/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp

Bug Summary

File:	llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
Warning:	line 1549, column 28 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 -disable-llvm-verifier -discard-value-names -main-file-name MemCpyOptimizer.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -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 -fhalf-no-semantic-interposition -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-13/lib/clang/13.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/build-llvm/include -I /build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-13/lib/clang/13.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/build-llvm/lib/Transforms/Scalar -fdebug-prefix-map=/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2021-02-22-143117-42893-1 -x c++ /build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
1//===- MemCpyOptimizer.cpp - Optimize use of memcpy and friends -----------===//
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 performs various transformations related to eliminating memcpy
10// calls, or transforming sets of stores into memset's.
11//
12//===----------------------------------------------------------------------===//

14#include "llvm/Transforms/Scalar/MemCpyOptimizer.h"
15#include "llvm/ADT/DenseSet.h"
16#include "llvm/ADT/None.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallVector.h"
19#include "llvm/ADT/Statistic.h"
20#include "llvm/ADT/iterator_range.h"
21#include "llvm/Analysis/AliasAnalysis.h"
22#include "llvm/Analysis/AssumptionCache.h"
23#include "llvm/Analysis/GlobalsModRef.h"
24#include "llvm/Analysis/Loads.h"
25#include "llvm/Analysis/MemoryDependenceAnalysis.h"
26#include "llvm/Analysis/MemoryLocation.h"
27#include "llvm/Analysis/MemorySSA.h"
28#include "llvm/Analysis/MemorySSAUpdater.h"
29#include "llvm/Analysis/TargetLibraryInfo.h"
30#include "llvm/Analysis/ValueTracking.h"
31#include "llvm/IR/Argument.h"
32#include "llvm/IR/BasicBlock.h"
33#include "llvm/IR/Constants.h"
34#include "llvm/IR/DataLayout.h"
35#include "llvm/IR/DerivedTypes.h"
36#include "llvm/IR/Dominators.h"
37#include "llvm/IR/Function.h"
38#include "llvm/IR/GetElementPtrTypeIterator.h"
39#include "llvm/IR/GlobalVariable.h"
40#include "llvm/IR/IRBuilder.h"
41#include "llvm/IR/InstrTypes.h"
42#include "llvm/IR/Instruction.h"
43#include "llvm/IR/Instructions.h"
44#include "llvm/IR/IntrinsicInst.h"
45#include "llvm/IR/Intrinsics.h"
46#include "llvm/IR/LLVMContext.h"
47#include "llvm/IR/Module.h"
48#include "llvm/IR/Operator.h"
49#include "llvm/IR/PassManager.h"
50#include "llvm/IR/Type.h"
51#include "llvm/IR/User.h"
52#include "llvm/IR/Value.h"
53#include "llvm/InitializePasses.h"
54#include "llvm/Pass.h"
55#include "llvm/Support/Casting.h"
56#include "llvm/Support/Debug.h"
57#include "llvm/Support/MathExtras.h"
58#include "llvm/Support/raw_ostream.h"
59#include "llvm/Transforms/Scalar.h"
60#include "llvm/Transforms/Utils/Local.h"
61#include <algorithm>
62#include <cassert>
63#include <cstdint>
64#include <utility>

66using namespace llvm;

68#define DEBUG_TYPE"memcpyopt" "memcpyopt"

70static cl::opt<bool>
  EnableMemorySSA("enable-memcpyopt-memoryssa", cl::init(true), cl::Hidden,
                  cl::desc("Use MemorySSA-backed MemCpyOpt."));

74STATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted")static llvm::Statistic NumMemCpyInstr = {"memcpyopt", "NumMemCpyInstr"
, "Number of memcpy instructions deleted"};
75STATISTIC(NumMemSetInfer, "Number of memsets inferred")static llvm::Statistic NumMemSetInfer = {"memcpyopt", "NumMemSetInfer"
, "Number of memsets inferred"};
76STATISTIC(NumMoveToCpy,   "Number of memmoves converted to memcpy")static llvm::Statistic NumMoveToCpy = {"memcpyopt", "NumMoveToCpy"
, "Number of memmoves converted to memcpy"};
77STATISTIC(NumCpyToSet,    "Number of memcpys converted to memset")static llvm::Statistic NumCpyToSet = {"memcpyopt", "NumCpyToSet"
, "Number of memcpys converted to memset"};
78STATISTIC(NumCallSlot,    "Number of call slot optimizations performed")static llvm::Statistic NumCallSlot = {"memcpyopt", "NumCallSlot"
, "Number of call slot optimizations performed"};

80namespace {

82/// Represents a range of memset'd bytes with the ByteVal value.
83/// This allows us to analyze stores like:
84///   store 0 -> P+1
85///   store 0 -> P+0
86///   store 0 -> P+3
87///   store 0 -> P+2
88/// which sometimes happens with stores to arrays of structs etc.  When we see
89/// the first store, we make a range [1, 2).  The second store extends the range
90/// to [0, 2).  The third makes a new range [2, 3).  The fourth store joins the
91/// two ranges into [0, 3) which is memset'able.
92struct MemsetRange {
// Start/End - A semi range that describes the span that this range covers.
// The range is closed at the start and open at the end: [Start, End).
int64_t Start, End;

/// StartPtr - The getelementptr instruction that points to the start of the
/// range.
Value *StartPtr;

/// Alignment - The known alignment of the first store.
unsigned Alignment;

/// TheStores - The actual stores that make up this range.
SmallVector<Instruction*, 16> TheStores;

bool isProfitableToUseMemset(const DataLayout &DL) const;
108};

110} // end anonymous namespace

112bool MemsetRange::isProfitableToUseMemset(const DataLayout &DL) const {
// If we found more than 4 stores to merge or 16 bytes, use memset.
if (TheStores.size() >= 4 || End-Start >= 16) return true;

// If there is nothing to merge, don't do anything.
if (TheStores.size() < 2) return false;

// If any of the stores are a memset, then it is always good to extend the
// memset.
for (Instruction *SI : TheStores)
  if (!isa<StoreInst>(SI))
    return true;

// Assume that the code generator is capable of merging pairs of stores
// together if it wants to.
if (TheStores.size() == 2) return false;

// If we have fewer than 8 stores, it can still be worthwhile to do this.
// For example, merging 4 i8 stores into an i32 store is useful almost always.
// However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the
// memset will be split into 2 32-bit stores anyway) and doing so can
// pessimize the llvm optimizer.
//
// Since we don't have perfect knowledge here, make some assumptions: assume
// the maximum GPR width is the same size as the largest legal integer
// size. If so, check to see whether we will end up actually reducing the
// number of stores used.
unsigned Bytes = unsigned(End-Start);
unsigned MaxIntSize = DL.getLargestLegalIntTypeSizeInBits() / 8;
if (MaxIntSize == 0)
  MaxIntSize = 1;
unsigned NumPointerStores = Bytes / MaxIntSize;

// Assume the remaining bytes if any are done a byte at a time.
unsigned NumByteStores = Bytes % MaxIntSize;

// If we will reduce the # stores (according to this heuristic), do the
// transformation.  This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32
// etc.
return TheStores.size() > NumPointerStores+NumByteStores;
152}

154namespace {

156class MemsetRanges {
using range_iterator = SmallVectorImpl<MemsetRange>::iterator;

/// A sorted list of the memset ranges.
SmallVector<MemsetRange, 8> Ranges;

const DataLayout &DL;

164public:
MemsetRanges(const DataLayout &DL) : DL(DL) {}

using const_iterator = SmallVectorImpl<MemsetRange>::const_iterator;

const_iterator begin() const { return Ranges.begin(); }
const_iterator end() const { return Ranges.end(); }
bool empty() const { return Ranges.empty(); }

void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
  if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
    addStore(OffsetFromFirst, SI);
  else
    addMemSet(OffsetFromFirst, cast<MemSetInst>(Inst));
}

void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
  int64_t StoreSize = DL.getTypeStoreSize(SI->getOperand(0)->getType());

  addRange(OffsetFromFirst, StoreSize, SI->getPointerOperand(),
           SI->getAlign().value(), SI);
}

void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
  int64_t Size = cast<ConstantInt>(MSI->getLength())->getZExtValue();
  addRange(OffsetFromFirst, Size, MSI->getDest(), MSI->getDestAlignment(), MSI);
}

void addRange(int64_t Start, int64_t Size, Value *Ptr,
              unsigned Alignment, Instruction *Inst);
194};

196} // end anonymous namespace

198/// Add a new store to the MemsetRanges data structure.  This adds a
199/// new range for the specified store at the specified offset, merging into
200/// existing ranges as appropriate.
201void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
                          unsigned Alignment, Instruction *Inst) {
int64_t End = Start+Size;

range_iterator I = partition_point(
    Ranges, [=](const MemsetRange &O) { return O.End < Start; });

// We now know that I == E, in which case we didn't find anything to merge
// with, or that Start <= I->End.  If End < I->Start or I == E, then we need
// to insert a new range.  Handle this now.
if (I == Ranges.end() || End < I->Start) {
  MemsetRange &R = *Ranges.insert(I, MemsetRange());
  R.Start        = Start;
  R.End          = End;
  R.StartPtr     = Ptr;
  R.Alignment    = Alignment;
  R.TheStores.push_back(Inst);
  return;
}

// This store overlaps with I, add it.
I->TheStores.push_back(Inst);

// At this point, we may have an interval that completely contains our store.
// If so, just add it to the interval and return.
if (I->Start <= Start && I->End >= End)
  return;

// Now we know that Start <= I->End and End >= I->Start so the range overlaps
// but is not entirely contained within the range.

