InstCombineInternal.h

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//===- InstCombineInternal.h - InstCombine pass internals -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
///
/// This file provides internal interfaces used to implement the InstCombine.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H
#define LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H
 
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/ProfDataUtils.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/KnownFPClass.h"
#include "llvm/Transforms/InstCombine/InstCombiner.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cassert>
 
#define DEBUG_TYPE "instcombine"
#include "llvm/Transforms/Utils/InstructionWorklist.h"
 
// As a default, let's assume that we want to be aggressive,
// and attempt to traverse with no limits in attempt to sink negation.
static constexpr unsigned NegatorDefaultMaxDepth = ~0U;
 
// Let's guesstimate that most often we will end up visiting/producing
// fairly small number of new instructions.
static constexpr unsigned NegatorMaxNodesSSO = 16;
 
namespace llvm {
 
class AAResults;
class APInt;
class AssumptionCache;
class BlockFrequencyInfo;
class DataLayout;
class DominatorTree;
class GEPOperator;
class GlobalVariable;
class OptimizationRemarkEmitter;
class ProfileSummaryInfo;
class TargetLibraryInfo;
class User;
 
/// Enum to specify how shift operations should be evaluated in
/// canEvaluateShifted.
/// Lossy: Allows lossy transformations
/// Signed: Requires lossless transformation, using ashr to restore for shl,
///         or represents ashr handling for right shifts
/// Unsigned: Requires lossless transformation, using lshr to restore for shl,
///           or represents lshr handling for right shifts
enum class ShiftSemantics { Lossy, Signed, Unsigned };
 
class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
    : public InstCombiner,
      public InstVisitor<InstCombinerImpl, Instruction *> {
public:
  InstCombinerImpl(InstructionWorklist &Worklist, Function &F, AAResults *AA,
                   AssumptionCache &AC, TargetLibraryInfo &TLI,
                   TargetTransformInfo &TTI, DominatorTree &DT,
                   OptimizationRemarkEmitter &ORE, BlockFrequencyInfo *BFI,
                   BranchProbabilityInfo *BPI, ProfileSummaryInfo *PSI,
                   const DataLayout &DL,
                   ReversePostOrderTraversal<BasicBlock *> &RPOT)
      : InstCombiner(Worklist, F, AA, AC, TLI, TTI, DT, ORE, BFI, BPI, PSI, DL,
                     RPOT) {}
 
  ~InstCombinerImpl() override = default;
 
  /// Perform early cleanup and prepare the InstCombine worklist.
  bool prepareWorklist(Function &F);
 
  /// Run the combiner over the entire worklist until it is empty.
  ///
  /// \returns true if the IR is changed.
  bool run();
 
  // Visitation implementation - Implement instruction combining for different
  // instruction types.  The semantics are as follows:
  // Return Value:
  //    null        - No change was made
  //     I          - Change was made, I is still valid, I may be dead though
  //   otherwise    - Change was made, replace I with returned instruction
  //
  Instruction *visitFNeg(UnaryOperator &I);
  Instruction *visitAdd(BinaryOperator &I);
  Instruction *visitFAdd(BinaryOperator &I);
  Value *OptimizePointerDifference(
      Value *LHS, Value *RHS, Type *Ty, bool isNUW);
  Instruction *visitSub(BinaryOperator &I);
  Instruction *visitFSub(BinaryOperator &I);
  Instruction *visitMul(BinaryOperator &I);
  Instruction *foldPowiReassoc(BinaryOperator &I);
  Instruction *foldFMulReassoc(BinaryOperator &I);
  Instruction *visitFMul(BinaryOperator &I);
  Instruction *visitURem(BinaryOperator &I);
  Instruction *visitSRem(BinaryOperator &I);
  Instruction *visitFRem(BinaryOperator &I);
  bool simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I);
  Instruction *commonIDivRemTransforms(BinaryOperator &I);
  Instruction *commonIRemTransforms(BinaryOperator &I);
  Instruction *commonIDivTransforms(BinaryOperator &I);
  Instruction *visitUDiv(BinaryOperator &I);
  Instruction *visitSDiv(BinaryOperator &I);
  Instruction *visitFDiv(BinaryOperator &I);
  Value *simplifyRangeCheck(CmpPredicate PredL, Value *LHS0, Value *LHS1,
                            CmpPredicate PredR, Value *RHS0, Value *RHS1,
                            Instruction *CxtI, bool Inverted);
  Instruction *FoldOrOfLogicalAnds(Value *Op0, Value *Op1);
  Instruction *visitAnd(BinaryOperator &I);
  Instruction *visitOr(BinaryOperator &I);
  bool sinkNotIntoLogicalOp(Instruction &I);
  bool sinkNotIntoOtherHandOfLogicalOp(Instruction &I);
  Instruction *visitXor(BinaryOperator &I);
  Instruction *visitShl(BinaryOperator &I);
  Value *reassociateShiftAmtsOfTwoSameDirectionShifts(
      BinaryOperator *Sh0, const SimplifyQuery &SQ,
      bool AnalyzeForSignBitExtraction = false);
  Instruction *canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(
      BinaryOperator &I);
  Instruction *foldVariableSignZeroExtensionOfVariableHighBitExtract(
      BinaryOperator &OldAShr);
  Instruction *visitAShr(BinaryOperator &I);
  Instruction *visitLShr(BinaryOperator &I);
  Instruction *commonShiftTransforms(BinaryOperator &I);
  Instruction *visitFCmpInst(FCmpInst &I);
  CmpInst *canonicalizeICmpPredicate(CmpInst &I);
  Instruction *visitICmpInst(ICmpInst &I);
  Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1,
                                   BinaryOperator &I);
  Instruction *commonCastTransforms(CastInst &CI);
  Instruction *visitTrunc(TruncInst &CI);
  Instruction *visitZExt(ZExtInst &Zext);
  Instruction *visitSExt(SExtInst &Sext);
  Instruction *visitFPTrunc(FPTruncInst &CI);
  Instruction *visitFPExt(CastInst &CI);
  Instruction *visitFPToUI(FPToUIInst &FI);
  Instruction *visitFPToSI(FPToSIInst &FI);
  Instruction *visitUIToFP(CastInst &CI);
  Instruction *visitSIToFP(CastInst &CI);
  Instruction *visitPtrToInt(PtrToIntInst &CI);
  Instruction *visitPtrToAddr(PtrToAddrInst &CI);
  Instruction *visitIntToPtr(IntToPtrInst &CI);
  Instruction *visitBitCast(BitCastInst &CI);
  Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI);
  template <typename FPToIntTy> Instruction *foldItoFPtoI(FPToIntTy &FI);
  Instruction *visitSelectInst(SelectInst &SI);
  Instruction *foldShuffledIntrinsicOperands(IntrinsicInst *II);
  Value *foldReversedIntrinsicOperands(IntrinsicInst *II);
  Instruction *visitCallInst(CallInst &CI);
  Instruction *visitInvokeInst(InvokeInst &II);
  Instruction *visitCallBrInst(CallBrInst &CBI);
 
