[PATCH] D22840: [InstCombine] Split int64 store into separate int32 stores

[Xinliang David Li via llvm-commits]

On Tue, Jul 26, 2016 at 11:11 PM, Chandler Carruth <chandlerc at google.com>
wrote:

> On Tue, Jul 26, 2016 at 11:08 PM Xinliang David Li via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Hmm, why does Clang change the return type from from struct to i64?  Set
>> aside whether it is always beneficial to do it or not, it certainly feels
>> like the wrong place to make such a change.
>>
>
> It's necessary to get the right ABI out of LLVM.
>
>
what ABI issue and what can be wrong without using i64? I might have missed
something obvious here.

David



> Lot's of folks have hypothesized about how to separate the ABI concerns
> from the LLVM IR representation but it has so far proved a really tricky
> problem and its not clear there is a good solution.
>
>



>
>> David
>>
>> On Tue, Jul 26, 2016 at 10:40 PM, Wei Mi <wmi at google.com> wrote:
>>
>>> wmi added a comment.
>>>
>>> Matt, David and Chandler, thanks for the review.
>>>
>>> I only looked at the code for x86-64, powerpc and aarch64 targets. For
>>> those targets, separate stores seemed better. I am not familiar with target
>>> like AMDGPU. I guess wider store is generally preferred than multiple
>>> narrower stores on AMDGPU? Since it may be undesirable on some targets, I
>>> agree it is more appropriate to implement it in SDAG pass. I will update
>>> the patch.
>>>
>>>
>>> Repository:
>>>   rL LLVM
>>>
>>> https://reviews.llvm.org/D22840
>>>
>>>
>>>
>>>
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