// See if the range extends the start of the range.  In this case, it couldn't
// possibly cause it to join the prior range, because otherwise we would have
// stopped on *it*.
if (Start < I->Start) {
  I->Start = Start;
  I->StartPtr = Ptr;
  I->Alignment = Alignment;
}

// Now we know that Start <= I->End and Start >= I->Start (so the startpoint
// is in or right at the end of I), and that End >= I->Start.  Extend I out to
// End.
if (End > I->End) {
  I->End = End;
  range_iterator NextI = I;
  while (++NextI != Ranges.end() && End >= NextI->Start) {
    // Merge the range in.
    I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end());
    if (NextI->End > I->End)
      I->End = NextI->End;
    Ranges.erase(NextI);
    NextI = I;
  }
}
256}

258//===----------------------------------------------------------------------===//
259//                         MemCpyOptLegacyPass Pass
260//===----------------------------------------------------------------------===//

262namespace {

264class MemCpyOptLegacyPass : public FunctionPass {
MemCpyOptPass Impl;

267public:
static char ID; // Pass identification, replacement for typeid

MemCpyOptLegacyPass() : FunctionPass(ID) {
  initializeMemCpyOptLegacyPassPass(*PassRegistry::getPassRegistry());
}

bool runOnFunction(Function &F) override;

276private:
// This transformation requires dominator postdominator info
void getAnalysisUsage(AnalysisUsage &AU) const override {
  AU.setPreservesCFG();
  AU.addRequired<AssumptionCacheTracker>();
  AU.addRequired<DominatorTreeWrapperPass>();
  AU.addPreserved<DominatorTreeWrapperPass>();
  AU.addPreserved<GlobalsAAWrapperPass>();
  AU.addRequired<TargetLibraryInfoWrapperPass>();
  if (!EnableMemorySSA)
    AU.addRequired<MemoryDependenceWrapperPass>();
  AU.addPreserved<MemoryDependenceWrapperPass>();
  AU.addRequired<AAResultsWrapperPass>();
  AU.addPreserved<AAResultsWrapperPass>();
  if (EnableMemorySSA)
    AU.addRequired<MemorySSAWrapperPass>();
  AU.addPreserved<MemorySSAWrapperPass>();
}
294};

296} // end anonymous namespace

298char MemCpyOptLegacyPass::ID = 0;

300/// The public interface to this file...
301FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOptLegacyPass(); }

303INITIALIZE_PASS_BEGIN(MemCpyOptLegacyPass, "memcpyopt", "MemCpy Optimization",static void *initializeMemCpyOptLegacyPassPassOnce(PassRegistry
 &Registry) {
                    false, false)static void *initializeMemCpyOptLegacyPassPassOnce(PassRegistry
 &Registry) {
305INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry);
306INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
307INITIALIZE_PASS_DEPENDENCY(MemoryDependenceWrapperPass)initializeMemoryDependenceWrapperPassPass(Registry);
308INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry);
309INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry);
310INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)initializeGlobalsAAWrapperPassPass(Registry);
311INITIALIZE_PASS_END(MemCpyOptLegacyPass, "memcpyopt", "MemCpy Optimization",PassInfo *PI = new PassInfo( "MemCpy Optimization", "memcpyopt"
, &MemCpyOptLegacyPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemCpyOptLegacyPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemCpyOptLegacyPassPassFlag
; void llvm::initializeMemCpyOptLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemCpyOptLegacyPassPassFlag
, initializeMemCpyOptLegacyPassPassOnce, std::ref(Registry));
 }
                  false, false)PassInfo *PI = new PassInfo( "MemCpy Optimization", "memcpyopt"
, &MemCpyOptLegacyPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemCpyOptLegacyPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemCpyOptLegacyPassPassFlag
; void llvm::initializeMemCpyOptLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemCpyOptLegacyPassPassFlag
, initializeMemCpyOptLegacyPassPassOnce, std::ref(Registry));
 }

314// Check that V is either not accessible by the caller, or unwinding cannot
315// occur between Start and End.
316static bool mayBeVisibleThroughUnwinding(Value *V, Instruction *Start,
                                       Instruction *End) {
assert(Start->getParent() == End->getParent() && "Must be in same block")((Start->getParent() == End->getParent() && "Must be in same block"
) ? static_cast<void> (0) : __assert_fail ("Start->getParent() == End->getParent() && \"Must be in same block\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 318, __PRETTY_FUNCTION__));
if (!Start->getFunction()->doesNotThrow() &&
    !isa<AllocaInst>(getUnderlyingObject(V))) {
  for (const Instruction &I :
       make_range(Start->getIterator(), End->getIterator())) {
    if (I.mayThrow())
      return true;
  }
}
return false;
328}

330void MemCpyOptPass::eraseInstruction(Instruction *I) {
if (MSSAU)
  MSSAU->removeMemoryAccess(I);
if (MD)
  MD->removeInstruction(I);
I->eraseFromParent();
336}

338// Check for mod or ref of Loc between Start and End, excluding both boundaries.
339// Start and End must be in the same block
340static bool accessedBetween(AliasAnalysis &AA, MemoryLocation Loc,
                          const MemoryUseOrDef *Start,
                          const MemoryUseOrDef *End) {
assert(Start->getBlock() == End->getBlock() && "Only local supported")((Start->getBlock() == End->getBlock() && "Only local supported"
) ? static_cast<void> (0) : __assert_fail ("Start->getBlock() == End->getBlock() && \"Only local supported\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 343, __PRETTY_FUNCTION__));
for (const MemoryAccess &MA :
     make_range(++Start->getIterator(), End->getIterator())) {
  if (isModOrRefSet(AA.getModRefInfo(cast<MemoryUseOrDef>(MA).getMemoryInst(),
                                     Loc)))
    return true;
}
return false;
351}

353// Check for mod of Loc between Start and End, excluding both boundaries.
354// Start and End can be in different blocks.
355static bool writtenBetween(MemorySSA *MSSA, MemoryLocation Loc,
                         const MemoryUseOrDef *Start,
                         const MemoryUseOrDef *End) {
// TODO: Only walk until we hit Start.
MemoryAccess *Clobber = MSSA->getWalker()->getClobberingMemoryAccess(
    End->getDefiningAccess(), Loc);
return !MSSA->dominates(Clobber, Start);
362}

364/// When scanning forward over instructions, we look for some other patterns to
365/// fold away. In particular, this looks for stores to neighboring locations of
366/// memory. If it sees enough consecutive ones, it attempts to merge them
367/// together into a memcpy/memset.
368Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
                                               Value *StartPtr,
                                               Value *ByteVal) {
const DataLayout &DL = StartInst->getModule()->getDataLayout();

// Okay, so we now have a single store that can be splatable.  Scan to find
// all subsequent stores of the same value to offset from the same pointer.
// Join these together into ranges, so we can decide whether contiguous blocks
// are stored.
MemsetRanges Ranges(DL);

BasicBlock::iterator BI(StartInst);

// Keeps track of the last memory use or def before the insertion point for
// the new memset. The new MemoryDef for the inserted memsets will be inserted
// after MemInsertPoint. It points to either LastMemDef or to the last user
// before the insertion point of the memset, if there are any such users.
MemoryUseOrDef *MemInsertPoint = nullptr;
// Keeps track of the last MemoryDef between StartInst and the insertion point
// for the new memset. This will become the defining access of the inserted
// memsets.
MemoryDef *LastMemDef = nullptr;
for (++BI; !BI->isTerminator(); ++BI) {
  if (MSSAU) {
    auto *CurrentAcc = cast_or_null<MemoryUseOrDef>(
        MSSAU->getMemorySSA()->getMemoryAccess(&*BI));
    if (CurrentAcc) {
      MemInsertPoint = CurrentAcc;
      if (auto *CurrentDef = dyn_cast<MemoryDef>(CurrentAcc))
        LastMemDef = CurrentDef;
    }
  }

  if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
    // If the instruction is readnone, ignore it, otherwise bail out.  We
    // don't even allow readonly here because we don't want something like:
    // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
    if (BI->mayWriteToMemory() || BI->mayReadFromMemory())
      break;
    continue;
  }

  if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
    // If this is a store, see if we can merge it in.
    if (!NextStore->isSimple()) break;

    Value *StoredVal = NextStore->getValueOperand();

    // Don't convert stores of non-integral pointer types to memsets (which
    // stores integers).
    if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()))
      break;

    // Check to see if this stored value is of the same byte-splattable value.
    Value *StoredByte = isBytewiseValue(StoredVal, DL);
    if (isa<UndefValue>(ByteVal) && StoredByte)
      ByteVal = StoredByte;
    if (ByteVal != StoredByte)
      break;

    // Check to see if this store is to a constant offset from the start ptr.
    Optional<int64_t> Offset =
        isPointerOffset(StartPtr, NextStore->getPointerOperand(), DL);
    if (!Offset)
      break;

    Ranges.addStore(*Offset, NextStore);
  } else {
    MemSetInst *MSI = cast<MemSetInst>(BI);

    if (MSI->isVolatile() || ByteVal != MSI->getValue() ||
        !isa<ConstantInt>(MSI->getLength()))
      break;

    // Check to see if this store is to a constant offset from the start ptr.
    Optional<int64_t> Offset = isPointerOffset(StartPtr, MSI->getDest(), DL);
    if (!Offset)
      break;