  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
  Instruction *visitPHINode(PHINode &PN);
  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
  Instruction *visitGEPOfGEP(GetElementPtrInst &GEP, GEPOperator *Src);
  Instruction *visitAllocaInst(AllocaInst &AI);
  Instruction *visitAllocSite(Instruction &FI);
  Instruction *visitFree(CallInst &FI, Value *FreedOp);
  Instruction *visitLoadInst(LoadInst &LI);
  Instruction *visitStoreInst(StoreInst &SI);
  Instruction *visitAtomicRMWInst(AtomicRMWInst &SI);
  Instruction *visitUncondBrInst(UncondBrInst &BI);
  Instruction *visitCondBrInst(CondBrInst &BI);
  Instruction *visitFenceInst(FenceInst &FI);
  Instruction *visitSwitchInst(SwitchInst &SI);
  Instruction *visitReturnInst(ReturnInst &RI);
  Instruction *visitUnreachableInst(UnreachableInst &I);
  Instruction *
  foldAggregateConstructionIntoAggregateReuse(InsertValueInst &OrigIVI);
  Instruction *visitInsertValueInst(InsertValueInst &IV);
  Instruction *visitInsertElementInst(InsertElementInst &IE);
  Instruction *visitExtractElementInst(ExtractElementInst &EI);
  Instruction *simplifyBinOpSplats(ShuffleVectorInst &SVI);
  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
  Instruction *visitExtractValueInst(ExtractValueInst &EV);
  Instruction *visitLandingPadInst(LandingPadInst &LI);
  Instruction *visitVAEndInst(VAEndInst &I);
  Value *pushFreezeToPreventPoisonFromPropagating(FreezeInst &FI);
  bool freezeOtherUses(FreezeInst &FI);
  Instruction *foldFreezeIntoRecurrence(FreezeInst &I, PHINode *PN);
  Instruction *visitFreeze(FreezeInst &I);
 
  /// Specify what to return for unhandled instructions.
  Instruction *visitInstruction(Instruction &I) { return nullptr; }
 
  /// True when DB dominates all uses of DI except UI.
  /// UI must be in the same block as DI.
  /// The routine checks that the DI parent and DB are different.
  bool dominatesAllUses(const Instruction *DI, const Instruction *UI,
                        const BasicBlock *DB) const;
 
  /// Try to replace select with select operand SIOpd in SI-ICmp sequence.
  bool replacedSelectWithOperand(SelectInst *SI, const ICmpInst *Icmp,
                                 const unsigned SIOpd);
 
  LoadInst *combineLoadToNewType(LoadInst &LI, Type *NewTy,
                                 const Twine &Suffix = "");
 
  /// Check if fmul \p MulVal, +0.0 will yield +0.0 (or signed zero is
  /// ignorable).
  bool fmulByZeroIsZero(Value *MulVal, FastMathFlags FMF,
                        const Instruction *CtxI) const;
 
  std::optional<std::pair<Intrinsic::ID, SmallVector<Value *, 3>>>
  convertOrOfShiftsToFunnelShift(Instruction &Or);
 
private:
  bool annotateAnyAllocSite(CallBase &Call, const TargetLibraryInfo *TLI);
  bool isDesirableIntType(unsigned BitWidth) const;
  bool shouldChangeType(unsigned FromBitWidth, unsigned ToBitWidth) const;
  bool shouldChangeType(Type *From, Type *To) const;
  Value *dyn_castNegVal(Value *V) const;
 
  /// Classify whether a cast is worth optimizing.
  ///
  /// This is a helper to decide whether the simplification of
  /// logic(cast(A), cast(B)) to cast(logic(A, B)) should be performed.
  ///
  /// \param CI The cast we are interested in.
  ///
  /// \return true if this cast actually results in any code being generated and
  /// if it cannot already be eliminated by some other transformation.
  bool shouldOptimizeCast(CastInst *CI);
 
  /// Try to optimize a sequence of instructions checking if an operation
  /// on LHS and RHS overflows.
  ///
  /// If this overflow check is done via one of the overflow check intrinsics,
  /// then CtxI has to be the call instruction calling that intrinsic.  If this
  /// overflow check is done by arithmetic followed by a compare, then CtxI has
  /// to be the arithmetic instruction.
  ///
  /// If a simplification is possible, stores the simplified result of the
  /// operation in OperationResult and result of the overflow check in
  /// OverflowResult, and return true.  If no simplification is possible,
  /// returns false.
  bool OptimizeOverflowCheck(Instruction::BinaryOps BinaryOp, bool IsSigned,
                             Value *LHS, Value *RHS,
                             Instruction &CtxI, Value *&OperationResult,
                             Constant *&OverflowResult);
 
