/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Transforms/Scalar/LICM.cpp

Bug Summary

File:	llvm/lib/Transforms/Scalar/LICM.cpp
Warning:	line 1141, column 22 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name LICM.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/Transforms/Scalar -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/Transforms/Scalar -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Transforms/Scalar -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/Transforms/Scalar -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/Transforms/Scalar/LICM.cpp
1//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass performs loop invariant code motion, attempting to remove as much
10// code from the body of a loop as possible.  It does this by either hoisting
11// code into the preheader block, or by sinking code to the exit blocks if it is
12// safe.  This pass also promotes must-aliased memory locations in the loop to
13// live in registers, thus hoisting and sinking "invariant" loads and stores.
14//
15// Hoisting operations out of loops is a canonicalization transform.  It
16// enables and simplifies subsequent optimizations in the middle-end.
17// Rematerialization of hoisted instructions to reduce register pressure is the
18// responsibility of the back-end, which has more accurate information about
19// register pressure and also handles other optimizations than LICM that
20// increase live-ranges.
21//
22// This pass uses alias analysis for two purposes:
23//
24//  1. Moving loop invariant loads and calls out of loops.  If we can determine
25//     that a load or call inside of a loop never aliases anything stored to,
26//     we can hoist it or sink it like any other instruction.
27//  2. Scalar Promotion of Memory - If there is a store instruction inside of
28//     the loop, we try to move the store to happen AFTER the loop instead of
29//     inside of the loop.  This can only happen if a few conditions are true:
30//       A. The pointer stored through is loop invariant
31//       B. There are no stores or loads in the loop which _may_ alias the
32//          pointer.  There are no calls in the loop which mod/ref the pointer.
33//     If these conditions are true, we can promote the loads and stores in the
34//     loop of the pointer to use a temporary alloca'd variable.  We then use
35//     the SSAUpdater to construct the appropriate SSA form for the value.
36//
37//===----------------------------------------------------------------------===//

39#include "llvm/Transforms/Scalar/LICM.h"
40#include "llvm/ADT/SetOperations.h"
41#include "llvm/ADT/Statistic.h"
42#include "llvm/Analysis/AliasAnalysis.h"
43#include "llvm/Analysis/AliasSetTracker.h"
44#include "llvm/Analysis/BasicAliasAnalysis.h"
45#include "llvm/Analysis/BlockFrequencyInfo.h"
46#include "llvm/Analysis/CaptureTracking.h"
47#include "llvm/Analysis/ConstantFolding.h"
48#include "llvm/Analysis/GlobalsModRef.h"
49#include "llvm/Analysis/GuardUtils.h"
50#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
51#include "llvm/Analysis/Loads.h"
52#include "llvm/Analysis/LoopInfo.h"
53#include "llvm/Analysis/LoopIterator.h"
54#include "llvm/Analysis/LoopPass.h"
55#include "llvm/Analysis/MemoryBuiltins.h"
56#include "llvm/Analysis/MemorySSA.h"
57#include "llvm/Analysis/MemorySSAUpdater.h"
58#include "llvm/Analysis/MustExecute.h"
59#include "llvm/Analysis/OptimizationRemarkEmitter.h"
60#include "llvm/Analysis/ScalarEvolution.h"
61#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
62#include "llvm/Analysis/TargetLibraryInfo.h"
63#include "llvm/Analysis/ValueTracking.h"
64#include "llvm/IR/CFG.h"
65#include "llvm/IR/Constants.h"
66#include "llvm/IR/DataLayout.h"
67#include "llvm/IR/DebugInfoMetadata.h"
68#include "llvm/IR/DerivedTypes.h"
69#include "llvm/IR/Dominators.h"
70#include "llvm/IR/Instructions.h"
71#include "llvm/IR/IntrinsicInst.h"
72#include "llvm/IR/LLVMContext.h"
73#include "llvm/IR/Metadata.h"
74#include "llvm/IR/PatternMatch.h"
75#include "llvm/IR/PredIteratorCache.h"
76#include "llvm/InitializePasses.h"
77#include "llvm/Support/CommandLine.h"
78#include "llvm/Support/Debug.h"
79#include "llvm/Support/raw_ostream.h"
80#include "llvm/Transforms/Scalar.h"
81#include "llvm/Transforms/Scalar/LoopPassManager.h"
82#include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
83#include "llvm/Transforms/Utils/BasicBlockUtils.h"
84#include "llvm/Transforms/Utils/Local.h"
85#include "llvm/Transforms/Utils/LoopUtils.h"
86#include "llvm/Transforms/Utils/SSAUpdater.h"
87#include <algorithm>
88#include <utility>
89using namespace llvm;

91#define DEBUG_TYPE"licm" "licm"

93STATISTIC(NumCreatedBlocks, "Number of blocks created")static llvm::Statistic NumCreatedBlocks = {"licm", "NumCreatedBlocks"
, "Number of blocks created"};
94STATISTIC(NumClonedBranches, "Number of branches cloned")static llvm::Statistic NumClonedBranches = {"licm", "NumClonedBranches"
, "Number of branches cloned"};
95STATISTIC(NumSunk, "Number of instructions sunk out of loop")static llvm::Statistic NumSunk = {"licm", "NumSunk", "Number of instructions sunk out of loop"
};
96STATISTIC(NumHoisted, "Number of instructions hoisted out of loop")static llvm::Statistic NumHoisted = {"licm", "NumHoisted", "Number of instructions hoisted out of loop"
};
97STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk")static llvm::Statistic NumMovedLoads = {"licm", "NumMovedLoads"
, "Number of load insts hoisted or sunk"};
98STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk")static llvm::Statistic NumMovedCalls = {"licm", "NumMovedCalls"
, "Number of call insts hoisted or sunk"};
99STATISTIC(NumPromoted, "Number of memory locations promoted to registers")static llvm::Statistic NumPromoted = {"licm", "NumPromoted", "Number of memory locations promoted to registers"
};

101/// Memory promotion is enabled by default.
102static cl::opt<bool>
  DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false),
                   cl::desc("Disable memory promotion in LICM pass"));

106static cl::opt<bool> ControlFlowHoisting(
  "licm-control-flow-hoisting", cl::Hidden, cl::init(false),
  cl::desc("Enable control flow (and PHI) hoisting in LICM"));

110static cl::opt<unsigned> HoistSinkColdnessThreshold(
  "licm-coldness-threshold", cl::Hidden, cl::init(4),
  cl::desc("Relative coldness Threshold of hoisting/sinking destination "
           "block for LICM to be considered beneficial"));

115static cl::opt<uint32_t> MaxNumUsesTraversed(
  "licm-max-num-uses-traversed", cl::Hidden, cl::init(8),
  cl::desc("Max num uses visited for identifying load "
           "invariance in loop using invariant start (default = 8)"));

120// Experimental option to allow imprecision in LICM in pathological cases, in
121// exchange for faster compile. This is to be removed if MemorySSA starts to
122// address the same issue. This flag applies only when LICM uses MemorySSA
123// instead on AliasSetTracker. LICM calls MemorySSAWalker's
124// getClobberingMemoryAccess, up to the value of the Cap, getting perfect
125// accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess,
126// which may not be precise, since optimizeUses is capped. The result is
127// correct, but we may not get as "far up" as possible to get which access is
128// clobbering the one queried.
129cl::opt<unsigned> llvm::SetLicmMssaOptCap(
  "licm-mssa-optimization-cap", cl::init(100), cl::Hidden,
  cl::desc("Enable imprecision in LICM in pathological cases, in exchange "
           "for faster compile. Caps the MemorySSA clobbering calls."));

134// Experimentally, memory promotion carries less importance than sinking and
135// hoisting. Limit when we do promotion when using MemorySSA, in order to save
136// compile time.
137cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap(
  "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden,
  cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no "
           "effect. When MSSA in LICM is enabled, then this is the maximum "
           "number of accesses allowed to be present in a loop in order to "
           "enable memory promotion."));

144static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI);
145static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop,
                                const LoopSafetyInfo *SafetyInfo,
                                TargetTransformInfo *TTI, bool &FreeInLoop,
                                bool LoopNestMode);
149static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
                MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
                OptimizationRemarkEmitter *ORE);
153static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
               BlockFrequencyInfo *BFI, const Loop *CurLoop,
               ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU,
               OptimizationRemarkEmitter *ORE);
157static bool isSafeToExecuteUnconditionally(Instruction &Inst,
                                         const DominatorTree *DT,
                                         const TargetLibraryInfo *TLI,
                                         const Loop *CurLoop,
                                         const LoopSafetyInfo *SafetyInfo,
                                         OptimizationRemarkEmitter *ORE,
                                         const Instruction *CtxI = nullptr);
164static bool pointerInvalidatedByLoop(MemoryLocation MemLoc,
                                   AliasSetTracker *CurAST, Loop *CurLoop,
                                   AAResults *AA);
167static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU,
                                           Loop *CurLoop, Instruction &I,
                                           SinkAndHoistLICMFlags &Flags);
170static bool pointerInvalidatedByBlockWithMSSA(BasicBlock &BB, MemorySSA &MSSA,
                                            MemoryUse &MU);
172static Instruction *cloneInstructionInExitBlock(
  Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI,
  const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU);

176static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
                           MemorySSAUpdater *MSSAU);

179static void moveInstructionBefore(Instruction &I, Instruction &Dest,
                                ICFLoopSafetyInfo &SafetyInfo,
                                MemorySSAUpdater *MSSAU, ScalarEvolution *SE);

183static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L,
                              function_ref<void(Instruction *)> Fn);
185static SmallVector<SmallSetVector<Value *, 8>, 0>
186collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L);

188namespace {
189struct LoopInvariantCodeMotion {
bool runOnLoop(Loop *L, AAResults *AA, LoopInfo *LI, DominatorTree *DT,
               BlockFrequencyInfo *BFI, TargetLibraryInfo *TLI,
               TargetTransformInfo *TTI, ScalarEvolution *SE, MemorySSA *MSSA,
               OptimizationRemarkEmitter *ORE, bool LoopNestMode = false);

LoopInvariantCodeMotion(unsigned LicmMssaOptCap,
                        unsigned LicmMssaNoAccForPromotionCap)
    : LicmMssaOptCap(LicmMssaOptCap),
      LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap) {}

200private:
unsigned LicmMssaOptCap;
unsigned LicmMssaNoAccForPromotionCap;
203};

205struct LegacyLICMPass : public LoopPass {
static char ID; // Pass identification, replacement for typeid
LegacyLICMPass(
    unsigned LicmMssaOptCap = SetLicmMssaOptCap,
    unsigned LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap)
    : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) {
  initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry());
}

bool runOnLoop(Loop *L, LPPassManager &LPM) override {
  if (skipLoop(L))
    return false;

  LLVM_DEBUG(dbgs() << "Perform LICM on Loop with header at block "do { } while (false)
                    << L->getHeader()->getNameOrAsOperand() << "\n")do { } while (false);

  auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
  MemorySSA *MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
  bool hasProfileData = L->getHeader()->getParent()->hasProfileData();
  BlockFrequencyInfo *BFI =
      hasProfileData ? &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI()
                     : nullptr;
  // For the old PM, we can't use OptimizationRemarkEmitter as an analysis
  // pass. Function analyses need to be preserved across loop transformations
  // but ORE cannot be preserved (see comment before the pass definition).
  OptimizationRemarkEmitter ORE(L->getHeader()->getParent());
  return LICM.runOnLoop(
      L, &getAnalysis<AAResultsWrapperPass>().getAAResults(),
      &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(),
      &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), BFI,
      &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(
          *L->getHeader()->getParent()),
      &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
          *L->getHeader()->getParent()),
      SE ? &SE->getSE() : nullptr, MSSA, &ORE);
}

/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG...
///
void getAnalysisUsage(AnalysisUsage &AU) const override {
  AU.addPreserved<DominatorTreeWrapperPass>();
  AU.addPreserved<LoopInfoWrapperPass>();
  AU.addRequired<TargetLibraryInfoWrapperPass>();
  AU.addRequired<MemorySSAWrapperPass>();
  AU.addPreserved<MemorySSAWrapperPass>();
  AU.addRequired<TargetTransformInfoWrapperPass>();
  getLoopAnalysisUsage(AU);
  LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU);
  AU.addPreserved<LazyBlockFrequencyInfoPass>();
  AU.addPreserved<LazyBranchProbabilityInfoPass>();
}

