Remove LLVM 8.0.1 files.

1 files changed, 0 insertions, 1781 deletions

diff --git a/gnu/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/gnu/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
deleted file mode 100644
index 10073457f6b..00000000000
--- a/gnu/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ /dev/null
@@ -1,1781 +0,0 @@
-//===- LoopIdiomRecognize.cpp - Loop idiom recognition --------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass implements an idiom recognizer that transforms simple loops into a
-// non-loop form.  In cases that this kicks in, it can be a significant
-// performance win.
-//
-// If compiling for code size we avoid idiom recognition if the resulting
-// code could be larger than the code for the original loop. One way this could
-// happen is if the loop is not removable after idiom recognition due to the
-// presence of non-idiom instructions. The initial implementation of the
-// heuristics applies to idioms in multi-block loops.
-//
-//===----------------------------------------------------------------------===//
-//
-// TODO List:
-//
-// Future loop memory idioms to recognize:
-//   memcmp, memmove, strlen, etc.
-// Future floating point idioms to recognize in -ffast-math mode:
-//   fpowi
-// Future integer operation idioms to recognize:
-//   ctpop
-//
-// Beware that isel's default lowering for ctpop is highly inefficient for
-// i64 and larger types when i64 is legal and the value has few bits set.  It
-// would be good to enhance isel to emit a loop for ctpop in this case.
-//
-// This could recognize common matrix multiplies and dot product idioms and
-// replace them with calls to BLAS (if linked in??).
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/APInt.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/MapVector.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/LoopAccessAnalysis.h"
-#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Analysis/MemoryLocation.h"
-#include "llvm/Analysis/ScalarEvolution.h"
-#include "llvm/Analysis/ScalarEvolutionExpander.h"
-#include "llvm/Analysis/ScalarEvolutionExpressions.h"
-#include "llvm/Analysis/TargetLibraryInfo.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/IR/Attributes.h"
-#include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/Constant.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/DebugLoc.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Dominators.h"
-#include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/GlobalVariable.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/InstrTypes.h"
-#include "llvm/IR/Instruction.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/PassManager.h"
-#include "llvm/IR/Type.h"
-#include "llvm/IR/User.h"
-#include "llvm/IR/Value.h"
-#include "llvm/IR/ValueHandle.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
-#include "llvm/Transforms/Utils/BuildLibCalls.h"
-#include "llvm/Transforms/Utils/LoopUtils.h"
-#include <algorithm>
-#include <cassert>
-#include <cstdint>
-#include <utility>
-#include <vector>
-
-using namespace llvm;
-
-#define DEBUG_TYPE "loop-idiom"
-
-STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
-STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
-
-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);
-
-namespace {
-
-class LoopIdiomRecognize {
-  Loop *CurLoop = nullptr;
-  AliasAnalysis *AA;
-  DominatorTree *DT;
-  LoopInfo *LI;
-  ScalarEvolution *SE;
-  TargetLibraryInfo *TLI;
-  const TargetTransformInfo *TTI;
-  const DataLayout *DL;
-  bool ApplyCodeSizeHeuristics;
-
-public:
-  explicit LoopIdiomRecognize(AliasAnalysis *AA, DominatorTree *DT,
-                              LoopInfo *LI, ScalarEvolution *SE,
-                              TargetLibraryInfo *TLI,
-                              const TargetTransformInfo *TTI,
-                              const DataLayout *DL)
-      : AA(AA), DT(DT), LI(LI), SE(SE), TLI(TLI), TTI(TTI), DL(DL) {}
-
-  bool runOnLoop(Loop *L);
-
-private:
-  using StoreList = SmallVector<StoreInst *, 8>;
-  using StoreListMap = MapVector<Value *, StoreList>;
-
-  StoreListMap StoreRefsForMemset;
-  StoreListMap StoreRefsForMemsetPattern;
-  StoreList StoreRefsForMemcpy;
-  bool HasMemset;
-  bool HasMemsetPattern;
-  bool HasMemcpy;
-
-  /// Return code for isLegalStore()
-  enum LegalStoreKind {
-    None = 0,
-    Memset,
-    MemsetPattern,
-    Memcpy,
-    UnorderedAtomicMemcpy,
-    DontUse // Dummy retval never to be used. Allows catching errors in retval
-            // handling.
-  };
-
-  /// \name Countable Loop Idiom Handling
-  /// @{
-
-  bool runOnCountableLoop();
-  bool runOnLoopBlock(BasicBlock *BB, const SCEV *BECount,
-                      SmallVectorImpl<BasicBlock *> &ExitBlocks);
-
-  void collectStores(BasicBlock *BB);
-  LegalStoreKind isLegalStore(StoreInst *SI);
-  enum class ForMemset { No, Yes };
-  bool processLoopStores(SmallVectorImpl<StoreInst *> &SL, const SCEV *BECount,
-                         ForMemset For);
-  bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount);
-
-  bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
-                               unsigned StoreAlignment, Value *StoredVal,
-                               Instruction *TheStore,
-                               SmallPtrSetImpl<Instruction *> &Stores,
-                               const SCEVAddRecExpr *Ev, const SCEV *BECount,
-                               bool NegStride, bool IsLoopMemset = false);
-  bool processLoopStoreOfLoopLoad(StoreInst *SI, const SCEV *BECount);
-  bool avoidLIRForMultiBlockLoop(bool IsMemset = false,
-                                 bool IsLoopMemset = false);
-
-  /// @}
-  /// \name Noncountable Loop Idiom Handling
-  /// @{
-
-  bool runOnNoncountableLoop();
-
-  bool recognizePopcount();
-  void transformLoopToPopcount(BasicBlock *PreCondBB, Instruction *CntInst,
-                               PHINode *CntPhi, Value *Var);
-  bool recognizeAndInsertFFS();  /// Find First Set: ctlz or cttz
-  void transformLoopToCountable(Intrinsic::ID IntrinID, BasicBlock *PreCondBB,
-                                Instruction *CntInst, PHINode *CntPhi,
-                                Value *Var, Instruction *DefX,
-                                const DebugLoc &DL, bool ZeroCheck,
-                                bool IsCntPhiUsedOutsideLoop);
-
-  /// @}
-};
-
-class LoopIdiomRecognizeLegacyPass : public LoopPass {
-public:
-  static char ID;
-
-  explicit LoopIdiomRecognizeLegacyPass() : LoopPass(ID) {
-    initializeLoopIdiomRecognizeLegacyPassPass(
-        *PassRegistry::getPassRegistry());
-  }
-
-  bool runOnLoop(Loop *L, LPPassManager &LPM) override {
-    if (skipLoop(L))
-      return false;
-
-    AliasAnalysis *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
-    DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
-    LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
-    ScalarEvolution *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
-    TargetLibraryInfo *TLI =
-        &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
-    const TargetTransformInfo *TTI =
-        &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
-            *L->getHeader()->getParent());
-    const DataLayout *DL = &L->getHeader()->getModule()->getDataLayout();
-
-    LoopIdiomRecognize LIR(AA, DT, LI, SE, TLI, TTI, DL);
-    return LIR.runOnLoop(L);
-  }
-
-  /// This transformation requires natural loop information & requires that
-  /// loop preheaders be inserted into the CFG.
-  void getAnalysisUsage(AnalysisUsage &AU) const override {
-    AU.addRequired<TargetLibraryInfoWrapperPass>();
-    AU.addRequired<TargetTransformInfoWrapperPass>();
-    getLoopAnalysisUsage(AU);
-  }
-};
-
-} // end anonymous namespace
-
-char LoopIdiomRecognizeLegacyPass::ID = 0;
-
-PreservedAnalyses LoopIdiomRecognizePass::run(Loop &L, LoopAnalysisManager &AM,
-                                              LoopStandardAnalysisResults &AR,
-                                              LPMUpdater &) {
-  const auto *DL = &L.getHeader()->getModule()->getDataLayout();
-
-  LoopIdiomRecognize LIR(&AR.AA, &AR.DT, &AR.LI, &AR.SE, &AR.TLI, &AR.TTI, DL);
-  if (!LIR.runOnLoop(&L))
-    return PreservedAnalyses::all();
-
-  return getLoopPassPreservedAnalyses();
-}
-
-INITIALIZE_PASS_BEGIN(LoopIdiomRecognizeLegacyPass, "loop-idiom",
-                      "Recognize loop idioms", false, false)
-INITIALIZE_PASS_DEPENDENCY(LoopPass)
-INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
-INITIALIZE_PASS_END(LoopIdiomRecognizeLegacyPass, "loop-idiom",
-                    "Recognize loop idioms", false, false)
-
-Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognizeLegacyPass(); }
-
-static void deleteDeadInstruction(Instruction *I) {
-  I->replaceAllUsesWith(UndefValue::get(I->getType()));
-  I->eraseFromParent();
-}
-
-//===----------------------------------------------------------------------===//
-//
-//          Implementation of LoopIdiomRecognize
-//
-//===----------------------------------------------------------------------===//
-
-bool LoopIdiomRecognize::runOnLoop(Loop *L) {
-  CurLoop = L;
-  // If the loop could not be converted to canonical form, it must have an
-  // indirectbr in it, just give up.
