C++ MDNode::replaceAllUsesWith方法代码示例

// Replace value from this node's operand list.
void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {
  Value *From = *Op;

  // If is possible that someone did GV->RAUW(inst), replacing a global variable
  // with an instruction or some other function-local object.  If this is a
  // non-function-local MDNode, it can't point to a function-local object.
  // Handle this case by implicitly dropping the MDNode reference to null.
  if (!isFunctionLocal() && To && isFunctionLocalValue(To))
    To = 0;
  
  if (From == To)
    return;

  // Update the operand.
  Op->set(To);

  // If this node is already not being uniqued (because one of the operands
  // already went to null), then there is nothing else to do here.
  if (isNotUniqued()) return;

  LLVMContextImpl *pImpl = getType()->getContext().pImpl;

  // Remove "this" from the context map.  FoldingSet doesn't have to reprofile
  // this node to remove it, so we don't care what state the operands are in.
  pImpl->MDNodeSet.RemoveNode(this);

  // If we are dropping an argument to null, we choose to not unique the MDNode
  // anymore.  This commonly occurs during destruction, and uniquing these
  // brings little reuse.
  if (To == 0) {
    setIsNotUniqued();
    return;
  }

  // Now that the node is out of the folding set, get ready to reinsert it.
  // First, check to see if another node with the same operands already exists
  // in the set.  If it doesn't exist, this returns the position to insert it.
  FoldingSetNodeID ID;
  Profile(ID);
  void *InsertPoint;
  MDNode *N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);

  if (N) {
    N->replaceAllUsesWith(this);
    N->destroy();
    N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);
    assert(N == 0 && "shouldn't be in the map now!"); (void)N;
  }

  // InsertPoint will have been set by the FindNodeOrInsertPos call.
  pImpl->MDNodeSet.InsertNode(this, InsertPoint);
}

/// replaceAllUsesWith - Replace all uses of debug info referenced by
/// this descriptor.
void DIType::replaceAllUsesWith(MDNode *D) {
  if (!DbgNode)
    return;

  // Since we use a TrackingVH for the node, its easy for clients to manufacture
  // legitimate situations where they want to replaceAllUsesWith() on something
  // which, due to uniquing, has merged with the source. We shield clients from
  // this detail by allowing a value to be replaced with replaceAllUsesWith()
  // itself.
  if (DbgNode != D) {
    MDNode *Node = const_cast<MDNode*>(DbgNode);
    const MDNode *DN = D;
    const Value *V = cast_or_null<Value>(DN);
    Node->replaceAllUsesWith(const_cast<Value*>(V));
    MDNode::deleteTemporary(Node);
  }
}

Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
                      ValueMapTypeRemapper *TypeMapper) {
  ValueToValueMapTy::iterator I = VM.find(V);
  
  // If the value already exists in the map, use it.
  if (I != VM.end() && I->second) return I->second;
  
  // Global values do not need to be seeded into the VM if they
  // are using the identity mapping.
  if (isa<GlobalValue>(V) || isa<MDString>(V))
    return VM[V] = const_cast<Value*>(V);
  
  if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
    // Inline asm may need *type* remapping.
    FunctionType *NewTy = IA->getFunctionType();
    if (TypeMapper) {
      NewTy = cast<FunctionType>(TypeMapper->remapType(NewTy));

      if (NewTy != IA->getFunctionType())
        V = InlineAsm::get(NewTy, IA->getAsmString(), IA->getConstraintString(),
                           IA->hasSideEffects(), IA->isAlignStack());
    }
    
    return VM[V] = const_cast<Value*>(V);
  }
  

  if (const MDNode *MD = dyn_cast<MDNode>(V)) {
    // If this is a module-level metadata and we know that nothing at the module
    // level is changing, then use an identity mapping.
    if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
      return VM[V] = const_cast<Value*>(V);
    
    // Create a dummy node in case we have a metadata cycle.
    MDNode *Dummy = MDNode::getTemporary(V->getContext(), ArrayRef<Value*>());
    VM[V] = Dummy;
    
