(In reply to Pierre-Eric Pelloux-Prayer from comment #12)
> Does using "AMD_DEBUG=nodcc" Mesa environment variable help?

It does. Exporting that in my ~/.profile makes the desktop usable.

> Could you capture an apitrace of the issue in Dolphin so I can reproduce
> more easily?

It seems that the Dolphin issue is not related to the desktop graphics
corruption. I tested it again using a kernel that had my hack to under-report
the version number and saw the same rendering issues in Dolphin, but that
kernel doesn't require the nodcc environment variable.