[Bug tree-optimization/68955] [6 Regression] wrong code at -O3 on x86-64-linux-gnu in 32-bit mode

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68955

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so disabling cunroll after unswitching fixes the testcase as well. 
Disabling IVOPTs fixes it also (we have a IVOPTs wrong-code bug elsewhere). 
IVOPTs
would explain -m32 vs. -m64.

Disabling DOM3 also fixes the bug. (-O3 -m32 -fdisable-tree-dom3)