[PATCH] Add experimental PBQP support

[Lang Hames]

Hi Dave,

Out-of-the-box PBQP knows about the standard constraints that CodeGen
models. Any Target that works with the standard allocators (E.g. greedy)
should also work with PBQP. I believe Arnaud's patch is an optimisation.
(Arnaud - please correct me if I'm wrong and AArch64 did require extra
constraints, but I don't think it should?)

- Lang.


On Fri, Sep 5, 2014 at 3:45 PM, David Blaikie <dblaikie at gmail.com> wrote:

> This'll probably show how little I know about register allocation - but I
> thought Lang was telling me the other day that PBQP is essentially a
> drop/opt in for any architecture without having specific code for it
> (learning about the register set from the tablegen files and that was all
> it needed).
>
> Is that the case? Is the extra code in your patch then tuning, essentially
> - making PBQP better than the baseline table-driven PBQP for AArch64/A57?
> Or is my understanding incorrect?
>
> - David
>
>
> On Fri, Sep 5, 2014 at 1:49 PM, Arnaud A. de Grandmaison <
> arnaud.degrandmaison at arm.com> wrote:
>
>> I am currently investigating the benefits the PBQP register allocator
>> could bring to the AArch64/A57.
>>
>>
>>
>> This patch adds experimental support for PBQP. The PBQP is disabled by
>> default, and can be enabled with the ‘–aarch64-pbqp’ command line option to
>> llc when the cortex-a57 is in use.
>>
>>
>>
>> I thought it would be a good thing to upstream this patch, as some other
>> people in the community could be interested in experimenting with this
>> allocator.
>>
>>
>>
>> It passes all the tests (LNT, spec, …), but the performance of the
>> generated code is not optimal yet. Expect some more patches in the coming
>> days to improve the performance.
>>
>>
>>
>> Cheers,
>>
>> --
>>
>> Arnaud A. de Grandmaison
>>
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140905/2ce148e9/attachment.html>