[PATCH] X86: fold SSE2/AVX2 logical shift by immediate amout into zero vector when possible

[Duncan Sands]

Hi Andrea,

On 12/07/13 15:57, Andrea_DiBiagio at sn.scee.net wrote:
> Hi,
> I attached the patch against the most recent tot.
> Could you please commit this patch for me? (I have no commit access)

I don't understand why this is an X86 specific combine rather than a general
one in the DAG combiner.

Ciao, Duncan.

>
> Thanks,
> Andrea Di Biagio
> SN Systems - Sony Computer Entertainment Group
>
>
>
>> From: Andrea DiBiagio/SN R&D/BS/UK/SCEE
>>> From: Nadav Rotem <nrotem at apple.com>
>>> These vectors with these constants can be generated during
>>> legalization.  But it’s not a big deal and we can do without it.
>>>
>>
>> True..
>>
>>> The behavior of shifts by amount larger than the element size is
> defined
>>> for x86 SSE2/AVX2.
>>>
>>> Yes, but we are looking at the semantics of the llvm SelectionDAG,
>>> and we want to lower it to x86.  :)
>>>
>>> In any case, this is correct and I don’t see any reason not to
>>> commit the patch as is.
>>
>> Thanks.
>> Btw. I have no commit access to the repository.
>> Could (any of) you please commit this change for me? :-)
>>
>> Andrea Di Biagio
>> SN Systems - Sony Computer Entertainment Group
>
>
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