    Ranges.addMemSet(*Offset, MSI);
  }
}

// If we have no ranges, then we just had a single store with nothing that
// could be merged in.  This is a very common case of course.
if (Ranges.empty())
  return nullptr;

// If we had at least one store that could be merged in, add the starting
// store as well.  We try to avoid this unless there is at least something
// interesting as a small compile-time optimization.
Ranges.addInst(0, StartInst);

// If we create any memsets, we put it right before the first instruction that
// isn't part of the memset block.  This ensure that the memset is dominated
// by any addressing instruction needed by the start of the block.
IRBuilder<> Builder(&*BI);

// Now that we have full information about ranges, loop over the ranges and
// emit memset's for anything big enough to be worthwhile.
Instruction *AMemSet = nullptr;
for (const MemsetRange &Range : Ranges) {
  if (Range.TheStores.size() == 1) continue;

  // If it is profitable to lower this range to memset, do so now.
  if (!Range.isProfitableToUseMemset(DL))
    continue;

  // Otherwise, we do want to transform this!  Create a new memset.
  // Get the starting pointer of the block.
  StartPtr = Range.StartPtr;

  AMemSet = Builder.CreateMemSet(StartPtr, ByteVal, Range.End - Range.Start,
                                 MaybeAlign(Range.Alignment));
  LLVM_DEBUG(dbgs() << "Replace stores:\n"; for (Instruction *SIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Replace stores:\n"; for (Instruction
 *SI : Range.TheStores) dbgs() << *SI << '\n'; dbgs
() << "With: " << *AMemSet << '\n'; } } while
 (false)
                                                 : Range.TheStores) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Replace stores:\n"; for (Instruction
 *SI : Range.TheStores) dbgs() << *SI << '\n'; dbgs
() << "With: " << *AMemSet << '\n'; } } while
 (false)
                                            << *SI << '\n';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Replace stores:\n"; for (Instruction
 *SI : Range.TheStores) dbgs() << *SI << '\n'; dbgs
() << "With: " << *AMemSet << '\n'; } } while
 (false)
             dbgs() << "With: " << *AMemSet << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Replace stores:\n"; for (Instruction
 *SI : Range.TheStores) dbgs() << *SI << '\n'; dbgs
() << "With: " << *AMemSet << '\n'; } } while
 (false);
  if (!Range.TheStores.empty())
    AMemSet->setDebugLoc(Range.TheStores[0]->getDebugLoc());

  if (MSSAU) {
    assert(LastMemDef && MemInsertPoint &&((LastMemDef && MemInsertPoint && "Both LastMemDef and MemInsertPoint need to be set"
) ? static_cast<void> (0) : __assert_fail ("LastMemDef && MemInsertPoint && \"Both LastMemDef and MemInsertPoint need to be set\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 491, __PRETTY_FUNCTION__))
           "Both LastMemDef and MemInsertPoint need to be set")((LastMemDef && MemInsertPoint && "Both LastMemDef and MemInsertPoint need to be set"
) ? static_cast<void> (0) : __assert_fail ("LastMemDef && MemInsertPoint && \"Both LastMemDef and MemInsertPoint need to be set\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 491, __PRETTY_FUNCTION__));
    auto *NewDef =
        cast<MemoryDef>(MemInsertPoint->getMemoryInst() == &*BI
                            ? MSSAU->createMemoryAccessBefore(
                                  AMemSet, LastMemDef, MemInsertPoint)
                            : MSSAU->createMemoryAccessAfter(
                                  AMemSet, LastMemDef, MemInsertPoint));
    MSSAU->insertDef(NewDef, /*RenameUses=*/true);
    LastMemDef = NewDef;
    MemInsertPoint = NewDef;
  }

  // Zap all the stores.
  for (Instruction *SI : Range.TheStores)
    eraseInstruction(SI);

  ++NumMemSetInfer;
}

return AMemSet;
511}

513// This method try to lift a store instruction before position P.
514// It will lift the store and its argument + that anything that
515// may alias with these.
516// The method returns true if it was successful.
517bool MemCpyOptPass::moveUp(StoreInst *SI, Instruction *P, const LoadInst *LI) {
// If the store alias this position, early bail out.
MemoryLocation StoreLoc = MemoryLocation::get(SI);
if (isModOrRefSet(AA->getModRefInfo(P, StoreLoc)))
  return false;

// Keep track of the arguments of all instruction we plan to lift
// so we can make sure to lift them as well if appropriate.
DenseSet<Instruction*> Args;
if (auto *Ptr = dyn_cast<Instruction>(SI->getPointerOperand()))
  if (Ptr->getParent() == SI->getParent())
    Args.insert(Ptr);

// Instruction to lift before P.
SmallVector<Instruction *, 8> ToLift{SI};

// Memory locations of lifted instructions.
SmallVector<MemoryLocation, 8> MemLocs{StoreLoc};

// Lifted calls.
SmallVector<const CallBase *, 8> Calls;

const MemoryLocation LoadLoc = MemoryLocation::get(LI);

for (auto I = --SI->getIterator(), E = P->getIterator(); I != E; --I) {
  auto *C = &*I;

  // Make sure hoisting does not perform a store that was not guaranteed to
  // happen.
  if (!isGuaranteedToTransferExecutionToSuccessor(C))
    return false;

  bool MayAlias = isModOrRefSet(AA->getModRefInfo(C, None));

  bool NeedLift = false;
  if (Args.erase(C))
    NeedLift = true;
  else if (MayAlias) {
    NeedLift = llvm::any_of(MemLocs, [C, this](const MemoryLocation &ML) {
      return isModOrRefSet(AA->getModRefInfo(C, ML));
    });

    if (!NeedLift)
      NeedLift = llvm::any_of(Calls, [C, this](const CallBase *Call) {
        return isModOrRefSet(AA->getModRefInfo(C, Call));
      });
  }

  if (!NeedLift)
    continue;

  if (MayAlias) {
    // Since LI is implicitly moved downwards past the lifted instructions,
    // none of them may modify its source.
    if (isModSet(AA->getModRefInfo(C, LoadLoc)))
      return false;
    else if (const auto *Call = dyn_cast<CallBase>(C)) {
      // If we can't lift this before P, it's game over.
      if (isModOrRefSet(AA->getModRefInfo(P, Call)))
        return false;

      Calls.push_back(Call);
    } else if (isa<LoadInst>(C) || isa<StoreInst>(C) || isa<VAArgInst>(C)) {
      // If we can't lift this before P, it's game over.
      auto ML = MemoryLocation::get(C);
      if (isModOrRefSet(AA->getModRefInfo(P, ML)))
        return false;

      MemLocs.push_back(ML);
    } else
      // We don't know how to lift this instruction.
      return false;
  }

  ToLift.push_back(C);
  for (unsigned k = 0, e = C->getNumOperands(); k != e; ++k)
    if (auto *A = dyn_cast<Instruction>(C->getOperand(k))) {
      if (A->getParent() == SI->getParent()) {
        // Cannot hoist user of P above P
        if(A == P) return false;
        Args.insert(A);
      }
    }
}

// Find MSSA insertion point. Normally P will always have a corresponding
// memory access before which we can insert. However, with non-standard AA
// pipelines, there may be a mismatch between AA and MSSA, in which case we
// will scan for a memory access before P. In either case, we know for sure
// that at least the load will have a memory access.
// TODO: Simplify this once P will be determined by MSSA, in which case the
// discrepancy can no longer occur.
MemoryUseOrDef *MemInsertPoint = nullptr;
if (MSSAU) {
  if (MemoryUseOrDef *MA = MSSAU->getMemorySSA()->getMemoryAccess(P)) {
    MemInsertPoint = cast<MemoryUseOrDef>(--MA->getIterator());
  } else {
    const Instruction *ConstP = P;
    for (const Instruction &I : make_range(++ConstP->getReverseIterator(),
                                           ++LI->getReverseIterator())) {
      if (MemoryUseOrDef *MA = MSSAU->getMemorySSA()->getMemoryAccess(&I)) {
        MemInsertPoint = MA;
        break;
      }
    }
  }
}

// We made it, we need to lift.
for (auto *I : llvm::reverse(ToLift)) {
  LLVM_DEBUG(dbgs() << "Lifting " << *I << " before " << *P << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Lifting " << *I <<
 " before " << *P << "\n"; } } while (false);
  I->moveBefore(P);
  if (MSSAU) {
    assert(MemInsertPoint && "Must have found insert point")((MemInsertPoint && "Must have found insert point") ?
 static_cast<void> (0) : __assert_fail ("MemInsertPoint && \"Must have found insert point\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 630, __PRETTY_FUNCTION__));
    if (MemoryUseOrDef *MA = MSSAU->getMemorySSA()->getMemoryAccess(I)) {
      MSSAU->moveAfter(MA, MemInsertPoint);
      MemInsertPoint = MA;
    }
  }
}

return true;
639}

641bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (!SI->isSimple()) return false;

// Avoid merging nontemporal stores since the resulting
// memcpy/memset would not be able to preserve the nontemporal hint.
// In theory we could teach how to propagate the !nontemporal metadata to
// memset calls. However, that change would force the backend to
// conservatively expand !nontemporal memset calls back to sequences of
// store instructions (effectively undoing the merging).
if (SI->getMetadata(LLVMContext::MD_nontemporal))
  return false;

const DataLayout &DL = SI->getModule()->getDataLayout();

Value *StoredVal = SI->getValueOperand();

