[llvmlinux] More VLAIS code ...

Tinti viniciustinti at gmail.com
Wed Nov 20 10:38:48 UTC 2013

On Wed, Nov 20, 2013 at 8:29 AM, Renato Golin <renato.golin at linaro.org>wrote:

> On 20 November 2013 10:18, Tinti <viniciustinti at gmail.com> wrote:
>> What kind of adaptation do you want? If you have a patch or something, I
>>> can talk to him, or you can send him and copy me, if you want. I think the
>>> latter is better, since I'm not directly involved in the issue, myself.
>> This code inserts a VLAIS.
> Unless we have an alternative, I don't think "please, re-implement your
> code without VLAIS" would cut.

 Agreed. This is a suicide request.

The main issues are:
>  * VLA is much simpler to code and understand
>  * GCC produces very good code from it
> So, at the toolchain group, we're tackling this problem from two sides:
>  * Trying to find alternatives to VLAIS that are simple and perform well,
> and convincing kernel folks to use it

Mark has made some implementations. Some of them as far as I remember can
perform as well as VLAIS in GCC side.

>  * Improving GCC to generate good code on those cases and hopefully emit a
> warning on VLAIS

This might work too. Since C standard forbids the usage of VLAIS.

But for now, we'll have to suffer a bit... Which means, for every VLAIS
> patch, we should email back the submitter asking for a different approach.
> Submitting an alternative would make it a lot easier to be accepted. Also,
> feel free to copy me on any email, especially if it's a Linaro engineer.
> I'm sorry I can't do much more than that. They have some very hard
> deadlines for feature support and performance improvements, and I don't
> want to be in between them and their targets, as I know I'll be shot very
> quickly and thoroughly.

Thanks, that is the best we can do. But we need to take care also to not be
annoying people.

> cheers,
> --renato
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Simplicity is the ultimate sophistication
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