/*===================== begin_copyright_notice ==================================

Copyright (c) 2017 Intel Corporation

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


======================= end_copyright_notice ==================================*/
//===- InstCombineInternal.h - InstCombine pass internals -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \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/ArrayRef.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/InstCombine/InstCombineWorklist.h"
#include <cassert>
#include <cstdint>

#define DEBUG_TYPE "instcombine"

namespace llvm {
class APInt;
class AssumptionCache;
class CallSite;
class DataLayout;
class DominatorTree;
class GEPOperator;
class GlobalVariable;
class LoopInfo;
class OptimizationRemarkEmitter;
class TargetLibraryInfo;
class User;
};


namespace IGCombiner {

using namespace llvm;
/// Assign a complexity or rank value to LLVM Values. This is used to reduce
/// the amount of pattern matching needed for compares and commutative
/// instructions. For example, if we have:
///   icmp ugt X, Constant
/// or
///   xor (add X, Constant), cast Z
///
/// We do not have to consider the commuted variants of these patterns because
/// canonicalization based on complexity guarantees the above ordering.
///
/// This routine maps IR values to various complexity ranks:
///   0 -> undef
///   1 -> Constants
///   2 -> Other non-instructions
///   3 -> Arguments
///   4 -> Cast and (f)neg/not instructions
///   5 -> Other instructions
static inline unsigned getComplexity(Value *V) {
  if (isa<Instruction>(V)) {
    if (isa<CastInst>(V) || BinaryOperator::isNeg(V) ||
        BinaryOperator::isFNeg(V) || BinaryOperator::isNot(V))
      return 4;
    return 5;
  }
  if (isa<Argument>(V))
    return 3;
  return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}

/// Predicate canonicalization reduces the number of patterns that need to be
/// matched by other transforms. For example, we may swap the operands of a
/// conditional branch or select to create a compare with a canonical (inverted)
/// predicate which is then more likely to be matched with other values.
static inline bool isCanonicalPredicate(CmpInst::Predicate Pred) {
  switch (Pred) {
  case CmpInst::ICMP_NE:
  case CmpInst::ICMP_ULE:
  case CmpInst::ICMP_SLE:
  case CmpInst::ICMP_UGE:
  case CmpInst::ICMP_SGE:
  // TODO: There are 16 FCMP predicates. Should others be (not) canonical?
  case CmpInst::FCMP_ONE:
  case CmpInst::FCMP_OLE:
  case CmpInst::FCMP_OGE:
    return false;
  default:
    return true;
  }
}

/// Return the source operand of a potentially bitcasted value while optionally
/// checking if it has one use. If there is no bitcast or the one use check is
/// not met, return the input value itself.
static inline Value *peekThroughBitcast(Value *V, bool OneUseOnly = false) {
  if (auto *BitCast = dyn_cast<BitCastInst>(V))
    if (!OneUseOnly || BitCast->hasOneUse())
      return BitCast->getOperand(0);

  // V is not a bitcast or V has more than one use and OneUseOnly is true.
  return V;
}

/// Add one to a Constant
static inline Constant *AddOne(Constant *C) {
  return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
}

/// Subtract one from a Constant
static inline Constant *SubOne(Constant *C) {
  return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
}

/// Return true if the specified value is free to invert (apply ~ to).
/// This happens in cases where the ~ can be eliminated.  If WillInvertAllUses
/// is true, work under the assumption that the caller intends to remove all
/// uses of V and only keep uses of ~V.
static inline bool IsFreeToInvert(Value *V, bool WillInvertAllUses) {
  // ~(~(X)) -> X.
  if (BinaryOperator::isNot(V))
    return true;

  // Constants can be considered to be not'ed values.
  if (isa<ConstantInt>(V))
    return true;

  // A vector of constant integers can be inverted easily.
  if (V->getType()->isVectorTy() && isa<Constant>(V)) {
    unsigned NumElts = V->getType()->getVectorNumElements();
    for (unsigned i = 0; i != NumElts; ++i) {
      Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
      if (!Elt)
        return false;

      if (isa<UndefValue>(Elt))
        continue;

      if (!isa<ConstantInt>(Elt))
        return false;
    }
    return true;
  }

  // Compares can be inverted if all of their uses are being modified to use the
  // ~V.
  if (isa<CmpInst>(V))
    return WillInvertAllUses;

