> asm.js javascript offers subpar performance on non asm.js platforms

What kind of browser do you consider a "non-asm.js platform"? Chrome for example is not detecting asm.js specifically, but still optimizes for the types of patterns in asm.js code. As a consequence it can run asm.js code very well, on par with Firefox in many cases, for example

https://docs.google.com/a/mozilla.com/spreadsheet/ccc?key=0A...