How does this benefit performance?
Each time Minecraft wants to draw a frame, ALL entities recalculate the angles of each of their limbs. However, due to a huge oversight by Mojang, MANY of these calculations can easily be sped up, and are sometimes flat-out unnecessary. This mod fixes that by making PI/180 a stored value that isn't calculated multiple times for each entity, using variables instead of repeated calculations, getting rid of all unneeded rotation-setting, calculations, and variables, and eliminating scenarios where a rotation is calculated, set, and is then overwritten by another calculation. This, when applied to all entities, does indeed speed up performance, whether it be a small bit or a noticeable bit, depending on the surrounding entities and your PC.