/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Analysis/MemorySSA.cpp

Bug Summary

File:	llvm/lib/Analysis/MemorySSA.cpp
Warning:	line 2548, column 3 Address of stack memory associated with local variable 'Q' is still referred to by the stack variable 'WalkerBase' upon returning to the caller. This will be a dangling reference
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 MemorySSA.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 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Analysis -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Analysis -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Analysis -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/include -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/include -D 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-14/lib/clang/14.0.0/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 -O2 -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 -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Analysis -fdebug-prefix-map=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e=. -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 -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-09-04-040900-46481-1 -x c++ /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Analysis/MemorySSA.cpp
1//===- MemorySSA.cpp - Memory SSA Builder ---------------------------------===//
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 file implements the MemorySSA class.
10//
11//===----------------------------------------------------------------------===//

13#include "llvm/Analysis/MemorySSA.h"
14#include "llvm/ADT/DenseMap.h"
15#include "llvm/ADT/DenseMapInfo.h"
16#include "llvm/ADT/DenseSet.h"
17#include "llvm/ADT/DepthFirstIterator.h"
18#include "llvm/ADT/Hashing.h"
19#include "llvm/ADT/None.h"
20#include "llvm/ADT/Optional.h"
21#include "llvm/ADT/STLExtras.h"
22#include "llvm/ADT/SmallPtrSet.h"
23#include "llvm/ADT/SmallVector.h"
24#include "llvm/ADT/StringExtras.h"
25#include "llvm/ADT/iterator.h"
26#include "llvm/ADT/iterator_range.h"
27#include "llvm/Analysis/AliasAnalysis.h"
28#include "llvm/Analysis/CFGPrinter.h"
29#include "llvm/Analysis/IteratedDominanceFrontier.h"
30#include "llvm/Analysis/MemoryLocation.h"
31#include "llvm/Config/llvm-config.h"
32#include "llvm/IR/AssemblyAnnotationWriter.h"
33#include "llvm/IR/BasicBlock.h"
34#include "llvm/IR/Dominators.h"
35#include "llvm/IR/Function.h"
36#include "llvm/IR/Instruction.h"
37#include "llvm/IR/Instructions.h"
38#include "llvm/IR/IntrinsicInst.h"
39#include "llvm/IR/Intrinsics.h"
40#include "llvm/IR/LLVMContext.h"
41#include "llvm/IR/PassManager.h"
42#include "llvm/IR/Use.h"
43#include "llvm/InitializePasses.h"
44#include "llvm/Pass.h"
45#include "llvm/Support/AtomicOrdering.h"
46#include "llvm/Support/Casting.h"
47#include "llvm/Support/CommandLine.h"
48#include "llvm/Support/Compiler.h"
49#include "llvm/Support/Debug.h"
50#include "llvm/Support/ErrorHandling.h"
51#include "llvm/Support/FormattedStream.h"
52#include "llvm/Support/raw_ostream.h"
53#include <algorithm>
54#include <cassert>
55#include <cstdlib>
56#include <iterator>
57#include <memory>
58#include <utility>

60using namespace llvm;

62#define DEBUG_TYPE"memoryssa" "memoryssa"

64static cl::opt<std::string>
  DotCFGMSSA("dot-cfg-mssa",
             cl::value_desc("file name for generated dot file"),
             cl::desc("file name for generated dot file"), cl::init(""));

69INITIALIZE_PASS_BEGIN(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
 &Registry) {
                    true)static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
 &Registry) {
71INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
72INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry);
73INITIALIZE_PASS_END(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,PassInfo *PI = new PassInfo( "Memory SSA", "memoryssa", &
MemorySSAWrapperPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemorySSAWrapperPass>), false, true); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemorySSAWrapperPassPassFlag
; void llvm::initializeMemorySSAWrapperPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAWrapperPassPassFlag
, initializeMemorySSAWrapperPassPassOnce, std::ref(Registry))
; }
                  true)PassInfo *PI = new PassInfo( "Memory SSA", "memoryssa", &
MemorySSAWrapperPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemorySSAWrapperPass>), false, true); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemorySSAWrapperPassPassFlag
; void llvm::initializeMemorySSAWrapperPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAWrapperPassPassFlag
, initializeMemorySSAWrapperPassPassOnce, std::ref(Registry))
; }

76INITIALIZE_PASS_BEGIN(MemorySSAPrinterLegacyPass, "print-memoryssa",static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
 &Registry) {
                    "Memory SSA Printer", false, false)static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
 &Registry) {
78INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
79INITIALIZE_PASS_END(MemorySSAPrinterLegacyPass, "print-memoryssa",PassInfo *PI = new PassInfo( "Memory SSA Printer", "print-memoryssa"
, &MemorySSAPrinterLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MemorySSAPrinterLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMemorySSAPrinterLegacyPassPassFlag; void
 llvm::initializeMemorySSAPrinterLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAPrinterLegacyPassPassFlag
, initializeMemorySSAPrinterLegacyPassPassOnce, std::ref(Registry
)); }
                  "Memory SSA Printer", false, false)PassInfo *PI = new PassInfo( "Memory SSA Printer", "print-memoryssa"
, &MemorySSAPrinterLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MemorySSAPrinterLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMemorySSAPrinterLegacyPassPassFlag; void
 llvm::initializeMemorySSAPrinterLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAPrinterLegacyPassPassFlag
, initializeMemorySSAPrinterLegacyPassPassOnce, std::ref(Registry
)); }

82static cl::opt<unsigned> MaxCheckLimit(
  "memssa-check-limit", cl::Hidden, cl::init(100),
  cl::desc("The maximum number of stores/phis MemorySSA"
           "will consider trying to walk past (default = 100)"));

87// Always verify MemorySSA if expensive checking is enabled.
88#ifdef EXPENSIVE_CHECKS
89bool llvm::VerifyMemorySSA = true;
90#else
91bool llvm::VerifyMemorySSA = false;
92#endif

94static cl::opt<bool, true>
  VerifyMemorySSAX("verify-memoryssa", cl::location(VerifyMemorySSA),
                   cl::Hidden, cl::desc("Enable verification of MemorySSA."));

98const static char LiveOnEntryStr[] = "liveOnEntry";

100namespace {

102/// An assembly annotator class to print Memory SSA information in
103/// comments.
104class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter {
const MemorySSA *MSSA;

107public:
MemorySSAAnnotatedWriter(const MemorySSA *M) : MSSA(M) {}

void emitBasicBlockStartAnnot(const BasicBlock *BB,
                              formatted_raw_ostream &OS) override {
  if (MemoryAccess *MA = MSSA->getMemoryAccess(BB))
    OS << "; " << *MA << "\n";
}

void emitInstructionAnnot(const Instruction *I,
                          formatted_raw_ostream &OS) override {
  if (MemoryAccess *MA = MSSA->getMemoryAccess(I))
    OS << "; " << *MA << "\n";
}
121};

123/// An assembly annotator class to print Memory SSA information in
124/// comments.
125class MemorySSAWalkerAnnotatedWriter : public AssemblyAnnotationWriter {
MemorySSA *MSSA;
MemorySSAWalker *Walker;

129public:
MemorySSAWalkerAnnotatedWriter(MemorySSA *M)
    : MSSA(M), Walker(M->getWalker()) {}

void emitInstructionAnnot(const Instruction *I,
                          formatted_raw_ostream &OS) override {
  if (MemoryAccess *MA = MSSA->getMemoryAccess(I)) {
    MemoryAccess *Clobber = Walker->getClobberingMemoryAccess(MA);
    OS << "; " << *MA;
    if (Clobber) {
      OS << " - clobbered by ";
      if (MSSA->isLiveOnEntryDef(Clobber))
        OS << LiveOnEntryStr;
      else
        OS << *Clobber;
    }
    OS << "\n";
  }
}
148};

150} // namespace

152namespace {

154/// Our current alias analysis API differentiates heavily between calls and
155/// non-calls, and functions called on one usually assert on the other.
156/// This class encapsulates the distinction to simplify other code that wants
157/// "Memory affecting instructions and related data" to use as a key.
158/// For example, this class is used as a densemap key in the use optimizer.
159class MemoryLocOrCall {
160public:
bool IsCall = false;

MemoryLocOrCall(MemoryUseOrDef *MUD)
    : MemoryLocOrCall(MUD->getMemoryInst()) {}
MemoryLocOrCall(const MemoryUseOrDef *MUD)
    : MemoryLocOrCall(MUD->getMemoryInst()) {}

MemoryLocOrCall(Instruction *Inst) {
  if (auto *C = dyn_cast<CallBase>(Inst)) {
    IsCall = true;
    Call = C;
  } else {
    IsCall = false;
    // There is no such thing as a memorylocation for a fence inst, and it is
    // unique in that regard.
    if (!isa<FenceInst>(Inst))
      Loc = MemoryLocation::get(Inst);
  }
}

explicit MemoryLocOrCall(const MemoryLocation &Loc) : Loc(Loc) {}

const CallBase *getCall() const {
  assert(IsCall)(static_cast<void> (0));
  return Call;
}

MemoryLocation getLoc() const {
  assert(!IsCall)(static_cast<void> (0));
  return Loc;
}

bool operator==(const MemoryLocOrCall &Other) const {
  if (IsCall != Other.IsCall)
    return false;

  if (!IsCall)
    return Loc == Other.Loc;

  if (Call->getCalledOperand() != Other.Call->getCalledOperand())
    return false;

  return Call->arg_size() == Other.Call->arg_size() &&
         std::equal(Call->arg_begin(), Call->arg_end(),
                    Other.Call->arg_begin());
}

208private:
union {
  const CallBase *Call;
  MemoryLocation Loc;
};
213};

215} // end anonymous namespace

217namespace llvm {

219template <> struct DenseMapInfo<MemoryLocOrCall> {
static inline MemoryLocOrCall getEmptyKey() {
  return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getEmptyKey());
}

static inline MemoryLocOrCall getTombstoneKey() {
  return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getTombstoneKey());
}

static unsigned getHashValue(const MemoryLocOrCall &MLOC) {
  if (!MLOC.IsCall)
    return hash_combine(
        MLOC.IsCall,
        DenseMapInfo<MemoryLocation>::getHashValue(MLOC.getLoc()));

  hash_code hash =
      hash_combine(MLOC.IsCall, DenseMapInfo<const Value *>::getHashValue(
                                    MLOC.getCall()->getCalledOperand()));

  for (const Value *Arg : MLOC.getCall()->args())
    hash = hash_combine(hash, DenseMapInfo<const Value *>::getHashValue(Arg));
  return hash;
}

static bool isEqual(const MemoryLocOrCall &LHS, const MemoryLocOrCall &RHS) {
  return LHS == RHS;
}
246};

248} // end namespace llvm

250/// This does one-way checks to see if Use could theoretically be hoisted above
251/// MayClobber. This will not check the other way around.
252///
253/// This assumes that, for the purposes of MemorySSA, Use comes directly after
254/// MayClobber, with no potentially clobbering operations in between them.
255/// (Where potentially clobbering ops are memory barriers, aliased stores, etc.)
256static bool areLoadsReorderable(const LoadInst *Use,
                              const LoadInst *MayClobber) {
bool VolatileUse = Use->isVolatile();
bool VolatileClobber = MayClobber->isVolatile();
// Volatile operations may never be reordered with other volatile operations.
if (VolatileUse && VolatileClobber)
  return false;
// Otherwise, volatile doesn't matter here. From the language reference:
// 'optimizers may change the order of volatile operations relative to
// non-volatile operations.'"

