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

Bug Summary

File:	build/source/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
Warning:	line 1527, column 7 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name LoopInterchange.cpp -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/source/build-llvm -resource-dir /usr/lib/llvm-17/lib/clang/17 -I lib/Transforms/Scalar -I /build/source/llvm/lib/Transforms/Scalar -I include -I /build/source/llvm/include -D _DEBUG -D _GLIBCXX_ASSERTIONS -D _GNU_SOURCE -D _LIBCPP_ENABLE_ASSERTIONS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-17/lib/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/source/build-llvm=build-llvm -fmacro-prefix-map=/build/source/= -fcoverage-prefix-map=/build/source/build-llvm=build-llvm -fcoverage-prefix-map=/build/source/= -source-date-epoch 1677881322 -O3 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -Wno-misleading-indentation -std=c++17 -fdeprecated-macro -fdebug-compilation-dir=/build/source/build-llvm -fdebug-prefix-map=/build/source/build-llvm=build-llvm -fdebug-prefix-map=/build/source/= -fdebug-prefix-map=/build/source/build-llvm=build-llvm -fdebug-prefix-map=/build/source/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2023-03-04-000721-16503-1 -x c++ /build/source/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
1//===- LoopInterchange.cpp - Loop interchange 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 handles loop interchange transform.
10// This pass interchanges loops to provide a more cache-friendly memory access
11// patterns.
12//
13//===----------------------------------------------------------------------===//

15#include "llvm/Transforms/Scalar/LoopInterchange.h"
16#include "llvm/ADT/STLExtras.h"
17#include "llvm/ADT/SmallVector.h"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/ADT/StringRef.h"
20#include "llvm/Analysis/DependenceAnalysis.h"
21#include "llvm/Analysis/LoopCacheAnalysis.h"
22#include "llvm/Analysis/LoopInfo.h"
23#include "llvm/Analysis/LoopNestAnalysis.h"
24#include "llvm/Analysis/LoopPass.h"
25#include "llvm/Analysis/OptimizationRemarkEmitter.h"
26#include "llvm/Analysis/ScalarEvolution.h"
27#include "llvm/Analysis/ScalarEvolutionExpressions.h"
28#include "llvm/IR/BasicBlock.h"
29#include "llvm/IR/Constants.h"
30#include "llvm/IR/DiagnosticInfo.h"
31#include "llvm/IR/Dominators.h"
32#include "llvm/IR/Function.h"
33#include "llvm/IR/IRBuilder.h"
34#include "llvm/IR/InstrTypes.h"
35#include "llvm/IR/Instruction.h"
36#include "llvm/IR/Instructions.h"
37#include "llvm/IR/User.h"
38#include "llvm/IR/Value.h"
39#include "llvm/InitializePasses.h"
40#include "llvm/Pass.h"
41#include "llvm/Support/Casting.h"
42#include "llvm/Support/CommandLine.h"
43#include "llvm/Support/Debug.h"
44#include "llvm/Support/ErrorHandling.h"
45#include "llvm/Support/raw_ostream.h"
46#include "llvm/Transforms/Scalar.h"
47#include "llvm/Transforms/Scalar/LoopPassManager.h"
48#include "llvm/Transforms/Utils/BasicBlockUtils.h"
49#include "llvm/Transforms/Utils/LoopUtils.h"
50#include <cassert>
51#include <utility>
52#include <vector>

54using namespace llvm;

56#define DEBUG_TYPE"loop-interchange" "loop-interchange"

58STATISTIC(LoopsInterchanged, "Number of loops interchanged")static llvm::Statistic LoopsInterchanged = {"loop-interchange"
, "LoopsInterchanged", "Number of loops interchanged"};

60static cl::opt<int> LoopInterchangeCostThreshold(
  "loop-interchange-threshold", cl::init(0), cl::Hidden,
  cl::desc("Interchange if you gain more than this number"));

64namespace {

66using LoopVector = SmallVector<Loop *, 8>;

68// TODO: Check if we can use a sparse matrix here.
69using CharMatrix = std::vector<std::vector<char>>;

71} // end anonymous namespace

73// Maximum number of dependencies that can be handled in the dependency matrix.
74static const unsigned MaxMemInstrCount = 100;

76// Maximum loop depth supported.
77static const unsigned MaxLoopNestDepth = 10;

79#ifdef DUMP_DEP_MATRICIES
80static void printDepMatrix(CharMatrix &DepMatrix) {
for (auto &Row : DepMatrix) {
  for (auto D : Row)
    LLVM_DEBUG(dbgs() << D << " ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << D << " "; } } while
 (false);
  LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "\n"; } } while (false
);
}
86}
87#endif

89static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level,
                                   Loop *L, DependenceInfo *DI,
                                   ScalarEvolution *SE) {
using ValueVector = SmallVector<Value *, 16>;

ValueVector MemInstr;

// For each block.
for (BasicBlock *BB : L->blocks()) {
  // Scan the BB and collect legal loads and stores.
  for (Instruction &I : *BB) {
    if (!isa<Instruction>(I))
      return false;
    if (auto *Ld = dyn_cast<LoadInst>(&I)) {
      if (!Ld->isSimple())
        return false;
      MemInstr.push_back(&I);
    } else if (auto *St = dyn_cast<StoreInst>(&I)) {
      if (!St->isSimple())
        return false;
      MemInstr.push_back(&I);
    }
  }
}

LLVM_DEBUG(dbgs() << "Found " << MemInstr.size()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Found " << MemInstr
.size() << " Loads and Stores to analyze\n"; } } while (
false)
                  << " Loads and Stores to analyze\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Found " << MemInstr
.size() << " Loads and Stores to analyze\n"; } } while (
false);

ValueVector::iterator I, IE, J, JE;

for (I = MemInstr.begin(), IE = MemInstr.end(); I != IE; ++I) {
  for (J = I, JE = MemInstr.end(); J != JE; ++J) {
    std::vector<char> Dep;
    Instruction *Src = cast<Instruction>(*I);
    Instruction *Dst = cast<Instruction>(*J);
    // Ignore Input dependencies.
    if (isa<LoadInst>(Src) && isa<LoadInst>(Dst))
      continue;
    // Track Output, Flow, and Anti dependencies.
    if (auto D = DI->depends(Src, Dst, true)) {
      assert(D->isOrdered() && "Expected an output, flow or anti dep.")(static_cast <bool> (D->isOrdered() && "Expected an output, flow or anti dep."
) ? void (0) : __assert_fail ("D->isOrdered() && \"Expected an output, flow or anti dep.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 129, __extension__
 __PRETTY_FUNCTION__));
      // If the direction vector is negative, normalize it to
      // make it non-negative.
      if (D->normalize(SE))
        LLVM_DEBUG(dbgs() << "Negative dependence vector normalized.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Negative dependence vector normalized.\n"
; } } while (false);
      LLVM_DEBUG(StringRef DepType =do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { StringRef DepType = D->isFlow() ? "flow"
 : D->isAnti() ? "anti" : "output"; dbgs() << "Found "
 << DepType << " dependency between Src and Dst\n"
 << " Src:" << *Src << "\n Dst:" << *
Dst << '\n'; } } while (false)
                     D->isFlow() ? "flow" : D->isAnti() ? "anti" : "output";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { StringRef DepType = D->isFlow() ? "flow"
 : D->isAnti() ? "anti" : "output"; dbgs() << "Found "
 << DepType << " dependency between Src and Dst\n"
 << " Src:" << *Src << "\n Dst:" << *
Dst << '\n'; } } while (false)
                 dbgs() << "Found " << DepTypedo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { StringRef DepType = D->isFlow() ? "flow"
 : D->isAnti() ? "anti" : "output"; dbgs() << "Found "
 << DepType << " dependency between Src and Dst\n"
 << " Src:" << *Src << "\n Dst:" << *
Dst << '\n'; } } while (false)
                        << " dependency between Src and Dst\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { StringRef DepType = D->isFlow() ? "flow"
 : D->isAnti() ? "anti" : "output"; dbgs() << "Found "
 << DepType << " dependency between Src and Dst\n"
 << " Src:" << *Src << "\n Dst:" << *
Dst << '\n'; } } while (false)
                        << " Src:" << *Src << "\n Dst:" << *Dst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { StringRef DepType = D->isFlow() ? "flow"
 : D->isAnti() ? "anti" : "output"; dbgs() << "Found "
 << DepType << " dependency between Src and Dst\n"
 << " Src:" << *Src << "\n Dst:" << *
Dst << '\n'; } } while (false);
      unsigned Levels = D->getLevels();
      char Direction;
      for (unsigned II = 1; II <= Levels; ++II) {
        if (D->isScalar(II)) {
          Direction = 'S';
          Dep.push_back(Direction);
        } else {
          unsigned Dir = D->getDirection(II);
          if (Dir == Dependence::DVEntry::LT ||
              Dir == Dependence::DVEntry::LE)
            Direction = '<';
          else if (Dir == Dependence::DVEntry::GT ||
                   Dir == Dependence::DVEntry::GE)
            Direction = '>';
          else if (Dir == Dependence::DVEntry::EQ)
            Direction = '=';
          else
            Direction = '*';
          Dep.push_back(Direction);
        }
      }
      while (Dep.size() != Level) {
        Dep.push_back('I');
      }

      DepMatrix.push_back(Dep);
      if (DepMatrix.size() > MaxMemInstrCount) {
        LLVM_DEBUG(dbgs() << "Cannot handle more than " << MaxMemInstrCountdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cannot handle more than "
 << MaxMemInstrCount << " dependencies inside loop\n"
; } } while (false)
                          << " dependencies inside loop\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cannot handle more than "
 << MaxMemInstrCount << " dependencies inside loop\n"
; } } while (false);
        return false;
      }
    }
  }
}

return true;
175}

177// A loop is moved from index 'from' to an index 'to'. Update the Dependence
178// matrix by exchanging the two columns.
179static void interChangeDependencies(CharMatrix &DepMatrix, unsigned FromIndx,
                                  unsigned ToIndx) {
for (unsigned I = 0, E = DepMatrix.size(); I < E; ++I)
  std::swap(DepMatrix[I][ToIndx], DepMatrix[I][FromIndx]);
183}

185// After interchanging, check if the direction vector is valid.
186// [Theorem] A permutation of the loops in a perfect nest is legal if and only
187// if the direction matrix, after the same permutation is applied to its
188// columns, has no ">" direction as the leftmost non-"=" direction in any row.
189static bool isLexicographicallyPositive(std::vector<char> &DV) {
for (unsigned Level = 0; Level < DV.size(); ++Level) {
  unsigned char Direction = DV[Level];
  if (Direction == '<')
    return true;
  if (Direction == '>' || Direction == '*')
    return false;
}
return true;
198}

