text: //===-- Instruction.cpp - Implement the Instruction class -----------------===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the Instruction class for the IR library.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/IR/Instruction.h"
  #include "llvm/ADT/DenseSet.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/MDBuilder.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/Type.h"
  using namespace llvm;
  
  Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
                           Instruction *InsertBefore)
    : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(nullptr) {
  
    // If requested, insert this instruction into a basic block...
    if (InsertBefore) {
      BasicBlock *BB = InsertBefore->getParent();
      assert(BB && "Instruction to insert before is not in a basic block!");
      BB->getInstList().insert(InsertBefore->getIterator(), this);
    }
  }
  
  Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
                           BasicBlock *InsertAtEnd)
    : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(nullptr) {
  
    // append this instruction into the basic block
    assert(InsertAtEnd && "Basic block to append to may not be NULL!");
    InsertAtEnd->getInstList().push_back(this);
  }
  
  Instruction::~Instruction() {
    assert(!Parent && "Instruction still linked in the program!");
  
    // Replace any extant metadata uses of this instruction with undef to
    // preserve debug info accuracy. Some alternatives include:
    // - Treat Instruction like any other Value, and point its extant metadata
    //   uses to an empty ValueAsMetadata node. This makes extant dbg.value uses
    //   trivially dead (i.e. fair game for deletion in many passes), leading to
    //   stale dbg.values being in effect for too long.
    // - Call salvageDebugInfoOrMarkUndef. Not needed to make instruction removal
    //   correct. OTOH results in wasted work in some common cases (e.g. when all
    //   instructions in a BasicBlock are deleted).
    if (isUsedByMetadata())
      ValueAsMetadata::handleRAUW(this, UndefValue::get(getType()));
  }
  
  
  void Instruction::setParent(BasicBlock *P) {
    Parent = P;
  }
  
  const Module *Instruction::getModule() const {
    return getParent()->getModule();
  }
  
  const Function *Instruction::getFunction() const {
    return getParent()->getParent();
  }
  
  void Instruction::removeFromParent() {
    getParent()->getInstList().remove(getIterator());
  }
  
  iplist<Instruction>::iterator Instruction::eraseFromParent() {
    return getParent()->getInstList().erase(getIterator());
  }
  
  /// Insert an unlinked instruction into a basic block immediately before the
  /// specified instruction.
  void Instruction::insertBefore(Instruction *InsertPos) {
    InsertPos->getParent()->getInstList().insert(InsertPos->getIterator(), this);
  }
  
  /// Insert an unlinked instruction into a basic block immediately after the
  /// specified instruction.
  void Instruction::insertAfter(Instruction *InsertPos) {
    InsertPos->getParent()->getInstList().insertAfter(InsertPos->getIterator(),
                                                      this);
  }
  
  /// Unlink this instruction from its current basic block and insert it into the
  /// basic block that MovePos lives in, right before MovePos.
  void Instruction::moveBefore(Instruction *MovePos) {
    moveBefore(*MovePos->getParent(), MovePos->getIterator());
  }
  
  void Instruction::moveAfter(Instruction *MovePos) {
    moveBefore(*MovePos->getParent(), ++MovePos->getIterator());
  }
  
  void Instruction::moveBefore(BasicBlock &BB,
                               SymbolTableList<Instruction>::iterator I) {
    assert(I == BB.end() || I->getParent() == &BB);
    BB.getInstList().splice(I, getParent()->getInstList(), getIterator());
  }
  
  bool Instruction::comesBefore(const Instruction *Other) const {
    assert(Parent && Other->Parent &&
           "instructions without BB parents have no order");
    assert(Parent == Other->Parent && "cross-BB instruction order comparison");
    if (!Parent->isInstrOrderValid())
      Parent->renumberInstructions();
    return Order < Other->Order;
  }
  
  bool Instruction::isOnlyUserOfAnyOperand() {
    return any_of(operands(), [](Value *V) { return V->hasOneUser(); });
  }
  
