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0 pointsazakai10y ago0 comments

SIMD.js is in progress for JS, so JS VMs are already working on it. It is on the roadmap for being added to WebAssembly, likely with a similar API.

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zurn10y ago

Is there a technical restriction why JS JITs don't transparently apply SIMD to existing loops like normal compilers (=autovectorization)? Or is it in the cards to build it on top of SIMD.js?

yoklov10y ago

Autovectorization is hard and fragile in the best of times -- tight stable loops with no (or few) branches and little/no memory access that may be aliased, etc.

For a dynamic language JIT this is pretty much infeasible (as I understand it). Every loop might have branches for guards/bailing out due to deopts, and at least in JS, TypedArrays are allowed to alias eachother.

j / k navigate · click thread line to collapse

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zurn10y ago

Is there a technical restriction why JS JITs don't transparently apply SIMD to existing loops like normal compilers (=autovectorization)? Or is it in the cards to build it on top of SIMD.js?

yoklov10y ago

Autovectorization is hard and fragile in the best of times -- tight stable loops with no (or few) branches and little/no memory access that may be aliased, etc.

j / k navigate · click thread line to collapse