What does Fast Depth Calculation actually do?

[arwing92x]

In the hacks tab of the graphic settings there is a setting called Fast Depth Calculation, does this provide a visual increase or does it make the game run better?

Thanks!

[alhanelem]

This is from the performance guide on the dolphin wiki: https://wiki.dolphin-emu.org/index.php?title=Performance_Guide

Fast Depth Calculation - Uses a less accurate method of calculating depth values. Gives a decent speedup, but can cause flickering textures.