FEX-Emu – A fast linux usermode x86 and x86-64 emulator

FEX allows you to run x86 applications on ARM64 Linux devices, similar to Qemu-user and Box64. It offers wide compatibility with both 32-bit and 64-bit binaries, and can be used with Wine/Proton to play Windows games.

It supports forwarding API calls to host system libraries such as OpenGL or Vulkan to reduce emulation overhead. An experimental code cache helps reduce stuttering in games as much as possible. Furthermore, a per-app configuration system allows performance changes per game, for example bypassing expensive memory model emulation. We also provide a user-friendly FEXConfig GUI to locate and change these settings.

On the technical side, FEX has an advanced binary recompiler that supports all modern extensions of the x86(-64) instruction set, including AVX/AVX2. The heart of this recompiler is a custom IR that allows us to generate more optimized code than the traditional Splatter JIT. A comprehensive system call translation layer takes care of the differences between the emulated and host operating systems and even implements specific features like seccomp. A modular core enables FEX to be used as a WoW64/ARM64EC backend in Wine.

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