/build/source/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

Bug Summary

File:	build/source/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
Warning:	line 1824, column 47 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name LoopIdiomRecognize.cpp -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/source/build-llvm/tools/clang/stage2-bins -resource-dir /usr/lib/llvm-17/lib/clang/17 -D _DEBUG -D _GLIBCXX_ASSERTIONS -D _GNU_SOURCE -D _LIBCPP_ENABLE_ASSERTIONS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I lib/Transforms/Scalar -I /build/source/llvm/lib/Transforms/Scalar -I include -I /build/source/llvm/include -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-17/lib/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fmacro-prefix-map=/build/source/= -fcoverage-prefix-map=/build/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fcoverage-prefix-map=/build/source/= -source-date-epoch 1683717183 -O2 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -Wno-misleading-indentation -std=c++17 -fdeprecated-macro -fdebug-compilation-dir=/build/source/build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/source/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2023-05-10-133810-16478-1 -x c++ /build/source/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
1//===- LoopIdiomRecognize.cpp - Loop idiom recognition --------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass implements an idiom recognizer that transforms simple loops into a
10// non-loop form.  In cases that this kicks in, it can be a significant
11// performance win.
12//
13// If compiling for code size we avoid idiom recognition if the resulting
14// code could be larger than the code for the original loop. One way this could
15// happen is if the loop is not removable after idiom recognition due to the
16// presence of non-idiom instructions. The initial implementation of the
17// heuristics applies to idioms in multi-block loops.
18//
19//===----------------------------------------------------------------------===//
20//
21// TODO List:
22//
23// Future loop memory idioms to recognize:
24//   memcmp, strlen, etc.
25// Future floating point idioms to recognize in -ffast-math mode:
26//   fpowi
27// Future integer operation idioms to recognize:
28//   ctpop
29//
30// Beware that isel's default lowering for ctpop is highly inefficient for
31// i64 and larger types when i64 is legal and the value has few bits set.  It
32// would be good to enhance isel to emit a loop for ctpop in this case.
33//
34// This could recognize common matrix multiplies and dot product idioms and
35// replace them with calls to BLAS (if linked in??).
36//
37//===----------------------------------------------------------------------===//

39#include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
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"
49#include "llvm/Analysis/AliasAnalysis.h"
50#include "llvm/Analysis/CmpInstAnalysis.h"
51#include "llvm/Analysis/LoopAccessAnalysis.h"
52#include "llvm/Analysis/LoopInfo.h"
53#include "llvm/Analysis/LoopPass.h"
54#include "llvm/Analysis/MemoryLocation.h"
55#include "llvm/Analysis/MemorySSA.h"
56#include "llvm/Analysis/MemorySSAUpdater.h"
57#include "llvm/Analysis/MustExecute.h"
58#include "llvm/Analysis/OptimizationRemarkEmitter.h"
59#include "llvm/Analysis/ScalarEvolution.h"
60#include "llvm/Analysis/ScalarEvolutionExpressions.h"
61#include "llvm/Analysis/TargetLibraryInfo.h"
62#include "llvm/Analysis/TargetTransformInfo.h"
63#include "llvm/Analysis/ValueTracking.h"
64#include "llvm/IR/BasicBlock.h"
65#include "llvm/IR/Constant.h"
66#include "llvm/IR/Constants.h"
67#include "llvm/IR/DataLayout.h"
68#include "llvm/IR/DebugLoc.h"
69#include "llvm/IR/DerivedTypes.h"
70#include "llvm/IR/Dominators.h"
71#include "llvm/IR/GlobalValue.h"
72#include "llvm/IR/GlobalVariable.h"
73#include "llvm/IR/IRBuilder.h"
74#include "llvm/IR/InstrTypes.h"
75#include "llvm/IR/Instruction.h"
76#include "llvm/IR/Instructions.h"
77#include "llvm/IR/IntrinsicInst.h"
78#include "llvm/IR/Intrinsics.h"
79#include "llvm/IR/LLVMContext.h"
80#include "llvm/IR/Module.h"
81#include "llvm/IR/PassManager.h"
82#include "llvm/IR/PatternMatch.h"
83#include "llvm/IR/Type.h"
84#include "llvm/IR/User.h"
85#include "llvm/IR/Value.h"
86#include "llvm/IR/ValueHandle.h"
87#include "llvm/Support/Casting.h"
88#include "llvm/Support/CommandLine.h"
89#include "llvm/Support/Debug.h"
90#include "llvm/Support/InstructionCost.h"
91#include "llvm/Support/raw_ostream.h"
92#include "llvm/Transforms/Utils/BuildLibCalls.h"
93#include "llvm/Transforms/Utils/Local.h"
94#include "llvm/Transforms/Utils/LoopUtils.h"
95#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
96#include <algorithm>
97#include <cassert>
98#include <cstdint>
99#include <utility>
100#include <vector>

102using namespace llvm;

104#define DEBUG_TYPE"loop-idiom" "loop-idiom"

106STATISTIC(NumMemSet, "Number of memset's formed from loop stores")static llvm::Statistic NumMemSet = {"loop-idiom", "NumMemSet"
, "Number of memset's formed from loop stores"};
107STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores")static llvm::Statistic NumMemCpy = {"loop-idiom", "NumMemCpy"
, "Number of memcpy's formed from loop load+stores"};
108STATISTIC(NumMemMove, "Number of memmove's formed from loop load+stores")static llvm::Statistic NumMemMove = {"loop-idiom", "NumMemMove"
, "Number of memmove's formed from loop load+stores"};
109STATISTIC(static llvm::Statistic NumShiftUntilBitTest = {"loop-idiom", "NumShiftUntilBitTest"
, "Number of uncountable loops recognized as 'shift until bitttest' idiom"
}
  NumShiftUntilBitTest,static llvm::Statistic NumShiftUntilBitTest = {"loop-idiom", "NumShiftUntilBitTest"
, "Number of uncountable loops recognized as 'shift until bitttest' idiom"
}
  "Number of uncountable loops recognized as 'shift until bitttest' idiom")static llvm::Statistic NumShiftUntilBitTest = {"loop-idiom", "NumShiftUntilBitTest"
, "Number of uncountable loops recognized as 'shift until bitttest' idiom"
};
112STATISTIC(NumShiftUntilZero,static llvm::Statistic NumShiftUntilZero = {"loop-idiom", "NumShiftUntilZero"
, "Number of uncountable loops recognized as 'shift until zero' idiom"
}
        "Number of uncountable loops recognized as 'shift until zero' idiom")static llvm::Statistic NumShiftUntilZero = {"loop-idiom", "NumShiftUntilZero"
, "Number of uncountable loops recognized as 'shift until zero' idiom"
};

115bool DisableLIRP::All;
116static cl::opt<bool, true>
  DisableLIRPAll("disable-" DEBUG_TYPE"loop-idiom" "-all",
                 cl::desc("Options to disable Loop Idiom Recognize Pass."),
                 cl::location(DisableLIRP::All), cl::init(false),
                 cl::ReallyHidden);

122bool DisableLIRP::Memset;
123static cl::opt<bool, true>
  DisableLIRPMemset("disable-" DEBUG_TYPE"loop-idiom" "-memset",
                    cl::desc("Proceed with loop idiom recognize pass, but do "
                             "not convert loop(s) to memset."),
                    cl::location(DisableLIRP::Memset), cl::init(false),
                    cl::ReallyHidden);

130bool DisableLIRP::Memcpy;
131static cl::opt<bool, true>
  DisableLIRPMemcpy("disable-" DEBUG_TYPE"loop-idiom" "-memcpy",
                    cl::desc("Proceed with loop idiom recognize pass, but do "
                             "not convert loop(s) to memcpy."),
                    cl::location(DisableLIRP::Memcpy), cl::init(false),
                    cl::ReallyHidden);

138static 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);

144namespace {

146class LoopIdiomRecognize {
Loop *CurLoop = nullptr;
AliasAnalysis *AA;
DominatorTree *DT;
LoopInfo *LI;
ScalarEvolution *SE;
TargetLibraryInfo *TLI;
const TargetTransformInfo *TTI;
const DataLayout *DL;
OptimizationRemarkEmitter &ORE;
bool ApplyCodeSizeHeuristics;
std::unique_ptr<MemorySSAUpdater> MSSAU;

159public:
explicit LoopIdiomRecognize(AliasAnalysis *AA, DominatorTree *DT,
                            LoopInfo *LI, ScalarEvolution *SE,
                            TargetLibraryInfo *TLI,
                            const TargetTransformInfo *TTI, MemorySSA *MSSA,
                            const DataLayout *DL,
                            OptimizationRemarkEmitter &ORE)
    : AA(AA), DT(DT), LI(LI), SE(SE), TLI(TLI), TTI(TTI), DL(DL), ORE(ORE) {
  if (MSSA)
    MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
}

bool runOnLoop(Loop *L);

173private:
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);

template <typename MemInst>
bool processLoopMemIntrinsic(
    BasicBlock *BB,
    bool (LoopIdiomRecognize::*Processor)(MemInst *, const SCEV *),
    const SCEV *BECount);
bool processLoopMemCpy(MemCpyInst *MCI, const SCEV *BECount);
bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount);

bool processLoopStridedStore(Value *DestPtr, const SCEV *StoreSizeSCEV,
                             MaybeAlign StoreAlignment, Value *StoredVal,
                             Instruction *TheStore,
                             SmallPtrSetImpl<Instruction *> &Stores,
                             const SCEVAddRecExpr *Ev, const SCEV *BECount,
                             bool IsNegStride, bool IsLoopMemset = false);
bool processLoopStoreOfLoopLoad(StoreInst *SI, const SCEV *BECount);
bool processLoopStoreOfLoopLoad(Value *DestPtr, Value *SourcePtr,
                                const SCEV *StoreSize, MaybeAlign StoreAlign,
                                MaybeAlign LoadAlign, Instruction *TheStore,
                                Instruction *TheLoad,
                                const SCEVAddRecExpr *StoreEv,
                                const SCEVAddRecExpr *LoadEv,
                                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);

bool recognizeShiftUntilBitTest();
bool recognizeShiftUntilZero();

/// @}
253};
254} // end anonymous namespace

256PreservedAnalyses LoopIdiomRecognizePass::run(Loop &L, LoopAnalysisManager &AM,
                                            LoopStandardAnalysisResults &AR,
                                            LPMUpdater &) {
if (DisableLIRP::All)
1
Assuming 'All' is false→
2
←
Taking false branch→
  return PreservedAnalyses::all();

const auto *DL = &L.getHeader()->getModule()->getDataLayout();

// For the new PM, we also can't use OptimizationRemarkEmitter as an analysis
// pass.  Function analyses need to be preserved across loop transformations
// but ORE cannot be preserved (see comment before the pass definition).
OptimizationRemarkEmitter ORE(L.getHeader()->getParent());

LoopIdiomRecognize LIR(&AR.AA, &AR.DT, &AR.LI, &AR.SE, &AR.TLI, &AR.TTI,
                       AR.MSSA, DL, ORE);
if (!LIR.runOnLoop(&L))
3
←
Calling 'LoopIdiomRecognize::runOnLoop'→
  return PreservedAnalyses::all();

auto PA = getLoopPassPreservedAnalyses();
if (AR.MSSA)
  PA.preserve<MemorySSAAnalysis>();
return PA;
278}

280static void deleteDeadInstruction(Instruction *I) {
I->replaceAllUsesWith(PoisonValue::get(I->getType()));
I->eraseFromParent();
283}

285//===----------------------------------------------------------------------===//
286//
287//          Implementation of LoopIdiomRecognize
288//
289//===----------------------------------------------------------------------===//

291bool 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())
4
←
Assuming the condition is false→
5
←
Taking false branch→
  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")
6
←
Assuming the condition is false→
7
←
Assuming the condition is false→
  return false;

// Determine if code size heuristics need to be applied.
ApplyCodeSizeHeuristics =
    L->getHeader()->getParent()->hasOptSize() && UseLIRCodeSizeHeurs;
8
←
Assuming the condition is false→

HasMemset = TLI->has(LibFunc_memset);
HasMemsetPattern = TLI->has(LibFunc_memset_pattern16);
HasMemcpy = TLI->has(LibFunc_memcpy);

if (HasMemset8.1
Field 'HasMemset' is false
 || HasMemsetPattern8.2
Field 'HasMemsetPattern' is false
 || HasMemcpy8.3
Field 'HasMemcpy' is false
)
9
←
Taking false branch→
  if (SE->hasLoopInvariantBackedgeTakenCount(L))
    return runOnCountableLoop();

return runOnNoncountableLoop();
10
←
Calling 'LoopIdiomRecognize::runOnNoncountableLoop'→
316}

