mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L, const SCEV *BECount, unsigned StoreSize, AliasAnalysis &AA, SmallPtrSetImpl< Instruction *> &IgnoredStores)
mayLoopAccessLocation - Return true if the specified loop might access the specified pointer location...
ModRefInfo
Flags indicating whether a memory access modifies or references memory.
unsigned greater than
Definition: InstrTypes.h:680
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
A container for analyses that lazily runs them and caches their results.
void replaceUsesOutsideBlock(Value *V, BasicBlock *BB)
replaceUsesOutsideBlock - Go through the uses list for this definition and make each use point to "V"...
Definition: Value.cpp:449
const SCEV * getTruncateOrZeroExtend(const SCEV *V, Type *Ty)
Return a SCEV corresponding to a conversion of the input value to the specified type.
This pass exposes codegen information to IR-level passes.
LLVM_NODISCARD bool isModOrRefSet(const ModRefInfo MRI)
bool isSimple() const
Definition: Instructions.h:391
This header defines various interfaces for pass management in LLVM.
bool isBigEndian() const
Definition: DataLayout.h:222
virtual bool anyBlockMayThrow() const
Returns true iff any block of the loop for which this info is contains an instruction that may throw ...
Definition: MustExecute.cpp:41
#define LLVM_DEBUG(X)
Definition: Debug.h:123
bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE)
Return true if the given expression is safe to expand in the sense that all materialized values are s...
block_iterator block_begin() const
Definition: LoopInfo.h:154
bool hasLoopInvariantBackedgeTakenCount(const Loop *L)
Return true if the specified loop has an analyzable loop-invariant backedge-taken count...
Value * getPointerOperand()
Definition: Instructions.h:402
const SCEV * getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth=0)
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR, LPMUpdater &U)
This class represents a constant integer value.
CallInst * CreateCall(Value *Callee, ArrayRef< Value *> Args=None, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:1883