[PATCH] D102766: [SelectionDAG] Implement PromoteIntRes_INSERT_SUBVECTOR

[Bradley Smith via Phabricator via llvm-commits]

bsmith added a comment.

In D102766#2853500 <https://reviews.llvm.org/D102766#2853500>, @efriedma wrote:

> Sorry about the late reply here, but I'm not sure why PromoteIntRes_INSERT_SUBVECTOR needs to go through the stack.  Can't you just ANY_EXTEND the operand and the result?
>
> At that point, you might end up with a node that needs to be legalized by PromoteIntOp_INSERT_SUBVECTOR, but better to take legalization one step at a time.

I'm not sure I fully understand how you are thinking this would look, bare in mind that we also need to handle inserting scalable into scalable here.

If you had something like:

  `%ins = call <vscale x 4 x i16> @llvm.experimental.vector.insert.nxv4i16.nxv2i16(<vscale x 4 x i16> %vec, <vscale x 2 x i16> %subvec, i64 4)`

and you promoted all of the scalable types to their equivalent legal types you'd end up with:

  `%ins = call <vscale x 4 x i32> @llvm.experimental.vector.insert.nxv4i16.nxv2i16(<vscale x 4 x i32> %vec, <vscale x 2 x i64> %subvec, i64 4)`

This ends up no longer being a valid use of vector.insert since the element types differ.


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