Removing trig functions from mobile shaders

Hello,

I'm wondering about low level optimizations for shader performance on mobile devices. Are trig functions single cycle operations on modern mobile GPUs, or are they implemented with lower level intrinsics?

I can afford (visually) to replace trig functions with a triangle wave like the following snippet; however, I'm not sure how to know if this would make sense. /* Returns the value of a signed periodic triangle wave (1 periodic) */ half triangle_wave (half x) { return 4.0*(abs(frac(x) - 0.5) - 0.25); }

Thanks!