VCC Listing
Adds a hook to UdonSharp to process the generated Udon, reducing the number of instructions and making better use of temporary variables, as well as fixing a bug resulting in unnecessary variables. This results in udon programs that are faster and smaller.
After any UdonSharp compile, a line will appear in the console similar to the following:
[Optimizer] Removed # instructions, # variables, and # extra __this total
For Unity 2022, no permanent changes are made to the VRCSDK, all changes are made in memory and can be easily removed by removing this package.
For Unity 2019, an additional file is added to the VRCSDK to allow the optimizer to function.
This can be found at the path Packages/com.vrchat.worlds/Integrations/UdonSharp/Editor/USOInternals.cs
There are currently 3 class of optimizations:
UdonSharp likes to copy values into variables that only get used once or never at all, we eliminate these COPY instructions by modifying other instructions to store directly to the copy's target, or load directly from the copy's source.
Any call to another Udon function followed by a return, can have its setup and the corresponding return removed, utilizing the return instructions of the called Udon function instead.
UdonSharp makes a LOT of temporary variables. We detect places where we can reuse existing temporary variables instead of creating new ones. This does not make the program faster but does make the program smaller.