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Re: [PATCH] Simple optimization for MASK_STORE.


On May 8, 2015 8:43:15 PM GMT+02:00, Jeff Law <law@redhat.com> wrote:
>On 05/08/2015 03:27 AM, Richard Biener wrote:
>> On Wed, May 6, 2015 at 4:04 PM, Yuri Rumyantsev <ysrumyan@gmail.com>
>wrote:
>>> Hi All,
>>>
>>> Here is a patch which gives us significant speed-up on HASWELL for
>>> test containing masked stores. The main goal of that patch is
>attempt
>>> to avoid HW hazard for maskmove instructions through inserting
>>> additional check on zero mask and putting all masked store
>statements
>>> into separate block on false edge.All MASK_STORE statements having
>the
>>> same mask put into one block. Any comments will be appreciate.
>>
>> Hmm.  I'm not very happy with this "optimization" happening at the
>> GIMPLE level - it feels more like a mdreorg thing...
>I haven't looked at the patch, but it sounds like just specialization 
>using a runtime check to select between the implementations which is 
>fairly natural to do at the gimple level.

Well, sure.  Which is why I suggested a un-ifcvt pass instead.

Anyway, the implementation has multiple issues.

Richard.

>Jeff



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