[PATCH] D107068: [DAG] DAGCombiner::visitVECTOR_SHUFFLE - recognise INSERT_SUBVECTOR patterns.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

What about insertion of multiple subvectors?

This looks complicated. Can't we do this simpler?
If we want to keep the current general logic,
can't you just generate a shuffle mask that you'd need
when inserting n'th subvector of RHS into identity LHS,
and compare that the mask matches the actual mask? (modulo `undef`s)

Otherwise, can't you just go through the mask, record the elements that are identity,
then go through the elements that aren't identity, see that they are sequential,
that there are only enough of them for a single subvector insertion,
and decode which subvector is being inserted?


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