Enable Link-Time Optimization (LTO)

[zamazan4ik]

Hi!

I noticed that in the Cargo.toml file Link-Time Optimization (LTO) for the project is not enabled. I suggest switching it on since it will reduce the binary size (always a good thing to have) and will likely improve the application's performance a bit.

I suggest enabling LTO only for the Release builds so as not to sacrifice the developers' experience while working on the project since LTO consumes an additional amount of time to finish the compilation routine. If you think that a regular Release build should not be affected by such a change as well, then I suggest adding an additional dist or release-lto profile where additionally to regular release optimizations LTO will also be added. Such a change simplifies life for maintainers and others interested in the project persons who want to build the most performant version of the application. Using ThinLTO should also help to reduce the build-time overhead with LTO. If we enable it on the Cargo profile level, users, who install the application with cargo install, will get the LTO-optimized version "automatically". E.g., check cargo-outdated Release profile.

Basically, it can be enabled with the following lines:

[profile.release]
lto = true

I have made quick local tests (Rustc 1.81, Fedora 40, the latest gameboy sources version): from enabling lto = true the resulting binary size dropped from 1.7 Mib to 1.3 Mib.

Thank you.

P.S. It's more like an improvement idea rather than a bug. I created the issue just because the Discussions are disabled for the repo for now.

[mohanson]

Currently, lto is still an experimental option, and it is not always completely reliable. In my development experience, I have encountered at least two unexpected errors in the program caused by using lto.

The premise of opening lto is that we already have very detailed tests (written based on non-lto premise), which is exactly what simulator projects lack. Therefore, I will not enable lto in this project unless the llvm and rust teams are confident enough to enable lto by default.