[LLVMdev] Enhancing TableGen
David A. Greene
greened at obbligato.org
Fri Oct 7 12:03:53 PDT 2011
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.
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
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.
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