Adds support for suggesting profitable llvm.expect based on frontend
I'm not sure of the status of these patches, since the base one is still marked "WIP". Some comments below on this patch, but are they all ready for review? If so, WIP should probably be removed from D129889.
Needs its own comment.
I take it a return value of false from then handle*Expect functions means there was not an expect? Would be good to note this in a comment (here and in the switch handling later). Also, suggest moving this down into lowerExpectIntrinsic to mirror where/how switch are handled.
It doesn't seem like this patch includes a test for this new invocation of verifyMissingAnnotations - can one be added?
Should these commented out lines be removed now?