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 specification has the details.