  // If `V` is of the form `A + Constant` then `-1 - V` can be folded into `(-1
  // - Constant) - A` if we are willing to invert all of the uses.
  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
    if (BO->getOpcode() == Instruction::Add ||
        BO->getOpcode() == Instruction::Sub)
      if (isa<Constant>(BO->getOperand(0)) || isa<Constant>(BO->getOperand(1)))
        return WillInvertAllUses;

  return false;
}

/// Specific patterns of overflow check idioms that we match.
enum OverflowCheckFlavor {
  OCF_UNSIGNED_ADD,
  OCF_SIGNED_ADD,
  OCF_UNSIGNED_SUB,
  OCF_SIGNED_SUB,
  OCF_UNSIGNED_MUL,
  OCF_SIGNED_MUL,

  OCF_INVALID
};

/// Returns the OverflowCheckFlavor corresponding to a overflow_with_op
/// intrinsic.
static inline OverflowCheckFlavor
IntrinsicIDToOverflowCheckFlavor(unsigned ID) {
  switch (ID) {
  default:
    return OCF_INVALID;
  case Intrinsic::uadd_with_overflow:
    return OCF_UNSIGNED_ADD;
  case Intrinsic::sadd_with_overflow:
    return OCF_SIGNED_ADD;
  case Intrinsic::usub_with_overflow:
    return OCF_UNSIGNED_SUB;
  case Intrinsic::ssub_with_overflow:
    return OCF_SIGNED_SUB;
  case Intrinsic::umul_with_overflow:
    return OCF_UNSIGNED_MUL;
  case Intrinsic::smul_with_overflow:
    return OCF_SIGNED_MUL;
  }
}

/// Some binary operators require special handling to avoid poison and undefined
/// behavior. If a constant vector has undef elements, replace those undefs with
/// identity constants if possible because those are always safe to execute.
/// If no identity constant exists, replace undef with some other safe constant.
static inline Constant *getSafeVectorConstantForBinop(
      BinaryOperator::BinaryOps Opcode, Constant *In, bool IsRHSConstant) {
  assert(In->getType()->isVectorTy() && "Not expecting scalars here");

  Type *EltTy = In->getType()->getVectorElementType();
  auto *SafeC = ConstantExpr::getBinOpIdentity(Opcode, EltTy, IsRHSConstant);
  if (!SafeC) {
    // TODO: Should this be available as a constant utility function? It is
    // similar to getBinOpAbsorber().
    if (IsRHSConstant) {
      switch (Opcode) {
      case Instruction::SRem: // X % 1 = 0
      case Instruction::URem: // X %u 1 = 0
        SafeC = ConstantInt::get(EltTy, 1);
        break;
      case Instruction::FRem: // X % 1.0 (doesn't simplify, but it is safe)
        SafeC = ConstantFP::get(EltTy, 1.0);
        break;
      default:
        llvm_unreachable("Only rem opcodes have no identity constant for RHS");
      }
    } else {
      switch (Opcode) {
      case Instruction::Shl:  // 0 << X = 0
      case Instruction::LShr: // 0 >>u X = 0
      case Instruction::AShr: // 0 >> X = 0
      case Instruction::SDiv: // 0 / X = 0
      case Instruction::UDiv: // 0 /u X = 0
      case Instruction::SRem: // 0 % X = 0
      case Instruction::URem: // 0 %u X = 0
      case Instruction::Sub:  // 0 - X (doesn't simplify, but it is safe)
      case Instruction::FSub: // 0.0 - X (doesn't simplify, but it is safe)
      case Instruction::FDiv: // 0.0 / X (doesn't simplify, but it is safe)
      case Instruction::FRem: // 0.0 % X = 0
        SafeC = Constant::getNullValue(EltTy);
        break;
      default:
        llvm_unreachable("Expected to find identity constant for opcode");
      }
    }
  }
  assert(SafeC && "Must have safe constant for binop");
  unsigned NumElts = In->getType()->getVectorNumElements();
  SmallVector<Constant *, 16> Out(NumElts);
  for (unsigned i = 0; i != NumElts; ++i) {
    Constant *C = In->getAggregateElement(i);
    Out[i] = isa<UndefValue>(C) ? SafeC : C;
  }
  return ConstantVector::get(Out);
}

/// The core instruction combiner logic.
///
/// This class provides both the logic to recursively visit instructions and
/// combine them.
class LLVM_LIBRARY_VISIBILITY InstCombiner
    : public InstVisitor<InstCombiner, Instruction *> {
  // FIXME: These members shouldn't be public.
public:
  /// A worklist of the instructions that need to be simplified.
  InstCombineWorklist &Worklist;

