[LLVMdev] Please benchmark new x86 vector shuffle lowering, planning to make it the default very soon!

[Quentin Colombet]

Thanks Chandler!

Here are two more test cases :).

I kept the format of my previous email.

1. avx_unpck.ll avx
Instead of issueing a single unpck with use a sequence of extrats, inserts, shuffles, and blends.

2. none_useless_shuflle none
Instead of using a single move to materialize a zero extended constant into a vector register, we explicitly zeroed a vector register and use a shuffle.

Cheers,
-Quentin


On Sep 18, 2014, at 2:13 AM, Chandler Carruth <chandlerc at google.com> wrote:

> As of r218038 we should get palign for all integer shuffles. That fixes the test case you reduced for me. If you have any other regressions that point to palignr, I'd be especially interested to have an actual test case. As I noted in my commit log, there seems to be a clear place where using this could be faster but it introduces domain crossing. I don't really have a good model for the cost there and so am hesitant to go down that route without good evidence of the need.
> 
> On Wed, Sep 17, 2014 at 1:30 PM, Chandler Carruth <chandlerc at google.com> wrote:
> 
> On Wed, Sep 17, 2014 at 12:51 PM, Quentin Colombet <qcolombet at apple.com> wrote:
> We use two shuffles instead of 1 palign.
> 
> Doh! I just forgot to teach it about palign... This one should at least be easy.
> 

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