  Instruction *visitCallBase(CallBase &Call);
  Instruction *tryOptimizeCall(CallInst *CI);
  bool transformConstExprCastCall(CallBase &Call);
  Instruction *transformCallThroughTrampoline(CallBase &Call,
                                              IntrinsicInst &Tramp);
 
  /// Try to optimize a call to the result of a ptrauth intrinsic, potentially
  /// into the ptrauth call bundle:
  /// - call(ptrauth.resign(p)), ["ptrauth"()] ->  call p, ["ptrauth"()]
  /// - call(ptrauth.sign(p)),   ["ptrauth"()] ->  call p
  /// as long as the key/discriminator are the same in sign and auth-bundle,
  /// and we don't change the key in the bundle (to a potentially-invalid key.)
  Instruction *foldPtrAuthIntrinsicCallee(CallBase &Call);
 
  /// Try to optimize a call to a ptrauth constant, into its ptrauth bundle:
  ///   call(ptrauth(f)), ["ptrauth"()] ->  call f
  /// as long as the key/discriminator are the same in constant and bundle.
  Instruction *foldPtrAuthConstantCallee(CallBase &Call);
 
  // Return (a, b) if (LHS, RHS) is known to be (a, b) or (b, a).
  // Otherwise, return std::nullopt
  // Currently it matches:
  // - LHS = (select c, a, b), RHS = (select c, b, a)
  // - LHS = (phi [a, BB0], [b, BB1]), RHS = (phi [b, BB0], [a, BB1])
  // - LHS = min(a, b), RHS = max(a, b)
  std::optional<std::pair<Value *, Value *>> matchSymmetricPair(Value *LHS,
                                                                Value *RHS);
 
  Value *simplifyMaskedLoad(IntrinsicInst &II);
  Instruction *simplifyMaskedStore(IntrinsicInst &II);
  Instruction *simplifyMaskedGather(IntrinsicInst &II);
  Instruction *simplifyMaskedScatter(IntrinsicInst &II);
 
  /// Transform (zext icmp) to bitwise / integer operations in order to
  /// eliminate it.
  ///
  /// \param ICI The icmp of the (zext icmp) pair we are interested in.
  /// \parem CI The zext of the (zext icmp) pair we are interested in.
  ///
  /// \return null if the transformation cannot be performed. If the
  /// transformation can be performed the new instruction that replaces the
  /// (zext icmp) pair will be returned.
  Instruction *transformZExtICmp(ICmpInst *Cmp, ZExtInst &Zext);
 
  Instruction *transformSExtICmp(ICmpInst *Cmp, SExtInst &Sext);
 
  bool willNotOverflowSignedAdd(const WithCache<const Value *> &LHS,
                                const WithCache<const Value *> &RHS,
                                const Instruction &CxtI) const {
    return computeOverflowForSignedAdd(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowUnsignedAdd(const WithCache<const Value *> &LHS,
                                  const WithCache<const Value *> &RHS,
                                  const Instruction &CxtI) const {
    return computeOverflowForUnsignedAdd(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowAdd(const Value *LHS, const Value *RHS,
                          const Instruction &CxtI, bool IsSigned) const {
    return IsSigned ? willNotOverflowSignedAdd(LHS, RHS, CxtI)
                    : willNotOverflowUnsignedAdd(LHS, RHS, CxtI);
  }
 
  bool willNotOverflowSignedSub(const Value *LHS, const Value *RHS,
                                const Instruction &CxtI) const {
    return computeOverflowForSignedSub(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowUnsignedSub(const Value *LHS, const Value *RHS,
                                  const Instruction &CxtI) const {
    return computeOverflowForUnsignedSub(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowSub(const Value *LHS, const Value *RHS,
                          const Instruction &CxtI, bool IsSigned) const {
    return IsSigned ? willNotOverflowSignedSub(LHS, RHS, CxtI)
                    : willNotOverflowUnsignedSub(LHS, RHS, CxtI);
  }
 
  bool willNotOverflowSignedMul(const Value *LHS, const Value *RHS,
                                const Instruction &CxtI) const {
    return computeOverflowForSignedMul(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowUnsignedMul(const Value *LHS, const Value *RHS,
                                  const Instruction &CxtI,
                                  bool IsNSW = false) const {
    return computeOverflowForUnsignedMul(LHS, RHS, &CxtI, IsNSW) ==
           OverflowResult::NeverOverflows;
  }
 
  bool willNotOverflowMul(const Value *LHS, const Value *RHS,
                          const Instruction &CxtI, bool IsSigned) const {
    return IsSigned ? willNotOverflowSignedMul(LHS, RHS, CxtI)
                    : willNotOverflowUnsignedMul(LHS, RHS, CxtI);
  }
 
  bool willNotOverflow(BinaryOperator::BinaryOps Opcode, const Value *LHS,
                       const Value *RHS, const Instruction &CxtI,
                       bool IsSigned) const {
    switch (Opcode) {
    case Instruction::Add: return willNotOverflowAdd(LHS, RHS, CxtI, IsSigned);
    case Instruction::Sub: return willNotOverflowSub(LHS, RHS, CxtI, IsSigned);
    case Instruction::Mul: return willNotOverflowMul(LHS, RHS, CxtI, IsSigned);
    default: llvm_unreachable("Unexpected opcode for overflow query");
    }
  }
 
