Sad day. I have a sha256 hasher in asm.js that's faster than any wasm solution.

bvisness 5 hours ago | parent | next [-]

In SpiderMonkey, asm.js code has been compiled by exactly the same pipeline as wasm since at least 2019. In fact, the way we compile it is literally to construct a pseudo-wasm module and run it through our wasm compiler (with a few flags to tweak the behavior to fit the asm.js semantics). In other words, if you're running asm.js in Firefox, you're literally just running wasm anyway, so how could it possibly be faster?

Furthermore, if you use wasm, you'll have fewer bounds checks (because of better memory allocation strategies[1]), access to SIMD, bulk memory operations, and a host of other niceties that have been added to wasm over the years. If your asm.js code is outperforming someone else's wasm code, that probably just means their wasm code is worse.

[1]: https://spidermonkey.dev/blog/2025/01/15/is-memory64-actuall...

	▲	theultdev 3 hours ago \| parent [-]
		yeah turns out it was chrome that was slow, not firefox. wasm hashing in chrome is half the speed of firefox for me. https://theultdev.github.io/web-sha256-benchmark

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lukan 6 hours ago | parent | prev | next [-]

That is surprising. Do you know the reasons? Is it a special use case or was asm really faster? I find that hard to believe.

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theultdev 6 hours ago | parent [-]

It's a custom solution, but nothing special just incremental hashing for large files.

I took off the shelf wasm crypto libraries to compare it, but the leading one was 10x slower.

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throawayonthe 6 hours ago | parent [-]

can we see?

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theultdev 6 hours ago | parent [-]

yeah check back at the end of the day.

will try to rip it out of the project and put it in a standalone benchmark.

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titzer 6 hours ago | parent [-]

It'd be interesting to compare it to a SHA-256 algorithm that uses Wasm simd: https://github.com/ChrisWhealy/wasm_sha256

	▲	theultdev 5 hours ago \| parent [-]
		Noted, will add that. Last time I tried https://github.com/Daninet/hash-wasm edit: I focus on browsers, that's wasm but not for browser envs. ---- https://theultdev.github.io/web-sha256-benchmark https://github.com/TheUltDev/web-sha256-benchmark seems it is chrome wasm that is slow. asmjs is about the same speed in chrome and firefox (with asm optimizations still enabled) but wasm is slow as hell in chrome, asm still better. side note: someone mentioned native crypto.subtle, but that doesn't have incremental hashing so can't use it for large files. however I do use it in practice for smaller files.

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theultdev 3 hours ago | parent | prev | next [-]

Made the requested benchmark:

https://theultdev.github.io/web-sha256-benchmark

https://github.com/TheUltDev/web-sha256-benchmark

It's Chrome wasm (windows) that is slow for me, 2x slower than asmjs.

FF with asmjs optimizations are 2x slower than wasm on FF.

Wasm in FF is 2x faster than wasm in Chrome for this hashing solution (for me).

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dist-epoch 5 hours ago | parent | prev [-]

what's wrong with the built in one?

https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypt...

	▲	wren6991 4 hours ago \| parent \| next [-]
		Requires a secure origin. If you serve a local (but non-localhost) SPA over HTTP then you're blocked from using crypto.subtle.digest. At least, that is one reason I have seen a hand-rolled SHA-256 deployed. Edit: oh, and it forces async.
	▲	theultdev 3 hours ago \| parent \| prev [-]
		no incremental hashing, so you can't hash files too large for ram. I do use it for smaller files though, it's much faster.