// If a load is seq_cst, it cannot be moved above other loads. If its ordering
// is weaker, it can be moved above other loads. We just need to be sure that
// MayClobber isn't an acquire load, because loads can't be moved above
// acquire loads.
//
// Note that this explicitly *does* allow the free reordering of monotonic (or
// weaker) loads of the same address.
bool SeqCstUse = Use->getOrdering() == AtomicOrdering::SequentiallyConsistent;
bool MayClobberIsAcquire = isAtLeastOrStrongerThan(MayClobber->getOrdering(),
                                                   AtomicOrdering::Acquire);
return !(SeqCstUse || MayClobberIsAcquire);
278}

280namespace {

282struct ClobberAlias {
bool IsClobber;
Optional<AliasResult> AR;
285};

287} // end anonymous namespace

289// Return a pair of {IsClobber (bool), AR (AliasResult)}. It relies on AR being
290// ignored if IsClobber = false.
291template <typename AliasAnalysisType>
292static ClobberAlias
293instructionClobbersQuery(const MemoryDef *MD, const MemoryLocation &UseLoc,
                       const Instruction *UseInst, AliasAnalysisType &AA) {
Instruction *DefInst = MD->getMemoryInst();
assert(DefInst && "Defining instruction not actually an instruction")(static_cast<void> (0));
Optional<AliasResult> AR;

if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
  // These intrinsics will show up as affecting memory, but they are just
  // markers, mostly.
  //
  // FIXME: We probably don't actually want MemorySSA to model these at all
  // (including creating MemoryAccesses for them): we just end up inventing
  // clobbers where they don't really exist at all. Please see D43269 for
  // context.
  switch (II->getIntrinsicID()) {
  case Intrinsic::invariant_start:
  case Intrinsic::invariant_end:
  case Intrinsic::assume:
  case Intrinsic::experimental_noalias_scope_decl:
    return {false, AliasResult(AliasResult::NoAlias)};
  case Intrinsic::dbg_addr:
  case Intrinsic::dbg_declare:
  case Intrinsic::dbg_label:
  case Intrinsic::dbg_value:
    llvm_unreachable("debuginfo shouldn't have associated defs!")__builtin_unreachable();
  default:
    break;
  }
}

if (auto *CB = dyn_cast_or_null<CallBase>(UseInst)) {
  ModRefInfo I = AA.getModRefInfo(DefInst, CB);
  AR = isMustSet(I) ? AliasResult::MustAlias : AliasResult::MayAlias;
  return {isModOrRefSet(I), AR};
}

if (auto *DefLoad = dyn_cast<LoadInst>(DefInst))
  if (auto *UseLoad = dyn_cast_or_null<LoadInst>(UseInst))
    return {!areLoadsReorderable(UseLoad, DefLoad),
            AliasResult(AliasResult::MayAlias)};

ModRefInfo I = AA.getModRefInfo(DefInst, UseLoc);
AR = isMustSet(I) ? AliasResult::MustAlias : AliasResult::MayAlias;
return {isModSet(I), AR};
337}

339template <typename AliasAnalysisType>
340static ClobberAlias instructionClobbersQuery(MemoryDef *MD,
                                           const MemoryUseOrDef *MU,
                                           const MemoryLocOrCall &UseMLOC,
                                           AliasAnalysisType &AA) {
// FIXME: This is a temporary hack to allow a single instructionClobbersQuery
// to exist while MemoryLocOrCall is pushed through places.
if (UseMLOC.IsCall)
  return instructionClobbersQuery(MD, MemoryLocation(), MU->getMemoryInst(),
                                  AA);
return instructionClobbersQuery(MD, UseMLOC.getLoc(), MU->getMemoryInst(),
                                AA);
351}

353// Return true when MD may alias MU, return false otherwise.
354bool MemorySSAUtil::defClobbersUseOrDef(MemoryDef *MD, const MemoryUseOrDef *MU,
                                      AliasAnalysis &AA) {
return instructionClobbersQuery(MD, MU, MemoryLocOrCall(MU), AA).IsClobber;
357}

359namespace {

361struct UpwardsMemoryQuery {
// True if our original query started off as a call
bool IsCall = false;
// The pointer location we started the query with. This will be empty if
// IsCall is true.
MemoryLocation StartingLoc;
// This is the instruction we were querying about.
const Instruction *Inst = nullptr;
// The MemoryAccess we actually got called with, used to test local domination
const MemoryAccess *OriginalAccess = nullptr;
Optional<AliasResult> AR = AliasResult(AliasResult::MayAlias);
bool SkipSelfAccess = false;

UpwardsMemoryQuery() = default;

UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
    : IsCall(isa<CallBase>(Inst)), Inst(Inst), OriginalAccess(Access) {
  if (!IsCall)
    StartingLoc = MemoryLocation::get(Inst);
}
381};

383} // end anonymous namespace

385template <typename AliasAnalysisType>
386static bool isUseTriviallyOptimizableToLiveOnEntry(AliasAnalysisType &AA,
                                                 const Instruction *I) {
// If the memory can't be changed, then loads of the memory can't be
// clobbered.
if (auto *LI = dyn_cast<LoadInst>(I))
  return I->hasMetadata(LLVMContext::MD_invariant_load) ||
         AA.pointsToConstantMemory(MemoryLocation::get(LI));
return false;
394}

396/// Verifies that `Start` is clobbered by `ClobberAt`, and that nothing
397/// inbetween `Start` and `ClobberAt` can clobbers `Start`.
398///
399/// This is meant to be as simple and self-contained as possible. Because it
400/// uses no cache, etc., it can be relatively expensive.
401///
402/// \param Start     The MemoryAccess that we want to walk from.
403/// \param ClobberAt A clobber for Start.
404/// \param StartLoc  The MemoryLocation for Start.
405/// \param MSSA      The MemorySSA instance that Start and ClobberAt belong to.
406/// \param Query     The UpwardsMemoryQuery we used for our search.
407/// \param AA        The AliasAnalysis we used for our search.
408/// \param AllowImpreciseClobber Always false, unless we do relaxed verify.

410template <typename AliasAnalysisType>
411LLVM_ATTRIBUTE_UNUSED__attribute__((__unused__)) static void
412checkClobberSanity(const MemoryAccess *Start, MemoryAccess *ClobberAt,
                 const MemoryLocation &StartLoc, const MemorySSA &MSSA,
                 const UpwardsMemoryQuery &Query, AliasAnalysisType &AA,
                 bool AllowImpreciseClobber = false) {
assert(MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?")(static_cast<void> (0));

if (MSSA.isLiveOnEntryDef(Start)) {
  assert(MSSA.isLiveOnEntryDef(ClobberAt) &&(static_cast<void> (0))
         "liveOnEntry must clobber itself")(static_cast<void> (0));
  return;
}

bool FoundClobber = false;
DenseSet<ConstMemoryAccessPair> VisitedPhis;
SmallVector<ConstMemoryAccessPair, 8> Worklist;
Worklist.emplace_back(Start, StartLoc);
// Walk all paths from Start to ClobberAt, while looking for clobbers. If one
// is found, complain.
while (!Worklist.empty()) {
  auto MAP = Worklist.pop_back_val();
  // All we care about is that nothing from Start to ClobberAt clobbers Start.
  // We learn nothing from revisiting nodes.
  if (!VisitedPhis.insert(MAP).second)
    continue;

  for (const auto *MA : def_chain(MAP.first)) {
    if (MA == ClobberAt) {
      if (const auto *MD = dyn_cast<MemoryDef>(MA)) {
        // instructionClobbersQuery isn't essentially free, so don't use `|=`,
        // since it won't let us short-circuit.
        //
        // Also, note that this can't be hoisted out of the `Worklist` loop,
        // since MD may only act as a clobber for 1 of N MemoryLocations.
        FoundClobber = FoundClobber || MSSA.isLiveOnEntryDef(MD);
        if (!FoundClobber) {
          ClobberAlias CA =
              instructionClobbersQuery(MD, MAP.second, Query.Inst, AA);
          if (CA.IsClobber) {
            FoundClobber = true;
            // Not used: CA.AR;
          }
        }
      }
      break;
    }

    // We should never hit liveOnEntry, unless it's the clobber.
    assert(!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?")(static_cast<void> (0));

    if (const auto *MD = dyn_cast<MemoryDef>(MA)) {
      // If Start is a Def, skip self.
      if (MD == Start)
        continue;

      assert(!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA)(static_cast<void> (0))
                  .IsClobber &&(static_cast<void> (0))
             "Found clobber before reaching ClobberAt!")(static_cast<void> (0));
      continue;
    }

    if (const auto *MU = dyn_cast<MemoryUse>(MA)) {
      (void)MU;
      assert (MU == Start &&(static_cast<void> (0))
              "Can only find use in def chain if Start is a use")(static_cast<void> (0));
      continue;
    }

    assert(isa<MemoryPhi>(MA))(static_cast<void> (0));

    // Add reachable phi predecessors
    for (auto ItB = upward_defs_begin(
                  {const_cast<MemoryAccess *>(MA), MAP.second},
                  MSSA.getDomTree()),
              ItE = upward_defs_end();
         ItB != ItE; ++ItB)
      if (MSSA.getDomTree().isReachableFromEntry(ItB.getPhiArgBlock()))
        Worklist.emplace_back(*ItB);
  }
}

// If the verify is done following an optimization, it's possible that
// ClobberAt was a conservative clobbering, that we can now infer is not a
// true clobbering access. Don't fail the verify if that's the case.
// We do have accesses that claim they're optimized, but could be optimized
// further. Updating all these can be expensive, so allow it for now (FIXME).
if (AllowImpreciseClobber)
  return;

// If ClobberAt is a MemoryPhi, we can assume something above it acted as a
// clobber. Otherwise, `ClobberAt` should've acted as a clobber at some point.
assert((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&(static_cast<void> (0))
       "ClobberAt never acted as a clobber")(static_cast<void> (0));
504}

506namespace {

508/// Our algorithm for walking (and trying to optimize) clobbers, all wrapped up
509/// in one class.
510template <class AliasAnalysisType> class ClobberWalker {
/// Save a few bytes by using unsigned instead of size_t.
using ListIndex = unsigned;

/// Represents a span of contiguous MemoryDefs, potentially ending in a
/// MemoryPhi.
struct DefPath {
  MemoryLocation Loc;
  // Note that, because we always walk in reverse, Last will always dominate
  // First. Also note that First and Last are inclusive.
  MemoryAccess *First;
  MemoryAccess *Last;
  Optional<ListIndex> Previous;

  DefPath(const MemoryLocation &Loc, MemoryAccess *First, MemoryAccess *Last,
          Optional<ListIndex> Previous)
      : Loc(Loc), First(First), Last(Last), Previous(Previous) {}

  DefPath(const MemoryLocation &Loc, MemoryAccess *Init,
          Optional<ListIndex> Previous)
      : DefPath(Loc, Init, Init, Previous) {}
};

const MemorySSA &MSSA;
AliasAnalysisType &AA;
DominatorTree &DT;
UpwardsMemoryQuery *Query;
unsigned *UpwardWalkLimit;

// Phi optimization bookkeeping:
// List of DefPath to process during the current phi optimization walk.
SmallVector<DefPath, 32> Paths;
// List of visited <Access, Location> pairs; we can skip paths already
// visited with the same memory location.
DenseSet<ConstMemoryAccessPair> VisitedPhis;
// Record if phi translation has been performed during the current phi
// optimization walk, as merging alias results after phi translation can
// yield incorrect results. Context in PR46156.
bool PerformedPhiTranslation = false;

/// Find the nearest def or phi that `From` can legally be optimized to.
const MemoryAccess *getWalkTarget(const MemoryPhi *From) const {
  assert(From->getNumOperands() && "Phi with no operands?")(static_cast<void> (0));

  BasicBlock *BB = From->getBlock();
  MemoryAccess *Result = MSSA.getLiveOnEntryDef();
  DomTreeNode *Node = DT.getNode(BB);
  while ((Node = Node->getIDom())) {
    auto *Defs = MSSA.getBlockDefs(Node->getBlock());
    if (Defs)
      return &*Defs->rbegin();
  }
  return Result;
}

/// Result of calling walkToPhiOrClobber.
struct UpwardsWalkResult {
  /// The "Result" of the walk. Either a clobber, the last thing we walked, or
  /// both. Include alias info when clobber found.
  MemoryAccess *Result;
  bool IsKnownClobber;
  Optional<AliasResult> AR;
};

/// Walk to the next Phi or Clobber in the def chain starting at Desc.Last.
/// This will update Desc.Last as it walks. It will (optionally) also stop at
/// StopAt.
///
/// This does not test for whether StopAt is a clobber
UpwardsWalkResult
walkToPhiOrClobber(DefPath &Desc, const MemoryAccess *StopAt = nullptr,
                   const MemoryAccess *SkipStopAt = nullptr) const {
  assert(!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world")(static_cast<void> (0));
  assert(UpwardWalkLimit && "Need a valid walk limit")(static_cast<void> (0));
  bool LimitAlreadyReached = false;
  // (*UpwardWalkLimit) may be 0 here, due to the loop in tryOptimizePhi. Set
  // it to 1. This will not do any alias() calls. It either returns in the
  // first iteration in the loop below, or is set back to 0 if all def chains
  // are free of MemoryDefs.
  if (!*UpwardWalkLimit) {
    *UpwardWalkLimit = 1;
    LimitAlreadyReached = true;
  }

  for (MemoryAccess *Current : def_chain(Desc.Last)) {
    Desc.Last = Current;
    if (Current == StopAt || Current == SkipStopAt)
      return {Current, false, AliasResult(AliasResult::MayAlias)};

    if (auto *MD = dyn_cast<MemoryDef>(Current)) {
      if (MSSA.isLiveOnEntryDef(MD))
        return {MD, true, AliasResult(AliasResult::MustAlias)};

      if (!--*UpwardWalkLimit)
        return {Current, true, AliasResult(AliasResult::MayAlias)};

      ClobberAlias CA =
          instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA);
      if (CA.IsClobber)
        return {MD, true, CA.AR};
    }
  }

  if (LimitAlreadyReached)
    *UpwardWalkLimit = 0;

  assert(isa<MemoryPhi>(Desc.Last) &&(static_cast<void> (0))
         "Ended at a non-clobber that's not a phi?")(static_cast<void> (0));
  return {Desc.Last, false, AliasResult(AliasResult::MayAlias)};
}

void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
                 ListIndex PriorNode) {
  auto UpwardDefsBegin = upward_defs_begin({Phi, Paths[PriorNode].Loc}, DT,
                                           &PerformedPhiTranslation);
  auto UpwardDefs = make_range(UpwardDefsBegin, upward_defs_end());
  for (const MemoryAccessPair &P : UpwardDefs) {
    PausedSearches.push_back(Paths.size());
    Paths.emplace_back(P.second, P.first, PriorNode);
  }
}

/// Represents a search that terminated after finding a clobber. This clobber
/// may or may not be present in the path of defs from LastNode..SearchStart,
/// since it may have been retrieved from cache.
struct TerminatedPath {
  MemoryAccess *Clobber;
  ListIndex LastNode;
};

