This should make it easier for all further passes in the code generator -- they can just look at macros, ignoring the singleton instructions. @markshannon tried this in #108997 but got stuck, I hope I can get it unstuck.

It's possible that the synthetic uop will be named __X instead of _X, since the latter would create some name conflicts. (I don't think that this causes issues with __X being treated as "private" in Python, since we won't have Python-level variables named after uops.) (UPDATE: The synthetic uop and macro will both be called X.)

Linked PRs

• gh-109287: Desugar inst(X) to op(X); macro(X) = X #109294
• gh-109287: fix overrides in cases generator #110419