// Not all the transforms below are correct for non-integral pointers, bail
// until we've audited the individual pieces.
if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()))
  return false;

// Load to store forwarding can be interpreted as memcpy.
if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
  if (LI->isSimple() && LI->hasOneUse() &&
      LI->getParent() == SI->getParent()) {

    auto *T = LI->getType();
    if (T->isAggregateType()) {
      MemoryLocation LoadLoc = MemoryLocation::get(LI);

      // We use alias analysis to check if an instruction may store to
      // the memory we load from in between the load and the store. If
      // such an instruction is found, we try to promote there instead
      // of at the store position.
      // TODO: Can use MSSA for this.
      Instruction *P = SI;
      for (auto &I : make_range(++LI->getIterator(), SI->getIterator())) {
        if (isModSet(AA->getModRefInfo(&I, LoadLoc))) {
          P = &I;
          break;
        }
      }

      // We found an instruction that may write to the loaded memory.
      // We can try to promote at this position instead of the store
      // position if nothing alias the store memory after this and the store
      // destination is not in the range.
      if (P && P != SI) {
        if (!moveUp(SI, P, LI))
          P = nullptr;
      }

      // If a valid insertion position is found, then we can promote
      // the load/store pair to a memcpy.
      if (P) {
        // If we load from memory that may alias the memory we store to,
        // memmove must be used to preserve semantic. If not, memcpy can
        // be used.
        bool UseMemMove = false;
        if (!AA->isNoAlias(MemoryLocation::get(SI), LoadLoc))
          UseMemMove = true;

        uint64_t Size = DL.getTypeStoreSize(T);

        IRBuilder<> Builder(P);
        Instruction *M;
        if (UseMemMove)
          M = Builder.CreateMemMove(
              SI->getPointerOperand(), SI->getAlign(),
              LI->getPointerOperand(), LI->getAlign(), Size);
        else
          M = Builder.CreateMemCpy(
              SI->getPointerOperand(), SI->getAlign(),
              LI->getPointerOperand(), LI->getAlign(), Size);

        LLVM_DEBUG(dbgs() << "Promoting " << *LI << " to " << *SI << " => "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Promoting " << *LI <<
 " to " << *SI << " => " << *M << "\n"
; } } while (false)
                          << *M << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Promoting " << *LI <<
 " to " << *SI << " => " << *M << "\n"
; } } while (false);

        if (MSSAU) {
          auto *LastDef =
              cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(SI));
          auto *NewAccess =
              MSSAU->createMemoryAccessAfter(M, LastDef, LastDef);
          MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
        }

        eraseInstruction(SI);
        eraseInstruction(LI);
        ++NumMemCpyInstr;

        // Make sure we do not invalidate the iterator.
        BBI = M->getIterator();
        return true;
      }
    }

    // Detect cases where we're performing call slot forwarding, but
    // happen to be using a load-store pair to implement it, rather than
    // a memcpy.
    CallInst *C = nullptr;
    if (EnableMemorySSA) {
      if (auto *LoadClobber = dyn_cast<MemoryUseOrDef>(
              MSSA->getWalker()->getClobberingMemoryAccess(LI))) {
        // The load most post-dom the call. Limit to the same block for now.
        // TODO: Support non-local call-slot optimization?
        if (LoadClobber->getBlock() == SI->getParent())
          C = dyn_cast_or_null<CallInst>(LoadClobber->getMemoryInst());
      }
    } else {
      MemDepResult ldep = MD->getDependency(LI);
      if (ldep.isClobber() && !isa<MemCpyInst>(ldep.getInst()))
        C = dyn_cast<CallInst>(ldep.getInst());
    }

    if (C) {
      // Check that nothing touches the dest of the "copy" between
      // the call and the store.
      MemoryLocation StoreLoc = MemoryLocation::get(SI);
      if (EnableMemorySSA) {
        if (accessedBetween(*AA, StoreLoc, MSSA->getMemoryAccess(C),
                            MSSA->getMemoryAccess(SI)))
          C = nullptr;
      } else {
        for (BasicBlock::iterator I = --SI->getIterator(),
                                  E = C->getIterator();
             I != E; --I) {
          if (isModOrRefSet(AA->getModRefInfo(&*I, StoreLoc))) {
            C = nullptr;
            break;
          }
        }
      }
    }

    if (C) {
      bool changed = performCallSlotOptzn(
          LI, SI, SI->getPointerOperand()->stripPointerCasts(),
          LI->getPointerOperand()->stripPointerCasts(),
          DL.getTypeStoreSize(SI->getOperand(0)->getType()),
          commonAlignment(SI->getAlign(), LI->getAlign()), C);
      if (changed) {
        eraseInstruction(SI);
        eraseInstruction(LI);
        ++NumMemCpyInstr;
        return true;
      }
    }
  }
}

// There are two cases that are interesting for this code to handle: memcpy
// and memset.  Right now we only handle memset.

// Ensure that the value being stored is something that can be memset'able a
// byte at a time like "0" or "-1" or any width, as well as things like
// 0xA0A0A0A0 and 0.0.
auto *V = SI->getOperand(0);
if (Value *ByteVal = isBytewiseValue(V, DL)) {
  if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
                                            ByteVal)) {
    BBI = I->getIterator(); // Don't invalidate iterator.
    return true;
  }

  // If we have an aggregate, we try to promote it to memset regardless
  // of opportunity for merging as it can expose optimization opportunities
  // in subsequent passes.
  auto *T = V->getType();
  if (T->isAggregateType()) {
    uint64_t Size = DL.getTypeStoreSize(T);
    IRBuilder<> Builder(SI);
    auto *M = Builder.CreateMemSet(SI->getPointerOperand(), ByteVal, Size,
                                   SI->getAlign());

    LLVM_DEBUG(dbgs() << "Promoting " << *SI << " to " << *M << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Promoting " << *SI <<
 " to " << *M << "\n"; } } while (false);

    if (MSSAU) {
      assert(isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(SI)))((isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess
(SI))) ? static_cast<void> (0) : __assert_fail ("isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(SI))"
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 818, __PRETTY_FUNCTION__));
      auto *LastDef =
          cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(SI));
      auto *NewAccess = MSSAU->createMemoryAccessAfter(M, LastDef, LastDef);
      MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
    }

    eraseInstruction(SI);
    NumMemSetInfer++;

    // Make sure we do not invalidate the iterator.
    BBI = M->getIterator();
    return true;
  }
}

return false;
835}

837bool MemCpyOptPass::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
// See if there is another memset or store neighboring this memset which
// allows us to widen out the memset to do a single larger store.
if (isa<ConstantInt>(MSI->getLength()) && !MSI->isVolatile())
  if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
                                            MSI->getValue())) {
    BBI = I->getIterator(); // Don't invalidate iterator.
    return true;
  }
return false;
847}

849/// Takes a memcpy and a call that it depends on,
850/// and checks for the possibility of a call slot optimization by having
851/// the call write its result directly into the destination of the memcpy.
852bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
                                       Instruction *cpyStore, Value *cpyDest,
                                       Value *cpySrc, uint64_t cpyLen,
                                       Align cpyAlign, CallInst *C) {
// The general transformation to keep in mind is
//
//   call @func(..., src, ...)
//   memcpy(dest, src, ...)
//
// ->
//
//   memcpy(dest, src, ...)
//   call @func(..., dest, ...)
//
// Since moving the memcpy is technically awkward, we additionally check that
// src only holds uninitialized values at the moment of the call, meaning that
// the memcpy can be discarded rather than moved.

// Lifetime marks shouldn't be operated on.
if (Function *F = C->getCalledFunction())
  if (F->isIntrinsic() && F->getIntrinsicID() == Intrinsic::lifetime_start)
    return false;

// Require that src be an alloca.  This simplifies the reasoning considerably.
AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
if (!srcAlloca)
  return false;

ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
if (!srcArraySize)
  return false;

const DataLayout &DL = cpyLoad->getModule()->getDataLayout();
uint64_t srcSize = DL.getTypeAllocSize(srcAlloca->getAllocatedType()) *
                   srcArraySize->getZExtValue();

if (cpyLen < srcSize)
  return false;

// Check that accessing the first srcSize bytes of dest will not cause a
// trap.  Otherwise the transform is invalid since it might cause a trap
// to occur earlier than it otherwise would.
if (!isDereferenceableAndAlignedPointer(cpyDest, Align(1), APInt(64, cpyLen),
                                        DL, C, DT))
  return false;

// Make sure that nothing can observe cpyDest being written early. There are
// a number of cases to consider:
//  1. cpyDest cannot be accessed between C and cpyStore as a precondition of
//     the transform.
//  2. C itself may not access cpyDest (prior to the transform). This is
//     checked further below.
//  3. If cpyDest is accessible to the caller of this function (potentially
//     captured and not based on an alloca), we need to ensure that we cannot
//     unwind between C and cpyStore. This is checked here.
//  4. If cpyDest is potentially captured, there may be accesses to it from
//     another thread. In this case, we need to check that cpyStore is
//     guaranteed to be executed if C is. As it is a non-atomic access, it
//     renders accesses from other threads undefined.
//     TODO: This is currently not checked.
if (mayBeVisibleThroughUnwinding(cpyDest, C, cpyStore))
  return false;

// Check that dest points to memory that is at least as aligned as src.
Align srcAlign = srcAlloca->getAlign();
bool isDestSufficientlyAligned = srcAlign <= cpyAlign;
// If dest is not aligned enough and we can't increase its alignment then
// bail out.
if (!isDestSufficientlyAligned && !isa<AllocaInst>(cpyDest))
  return false;

