(In reply to comment #2)
> [...] compiling takes many minutes as it is.

git bisect minimizes the number of times you need to compile Mesa to isolate
the change introducing the problem.

> I can't estimate where it might have broken either,

Your initial report says it's working with Mesa 9.2.3 but broken with current
Git, that's good enough for bisecting.

> nor risk experiencing the problem too many times (given it almost
> brings the system down).

I don't think it's that dramatic. It sounds like the usual symptoms of the GPU
repeatedly hanging and being reset by the driver.