[Bug tree-optimization/67666] single restrict pointer in struct looses restrict

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67666

--- Comment #1 from vries at gcc dot gnu.org ---
Created attachment 36360
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36360&action=edit
Tentative patch