[Bug rtl-optimization/68376] [4.9/5/6 Regression] wrong code at -O1 and above on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68376

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 36751
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36751&action=edit
gcc6-pr68376.patch

Untested fix.