// Check that src is not accessed except via the call and the memcpy.  This
// guarantees that it holds only undefined values when passed in (so the final
// memcpy can be dropped), that it is not read or written between the call and
// the memcpy, and that writing beyond the end of it is undefined.
SmallVector<User *, 8> srcUseList(srcAlloca->users());
while (!srcUseList.empty()) {
  User *U = srcUseList.pop_back_val();

  if (isa<BitCastInst>(U) || isa<AddrSpaceCastInst>(U)) {
    append_range(srcUseList, U->users());
    continue;
  }
  if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(U)) {
    if (!G->hasAllZeroIndices())
      return false;

    append_range(srcUseList, U->users());
    continue;
  }
  if (const IntrinsicInst *IT = dyn_cast<IntrinsicInst>(U))
    if (IT->isLifetimeStartOrEnd())
      continue;

  if (U != C && U != cpyLoad)
    return false;
}

// Check that src isn't captured by the called function since the
// transformation can cause aliasing issues in that case.
for (unsigned ArgI = 0, E = C->arg_size(); ArgI != E; ++ArgI)
  if (C->getArgOperand(ArgI) == cpySrc && !C->doesNotCapture(ArgI))
    return false;

// Since we're changing the parameter to the callsite, we need to make sure
// that what would be the new parameter dominates the callsite.
if (!DT->dominates(cpyDest, C)) {
  // Support moving a constant index GEP before the call.
  auto *GEP = dyn_cast<GetElementPtrInst>(cpyDest);
  if (GEP && GEP->hasAllConstantIndices() &&
      DT->dominates(GEP->getPointerOperand(), C))
    GEP->moveBefore(C);
  else
    return false;
}

// In addition to knowing that the call does not access src in some
// unexpected manner, for example via a global, which we deduce from
// the use analysis, we also need to know that it does not sneakily
// access dest.  We rely on AA to figure this out for us.
ModRefInfo MR = AA->getModRefInfo(C, cpyDest, LocationSize::precise(srcSize));
// If necessary, perform additional analysis.
if (isModOrRefSet(MR))
  MR = AA->callCapturesBefore(C, cpyDest, LocationSize::precise(srcSize), DT);
if (isModOrRefSet(MR))
  return false;

// We can't create address space casts here because we don't know if they're
// safe for the target.
if (cpySrc->getType()->getPointerAddressSpace() !=
    cpyDest->getType()->getPointerAddressSpace())
  return false;
for (unsigned ArgI = 0; ArgI < C->arg_size(); ++ArgI)
  if (C->getArgOperand(ArgI)->stripPointerCasts() == cpySrc &&
      cpySrc->getType()->getPointerAddressSpace() !=
          C->getArgOperand(ArgI)->getType()->getPointerAddressSpace())
    return false;

// All the checks have passed, so do the transformation.
bool changedArgument = false;
for (unsigned ArgI = 0; ArgI < C->arg_size(); ++ArgI)
  if (C->getArgOperand(ArgI)->stripPointerCasts() == cpySrc) {
    Value *Dest = cpySrc->getType() == cpyDest->getType() ?  cpyDest
      : CastInst::CreatePointerCast(cpyDest, cpySrc->getType(),
                                    cpyDest->getName(), C);
    changedArgument = true;
    if (C->getArgOperand(ArgI)->getType() == Dest->getType())
      C->setArgOperand(ArgI, Dest);
    else
      C->setArgOperand(ArgI, CastInst::CreatePointerCast(
                                 Dest, C->getArgOperand(ArgI)->getType(),
                                 Dest->getName(), C));
  }

if (!changedArgument)
  return false;

// If the destination wasn't sufficiently aligned then increase its alignment.
if (!isDestSufficientlyAligned) {
  assert(isa<AllocaInst>(cpyDest) && "Can only increase alloca alignment!")((isa<AllocaInst>(cpyDest) && "Can only increase alloca alignment!"
) ? static_cast<void> (0) : __assert_fail ("isa<AllocaInst>(cpyDest) && \"Can only increase alloca alignment!\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 1011, __PRETTY_FUNCTION__));
  cast<AllocaInst>(cpyDest)->setAlignment(srcAlign);
}

// Drop any cached information about the call, because we may have changed
// its dependence information by changing its parameter.
if (MD)
  MD->removeInstruction(C);

// Update AA metadata
// FIXME: MD_tbaa_struct and MD_mem_parallel_loop_access should also be
// handled here, but combineMetadata doesn't support them yet
unsigned KnownIDs[] = {LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
                       LLVMContext::MD_noalias,
                       LLVMContext::MD_invariant_group,
                       LLVMContext::MD_access_group};
combineMetadata(C, cpyLoad, KnownIDs, true);

++NumCallSlot;
return true;
1031}

1033/// We've found that the (upward scanning) memory dependence of memcpy 'M' is
1034/// the memcpy 'MDep'. Try to simplify M to copy from MDep's input if we can.
1035bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
                                                MemCpyInst *MDep) {
// We can only transforms memcpy's where the dest of one is the source of the
// other.
if (M->getSource() != MDep->getDest() || MDep->isVolatile())
  return false;

// If dep instruction is reading from our current input, then it is a noop
// transfer and substituting the input won't change this instruction.  Just
// ignore the input and let someone else zap MDep.  This handles cases like:
//    memcpy(a <- a)
//    memcpy(b <- a)
if (M->getSource() == MDep->getSource())
  return false;

// Second, the length of the memcpy's must be the same, or the preceding one
// must be larger than the following one.
ConstantInt *MDepLen = dyn_cast<ConstantInt>(MDep->getLength());
ConstantInt *MLen = dyn_cast<ConstantInt>(M->getLength());
if (!MDepLen || !MLen || MDepLen->getZExtValue() < MLen->getZExtValue())
  return false;

// Verify that the copied-from memory doesn't change in between the two
// transfers.  For example, in:
//    memcpy(a <- b)
//    *b = 42;
//    memcpy(c <- a)
// It would be invalid to transform the second memcpy into memcpy(c <- b).
//
// TODO: If the code between M and MDep is transparent to the destination "c",
// then we could still perform the xform by moving M up to the first memcpy.
if (EnableMemorySSA) {
  // TODO: It would be sufficient to check the MDep source up to the memcpy
  // size of M, rather than MDep.
  if (writtenBetween(MSSA, MemoryLocation::getForSource(MDep),
                     MSSA->getMemoryAccess(MDep), MSSA->getMemoryAccess(M)))
    return false;
} else {
  // NOTE: This is conservative, it will stop on any read from the source loc,
  // not just the defining memcpy.
  MemDepResult SourceDep =
      MD->getPointerDependencyFrom(MemoryLocation::getForSource(MDep), false,
                                   M->getIterator(), M->getParent());
  if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
    return false;
}

// If the dest of the second might alias the source of the first, then the
// source and dest might overlap.  We still want to eliminate the intermediate
// value, but we have to generate a memmove instead of memcpy.
bool UseMemMove = false;
if (!AA->isNoAlias(MemoryLocation::getForDest(M),
                   MemoryLocation::getForSource(MDep)))
  UseMemMove = true;

// If all checks passed, then we can transform M.
LLVM_DEBUG(dbgs() << "MemCpyOptPass: Forwarding memcpy->memcpy src:\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Forwarding memcpy->memcpy src:\n"
 << *MDep << '\n' << *M << '\n'; } } while
 (false)
                  << *MDep << '\n' << *M << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Forwarding memcpy->memcpy src:\n"
 << *MDep << '\n' << *M << '\n'; } } while
 (false);

// TODO: Is this worth it if we're creating a less aligned memcpy? For
// example we could be moving from movaps -> movq on x86.
IRBuilder<> Builder(M);
Instruction *NewM;
if (UseMemMove)
  NewM = Builder.CreateMemMove(M->getRawDest(), M->getDestAlign(),
                               MDep->getRawSource(), MDep->getSourceAlign(),
                               M->getLength(), M->isVolatile());
else
  NewM = Builder.CreateMemCpy(M->getRawDest(), M->getDestAlign(),
                              MDep->getRawSource(), MDep->getSourceAlign(),
                              M->getLength(), M->isVolatile());

if (MSSAU) {
  assert(isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(M)))((isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess
(M))) ? static_cast<void> (0) : __assert_fail ("isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(M))"
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 1108, __PRETTY_FUNCTION__));
  auto *LastDef = cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(M));
  auto *NewAccess = MSSAU->createMemoryAccessAfter(NewM, LastDef, LastDef);
  MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
}

// Remove the instruction we're replacing.
eraseInstruction(M);
++NumMemCpyInstr;
return true;
1118}

1120/// We've found that the (upward scanning) memory dependence of \p MemCpy is
1121/// \p MemSet.  Try to simplify \p MemSet to only set the trailing bytes that
1122/// weren't copied over by \p MemCpy.
1123///
1124/// In other words, transform:
1125/// \code
1126///   memset(dst, c, dst_size);
1127///   memcpy(dst, src, src_size);
1128/// \endcode
1129/// into:
1130/// \code
1131///   memcpy(dst, src, src_size);
1132///   memset(dst + src_size, c, dst_size <= src_size ? 0 : dst_size - src_size);
1133/// \endcode
1134bool MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
                                                MemSetInst *MemSet) {
// We can only transform memset/memcpy with the same destination.
if (MemSet->getDest() != MemCpy->getDest())
  return false;

