(In reply to smoki from comment #29)
> I did fresh piglit run now and it shows there are 159 regressed now...

I think at least the piglit regressions aren't directly related to sub-register
liveness and should be tracked in a separate bug report:

On my Kaveri, I've been seeing random failures of some (of the same as yours)
piglit tests recently (with sub-register liveness disabled). The only way I've
found to avoid those failures is to keep rebooting until I get lucky. It seems
like some recent change (most likely in Mesa?) causes the hardware to go into a
weird, semi-persistent state.

I'm afraid it might be tricky to bisect that, but it would be very helpful.