refactor(codegen-masm): remove petgraph from Linear tactic, add no_std SCC

[radik878]

• Replace DiGraphMap + kosaraju_scc with a minimal no_std-friendly SimpleDiGraph and local Kosaraju SCC.
• Remove petgraph from codegen/masm/Cargo.toml.
• Use FxHashMap and SmallVec; avoid std-only types.

fix #447

[bitwalker]

Looks great! I'd like to extract the basic digraph data structure so we can use it elsewhere when needed, but we don't need to expand on the APIs you've provided here now. See my other comment for details.

Aside from that, and a few tests to cover the new data structure, it'll be nice to finally close out this issue!

[bitwalker]

I think it'd be worthwhile to extract this to hir/src/adt/digraph.rs, and make it generic over the node type, but only provide an implementation of the graph for node types which implement Hash.

We may have other uses for a basic digraph data structure, so it makes sense to provide a common implementation that we can extend as needed.

Other than that, providing some tests for the provided APIs (namely neighbors_outgoing, reverse, and sccs) and we're good to go!

[radik878]

Looks great! I'd like to extract the basic digraph data structure so we can use it elsewhere when needed, but we don't need to expand on the APIs you've provided here now. See my other comment for details.

Aside from that, and a few tests to cover the new data structure, it'll be nice to finally close out this issue!

Thanks for review, ser, i've made corrections

[bitwalker]

Turns out petgraph now supports no-std builds, so I've modified this PR to use that instead, as well as clean up a few other dep-related things I spotted

[radik878]

Turns out petgraph now supports no-std builds, so I've modified this PR to use that instead, as well as clean up a few other dep-related things I spotted

Thank you very much for your help