-  if (!L->getLoopPreheader())
-    return false;
-
-  // Disable loop idiom recognition if the function's name is a common idiom.
-  StringRef Name = L->getHeader()->getParent()->getName();
-  if (Name == "memset" || Name == "memcpy")
-    return false;
-  if (Name == "_libc_memset" || Name == "_libc_memcpy")
-    return false;
-
-  // Determine if code size heuristics need to be applied.
-  ApplyCodeSizeHeuristics =
-      L->getHeader()->getParent()->optForSize() && UseLIRCodeSizeHeurs;
-
-  HasMemset = TLI->has(LibFunc_memset);
-  HasMemsetPattern = TLI->has(LibFunc_memset_pattern16);
-  HasMemcpy = TLI->has(LibFunc_memcpy);
-
-  if (HasMemset || HasMemsetPattern || HasMemcpy)
-    if (SE->hasLoopInvariantBackedgeTakenCount(L))
-      return runOnCountableLoop();
-
-  return runOnNoncountableLoop();
-}
-
-bool LoopIdiomRecognize::runOnCountableLoop() {
-  const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop);
-  assert(!isa<SCEVCouldNotCompute>(BECount) &&
-         "runOnCountableLoop() called on a loop without a predictable"
-         "backedge-taken count");
-
-  // If this loop executes exactly one time, then it should be peeled, not
-  // optimized by this pass.
-  if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
-    if (BECst->getAPInt() == 0)
-      return false;
-
-  SmallVector<BasicBlock *, 8> ExitBlocks;
-  CurLoop->getUniqueExitBlocks(ExitBlocks);
-
-  LLVM_DEBUG(dbgs() << "loop-idiom Scanning: F["
-                    << CurLoop->getHeader()->getParent()->getName()
-                    << "] Loop %" << CurLoop->getHeader()->getName() << "\n");
-
-  bool MadeChange = false;
-
-  // The following transforms hoist stores/memsets into the loop pre-header.
-  // Give up if the loop has instructions may throw.
-  SimpleLoopSafetyInfo SafetyInfo;
-  SafetyInfo.computeLoopSafetyInfo(CurLoop);
-  if (SafetyInfo.anyBlockMayThrow())
-    return MadeChange;
-
-  // Scan all the blocks in the loop that are not in subloops.
-  for (auto *BB : CurLoop->getBlocks()) {
-    // Ignore blocks in subloops.
-    if (LI->getLoopFor(BB) != CurLoop)
-      continue;
-
-    MadeChange |= runOnLoopBlock(BB, BECount, ExitBlocks);
-  }
-  return MadeChange;
-}
-
-static APInt getStoreStride(const SCEVAddRecExpr *StoreEv) {
-  const SCEVConstant *ConstStride = cast<SCEVConstant>(StoreEv->getOperand(1));
-  return ConstStride->getAPInt();
-}
-
-/// getMemSetPatternValue - If a strided store of the specified value is safe to
-/// turn into a memset_pattern16, return a ConstantArray of 16 bytes that should
-/// be passed in.  Otherwise, return null.
-///
-/// Note that we don't ever attempt to use memset_pattern8 or 4, because these
-/// just replicate their input array and then pass on to memset_pattern16.
-static Constant *getMemSetPatternValue(Value *V, const DataLayout *DL) {
-  // FIXME: This could check for UndefValue because it can be merged into any
-  // other valid pattern.
-
-  // If the value isn't a constant, we can't promote it to being in a constant
-  // array.  We could theoretically do a store to an alloca or something, but
-  // that doesn't seem worthwhile.
-  Constant *C = dyn_cast<Constant>(V);
-  if (!C)
-    return nullptr;
-
-  // Only handle simple values that are a power of two bytes in size.
-  uint64_t Size = DL->getTypeSizeInBits(V->getType());
-  if (Size == 0 || (Size & 7) || (Size & (Size - 1)))
-    return nullptr;
-
-  // Don't care enough about darwin/ppc to implement this.
-  if (DL->isBigEndian())
-    return nullptr;
-
-  // Convert to size in bytes.
-  Size /= 8;
-
-  // TODO: If CI is larger than 16-bytes, we can try slicing it in half to see
-  // if the top and bottom are the same (e.g. for vectors and large integers).
-  if (Size > 16)
-    return nullptr;
-
-  // If the constant is exactly 16 bytes, just use it.
-  if (Size == 16)
-    return C;
-
-  // Otherwise, we'll use an array of the constants.
-  unsigned ArraySize = 16 / Size;
-  ArrayType *AT = ArrayType::get(V->getType(), ArraySize);
-  return ConstantArray::get(AT, std::vector<Constant *>(ArraySize, C));
-}
-
-LoopIdiomRecognize::LegalStoreKind
-LoopIdiomRecognize::isLegalStore(StoreInst *SI) {
-  // Don't touch volatile stores.
-  if (SI->isVolatile())
-    return LegalStoreKind::None;
-  // We only want simple or unordered-atomic stores.
-  if (!SI->isUnordered())
-    return LegalStoreKind::None;
-
-  // Don't convert stores of non-integral pointer types to memsets (which stores
-  // integers).
-  if (DL->isNonIntegralPointerType(SI->getValueOperand()->getType()))
-    return LegalStoreKind::None;
-
-  // Avoid merging nontemporal stores.
-  if (SI->getMetadata(LLVMContext::MD_nontemporal))
-    return LegalStoreKind::None;
-
-  Value *StoredVal = SI->getValueOperand();
-  Value *StorePtr = SI->getPointerOperand();
-
-  // Reject stores that are so large that they overflow an unsigned.
-  uint64_t SizeInBits = DL->getTypeSizeInBits(StoredVal->getType());
-  if ((SizeInBits & 7) || (SizeInBits >> 32) != 0)
-    return LegalStoreKind::None;
-
-  // See if the pointer expression is an AddRec like {base,+,1} on the current
-  // loop, which indicates a strided store.  If we have something else, it's a
-  // random store we can't handle.
-  const SCEVAddRecExpr *StoreEv =
-      dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
-  if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine())
-    return LegalStoreKind::None;
-
-  // Check to see if we have a constant stride.
-  if (!isa<SCEVConstant>(StoreEv->getOperand(1)))
-    return LegalStoreKind::None;
-
-  // See if the store can be turned into a memset.
-
-  // If the stored value is a byte-wise value (like i32 -1), then it may be
-  // turned into a memset of i8 -1, assuming that all the consecutive bytes
-  // are stored.  A store of i32 0x01020304 can never be turned into a memset,
-  // but it can be turned into memset_pattern if the target supports it.
-  Value *SplatValue = isBytewiseValue(StoredVal);
-  Constant *PatternValue = nullptr;
-
-  // Note: memset and memset_pattern on unordered-atomic is yet not supported
-  bool UnorderedAtomic = SI->isUnordered() && !SI->isSimple();
-
-  // If we're allowed to form a memset, and the stored value would be
-  // acceptable for memset, use it.
-  if (!UnorderedAtomic && HasMemset && SplatValue &&
-      // Verify that the stored value is loop invariant.  If not, we can't
-      // promote the memset.
-      CurLoop->isLoopInvariant(SplatValue)) {
-    // It looks like we can use SplatValue.
-    return LegalStoreKind::Memset;
-  } else if (!UnorderedAtomic && HasMemsetPattern &&
-             // Don't create memset_pattern16s with address spaces.
-             StorePtr->getType()->getPointerAddressSpace() == 0 &&
-             (PatternValue = getMemSetPatternValue(StoredVal, DL))) {
-    // It looks like we can use PatternValue!
-    return LegalStoreKind::MemsetPattern;
-  }
-
-  // Otherwise, see if the store can be turned into a memcpy.
-  if (HasMemcpy) {
-    // Check to see if the stride matches the size of the store.  If so, then we
-    // know that every byte is touched in the loop.
-    APInt Stride = getStoreStride(StoreEv);
-    unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
-    if (StoreSize != Stride && StoreSize != -Stride)
-      return LegalStoreKind::None;
-
-    // The store must be feeding a non-volatile load.
-    LoadInst *LI = dyn_cast<LoadInst>(SI->getValueOperand());
-
-    // Only allow non-volatile loads
-    if (!LI || LI->isVolatile())
-      return LegalStoreKind::None;
-    // Only allow simple or unordered-atomic loads
-    if (!LI->isUnordered())
-      return LegalStoreKind::None;
-
-    // See if the pointer expression is an AddRec like {base,+,1} on the current
-    // loop, which indicates a strided load.  If we have something else, it's a
-    // random load we can't handle.
-    const SCEVAddRecExpr *LoadEv =
-        dyn_cast<SCEVAddRecExpr>(SE->getSCEV(LI->getPointerOperand()));
-    if (!LoadEv || LoadEv->getLoop() != CurLoop || !LoadEv->isAffine())
-      return LegalStoreKind::None;
-
-    // The store and load must share the same stride.
-    if (StoreEv->getOperand(1) != LoadEv->getOperand(1))
-      return LegalStoreKind::None;
-
-    // Success.  This store can be converted into a memcpy.