258private:
LoopInvariantCodeMotion LICM;
260};
261} // namespace

263PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
                              LoopStandardAnalysisResults &AR, LPMUpdater &) {
if (!AR.MSSA)
  report_fatal_error("LICM requires MemorySSA (loop-mssa)");

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

LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap);
if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, AR.BFI, &AR.TLI, &AR.TTI,
                    &AR.SE, AR.MSSA, &ORE))
  return PreservedAnalyses::all();

auto PA = getLoopPassPreservedAnalyses();

PA.preserve<DominatorTreeAnalysis>();
PA.preserve<LoopAnalysis>();
PA.preserve<MemorySSAAnalysis>();

return PA;
285}

287PreservedAnalyses LNICMPass::run(LoopNest &LN, LoopAnalysisManager &AM,
                               LoopStandardAnalysisResults &AR,
                               LPMUpdater &) {
if (!AR.MSSA)
  report_fatal_error("LNICM requires MemorySSA (loop-mssa)");

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

LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap);

Loop &OutermostLoop = LN.getOutermostLoop();
bool Changed = LICM.runOnLoop(&OutermostLoop, &AR.AA, &AR.LI, &AR.DT, AR.BFI,
                              &AR.TLI, &AR.TTI, &AR.SE, AR.MSSA, &ORE, true);

if (!Changed)
  return PreservedAnalyses::all();

auto PA = getLoopPassPreservedAnalyses();

PA.preserve<DominatorTreeAnalysis>();
PA.preserve<LoopAnalysis>();
PA.preserve<MemorySSAAnalysis>();

return PA;
314}

316char LegacyLICMPass::ID = 0;
317INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion",static void *initializeLegacyLICMPassPassOnce(PassRegistry &
Registry) {
                    false, false)static void *initializeLegacyLICMPassPassOnce(PassRegistry &
Registry) {
319INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry);
320INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry);
321INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
322INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
323INITIALIZE_PASS_DEPENDENCY(LazyBFIPass)initializeLazyBFIPassPass(Registry);
324INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false,PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm"
, &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LegacyLICMPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag
; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce
, std::ref(Registry)); }
                  false)PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm"
, &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LegacyLICMPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag
; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce
, std::ref(Registry)); }

327Pass *llvm::createLICMPass() { return new LegacyLICMPass(); }
328Pass *llvm::createLICMPass(unsigned LicmMssaOptCap,
                         unsigned LicmMssaNoAccForPromotionCap) {
return new LegacyLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap);
331}

333llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags(bool IsSink, Loop *L,
                                                 MemorySSA *MSSA)
  : SinkAndHoistLICMFlags(SetLicmMssaOptCap, SetLicmMssaNoAccForPromotionCap,
                          IsSink, L, MSSA) {}

338llvm::SinkAndHoistLICMFlags::SinkAndHoistLICMFlags(
  unsigned LicmMssaOptCap, unsigned LicmMssaNoAccForPromotionCap, bool IsSink,
  Loop *L, MemorySSA *MSSA)
  : LicmMssaOptCap(LicmMssaOptCap),
    LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap),
    IsSink(IsSink) {
assert(((L != nullptr) == (MSSA != nullptr)) &&(static_cast<void> (0))
       "Unexpected values for SinkAndHoistLICMFlags")(static_cast<void> (0));
if (!MSSA)
  return;

unsigned AccessCapCount = 0;
for (auto *BB : L->getBlocks())
  if (const auto *Accesses = MSSA->getBlockAccesses(BB))
    for (const auto &MA : *Accesses) {
      (void)MA;
      ++AccessCapCount;
      if (AccessCapCount > LicmMssaNoAccForPromotionCap) {
        NoOfMemAccTooLarge = true;
        return;
      }
    }
360}

362/// Hoist expressions out of the specified loop. Note, alias info for inner
363/// loop is not preserved so it is not a good idea to run LICM multiple
364/// times on one loop.
365bool LoopInvariantCodeMotion::runOnLoop(
  Loop *L, AAResults *AA, LoopInfo *LI, DominatorTree *DT,
  BlockFrequencyInfo *BFI, TargetLibraryInfo *TLI, TargetTransformInfo *TTI,
  ScalarEvolution *SE, MemorySSA *MSSA, OptimizationRemarkEmitter *ORE,
  bool LoopNestMode) {
bool Changed = false;

assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.")(static_cast<void> (0));

// If this loop has metadata indicating that LICM is not to be performed then
// just exit.
if (hasDisableLICMTransformsHint(L)) {
  return false;
}

// Don't sink stores from loops with coroutine suspend instructions.
// LICM would sink instructions into the default destination of
// the coroutine switch. The default destination of the switch is to
// handle the case where the coroutine is suspended, by which point the
// coroutine frame may have been destroyed. No instruction can be sunk there.
// FIXME: This would unfortunately hurt the performance of coroutines, however
// there is currently no general solution for this. Similar issues could also
// potentially happen in other passes where instructions are being moved
// across that edge.
bool HasCoroSuspendInst = llvm::any_of(L->getBlocks(), [](BasicBlock *BB) {
  return llvm::any_of(*BB, [](Instruction &I) {
    IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
    return II && II->getIntrinsicID() == Intrinsic::coro_suspend;
  });
});

MemorySSAUpdater MSSAU(MSSA);
SinkAndHoistLICMFlags Flags(LicmMssaOptCap, LicmMssaNoAccForPromotionCap,
                            /*IsSink=*/true, L, MSSA);

// Get the preheader block to move instructions into...
BasicBlock *Preheader = L->getLoopPreheader();

// Compute loop safety information.
ICFLoopSafetyInfo SafetyInfo;
SafetyInfo.computeLoopSafetyInfo(L);

// We want to visit all of the instructions in this loop... that are not parts
// of our subloops (they have already had their invariants hoisted out of
// their loop, into this loop, so there is no need to process the BODIES of
// the subloops).
//
// Traverse the body of the loop in depth first order on the dominator tree so
// that we are guaranteed to see definitions before we see uses.  This allows
// us to sink instructions in one pass, without iteration.  After sinking
// instructions, we perform another pass to hoist them out of the loop.
if (L->hasDedicatedExits())
  Changed |= LoopNestMode
                 ? sinkRegionForLoopNest(DT->getNode(L->getHeader()), AA, LI,
                                         DT, BFI, TLI, TTI, L, &MSSAU,
                                         &SafetyInfo, Flags, ORE)
                 : sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, BFI,
                              TLI, TTI, L, &MSSAU, &SafetyInfo, Flags, ORE);
Flags.setIsSink(false);
if (Preheader)
  Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, BFI, TLI, L,
                         &MSSAU, SE, &SafetyInfo, Flags, ORE, LoopNestMode);

// Now that all loop invariants have been removed from the loop, promote any
// memory references to scalars that we can.
// Don't sink stores from loops without dedicated block exits. Exits
// containing indirect branches are not transformed by loop simplify,
// make sure we catch that. An additional load may be generated in the
// preheader for SSA updater, so also avoid sinking when no preheader
// is available.
if (!DisablePromotion && Preheader && L->hasDedicatedExits() &&
    !Flags.tooManyMemoryAccesses() && !HasCoroSuspendInst) {
  // Figure out the loop exits and their insertion points
  SmallVector<BasicBlock *, 8> ExitBlocks;
  L->getUniqueExitBlocks(ExitBlocks);

  // We can't insert into a catchswitch.
  bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) {
    return isa<CatchSwitchInst>(Exit->getTerminator());
  });

  if (!HasCatchSwitch) {
    SmallVector<Instruction *, 8> InsertPts;
    SmallVector<MemoryAccess *, 8> MSSAInsertPts;
    InsertPts.reserve(ExitBlocks.size());
    MSSAInsertPts.reserve(ExitBlocks.size());
    for (BasicBlock *ExitBlock : ExitBlocks) {
      InsertPts.push_back(&*ExitBlock->getFirstInsertionPt());
      MSSAInsertPts.push_back(nullptr);
    }

    PredIteratorCache PIC;

    // Promoting one set of accesses may make the pointers for another set
    // loop invariant, so run this in a loop (with the MaybePromotable set
    // decreasing in size over time).
    bool Promoted = false;
    bool LocalPromoted;
    do {
      LocalPromoted = false;
      for (const SmallSetVector<Value *, 8> &PointerMustAliases :
           collectPromotionCandidates(MSSA, AA, L)) {
        LocalPromoted |= promoteLoopAccessesToScalars(
            PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC,
            LI, DT, TLI, L, &MSSAU, &SafetyInfo, ORE);
      }
      Promoted |= LocalPromoted;
    } while (LocalPromoted);

    // Once we have promoted values across the loop body we have to
    // recursively reform LCSSA as any nested loop may now have values defined
    // within the loop used in the outer loop.
    // FIXME: This is really heavy handed. It would be a bit better to use an
    // SSAUpdater strategy during promotion that was LCSSA aware and reformed
    // it as it went.
    if (Promoted)
      formLCSSARecursively(*L, *DT, LI, SE);

    Changed |= Promoted;
  }
}

// Check that neither this loop nor its parent have had LCSSA broken. LICM is
// specifically moving instructions across the loop boundary and so it is
// especially in need of sanity checking here.
assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!")(static_cast<void> (0));
assert((L->isOutermost() || L->getParentLoop()->isLCSSAForm(*DT)) &&(static_cast<void> (0))
       "Parent loop not left in LCSSA form after LICM!")(static_cast<void> (0));

if (VerifyMemorySSA)
  MSSA->verifyMemorySSA();

if (Changed && SE)
  SE->forgetLoopDispositions(L);
return Changed;
500}

502/// Walk the specified region of the CFG (defined by all blocks dominated by
503/// the specified block, and that are in the current loop) in reverse depth
504/// first order w.r.t the DominatorTree.  This allows us to visit uses before
505/// definitions, allowing us to sink a loop body in one pass without iteration.
506///
507bool llvm::sinkRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
                    DominatorTree *DT, BlockFrequencyInfo *BFI,
                    TargetLibraryInfo *TLI, TargetTransformInfo *TTI,
                    Loop *CurLoop, MemorySSAUpdater *MSSAU,
                    ICFLoopSafetyInfo *SafetyInfo,
                    SinkAndHoistLICMFlags &Flags,
                    OptimizationRemarkEmitter *ORE, Loop *OutermostLoop) {

// Verify inputs.
assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&(static_cast<void> (0))
       CurLoop != nullptr && MSSAU != nullptr && SafetyInfo != nullptr &&(static_cast<void> (0))
       "Unexpected input to sinkRegion.")(static_cast<void> (0));

// We want to visit children before parents. We will enque all the parents
// before their children in the worklist and process the worklist in reverse
// order.
SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop);

bool Changed = false;
for (DomTreeNode *DTN : reverse(Worklist)) {
  BasicBlock *BB = DTN->getBlock();
  // Only need to process the contents of this block if it is not part of a
  // subloop (which would already have been processed).
  if (inSubLoop(BB, CurLoop, LI))
    continue;

  for (BasicBlock::iterator II = BB->end(); II != BB->begin();) {
    Instruction &I = *--II;

    // The instruction is not used in the loop if it is dead.  In this case,
    // we just delete it instead of sinking it.
    if (isInstructionTriviallyDead(&I, TLI)) {
      LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n')do { } while (false);
      salvageKnowledge(&I);
      salvageDebugInfo(I);
      ++II;
      eraseInstruction(I, *SafetyInfo, MSSAU);
      Changed = true;
      continue;
    }

    // Check to see if we can sink this instruction to the exit blocks
    // of the loop.  We can do this if the all users of the instruction are
    // outside of the loop.  In this case, it doesn't even matter if the
    // operands of the instruction are loop invariant.
    //
    bool FreeInLoop = false;
    bool LoopNestMode = OutermostLoop != nullptr;
    if (!I.mayHaveSideEffects() &&
        isNotUsedOrFreeInLoop(I, LoopNestMode ? OutermostLoop : CurLoop,
                              SafetyInfo, TTI, FreeInLoop, LoopNestMode) &&
        canSinkOrHoistInst(I, AA, DT, CurLoop, /*CurAST*/nullptr, MSSAU, true,
                           &Flags, ORE)) {
      if (sink(I, LI, DT, BFI, CurLoop, SafetyInfo, MSSAU, ORE)) {
        if (!FreeInLoop) {
          ++II;
          salvageDebugInfo(I);
          eraseInstruction(I, *SafetyInfo, MSSAU);
        }
        Changed = true;
      }
    }
  }
}
if (VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();
return Changed;
574}