// Check that src and dst of the memcpy aren't the same. While memcpy
// operands cannot partially overlap, exact equality is allowed.
if (!AA->isNoAlias(MemoryLocation(MemCpy->getSource(),
                                  LocationSize::precise(1)),
                   MemoryLocation(MemCpy->getDest(),
                                  LocationSize::precise(1))))
  return false;

if (EnableMemorySSA) {
  // We know that dst up to src_size is not written. We now need to make sure
  // that dst up to dst_size is not accessed. (If we did not move the memset,
  // checking for reads would be sufficient.)
  if (accessedBetween(*AA, MemoryLocation::getForDest(MemSet),
                      MSSA->getMemoryAccess(MemSet),
                      MSSA->getMemoryAccess(MemCpy))) {
    return false;
  }
} else {
  // We have already checked that dst up to src_size is not accessed. We
  // need to make sure that there are no accesses up to dst_size either.
  MemDepResult DstDepInfo = MD->getPointerDependencyFrom(
      MemoryLocation::getForDest(MemSet), false, MemCpy->getIterator(),
      MemCpy->getParent());
  if (DstDepInfo.getInst() != MemSet)
    return false;
}

// Use the same i8* dest as the memcpy, killing the memset dest if different.
Value *Dest = MemCpy->getRawDest();
Value *DestSize = MemSet->getLength();
Value *SrcSize = MemCpy->getLength();

if (mayBeVisibleThroughUnwinding(Dest, MemSet, MemCpy))
  return false;

// By default, create an unaligned memset.
unsigned Align = 1;
// If Dest is aligned, and SrcSize is constant, use the minimum alignment
// of the sum.
const unsigned DestAlign =
    std::max(MemSet->getDestAlignment(), MemCpy->getDestAlignment());
if (DestAlign > 1)
  if (ConstantInt *SrcSizeC = dyn_cast<ConstantInt>(SrcSize))
    Align = MinAlign(SrcSizeC->getZExtValue(), DestAlign);

IRBuilder<> Builder(MemCpy);

// If the sizes have different types, zext the smaller one.
if (DestSize->getType() != SrcSize->getType()) {
  if (DestSize->getType()->getIntegerBitWidth() >
      SrcSize->getType()->getIntegerBitWidth())
    SrcSize = Builder.CreateZExt(SrcSize, DestSize->getType());
  else
    DestSize = Builder.CreateZExt(DestSize, SrcSize->getType());
}

Value *Ule = Builder.CreateICmpULE(DestSize, SrcSize);
Value *SizeDiff = Builder.CreateSub(DestSize, SrcSize);
Value *MemsetLen = Builder.CreateSelect(
    Ule, ConstantInt::getNullValue(DestSize->getType()), SizeDiff);
Instruction *NewMemSet = Builder.CreateMemSet(
    Builder.CreateGEP(Dest->getType()->getPointerElementType(), Dest,
                      SrcSize),
    MemSet->getOperand(1), MemsetLen, MaybeAlign(Align));

if (MSSAU) {
  assert(isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(MemCpy)) &&((isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess
(MemCpy)) && "MemCpy must be a MemoryDef") ? static_cast
<void> (0) : __assert_fail ("isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(MemCpy)) && \"MemCpy must be a MemoryDef\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 1207, __PRETTY_FUNCTION__))
         "MemCpy must be a MemoryDef")((isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess
(MemCpy)) && "MemCpy must be a MemoryDef") ? static_cast
<void> (0) : __assert_fail ("isa<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(MemCpy)) && \"MemCpy must be a MemoryDef\""
, "/build/llvm-toolchain-snapshot-13~++20210222111131+188f15d97310/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp"
, 1207, __PRETTY_FUNCTION__));
  // The new memset is inserted after the memcpy, but it is known that its
  // defining access is the memset about to be removed which immediately
  // precedes the memcpy.
  auto *LastDef =
      cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(MemCpy));
  auto *NewAccess = MSSAU->createMemoryAccessBefore(
      NewMemSet, LastDef->getDefiningAccess(), LastDef);
  MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
}

eraseInstruction(MemSet);
return true;
1220}

1222/// Determine whether the instruction has undefined content for the given Size,
1223/// either because it was freshly alloca'd or started its lifetime.
1224static bool hasUndefContents(Instruction *I, ConstantInt *Size) {
if (isa<AllocaInst>(I))
  return true;

if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
  if (II->getIntrinsicID() == Intrinsic::lifetime_start)
    if (ConstantInt *LTSize = dyn_cast<ConstantInt>(II->getArgOperand(0)))
      if (LTSize->getZExtValue() >= Size->getZExtValue())
        return true;

return false;
1235}

1237static bool hasUndefContentsMSSA(MemorySSA *MSSA, AliasAnalysis *AA, Value *V,
                               MemoryDef *Def, ConstantInt *Size) {
if (MSSA->isLiveOnEntryDef(Def))
  return isa<AllocaInst>(getUnderlyingObject(V));

if (IntrinsicInst *II =
        dyn_cast_or_null<IntrinsicInst>(Def->getMemoryInst())) {
  if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
    ConstantInt *LTSize = cast<ConstantInt>(II->getArgOperand(0));
    if (AA->isMustAlias(V, II->getArgOperand(1)) &&
        LTSize->getZExtValue() >= Size->getZExtValue())
      return true;
  }
}

return false;
1253}

1255/// Transform memcpy to memset when its source was just memset.
1256/// In other words, turn:
1257/// \code
1258///   memset(dst1, c, dst1_size);
1259///   memcpy(dst2, dst1, dst2_size);
1260/// \endcode
1261/// into:
1262/// \code
1263///   memset(dst1, c, dst1_size);
1264///   memset(dst2, c, dst2_size);
1265/// \endcode
1266/// When dst2_size <= dst1_size.
1267///
1268/// The \p MemCpy must have a Constant length.
1269bool MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
                                             MemSetInst *MemSet) {
// Make sure that memcpy(..., memset(...), ...), that is we are memsetting and
// memcpying from the same address. Otherwise it is hard to reason about.
if (!AA->isMustAlias(MemSet->getRawDest(), MemCpy->getRawSource()))
  return false;

// A known memset size is required.
ConstantInt *MemSetSize = dyn_cast<ConstantInt>(MemSet->getLength());
if (!MemSetSize)
  return false;

// Make sure the memcpy doesn't read any more than what the memset wrote.
// Don't worry about sizes larger than i64.
ConstantInt *CopySize = cast<ConstantInt>(MemCpy->getLength());
if (CopySize->getZExtValue() > MemSetSize->getZExtValue()) {
  // If the memcpy is larger than the memset, but the memory was undef prior
  // to the memset, we can just ignore the tail. Technically we're only
  // interested in the bytes from MemSetSize..CopySize here, but as we can't
  // easily represent this location, we use the full 0..CopySize range.
  MemoryLocation MemCpyLoc = MemoryLocation::getForSource(MemCpy);
  bool CanReduceSize = false;
  if (EnableMemorySSA) {
    MemoryUseOrDef *MemSetAccess = MSSA->getMemoryAccess(MemSet);
    MemoryAccess *Clobber = MSSA->getWalker()->getClobberingMemoryAccess(
        MemSetAccess->getDefiningAccess(), MemCpyLoc);
    if (auto *MD = dyn_cast<MemoryDef>(Clobber))
      if (hasUndefContentsMSSA(MSSA, AA, MemCpy->getSource(), MD, CopySize))
        CanReduceSize = true;
  } else {
    MemDepResult DepInfo = MD->getPointerDependencyFrom(
        MemCpyLoc, true, MemSet->getIterator(), MemSet->getParent());
    if (DepInfo.isDef() && hasUndefContents(DepInfo.getInst(), CopySize))
      CanReduceSize = true;
  }

  if (!CanReduceSize)
    return false;
  CopySize = MemSetSize;
}

IRBuilder<> Builder(MemCpy);
Instruction *NewM =
    Builder.CreateMemSet(MemCpy->getRawDest(), MemSet->getOperand(1),
                         CopySize, MaybeAlign(MemCpy->getDestAlignment()));
if (MSSAU) {
  auto *LastDef =
      cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(MemCpy));
  auto *NewAccess = MSSAU->createMemoryAccessAfter(NewM, LastDef, LastDef);
  MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
}

return true;
1322}

1324/// Perform simplification of memcpy's.  If we have memcpy A
1325/// which copies X to Y, and memcpy B which copies Y to Z, then we can rewrite
1326/// B to be a memcpy from X to Z (or potentially a memmove, depending on
1327/// circumstances). This allows later passes to remove the first memcpy
1328/// altogether.
1329bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
// We can only optimize non-volatile memcpy's.
if (M->isVolatile()) return false;

// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
  ++BBI;
  eraseInstruction(M);
  return true;
}

// If copying from a constant, try to turn the memcpy into a memset.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
  if (GV->isConstant() && GV->hasDefinitiveInitializer())
    if (Value *ByteVal = isBytewiseValue(GV->getInitializer(),
                                         M->getModule()->getDataLayout())) {
      IRBuilder<> Builder(M);
      Instruction *NewM =
          Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
                               MaybeAlign(M->getDestAlignment()), false);
      if (MSSAU) {
        auto *LastDef =
            cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(M));
        auto *NewAccess =
            MSSAU->createMemoryAccessAfter(NewM, LastDef, LastDef);
        MSSAU->insertDef(cast<MemoryDef>(NewAccess), /*RenameUses=*/true);
      }

      eraseInstruction(M);
      ++NumCpyToSet;
      return true;
    }

if (EnableMemorySSA) {
  MemoryUseOrDef *MA = MSSA->getMemoryAccess(M);
  MemoryAccess *AnyClobber = MSSA->getWalker()->getClobberingMemoryAccess(MA);
  MemoryLocation DestLoc = MemoryLocation::getForDest(M);
  const MemoryAccess *DestClobber =
      MSSA->getWalker()->getClobberingMemoryAccess(AnyClobber, DestLoc);