-    UnorderedAtomic = UnorderedAtomic || LI->isAtomic();
-    return UnorderedAtomic ? LegalStoreKind::UnorderedAtomicMemcpy
-                           : LegalStoreKind::Memcpy;
-  }
-  // This store can't be transformed into a memset/memcpy.
-  return LegalStoreKind::None;
-}
-
-void LoopIdiomRecognize::collectStores(BasicBlock *BB) {
-  StoreRefsForMemset.clear();
-  StoreRefsForMemsetPattern.clear();
-  StoreRefsForMemcpy.clear();
-  for (Instruction &I : *BB) {
-    StoreInst *SI = dyn_cast<StoreInst>(&I);
-    if (!SI)
-      continue;
-
-    // Make sure this is a strided store with a constant stride.
-    switch (isLegalStore(SI)) {
-    case LegalStoreKind::None:
-      // Nothing to do
-      break;
-    case LegalStoreKind::Memset: {
-      // Find the base pointer.
-      Value *Ptr = GetUnderlyingObject(SI->getPointerOperand(), *DL);
-      StoreRefsForMemset[Ptr].push_back(SI);
-    } break;
-    case LegalStoreKind::MemsetPattern: {
-      // Find the base pointer.
-      Value *Ptr = GetUnderlyingObject(SI->getPointerOperand(), *DL);
-      StoreRefsForMemsetPattern[Ptr].push_back(SI);
-    } break;
-    case LegalStoreKind::Memcpy:
-    case LegalStoreKind::UnorderedAtomicMemcpy:
-      StoreRefsForMemcpy.push_back(SI);
-      break;
-    default:
-      assert(false && "unhandled return value");
-      break;
-    }
-  }
-}
-
-/// runOnLoopBlock - Process the specified block, which lives in a counted loop
-/// with the specified backedge count.  This block is known to be in the current
-/// loop and not in any subloops.
-bool LoopIdiomRecognize::runOnLoopBlock(
-    BasicBlock *BB, const SCEV *BECount,
-    SmallVectorImpl<BasicBlock *> &ExitBlocks) {
-  // We can only promote stores in this block if they are unconditionally
-  // executed in the loop.  For a block to be unconditionally executed, it has
-  // to dominate all the exit blocks of the loop.  Verify this now.
-  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
-    if (!DT->dominates(BB, ExitBlocks[i]))
-      return false;
-
-  bool MadeChange = false;
-  // Look for store instructions, which may be optimized to memset/memcpy.
-  collectStores(BB);
-
-  // Look for a single store or sets of stores with a common base, which can be
-  // optimized into a memset (memset_pattern).  The latter most commonly happens
-  // with structs and handunrolled loops.
-  for (auto &SL : StoreRefsForMemset)
-    MadeChange |= processLoopStores(SL.second, BECount, ForMemset::Yes);
-
-  for (auto &SL : StoreRefsForMemsetPattern)
-    MadeChange |= processLoopStores(SL.second, BECount, ForMemset::No);
-
-  // Optimize the store into a memcpy, if it feeds an similarly strided load.
-  for (auto &SI : StoreRefsForMemcpy)
-    MadeChange |= processLoopStoreOfLoopLoad(SI, BECount);
-
-  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
-    Instruction *Inst = &*I++;
-    // Look for memset instructions, which may be optimized to a larger memset.
-    if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst)) {
-      WeakTrackingVH InstPtr(&*I);
-      if (!processLoopMemSet(MSI, BECount))
-        continue;
-      MadeChange = true;
-
-      // If processing the memset invalidated our iterator, start over from the
-      // top of the block.
-      if (!InstPtr)
-        I = BB->begin();
-      continue;
-    }
-  }
-
-  return MadeChange;
-}
-
-/// See if this store(s) can be promoted to a memset.
-bool LoopIdiomRecognize::processLoopStores(SmallVectorImpl<StoreInst *> &SL,
-                                           const SCEV *BECount, ForMemset For) {
-  // Try to find consecutive stores that can be transformed into memsets.
-  SetVector<StoreInst *> Heads, Tails;
-  SmallDenseMap<StoreInst *, StoreInst *> ConsecutiveChain;
-
-  // Do a quadratic search on all of the given stores and find
-  // all of the pairs of stores that follow each other.
-  SmallVector<unsigned, 16> IndexQueue;
-  for (unsigned i = 0, e = SL.size(); i < e; ++i) {
-    assert(SL[i]->isSimple() && "Expected only non-volatile stores.");
-
-    Value *FirstStoredVal = SL[i]->getValueOperand();
-    Value *FirstStorePtr = SL[i]->getPointerOperand();
-    const SCEVAddRecExpr *FirstStoreEv =
-        cast<SCEVAddRecExpr>(SE->getSCEV(FirstStorePtr));
-    APInt FirstStride = getStoreStride(FirstStoreEv);
-    unsigned FirstStoreSize = DL->getTypeStoreSize(SL[i]->getValueOperand()->getType());
-
-    // See if we can optimize just this store in isolation.
-    if (FirstStride == FirstStoreSize || -FirstStride == FirstStoreSize) {
-      Heads.insert(SL[i]);
-      continue;
-    }
-
-    Value *FirstSplatValue = nullptr;
-    Constant *FirstPatternValue = nullptr;
-
-    if (For == ForMemset::Yes)
-      FirstSplatValue = isBytewiseValue(FirstStoredVal);
-    else
-      FirstPatternValue = getMemSetPatternValue(FirstStoredVal, DL);
-
-    assert((FirstSplatValue || FirstPatternValue) &&
-           "Expected either splat value or pattern value.");
-
-    IndexQueue.clear();
-    // If a store has multiple consecutive store candidates, search Stores
-    // array according to the sequence: from i+1 to e, then from i-1 to 0.
-    // This is because usually pairing with immediate succeeding or preceding
-    // candidate create the best chance to find memset opportunity.
-    unsigned j = 0;
-    for (j = i + 1; j < e; ++j)
-      IndexQueue.push_back(j);
-    for (j = i; j > 0; --j)
-      IndexQueue.push_back(j - 1);
-
-    for (auto &k : IndexQueue) {
-      assert(SL[k]->isSimple() && "Expected only non-volatile stores.");
-      Value *SecondStorePtr = SL[k]->getPointerOperand();
-      const SCEVAddRecExpr *SecondStoreEv =
-          cast<SCEVAddRecExpr>(SE->getSCEV(SecondStorePtr));
-      APInt SecondStride = getStoreStride(SecondStoreEv);
-
-      if (FirstStride != SecondStride)
-        continue;
-
-      Value *SecondStoredVal = SL[k]->getValueOperand();
-      Value *SecondSplatValue = nullptr;
-      Constant *SecondPatternValue = nullptr;
-
-      if (For == ForMemset::Yes)
-        SecondSplatValue = isBytewiseValue(SecondStoredVal);
-      else
-        SecondPatternValue = getMemSetPatternValue(SecondStoredVal, DL);
-
-      assert((SecondSplatValue || SecondPatternValue) &&
-             "Expected either splat value or pattern value.");
-
-      if (isConsecutiveAccess(SL[i], SL[k], *DL, *SE, false)) {
-        if (For == ForMemset::Yes) {
-          if (isa<UndefValue>(FirstSplatValue))
-            FirstSplatValue = SecondSplatValue;
-          if (FirstSplatValue != SecondSplatValue)
-            continue;
-        } else {
-          if (isa<UndefValue>(FirstPatternValue))
-            FirstPatternValue = SecondPatternValue;
-          if (FirstPatternValue != SecondPatternValue)
-            continue;
-        }
-        Tails.insert(SL[k]);
-        Heads.insert(SL[i]);
-        ConsecutiveChain[SL[i]] = SL[k];
-        break;
-      }
-    }
-  }
-
-  // We may run into multiple chains that merge into a single chain. We mark the
-  // stores that we transformed so that we don't visit the same store twice.
-  SmallPtrSet<Value *, 16> TransformedStores;
-  bool Changed = false;
-
-  // For stores that start but don't end a link in the chain:
-  for (SetVector<StoreInst *>::iterator it = Heads.begin(), e = Heads.end();
-       it != e; ++it) {
-    if (Tails.count(*it))
-      continue;
-
-    // We found a store instr that starts a chain. Now follow the chain and try
-    // to transform it.
-    SmallPtrSet<Instruction *, 8> AdjacentStores;
-    StoreInst *I = *it;
-
-    StoreInst *HeadStore = I;
-    unsigned StoreSize = 0;
-
-    // Collect the chain into a list.
-    while (Tails.count(I) || Heads.count(I)) {
-      if (TransformedStores.count(I))
-        break;
-      AdjacentStores.insert(I);
-
-      StoreSize += DL->getTypeStoreSize(I->getValueOperand()->getType());
-      // Move to the next value in the chain.
-      I = ConsecutiveChain[I];
-    }
-
-    Value *StoredVal = HeadStore->getValueOperand();
-    Value *StorePtr = HeadStore->getPointerOperand();
-    const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
-    APInt Stride = getStoreStride(StoreEv);
-
-    // Check to see if the stride matches the size of the stores.  If so, then
-    // we know that every byte is touched in the loop.
