[PATCH] D47215: DAG: Fix extract_subvector combine for a single element

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In https://reviews.llvm.org/D47215#1123942, @craig.topper wrote:

> Can you clarify what "fails" means in your description? It would have create a <1 x iX> or <1 x fX> BUILD_VECTOR but it could only do that before type legalization if that type isn't legal. Type legalization should then scalarize that since its an illegal type.


I mean the optimization doesn't happen, because the the "isOperationLegal(ISD::BUILD_VECTOR, MVT::v1X)" check fails after legalization.


https://reviews.llvm.org/D47215