[PATCH] D101005: [AArch64][GlobalISel] Simplify out of range rotate amount.

[Amara Emerson via Phabricator via llvm-commits]

aemerson added a comment.

In D101005#2711425 <https://reviews.llvm.org/D101005#2711425>, @foad wrote:

>>> What's the point of this? Does it somehow end up generating better code?
>>
>> It allows us to select immediate forms of rotate instructions for AArch64.
>
> I would expect most targets to handle that during instruction selection by ignoring the high bits of the rotate amount, but perhaps there's some reason why it's awkward to do that for AArch64. Would it make sense for your new combine to be completely AArch64-specific? Currently you have added it to all_combines so it will be run on other targets too.

That's possible, but I assumed that generic code wanted this since this is already done in DAGCombine for rotates.


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https://reviews.llvm.org/D101005