318bool LoopIdiomRecognize::runOnCountableLoop() {
const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop);
assert(!isa<SCEVCouldNotCompute>(BECount) &&(static_cast <bool> (!isa<SCEVCouldNotCompute>(BECount
) && "runOnCountableLoop() called on a loop without a predictable"
 "backedge-taken count") ? void (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(BECount) && \"runOnCountableLoop() called on a loop without a predictable\" \"backedge-taken count\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 322, __extension__
 __PRETTY_FUNCTION__))
       "runOnCountableLoop() called on a loop without a predictable"(static_cast <bool> (!isa<SCEVCouldNotCompute>(BECount
) && "runOnCountableLoop() called on a loop without a predictable"
 "backedge-taken count") ? void (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(BECount) && \"runOnCountableLoop() called on a loop without a predictable\" \"backedge-taken count\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 322, __extension__
 __PRETTY_FUNCTION__))
       "backedge-taken count")(static_cast <bool> (!isa<SCEVCouldNotCompute>(BECount
) && "runOnCountableLoop() called on a loop without a predictable"
 "backedge-taken count") ? void (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(BECount) && \"runOnCountableLoop() called on a loop without a predictable\" \"backedge-taken count\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 322, __extension__
 __PRETTY_FUNCTION__));

// 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() << DEBUG_TYPE " Scanning: F["do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Countable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
                  << CurLoop->getHeader()->getParent()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Countable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
                  << "] Countable Loop %" << CurLoop->getHeader()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Countable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
                  << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Countable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false);

// The following transforms hoist stores/memsets into the loop pre-header.
// Give up if the loop has instructions that may throw.
SimpleLoopSafetyInfo SafetyInfo;
SafetyInfo.computeLoopSafetyInfo(CurLoop);
if (SafetyInfo.anyBlockMayThrow())
  return false;

bool MadeChange = false;

// 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;
356}

358static APInt getStoreStride(const SCEVAddRecExpr *StoreEv) {
const SCEVConstant *ConstStride = cast<SCEVConstant>(StoreEv->getOperand(1));
return ConstStride->getAPInt();
361}

363/// getMemSetPatternValue - If a strided store of the specified value is safe to
364/// turn into a memset_pattern16, return a ConstantArray of 16 bytes that should
365/// be passed in.  Otherwise, return null.
366///
367/// Note that we don't ever attempt to use memset_pattern8 or 4, because these
368/// just replicate their input array and then pass on to memset_pattern16.
369static 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 || isa<ConstantExpr>(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));
405}

407LoopIdiomRecognize::LegalStoreKind
408LoopIdiomRecognize::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;

// Avoid merging nontemporal stores.
if (SI->getMetadata(LLVMContext::MD_nontemporal))
  return LegalStoreKind::None;

Value *StoredVal = SI->getValueOperand();
Value *StorePtr = SI->getPointerOperand();

// Don't convert stores of non-integral pointer types to memsets (which stores
// integers).
if (DL->isNonIntegralPointerType(StoredVal->getType()->getScalarType()))
  return LegalStoreKind::None;

// Reject stores that are so large that they overflow an unsigned.
// When storing out scalable vectors we bail out for now, since the code
// below currently only works for constant strides.
TypeSize SizeInBits = DL->getTypeSizeInBits(StoredVal->getType());
if (SizeInBits.isScalable() || (SizeInBits.getFixedValue() & 7) ||
    (SizeInBits.getFixedValue() >> 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, *DL);

// 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 && !DisableLIRP::Memset &&
    // 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;
}
if (!UnorderedAtomic && HasMemsetPattern && !DisableLIRP::Memset &&
    // Don't create memset_pattern16s with address spaces.
    StorePtr->getType()->getPointerAddressSpace() == 0 &&
    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 && !DisableLIRP::Memcpy) {
  // 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;
514}

516void 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());
    StoreRefsForMemset[Ptr].push_back(SI);
  } break;
  case LegalStoreKind::MemsetPattern: {
    // Find the base pointer.
    Value *Ptr = getUnderlyingObject(SI->getPointerOperand());
    StoreRefsForMemsetPattern[Ptr].push_back(SI);
  } break;
  case LegalStoreKind::Memcpy:
  case LegalStoreKind::UnorderedAtomicMemcpy:
    StoreRefsForMemcpy.push_back(SI);
    break;
  default:
    assert(false && "unhandled return value")(static_cast <bool> (false && "unhandled return value"
) ? void (0) : __assert_fail ("false && \"unhandled return value\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 545, __extension__
 __PRETTY_FUNCTION__));
    break;
  }
}
549}

551/// runOnLoopBlock - Process the specified block, which lives in a counted loop
552/// with the specified backedge count.  This block is known to be in the current
553/// loop and not in any subloops.
554bool 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 (BasicBlock *ExitBlock : ExitBlocks)
  if (!DT->dominates(BB, ExitBlock))
    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);

MadeChange |= processLoopMemIntrinsic<MemCpyInst>(
    BB, &LoopIdiomRecognize::processLoopMemCpy, BECount);
MadeChange |= processLoopMemIntrinsic<MemSetInst>(
    BB, &LoopIdiomRecognize::processLoopMemSet, BECount);

return MadeChange;
587}

589/// See if this store(s) can be promoted to a memset.
590bool 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.")(static_cast <bool> (SL[i]->isSimple() && "Expected only non-volatile stores."
) ? void (0) : __assert_fail ("SL[i]->isSimple() && \"Expected only non-volatile stores.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 600, __extension__
 __PRETTY_FUNCTION__));

  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, *DL);
  else
    FirstPatternValue = getMemSetPatternValue(FirstStoredVal, DL);

  assert((FirstSplatValue || FirstPatternValue) &&(static_cast <bool> ((FirstSplatValue || FirstPatternValue
) && "Expected either splat value or pattern value.")
 ? void (0) : __assert_fail ("(FirstSplatValue || FirstPatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 624, __extension__
 __PRETTY_FUNCTION__))
         "Expected either splat value or pattern value.")(static_cast <bool> ((FirstSplatValue || FirstPatternValue
) && "Expected either splat value or pattern value.")
 ? void (0) : __assert_fail ("(FirstSplatValue || FirstPatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 624, __extension__
 __PRETTY_FUNCTION__));

  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.")(static_cast <bool> (SL[k]->isSimple() && "Expected only non-volatile stores."
) ? void (0) : __assert_fail ("SL[k]->isSimple() && \"Expected only non-volatile stores.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 638, __extension__
 __PRETTY_FUNCTION__));
    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, *DL);
    else
      SecondPatternValue = getMemSetPatternValue(SecondStoredVal, DL);

    assert((SecondSplatValue || SecondPatternValue) &&(static_cast <bool> ((SecondSplatValue || SecondPatternValue
) && "Expected either splat value or pattern value.")
 ? void (0) : __assert_fail ("(SecondSplatValue || SecondPatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 657, __extension__
 __PRETTY_FUNCTION__))
           "Expected either splat value or pattern value.")(static_cast <bool> ((SecondSplatValue || SecondPatternValue
) && "Expected either splat value or pattern value.")
 ? void (0) : __assert_fail ("(SecondSplatValue || SecondPatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 657, __extension__
 __PRETTY_FUNCTION__));

    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 (StoreInst *I : Heads) {
  if (Tails.count(I))
    continue;

  // We found a store instr that starts a chain. Now follow the chain and try
  // to transform it.
  SmallPtrSet<Instruction *, 8> AdjacentStores;
  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 IsNegStride = StoreSize == -Stride;

  Type *IntIdxTy = DL->getIndexType(StorePtr->getType());
  const SCEV *StoreSizeSCEV = SE->getConstant(IntIdxTy, StoreSize);
  if (processLoopStridedStore(StorePtr, StoreSizeSCEV,
                              MaybeAlign(HeadStore->getAlign()), StoredVal,
                              HeadStore, AdjacentStores, StoreEv, BECount,
                              IsNegStride)) {
    TransformedStores.insert(AdjacentStores.begin(), AdjacentStores.end());
    Changed = true;
  }
}

return Changed;
730}

732/// processLoopMemIntrinsic - Template function for calling different processor
733/// functions based on mem intrinsic type.
734template <typename MemInst>
735bool LoopIdiomRecognize::processLoopMemIntrinsic(
  BasicBlock *BB,
  bool (LoopIdiomRecognize::*Processor)(MemInst *, const SCEV *),
  const SCEV *BECount) {
bool MadeChange = false;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
  Instruction *Inst = &*I++;
  // Look for memory instructions, which may be optimized to a larger one.
  if (MemInst *MI = dyn_cast<MemInst>(Inst)) {
    WeakTrackingVH InstPtr(&*I);
    if (!(this->*Processor)(MI, BECount))
      continue;
    MadeChange = true;

    // If processing the instruction invalidated our iterator, start over from
    // the top of the block.
    if (!InstPtr)
      I = BB->begin();
  }
}
return MadeChange;
756}

758/// processLoopMemCpy - See if this memcpy can be promoted to a large memcpy
759bool LoopIdiomRecognize::processLoopMemCpy(MemCpyInst *MCI,
                                         const SCEV *BECount) {
// We can only handle non-volatile memcpys with a constant size.
if (MCI->isVolatile() || !isa<ConstantInt>(MCI->getLength()))
  return false;

// If we're not allowed to hack on memcpy, we fail.
if ((!HasMemcpy && !isa<MemCpyInlineInst>(MCI)) || DisableLIRP::Memcpy)
  return false;

Value *Dest = MCI->getDest();
Value *Source = MCI->getSource();
if (!Dest || !Source)
  return false;

// See if the load and store pointer expressions are AddRec like {base,+,1} on
// the current loop, which indicates a strided load and store.  If we have
// something else, it's a random load or store we can't handle.
const SCEVAddRecExpr *StoreEv = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Dest));
if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine())
  return false;
const SCEVAddRecExpr *LoadEv = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Source));
if (!LoadEv || LoadEv->getLoop() != CurLoop || !LoadEv->isAffine())
  return false;

// Reject memcpys that are so large that they overflow an unsigned.
uint64_t SizeInBytes = cast<ConstantInt>(MCI->getLength())->getZExtValue();
if ((SizeInBytes >> 32) != 0)
  return false;

// Check if the stride matches the size of the memcpy. If so, then we know
// that every byte is touched in the loop.
const SCEVConstant *ConstStoreStride =
    dyn_cast<SCEVConstant>(StoreEv->getOperand(1));
const SCEVConstant *ConstLoadStride =
    dyn_cast<SCEVConstant>(LoadEv->getOperand(1));
if (!ConstStoreStride || !ConstLoadStride)
  return false;

APInt StoreStrideValue = ConstStoreStride->getAPInt();
APInt LoadStrideValue = ConstLoadStride->getAPInt();
// Huge stride value - give up
if (StoreStrideValue.getBitWidth() > 64 || LoadStrideValue.getBitWidth() > 64)
  return false;

if (SizeInBytes != StoreStrideValue && SizeInBytes != -StoreStrideValue) {
  ORE.emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-idiom", "SizeStrideUnequal", MCI)
           << ore::NV("Inst", "memcpy") << " in "
           << ore::NV("Function", MCI->getFunction())
           << " function will not be hoisted: "
           << ore::NV("Reason", "memcpy size is not equal to stride");
  });
  return false;
}

int64_t StoreStrideInt = StoreStrideValue.getSExtValue();
int64_t LoadStrideInt = LoadStrideValue.getSExtValue();
// Check if the load stride matches the store stride.
if (StoreStrideInt != LoadStrideInt)
  return false;

return processLoopStoreOfLoopLoad(
    Dest, Source, SE->getConstant(Dest->getType(), SizeInBytes),
    MCI->getDestAlign(), MCI->getSourceAlign(), MCI, MCI, StoreEv, LoadEv,
    BECount);
825}

827/// processLoopMemSet - See if this memset can be promoted to a large memset.
828bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
                                         const SCEV *BECount) {
// We can only handle non-volatile memsets.
if (MSI->isVolatile())
  return false;

// If we're not allowed to hack on memset, we fail.
if (!HasMemset || DisableLIRP::Memset)
  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)
  return false;
if (!Ev->isAffine()) {
  LLVM_DEBUG(dbgs() << "  Pointer is not affine, abort\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Pointer is not affine, abort\n"
; } } while (false);
  return false;
}

const SCEV *PointerStrideSCEV = Ev->getOperand(1);
const SCEV *MemsetSizeSCEV = SE->getSCEV(MSI->getLength());
if (!PointerStrideSCEV || !MemsetSizeSCEV)
  return false;

bool IsNegStride = false;
const bool IsConstantSize = isa<ConstantInt>(MSI->getLength());

if (IsConstantSize) {
  // Memset size is constant.
  // Check if the pointer stride matches the memset size. If so, then
  // we know that every byte is touched in the loop.
  LLVM_DEBUG(dbgs() << "  memset size is constant\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  memset size is constant\n"
; } } while (false);
  uint64_t SizeInBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
  const SCEVConstant *ConstStride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
  if (!ConstStride)
    return false;