    // Check all operands to see if any need to be remapped.
    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
      Value *OP = MD->getOperand(i);
      if (OP == 0 || MapValue(OP, VM, Flags, TypeMapper) == OP) continue;

      // Ok, at least one operand needs remapping.  
      SmallVector<Value*, 4> Elts;
      Elts.reserve(MD->getNumOperands());
      for (i = 0; i != e; ++i) {
        Value *Op = MD->getOperand(i);
        Elts.push_back(Op ? MapValue(Op, VM, Flags, TypeMapper) : 0);
      }
      MDNode *NewMD = MDNode::get(V->getContext(), Elts);
      Dummy->replaceAllUsesWith(NewMD);
      VM[V] = NewMD;
      MDNode::deleteTemporary(Dummy);
      return NewMD;
    }

    VM[V] = const_cast<Value*>(V);
    MDNode::deleteTemporary(Dummy);

    // No operands needed remapping.  Use an identity mapping.
    return const_cast<Value*>(V);
  }

  // Okay, this either must be a constant (which may or may not be mappable) or
  // is something that is not in the mapping table.
  Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
  if (C == 0)
    return 0;
  
  if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
    Function *F = 
      cast<Function>(MapValue(BA->getFunction(), VM, Flags, TypeMapper));
    BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
                                                       Flags, TypeMapper));
    return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
  }
  
  // Otherwise, we have some other constant to remap.  Start by checking to see
  // if all operands have an identity remapping.
  unsigned OpNo = 0, NumOperands = C->getNumOperands();
  Value *Mapped = 0;
  for (; OpNo != NumOperands; ++OpNo) {
    Value *Op = C->getOperand(OpNo);
    Mapped = MapValue(Op, VM, Flags, TypeMapper);
    if (Mapped != C) break;
  }
  
  // See if the type mapper wants to remap the type as well.
  Type *NewTy = C->getType();
  if (TypeMapper)
    NewTy = TypeMapper->remapType(NewTy);

  // If the result type and all operands match up, then just insert an identity
  // mapping.
  if (OpNo == NumOperands && NewTy == C->getType())
    return VM[V] = C;
  
  // Okay, we need to create a new constant.  We've already processed some or
  // all of the operands, set them all up now.
  SmallVector<Constant*, 8> Ops;
//.........这里部分代码省略.........

// Replace value from this node's operand list.
void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {
  Value *From = *Op;

  // If is possible that someone did GV->RAUW(inst), replacing a global variable
  // with an instruction or some other function-local object.  If this is a
  // non-function-local MDNode, it can't point to a function-local object.
  // Handle this case by implicitly dropping the MDNode reference to null.
  // Likewise if the MDNode is function-local but for a different function.
  if (To && isFunctionLocalValue(To)) {
    if (!isFunctionLocal())
      To = 0;
    else {
      const Function *F = getFunction();
      const Function *FV = getFunctionForValue(To);
      // Metadata can be function-local without having an associated function.
      // So only consider functions to have changed if non-null.
      if (F && FV && F != FV)
        To = 0;
    }
  }
  
  if (From == To)
    return;

  // Update the operand.
  Op->set(To);

  // If this node is already not being uniqued (because one of the operands
  // already went to null), then there is nothing else to do here.
  if (isNotUniqued()) return;

  LLVMContextImpl *pImpl = getType()->getContext().pImpl;

  // Remove "this" from the context map.  FoldingSet doesn't have to reprofile
  // this node to remove it, so we don't care what state the operands are in.
  pImpl->MDNodeSet.RemoveNode(this);

  // If we are dropping an argument to null, we choose to not unique the MDNode
  // anymore.  This commonly occurs during destruction, and uniquing these
  // brings little reuse.  Also, this means we don't need to include
  // isFunctionLocal bits in FoldingSetNodeIDs for MDNodes.
  if (To == 0) {
    setIsNotUniqued();
    return;
  }

  // Now that the node is out of the folding set, get ready to reinsert it.
  // First, check to see if another node with the same operands already exists
  // in the set.  If it doesn't exist, this returns the position to insert it.
  FoldingSetNodeID ID;
  Profile(ID);
  void *InsertPoint;
  MDNode *N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);

  if (N) {
    N->replaceAllUsesWith(this);
    N->destroy();
    N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);
    assert(N == 0 && "shouldn't be in the map now!"); (void)N;
  }

