In Rust, monomorphization is a compile-time process where polymorphic functions are replaced by many monomorphic functions for each unique instantiation. [1] It is considered beneficial to undergo the mentioned transformation because it results in the output intermediate representation (IR) having specific types, which allows for more effective optimization. Additionally, many IRs are intended to be low-level and do not accommodate polymorphism. The resulting code is generally faster than dynamic dispatch, but may require more compilation time and storage space due to duplicating the function body. [2] [3] [4] [5] [6] [7]
The term "monomorphization" appears to be used exclusively by Rust and Rust-related literature. The C++ standard and community, for example, refers to the near-equivalent process as template instantiation instead.
This is an example of a use of a generic identity function in Rust
fnid<T>(x: T)-> T{returnx;}fnmain(){letint=id(10);letstring=id("some text");println!("{int}, {string}");}
After monomorphization, this would become equivalent to
fnid_i32(x: i32)-> i32{returnx;}fnid_str(x: &str)-> &str{returnx;}fnmain(){letint=id_i32(10);letstring=id_str("some text");println!("{int}, {string}");}
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