  /// An IRBuilder that automatically inserts new instructions into the
  /// worklist.
  using BuilderTy = IRBuilder<TargetFolder, IRBuilderCallbackInserter>;
  BuilderTy &Builder;

private:
  // Mode in which we are running the combiner.
  const bool MinimizeSize;

  /// Enable combines that trigger rarely but are costly in compiletime.
  const bool ExpensiveCombines;

  AliasAnalysis *AA;

  // Required analyses.
  AssumptionCache &AC;
  TargetLibraryInfo &TLI;
  DominatorTree &DT;
  const DataLayout &DL;
  const SimplifyQuery SQ;
  OptimizationRemarkEmitter &ORE;

  // Optional analyses. When non-null, these can both be used to do better
  // combining and will be updated to reflect any changes.
  LoopInfo *LI;

  bool MadeIRChange = false;

public:
  InstCombiner(InstCombineWorklist &Worklist, BuilderTy &Builder,
               bool MinimizeSize, bool ExpensiveCombines, AliasAnalysis *AA,
               AssumptionCache &AC, TargetLibraryInfo &TLI, DominatorTree &DT,
               OptimizationRemarkEmitter &ORE, const DataLayout &DL,
               LoopInfo *LI)
      : Worklist(Worklist), Builder(Builder), MinimizeSize(MinimizeSize),
        ExpensiveCombines(ExpensiveCombines), AA(AA), AC(AC), TLI(TLI), DT(DT),
        DL(DL), SQ(DL, &TLI, &DT, &AC), ORE(ORE), LI(LI) {}

  /// Run the combiner over the entire worklist until it is empty.
  ///
  /// \returns true if the IR is changed.
  bool run();

  AssumptionCache &getAssumptionCache() const { return AC; }

  const DataLayout &getDataLayout() const { return DL; }

  DominatorTree &getDominatorTree() const { return DT; }

  LoopInfo *getLoopInfo() const { return LI; }

  TargetLibraryInfo &getTargetLibraryInfo() const { return TLI; }

  // 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 *visitAdd(BinaryOperator &I);
  Instruction *visitFAdd(BinaryOperator &I);
  Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
  Instruction *visitSub(BinaryOperator &I);
  Instruction *visitFSub(BinaryOperator &I);
  Instruction *visitMul(BinaryOperator &I);
  Instruction *visitFMul(BinaryOperator &I);
  Instruction *visitURem(BinaryOperator &I);
  Instruction *visitSRem(BinaryOperator &I);
  Instruction *visitFRem(BinaryOperator &I);
  bool simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I);
  Instruction *commonRemTransforms(BinaryOperator &I);
  Instruction *commonIRemTransforms(BinaryOperator &I);
  Instruction *commonDivTransforms(BinaryOperator &I);
  Instruction *commonIDivTransforms(BinaryOperator &I);
  Instruction *visitUDiv(BinaryOperator &I);
  Instruction *visitSDiv(BinaryOperator &I);
  Instruction *visitFDiv(BinaryOperator &I);
  Value *simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1, bool Inverted);
  Instruction *visitAnd(BinaryOperator &I);
  Instruction *visitOr(BinaryOperator &I);
  Instruction *visitXor(BinaryOperator &I);
  Instruction *visitShl(BinaryOperator &I);
  Instruction *visitAShr(BinaryOperator &I);
  Instruction *visitLShr(BinaryOperator &I);
  Instruction *commonShiftTransforms(BinaryOperator &I);
  Instruction *visitFCmpInst(FCmpInst &I);
  Instruction *visitICmpInst(ICmpInst &I);
  Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1,
                                   BinaryOperator &I);
  Instruction *commonCastTransforms(CastInst &CI);
  Instruction *commonPointerCastTransforms(CastInst &CI);
  Instruction *visitTrunc(TruncInst &CI);
  Instruction *visitZExt(ZExtInst &CI);
  Instruction *visitSExt(SExtInst &CI);
  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 *visitIntToPtr(IntToPtrInst &CI);
  Instruction *visitBitCast(BitCastInst &CI);
  Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI);
  Instruction *FoldItoFPtoI(Instruction &FI);
  Instruction *visitSelectInst(SelectInst &SI);
  Instruction *visitCallInst(CallInst &CI);
  Instruction *visitInvokeInst(InvokeInst &II);

