First special instruction
Start Load/Store implementation
Start TextureSample
Sample progress
I/O Load/Store Progress
Rest of load/store
TODO: Currently, the generator still assumes the GLSL style of I/O attributres. On MSL, the vertex function should output a struct which contains a float4 with the required position attribute.
TextureSize and VectorExtract
Fix UserDefined IO Vars
Fix stage input struct names