> I don't know enough about asm to know if their annotations are slower than vanilla JS in unoptimized engines, but I suspect they might be. The opposite is tr

> I don't know enough about asm to know if their annotations are slower than vanilla JS in unoptimized engines, but I suspect they might be. The opposite is true, for the most part. JS engines, even without asm.js optimizations, utilize the fact that the | operator emits a 32-bit integer (per the JS semantics), so it helps their type inference. (The engine needs to be good enough to get rid of the actual 0 value in the |0 coercions, but JS engines have been that good for several years now anyhow.) > I was also surprised that asm still won in Chrome - I thought Chrome optimized for asm-like code without checking for the "use asm" flag. Chrome detects "use asm", and enables TurboFan on such code. All JS engines today detect "use asm", except for JavaScriptCore.