[Buffers] Synchronizing cyle enumeration

[ziadomalik]

See also related PR for Reconvergent paths enumeration.

This feature enumerates synchronizing cycles, as they are defined in Xu, Josipović, FPGA'24, Section 4:

Definition 3: Two cycles are a pair of synchronizing cycles in a
dataflow circuit if the following properties hold: (1) The two cycles
are disjoint (i.e. they do not have any common units) and belong to
the same CFC (defined in Section 3.2). (2) There exists at least one
join that is reachable from both cycles without crossing any edge
on the cycle in the CFC they belong to.

We start out by computing all the strongly-connected-components of the CFC using Kosaraju's algorithm, then we find all the cycles in the CFC using Boost's tiernan_all_cycles function. Using both of our findings, we can enumerate each pair of cycles, check them against above criteria and reconstruct a path between the pair and the common join if they do match.

[ziadomalik]

Btw I have no idea what this aig change is, not sure how to get rid of it, but it seems to be from a submodule, let me know.

[Jiahui17]

Some

[Jiahui17]

Could you remove the aig from the commit?