  void Instruction::setHasNoUnsignedWrap(bool b) {
    cast<OverflowingBinaryOperator>(this)->setHasNoUnsignedWrap(b);
  }
  
  void Instruction::setHasNoSignedWrap(bool b) {
    cast<OverflowingBinaryOperator>(this)->setHasNoSignedWrap(b);
  }
  
  void Instruction::setIsExact(bool b) {
    cast<PossiblyExactOperator>(this)->setIsExact(b);
  }
  
  bool Instruction::hasNoUnsignedWrap() const {
    return cast<OverflowingBinaryOperator>(this)->hasNoUnsignedWrap();
  }
  
  bool Instruction::hasNoSignedWrap() const {
    return cast<OverflowingBinaryOperator>(this)->hasNoSignedWrap();
  }
  
  void Instruction::dropPoisonGeneratingFlags() {
    switch (getOpcode()) {
    case Instruction::Add:
    case Instruction::Sub:
    case Instruction::Mul:
    case Instruction::Shl:
      cast<OverflowingBinaryOperator>(this)->setHasNoUnsignedWrap(false);
      cast<OverflowingBinaryOperator>(this)->setHasNoSignedWrap(false);
      break;
  
    case Instruction::UDiv:
    case Instruction::SDiv:
    case Instruction::AShr:
    case Instruction::LShr:
      cast<PossiblyExactOperator>(this)->setIsExact(false);
      break;
  
    case Instruction::GetElementPtr:
      cast<GetElementPtrInst>(this)->setIsInBounds(false);
      break;
    }
    // TODO: FastMathFlags!
  }
  
  void Instruction::dropUndefImplyingAttrsAndUnknownMetadata(
      ArrayRef<unsigned> KnownIDs) {
    dropUnknownNonDebugMetadata(KnownIDs);
    auto *CB = dyn_cast<CallBase>(this);
    if (!CB)
      return;
    // For call instructions, we also need to drop parameter and return attributes
    // that are can cause UB if the call is moved to a location where the
    // attribute is not valid.
    AttributeList AL = CB->getAttributes();
    if (AL.isEmpty())
      return;
    AttrBuilder UBImplyingAttributes = AttributeFuncs::getUBImplyingAttributes();
    for (unsigned ArgNo = 0; ArgNo < CB->getNumArgOperands(); ArgNo++)
      CB->removeParamAttrs(ArgNo, UBImplyingAttributes);
    CB->removeAttributes(AttributeList::ReturnIndex, UBImplyingAttributes);
  }
  
  bool Instruction::isExact() const {
    return cast<PossiblyExactOperator>(this)->isExact();
  }
  
  void Instruction::setFast(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setFast(B);
  }
  
  void Instruction::setHasAllowReassoc(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasAllowReassoc(B);
  }
  
  void Instruction::setHasNoNaNs(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasNoNaNs(B);
  }
  
  void Instruction::setHasNoInfs(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasNoInfs(B);
  }
  
  void Instruction::setHasNoSignedZeros(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasNoSignedZeros(B);
  }
  
  void Instruction::setHasAllowReciprocal(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasAllowReciprocal(B);
  }
  
  void Instruction::setHasAllowContract(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasAllowContract(B);
  }
  
  void Instruction::setHasApproxFunc(bool B) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setHasApproxFunc(B);
  }
  
  void Instruction::setFastMathFlags(FastMathFlags FMF) {
    assert(isa<FPMathOperator>(this) && "setting fast-math flag on invalid op");
    cast<FPMathOperator>(this)->setFastMathFlags(FMF);
  }
  
  void Instruction::copyFastMathFlags(FastMathFlags FMF) {
    assert(isa<FPMathOperator>(this) && "copying fast-math flag on invalid op");
    cast<FPMathOperator>(this)->copyFastMathFlags(FMF);
  }
  
  bool Instruction::isFast() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->isFast();
  }
  
  bool Instruction::hasAllowReassoc() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasAllowReassoc();
  }
  
  bool Instruction::hasNoNaNs() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasNoNaNs();
  }
  
  bool Instruction::hasNoInfs() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasNoInfs();
  }
  
  bool Instruction::hasNoSignedZeros() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasNoSignedZeros();
  }
  
  bool Instruction::hasAllowReciprocal() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasAllowReciprocal();
  }
  
  bool Instruction::hasAllowContract() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasAllowContract();
  }
  
  bool Instruction::hasApproxFunc() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->hasApproxFunc();
  }
  
