asm.js is not a redesign of JS from the ground up, it is an evolutionary step in improving support for a certain style of Emscripten/Mandreel generated code tha

asm.js is not a redesign of JS from the ground up, it is an evolutionary step in improving support for a certain style of Emscripten/Mandreel generated code that Google is at least somewhat interested in, given its inclusion in the Octane benchmark. Performance improved in Chrome on at least one Emscripten benchmark when generating asm.js code rather than the previous backend, without any further change to Chrome, probably because asm.js does a better job at formalizing the various assumptions that this style of code relies on.