« on: April 22, 2010, 11:37:10 PM »
For most of the early evolution of the HLSL language, the compiler was part of the D3DX utility library (aka D3DX9). This compiler supported Shader Models 1.x, 2.0, and 3.0 for Direct3D 9 vertex shaders and pixel shaders. For Direct3D 10, the graphics team started a new compiler to support the demands of the new Direct3D 10 API with Shader Model 4.0 versions of vertex, pixel, and geometry shaders. Direct3D 10.x added Shader Model 4.1 variants. Direct3D 11 adds Shader Model 5.0 and two new classes of shaders for tessellation (hull & domain) shaders.
There have been two main consequences to this new HLSL compiler development effort.
Full story at MSDN