576bool llvm::sinkRegionForLoopNest(
  DomTreeNode *N, AAResults *AA, LoopInfo *LI, DominatorTree *DT,
  BlockFrequencyInfo *BFI, TargetLibraryInfo *TLI, TargetTransformInfo *TTI,
  Loop *CurLoop, MemorySSAUpdater *MSSAU, ICFLoopSafetyInfo *SafetyInfo,
  SinkAndHoistLICMFlags &Flags, OptimizationRemarkEmitter *ORE) {

bool Changed = false;
SmallPriorityWorklist<Loop *, 4> Worklist;
Worklist.insert(CurLoop);
appendLoopsToWorklist(*CurLoop, Worklist);
while (!Worklist.empty()) {
  Loop *L = Worklist.pop_back_val();
  Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, BFI, TLI,
                        TTI, L, MSSAU, SafetyInfo, Flags, ORE, CurLoop);
}
return Changed;
592}

594namespace {
595// This is a helper class for hoistRegion to make it able to hoist control flow
596// in order to be able to hoist phis. The way this works is that we initially
597// start hoisting to the loop preheader, and when we see a loop invariant branch
598// we make note of this. When we then come to hoist an instruction that's
599// conditional on such a branch we duplicate the branch and the relevant control
600// flow, then hoist the instruction into the block corresponding to its original
601// block in the duplicated control flow.
602class ControlFlowHoister {
603private:
// Information about the loop we are hoisting from
LoopInfo *LI;
DominatorTree *DT;
Loop *CurLoop;
MemorySSAUpdater *MSSAU;

// A map of blocks in the loop to the block their instructions will be hoisted
// to.
DenseMap<BasicBlock *, BasicBlock *> HoistDestinationMap;

// The branches that we can hoist, mapped to the block that marks a
// convergence point of their control flow.
DenseMap<BranchInst *, BasicBlock *> HoistableBranches;

618public:
ControlFlowHoister(LoopInfo *LI, DominatorTree *DT, Loop *CurLoop,
                   MemorySSAUpdater *MSSAU)
    : LI(LI), DT(DT), CurLoop(CurLoop), MSSAU(MSSAU) {}

void registerPossiblyHoistableBranch(BranchInst *BI) {
  // We can only hoist conditional branches with loop invariant operands.
  if (!ControlFlowHoisting || !BI->isConditional() ||
      !CurLoop->hasLoopInvariantOperands(BI))
    return;

  // The branch destinations need to be in the loop, and we don't gain
  // anything by duplicating conditional branches with duplicate successors,
  // as it's essentially the same as an unconditional branch.
  BasicBlock *TrueDest = BI->getSuccessor(0);
  BasicBlock *FalseDest = BI->getSuccessor(1);
  if (!CurLoop->contains(TrueDest) || !CurLoop->contains(FalseDest) ||
      TrueDest == FalseDest)
    return;

  // We can hoist BI if one branch destination is the successor of the other,
  // or both have common successor which we check by seeing if the
  // intersection of their successors is non-empty.
  // TODO: This could be expanded to allowing branches where both ends
  // eventually converge to a single block.
  SmallPtrSet<BasicBlock *, 4> TrueDestSucc, FalseDestSucc;
  TrueDestSucc.insert(succ_begin(TrueDest), succ_end(TrueDest));
  FalseDestSucc.insert(succ_begin(FalseDest), succ_end(FalseDest));
  BasicBlock *CommonSucc = nullptr;
  if (TrueDestSucc.count(FalseDest)) {
    CommonSucc = FalseDest;
  } else if (FalseDestSucc.count(TrueDest)) {
    CommonSucc = TrueDest;
  } else {
    set_intersect(TrueDestSucc, FalseDestSucc);
    // If there's one common successor use that.
    if (TrueDestSucc.size() == 1)
      CommonSucc = *TrueDestSucc.begin();
    // If there's more than one pick whichever appears first in the block list
    // (we can't use the value returned by TrueDestSucc.begin() as it's
    // unpredicatable which element gets returned).
    else if (!TrueDestSucc.empty()) {
      Function *F = TrueDest->getParent();
      auto IsSucc = [&](BasicBlock &BB) { return TrueDestSucc.count(&BB); };
      auto It = llvm::find_if(*F, IsSucc);
      assert(It != F->end() && "Could not find successor in function")(static_cast<void> (0));
      CommonSucc = &*It;
    }
  }
  // The common successor has to be dominated by the branch, as otherwise
  // there will be some other path to the successor that will not be
  // controlled by this branch so any phi we hoist would be controlled by the
  // wrong condition. This also takes care of avoiding hoisting of loop back
  // edges.
  // TODO: In some cases this could be relaxed if the successor is dominated
  // by another block that's been hoisted and we can guarantee that the
  // control flow has been replicated exactly.
  if (CommonSucc && DT->dominates(BI, CommonSucc))
    HoistableBranches[BI] = CommonSucc;
}

bool canHoistPHI(PHINode *PN) {
  // The phi must have loop invariant operands.
  if (!ControlFlowHoisting || !CurLoop->hasLoopInvariantOperands(PN))
    return false;
  // We can hoist phis if the block they are in is the target of hoistable
  // branches which cover all of the predecessors of the block.
  SmallPtrSet<BasicBlock *, 8> PredecessorBlocks;
  BasicBlock *BB = PN->getParent();
  for (BasicBlock *PredBB : predecessors(BB))
    PredecessorBlocks.insert(PredBB);
  // If we have less predecessor blocks than predecessors then the phi will
  // have more than one incoming value for the same block which we can't
  // handle.
  // TODO: This could be handled be erasing some of the duplicate incoming
  // values.
  if (PredecessorBlocks.size() != pred_size(BB))
    return false;
  for (auto &Pair : HoistableBranches) {
    if (Pair.second == BB) {
      // Which blocks are predecessors via this branch depends on if the
      // branch is triangle-like or diamond-like.
      if (Pair.first->getSuccessor(0) == BB) {
        PredecessorBlocks.erase(Pair.first->getParent());
        PredecessorBlocks.erase(Pair.first->getSuccessor(1));
      } else if (Pair.first->getSuccessor(1) == BB) {
        PredecessorBlocks.erase(Pair.first->getParent());
        PredecessorBlocks.erase(Pair.first->getSuccessor(0));
      } else {
        PredecessorBlocks.erase(Pair.first->getSuccessor(0));
        PredecessorBlocks.erase(Pair.first->getSuccessor(1));
      }
    }
  }
  // PredecessorBlocks will now be empty if for every predecessor of BB we
  // found a hoistable branch source.
  return PredecessorBlocks.empty();
}

BasicBlock *getOrCreateHoistedBlock(BasicBlock *BB) {
  if (!ControlFlowHoisting)
    return CurLoop->getLoopPreheader();
  // If BB has already been hoisted, return that
  if (HoistDestinationMap.count(BB))
    return HoistDestinationMap[BB];

  // Check if this block is conditional based on a pending branch
  auto HasBBAsSuccessor =
      [&](DenseMap<BranchInst *, BasicBlock *>::value_type &Pair) {
        return BB != Pair.second && (Pair.first->getSuccessor(0) == BB ||
                                     Pair.first->getSuccessor(1) == BB);
      };
  auto It = llvm::find_if(HoistableBranches, HasBBAsSuccessor);

  // If not involved in a pending branch, hoist to preheader
  BasicBlock *InitialPreheader = CurLoop->getLoopPreheader();
  if (It == HoistableBranches.end()) {
    LLVM_DEBUG(dbgs() << "LICM using "do { } while (false)
                      << InitialPreheader->getNameOrAsOperand()do { } while (false)
                      << " as hoist destination for "do { } while (false)
                      << BB->getNameOrAsOperand() << "\n")do { } while (false);
    HoistDestinationMap[BB] = InitialPreheader;
    return InitialPreheader;
  }
  BranchInst *BI = It->first;
  assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) ==(static_cast<void> (0))
             HoistableBranches.end() &&(static_cast<void> (0))
         "BB is expected to be the target of at most one branch")(static_cast<void> (0));

  LLVMContext &C = BB->getContext();
  BasicBlock *TrueDest = BI->getSuccessor(0);
  BasicBlock *FalseDest = BI->getSuccessor(1);
  BasicBlock *CommonSucc = HoistableBranches[BI];
  BasicBlock *HoistTarget = getOrCreateHoistedBlock(BI->getParent());

  // Create hoisted versions of blocks that currently don't have them
  auto CreateHoistedBlock = [&](BasicBlock *Orig) {
    if (HoistDestinationMap.count(Orig))
      return HoistDestinationMap[Orig];
    BasicBlock *New =
        BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent());
    HoistDestinationMap[Orig] = New;
    DT->addNewBlock(New, HoistTarget);
    if (CurLoop->getParentLoop())
      CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI);
    ++NumCreatedBlocks;
    LLVM_DEBUG(dbgs() << "LICM created " << New->getName()do { } while (false)
                      << " as hoist destination for " << Orig->getName()do { } while (false)
                      << "\n")do { } while (false);
    return New;
  };
  BasicBlock *HoistTrueDest = CreateHoistedBlock(TrueDest);
  BasicBlock *HoistFalseDest = CreateHoistedBlock(FalseDest);
  BasicBlock *HoistCommonSucc = CreateHoistedBlock(CommonSucc);

  // Link up these blocks with branches.
  if (!HoistCommonSucc->getTerminator()) {
    // The new common successor we've generated will branch to whatever that
    // hoist target branched to.
    BasicBlock *TargetSucc = HoistTarget->getSingleSuccessor();
    assert(TargetSucc && "Expected hoist target to have a single successor")(static_cast<void> (0));
    HoistCommonSucc->moveBefore(TargetSucc);
    BranchInst::Create(TargetSucc, HoistCommonSucc);
  }
  if (!HoistTrueDest->getTerminator()) {
    HoistTrueDest->moveBefore(HoistCommonSucc);
    BranchInst::Create(HoistCommonSucc, HoistTrueDest);
  }
  if (!HoistFalseDest->getTerminator()) {
    HoistFalseDest->moveBefore(HoistCommonSucc);
    BranchInst::Create(HoistCommonSucc, HoistFalseDest);
  }

  // If BI is being cloned to what was originally the preheader then
  // HoistCommonSucc will now be the new preheader.
  if (HoistTarget == InitialPreheader) {
    // Phis in the loop header now need to use the new preheader.
    InitialPreheader->replaceSuccessorsPhiUsesWith(HoistCommonSucc);
    MSSAU->wireOldPredecessorsToNewImmediatePredecessor(
        HoistTarget->getSingleSuccessor(), HoistCommonSucc, {HoistTarget});
    // The new preheader dominates the loop header.
    DomTreeNode *PreheaderNode = DT->getNode(HoistCommonSucc);
    DomTreeNode *HeaderNode = DT->getNode(CurLoop->getHeader());
    DT->changeImmediateDominator(HeaderNode, PreheaderNode);
    // The preheader hoist destination is now the new preheader, with the
    // exception of the hoist destination of this branch.
    for (auto &Pair : HoistDestinationMap)
      if (Pair.second == InitialPreheader && Pair.first != BI->getParent())
        Pair.second = HoistCommonSucc;
  }

  // Now finally clone BI.
  ReplaceInstWithInst(
      HoistTarget->getTerminator(),
      BranchInst::Create(HoistTrueDest, HoistFalseDest, BI->getCondition()));
  ++NumClonedBranches;

  assert(CurLoop->getLoopPreheader() &&(static_cast<void> (0))
         "Hoisting blocks should not have destroyed preheader")(static_cast<void> (0));
  return HoistDestinationMap[BB];
}
819};
820} // namespace

822// Hoisting/sinking instruction out of a loop isn't always beneficial. It's only
823// only worthwhile if the destination block is actually colder than current
824// block.
825static bool worthSinkOrHoistInst(Instruction &I, BasicBlock *DstBlock,
                               OptimizationRemarkEmitter *ORE,
                               BlockFrequencyInfo *BFI) {
// Check block frequency only when runtime profile is available
// to avoid pathological cases. With static profile, lean towards
// hosting because it helps canonicalize the loop for vectorizer.
if (!DstBlock->getParent()->hasProfileData())
  return true;

if (!HoistSinkColdnessThreshold || !BFI)
  return true;

