Alexander, my patch does 2 optimizations: doesn't insert a new constant if one already exist and removes unused constants after peephole is done. You patch seems to do only the latter. It's very similar, from a quick look at your patch:
- My patch doesn't introduce any additional passes over the code (you added 2 passes).
- It preserves doc string.
- It's less code, because I reuse more of existing code.

Feel free to look at the patch and tell me if you don't agree.