Would be interested if its worthwhile/possible using shaders as a wrapper for three.js. All I got when I was searching was there was a mozilla bug report and a hacked patch to expose SIMD through js[1], and a project to add SIMD support to vectors in Dart[2].

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=644389

[2] http://www.altdevblogaday.com/2012/06/18/bringing-simd-accel...