  // Try to turn a partially redundant memset + memcpy into
  // memcpy + smaller memset.  We don't need the memcpy size for this.
  // The memcpy most post-dom the memset, so limit this to the same basic
  // block. A non-local generalization is likely not worthwhile.
  if (auto *MD = dyn_cast<MemoryDef>(DestClobber))
    if (auto *MDep = dyn_cast_or_null<MemSetInst>(MD->getMemoryInst()))
      if (DestClobber->getBlock() == M->getParent())
        if (processMemSetMemCpyDependence(M, MDep))
          return true;

  // The optimizations after this point require the memcpy size.
  ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
  if (!CopySize) return false;

  MemoryAccess *SrcClobber = MSSA->getWalker()->getClobberingMemoryAccess(
      AnyClobber, MemoryLocation::getForSource(M));

  // There are four possible optimizations we can do for memcpy:
  //   a) memcpy-memcpy xform which exposes redundance for DSE.
  //   b) call-memcpy xform for return slot optimization.
  //   c) memcpy from freshly alloca'd space or space that has just started
  //      its lifetime copies undefined data, and we can therefore eliminate
  //      the memcpy in favor of the data that was already at the destination.
  //   d) memcpy from a just-memset'd source can be turned into memset.
  if (auto *MD = dyn_cast<MemoryDef>(SrcClobber)) {
    if (Instruction *MI = MD->getMemoryInst()) {
      if (auto *C = dyn_cast<CallInst>(MI)) {
        // The memcpy must post-dom the call. Limit to the same block for now.
        // Additionally, we need to ensure that there are no accesses to dest
        // between the call and the memcpy. Accesses to src will be checked
        // by performCallSlotOptzn().
        // TODO: Support non-local call-slot optimization?
        if (C->getParent() == M->getParent() &&
            !accessedBetween(*AA, DestLoc, MD, MA)) {
          // FIXME: Can we pass in either of dest/src alignment here instead
          // of conservatively taking the minimum?
          Align Alignment = std::min(M->getDestAlign().valueOrOne(),
                                     M->getSourceAlign().valueOrOne());
          if (performCallSlotOptzn(M, M, M->getDest(), M->getSource(),
                                   CopySize->getZExtValue(), Alignment, C)) {
            LLVM_DEBUG(dbgs() << "Performed call slot optimization:\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Performed call slot optimization:\n"
 << "    call: " << *C << "\n" << "    memcpy: "
 << *M << "\n"; } } while (false)
                              << "    call: " << *C << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Performed call slot optimization:\n"
 << "    call: " << *C << "\n" << "    memcpy: "
 << *M << "\n"; } } while (false)
                              << "    memcpy: " << *M << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Performed call slot optimization:\n"
 << "    call: " << *C << "\n" << "    memcpy: "
 << *M << "\n"; } } while (false);
            eraseInstruction(M);
            ++NumMemCpyInstr;
            return true;
          }
        }
      }
      if (auto *MDep = dyn_cast<MemCpyInst>(MI))
        return processMemCpyMemCpyDependence(M, MDep);
      if (auto *MDep = dyn_cast<MemSetInst>(MI)) {
        if (performMemCpyToMemSetOptzn(M, MDep)) {
          LLVM_DEBUG(dbgs() << "Converted memcpy to memset\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Converted memcpy to memset\n"
; } } while (false);
          eraseInstruction(M);
          ++NumCpyToSet;
          return true;
        }
      }
    }

    if (hasUndefContentsMSSA(MSSA, AA, M->getSource(), MD, CopySize)) {
      LLVM_DEBUG(dbgs() << "Removed memcpy from undef\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "Removed memcpy from undef\n"
; } } while (false);
      eraseInstruction(M);
      ++NumMemCpyInstr;
      return true;
    }
  }
} else {
  MemDepResult DepInfo = MD->getDependency(M);

  // Try to turn a partially redundant memset + memcpy into
  // memcpy + smaller memset.  We don't need the memcpy size for this.
  if (DepInfo.isClobber())
    if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst()))
      if (processMemSetMemCpyDependence(M, MDep))
        return true;

  // The optimizations after this point require the memcpy size.
  ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
  if (!CopySize) return false;

  // There are four possible optimizations we can do for memcpy:
  //   a) memcpy-memcpy xform which exposes redundance for DSE.
  //   b) call-memcpy xform for return slot optimization.
  //   c) memcpy from freshly alloca'd space or space that has just started
  //      its lifetime copies undefined data, and we can therefore eliminate
  //      the memcpy in favor of the data that was already at the destination.
  //   d) memcpy from a just-memset'd source can be turned into memset.
  if (DepInfo.isClobber()) {
    if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
      // FIXME: Can we pass in either of dest/src alignment here instead
      // of conservatively taking the minimum?
      Align Alignment = std::min(M->getDestAlign().valueOrOne(),
                                 M->getSourceAlign().valueOrOne());
      if (performCallSlotOptzn(M, M, M->getDest(), M->getSource(),
                               CopySize->getZExtValue(), Alignment, C)) {
        eraseInstruction(M);
        ++NumMemCpyInstr;
        return true;
      }
    }
  }

  MemoryLocation SrcLoc = MemoryLocation::getForSource(M);
  MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(
      SrcLoc, true, M->getIterator(), M->getParent());

  if (SrcDepInfo.isClobber()) {
    if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
      return processMemCpyMemCpyDependence(M, MDep);
  } else if (SrcDepInfo.isDef()) {
    if (hasUndefContents(SrcDepInfo.getInst(), CopySize)) {
      eraseInstruction(M);
      ++NumMemCpyInstr;
      return true;
    }
  }

  if (SrcDepInfo.isClobber())
    if (MemSetInst *MDep = dyn_cast<MemSetInst>(SrcDepInfo.getInst()))
      if (performMemCpyToMemSetOptzn(M, MDep)) {
        eraseInstruction(M);
        ++NumCpyToSet;
        return true;
      }
}

return false;
1498}

1500/// Transforms memmove calls to memcpy calls when the src/dst are guaranteed
1501/// not to alias.
1502bool MemCpyOptPass::processMemMove(MemMoveInst *M) {
if (!TLI->has(LibFunc_memmove))
  return false;

// See if the pointers alias.
if (!AA->isNoAlias(MemoryLocation::getForDest(M),
                   MemoryLocation::getForSource(M)))
  return false;

LLVM_DEBUG(dbgs() << "MemCpyOptPass: Optimizing memmove -> memcpy: " << *Mdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Optimizing memmove -> memcpy: "
 << *M << "\n"; } } while (false)
                  << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Optimizing memmove -> memcpy: "
 << *M << "\n"; } } while (false);

// If not, then we know we can transform this.
Type *ArgTys[3] = { M->getRawDest()->getType(),
                    M->getRawSource()->getType(),
                    M->getLength()->getType() };
M->setCalledFunction(Intrinsic::getDeclaration(M->getModule(),
                                               Intrinsic::memcpy, ArgTys));

// For MemorySSA nothing really changes (except that memcpy may imply stricter
// aliasing guarantees).

// MemDep may have over conservative information about this instruction, just
// conservatively flush it from the cache.
if (MD)
  MD->removeInstruction(M);

++NumMoveToCpy;
return true;
1531}

1533/// This is called on every byval argument in call sites.
1534bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
const DataLayout &DL = CB.getCaller()->getParent()->getDataLayout();
// Find out what feeds this byval argument.
Value *ByValArg = CB.getArgOperand(ArgNo);
Type *ByValTy = cast<PointerType>(ByValArg->getType())->getElementType();
35
←
The object is a 'PointerType'→
uint64_t ByValSize = DL.getTypeAllocSize(ByValTy);
MemoryLocation Loc(ByValArg, LocationSize::precise(ByValSize));
MemCpyInst *MDep = nullptr;
if (EnableMemorySSA) {
36
←
Assuming the condition is false→
37
←
Taking false branch→
  MemoryUseOrDef *CallAccess = MSSA->getMemoryAccess(&CB);
  MemoryAccess *Clobber = MSSA->getWalker()->getClobberingMemoryAccess(
      CallAccess->getDefiningAccess(), Loc);
  if (auto *MD = dyn_cast<MemoryDef>(Clobber))
    MDep = dyn_cast_or_null<MemCpyInst>(MD->getMemoryInst());
} else {
  MemDepResult DepInfo = MD->getPointerDependencyFrom(
38
←
Called C++ object pointer is null
      Loc, true, CB.getIterator(), CB.getParent());
  if (!DepInfo.isClobber())
    return false;
  MDep = dyn_cast<MemCpyInst>(DepInfo.getInst());
}

// If the byval argument isn't fed by a memcpy, ignore it.  If it is fed by
// a memcpy, see if we can byval from the source of the memcpy instead of the
// result.
if (!MDep || MDep->isVolatile() ||
    ByValArg->stripPointerCasts() != MDep->getDest())
  return false;

