# FEXCore - Fast x86 Core emulation library
This is the core emulation library that is used for the FEX emulator project.
This project aims to provide a fast and functional x86-64 emulation library that can meet and surpass other x86-64 emulation libraries.
### Goals
* Be as fast as possible, beating and exceeding current options for x86-64 emulation
  * 25% - 50% lower performance than native code would be desired target
  * Use an IR to efficiently translate x86-64 to our host architecture
  * Support a tiered recompiler to allow for fast runtime performance
  * Support offline compilation and offline tooling for inspection and performance analysis
  * Support threaded emulation. Including emulating x86-64's strong memory model on weak memory model architectures
* Support a significant portion of the x86-64 instruction space.
  * Including MMX, SSE, SSE2, SSE3, SSSE3, and SSE4*
* Support fallback routines for uncommonly used x86-64 instructions
  * Including x87 and 3DNow!
* Only support userspace emulation.
  * All x86-64 instructions run as if they are under CPL-3(userland) security layer
* Minimal Linux Syscall emulation for testing purposes
* Portable library implementation in order to support easy integration in to applications
### Target Host Architecture
The target host architecture for this library is AArch64. Specifically the ARMv8.1 version or newer.
The CPU IR is designed with AArch64 in mind but there is a desire to run the recompiled code on other architectures as well.
Multiple architecture support is desired for easier bringup and debugging, performance isn't as much of a priority there (ex. x86-64(guest) translated to x86-64(host))
### Not currently goals but will be in the future
* 32bit x86 support
  * This will be a desire in the future, but to lower the amount of work required, decided to push this off for now.
* Integration in to WINE
* Later generation of x86-64 instruction sets
  * Including AVX, F16C, XOP, FMA, AVX2, etc
### Not desired
* Kernel space emulation
* CPL0-2 emulation
* Real Mode, Protected Mode, Virtual-8086 Mode, System Management Mode
* IRQs
* SVM
* "Cycle Accurate" emulation
### Dependencies
 * clang-tidy if you want to ensure the code stays tidy
 * cmake
 * A C++17 compliant compiler (There are assumptions made about using Clang and LTO)