During July 2025, Romain Machet contributed backend performance enhancements to the rust-lang/gcc repository, focusing on AArch64 SIMD optimization. He replaced the mvn+shrn instruction sequence with mvni+subhn, leveraging assembly language and compiler optimization expertise to improve loop performance on 64-bit ARM architectures. Romain integrated automated tests in C to ensure the correctness and regression safety of the new optimization, demonstrating a thorough approach to stability. His work refined the backend code path for SIMD instruction handling, addressing performance-critical paths and aligning with the repository’s goals for efficient execution on modern ARM platforms. The contribution reflects strong low-level engineering depth.