[Mesa-dev] [RFC PATCH 00/16] A new IR for Mesa

[Tom Stellard]

On Fri, Aug 22, 2014 at 01:08:02PM +1000, Dave Airlie wrote:
> On 22 August 2014 12:46, Jason Ekstrand <jason at jlekstrand.net> wrote:
> > On Thu, Aug 21, 2014 at 7:36 PM, Dave Airlie <airlied at gmail.com> wrote:
> >>
> >> On 21 August 2014 19:10, Henri Verbeet <hverbeet at gmail.com> wrote:
> >> > On 21 August 2014 04:56, Michel Dänzer <michel at daenzer.net> wrote:
> >> >> On 21.08.2014 04:29, Henri Verbeet wrote:
> >> >>> For whatever it's worth, I have been avoiding radeonsi in part because
> >> >>> of the LLVM dependency. Some of the other issues already mentioned
> >> >>> aside, I also think it makes it just painful to do bisects over
> >> >>> moderate/longer periods of time.
> >> >>
> >> >> More painful, sure, but not too bad IME. In particular, if you know the
> >> >> regression is in Mesa, you can always use a stable release of LLVM for
> >> >> the bisect. You only need to change the --with-llvm-prefix= parameter
> >> >> to
> >> >> Mesa's configure for that. Of course, it could still be mildly painful
> >> >> if you need to go so far back that the current stable LLVM release
> >> >> wasn't supported yet. But how often does that happen? Very rarely for
> >> >> me.
> >> >>
> >> > Sure, it's not impossible, but is that really the kind of process you
> >> > want users to go through when bisecting a regression? Perhaps throw in
> >> > building 32-bit versions of both Mesa and LLVM on 64-bit as well if
> >> > they want to run 32-bit applications.
> >> >
> >> >> Without LLVM, I'm not sure there would be a driver you could avoid. :)
> >> >>
> >> > R600g didn't really exist either, and that one seems to have worked
> >> > out fine. I think in a large part because of work done by Jerome and
> >> > Dave in the early days, but regardless. From what I've seen from SI, I
> >> > don't think radeonsi needed to be a separate driver to start with, and
> >> > while its ISA is certainly different from R600-Cayman, it doesn't
> >> > particularly strike me as much harder to work with.
> >> >
> >> > Back to the more immediate topic though, I think think that on
> >> > occasion the discussion is framed as "Is there any reason using LLVM
> >> > IR wouldn't work?", while it would perhaps be more appropriate to
> >> > think of as "Would using LLVM IR provide enough advantages to justify
> >> > adding a LLVM dependency to core Mesa?".
> >>
> >> Could we use an llvm compatible IR? is also a question I'd like to see
> >> answered.
> >
> >
> > What do you mean by llvm compatible?  Do you mean forking their IR inside
> > mesa or just something that's easy to translate back and forth?
> >
> 
> Importing/forking the llvm IR code with a different symbol set, and
> trying to not intentionally
> be incompatible with their llvm.
> 

What would be the purpose of doing this?  Avoiding a dependency on the LLVM libraries?

-Tom

> Dave.
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