[PATCH] D86894: [SVE] Disable INSERT_SUBVECTOR DAGCombine for scalable vectors

[David Sherwood via Phabricator via llvm-commits]

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Herald added a subscriber: ecnelises.

Hi, there was quite a lot of discussion about the use of operators in ElementCount recently (see https://reviews.llvm.org/D86065). I think the consensus was that this needs quite a bit more thought and discussion. My patch was accepted on the basis that we'd revisit this and come up with a better plan going forward. The general problem with "/" and "%" operators is that the caller needs to be careful if the operation is lossy. I introduced the "/" operator for a specific case of dividing by 2, where the Min value was known in advance to be a power of 2. I was thinking to raise this topic at the next SVE sync call. Looking at the code above it seems like all we're asking is if one thing is a multiple of another, which could be done with a function such as isKnownMultipleOf(...), where returning true guarantees we know at compile time the answer to be true.


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https://reviews.llvm.org/D86894