[Bug tree-optimization/71947] [6/7 Regression] x ^ y not folded to 0 if x == y by DOM

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71947

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Now the testcase is optimized at -O2 by VRP but still not at -O1.