  Value *EmitGEPOffset(GEPOperator *GEP, bool RewriteGEP = false);
  /// Emit sum of multiple GEP offsets. The GEPs are processed in reverse
  /// order.
  Value *EmitGEPOffsets(ArrayRef<GEPOperator *> GEPs, GEPNoWrapFlags NW,
                        Type *IdxTy, bool RewriteGEPs);
  Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
  Instruction *foldBitcastExtElt(ExtractElementInst &ExtElt);
  Instruction *foldCastedBitwiseLogic(BinaryOperator &I);
  Instruction *foldFBinOpOfIntCasts(BinaryOperator &I);
  // Should only be called by `foldFBinOpOfIntCasts`.
  Instruction *foldFBinOpOfIntCastsFromSign(
      BinaryOperator &BO, bool OpsFromSigned, std::array<Value *, 2> IntOps,
      Constant *Op1FpC, SmallVectorImpl<WithCache<const Value *>> &OpsKnown);
  Instruction *foldBinopOfSextBoolToSelect(BinaryOperator &I);
  Instruction *narrowBinOp(TruncInst &Trunc);
  Instruction *narrowMaskedBinOp(BinaryOperator &And);
  Instruction *narrowMathIfNoOverflow(BinaryOperator &I);
  Instruction *narrowFunnelShift(TruncInst &Trunc);
  Instruction *optimizeBitCastFromPhi(CastInst &CI, PHINode *PN);
  Instruction *matchSAddSubSat(IntrinsicInst &MinMax1);
  Instruction *foldNot(BinaryOperator &I);
  Instruction *foldBinOpOfDisplacedShifts(BinaryOperator &I);
 
  /// Determine if a pair of casts can be replaced by a single cast.
  ///
  /// \param CI1 The first of a pair of casts.
  /// \param CI2 The second of a pair of casts.
  ///
  /// \return 0 if the cast pair cannot be eliminated, otherwise returns an
  /// Instruction::CastOps value for a cast that can replace the pair, casting
  /// CI1->getSrcTy() to CI2->getDstTy().
  ///
  /// \see CastInst::isEliminableCastPair
  Instruction::CastOps isEliminableCastPair(const CastInst *CI1,
                                            const CastInst *CI2);
  Value *simplifyIntToPtrRoundTripCast(Value *Val);
 
  Value *foldAndOrOfICmps(Value *LHS, Value *RHS, Instruction &I, bool IsAnd,
                          bool IsLogical = false);
  Value *foldXorOfICmps(ICmpInst *LHS, ICmpInst *RHS, BinaryOperator &Xor);
 
  Value *foldEqOfParts(Value *Cmp0, Value *Cmp1, bool IsAnd);
 
  Value *foldAndOrOfICmpsUsingRanges(CmpPredicate PredL, Value *LHS0,
                                     Value *LHS1, bool LHSOneUse,
                                     CmpPredicate PredR, Value *RHS0,
                                     Value *RHS1, bool RHSOneUse, bool IsAnd);
 
  /// Optimize (fcmp)&(fcmp) or (fcmp)|(fcmp).
  /// NOTE: Unlike most of instcombine, this returns a Value which should
  /// already be inserted into the function.
  Value *foldLogicOfFCmps(FCmpInst *LHS, FCmpInst *RHS, bool IsAnd,
                          bool IsLogicalSelect = false);
 
  Instruction *foldLogicOfIsFPClass(BinaryOperator &Operator, Value *LHS,
                                    Value *RHS);
 
  Value *foldBooleanAndOr(Value *LHS, Value *RHS, Instruction &I, bool IsAnd,
                          bool IsLogical);
 
  Value *reassociateBooleanAndOr(Value *LHS, Value *X, Value *Y, Instruction &I,
                                 bool IsAnd, bool RHSIsLogical);
 
  Value *foldDisjointOr(Value *LHS, Value *RHS);
 
  Value *reassociateDisjointOr(Value *LHS, Value *RHS);
 
  Instruction *
  canonicalizeConditionalNegationViaMathToSelect(BinaryOperator &i);
 
  Value *matchSelectFromAndOr(Value *A, Value *B, Value *C, Value *D,
                              bool InvertFalseVal = false);
  Value *getSelectCondition(Value *A, Value *B, bool ABIsTheSame);
 
  bool canEvaluateShifted(Value *V, unsigned NumBits, bool IsLeftShift,
                          ShiftSemantics Semantics, Instruction *CxtI);
  Value *getShiftedValue(Value *V, unsigned NumBits, bool IsLeftShift,
                         ShiftSemantics Semantics);
 
  Instruction *foldLShrOverflowBit(BinaryOperator &I);
  Instruction *foldExtractOfOverflowIntrinsic(ExtractValueInst &EV);
  Instruction *foldIntrinsicWithOverflowCommon(IntrinsicInst *II);
  Instruction *foldIntrinsicIsFPClass(IntrinsicInst &II);
  Instruction *foldFPSignBitOps(BinaryOperator &I);
  Instruction *foldFDivConstantDivisor(BinaryOperator &I);
 
  // Optimize one of these forms:
  //   and i1 Op, SI / select i1 Op, i1 SI, i1 false (if IsAnd = true)
  //   or i1 Op, SI  / select i1 Op, i1 true, i1 SI  (if IsAnd = false)
  // into simplier select instruction using isImpliedCondition.
  Instruction *foldAndOrOfSelectUsingImpliedCond(Value *Op, SelectInst &SI,
                                                 bool IsAnd);
 
  Instruction *hoistFNegAboveFMulFDiv(Value *FNegOp, Instruction &FMFSource);
 
  /// Simplify \p V given that it is known to be non-null.
  /// Returns the simplified value if possible, otherwise returns nullptr.
  /// If \p HasDereferenceable is true, the simplification will not perform
  /// same object checks.
  Value *simplifyNonNullOperand(Value *V, bool HasDereferenceable,
                                unsigned Depth = 0);
 
  /// Create `select C, S1, S2`. Use only when the profile cannot be calculated
  /// from existing profile metadata: if the Function has profiles, this will
  /// set the profile of this select to "unknown".
  SelectInst *
  createSelectInstWithUnknownProfile(Value *C, Value *S1, Value *S2,
                                     const Twine &NameStr = "",
                                     InsertPosition InsertBefore = nullptr) {
    auto *Sel = SelectInst::Create(C, S1, S2, NameStr, InsertBefore, nullptr);
    setExplicitlyUnknownBranchWeightsIfProfiled(*Sel, DEBUG_TYPE, &F);
    return Sel;
  }
 
public:
  /// Create and insert the idiom we use to indicate a block is unreachable
  /// without having to rewrite the CFG from within InstCombine.
  void CreateNonTerminatorUnreachable(Instruction *InsertAt) {
    auto &Ctx = InsertAt->getContext();
    auto *SI = new StoreInst(ConstantInt::getTrue(Ctx),
                             PoisonValue::get(PointerType::getUnqual(Ctx)),
                             /*isVolatile*/ false, Align(1));
    InsertNewInstWith(SI, InsertAt->getIterator());
  }
 
