llvm dev - Oct 2011 - [LLVMdev] Enhancing TableGen

Evan Cheng <evan.cheng at apple.com> writes:
> On Oct 7, 2011, at 11:23 AM, David A. Greene wrote:
>
>> Evan Cheng <evan.cheng at apple.com> writes:
>> 
>>> David, we cannot accept the 'multidef' keyword. Please
revert it.
>> 
>> Working on it now.
>
> Thanks.
No problem.  I agree that multidef was sort of a half-baked idea.  I did
it for practical purposes here but Che-Liang developed a much better,
mroe general solution to the problem.
>> How about a less massive and complicated scheme?  I think we can
>> make some good improvements to the current spec that will help
>> with the MIC work.
>
> I'd like to defer MIC work until it's finalized. But yes,
incremental
> refinement is always welcome.
Ok.  I'd like to do some of this incremental work to prepare for MIC.  I
will do this in small batches and please do keep telling me when I'm
heading off track.  :)
>> Frankly, the way things are with the x86 SIMD stuff is not scalable.
>> I'd like to clean some of that up, in an incremental way, of
course.
>
> It's not like we are against improvements that make td files
> better. But there is fine balance we should strive for. Readability,
> maintainability, and ease of debugging are very important.
Absolutely.  I don't think I've ever claimed that what I did for AVX
here should go whole hog into upstream.  I certainly never had that view
in my head.  On the contrary, I learned a lot doing it and know all the
mistakes and skeletons quite well.  :)

I'd would like to use that experience to inform how we might structure
the x86 specification a bit better to make maintenance, readability and
debuggability better.

I plan to continue to work on a non-preprocessor for loop because I see
immediate value to it, it is much clearer that what I have currently and
it allows incremental improvements to existing code.

My overarching goal is to get our trees in sync before heavy-duty AVX2
or MIC work begins.

                              -Dave

On Oct 7, 2011, at 12:03 PM, David A. Greene wrote:
> 
>>> How about a less massive and complicated scheme?  I think we can
>>> make some good improvements to the current spec that will help
>>> with the MIC work.
>> 
>> I'd like to defer MIC work until it's finalized. But yes,
incremental
>> refinement is always welcome.
> 
> Ok.  I'd like to do some of this incremental work to prepare for MIC. 
I
> will do this in small batches and please do keep telling me when I'm
> heading off track.  :)
> 
As the release enginerd, I would encourage you to hold off any changes to
TableGen until after Friday, if they can wait. :-) Of course, Jakob gets the
final say on whether they go in or not.

-bw

Bill Wendling <wendling at apple.com> writes:
> On Oct 7, 2011, at 12:03 PM, David A. Greene wrote:
>> 
>>>> How about a less massive and complicated scheme?  I think we
can
>>>> make some good improvements to the current spec that will help
>>>> with the MIC work.
>>> 
>>> I'd like to defer MIC work until it's finalized. But yes,
incremental
>>> refinement is always welcome.
>> 
>> Ok.  I'd like to do some of this incremental work to prepare for
MIC.  I
>> will do this in small batches and please do keep telling me when
I'm
>> heading off track.  :)
>> 
> As the release enginerd, I would encourage you to hold off any changes
> to TableGen until after Friday, if they can wait. :-) Of course, Jakob
> gets the final say on whether they go in or not.
If I can get the for loop done, it would benefit all targets even if
it's just used for top-level defs.  It would be a nice 3.0 feature, I
think.

What do you think, Jakob?

I would not do any other major changes before the branch.  Doing
otherwise would be mostly insane.  :)

                              -Dave