  FastMathFlags Instruction::getFastMathFlags() const {
    assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
    return cast<FPMathOperator>(this)->getFastMathFlags();
  }
  
  void Instruction::copyFastMathFlags(const Instruction *I) {
    copyFastMathFlags(I->getFastMathFlags());
  }
  
  void Instruction::copyIRFlags(const Value *V, bool IncludeWrapFlags) {
    // Copy the wrapping flags.
    if (IncludeWrapFlags && isa<OverflowingBinaryOperator>(this)) {
      if (auto *OB = dyn_cast<OverflowingBinaryOperator>(V)) {
        setHasNoSignedWrap(OB->hasNoSignedWrap());
        setHasNoUnsignedWrap(OB->hasNoUnsignedWrap());
      }
    }
  
    // Copy the exact flag.
    if (auto *PE = dyn_cast<PossiblyExactOperator>(V))
      if (isa<PossiblyExactOperator>(this))
        setIsExact(PE->isExact());
  
    // Copy the fast-math flags.
    if (auto *FP = dyn_cast<FPMathOperator>(V))
      if (isa<FPMathOperator>(this))
        copyFastMathFlags(FP->getFastMathFlags());
  
    if (auto *SrcGEP = dyn_cast<GetElementPtrInst>(V))
      if (auto *DestGEP = dyn_cast<GetElementPtrInst>(this))
        DestGEP->setIsInBounds(SrcGEP->isInBounds() | DestGEP->isInBounds());
  }
  
  void Instruction::andIRFlags(const Value *V) {
    if (auto *OB = dyn_cast<OverflowingBinaryOperator>(V)) {
      if (isa<OverflowingBinaryOperator>(this)) {
        setHasNoSignedWrap(hasNoSignedWrap() & OB->hasNoSignedWrap());
        setHasNoUnsignedWrap(hasNoUnsignedWrap() & OB->hasNoUnsignedWrap());
      }
    }
  
    if (auto *PE = dyn_cast<PossiblyExactOperator>(V))
      if (isa<PossiblyExactOperator>(this))
        setIsExact(isExact() & PE->isExact());
  
    if (auto *FP = dyn_cast<FPMathOperator>(V)) {
      if (isa<FPMathOperator>(this)) {
        FastMathFlags FM = getFastMathFlags();
        FM &= FP->getFastMathFlags();
        copyFastMathFlags(FM);
      }
    }
  
    if (auto *SrcGEP = dyn_cast<GetElementPtrInst>(V))
      if (auto *DestGEP = dyn_cast<GetElementPtrInst>(this))
        DestGEP->setIsInBounds(SrcGEP->isInBounds() & DestGEP->isInBounds());
  }
  
  const char *Instruction::getOpcodeName(unsigned OpCode) {
    switch (OpCode) {
    // Terminators
    case Ret:    return "ret";
    case Br:     return "br";
    case Switch: return "switch";
    case IndirectBr: return "indirectbr";
    case Invoke: return "invoke";
    case Resume: return "resume";
    case Unreachable: return "unreachable";
    case CleanupRet: return "cleanupret";
    case CatchRet: return "catchret";
    case CatchPad: return "catchpad";
    case CatchSwitch: return "catchswitch";
    case CallBr: return "callbr";
  
    // Standard unary operators...
    case FNeg: return "fneg";
  
