[Bug rtl-optimization/85167] [6/7/8 Regression] shrink-wrap.c:333:15: runtime error with UBSAN

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85167

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 43821
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43821&action=edit
gcc8-pr85167.patch

Untested fix.