  APInt Stride = ConstStride->getAPInt();
  if (SizeInBytes != Stride && SizeInBytes != -Stride)
    return false;

  IsNegStride = SizeInBytes == -Stride;
} else {
  // Memset size is non-constant.
  // Check if the pointer stride matches the memset size.
  // To be conservative, the pass would not promote pointers that aren't in
  // address space zero. Also, the pass only handles memset length and stride
  // that are invariant for the top level loop.
  LLVM_DEBUG(dbgs() << "  memset size is non-constant\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  memset size is non-constant\n"
; } } while (false);
  if (Pointer->getType()->getPointerAddressSpace() != 0) {
    LLVM_DEBUG(dbgs() << "  pointer is not in address space zero, "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  pointer is not in address space zero, "
 << "abort\n"; } } while (false)
                      << "abort\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  pointer is not in address space zero, "
 << "abort\n"; } } while (false);
    return false;
  }
  if (!SE->isLoopInvariant(MemsetSizeSCEV, CurLoop)) {
    LLVM_DEBUG(dbgs() << "  memset size is not a loop-invariant, "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  memset size is not a loop-invariant, "
 << "abort\n"; } } while (false)
                      << "abort\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  memset size is not a loop-invariant, "
 << "abort\n"; } } while (false);
    return false;
  }

  // Compare positive direction PointerStrideSCEV with MemsetSizeSCEV
  IsNegStride = PointerStrideSCEV->isNonConstantNegative();
  const SCEV *PositiveStrideSCEV =
      IsNegStride ? SE->getNegativeSCEV(PointerStrideSCEV)
                  : PointerStrideSCEV;
  LLVM_DEBUG(dbgs() << "  MemsetSizeSCEV: " << *MemsetSizeSCEV << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  MemsetSizeSCEV: " <<
 *MemsetSizeSCEV << "\n" << "  PositiveStrideSCEV: "
 << *PositiveStrideSCEV << "\n"; } } while (false
)
                    << "  PositiveStrideSCEV: " << *PositiveStrideSCEVdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  MemsetSizeSCEV: " <<
 *MemsetSizeSCEV << "\n" << "  PositiveStrideSCEV: "
 << *PositiveStrideSCEV << "\n"; } } while (false
)
                    << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  MemsetSizeSCEV: " <<
 *MemsetSizeSCEV << "\n" << "  PositiveStrideSCEV: "
 << *PositiveStrideSCEV << "\n"; } } while (false
);

  if (PositiveStrideSCEV != MemsetSizeSCEV) {
    // If an expression is covered by the loop guard, compare again and
    // proceed with optimization if equal.
    const SCEV *FoldedPositiveStride =
        SE->applyLoopGuards(PositiveStrideSCEV, CurLoop);
    const SCEV *FoldedMemsetSize =
        SE->applyLoopGuards(MemsetSizeSCEV, CurLoop);

    LLVM_DEBUG(dbgs() << "  Try to fold SCEV based on loop guard\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Try to fold SCEV based on loop guard\n"
 << "    FoldedMemsetSize: " << *FoldedMemsetSize
 << "\n" << "    FoldedPositiveStride: " <<
 *FoldedPositiveStride << "\n"; } } while (false)
                      << "    FoldedMemsetSize: " << *FoldedMemsetSize << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Try to fold SCEV based on loop guard\n"
 << "    FoldedMemsetSize: " << *FoldedMemsetSize
 << "\n" << "    FoldedPositiveStride: " <<
 *FoldedPositiveStride << "\n"; } } while (false)
                      << "    FoldedPositiveStride: " << *FoldedPositiveStridedo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Try to fold SCEV based on loop guard\n"
 << "    FoldedMemsetSize: " << *FoldedMemsetSize
 << "\n" << "    FoldedPositiveStride: " <<
 *FoldedPositiveStride << "\n"; } } while (false)
                      << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Try to fold SCEV based on loop guard\n"
 << "    FoldedMemsetSize: " << *FoldedMemsetSize
 << "\n" << "    FoldedPositiveStride: " <<
 *FoldedPositiveStride << "\n"; } } while (false);

    if (FoldedPositiveStride != FoldedMemsetSize) {
      LLVM_DEBUG(dbgs() << "  SCEV don't match, abort\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  SCEV don't match, abort\n"
; } } while (false);
      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);
return processLoopStridedStore(Pointer, SE->getSCEV(MSI->getLength()),
                               MSI->getDestAlign(), SplatValue, MSI, MSIs, Ev,
                               BECount, IsNegStride, /*IsLoopMemset=*/true);
932}

934/// mayLoopAccessLocation - Return true if the specified loop might access the
935/// specified pointer location, which is a loop-strided access.  The 'Access'
936/// argument specifies what the verboten forms of access are (read or write).
937static bool
938mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L,
                    const SCEV *BECount, const SCEV *StoreSizeSCEV,
                    AliasAnalysis &AA,
                    SmallPtrSetImpl<Instruction *> &IgnoredInsts) {
// 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::afterPointer();

// 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
const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount);
const SCEVConstant *ConstSize = dyn_cast<SCEVConstant>(StoreSizeSCEV);
if (BECst && ConstSize)
  AccessSize = LocationSize::precise((BECst->getValue()->getZExtValue() + 1) *
                                     ConstSize->getValue()->getZExtValue());

// 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 (BasicBlock *B : L->blocks())
  for (Instruction &I : *B)
    if (!IgnoredInsts.contains(&I) &&
        isModOrRefSet(AA.getModRefInfo(&I, StoreLoc) & Access))
      return true;
return false;
967}

969// If we have a negative stride, Start refers to the end of the memory location
970// we're trying to memset.  Therefore, we need to recompute the base pointer,
971// which is just Start - BECount*Size.
972static const SCEV *getStartForNegStride(const SCEV *Start, const SCEV *BECount,
                                      Type *IntPtr, const SCEV *StoreSizeSCEV,
                                      ScalarEvolution *SE) {
const SCEV *Index = SE->getTruncateOrZeroExtend(BECount, IntPtr);
if (!StoreSizeSCEV->isOne()) {
  // index = back edge count * store size
  Index = SE->getMulExpr(Index,
                         SE->getTruncateOrZeroExtend(StoreSizeSCEV, IntPtr),
                         SCEV::FlagNUW);
}
// base pointer = start - index * store size
return SE->getMinusSCEV(Start, Index);
984}

986/// Compute the number of bytes as a SCEV from the backedge taken count.
987///
988/// This also maps the SCEV into the provided type and tries to handle the
989/// computation in a way that will fold cleanly.
990static const SCEV *getNumBytes(const SCEV *BECount, Type *IntPtr,
                             const SCEV *StoreSizeSCEV, Loop *CurLoop,
                             const DataLayout *DL, ScalarEvolution *SE) {
const SCEV *TripCountSCEV =
    SE->getTripCountFromExitCount(BECount, IntPtr, CurLoop);
return SE->getMulExpr(TripCountSCEV,
                      SE->getTruncateOrZeroExtend(StoreSizeSCEV, IntPtr),
                      SCEV::FlagNUW);
998}

1000/// processLoopStridedStore - We see a strided store of some value.  If we can
1001/// transform this into a memset or memset_pattern in the loop preheader, do so.
1002bool LoopIdiomRecognize::processLoopStridedStore(
  Value *DestPtr, const SCEV *StoreSizeSCEV, MaybeAlign StoreAlignment,
  Value *StoredVal, Instruction *TheStore,
  SmallPtrSetImpl<Instruction *> &Stores, const SCEVAddRecExpr *Ev,
  const SCEV *BECount, bool IsNegStride, bool IsLoopMemset) {
Module *M = TheStore->getModule();
Value *SplatValue = isBytewiseValue(StoredVal, *DL);
Constant *PatternValue = nullptr;

if (!SplatValue)
  PatternValue = getMemSetPatternValue(StoredVal, DL);

assert((SplatValue || PatternValue) &&(static_cast <bool> ((SplatValue || PatternValue) &&
 "Expected either splat value or pattern value.") ? void (0) :
 __assert_fail ("(SplatValue || PatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1015, __extension__
 __PRETTY_FUNCTION__))
       "Expected either splat value or pattern value.")(static_cast <bool> ((SplatValue || PatternValue) &&
 "Expected either splat value or pattern value.") ? void (0) :
 __assert_fail ("(SplatValue || PatternValue) && \"Expected either splat value or pattern value.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1015, __extension__
 __PRETTY_FUNCTION__));

// 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");
SCEVExpanderCleaner ExpCleaner(Expander);

Type *DestInt8PtrTy = Builder.getInt8PtrTy(DestAS);
Type *IntIdxTy = DL->getIndexType(DestPtr->getType());

bool Changed = false;
const SCEV *Start = Ev->getStart();
// Handle negative strided loops.
if (IsNegStride)
  Start = getStartForNegStride(Start, BECount, IntIdxTy, StoreSizeSCEV, 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 (!Expander.isSafeToExpand(Start))
  return Changed;

// 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());

// From here on out, conservatively report to the pass manager that we've
// changed the IR, even if we later clean up these added instructions. There
// may be structural differences e.g. in the order of use lists not accounted
// for in just a textual dump of the IR. This is written as a variable, even
// though statically all the places this dominates could be replaced with
// 'true', with the hope that anyone trying to be clever / "more precise" with
// the return value will read this comment, and leave them alone.
Changed = true;

if (mayLoopAccessLocation(BasePtr, ModRefInfo::ModRef, CurLoop, BECount,
                          StoreSizeSCEV, *AA, Stores))
  return Changed;

if (avoidLIRForMultiBlockLoop(/*IsMemset=*/true, IsLoopMemset))
  return Changed;

// Okay, everything looks good, insert the memset.

const SCEV *NumBytesS =
    getNumBytes(BECount, IntIdxTy, StoreSizeSCEV, 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 (!Expander.isSafeToExpand(NumBytesS))
  return Changed;

Value *NumBytes =
    Expander.expandCodeFor(NumBytesS, IntIdxTy, Preheader->getTerminator());

CallInst *NewCall;
if (SplatValue) {
  AAMDNodes AATags = TheStore->getAAMetadata();
  for (Instruction *Store : Stores)
    AATags = AATags.merge(Store->getAAMetadata());
  if (auto CI = dyn_cast<ConstantInt>(NumBytes))
    AATags = AATags.extendTo(CI->getZExtValue());
  else
    AATags = AATags.extendTo(-1);

  NewCall = Builder.CreateMemSet(
      BasePtr, SplatValue, NumBytes, MaybeAlign(StoreAlignment),
      /*isVolatile=*/false, AATags.TBAA, AATags.Scope, AATags.NoAlias);
} else if (isLibFuncEmittable(M, TLI, LibFunc_memset_pattern16)) {
  // Everything is emitted in default address space
  Type *Int8PtrTy = DestInt8PtrTy;

  StringRef FuncName = "memset_pattern16";
  FunctionCallee MSP = getOrInsertLibFunc(M, *TLI, LibFunc_memset_pattern16,
                          Builder.getVoidTy(), Int8PtrTy, Int8PtrTy, IntIdxTy);
  inferNonMandatoryLibFuncAttrs(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(Align(16));
  Value *PatternPtr = ConstantExpr::getBitCast(GV, Int8PtrTy);
  NewCall = Builder.CreateCall(MSP, {BasePtr, PatternPtr, NumBytes});
} else
  return Changed;

NewCall->setDebugLoc(TheStore->getDebugLoc());

if (MSSAU) {
  MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB(
      NewCall, nullptr, NewCall->getParent(), MemorySSA::BeforeTerminator);
  MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true);
}

LLVM_DEBUG(dbgs() << "  Formed memset: " << *NewCall << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed memset: " <<
 *NewCall << "\n" << "    from store to: " <<
 *Ev << " at: " << *TheStore << "\n"; } } while
 (false)
                  << "    from store to: " << *Ev << " at: " << *TheStoredo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed memset: " <<
 *NewCall << "\n" << "    from store to: " <<
 *Ev << " at: " << *TheStore << "\n"; } } while
 (false)
                  << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed memset: " <<
 *NewCall << "\n" << "    from store to: " <<
 *Ev << " at: " << *TheStore << "\n"; } } while
 (false);

ORE.emit([&]() {
  OptimizationRemark R(DEBUG_TYPE"loop-idiom", "ProcessLoopStridedStore",
                       NewCall->getDebugLoc(), Preheader);
  R << "Transformed loop-strided store in "
    << ore::NV("Function", TheStore->getFunction())
    << " function into a call to "
    << ore::NV("NewFunction", NewCall->getCalledFunction())
    << "() intrinsic";
  if (!Stores.empty())
    R << ore::setExtraArgs();
  for (auto *I : Stores) {
    R << ore::NV("FromBlock", I->getParent()->getName())
      << ore::NV("ToBlock", Preheader->getName());
  }
  return R;
});