    // Standard binary operators...
    case Add: return "add";
    case FAdd: return "fadd";
    case Sub: return "sub";
    case FSub: return "fsub";
    case Mul: return "mul";
    case FMul: return "fmul";
    case UDiv: return "udiv";
    case SDiv: return "sdiv";
    case FDiv: return "fdiv";
    case URem: return "urem";
    case SRem: return "srem";
    case FRem: return "frem";
  
    // Logical operators...
    case And: return "and";
    case Or : return "or";
    case Xor: return "xor";
  
    // Memory instructions...
    case Alloca:        return "alloca";
    case Load:          return "load";
    case Store:         return "store";
    case AtomicCmpXchg: return "cmpxchg";
    case AtomicRMW:     return "atomicrmw";
    case Fence:         return "fence";
    case GetElementPtr: return "getelementptr";
  
    // Convert instructions...
    case Trunc:         return "trunc";
    case ZExt:          return "zext";
    case SExt:          return "sext";
    case FPTrunc:       return "fptrunc";
    case FPExt:         return "fpext";
    case FPToUI:        return "fptoui";
    case FPToSI:        return "fptosi";
    case UIToFP:        return "uitofp";
    case SIToFP:        return "sitofp";
    case IntToPtr:      return "inttoptr";
    case PtrToInt:      return "ptrtoint";
    case BitCast:       return "bitcast";
    case AddrSpaceCast: return "addrspacecast";
  
    // Other instructions...
    case ICmp:           return "icmp";
    case FCmp:           return "fcmp";
    case PHI:            return "phi";
    case Select:         return "select";
    case Call:           return "call";
    case Shl:            return "shl";
    case LShr:           return "lshr";
    case AShr:           return "ashr";
    case VAArg:          return "va_arg";
    case ExtractElement: return "extractelement";
    case InsertElement:  return "insertelement";
    case ShuffleVector:  return "shufflevector";
    case ExtractValue:   return "extractvalue";
    case InsertValue:    return "insertvalue";
    case LandingPad:     return "landingpad";
    case CleanupPad:     return "cleanuppad";
    case Freeze:         return "freeze";
  
    default: return "<Invalid operator> ";
    }
  }
  
  /// Return true if both instructions have the same special state. This must be
  /// kept in sync with FunctionComparator::cmpOperations in
  /// lib/Transforms/IPO/MergeFunctions.cpp.
  static bool haveSameSpecialState(const Instruction *I1, const Instruction *I2,
                                   bool IgnoreAlignment = false) {
    assert(I1->getOpcode() == I2->getOpcode() &&
           "Can not compare special state of different instructions");
  
