Short answer: NO

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Can I use IL2CPP (Intermediate Language To C++) for non-Unity applications?

IL2CPP.exe is a Unity utility for converting C# IL code to C++. My question is: can this executable be used outside of the Unity game-development environment as a general-purpose tool for converting any .NET application (not just games) to a high-performance native executable?

Although I do know some C++, It would certainly be nice to be able write all kinds of programs in a language I am comfortable and fluent with (C#)......whether they be audio/video/music-production DAWs or OS-level security/forensics tools or machine-learning platforms or anything else that's resource-intensive.......and know that they will run as efficiently as an app written in straight C++.

9 months ago · Santiago Trujillo

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Accepted Answer · 2022-05-13T20:32:52.256Z

Short answer: NO

IL2CPP is tightly connected to the Unity environment and it's not possible to use it outside of Unity. You would need to write your own converter(?) to do such a thing.

Longer answer

IL2CPP doesn't do any magic in terms of performance improvement. Comparing C++ with C# with IL2CPP code should give (almost - more below) no performance benefit.

IL2CPP is performant compared to C# code written for Unity specifically for few reasons that have nothing to do with C++.

Why Unity is unique and needs IL2CPP:

Unity API is very heavily reliant on main thread performance, as the whole Unity API was written almost 10 years ago, where 2 Core CPUs were top-notch and everyone believed that we will have 20-50GHz single-core CPUs by now.
Unity makes a lot of assumptions that you will use their API for everything, begging from IO to Threading and GPU access, which is heavily bound to C++ core.
Unity needs to be wrapped with Unity objects (MonoBehaviours and GameObjects) to be used for almost anything, you cannot write your own native anything. (This is a simplification)
Unity is written in C++, so it needs to do something very similar to Marshalling, and it's not very efficient.

So why IL2CPP?

Unity cannot convert its already very legacy backend (Mono) and its legacy API to be multithreaded since Mono have a lot of assumptions about your code that are not easily convertible to "simple" unity API.
Unity core is written in C++, so they are eliminating any form of Marshalling all together by skipping Mono "translator".
IL2CPP converts highly inefficient C#, single-threaded code to multithreaded C++, where possible, and it does this by analyzing IL code.

Is it worth converting other C# to C++?

No! Compare any arbitrary, optimized C# code that was precompiled by AOT to (modern) C++. You should get the same performance! Identical I would say.

C# is compiled to IL (Intermediate Language) which as the name suggests is Intermediate. It's converted in runtime to Native Binary code (only when needed), that is what C++ is compiled into. You can force this conversion by skipping IL generation by running Ahead of Time compilation (AOT).

The ONLY thing that your C# code will be less performant is when you are abusing GC's ability to clean up after you.