emscripten: use wasm-exceptions for better performance

[kzhsw]

Using this project to parse a large (~80MB) stp file, I waited for more 4 hours but it wouldn't finish, when I pause the script in devtools, it stops at some js glue code generated by emscripten, which is supposed to be exception handling. The docs said wasm-exceptions should be faster, but I failed to compile it. The same model took about 2 minutes to be converted to gltf using mayo, which is a native app using the same OpenCascade to handle stp files. I had tried foxtrot on browser, but it just failed.

Other useful links:

• WebAssembly exception handling proposal
• https://github.com/llvm/llvm-project/issues/62877
• https://webassembly.org/roadmap/

[longhan]

Hello,

Can you please share your .stp?

[kzhsw]

Hello,

Can you please share your .stp?

No, it's commercial stuff. During a quick look of OpenCascade code, I found that c++ exceptions are widely used in it, so using wasm-exceptions should improve the overall performance by reducing wasm-js calls, not limited to specify model.

[kovacsv]

@kzhsw I managed to compile the library with -fwasm-exceptions, tests are running fine, and the binary is even smaller than before. Now I would like to test with your model, could you please share it with me somehow?

[kzhsw]

@kzhsw I managed to compile the library with -fwasm-exceptions, tests are running fine, and the binary is even smaller than before. Now I would like to test with your model, could you please share it with me somehow?

Thank you for this, I'll try to find a model that can be uploaded here. Could you upload the compiled binary here, or benchmark it with some smaller models?

[kovacsv]

Some measurements for files I got at hand. It's definitely faster, but I guess the difference depends on the number of exceptions coming from the import.

File Name	File Size	Old version	New version
as1_pe_203.stp	0.2Mb	0.671s	0.307s
GPT-05-BL.stp	0.5Mb	1.650s	0.956s
MDrive23Plus.stp	3.2Mb	9.127s	4.999s
MD34AC_single.stp	10.9Mb	26.869s	13.233s
Product1TamMontaj.stp	12.2Mb	40.710s	20.810s

[kovacsv]

@kzhsw even if it doesn't solve your problem it's definitely better than it was before, so I committed the new compiled version. Please check it with your file.

[kzhsw]

Thank you for this great work! Also note for best browser compatibility, both version should be compiled, and load the supported version based on browser version check or wasm-feature-detect. BTW, it would be better to upload compiled wasm dist to releases, allowing devs to have a faster checkout.

[kovacsv]

Browsers and node.js supports this feature for more than a year, I think it's fine to have only the new version.