    if (const AllocaInst *AI = dyn_cast<AllocaInst>(I1))
      return AI->getAllocatedType() == cast<AllocaInst>(I2)->getAllocatedType() &&
             (AI->getAlignment() == cast<AllocaInst>(I2)->getAlignment() ||
              IgnoreAlignment);
    if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
      return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
             (LI->getAlignment() == cast<LoadInst>(I2)->getAlignment() ||
              IgnoreAlignment) &&
             LI->getOrdering() == cast<LoadInst>(I2)->getOrdering() &&
             LI->getSyncScopeID() == cast<LoadInst>(I2)->getSyncScopeID();
    if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
      return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
             (SI->getAlignment() == cast<StoreInst>(I2)->getAlignment() ||
              IgnoreAlignment) &&
             SI->getOrdering() == cast<StoreInst>(I2)->getOrdering() &&
             SI->getSyncScopeID() == cast<StoreInst>(I2)->getSyncScopeID();
    if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
      return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
    if (const CallInst *CI = dyn_cast<CallInst>(I1))
      return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
             CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
             CI->getAttributes() == cast<CallInst>(I2)->getAttributes() &&
             CI->hasIdenticalOperandBundleSchema(*cast<CallInst>(I2));
    if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
      return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
             CI->getAttributes() == cast<InvokeInst>(I2)->getAttributes() &&
             CI->hasIdenticalOperandBundleSchema(*cast<InvokeInst>(I2));
    if (const CallBrInst *CI = dyn_cast<CallBrInst>(I1))
      return CI->getCallingConv() == cast<CallBrInst>(I2)->getCallingConv() &&
             CI->getAttributes() == cast<CallBrInst>(I2)->getAttributes() &&
             CI->hasIdenticalOperandBundleSchema(*cast<CallBrInst>(I2));
    if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1))
      return IVI->getIndices() == cast<InsertValueInst>(I2)->getIndices();
    if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1))
      return EVI->getIndices() == cast<ExtractValueInst>(I2)->getIndices();
    if (const FenceInst *FI = dyn_cast<FenceInst>(I1))
      return FI->getOrdering() == cast<FenceInst>(I2)->getOrdering() &&
             FI->getSyncScopeID() == cast<FenceInst>(I2)->getSyncScopeID();
    if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(I1))
      return CXI->isVolatile() == cast<AtomicCmpXchgInst>(I2)->isVolatile() &&
             CXI->isWeak() == cast<AtomicCmpXchgInst>(I2)->isWeak() &&
             CXI->getSuccessOrdering() ==
                 cast<AtomicCmpXchgInst>(I2)->getSuccessOrdering() &&
             CXI->getFailureOrdering() ==
                 cast<AtomicCmpXchgInst>(I2)->getFailureOrdering() &&
             CXI->getSyncScopeID() ==
                 cast<AtomicCmpXchgInst>(I2)->getSyncScopeID();
    if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I1))
      return RMWI->getOperation() == cast<AtomicRMWInst>(I2)->getOperation() &&
             RMWI->isVolatile() == cast<AtomicRMWInst>(I2)->isVolatile() &&
             RMWI->getOrdering() == cast<AtomicRMWInst>(I2)->getOrdering() &&
             RMWI->getSyncScopeID() == cast<AtomicRMWInst>(I2)->getSyncScopeID();
    if (const ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I1))
      return SVI->getShuffleMask() ==
             cast<ShuffleVectorInst>(I2)->getShuffleMask();
  
    return true;
  }
  
  bool Instruction::isIdenticalTo(const Instruction *I) const {
    return isIdenticalToWhenDefined(I) &&
           SubclassOptionalData == I->SubclassOptionalData;
  }
  
  bool Instruction::isIdenticalToWhenDefined(const Instruction *I) const {
    if (getOpcode() != I->getOpcode() ||
        getNumOperands() != I->getNumOperands() ||
        getType() != I->getType())
      return false;
  
    // If both instructions have no operands, they are identical.
    if (getNumOperands() == 0 && I->getNumOperands() == 0)
      return haveSameSpecialState(this, I);
  
    // We have two instructions of identical opcode and #operands.  Check to see
    // if all operands are the same.
    if (!std::equal(op_begin(), op_end(), I->op_begin()))
      return false;
  
    // WARNING: this logic must be kept in sync with EliminateDuplicatePHINodes()!
    if (const PHINode *thisPHI = dyn_cast<PHINode>(this)) {
      const PHINode *otherPHI = cast<PHINode>(I);
      return std::equal(thisPHI->block_begin(), thisPHI->block_end(),
                        otherPHI->block_begin());
    }
  
    return haveSameSpecialState(this, I);
  }
  
  // Keep this in sync with FunctionComparator::cmpOperations in
  // lib/Transforms/IPO/MergeFunctions.cpp.
  bool Instruction::isSameOperationAs(const Instruction *I,
                                      unsigned flags) const {
    bool IgnoreAlignment = flags & CompareIgnoringAlignment;
    bool UseScalarTypes  = flags & CompareUsingScalarTypes;
  
    if (getOpcode() != I->getOpcode() ||
        getNumOperands() != I->getNumOperands() ||
        (UseScalarTypes ?
         getType()->getScalarType() != I->getType()->getScalarType() :
         getType() != I->getType()))
      return false;
  