-    if (StoreSize != Stride && StoreSize != -Stride)
-      continue;
-
-    bool NegStride = StoreSize == -Stride;
-
-    if (processLoopStridedStore(StorePtr, StoreSize, HeadStore->getAlignment(),
-                                StoredVal, HeadStore, AdjacentStores, StoreEv,
-                                BECount, NegStride)) {
-      TransformedStores.insert(AdjacentStores.begin(), AdjacentStores.end());
-      Changed = true;
-    }
-  }
-
-  return Changed;
-}
-
-/// processLoopMemSet - See if this memset can be promoted to a large memset.
-bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
-                                           const SCEV *BECount) {
-  // We can only handle non-volatile memsets with a constant size.
-  if (MSI->isVolatile() || !isa<ConstantInt>(MSI->getLength()))
-    return false;
-
-  // If we're not allowed to hack on memset, we fail.
-  if (!HasMemset)
-    return false;
-
-  Value *Pointer = MSI->getDest();
-
-  // See if the pointer expression is an AddRec like {base,+,1} on the current
-  // loop, which indicates a strided store.  If we have something else, it's a
-  // random store we can't handle.
-  const SCEVAddRecExpr *Ev = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Pointer));
-  if (!Ev || Ev->getLoop() != CurLoop || !Ev->isAffine())
-    return false;
-
-  // Reject memsets that are so large that they overflow an unsigned.
-  uint64_t SizeInBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
-  if ((SizeInBytes >> 32) != 0)
-    return false;
-
-  // Check to see if the stride matches the size of the memset.  If so, then we
-  // know that every byte is touched in the loop.
-  const SCEVConstant *ConstStride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
-  if (!ConstStride)
-    return false;
-
-  APInt Stride = ConstStride->getAPInt();
-  if (SizeInBytes != Stride && SizeInBytes != -Stride)
-    return false;
-
-  // Verify that the memset value is loop invariant.  If not, we can't promote
-  // the memset.
-  Value *SplatValue = MSI->getValue();
-  if (!SplatValue || !CurLoop->isLoopInvariant(SplatValue))
-    return false;
-
-  SmallPtrSet<Instruction *, 1> MSIs;
-  MSIs.insert(MSI);
-  bool NegStride = SizeInBytes == -Stride;
-  return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
-                                 MSI->getDestAlignment(), SplatValue, MSI, MSIs,
-                                 Ev, BECount, NegStride, /*IsLoopMemset=*/true);
-}
-
-/// mayLoopAccessLocation - Return true if the specified loop might access the
-/// specified pointer location, which is a loop-strided access.  The 'Access'
-/// argument specifies what the verboten forms of access are (read or write).
-static bool
-mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L,
-                      const SCEV *BECount, unsigned StoreSize,
-                      AliasAnalysis &AA,
-                      SmallPtrSetImpl<Instruction *> &IgnoredStores) {
-  // Get the location that may be stored across the loop.  Since the access is
-  // strided positively through memory, we say that the modified location starts
-  // at the pointer and has infinite size.
-  LocationSize AccessSize = LocationSize::unknown();
-
-  // If the loop iterates a fixed number of times, we can refine the access size
-  // to be exactly the size of the memset, which is (BECount+1)*StoreSize
-  if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
-    AccessSize = LocationSize::precise((BECst->getValue()->getZExtValue() + 1) *
-                                       StoreSize);
-
-  // TODO: For this to be really effective, we have to dive into the pointer
-  // operand in the store.  Store to &A[i] of 100 will always return may alias
-  // with store of &A[100], we need to StoreLoc to be "A" with size of 100,
-  // which will then no-alias a store to &A[100].
-  MemoryLocation StoreLoc(Ptr, AccessSize);
-
-  for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
-       ++BI)
-    for (Instruction &I : **BI)
-      if (IgnoredStores.count(&I) == 0 &&
-          isModOrRefSet(
-              intersectModRef(AA.getModRefInfo(&I, StoreLoc), Access)))
-        return true;
-
-  return false;
-}
-
-// If we have a negative stride, Start refers to the end of the memory location
-// we're trying to memset.  Therefore, we need to recompute the base pointer,
-// which is just Start - BECount*Size.
-static const SCEV *getStartForNegStride(const SCEV *Start, const SCEV *BECount,
-                                        Type *IntPtr, unsigned StoreSize,
-                                        ScalarEvolution *SE) {
-  const SCEV *Index = SE->getTruncateOrZeroExtend(BECount, IntPtr);
-  if (StoreSize != 1)
-    Index = SE->getMulExpr(Index, SE->getConstant(IntPtr, StoreSize),
-                           SCEV::FlagNUW);
-  return SE->getMinusSCEV(Start, Index);
-}
-
-/// Compute the number of bytes as a SCEV from the backedge taken count.
-///
-/// This also maps the SCEV into the provided type and tries to handle the
-/// computation in a way that will fold cleanly.
-static const SCEV *getNumBytes(const SCEV *BECount, Type *IntPtr,
-                               unsigned StoreSize, Loop *CurLoop,
-                               const DataLayout *DL, ScalarEvolution *SE) {
-  const SCEV *NumBytesS;
-  // The # stored bytes is (BECount+1)*Size.  Expand the trip count out to
-  // pointer size if it isn't already.
-  //
-  // If we're going to need to zero extend the BE count, check if we can add
-  // one to it prior to zero extending without overflow. Provided this is safe,
-  // it allows better simplification of the +1.
-  if (DL->getTypeSizeInBits(BECount->getType()) <
-          DL->getTypeSizeInBits(IntPtr) &&
-      SE->isLoopEntryGuardedByCond(
-          CurLoop, ICmpInst::ICMP_NE, BECount,
-          SE->getNegativeSCEV(SE->getOne(BECount->getType())))) {
-    NumBytesS = SE->getZeroExtendExpr(
-        SE->getAddExpr(BECount, SE->getOne(BECount->getType()), SCEV::FlagNUW),
-        IntPtr);
-  } else {
-    NumBytesS = SE->getAddExpr(SE->getTruncateOrZeroExtend(BECount, IntPtr),
-                               SE->getOne(IntPtr), SCEV::FlagNUW);
-  }
-
-  // And scale it based on the store size.
-  if (StoreSize != 1) {
-    NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
-                               SCEV::FlagNUW);
-  }
-  return NumBytesS;
-}
-
-/// processLoopStridedStore - We see a strided store of some value.  If we can
-/// transform this into a memset or memset_pattern in the loop preheader, do so.
-bool LoopIdiomRecognize::processLoopStridedStore(
-    Value *DestPtr, unsigned StoreSize, unsigned StoreAlignment,
-    Value *StoredVal, Instruction *TheStore,
-    SmallPtrSetImpl<Instruction *> &Stores, const SCEVAddRecExpr *Ev,
-    const SCEV *BECount, bool NegStride, bool IsLoopMemset) {
-  Value *SplatValue = isBytewiseValue(StoredVal);
-  Constant *PatternValue = nullptr;
-
-  if (!SplatValue)
-    PatternValue = getMemSetPatternValue(StoredVal, DL);
-
-  assert((SplatValue || PatternValue) &&
-         "Expected either splat value or pattern value.");
-
-  // The trip count of the loop and the base pointer of the addrec SCEV is
-  // guaranteed to be loop invariant, which means that it should dominate the
-  // header.  This allows us to insert code for it in the preheader.
-  unsigned DestAS = DestPtr->getType()->getPointerAddressSpace();
-  BasicBlock *Preheader = CurLoop->getLoopPreheader();
-  IRBuilder<> Builder(Preheader->getTerminator());
-  SCEVExpander Expander(*SE, *DL, "loop-idiom");
-
-  Type *DestInt8PtrTy = Builder.getInt8PtrTy(DestAS);
-  Type *IntPtr = Builder.getIntPtrTy(*DL, DestAS);
-
-  const SCEV *Start = Ev->getStart();
-  // Handle negative strided loops.
-  if (NegStride)
-    Start = getStartForNegStride(Start, BECount, IntPtr, StoreSize, SE);
-
-  // TODO: ideally we should still be able to generate memset if SCEV expander
-  // is taught to generate the dependencies at the latest point.
-  if (!isSafeToExpand(Start, *SE))
-    return false;
-
-  // Okay, we have a strided store "p[i]" of a splattable value.  We can turn
-  // this into a memset in the loop preheader now if we want.  However, this
-  // would be unsafe to do if there is anything else in the loop that may read
-  // or write to the aliased location.  Check for any overlap by generating the
-  // base pointer and checking the region.
-  Value *BasePtr =
-      Expander.expandCodeFor(Start, DestInt8PtrTy, Preheader->getTerminator());
-  if (mayLoopAccessLocation(BasePtr, ModRefInfo::ModRef, CurLoop, BECount,
-                            StoreSize, *AA, Stores)) {
-    Expander.clear();
-    // If we generated new code for the base pointer, clean up.
