[PATCH] D122829: [AArch64] Optimize SDIV with pow2 constant divisor

Thu Mar 31 10:09:53 PDT 2022

bcl5980 added a comment.

In D122829#3419867 <https://reviews.llvm.org/D122829#3419867>, @craig.topper wrote:

> In D122829#3419836 <https://reviews.llvm.org/D122829#3419836>, @bcl5980 wrote:
>
>> In D122829#3419777 <https://reviews.llvm.org/D122829#3419777>, @craig.topper wrote:
>>
>>> Does this differ in an important way from what you get if you remove BuildSDIVPow2? I think you'll get sign bit shifted all the way to the right followed by a lsr. While this patch will shift the sign bit only as far as it needs to.
>>
>> remove BuildSDIVPow2 also works for scalar cases. But test failed on sve cases. 
>> I can also shift 31/63 everytime but I think currect code is also correct.
>
> Is that because of the SVE special case on line 13536? What if you left that code and returned SDValue() after it?

Yeah, you are right. Return after 13536 is correct.

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https://reviews.llvm.org/D122829