[PATCH] D109509: [SelectionDAG] PromoteIntRes_EXTRACT_SUBVECTOR for scalable vectors (widening).

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added a comment.

In D109509#2994261 <https://reviews.llvm.org/D109509#2994261>, @frasercrmck wrote:

> In D109509#2994216 <https://reviews.llvm.org/D109509#2994216>, @sdesmalen wrote:
>
>> It seems that trying with an example of i4's (e.g. extracting nxv2i4 from nxv12i4), it actually runs into various other failures that would need fixing first, e.g. widening the truncate to i4's of the input vector. The exact example you gave above (where both need widening), actually fails even earlier in SelectionDAGBuilder::getCopyToPartsVector.
>>
>> I'm not sure I can come up with an example where it does go down this code path though. Do you want me to keep the tests even if they don't exactly test the code in this patch?
>
> Ah yes I see, in the former the truncate is generated during argument lowering. That's a shame.
>
> Then no, I don't think I need these tests because widening the `EXTRACT_SUBVECTOR` operand is trivial.
>
> Sorry for wasting your time, @sdesmalen. I think this patch LGTM.

No worries, thanks for having a look! I'll remove the tests before committing.


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