-    RecursivelyDeleteTriviallyDeadInstructions(BasePtr, TLI);
-    return false;
-  }
-
-  if (avoidLIRForMultiBlockLoop(/*IsMemset=*/true, IsLoopMemset))
-    return false;
-
-  // Okay, everything looks good, insert the memset.
-
-  const SCEV *NumBytesS =
-      getNumBytes(BECount, IntPtr, StoreSize, CurLoop, DL, SE);
-
-  // TODO: ideally we should still be able to generate memset if SCEV expander
-  // is taught to generate the dependencies at the latest point.
-  if (!isSafeToExpand(NumBytesS, *SE))
-    return false;
-
-  Value *NumBytes =
-      Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
-
-  CallInst *NewCall;
-  if (SplatValue) {
-    NewCall =
-        Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, StoreAlignment);
-  } else {
-    // Everything is emitted in default address space
-    Type *Int8PtrTy = DestInt8PtrTy;
-
-    Module *M = TheStore->getModule();
-    StringRef FuncName = "memset_pattern16";
-    Value *MSP =
-        M->getOrInsertFunction(FuncName, Builder.getVoidTy(),
-                               Int8PtrTy, Int8PtrTy, IntPtr);
-    inferLibFuncAttributes(M, FuncName, *TLI);
-
-    // Otherwise we should form a memset_pattern16.  PatternValue is known to be
-    // an constant array of 16-bytes.  Plop the value into a mergable global.
-    GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true,
-                                            GlobalValue::PrivateLinkage,
-                                            PatternValue, ".memset_pattern");
-    GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global); // Ok to merge these.
-    GV->setAlignment(16);
-    Value *PatternPtr = ConstantExpr::getBitCast(GV, Int8PtrTy);
-    NewCall = Builder.CreateCall(MSP, {BasePtr, PatternPtr, NumBytes});
-  }
-
-  LLVM_DEBUG(dbgs() << "  Formed memset: " << *NewCall << "\n"
-                    << "    from store to: " << *Ev << " at: " << *TheStore
-                    << "\n");
-  NewCall->setDebugLoc(TheStore->getDebugLoc());
-
-  // Okay, the memset has been formed.  Zap the original store and anything that
-  // feeds into it.
-  for (auto *I : Stores)
-    deleteDeadInstruction(I);
-  ++NumMemSet;
-  return true;
-}
-
-/// If the stored value is a strided load in the same loop with the same stride
-/// this may be transformable into a memcpy.  This kicks in for stuff like
-/// for (i) A[i] = B[i];
-bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(StoreInst *SI,
-                                                    const SCEV *BECount) {
-  assert(SI->isUnordered() && "Expected only non-volatile non-ordered stores.");
-
-  Value *StorePtr = SI->getPointerOperand();
-  const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
-  APInt Stride = getStoreStride(StoreEv);
-  unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
-  bool NegStride = StoreSize == -Stride;
-
-  // The store must be feeding a non-volatile load.
-  LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
-  assert(LI->isUnordered() && "Expected only non-volatile non-ordered loads.");
-
-  // See if the pointer expression is an AddRec like {base,+,1} on the current
-  // loop, which indicates a strided load.  If we have something else, it's a
-  // random load we can't handle.
-  const SCEVAddRecExpr *LoadEv =
-      cast<SCEVAddRecExpr>(SE->getSCEV(LI->getPointerOperand()));
-
-  // The trip count of the loop and the base pointer of the addrec SCEV is
-  // guaranteed to be loop invariant, which means that it should dominate the
-  // header.  This allows us to insert code for it in the preheader.
-  BasicBlock *Preheader = CurLoop->getLoopPreheader();
-  IRBuilder<> Builder(Preheader->getTerminator());
-  SCEVExpander Expander(*SE, *DL, "loop-idiom");
-
-  const SCEV *StrStart = StoreEv->getStart();
-  unsigned StrAS = SI->getPointerAddressSpace();
-  Type *IntPtrTy = Builder.getIntPtrTy(*DL, StrAS);
-
-  // Handle negative strided loops.
-  if (NegStride)
-    StrStart = getStartForNegStride(StrStart, BECount, IntPtrTy, StoreSize, SE);
-
-  // Okay, we have a strided store "p[i]" of a loaded value.  We can turn
-  // this into a memcpy in the loop preheader now if we want.  However, this
-  // would be unsafe to do if there is anything else in the loop that may read
-  // or write the memory region we're storing to.  This includes the load that
-  // feeds the stores.  Check for an alias by generating the base address and
-  // checking everything.
-  Value *StoreBasePtr = Expander.expandCodeFor(
-      StrStart, Builder.getInt8PtrTy(StrAS), Preheader->getTerminator());
-
-  SmallPtrSet<Instruction *, 1> Stores;
-  Stores.insert(SI);
-  if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
-                            StoreSize, *AA, Stores)) {
-    Expander.clear();
-    // If we generated new code for the base pointer, clean up.
-    RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
-    return false;
-  }
-
-  const SCEV *LdStart = LoadEv->getStart();
-  unsigned LdAS = LI->getPointerAddressSpace();
-
-  // Handle negative strided loops.
-  if (NegStride)
-    LdStart = getStartForNegStride(LdStart, BECount, IntPtrTy, StoreSize, SE);
-
-  // For a memcpy, we have to make sure that the input array is not being
-  // mutated by the loop.
-  Value *LoadBasePtr = Expander.expandCodeFor(
-      LdStart, Builder.getInt8PtrTy(LdAS), Preheader->getTerminator());
-
-  if (mayLoopAccessLocation(LoadBasePtr, ModRefInfo::Mod, CurLoop, BECount,
-                            StoreSize, *AA, Stores)) {
-    Expander.clear();
-    // If we generated new code for the base pointer, clean up.
-    RecursivelyDeleteTriviallyDeadInstructions(LoadBasePtr, TLI);
-    RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
-    return false;
-  }
-
-  if (avoidLIRForMultiBlockLoop())
-    return false;
-
-  // Okay, everything is safe, we can transform this!
-
-  const SCEV *NumBytesS =
-      getNumBytes(BECount, IntPtrTy, StoreSize, CurLoop, DL, SE);
-
-  Value *NumBytes =
-      Expander.expandCodeFor(NumBytesS, IntPtrTy, Preheader->getTerminator());
-
-  CallInst *NewCall = nullptr;
-  // Check whether to generate an unordered atomic memcpy:
-  //  If the load or store are atomic, then they must necessarily be unordered
-  //  by previous checks.
-  if (!SI->isAtomic() && !LI->isAtomic())
-    NewCall = Builder.CreateMemCpy(StoreBasePtr, SI->getAlignment(),
-                                   LoadBasePtr, LI->getAlignment(), NumBytes);
-  else {
-    // We cannot allow unaligned ops for unordered load/store, so reject
-    // anything where the alignment isn't at least the element size.
-    unsigned Align = std::min(SI->getAlignment(), LI->getAlignment());
-    if (Align < StoreSize)
-      return false;
-
-    // If the element.atomic memcpy is not lowered into explicit
-    // loads/stores later, then it will be lowered into an element-size
-    // specific lib call. If the lib call doesn't exist for our store size, then
-    // we shouldn't generate the memcpy.
-    if (StoreSize > TTI->getAtomicMemIntrinsicMaxElementSize())
-      return false;
-
-    // Create the call.
-    // Note that unordered atomic loads/stores are *required* by the spec to
-    // have an alignment but non-atomic loads/stores may not.
-    NewCall = Builder.CreateElementUnorderedAtomicMemCpy(
-        StoreBasePtr, SI->getAlignment(), LoadBasePtr, LI->getAlignment(),
-        NumBytes, StoreSize);
-  }
-  NewCall->setDebugLoc(SI->getDebugLoc());
-
-  LLVM_DEBUG(dbgs() << "  Formed memcpy: " << *NewCall << "\n"
-                    << "    from load ptr=" << *LoadEv << " at: " << *LI << "\n"
-                    << "    from store ptr=" << *StoreEv << " at: " << *SI
-                    << "\n");
-
-  // Okay, the memcpy has been formed.  Zap the original store and anything that
-  // feeds into it.
-  deleteDeadInstruction(SI);
-  ++NumMemCpy;
-  return true;
-}
-
-// When compiling for codesize we avoid idiom recognition for a multi-block loop
-// unless it is a loop_memset idiom or a memset/memcpy idiom in a nested loop.
-//
-bool LoopIdiomRecognize::avoidLIRForMultiBlockLoop(bool IsMemset,
-                                                   bool IsLoopMemset) {
-  if (ApplyCodeSizeHeuristics && CurLoop->getNumBlocks() > 1) {
-    if (!CurLoop->getParentLoop() && (!IsMemset || !IsLoopMemset)) {
-      LLVM_DEBUG(dbgs() << "  " << CurLoop->getHeader()->getParent()->getName()
-                        << " : LIR " << (IsMemset ? "Memset" : "Memcpy")
-                        << " avoided: multi-block top-level loop\n");
-      return true;
-    }
-  }
-
-  return false;
-}
-
-bool LoopIdiomRecognize::runOnNoncountableLoop() {
-  return recognizePopcount() || recognizeAndInsertFFS();
-}
-
-/// Check if the given conditional branch is based on the comparison between
-/// a variable and zero, and if the variable is non-zero or zero (JmpOnZero is
-/// true), the control yields to the loop entry. If the branch matches the
-/// behavior, the variable involved in the comparison is returned. This function
-/// will be called to see if the precondition and postcondition of the loop are
-/// in desirable form.
