how usf shaders works?

Normally the shader compiler is in the driver,but I don’t think that the drivers has got the unreal shader compiler,so how these shaders are compiled?They are converted to glsl or hlsl ?

Usf are actually HLSL files, unreal engine just does a few tweaks and sends them to the driver. There’s also a HLSL to GLSL converter built in with ue that does the conversion when loading usf on OpenGL