swift234

[sil-combine] Add a new peephole for alloc_ref_dynamic -> alloc_ref transformations.

If a metatype used by alloc_ref_dynamic is coming from a successful checked_cast_br [exact], then we know that this is the exact metatype. Therefore, we can simplify:

  checked_cast_br [exact] $Y.Type to $X.Type, bbSuccess, bbFailure
  ...
  bbSuccess(%T: $X.Type):
  alloc_ref_dynamic %T : $X.Type, $X

into:

  checked_cast_br [exact] $Y.Type to $X.Type, bbSuccess, bbFailure
  ...
  bbSuccess(%T: $X.Type):
  alloc_ref $X

Swift SVN r26276