    // We have two instructions of identical opcode and #operands.  Check to see
    // if all operands are the same type
    for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
      if (UseScalarTypes ?
          getOperand(i)->getType()->getScalarType() !=
            I->getOperand(i)->getType()->getScalarType() :
          getOperand(i)->getType() != I->getOperand(i)->getType())
        return false;
  
    return haveSameSpecialState(this, I, IgnoreAlignment);
  }
  
  bool Instruction::isUsedOutsideOfBlock(const BasicBlock *BB) const {
    for (const Use &U : uses()) {
      // PHI nodes uses values in the corresponding predecessor block.  For other
      // instructions, just check to see whether the parent of the use matches up.
      const Instruction *I = cast<Instruction>(U.getUser());
      const PHINode *PN = dyn_cast<PHINode>(I);
      if (!PN) {
        if (I->getParent() != BB)
          return true;
        continue;
      }
  
      if (PN->getIncomingBlock(U) != BB)
        return true;
    }
    return false;
  }
  
  bool Instruction::mayReadFromMemory() const {
    switch (getOpcode()) {
    default: return false;
    case Instruction::VAArg:
    case Instruction::Load:
    case Instruction::Fence: // FIXME: refine definition of mayReadFromMemory
    case Instruction::AtomicCmpXchg:
    case Instruction::AtomicRMW:
    case Instruction::CatchPad:
    case Instruction::CatchRet:
      return true;
    case Instruction::Call:
    case Instruction::Invoke:
    case Instruction::CallBr:
      return !cast<CallBase>(this)->doesNotReadMemory();
    case Instruction::Store:
      return !cast<StoreInst>(this)->isUnordered();
    }
  }
  
  bool Instruction::mayWriteToMemory() const {
    switch (getOpcode()) {
    default: return false;
    case Instruction::Fence: // FIXME: refine definition of mayWriteToMemory
    case Instruction::Store:
    case Instruction::VAArg:
    case Instruction::AtomicCmpXchg:
    case Instruction::AtomicRMW:
    case Instruction::CatchPad:
    case Instruction::CatchRet:
      return true;
    case Instruction::Call:
    case Instruction::Invoke:
    case Instruction::CallBr:
      return !cast<CallBase>(this)->onlyReadsMemory();
    case Instruction::Load:
      return !cast<LoadInst>(this)->isUnordered();
    }
  }
  
  bool Instruction::isAtomic() const {
    switch (getOpcode()) {
    default:
      return false;
    case Instruction::AtomicCmpXchg:
    case Instruction::AtomicRMW:
    case Instruction::Fence:
      return true;
    case Instruction::Load:
      return cast<LoadInst>(this)->getOrdering() != AtomicOrdering::NotAtomic;
    case Instruction::Store:
      return cast<StoreInst>(this)->getOrdering() != AtomicOrdering::NotAtomic;
    }
  }
  
  bool Instruction::hasAtomicLoad() const {
    assert(isAtomic());
    switch (getOpcode()) {
    default:
      return false;
    case Instruction::AtomicCmpXchg:
    case Instruction::AtomicRMW:
    case Instruction::Load:
      return true;
    }
  }
  
  bool Instruction::hasAtomicStore() const {
    assert(isAtomic());
    switch (getOpcode()) {
    default:
      return false;
    case Instruction::AtomicCmpXchg:
    case Instruction::AtomicRMW:
    case Instruction::Store:
      return true;
    }
  }
  
  bool Instruction::isVolatile() const {
    switch (getOpcode()) {
    default:
      return false;
    case Instruction::AtomicRMW:
      return cast<AtomicRMWInst>(this)->isVolatile();
    case Instruction::Store:
      return cast<StoreInst>(this)->isVolatile();
    case Instruction::Load:
      return cast<LoadInst>(this)->isVolatile();
    case Instruction::AtomicCmpXchg:
      return cast<AtomicCmpXchgInst>(this)->isVolatile();
    case Instruction::Call:
    case Instruction::Invoke:
      // There are a very limited number of intrinsics with volatile flags.
      if (auto *II = dyn_cast<IntrinsicInst>(this)) {
        if (auto *MI = dyn_cast<MemIntrinsic>(II))
          return MI->isVolatile();
        switch (II->getIntrinsicID()) {
        default: break;
        case Intrinsic::matrix_column_major_load:
          return cast<ConstantInt>(II->getArgOperand(2))->isOne();
        case Intrinsic::matrix_column_major_store:
          return cast<ConstantInt>(II->getArgOperand(3))->isOne();
        }
      }
      return false;
    }
  }
  