-static Value *matchCondition(BranchInst *BI, BasicBlock *LoopEntry,
-                             bool JmpOnZero = false) {
-  if (!BI || !BI->isConditional())
-    return nullptr;
-
-  ICmpInst *Cond = dyn_cast<ICmpInst>(BI->getCondition());
-  if (!Cond)
-    return nullptr;
-
-  ConstantInt *CmpZero = dyn_cast<ConstantInt>(Cond->getOperand(1));
-  if (!CmpZero || !CmpZero->isZero())
-    return nullptr;
-
-  BasicBlock *TrueSucc = BI->getSuccessor(0);
-  BasicBlock *FalseSucc = BI->getSuccessor(1);
-  if (JmpOnZero)
-    std::swap(TrueSucc, FalseSucc);
-
-  ICmpInst::Predicate Pred = Cond->getPredicate();
-  if ((Pred == ICmpInst::ICMP_NE && TrueSucc == LoopEntry) ||
-      (Pred == ICmpInst::ICMP_EQ && FalseSucc == LoopEntry))
-    return Cond->getOperand(0);
-
-  return nullptr;
-}
-
-// Check if the recurrence variable `VarX` is in the right form to create
-// the idiom. Returns the value coerced to a PHINode if so.
-static PHINode *getRecurrenceVar(Value *VarX, Instruction *DefX,
-                                 BasicBlock *LoopEntry) {
-  auto *PhiX = dyn_cast<PHINode>(VarX);
-  if (PhiX && PhiX->getParent() == LoopEntry &&
-      (PhiX->getOperand(0) == DefX || PhiX->getOperand(1) == DefX))
-    return PhiX;
-  return nullptr;
-}
-
-/// Return true iff the idiom is detected in the loop.
-///
-/// Additionally:
-/// 1) \p CntInst is set to the instruction counting the population bit.
-/// 2) \p CntPhi is set to the corresponding phi node.
-/// 3) \p Var is set to the value whose population bits are being counted.
-///
-/// The core idiom we are trying to detect is:
-/// \code
-///    if (x0 != 0)
-///      goto loop-exit // the precondition of the loop
-///    cnt0 = init-val;
-///    do {
-///       x1 = phi (x0, x2);
-///       cnt1 = phi(cnt0, cnt2);
-///
-///       cnt2 = cnt1 + 1;
-///        ...
-///       x2 = x1 & (x1 - 1);
-///        ...
-///    } while(x != 0);
-///
-/// loop-exit:
-/// \endcode
-static bool detectPopcountIdiom(Loop *CurLoop, BasicBlock *PreCondBB,
-                                Instruction *&CntInst, PHINode *&CntPhi,
-                                Value *&Var) {
-  // step 1: Check to see if the look-back branch match this pattern:
-  //    "if (a!=0) goto loop-entry".
-  BasicBlock *LoopEntry;
-  Instruction *DefX2, *CountInst;
-  Value *VarX1, *VarX0;
-  PHINode *PhiX, *CountPhi;
-
-  DefX2 = CountInst = nullptr;
-  VarX1 = VarX0 = nullptr;
-  PhiX = CountPhi = nullptr;
-  LoopEntry = *(CurLoop->block_begin());
-
-  // step 1: Check if the loop-back branch is in desirable form.
-  {
-    if (Value *T = matchCondition(
-            dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
-      DefX2 = dyn_cast<Instruction>(T);
-    else
-      return false;
-  }
-
-  // step 2: detect instructions corresponding to "x2 = x1 & (x1 - 1)"
-  {
-    if (!DefX2 || DefX2->getOpcode() != Instruction::And)
-      return false;
-
-    BinaryOperator *SubOneOp;
-
-    if ((SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(0))))
-      VarX1 = DefX2->getOperand(1);
-    else {
-      VarX1 = DefX2->getOperand(0);
-      SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(1));
-    }
-    if (!SubOneOp || SubOneOp->getOperand(0) != VarX1)
-      return false;
-
-    ConstantInt *Dec = dyn_cast<ConstantInt>(SubOneOp->getOperand(1));
-    if (!Dec ||
-        !((SubOneOp->getOpcode() == Instruction::Sub && Dec->isOne()) ||
-          (SubOneOp->getOpcode() == Instruction::Add &&
-           Dec->isMinusOne()))) {
-      return false;
-    }
-  }
-
-  // step 3: Check the recurrence of variable X
-  PhiX = getRecurrenceVar(VarX1, DefX2, LoopEntry);
-  if (!PhiX)
-    return false;
-
-  // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1
-  {
-    CountInst = nullptr;
-    for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI()->getIterator(),
-                              IterE = LoopEntry->end();
-         Iter != IterE; Iter++) {
-      Instruction *Inst = &*Iter;
-      if (Inst->getOpcode() != Instruction::Add)
-        continue;
-
-      ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
-      if (!Inc || !Inc->isOne())
-        continue;
-
-      PHINode *Phi = getRecurrenceVar(Inst->getOperand(0), Inst, LoopEntry);
-      if (!Phi)
-        continue;
-
-      // Check if the result of the instruction is live of the loop.
-      bool LiveOutLoop = false;
-      for (User *U : Inst->users()) {
-        if ((cast<Instruction>(U))->getParent() != LoopEntry) {
-          LiveOutLoop = true;
-          break;
-        }
-      }
-
-      if (LiveOutLoop) {
-        CountInst = Inst;
-        CountPhi = Phi;
-        break;
-      }
-    }
-
-    if (!CountInst)
-      return false;
-  }
-
-  // step 5: check if the precondition is in this form:
-  //   "if (x != 0) goto loop-head ; else goto somewhere-we-don't-care;"
-  {
-    auto *PreCondBr = dyn_cast<BranchInst>(PreCondBB->getTerminator());
-    Value *T = matchCondition(PreCondBr, CurLoop->getLoopPreheader());
-    if (T != PhiX->getOperand(0) && T != PhiX->getOperand(1))
-      return false;
-
-    CntInst = CountInst;
-    CntPhi = CountPhi;
-    Var = T;
-  }
-
-  return true;
-}
-
-/// Return true if the idiom is detected in the loop.
-///
-/// Additionally:
-/// 1) \p CntInst is set to the instruction Counting Leading Zeros (CTLZ)
-///       or nullptr if there is no such.
-/// 2) \p CntPhi is set to the corresponding phi node
-///       or nullptr if there is no such.
-/// 3) \p Var is set to the value whose CTLZ could be used.
-/// 4) \p DefX is set to the instruction calculating Loop exit condition.
-///
-/// The core idiom we are trying to detect is:
-/// \code
-///    if (x0 == 0)
-///      goto loop-exit // the precondition of the loop
-///    cnt0 = init-val;
-///    do {
-///       x = phi (x0, x.next);   //PhiX
-///       cnt = phi(cnt0, cnt.next);
-///
-///       cnt.next = cnt + 1;
-///        ...
-///       x.next = x >> 1;   // DefX
-///        ...
-///    } while(x.next != 0);
-///
-/// loop-exit:
-/// \endcode
-static bool detectShiftUntilZeroIdiom(Loop *CurLoop, const DataLayout &DL,
-                                      Intrinsic::ID &IntrinID, Value *&InitX,
-                                      Instruction *&CntInst, PHINode *&CntPhi,
-                                      Instruction *&DefX) {
-  BasicBlock *LoopEntry;
-  Value *VarX = nullptr;
-
-  DefX = nullptr;
-  CntInst = nullptr;
-  CntPhi = nullptr;
-  LoopEntry = *(CurLoop->block_begin());
-
-  // step 1: Check if the loop-back branch is in desirable form.
-  if (Value *T = matchCondition(
-          dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
-    DefX = dyn_cast<Instruction>(T);
-  else
-    return false;
-
-  // step 2: detect instructions corresponding to "x.next = x >> 1 or x << 1"
-  if (!DefX || !DefX->isShift())
-    return false;
-  IntrinID = DefX->getOpcode() == Instruction::Shl ? Intrinsic::cttz :
-                                                     Intrinsic::ctlz;
-  ConstantInt *Shft = dyn_cast<ConstantInt>(DefX->getOperand(1));
-  if (!Shft || !Shft->isOne())
-    return false;
-  VarX = DefX->getOperand(0);
-
-  // step 3: Check the recurrence of variable X
-  PHINode *PhiX = getRecurrenceVar(VarX, DefX, LoopEntry);
-  if (!PhiX)
-    return false;
-
-  InitX = PhiX->getIncomingValueForBlock(CurLoop->getLoopPreheader());
-
-  // Make sure the initial value can't be negative otherwise the ashr in the
-  // loop might never reach zero which would make the loop infinite.