  /// Combiner aware instruction erasure.
  ///
  /// When dealing with an instruction that has side effects or produces a void
  /// value, we can't rely on DCE to delete the instruction. Instead, visit
  /// methods should return the value returned by this function.
  Instruction *eraseInstFromFunction(Instruction &I) override {
    LLVM_DEBUG(dbgs() << "IC: ERASE " << I << '\n');
    assert(I.use_empty() && "Cannot erase instruction that is used!");
    salvageDebugInfo(I);
 
    // Make sure that we reprocess all operands now that we reduced their
    // use counts.
    SmallVector<Value *> Ops(I.operands());
    Worklist.remove(&I);
    DC.removeValue(&I);
    I.eraseFromParent();
    for (Value *Op : Ops)
      Worklist.handleUseCountDecrement(Op);
    MadeIRChange = true;
    return nullptr; // Don't do anything with FI
  }
 
  OverflowResult computeOverflow(
      Instruction::BinaryOps BinaryOp, bool IsSigned,
      Value *LHS, Value *RHS, Instruction *CxtI) const;
 
  /// Performs a few simplifications for operators which are associative
  /// or commutative.
  bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
 
  /// Tries to simplify binary operations which some other binary
  /// operation distributes over.
  ///
  /// It does this by either by factorizing out common terms (eg "(A*B)+(A*C)"
  /// -> "A*(B+C)") or expanding out if this results in simplifications (eg: "A
  /// & (B | C) -> (A&B) | (A&C)" if this is a win).  Returns the simplified
  /// value, or null if it didn't simplify.
  Value *foldUsingDistributiveLaws(BinaryOperator &I);
 
  /// Tries to simplify add operations using the definition of remainder.
  ///
  /// The definition of remainder is X % C = X - (X / C ) * C. The add
  /// expression X % C0 + (( X / C0 ) % C1) * C0 can be simplified to
  /// X % (C0 * C1)
  Value *SimplifyAddWithRemainder(BinaryOperator &I);
 
  // Binary Op helper for select operations where the expression can be
  // efficiently reorganized.
  Value *SimplifySelectsFeedingBinaryOp(BinaryOperator &I, Value *LHS,
                                        Value *RHS);
 
  // If `I` has operand `(ctpop (not x))`, fold `I` with `(sub nuw nsw
  // BitWidth(x), (ctpop x))`.
  Instruction *tryFoldInstWithCtpopWithNot(Instruction *I);
 
  // (Binop1 (Binop2 (logic_shift X, C), C1), (logic_shift Y, C))
  //    -> (logic_shift (Binop1 (Binop2 X, inv_logic_shift(C1, C)), Y), C)
  // (Binop1 (Binop2 (logic_shift X, Amt), Mask), (logic_shift Y, Amt))
  //    -> (BinOp (logic_shift (BinOp X, Y)), Mask)
  Instruction *foldBinOpShiftWithShift(BinaryOperator &I);
 
  /// Tries to simplify binops of select and cast of the select condition.
  ///
  /// (Binop (cast C), (select C, T, F))
  ///    -> (select C, C0, C1)
  Instruction *foldBinOpOfSelectAndCastOfSelectCondition(BinaryOperator &I);
  /// Fold both forms of the div_ceil idiom:
  ///   (add (udiv X, Y), (zext (icmp ne (urem X, Y), 0)))
  ///     -> (udiv (add nuw X, Y-1), Y)
  ///   (add (zext (udiv X, Y)), (zext (icmp ne (urem X, Y), 0)))
  ///     -> (zext (udiv (add nuw X, Y-1), Y))
  Instruction *foldDivCeil(BinaryOperator &I);
 
  /// This tries to simplify binary operations by factorizing out common terms
  /// (e. g. "(A*B)+(A*C)" -> "A*(B+C)").
  Value *tryFactorizationFolds(BinaryOperator &I);
 
  /// Match a select chain which produces one of three values based on whether
  /// the LHS is less than, equal to, or greater than RHS respectively.
  /// Return true if we matched a three way compare idiom. The LHS, RHS, Less,
  /// Equal and Greater values are saved in the matching process and returned to
  /// the caller.
  bool matchThreeWayIntCompare(SelectInst *SI, Value *&LHS, Value *&RHS,
                               ConstantInt *&Less, ConstantInt *&Equal,
                               ConstantInt *&Greater);
 
  /// Attempts to replace I with a simpler value based on the demanded
  /// bits.
  Value *SimplifyDemandedUseBits(Instruction *I, const APInt &DemandedMask,
                                 KnownBits &Known, const SimplifyQuery &Q,
                                 unsigned Depth = 0);
  using InstCombiner::SimplifyDemandedBits;
  bool SimplifyDemandedBits(Instruction *I, unsigned Op,
                            const APInt &DemandedMask, KnownBits &Known,
                            const SimplifyQuery &Q,
                            unsigned Depth = 0) override;
 
  /// Helper routine of SimplifyDemandedUseBits. It computes KnownZero/KnownOne
  /// bits. It also tries to handle simplifications that can be done based on
  /// DemandedMask, but without modifying the Instruction.
  Value *SimplifyMultipleUseDemandedBits(Instruction *I,
                                         const APInt &DemandedMask,
                                         KnownBits &Known,
                                         const SimplifyQuery &Q,
                                         unsigned Depth = 0);
 