  bool Instruction::mayThrow() const {
    if (const CallInst *CI = dyn_cast<CallInst>(this))
      return !CI->doesNotThrow();
    if (const auto *CRI = dyn_cast<CleanupReturnInst>(this))
      return CRI->unwindsToCaller();
    if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(this))
      return CatchSwitch->unwindsToCaller();
    return isa<ResumeInst>(this);
  }
  
  bool Instruction::mayHaveSideEffects() const {
    return mayWriteToMemory() || mayThrow() || !willReturn();
  }
  
  bool Instruction::isSafeToRemove() const {
    return (!isa<CallInst>(this) || !this->mayHaveSideEffects()) &&
           !this->isTerminator();
  }
  
  bool Instruction::willReturn() const {
    // Volatile store isn't guaranteed to return; see LangRef.
    if (auto *SI = dyn_cast<StoreInst>(this))
      return !SI->isVolatile();
  
    if (const auto *CB = dyn_cast<CallBase>(this))
      // FIXME: Temporarily assume that all side-effect free intrinsics will
      // return. Remove this workaround once all intrinsics are appropriately
      // annotated.
      return CB->hasFnAttr(Attribute::WillReturn) ||
             (isa<IntrinsicInst>(CB) && CB->onlyReadsMemory());
    return true;
  }
  
  bool Instruction::isLifetimeStartOrEnd() const {
    auto *II = dyn_cast<IntrinsicInst>(this);
    if (!II)
      return false;
    Intrinsic::ID ID = II->getIntrinsicID();
    return ID == Intrinsic::lifetime_start || ID == Intrinsic::lifetime_end;
  }
  
  bool Instruction::isLaunderOrStripInvariantGroup() const {
    auto *II = dyn_cast<IntrinsicInst>(this);
    if (!II)
      return false;
    Intrinsic::ID ID = II->getIntrinsicID();
    return ID == Intrinsic::launder_invariant_group ||
           ID == Intrinsic::strip_invariant_group;
  }
  
  bool Instruction::isDebugOrPseudoInst() const {
    return isa<DbgInfoIntrinsic>(this) || isa<PseudoProbeInst>(this);
  }
  
  const Instruction *
  Instruction::getNextNonDebugInstruction(bool SkipPseudoOp) const {
    for (const Instruction *I = getNextNode(); I; I = I->getNextNode())
      if (!isa<DbgInfoIntrinsic>(I) && !(SkipPseudoOp && isa<PseudoProbeInst>(I)))
        return I;
    return nullptr;
  }
  
  const Instruction *
  Instruction::getPrevNonDebugInstruction(bool SkipPseudoOp) const {
    for (const Instruction *I = getPrevNode(); I; I = I->getPrevNode())
      if (!isa<DbgInfoIntrinsic>(I) && !(SkipPseudoOp && isa<PseudoProbeInst>(I)))
        return I;
    return nullptr;
  }
  
  bool Instruction::isAssociative() const {
    unsigned Opcode = getOpcode();
    if (isAssociative(Opcode))
      return true;
  
    switch (Opcode) {
    case FMul:
    case FAdd:
      return cast<FPMathOperator>(this)->hasAllowReassoc() &&
             cast<FPMathOperator>(this)->hasNoSignedZeros();
    default:
      return false;
    }
  }
  
  bool Instruction::isCommutative() const {
    if (auto *II = dyn_cast<IntrinsicInst>(this))
      return II->isCommutative();
    // TODO: Should allow icmp/fcmp?
    return isCommutative(getOpcode());
  }
  
  unsigned Instruction::getNumSuccessors() const {
    switch (getOpcode()) {
  #define HANDLE_TERM_INST(N, OPC, CLASS)                                        \
    case Instruction::OPC:                                                       \
      return static_cast<const CLASS *>(this)->getNumSuccessors();
  #include "llvm/IR/Instruction.def"
    default:
      break;
    }
    llvm_unreachable("not a terminator");
  }
  
