[PATCH] D24625: [DAG] Remove isVectorClearMaskLegal() check from vector_build dagcombine

[Michael Kuperstein via llvm-commits]

mkuper added a comment.

In https://reviews.llvm.org/D24625#545635, @RKSimon wrote:

> I agree that the UsesZeroVector test shouldn't be there but we should probably use a TLI.isShuffleMaskLegal(Mask, InVT1) test and not just blindly combine to a shuffle.


We already blindly combine to a shuffle in all the other cases, the "blend with 0" case was the only one that had a check. I'm not saying that's necessarily what we should be doing, but I'm not sure I really want to change that behavior right now.
(My main motivation for removing the check is wanting to regularize this before committing https://reviews.llvm.org/D24683, because special-casing zero there would have been much uglier. )

Anyway, I'll try and see if it affects any of our tests.


https://reviews.llvm.org/D24625