What is link time optimization LTO

Link Time Optimization (LTO) is a compiler technique that optimizes code across multiple compilation units during the linking phase to improve performance. In the Rust compiler build system, LTO is configured via the rust.lto setting in bootstrap.toml or the --set rust.lto=thin flag in the ./configure script. To enable thin LTO for the Rust compiler build, run: ./configure --set rust.lto=thin

Link Time Optimization is like a final quality check that happens after all the pieces of your software are built but before they are glued together. Instead of optimizing each piece in isolation, the compiler looks at the whole picture to remove unnecessary code and speed up execution. This results in a faster program but takes longer to build.