// Okay, the memset has been formed.  Zap the original store and anything that
// feeds into it.
for (auto *I : Stores) {
  if (MSSAU)
    MSSAU->removeMemoryAccess(I, true);
  deleteDeadInstruction(I);
}
if (MSSAU && VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();
++NumMemSet;
ExpCleaner.markResultUsed();
return true;
1152}

1154/// If the stored value is a strided load in the same loop with the same stride
1155/// this may be transformable into a memcpy.  This kicks in for stuff like
1156/// for (i) A[i] = B[i];
1157bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(StoreInst *SI,
                                                  const SCEV *BECount) {
assert(SI->isUnordered() && "Expected only non-volatile non-ordered stores.")(static_cast <bool> (SI->isUnordered() && "Expected only non-volatile non-ordered stores."
) ? void (0) : __assert_fail ("SI->isUnordered() && \"Expected only non-volatile non-ordered stores.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1159, __extension__
 __PRETTY_FUNCTION__));

Value *StorePtr = SI->getPointerOperand();
const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());

// 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.")(static_cast <bool> (LI->isUnordered() && "Expected only non-volatile non-ordered loads."
) ? void (0) : __assert_fail ("LI->isUnordered() && \"Expected only non-volatile non-ordered loads.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1167, __extension__
 __PRETTY_FUNCTION__));

// 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.
Value *LoadPtr = LI->getPointerOperand();
const SCEVAddRecExpr *LoadEv = cast<SCEVAddRecExpr>(SE->getSCEV(LoadPtr));

const SCEV *StoreSizeSCEV = SE->getConstant(StorePtr->getType(), StoreSize);
return processLoopStoreOfLoopLoad(StorePtr, LoadPtr, StoreSizeSCEV,
                                  SI->getAlign(), LI->getAlign(), SI, LI,
                                  StoreEv, LoadEv, BECount);
1179}

1181namespace {
1182class MemmoveVerifier {
1183public:
explicit MemmoveVerifier(const Value &LoadBasePtr, const Value &StoreBasePtr,
                         const DataLayout &DL)
    : DL(DL), BP1(llvm::GetPointerBaseWithConstantOffset(
                  LoadBasePtr.stripPointerCasts(), LoadOff, DL)),
      BP2(llvm::GetPointerBaseWithConstantOffset(
          StoreBasePtr.stripPointerCasts(), StoreOff, DL)),
      IsSameObject(BP1 == BP2) {}

bool loadAndStoreMayFormMemmove(unsigned StoreSize, bool IsNegStride,
                                const Instruction &TheLoad,
                                bool IsMemCpy) const {
  if (IsMemCpy) {
    // Ensure that LoadBasePtr is after StoreBasePtr or before StoreBasePtr
    // for negative stride.
    if ((!IsNegStride && LoadOff <= StoreOff) ||
        (IsNegStride && LoadOff >= StoreOff))
      return false;
  } else {
    // Ensure that LoadBasePtr is after StoreBasePtr or before StoreBasePtr
    // for negative stride. LoadBasePtr shouldn't overlap with StoreBasePtr.
    int64_t LoadSize =
        DL.getTypeSizeInBits(TheLoad.getType()).getFixedValue() / 8;
    if (BP1 != BP2 || LoadSize != int64_t(StoreSize))
      return false;
    if ((!IsNegStride && LoadOff < StoreOff + int64_t(StoreSize)) ||
        (IsNegStride && LoadOff + LoadSize > StoreOff))
      return false;
  }
  return true;
}

1215private:
const DataLayout &DL;
int64_t LoadOff = 0;
int64_t StoreOff = 0;
const Value *BP1;
const Value *BP2;

1222public:
const bool IsSameObject;
1224};
1225} // namespace

1227bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(
  Value *DestPtr, Value *SourcePtr, const SCEV *StoreSizeSCEV,
  MaybeAlign StoreAlign, MaybeAlign LoadAlign, Instruction *TheStore,
  Instruction *TheLoad, const SCEVAddRecExpr *StoreEv,
  const SCEVAddRecExpr *LoadEv, const SCEV *BECount) {

// FIXME: until llvm.memcpy.inline supports dynamic sizes, we need to
// conservatively bail here, since otherwise we may have to transform
// llvm.memcpy.inline into llvm.memcpy which is illegal.
if (isa<MemCpyInlineInst>(TheStore))
  return false;

// 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");

SCEVExpanderCleaner ExpCleaner(Expander);

bool Changed = false;
const SCEV *StrStart = StoreEv->getStart();
unsigned StrAS = DestPtr->getType()->getPointerAddressSpace();
Type *IntIdxTy = Builder.getIntNTy(DL->getIndexSizeInBits(StrAS));

APInt Stride = getStoreStride(StoreEv);
const SCEVConstant *ConstStoreSize = dyn_cast<SCEVConstant>(StoreSizeSCEV);

// TODO: Deal with non-constant size; Currently expect constant store size
assert(ConstStoreSize && "store size is expected to be a constant")(static_cast <bool> (ConstStoreSize && "store size is expected to be a constant"
) ? void (0) : __assert_fail ("ConstStoreSize && \"store size is expected to be a constant\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1257, __extension__
 __PRETTY_FUNCTION__));

int64_t StoreSize = ConstStoreSize->getValue()->getZExtValue();
bool IsNegStride = StoreSize == -Stride;

// Handle negative strided loops.
if (IsNegStride)
  StrStart =
      getStartForNegStride(StrStart, BECount, IntIdxTy, StoreSizeSCEV, 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());

// From here on out, conservatively report to the pass manager that we've
// changed the IR, even if we later clean up these added instructions. There
// may be structural differences e.g. in the order of use lists not accounted
// for in just a textual dump of the IR. This is written as a variable, even
// though statically all the places this dominates could be replaced with
// 'true', with the hope that anyone trying to be clever / "more precise" with
// the return value will read this comment, and leave them alone.
Changed = true;

SmallPtrSet<Instruction *, 2> IgnoredInsts;
IgnoredInsts.insert(TheStore);

bool IsMemCpy = isa<MemCpyInst>(TheStore);
const StringRef InstRemark = IsMemCpy ? "memcpy" : "load and store";

bool LoopAccessStore =
    mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
                          StoreSizeSCEV, *AA, IgnoredInsts);
if (LoopAccessStore) {
  // For memmove case it's not enough to guarantee that loop doesn't access
  // TheStore and TheLoad. Additionally we need to make sure that TheStore is
  // the only user of TheLoad.
  if (!TheLoad->hasOneUse())
    return Changed;
  IgnoredInsts.insert(TheLoad);
  if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop,
                            BECount, StoreSizeSCEV, *AA, IgnoredInsts)) {
    ORE.emit([&]() {
      return OptimizationRemarkMissed(DEBUG_TYPE"loop-idiom", "LoopMayAccessStore",
                                      TheStore)
             << ore::NV("Inst", InstRemark) << " in "
             << ore::NV("Function", TheStore->getFunction())
             << " function will not be hoisted: "
             << ore::NV("Reason", "The loop may access store location");
    });
    return Changed;
  }
  IgnoredInsts.erase(TheLoad);
}

const SCEV *LdStart = LoadEv->getStart();
unsigned LdAS = SourcePtr->getType()->getPointerAddressSpace();

// Handle negative strided loops.
if (IsNegStride)
  LdStart =
      getStartForNegStride(LdStart, BECount, IntIdxTy, StoreSizeSCEV, 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 the store is a memcpy instruction, we must check if it will write to
// the load memory locations. So remove it from the ignored stores.
MemmoveVerifier Verifier(*LoadBasePtr, *StoreBasePtr, *DL);
if (IsMemCpy && !Verifier.IsSameObject)
  IgnoredInsts.erase(TheStore);
if (mayLoopAccessLocation(LoadBasePtr, ModRefInfo::Mod, CurLoop, BECount,
                          StoreSizeSCEV, *AA, IgnoredInsts)) {
  ORE.emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-idiom", "LoopMayAccessLoad", TheLoad)
           << ore::NV("Inst", InstRemark) << " in "
           << ore::NV("Function", TheStore->getFunction())
           << " function will not be hoisted: "
           << ore::NV("Reason", "The loop may access load location");
  });
  return Changed;
}

bool UseMemMove = IsMemCpy ? Verifier.IsSameObject : LoopAccessStore;
if (UseMemMove)
  if (!Verifier.loadAndStoreMayFormMemmove(StoreSize, IsNegStride, *TheLoad,
                                           IsMemCpy))
    return Changed;

if (avoidLIRForMultiBlockLoop())
  return Changed;

// Okay, everything is safe, we can transform this!

const SCEV *NumBytesS =
    getNumBytes(BECount, IntIdxTy, StoreSizeSCEV, CurLoop, DL, SE);

Value *NumBytes =
    Expander.expandCodeFor(NumBytesS, IntIdxTy, Preheader->getTerminator());

AAMDNodes AATags = TheLoad->getAAMetadata();
AAMDNodes StoreAATags = TheStore->getAAMetadata();
AATags = AATags.merge(StoreAATags);
if (auto CI = dyn_cast<ConstantInt>(NumBytes))
  AATags = AATags.extendTo(CI->getZExtValue());
else
  AATags = AATags.extendTo(-1);

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 (!TheStore->isAtomic() && !TheLoad->isAtomic()) {
  if (UseMemMove)
    NewCall = Builder.CreateMemMove(
        StoreBasePtr, StoreAlign, LoadBasePtr, LoadAlign, NumBytes,
        /*isVolatile=*/false, AATags.TBAA, AATags.Scope, AATags.NoAlias);
  else
    NewCall =
        Builder.CreateMemCpy(StoreBasePtr, StoreAlign, LoadBasePtr, LoadAlign,
                             NumBytes, /*isVolatile=*/false, AATags.TBAA,
                             AATags.TBAAStruct, AATags.Scope, AATags.NoAlias);
} else {
  // For now don't support unordered atomic memmove.
  if (UseMemMove)
    return Changed;
  // We cannot allow unaligned ops for unordered load/store, so reject
  // anything where the alignment isn't at least the element size.
  assert((StoreAlign && LoadAlign) &&(static_cast <bool> ((StoreAlign && LoadAlign) &&
 "Expect unordered load/store to have align.") ? void (0) : __assert_fail
 ("(StoreAlign && LoadAlign) && \"Expect unordered load/store to have align.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1392, __extension__
 __PRETTY_FUNCTION__))
         "Expect unordered load/store to have align.")(static_cast <bool> ((StoreAlign && LoadAlign) &&
 "Expect unordered load/store to have align.") ? void (0) : __assert_fail
 ("(StoreAlign && LoadAlign) && \"Expect unordered load/store to have align.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 1392, __extension__
 __PRETTY_FUNCTION__));
  if (*StoreAlign < StoreSize || *LoadAlign < StoreSize)
    return Changed;

  // 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 Changed;

  // 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, *StoreAlign, LoadBasePtr, *LoadAlign, NumBytes, StoreSize,
      AATags.TBAA, AATags.TBAAStruct, AATags.Scope, AATags.NoAlias);
}
NewCall->setDebugLoc(TheStore->getDebugLoc());

if (MSSAU) {
  MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB(
      NewCall, nullptr, NewCall->getParent(), MemorySSA::BeforeTerminator);
  MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true);
}

LLVM_DEBUG(dbgs() << "  Formed new call: " << *NewCall << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed new call: " <<
 *NewCall << "\n" << "    from load ptr=" <<
 *LoadEv << " at: " << *TheLoad << "\n" <<
 "    from store ptr=" << *StoreEv << " at: " <<
 *TheStore << "\n"; } } while (false)
                  << "    from load ptr=" << *LoadEv << " at: " << *TheLoaddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed new call: " <<
 *NewCall << "\n" << "    from load ptr=" <<
 *LoadEv << " at: " << *TheLoad << "\n" <<
 "    from store ptr=" << *StoreEv << " at: " <<
 *TheStore << "\n"; } } while (false)
                  << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed new call: " <<
 *NewCall << "\n" << "    from load ptr=" <<
 *LoadEv << " at: " << *TheLoad << "\n" <<
 "    from store ptr=" << *StoreEv << " at: " <<
 *TheStore << "\n"; } } while (false)
                  << "    from store ptr=" << *StoreEv << " at: " << *TheStoredo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed new call: " <<
 *NewCall << "\n" << "    from load ptr=" <<
 *LoadEv << " at: " << *TheLoad << "\n" <<
 "    from store ptr=" << *StoreEv << " at: " <<
 *TheStore << "\n"; } } while (false)
                  << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  Formed new call: " <<
 *NewCall << "\n" << "    from load ptr=" <<
 *LoadEv << " at: " << *TheLoad << "\n" <<
 "    from store ptr=" << *StoreEv << " at: " <<
 *TheStore << "\n"; } } while (false);

