// Use is here to make keeping the "use" list of a Value up-to-date really easy.
//
class Use {
- Value *Val;
- User *U;
- Use *Prev, *Next;
- friend struct ilist_traits<Use>;
public:
inline void init(Value *V, User *U);
Value *operator->() { return Val; }
const Value *operator->() const { return Val; }
+
+private:
+ // NOTE!! The Next/Prev fields MUST stay at the start of this structure. The
+ // end-token for the ilist is allocated as JUST the next/prev pair to reduce
+ // memory usage instead of allocating an entire Use.
+ struct NextPrevPtrs {
+ Use *Next, *Prev;
+ } UseLinks;
+
+ Value *Val;
+ User *U;
+ friend struct ilist_traits<Use>;
};
template<>
struct ilist_traits<Use> {
- static Use *getPrev(Use *N) { return N->Prev; }
- static Use *getNext(Use *N) { return N->Next; }
- static const Use *getPrev(const Use *N) { return N->Prev; }
- static const Use *getNext(const Use *N) { return N->Next; }
- static void setPrev(Use *N, Use *Prev) { N->Prev = Prev; }
- static void setNext(Use *N, Use *Next) { N->Next = Next; }
-
- // createNode - this is used to create the end marker for the use list
- static Use *createNode() { return new Use(0,0); }
+ static Use *getPrev(Use *N) { return N->UseLinks.Prev; }
+ static Use *getNext(Use *N) { return N->UseLinks.Next; }
+ static const Use *getPrev(const Use *N) { return N->UseLinks.Prev; }
+ static const Use *getNext(const Use *N) { return N->UseLinks.Next; }
+ static void setPrev(Use *N, Use *Prev) { N->UseLinks.Prev = Prev; }
+ static void setNext(Use *N, Use *Next) { N->UseLinks.Next = Next; }
+
+ /// createSentinal - this is used to create the end marker for the use list.
+ /// Note that we only allocate a UseLinks structure, which is just enough to
+ /// hold the next/prev pointers. This saves us 8 bytes of memory for every
+ /// Value allocated.
+ static Use *createSentinal() { return (Use*)new Use::NextPrevPtrs(); }
+ static void destroySentinal(Use *S) { delete (Use::NextPrevPtrs*)S; }
void addNodeToList(Use *NTy) {}
void removeNodeFromList(Use *NTy) {}