These should be assumed to be called from a compute context. Also don't use a 2 entry switch over constants.
Reviewers: arsenm, nhaehnle Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D52944 llvm-svn: 351351