BasicBlock *SrcBlock = I.getParent();
if (BFI->getBlockFreq(DstBlock).getFrequency() / HoistSinkColdnessThreshold >
    BFI->getBlockFreq(SrcBlock).getFrequency()) {
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"licm", "SinkHoistInst", &I)
           << "failed to sink or hoist instruction because containing block "
              "has lower frequency than destination block";
  });
  return false;
}

return true;
849}

851/// Walk the specified region of the CFG (defined by all blocks dominated by
852/// the specified block, and that are in the current loop) in depth first
853/// order w.r.t the DominatorTree.  This allows us to visit definitions before
854/// uses, allowing us to hoist a loop body in one pass without iteration.
855///
856bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
                     DominatorTree *DT, BlockFrequencyInfo *BFI,
                     TargetLibraryInfo *TLI, Loop *CurLoop,
                     MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
                     ICFLoopSafetyInfo *SafetyInfo,
                     SinkAndHoistLICMFlags &Flags,
                     OptimizationRemarkEmitter *ORE, bool LoopNestMode) {
// Verify inputs.
assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&(static_cast<void> (0))
       CurLoop != nullptr && MSSAU != nullptr && SafetyInfo != nullptr &&(static_cast<void> (0))
       "Unexpected input to hoistRegion.")(static_cast<void> (0));

ControlFlowHoister CFH(LI, DT, CurLoop, MSSAU);

// Keep track of instructions that have been hoisted, as they may need to be
// re-hoisted if they end up not dominating all of their uses.
SmallVector<Instruction *, 16> HoistedInstructions;

// For PHI hoisting to work we need to hoist blocks before their successors.
// We can do this by iterating through the blocks in the loop in reverse
// post-order.
LoopBlocksRPO Worklist(CurLoop);
Worklist.perform(LI);
bool Changed = false;
for (BasicBlock *BB : Worklist) {
  // Only need to process the contents of this block if it is not part of a
  // subloop (which would already have been processed).
  if (!LoopNestMode && inSubLoop(BB, CurLoop, LI))
    continue;

  for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) {
    Instruction &I = *II++;
    // Try constant folding this instruction.  If all the operands are
    // constants, it is technically hoistable, but it would be better to
    // just fold it.
    if (Constant *C = ConstantFoldInstruction(
            &I, I.getModule()->getDataLayout(), TLI)) {
      LLVM_DEBUG(dbgs() << "LICM folding inst: " << I << "  --> " << *Cdo { } while (false)
                        << '\n')do { } while (false);
      // FIXME MSSA: Such replacements may make accesses unoptimized (D51960).
      I.replaceAllUsesWith(C);
      if (isInstructionTriviallyDead(&I, TLI))
        eraseInstruction(I, *SafetyInfo, MSSAU);
      Changed = true;
      continue;
    }

    // Try hoisting the instruction out to the preheader.  We can only do
    // this if all of the operands of the instruction are loop invariant and
    // if it is safe to hoist the instruction. We also check block frequency
    // to make sure instruction only gets hoisted into colder blocks.
    // TODO: It may be safe to hoist if we are hoisting to a conditional block
    // and we have accurately duplicated the control flow from the loop header
    // to that block.
    if (CurLoop->hasLoopInvariantOperands(&I) &&
        canSinkOrHoistInst(I, AA, DT, CurLoop, /*CurAST*/ nullptr, MSSAU,
                           true, &Flags, ORE) &&
        worthSinkOrHoistInst(I, CurLoop->getLoopPreheader(), ORE, BFI) &&
        isSafeToExecuteUnconditionally(
            I, DT, TLI, CurLoop, SafetyInfo, ORE,
            CurLoop->getLoopPreheader()->getTerminator())) {
      hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
            MSSAU, SE, ORE);
      HoistedInstructions.push_back(&I);
      Changed = true;
      continue;
    }

    // Attempt to remove floating point division out of the loop by
    // converting it to a reciprocal multiplication.
    if (I.getOpcode() == Instruction::FDiv && I.hasAllowReciprocal() &&
        CurLoop->isLoopInvariant(I.getOperand(1))) {
      auto Divisor = I.getOperand(1);
      auto One = llvm::ConstantFP::get(Divisor->getType(), 1.0);
      auto ReciprocalDivisor = BinaryOperator::CreateFDiv(One, Divisor);
      ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags());
      SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent());
      ReciprocalDivisor->insertBefore(&I);

      auto Product =
          BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor);
      Product->setFastMathFlags(I.getFastMathFlags());
      SafetyInfo->insertInstructionTo(Product, I.getParent());
      Product->insertAfter(&I);
      I.replaceAllUsesWith(Product);
      eraseInstruction(I, *SafetyInfo, MSSAU);

      hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB),
            SafetyInfo, MSSAU, SE, ORE);
      HoistedInstructions.push_back(ReciprocalDivisor);
      Changed = true;
      continue;
    }

    auto IsInvariantStart = [&](Instruction &I) {
      using namespace PatternMatch;
      return I.use_empty() &&
             match(&I, m_Intrinsic<Intrinsic::invariant_start>());
    };
    auto MustExecuteWithoutWritesBefore = [&](Instruction &I) {
      return SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) &&
             SafetyInfo->doesNotWriteMemoryBefore(I, CurLoop);
    };
    if ((IsInvariantStart(I) || isGuard(&I)) &&
        CurLoop->hasLoopInvariantOperands(&I) &&
        MustExecuteWithoutWritesBefore(I)) {
      hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
            MSSAU, SE, ORE);
      HoistedInstructions.push_back(&I);
      Changed = true;
      continue;
    }

    if (PHINode *PN = dyn_cast<PHINode>(&I)) {
      if (CFH.canHoistPHI(PN)) {
        // Redirect incoming blocks first to ensure that we create hoisted
        // versions of those blocks before we hoist the phi.
        for (unsigned int i = 0; i < PN->getNumIncomingValues(); ++i)
          PN->setIncomingBlock(
              i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i)));
        hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
              MSSAU, SE, ORE);
        assert(DT->dominates(PN, BB) && "Conditional PHIs not expected")(static_cast<void> (0));
        Changed = true;
        continue;
      }
    }

    // Remember possibly hoistable branches so we can actually hoist them
    // later if needed.
    if (BranchInst *BI = dyn_cast<BranchInst>(&I))
      CFH.registerPossiblyHoistableBranch(BI);
  }
}

// If we hoisted instructions to a conditional block they may not dominate
// their uses that weren't hoisted (such as phis where some operands are not
// loop invariant). If so make them unconditional by moving them to their
// immediate dominator. We iterate through the instructions in reverse order
// which ensures that when we rehoist an instruction we rehoist its operands,
// and also keep track of where in the block we are rehoisting to to make sure
// that we rehoist instructions before the instructions that use them.
Instruction *HoistPoint = nullptr;
if (ControlFlowHoisting) {
  for (Instruction *I : reverse(HoistedInstructions)) {
    if (!llvm::all_of(I->uses(),
                      [&](Use &U) { return DT->dominates(I, U); })) {
      BasicBlock *Dominator =
          DT->getNode(I->getParent())->getIDom()->getBlock();
      if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) {
        if (HoistPoint)
          assert(DT->dominates(Dominator, HoistPoint->getParent()) &&(static_cast<void> (0))
                 "New hoist point expected to dominate old hoist point")(static_cast<void> (0));
        HoistPoint = Dominator->getTerminator();
      }
      LLVM_DEBUG(dbgs() << "LICM rehoisting to "do { } while (false)
                        << HoistPoint->getParent()->getNameOrAsOperand()do { } while (false)
                        << ": " << *I << "\n")do { } while (false);
      moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU, SE);
      HoistPoint = I;
      Changed = true;
    }
  }
}
if (VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();

  // Now that we've finished hoisting make sure that LI and DT are still
  // valid.
1025#ifdef EXPENSIVE_CHECKS
if (Changed) {
  assert(DT->verify(DominatorTree::VerificationLevel::Fast) &&(static_cast<void> (0))
         "Dominator tree verification failed")(static_cast<void> (0));
  LI->verify(*DT);
}
1031#endif

return Changed;
1034}

1036// Return true if LI is invariant within scope of the loop. LI is invariant if
1037// CurLoop is dominated by an invariant.start representing the same memory
1038// location and size as the memory location LI loads from, and also the
1039// invariant.start has no uses.
1040static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT,
                                Loop *CurLoop) {
Value *Addr = LI->getOperand(0);
const DataLayout &DL = LI->getModule()->getDataLayout();
const TypeSize LocSizeInBits = DL.getTypeSizeInBits(LI->getType());

// It is not currently possible for clang to generate an invariant.start
// intrinsic with scalable vector types because we don't support thread local
// sizeless types and we don't permit sizeless types in structs or classes.
// Furthermore, even if support is added for this in future the intrinsic
// itself is defined to have a size of -1 for variable sized objects. This
// makes it impossible to verify if the intrinsic envelops our region of
// interest. For example, both <vscale x 32 x i8> and <vscale x 16 x i8>
// types would have a -1 parameter, but the former is clearly double the size
// of the latter.
if (LocSizeInBits.isScalable())
  return false;

// if the type is i8 addrspace(x)*, we know this is the type of
// llvm.invariant.start operand
auto *PtrInt8Ty = PointerType::get(Type::getInt8Ty(LI->getContext()),
                                   LI->getPointerAddressSpace());
unsigned BitcastsVisited = 0;
// Look through bitcasts until we reach the i8* type (this is invariant.start
// operand type).
while (Addr->getType() != PtrInt8Ty) {
  auto *BC = dyn_cast<BitCastInst>(Addr);
  // Avoid traversing high number of bitcast uses.
  if (++BitcastsVisited > MaxNumUsesTraversed || !BC)
    return false;
  Addr = BC->getOperand(0);
}

unsigned UsesVisited = 0;
// Traverse all uses of the load operand value, to see if invariant.start is
// one of the uses, and whether it dominates the load instruction.
for (auto *U : Addr->users()) {
  // Avoid traversing for Load operand with high number of users.
  if (++UsesVisited > MaxNumUsesTraversed)
    return false;
  IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
  // If there are escaping uses of invariant.start instruction, the load maybe
  // non-invariant.
  if (!II || II->getIntrinsicID() != Intrinsic::invariant_start ||
      !II->use_empty())
    continue;
  ConstantInt *InvariantSize = cast<ConstantInt>(II->getArgOperand(0));
  // The intrinsic supports having a -1 argument for variable sized objects
  // so we should check for that here.
  if (InvariantSize->isNegative())
    continue;
  uint64_t InvariantSizeInBits = InvariantSize->getSExtValue() * 8;
  // Confirm the invariant.start location size contains the load operand size
  // in bits. Also, the invariant.start should dominate the load, and we
  // should not hoist the load out of a loop that contains this dominating
  // invariant.start.
  if (LocSizeInBits.getFixedSize() <= InvariantSizeInBits &&
      DT->properlyDominates(II->getParent(), CurLoop->getHeader()))
    return true;
}

return false;
1102}

1104namespace {
1105/// Return true if-and-only-if we know how to (mechanically) both hoist and
1106/// sink a given instruction out of a loop.  Does not address legality
1107/// concerns such as aliasing or speculation safety.
1108bool isHoistableAndSinkableInst(Instruction &I) {
// Only these instructions are hoistable/sinkable.
return (isa<LoadInst>(I) || isa<StoreInst>(I) || isa<CallInst>(I) ||
2
←
Assuming 'I' is a 'LoadInst'→
3
←
Returning the value 1, which participates in a condition later→
        isa<FenceInst>(I) || isa<CastInst>(I) || isa<UnaryOperator>(I) ||
        isa<BinaryOperator>(I) || isa<SelectInst>(I) ||
        isa<GetElementPtrInst>(I) || isa<CmpInst>(I) ||
        isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) ||
        isa<ShuffleVectorInst>(I) || isa<ExtractValueInst>(I) ||
        isa<InsertValueInst>(I) || isa<FreezeInst>(I));
1117}
1118/// Return true if all of the alias sets within this AST are known not to
1119/// contain a Mod, or if MSSA knows there are no MemoryDefs in the loop.
1120bool isReadOnly(AliasSetTracker *CurAST, const MemorySSAUpdater *MSSAU,
              const Loop *L) {
if (CurAST) {
  for (AliasSet &AS : *CurAST) {
    if (!AS.isForwardingAliasSet() && AS.isMod()) {
      return false;
    }
  }
  return true;
} else { /*MSSAU*/
  for (auto *BB : L->getBlocks())
    if (MSSAU->getMemorySSA()->getBlockDefs(BB))
      return false;
  return true;
}
1135}

