While the goal is definitely still Cranelift focused, (a) this should be obvious
based on the fact that this is nested under the `cranelift/` directory, and (b)
Peepmatic *is* now generic over the IR it is optimizing, so it could potentially
be used on (say) rustc's MIR now.
* This PR is against a branch called `main`
* Internally all docs/CI/etc is updated
* The default branch of the repo is now `main`
* All active PRs have been updated to retarget `main`
Closes#1914
Peepmatic is a DSL for peephole optimizations and compiler for generating
peephole optimizers from them. The user writes a set of optimizations in the
DSL, and then `peepmatic` compiles the set of optimizations into an efficient
peephole optimizer:
```
DSL ----peepmatic----> Peephole Optimizer
```
The generated peephole optimizer has all of its optimizations' left-hand sides
collapsed into a compact automata that makes matching candidate instruction
sequences fast.
The DSL's optimizations may be written by hand or discovered mechanically with a
superoptimizer like [Souper][]. Eventually, `peepmatic` should have a verifier
that ensures that the DSL's optimizations are sound, similar to what [Alive][]
does for LLVM optimizations.
[Souper]: https://github.com/google/souper
[Alive]: https://github.com/AliveToolkit/alive2
