Parsing Protobuf at 2GBs

https://blog.reverberate.org/2021/04/21/musttail-efficient-interpreters.html

An exciting feature just landed in the main branch of the Clang compiler. Using the [[clang::musttail]] or __attribute__((musttail)) statement attributes, you can now get guaranteed tail calls in C, C++, and Objective-C.

Goes on to describe how mandatory tail calls solve the "an intepreter as a giant switch in a loop is slow" problem I have referenced previously.

Our design does away with a single big parse function and instead gives each operation its own small function. Each function tail calls the next operation in sequence.