jnorthrup/mlir-nix is a C++ project providing an evaluator compatible with Nix 2.35.4, a store, and the mlnix command-line tool. According to the repository, the latest release is v0.4.0. The provided information does not state what changes this release contains. The project describes an architecture that lowers Nix expressions to MLIR's Nix dialect and evaluates them at the point where they are needed. In other words, instead of evaluating expressions outright, evaluation proceeds when a value is required.
This approach implements a Nix evaluator through a different execution path while checking whether the results match. The README states that it compares the results of the reference implementations, Nix and Lix, for every change. It verifies that computation results also match on real system evaluations and package sets, and it covers lazy evaluation and the LLVM-based execution path. It says performance comparisons and design rationale are also published as documentation. The core of this repository lies not in proposing new syntax, but in moving the evaluation of existing Nix expressions onto MLIR and aligning it with the reference implementations.
However, the provided information contains neither the specific change log for v0.4.0 nor performance comparison results. The README explains that it measures the benefit of lazy evaluation on real workloads and holds back changes that bring no benefit, but no measurement values are presented here. Therefore, while the implementation direction and verification policy can be confirmed, it is difficult to judge the effect of this release or its performance advantages.