  /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
  /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
  Value *simplifyShrShlDemandedBits(
      Instruction *Shr, const APInt &ShrOp1, Instruction *Shl,
      const APInt &ShlOp1, const APInt &DemandedMask, KnownBits &Known);
 
  /// Tries to simplify operands to an integer instruction based on its
  /// demanded bits.
  bool SimplifyDemandedInstructionBits(Instruction &Inst);
  bool SimplifyDemandedInstructionBits(Instruction &Inst, KnownBits &Known);
 
  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
                                    APInt &PoisonElts, unsigned Depth = 0,
                                    bool AllowMultipleUsers = false) override;
 
  /// Attempts to replace V with a simpler value based on the demanded
  /// floating-point classes
  Value *SimplifyDemandedUseFPClass(Instruction *I, FPClassTest DemandedMask,
                                    KnownFPClass &Known, const SimplifyQuery &Q,
                                    unsigned Depth = 0);
  Value *SimplifyMultipleUseDemandedFPClass(Instruction *I,
                                            FPClassTest DemandedMask,
                                            KnownFPClass &Known,
                                            const SimplifyQuery &Q,
                                            unsigned Depth);
 
  bool SimplifyDemandedFPClass(Instruction *I, unsigned Op,
                               FPClassTest DemandedMask, KnownFPClass &Known,
                               const SimplifyQuery &Q, unsigned Depth = 0);
 
  bool SimplifyDemandedInstructionFPClass(Instruction &Inst);
 
  /// Common transforms for add / disjoint or
  Instruction *foldAddLikeCommutative(Value *LHS, Value *RHS, bool NSW,
                                      bool NUW);
 
  /// Canonicalize the position of binops relative to shufflevector.
  Instruction *foldVectorBinop(BinaryOperator &Inst);
  Instruction *foldVectorSelect(SelectInst &Sel);
  Instruction *foldSelectShuffle(ShuffleVectorInst &Shuf);
  Constant *unshuffleConstant(ArrayRef<int> ShMask, Constant *C,
                              VectorType *NewCTy);
 
  /// Given a binary operator, cast instruction, or select which has a PHI node
  /// as operand #0, see if we can fold the instruction into the PHI (which is
  /// only possible if all operands to the PHI are constants).
  Instruction *foldOpIntoPhi(Instruction &I, PHINode *PN,
                             bool AllowMultipleUses = false);
 
  /// Try to fold binary operators whose operands are simple interleaved
  /// recurrences to a single recurrence. This is a common pattern in reduction
  /// operations.
  /// Example:
  ///   %phi1 = phi [init1, %BB1], [%op1, %BB2]
  ///   %phi2 = phi [init2, %BB1], [%op2, %BB2]
  ///   %op1 = binop %phi1, constant1
  ///   %op2 = binop %phi2, constant2
  ///   %rdx = binop %op1, %op2
  /// -->
  ///   %phi_combined = phi [init_combined, %BB1], [%op_combined, %BB2]
  ///   %rdx_combined = binop %phi_combined, constant_combined
  Instruction *foldBinopWithRecurrence(BinaryOperator &BO);
 
  /// For a binary operator with 2 phi operands, try to hoist the binary
  /// operation before the phi. This can result in fewer instructions in
  /// patterns where at least one set of phi operands simplifies.
  /// Example:
  /// BB3: binop (phi [X, BB1], [C1, BB2]), (phi [Y, BB1], [C2, BB2])
  /// -->
  /// BB1: BO = binop X, Y
  /// BB3: phi [BO, BB1], [(binop C1, C2), BB2]
  Instruction *foldBinopWithPhiOperands(BinaryOperator &BO);
 
  /// Given an instruction with a select as one operand and a constant as the
  /// other operand, try to fold the binary operator into the select arguments.
  /// This also works for Cast instructions, which obviously do not have a
  /// second operand.
  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
                                bool FoldWithMultiUse = false,
                                bool SimplifyBothArms = false);
 
  Instruction *foldBinOpSelectBinOp(BinaryOperator &Op);
 
  /// This is a convenience wrapper function for the above two functions.
  Instruction *foldBinOpIntoSelectOrPhi(BinaryOperator &I);
 
  Instruction *foldAddWithConstant(BinaryOperator &Add);
 
  Instruction *foldSquareSumInt(BinaryOperator &I);
  Instruction *foldSquareSumFP(BinaryOperator &I);
 
  /// Try to rotate an operation below a PHI node, using PHI nodes for
  /// its operands.
  Instruction *foldPHIArgOpIntoPHI(PHINode &PN);
  Instruction *foldPHIArgBinOpIntoPHI(PHINode &PN);
  Instruction *foldPHIArgInsertValueInstructionIntoPHI(PHINode &PN);
  Instruction *foldPHIArgExtractValueInstructionIntoPHI(PHINode &PN);
  Instruction *foldPHIArgGEPIntoPHI(PHINode &PN);
  Instruction *foldPHIArgLoadIntoPHI(PHINode &PN);
  Instruction *foldPHIArgZextsIntoPHI(PHINode &PN);
  Instruction *foldPHIArgIntToPtrToPHI(PHINode &PN);
 
  /// If the phi is within a phi web, which is formed by the def-use chain
  /// of phis and all the phis in the web are only used in the other phis.
  /// In this case, these phis are dead and we will remove all of them.
  bool foldDeadPhiWeb(PHINode &PN);
 
  /// If an integer typed PHI has only one use which is an IntToPtr operation,
  /// replace the PHI with an existing pointer typed PHI if it exists. Otherwise
  /// insert a new pointer typed PHI and replace the original one.
  bool foldIntegerTypedPHI(PHINode &PN);
 
  /// Helper function for FoldPHIArgXIntoPHI() to set debug location for the
  /// folded operation.
  void PHIArgMergedDebugLoc(Instruction *Inst, PHINode &PN);
 