  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
  Instruction *visitPHINode(PHINode &PN);
  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
  Instruction *visitAllocaInst(AllocaInst &AI);
  Instruction *visitAllocSite(Instruction &FI);
  Instruction *visitFree(CallInst &FI);
  Instruction *visitLoadInst(LoadInst &LI);
  Instruction *visitStoreInst(StoreInst &SI);
  Instruction *visitBranchInst(BranchInst &BI);
  Instruction *visitFenceInst(FenceInst &FI);
  Instruction *visitSwitchInst(SwitchInst &SI);
  Instruction *visitReturnInst(ReturnInst &RI);
  Instruction *visitInsertValueInst(InsertValueInst &IV);
  Instruction *visitInsertElementInst(InsertElementInst &IE);
  Instruction *visitExtractElementInst(ExtractElementInst &EI);
  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
  Instruction *visitExtractValueInst(ExtractValueInst &EV);
  Instruction *visitLandingPadInst(LandingPadInst &LI);
  Instruction *visitVAStartInst(VAStartInst &I);
  Instruction *visitVACopyInst(VACopyInst &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);

  /// Try to replace instruction \p I with value \p V which are pointers
  /// in different address space.
  /// \return true if successful.
  bool replacePointer(Instruction &I, Value *V);

private:
  bool shouldChangeType(unsigned FromBitWidth, unsigned ToBitWidth) const;
  bool shouldChangeType(Type *From, Type *To) const;
  Value *dyn_castNegVal(Value *V) const;
  Type *FindElementAtOffset(PointerType *PtrTy, int64_t Offset,
                            SmallVectorImpl<Value *> &NewIndices);

  /// 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(OverflowCheckFlavor OCF, Value *LHS, Value *RHS,
                             Instruction &CtxI, Value *&OperationResult,
                             Constant *&OverflowResult);

  Instruction *visitCallSite(CallSite CS);
  Instruction *tryOptimizeCall(CallInst *CI);
  bool transformConstExprCastCall(CallSite CS);
  Instruction *transformCallThroughTrampoline(CallSite CS,
                                              IntrinsicInst *Tramp);

  /// 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.
  /// \param DoTransform Pass false to just test whether the given (zext icmp)
  /// would be transformed. Pass true to actually perform the transformation.
  ///
  /// \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 (if \p DoTransform is false the
  /// unmodified \p ICI will be returned in this case).
  Instruction *transformZExtICmp(ICmpInst *ICI, ZExtInst &CI,
                                 bool DoTransform = true);

  Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);

  bool willNotOverflowSignedAdd(const Value *LHS, const Value *RHS,
                                const Instruction &CxtI) const {
    return computeOverflowForSignedAdd(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }

  bool willNotOverflowUnsignedAdd(const Value *LHS, const Value *RHS,
                                  const Instruction &CxtI) const {
    return computeOverflowForUnsignedAdd(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }

  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 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) const {
    return computeOverflowForUnsignedMul(LHS, RHS, &CxtI) ==
           OverflowResult::NeverOverflows;
  }

  Value *EmitGEPOffset(User *GEP);
  Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
  Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
  Instruction *foldCastedBitwiseLogic(BinaryOperator &I);
  Instruction *narrowBinOp(TruncInst &Trunc);
  Instruction *narrowMaskedBinOp(BinaryOperator &And);
  Instruction *narrowRotate(TruncInst &Trunc);
  Instruction *optimizeBitCastFromPhi(CastInst &CI, PHINode *PN);

  /// 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 *foldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS, Instruction &CxtI);
  Value *foldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS, Instruction &CxtI);
  Value *foldXorOfICmps(ICmpInst *LHS, ICmpInst *RHS);

  /// 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);

  Value *foldAndOrOfICmpsOfAndWithPow2(ICmpInst *LHS, ICmpInst *RHS,
                                       bool JoinedByAnd, Instruction &CxtI);
public:
  /// Inserts an instruction \p New before instruction \p Old
  ///
  /// Also adds the new instruction to the worklist and returns \p New so that
  /// it is suitable for use as the return from the visitation patterns.
  Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
    assert(New && !New->getParent() &&
           "New instruction already inserted into a basic block!");
    BasicBlock *BB = Old.getParent();
    BB->getInstList().insert(Old.getIterator(), New); // Insert inst
    Worklist.Add(New);
    return New;
  }

  /// Same as InsertNewInstBefore, but also sets the debug loc.
  Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
    New->setDebugLoc(Old.getDebugLoc());
    return InsertNewInstBefore(New, Old);
  }

  /// A combiner-aware RAUW-like routine.
  ///
  /// This method is to be used when an instruction is found to be dead,
  /// replaceable with another preexisting expression. Here we add all uses of
  /// I to the worklist, replace all uses of I with the new value, then return
  /// I, so that the inst combiner will know that I was modified.
  Instruction *replaceInstUsesWith(Instruction &I, Value *V) {
    // If there are no uses to replace, then we return nullptr to indicate that
    // no changes were made to the program.
    if (I.use_empty()) return nullptr;

    Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.

