[Bug middle-end/66661] incorrect memory access in optimization with flexible array member

[P at draigBrady dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66661

--- Comment #7 from Pádraig Brady <P at draigBrady dot com> ---
Created attachment 35852
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35852&action=edit
reproducer