/// Get an access that keeps us from optimizing to the given phi.
///
/// PausedSearches is an array of indices into the Paths array. Its incoming
/// value is the indices of searches that stopped at the last phi optimization
/// target. It's left in an unspecified state.
///
/// If this returns None, NewPaused is a vector of searches that terminated
/// at StopWhere. Otherwise, NewPaused is left in an unspecified state.
Optional<TerminatedPath>
getBlockingAccess(const MemoryAccess *StopWhere,
                  SmallVectorImpl<ListIndex> &PausedSearches,
                  SmallVectorImpl<ListIndex> &NewPaused,
                  SmallVectorImpl<TerminatedPath> &Terminated) {
  assert(!PausedSearches.empty() && "No searches to continue?")(static_cast<void> (0));

  // BFS vs DFS really doesn't make a difference here, so just do a DFS with
  // PausedSearches as our stack.
  while (!PausedSearches.empty()) {
    ListIndex PathIndex = PausedSearches.pop_back_val();
    DefPath &Node = Paths[PathIndex];

    // If we've already visited this path with this MemoryLocation, we don't
    // need to do so again.
    //
    // NOTE: That we just drop these paths on the ground makes caching
    // behavior sporadic. e.g. given a diamond:
    //  A
    // B C
    //  D
    //
    // ...If we walk D, B, A, C, we'll only cache the result of phi
    // optimization for A, B, and D; C will be skipped because it dies here.
    // This arguably isn't the worst thing ever, since:
    //   - We generally query things in a top-down order, so if we got below D
    //     without needing cache entries for {C, MemLoc}, then chances are
    //     that those cache entries would end up ultimately unused.
    //   - We still cache things for A, so C only needs to walk up a bit.
    // If this behavior becomes problematic, we can fix without a ton of extra
    // work.
    if (!VisitedPhis.insert({Node.Last, Node.Loc}).second) {
      if (PerformedPhiTranslation) {
        // If visiting this path performed Phi translation, don't continue,
        // since it may not be correct to merge results from two paths if one
        // relies on the phi translation.
        TerminatedPath Term{Node.Last, PathIndex};
        return Term;
      }
      continue;
    }

    const MemoryAccess *SkipStopWhere = nullptr;
    if (Query->SkipSelfAccess && Node.Loc == Query->StartingLoc) {
      assert(isa<MemoryDef>(Query->OriginalAccess))(static_cast<void> (0));
      SkipStopWhere = Query->OriginalAccess;
    }

    UpwardsWalkResult Res = walkToPhiOrClobber(Node,
                                               /*StopAt=*/StopWhere,
                                               /*SkipStopAt=*/SkipStopWhere);
    if (Res.IsKnownClobber) {
      assert(Res.Result != StopWhere && Res.Result != SkipStopWhere)(static_cast<void> (0));

      // If this wasn't a cache hit, we hit a clobber when walking. That's a
      // failure.
      TerminatedPath Term{Res.Result, PathIndex};
      if (!MSSA.dominates(Res.Result, StopWhere))
        return Term;

      // Otherwise, it's a valid thing to potentially optimize to.
      Terminated.push_back(Term);
      continue;
    }

    if (Res.Result == StopWhere || Res.Result == SkipStopWhere) {
      // We've hit our target. Save this path off for if we want to continue
      // walking. If we are in the mode of skipping the OriginalAccess, and
      // we've reached back to the OriginalAccess, do not save path, we've
      // just looped back to self.
      if (Res.Result != SkipStopWhere)
        NewPaused.push_back(PathIndex);
      continue;
    }

    assert(!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber")(static_cast<void> (0));
    addSearches(cast<MemoryPhi>(Res.Result), PausedSearches, PathIndex);
  }

  return None;
}

template <typename T, typename Walker>
struct generic_def_path_iterator
    : public iterator_facade_base<generic_def_path_iterator<T, Walker>,
                                  std::forward_iterator_tag, T *> {
  generic_def_path_iterator() {}
  generic_def_path_iterator(Walker *W, ListIndex N) : W(W), N(N) {}

  T &operator*() const { return curNode(); }

  generic_def_path_iterator &operator++() {
    N = curNode().Previous;
    return *this;
  }

  bool operator==(const generic_def_path_iterator &O) const {
    if (N.hasValue() != O.N.hasValue())
      return false;
    return !N.hasValue() || *N == *O.N;
  }

private:
  T &curNode() const { return W->Paths[*N]; }

  Walker *W = nullptr;
  Optional<ListIndex> N = None;
};

using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
using const_def_path_iterator =
    generic_def_path_iterator<const DefPath, const ClobberWalker>;

iterator_range<def_path_iterator> def_path(ListIndex From) {
  return make_range(def_path_iterator(this, From), def_path_iterator());
}

iterator_range<const_def_path_iterator> const_def_path(ListIndex From) const {
  return make_range(const_def_path_iterator(this, From),
                    const_def_path_iterator());
}

struct OptznResult {
  /// The path that contains our result.
  TerminatedPath PrimaryClobber;
  /// The paths that we can legally cache back from, but that aren't
  /// necessarily the result of the Phi optimization.
  SmallVector<TerminatedPath, 4> OtherClobbers;
};

ListIndex defPathIndex(const DefPath &N) const {
  // The assert looks nicer if we don't need to do &N
  const DefPath *NP = &N;
  assert(!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() &&(static_cast<void> (0))
         "Out of bounds DefPath!")(static_cast<void> (0));
  return NP - &Paths.front();
}

/// Try to optimize a phi as best as we can. Returns a SmallVector of Paths
/// that act as legal clobbers. Note that this won't return *all* clobbers.
///
/// Phi optimization algorithm tl;dr:
///   - Find the earliest def/phi, A, we can optimize to
///   - Find if all paths from the starting memory access ultimately reach A
///     - If not, optimization isn't possible.
///     - Otherwise, walk from A to another clobber or phi, A'.
///       - If A' is a def, we're done.
///       - If A' is a phi, try to optimize it.
///
/// A path is a series of {MemoryAccess, MemoryLocation} pairs. A path
/// terminates when a MemoryAccess that clobbers said MemoryLocation is found.
OptznResult tryOptimizePhi(MemoryPhi *Phi, MemoryAccess *Start,
                           const MemoryLocation &Loc) {
  assert(Paths.empty() && VisitedPhis.empty() && !PerformedPhiTranslation &&(static_cast<void> (0))
         "Reset the optimization state.")(static_cast<void> (0));

  Paths.emplace_back(Loc, Start, Phi, None);
  // Stores how many "valid" optimization nodes we had prior to calling
  // addSearches/getBlockingAccess. Necessary for caching if we had a blocker.
  auto PriorPathsSize = Paths.size();

  SmallVector<ListIndex, 16> PausedSearches;
  SmallVector<ListIndex, 8> NewPaused;
  SmallVector<TerminatedPath, 4> TerminatedPaths;

  addSearches(Phi, PausedSearches, 0);

  // Moves the TerminatedPath with the "most dominated" Clobber to the end of
  // Paths.
  auto MoveDominatedPathToEnd = [&](SmallVectorImpl<TerminatedPath> &Paths) {
    assert(!Paths.empty() && "Need a path to move")(static_cast<void> (0));
    auto Dom = Paths.begin();
    for (auto I = std::next(Dom), E = Paths.end(); I != E; ++I)
      if (!MSSA.dominates(I->Clobber, Dom->Clobber))
        Dom = I;
    auto Last = Paths.end() - 1;
    if (Last != Dom)
      std::iter_swap(Last, Dom);
  };

  MemoryPhi *Current = Phi;
  while (true) {
    assert(!MSSA.isLiveOnEntryDef(Current) &&(static_cast<void> (0))
           "liveOnEntry wasn't treated as a clobber?")(static_cast<void> (0));

    const auto *Target = getWalkTarget(Current);
    // If a TerminatedPath doesn't dominate Target, then it wasn't a legal
    // optimization for the prior phi.
    assert(all_of(TerminatedPaths, [&](const TerminatedPath &P) {(static_cast<void> (0))
      return MSSA.dominates(P.Clobber, Target);(static_cast<void> (0))
    }))(static_cast<void> (0));

    // FIXME: This is broken, because the Blocker may be reported to be
    // liveOnEntry, and we'll happily wait for that to disappear (read: never)
    // For the moment, this is fine, since we do nothing with blocker info.
    if (Optional<TerminatedPath> Blocker = getBlockingAccess(
            Target, PausedSearches, NewPaused, TerminatedPaths)) {

      // Find the node we started at. We can't search based on N->Last, since
      // we may have gone around a loop with a different MemoryLocation.
      auto Iter = find_if(def_path(Blocker->LastNode), [&](const DefPath &N) {
        return defPathIndex(N) < PriorPathsSize;
      });
      assert(Iter != def_path_iterator())(static_cast<void> (0));

      DefPath &CurNode = *Iter;
      assert(CurNode.Last == Current)(static_cast<void> (0));

      // Two things:
      // A. We can't reliably cache all of NewPaused back. Consider a case
      //    where we have two paths in NewPaused; one of which can't optimize
      //    above this phi, whereas the other can. If we cache the second path
      //    back, we'll end up with suboptimal cache entries. We can handle
      //    cases like this a bit better when we either try to find all
      //    clobbers that block phi optimization, or when our cache starts
      //    supporting unfinished searches.
      // B. We can't reliably cache TerminatedPaths back here without doing
      //    extra checks; consider a case like:
      //       T
      //      / \
      //     D   C
      //      \ /
      //       S
      //    Where T is our target, C is a node with a clobber on it, D is a
      //    diamond (with a clobber *only* on the left or right node, N), and
      //    S is our start. Say we walk to D, through the node opposite N
      //    (read: ignoring the clobber), and see a cache entry in the top
      //    node of D. That cache entry gets put into TerminatedPaths. We then
      //    walk up to C (N is later in our worklist), find the clobber, and
      //    quit. If we append TerminatedPaths to OtherClobbers, we'll cache
      //    the bottom part of D to the cached clobber, ignoring the clobber
      //    in N. Again, this problem goes away if we start tracking all
      //    blockers for a given phi optimization.
      TerminatedPath Result{CurNode.Last, defPathIndex(CurNode)};
      return {Result, {}};
    }

    // If there's nothing left to search, then all paths led to valid clobbers
    // that we got from our cache; pick the nearest to the start, and allow
    // the rest to be cached back.
    if (NewPaused.empty()) {
      MoveDominatedPathToEnd(TerminatedPaths);
      TerminatedPath Result = TerminatedPaths.pop_back_val();
      return {Result, std::move(TerminatedPaths)};
    }

    MemoryAccess *DefChainEnd = nullptr;
    SmallVector<TerminatedPath, 4> Clobbers;
    for (ListIndex Paused : NewPaused) {
      UpwardsWalkResult WR = walkToPhiOrClobber(Paths[Paused]);
      if (WR.IsKnownClobber)
        Clobbers.push_back({WR.Result, Paused});
      else
        // Micro-opt: If we hit the end of the chain, save it.
        DefChainEnd = WR.Result;
    }

    if (!TerminatedPaths.empty()) {
      // If we couldn't find the dominating phi/liveOnEntry in the above loop,
      // do it now.
      if (!DefChainEnd)
        for (auto *MA : def_chain(const_cast<MemoryAccess *>(Target)))
          DefChainEnd = MA;
      assert(DefChainEnd && "Failed to find dominating phi/liveOnEntry")(static_cast<void> (0));

      // If any of the terminated paths don't dominate the phi we'll try to
      // optimize, we need to figure out what they are and quit.
      const BasicBlock *ChainBB = DefChainEnd->getBlock();
      for (const TerminatedPath &TP : TerminatedPaths) {
        // Because we know that DefChainEnd is as "high" as we can go, we
        // don't need local dominance checks; BB dominance is sufficient.
        if (DT.dominates(ChainBB, TP.Clobber->getBlock()))
          Clobbers.push_back(TP);
      }
    }

    // If we have clobbers in the def chain, find the one closest to Current
    // and quit.
    if (!Clobbers.empty()) {
      MoveDominatedPathToEnd(Clobbers);
      TerminatedPath Result = Clobbers.pop_back_val();
      return {Result, std::move(Clobbers)};
    }

    assert(all_of(NewPaused,(static_cast<void> (0))
                  [&](ListIndex I) { return Paths[I].Last == DefChainEnd; }))(static_cast<void> (0));

    // Because liveOnEntry is a clobber, this must be a phi.
    auto *DefChainPhi = cast<MemoryPhi>(DefChainEnd);

    PriorPathsSize = Paths.size();
    PausedSearches.clear();
    for (ListIndex I : NewPaused)
      addSearches(DefChainPhi, PausedSearches, I);
    NewPaused.clear();

    Current = DefChainPhi;
  }
}

void verifyOptResult(const OptznResult &R) const {
  assert(all_of(R.OtherClobbers, [&](const TerminatedPath &P) {(static_cast<void> (0))
    return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber);(static_cast<void> (0))
  }))(static_cast<void> (0));
}

void resetPhiOptznState() {
  Paths.clear();
  VisitedPhis.clear();
  PerformedPhiTranslation = false;
}

960public:
ClobberWalker(const MemorySSA &MSSA, AliasAnalysisType &AA, DominatorTree &DT)
    : MSSA(MSSA), AA(AA), DT(DT) {}

AliasAnalysisType *getAA() { return &AA; }
/// Finds the nearest clobber for the given query, optimizing phis if
/// possible.
MemoryAccess *findClobber(MemoryAccess *Start, UpwardsMemoryQuery &Q,
                          unsigned &UpWalkLimit) {
  Query = &Q;
  UpwardWalkLimit = &UpWalkLimit;
  // Starting limit must be > 0.
  if (!UpWalkLimit)
    UpWalkLimit++;

