Jan de Mooij writing on the SpiderMonkey blog:
In September, machine learning engineers at Mozilla filed a bug report indicating that Firefox was consuming excessive memory and CPU resources while running Microsoft’s ONNX Runtime (a machine learning library) compiled to WebAssembly.
The issue with the ONNX module was that the Ion compiler backend took a long time and used a lot of memory to compile it. On my Linux x64 machine, Ion-compiling this module took about 5 minutes and used more than 4 GB of memory.
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With these changes, Ion can compile the ONNX Wasm module in less than 3.9 seconds on my machine, more than 75x faster than before these changes.
I find it satisfying reading about optimisations like this. The same end-state is achieved, but in vastly less time and space—it feels like magic.