SmallPtrSet: Provide a more efficient implementation of swap than the default triple-copy std::swap.

This currently assumes that both sets have the same SmallSize to keep the implementation simple,
a limitation that can be lifted if someone cares.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152143 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/ADT/SmallPtrSet.h b/include/llvm/ADT/SmallPtrSet.h
index 9992858..70693d5 100644
--- a/include/llvm/ADT/SmallPtrSet.h
+++ b/include/llvm/ADT/SmallPtrSet.h
@@ -137,6 +137,10 @@ private:
 
   void operator=(const SmallPtrSetImpl &RHS);  // DO NOT IMPLEMENT.
 protected:
+  /// swap - Swaps the elements of two sets.
+  /// Note: This method assumes that both sets have the same small size.
+  void swap(SmallPtrSetImpl &RHS);
+
   void CopyFrom(const SmallPtrSetImpl &RHS);
 };
 
@@ -287,8 +291,20 @@ public:
     return *this;
   }
 
+  /// swap - Swaps the elements of two sets.
+  void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
+    SmallPtrSetImpl::swap(RHS);
+  }
 };
 
 }
 
+namespace std {
+  /// Implement std::swap in terms of SmallPtrSet swap.
+  template<class T, unsigned N>
+  inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {
+    LHS.swap(RHS);
+  }
+}
+
 #endif