  MemoryAccess *Current = Start;
  // This walker pretends uses don't exist. If we're handed one, silently grab
  // its def. (This has the nice side-effect of ensuring we never cache uses)
  if (auto *MU = dyn_cast<MemoryUse>(Start))
    Current = MU->getDefiningAccess();

  DefPath FirstDesc(Q.StartingLoc, Current, Current, None);
  // Fast path for the overly-common case (no crazy phi optimization
  // necessary)
  UpwardsWalkResult WalkResult = walkToPhiOrClobber(FirstDesc);
  MemoryAccess *Result;
  if (WalkResult.IsKnownClobber) {
    Result = WalkResult.Result;
    Q.AR = WalkResult.AR;
  } else {
    OptznResult OptRes = tryOptimizePhi(cast<MemoryPhi>(FirstDesc.Last),
                                        Current, Q.StartingLoc);
    verifyOptResult(OptRes);
    resetPhiOptznState();
    Result = OptRes.PrimaryClobber.Clobber;
  }

997#ifdef EXPENSIVE_CHECKS
  if (!Q.SkipSelfAccess && *UpwardWalkLimit > 0)
    checkClobberSanity(Current, Result, Q.StartingLoc, MSSA, Q, AA);
1000#endif
  return Result;
}
1003};

1005struct RenamePassData {
DomTreeNode *DTN;
DomTreeNode::const_iterator ChildIt;
MemoryAccess *IncomingVal;

RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
               MemoryAccess *M)
    : DTN(D), ChildIt(It), IncomingVal(M) {}

void swap(RenamePassData &RHS) {
  std::swap(DTN, RHS.DTN);
  std::swap(ChildIt, RHS.ChildIt);
  std::swap(IncomingVal, RHS.IncomingVal);
}
1019};

1021} // end anonymous namespace

1023namespace llvm {

1025template <class AliasAnalysisType> class MemorySSA::ClobberWalkerBase {
ClobberWalker<AliasAnalysisType> Walker;
MemorySSA *MSSA;

1029public:
ClobberWalkerBase(MemorySSA *M, AliasAnalysisType *A, DominatorTree *D)
    : Walker(*M, *A, *D), MSSA(M) {}

MemoryAccess *getClobberingMemoryAccessBase(MemoryAccess *,
                                            const MemoryLocation &,
                                            unsigned &);
// Third argument (bool), defines whether the clobber search should skip the
// original queried access. If true, there will be a follow-up query searching
// for a clobber access past "self". Note that the Optimized access is not
// updated if a new clobber is found by this SkipSelf search. If this
// additional query becomes heavily used we may decide to cache the result.
// Walker instantiations will decide how to set the SkipSelf bool.
MemoryAccess *getClobberingMemoryAccessBase(MemoryAccess *, unsigned &, bool);
1043};

1045/// A MemorySSAWalker that does AA walks to disambiguate accesses. It no
1046/// longer does caching on its own, but the name has been retained for the
1047/// moment.
1048template <class AliasAnalysisType>
1049class MemorySSA::CachingWalker final : public MemorySSAWalker {
ClobberWalkerBase<AliasAnalysisType> *Walker;

1052public:
CachingWalker(MemorySSA *M, ClobberWalkerBase<AliasAnalysisType> *W)
    : MemorySSAWalker(M), Walker(W) {}
~CachingWalker() override = default;

using MemorySSAWalker::getClobberingMemoryAccess;

MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA, unsigned &UWL) {
  return Walker->getClobberingMemoryAccessBase(MA, UWL, false);
26
←
Calling 'ClobberWalkerBase::getClobberingMemoryAccessBase'→
}
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
                                        const MemoryLocation &Loc,
                                        unsigned &UWL) {
  return Walker->getClobberingMemoryAccessBase(MA, Loc, UWL);
}

MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA) override {
  unsigned UpwardWalkLimit = MaxCheckLimit;
  return getClobberingMemoryAccess(MA, UpwardWalkLimit);
}
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
                                        const MemoryLocation &Loc) override {
  unsigned UpwardWalkLimit = MaxCheckLimit;
  return getClobberingMemoryAccess(MA, Loc, UpwardWalkLimit);
}

void invalidateInfo(MemoryAccess *MA) override {
  if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
    MUD->resetOptimized();
}
1082};

1084template <class AliasAnalysisType>
1085class MemorySSA::SkipSelfWalker final : public MemorySSAWalker {
ClobberWalkerBase<AliasAnalysisType> *Walker;

1088public:
SkipSelfWalker(MemorySSA *M, ClobberWalkerBase<AliasAnalysisType> *W)
    : MemorySSAWalker(M), Walker(W) {}
~SkipSelfWalker() override = default;

using MemorySSAWalker::getClobberingMemoryAccess;

MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA, unsigned &UWL) {
  return Walker->getClobberingMemoryAccessBase(MA, UWL, true);
}
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
                                        const MemoryLocation &Loc,
                                        unsigned &UWL) {
  return Walker->getClobberingMemoryAccessBase(MA, Loc, UWL);
}

MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA) override {
  unsigned UpwardWalkLimit = MaxCheckLimit;
  return getClobberingMemoryAccess(MA, UpwardWalkLimit);
}
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
                                        const MemoryLocation &Loc) override {
  unsigned UpwardWalkLimit = MaxCheckLimit;
  return getClobberingMemoryAccess(MA, Loc, UpwardWalkLimit);
}

void invalidateInfo(MemoryAccess *MA) override {
  if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
    MUD->resetOptimized();
}
1118};

1120} // end namespace llvm

1122void MemorySSA::renameSuccessorPhis(BasicBlock *BB, MemoryAccess *IncomingVal,
                                  bool RenameAllUses) {
// Pass through values to our successors
for (const BasicBlock *S : successors(BB)) {
  auto It = PerBlockAccesses.find(S);
  // Rename the phi nodes in our successor block
  if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
    continue;
  AccessList *Accesses = It->second.get();
  auto *Phi = cast<MemoryPhi>(&Accesses->front());
  if (RenameAllUses) {
    bool ReplacementDone = false;
    for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I)
      if (Phi->getIncomingBlock(I) == BB) {
        Phi->setIncomingValue(I, IncomingVal);
        ReplacementDone = true;
      }
    (void) ReplacementDone;
    assert(ReplacementDone && "Incomplete phi during partial rename")(static_cast<void> (0));
  } else
    Phi->addIncoming(IncomingVal, BB);
}
1144}

1146/// Rename a single basic block into MemorySSA form.
1147/// Uses the standard SSA renaming algorithm.
1148/// \returns The new incoming value.
1149MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB, MemoryAccess *IncomingVal,
                                   bool RenameAllUses) {
auto It = PerBlockAccesses.find(BB);
// Skip most processing if the list is empty.
if (It != PerBlockAccesses.end()) {
  AccessList *Accesses = It->second.get();
  for (MemoryAccess &L : *Accesses) {
    if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(&L)) {
      if (MUD->getDefiningAccess() == nullptr || RenameAllUses)
        MUD->setDefiningAccess(IncomingVal);
      if (isa<MemoryDef>(&L))
        IncomingVal = &L;
    } else {
      IncomingVal = &L;
    }
  }
}
return IncomingVal;
1167}

1169/// This is the standard SSA renaming algorithm.
1170///
1171/// We walk the dominator tree in preorder, renaming accesses, and then filling
1172/// in phi nodes in our successors.
1173void MemorySSA::renamePass(DomTreeNode *Root, MemoryAccess *IncomingVal,
                         SmallPtrSetImpl<BasicBlock *> &Visited,
                         bool SkipVisited, bool RenameAllUses) {
assert(Root && "Trying to rename accesses in an unreachable block")(static_cast<void> (0));

SmallVector<RenamePassData, 32> WorkStack;
// Skip everything if we already renamed this block and we are skipping.
// Note: You can't sink this into the if, because we need it to occur
// regardless of whether we skip blocks or not.
bool AlreadyVisited = !Visited.insert(Root->getBlock()).second;
if (SkipVisited && AlreadyVisited)
  return;

IncomingVal = renameBlock(Root->getBlock(), IncomingVal, RenameAllUses);
renameSuccessorPhis(Root->getBlock(), IncomingVal, RenameAllUses);
WorkStack.push_back({Root, Root->begin(), IncomingVal});

while (!WorkStack.empty()) {
  DomTreeNode *Node = WorkStack.back().DTN;
  DomTreeNode::const_iterator ChildIt = WorkStack.back().ChildIt;
  IncomingVal = WorkStack.back().IncomingVal;

  if (ChildIt == Node->end()) {
    WorkStack.pop_back();
  } else {
    DomTreeNode *Child = *ChildIt;
    ++WorkStack.back().ChildIt;
    BasicBlock *BB = Child->getBlock();
    // Note: You can't sink this into the if, because we need it to occur
    // regardless of whether we skip blocks or not.
    AlreadyVisited = !Visited.insert(BB).second;
    if (SkipVisited && AlreadyVisited) {
      // We already visited this during our renaming, which can happen when
      // being asked to rename multiple blocks. Figure out the incoming val,
      // which is the last def.
      // Incoming value can only change if there is a block def, and in that
      // case, it's the last block def in the list.
      if (auto *BlockDefs = getWritableBlockDefs(BB))
        IncomingVal = &*BlockDefs->rbegin();
    } else
      IncomingVal = renameBlock(BB, IncomingVal, RenameAllUses);
    renameSuccessorPhis(BB, IncomingVal, RenameAllUses);
    WorkStack.push_back({Child, Child->begin(), IncomingVal});
  }
}
1218}

1220/// This handles unreachable block accesses by deleting phi nodes in
1221/// unreachable blocks, and marking all other unreachable MemoryAccess's as
1222/// being uses of the live on entry definition.
1223void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
assert(!DT->isReachableFromEntry(BB) &&(static_cast<void> (0))
       "Reachable block found while handling unreachable blocks")(static_cast<void> (0));

// Make sure phi nodes in our reachable successors end up with a
// LiveOnEntryDef for our incoming edge, even though our block is forward
// unreachable.  We could just disconnect these blocks from the CFG fully,
// but we do not right now.
for (const BasicBlock *S : successors(BB)) {
  if (!DT->isReachableFromEntry(S))
    continue;
  auto It = PerBlockAccesses.find(S);
  // Rename the phi nodes in our successor block
  if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
    continue;
  AccessList *Accesses = It->second.get();
  auto *Phi = cast<MemoryPhi>(&Accesses->front());
  Phi->addIncoming(LiveOnEntryDef.get(), BB);
}

auto It = PerBlockAccesses.find(BB);
if (It == PerBlockAccesses.end())
  return;

auto &Accesses = It->second;
for (auto AI = Accesses->begin(), AE = Accesses->end(); AI != AE;) {
  auto Next = std::next(AI);
  // If we have a phi, just remove it. We are going to replace all
  // users with live on entry.
  if (auto *UseOrDef = dyn_cast<MemoryUseOrDef>(AI))
    UseOrDef->setDefiningAccess(LiveOnEntryDef.get());
  else
    Accesses->erase(AI);
  AI = Next;
}
1258}

1260MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
  : AA(nullptr), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
    SkipWalker(nullptr), NextID(0) {
// Build MemorySSA using a batch alias analysis. This reuses the internal
// state that AA collects during an alias()/getModRefInfo() call. This is
// safe because there are no CFG changes while building MemorySSA and can
// significantly reduce the time spent by the compiler in AA, because we will
// make queries about all the instructions in the Function.
assert(AA && "No alias analysis?")(static_cast<void> (0));
BatchAAResults BatchAA(*AA);
buildMemorySSA(BatchAA);
2
←
Calling 'MemorySSA::buildMemorySSA'→
// Intentionally leave AA to nullptr while building so we don't accidently
// use non-batch AliasAnalysis.
this->AA = AA;
// Also create the walker here.
getWalker();
1276}

1278MemorySSA::~MemorySSA() {
// Drop all our references
for (const auto &Pair : PerBlockAccesses)
  for (MemoryAccess &MA : *Pair.second)
    MA.dropAllReferences();
1283}

1285MemorySSA::AccessList *MemorySSA::getOrCreateAccessList(const BasicBlock *BB) {
auto Res = PerBlockAccesses.insert(std::make_pair(BB, nullptr));

if (Res.second)
  Res.first->second = std::make_unique<AccessList>();
return Res.first->second.get();
1291}

1293MemorySSA::DefsList *MemorySSA::getOrCreateDefsList(const BasicBlock *BB) {
auto Res = PerBlockDefs.insert(std::make_pair(BB, nullptr));

if (Res.second)
  Res.first->second = std::make_unique<DefsList>();
return Res.first->second.get();
1299}

1301namespace llvm {

1303/// This class is a batch walker of all MemoryUse's in the program, and points
1304/// their defining access at the thing that actually clobbers them.  Because it
1305/// is a batch walker that touches everything, it does not operate like the
1306/// other walkers.  This walker is basically performing a top-down SSA renaming
1307/// pass, where the version stack is used as the cache.  This enables it to be
1308/// significantly more time and memory efficient than using the regular walker,
1309/// which is walking bottom-up.
1310class MemorySSA::OptimizeUses {
1311public:
OptimizeUses(MemorySSA *MSSA, CachingWalker<BatchAAResults> *Walker,
             BatchAAResults *BAA, DominatorTree *DT)
    : MSSA(MSSA), Walker(Walker), AA(BAA), DT(DT) {}

void optimizeUses();

