my attempt at mapping adders/incrementers to RCA with half/full adder standard cells

[jeras]

I wrote a techmap file for mapping $add to Sky130 half/full adder standard cells.
I do not have enough knowledge to fit it into Yosis source code, but I did run a few synthesis tests, to see if it works, and it did what I expected.

https://github.com/jeras/synthesis-primitives/blob/main/techmap/rca_map.v

The idea is to be able to map incrementers (counters) to half adder cells, and I wrote it, since I could not find any existing mapping which would explicitly use half adder cells.

It works by checking each bit in A/B operands to see whether they are constant and uses half adders when one of the bits is a constant zero.

Does this seem like it could be integrated into Yosis? If yes, is it ok to map $add/$sub, or should I map $lcu/$alu or other primitives?