[PATCH] D38318: [X86][SSE] Match PSHUFLW/PSHUFHW + PSHUFD vXi16 shuffle patterns (PR34686)

[Elena Demikhovsky via Phabricator via llvm-commits]

delena added a comment.

In https://reviews.llvm.org/D38318#891595, @RKSimon wrote:

> @delena @zvi What do you want to do with this. IMO we shouldn't be prematurely combining to variable mask shuffles, and this should be performed later as a scheduler based decision. But that will involve a lot of work that I don't think we're ready for (https://reviews.llvm.org/D26855 tried to move some other code to the MC and hit a lot of issues).
>
> What we could do is add a FeatureFastVariableShuffle feature flag to Haswell and later Intel CPUs and perform the decision in combineX86ShuffleChain off that?


May be just add something like this:
bool hasVariableShuffle(MVT Ty) {

  if ((hasAVX2() && Ty == XXX) || hasAVX512() && Ty == YYY)
    return true;

return false;

      


Repository:
  rL LLVM

https://reviews.llvm.org/D38318