Intent to Extend Origin Trial: WebAssembly SIMD
Zhi An Ng
Contact emails
zh...@chromium.org, natt...@chromium.org, gde...@chromium.org
Spec
Overview document: https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md
Proposal directory: https://github.com/WebAssembly/simd/tree/master/proposals/simd
Tag review: https://github.com/w3ctag/design-reviews/issues/487
Summary
The WebAssembly SIMD proposal defines a portable, performant subset of SIMD operations that map to vector instructions that are available across most modern hardware platforms.
This is purely a WebAssembly performance feature that adds WebAssembly operations and does not affect web API behavior, but is still useful for developers to be aware of as it can change performance characteristics of applications using WebAssembly.
An Origin Trial for WebAssembly SIMD started in Chrome 84 and is scheduled to end in Chrome 86. The results of the Origin Trial are:
gaps identified in V8 and Emscripten toolchain, bugs, optimization opportunities
We are not ready to ship this, and still need more feedback:
couple more instructions were merged/will be merged into the SIMD proposal, but have not yet been in any OT, e.g. https://github.com/WebAssembly/simd/pull/201 https://github.com/WebAssembly/simd/pull/122
Link to “Intent to Prototype” blink-dev discussion
https://groups.google.com/a/chromium.org/g/blink-dev/c/y3z1Q4HnpgY/m/SpWP6YNJAwAJ
Goals for experimentation
New instructions added to the proposal, so we would like some time for developers to update their code base, examine the usefulness and performance of the new instructions, and for us to incorporate feedback in implementation or specification.
Experimental timeline
M87-M88
Any risks when the experiment finishes?
Performance loss from not using SIMD.
Reason this experiment is being extended
Couple more instructions were merged/will be merged into the proposal, but have not yet been in any OT, e.g. https://github.com/WebAssembly/simd/pull/201 and https://github.com/WebAssembly/simd/pull/122. We want some time for developers to upgrade, test the changes and for us to incorporate feedback.
Ongoing technical constraints
None.
Debuggability
Devtools is actively working on improving Wasm debuggability, and SIMD instructions are supported.
Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)?
Yes.
Link to entry on the feature dashboard
Chris Harrelson
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Zhi An Ng
LGTMI assume the overview document been updated to include the new instructions?
Also, curious what the feedback has been so far and whether these changes were directly related to OT feedback.