X86.td file contains number of features that can be arrange in more general pattern . We can combine features that include in number of atom into single processor and create a inheritance ratio between them all.
This looks to be adding RDRAND to SLM. Whether that's correct or not, that's a functional change which should not be part of this patch.
Should SSSE3 be part of AtomValues instead? The rest of these are uarch details, but that one is a real feature and should be with the other features.
I agree that it's part of SLM and that it should be fixed. But this patch should be treated as a refactor that doesn't change behavior. Especially since your description makes no mention of this change. And clang needs to be updated too. So submit a separate pre or post patch for the SLM rdrand change.