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As I understand it, template interpreters work by generating machine code corresponding to the virtual machine instructions and jumping to that machine code. As
by scaramanga 6y ago
As I understand it, template interpreters work by generating machine code corresponding to the virtual machine instructions and jumping to that machine code. As opposed to sort of a big switch statement that you'd get in a normal bytecode interpreter.
A good intro to it here:
https://programmersought.com/article/5521858566/ https://programmersought.com/article/5521858566/
- pansa2 6y agoThanks. Is there a performance advantage to the template approach - compared to writing the handler for each opcode directly in assembly language? Or is it just easier to implement?
- KMag 6y agoYou cut out the code between the opcodes that's used for figuring out what to do next. (Removing an indirect jump at the end of each opcode execution.)
- pansa2 6y agoThat sounds more like an advantage of a template compiler, not a template interpreter?
- chrisseaton 6y agoYes people in this thread are confusing the two. It reduces overhead because it directly refers to machine registers and the machine stack to pass information between instructions, and directly uses machine jumps, rather than going through a switch and method calls.
- pansa2 6y agoSounds like it’s similar to how LuaJIT works [0], using a machine-code handler for each VM opcode. AFAICT LuaJIT also uses a templating system to build these, except it generates them at compile-time instead of at run-time. I assume that’s easier than explicitly writing out each handler in assembly language. [0] https://www.reddit.com/r/programming/comments/badl2/luajit_2_beta_3_is_out_support_both_x32_x64/c0lrus0/ https://www.reddit.com/r/programming/comments/badl2/luajit_2...
- tekknolagi 6y agoYep, this is very similar.