1137/// Return true if I is the only Instruction with a MemoryAccess in L.
1138bool isOnlyMemoryAccess(const Instruction *I, const Loop *L,
                      const MemorySSAUpdater *MSSAU) {
for (auto *BB : L->getBlocks())
19
←
Assuming '__begin1' is not equal to '__end1'→
  if (auto *Accs = MSSAU->getMemorySSA()->getBlockAccesses(BB)) {
20
←
Called C++ object pointer is null
    int NotAPhi = 0;
    for (const auto &Acc : *Accs) {
      if (isa<MemoryPhi>(&Acc))
        continue;
      const auto *MUD = cast<MemoryUseOrDef>(&Acc);
      if (MUD->getMemoryInst() != I || NotAPhi++ == 1)
        return false;
    }
  }
return true;
1152}
1153}

1155bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
                            Loop *CurLoop, AliasSetTracker *CurAST,
                            MemorySSAUpdater *MSSAU,
                            bool TargetExecutesOncePerLoop,
                            SinkAndHoistLICMFlags *Flags,
                            OptimizationRemarkEmitter *ORE) {
assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&(static_cast<void> (0))
       "Either AliasSetTracker or MemorySSA should be initialized.")(static_cast<void> (0));

// If we don't understand the instruction, bail early.
if (!isHoistableAndSinkableInst(I))
1
Calling 'isHoistableAndSinkableInst'→
4
←
Returning from 'isHoistableAndSinkableInst'→
  return false;

MemorySSA *MSSA = MSSAU ? MSSAU->getMemorySSA() : nullptr;
5
←
Taking false branch→
6
←
Assuming 'MSSAU' is null→
7
←
'?' condition is false→
if (MSSA7.1
'MSSA' is null
)
8
←
Taking false branch→
  assert(Flags != nullptr && "Flags cannot be null.")(static_cast<void> (0));

// Loads have extra constraints we have to verify before we can hoist them.
if (LoadInst *LI9.1
'LI' is null
 = dyn_cast<LoadInst>(&I)) {
9
←
Assuming the object is not a 'LoadInst'→
10
←
Taking false branch→
  if (!LI->isUnordered())
    return false; // Don't sink/hoist volatile or ordered atomic loads!

  // Loads from constant memory are always safe to move, even if they end up
  // in the same alias set as something that ends up being modified.
  if (AA->pointsToConstantMemory(LI->getOperand(0)))
    return true;
  if (LI->hasMetadata(LLVMContext::MD_invariant_load))
    return true;

  if (LI->isAtomic() && !TargetExecutesOncePerLoop)
    return false; // Don't risk duplicating unordered loads

  // This checks for an invariant.start dominating the load.
  if (isLoadInvariantInLoop(LI, DT, CurLoop))
    return true;

  bool Invalidated;
  if (CurAST)
    Invalidated = pointerInvalidatedByLoop(MemoryLocation::get(LI), CurAST,
                                           CurLoop, AA);
  else
    Invalidated = pointerInvalidatedByLoopWithMSSA(
        MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(LI)), CurLoop, I, *Flags);
  // Check loop-invariant address because this may also be a sinkable load
  // whose address is not necessarily loop-invariant.
  if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand()))
    ORE->emit([&]() {
      return OptimizationRemarkMissed(
                 DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressInvalidated", LI)
             << "failed to move load with loop-invariant address "
                "because the loop may invalidate its value";
    });

  return !Invalidated;
} else if (CallInst *CI11.1
'CI' is null
 = dyn_cast<CallInst>(&I)) {
11
←
Assuming the object is not a 'CallInst'→
12
←
Taking false branch→
  // Don't sink or hoist dbg info; it's legal, but not useful.
  if (isa<DbgInfoIntrinsic>(I))
    return false;

  // Don't sink calls which can throw.
  if (CI->mayThrow())
    return false;

  // Convergent attribute has been used on operations that involve
  // inter-thread communication which results are implicitly affected by the
  // enclosing control flows. It is not safe to hoist or sink such operations
  // across control flow.
  if (CI->isConvergent())
    return false;

  using namespace PatternMatch;
  if (match(CI, m_Intrinsic<Intrinsic::assume>()))
    // Assumes don't actually alias anything or throw
    return true;

  if (match(CI, m_Intrinsic<Intrinsic::experimental_widenable_condition>()))
    // Widenable conditions don't actually alias anything or throw
    return true;

  // Handle simple cases by querying alias analysis.
  FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI);
  if (Behavior == FMRB_DoesNotAccessMemory)
    return true;
  if (AAResults::onlyReadsMemory(Behavior)) {
    // A readonly argmemonly function only reads from memory pointed to by
    // it's arguments with arbitrary offsets.  If we can prove there are no
    // writes to this memory in the loop, we can hoist or sink.
    if (AAResults::onlyAccessesArgPointees(Behavior)) {
      // TODO: expand to writeable arguments
      for (Value *Op : CI->arg_operands())
        if (Op->getType()->isPointerTy()) {
          bool Invalidated;
          if (CurAST)
            Invalidated = pointerInvalidatedByLoop(
                MemoryLocation::getBeforeOrAfter(Op), CurAST, CurLoop, AA);
          else
            Invalidated = pointerInvalidatedByLoopWithMSSA(
                MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(CI)), CurLoop, I,
                *Flags);
          if (Invalidated)
            return false;
        }
      return true;
    }

    // If this call only reads from memory and there are no writes to memory
    // in the loop, we can hoist or sink the call as appropriate.
    if (isReadOnly(CurAST, MSSAU, CurLoop))
      return true;
  }

  // FIXME: This should use mod/ref information to see if we can hoist or
  // sink the call.

  return false;
} else if (auto *FI13.1
'FI' is non-null
 = dyn_cast<FenceInst>(&I)) {
13
←
Assuming the object is a 'FenceInst'→
14
←
Taking true branch→
  // Fences alias (most) everything to provide ordering.  For the moment,
  // just give up if there are any other memory operations in the loop.
  if (CurAST) {
15
←
Assuming 'CurAST' is null→
16
←
Taking false branch→
    auto Begin = CurAST->begin();
    assert(Begin != CurAST->end() && "must contain FI")(static_cast<void> (0));
    if (std::next(Begin) != CurAST->end())
      // constant memory for instance, TODO: handle better
      return false;
    auto *UniqueI = Begin->getUniqueInstruction();
    if (!UniqueI)
      // other memory op, give up
      return false;
    (void)FI; // suppress unused variable warning
    assert(UniqueI == FI && "AS must contain FI")(static_cast<void> (0));
    return true;
  } else // MSSAU
    return isOnlyMemoryAccess(FI, CurLoop, MSSAU);
17
←
Passing null pointer value via 3rd parameter 'MSSAU'→
18
←
Calling 'isOnlyMemoryAccess'→
} else if (auto *SI = dyn_cast<StoreInst>(&I)) {
  if (!SI->isUnordered())
    return false; // Don't sink/hoist volatile or ordered atomic store!

  // We can only hoist a store that we can prove writes a value which is not
  // read or overwritten within the loop.  For those cases, we fallback to
  // load store promotion instead.  TODO: We can extend this to cases where
  // there is exactly one write to the location and that write dominates an
  // arbitrary number of reads in the loop.
  if (CurAST) {
    auto &AS = CurAST->getAliasSetFor(MemoryLocation::get(SI));

    if (AS.isRef() || !AS.isMustAlias())
      // Quick exit test, handled by the full path below as well.
      return false;
    auto *UniqueI = AS.getUniqueInstruction();
    if (!UniqueI)
      // other memory op, give up
      return false;
    assert(UniqueI == SI && "AS must contain SI")(static_cast<void> (0));
    return true;
  } else { // MSSAU
    if (isOnlyMemoryAccess(SI, CurLoop, MSSAU))
      return true;
    // If there are more accesses than the Promotion cap or no "quota" to
    // check clobber, then give up as we're not walking a list that long.
    if (Flags->tooManyMemoryAccesses() || Flags->tooManyClobberingCalls())
      return false;
    // If there are interfering Uses (i.e. their defining access is in the
    // loop), or ordered loads (stored as Defs!), don't move this store.
    // Could do better here, but this is conservatively correct.
    // TODO: Cache set of Uses on the first walk in runOnLoop, update when
    // moving accesses. Can also extend to dominating uses.
    auto *SIMD = MSSA->getMemoryAccess(SI);
    for (auto *BB : CurLoop->getBlocks())
      if (auto *Accesses = MSSA->getBlockAccesses(BB)) {
        for (const auto &MA : *Accesses)
          if (const auto *MU = dyn_cast<MemoryUse>(&MA)) {
            auto *MD = MU->getDefiningAccess();
            if (!MSSA->isLiveOnEntryDef(MD) &&
                CurLoop->contains(MD->getBlock()))
              return false;
            // Disable hoisting past potentially interfering loads. Optimized
            // Uses may point to an access outside the loop, as getClobbering
            // checks the previous iteration when walking the backedge.
            // FIXME: More precise: no Uses that alias SI.
            if (!Flags->getIsSink() && !MSSA->dominates(SIMD, MU))
              return false;
          } else if (const auto *MD = dyn_cast<MemoryDef>(&MA)) {
            if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) {
              (void)LI; // Silence warning.
              assert(!LI->isUnordered() && "Expected unordered load")(static_cast<void> (0));
              return false;
            }
            // Any call, while it may not be clobbering SI, it may be a use.
            if (auto *CI = dyn_cast<CallInst>(MD->getMemoryInst())) {
              // Check if the call may read from the memory location written
              // to by SI. Check CI's attributes and arguments; the number of
              // such checks performed is limited above by NoOfMemAccTooLarge.
              ModRefInfo MRI = AA->getModRefInfo(CI, MemoryLocation::get(SI));
              if (isModOrRefSet(MRI))
                return false;
            }
          }
      }
    auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI);
    Flags->incrementClobberingCalls();
    // If there are no clobbering Defs in the loop, store is safe to hoist.
    return MSSA->isLiveOnEntryDef(Source) ||
           !CurLoop->contains(Source->getBlock());
  }
}

assert(!I.mayReadOrWriteMemory() && "unhandled aliasing")(static_cast<void> (0));

// We've established mechanical ability and aliasing, it's up to the caller
// to check fault safety
return true;
1366}

1368/// Returns true if a PHINode is a trivially replaceable with an
1369/// Instruction.
1370/// This is true when all incoming values are that instruction.
1371/// This pattern occurs most often with LCSSA PHI nodes.
1372///
1373static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) {
for (const Value *IncValue : PN.incoming_values())
  if (IncValue != &I)
    return false;

return true;
1379}

1381/// Return true if the instruction is free in the loop.
1382static bool isFreeInLoop(const Instruction &I, const Loop *CurLoop,
                       const TargetTransformInfo *TTI) {

if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I)) {
  if (TTI->getUserCost(GEP, TargetTransformInfo::TCK_SizeAndLatency) !=
      TargetTransformInfo::TCC_Free)
    return false;
  // For a GEP, we cannot simply use getUserCost because currently it
  // optimistically assume that a GEP will fold into addressing mode
  // regardless of its users.
  const BasicBlock *BB = GEP->getParent();
  for (const User *U : GEP->users()) {
    const Instruction *UI = cast<Instruction>(U);
    if (CurLoop->contains(UI) &&
        (BB != UI->getParent() ||
         (!isa<StoreInst>(UI) && !isa<LoadInst>(UI))))
      return false;
  }
  return true;
} else
  return TTI->getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
         TargetTransformInfo::TCC_Free;
1404}