  // InsertPoint will have been set by the FindNodeOrInsertPos call.
  pImpl->MDNodeSet.InsertNode(this, InsertPoint);

  // If this MDValue was previously function-local but no longer is, clear
  // its function-local flag.
  if (isFunctionLocal() && !isFunctionLocalValue(To)) {
    bool isStillFunctionLocal = false;
    for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
      Value *V = getOperand(i);
      if (!V) continue;
      if (isFunctionLocalValue(V)) {
        isStillFunctionLocal = true;
        break;
      }
    }
    if (!isStillFunctionLocal)
      setValueSubclassData(getSubclassDataFromValue() & ~FunctionLocalBit);
  }
}

Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM,
                      RemapFlags Flags) {
  ValueToValueMapTy::iterator I = VM.find(V);
  
  // If the value already exists in the map, use it.
  if (I != VM.end() && I->second) return I->second;
  
  // Global values do not need to be seeded into the VM if they
  // are using the identity mapping.
  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V))
    return VM[V] = const_cast<Value*>(V);

  if (const MDNode *MD = dyn_cast<MDNode>(V)) {
    // If this is a module-level metadata and we know that nothing at the module
    // level is changing, then use an identity mapping.
    if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
      return VM[V] = const_cast<Value*>(V);
    
    // Create a dummy node in case we have a metadata cycle.
    MDNode *Dummy = MDNode::getTemporary(V->getContext(), 0, 0);
    VM[V] = Dummy;
    
    // Check all operands to see if any need to be remapped.
    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
      Value *OP = MD->getOperand(i);
      if (OP == 0 || MapValue(OP, VM, Flags) == OP) continue;

      // Ok, at least one operand needs remapping.  
      SmallVector<Value*, 4> Elts;
      Elts.reserve(MD->getNumOperands());
      for (i = 0; i != e; ++i) {
        Value *Op = MD->getOperand(i);
        Elts.push_back(Op ? MapValue(Op, VM, Flags) : 0);
      }
      MDNode *NewMD = MDNode::get(V->getContext(), Elts.data(), Elts.size());
      Dummy->replaceAllUsesWith(NewMD);
      VM[V] = NewMD;
      MDNode::deleteTemporary(Dummy);
      return NewMD;
    }

    VM[V] = const_cast<Value*>(V);
    MDNode::deleteTemporary(Dummy);

    // No operands needed remapping.  Use an identity mapping.
    return const_cast<Value*>(V);
  }

  // Okay, this either must be a constant (which may or may not be mappable) or
  // is something that is not in the mapping table.
  Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
  if (C == 0)
    return 0;
  
  if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
    Function *F = cast<Function>(MapValue(BA->getFunction(), VM, Flags));
    BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
                                                       Flags));
    return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
  }
  
  for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
    Value *Op = C->getOperand(i);
    Value *Mapped = MapValue(Op, VM, Flags);
    if (Mapped == C) continue;
    
    // Okay, the operands don't all match.  We've already processed some or all
    // of the operands, set them up now.
    std::vector<Constant*> Ops;
    Ops.reserve(C->getNumOperands());
    for (unsigned j = 0; j != i; ++j)
      Ops.push_back(cast<Constant>(C->getOperand(i)));
    Ops.push_back(cast<Constant>(Mapped));
    
    // Map the rest of the operands that aren't processed yet.
    for (++i; i != e; ++i)
      Ops.push_back(cast<Constant>(MapValue(C->getOperand(i), VM, Flags)));
    
    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
      return VM[V] = CE->getWithOperands(Ops);
    if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
      return VM[V] = ConstantArray::get(CA->getType(), Ops);
    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C))
      return VM[V] = ConstantStruct::get(CS->getType(), Ops);
    assert(isa<ConstantVector>(C) && "Unknown mapped constant type");
    return VM[V] = ConstantVector::get(Ops);
  }

  // If we reach here, all of the operands of the constant match.
  return VM[V] = C;
}