Lift self-copy protection up to the header file and add self-move

protection to the same layer.

This is in line with Howard's advice on how best to handle self-move
assignment as he explained on SO[1]. It also ensures that implementing
swap with move assignment continues to work in the case of self-swap.

[1]: http://stackoverflow.com/questions/9322174/move-assignment-operator-and-if-this-rhs

llvm-svn: 195705

llvm/include/llvm/ADT/SmallPtrSet.h

@@ -293,14 +293,16 @@ public:
 
   SmallPtrSet<PtrType, SmallSize> &
   operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
-    CopyFrom(RHS);
+    if (&RHS != this)
+      CopyFrom(RHS);
     return *this;
   }
 
 #if LLVM_HAS_RVALUE_REFERENCES
   SmallPtrSet<PtrType, SmallSize>&
   operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
-    MoveFrom(SmallSizePowTwo, std::move(RHS));
+    if (&RHS != this)
+      MoveFrom(SmallSizePowTwo, std::move(RHS));
     return *this;
   }
 #endif

llvm/lib/Support/SmallPtrSet.cpp

@@ -218,8 +218,7 @@ SmallPtrSetImpl::SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
 /// CopyFrom - implement operator= from a smallptrset that has the same pointer
 /// type, but may have a different small size.
 void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
-  if (&RHS == this)
-    return;
+  assert(&RHS != this && "Self-copy should be handled by the caller.");
 
   if (isSmall() && RHS.isSmall())
     assert(CurArraySize == RHS.CurArraySize &&
@@ -256,6 +255,8 @@ void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
 
 #if LLVM_HAS_RVALUE_REFERENCES
 void SmallPtrSetImpl::MoveFrom(unsigned SmallSize, SmallPtrSetImpl &&RHS) {
+  assert(&RHS != this && "Self-move should be handled by the caller.");
+
   if (!isSmall())
     free(CurArray);