1318private:
/// This represents where a given memorylocation is in the stack.
struct MemlocStackInfo {
  // This essentially is keeping track of versions of the stack. Whenever
  // the stack changes due to pushes or pops, these versions increase.
  unsigned long StackEpoch;
  unsigned long PopEpoch;
  // This is the lower bound of places on the stack to check. It is equal to
  // the place the last stack walk ended.
  // Note: Correctness depends on this being initialized to 0, which densemap
  // does
  unsigned long LowerBound;
  const BasicBlock *LowerBoundBlock;
  // This is where the last walk for this memory location ended.
  unsigned long LastKill;
  bool LastKillValid;
  Optional<AliasResult> AR;
};

void optimizeUsesInBlock(const BasicBlock *, unsigned long &, unsigned long &,
                         SmallVectorImpl<MemoryAccess *> &,
                         DenseMap<MemoryLocOrCall, MemlocStackInfo> &);

MemorySSA *MSSA;
CachingWalker<BatchAAResults> *Walker;
BatchAAResults *AA;
DominatorTree *DT;
1345};

1347} // end namespace llvm

1349/// Optimize the uses in a given block This is basically the SSA renaming
1350/// algorithm, with one caveat: We are able to use a single stack for all
1351/// MemoryUses.  This is because the set of *possible* reaching MemoryDefs is
1352/// the same for every MemoryUse.  The *actual* clobbering MemoryDef is just
1353/// going to be some position in that stack of possible ones.
1354///
1355/// We track the stack positions that each MemoryLocation needs
1356/// to check, and last ended at.  This is because we only want to check the
1357/// things that changed since last time.  The same MemoryLocation should
1358/// get clobbered by the same store (getModRefInfo does not use invariantness or
1359/// things like this, and if they start, we can modify MemoryLocOrCall to
1360/// include relevant data)
1361void MemorySSA::OptimizeUses::optimizeUsesInBlock(
  const BasicBlock *BB, unsigned long &StackEpoch, unsigned long &PopEpoch,
  SmallVectorImpl<MemoryAccess *> &VersionStack,
  DenseMap<MemoryLocOrCall, MemlocStackInfo> &LocStackInfo) {

/// If no accesses, nothing to do.
MemorySSA::AccessList *Accesses = MSSA->getWritableBlockAccesses(BB);
if (Accesses == nullptr)
5
←
Assuming the condition is false→
6
←
Taking false branch→
  return;

// Pop everything that doesn't dominate the current block off the stack,
// increment the PopEpoch to account for this.
while (true) {
7
←
Loop condition is true.  Entering loop body→
  assert((static_cast<void> (0))
      !VersionStack.empty() &&(static_cast<void> (0))
      "Version stack should have liveOnEntry sentinel dominating everything")(static_cast<void> (0));
  BasicBlock *BackBlock = VersionStack.back()->getBlock();
  if (DT->dominates(BackBlock, BB))
8
←
Assuming the condition is true→
9
←
Taking true branch→
    break;
  while (VersionStack.back()->getBlock() == BackBlock)
    VersionStack.pop_back();
  ++PopEpoch;
}

for (MemoryAccess &MA : *Accesses) {
  auto *MU = dyn_cast<MemoryUse>(&MA);
10
←
Assuming the object is a 'MemoryUse'→
  if (!MU10.1
'MU' is non-null
) {
11
←
Taking false branch→
    VersionStack.push_back(&MA);
    ++StackEpoch;
    continue;
  }

  if (isUseTriviallyOptimizableToLiveOnEntry(*AA, MU->getMemoryInst())) {
12
←
Taking false branch→
    MU->setDefiningAccess(MSSA->getLiveOnEntryDef(), true, None);
    continue;
  }

  MemoryLocOrCall UseMLOC(MU);
  auto &LocInfo = LocStackInfo[UseMLOC];
  // If the pop epoch changed, it means we've removed stuff from top of
  // stack due to changing blocks. We may have to reset the lower bound or
  // last kill info.
  if (LocInfo.PopEpoch != PopEpoch) {
13
←
Assuming 'PopEpoch' is equal to field 'PopEpoch'→
14
←
Taking false branch→
    LocInfo.PopEpoch = PopEpoch;
    LocInfo.StackEpoch = StackEpoch;
    // If the lower bound was in something that no longer dominates us, we
    // have to reset it.
    // We can't simply track stack size, because the stack may have had
    // pushes/pops in the meantime.
    // XXX: This is non-optimal, but only is slower cases with heavily
    // branching dominator trees.  To get the optimal number of queries would
    // be to make lowerbound and lastkill a per-loc stack, and pop it until
    // the top of that stack dominates us.  This does not seem worth it ATM.
    // A much cheaper optimization would be to always explore the deepest
    // branch of the dominator tree first. This will guarantee this resets on
    // the smallest set of blocks.
    if (LocInfo.LowerBoundBlock && LocInfo.LowerBoundBlock != BB &&
        !DT->dominates(LocInfo.LowerBoundBlock, BB)) {
      // Reset the lower bound of things to check.
      // TODO: Some day we should be able to reset to last kill, rather than
      // 0.
      LocInfo.LowerBound = 0;
      LocInfo.LowerBoundBlock = VersionStack[0]->getBlock();
      LocInfo.LastKillValid = false;
    }
  } else if (LocInfo.StackEpoch != StackEpoch) {
15
←
Assuming 'StackEpoch' is equal to field 'StackEpoch'→
16
←
Taking false branch→
    // If all that has changed is the StackEpoch, we only have to check the
    // new things on the stack, because we've checked everything before.  In
    // this case, the lower bound of things to check remains the same.
    LocInfo.PopEpoch = PopEpoch;
    LocInfo.StackEpoch = StackEpoch;
  }
  if (!LocInfo.LastKillValid) {
17
←
Assuming field 'LastKillValid' is true→
18
←
Taking false branch→
    LocInfo.LastKill = VersionStack.size() - 1;
    LocInfo.LastKillValid = true;
    LocInfo.AR = AliasResult::MayAlias;
  }

  // At this point, we should have corrected last kill and LowerBound to be
  // in bounds.
  assert(LocInfo.LowerBound < VersionStack.size() &&(static_cast<void> (0))
         "Lower bound out of range")(static_cast<void> (0));
  assert(LocInfo.LastKill < VersionStack.size() &&(static_cast<void> (0))
         "Last kill info out of range")(static_cast<void> (0));
  // In any case, the new upper bound is the top of the stack.
  unsigned long UpperBound = VersionStack.size() - 1;

  if (UpperBound - LocInfo.LowerBound > MaxCheckLimit) {
19
←
Assuming the condition is false→
20
←
Taking false branch→
    LLVM_DEBUG(dbgs() << "MemorySSA skipping optimization of " << *MU << " ("do { } while (false)
                      << *(MU->getMemoryInst()) << ")"do { } while (false)
                      << " because there are "do { } while (false)
                      << UpperBound - LocInfo.LowerBounddo { } while (false)
                      << " stores to disambiguate\n")do { } while (false);
    // Because we did not walk, LastKill is no longer valid, as this may
    // have been a kill.
    LocInfo.LastKillValid = false;
    continue;
  }
  bool FoundClobberResult = false;
  unsigned UpwardWalkLimit = MaxCheckLimit;
  while (UpperBound > LocInfo.LowerBound) {
21
←
Assuming 'UpperBound' is > field 'LowerBound'→
22
←
Loop condition is true.  Entering loop body→
    if (isa<MemoryPhi>(VersionStack[UpperBound])) {
23
←
Assuming the object is a 'MemoryPhi'→
24
←
Taking true branch→
      // For phis, use the walker, see where we ended up, go there
      MemoryAccess *Result =
          Walker->getClobberingMemoryAccess(MU, UpwardWalkLimit);
25
←
Calling 'CachingWalker::getClobberingMemoryAccess'→
      // We are guaranteed to find it or something is wrong
      while (VersionStack[UpperBound] != Result) {
        assert(UpperBound != 0)(static_cast<void> (0));
        --UpperBound;
      }
      FoundClobberResult = true;
      break;
    }

    MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
    ClobberAlias CA = instructionClobbersQuery(MD, MU, UseMLOC, *AA);
    if (CA.IsClobber) {
      FoundClobberResult = true;
      LocInfo.AR = CA.AR;
      break;
    }
    --UpperBound;
  }

  // Note: Phis always have AliasResult AR set to MayAlias ATM.

  // At the end of this loop, UpperBound is either a clobber, or lower bound
  // PHI walking may cause it to be < LowerBound, and in fact, < LastKill.
  if (FoundClobberResult || UpperBound < LocInfo.LastKill) {
    // We were last killed now by where we got to
    if (MSSA->isLiveOnEntryDef(VersionStack[UpperBound]))
      LocInfo.AR = None;
    MU->setDefiningAccess(VersionStack[UpperBound], true, LocInfo.AR);
    LocInfo.LastKill = UpperBound;
  } else {
    // Otherwise, we checked all the new ones, and now we know we can get to
    // LastKill.
    MU->setDefiningAccess(VersionStack[LocInfo.LastKill], true, LocInfo.AR);
  }
  LocInfo.LowerBound = VersionStack.size() - 1;
  LocInfo.LowerBoundBlock = BB;
}
1503}

1505/// Optimize uses to point to their actual clobbering definitions.
1506void MemorySSA::OptimizeUses::optimizeUses() {
SmallVector<MemoryAccess *, 16> VersionStack;
DenseMap<MemoryLocOrCall, MemlocStackInfo> LocStackInfo;
VersionStack.push_back(MSSA->getLiveOnEntryDef());

unsigned long StackEpoch = 1;
unsigned long PopEpoch = 1;
// We perform a non-recursive top-down dominator tree walk.
for (const auto *DomNode : depth_first(DT->getRootNode()))
  optimizeUsesInBlock(DomNode->getBlock(), StackEpoch, PopEpoch, VersionStack,
4
←
Calling 'OptimizeUses::optimizeUsesInBlock'→
                      LocStackInfo);
1517}

1519void MemorySSA::placePHINodes(
  const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks) {
// Determine where our MemoryPhi's should go
ForwardIDFCalculator IDFs(*DT);
IDFs.setDefiningBlocks(DefiningBlocks);
SmallVector<BasicBlock *, 32> IDFBlocks;
IDFs.calculate(IDFBlocks);

// Now place MemoryPhi nodes.
for (auto &BB : IDFBlocks)
  createMemoryPhi(BB);
1530}

1532void MemorySSA::buildMemorySSA(BatchAAResults &BAA) {
// We create an access to represent "live on entry", for things like
// arguments or users of globals, where the memory they use is defined before
// the beginning of the function. We do not actually insert it into the IR.
// We do not define a live on exit for the immediate uses, and thus our
// semantics do *not* imply that something with no immediate uses can simply
// be removed.
BasicBlock &StartingPoint = F.getEntryBlock();
LiveOnEntryDef.reset(new MemoryDef(F.getContext(), nullptr, nullptr,
                                   &StartingPoint, NextID++));

// We maintain lists of memory accesses per-block, trading memory for time. We
// could just look up the memory access for every possible instruction in the
// stream.
SmallPtrSet<BasicBlock *, 32> DefiningBlocks;
// Go through each block, figure out where defs occur, and chain together all
// the accesses.
for (BasicBlock &B : F) {
  bool InsertIntoDef = false;
  AccessList *Accesses = nullptr;
  DefsList *Defs = nullptr;
  for (Instruction &I : B) {
    MemoryUseOrDef *MUD = createNewAccess(&I, &BAA);
    if (!MUD)
      continue;

    if (!Accesses)
      Accesses = getOrCreateAccessList(&B);
    Accesses->push_back(MUD);
    if (isa<MemoryDef>(MUD)) {
      InsertIntoDef = true;
      if (!Defs)
        Defs = getOrCreateDefsList(&B);
      Defs->push_back(*MUD);
    }
  }
  if (InsertIntoDef)
    DefiningBlocks.insert(&B);
}
placePHINodes(DefiningBlocks);

// Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
// filled in with all blocks.
SmallPtrSet<BasicBlock *, 16> Visited;
renamePass(DT->getRootNode(), LiveOnEntryDef.get(), Visited);

ClobberWalkerBase<BatchAAResults> WalkerBase(this, &BAA, DT);
CachingWalker<BatchAAResults> WalkerLocal(this, &WalkerBase);
OptimizeUses(this, &WalkerLocal, &BAA, DT).optimizeUses();
3
←
Calling 'OptimizeUses::optimizeUses'→

// Mark the uses in unreachable blocks as live on entry, so that they go
// somewhere.
for (auto &BB : F)
  if (!Visited.count(&BB))
    markUnreachableAsLiveOnEntry(&BB);
1587}

1589MemorySSAWalker *MemorySSA::getWalker() { return getWalkerImpl(); }

1591MemorySSA::CachingWalker<AliasAnalysis> *MemorySSA::getWalkerImpl() {
if (Walker)
  return Walker.get();

if (!WalkerBase)
  WalkerBase =
      std::make_unique<ClobberWalkerBase<AliasAnalysis>>(this, AA, DT);

Walker =
    std::make_unique<CachingWalker<AliasAnalysis>>(this, WalkerBase.get());
return Walker.get();
1602}