1406/// Return true if the only users of this instruction are outside of
1407/// the loop. If this is true, we can sink the instruction to the exit
1408/// blocks of the loop.
1409///
1410/// We also return true if the instruction could be folded away in lowering.
1411/// (e.g.,  a GEP can be folded into a load as an addressing mode in the loop).
1412static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop,
                                const LoopSafetyInfo *SafetyInfo,
                                TargetTransformInfo *TTI, bool &FreeInLoop,
                                bool LoopNestMode) {
const auto &BlockColors = SafetyInfo->getBlockColors();
bool IsFree = isFreeInLoop(I, CurLoop, TTI);
for (const User *U : I.users()) {
  const Instruction *UI = cast<Instruction>(U);
  if (const PHINode *PN = dyn_cast<PHINode>(UI)) {
    const BasicBlock *BB = PN->getParent();
    // We cannot sink uses in catchswitches.
    if (isa<CatchSwitchInst>(BB->getTerminator()))
      return false;

    // We need to sink a callsite to a unique funclet.  Avoid sinking if the
    // phi use is too muddled.
    if (isa<CallInst>(I))
      if (!BlockColors.empty() &&
          BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1)
        return false;

    if (LoopNestMode) {
      while (isa<PHINode>(UI) && UI->hasOneUser() &&
             UI->getNumOperands() == 1) {
        if (!CurLoop->contains(UI))
          break;
        UI = cast<Instruction>(UI->user_back());
      }
    }
  }

  if (CurLoop->contains(UI)) {
    if (IsFree) {
      FreeInLoop = true;
      continue;
    }
    return false;
  }
}
return true;
1452}

1454static Instruction *cloneInstructionInExitBlock(
  Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI,
  const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) {
Instruction *New;
if (auto *CI = dyn_cast<CallInst>(&I)) {
  const auto &BlockColors = SafetyInfo->getBlockColors();

  // Sinking call-sites need to be handled differently from other
  // instructions.  The cloned call-site needs a funclet bundle operand
  // appropriate for its location in the CFG.
  SmallVector<OperandBundleDef, 1> OpBundles;
  for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles();
       BundleIdx != BundleEnd; ++BundleIdx) {
    OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx);
    if (Bundle.getTagID() == LLVMContext::OB_funclet)
      continue;

    OpBundles.emplace_back(Bundle);
  }

  if (!BlockColors.empty()) {
    const ColorVector &CV = BlockColors.find(&ExitBlock)->second;
    assert(CV.size() == 1 && "non-unique color for exit block!")(static_cast<void> (0));
    BasicBlock *BBColor = CV.front();
    Instruction *EHPad = BBColor->getFirstNonPHI();
    if (EHPad->isEHPad())
      OpBundles.emplace_back("funclet", EHPad);
  }

  New = CallInst::Create(CI, OpBundles);
} else {
  New = I.clone();
}

ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New);
if (!I.getName().empty())
  New->setName(I.getName() + ".le");

if (MSSAU && MSSAU->getMemorySSA()->getMemoryAccess(&I)) {
  // Create a new MemoryAccess and let MemorySSA set its defining access.
  MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB(
      New, nullptr, New->getParent(), MemorySSA::Beginning);
  if (NewMemAcc) {
    if (auto *MemDef = dyn_cast<MemoryDef>(NewMemAcc))
      MSSAU->insertDef(MemDef, /*RenameUses=*/true);
    else {
      auto *MemUse = cast<MemoryUse>(NewMemAcc);
      MSSAU->insertUse(MemUse, /*RenameUses=*/true);
    }
  }
}

// Build LCSSA PHI nodes for any in-loop operands (if legal).  Note that
// this is particularly cheap because we can rip off the PHI node that we're
// replacing for the number and blocks of the predecessors.
// OPT: If this shows up in a profile, we can instead finish sinking all
// invariant instructions, and then walk their operands to re-establish
// LCSSA. That will eliminate creating PHI nodes just to nuke them when
// sinking bottom-up.
for (Use &Op : New->operands())
  if (LI->wouldBeOutOfLoopUseRequiringLCSSA(Op.get(), PN.getParent())) {
    auto *OInst = cast<Instruction>(Op.get());
    PHINode *OpPN =
      PHINode::Create(OInst->getType(), PN.getNumIncomingValues(),
                      OInst->getName() + ".lcssa", &ExitBlock.front());
    for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
      OpPN->addIncoming(OInst, PN.getIncomingBlock(i));
    Op = OpPN;
  }
return New;
1524}

1526static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
                           MemorySSAUpdater *MSSAU) {
if (MSSAU)
  MSSAU->removeMemoryAccess(&I);
SafetyInfo.removeInstruction(&I);
I.eraseFromParent();
1532}

1534static void moveInstructionBefore(Instruction &I, Instruction &Dest,
                                ICFLoopSafetyInfo &SafetyInfo,
                                MemorySSAUpdater *MSSAU,
                                ScalarEvolution *SE) {
SafetyInfo.removeInstruction(&I);
SafetyInfo.insertInstructionTo(&I, Dest.getParent());
I.moveBefore(&Dest);
if (MSSAU)
  if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>(
          MSSAU->getMemorySSA()->getMemoryAccess(&I)))
    MSSAU->moveToPlace(OldMemAcc, Dest.getParent(),
                       MemorySSA::BeforeTerminator);
if (SE)
  SE->forgetValue(&I);
1548}

1550static Instruction *sinkThroughTriviallyReplaceablePHI(
  PHINode *TPN, Instruction *I, LoopInfo *LI,
  SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies,
  const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop,
  MemorySSAUpdater *MSSAU) {
assert(isTriviallyReplaceablePHI(*TPN, *I) &&(static_cast<void> (0))
       "Expect only trivially replaceable PHI")(static_cast<void> (0));
BasicBlock *ExitBlock = TPN->getParent();
Instruction *New;
auto It = SunkCopies.find(ExitBlock);
if (It != SunkCopies.end())
  New = It->second;
else
  New = SunkCopies[ExitBlock] = cloneInstructionInExitBlock(
      *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU);
return New;
1566}

1568static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) {
BasicBlock *BB = PN->getParent();
if (!BB->canSplitPredecessors())
  return false;
// It's not impossible to split EHPad blocks, but if BlockColors already exist
// it require updating BlockColors for all offspring blocks accordingly. By
// skipping such corner case, we can make updating BlockColors after splitting
// predecessor fairly simple.
if (!SafetyInfo->getBlockColors().empty() && BB->getFirstNonPHI()->isEHPad())
  return false;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
  BasicBlock *BBPred = *PI;
  if (isa<IndirectBrInst>(BBPred->getTerminator()) ||
      isa<CallBrInst>(BBPred->getTerminator()))
    return false;
}
return true;
1585}

1587static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT,
                                      LoopInfo *LI, const Loop *CurLoop,
                                      LoopSafetyInfo *SafetyInfo,
                                      MemorySSAUpdater *MSSAU) {
1591#ifndef NDEBUG1
SmallVector<BasicBlock *, 32> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(),
                                           ExitBlocks.end());
1596#endif
BasicBlock *ExitBB = PN->getParent();
assert(ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block.")(static_cast<void> (0));

// Split predecessors of the loop exit to make instructions in the loop are
// exposed to exit blocks through trivially replaceable PHIs while keeping the
// loop in the canonical form where each predecessor of each exit block should
// be contained within the loop. For example, this will convert the loop below
// from
//
// LB1:
//   %v1 =
//   br %LE, %LB2
// LB2:
//   %v2 =
//   br %LE, %LB1
// LE:
//   %p = phi [%v1, %LB1], [%v2, %LB2] <-- non-trivially replaceable
//
// to
//
// LB1:
//   %v1 =
//   br %LE.split, %LB2
// LB2:
//   %v2 =
//   br %LE.split2, %LB1
// LE.split:
//   %p1 = phi [%v1, %LB1]  <-- trivially replaceable
//   br %LE
// LE.split2:
//   %p2 = phi [%v2, %LB2]  <-- trivially replaceable
//   br %LE
// LE:
//   %p = phi [%p1, %LE.split], [%p2, %LE.split2]
//
const auto &BlockColors = SafetyInfo->getBlockColors();
SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB));
while (!PredBBs.empty()) {
  BasicBlock *PredBB = *PredBBs.begin();
  assert(CurLoop->contains(PredBB) &&(static_cast<void> (0))
         "Expect all predecessors are in the loop")(static_cast<void> (0));
  if (PN->getBasicBlockIndex(PredBB) >= 0) {
    BasicBlock *NewPred = SplitBlockPredecessors(
        ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true);
    // Since we do not allow splitting EH-block with BlockColors in
    // canSplitPredecessors(), we can simply assign predecessor's color to
    // the new block.
    if (!BlockColors.empty())
      // Grab a reference to the ColorVector to be inserted before getting the
      // reference to the vector we are copying because inserting the new
      // element in BlockColors might cause the map to be reallocated.
      SafetyInfo->copyColors(NewPred, PredBB);
  }
  PredBBs.remove(PredBB);
}
1652}

1654/// When an instruction is found to only be used outside of the loop, this
1655/// function moves it to the exit blocks and patches up SSA form as needed.
1656/// This method is guaranteed to remove the original instruction from its
1657/// position, and may either delete it or move it to outside of the loop.
1658///
1659static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
               BlockFrequencyInfo *BFI, const Loop *CurLoop,
               ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU,
               OptimizationRemarkEmitter *ORE) {
bool Changed = false;
LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n")do { } while (false);

// Iterate over users to be ready for actual sinking. Replace users via
// unreachable blocks with undef and make all user PHIs trivially replaceable.
SmallPtrSet<Instruction *, 8> VisitedUsers;
for (Value::user_iterator UI = I.user_begin(), UE = I.user_end(); UI != UE;) {
  auto *User = cast<Instruction>(*UI);
  Use &U = UI.getUse();
  ++UI;

  if (VisitedUsers.count(User) || CurLoop->contains(User))
    continue;

  if (!DT->isReachableFromEntry(User->getParent())) {
    U = UndefValue::get(I.getType());
    Changed = true;
    continue;
  }

  // The user must be a PHI node.
  PHINode *PN = cast<PHINode>(User);

  // Surprisingly, instructions can be used outside of loops without any
  // exits.  This can only happen in PHI nodes if the incoming block is
  // unreachable.
  BasicBlock *BB = PN->getIncomingBlock(U);
  if (!DT->isReachableFromEntry(BB)) {
    U = UndefValue::get(I.getType());
    Changed = true;
    continue;
  }

  VisitedUsers.insert(PN);
  if (isTriviallyReplaceablePHI(*PN, I))
    continue;

  if (!canSplitPredecessors(PN, SafetyInfo))
    return Changed;

  // Split predecessors of the PHI so that we can make users trivially
  // replaceable.
  splitPredecessorsOfLoopExit(PN, DT, LI, CurLoop, SafetyInfo, MSSAU);

  // Should rebuild the iterators, as they may be invalidated by
  // splitPredecessorsOfLoopExit().
  UI = I.user_begin();
  UE = I.user_end();
}

if (VisitedUsers.empty())
  return Changed;

ORE->emit([&]() {
  return OptimizationRemark(DEBUG_TYPE"licm", "InstSunk", &I)
         << "sinking " << ore::NV("Inst", &I);
});
if (isa<LoadInst>(I))
  ++NumMovedLoads;
else if (isa<CallInst>(I))
  ++NumMovedCalls;
++NumSunk;

1726#ifndef NDEBUG1
SmallVector<BasicBlock *, 32> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(),
                                           ExitBlocks.end());
1731#endif

// Clones of this instruction. Don't create more than one per exit block!
SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies;

// If this instruction is only used outside of the loop, then all users are
// PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of
// the instruction.
// First check if I is worth sinking for all uses. Sink only when it is worth
// across all uses.
SmallSetVector<User*, 8> Users(I.user_begin(), I.user_end());
SmallVector<PHINode *, 8> ExitPNs;
for (auto *UI : Users) {
  auto *User = cast<Instruction>(UI);

  if (CurLoop->contains(User))
    continue;

  PHINode *PN = cast<PHINode>(User);
  assert(ExitBlockSet.count(PN->getParent()) &&(static_cast<void> (0))
         "The LCSSA PHI is not in an exit block!")(static_cast<void> (0));
  if (!worthSinkOrHoistInst(I, PN->getParent(), ORE, BFI)) {
    return Changed;
  }