200// Checks if it is legal to interchange 2 loops.
201static bool isLegalToInterChangeLoops(CharMatrix &DepMatrix,
                                    unsigned InnerLoopId,
                                    unsigned OuterLoopId) {
unsigned NumRows = DepMatrix.size();
std::vector<char> Cur;
// For each row check if it is valid to interchange.
for (unsigned Row = 0; Row < NumRows; ++Row) {
  // Create temporary DepVector check its lexicographical order
  // before and after swapping OuterLoop vs InnerLoop
  Cur = DepMatrix[Row];
  if (!isLexicographicallyPositive(Cur))
    return false;
  std::swap(Cur[InnerLoopId], Cur[OuterLoopId]);
  if (!isLexicographicallyPositive(Cur))
    return false;
}
return true;
218}

220static void populateWorklist(Loop &L, LoopVector &LoopList) {
LLVM_DEBUG(dbgs() << "Calling populateWorklist on Func: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Calling populateWorklist on Func: "
 << L.getHeader()->getParent()->getName() <<
 " Loop: %" << L.getHeader()->getName() << '\n'
; } } while (false)
                  << L.getHeader()->getParent()->getName() << " Loop: %"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Calling populateWorklist on Func: "
 << L.getHeader()->getParent()->getName() <<
 " Loop: %" << L.getHeader()->getName() << '\n'
; } } while (false)
                  << L.getHeader()->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Calling populateWorklist on Func: "
 << L.getHeader()->getParent()->getName() <<
 " Loop: %" << L.getHeader()->getName() << '\n'
; } } while (false);
assert(LoopList.empty() && "LoopList should initially be empty!")(static_cast <bool> (LoopList.empty() && "LoopList should initially be empty!"
) ? void (0) : __assert_fail ("LoopList.empty() && \"LoopList should initially be empty!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 224, __extension__
 __PRETTY_FUNCTION__));
Loop *CurrentLoop = &L;
const std::vector<Loop *> *Vec = &CurrentLoop->getSubLoops();
while (!Vec->empty()) {
  // The current loop has multiple subloops in it hence it is not tightly
  // nested.
  // Discard all loops above it added into Worklist.
  if (Vec->size() != 1) {
    LoopList = {};
    return;
  }

  LoopList.push_back(CurrentLoop);
  CurrentLoop = Vec->front();
  Vec = &CurrentLoop->getSubLoops();
}
LoopList.push_back(CurrentLoop);
241}

243namespace {

245/// LoopInterchangeLegality checks if it is legal to interchange the loop.
246class LoopInterchangeLegality {
247public:
LoopInterchangeLegality(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
                        OptimizationRemarkEmitter *ORE)
    : OuterLoop(Outer), InnerLoop(Inner), SE(SE), ORE(ORE) {}

/// Check if the loops can be interchanged.
bool canInterchangeLoops(unsigned InnerLoopId, unsigned OuterLoopId,
                         CharMatrix &DepMatrix);

/// Discover induction PHIs in the header of \p L. Induction
/// PHIs are added to \p Inductions.
bool findInductions(Loop *L, SmallVectorImpl<PHINode *> &Inductions);

/// Check if the loop structure is understood. We do not handle triangular
/// loops for now.
bool isLoopStructureUnderstood();

bool currentLimitations();

const SmallPtrSetImpl<PHINode *> &getOuterInnerReductions() const {
  return OuterInnerReductions;
}

const SmallVectorImpl<PHINode *> &getInnerLoopInductions() const {
  return InnerLoopInductions;
}

274private:
bool tightlyNested(Loop *Outer, Loop *Inner);
bool containsUnsafeInstructions(BasicBlock *BB);

/// Discover induction and reduction PHIs in the header of \p L. Induction
/// PHIs are added to \p Inductions, reductions are added to
/// OuterInnerReductions. When the outer loop is passed, the inner loop needs
/// to be passed as \p InnerLoop.
bool findInductionAndReductions(Loop *L,
                                SmallVector<PHINode *, 8> &Inductions,
                                Loop *InnerLoop);

Loop *OuterLoop;
Loop *InnerLoop;

ScalarEvolution *SE;

/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;

/// Set of reduction PHIs taking part of a reduction across the inner and
/// outer loop.
SmallPtrSet<PHINode *, 4> OuterInnerReductions;

/// Set of inner loop induction PHIs
SmallVector<PHINode *, 8> InnerLoopInductions;
300};

302/// LoopInterchangeProfitability checks if it is profitable to interchange the
303/// loop.
304class LoopInterchangeProfitability {
305public:
LoopInterchangeProfitability(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
                             OptimizationRemarkEmitter *ORE)
    : OuterLoop(Outer), InnerLoop(Inner), SE(SE), ORE(ORE) {}

/// Check if the loop interchange is profitable.
bool isProfitable(const Loop *InnerLoop, const Loop *OuterLoop,
                  unsigned InnerLoopId, unsigned OuterLoopId,
                  CharMatrix &DepMatrix,
                  const DenseMap<const Loop *, unsigned> &CostMap,
                  std::unique_ptr<CacheCost> &CC);

317private:
int getInstrOrderCost();
std::optional<bool> isProfitablePerLoopCacheAnalysis(
    const DenseMap<const Loop *, unsigned> &CostMap,
    std::unique_ptr<CacheCost> &CC);
std::optional<bool> isProfitablePerInstrOrderCost();
std::optional<bool> isProfitableForVectorization(unsigned InnerLoopId,
                                                 unsigned OuterLoopId,
                                                 CharMatrix &DepMatrix);
Loop *OuterLoop;
Loop *InnerLoop;

/// Scev analysis.
ScalarEvolution *SE;

/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;
334};

336/// LoopInterchangeTransform interchanges the loop.
337class LoopInterchangeTransform {
338public:
LoopInterchangeTransform(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
                         LoopInfo *LI, DominatorTree *DT,
                         const LoopInterchangeLegality &LIL)
    : OuterLoop(Outer), InnerLoop(Inner), SE(SE), LI(LI), DT(DT), LIL(LIL) {}

/// Interchange OuterLoop and InnerLoop.
bool transform();
void restructureLoops(Loop *NewInner, Loop *NewOuter,
                      BasicBlock *OrigInnerPreHeader,
                      BasicBlock *OrigOuterPreHeader);
void removeChildLoop(Loop *OuterLoop, Loop *InnerLoop);

351private:
bool adjustLoopLinks();
bool adjustLoopBranches();

Loop *OuterLoop;
Loop *InnerLoop;

/// Scev analysis.
ScalarEvolution *SE;

LoopInfo *LI;
DominatorTree *DT;

const LoopInterchangeLegality &LIL;
365};

367struct LoopInterchange {
ScalarEvolution *SE = nullptr;
LoopInfo *LI = nullptr;
DependenceInfo *DI = nullptr;
DominatorTree *DT = nullptr;
std::unique_ptr<CacheCost> CC = nullptr;

/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;

LoopInterchange(ScalarEvolution *SE, LoopInfo *LI, DependenceInfo *DI,
                DominatorTree *DT, std::unique_ptr<CacheCost> &CC,
                OptimizationRemarkEmitter *ORE)
    : SE(SE), LI(LI), DI(DI), DT(DT), CC(std::move(CC)), ORE(ORE) {}

bool run(Loop *L) {
  if (L->getParentLoop())
    return false;
  SmallVector<Loop *, 8> LoopList;
  populateWorklist(*L, LoopList);
  return processLoopList(LoopList);
}

bool run(LoopNest &LN) {
  SmallVector<Loop *, 8> LoopList(LN.getLoops().begin(), LN.getLoops().end());
  for (unsigned I = 1; I < LoopList.size(); ++I)
    if (LoopList[I]->getParentLoop() != LoopList[I - 1])
      return false;
  return processLoopList(LoopList);
}

bool isComputableLoopNest(ArrayRef<Loop *> LoopList) {
  for (Loop *L : LoopList) {
    const SCEV *ExitCountOuter = SE->getBackedgeTakenCount(L);
    if (isa<SCEVCouldNotCompute>(ExitCountOuter)) {
      LLVM_DEBUG(dbgs() << "Couldn't compute backedge count\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Couldn't compute backedge count\n"
; } } while (false);
      return false;
    }
    if (L->getNumBackEdges() != 1) {
      LLVM_DEBUG(dbgs() << "NumBackEdges is not equal to 1\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "NumBackEdges is not equal to 1\n"
; } } while (false);
      return false;
    }
    if (!L->getExitingBlock()) {
      LLVM_DEBUG(dbgs() << "Loop doesn't have unique exit block\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loop doesn't have unique exit block\n"
; } } while (false);
      return false;
    }
  }
  return true;
}

unsigned selectLoopForInterchange(ArrayRef<Loop *> LoopList) {
  // TODO: Add a better heuristic to select the loop to be interchanged based
  // on the dependence matrix. Currently we select the innermost loop.
  return LoopList.size() - 1;
}

bool processLoopList(SmallVectorImpl<Loop *> &LoopList) {
  bool Changed = false;
  unsigned LoopNestDepth = LoopList.size();
  if (LoopNestDepth < 2) {
    LLVM_DEBUG(dbgs() << "Loop doesn't contain minimum nesting level.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loop doesn't contain minimum nesting level.\n"
; } } while (false);
    return false;
  }
  if (LoopNestDepth > MaxLoopNestDepth) {
    LLVM_DEBUG(dbgs() << "Cannot handle loops of depth greater than "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cannot handle loops of depth greater than "
 << MaxLoopNestDepth << "\n"; } } while (false)
                      << MaxLoopNestDepth << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cannot handle loops of depth greater than "
 << MaxLoopNestDepth << "\n"; } } while (false);
    return false;
  }
  if (!isComputableLoopNest(LoopList)) {
    LLVM_DEBUG(dbgs() << "Not valid loop candidate for interchange\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Not valid loop candidate for interchange\n"
; } } while (false);
    return false;
  }

  LLVM_DEBUG(dbgs() << "Processing LoopList of size = " << LoopNestDepthdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Processing LoopList of size = "
 << LoopNestDepth << "\n"; } } while (false)
                    << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Processing LoopList of size = "
 << LoopNestDepth << "\n"; } } while (false);

  CharMatrix DependencyMatrix;
  Loop *OuterMostLoop = *(LoopList.begin());
  if (!populateDependencyMatrix(DependencyMatrix, LoopNestDepth,
                                OuterMostLoop, DI, SE)) {
    LLVM_DEBUG(dbgs() << "Populating dependency matrix failed\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Populating dependency matrix failed\n"
; } } while (false);
    return false;
  }
450#ifdef DUMP_DEP_MATRICIES
  LLVM_DEBUG(dbgs() << "Dependence before interchange\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Dependence before interchange\n"
; } } while (false);
  printDepMatrix(DependencyMatrix);
453#endif