1604MemorySSAWalker *MemorySSA::getSkipSelfWalker() {
if (SkipWalker)
  return SkipWalker.get();

if (!WalkerBase)
  WalkerBase =
      std::make_unique<ClobberWalkerBase<AliasAnalysis>>(this, AA, DT);

SkipWalker =
    std::make_unique<SkipSelfWalker<AliasAnalysis>>(this, WalkerBase.get());
return SkipWalker.get();
}


1618// This is a helper function used by the creation routines. It places NewAccess
1619// into the access and defs lists for a given basic block, at the given
1620// insertion point.
1621void MemorySSA::insertIntoListsForBlock(MemoryAccess *NewAccess,
                                      const BasicBlock *BB,
                                      InsertionPlace Point) {
auto *Accesses = getOrCreateAccessList(BB);
if (Point == Beginning) {
  // If it's a phi node, it goes first, otherwise, it goes after any phi
  // nodes.
  if (isa<MemoryPhi>(NewAccess)) {
    Accesses->push_front(NewAccess);
    auto *Defs = getOrCreateDefsList(BB);
    Defs->push_front(*NewAccess);
  } else {
    auto AI = find_if_not(
        *Accesses, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
    Accesses->insert(AI, NewAccess);
    if (!isa<MemoryUse>(NewAccess)) {
      auto *Defs = getOrCreateDefsList(BB);
      auto DI = find_if_not(
          *Defs, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
      Defs->insert(DI, *NewAccess);
    }
  }
} else {
  Accesses->push_back(NewAccess);
  if (!isa<MemoryUse>(NewAccess)) {
    auto *Defs = getOrCreateDefsList(BB);
    Defs->push_back(*NewAccess);
  }
}
BlockNumberingValid.erase(BB);
1651}

1653void MemorySSA::insertIntoListsBefore(MemoryAccess *What, const BasicBlock *BB,
                                    AccessList::iterator InsertPt) {
auto *Accesses = getWritableBlockAccesses(BB);
bool WasEnd = InsertPt == Accesses->end();
Accesses->insert(AccessList::iterator(InsertPt), What);
if (!isa<MemoryUse>(What)) {
  auto *Defs = getOrCreateDefsList(BB);
  // If we got asked to insert at the end, we have an easy job, just shove it
  // at the end. If we got asked to insert before an existing def, we also get
  // an iterator. If we got asked to insert before a use, we have to hunt for
  // the next def.
  if (WasEnd) {
    Defs->push_back(*What);
  } else if (isa<MemoryDef>(InsertPt)) {
    Defs->insert(InsertPt->getDefsIterator(), *What);
  } else {
    while (InsertPt != Accesses->end() && !isa<MemoryDef>(InsertPt))
      ++InsertPt;
    // Either we found a def, or we are inserting at the end
    if (InsertPt == Accesses->end())
      Defs->push_back(*What);
    else
      Defs->insert(InsertPt->getDefsIterator(), *What);
  }
}
BlockNumberingValid.erase(BB);
1679}

1681void MemorySSA::prepareForMoveTo(MemoryAccess *What, BasicBlock *BB) {
// Keep it in the lookup tables, remove from the lists
removeFromLists(What, false);

// Note that moving should implicitly invalidate the optimized state of a
// MemoryUse (and Phis can't be optimized). However, it doesn't do so for a
// MemoryDef.
if (auto *MD = dyn_cast<MemoryDef>(What))
  MD->resetOptimized();
What->setBlock(BB);
1691}

1693// Move What before Where in the IR.  The end result is that What will belong to
1694// the right lists and have the right Block set, but will not otherwise be
1695// correct. It will not have the right defining access, and if it is a def,
1696// things below it will not properly be updated.
1697void MemorySSA::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
                     AccessList::iterator Where) {
prepareForMoveTo(What, BB);
insertIntoListsBefore(What, BB, Where);
1701}

1703void MemorySSA::moveTo(MemoryAccess *What, BasicBlock *BB,
                     InsertionPlace Point) {
if (isa<MemoryPhi>(What)) {
  assert(Point == Beginning &&(static_cast<void> (0))
         "Can only move a Phi at the beginning of the block")(static_cast<void> (0));
  // Update lookup table entry
  ValueToMemoryAccess.erase(What->getBlock());
  bool Inserted = ValueToMemoryAccess.insert({BB, What}).second;
  (void)Inserted;
  assert(Inserted && "Cannot move a Phi to a block that already has one")(static_cast<void> (0));
}

prepareForMoveTo(What, BB);
insertIntoListsForBlock(What, BB, Point);
1717}

1719MemoryPhi *MemorySSA::createMemoryPhi(BasicBlock *BB) {
assert(!getMemoryAccess(BB) && "MemoryPhi already exists for this BB")(static_cast<void> (0));
MemoryPhi *Phi = new MemoryPhi(BB->getContext(), BB, NextID++);
// Phi's always are placed at the front of the block.
insertIntoListsForBlock(Phi, BB, Beginning);
ValueToMemoryAccess[BB] = Phi;
return Phi;
1726}

1728MemoryUseOrDef *MemorySSA::createDefinedAccess(Instruction *I,
                                             MemoryAccess *Definition,
                                             const MemoryUseOrDef *Template,
                                             bool CreationMustSucceed) {
assert(!isa<PHINode>(I) && "Cannot create a defined access for a PHI")(static_cast<void> (0));
MemoryUseOrDef *NewAccess = createNewAccess(I, AA, Template);
if (CreationMustSucceed)
  assert(NewAccess != nullptr && "Tried to create a memory access for a "(static_cast<void> (0))
                                 "non-memory touching instruction")(static_cast<void> (0));
if (NewAccess) {
  assert((!Definition || !isa<MemoryUse>(Definition)) &&(static_cast<void> (0))
         "A use cannot be a defining access")(static_cast<void> (0));
  NewAccess->setDefiningAccess(Definition);
}
return NewAccess;
1743}

1745// Return true if the instruction has ordering constraints.
1746// Note specifically that this only considers stores and loads
1747// because others are still considered ModRef by getModRefInfo.
1748static inline bool isOrdered(const Instruction *I) {
if (auto *SI = dyn_cast<StoreInst>(I)) {
  if (!SI->isUnordered())
    return true;
} else if (auto *LI = dyn_cast<LoadInst>(I)) {
  if (!LI->isUnordered())
    return true;
}
return false;
1757}

1759/// Helper function to create new memory accesses
1760template <typename AliasAnalysisType>
1761MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I,
                                         AliasAnalysisType *AAP,
                                         const MemoryUseOrDef *Template) {
// The assume intrinsic has a control dependency which we model by claiming
// that it writes arbitrarily. Debuginfo intrinsics may be considered
// clobbers when we have a nonstandard AA pipeline. Ignore these fake memory
// dependencies here.
// FIXME: Replace this special casing with a more accurate modelling of
// assume's control dependency.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
  switch (II->getIntrinsicID()) {
  default:
    break;
  case Intrinsic::assume:
  case Intrinsic::experimental_noalias_scope_decl:
    return nullptr;
  }
}

// Using a nonstandard AA pipelines might leave us with unexpected modref
// results for I, so add a check to not model instructions that may not read
// from or write to memory. This is necessary for correctness.
if (!I->mayReadFromMemory() && !I->mayWriteToMemory())
  return nullptr;

bool Def, Use;
if (Template) {
  Def = isa<MemoryDef>(Template);
  Use = isa<MemoryUse>(Template);
1790#if !defined(NDEBUG1)
  ModRefInfo ModRef = AAP->getModRefInfo(I, None);
  bool DefCheck, UseCheck;
  DefCheck = isModSet(ModRef) || isOrdered(I);
  UseCheck = isRefSet(ModRef);
  assert(Def == DefCheck && (Def || Use == UseCheck) && "Invalid template")(static_cast<void> (0));
1796#endif
} else {
  // Find out what affect this instruction has on memory.
  ModRefInfo ModRef = AAP->getModRefInfo(I, None);
  // The isOrdered check is used to ensure that volatiles end up as defs
  // (atomics end up as ModRef right now anyway).  Until we separate the
  // ordering chain from the memory chain, this enables people to see at least
  // some relative ordering to volatiles.  Note that getClobberingMemoryAccess
  // will still give an answer that bypasses other volatile loads.  TODO:
  // Separate memory aliasing and ordering into two different chains so that
  // we can precisely represent both "what memory will this read/write/is
  // clobbered by" and "what instructions can I move this past".
  Def = isModSet(ModRef) || isOrdered(I);
  Use = isRefSet(ModRef);
}

// It's possible for an instruction to not modify memory at all. During
// construction, we ignore them.
if (!Def && !Use)
  return nullptr;

MemoryUseOrDef *MUD;
if (Def)
  MUD = new MemoryDef(I->getContext(), nullptr, I, I->getParent(), NextID++);
else
  MUD = new MemoryUse(I->getContext(), nullptr, I, I->getParent());
ValueToMemoryAccess[I] = MUD;
return MUD;
1824}

1826/// Properly remove \p MA from all of MemorySSA's lookup tables.
1827void MemorySSA::removeFromLookups(MemoryAccess *MA) {
assert(MA->use_empty() &&(static_cast<void> (0))
       "Trying to remove memory access that still has uses")(static_cast<void> (0));
BlockNumbering.erase(MA);
if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
  MUD->setDefiningAccess(nullptr);
// Invalidate our walker's cache if necessary
if (!isa<MemoryUse>(MA))
  getWalker()->invalidateInfo(MA);

Value *MemoryInst;
if (const auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
  MemoryInst = MUD->getMemoryInst();
else
  MemoryInst = MA->getBlock();

auto VMA = ValueToMemoryAccess.find(MemoryInst);
if (VMA->second == MA)
  ValueToMemoryAccess.erase(VMA);
1846}

1848/// Properly remove \p MA from all of MemorySSA's lists.
1849///
1850/// Because of the way the intrusive list and use lists work, it is important to
1851/// do removal in the right order.
1852/// ShouldDelete defaults to true, and will cause the memory access to also be
1853/// deleted, not just removed.
1854void MemorySSA::removeFromLists(MemoryAccess *MA, bool ShouldDelete) {
BasicBlock *BB = MA->getBlock();
// The access list owns the reference, so we erase it from the non-owning list
// first.
if (!isa<MemoryUse>(MA)) {
  auto DefsIt = PerBlockDefs.find(BB);
  std::unique_ptr<DefsList> &Defs = DefsIt->second;
  Defs->remove(*MA);
  if (Defs->empty())
    PerBlockDefs.erase(DefsIt);
}

// The erase call here will delete it. If we don't want it deleted, we call
// remove instead.
auto AccessIt = PerBlockAccesses.find(BB);
std::unique_ptr<AccessList> &Accesses = AccessIt->second;
if (ShouldDelete)
  Accesses->erase(MA);
else
  Accesses->remove(MA);

if (Accesses->empty()) {
  PerBlockAccesses.erase(AccessIt);
  BlockNumberingValid.erase(BB);
}
1879}

1881void MemorySSA::print(raw_ostream &OS) const {
MemorySSAAnnotatedWriter Writer(this);
F.print(OS, &Writer);
1884}

1886#if !defined(NDEBUG1) || defined(LLVM_ENABLE_DUMP)
1887LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void MemorySSA::dump() const { print(dbgs()); }
1888#endif

1890void MemorySSA::verifyMemorySSA() const {
verifyOrderingDominationAndDefUses(F);
verifyDominationNumbers(F);
verifyPrevDefInPhis(F);
// Previously, the verification used to also verify that the clobberingAccess
// cached by MemorySSA is the same as the clobberingAccess found at a later
// query to AA. This does not hold true in general due to the current fragility
// of BasicAA which has arbitrary caps on the things it analyzes before giving
// up. As a result, transformations that are correct, will lead to BasicAA
// returning different Alias answers before and after that transformation.
// Invalidating MemorySSA is not an option, as the results in BasicAA can be so
// random, in the worst case we'd need to rebuild MemorySSA from scratch after
// every transformation, which defeats the purpose of using it. For such an
// example, see test4 added in D51960.
1904}

1906void MemorySSA::verifyPrevDefInPhis(Function &F) const {
1907#if !defined(NDEBUG1) && defined(EXPENSIVE_CHECKS)
for (const BasicBlock &BB : F) {
  if (MemoryPhi *Phi = getMemoryAccess(&BB)) {
    for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
      auto *Pred = Phi->getIncomingBlock(I);
      auto *IncAcc = Phi->getIncomingValue(I);
      // If Pred has no unreachable predecessors, get last def looking at
      // IDoms. If, while walkings IDoms, any of these has an unreachable
      // predecessor, then the incoming def can be any access.
      if (auto *DTNode = DT->getNode(Pred)) {
        while (DTNode) {
          if (auto *DefList = getBlockDefs(DTNode->getBlock())) {
            auto *LastAcc = &*(--DefList->end());
            assert(LastAcc == IncAcc &&(static_cast<void> (0))
                   "Incorrect incoming access into phi.")(static_cast<void> (0));
            break;
          }
          DTNode = DTNode->getIDom();
        }
      } else {
        // If Pred has unreachable predecessors, but has at least a Def, the
        // incoming access can be the last Def in Pred, or it could have been
        // optimized to LoE. After an update, though, the LoE may have been
        // replaced by another access, so IncAcc may be any access.
        // If Pred has unreachable predecessors and no Defs, incoming access
        // should be LoE; However, after an update, it may be any access.
      }
    }
  }
}
1937#endif
1938}

