llvm-svn: 171363

The single-element ilist::splice() function supports a noop move:

  List.splice(I, List, I);

The corresponding std::list function doesn't allow that, so add a unit
test to document that behavior.

This also means that

  List.splice(I, List, F);

is somewhat surprisingly not equivalent to

  List.splice(I, List, F, next(F));

This patch adds an assertion to catch the illegal case I == F above.
Alternatively, we could make I == F a legal noop, but that would make
ilist differ even more from std::list.

llvm-svn: 170443

llvm-svn: 169250

llvm-svn: 103723

 - This provides a convenient alternative to using something llvm::prior or
   manual iterator access, for example::

    if (T *Prev = foo->getPrevNode())
      ...

   instead of::

     iterator it(foo);
     if (it != begin()) {
       --it;
       ... 
     }

 - Chris, please review.

llvm-svn: 103647