  // Get the Outermost loop exit.
  BasicBlock *LoopNestExit = OuterMostLoop->getExitBlock();
  if (!LoopNestExit) {
    LLVM_DEBUG(dbgs() << "OuterMostLoop needs an unique exit block")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "OuterMostLoop needs an unique exit block"
; } } while (false);
    return false;
  }

  unsigned SelecLoopId = selectLoopForInterchange(LoopList);
  // Obtain the loop vector returned from loop cache analysis beforehand,
  // and put each <Loop, index> pair into a map for constant time query
  // later. Indices in loop vector reprsent the optimal order of the
  // corresponding loop, e.g., given a loopnest with depth N, index 0
  // indicates the loop should be placed as the outermost loop and index N
  // indicates the loop should be placed as the innermost loop.
  //
  // For the old pass manager CacheCost would be null.
  DenseMap<const Loop *, unsigned> CostMap;
  if (CC != nullptr) {
    const auto &LoopCosts = CC->getLoopCosts();
    for (unsigned i = 0; i < LoopCosts.size(); i++) {
      CostMap[LoopCosts[i].first] = i;
    }
  }
  // We try to achieve the globally optimal memory access for the loopnest,
  // and do interchange based on a bubble-sort fasion. We start from
  // the innermost loop, move it outwards to the best possible position
  // and repeat this process.
  for (unsigned j = SelecLoopId; j > 0; j--) {
    bool ChangedPerIter = false;
    for (unsigned i = SelecLoopId; i > SelecLoopId - j; i--) {
      bool Interchanged = processLoop(LoopList[i], LoopList[i - 1], i, i - 1,
                                      DependencyMatrix, CostMap);
      if (!Interchanged)
        continue;
      // Loops interchanged, update LoopList accordingly.
      std::swap(LoopList[i - 1], LoopList[i]);
      // Update the DependencyMatrix
      interChangeDependencies(DependencyMatrix, i, i - 1);
493#ifdef DUMP_DEP_MATRICIES
      LLVM_DEBUG(dbgs() << "Dependence after interchange\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Dependence after interchange\n"
; } } while (false);
      printDepMatrix(DependencyMatrix);
496#endif
      ChangedPerIter |= Interchanged;
      Changed |= Interchanged;
    }
    // Early abort if there was no interchange during an entire round of
    // moving loops outwards.
    if (!ChangedPerIter)
      break;
  }
  return Changed;
}

bool processLoop(Loop *InnerLoop, Loop *OuterLoop, unsigned InnerLoopId,
                 unsigned OuterLoopId,
                 std::vector<std::vector<char>> &DependencyMatrix,
                 const DenseMap<const Loop *, unsigned> &CostMap) {
  LLVM_DEBUG(dbgs() << "Processing InnerLoopId = " << InnerLoopIddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Processing InnerLoopId = "
 << InnerLoopId << " and OuterLoopId = " <<
 OuterLoopId << "\n"; } } while (false)
                    << " and OuterLoopId = " << OuterLoopId << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Processing InnerLoopId = "
 << InnerLoopId << " and OuterLoopId = " <<
 OuterLoopId << "\n"; } } while (false);
  LoopInterchangeLegality LIL(OuterLoop, InnerLoop, SE, ORE);
  if (!LIL.canInterchangeLoops(InnerLoopId, OuterLoopId, DependencyMatrix)) {
    LLVM_DEBUG(dbgs() << "Not interchanging loops. Cannot prove legality.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Not interchanging loops. Cannot prove legality.\n"
; } } while (false);
    return false;
  }
  LLVM_DEBUG(dbgs() << "Loops are legal to interchange\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops are legal to interchange\n"
; } } while (false);
  LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE, ORE);
  if (!LIP.isProfitable(InnerLoop, OuterLoop, InnerLoopId, OuterLoopId,
                        DependencyMatrix, CostMap, CC)) {
    LLVM_DEBUG(dbgs() << "Interchanging loops not profitable.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Interchanging loops not profitable.\n"
; } } while (false);
    return false;
  }

  ORE->emit([&]() {
    return OptimizationRemark(DEBUG_TYPE"loop-interchange", "Interchanged",
                              InnerLoop->getStartLoc(),
                              InnerLoop->getHeader())
           << "Loop interchanged with enclosing loop.";
  });

  LoopInterchangeTransform LIT(OuterLoop, InnerLoop, SE, LI, DT, LIL);
  LIT.transform();
  LLVM_DEBUG(dbgs() << "Loops interchanged.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops interchanged.\n"
; } } while (false);
  LoopsInterchanged++;

  llvm::formLCSSARecursively(*OuterLoop, *DT, LI, SE);
  return true;
}
542};

544} // end anonymous namespace

546bool LoopInterchangeLegality::containsUnsafeInstructions(BasicBlock *BB) {
return any_of(*BB, [](const Instruction &I) {
  return I.mayHaveSideEffects() || I.mayReadFromMemory();
});
550}

552bool LoopInterchangeLegality::tightlyNested(Loop *OuterLoop, Loop *InnerLoop) {
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();

LLVM_DEBUG(dbgs() << "Checking if loops are tightly nested\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Checking if loops are tightly nested\n"
; } } while (false);

// A perfectly nested loop will not have any branch in between the outer and
// inner block i.e. outer header will branch to either inner preheader and
// outerloop latch.
BranchInst *OuterLoopHeaderBI =
    dyn_cast<BranchInst>(OuterLoopHeader->getTerminator());
if (!OuterLoopHeaderBI)
  return false;

for (BasicBlock *Succ : successors(OuterLoopHeaderBI))
  if (Succ != InnerLoopPreHeader && Succ != InnerLoop->getHeader() &&
      Succ != OuterLoopLatch)
    return false;

LLVM_DEBUG(dbgs() << "Checking instructions in Loop header and Loop latch\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Checking instructions in Loop header and Loop latch\n"
; } } while (false);
// We do not have any basic block in between now make sure the outer header
// and outer loop latch doesn't contain any unsafe instructions.
if (containsUnsafeInstructions(OuterLoopHeader) ||
    containsUnsafeInstructions(OuterLoopLatch))
  return false;

// Also make sure the inner loop preheader does not contain any unsafe
// instructions. Note that all instructions in the preheader will be moved to
// the outer loop header when interchanging.
if (InnerLoopPreHeader != OuterLoopHeader &&
    containsUnsafeInstructions(InnerLoopPreHeader))
  return false;

BasicBlock *InnerLoopExit = InnerLoop->getExitBlock();
// Ensure the inner loop exit block flows to the outer loop latch possibly
// through empty blocks.
const BasicBlock &SuccInner =
    LoopNest::skipEmptyBlockUntil(InnerLoopExit, OuterLoopLatch);
if (&SuccInner != OuterLoopLatch) {
  LLVM_DEBUG(dbgs() << "Inner loop exit block " << *InnerLoopExitdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Inner loop exit block "
 << *InnerLoopExit << " does not lead to the outer loop latch.\n"
;; } } while (false)
                    << " does not lead to the outer loop latch.\n";)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Inner loop exit block "
 << *InnerLoopExit << " does not lead to the outer loop latch.\n"
;; } } while (false);
  return false;
}
// The inner loop exit block does flow to the outer loop latch and not some
// other BBs, now make sure it contains safe instructions, since it will be
// moved into the (new) inner loop after interchange.
if (containsUnsafeInstructions(InnerLoopExit))
  return false;

LLVM_DEBUG(dbgs() << "Loops are perfectly nested\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops are perfectly nested\n"
; } } while (false);
// We have a perfect loop nest.
return true;
605}

607bool LoopInterchangeLegality::isLoopStructureUnderstood() {
BasicBlock *InnerLoopPreheader = InnerLoop->getLoopPreheader();
for (PHINode *InnerInduction : InnerLoopInductions) {
  unsigned Num = InnerInduction->getNumOperands();
  for (unsigned i = 0; i < Num; ++i) {
    Value *Val = InnerInduction->getOperand(i);
    if (isa<Constant>(Val))
      continue;
    Instruction *I = dyn_cast<Instruction>(Val);
    if (!I)
      return false;
    // TODO: Handle triangular loops.
    // e.g. for(int i=0;i<N;i++)
    //        for(int j=i;j<N;j++)
    unsigned IncomBlockIndx = PHINode::getIncomingValueNumForOperand(i);
    if (InnerInduction->getIncomingBlock(IncomBlockIndx) ==
            InnerLoopPreheader &&
        !OuterLoop->isLoopInvariant(I)) {
      return false;
    }
  }
}

// TODO: Handle triangular loops of another form.
// e.g. for(int i=0;i<N;i++)
//        for(int j=0;j<i;j++)
// or,
//      for(int i=0;i<N;i++)
//        for(int j=0;j*i<N;j++)
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
BranchInst *InnerLoopLatchBI =
    dyn_cast<BranchInst>(InnerLoopLatch->getTerminator());
if (!InnerLoopLatchBI->isConditional())
  return false;
if (CmpInst *InnerLoopCmp =
        dyn_cast<CmpInst>(InnerLoopLatchBI->getCondition())) {
  Value *Op0 = InnerLoopCmp->getOperand(0);
  Value *Op1 = InnerLoopCmp->getOperand(1);

  // LHS and RHS of the inner loop exit condition, e.g.,
  // in "for(int j=0;j<i;j++)", LHS is j and RHS is i.
  Value *Left = nullptr;
  Value *Right = nullptr;

  // Check if V only involves inner loop induction variable.
  // Return true if V is InnerInduction, or a cast from
  // InnerInduction, or a binary operator that involves
  // InnerInduction and a constant.
  std::function<bool(Value *)> IsPathToInnerIndVar;
  IsPathToInnerIndVar = [this, &IsPathToInnerIndVar](const Value *V) -> bool {
    if (llvm::is_contained(InnerLoopInductions, V))
      return true;
    if (isa<Constant>(V))
      return true;
    const Instruction *I = dyn_cast<Instruction>(V);
    if (!I)
      return false;
    if (isa<CastInst>(I))
      return IsPathToInnerIndVar(I->getOperand(0));
    if (isa<BinaryOperator>(I))
      return IsPathToInnerIndVar(I->getOperand(0)) &&
             IsPathToInnerIndVar(I->getOperand(1));
    return false;
  };

  // In case of multiple inner loop indvars, it is okay if LHS and RHS
  // are both inner indvar related variables.
  if (IsPathToInnerIndVar(Op0) && IsPathToInnerIndVar(Op1))
    return true;

  // Otherwise we check if the cmp instruction compares an inner indvar
  // related variable (Left) with a outer loop invariant (Right).
  if (IsPathToInnerIndVar(Op0) && !isa<Constant>(Op0)) {
    Left = Op0;
    Right = Op1;
  } else if (IsPathToInnerIndVar(Op1) && !isa<Constant>(Op1)) {
    Left = Op1;
    Right = Op0;
  }

  if (Left == nullptr)
    return false;

  const SCEV *S = SE->getSCEV(Right);
  if (!SE->isLoopInvariant(S, OuterLoop))
    return false;
}

return true;
696}

698// If SV is a LCSSA PHI node with a single incoming value, return the incoming
699// value.
700static Value *followLCSSA(Value *SV) {
PHINode *PHI = dyn_cast<PHINode>(SV);
if (!PHI)
  return SV;

if (PHI->getNumIncomingValues() != 1)
  return SV;
return followLCSSA(PHI->getIncomingValue(0));
708}

