I remember when Mozilla released OdinMonkey that was hyper-specialized for asm.js code, the Chrome / V8 team instead worked on general-purpose optimizations in their JIT that would run normal JavaScript faster but also would help asm.js. The difference in speed was 2-4x in favor of Firefox, and they hyped it a lot :D

Nowadays most browser JavaScript VMs converged to very similar designs and optimizations, so even without Odin asm.js code would run pretty fast anyway.