[PATCH] D80485: [DAGCombiner][PowerPC][AArch64] Remove isMulhCheaperThanMulShift TLI hook. Use isOperationLegal directly instead.

[Amy Kwan via Phabricator via llvm-commits]

amyk added a comment.

Hi! I should have made it more clear in the revision, but my intention for adding the `isMulhCheaperThanMulShift` TLI hook was also for it to be used with the DAG Combine in https://reviews.llvm.org/D78272.

That patch has the DAG Combine in PPC only right now. After receiving some comments on it, I was thinking of putting this DAG combine into the target independent code instead. I was only going to enable it only on PPC first by calling the `isMulhCheaperThanMulShift` TLI hook in the combine since only PPC has an implementation of the function. I see that without the TLI hook, making the DAG combine target independent would allow it to run on all targets, which would result in some LIT failures on other targets.

Do you have any thoughts regarding this? I hope I have my made intentions more clear.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80485/new/

https://reviews.llvm.org/D80485