710// Check V's users to see if it is involved in a reduction in L.
711static PHINode *findInnerReductionPhi(Loop *L, Value *V) {
// Reduction variables cannot be constants.
if (isa<Constant>(V))
  return nullptr;

for (Value *User : V->users()) {
  if (PHINode *PHI = dyn_cast<PHINode>(User)) {
    if (PHI->getNumIncomingValues() == 1)
      continue;
    RecurrenceDescriptor RD;
    if (RecurrenceDescriptor::isReductionPHI(PHI, L, RD)) {
      // Detect floating point reduction only when it can be reordered.
      if (RD.getExactFPMathInst() != nullptr)
        return nullptr;
      return PHI;
    }
    return nullptr;
  }
}

return nullptr;
732}

734bool LoopInterchangeLegality::findInductionAndReductions(
  Loop *L, SmallVector<PHINode *, 8> &Inductions, Loop *InnerLoop) {
if (!L->getLoopLatch() || !L->getLoopPredecessor())
  return false;
for (PHINode &PHI : L->getHeader()->phis()) {
  RecurrenceDescriptor RD;
  InductionDescriptor ID;
  if (InductionDescriptor::isInductionPHI(&PHI, L, SE, ID))
    Inductions.push_back(&PHI);
  else {
    // PHIs in inner loops need to be part of a reduction in the outer loop,
    // discovered when checking the PHIs of the outer loop earlier.
    if (!InnerLoop) {
      if (!OuterInnerReductions.count(&PHI)) {
        LLVM_DEBUG(dbgs() << "Inner loop PHI is not part of reductions "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Inner loop PHI is not part of reductions "
 "across the outer loop.\n"; } } while (false)
                             "across the outer loop.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Inner loop PHI is not part of reductions "
 "across the outer loop.\n"; } } while (false);
        return false;
      }
    } else {
      assert(PHI.getNumIncomingValues() == 2 &&(static_cast <bool> (PHI.getNumIncomingValues() == 2 &&
 "Phis in loop header should have exactly 2 incoming values")
 ? void (0) : __assert_fail ("PHI.getNumIncomingValues() == 2 && \"Phis in loop header should have exactly 2 incoming values\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 754, __extension__
 __PRETTY_FUNCTION__))
             "Phis in loop header should have exactly 2 incoming values")(static_cast <bool> (PHI.getNumIncomingValues() == 2 &&
 "Phis in loop header should have exactly 2 incoming values")
 ? void (0) : __assert_fail ("PHI.getNumIncomingValues() == 2 && \"Phis in loop header should have exactly 2 incoming values\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 754, __extension__
 __PRETTY_FUNCTION__));
      // Check if we have a PHI node in the outer loop that has a reduction
      // result from the inner loop as an incoming value.
      Value *V = followLCSSA(PHI.getIncomingValueForBlock(L->getLoopLatch()));
      PHINode *InnerRedPhi = findInnerReductionPhi(InnerLoop, V);
      if (!InnerRedPhi ||
          !llvm::is_contained(InnerRedPhi->incoming_values(), &PHI)) {
        LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed to recognize PHI as an induction or reduction.\n"
; } } while (false)
            dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed to recognize PHI as an induction or reduction.\n"
; } } while (false)
            << "Failed to recognize PHI as an induction or reduction.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed to recognize PHI as an induction or reduction.\n"
; } } while (false);
        return false;
      }
      OuterInnerReductions.insert(&PHI);
      OuterInnerReductions.insert(InnerRedPhi);
    }
  }
}
return true;
772}

774// This function indicates the current limitations in the transform as a result
775// of which we do not proceed.
776bool LoopInterchangeLegality::currentLimitations() {
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();

// transform currently expects the loop latches to also be the exiting
// blocks.
if (InnerLoop->getExitingBlock() != InnerLoopLatch ||
    OuterLoop->getExitingBlock() != OuterLoop->getLoopLatch() ||
    !isa<BranchInst>(InnerLoopLatch->getTerminator()) ||
    !isa<BranchInst>(OuterLoop->getLoopLatch()->getTerminator())) {
  LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops where the latch is not the exiting block are not"
 << " supported currently.\n"; } } while (false)
      dbgs() << "Loops where the latch is not the exiting block are not"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops where the latch is not the exiting block are not"
 << " supported currently.\n"; } } while (false)
             << " supported currently.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops where the latch is not the exiting block are not"
 << " supported currently.\n"; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "ExitingNotLatch",
                                    OuterLoop->getStartLoc(),
                                    OuterLoop->getHeader())
           << "Loops where the latch is not the exiting block cannot be"
              " interchange currently.";
  });
  return true;
}

SmallVector<PHINode *, 8> Inductions;
if (!findInductionAndReductions(OuterLoop, Inductions, InnerLoop)) {
  LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only outer loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false)
      dbgs() << "Only outer loops with induction or reduction PHI nodes "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only outer loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false)
             << "are supported currently.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only outer loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedPHIOuter",
                                    OuterLoop->getStartLoc(),
                                    OuterLoop->getHeader())
           << "Only outer loops with induction or reduction PHI nodes can be"
              " interchanged currently.";
  });
  return true;
}

Inductions.clear();
// For multi-level loop nests, make sure that all phi nodes for inner loops
// at all levels can be recognized as a induction or reduction phi. Bail out
// if a phi node at a certain nesting level cannot be properly recognized.
Loop *CurLevelLoop = OuterLoop;
while (!CurLevelLoop->getSubLoops().empty()) {
  // We already made sure that the loop nest is tightly nested.
  CurLevelLoop = CurLevelLoop->getSubLoops().front();
  if (!findInductionAndReductions(CurLevelLoop, Inductions, nullptr)) {
    LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only inner loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false)
        dbgs() << "Only inner loops with induction or reduction PHI nodes "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only inner loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false)
              << "are supported currently.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Only inner loops with induction or reduction PHI nodes "
 << "are supported currently.\n"; } } while (false);
    ORE->emit([&]() {
      return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedPHIInner",
                                      CurLevelLoop->getStartLoc(),
                                      CurLevelLoop->getHeader())
            << "Only inner loops with induction or reduction PHI nodes can be"
                " interchange currently.";
    });
    return true;
  }
}

// TODO: Triangular loops are not handled for now.
if (!isLoopStructureUnderstood()) {
  LLVM_DEBUG(dbgs() << "Loop structure not understood by pass\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loop structure not understood by pass\n"
; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedStructureInner",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Inner loop structure not understood currently.";
  });
  return true;
}

return false;
849}

851bool LoopInterchangeLegality::findInductions(
  Loop *L, SmallVectorImpl<PHINode *> &Inductions) {
for (PHINode &PHI : L->getHeader()->phis()) {
  InductionDescriptor ID;
  if (InductionDescriptor::isInductionPHI(&PHI, L, SE, ID))
    Inductions.push_back(&PHI);
}
return !Inductions.empty();
859}

861// We currently only support LCSSA PHI nodes in the inner loop exit, if their
862// users are either reduction PHIs or PHIs outside the outer loop (which means
863// the we are only interested in the final value after the loop).
864static bool
865areInnerLoopExitPHIsSupported(Loop *InnerL, Loop *OuterL,
                            SmallPtrSetImpl<PHINode *> &Reductions) {
BasicBlock *InnerExit = OuterL->getUniqueExitBlock();
for (PHINode &PHI : InnerExit->phis()) {
  // Reduction lcssa phi will have only 1 incoming block that from loop latch.
  if (PHI.getNumIncomingValues() > 1)
    return false;
  if (any_of(PHI.users(), [&Reductions, OuterL](User *U) {
        PHINode *PN = dyn_cast<PHINode>(U);
        return !PN ||
               (!Reductions.count(PN) && OuterL->contains(PN->getParent()));
      })) {
    return false;
  }
}
return true;
881}

883// We currently support LCSSA PHI nodes in the outer loop exit, if their
884// incoming values do not come from the outer loop latch or if the
885// outer loop latch has a single predecessor. In that case, the value will
886// be available if both the inner and outer loop conditions are true, which
887// will still be true after interchanging. If we have multiple predecessor,
888// that may not be the case, e.g. because the outer loop latch may be executed
889// if the inner loop is not executed.
890static bool areOuterLoopExitPHIsSupported(Loop *OuterLoop, Loop *InnerLoop) {
BasicBlock *LoopNestExit = OuterLoop->getUniqueExitBlock();
for (PHINode &PHI : LoopNestExit->phis()) {
  for (unsigned i = 0; i < PHI.getNumIncomingValues(); i++) {
    Instruction *IncomingI = dyn_cast<Instruction>(PHI.getIncomingValue(i));
    if (!IncomingI || IncomingI->getParent() != OuterLoop->getLoopLatch())
      continue;

    // The incoming value is defined in the outer loop latch. Currently we
    // only support that in case the outer loop latch has a single predecessor.
    // This guarantees that the outer loop latch is executed if and only if
    // the inner loop is executed (because tightlyNested() guarantees that the
    // outer loop header only branches to the inner loop or the outer loop
    // latch).
    // FIXME: We could weaken this logic and allow multiple predecessors,
    //        if the values are produced outside the loop latch. We would need
    //        additional logic to update the PHI nodes in the exit block as
    //        well.
    if (OuterLoop->getLoopLatch()->getUniquePredecessor() == nullptr)
      return false;
  }
}
return true;
913}

915// In case of multi-level nested loops, it may occur that lcssa phis exist in
916// the latch of InnerLoop, i.e., when defs of the incoming values are further
917// inside the loopnest. Sometimes those incoming values are not available
918// after interchange, since the original inner latch will become the new outer
919// latch which may have predecessor paths that do not include those incoming
920// values.
921// TODO: Handle transformation of lcssa phis in the InnerLoop latch in case of
922// multi-level loop nests.
923static bool areInnerLoopLatchPHIsSupported(Loop *OuterLoop, Loop *InnerLoop) {
if (InnerLoop->getSubLoops().empty())
  return true;
// If the original outer latch has only one predecessor, then values defined
// further inside the looploop, e.g., in the innermost loop, will be available
// at the new outer latch after interchange.
if (OuterLoop->getLoopLatch()->getUniquePredecessor() != nullptr)
  return true;

