[ADT] Refactor SmallPtrSetImplBase::swap (NFC) (#154261)

SmallPtrSetImplBase::swap needs to deal with four cases depending on
whether LHS is small and whether RHS is small.  Now, the code to swap
small LHS and large RHS is symmetric with the code to swap large LHS
and small RHS.

This patch rearranges code so that we first take care of the case
where both LHS and RHS are small.  Then we compute references
SmallSide and LargeSide and actually swap the two instances.

This refactoing saves about 11 lines of code.  Note that
SmallDenseMap::swap also uses a similar trick.

0 files changed, 0 insertions, 0 deletions