// The length of the memcpy must be larger or equal to the size of the byval.
ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
if (!C1 || C1->getValue().getZExtValue() < ByValSize)
  return false;

// Get the alignment of the byval.  If the call doesn't specify the alignment,
// then it is some target specific value that we can't know.
MaybeAlign ByValAlign = CB.getParamAlign(ArgNo);
if (!ByValAlign) return false;

// If it is greater than the memcpy, then we check to see if we can force the
// source of the memcpy to the alignment we need.  If we fail, we bail out.
MaybeAlign MemDepAlign = MDep->getSourceAlign();
if ((!MemDepAlign || *MemDepAlign < *ByValAlign) &&
    getOrEnforceKnownAlignment(MDep->getSource(), ByValAlign, DL, &CB, AC,
                               DT) < *ByValAlign)
  return false;

// The address space of the memcpy source must match the byval argument
if (MDep->getSource()->getType()->getPointerAddressSpace() !=
    ByValArg->getType()->getPointerAddressSpace())
  return false;

// Verify that the copied-from memory doesn't change in between the memcpy and
// the byval call.
//    memcpy(a <- b)
//    *b = 42;
//    foo(*a)
// It would be invalid to transform the second memcpy into foo(*b).
if (EnableMemorySSA) {
  if (writtenBetween(MSSA, MemoryLocation::getForSource(MDep),
                     MSSA->getMemoryAccess(MDep), MSSA->getMemoryAccess(&CB)))
    return false;
} else {
  // NOTE: This is conservative, it will stop on any read from the source loc,
  // not just the defining memcpy.
  MemDepResult SourceDep = MD->getPointerDependencyFrom(
      MemoryLocation::getForSource(MDep), false,
      CB.getIterator(), MDep->getParent());
  if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
    return false;
}

Value *TmpCast = MDep->getSource();
if (MDep->getSource()->getType() != ByValArg->getType()) {
  BitCastInst *TmpBitCast = new BitCastInst(MDep->getSource(), ByValArg->getType(),
                                            "tmpcast", &CB);
  // Set the tmpcast's DebugLoc to MDep's
  TmpBitCast->setDebugLoc(MDep->getDebugLoc());
  TmpCast = TmpBitCast;
}

LLVM_DEBUG(dbgs() << "MemCpyOptPass: Forwarding memcpy to byval:\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Forwarding memcpy to byval:\n"
 << "  " << *MDep << "\n" << "  " <<
 CB << "\n"; } } while (false)
                  << "  " << *MDep << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Forwarding memcpy to byval:\n"
 << "  " << *MDep << "\n" << "  " <<
 CB << "\n"; } } while (false)
                  << "  " << CB << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memcpyopt")) { dbgs() << "MemCpyOptPass: Forwarding memcpy to byval:\n"
 << "  " << *MDep << "\n" << "  " <<
 CB << "\n"; } } while (false);

// Otherwise we're good!  Update the byval argument.
CB.setArgOperand(ArgNo, TmpCast);
++NumMemCpyInstr;
return true;
1623}

1625/// Executes one iteration of MemCpyOptPass.
1626bool MemCpyOptPass::iterateOnFunction(Function &F) {
bool MadeChange = false;

// Walk all instruction in the function.
for (BasicBlock &BB : F) {
  // Skip unreachable blocks. For example processStore assumes that an
  // instruction in a BB can't be dominated by a later instruction in the
  // same BB (which is a scenario that can happen for an unreachable BB that
  // has itself as a predecessor).
  if (!DT->isReachableFromEntry(&BB))
17
←
Assuming the condition is false→
18
←
Taking false branch→
    continue;

  for (BasicBlock::iterator BI = BB.begin(), BE = BB.end(); BI != BE;) {
19
←
Loop condition is true.  Entering loop body→
      // Avoid invalidating the iterator.
    Instruction *I = &*BI++;

    bool RepeatInstruction = false;

    if (StoreInst *SI20.1
'SI' is null
 = dyn_cast<StoreInst>(I))
20
←
Assuming 'I' is not a 'StoreInst'→
21
←
Taking false branch→
      MadeChange |= processStore(SI, BI);
    else if (MemSetInst *M22.1
'M' is null
 = dyn_cast<MemSetInst>(I))
22
←
Assuming 'I' is not a 'MemSetInst'→
23
←
Taking false branch→
      RepeatInstruction = processMemSet(M, BI);
    else if (MemCpyInst *M24.1
'M' is null
 = dyn_cast<MemCpyInst>(I))
24
←
Assuming 'I' is not a 'MemCpyInst'→
25
←
Taking false branch→
      RepeatInstruction = processMemCpy(M, BI);
    else if (MemMoveInst *M26.1
'M' is null
 = dyn_cast<MemMoveInst>(I))
26
←
Assuming 'I' is not a 'MemMoveInst'→
27
←
Taking false branch→
      RepeatInstruction = processMemMove(M);
    else if (auto *CB28.1
'CB' is non-null
 = dyn_cast<CallBase>(I)) {
28
←
Assuming 'I' is a 'CallBase'→
29
←
Taking true branch→
      for (unsigned i = 0, e = CB->arg_size(); i != e; ++i)
30
←
Assuming 'i' is not equal to 'e'→
31
←
Loop condition is true.  Entering loop body→
        if (CB->isByValArgument(i))
32
←
Assuming the condition is true→
33
←
Taking true branch→
          MadeChange |= processByValArgument(*CB, i);
34
←
Calling 'MemCpyOptPass::processByValArgument'→
    }

    // Reprocess the instruction if desired.
    if (RepeatInstruction) {
      if (BI != BB.begin())
        --BI;
      MadeChange = true;
    }
  }
}

return MadeChange;
1668}

1670PreservedAnalyses MemCpyOptPass::run(Function &F, FunctionAnalysisManager &AM) {
auto *MD = !EnableMemorySSA ? &AM.getResult<MemoryDependenceAnalysis>(F)
                            : AM.getCachedResult<MemoryDependenceAnalysis>(F);
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
auto *AA = &AM.getResult<AAManager>(F);
auto *AC = &AM.getResult<AssumptionAnalysis>(F);
auto *DT = &AM.getResult<DominatorTreeAnalysis>(F);
auto *MSSA = EnableMemorySSA ? &AM.getResult<MemorySSAAnalysis>(F)
                             : AM.getCachedResult<MemorySSAAnalysis>(F);

bool MadeChange =
    runImpl(F, MD, &TLI, AA, AC, DT, MSSA ? &MSSA->getMSSA() : nullptr);
if (!MadeChange)
  return PreservedAnalyses::all();

PreservedAnalyses PA;
PA.preserveSet<CFGAnalyses>();
PA.preserve<GlobalsAA>();
if (MD)
  PA.preserve<MemoryDependenceAnalysis>();
if (MSSA)
  PA.preserve<MemorySSAAnalysis>();
return PA;
1693}

1695bool MemCpyOptPass::runImpl(Function &F, MemoryDependenceResults *MD_,
                          TargetLibraryInfo *TLI_, AliasAnalysis *AA_,
                          AssumptionCache *AC_, DominatorTree *DT_,
                          MemorySSA *MSSA_) {
bool MadeChange = false;
MD = MD_;
12
←
Null pointer value stored to field 'MD'→
TLI = TLI_;
AA = AA_;
AC = AC_;
DT = DT_;
MSSA = MSSA_;
MemorySSAUpdater MSSAU_(MSSA_);
MSSAU = MSSA_12.1
'MSSA_' is null
 ? &MSSAU_ : nullptr;
13
←
'?' condition is false→
// If we don't have at least memset and memcpy, there is little point of doing
// anything here.  These are required by a freestanding implementation, so if
// even they are disabled, there is no point in trying hard.
if (!TLI->has(LibFunc_memset) || !TLI->has(LibFunc_memcpy))
14
←
Taking false branch→
  return false;

while (true) {
15
←
Loop condition is true.  Entering loop body→
  if (!iterateOnFunction(F))
16
←
Calling 'MemCpyOptPass::iterateOnFunction'→
    break;
  MadeChange = true;
}

if (MSSA_ && VerifyMemorySSA)
  MSSA_->verifyMemorySSA();

MD = nullptr;
return MadeChange;
1725}

1727/// This is the main transformation entry point for a function.
1728bool MemCpyOptLegacyPass::runOnFunction(Function &F) {
if (skipFunction(F))
1
Assuming the condition is false→
2
←
Taking false branch→
  return false;

auto *MDWP = !EnableMemorySSA
3
←
Assuming the condition is false→
4
←
'?' condition is false→
    ? &getAnalysis<MemoryDependenceWrapperPass>()
    : getAnalysisIfAvailable<MemoryDependenceWrapperPass>();
auto *TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
auto *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto *MSSAWP = EnableMemorySSA
5
←
Assuming the condition is false→
6
←
'?' condition is false→
    ? &getAnalysis<MemorySSAWrapperPass>()
    : getAnalysisIfAvailable<MemorySSAWrapperPass>();

return Impl.runImpl(F, MDWP ? & MDWP->getMemDep() : nullptr, TLI, AA, AC, DT,
7
←
Assuming 'MDWP' is null→
8
←
'?' condition is false→
10
←
Passing null pointer value via 2nd parameter 'MD_'→
11
←
Calling 'MemCpyOptPass::runImpl'→
                    MSSAWP8.1
'MSSAWP' is null
 ? &MSSAWP->getMSSA() : nullptr);
9
←
'?' condition is false→
1745}