Improve SmallPtrSetImpl::count implementation

[serge-sans-paille]

Summary

Relying on the find method implies a roundtrip to the iterator world, which is not costless because iterator creation involves a few check to ensure the iterator is in a valid position (through the SmallPtrSetIteratorImpl::AdvanceIfNotValid method). It turns out that the result of SmallPtrSetImpl::find_imp is either valid or the EndPointer, so there's no need to go through that abstraction, and the compiler cannot guess it.

[bkramer]

lg

llvm/include/llvm/ADT/SmallPtrSet.h

public:
   }
 
   /// erase - If the set contains the specified pointer, remove it and return
   /// true, otherwise return false.
   bool erase(PtrType Ptr) {
     return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
   }
   /// count - Return 1 if the specified pointer is in the set, 0 otherwise.
-  size_type count(ConstPtrType Ptr) const { return find(Ptr) != end() ? 1 : 0; }
+  size_type count(ConstPtrType Ptr) const {
+    return find_imp(ConstPtrTraits::getAsVoidPointer(Ptr)) != EndPointer();
+  }
   iterator find(ConstPtrType Ptr) const {
     return makeIterator(find_imp(ConstPtrTraits::getAsVoidPointer(Ptr)));
   }
 
   template <typename IterT>
   void insert(IterT I, IterT E) {
     for (; I != E; ++I)
       insert(*I);