Custom nodes on GPU? I want to create a custom perlin noise node (NOT a node group, an actual scripted one), and be able to run it on GPU. Is this possible? OSL does not seem to be 100% supported on GPU, so is it still possible? 
The idea is essentially to create a node similar to the Noise Texture or Musgrave Texture. Could I do this without OSL, or somehow compile it so it is available on GPU? I think all the standard nodes are in OSL, so what makes them work on GPU?
As far as I am aware there is still no support for OSL on GPU - if you enable the Open Shader Language checkbox then you are limited to CPU.

Perhaps if you can describe what you want to achieve with your custom noise node then someone might be able to offer a suggestion that would not require OSL.