    // If we are replacing the instruction with itself, this must be in a
    // segment of unreachable code, so just clobber the instruction.
    if (&I == V)
      V = UndefValue::get(I.getType());

    LLVM_DEBUG(dbgs() << "IC: Replacing " << I << "\n"
                      << "    with " << *V << '\n');

    I.replaceAllUsesWith(V);
    return &I;
  }

  /// Creates a result tuple for an overflow intrinsic \p II with a given
  /// \p Result and a constant \p Overflow value.
  Instruction *CreateOverflowTuple(IntrinsicInst *II, Value *Result,
                                   Constant *Overflow) {
    Constant *V[] = {UndefValue::get(Result->getType()), Overflow};
    StructType *ST = cast<StructType>(II->getType());
    Constant *Struct = ConstantStruct::get(ST, V);
    return InsertValueInst::Create(Struct, Result, 0);
  }

  /// 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) {
    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.
    if (I.getNumOperands() < 8) {
      for (Use &Operand : I.operands())
        if (auto *Inst = dyn_cast<Instruction>(Operand))
          Worklist.Add(Inst);
    }
    Worklist.Remove(&I);
    I.eraseFromParent();
    MadeIRChange = true;
    return nullptr; // Don't do anything with FI
  }

  void computeKnownBits(const Value *V, KnownBits &Known,
                        unsigned Depth, const Instruction *CxtI) const {
    llvm::computeKnownBits(V, Known, DL, Depth, &AC, CxtI, &DT);
  }

  KnownBits computeKnownBits(const Value *V, unsigned Depth,
                             const Instruction *CxtI) const {
    return llvm::computeKnownBits(V, DL, Depth, &AC, CxtI, &DT);
  }

  bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero = false,
                              unsigned Depth = 0,
                              const Instruction *CxtI = nullptr) {
    return llvm::isKnownToBeAPowerOfTwo(V, DL, OrZero, Depth, &AC, CxtI, &DT);
  }

  bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth = 0,
                         const Instruction *CxtI = nullptr) const {
    return llvm::MaskedValueIsZero(V, Mask, DL, Depth, &AC, CxtI, &DT);
  }

  unsigned ComputeNumSignBits(const Value *Op, unsigned Depth = 0,
                              const Instruction *CxtI = nullptr) const {
    return llvm::ComputeNumSignBits(Op, DL, Depth, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForUnsignedMul(const Value *LHS,
                                               const Value *RHS,
                                               const Instruction *CxtI) const {
    return llvm::computeOverflowForUnsignedMul(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForSignedMul(const Value *LHS,
	                                         const Value *RHS,
                                             const Instruction *CxtI) const {
    return llvm::computeOverflowForSignedMul(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForUnsignedAdd(const Value *LHS,
                                               const Value *RHS,
                                               const Instruction *CxtI) const {
    return llvm::computeOverflowForUnsignedAdd(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForSignedAdd(const Value *LHS,
                                             const Value *RHS,
                                             const Instruction *CxtI) const {
    return llvm::computeOverflowForSignedAdd(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForUnsignedSub(const Value *LHS,
                                               const Value *RHS,
                                               const Instruction *CxtI) const {
    return llvm::computeOverflowForUnsignedSub(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS,
                                             const Instruction *CxtI) const {
    return llvm::computeOverflowForSignedSub(LHS, RHS, DL, &AC, CxtI, &DT);
  }

  /// Maximum size of array considered when transforming.
  uint64_t MaxArraySizeForCombine;

private:
  /// 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 *SimplifyUsingDistributiveLaws(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);

  /// This tries to simplify binary operations by factorizing out common terms
  /// (e. g. "(A*B)+(A*C)" -> "A*(B+C)").
  Value *tryFactorization(BinaryOperator &, Instruction::BinaryOps, Value *,
                          Value *, Value *, Value *);

