So I've gotten a chance to try this, but on test code it seems to enter an infinite loop. I left it running overnight. Is there some steps I can take to debug what's being run and why?
On Tuesday, March 8, 2016 at 9:06:48 PM UTC-8, Alon Zakai wrote: > > For an interpreter, there's the emterpreter in emscripten. Not sure it's > the simplest possible, though, it's more designed for speed. > > On Tue, Mar 8, 2016 at 6:21 PM, Aidan Hobson Sayers <[email protected] > <javascript:>> wrote: > >> This sounds neat! I've been pondering on an 'early-executor' and this is >> a really nice demonstration of both viability and utility. >> >> The things I've been thinking about is attempting to start running `main` >> as far as possible, so non-deterministic functions would end up bubbling up >> to the beginning. Are there any simple asm.js interpreters (i.e. reduced js >> interpreter) you're aware of? I suppose would need to be the first step - >> unlike the 'global ctors' work which looks like it effectively does 'dirty >> checking', I'd imagine this pass doing data dependency analysis to skip >> over e.g. `printf` calls since they might not have much impact on the >> actual flow of code (depending on the memory accesses etc inside these >> calls). >> >> On 8 March 2016 at 23:25, Alon Zakai <[email protected] <javascript:>> >> wrote: >> >>> The incoming branch (now 1.36.1) now has a new optimization when >>> building to JS with -Oz. It will eliminate C++ global constructor functions >>> aggressively, removing them from the codebase, removing the need to call >>> them during startup, and removing code that would otherwise be used only by >>> them. >>> >>> This makes -Oz when compiling to JS slower to compile than before, >>> almost 2x slower. To avoid that, you can disable this optimization (-s >>> EVAL_CTORS=0), or just use -Os. In general, -Oz is kind of the "try at all >>> costs to reduce code size", so it felt natural to include this optimization >>> there. >>> >>> The benefit can be noticeable. For example, this removes the 2 global >>> ctors that doing any C++ iostream usage would normally bring in, that >>> create the standard streams. This reduces code size by a few percent, as >>> well as JS compilation time, and startup is faster also because we can jump >>> right to executing main(). In general, of course, we can't remove all >>> ctors, as it might do something with side effects like printf or malloc, >>> which we can't optimize away. With EMCC_DEBUG=1 in the env, you'll see >>> logging that shows an error in such a case (which you can use to optimize >>> your codebase, if you want). >>> >>> This optimization was inspired by Cheerp's PreExecutor ( >>> http://blog.leaningtech.com/2016/02/cheerp-preexecuter-compile-time.html >>> ). That made me wonder, doesn't LLVM already do this? Turns out, yes, it >>> does, but at the IR level, and as a result is not as successful as it could >>> be, due to the complexity of LLVM IR. But at the asm.js level things are >>> very simple - in fact, this optimization just literally runs the code in a >>> JS sandbox, and sees if it ran without using anything nondeterministic. >>> That's after all the LLVM complexity was lowered out, and is basically >>> guaranteed to work when it should work. More details at >>> >>> https://github.com/kripken/emscripten/blob/incoming/src/settings.js#L699 >>> >>> - 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] >>> <javascript:>. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> >> >> -- >> Aidan >> >> Currently co-authoring a book on Docker >> <http://manning.com/miell/?a_aid=aidanhs&a_bid=e0d48f62> - get 39% off >> with the code 39miell >> >> -- >> 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] <javascript:>. >> 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.
