[Bug tree-optimization/90018] [7/8/9 Regression] r265453 miscompiled 527.cam4_r in SPEC CPU 2017

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90018

--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 46130
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46130&action=edit
patch for GCC 8

I am testing the attached, now forward-porting to GCC 9.