Comment # 24 on bug 90887 from Ilia Mirkin

(In reply to jr from comment #23)
> (In reply to Ilia Mirkin from comment #22)
> > (In reply to jr from comment #21)
> > > Created attachment 117077 [details] [review] [review] [review] [review]
> > > Prototype of a more highlevel graph modification api
> > > 
> > > ...
> > 
> > Hrm, I was about to (try to) push this out, but it doesn't seem to work. I
> > made a few local adjustments, like
> > 
> > RegAlloc::PhiMovesPass::isCriticalEdge(BasicBlock *b, BasicBlock *p)
> > {
> >    return b->cfg.incidentCount() > 1 && p->cfg.outgoingCount() > 1;
> > }
> > 
> > ...
> > 
> > 
> > where did BB:4 go? poof. not great :( this is with piglit's
> > tests/shaders/ssa/fs-critical-edge.shader_test
> > 
> > I guess I'll go with either your or my first patches. Want to get this fixed
> > for Mesa 11, which is going to get branched off some time tomorrow.
> 
> Sorry, most probably my prototype code is crap. I'll have an hour now to
> look at it. I'll let you know if I find something. Otherwise I'm fine with
> your first patch.

Awesome! While I don't know whether the isCriticalEdge thing is the right thing
to do instead of the current needNewElseBlock logic, I do think that splitEdge
should be able to work properly even if needNewElseBlock always returns true.