[PATCH] D62392: [DAGCombine][ARM] (sub Carry, X) -> (addcarry (sub 0, X), 0, Carry) fold

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D62392#1587798 <https://reviews.llvm.org/D62392#1587798>, @deadalnix wrote:

> Maybe it is worth adding some platform dependent check to actually make sure turning the carry into a scalar is expensive? Or is it a reasonable assumption to make that it expensive on all plateforms?


I honestly don't know the answers to these questions, carry nodes are not my strong side,
If you want (given your recent carry patches), you can totally take this patch over.

> In any case, this is more likely than not that this will optimize better down the road anyways, so maybe, if such plateform exist, we may want to delegate the cleanup to plateform specific transforms.
> 
> I think it would be beneficial to have an X86 test case for this pattern.




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