From Rust to Reality: The Hidden Journey of Fetch_max
13 hours ago
- #Rust
- #Compiler
- #Concurrency
- The article explores the journey of the `fetch_max` operation in Rust, from high-level code to assembly.
- It starts with a job interview scenario where a candidate uses Rust's `fetch_max` for atomic operations, sparking curiosity.
- The author investigates how Rust's `fetch_max` is implemented, uncovering layers of compiler transformations.
- The first layer is the Rust code itself, which is concise and safe for concurrent programming.
- The second layer involves macro expansion, where `fetch_max` is generated by a Rust macro for various atomic types.
- The third layer delves into LLVM IR, where Rust's high-level atomic operations are translated into intermediate representations.
- The fourth layer examines the transformation of LLVM IR into a compare-and-swap (CAS) loop for architectures like x86-64.
- The fifth layer reveals the final assembly code, showing how the CAS loop is implemented at the hardware level.
- The article highlights the power of modern compilers in abstracting complex, low-level details for developers.
- It also notes that some architectures, like Apple Silicon (AArch64), have native atomic max instructions, avoiding the need for a CAS loop.
- The author concludes by appreciating the abstraction and efficiency of Rust's compiler, which handles complex tasks seamlessly.