Created attachment 531938 [details] gcc6-retpoline-patches.tar.xz Hongjiu Liu from Intel has backported support for this to gcc-6 so unless we expect to stabilise gcc-7 soon, it might be worth it to incorporate his patches. I have been using gcc-6 with those patches applied, along with both the kernel and large parts of userspace recompiled to use these features, since late February and have yet to run into any issues with them. Moreover, they have been added to Debian Stretch builds of gcc-6 so chances are they have quite thoroughly tested them as well.
Do you know if they appeared in gcc-6.5.0? I'd prefer to avoid carrying invasive patches downstream if possible.
Let's drop it in favour of gcc-7 (stable everywhere).