  Value *foldPtrToIntOrAddrOfGEP(Type *IntTy, Value *Ptr);
  Instruction *foldGEPICmp(GEPOperator *GEPLHS, Value *RHS, CmpPredicate Cond,
                           Instruction &I);
  Instruction *foldSelectICmp(CmpPredicate Pred, SelectInst *SI, Value *RHS,
                              const ICmpInst &I);
  bool foldAllocaCmp(AllocaInst *Alloca);
  Instruction *foldCmpLoadFromIndexedGlobal(LoadInst *LI,
                                            GetElementPtrInst *GEP,
                                            CmpInst &ICI,
                                            ConstantInt *AndCst = nullptr);
  Instruction *foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
                                    Constant *RHSC);
  Instruction *foldICmpAddOpConst(Value *X, const APInt &C, CmpPredicate Pred);
  Instruction *foldCmpSelectOfConstants(CmpInst &I);
  Instruction *foldICmpWithCastOp(ICmpInst &ICmp);
  Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp);
 
  Instruction *foldICmpUsingKnownBits(ICmpInst &Cmp);
  Instruction *foldICmpWithDominatingICmp(ICmpInst &Cmp);
  Instruction *foldICmpWithConstant(ICmpInst &Cmp);
  Instruction *foldIsMultipleOfAPowerOfTwo(ICmpInst &Cmp);
  Instruction *foldICmpUsingBoolRange(ICmpInst &I);
  Instruction *foldICmpInstWithConstant(ICmpInst &Cmp);
  Instruction *foldICmpInstWithConstantNotInt(ICmpInst &Cmp);
  Instruction *foldICmpInstWithConstantAllowPoison(ICmpInst &Cmp,
                                                   const APInt &C);
  Instruction *foldICmpBinOp(ICmpInst &Cmp, const SimplifyQuery &SQ);
  Instruction *foldICmpWithMinMax(Instruction &I, MinMaxIntrinsic *MinMax,
                                  Value *Z, CmpPredicate Pred);
  Instruction *foldICmpWithClamp(ICmpInst &Cmp, Value *X, MinMaxIntrinsic *Min);
  Instruction *foldICmpEquality(ICmpInst &Cmp);
  Instruction *foldIRemByPowerOfTwoToBitTest(ICmpInst &I);
  Instruction *foldSignBitTest(ICmpInst &I);
  Instruction *foldICmpWithZero(ICmpInst &Cmp);
 
  Value *foldMultiplicationOverflowCheck(ICmpInst &Cmp);
 
  Instruction *foldICmpBinOpWithConstant(ICmpInst &Cmp, BinaryOperator *BO,
                                         const APInt &C);
  Instruction *foldICmpSelectConstant(ICmpInst &Cmp, SelectInst *Select,
                                      ConstantInt *C);
  Instruction *foldICmpTruncConstant(ICmpInst &Cmp, TruncInst *Trunc,
                                     const APInt &C);
  Instruction *foldICmpTruncWithTruncOrExt(ICmpInst &Cmp,
                                           const SimplifyQuery &Q);
  Instruction *foldICmpAndConstant(ICmpInst &Cmp, BinaryOperator *And,
                                   const APInt &C);
  Instruction *foldICmpXorConstant(ICmpInst &Cmp, BinaryOperator *Xor,
                                   const APInt &C);
  Instruction *foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
                                  const APInt &C);
  Instruction *foldICmpMulConstant(ICmpInst &Cmp, BinaryOperator *Mul,
                                   const APInt &C);
  Instruction *foldICmpShlConstant(ICmpInst &Cmp, BinaryOperator *Shl,
                                   const APInt &C);
  Instruction *foldICmpShrConstant(ICmpInst &Cmp, BinaryOperator *Shr,
                                   const APInt &C);
  Instruction *foldICmpSRemConstant(ICmpInst &Cmp, BinaryOperator *UDiv,
                                    const APInt &C);
  Instruction *foldICmpUDivConstant(ICmpInst &Cmp, BinaryOperator *UDiv,
                                    const APInt &C);
  Instruction *foldICmpDivConstant(ICmpInst &Cmp, BinaryOperator *Div,
                                   const APInt &C);
  Instruction *foldICmpSubConstant(ICmpInst &Cmp, BinaryOperator *Sub,
                                   const APInt &C);
  Instruction *foldICmpAddConstant(ICmpInst &Cmp, BinaryOperator *Add,
                                   const APInt &C);
  Instruction *foldICmpAndConstConst(ICmpInst &Cmp, BinaryOperator *And,
                                     const APInt &C1);
  Instruction *foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
                                const APInt &C1, const APInt &C2);
  Instruction *foldICmpXorShiftConst(ICmpInst &Cmp, BinaryOperator *Xor,
                                     const APInt &C);
  Instruction *foldICmpShrConstConst(ICmpInst &I, Value *ShAmt, const APInt &C1,
                                     const APInt &C2);
  Instruction *foldICmpShlConstConst(ICmpInst &I, Value *ShAmt, const APInt &C1,
                                     const APInt &C2);
 
  Instruction *foldICmpBinOpWithConstantViaTruthTable(ICmpInst &Cmp,
                                                      BinaryOperator *BO,
                                                      const APInt &C);
  Instruction *foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
                                                 BinaryOperator *BO,
                                                 const APInt &C);
  Instruction *foldICmpIntrinsicWithConstant(ICmpInst &ICI, IntrinsicInst *II,
                                             const APInt &C);
  Instruction *foldICmpEqIntrinsicWithConstant(ICmpInst &ICI, IntrinsicInst *II,
                                               const APInt &C);
  Instruction *foldICmpBitCast(ICmpInst &Cmp);
  Instruction *foldICmpWithTrunc(ICmpInst &Cmp);
  Instruction *foldICmpCommutative(CmpPredicate Pred, Value *Op0, Value *Op1,
                                   ICmpInst &CxtI);
 
