Improving reasoning for the BV theory

[Halbaroth]

This umbrella issue tracks the progression of the BV theory reasoning. Please add related issue here and what we plan to improve in the future.

• [X] Support of bvnot reasoning, see #800 and #856.
• [X] Constraint propagation for bvand, bvor, bvxor, etc (see #944)
• [ ] Constraint simplification (from (bvand (concat a b) (concat c d)) to (concat (bvand a c) (bvand b d)))
• [x] Constraint propagation for bv2nat and int2bv

[bclement-ocp]

Some updates here:

• Doing constraint propagation on bv2nat and int2bv is not easy to do properly, because we don't have access to the arithmetic domains from Bitv_rel
• This is even more true if we want to do interreductions between arithmetic and bitwise domains
• The plan is now to instead add separate interval domains for bitvectors to Bitv_rel and to perform interreductions following Sharpening Constraint Programming approaches for Bit-Vector Theory

• 1040 #1044 #1054 #1055 #1056 do some groundwork to prepare the addition of the new domains, including reworking some of the constraint APIs to be easier to use with multiple domains

• Additional PRs are currently being tested that actually add the interval domains & arithmetic propagators following the paper above
• At some point we might want to figure out how to reconcile the BV and Arith interval domains
• No progress on the "constraint simplification" part yet

[Halbaroth]

I think we can remove the milestone on this issue because we do not plan extra works on it before the next release.

[bclement-ocp]

Yes, we won't have constraint simplification for 2.6. Let's keep it to track bv2nat(bvadd) support.