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This repository has been archived by the owner on Dec 22, 2021. It is now read-only.


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SIMD proposal for WebAssembly

This repository holds a proposal for adding 128-bit SIMD support to WebAssembly. It is a copy of the WebAssembly/spec repository with the addition of a proposals/simd directory. The proposal describes how 128-bit packed SIMD types and operations can be added to WebAssembly. It is based on previous work on SIMD.js in the Ecma TC39 ECMAScript committee and the portable SIMD specification that resulted.

The proposed semantics has the details.

Note: Consult the implementation status document to get an idea of the state of implementation across toolchains and embedders.

Usage documentation is being collected at (make PRs here) and may be moved to a more vendor-neutral location in the future.

Design issue

Original README from upstream repo follows...


This repository holds a prototypical reference implementation for WebAssembly, which is currently serving as the official specification. Eventually, we expect to produce a specification either written in human-readable prose or in a formal specification language.

It also holds the WebAssembly testsuite, which tests numerous aspects of conformance to the spec.

View the work-in-progress spec at

At this time, the contents of this repository are under development and known to be "incomplet and inkorrect".

Participation is welcome. Discussions about new features, significant semantic changes, or any specification change likely to generate substantial discussion should take place in the WebAssembly design repository first, so that this spec repository can remain focused. And please follow the guidelines for contributing.


For citing WebAssembly in LaTeX, use this bibtex file.