I was thinking specifically of the 'add with shift' instructions in the Zba extension (sh[123]add[.w] they seems to be called) vs. using separate shift + add in

I was thinking specifically of the 'add with shift' instructions in the Zba extension (sh[123]add[.w] they seems to be called) vs. using separate shift + add instructions from the C extension and hope the CPU frontend will fuse them together. Code size would be the same, and assuming the CPU fuses them they should be pretty close performance-wise as well.