ad41f8a7a5
This resolves an issue seen when the source program uses multiple regclasses (Int and Float): in some cases, the logic that grabs the vregs and retains them (with class) in `vreg_regs` missed a register and we had a class mismatch. This occurred because data structures were initialized assuming `Int` regclass at first. This PR instead removes the `vreg_regs` array, stores the class explicitly as an `Option<RegClass>` in the `VRegData`, and provides a `Env::vreg()` method that reconstitutes a `VReg` given its index and its observed class. We "observe" the class of every vreg seen during the liveness pass (and we assert that every occurrence of the vreg index has the same class). In this way, we still have a single source-of-truth for the vreg class (the mention of the vreg itself) and we explicitly represent the "not observed yet" state (and panic on attempting to use such a vreg) rather than implicitly taking the wrong class.
regalloc2: another register allocator
This is a register allocator that started life as, and is about 50% still, a port of IonMonkey's backtracking register allocator to Rust. In many regards, it has been generalized, optimized, and improved since the initial port, and now supports both SSA and non-SSA use-cases.
In addition, it contains substantial amounts of testing infrastructure (fuzzing harnesses and checkers) that does not exist in the original IonMonkey allocator.
See the design overview for (much!) more detail on how the allocator works.
License
This crate is licensed under the Apache 2.0 License with LLVM
Exception. This license text can be found in the file LICENSE.
Parts of the code are derived from regalloc.rs: in particular,
src/checker.rs and src/domtree.rs. This crate has the same license
as regalloc.rs, so the license on these files does not differ.