https://github.com/reignstudios/IL2X
This would end up making CS2X mostly for GPU targets.

Transpiles a C# subset to non .NET languages, platforms, runtimes and enviroments. (Powered by Roslyn)

CS2X is activily being tested in the development of the Orbital-Framework:
https://github.com/reignstudios/Orbital-Framework
This provides real-world tests and as things progress more features will tested and supported here.

Renders a 1280x720 image then prints how long it took in seconds.
http://reign-studios.com/wasm/cs2x/ray-trace-benchmark/cs2x.html

This project will focus on transpiling a C# subset with a modified type system for writing CPU and GPU programs.

• Custom Standard lib(s) for various targets.
• Documentation

• C89
  • Native C performance
  • C89: modern, legacy and embedded platforms (x86, MIPS, SPARC, RISC-V, PPC, M68K, AVR, etc)
  • CC65: 6502 platforms (Atari, C64, NES, Apple II, etc)
  • SDCC: Many targets (ColecoVision, ZX Spectrum, etc)
  • z88dk: Z80 platforms
• LLVM
• LLVM IR => Assembly: CP1610 (Intellivision)
• LLVM IR => Assembly: Intel 8048 (Magnavox Odyssey 2)
• LLVM IR => Retarget: Custom assembly targets (FPGA CPU, 16bit bytes, etc)
• Java
• Kotlin
• javaScript
• Python
• ActionScript

• HLSL (DirectX Shader Assembly Language) [D3D9.0c +]
• ALS (DirectX Shader Assembly Language) [D3D8.0 - D3D9.0c]
• GLSL (OpenGL shading language) [OpenGL2.0 / GLES2 +]
• ARB (ARB assembly language) [legacy / homebrew systems]
• CG (Cg programming language) [PSVita, Nvidia / other]
• PSSL (PlayStation Shader Language) [PS4]
• MSL (Metal Shading Language) [macOS / iOS]
• AGAL (Adobe Graphics Assembly Language)
• Custom: Plugin system

• CS2X.Core: .NET transpiler lib
• CS2X.CLI: CLI interface for CS2X.Core
• CS2X.Analyzer: C# syntax analyzer to limit unsuported features.
• CS2X.CoreLib: Portable CoreLib subset

• C89
  • Each executable gets built to a single '.c' source file including all dependencies.
  • String literals on embedded devices, cartridges, etc can be stored in program memory / ROM to save ram.
  • All GC methods are agnostic allowing any built-in or custom GC backend.
• Other: TODO

Almost zero performance loss. C# code will generate in a manner as if hand written in the target language in many respects. There are a couple key differences in the CS2X runtime / type system vs .NET CLR

• Structs are not part of the object system as they are in the .NET runtime.
  • No auto boxing for value types are supported (.NET has many easy to fall in syntax performance pitfalls here).
  • System.Object can never equal a 'struct', 'enum' or 'primitive' type.
  • Virtuals like 'MyStruct.GetType()' or 'MyEnum.GetType()' give compile time errors (use typeof instead).
  • Cannot bind a delegate to a structs non-static method.
• Interfaces are considered 'type-classes' and are compile time only.
  • Used for generics or general code consistency.
  • No casting to them or variable declarations of them.
• No up-casting performance loss in C and down-casting checks can be disabled for C output.
• Auto-Marshalling of managed types not supported.
  • Varies to much between platforms in contrast to .NET making writing portable code confusing.
  • Auto string marshalling has way to many implicits that depend on to many factors to keep track of.
  • Redundant allocations. If you want to pass the same string multiple times in multiple methods for example auto-marshaling it everytime doesn't make sense. Its far better to be explicit here and make that obvious by pre-marshalling the type once.
  • Portability. Forcing PInvokes to be used this way ensures code functions the same in all runtimes.

• Prerequisites
  • Visual Studios 2019 (VS for Mac / MonoDevelop or VSCode have not yet been tested)
  • .NET Core 5
  • .NET Compiler Platform SDK
• Run: CS2X.Core.Test proj in VS. This will build "PortableTestApp.csproj" to "TestOutput" folder
• NOTE: Early stages so nothing else is supported yet.