The Rust Calling Convention We Deserve
Summary
This article argues that Rust's current calling conventions are overly conservative and suboptimal for passing complex types, and it outlines a vision for a faster, per-crate ABI (-Zcallconv) that could improve codegen and performance. It discusses architectural ideas, including shims, function-pointer handling, and profiling-based ABIs, with detailed examples across x86, ARM, and LLVM IR. The piece blends critique with a concrete, albeit long-term, proposal for evolving Rust's ABI and LLVM integration.