  // Helpers of visitSelectInst().
  Instruction *foldSelectOfBools(SelectInst &SI);
  Instruction *foldSelectToCmp(SelectInst &SI);
  Instruction *foldSelectExtConst(SelectInst &Sel);
  Instruction *foldSelectEqualityTest(SelectInst &SI);
  Instruction *foldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
  Instruction *foldSelectIntrinsic(SelectInst &SI);
  Instruction *foldSelectIntoOp(SelectInst &SI, Value *, Value *);
  Instruction *foldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
                            Value *A, Value *B, Instruction &Outer,
                            SelectPatternFlavor SPF2, Value *C);
  Instruction *foldSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
  Value *foldSelectWithConstOpToBinOp(ICmpInst *Cmp, Value *TrueVal,
                                      Value *FalseVal);
  Instruction *foldSelectValueEquivalence(SelectInst &SI, CmpInst &CI);
 
  Instruction *foldExtractionOfVectorDeinterleave(ZExtInst &RootZExt);
 
  bool replaceInInstruction(Value *V, Value *Old, Value *New,
                            unsigned Depth = 0);
 
  Value *insertRangeTest(Value *V, const APInt &Lo, const APInt &Hi,
                         bool isSigned, bool Inside);
  bool mergeStoreIntoSuccessor(StoreInst &SI);
 
  /// Given an initial instruction, check to see if it is the root of a
  /// bswap/bitreverse idiom. If so, return the equivalent bswap/bitreverse
  /// intrinsic.
  Instruction *matchBSwapOrBitReverse(Instruction &I, bool MatchBSwaps,
                                      bool MatchBitReversals);
 
  Instruction *SimplifyAnyMemTransfer(AnyMemTransferInst *MI);
  Instruction *SimplifyAnyMemSet(AnyMemSetInst *MI);
 
  Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
 
  bool tryToSinkInstruction(Instruction *I, BasicBlock *DestBlock);
  void tryToSinkInstructionDbgVariableRecords(
      Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
      BasicBlock *DestBlock, SmallVectorImpl<DbgVariableRecord *> &DPUsers);
 
  bool removeInstructionsBeforeUnreachable(Instruction &I);
  void addDeadEdge(BasicBlock *From, BasicBlock *To,
                   SmallVectorImpl<BasicBlock *> &Worklist);
  void handleUnreachableFrom(Instruction *I,
                             SmallVectorImpl<BasicBlock *> &Worklist);
  void handlePotentiallyDeadBlocks(SmallVectorImpl<BasicBlock *> &Worklist);
  void handlePotentiallyDeadSuccessors(BasicBlock *BB, BasicBlock *LiveSucc);
  void freelyInvertAllUsersOf(Value *V, Value *IgnoredUser = nullptr);
 
  /// Take the exact integer log2 of the value. If DoFold is true, create the
  /// actual instructions, otherwise return a non-null dummy value. Return
  /// nullptr on failure. Note, if DoFold is true the caller must ensure that
  /// takeLog2 will succeed, otherwise it may create stray instructions.
  Value *takeLog2(Value *Op, unsigned Depth, bool AssumeNonZero, bool DoFold);
 
  Value *tryGetLog2(Value *Op, bool AssumeNonZero) {
    if (takeLog2(Op, /*Depth=*/0, AssumeNonZero, /*DoFold=*/false))
      return takeLog2(Op, /*Depth=*/0, AssumeNonZero, /*DoFold=*/true);
    return nullptr;
  }
};
 
class Negator final {
  /// Top-to-bottom, def-to-use negated instruction tree we produced.
  SmallVector<Instruction *, NegatorMaxNodesSSO> NewInstructions;
 
  using BuilderTy = IRBuilder<TargetFolder, IRBuilderCallbackInserter>;
  BuilderTy Builder;
 
  const DominatorTree &DT;
 
  const bool IsTrulyNegation;
 
  SmallDenseMap<Value *, Value *> NegationsCache;
 
  Negator(LLVMContext &C, const DataLayout &DL, const DominatorTree &DT,
          bool IsTrulyNegation);
 
#if LLVM_ENABLE_STATS
  unsigned NumValuesVisitedInThisNegator = 0;
  ~Negator();
#endif
 
  using Result = std::pair<ArrayRef<Instruction *> /*NewInstructions*/,
                           Value * /*NegatedRoot*/>;
 
  std::array<Value *, 2> getSortedOperandsOfBinOp(Instruction *I);
 
  [[nodiscard]] Value *visitImpl(Value *V, bool IsNSW, unsigned Depth);
 
  [[nodiscard]] Value *negate(Value *V, bool IsNSW, unsigned Depth);
 
  /// Recurse depth-first and attempt to sink the negation.
  /// FIXME: use worklist?
  [[nodiscard]] std::optional<Result> run(Value *Root, bool IsNSW);
 
  Negator(const Negator &) = delete;
  Negator(Negator &&) = delete;
  Negator &operator=(const Negator &) = delete;
  Negator &operator=(Negator &&) = delete;
 
public:
  /// Attempt to negate \p Root. Retuns nullptr if negation can't be performed,
  /// otherwise returns negated value.
  [[nodiscard]] static Value *Negate(bool LHSIsZero, bool IsNSW, Value *Root,
                                     InstCombinerImpl &IC);
};
 
struct CommonPointerBase {
  /// Common base pointer.
  Value *Ptr = nullptr;
  /// LHS GEPs until common base.
  SmallVector<GEPOperator *> LHSGEPs;
  /// RHS GEPs until common base.
  SmallVector<GEPOperator *> RHSGEPs;
  /// LHS GEP NoWrapFlags until common base.
  GEPNoWrapFlags LHSNW = GEPNoWrapFlags::all();
  /// RHS GEP NoWrapFlags until common base.
  GEPNoWrapFlags RHSNW = GEPNoWrapFlags::all();
 
  static CommonPointerBase compute(Value *LHS, Value *RHS);
 
  /// Whether expanding the GEP chains is expensive.
  bool isExpensive() const;
};
 
} // end namespace llvm
 
#undef DEBUG_TYPE
 
#endif // LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H