// The outer latch has more than one predecessors, i.e., the inner
// exit and the inner header.
// PHI nodes in the inner latch are lcssa phis where the incoming values
// are defined further inside the loopnest. Check if those phis are used
// in the original inner latch. If that is the case then bail out since
// those incoming values may not be available at the new outer latch.
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
for (PHINode &PHI : InnerLoopLatch->phis()) {
  for (auto *U : PHI.users()) {
    Instruction *UI = cast<Instruction>(U);
    if (InnerLoopLatch == UI->getParent())
      return false;
  }
}
return true;
947}

949bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId,
                                                unsigned OuterLoopId,
                                                CharMatrix &DepMatrix) {
if (!isLegalToInterChangeLoops(DepMatrix, InnerLoopId, OuterLoopId)) {
  LLVM_DEBUG(dbgs() << "Failed interchange InnerLoopId = " << InnerLoopIddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed interchange InnerLoopId = "
 << InnerLoopId << " and OuterLoopId = " <<
 OuterLoopId << " due to dependence\n"; } } while (false
)
                    << " and OuterLoopId = " << OuterLoopIddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed interchange InnerLoopId = "
 << InnerLoopId << " and OuterLoopId = " <<
 OuterLoopId << " due to dependence\n"; } } while (false
)
                    << " due to dependence\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed interchange InnerLoopId = "
 << InnerLoopId << " and OuterLoopId = " <<
 OuterLoopId << " due to dependence\n"; } } while (false
);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "Dependence",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Cannot interchange loops due to dependences.";
  });
  return false;
}
// Check if outer and inner loop contain legal instructions only.
for (auto *BB : OuterLoop->blocks())
  for (Instruction &I : BB->instructionsWithoutDebug())
    if (CallInst *CI = dyn_cast<CallInst>(&I)) {
      // readnone functions do not prevent interchanging.
      if (CI->onlyWritesMemory())
        continue;
      LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops with call instructions cannot be interchanged "
 << "safely."; } } while (false)
          dbgs() << "Loops with call instructions cannot be interchanged "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops with call instructions cannot be interchanged "
 << "safely."; } } while (false)
                 << "safely.")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops with call instructions cannot be interchanged "
 << "safely."; } } while (false);
      ORE->emit([&]() {
        return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "CallInst",
                                        CI->getDebugLoc(),
                                        CI->getParent())
               << "Cannot interchange loops due to call instruction.";
      });

      return false;
    }

if (!findInductions(InnerLoop, InnerLoopInductions)) {
  LLVM_DEBUG(dbgs() << "Cound not find inner loop induction variables.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cound not find inner loop induction variables.\n"
; } } while (false);
  return false;
}

if (!areInnerLoopLatchPHIsSupported(OuterLoop, InnerLoop)) {
  LLVM_DEBUG(dbgs() << "Found unsupported PHI nodes in inner loop latch.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Found unsupported PHI nodes in inner loop latch.\n"
; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedInnerLatchPHI",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Cannot interchange loops because unsupported PHI nodes found "
              "in inner loop latch.";
  });
  return false;
}

// TODO: The loops could not be interchanged due to current limitations in the
// transform module.
if (currentLimitations()) {
  LLVM_DEBUG(dbgs() << "Not legal because of current transform limitation\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Not legal because of current transform limitation\n"
; } } while (false);
  return false;
}

// Check if the loops are tightly nested.
if (!tightlyNested(OuterLoop, InnerLoop)) {
  LLVM_DEBUG(dbgs() << "Loops not tightly nested\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Loops not tightly nested\n"
; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "NotTightlyNested",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Cannot interchange loops because they are not tightly "
              "nested.";
  });
  return false;
}

if (!areInnerLoopExitPHIsSupported(OuterLoop, InnerLoop,
                                   OuterInnerReductions)) {
  LLVM_DEBUG(dbgs() << "Found unsupported PHI nodes in inner loop exit.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Found unsupported PHI nodes in inner loop exit.\n"
; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedExitPHI",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Found unsupported PHI node in loop exit.";
  });
  return false;
}

if (!areOuterLoopExitPHIsSupported(OuterLoop, InnerLoop)) {
  LLVM_DEBUG(dbgs() << "Found unsupported PHI nodes in outer loop exit.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Found unsupported PHI nodes in outer loop exit.\n"
; } } while (false);
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "UnsupportedExitPHI",
                                    OuterLoop->getStartLoc(),
                                    OuterLoop->getHeader())
           << "Found unsupported PHI node in loop exit.";
  });
  return false;
}

return true;
1045}

1047int LoopInterchangeProfitability::getInstrOrderCost() {
unsigned GoodOrder, BadOrder;
BadOrder = GoodOrder = 0;
for (BasicBlock *BB : InnerLoop->blocks()) {
  for (Instruction &Ins : *BB) {
    if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Ins)) {
      unsigned NumOp = GEP->getNumOperands();
      bool FoundInnerInduction = false;
      bool FoundOuterInduction = false;
      for (unsigned i = 0; i < NumOp; ++i) {
        // Skip operands that are not SCEV-able.
        if (!SE->isSCEVable(GEP->getOperand(i)->getType()))
          continue;

        const SCEV *OperandVal = SE->getSCEV(GEP->getOperand(i));
        const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(OperandVal);
        if (!AR)
          continue;

        // If we find the inner induction after an outer induction e.g.
        // for(int i=0;i<N;i++)
        //   for(int j=0;j<N;j++)
        //     A[i][j] = A[i-1][j-1]+k;
        // then it is a good order.
        if (AR->getLoop() == InnerLoop) {
          // We found an InnerLoop induction after OuterLoop induction. It is
          // a good order.
          FoundInnerInduction = true;
          if (FoundOuterInduction) {
            GoodOrder++;
            break;
          }
        }
        // If we find the outer induction after an inner induction e.g.
        // for(int i=0;i<N;i++)
        //   for(int j=0;j<N;j++)
        //     A[j][i] = A[j-1][i-1]+k;
        // then it is a bad order.
        if (AR->getLoop() == OuterLoop) {
          // We found an OuterLoop induction after InnerLoop induction. It is
          // a bad order.
          FoundOuterInduction = true;
          if (FoundInnerInduction) {
            BadOrder++;
            break;
          }
        }
      }
    }
  }
}
return GoodOrder - BadOrder;
1099}

1101std::optional<bool>
1102LoopInterchangeProfitability::isProfitablePerLoopCacheAnalysis(
  const DenseMap<const Loop *, unsigned> &CostMap,
  std::unique_ptr<CacheCost> &CC) {
// This is the new cost model returned from loop cache analysis.
// A smaller index means the loop should be placed an outer loop, and vice
// versa.
if (CostMap.find(InnerLoop) != CostMap.end() &&
    CostMap.find(OuterLoop) != CostMap.end()) {
  unsigned InnerIndex = 0, OuterIndex = 0;
  InnerIndex = CostMap.find(InnerLoop)->second;
  OuterIndex = CostMap.find(OuterLoop)->second;
  LLVM_DEBUG(dbgs() << "InnerIndex = " << InnerIndexdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "InnerIndex = " <<
 InnerIndex << ", OuterIndex = " << OuterIndex <<
 "\n"; } } while (false)
                    << ", OuterIndex = " << OuterIndex << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "InnerIndex = " <<
 InnerIndex << ", OuterIndex = " << OuterIndex <<
 "\n"; } } while (false);
  if (InnerIndex < OuterIndex)
    return std::optional<bool>(true);
  assert(InnerIndex != OuterIndex && "CostMap should assign unique "(static_cast <bool> (InnerIndex != OuterIndex &&
 "CostMap should assign unique " "numbers to each loop") ? void
 (0) : __assert_fail ("InnerIndex != OuterIndex && \"CostMap should assign unique \" \"numbers to each loop\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1118, __extension__
 __PRETTY_FUNCTION__))
                                     "numbers to each loop")(static_cast <bool> (InnerIndex != OuterIndex &&
 "CostMap should assign unique " "numbers to each loop") ? void
 (0) : __assert_fail ("InnerIndex != OuterIndex && \"CostMap should assign unique \" \"numbers to each loop\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1118, __extension__
 __PRETTY_FUNCTION__));
  if (CC->getLoopCost(*OuterLoop) == CC->getLoopCost(*InnerLoop))
    return std::nullopt;
  return std::optional<bool>(false);
}
return std::nullopt;
1124}

1126std::optional<bool>
1127LoopInterchangeProfitability::isProfitablePerInstrOrderCost() {
// Legacy cost model: this is rough cost estimation algorithm. It counts the
// good and bad order of induction variables in the instruction and allows
// reordering if number of bad orders is more than good.
int Cost = getInstrOrderCost();
LLVM_DEBUG(dbgs() << "Cost = " << Cost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Cost = " << Cost
 << "\n"; } } while (false);
if (Cost < 0 && Cost < LoopInterchangeCostThreshold)
  return std::optional<bool>(true);

return std::nullopt;
1137}

1139std::optional<bool> LoopInterchangeProfitability::isProfitableForVectorization(
  unsigned InnerLoopId, unsigned OuterLoopId, CharMatrix &DepMatrix) {
for (auto &Row : DepMatrix) {
  // If the inner loop is loop independent or doesn't carry any dependency
  // it is not profitable to move this to outer position, since we are
  // likely able to do inner loop vectorization already.
  if (Row[InnerLoopId] == 'I' || Row[InnerLoopId] == '=')
    return std::optional<bool>(false);

  // If the outer loop is not loop independent it is not profitable to move
  // this to inner position, since doing so would not enable inner loop
  // parallelism.
  if (Row[OuterLoopId] != 'I' && Row[OuterLoopId] != '=')
    return std::optional<bool>(false);
}
// If inner loop has dependence and outer loop is loop independent then it
// is/ profitable to interchange to enable inner loop parallelism.
// If there are no dependences, interchanging will not improve anything.
return std::optional<bool>(!DepMatrix.empty());
1158}

1160bool LoopInterchangeProfitability::isProfitable(
  const Loop *InnerLoop, const Loop *OuterLoop, unsigned InnerLoopId,
  unsigned OuterLoopId, CharMatrix &DepMatrix,
  const DenseMap<const Loop *, unsigned> &CostMap,
  std::unique_ptr<CacheCost> &CC) {
// isProfitable() is structured to avoid endless loop interchange.
// If loop cache analysis could decide the profitability then,
// profitability check will stop and return the analysis result.
// If cache analysis failed to analyze the loopnest (e.g.,
// due to delinearization issues) then only check whether it is
// profitable for InstrOrderCost. Likewise, if InstrOrderCost failed to
// analysis the profitability then only, isProfitableForVectorization
// will decide.
std::optional<bool> shouldInterchange =
    isProfitablePerLoopCacheAnalysis(CostMap, CC);
if (!shouldInterchange.has_value()) {
  shouldInterchange = isProfitablePerInstrOrderCost();
  if (!shouldInterchange.has_value())
    shouldInterchange =
        isProfitableForVectorization(InnerLoopId, OuterLoopId, DepMatrix);
}
if (!shouldInterchange.has_value()) {
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "InterchangeNotProfitable",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Insufficient information to calculate the cost of loop for "
              "interchange.";
  });
  return false;
} else if (!shouldInterchange.value()) {
  ORE->emit([&]() {
    return OptimizationRemarkMissed(DEBUG_TYPE"loop-interchange", "InterchangeNotProfitable",
                                    InnerLoop->getStartLoc(),
                                    InnerLoop->getHeader())
           << "Interchanging loops is not considered to improve cache "
              "locality nor vectorization.";
  });
  return false;
}
return true;
1201}

