I am trying to setup AVX support for Unreal Engine 4. It is using SSE2 by default as far as I know and it's own NMake so there are no Visual Studio properties page to access and add arch to.
Where am I supposed to set this up?
NOTE: Trying to support AVX, AVX2 and AVX512.
Look for the VSToolChain.cs file in the UE4 source code. That file is setting up all the compiler flags for MSVC.
In there, search for where it's doing /arch:AVX. It's in some if(). To force usage of AVX or AVX2 or AVX512, just put /arch:AVX or /arch:AVX2 or /arch:AVX512 at the top of that function so that the flag always gets added. Then recompile the engine.