PowerVR SGX535 Shader Performance (OpenGL ES 2.0)

Question

I'm currently working on a couple of shaders for an iPad game and it seems as if Apple's GLSL compiler isn't doing any optimizations (or very few). I can move a single line in a shader and drop my FPS from 30 to 24 but I really have no idea why this is happening.

Does anyone have any references for the following:

• what PowerVR instructions are generated from GLSL instructions?
• what are the timings of the PowerVR instructions?
• what sort of parallel processing units are in the PowerVR535 and how can they be exploited?

Thanks, Tristan

Answer 1

http://www.imgtec.net/factsheets/SDK/POWERVR%20SGX.OpenGL%20ES%202.0%20Application%20Development%20Recommendations.1.1f.External.pdf

This documet should help you to optimize your shaders for maximum performance. Apple should provide similar information as well.