1203void LoopInterchangeTransform::removeChildLoop(Loop *OuterLoop,
                                             Loop *InnerLoop) {
for (Loop *L : *OuterLoop)
  if (L == InnerLoop) {
    OuterLoop->removeChildLoop(L);
    return;
  }
llvm_unreachable("Couldn't find loop")::llvm::llvm_unreachable_internal("Couldn't find loop", "llvm/lib/Transforms/Scalar/LoopInterchange.cpp"
, 1210);
1211}

1213/// Update LoopInfo, after interchanging. NewInner and NewOuter refer to the
1214/// new inner and outer loop after interchanging: NewInner is the original
1215/// outer loop and NewOuter is the original inner loop.
1216///
1217/// Before interchanging, we have the following structure
1218/// Outer preheader
1219//  Outer header
1220//    Inner preheader
1221//    Inner header
1222//      Inner body
1223//      Inner latch
1224//   outer bbs
1225//   Outer latch
1226//
1227// After interchanging:
1228// Inner preheader
1229// Inner header
1230//   Outer preheader
1231//   Outer header
1232//     Inner body
1233//     outer bbs
1234//     Outer latch
1235//   Inner latch
1236void LoopInterchangeTransform::restructureLoops(
  Loop *NewInner, Loop *NewOuter, BasicBlock *OrigInnerPreHeader,
  BasicBlock *OrigOuterPreHeader) {
Loop *OuterLoopParent = OuterLoop->getParentLoop();
// The original inner loop preheader moves from the new inner loop to
// the parent loop, if there is one.
NewInner->removeBlockFromLoop(OrigInnerPreHeader);
LI->changeLoopFor(OrigInnerPreHeader, OuterLoopParent);

// Switch the loop levels.
if (OuterLoopParent) {
  // Remove the loop from its parent loop.
  removeChildLoop(OuterLoopParent, NewInner);
  removeChildLoop(NewInner, NewOuter);
  OuterLoopParent->addChildLoop(NewOuter);
} else {
  removeChildLoop(NewInner, NewOuter);
  LI->changeTopLevelLoop(NewInner, NewOuter);
}
while (!NewOuter->isInnermost())
  NewInner->addChildLoop(NewOuter->removeChildLoop(NewOuter->begin()));
NewOuter->addChildLoop(NewInner);

// BBs from the original inner loop.
SmallVector<BasicBlock *, 8> OrigInnerBBs(NewOuter->blocks());

// Add BBs from the original outer loop to the original inner loop (excluding
// BBs already in inner loop)
for (BasicBlock *BB : NewInner->blocks())
  if (LI->getLoopFor(BB) == NewInner)
    NewOuter->addBlockEntry(BB);

// Now remove inner loop header and latch from the new inner loop and move
// other BBs (the loop body) to the new inner loop.
BasicBlock *OuterHeader = NewOuter->getHeader();
BasicBlock *OuterLatch = NewOuter->getLoopLatch();
for (BasicBlock *BB : OrigInnerBBs) {
  // Nothing will change for BBs in child loops.
  if (LI->getLoopFor(BB) != NewOuter)
    continue;
  // Remove the new outer loop header and latch from the new inner loop.
  if (BB == OuterHeader || BB == OuterLatch)
    NewInner->removeBlockFromLoop(BB);
  else
    LI->changeLoopFor(BB, NewInner);
}

// The preheader of the original outer loop becomes part of the new
// outer loop.
NewOuter->addBlockEntry(OrigOuterPreHeader);
LI->changeLoopFor(OrigOuterPreHeader, NewOuter);

// Tell SE that we move the loops around.
SE->forgetLoop(NewOuter);
1290}

1292bool LoopInterchangeTransform::transform() {
bool Transformed = false;

if (InnerLoop->getSubLoops().empty()) {
  BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
  LLVM_DEBUG(dbgs() << "Splitting the inner loop latch\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Splitting the inner loop latch\n"
; } } while (false);
  auto &InductionPHIs = LIL.getInnerLoopInductions();
  if (InductionPHIs.empty()) {
    LLVM_DEBUG(dbgs() << "Failed to find the point to split loop latch \n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Failed to find the point to split loop latch \n"
; } } while (false);
    return false;
  }

  SmallVector<Instruction *, 8> InnerIndexVarList;
  for (PHINode *CurInductionPHI : InductionPHIs) {
    if (CurInductionPHI->getIncomingBlock(0) == InnerLoopPreHeader)
      InnerIndexVarList.push_back(
          dyn_cast<Instruction>(CurInductionPHI->getIncomingValue(1)));
    else
      InnerIndexVarList.push_back(
          dyn_cast<Instruction>(CurInductionPHI->getIncomingValue(0)));
  }

  // Create a new latch block for the inner loop. We split at the
  // current latch's terminator and then move the condition and all
  // operands that are not either loop-invariant or the induction PHI into the
  // new latch block.
  BasicBlock *NewLatch =
      SplitBlock(InnerLoop->getLoopLatch(),
                 InnerLoop->getLoopLatch()->getTerminator(), DT, LI);

  SmallSetVector<Instruction *, 4> WorkList;
  unsigned i = 0;
  auto MoveInstructions = [&i, &WorkList, this, &InductionPHIs, NewLatch]() {
    for (; i < WorkList.size(); i++) {
      // Duplicate instruction and move it the new latch. Update uses that
      // have been moved.
      Instruction *NewI = WorkList[i]->clone();
      NewI->insertBefore(NewLatch->getFirstNonPHI());
      assert(!NewI->mayHaveSideEffects() &&(static_cast <bool> (!NewI->mayHaveSideEffects() &&
 "Moving instructions with side-effects may change behavior of "
 "the loop nest!") ? void (0) : __assert_fail ("!NewI->mayHaveSideEffects() && \"Moving instructions with side-effects may change behavior of \" \"the loop nest!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1332, __extension__
 __PRETTY_FUNCTION__))
             "Moving instructions with side-effects may change behavior of "(static_cast <bool> (!NewI->mayHaveSideEffects() &&
 "Moving instructions with side-effects may change behavior of "
 "the loop nest!") ? void (0) : __assert_fail ("!NewI->mayHaveSideEffects() && \"Moving instructions with side-effects may change behavior of \" \"the loop nest!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1332, __extension__
 __PRETTY_FUNCTION__))
             "the loop nest!")(static_cast <bool> (!NewI->mayHaveSideEffects() &&
 "Moving instructions with side-effects may change behavior of "
 "the loop nest!") ? void (0) : __assert_fail ("!NewI->mayHaveSideEffects() && \"Moving instructions with side-effects may change behavior of \" \"the loop nest!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1332, __extension__
 __PRETTY_FUNCTION__));
      for (Use &U : llvm::make_early_inc_range(WorkList[i]->uses())) {
        Instruction *UserI = cast<Instruction>(U.getUser());
        if (!InnerLoop->contains(UserI->getParent()) ||
            UserI->getParent() == NewLatch ||
            llvm::is_contained(InductionPHIs, UserI))
          U.set(NewI);
      }
      // Add operands of moved instruction to the worklist, except if they are
      // outside the inner loop or are the induction PHI.
      for (Value *Op : WorkList[i]->operands()) {
        Instruction *OpI = dyn_cast<Instruction>(Op);
        if (!OpI ||
            this->LI->getLoopFor(OpI->getParent()) != this->InnerLoop ||
            llvm::is_contained(InductionPHIs, OpI))
          continue;
        WorkList.insert(OpI);
      }
    }
  };

  // FIXME: Should we interchange when we have a constant condition?
  Instruction *CondI = dyn_cast<Instruction>(
      cast<BranchInst>(InnerLoop->getLoopLatch()->getTerminator())
          ->getCondition());
  if (CondI)
    WorkList.insert(CondI);
  MoveInstructions();
  for (Instruction *InnerIndexVar : InnerIndexVarList)
    WorkList.insert(cast<Instruction>(InnerIndexVar));
  MoveInstructions();
}

// Ensure the inner loop phi nodes have a separate basic block.
BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
if (InnerLoopHeader->getFirstNonPHI() != InnerLoopHeader->getTerminator()) {
  SplitBlock(InnerLoopHeader, InnerLoopHeader->getFirstNonPHI(), DT, LI);
  LLVM_DEBUG(dbgs() << "splitting InnerLoopHeader done\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "splitting InnerLoopHeader done\n"
; } } while (false);
}

// Instructions in the original inner loop preheader may depend on values
// defined in the outer loop header. Move them there, because the original
// inner loop preheader will become the entry into the interchanged loop nest.
// Currently we move all instructions and rely on LICM to move invariant
// instructions outside the loop nest.
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
if (InnerLoopPreHeader != OuterLoopHeader) {
  SmallPtrSet<Instruction *, 4> NeedsMoving;
  for (Instruction &I :
       make_early_inc_range(make_range(InnerLoopPreHeader->begin(),
                                       std::prev(InnerLoopPreHeader->end()))))
    I.moveBefore(OuterLoopHeader->getTerminator());
}

Transformed |= adjustLoopLinks();
if (!Transformed) {
  LLVM_DEBUG(dbgs() << "adjustLoopLinks failed\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "adjustLoopLinks failed\n"
; } } while (false);
  return false;
}

return true;
1394}

1396/// \brief Move all instructions except the terminator from FromBB right before
1397/// InsertBefore
1398static void moveBBContents(BasicBlock *FromBB, Instruction *InsertBefore) {
BasicBlock *ToBB = InsertBefore->getParent();

ToBB->splice(InsertBefore->getIterator(), FromBB, FromBB->begin(),
             FromBB->getTerminator()->getIterator());
1403}

1405/// Swap instructions between \p BB1 and \p BB2 but keep terminators intact.
1406static void swapBBContents(BasicBlock *BB1, BasicBlock *BB2) {
// Save all non-terminator instructions of BB1 into TempInstrs and unlink them
// from BB1 afterwards.
auto Iter = map_range(*BB1, [](Instruction &I) { return &I; });
SmallVector<Instruction *, 4> TempInstrs(Iter.begin(), std::prev(Iter.end()));
for (Instruction *I : TempInstrs)
  I->removeFromParent();

// Move instructions from BB2 to BB1.
moveBBContents(BB2, BB1->getTerminator());

// Move instructions from TempInstrs to BB2.
for (Instruction *I : TempInstrs)
  I->insertBefore(BB2->getTerminator());
1420}