ORE.emit([&]() {
  return OptimizationRemark(DEBUG_TYPE"loop-idiom", "ProcessLoopStoreOfLoopLoad",
                            NewCall->getDebugLoc(), Preheader)
         << "Formed a call to "
         << ore::NV("NewFunction", NewCall->getCalledFunction())
         << "() intrinsic from " << ore::NV("Inst", InstRemark)
         << " instruction in " << ore::NV("Function", TheStore->getFunction())
         << " function"
         << ore::setExtraArgs()
         << ore::NV("FromBlock", TheStore->getParent()->getName())
         << ore::NV("ToBlock", Preheader->getName());
});

// Okay, a new call to memcpy/memmove has been formed.  Zap the original store
// and anything that feeds into it.
if (MSSAU)
  MSSAU->removeMemoryAccess(TheStore, true);
deleteDeadInstruction(TheStore);
if (MSSAU && VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();
if (UseMemMove)
  ++NumMemMove;
else
  ++NumMemCpy;
ExpCleaner.markResultUsed();
return true;
1450}

1452// When compiling for codesize we avoid idiom recognition for a multi-block loop
1453// unless it is a loop_memset idiom or a memset/memcpy idiom in a nested loop.
1454//
1455bool LoopIdiomRecognize::avoidLIRForMultiBlockLoop(bool IsMemset,
                                                 bool IsLoopMemset) {
if (ApplyCodeSizeHeuristics && CurLoop->getNumBlocks() > 1) {
  if (CurLoop->isOutermost() && (!IsMemset || !IsLoopMemset)) {
    LLVM_DEBUG(dbgs() << "  " << CurLoop->getHeader()->getParent()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  " << CurLoop->getHeader
()->getParent()->getName() << " : LIR " << (
IsMemset ? "Memset" : "Memcpy") << " avoided: multi-block top-level loop\n"
; } } while (false)
                      << " : LIR " << (IsMemset ? "Memset" : "Memcpy")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  " << CurLoop->getHeader
()->getParent()->getName() << " : LIR " << (
IsMemset ? "Memset" : "Memcpy") << " avoided: multi-block top-level loop\n"
; } } while (false)
                      << " avoided: multi-block top-level loop\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "  " << CurLoop->getHeader
()->getParent()->getName() << " : LIR " << (
IsMemset ? "Memset" : "Memcpy") << " avoided: multi-block top-level loop\n"
; } } while (false);
    return true;
  }
}

return false;
1467}

1469bool LoopIdiomRecognize::runOnNoncountableLoop() {
LLVM_DEBUG(dbgs() << DEBUG_TYPE " Scanning: F["do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Noncountable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
11
←
Assuming 'DebugFlag' is false→
                  << CurLoop->getHeader()->getParent()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Noncountable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
                  << "] Noncountable Loop %"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Noncountable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false)
                  << CurLoop->getHeader()->getName() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Scanning: F["
 << CurLoop->getHeader()->getParent()->getName
() << "] Noncountable Loop %" << CurLoop->getHeader
()->getName() << "\n"; } } while (false);

return recognizePopcount() || recognizeAndInsertFFS() ||
12
←
Calling 'LoopIdiomRecognize::recognizeAndInsertFFS'→
       recognizeShiftUntilBitTest() || recognizeShiftUntilZero();
1477}

1479/// Check if the given conditional branch is based on the comparison between
1480/// a variable and zero, and if the variable is non-zero or zero (JmpOnZero is
1481/// true), the control yields to the loop entry. If the branch matches the
1482/// behavior, the variable involved in the comparison is returned. This function
1483/// will be called to see if the precondition and postcondition of the loop are
1484/// in desirable form.
1485static 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;
1509}

1511// Check if the recurrence variable `VarX` is in the right form to create
1512// the idiom. Returns the value coerced to a PHINode if so.
1513static 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;
1520}

1522/// Return true iff the idiom is detected in the loop.
1523///
1524/// Additionally:
1525/// 1) \p CntInst is set to the instruction counting the population bit.
1526/// 2) \p CntPhi is set to the corresponding phi node.
1527/// 3) \p Var is set to the value whose population bits are being counted.
1528///
1529/// The core idiom we are trying to detect is:
1530/// \code
1531///    if (x0 != 0)
1532///      goto loop-exit // the precondition of the loop
1533///    cnt0 = init-val;
1534///    do {
1535///       x1 = phi (x0, x2);
1536///       cnt1 = phi(cnt0, cnt2);
1537///
1538///       cnt2 = cnt1 + 1;
1539///        ...
1540///       x2 = x1 & (x1 - 1);
1541///        ...
1542///    } while(x != 0);
1543///
1544/// loop-exit:
1545/// \endcode
1546static 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 (Instruction &Inst : llvm::make_range(
           LoopEntry->getFirstNonPHI()->getIterator(), LoopEntry->end())) {
    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;
1650}

1652/// Return true if the idiom is detected in the loop.
1653///
1654/// Additionally:
1655/// 1) \p CntInst is set to the instruction Counting Leading Zeros (CTLZ)
1656///       or nullptr if there is no such.
1657/// 2) \p CntPhi is set to the corresponding phi node
1658///       or nullptr if there is no such.
1659/// 3) \p Var is set to the value whose CTLZ could be used.
1660/// 4) \p DefX is set to the instruction calculating Loop exit condition.
1661///
1662/// The core idiom we are trying to detect is:
1663/// \code
1664///    if (x0 == 0)
1665///      goto loop-exit // the precondition of the loop
1666///    cnt0 = init-val;
1667///    do {
1668///       x = phi (x0, x.next);   //PhiX
1669///       cnt = phi(cnt0, cnt.next);
1670///
1671///       cnt.next = cnt + 1;
1672///        ...
1673///       x.next = x >> 1;   // DefX
1674///        ...
1675///    } while(x.next != 0);
1676///
1677/// loop-exit:
1678/// \endcode
1679static 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(
18
←
Assuming 'T' is non-null, which participates in a condition later→
19
←
Taking true branch→
        dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
17
←
Assuming the object is not a 'CastReturnType'→
  DefX = dyn_cast<Instruction>(T);
20
←
Assuming 'T' is a 'CastReturnType'→
else
  return false;

// step 2: detect instructions corresponding to "x.next = x >> 1 or x << 1"
if (!DefX20.1
'DefX' is non-null
 || !DefX->isShift())
21
←
Assuming the condition is false→
  return false;
IntrinID = DefX->getOpcode() == Instruction::Shl ? Intrinsic::cttz :
22
←
Taking false branch→
23
←
Assuming the condition is false→
24
←
'?' condition is false→
                                                   Intrinsic::ctlz;
ConstantInt *Shft = dyn_cast<ConstantInt>(DefX->getOperand(1));
25
←
Assuming the object is a 'CastReturnType'→
if (!Shft25.1
'Shft' is non-null, which participates in a condition later
 || !Shft->isOne())
26
←
Assuming the condition is false→
27
←
Taking false branch→
  return false;
VarX = DefX->getOperand(0);

// step 3: Check the recurrence of variable X
PHINode *PhiX = getRecurrenceVar(VarX, DefX, LoopEntry);
if (!PhiX)
28
←
Assuming 'PhiX' is non-null, which participates in a condition later→
29
←
Taking false branch→
  return false;

InitX = PhiX->getIncomingValueForBlock(CurLoop->getLoopPreheader());
30
←
Value assigned to 'InitX'→

// 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))
31
←
Assuming the condition is false→
  return false;

// step 4: Find the instruction which count the CTLZ: cnt.next = cnt + 1
//         or 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 (Instruction &Inst : llvm::make_range(
         LoopEntry->getFirstNonPHI()->getIterator(), LoopEntry->end())) {
  if (Inst.getOpcode() != Instruction::Add)
32
←
Assuming the condition is false→
33
←
Taking false branch→
    continue;

  ConstantInt *Inc = dyn_cast<ConstantInt>(Inst.getOperand(1));
34
←
Assuming the object is a 'CastReturnType'→
  if (!Inc34.1
'Inc' is non-null
 || (!Inc->isOne() && !Inc->isMinusOne()))
35
←
Assuming the condition is false→
    continue;

  PHINode *Phi = getRecurrenceVar(Inst.getOperand(0), &Inst, LoopEntry);
  if (!Phi)
36
←
Assuming 'Phi' is non-null→
37
←
Taking false branch→
    continue;

  CntInst = &Inst;
  CntPhi = Phi;
  break;
}
if (!CntInst38.1
'CntInst' is non-null
)
38
←
 Execution continues on line 1744→
39
←
Taking false branch→
  return false;

return true;
1748}

1750/// Recognize CTLZ or CTTZ idiom in a non-countable loop and convert the loop
1751/// to countable (with CTLZ / CTTZ trip count). If CTLZ / CTTZ inserted as a new
1752/// trip count returns true; otherwise, returns false.
1753bool LoopIdiomRecognize::recognizeAndInsertFFS() {
// Give up if the loop has multiple blocks or multiple backedges.
if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
13
←
Assuming the condition is false→
14
←
Assuming the condition is false→
15
←
Taking false branch→
  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,
16
←
Calling 'detectShiftUntilZeroIdiom'→
40
←
Returning from 'detectShiftUntilZeroIdiom'→
41
←
Taking false branch→
                               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 (IsCntInstUsedOutsideLoop41.1
'IsCntInstUsedOutsideLoop' is false
 && 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 (!IsCntPhiUsedOutsideLoop41.2
'IsCntPhiUsedOutsideLoop' is false
) {
42
←
Taking true branch→
  auto *PreCondBB = PH->getSinglePredecessor();
  if (!PreCondBB)
43
←
Assuming 'PreCondBB' is non-null→
44
←
Taking false branch→
    return false;
  auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
45
←
Assuming the object is a 'CastReturnType'→
  if (!PreCondBI45.1
'PreCondBI' is non-null
)
46
←
Taking false branch→
    return false;
  if (matchCondition(PreCondBI, PH) != InitX)
47
←
Assuming pointer value is null→
48
←
Taking false branch→
    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,
                       ConstantInt::getBool(InitX->getContext(), ZeroCheck)};
49
←
Called C++ object pointer is null

// @llvm.dbg doesn't count as they have no semantic effect.
auto InstWithoutDebugIt = CurLoop->getHeader()->instructionsWithoutDebug();
uint32_t HeaderSize =
    std::distance(InstWithoutDebugIt.begin(), InstWithoutDebugIt.end());

IntrinsicCostAttributes Attrs(IntrinID, InitX->getType(), Args);
InstructionCost Cost =
  TTI->getIntrinsicInstrCost(Attrs, TargetTransformInfo::TCK_SizeAndLatency);
if (HeaderSize != IdiomCanonicalSize &&
    Cost > TargetTransformInfo::TCC_Basic)
  return false;

transformLoopToCountable(IntrinID, PH, CntInst, CntPhi, InitX, DefX,
                         DefX->getDebugLoc(), ZeroCheck,
                         IsCntPhiUsedOutsideLoop);
return true;
1842}

1844/// Recognizes a population count idiom in a non-countable loop.
1845///
1846/// If detected, transforms the relevant code to issue the popcount intrinsic
1847/// function call, and returns true; otherwise, returns false.
1848bool 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;
1892}

1894static CallInst *createPopcntIntrinsic(IRBuilder<> &IRBuilder, Value *Val,
                                     const DebugLoc &DL) {
Value *Ops[] = {Val};
Type *Tys[] = {Val->getType()};

Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
Function *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys);
CallInst *CI = IRBuilder.CreateCall(Func, Ops);
CI->setDebugLoc(DL);

return CI;
1905}

1907static CallInst *createFFSIntrinsic(IRBuilder<> &IRBuilder, Value *Val,
                                  const DebugLoc &DL, bool ZeroCheck,
                                  Intrinsic::ID IID) {
Value *Ops[] = {Val, IRBuilder.getInt1(ZeroCheck)};
Type *Tys[] = {Val->getType()};

Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
Function *Func = Intrinsic::getDeclaration(M, IID, Tys);
CallInst *CI = IRBuilder.CreateCall(Func, Ops);
CI->setDebugLoc(DL);

return CI;
1919}

1921/// Transform the following loop (Using CTLZ, CTTZ is similar):
1922/// loop:
1923///   CntPhi = PHI [Cnt0, CntInst]
1924///   PhiX = PHI [InitX, DefX]
1925///   CntInst = CntPhi + 1
1926///   DefX = PhiX >> 1
1927///   LOOP_BODY
1928///   Br: loop if (DefX != 0)
1929/// Use(CntPhi) or Use(CntInst)
1930///
1931/// Into:
1932/// If CntPhi used outside the loop:
1933///   CountPrev = BitWidth(InitX) - CTLZ(InitX >> 1)
1934///   Count = CountPrev + 1
1935/// else
1936///   Count = BitWidth(InitX) - CTLZ(InitX)
1937/// loop:
1938///   CntPhi = PHI [Cnt0, CntInst]
1939///   PhiX = PHI [InitX, DefX]
1940///   PhiCount = PHI [Count, Dec]
1941///   CntInst = CntPhi + 1
1942///   DefX = PhiX >> 1
1943///   Dec = PhiCount - 1
1944///   LOOP_BODY
1945///   Br: loop if (Dec != 0)
1946/// Use(CountPrev + Cnt0) // Use(CntPhi)
1947/// or
1948/// Use(Count + Cnt0) // Use(CntInst)
1949///
1950/// If LOOP_BODY is empty the loop will be deleted.
1951/// If CntInst and DefX are not used in LOOP_BODY they will be removed.
1952void 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);