  /// 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 V with a simpler value based on the demanded
  /// bits.
  Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, KnownBits &Known,
                                 unsigned Depth, Instruction *CxtI);
  bool SimplifyDemandedBits(Instruction *I, unsigned Op,
                            const APInt &DemandedMask, KnownBits &Known,
                            unsigned Depth = 0);

  /// 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,
                                         unsigned Depth, Instruction *CxtI);

  /// 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);

  Value *simplifyAMDGCNMemoryIntrinsicDemanded(IntrinsicInst *II,
                                               APInt DemandedElts,
                                               int DmaskIdx = -1);

  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
                                    APInt &UndefElts, unsigned Depth = 0);

  /// Canonicalize the position of binops relative to shufflevector.
  Instruction *foldShuffledBinop(BinaryOperator &Inst);

  /// 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);

  /// 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);

  /// This is a convenience wrapper function for the above two functions.
  Instruction *foldBinOpIntoSelectOrPhi(BinaryOperator &I);

  Instruction *foldAddWithConstant(BinaryOperator &Add);

  /// Try to rotate an operation below a PHI node, using PHI nodes for
  /// its operands.
  Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
  Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
  Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
  Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
  Instruction *FoldPHIArgZextsIntoPHI(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.
  Instruction *FoldIntegerTypedPHI(PHINode &PN);

  /// Helper function for FoldPHIArgXIntoPHI() to set debug location for the
  /// folded operation.
  void PHIArgMergedDebugLoc(Instruction *Inst, PHINode &PN);

  Instruction *foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
                           ICmpInst::Predicate Cond, Instruction &I);
  Instruction *foldAllocaCmp(ICmpInst &ICI, const AllocaInst *Alloca,
                             const Value *Other);
  Instruction *foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
                                            GlobalVariable *GV, CmpInst &ICI,
                                            ConstantInt *AndCst = nullptr);
  Instruction *foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
                                    Constant *RHSC);
  Instruction *foldICmpAddOpConst(Value *X, ConstantInt *CI,
                                  ICmpInst::Predicate Pred);
  Instruction *foldICmpWithCastAndCast(ICmpInst &ICI);

  Instruction *foldICmpUsingKnownBits(ICmpInst &Cmp);
  Instruction *foldICmpWithConstant(ICmpInst &Cmp);
  Instruction *foldICmpInstWithConstant(ICmpInst &Cmp);
  Instruction *foldICmpInstWithConstantNotInt(ICmpInst &Cmp);
  Instruction *foldICmpBinOp(ICmpInst &Cmp);
  Instruction *foldICmpEquality(ICmpInst &Cmp);
  Instruction *foldICmpWithZero(ICmpInst &Cmp);

  Instruction *foldICmpSelectConstant(ICmpInst &Cmp, SelectInst *Select,
                                      ConstantInt *C);
  Instruction *foldICmpBitCastConstant(ICmpInst &Cmp, BitCastInst *Bitcast,
                                       const APInt &C);
  Instruction *foldICmpTruncConstant(ICmpInst &Cmp, TruncInst *Trunc,
                                     const APInt &C);
  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 *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 *foldICmpShrConstConst(ICmpInst &I, Value *ShAmt, const APInt &C1,
                                     const APInt &C2);
  Instruction *foldICmpShlConstConst(ICmpInst &I, Value *ShAmt, const APInt &C1,
                                     const APInt &C2);

  Instruction *foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
                                                 BinaryOperator *BO,
                                                 const APInt &C);
  Instruction *foldICmpIntrinsicWithConstant(ICmpInst &ICI, const APInt &C);

  // Helpers of visitSelectInst().
  Instruction *foldSelectExtConst(SelectInst &Sel);
  Instruction *foldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
  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);

  Instruction *OptAndOp(BinaryOperator *Op, ConstantInt *OpRHS,
                        ConstantInt *AndRHS, BinaryOperator &TheAnd);

  Value *insertRangeTest(Value *V, const APInt &Lo, const APInt &Hi,
                         bool isSigned, bool Inside);
  Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
  Instruction *MatchBSwap(BinaryOperator &I);
  bool SimplifyStoreAtEndOfBlock(StoreInst &SI);

  Instruction *SimplifyAnyMemTransfer(AnyMemTransferInst *MI);
  Instruction *SimplifyAnyMemSet(AnyMemSetInst *MI);

  Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);

  /// Returns a value X such that Val = X * Scale, or null if none.
  ///
  /// If the multiplication is known not to overflow then NoSignedWrap is set.
  Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
};

} // end namespace IGCombiner

#undef DEBUG_TYPE

#endif // LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H