1940/// Verify that all of the blocks we believe to have valid domination numbers
1941/// actually have valid domination numbers.
1942void MemorySSA::verifyDominationNumbers(const Function &F) const {
1943#ifndef NDEBUG1
if (BlockNumberingValid.empty())
  return;

SmallPtrSet<const BasicBlock *, 16> ValidBlocks = BlockNumberingValid;
for (const BasicBlock &BB : F) {
  if (!ValidBlocks.count(&BB))
    continue;

  ValidBlocks.erase(&BB);

  const AccessList *Accesses = getBlockAccesses(&BB);
  // It's correct to say an empty block has valid numbering.
  if (!Accesses)
    continue;

  // Block numbering starts at 1.
  unsigned long LastNumber = 0;
  for (const MemoryAccess &MA : *Accesses) {
    auto ThisNumberIter = BlockNumbering.find(&MA);
    assert(ThisNumberIter != BlockNumbering.end() &&(static_cast<void> (0))
           "MemoryAccess has no domination number in a valid block!")(static_cast<void> (0));

    unsigned long ThisNumber = ThisNumberIter->second;
    assert(ThisNumber > LastNumber &&(static_cast<void> (0))
           "Domination numbers should be strictly increasing!")(static_cast<void> (0));
    LastNumber = ThisNumber;
  }
}

assert(ValidBlocks.empty() &&(static_cast<void> (0))
       "All valid BasicBlocks should exist in F -- dangling pointers?")(static_cast<void> (0));
1975#endif
1976}

1978/// Verify ordering: the order and existence of MemoryAccesses matches the
1979/// order and existence of memory affecting instructions.
1980/// Verify domination: each definition dominates all of its uses.
1981/// Verify def-uses: the immediate use information - walk all the memory
1982/// accesses and verifying that, for each use, it appears in the appropriate
1983/// def's use list
1984void MemorySSA::verifyOrderingDominationAndDefUses(Function &F) const {
1985#if !defined(NDEBUG1)
// Walk all the blocks, comparing what the lookups think and what the access
// lists think, as well as the order in the blocks vs the order in the access
// lists.
SmallVector<MemoryAccess *, 32> ActualAccesses;
SmallVector<MemoryAccess *, 32> ActualDefs;
for (BasicBlock &B : F) {
  const AccessList *AL = getBlockAccesses(&B);
  const auto *DL = getBlockDefs(&B);
  MemoryPhi *Phi = getMemoryAccess(&B);
  if (Phi) {
    // Verify ordering.
    ActualAccesses.push_back(Phi);
    ActualDefs.push_back(Phi);
    // Verify domination
    for (const Use &U : Phi->uses())
      assert(dominates(Phi, U) && "Memory PHI does not dominate it's uses")(static_cast<void> (0));
2002#if defined(EXPENSIVE_CHECKS)
    // Verify def-uses.
    assert(Phi->getNumOperands() == static_cast<unsigned>(std::distance((static_cast<void> (0))
                                        pred_begin(&B), pred_end(&B))) &&(static_cast<void> (0))
           "Incomplete MemoryPhi Node")(static_cast<void> (0));
    for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
      verifyUseInDefs(Phi->getIncomingValue(I), Phi);
      assert(is_contained(predecessors(&B), Phi->getIncomingBlock(I)) &&(static_cast<void> (0))
             "Incoming phi block not a block predecessor")(static_cast<void> (0));
    }
2012#endif
  }

  for (Instruction &I : B) {
    MemoryUseOrDef *MA = getMemoryAccess(&I);
    assert((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&(static_cast<void> (0))
           "We have memory affecting instructions "(static_cast<void> (0))
           "in this block but they are not in the "(static_cast<void> (0))
           "access list or defs list")(static_cast<void> (0));
    if (MA) {
      // Verify ordering.
      ActualAccesses.push_back(MA);
      if (MemoryAccess *MD = dyn_cast<MemoryDef>(MA)) {
        // Verify ordering.
        ActualDefs.push_back(MA);
        // Verify domination.
        for (const Use &U : MD->uses())
          assert(dominates(MD, U) &&(static_cast<void> (0))
                 "Memory Def does not dominate it's uses")(static_cast<void> (0));
      }
2032#if defined(EXPENSIVE_CHECKS)
      // Verify def-uses.
      verifyUseInDefs(MA->getDefiningAccess(), MA);
2035#endif
    }
  }
  // Either we hit the assert, really have no accesses, or we have both
  // accesses and an access list. Same with defs.
  if (!AL && !DL)
    continue;
  // Verify ordering.
  assert(AL->size() == ActualAccesses.size() &&(static_cast<void> (0))
         "We don't have the same number of accesses in the block as on the "(static_cast<void> (0))
         "access list")(static_cast<void> (0));
  assert((DL || ActualDefs.size() == 0) &&(static_cast<void> (0))
         "Either we should have a defs list, or we should have no defs")(static_cast<void> (0));
  assert((!DL || DL->size() == ActualDefs.size()) &&(static_cast<void> (0))
         "We don't have the same number of defs in the block as on the "(static_cast<void> (0))
         "def list")(static_cast<void> (0));
  auto ALI = AL->begin();
  auto AAI = ActualAccesses.begin();
  while (ALI != AL->end() && AAI != ActualAccesses.end()) {
    assert(&*ALI == *AAI && "Not the same accesses in the same order")(static_cast<void> (0));
    ++ALI;
    ++AAI;
  }
  ActualAccesses.clear();
  if (DL) {
    auto DLI = DL->begin();
    auto ADI = ActualDefs.begin();
    while (DLI != DL->end() && ADI != ActualDefs.end()) {
      assert(&*DLI == *ADI && "Not the same defs in the same order")(static_cast<void> (0));
      ++DLI;
      ++ADI;
    }
  }
  ActualDefs.clear();
}
2070#endif
2071}

2073/// Verify the def-use lists in MemorySSA, by verifying that \p Use
2074/// appears in the use list of \p Def.
2075void MemorySSA::verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use) const {
2076#ifndef NDEBUG1
// The live on entry use may cause us to get a NULL def here
if (!Def)
  assert(isLiveOnEntryDef(Use) &&(static_cast<void> (0))
         "Null def but use not point to live on entry def")(static_cast<void> (0));
else
  assert(is_contained(Def->users(), Use) &&(static_cast<void> (0))
         "Did not find use in def's use list")(static_cast<void> (0));
2084#endif
2085}

2087/// Perform a local numbering on blocks so that instruction ordering can be
2088/// determined in constant time.
2089/// TODO: We currently just number in order.  If we numbered by N, we could
2090/// allow at least N-1 sequences of insertBefore or insertAfter (and at least
2091/// log2(N) sequences of mixed before and after) without needing to invalidate
2092/// the numbering.
2093void MemorySSA::renumberBlock(const BasicBlock *B) const {
// The pre-increment ensures the numbers really start at 1.
unsigned long CurrentNumber = 0;
const AccessList *AL = getBlockAccesses(B);
assert(AL != nullptr && "Asking to renumber an empty block")(static_cast<void> (0));
for (const auto &I : *AL)
  BlockNumbering[&I] = ++CurrentNumber;
BlockNumberingValid.insert(B);
2101}

2103/// Determine, for two memory accesses in the same block,
2104/// whether \p Dominator dominates \p Dominatee.
2105/// \returns True if \p Dominator dominates \p Dominatee.
2106bool MemorySSA::locallyDominates(const MemoryAccess *Dominator,
                               const MemoryAccess *Dominatee) const {
const BasicBlock *DominatorBlock = Dominator->getBlock();

assert((DominatorBlock == Dominatee->getBlock()) &&(static_cast<void> (0))
       "Asking for local domination when accesses are in different blocks!")(static_cast<void> (0));
// A node dominates itself.
if (Dominatee == Dominator)
  return true;

// When Dominatee is defined on function entry, it is not dominated by another
// memory access.
if (isLiveOnEntryDef(Dominatee))
  return false;

// When Dominator is defined on function entry, it dominates the other memory
// access.
if (isLiveOnEntryDef(Dominator))
  return true;

if (!BlockNumberingValid.count(DominatorBlock))
  renumberBlock(DominatorBlock);

unsigned long DominatorNum = BlockNumbering.lookup(Dominator);
// All numbers start with 1
assert(DominatorNum != 0 && "Block was not numbered properly")(static_cast<void> (0));
unsigned long DominateeNum = BlockNumbering.lookup(Dominatee);
assert(DominateeNum != 0 && "Block was not numbered properly")(static_cast<void> (0));
return DominatorNum < DominateeNum;
2135}

2137bool MemorySSA::dominates(const MemoryAccess *Dominator,
                        const MemoryAccess *Dominatee) const {
if (Dominator == Dominatee)
  return true;

if (isLiveOnEntryDef(Dominatee))
  return false;

if (Dominator->getBlock() != Dominatee->getBlock())
  return DT->dominates(Dominator->getBlock(), Dominatee->getBlock());
return locallyDominates(Dominator, Dominatee);
2148}

2150bool MemorySSA::dominates(const MemoryAccess *Dominator,
                        const Use &Dominatee) const {
if (MemoryPhi *MP = dyn_cast<MemoryPhi>(Dominatee.getUser())) {
  BasicBlock *UseBB = MP->getIncomingBlock(Dominatee);
  // The def must dominate the incoming block of the phi.
  if (UseBB != Dominator->getBlock())
    return DT->dominates(Dominator->getBlock(), UseBB);
  // If the UseBB and the DefBB are the same, compare locally.
  return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
}
// If it's not a PHI node use, the normal dominates can already handle it.
return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
2162}

2164void MemoryAccess::print(raw_ostream &OS) const {
switch (getValueID()) {
case MemoryPhiVal: return static_cast<const MemoryPhi *>(this)->print(OS);
case MemoryDefVal: return static_cast<const MemoryDef *>(this)->print(OS);
case MemoryUseVal: return static_cast<const MemoryUse *>(this)->print(OS);
}
llvm_unreachable("invalid value id")__builtin_unreachable();
2171}

2173void MemoryDef::print(raw_ostream &OS) const {
MemoryAccess *UO = getDefiningAccess();

auto printID = [&OS](MemoryAccess *A) {
  if (A && A->getID())
    OS << A->getID();
  else
    OS << LiveOnEntryStr;
};

OS << getID() << " = MemoryDef(";
printID(UO);
OS << ")";

if (isOptimized()) {
  OS << "->";
  printID(getOptimized());

  if (Optional<AliasResult> AR = getOptimizedAccessType())
    OS << " " << *AR;
}
2194}

2196void MemoryPhi::print(raw_ostream &OS) const {
ListSeparator LS(",");
OS << getID() << " = MemoryPhi(";
for (const auto &Op : operands()) {
  BasicBlock *BB = getIncomingBlock(Op);
  MemoryAccess *MA = cast<MemoryAccess>(Op);

  OS << LS << '{';
  if (BB->hasName())
    OS << BB->getName();
  else
    BB->printAsOperand(OS, false);
  OS << ',';
  if (unsigned ID = MA->getID())
    OS << ID;
  else
    OS << LiveOnEntryStr;
  OS << '}';
}
OS << ')';
2216}

2218void MemoryUse::print(raw_ostream &OS) const {
MemoryAccess *UO = getDefiningAccess();
OS << "MemoryUse(";
if (UO && UO->getID())
  OS << UO->getID();
else
  OS << LiveOnEntryStr;
OS << ')';

if (Optional<AliasResult> AR = getOptimizedAccessType())
  OS << " " << *AR;
2229}

2231void MemoryAccess::dump() const {
2232// Cannot completely remove virtual function even in release mode.
2233#if !defined(NDEBUG1) || defined(LLVM_ENABLE_DUMP)
print(dbgs());
dbgs() << "\n";
2236#endif
2237}

2239char MemorySSAPrinterLegacyPass::ID = 0;

2241MemorySSAPrinterLegacyPass::MemorySSAPrinterLegacyPass() : FunctionPass(ID) {
initializeMemorySSAPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
2243}

2245void MemorySSAPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<MemorySSAWrapperPass>();
2248}

2250class DOTFuncMSSAInfo {
2251private:
const Function &F;
MemorySSAAnnotatedWriter MSSAWriter;

2255public:
DOTFuncMSSAInfo(const Function &F, MemorySSA &MSSA)
    : F(F), MSSAWriter(&MSSA) {}

const Function *getFunction() { return &F; }
MemorySSAAnnotatedWriter &getWriter() { return MSSAWriter; }
2261};

2263namespace llvm {

2265template <>
2266struct GraphTraits<DOTFuncMSSAInfo *> : public GraphTraits<const BasicBlock *> {
static NodeRef getEntryNode(DOTFuncMSSAInfo *CFGInfo) {
  return &(CFGInfo->getFunction()->getEntryBlock());
}

// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
using nodes_iterator = pointer_iterator<Function::const_iterator>;

static nodes_iterator nodes_begin(DOTFuncMSSAInfo *CFGInfo) {
  return nodes_iterator(CFGInfo->getFunction()->begin());
}

static nodes_iterator nodes_end(DOTFuncMSSAInfo *CFGInfo) {
  return nodes_iterator(CFGInfo->getFunction()->end());
}

static size_t size(DOTFuncMSSAInfo *CFGInfo) {
  return CFGInfo->getFunction()->size();
}
2285};

2287template <>
2288struct DOTGraphTraits<DOTFuncMSSAInfo *> : public DefaultDOTGraphTraits {