// If there are no uses of CntPhi crate:
//   Count = BitWidth - CTLZ(InitX);
//   NewCount = Count;
// If there are uses of CntPhi create:
//   NewCount = BitWidth - CTLZ(InitX >> 1);
//   Count = NewCount + 1;
Value *InitXNext;
if (IsCntPhiUsedOutsideLoop) {
  if (DefX->getOpcode() == Instruction::AShr)
    InitXNext = Builder.CreateAShr(InitX, 1);
  else if (DefX->getOpcode() == Instruction::LShr)
    InitXNext = Builder.CreateLShr(InitX, 1);
  else if (DefX->getOpcode() == Instruction::Shl) // cttz
    InitXNext = Builder.CreateShl(InitX, 1);
  else
    llvm_unreachable("Unexpected opcode!")::llvm::llvm_unreachable_internal("Unexpected opcode!", "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp"
, 1977);
} else
  InitXNext = InitX;
Value *Count =
    createFFSIntrinsic(Builder, InitXNext, DL, ZeroCheck, IntrinID);
Type *CountTy = Count->getType();
Count = Builder.CreateSub(
    ConstantInt::get(CountTy, CountTy->getIntegerBitWidth()), Count);
Value *NewCount = Count;
if (IsCntPhiUsedOutsideLoop)
  Count = Builder.CreateAdd(Count, ConstantInt::get(CountTy, 1));

NewCount = Builder.CreateZExtOrTrunc(NewCount, CntInst->getType());

Value *CntInitVal = CntPhi->getIncomingValueForBlock(Preheader);
if (cast<ConstantInt>(CntInst->getOperand(1))->isOne()) {
  // If the counter was being incremented in the loop, add NewCount to the
  // counter's initial value, but only if the initial value is not zero.
  ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
  if (!InitConst || !InitConst->isZero())
    NewCount = Builder.CreateAdd(NewCount, CntInitVal);
} else {
  // If the count was being decremented in the loop, subtract NewCount from
  // the counter's initial value.
  NewCount = Builder.CreateSub(CntInitVal, NewCount);
}

// 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());

PHINode *TcPhi = PHINode::Create(CountTy, 2, "tcphi", &Body->front());

Builder.SetInsertPoint(LbCond);
Instruction *TcDec = cast<Instruction>(Builder.CreateSub(
    TcPhi, ConstantInt::get(CountTy, 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(CountTy, 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);
2041}

2043void 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);
2147}

2149/// Match loop-invariant value.
2150template <typename SubPattern_t> struct match_LoopInvariant {
SubPattern_t SubPattern;
const Loop *L;

match_LoopInvariant(const SubPattern_t &SP, const Loop *L)
    : SubPattern(SP), L(L) {}

template <typename ITy> bool match(ITy *V) {
  return L->isLoopInvariant(V) && SubPattern.match(V);
}
2160};

2162/// Matches if the value is loop-invariant.
2163template <typename Ty>
2164inline match_LoopInvariant<Ty> m_LoopInvariant(const Ty &M, const Loop *L) {
return match_LoopInvariant<Ty>(M, L);
2166}

2168/// Return true if the idiom is detected in the loop.
2169///
2170/// The core idiom we are trying to detect is:
2171/// \code
2172///   entry:
2173///     <...>
2174///     %bitmask = shl i32 1, %bitpos
2175///     br label %loop
2176///
2177///   loop:
2178///     %x.curr = phi i32 [ %x, %entry ], [ %x.next, %loop ]
2179///     %x.curr.bitmasked = and i32 %x.curr, %bitmask
2180///     %x.curr.isbitunset = icmp eq i32 %x.curr.bitmasked, 0
2181///     %x.next = shl i32 %x.curr, 1
2182///     <...>
2183///     br i1 %x.curr.isbitunset, label %loop, label %end
2184///
2185///   end:
2186///     %x.curr.res = phi i32 [ %x.curr, %loop ] <...>
2187///     %x.next.res = phi i32 [ %x.next, %loop ] <...>
2188///     <...>
2189/// \endcode
2190static bool detectShiftUntilBitTestIdiom(Loop *CurLoop, Value *&BaseX,
                                       Value *&BitMask, Value *&BitPos,
                                       Value *&CurrX, Instruction *&NextX) {
LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Performing shift-until-bittest idiom detection.\n"
; } } while (false)
           " Performing shift-until-bittest idiom detection.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Performing shift-until-bittest idiom detection.\n"
; } } while (false);

// Give up if the loop has multiple blocks or multiple backedges.
if (CurLoop->getNumBlocks() != 1 || CurLoop->getNumBackEdges() != 1) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad block/backedge count.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad block/backedge count.\n"
; } } while (false);
  return false;
}

BasicBlock *LoopHeaderBB = CurLoop->getHeader();
BasicBlock *LoopPreheaderBB = CurLoop->getLoopPreheader();
assert(LoopPreheaderBB && "There is always a loop preheader.")(static_cast <bool> (LoopPreheaderBB && "There is always a loop preheader."
) ? void (0) : __assert_fail ("LoopPreheaderBB && \"There is always a loop preheader.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2204, __extension__
 __PRETTY_FUNCTION__));

using namespace PatternMatch;

// Step 1: Check if the loop backedge is in desirable form.

ICmpInst::Predicate Pred;
Value *CmpLHS, *CmpRHS;
BasicBlock *TrueBB, *FalseBB;
if (!match(LoopHeaderBB->getTerminator(),
           m_Br(m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)),
                m_BasicBlock(TrueBB), m_BasicBlock(FalseBB)))) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad backedge structure.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad backedge structure.\n"
; } } while (false);
  return false;
}

// Step 2: Check if the backedge's condition is in desirable form.

auto MatchVariableBitMask = [&]() {
  return ICmpInst::isEquality(Pred) && match(CmpRHS, m_Zero()) &&
         match(CmpLHS,
               m_c_And(m_Value(CurrX),
                       m_CombineAnd(
                           m_Value(BitMask),
                           m_LoopInvariant(m_Shl(m_One(), m_Value(BitPos)),
                                           CurLoop))));
};
auto MatchConstantBitMask = [&]() {
  return ICmpInst::isEquality(Pred) && match(CmpRHS, m_Zero()) &&
         match(CmpLHS, m_And(m_Value(CurrX),
                             m_CombineAnd(m_Value(BitMask), m_Power2()))) &&
         (BitPos = ConstantExpr::getExactLogBase2(cast<Constant>(BitMask)));
};
auto MatchDecomposableConstantBitMask = [&]() {
  APInt Mask;
  return llvm::decomposeBitTestICmp(CmpLHS, CmpRHS, Pred, CurrX, Mask) &&
         ICmpInst::isEquality(Pred) && Mask.isPowerOf2() &&
         (BitMask = ConstantInt::get(CurrX->getType(), Mask)) &&
         (BitPos = ConstantInt::get(CurrX->getType(), Mask.logBase2()));
};

if (!MatchVariableBitMask() && !MatchConstantBitMask() &&
    !MatchDecomposableConstantBitMask()) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad backedge comparison.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad backedge comparison.\n"
; } } while (false);
  return false;
}

// Step 3: Check if the recurrence is in desirable form.
auto *CurrXPN = dyn_cast<PHINode>(CurrX);
if (!CurrXPN || CurrXPN->getParent() != LoopHeaderBB) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Not an expected PHI node.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Not an expected PHI node.\n"
; } } while (false);
  return false;
}

BaseX = CurrXPN->getIncomingValueForBlock(LoopPreheaderBB);
NextX =
    dyn_cast<Instruction>(CurrXPN->getIncomingValueForBlock(LoopHeaderBB));

assert(CurLoop->isLoopInvariant(BaseX) &&(static_cast <bool> (CurLoop->isLoopInvariant(BaseX)
 && "Expected BaseX to be avaliable in the preheader!"
) ? void (0) : __assert_fail ("CurLoop->isLoopInvariant(BaseX) && \"Expected BaseX to be avaliable in the preheader!\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2263, __extension__
 __PRETTY_FUNCTION__))
       "Expected BaseX to be avaliable in the preheader!")(static_cast <bool> (CurLoop->isLoopInvariant(BaseX)
 && "Expected BaseX to be avaliable in the preheader!"
) ? void (0) : __assert_fail ("CurLoop->isLoopInvariant(BaseX) && \"Expected BaseX to be avaliable in the preheader!\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2263, __extension__
 __PRETTY_FUNCTION__));

if (!NextX || !match(NextX, m_Shl(m_Specific(CurrX), m_One()))) {
  // FIXME: support right-shift?
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad recurrence.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad recurrence.\n"
; } } while (false);
  return false;
}

// Step 4: Check if the backedge's destinations are in desirable form.

assert(ICmpInst::isEquality(Pred) &&(static_cast <bool> (ICmpInst::isEquality(Pred) &&
 "Should only get equality predicates here.") ? void (0) : __assert_fail
 ("ICmpInst::isEquality(Pred) && \"Should only get equality predicates here.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2274, __extension__
 __PRETTY_FUNCTION__))
       "Should only get equality predicates here.")(static_cast <bool> (ICmpInst::isEquality(Pred) &&
 "Should only get equality predicates here.") ? void (0) : __assert_fail
 ("ICmpInst::isEquality(Pred) && \"Should only get equality predicates here.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2274, __extension__
 __PRETTY_FUNCTION__));

// cmp-br is commutative, so canonicalize to a single variant.
if (Pred != ICmpInst::Predicate::ICMP_EQ) {
  Pred = ICmpInst::getInversePredicate(Pred);
  std::swap(TrueBB, FalseBB);
}

// We expect to exit loop when comparison yields false,
// so when it yields true we should branch back to loop header.
if (TrueBB != LoopHeaderBB) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad backedge flow.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad backedge flow.\n"
; } } while (false);
  return false;
}

// Okay, idiom checks out.
return true;
2291}

2293/// Look for the following loop:
2294/// \code
2295///   entry:
2296///     <...>
2297///     %bitmask = shl i32 1, %bitpos
2298///     br label %loop
2299///
2300///   loop:
2301///     %x.curr = phi i32 [ %x, %entry ], [ %x.next, %loop ]
2302///     %x.curr.bitmasked = and i32 %x.curr, %bitmask
2303///     %x.curr.isbitunset = icmp eq i32 %x.curr.bitmasked, 0
2304///     %x.next = shl i32 %x.curr, 1
2305///     <...>
2306///     br i1 %x.curr.isbitunset, label %loop, label %end
2307///
2308///   end:
2309///     %x.curr.res = phi i32 [ %x.curr, %loop ] <...>
2310///     %x.next.res = phi i32 [ %x.next, %loop ] <...>
2311///     <...>
2312/// \endcode
2313///
2314/// And transform it into:
2315/// \code
2316///   entry:
2317///     %bitmask = shl i32 1, %bitpos
2318///     %lowbitmask = add i32 %bitmask, -1
2319///     %mask = or i32 %lowbitmask, %bitmask
2320///     %x.masked = and i32 %x, %mask
2321///     %x.masked.numleadingzeros = call i32 @llvm.ctlz.i32(i32 %x.masked,
2322///                                                         i1 true)
2323///     %x.masked.numactivebits = sub i32 32, %x.masked.numleadingzeros
2324///     %x.masked.leadingonepos = add i32 %x.masked.numactivebits, -1
2325///     %backedgetakencount = sub i32 %bitpos, %x.masked.leadingonepos
2326///     %tripcount = add i32 %backedgetakencount, 1
2327///     %x.curr = shl i32 %x, %backedgetakencount
2328///     %x.next = shl i32 %x, %tripcount
2329///     br label %loop
2330///
2331///   loop:
2332///     %loop.iv = phi i32 [ 0, %entry ], [ %loop.iv.next, %loop ]
2333///     %loop.iv.next = add nuw i32 %loop.iv, 1
2334///     %loop.ivcheck = icmp eq i32 %loop.iv.next, %tripcount
2335///     <...>
2336///     br i1 %loop.ivcheck, label %end, label %loop
2337///
2338///   end:
2339///     %x.curr.res = phi i32 [ %x.curr, %loop ] <...>
2340///     %x.next.res = phi i32 [ %x.next, %loop ] <...>
2341///     <...>
2342/// \endcode
2343bool LoopIdiomRecognize::recognizeShiftUntilBitTest() {
bool MadeChange = false;

Value *X, *BitMask, *BitPos, *XCurr;
Instruction *XNext;
if (!detectShiftUntilBitTestIdiom(CurLoop, X, BitMask, BitPos, XCurr,
                                  XNext)) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-bittest idiom detection failed.\n"
; } } while (false)
             " shift-until-bittest idiom detection failed.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-bittest idiom detection failed.\n"
; } } while (false);
  return MadeChange;
}
LLVM_DEBUG(dbgs() << DEBUG_TYPE " shift-until-bittest idiom detected!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-bittest idiom detected!\n"
; } } while (false);

// Ok, it is the idiom we were looking for, we *could* transform this loop,
// but is it profitable to transform?

