[PATCH] D92760: [SelectionDAG] Implement SplitVecOp_INSERT_SUBVECTOR

[Joe Ellis via Phabricator via llvm-commits]

joechrisellis added a comment.

In D92760#2439765 <https://reviews.llvm.org/D92760#2439765>, @david-arm wrote:

> Is it possible to add a brief description of what the intent of this patch is? It's not immediately obvious why we're adding the split function from the code or summary. I'm assuming it's related to the new intrinsic in your test, since LLVM has not needed this function until now?

Yes, good idea. I am not sure, but I think it might have actually been possible to hit a codepath that expects the split function to exist even without the new `llvm.experimental.vector.insert` intrinsics (unless the `INSERT_SUBVECTOR` ISD nodes are never created?). From our experiments, it's pretty rare that we end up needing this function even with the intrinsics anyway. But it does prevent an assertion error in certain circumstances. 🙂

Also, it might be worth noting that operand splitting is already implemented for `EXTRACT_SUBVECTOR`.


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