I wasn't familiar with that, thanks. Looks interesting, however the GPL license is a problem as we do want the option to run the parser on the client machine, linked to other code, and this would limit the amount of people that would use it.
- Alon On Fri, Nov 14, 2014 at 3:04 AM, Marc <[email protected]> wrote: > Do you know this one? > https://github.com/cesanta/v7 > > Le Thu, 13 Nov 2014 17:19:46 -0800, > Alon Zakai <[email protected]> a écrit : > > > Early this year the fastcomp project replaced the core compiler, > > which was written in JS, with an LLVM backend in C++, and that > > brought large compilation speedups. However, the late JS optimization > > passes were still run in JS, which meant optimized builds could be > > slow (in unoptimized builds, we don't run those JS optimizations, > > typically). Especially in very large projects, this could be annoying. > > > > Progress towards speeding up those JS optimization passes just landed, > > turned off, on incoming. This is not yet stable or ready, so it is > > *not* enabled by default. Feel free to test it though and report > > bugs. To use it, build with > > > > EMCC_NATIVE_OPTIMIZER=1 > > > > in the environment, e.g. > > > > EMCC_NATIVE_OPTIMIZER=1 emcc -O2 tests/hello_world.c > > > > It just matters when building to JS (not building C++ to > > object/bitcode). When EMCC_DEBUG=1 is used, you should see it mention > > it uses the native optimizer. The first time you use it, it will also > > say it is compiling it, which can take several seconds. > > > > The native optimizer is basically a port of the JS optimizer passes > > from JS into c++11. c++11 features like lambdas made this much easier > > than it would have been otherwise, as the JS code has lots of > > lambdas. The ported code uses the same JSON-based AST, implemented in > > C++. > > > > Using c++11 is a little risky. We build the code natively, using > > clang from fastcomp, but we do use the system C++ standard libraries. > > In principle if those are not c++11-friendly, problems could happen. > > It seems to work fine where I tested so far. > > > > Not all passes have been converted, but the main time-consuming > > passes in -O2 have been (eliminator, simplifyExpresions, > > registerize). (Note that in -O3 the registerizeHarder pass has *not* > > yet been converted.) The toolchain can handle running some passes in > > JS and some passes natively, using JSON to serialize them. > > > > Potentially this approach can speed us up very significantly, but it > > isn't quite there yet. JSON parsing/unparsing and running the passes > > themselves can be done natively, and in tests I see that running 4x > > faster, and using about half as much memory. However, there is > > overhead from serializing JSON between native and JS, which will > > remain until 100% of the passes you use are native. Also, and more > > significantly, we do not have a parser from JS - the output of > > fastcomp - to the JSON AST. That means that we send fastcomp output > > into JS to be parsed, it emits JSON, and we read that in the native > > optimizer. > > > > For those reasons, the current speedup is not dramatic. I see around > > a 10% improvement, far from how much we could reach. > > > > Further speedups will happen as the final passes are converted. The > > bigger issue is to write a JS parser in C++ for this. This is not > > that easy as parsing JS is not that easy - there are some corner > > cases and ambiguities. I'm looking into existing code for this, but > > not sure there is anything we can easily use - JS engine parsers are > > in C++ but tend not to be easy to detach. If anyone has good ideas > > here that would be useful. > > > > - Alon > > > > -- > You received this message because you are subscribed to the Google Groups > "emscripten-discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