BasicBlock *LoopHeaderBB = CurLoop->getHeader();
BasicBlock *LoopPreheaderBB = CurLoop->getLoopPreheader();
assert(LoopPreheaderBB && "There is always a loop preheader.")(static_cast <bool> (LoopPreheaderBB && "There is always a loop preheader."
) ? void (0) : __assert_fail ("LoopPreheaderBB && \"There is always a loop preheader.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2361, __extension__
 __PRETTY_FUNCTION__));

BasicBlock *SuccessorBB = CurLoop->getExitBlock();
assert(SuccessorBB && "There is only a single successor.")(static_cast <bool> (SuccessorBB && "There is only a single successor."
) ? void (0) : __assert_fail ("SuccessorBB && \"There is only a single successor.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2364, __extension__
 __PRETTY_FUNCTION__));

IRBuilder<> Builder(LoopPreheaderBB->getTerminator());
Builder.SetCurrentDebugLocation(cast<Instruction>(XCurr)->getDebugLoc());

Intrinsic::ID IntrID = Intrinsic::ctlz;
Type *Ty = X->getType();
unsigned Bitwidth = Ty->getScalarSizeInBits();

TargetTransformInfo::TargetCostKind CostKind =
    TargetTransformInfo::TCK_SizeAndLatency;

// The rewrite is considered to be unprofitable iff and only iff the
// intrinsic/shift we'll use are not cheap. Note that we are okay with *just*
// making the loop countable, even if nothing else changes.
IntrinsicCostAttributes Attrs(
    IntrID, Ty, {UndefValue::get(Ty), /*is_zero_undef=*/Builder.getTrue()});
InstructionCost Cost = TTI->getIntrinsicInstrCost(Attrs, CostKind);
if (Cost > TargetTransformInfo::TCC_Basic) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Intrinsic is too costly, not beneficial\n"
; } } while (false)
             " Intrinsic is too costly, not beneficial\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Intrinsic is too costly, not beneficial\n"
; } } while (false);
  return MadeChange;
}
if (TTI->getArithmeticInstrCost(Instruction::Shl, Ty, CostKind) >
    TargetTransformInfo::TCC_Basic) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Shift is too costly, not beneficial\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Shift is too costly, not beneficial\n"
; } } while (false);
  return MadeChange;
}

// Ok, transform appears worthwhile.
MadeChange = true;

// Step 1: Compute the loop trip count.

Value *LowBitMask = Builder.CreateAdd(BitMask, Constant::getAllOnesValue(Ty),
                                      BitPos->getName() + ".lowbitmask");
Value *Mask =
    Builder.CreateOr(LowBitMask, BitMask, BitPos->getName() + ".mask");
Value *XMasked = Builder.CreateAnd(X, Mask, X->getName() + ".masked");
CallInst *XMaskedNumLeadingZeros = Builder.CreateIntrinsic(
    IntrID, Ty, {XMasked, /*is_zero_undef=*/Builder.getTrue()},
    /*FMFSource=*/nullptr, XMasked->getName() + ".numleadingzeros");
Value *XMaskedNumActiveBits = Builder.CreateSub(
    ConstantInt::get(Ty, Ty->getScalarSizeInBits()), XMaskedNumLeadingZeros,
    XMasked->getName() + ".numactivebits", /*HasNUW=*/true,
    /*HasNSW=*/Bitwidth != 2);
Value *XMaskedLeadingOnePos =
    Builder.CreateAdd(XMaskedNumActiveBits, Constant::getAllOnesValue(Ty),
                      XMasked->getName() + ".leadingonepos", /*HasNUW=*/false,
                      /*HasNSW=*/Bitwidth > 2);

Value *LoopBackedgeTakenCount = Builder.CreateSub(
    BitPos, XMaskedLeadingOnePos, CurLoop->getName() + ".backedgetakencount",
    /*HasNUW=*/true, /*HasNSW=*/true);
// We know loop's backedge-taken count, but what's loop's trip count?
// Note that while NUW is always safe, while NSW is only for bitwidths != 2.
Value *LoopTripCount =
    Builder.CreateAdd(LoopBackedgeTakenCount, ConstantInt::get(Ty, 1),
                      CurLoop->getName() + ".tripcount", /*HasNUW=*/true,
                      /*HasNSW=*/Bitwidth != 2);

// Step 2: Compute the recurrence's final value without a loop.

// NewX is always safe to compute, because `LoopBackedgeTakenCount`
// will always be smaller than `bitwidth(X)`, i.e. we never get poison.
Value *NewX = Builder.CreateShl(X, LoopBackedgeTakenCount);
NewX->takeName(XCurr);
if (auto *I = dyn_cast<Instruction>(NewX))
  I->copyIRFlags(XNext, /*IncludeWrapFlags=*/true);

Value *NewXNext;
// Rewriting XNext is more complicated, however, because `X << LoopTripCount`
// will be poison iff `LoopTripCount == bitwidth(X)` (which will happen
// iff `BitPos` is `bitwidth(x) - 1` and `X` is `1`). So unless we know
// that isn't the case, we'll need to emit an alternative, safe IR.
if (XNext->hasNoSignedWrap() || XNext->hasNoUnsignedWrap() ||
    PatternMatch::match(
        BitPos, PatternMatch::m_SpecificInt_ICMP(
                    ICmpInst::ICMP_NE, APInt(Ty->getScalarSizeInBits(),
                                             Ty->getScalarSizeInBits() - 1))))
  NewXNext = Builder.CreateShl(X, LoopTripCount);
else {
  // Otherwise, just additionally shift by one. It's the smallest solution,
  // alternatively, we could check that NewX is INT_MIN (or BitPos is )
  // and select 0 instead.
  NewXNext = Builder.CreateShl(NewX, ConstantInt::get(Ty, 1));
}

NewXNext->takeName(XNext);
if (auto *I = dyn_cast<Instruction>(NewXNext))
  I->copyIRFlags(XNext, /*IncludeWrapFlags=*/true);

// Step 3: Adjust the successor basic block to recieve the computed
//         recurrence's final value instead of the recurrence itself.

XCurr->replaceUsesOutsideBlock(NewX, LoopHeaderBB);
XNext->replaceUsesOutsideBlock(NewXNext, LoopHeaderBB);

// Step 4: Rewrite the loop into a countable form, with canonical IV.

// The new canonical induction variable.
Builder.SetInsertPoint(&LoopHeaderBB->front());
auto *IV = Builder.CreatePHI(Ty, 2, CurLoop->getName() + ".iv");

// The induction itself.
// Note that while NUW is always safe, while NSW is only for bitwidths != 2.
Builder.SetInsertPoint(LoopHeaderBB->getTerminator());
auto *IVNext =
    Builder.CreateAdd(IV, ConstantInt::get(Ty, 1), IV->getName() + ".next",
                      /*HasNUW=*/true, /*HasNSW=*/Bitwidth != 2);

// The loop trip count check.
auto *IVCheck = Builder.CreateICmpEQ(IVNext, LoopTripCount,
                                     CurLoop->getName() + ".ivcheck");
Builder.CreateCondBr(IVCheck, SuccessorBB, LoopHeaderBB);
LoopHeaderBB->getTerminator()->eraseFromParent();

// Populate the IV PHI.
IV->addIncoming(ConstantInt::get(Ty, 0), LoopPreheaderBB);
IV->addIncoming(IVNext, LoopHeaderBB);

// 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);

// Other passes will take care of actually deleting the loop if possible.

LLVM_DEBUG(dbgs() << DEBUG_TYPE " shift-until-bittest idiom optimized!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-bittest idiom optimized!\n"
; } } while (false);

++NumShiftUntilBitTest;
return MadeChange;
2496}

2498/// Return true if the idiom is detected in the loop.
2499///
2500/// The core idiom we are trying to detect is:
2501/// \code
2502///   entry:
2503///     <...>
2504///     %start = <...>
2505///     %extraoffset = <...>
2506///     <...>
2507///     br label %for.cond
2508///
2509///   loop:
2510///     %iv = phi i8 [ %start, %entry ], [ %iv.next, %for.cond ]
2511///     %nbits = add nsw i8 %iv, %extraoffset
2512///     %val.shifted = {{l,a}shr,shl} i8 %val, %nbits
2513///     %val.shifted.iszero = icmp eq i8 %val.shifted, 0
2514///     %iv.next = add i8 %iv, 1
2515///     <...>
2516///     br i1 %val.shifted.iszero, label %end, label %loop
2517///
2518///   end:
2519///     %iv.res = phi i8 [ %iv, %loop ] <...>
2520///     %nbits.res = phi i8 [ %nbits, %loop ] <...>
2521///     %val.shifted.res = phi i8 [ %val.shifted, %loop ] <...>
2522///     %val.shifted.iszero.res = phi i1 [ %val.shifted.iszero, %loop ] <...>
2523///     %iv.next.res = phi i8 [ %iv.next, %loop ] <...>
2524///     <...>
2525/// \endcode
2526static bool detectShiftUntilZeroIdiom(Loop *CurLoop, ScalarEvolution *SE,
                                    Instruction *&ValShiftedIsZero,
                                    Intrinsic::ID &IntrinID, Instruction *&IV,
                                    Value *&Start, Value *&Val,
                                    const SCEV *&ExtraOffsetExpr,
                                    bool &InvertedCond) {
LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Performing shift-until-zero idiom detection.\n"
; } } while (false)
           " Performing shift-until-zero idiom detection.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Performing shift-until-zero idiom detection.\n"
; } } while (false);

// Give up if the loop has multiple blocks or multiple backedges.
if (CurLoop->getNumBlocks() != 1 || CurLoop->getNumBackEdges() != 1) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad block/backedge count.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad block/backedge count.\n"
; } } while (false);
  return false;
}

Instruction *ValShifted, *NBits, *IVNext;
Value *ExtraOffset;

BasicBlock *LoopHeaderBB = CurLoop->getHeader();
BasicBlock *LoopPreheaderBB = CurLoop->getLoopPreheader();
assert(LoopPreheaderBB && "There is always a loop preheader.")(static_cast <bool> (LoopPreheaderBB && "There is always a loop preheader."
) ? void (0) : __assert_fail ("LoopPreheaderBB && \"There is always a loop preheader.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2546, __extension__
 __PRETTY_FUNCTION__));

using namespace PatternMatch;

// Step 1: Check if the loop backedge, condition is in desirable form.