-  if (DefX->getOpcode() == Instruction::AShr && !isKnownNonNegative(InitX, DL))
-    return false;
-
-  // step 4: Find the instruction which count the CTLZ: cnt.next = cnt + 1
-  // TODO: We can skip the step. If loop trip count is known (CTLZ),
-  //       then all uses of "cnt.next" could be optimized to the trip count
-  //       plus "cnt0". Currently it is not optimized.
-  //       This step could be used to detect POPCNT instruction:
-  //       cnt.next = cnt + (x.next & 1)
-  for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI()->getIterator(),
-                            IterE = LoopEntry->end();
-       Iter != IterE; Iter++) {
-    Instruction *Inst = &*Iter;
-    if (Inst->getOpcode() != Instruction::Add)
-      continue;
-
-    ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
-    if (!Inc || !Inc->isOne())
-      continue;
-
-    PHINode *Phi = getRecurrenceVar(Inst->getOperand(0), Inst, LoopEntry);
-    if (!Phi)
-      continue;
-
-    CntInst = Inst;
-    CntPhi = Phi;
-    break;
-  }
-  if (!CntInst)
-    return false;
-
-  return true;
-}
-
-/// Recognize CTLZ or CTTZ idiom in a non-countable loop and convert the loop
-/// to countable (with CTLZ / CTTZ trip count). If CTLZ / CTTZ inserted as a new
-/// trip count returns true; otherwise, returns false.
-bool LoopIdiomRecognize::recognizeAndInsertFFS() {
-  // Give up if the loop has multiple blocks or multiple backedges.
-  if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
-    return false;
-
-  Intrinsic::ID IntrinID;
-  Value *InitX;
-  Instruction *DefX = nullptr;
-  PHINode *CntPhi = nullptr;
-  Instruction *CntInst = nullptr;
-  // Help decide if transformation is profitable. For ShiftUntilZero idiom,
-  // this is always 6.
-  size_t IdiomCanonicalSize = 6;
-
-  if (!detectShiftUntilZeroIdiom(CurLoop, *DL, IntrinID, InitX,
-                                 CntInst, CntPhi, DefX))
-    return false;
-
-  bool IsCntPhiUsedOutsideLoop = false;
-  for (User *U : CntPhi->users())
-    if (!CurLoop->contains(cast<Instruction>(U))) {
-      IsCntPhiUsedOutsideLoop = true;
-      break;
-    }
-  bool IsCntInstUsedOutsideLoop = false;
-  for (User *U : CntInst->users())
-    if (!CurLoop->contains(cast<Instruction>(U))) {
-      IsCntInstUsedOutsideLoop = true;
-      break;
-    }
-  // If both CntInst and CntPhi are used outside the loop the profitability
-  // is questionable.
-  if (IsCntInstUsedOutsideLoop && IsCntPhiUsedOutsideLoop)
-    return false;
-
-  // For some CPUs result of CTLZ(X) intrinsic is undefined
-  // when X is 0. If we can not guarantee X != 0, we need to check this
-  // when expand.
-  bool ZeroCheck = false;
-  // It is safe to assume Preheader exist as it was checked in
-  // parent function RunOnLoop.
-  BasicBlock *PH = CurLoop->getLoopPreheader();
-
-  // If we are using the count instruction outside the loop, make sure we
-  // have a zero check as a precondition. Without the check the loop would run
-  // one iteration for before any check of the input value. This means 0 and 1
-  // would have identical behavior in the original loop and thus
-  if (!IsCntPhiUsedOutsideLoop) {
-    auto *PreCondBB = PH->getSinglePredecessor();
-    if (!PreCondBB)
-      return false;
-    auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
-    if (!PreCondBI)
-      return false;
-    if (matchCondition(PreCondBI, PH) != InitX)
-      return false;
-    ZeroCheck = true;
-  }
-
-  // Check if CTLZ / CTTZ intrinsic is profitable. Assume it is always
-  // profitable if we delete the loop.
-
-  // the loop has only 6 instructions:
-  //  %n.addr.0 = phi [ %n, %entry ], [ %shr, %while.cond ]
-  //  %i.0 = phi [ %i0, %entry ], [ %inc, %while.cond ]
-  //  %shr = ashr %n.addr.0, 1
-  //  %tobool = icmp eq %shr, 0
-  //  %inc = add nsw %i.0, 1
-  //  br i1 %tobool
-
-  const Value *Args[] =
-      {InitX, ZeroCheck ? ConstantInt::getTrue(InitX->getContext())
-                        : ConstantInt::getFalse(InitX->getContext())};
-  if (CurLoop->getHeader()->size() != IdiomCanonicalSize &&
-      TTI->getIntrinsicCost(IntrinID, InitX->getType(), Args) >
-        TargetTransformInfo::TCC_Basic)
-    return false;
-
-  transformLoopToCountable(IntrinID, PH, CntInst, CntPhi, InitX, DefX,
-                           DefX->getDebugLoc(), ZeroCheck,
-                           IsCntPhiUsedOutsideLoop);
-  return true;
-}
-
-/// Recognizes a population count idiom in a non-countable loop.
-///
-/// If detected, transforms the relevant code to issue the popcount intrinsic
-/// function call, and returns true; otherwise, returns false.
-bool LoopIdiomRecognize::recognizePopcount() {
-  if (TTI->getPopcntSupport(32) != TargetTransformInfo::PSK_FastHardware)
-    return false;
-
-  // Counting population are usually conducted by few arithmetic instructions.
-  // Such instructions can be easily "absorbed" by vacant slots in a
-  // non-compact loop. Therefore, recognizing popcount idiom only makes sense
-  // in a compact loop.
-
-  // Give up if the loop has multiple blocks or multiple backedges.
-  if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
-    return false;
-
-  BasicBlock *LoopBody = *(CurLoop->block_begin());
-  if (LoopBody->size() >= 20) {
-    // The loop is too big, bail out.
-    return false;
-  }
-
-  // It should have a preheader containing nothing but an unconditional branch.
-  BasicBlock *PH = CurLoop->getLoopPreheader();
-  if (!PH || &PH->front() != PH->getTerminator())
-    return false;
-  auto *EntryBI = dyn_cast<BranchInst>(PH->getTerminator());
-  if (!EntryBI || EntryBI->isConditional())
-    return false;
-
-  // It should have a precondition block where the generated popcount intrinsic
-  // function can be inserted.
-  auto *PreCondBB = PH->getSinglePredecessor();
-  if (!PreCondBB)
-    return false;
-  auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
-  if (!PreCondBI || PreCondBI->isUnconditional())
-    return false;
-
-  Instruction *CntInst;
-  PHINode *CntPhi;
-  Value *Val;
-  if (!detectPopcountIdiom(CurLoop, PreCondBB, CntInst, CntPhi, Val))
-    return false;
-
-  transformLoopToPopcount(PreCondBB, CntInst, CntPhi, Val);
-  return true;
-}
-
-static CallInst *createPopcntIntrinsic(IRBuilder<> &IRBuilder, Value *Val,
-                                       const DebugLoc &DL) {
-  Value *Ops[] = {Val};
-  Type *Tys[] = {Val->getType()};
-
-  Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
-  Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys);
-  CallInst *CI = IRBuilder.CreateCall(Func, Ops);
-  CI->setDebugLoc(DL);
-
-  return CI;
-}
-
-static CallInst *createFFSIntrinsic(IRBuilder<> &IRBuilder, Value *Val,
-                                    const DebugLoc &DL, bool ZeroCheck,
-                                    Intrinsic::ID IID) {
-  Value *Ops[] = {Val, ZeroCheck ? IRBuilder.getTrue() : IRBuilder.getFalse()};
-  Type *Tys[] = {Val->getType()};
-
-  Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
-  Value *Func = Intrinsic::getDeclaration(M, IID, Tys);
-  CallInst *CI = IRBuilder.CreateCall(Func, Ops);
-  CI->setDebugLoc(DL);
-
-  return CI;
-}
-
-/// Transform the following loop (Using CTLZ, CTTZ is similar):
-/// loop:
-///   CntPhi = PHI [Cnt0, CntInst]
-///   PhiX = PHI [InitX, DefX]
-///   CntInst = CntPhi + 1
-///   DefX = PhiX >> 1
-///   LOOP_BODY
-///   Br: loop if (DefX != 0)
-/// Use(CntPhi) or Use(CntInst)
-///
-/// Into:
-/// If CntPhi used outside the loop:
-///   CountPrev = BitWidth(InitX) - CTLZ(InitX >> 1)
-///   Count = CountPrev + 1
-/// else
-///   Count = BitWidth(InitX) - CTLZ(InitX)
-/// loop:
-///   CntPhi = PHI [Cnt0, CntInst]
-///   PhiX = PHI [InitX, DefX]
-///   PhiCount = PHI [Count, Dec]
-///   CntInst = CntPhi + 1
-///   DefX = PhiX >> 1
-///   Dec = PhiCount - 1
-///   LOOP_BODY
-///   Br: loop if (Dec != 0)
-/// Use(CountPrev + Cnt0) // Use(CntPhi)
-/// or
-/// Use(Count + Cnt0) // Use(CntInst)
-///
-/// If LOOP_BODY is empty the loop will be deleted.
-/// If CntInst and DefX are not used in LOOP_BODY they will be removed.
