Gamma Cross code seems to be coming from year 2005 or earlier, with complex
table based machinery to approximate "raise to power" calculations. Which,
for Gamma Cross, have always been hardcoded to 2.0 "since forever". So
simplify all that, i.e. replace all the table lookup/interpolation things
with just `x*x` and `sqrt(x)`.
Applying Gamma Cross on 4K UHD resolution, Windows Ryzen 5950X machine:
36.2ms -> 8.1ms
Pull Request: https://projects.blender.org/blender/blender/pulls/115801
Aras Pranckevicius
9cbc96194e