ICmpInst::Predicate Pred;
BasicBlock *TrueBB, *FalseBB;
if (!match(LoopHeaderBB->getTerminator(),
           m_Br(m_Instruction(ValShiftedIsZero), m_BasicBlock(TrueBB),
                m_BasicBlock(FalseBB))) ||
    !match(ValShiftedIsZero,
           m_ICmp(Pred, m_Instruction(ValShifted), m_Zero())) ||
    !ICmpInst::isEquality(Pred)) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad backedge structure.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad backedge structure.\n"
; } } while (false);
  return false;
}

// Step 2: Check if the comparison's operand is in desirable form.
// FIXME: Val could be a one-input PHI node, which we should look past.
if (!match(ValShifted, m_Shift(m_LoopInvariant(m_Value(Val), CurLoop),
                               m_Instruction(NBits)))) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad comparisons value computation.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad comparisons value computation.\n"
; } } while (false);
  return false;
}
IntrinID = ValShifted->getOpcode() == Instruction::Shl ? Intrinsic::cttz
                                                       : Intrinsic::ctlz;

// Step 3: Check if the shift amount is in desirable form.

if (match(NBits, m_c_Add(m_Instruction(IV),
                         m_LoopInvariant(m_Value(ExtraOffset), CurLoop))) &&
    (NBits->hasNoSignedWrap() || NBits->hasNoUnsignedWrap()))
  ExtraOffsetExpr = SE->getNegativeSCEV(SE->getSCEV(ExtraOffset));
else if (match(NBits,
               m_Sub(m_Instruction(IV),
                     m_LoopInvariant(m_Value(ExtraOffset), CurLoop))) &&
         NBits->hasNoSignedWrap())
  ExtraOffsetExpr = SE->getSCEV(ExtraOffset);
else {
  IV = NBits;
  ExtraOffsetExpr = SE->getZero(NBits->getType());
}

// Step 4: Check if the recurrence is in desirable form.
auto *IVPN = dyn_cast<PHINode>(IV);
if (!IVPN || IVPN->getParent() != LoopHeaderBB) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Not an expected PHI node.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Not an expected PHI node.\n"
; } } while (false);
  return false;
}

Start = IVPN->getIncomingValueForBlock(LoopPreheaderBB);
IVNext = dyn_cast<Instruction>(IVPN->getIncomingValueForBlock(LoopHeaderBB));

if (!IVNext || !match(IVNext, m_Add(m_Specific(IVPN), m_One()))) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad recurrence.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad recurrence.\n"
; } } while (false);
  return false;
}

// Step 4: Check if the backedge's destinations are in desirable form.

assert(ICmpInst::isEquality(Pred) &&(static_cast <bool> (ICmpInst::isEquality(Pred) &&
 "Should only get equality predicates here.") ? void (0) : __assert_fail
 ("ICmpInst::isEquality(Pred) && \"Should only get equality predicates here.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2608, __extension__
 __PRETTY_FUNCTION__))
       "Should only get equality predicates here.")(static_cast <bool> (ICmpInst::isEquality(Pred) &&
 "Should only get equality predicates here.") ? void (0) : __assert_fail
 ("ICmpInst::isEquality(Pred) && \"Should only get equality predicates here.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2608, __extension__
 __PRETTY_FUNCTION__));

// cmp-br is commutative, so canonicalize to a single variant.
InvertedCond = Pred != ICmpInst::Predicate::ICMP_EQ;
if (InvertedCond) {
  Pred = ICmpInst::getInversePredicate(Pred);
  std::swap(TrueBB, FalseBB);
}

// We expect to exit loop when comparison yields true,
// so when it yields false we should branch back to loop header.
if (FalseBB != LoopHeaderBB) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Bad backedge flow.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Bad backedge flow.\n"
; } } while (false);
  return false;
}

// The new, countable, loop will certainly only run a known number of
// iterations, It won't be infinite. But the old loop might be infinite
// under certain conditions. For logical shifts, the value will become zero
// after at most bitwidth(%Val) loop iterations. However, for arithmetic
// right-shift, iff the sign bit was set, the value will never become zero,
// and the loop may never finish.
if (ValShifted->getOpcode() == Instruction::AShr &&
    !isMustProgress(CurLoop) && !SE->isKnownNonNegative(SE->getSCEV(Val))) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Can not prove the loop is finite.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Can not prove the loop is finite.\n"
; } } while (false);
  return false;
}

// Okay, idiom checks out.
return true;
2638}

2640/// Look for the following loop:
2641/// \code
2642///   entry:
2643///     <...>
2644///     %start = <...>
2645///     %extraoffset = <...>
2646///     <...>
2647///     br label %for.cond
2648///
2649///   loop:
2650///     %iv = phi i8 [ %start, %entry ], [ %iv.next, %for.cond ]
2651///     %nbits = add nsw i8 %iv, %extraoffset
2652///     %val.shifted = {{l,a}shr,shl} i8 %val, %nbits
2653///     %val.shifted.iszero = icmp eq i8 %val.shifted, 0
2654///     %iv.next = add i8 %iv, 1
2655///     <...>
2656///     br i1 %val.shifted.iszero, label %end, label %loop
2657///
2658///   end:
2659///     %iv.res = phi i8 [ %iv, %loop ] <...>
2660///     %nbits.res = phi i8 [ %nbits, %loop ] <...>
2661///     %val.shifted.res = phi i8 [ %val.shifted, %loop ] <...>
2662///     %val.shifted.iszero.res = phi i1 [ %val.shifted.iszero, %loop ] <...>
2663///     %iv.next.res = phi i8 [ %iv.next, %loop ] <...>
2664///     <...>
2665/// \endcode
2666///
2667/// And transform it into:
2668/// \code
2669///   entry:
2670///     <...>
2671///     %start = <...>
2672///     %extraoffset = <...>
2673///     <...>
2674///     %val.numleadingzeros = call i8 @llvm.ct{l,t}z.i8(i8 %val, i1 0)
2675///     %val.numactivebits = sub i8 8, %val.numleadingzeros
2676///     %extraoffset.neg = sub i8 0, %extraoffset
2677///     %tmp = add i8 %val.numactivebits, %extraoffset.neg
2678///     %iv.final = call i8 @llvm.smax.i8(i8 %tmp, i8 %start)
2679///     %loop.tripcount = sub i8 %iv.final, %start
2680///     br label %loop
2681///
2682///   loop:
2683///     %loop.iv = phi i8 [ 0, %entry ], [ %loop.iv.next, %loop ]
2684///     %loop.iv.next = add i8 %loop.iv, 1
2685///     %loop.ivcheck = icmp eq i8 %loop.iv.next, %loop.tripcount
2686///     %iv = add i8 %loop.iv, %start
2687///     <...>
2688///     br i1 %loop.ivcheck, label %end, label %loop
2689///
2690///   end:
2691///     %iv.res = phi i8 [ %iv.final, %loop ] <...>
2692///     <...>
2693/// \endcode
2694bool LoopIdiomRecognize::recognizeShiftUntilZero() {
bool MadeChange = false;

Instruction *ValShiftedIsZero;
Intrinsic::ID IntrID;
Instruction *IV;
Value *Start, *Val;
const SCEV *ExtraOffsetExpr;
bool InvertedCond;
if (!detectShiftUntilZeroIdiom(CurLoop, SE, ValShiftedIsZero, IntrID, IV,
                               Start, Val, ExtraOffsetExpr, InvertedCond)) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-zero idiom detection failed.\n"
; } } while (false)
             " shift-until-zero idiom detection failed.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-zero idiom detection failed.\n"
; } } while (false);
  return MadeChange;
}
LLVM_DEBUG(dbgs() << DEBUG_TYPE " shift-until-zero idiom detected!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-zero idiom detected!\n"
; } } while (false);

// Ok, it is the idiom we were looking for, we *could* transform this loop,
// but is it profitable to transform?

BasicBlock *LoopHeaderBB = CurLoop->getHeader();
BasicBlock *LoopPreheaderBB = CurLoop->getLoopPreheader();
assert(LoopPreheaderBB && "There is always a loop preheader.")(static_cast <bool> (LoopPreheaderBB && "There is always a loop preheader."
) ? void (0) : __assert_fail ("LoopPreheaderBB && \"There is always a loop preheader.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2716, __extension__
 __PRETTY_FUNCTION__));

BasicBlock *SuccessorBB = CurLoop->getExitBlock();
assert(SuccessorBB && "There is only a single successor.")(static_cast <bool> (SuccessorBB && "There is only a single successor."
) ? void (0) : __assert_fail ("SuccessorBB && \"There is only a single successor.\""
, "llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp", 2719, __extension__
 __PRETTY_FUNCTION__));

IRBuilder<> Builder(LoopPreheaderBB->getTerminator());
Builder.SetCurrentDebugLocation(IV->getDebugLoc());

Type *Ty = Val->getType();
unsigned Bitwidth = Ty->getScalarSizeInBits();

TargetTransformInfo::TargetCostKind CostKind =
    TargetTransformInfo::TCK_SizeAndLatency;

// The rewrite is considered to be unprofitable iff and only iff the
// intrinsic we'll use are not cheap. Note that we are okay with *just*
// making the loop countable, even if nothing else changes.
IntrinsicCostAttributes Attrs(
    IntrID, Ty, {UndefValue::get(Ty), /*is_zero_undef=*/Builder.getFalse()});
InstructionCost Cost = TTI->getIntrinsicInstrCost(Attrs, CostKind);
if (Cost > TargetTransformInfo::TCC_Basic) {
  LLVM_DEBUG(dbgs() << DEBUG_TYPEdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Intrinsic is too costly, not beneficial\n"
; } } while (false)
             " Intrinsic is too costly, not beneficial\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " Intrinsic is too costly, not beneficial\n"
; } } while (false);
  return MadeChange;
}

// Ok, transform appears worthwhile.
MadeChange = true;

bool OffsetIsZero = false;
if (auto *ExtraOffsetExprC = dyn_cast<SCEVConstant>(ExtraOffsetExpr))
  OffsetIsZero = ExtraOffsetExprC->isZero();

// Step 1: Compute the loop's final IV value / trip count.

CallInst *ValNumLeadingZeros = Builder.CreateIntrinsic(
    IntrID, Ty, {Val, /*is_zero_undef=*/Builder.getFalse()},
    /*FMFSource=*/nullptr, Val->getName() + ".numleadingzeros");
Value *ValNumActiveBits = Builder.CreateSub(
    ConstantInt::get(Ty, Ty->getScalarSizeInBits()), ValNumLeadingZeros,
    Val->getName() + ".numactivebits", /*HasNUW=*/true,
    /*HasNSW=*/Bitwidth != 2);

SCEVExpander Expander(*SE, *DL, "loop-idiom");
Expander.setInsertPoint(&*Builder.GetInsertPoint());
Value *ExtraOffset = Expander.expandCodeFor(ExtraOffsetExpr);

Value *ValNumActiveBitsOffset = Builder.CreateAdd(
    ValNumActiveBits, ExtraOffset, ValNumActiveBits->getName() + ".offset",
    /*HasNUW=*/OffsetIsZero, /*HasNSW=*/true);
Value *IVFinal = Builder.CreateIntrinsic(Intrinsic::smax, {Ty},
                                         {ValNumActiveBitsOffset, Start},
                                         /*FMFSource=*/nullptr, "iv.final");

auto *LoopBackedgeTakenCount = cast<Instruction>(Builder.CreateSub(
    IVFinal, Start, CurLoop->getName() + ".backedgetakencount",
    /*HasNUW=*/OffsetIsZero, /*HasNSW=*/true));
// FIXME: or when the offset was `add nuw`

// We know loop's backedge-taken count, but what's loop's trip count?
Value *LoopTripCount =
    Builder.CreateAdd(LoopBackedgeTakenCount, ConstantInt::get(Ty, 1),
                      CurLoop->getName() + ".tripcount", /*HasNUW=*/true,
                      /*HasNSW=*/Bitwidth != 2);

// Step 2: Adjust the successor basic block to recieve the original
//         induction variable's final value instead of the orig. IV itself.

IV->replaceUsesOutsideBlock(IVFinal, LoopHeaderBB);

// Step 3: Rewrite the loop into a countable form, with canonical IV.

// The new canonical induction variable.
Builder.SetInsertPoint(&LoopHeaderBB->front());
auto *CIV = Builder.CreatePHI(Ty, 2, CurLoop->getName() + ".iv");

// The induction itself.
Builder.SetInsertPoint(LoopHeaderBB->getFirstNonPHI());
auto *CIVNext =
    Builder.CreateAdd(CIV, ConstantInt::get(Ty, 1), CIV->getName() + ".next",
                      /*HasNUW=*/true, /*HasNSW=*/Bitwidth != 2);

// The loop trip count check.
auto *CIVCheck = Builder.CreateICmpEQ(CIVNext, LoopTripCount,
                                      CurLoop->getName() + ".ivcheck");
auto *NewIVCheck = CIVCheck;
if (InvertedCond) {
  NewIVCheck = Builder.CreateNot(CIVCheck);
  NewIVCheck->takeName(ValShiftedIsZero);
}

// The original IV, but rebased to be an offset to the CIV.
auto *IVDePHId = Builder.CreateAdd(CIV, Start, "", /*HasNUW=*/false,
                                   /*HasNSW=*/true); // FIXME: what about NUW?
IVDePHId->takeName(IV);

// The loop terminator.
Builder.SetInsertPoint(LoopHeaderBB->getTerminator());
Builder.CreateCondBr(CIVCheck, SuccessorBB, LoopHeaderBB);
LoopHeaderBB->getTerminator()->eraseFromParent();

// Populate the IV PHI.
CIV->addIncoming(ConstantInt::get(Ty, 0), LoopPreheaderBB);
CIV->addIncoming(CIVNext, LoopHeaderBB);

// 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);

// Step 5: Try to cleanup the loop's body somewhat.
IV->replaceAllUsesWith(IVDePHId);
IV->eraseFromParent();

ValShiftedIsZero->replaceAllUsesWith(NewIVCheck);
ValShiftedIsZero->eraseFromParent();

// Other passes will take care of actually deleting the loop if possible.

LLVM_DEBUG(dbgs() << DEBUG_TYPE " shift-until-zero idiom optimized!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-idiom")) { dbgs() << "loop-idiom" " shift-until-zero idiom optimized!\n"
; } } while (false);

++NumShiftUntilZero;
return MadeChange;
2839}