-void LoopIdiomRecognize::transformLoopToCountable(
-    Intrinsic::ID IntrinID, BasicBlock *Preheader, Instruction *CntInst,
-    PHINode *CntPhi, Value *InitX, Instruction *DefX, const DebugLoc &DL,
-    bool ZeroCheck, bool IsCntPhiUsedOutsideLoop) {
-  BranchInst *PreheaderBr = cast<BranchInst>(Preheader->getTerminator());
-
-  // Step 1: Insert the CTLZ/CTTZ instruction at the end of the preheader block
-  IRBuilder<> Builder(PreheaderBr);
-  Builder.SetCurrentDebugLocation(DL);
-  Value *FFS, *Count, *CountPrev, *NewCount, *InitXNext;
-
-  //   Count = BitWidth - CTLZ(InitX);
-  // If there are uses of CntPhi create:
-  //   CountPrev = BitWidth - CTLZ(InitX >> 1);
-  if (IsCntPhiUsedOutsideLoop) {
-    if (DefX->getOpcode() == Instruction::AShr)
-      InitXNext =
-          Builder.CreateAShr(InitX, ConstantInt::get(InitX->getType(), 1));
-    else if (DefX->getOpcode() == Instruction::LShr)
-      InitXNext =
-          Builder.CreateLShr(InitX, ConstantInt::get(InitX->getType(), 1));
-    else if (DefX->getOpcode() == Instruction::Shl) // cttz
-      InitXNext =
-          Builder.CreateShl(InitX, ConstantInt::get(InitX->getType(), 1));
-    else
-      llvm_unreachable("Unexpected opcode!");
-  } else
-    InitXNext = InitX;
-  FFS = createFFSIntrinsic(Builder, InitXNext, DL, ZeroCheck, IntrinID);
-  Count = Builder.CreateSub(
-      ConstantInt::get(FFS->getType(),
-                       FFS->getType()->getIntegerBitWidth()),
-      FFS);
-  if (IsCntPhiUsedOutsideLoop) {
-    CountPrev = Count;
-    Count = Builder.CreateAdd(
-        CountPrev,
-        ConstantInt::get(CountPrev->getType(), 1));
-  }
-
-  NewCount = Builder.CreateZExtOrTrunc(
-                      IsCntPhiUsedOutsideLoop ? CountPrev : Count,
-                      cast<IntegerType>(CntInst->getType()));
-
-  // If the counter's initial value is not zero, insert Add Inst.
-  Value *CntInitVal = CntPhi->getIncomingValueForBlock(Preheader);
-  ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
-  if (!InitConst || !InitConst->isZero())
-    NewCount = Builder.CreateAdd(NewCount, CntInitVal);
-
-  // Step 2: Insert new IV and loop condition:
-  // loop:
-  //   ...
-  //   PhiCount = PHI [Count, Dec]
-  //   ...
-  //   Dec = PhiCount - 1
-  //   ...
-  //   Br: loop if (Dec != 0)
-  BasicBlock *Body = *(CurLoop->block_begin());
-  auto *LbBr = cast<BranchInst>(Body->getTerminator());
-  ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
-  Type *Ty = Count->getType();
-
-  PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", &Body->front());
-
-  Builder.SetInsertPoint(LbCond);
-  Instruction *TcDec = cast<Instruction>(
-      Builder.CreateSub(TcPhi, ConstantInt::get(Ty, 1),
-                        "tcdec", false, true));
-
-  TcPhi->addIncoming(Count, Preheader);
-  TcPhi->addIncoming(TcDec, Body);
-
-  CmpInst::Predicate Pred =
-      (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_NE : CmpInst::ICMP_EQ;
-  LbCond->setPredicate(Pred);
-  LbCond->setOperand(0, TcDec);
-  LbCond->setOperand(1, ConstantInt::get(Ty, 0));
-
-  // Step 3: All the references to the original counter outside
-  //  the loop are replaced with the NewCount
-  if (IsCntPhiUsedOutsideLoop)
-    CntPhi->replaceUsesOutsideBlock(NewCount, Body);
-  else
-    CntInst->replaceUsesOutsideBlock(NewCount, Body);
-
-  // step 4: Forget the "non-computable" trip-count SCEV associated with the
-  //   loop. The loop would otherwise not be deleted even if it becomes empty.
-  SE->forgetLoop(CurLoop);
-}
-
-void LoopIdiomRecognize::transformLoopToPopcount(BasicBlock *PreCondBB,
-                                                 Instruction *CntInst,
-                                                 PHINode *CntPhi, Value *Var) {
-  BasicBlock *PreHead = CurLoop->getLoopPreheader();
-  auto *PreCondBr = cast<BranchInst>(PreCondBB->getTerminator());
-  const DebugLoc &DL = CntInst->getDebugLoc();
-
-  // Assuming before transformation, the loop is following:
-  //  if (x) // the precondition
-  //     do { cnt++; x &= x - 1; } while(x);
-
-  // Step 1: Insert the ctpop instruction at the end of the precondition block
-  IRBuilder<> Builder(PreCondBr);
-  Value *PopCnt, *PopCntZext, *NewCount, *TripCnt;
-  {
-    PopCnt = createPopcntIntrinsic(Builder, Var, DL);
-    NewCount = PopCntZext =
-        Builder.CreateZExtOrTrunc(PopCnt, cast<IntegerType>(CntPhi->getType()));
-
-    if (NewCount != PopCnt)
-      (cast<Instruction>(NewCount))->setDebugLoc(DL);
-
-    // TripCnt is exactly the number of iterations the loop has
-    TripCnt = NewCount;
-
-    // If the population counter's initial value is not zero, insert Add Inst.
-    Value *CntInitVal = CntPhi->getIncomingValueForBlock(PreHead);
-    ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
-    if (!InitConst || !InitConst->isZero()) {
-      NewCount = Builder.CreateAdd(NewCount, CntInitVal);
-      (cast<Instruction>(NewCount))->setDebugLoc(DL);
-    }
-  }
-
-  // Step 2: Replace the precondition from "if (x == 0) goto loop-exit" to
-  //   "if (NewCount == 0) loop-exit". Without this change, the intrinsic
-  //   function would be partial dead code, and downstream passes will drag
-  //   it back from the precondition block to the preheader.
-  {
-    ICmpInst *PreCond = cast<ICmpInst>(PreCondBr->getCondition());
-
-    Value *Opnd0 = PopCntZext;
-    Value *Opnd1 = ConstantInt::get(PopCntZext->getType(), 0);
-    if (PreCond->getOperand(0) != Var)
-      std::swap(Opnd0, Opnd1);
-
-    ICmpInst *NewPreCond = cast<ICmpInst>(
-        Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1));
-    PreCondBr->setCondition(NewPreCond);
-
-    RecursivelyDeleteTriviallyDeadInstructions(PreCond, TLI);
-  }
-
-  // Step 3: Note that the population count is exactly the trip count of the
-  // loop in question, which enable us to convert the loop from noncountable
-  // loop into a countable one. The benefit is twofold:
-  //
-  //  - If the loop only counts population, the entire loop becomes dead after
-  //    the transformation. It is a lot easier to prove a countable loop dead
-  //    than to prove a noncountable one. (In some C dialects, an infinite loop
-  //    isn't dead even if it computes nothing useful. In general, DCE needs
-  //    to prove a noncountable loop finite before safely delete it.)
-  //
-  //  - If the loop also performs something else, it remains alive.
-  //    Since it is transformed to countable form, it can be aggressively
-  //    optimized by some optimizations which are in general not applicable
-  //    to a noncountable loop.
-  //
-  // After this step, this loop (conceptually) would look like following:
-  //   newcnt = __builtin_ctpop(x);
-  //   t = newcnt;
-  //   if (x)
-  //     do { cnt++; x &= x-1; t--) } while (t > 0);
-  BasicBlock *Body = *(CurLoop->block_begin());
-  {
-    auto *LbBr = cast<BranchInst>(Body->getTerminator());
-    ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
-    Type *Ty = TripCnt->getType();
-
-    PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", &Body->front());
-
-    Builder.SetInsertPoint(LbCond);
-    Instruction *TcDec = cast<Instruction>(
-        Builder.CreateSub(TcPhi, ConstantInt::get(Ty, 1),
-                          "tcdec", false, true));
-
-    TcPhi->addIncoming(TripCnt, PreHead);
-    TcPhi->addIncoming(TcDec, Body);
-
-    CmpInst::Predicate Pred =
-        (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_UGT : CmpInst::ICMP_SLE;
-    LbCond->setPredicate(Pred);
-    LbCond->setOperand(0, TcDec);
-    LbCond->setOperand(1, ConstantInt::get(Ty, 0));
-  }
-
-  // Step 4: All the references to the original population counter outside
-  //  the loop are replaced with the NewCount -- the value returned from
-  //  __builtin_ctpop().
-  CntInst->replaceUsesOutsideBlock(NewCount, Body);
-
-  // step 5: Forget the "non-computable" trip-count SCEV associated with the
-  //   loop. The loop would otherwise not be deleted even if it becomes empty.
-  SE->forgetLoop(CurLoop);
-}