1422// Update BI to jump to NewBB instead of OldBB. Records updates to the
1423// dominator tree in DTUpdates. If \p MustUpdateOnce is true, assert that
1424// \p OldBB  is exactly once in BI's successor list.
1425static void updateSuccessor(BranchInst *BI, BasicBlock *OldBB,
                          BasicBlock *NewBB,
                          std::vector<DominatorTree::UpdateType> &DTUpdates,
                          bool MustUpdateOnce = true) {
assert((!MustUpdateOnce ||(static_cast <bool> ((!MustUpdateOnce || llvm::count_if
(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB
; }) == 1) && "BI must jump to OldBB exactly once.") ?
 void (0) : __assert_fail ("(!MustUpdateOnce || llvm::count_if(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB; }) == 1) && \"BI must jump to OldBB exactly once.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1433, __extension__
 __PRETTY_FUNCTION__))
        llvm::count_if(successors(BI),(static_cast <bool> ((!MustUpdateOnce || llvm::count_if
(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB
; }) == 1) && "BI must jump to OldBB exactly once.") ?
 void (0) : __assert_fail ("(!MustUpdateOnce || llvm::count_if(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB; }) == 1) && \"BI must jump to OldBB exactly once.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1433, __extension__
 __PRETTY_FUNCTION__))
                       [OldBB](BasicBlock *BB) {(static_cast <bool> ((!MustUpdateOnce || llvm::count_if
(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB
; }) == 1) && "BI must jump to OldBB exactly once.") ?
 void (0) : __assert_fail ("(!MustUpdateOnce || llvm::count_if(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB; }) == 1) && \"BI must jump to OldBB exactly once.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1433, __extension__
 __PRETTY_FUNCTION__))
                         return BB == OldBB;(static_cast <bool> ((!MustUpdateOnce || llvm::count_if
(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB
; }) == 1) && "BI must jump to OldBB exactly once.") ?
 void (0) : __assert_fail ("(!MustUpdateOnce || llvm::count_if(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB; }) == 1) && \"BI must jump to OldBB exactly once.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1433, __extension__
 __PRETTY_FUNCTION__))
                       }) == 1) && "BI must jump to OldBB exactly once.")(static_cast <bool> ((!MustUpdateOnce || llvm::count_if
(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB
; }) == 1) && "BI must jump to OldBB exactly once.") ?
 void (0) : __assert_fail ("(!MustUpdateOnce || llvm::count_if(successors(BI), [OldBB](BasicBlock *BB) { return BB == OldBB; }) == 1) && \"BI must jump to OldBB exactly once.\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1433, __extension__
 __PRETTY_FUNCTION__));
bool Changed = false;
for (Use &Op : BI->operands())
  if (Op == OldBB) {
    Op.set(NewBB);
    Changed = true;
  }

if (Changed) {
  DTUpdates.push_back(
      {DominatorTree::UpdateKind::Insert, BI->getParent(), NewBB});
  DTUpdates.push_back(
      {DominatorTree::UpdateKind::Delete, BI->getParent(), OldBB});
}
assert(Changed && "Expected a successor to be updated")(static_cast <bool> (Changed && "Expected a successor to be updated"
) ? void (0) : __assert_fail ("Changed && \"Expected a successor to be updated\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1447, __extension__
 __PRETTY_FUNCTION__));
1448}

1450// Move Lcssa PHIs to the right place.
1451static void moveLCSSAPhis(BasicBlock *InnerExit, BasicBlock *InnerHeader,
                        BasicBlock *InnerLatch, BasicBlock *OuterHeader,
                        BasicBlock *OuterLatch, BasicBlock *OuterExit,
                        Loop *InnerLoop, LoopInfo *LI) {

// Deal with LCSSA PHI nodes in the exit block of the inner loop, that are
// defined either in the header or latch. Those blocks will become header and
// latch of the new outer loop, and the only possible users can PHI nodes
// in the exit block of the loop nest or the outer loop header (reduction
// PHIs, in that case, the incoming value must be defined in the inner loop
// header). We can just substitute the user with the incoming value and remove
// the PHI.
for (PHINode &P : make_early_inc_range(InnerExit->phis())) {
  assert(P.getNumIncomingValues() == 1 &&(static_cast <bool> (P.getNumIncomingValues() == 1 &&
 "Only loops with a single exit are supported!") ? void (0) :
 __assert_fail ("P.getNumIncomingValues() == 1 && \"Only loops with a single exit are supported!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1465, __extension__
 __PRETTY_FUNCTION__))
         "Only loops with a single exit are supported!")(static_cast <bool> (P.getNumIncomingValues() == 1 &&
 "Only loops with a single exit are supported!") ? void (0) :
 __assert_fail ("P.getNumIncomingValues() == 1 && \"Only loops with a single exit are supported!\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1465, __extension__
 __PRETTY_FUNCTION__));

  // Incoming values are guaranteed be instructions currently.
  auto IncI = cast<Instruction>(P.getIncomingValueForBlock(InnerLatch));
  // In case of multi-level nested loops, follow LCSSA to find the incoming
  // value defined from the innermost loop.
  auto IncIInnerMost = cast<Instruction>(followLCSSA(IncI));
  // Skip phis with incoming values from the inner loop body, excluding the
  // header and latch.
  if (IncIInnerMost->getParent() != InnerLatch &&
      IncIInnerMost->getParent() != InnerHeader)
    continue;

  assert(all_of(P.users(),(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
                [OuterHeader, OuterExit, IncI, InnerHeader](User *U) {(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
                  return (cast<PHINode>(U)->getParent() == OuterHeader &&(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
                          IncI->getParent() == InnerHeader) ||(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
                         cast<PHINode>(U)->getParent() == OuterExit;(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
                }) &&(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
         "Can only replace phis iff the uses are in the loop nest exit or "(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
         "the incoming value is defined in the inner header (it will "(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__))
         "dominate all loop blocks after interchanging)")(static_cast <bool> (all_of(P.users(), [OuterHeader, OuterExit
, IncI, InnerHeader](User *U) { return (cast<PHINode>(U
)->getParent() == OuterHeader && IncI->getParent
() == InnerHeader) || cast<PHINode>(U)->getParent() ==
 OuterExit; }) && "Can only replace phis iff the uses are in the loop nest exit or "
 "the incoming value is defined in the inner header (it will "
 "dominate all loop blocks after interchanging)") ? void (0) :
 __assert_fail ("all_of(P.users(), [OuterHeader, OuterExit, IncI, InnerHeader](User *U) { return (cast<PHINode>(U)->getParent() == OuterHeader && IncI->getParent() == InnerHeader) || cast<PHINode>(U)->getParent() == OuterExit; }) && \"Can only replace phis iff the uses are in the loop nest exit or \" \"the incoming value is defined in the inner header (it will \" \"dominate all loop blocks after interchanging)\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1486, __extension__
 __PRETTY_FUNCTION__));
  P.replaceAllUsesWith(IncI);
  P.eraseFromParent();
}

SmallVector<PHINode *, 8> LcssaInnerExit;
for (PHINode &P : InnerExit->phis())
  LcssaInnerExit.push_back(&P);

SmallVector<PHINode *, 8> LcssaInnerLatch;
for (PHINode &P : InnerLatch->phis())
  LcssaInnerLatch.push_back(&P);

// Lcssa PHIs for values used outside the inner loop are in InnerExit.
// If a PHI node has users outside of InnerExit, it has a use outside the
// interchanged loop and we have to preserve it. We move these to
// InnerLatch, which will become the new exit block for the innermost
// loop after interchanging.
for (PHINode *P : LcssaInnerExit)
1
Assuming '__begin1' is equal to '__end1'→
  P->moveBefore(InnerLatch->getFirstNonPHI());

// If the inner loop latch contains LCSSA PHIs, those come from a child loop
// and we have to move them to the new inner latch.
for (PHINode *P : LcssaInnerLatch)
2
←
Assuming '__begin1' is equal to '__end1'→
  P->moveBefore(InnerExit->getFirstNonPHI());

// Deal with LCSSA PHI nodes in the loop nest exit block. For PHIs that have
// incoming values defined in the outer loop, we have to add a new PHI
// in the inner loop latch, which became the exit block of the outer loop,
// after interchanging.
if (OuterExit) {
3
←
Assuming 'OuterExit' is non-null→
4
←
Taking true branch→
  for (PHINode &P : OuterExit->phis()) {
    if (P.getNumIncomingValues() != 1)
5
←
Assuming the condition is false→
6
←
Taking false branch→
      continue;
    // Skip Phis with incoming values defined in the inner loop. Those should
    // already have been updated.
    auto I = dyn_cast<Instruction>(P.getIncomingValue(0));
7
←
Assuming the object is a 'CastReturnType'→
    if (!I7.1
'I' is non-null
 || LI->getLoopFor(I->getParent()) == InnerLoop)
8
←
Assuming the condition is false→
9
←
Taking false branch→
      continue;

    PHINode *NewPhi = dyn_cast<PHINode>(P.clone());
10
←
Assuming the object is not a 'CastReturnType'→
11
←
'NewPhi' initialized to a null pointer value→
    NewPhi->setIncomingValue(0, P.getIncomingValue(0));
12
←
Called C++ object pointer is null
    NewPhi->setIncomingBlock(0, OuterLatch);
    // We might have incoming edges from other BBs, i.e., the original outer
    // header.
    for (auto *Pred : predecessors(InnerLatch)) {
      if (Pred == OuterLatch)
        continue;
      NewPhi->addIncoming(P.getIncomingValue(0), Pred);
    }
    NewPhi->insertBefore(InnerLatch->getFirstNonPHI());
    P.setIncomingValue(0, NewPhi);
  }
}

// Now adjust the incoming blocks for the LCSSA PHIs.
// For PHIs moved from Inner's exit block, we need to replace Inner's latch
// with the new latch.
InnerLatch->replacePhiUsesWith(InnerLatch, OuterLatch);
1545}

1547bool LoopInterchangeTransform::adjustLoopBranches() {
LLVM_DEBUG(dbgs() << "adjustLoopBranches called\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "adjustLoopBranches called\n"
; } } while (false);
std::vector<DominatorTree::UpdateType> DTUpdates;

BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();

assert(OuterLoopPreHeader != OuterLoop->getHeader() &&(static_cast <bool> (OuterLoopPreHeader != OuterLoop->
getHeader() && InnerLoopPreHeader != InnerLoop->getHeader
() && OuterLoopPreHeader && InnerLoopPreHeader
 && "Guaranteed by loop-simplify form") ? void (0) : __assert_fail
 ("OuterLoopPreHeader != OuterLoop->getHeader() && InnerLoopPreHeader != InnerLoop->getHeader() && OuterLoopPreHeader && InnerLoopPreHeader && \"Guaranteed by loop-simplify form\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1556, __extension__
 __PRETTY_FUNCTION__))
       InnerLoopPreHeader != InnerLoop->getHeader() && OuterLoopPreHeader &&(static_cast <bool> (OuterLoopPreHeader != OuterLoop->
getHeader() && InnerLoopPreHeader != InnerLoop->getHeader
() && OuterLoopPreHeader && InnerLoopPreHeader
 && "Guaranteed by loop-simplify form") ? void (0) : __assert_fail
 ("OuterLoopPreHeader != OuterLoop->getHeader() && InnerLoopPreHeader != InnerLoop->getHeader() && OuterLoopPreHeader && InnerLoopPreHeader && \"Guaranteed by loop-simplify form\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1556, __extension__
 __PRETTY_FUNCTION__))
       InnerLoopPreHeader && "Guaranteed by loop-simplify form")(static_cast <bool> (OuterLoopPreHeader != OuterLoop->
getHeader() && InnerLoopPreHeader != InnerLoop->getHeader
() && OuterLoopPreHeader && InnerLoopPreHeader
 && "Guaranteed by loop-simplify form") ? void (0) : __assert_fail
 ("OuterLoopPreHeader != OuterLoop->getHeader() && InnerLoopPreHeader != InnerLoop->getHeader() && OuterLoopPreHeader && InnerLoopPreHeader && \"Guaranteed by loop-simplify form\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1556, __extension__
 __PRETTY_FUNCTION__));
// Ensure that both preheaders do not contain PHI nodes and have single
// predecessors. This allows us to move them easily. We use
// InsertPreHeaderForLoop to create an 'extra' preheader, if the existing
// preheaders do not satisfy those conditions.
if (isa<PHINode>(OuterLoopPreHeader->begin()) ||
    !OuterLoopPreHeader->getUniquePredecessor())
  OuterLoopPreHeader =
      InsertPreheaderForLoop(OuterLoop, DT, LI, nullptr, true);
if (InnerLoopPreHeader == OuterLoop->getHeader())
  InnerLoopPreHeader =
      InsertPreheaderForLoop(InnerLoop, DT, LI, nullptr, true);

// Adjust the loop preheader
BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
BasicBlock *OuterLoopPredecessor = OuterLoopPreHeader->getUniquePredecessor();
BasicBlock *InnerLoopLatchPredecessor =
    InnerLoopLatch->getUniquePredecessor();
BasicBlock *InnerLoopLatchSuccessor;
BasicBlock *OuterLoopLatchSuccessor;

BranchInst *OuterLoopLatchBI =
    dyn_cast<BranchInst>(OuterLoopLatch->getTerminator());
BranchInst *InnerLoopLatchBI =
    dyn_cast<BranchInst>(InnerLoopLatch->getTerminator());
BranchInst *OuterLoopHeaderBI =
    dyn_cast<BranchInst>(OuterLoopHeader->getTerminator());
BranchInst *InnerLoopHeaderBI =
    dyn_cast<BranchInst>(InnerLoopHeader->getTerminator());

if (!OuterLoopPredecessor || !InnerLoopLatchPredecessor ||
    !OuterLoopLatchBI || !InnerLoopLatchBI || !OuterLoopHeaderBI ||
    !InnerLoopHeaderBI)
  return false;

BranchInst *InnerLoopLatchPredecessorBI =
    dyn_cast<BranchInst>(InnerLoopLatchPredecessor->getTerminator());
BranchInst *OuterLoopPredecessorBI =
    dyn_cast<BranchInst>(OuterLoopPredecessor->getTerminator());

if (!OuterLoopPredecessorBI || !InnerLoopLatchPredecessorBI)
  return false;
BasicBlock *InnerLoopHeaderSuccessor = InnerLoopHeader->getUniqueSuccessor();
if (!InnerLoopHeaderSuccessor)
  return false;

// Adjust Loop Preheader and headers.
// The branches in the outer loop predecessor and the outer loop header can
// be unconditional branches or conditional branches with duplicates. Consider
// this when updating the successors.
updateSuccessor(OuterLoopPredecessorBI, OuterLoopPreHeader,
                InnerLoopPreHeader, DTUpdates, /*MustUpdateOnce=*/false);
// The outer loop header might or might not branch to the outer latch.
// We are guaranteed to branch to the inner loop preheader.
if (llvm::is_contained(OuterLoopHeaderBI->successors(), OuterLoopLatch)) {
  // In this case the outerLoopHeader should branch to the InnerLoopLatch.
  updateSuccessor(OuterLoopHeaderBI, OuterLoopLatch, InnerLoopLatch,
                  DTUpdates,
                  /*MustUpdateOnce=*/false);
}
updateSuccessor(OuterLoopHeaderBI, InnerLoopPreHeader,
                InnerLoopHeaderSuccessor, DTUpdates,
                /*MustUpdateOnce=*/false);

// Adjust reduction PHI's now that the incoming block has changed.
InnerLoopHeaderSuccessor->replacePhiUsesWith(InnerLoopHeader,
                                             OuterLoopHeader);

updateSuccessor(InnerLoopHeaderBI, InnerLoopHeaderSuccessor,
                OuterLoopPreHeader, DTUpdates);

// -------------Adjust loop latches-----------
if (InnerLoopLatchBI->getSuccessor(0) == InnerLoopHeader)
  InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(1);
else
  InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(0);

updateSuccessor(InnerLoopLatchPredecessorBI, InnerLoopLatch,
                InnerLoopLatchSuccessor, DTUpdates);

if (OuterLoopLatchBI->getSuccessor(0) == OuterLoopHeader)
  OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(1);
else
  OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(0);

updateSuccessor(InnerLoopLatchBI, InnerLoopLatchSuccessor,
                OuterLoopLatchSuccessor, DTUpdates);
updateSuccessor(OuterLoopLatchBI, OuterLoopLatchSuccessor, InnerLoopLatch,
                DTUpdates);

DT->applyUpdates(DTUpdates);
restructureLoops(OuterLoop, InnerLoop, InnerLoopPreHeader,
                 OuterLoopPreHeader);

moveLCSSAPhis(InnerLoopLatchSuccessor, InnerLoopHeader, InnerLoopLatch,
              OuterLoopHeader, OuterLoopLatch, InnerLoop->getExitBlock(),
              InnerLoop, LI);
// For PHIs in the exit block of the outer loop, outer's latch has been
// replaced by Inners'.
OuterLoopLatchSuccessor->replacePhiUsesWith(OuterLoopLatch, InnerLoopLatch);

auto &OuterInnerReductions = LIL.getOuterInnerReductions();
// Now update the reduction PHIs in the inner and outer loop headers.
SmallVector<PHINode *, 4> InnerLoopPHIs, OuterLoopPHIs;
for (PHINode &PHI : InnerLoopHeader->phis())
  if (OuterInnerReductions.contains(&PHI))
    InnerLoopPHIs.push_back(&PHI);

for (PHINode &PHI : OuterLoopHeader->phis())
  if (OuterInnerReductions.contains(&PHI))
    OuterLoopPHIs.push_back(&PHI);

// Now move the remaining reduction PHIs from outer to inner loop header and
// vice versa. The PHI nodes must be part of a reduction across the inner and
// outer loop and all the remains to do is and updating the incoming blocks.
for (PHINode *PHI : OuterLoopPHIs) {
  LLVM_DEBUG(dbgs() << "Outer loop reduction PHIs:\n"; PHI->dump();)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Outer loop reduction PHIs:\n"
; PHI->dump();; } } while (false);
  PHI->moveBefore(InnerLoopHeader->getFirstNonPHI());
  assert(OuterInnerReductions.count(PHI) && "Expected a reduction PHI node")(static_cast <bool> (OuterInnerReductions.count(PHI) &&
 "Expected a reduction PHI node") ? void (0) : __assert_fail (
"OuterInnerReductions.count(PHI) && \"Expected a reduction PHI node\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1677, __extension__
 __PRETTY_FUNCTION__));
}
for (PHINode *PHI : InnerLoopPHIs) {
  LLVM_DEBUG(dbgs() << "Inner loop reduction PHIs:\n"; PHI->dump();)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-interchange")) { dbgs() << "Inner loop reduction PHIs:\n"
; PHI->dump();; } } while (false);
  PHI->moveBefore(OuterLoopHeader->getFirstNonPHI());
  assert(OuterInnerReductions.count(PHI) && "Expected a reduction PHI node")(static_cast <bool> (OuterInnerReductions.count(PHI) &&
 "Expected a reduction PHI node") ? void (0) : __assert_fail (
"OuterInnerReductions.count(PHI) && \"Expected a reduction PHI node\""
, "llvm/lib/Transforms/Scalar/LoopInterchange.cpp", 1682, __extension__
 __PRETTY_FUNCTION__));
}

// Update the incoming blocks for moved PHI nodes.
OuterLoopHeader->replacePhiUsesWith(InnerLoopPreHeader, OuterLoopPreHeader);
OuterLoopHeader->replacePhiUsesWith(InnerLoopLatch, OuterLoopLatch);
InnerLoopHeader->replacePhiUsesWith(OuterLoopPreHeader, InnerLoopPreHeader);
InnerLoopHeader->replacePhiUsesWith(OuterLoopLatch, InnerLoopLatch);

// Values defined in the outer loop header could be used in the inner loop
// latch. In that case, we need to create LCSSA phis for them, because after
// interchanging they will be defined in the new inner loop and used in the
// new outer loop.
IRBuilder<> Builder(OuterLoopHeader->getContext());
SmallVector<Instruction *, 4> MayNeedLCSSAPhis;
for (Instruction &I :
     make_range(OuterLoopHeader->begin(), std::prev(OuterLoopHeader->end())))
  MayNeedLCSSAPhis.push_back(&I);
formLCSSAForInstructions(MayNeedLCSSAPhis, *DT, *LI, SE, Builder);

return true;
1703}

1705bool LoopInterchangeTransform::adjustLoopLinks() {
// Adjust all branches in the inner and outer loop.
bool Changed = adjustLoopBranches();
if (Changed) {
  // We have interchanged the preheaders so we need to interchange the data in
  // the preheaders as well. This is because the content of the inner
  // preheader was previously executed inside the outer loop.
  BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
  BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
  swapBBContents(OuterLoopPreHeader, InnerLoopPreHeader);
}
return Changed;
1717}

1719PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
                                         LoopAnalysisManager &AM,
                                         LoopStandardAnalysisResults &AR,
                                         LPMUpdater &U) {
Function &F = *LN.getParent();

DependenceInfo DI(&F, &AR.AA, &AR.SE, &AR.LI);
std::unique_ptr<CacheCost> CC =
    CacheCost::getCacheCost(LN.getOutermostLoop(), AR, DI);
OptimizationRemarkEmitter ORE(&F);
if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, CC, &ORE).run(LN))
  return PreservedAnalyses::all();
U.markLoopNestChanged(true);
return getLoopPassPreservedAnalyses();
1733}