[PATCH] D101297: [SLP]Allow masked gathers only if allowed by target.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

In D101297#2719546 <https://reviews.llvm.org/D101297#2719546>, @lebedev.ri wrote:

> In D101297#2719522 <https://reviews.llvm.org/D101297#2719522>, @ABataev wrote:
>
>> In D101297#2719505 <https://reviews.llvm.org/D101297#2719505>, @spatel wrote:
>>
>>> In D101297#2719479 <https://reviews.llvm.org/D101297#2719479>, @ABataev wrote:
>>>
>>>> In D101297#2719468 <https://reviews.llvm.org/D101297#2719468>, @spatel wrote:
>>>>
>>>>> We seem to go back and forth on legality vs. pure cost model to decide what is allowed for vectorization.
>>>>> This would undo part of D90445 <https://reviews.llvm.org/D90445>, so adding potential reviewers for more feedback.
>>>>
>>>> Pure cost won't work here, we need to check if this is legal just to try to generate masked gather at all. Cost problem is different.
>>>
>>> Is there some gather construct that is impossible for the backend to expand correctly or just that it can't be expanded efficiently?
>>
>> There is known problem that after landing of the patch with masked gathers some of the code produces wrong results, so I suppose yes, there is a problem with lowering.
>
> Is there a bugreport with reproducer?

Not sure about it. @anton-afanasyev?

>> Generally speaking, would be good to calculate the cost/lower masked gathers to simple gathers if it is not legal/not profitable to use masked gathers. And tweak the cost model for such a case. AS temp solution we can add simple legality checks, at least, without early checks for the cost.




Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101297/new/

https://reviews.llvm.org/D101297