  BasicBlock *Instruction::getSuccessor(unsigned idx) const {
    switch (getOpcode()) {
  #define HANDLE_TERM_INST(N, OPC, CLASS)                                        \
    case Instruction::OPC:                                                       \
      return static_cast<const CLASS *>(this)->getSuccessor(idx);
  #include "llvm/IR/Instruction.def"
    default:
      break;
    }
    llvm_unreachable("not a terminator");
  }
  
  void Instruction::setSuccessor(unsigned idx, BasicBlock *B) {
    switch (getOpcode()) {
  #define HANDLE_TERM_INST(N, OPC, CLASS)                                        \
    case Instruction::OPC:                                                       \
      return static_cast<CLASS *>(this)->setSuccessor(idx, B);
  #include "llvm/IR/Instruction.def"
    default:
      break;
    }
    llvm_unreachable("not a terminator");
  }
  
  void Instruction::replaceSuccessorWith(BasicBlock *OldBB, BasicBlock *NewBB) {
    for (unsigned Idx = 0, NumSuccessors = Instruction::getNumSuccessors();
         Idx != NumSuccessors; ++Idx)
      if (getSuccessor(Idx) == OldBB)
        setSuccessor(Idx, NewBB);
  }
  
  Instruction *Instruction::cloneImpl() const {
    llvm_unreachable("Subclass of Instruction failed to implement cloneImpl");
  }
  
  void Instruction::swapProfMetadata() {
    MDNode *ProfileData = getMetadata(LLVMContext::MD_prof);
    if (!ProfileData || ProfileData->getNumOperands() != 3 ||
        !isa<MDString>(ProfileData->getOperand(0)))
      return;
  
    MDString *MDName = cast<MDString>(ProfileData->getOperand(0));
    if (MDName->getString() != "branch_weights")
      return;
  
    // The first operand is the name. Fetch them backwards and build a new one.
    Metadata *Ops[] = {ProfileData->getOperand(0), ProfileData->getOperand(2),
                       ProfileData->getOperand(1)};
    setMetadata(LLVMContext::MD_prof,
                MDNode::get(ProfileData->getContext(), Ops));
  }
  
  void Instruction::copyMetadata(const Instruction &SrcInst,
                                 ArrayRef<unsigned> WL) {
    if (!SrcInst.hasMetadata())
      return;
  
    DenseSet<unsigned> WLS;
    for (unsigned M : WL)
      WLS.insert(M);
  
    // Otherwise, enumerate and copy over metadata from the old instruction to the
    // new one.
    SmallVector<std::pair<unsigned, MDNode *>, 4> TheMDs;
    SrcInst.getAllMetadataOtherThanDebugLoc(TheMDs);
    for (const auto &MD : TheMDs) {
      if (WL.empty() || WLS.count(MD.first))
        setMetadata(MD.first, MD.second);
    }
    if (WL.empty() || WLS.count(LLVMContext::MD_dbg))
      setDebugLoc(SrcInst.getDebugLoc());
  }
  
  Instruction *Instruction::clone() const {
    Instruction *New = nullptr;
    switch (getOpcode()) {
    default:
      llvm_unreachable("Unhandled Opcode.");
  #define HANDLE_INST(num, opc, clas)                                            \
    case Instruction::opc:                                                       \
      New = cast<clas>(this)->cloneImpl();                                       \
      break;
  #include "llvm/IR/Instruction.def"
  #undef HANDLE_INST
    }
  
    New->SubclassOptionalData = SubclassOptionalData;
    New->copyMetadata(*this);
    return New;
  }
  