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I wonder, why they implemented Baseline JS interpreter in C++? Why not Rust?

by xvilka 7y ago

stuartd 7y ago
Because the interpreter pipeline shares code and data structures [0]: a couple of examples from the link below: > The Baseline Interpreter uses the same frame layout as the Baseline JIT, but we’ve added some interpreter-specific fields to the frame. > Because the Baseline Interpreter and JIT are so similar, a lot of the code generation code can be shared too. To do this, we added a templated BaselineCodeGen base class with two derived classes: - BaselineCompiler: used by the Baseline JIT to compile a script’s bytecode to machine code. - BaselineInterpreterGenerator: used to generate the Baseline Interpreter code. [0] https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a-faster-js-interpreter-in-firefox-70/ https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a...
pjc50 7y ago
I believe the Rust rewrite of parts is proceeding, but this tech blog explains what's going on: https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a-faster-js-interpreter-in-firefox-70/ https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a... > The Baseline Interpreter sits between the C++ interpreter and the Baseline JIT and has elements from both. It executes all bytecode instructions with a fixed interpreter loop (like the C++ interpreter). In addition, it uses Inline Caches to improve performance and collect type information (like the Baseline JIT). Including elements [of code] from both would be considerably harder in another language. If you read closely it appears the interpreter is "generated" - that it, it's not written directly in C++ or anything at all, but is instead an interpreter emitted by the JIT compiler!
eyegor 7y ago
I was under the impression that this was a side goal of the servo project. Of course now it looks like it is it's own thing: https://servo.org/ https://servo.org/ Does anyone know if servo is supposed to be related to Firefox in some way, or if it is always meant to be independent?
- timerol 7y ago
  Servo is supposed to be a playground of sorts for architectural innovations in the browser space. Successful experiments from Servo will then get ported to FF. Project Quantum ported over the Stylo CSS improvements from Servo: https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-engine-quantum-css-aka-stylo/ https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-en.... WebRender has also been making it's way over: https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-fps-how-webrender-gets-rid-of-jank/ https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-f...

I wonder, why they implemented Baseline JS interpreter in C++? Why not Rust?

by xvilka 7y ago

I wonder, why they implemented Baseline JS interpreter in C++? Why not Rust?

Because the interpreter pipeline shares code and data structures [0]: a couple of examples from the link below: > The Baseline Interpreter uses the same frame layout as the Baseline JIT, but we’ve added some interpreter-specific fields to the frame. > Because the Baseline Interpreter and JIT are so similar, a lot of the code generation code can be shared too. To do this, we added a templated BaselineCodeGen base class with two derived classes: - BaselineCompiler: used by the Baseline JIT to compile a script’s bytecode to machine code. - BaselineInterpreterGenerator: used to generate the Baseline Interpreter code. [0] https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a-faster-js-interpreter-in-firefox-70/ https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a...

pjc50 7y ago

I believe the Rust rewrite of parts is proceeding, but this tech blog explains what's going on: https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a-faster-js-interpreter-in-firefox-70/ https://hacks.mozilla.org/2019/08/the-baseline-interpreter-a... > The Baseline Interpreter sits between the C++ interpreter and the Baseline JIT and has elements from both. It executes all bytecode instructions with a fixed interpreter loop (like the C++ interpreter). In addition, it uses Inline Caches to improve performance and collect type information (like the Baseline JIT). Including elements [of code] from both would be considerably harder in another language. If you read closely it appears the interpreter is "generated" - that it, it's not written directly in C++ or anything at all, but is instead an interpreter emitted by the JIT compiler!

eyegor 7y ago

I was under the impression that this was a side goal of the servo project. Of course now it looks like it is it's own thing: https://servo.org/ https://servo.org/ Does anyone know if servo is supposed to be related to Firefox in some way, or if it is always meant to be independent?

timerol 7y ago
Servo is supposed to be a playground of sorts for architectural innovations in the browser space. Successful experiments from Servo will then get ported to FF. Project Quantum ported over the Stylo CSS improvements from Servo: https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-engine-quantum-css-aka-stylo/ https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-en.... WebRender has also been making it's way over: https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-fps-how-webrender-gets-rid-of-jank/ https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-f...