  ExitPNs.push_back(PN);
}

for (auto *PN : ExitPNs) {

  // The PHI must be trivially replaceable.
  Instruction *New = sinkThroughTriviallyReplaceablePHI(
      PN, &I, LI, SunkCopies, SafetyInfo, CurLoop, MSSAU);
  PN->replaceAllUsesWith(New);
  eraseInstruction(*PN, *SafetyInfo, nullptr);
  Changed = true;
}
return Changed;
1769}

1771/// When an instruction is found to only use loop invariant operands that
1772/// is safe to hoist, this instruction is called to do the dirty work.
1773///
1774static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
                MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
                OptimizationRemarkEmitter *ORE) {
LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getNameOrAsOperand() << ": "do { } while (false)
                  << I << "\n")do { } while (false);
ORE->emit([&]() {
  return OptimizationRemark(DEBUG_TYPE"licm", "Hoisted", &I) << "hoisting "
                                                       << ore::NV("Inst", &I);
});

// Metadata can be dependent on conditions we are hoisting above.
// Conservatively strip all metadata on the instruction unless we were
// guaranteed to execute I if we entered the loop, in which case the metadata
// is valid in the loop preheader.
// Similarly, If I is a call and it is not guaranteed to execute in the loop,
// then moving to the preheader means we should strip attributes on the call
// that can cause UB since we may be hoisting above conditions that allowed
// inferring those attributes. They may not be valid at the preheader.
if ((I.hasMetadataOtherThanDebugLoc() || isa<CallInst>(I)) &&
    // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning
    // time in isGuaranteedToExecute if we don't actually have anything to
    // drop.  It is a compile time optimization, not required for correctness.
    !SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop))
  I.dropUndefImplyingAttrsAndUnknownMetadata();

if (isa<PHINode>(I))
  // Move the new node to the end of the phi list in the destination block.
  moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU, SE);
else
  // Move the new node to the destination block, before its terminator.
  moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU, SE);

I.updateLocationAfterHoist();

if (isa<LoadInst>(I))
  ++NumMovedLoads;
else if (isa<CallInst>(I))
  ++NumMovedCalls;
++NumHoisted;
1814}

1816/// Only sink or hoist an instruction if it is not a trapping instruction,
1817/// or if the instruction is known not to trap when moved to the preheader.
1818/// or if it is a trapping instruction and is guaranteed to execute.
1819static bool isSafeToExecuteUnconditionally(Instruction &Inst,
                                         const DominatorTree *DT,
                                         const TargetLibraryInfo *TLI,
                                         const Loop *CurLoop,
                                         const LoopSafetyInfo *SafetyInfo,
                                         OptimizationRemarkEmitter *ORE,
                                         const Instruction *CtxI) {
if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT, TLI))
  return true;

bool GuaranteedToExecute =
    SafetyInfo->isGuaranteedToExecute(Inst, DT, CurLoop);

if (!GuaranteedToExecute) {
  auto *LI = dyn_cast<LoadInst>(&Inst);
  if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand()))
    ORE->emit([&]() {
      return OptimizationRemarkMissed(
                 DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressCondExecuted", LI)
             << "failed to hoist load with loop-invariant address "
                "because load is conditionally executed";
    });
}

return GuaranteedToExecute;
1844}

1846namespace {
1847class LoopPromoter : public LoadAndStorePromoter {
Value *SomePtr; // Designated pointer to store to.
const SmallSetVector<Value *, 8> &PointerMustAliases;
SmallVectorImpl<BasicBlock *> &LoopExitBlocks;
SmallVectorImpl<Instruction *> &LoopInsertPts;
SmallVectorImpl<MemoryAccess *> &MSSAInsertPts;
PredIteratorCache &PredCache;
MemorySSAUpdater *MSSAU;
LoopInfo &LI;
DebugLoc DL;
int Alignment;
bool UnorderedAtomic;
AAMDNodes AATags;
ICFLoopSafetyInfo &SafetyInfo;

// We're about to add a use of V in a loop exit block.  Insert an LCSSA phi
// (if legal) if doing so would add an out-of-loop use to an instruction
// defined in-loop.
Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const {
  if (!LI.wouldBeOutOfLoopUseRequiringLCSSA(V, BB))
    return V;

  Instruction *I = cast<Instruction>(V);
  // We need to create an LCSSA PHI node for the incoming value and
  // store that.
  PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB),
                                I->getName() + ".lcssa", &BB->front());
  for (BasicBlock *Pred : PredCache.get(BB))
    PN->addIncoming(I, Pred);
  return PN;
}

1879public:
LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S,
             const SmallSetVector<Value *, 8> &PMA,
             SmallVectorImpl<BasicBlock *> &LEB,
             SmallVectorImpl<Instruction *> &LIP,
             SmallVectorImpl<MemoryAccess *> &MSSAIP, PredIteratorCache &PIC,
             MemorySSAUpdater *MSSAU, LoopInfo &li, DebugLoc dl,
             int alignment, bool UnorderedAtomic, const AAMDNodes &AATags,
             ICFLoopSafetyInfo &SafetyInfo)
    : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA),
      LoopExitBlocks(LEB), LoopInsertPts(LIP), MSSAInsertPts(MSSAIP),
      PredCache(PIC), MSSAU(MSSAU), LI(li), DL(std::move(dl)),
      Alignment(alignment), UnorderedAtomic(UnorderedAtomic), AATags(AATags),
      SafetyInfo(SafetyInfo) {}

bool isInstInList(Instruction *I,
                  const SmallVectorImpl<Instruction *> &) const override {
  Value *Ptr;
  if (LoadInst *LI = dyn_cast<LoadInst>(I))
    Ptr = LI->getOperand(0);
  else
    Ptr = cast<StoreInst>(I)->getPointerOperand();
  return PointerMustAliases.count(Ptr);
}

void doExtraRewritesBeforeFinalDeletion() override {
  // Insert stores after in the loop exit blocks.  Each exit block gets a
  // store of the live-out values that feed them.  Since we've already told
  // the SSA updater about the defs in the loop and the preheader
  // definition, it is all set and we can start using it.
  for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
    BasicBlock *ExitBlock = LoopExitBlocks[i];
    Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
    LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock);
    Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock);
    Instruction *InsertPos = LoopInsertPts[i];
    StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos);
    if (UnorderedAtomic)
      NewSI->setOrdering(AtomicOrdering::Unordered);
    NewSI->setAlignment(Align(Alignment));
    NewSI->setDebugLoc(DL);
    if (AATags)
      NewSI->setAAMetadata(AATags);

    MemoryAccess *MSSAInsertPoint = MSSAInsertPts[i];
    MemoryAccess *NewMemAcc;
    if (!MSSAInsertPoint) {
      NewMemAcc = MSSAU->createMemoryAccessInBB(
          NewSI, nullptr, NewSI->getParent(), MemorySSA::Beginning);
    } else {
      NewMemAcc =
          MSSAU->createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint);
    }
    MSSAInsertPts[i] = NewMemAcc;
    MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true);
    // FIXME: true for safety, false may still be correct.
  }
}

void instructionDeleted(Instruction *I) const override {
  SafetyInfo.removeInstruction(I);
  MSSAU->removeMemoryAccess(I);
}
1942};

1944bool isNotCapturedBeforeOrInLoop(const Value *V, const Loop *L,
                               DominatorTree *DT) {
// We can perform the captured-before check against any instruction in the
// loop header, as the loop header is reachable from any instruction inside
// the loop.
// TODO: ReturnCaptures=true shouldn't be necessary here.
return !PointerMayBeCapturedBefore(V, /* ReturnCaptures */ true,
                                   /* StoreCaptures */ true,
                                   L->getHeader()->getTerminator(), DT);
1953}

1955/// Return true iff we can prove that a caller of this function can not inspect
1956/// the contents of the provided object in a well defined program.
1957bool isKnownNonEscaping(Value *Object, const Loop *L,
                      const TargetLibraryInfo *TLI, DominatorTree *DT) {
if (isa<AllocaInst>(Object))
  // Since the alloca goes out of scope, we know the caller can't retain a
  // reference to it and be well defined.  Thus, we don't need to check for
  // capture.
  return true;

// For all other objects we need to know that the caller can't possibly
// have gotten a reference to the object.  There are two components of
// that:
//   1) Object can't be escaped by this function.  This is what
//      PointerMayBeCaptured checks.
//   2) Object can't have been captured at definition site.  For this, we
//      need to know the return value is noalias.  At the moment, we use a
//      weaker condition and handle only AllocLikeFunctions (which are
//      known to be noalias).  TODO
return isAllocLikeFn(Object, TLI) &&
       isNotCapturedBeforeOrInLoop(Object, L, DT);
1976}

1978} // namespace

1980/// Try to promote memory values to scalars by sinking stores out of the
1981/// loop and moving loads to before the loop.  We do this by looping over
1982/// the stores in the loop, looking for stores to Must pointers which are
1983/// loop invariant.
1984///
1985bool llvm::promoteLoopAccessesToScalars(
  const SmallSetVector<Value *, 8> &PointerMustAliases,
  SmallVectorImpl<BasicBlock *> &ExitBlocks,
  SmallVectorImpl<Instruction *> &InsertPts,
  SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC,
  LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI,
  Loop *CurLoop, MemorySSAUpdater *MSSAU, ICFLoopSafetyInfo *SafetyInfo,
  OptimizationRemarkEmitter *ORE) {
// Verify inputs.
assert(LI != nullptr && DT != nullptr && CurLoop != nullptr &&(static_cast<void> (0))
       SafetyInfo != nullptr &&(static_cast<void> (0))
       "Unexpected Input to promoteLoopAccessesToScalars")(static_cast<void> (0));

Value *SomePtr = *PointerMustAliases.begin();
BasicBlock *Preheader = CurLoop->getLoopPreheader();

// It is not safe to promote a load/store from the loop if the load/store is
// conditional.  For example, turning:
//
//    for () { if (c) *P += 1; }
//
// into:
//
//    tmp = *P;  for () { if (c) tmp +=1; } *P = tmp;
//
// is not safe, because *P may only be valid to access if 'c' is true.
//
// The safety property divides into two parts:
// p1) The memory may not be dereferenceable on entry to the loop.  In this
//    case, we can't insert the required load in the preheader.
// p2) The memory model does not allow us to insert a store along any dynamic
//    path which did not originally have one.
//
// If at least one store is guaranteed to execute, both properties are
// satisfied, and promotion is legal.
//
// This, however, is not a necessary condition. Even if no store/load is
// guaranteed to execute, we can still establish these properties.
// We can establish (p1) by proving that hoisting the load into the preheader
// is safe (i.e. proving dereferenceability on all paths through the loop). We
// can use any access within the alias set to prove dereferenceability,
// since they're all must alias.
//
// There are two ways establish (p2):
// a) Prove the location is thread-local. In this case the memory model
// requirement does not apply, and stores are safe to insert.
// b) Prove a store dominates every exit block. In this case, if an exit
// blocks is reached, the original dynamic path would have taken us through
// the store, so inserting a store into the exit block is safe. Note that this
// is different from the store being guaranteed to execute. For instance,
// if an exception is thrown on the first iteration of the loop, the original
// store is never executed, but the exit blocks are not executed either.

bool DereferenceableInPH = false;
bool SafeToInsertStore = false;

SmallVector<Instruction *, 64> LoopUses;

// We start with an alignment of one and try to find instructions that allow
// us to prove better alignment.
Align Alignment;
// Keep track of which types of access we see
bool SawUnorderedAtomic = false;
bool SawNotAtomic = false;
AAMDNodes AATags;

const DataLayout &MDL = Preheader->getModule()->getDataLayout();

bool IsKnownThreadLocalObject = false;
if (SafetyInfo->anyBlockMayThrow()) {
  // If a loop can throw, we have to insert a store along each unwind edge.
  // That said, we can't actually make the unwind edge explicit. Therefore,
  // we have to prove that the store is dead along the unwind edge.  We do
  // this by proving that the caller can't have a reference to the object
  // after return and thus can't possibly load from the object.
  Value *Object = getUnderlyingObject(SomePtr);
  if (!isKnownNonEscaping(Object, CurLoop, TLI, DT))
    return false;
  // Subtlety: Alloca's aren't visible to callers, but *are* potentially
  // visible to other threads if captured and used during their lifetimes.
  IsKnownThreadLocalObject = !isa<AllocaInst>(Object);
}

