- Previously it was part of load-store optimisations, the rewrite now
works as a localopt.
- The new version works for address arithmetic and not for Sels anymore
  (while the old code only worked for Sels)
- The new version can handle some forms of initializer spanning loads
  like loading a string like "bla" with an mode_Iu to get all 3 chars
  and the zero in one load.