[PATCH] Improve performance of vector code on A15

[Jakob Stoklund Olesen]

On Feb 22, 2013, at 7:59 AM, James Molloy <James.Molloy at arm.com> wrote:
>> Passes like this are notoriously hard to get right
>> 
> Don't I know it - Myself and Silviu have been working on this for ages,
> paid careful attention to the impdef flags and still managed to cock
> them up royally.

Don't blame yourselves, blame me. I really think the current way of modeling liveness was a mistake, and we should try to correct it. My concern is that adding this pass makes it harder because it actually depends on the implicit operands.

>> I would actually like to get rid of all the implicit operands that are
>> currently added by the register allocator, and instead revert to a
>> more conservative liveness model for post-RA passes. The extra
>> complexity added by the implicit operands don't buy us a lot, and it
>> is just too hard to work with the post-RA code as it looks now.
> 
> I totally support this :)

Cool. Hopefully, we can avoid sabotaging that goal.

I think you should reconsider doing this before RA, and at least avoid depending on the implicit operands.

/jakob