// Check that all of the pointers in the alias set have the same type.  We
// cannot (yet) promote a memory location that is loaded and stored in
// different sizes.  While we are at it, collect alignment and AA info.
for (Value *ASIV : PointerMustAliases) {
  // Check that all of the pointers in the alias set have the same type.  We
  // cannot (yet) promote a memory location that is loaded and stored in
  // different sizes.
  if (SomePtr->getType() != ASIV->getType())
    return false;

  for (User *U : ASIV->users()) {
    // Ignore instructions that are outside the loop.
    Instruction *UI = dyn_cast<Instruction>(U);
    if (!UI || !CurLoop->contains(UI))
      continue;

    // If there is an non-load/store instruction in the loop, we can't promote
    // it.
    if (LoadInst *Load = dyn_cast<LoadInst>(UI)) {
      if (!Load->isUnordered())
        return false;

      SawUnorderedAtomic |= Load->isAtomic();
      SawNotAtomic |= !Load->isAtomic();

      Align InstAlignment = Load->getAlign();

      // Note that proving a load safe to speculate requires proving
      // sufficient alignment at the target location.  Proving it guaranteed
      // to execute does as well.  Thus we can increase our guaranteed
      // alignment as well.
      if (!DereferenceableInPH || (InstAlignment > Alignment))
        if (isSafeToExecuteUnconditionally(*Load, DT, TLI, CurLoop,
                                           SafetyInfo, ORE,
                                           Preheader->getTerminator())) {
          DereferenceableInPH = true;
          Alignment = std::max(Alignment, InstAlignment);
        }
    } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) {
      // Stores *of* the pointer are not interesting, only stores *to* the
      // pointer.
      if (UI->getOperand(1) != ASIV)
        continue;
      if (!Store->isUnordered())
        return false;

      SawUnorderedAtomic |= Store->isAtomic();
      SawNotAtomic |= !Store->isAtomic();

      // If the store is guaranteed to execute, both properties are satisfied.
      // We may want to check if a store is guaranteed to execute even if we
      // already know that promotion is safe, since it may have higher
      // alignment than any other guaranteed stores, in which case we can
      // raise the alignment on the promoted store.
      Align InstAlignment = Store->getAlign();

      if (!DereferenceableInPH || !SafeToInsertStore ||
          (InstAlignment > Alignment)) {
        if (SafetyInfo->isGuaranteedToExecute(*UI, DT, CurLoop)) {
          DereferenceableInPH = true;
          SafeToInsertStore = true;
          Alignment = std::max(Alignment, InstAlignment);
        }
      }

      // If a store dominates all exit blocks, it is safe to sink.
      // As explained above, if an exit block was executed, a dominating
      // store must have been executed at least once, so we are not
      // introducing stores on paths that did not have them.
      // Note that this only looks at explicit exit blocks. If we ever
      // start sinking stores into unwind edges (see above), this will break.
      if (!SafeToInsertStore)
        SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) {
          return DT->dominates(Store->getParent(), Exit);
        });

      // If the store is not guaranteed to execute, we may still get
      // deref info through it.
      if (!DereferenceableInPH) {
        DereferenceableInPH = isDereferenceableAndAlignedPointer(
            Store->getPointerOperand(), Store->getValueOperand()->getType(),
            Store->getAlign(), MDL, Preheader->getTerminator(), DT, TLI);
      }
    } else
      return false; // Not a load or store.

    // Merge the AA tags.
    if (LoopUses.empty()) {
      // On the first load/store, just take its AA tags.
      UI->getAAMetadata(AATags);
    } else if (AATags) {
      UI->getAAMetadata(AATags, /* Merge = */ true);
    }

    LoopUses.push_back(UI);
  }
}

// If we found both an unordered atomic instruction and a non-atomic memory
// access, bail.  We can't blindly promote non-atomic to atomic since we
// might not be able to lower the result.  We can't downgrade since that
// would violate memory model.  Also, align 0 is an error for atomics.
if (SawUnorderedAtomic && SawNotAtomic)
  return false;

// If we're inserting an atomic load in the preheader, we must be able to
// lower it.  We're only guaranteed to be able to lower naturally aligned
// atomics.
auto *SomePtrElemType = SomePtr->getType()->getPointerElementType();
if (SawUnorderedAtomic &&
    Alignment < MDL.getTypeStoreSize(SomePtrElemType))
  return false;

// If we couldn't prove we can hoist the load, bail.
if (!DereferenceableInPH)
  return false;

// We know we can hoist the load, but don't have a guaranteed store.
// Check whether the location is thread-local. If it is, then we can insert
// stores along paths which originally didn't have them without violating the
// memory model.
if (!SafeToInsertStore) {
  if (IsKnownThreadLocalObject)
    SafeToInsertStore = true;
  else {
    Value *Object = getUnderlyingObject(SomePtr);
    SafeToInsertStore =
        (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) &&
        isNotCapturedBeforeOrInLoop(Object, CurLoop, DT);
  }
}

// If we've still failed to prove we can sink the store, give up.
if (!SafeToInsertStore)
  return false;

// Otherwise, this is safe to promote, lets do it!
LLVM_DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtrdo { } while (false)
                  << '\n')do { } while (false);
ORE->emit([&]() {
  return OptimizationRemark(DEBUG_TYPE"licm", "PromoteLoopAccessesToScalar",
                            LoopUses[0])
         << "Moving accesses to memory location out of the loop";
});
++NumPromoted;

// Look at all the loop uses, and try to merge their locations.
std::vector<const DILocation *> LoopUsesLocs;
for (auto U : LoopUses)
  LoopUsesLocs.push_back(U->getDebugLoc().get());
auto DL = DebugLoc(DILocation::getMergedLocations(LoopUsesLocs));

// We use the SSAUpdater interface to insert phi nodes as required.
SmallVector<PHINode *, 16> NewPHIs;
SSAUpdater SSA(&NewPHIs);
LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
                      InsertPts, MSSAInsertPts, PIC, MSSAU, *LI, DL,
                      Alignment.value(), SawUnorderedAtomic, AATags,
                      *SafetyInfo);

// Set up the preheader to have a definition of the value.  It is the live-out
// value from the preheader that uses in the loop will use.
LoadInst *PreheaderLoad = new LoadInst(
    SomePtr->getType()->getPointerElementType(), SomePtr,
    SomePtr->getName() + ".promoted", Preheader->getTerminator());
if (SawUnorderedAtomic)
  PreheaderLoad->setOrdering(AtomicOrdering::Unordered);
PreheaderLoad->setAlignment(Alignment);
PreheaderLoad->setDebugLoc(DebugLoc());
if (AATags)
  PreheaderLoad->setAAMetadata(AATags);
SSA.AddAvailableValue(Preheader, PreheaderLoad);

MemoryAccess *PreheaderLoadMemoryAccess = MSSAU->createMemoryAccessInBB(
    PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End);
MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess);
MSSAU->insertUse(NewMemUse, /*RenameUses=*/true);

if (VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();
// Rewrite all the loads in the loop and remember all the definitions from
// stores in the loop.
Promoter.run(LoopUses);

if (VerifyMemorySSA)
  MSSAU->getMemorySSA()->verifyMemorySSA();
// If the SSAUpdater didn't use the load in the preheader, just zap it now.
if (PreheaderLoad->use_empty())
  eraseInstruction(*PreheaderLoad, *SafetyInfo, MSSAU);

return true;
2259}

2261static void foreachMemoryAccess(MemorySSA *MSSA, Loop *L,
                              function_ref<void(Instruction *)> Fn) {
for (const BasicBlock *BB : L->blocks())
  if (const auto *Accesses = MSSA->getBlockAccesses(BB))
    for (const auto &Access : *Accesses)
      if (const auto *MUD = dyn_cast<MemoryUseOrDef>(&Access))
        Fn(MUD->getMemoryInst());
2268}

2270static SmallVector<SmallSetVector<Value *, 8>, 0>
2271collectPromotionCandidates(MemorySSA *MSSA, AliasAnalysis *AA, Loop *L) {
AliasSetTracker AST(*AA);

auto IsPotentiallyPromotable = [L](const Instruction *I) {
  if (const auto *SI = dyn_cast<StoreInst>(I))
    return L->isLoopInvariant(SI->getPointerOperand());
  if (const auto *LI = dyn_cast<LoadInst>(I))
    return L->isLoopInvariant(LI->getPointerOperand());
  return false;
};

// Populate AST with potentially promotable accesses and remove them from
// MaybePromotable, so they will not be checked again on the next iteration.
SmallPtrSet<Value *, 16> AttemptingPromotion;
foreachMemoryAccess(MSSA, L, [&](Instruction *I) {
  if (IsPotentiallyPromotable(I)) {
    AttemptingPromotion.insert(I);
    AST.add(I);
  }
});

// We're only interested in must-alias sets that contain a mod.
SmallVector<const AliasSet *, 8> Sets;
for (AliasSet &AS : AST)
  if (!AS.isForwardingAliasSet() && AS.isMod() && AS.isMustAlias())
    Sets.push_back(&AS);

if (Sets.empty())
  return {}; // Nothing to promote...

// Discard any sets for which there is an aliasing non-promotable access.
foreachMemoryAccess(MSSA, L, [&](Instruction *I) {
  if (AttemptingPromotion.contains(I))
    return;

  llvm::erase_if(Sets, [&](const AliasSet *AS) {
    return AS->aliasesUnknownInst(I, *AA);
  });
});

SmallVector<SmallSetVector<Value *, 8>, 0> Result;
for (const AliasSet *Set : Sets) {
  SmallSetVector<Value *, 8> PointerMustAliases;
  for (const auto &ASI : *Set)
    PointerMustAliases.insert(ASI.getValue());
  Result.push_back(std::move(PointerMustAliases));
}

return Result;
2320}

2322static bool pointerInvalidatedByLoop(MemoryLocation MemLoc,
                                   AliasSetTracker *CurAST, Loop *CurLoop,
                                   AAResults *AA) {
return CurAST->getAliasSetFor(MemLoc).isMod();
2326}

2328bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU,
                                    Loop *CurLoop, Instruction &I,
                                    SinkAndHoistLICMFlags &Flags) {
// For hoisting, use the walker to determine safety
if (!Flags.getIsSink()) {
  MemoryAccess *Source;
  // See declaration of SetLicmMssaOptCap for usage details.
  if (Flags.tooManyClobberingCalls())
    Source = MU->getDefiningAccess();
  else {
    Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(MU);
    Flags.incrementClobberingCalls();
  }
  return !MSSA->isLiveOnEntryDef(Source) &&
         CurLoop->contains(Source->getBlock());
}

// For sinking, we'd need to check all Defs below this use. The getClobbering
// call will look on the backedge of the loop, but will check aliasing with
// the instructions on the previous iteration.
// For example:
// for (i ... )
//   load a[i] ( Use (LoE)
//   store a[i] ( 1 = Def (2), with 2 = Phi for the loop.
//   i++;
// The load sees no clobbering inside the loop, as the backedge alias check
// does phi translation, and will check aliasing against store a[i-1].
// However sinking the load outside the loop, below the store is incorrect.

// For now, only sink if there are no Defs in the loop, and the existing ones
// precede the use and are in the same block.
// FIXME: Increase precision: Safe to sink if Use post dominates the Def;
// needs PostDominatorTreeAnalysis.
// FIXME: More precise: no Defs that alias this Use.
if (Flags.tooManyMemoryAccesses())
  return true;
for (auto *BB : CurLoop->getBlocks())
  if (pointerInvalidatedByBlockWithMSSA(*BB, *MSSA, *MU))
    return true;
// When sinking, the source block may not be part of the loop so check it.
if (!CurLoop->contains(&I))
  return pointerInvalidatedByBlockWithMSSA(*I.getParent(), *MSSA, *MU);

return false;
2372}

2374bool pointerInvalidatedByBlockWithMSSA(BasicBlock &BB, MemorySSA &MSSA,
                                     MemoryUse &MU) {
if (const auto *Accesses = MSSA.getBlockDefs(&BB))
  for (const auto &MA : *Accesses)
    if (const auto *MD = dyn_cast<MemoryDef>(&MA))
      if (MU.getBlock() != MD->getBlock() || !MSSA.locallyDominates(MD, &MU))
        return true;
return false;
2382}

2384/// Little predicate that returns true if the specified basic block is in
2385/// a subloop of the current one, not the current one itself.
2386///
2387static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) {
assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop")(static_cast<void> (0));
return LI->getLoopFor(BB) != CurLoop;
2390}