Constant Data in Shaders

If used correctly, the const keyword can provide a significant performance boost. For example, a shader that declares a const array outside of the main() block can perform significantly better than the same shader with the array not marked as const, even if the array could be treated as such.

Another example is the use of a const value to reference an array member. In this example, if the value is const, the graphics core can know ahead of time that the number will not change, and data can be pre-fetched prior to the shader being run.