Re:Writing a register based VM in less than 125 lines of C code
by MaxBarraclough on Sunday December 12, 2021 @05:41PM
(#29534435)
Further to this: this kind of thing is something the Forth community takes seriously. They call these threaded code techniques. [0] (The Gforth interpreter, for instance, gives you the choice of various different techniques.)
Anton Ertl of Gforth fame published a microbenchmark performance comparison of toy interpreters, written in C, run on various CPUs. [1] As you say, the approach using function pointers (call threading) scores poorly.
Interestingly, direct threading and indirect threading are extremely close, with the winner seeming to depend on the specific CPU. [1] Branch-prediction differences seem to be the main reason. There was a 2001 paper on this. [2]
Anton Ertl of Gforth fame published a microbenchmark performance comparison of toy interpreters, written in C, run on various CPUs. [1] As you say, the approach using function pointers (call threading) scores poorly.
Interestingly, direct threading and indirect threading are extremely close, with the winner seeming to depend on the specific CPU. [1] Branch-prediction differences seem to be the main reason. There was a 2001 paper on this. [2]
[0] https://www.complang.tuwien.ac.at/forth/threaded-code.html
[1] https://www.complang.tuwien.ac.at/forth/threading/
[2] https://github.com/ForthPapersMirror/Papers/blob/master/Conv...