[SmallPtrSet] Add remove_if() method (#96468)

Add remove_if() method, similar to the one already present on SetVector.
It is intended to replace the following pattern:

    for (Foo *Ptr : Set)
      if (Pred(Ptr))
        Set.erase(Ptr);

With:

    Set.remove_if(Pred);

This pattern is commonly used for set intersection, where `Pred` is
something like `!OtherSet.contains(Ptr)`.

The implementation provided here is a bit more efficient than the naive
loop, because it does not require looking up the bucket during the
erase() operation again.

However, my actual motivation for this is to have a way to perform this
operation without relying on the current `std::set`-style guarantee that
erase() does not invalidate iterators. I'd like to stop making use of
tombstones in the small regime, which will make insertion operations a
good bit more efficient. However, this will invalidate iterators during
erase().

0 files changed, 0 insertions, 0 deletions