C++ FoldingSetNodeID::ComputeHash方法代码示例

static unsigned node_hash(GepNode *N) {
    // Include everything except flags and parent.
    FoldingSetNodeID ID;
    ID.AddPointer(N->Idx);
    ID.AddPointer(N->PTy);
    return ID.ComputeHash();
}

/// Creates a hash-code for the function which is the same for any two
/// functions that will compare equal, without looking at the instructions
/// inside the function.
static unsigned profileFunction(const Function *F) {
  FunctionType *FTy = F->getFunctionType();

  FoldingSetNodeID ID;
  ID.AddInteger(F->size());
  ID.AddInteger(F->getCallingConv());
  ID.AddBoolean(F->hasGC());
  ID.AddBoolean(FTy->isVarArg());
  ID.AddInteger(getTypeIDForHash(FTy->getReturnType()));
  for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
    ID.AddInteger(getTypeIDForHash(FTy->getParamType(i)));
  return ID.ComputeHash();
}

MDNode *MDNode::getMDNode(LLVMContext &Context, ArrayRef<Value*> Vals,
                          FunctionLocalness FL, bool Insert) {
  LLVMContextImpl *pImpl = Context.pImpl;

  // Add all the operand pointers. Note that we don't have to add the
  // isFunctionLocal bit because that's implied by the operands.
  // Note that if the operands are later nulled out, the node will be
  // removed from the uniquing map.
  FoldingSetNodeID ID;
  for (unsigned i = 0; i != Vals.size(); ++i)
    ID.AddPointer(Vals[i]);

  void *InsertPoint;
  MDNode *N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);

  if (N || !Insert)
    return N;

  bool isFunctionLocal = false;
  switch (FL) {
  case FL_Unknown:
    for (unsigned i = 0; i != Vals.size(); ++i) {
      Value *V = Vals[i];
      if (!V) continue;
      if (isFunctionLocalValue(V)) {
        isFunctionLocal = true;
        break;
      }
    }
    break;
  case FL_No:
    isFunctionLocal = false;
    break;
  case FL_Yes:
    isFunctionLocal = true;
    break;
  }

  // Coallocate space for the node and Operands together, then placement new.
  void *Ptr = malloc(sizeof(MDNode) + Vals.size() * sizeof(MDNodeOperand));
  N = new (Ptr) MDNode(Context, Vals, isFunctionLocal);

  // Cache the operand hash.
  N->Hash = ID.ComputeHash();

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

  return N;
}

// 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 so, then this node is redundant.
  FoldingSetNodeID ID;
  Profile(ID);
  void *InsertPoint;
  if (MDNode *N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint)) {
    replaceAllUsesWith(N);
    destroy();
    return;
  }

  // Cache the operand hash.
  Hash = ID.ComputeHash();
  // 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);
  }
}