[PATCH] D119075: [DAGCombine][ARM] Custom lower smaller-than-legal MULH/AVG/ABD

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

In D119075#3299246 <https://reviews.llvm.org/D119075#3299246>, @RKSimon wrote:

> Why not handle this generically - accept AVG patterns of any type pre-legalization and expand back during legalization if necessary?

Hmm. Won't that be quite inefficient? Creating nodes for architectures that don't even expect to use them? A mulh for example - I wouldn't expect the generic DAG combiner to create i8 mulh on Arm targets - it's not something it will ever need, and I feel it would just get in the way of the optimisations it is trying to make.


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