DOTGraphTraits(bool IsSimple = false) : DefaultDOTGraphTraits(IsSimple) {}

static std::string getGraphName(DOTFuncMSSAInfo *CFGInfo) {
  return "MSSA CFG for '" + CFGInfo->getFunction()->getName().str() +
         "' function";
}

std::string getNodeLabel(const BasicBlock *Node, DOTFuncMSSAInfo *CFGInfo) {
  return DOTGraphTraits<DOTFuncInfo *>::getCompleteNodeLabel(
      Node, nullptr,
      [CFGInfo](raw_string_ostream &OS, const BasicBlock &BB) -> void {
        BB.print(OS, &CFGInfo->getWriter(), true, true);
      },
      [](std::string &S, unsigned &I, unsigned Idx) -> void {
        std::string Str = S.substr(I, Idx - I);
        StringRef SR = Str;
        if (SR.count(" = MemoryDef(") || SR.count(" = MemoryPhi(") ||
            SR.count("MemoryUse("))
          return;
        DOTGraphTraits<DOTFuncInfo *>::eraseComment(S, I, Idx);
      });
}

static std::string getEdgeSourceLabel(const BasicBlock *Node,
                                      const_succ_iterator I) {
  return DOTGraphTraits<DOTFuncInfo *>::getEdgeSourceLabel(Node, I);
}

/// Display the raw branch weights from PGO.
std::string getEdgeAttributes(const BasicBlock *Node, const_succ_iterator I,
                              DOTFuncMSSAInfo *CFGInfo) {
  return "";
}

std::string getNodeAttributes(const BasicBlock *Node,
                              DOTFuncMSSAInfo *CFGInfo) {
  return getNodeLabel(Node, CFGInfo).find(';') != std::string::npos
             ? "style=filled, fillcolor=lightpink"
             : "";
}
2330};

2332} // namespace llvm

2334bool MemorySSAPrinterLegacyPass::runOnFunction(Function &F) {
auto &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
if (DotCFGMSSA != "") {
  DOTFuncMSSAInfo CFGInfo(F, MSSA);
  WriteGraph(&CFGInfo, "", false, "MSSA", DotCFGMSSA);
} else
  MSSA.print(dbgs());

if (VerifyMemorySSA)
  MSSA.verifyMemorySSA();
return false;
2345}

2347AnalysisKey MemorySSAAnalysis::Key;

2349MemorySSAAnalysis::Result MemorySSAAnalysis::run(Function &F,
                                               FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AA = AM.getResult<AAManager>(F);
return MemorySSAAnalysis::Result(std::make_unique<MemorySSA>(F, &AA, &DT));
2354}

2356bool MemorySSAAnalysis::Result::invalidate(
  Function &F, const PreservedAnalyses &PA,
  FunctionAnalysisManager::Invalidator &Inv) {
auto PAC = PA.getChecker<MemorySSAAnalysis>();
return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
       Inv.invalidate<AAManager>(F, PA) ||
       Inv.invalidate<DominatorTreeAnalysis>(F, PA);
2363}

2365PreservedAnalyses MemorySSAPrinterPass::run(Function &F,
                                          FunctionAnalysisManager &AM) {
auto &MSSA = AM.getResult<MemorySSAAnalysis>(F).getMSSA();
if (DotCFGMSSA != "") {
  DOTFuncMSSAInfo CFGInfo(F, MSSA);
  WriteGraph(&CFGInfo, "", false, "MSSA", DotCFGMSSA);
} else {
  OS << "MemorySSA for function: " << F.getName() << "\n";
  MSSA.print(OS);
}

return PreservedAnalyses::all();
2377}

2379PreservedAnalyses MemorySSAWalkerPrinterPass::run(Function &F,
                                                FunctionAnalysisManager &AM) {
auto &MSSA = AM.getResult<MemorySSAAnalysis>(F).getMSSA();
OS << "MemorySSA (walker) for function: " << F.getName() << "\n";
MemorySSAWalkerAnnotatedWriter Writer(&MSSA);
F.print(OS, &Writer);

return PreservedAnalyses::all();
2387}

2389PreservedAnalyses MemorySSAVerifierPass::run(Function &F,
                                           FunctionAnalysisManager &AM) {
AM.getResult<MemorySSAAnalysis>(F).getMSSA().verifyMemorySSA();

return PreservedAnalyses::all();
2394}

2396char MemorySSAWrapperPass::ID = 0;

2398MemorySSAWrapperPass::MemorySSAWrapperPass() : FunctionPass(ID) {
initializeMemorySSAWrapperPassPass(*PassRegistry::getPassRegistry());
2400}

2402void MemorySSAWrapperPass::releaseMemory() { MSSA.reset(); }

2404void MemorySSAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<DominatorTreeWrapperPass>();
AU.addRequiredTransitive<AAResultsWrapperPass>();
2408}

2410bool MemorySSAWrapperPass::runOnFunction(Function &F) {
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
MSSA.reset(new MemorySSA(F, &AA, &DT));
1
Calling constructor for 'MemorySSA'→
return false;
2415}

2417void MemorySSAWrapperPass::verifyAnalysis() const {
if (VerifyMemorySSA)
  MSSA->verifyMemorySSA();
2420}

2422void MemorySSAWrapperPass::print(raw_ostream &OS, const Module *M) const {
MSSA->print(OS);
2424}

2426MemorySSAWalker::MemorySSAWalker(MemorySSA *M) : MSSA(M) {}

2428/// Walk the use-def chains starting at \p StartingAccess and find
2429/// the MemoryAccess that actually clobbers Loc.
2430///
2431/// \returns our clobbering memory access
2432template <typename AliasAnalysisType>
2433MemoryAccess *
2434MemorySSA::ClobberWalkerBase<AliasAnalysisType>::getClobberingMemoryAccessBase(
  MemoryAccess *StartingAccess, const MemoryLocation &Loc,
  unsigned &UpwardWalkLimit) {
assert(!isa<MemoryUse>(StartingAccess) && "Use cannot be defining access")(static_cast<void> (0));

Instruction *I = nullptr;
if (auto *StartingUseOrDef = dyn_cast<MemoryUseOrDef>(StartingAccess)) {
  if (MSSA->isLiveOnEntryDef(StartingUseOrDef))
    return StartingUseOrDef;

  I = StartingUseOrDef->getMemoryInst();

  // Conservatively, fences are always clobbers, so don't perform the walk if
  // we hit a fence.
  if (!isa<CallBase>(I) && I->isFenceLike())
    return StartingUseOrDef;
}

UpwardsMemoryQuery Q;
Q.OriginalAccess = StartingAccess;
Q.StartingLoc = Loc;
Q.Inst = nullptr;
Q.IsCall = false;

// Unlike the other function, do not walk to the def of a def, because we are
// handed something we already believe is the clobbering access.
// We never set SkipSelf to true in Q in this method.
MemoryAccess *Clobber =
    Walker.findClobber(StartingAccess, Q, UpwardWalkLimit);
LLVM_DEBUG({do { } while (false)
  dbgs() << "Clobber starting at access " << *StartingAccess << "\n";do { } while (false)
  if (I)do { } while (false)
    dbgs() << "  for instruction " << *I << "\n";do { } while (false)
  dbgs() << "  is " << *Clobber << "\n";do { } while (false)
})do { } while (false);
return Clobber;
2470}

2472template <typename AliasAnalysisType>
2473MemoryAccess *
2474MemorySSA::ClobberWalkerBase<AliasAnalysisType>::getClobberingMemoryAccessBase(
  MemoryAccess *MA, unsigned &UpwardWalkLimit, bool SkipSelf) {
auto *StartingAccess = dyn_cast<MemoryUseOrDef>(MA);
27
←
Assuming 'MA' is a 'MemoryUseOrDef'→
// If this is a MemoryPhi, we can't do anything.
if (!StartingAccess27.1
'StartingAccess' is non-null
)
28
←
Taking false branch→
  return MA;

bool IsOptimized = false;

// If this is an already optimized use or def, return the optimized result.
// Note: Currently, we store the optimized def result in a separate field,
// since we can't use the defining access.
if (StartingAccess->isOptimized()) {
29
←
Assuming the condition is false→
30
←
Taking false branch→
  if (!SkipSelf || !isa<MemoryDef>(StartingAccess))
    return StartingAccess->getOptimized();
  IsOptimized = true;
}

const Instruction *I = StartingAccess->getMemoryInst();
// We can't sanely do anything with a fence, since they conservatively clobber
// all memory, and have no locations to get pointers from to try to
// disambiguate.
if (!isa<CallBase>(I) && I->isFenceLike())
31
←
Assuming 'I' is not a 'CallBase'→
32
←
Taking false branch→
  return StartingAccess;

UpwardsMemoryQuery Q(I, StartingAccess);

if (isUseTriviallyOptimizableToLiveOnEntry(*Walker.getAA(), I)) {
33
←
Taking false branch→
  MemoryAccess *LiveOnEntry = MSSA->getLiveOnEntryDef();
  StartingAccess->setOptimized(LiveOnEntry);
  StartingAccess->setOptimizedAccessType(None);
  return LiveOnEntry;
}

MemoryAccess *OptimizedAccess;
if (!IsOptimized33.1
'IsOptimized' is false
) {
34
←
Taking true branch→
  // Start with the thing we already think clobbers this location
  MemoryAccess *DefiningAccess = StartingAccess->getDefiningAccess();

  // At this point, DefiningAccess may be the live on entry def.
  // If it is, we will not get a better result.
  if (MSSA->isLiveOnEntryDef(DefiningAccess)) {
35
←
Taking false branch→
    StartingAccess->setOptimized(DefiningAccess);
    StartingAccess->setOptimizedAccessType(None);
    return DefiningAccess;
  }

  OptimizedAccess = Walker.findClobber(DefiningAccess, Q, UpwardWalkLimit);
  StartingAccess->setOptimized(OptimizedAccess);
  if (MSSA->isLiveOnEntryDef(OptimizedAccess))
    StartingAccess->setOptimizedAccessType(None);
  else if (Q.AR && *Q.AR == AliasResult::MustAlias)
36
←
Assuming the condition is false→
    StartingAccess->setOptimizedAccessType(
        AliasResult(AliasResult::MustAlias));
} else
  OptimizedAccess = StartingAccess->getOptimized();

LLVM_DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ")do { } while (false);
37
←
Loop condition is false.  Exiting loop→
LLVM_DEBUG(dbgs() << *StartingAccess << "\n")do { } while (false);
38
←
Loop condition is false.  Exiting loop→
LLVM_DEBUG(dbgs() << "Optimized Memory SSA clobber for " << *I << " is ")do { } while (false);
39
←
Loop condition is false.  Exiting loop→
LLVM_DEBUG(dbgs() << *OptimizedAccess << "\n")do { } while (false);
40
←
Loop condition is false.  Exiting loop→

MemoryAccess *Result;
if (SkipSelf40.1
'SkipSelf' is false
 && isa<MemoryPhi>(OptimizedAccess) &&
    isa<MemoryDef>(StartingAccess) && UpwardWalkLimit) {
  assert(isa<MemoryDef>(Q.OriginalAccess))(static_cast<void> (0));
  Q.SkipSelfAccess = true;
  Result = Walker.findClobber(OptimizedAccess, Q, UpwardWalkLimit);
} else
  Result = OptimizedAccess;

LLVM_DEBUG(dbgs() << "Result Memory SSA clobber [SkipSelf = " << SkipSelf)do { } while (false);
41
←
Loop condition is false.  Exiting loop→
LLVM_DEBUG(dbgs() << "] for " << *I << " is " << *Result << "\n")do { } while (false);
42
←
Loop condition is false.  Exiting loop→

return Result;
43
←
Address of stack memory associated with local variable 'Q' is still referred to by the stack variable 'WalkerBase' upon returning to the caller.  This will be a dangling reference
2549}

2551MemoryAccess *
2552DoNothingMemorySSAWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
if (auto *Use = dyn_cast<MemoryUseOrDef>(MA))
  return Use->getDefiningAccess();
return MA;
2556}

2558MemoryAccess *DoNothingMemorySSAWalker::getClobberingMemoryAccess(
  MemoryAccess *StartingAccess, const MemoryLocation &) {
if (auto *Use = dyn_cast<MemoryUseOrDef>(StartingAccess))
  return Use->getDefiningAccess();
return StartingAccess;
2563}

2565void MemoryPhi::deleteMe(DerivedUser *Self) {
delete static_cast<MemoryPhi *>(Self);
2567}

2569void MemoryDef::deleteMe(DerivedUser *Self) {
delete static_cast<MemoryDef *>(Self);
2571}

2573void MemoryUse::deleteMe(DerivedUser *Self) {
delete static_cast<MemoryUse *>(Self);
2575}

2577bool upward_defs_iterator::IsGuaranteedLoopInvariant(Value *Ptr) const {
auto IsGuaranteedLoopInvariantBase = [](Value *Ptr) {
  Ptr = Ptr->stripPointerCasts();
  if (!isa<Instruction>(Ptr))
    return true;
  return isa<AllocaInst>(Ptr);
};

Ptr = Ptr->stripPointerCasts();
if (auto *I = dyn_cast<Instruction>(Ptr)) {
  if (I->getParent()->isEntryBlock())
    return true;
}
if (auto *GEP = dyn_cast<GEPOperator>(Ptr)) {
  return IsGuaranteedLoopInvariantBase(GEP->getPointerOperand()) &&
         GEP->hasAllConstantIndices();
}
return IsGuaranteedLoopInvariantBase(Ptr);
2595}