[Bug ipa/91832] [10 Regression] ICE in scan_expr_access, at ipa-sra.c:1695 since r275982

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91832

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
negative offset can indeed happen.  Valid cases would be hidden inside
pointer-based MEM_REFs though, from code like

 p = p - 4;
 ... = *p;

which we'd represent as MEM[p, -4]