Thanks for the insight and the links! Scrolling down the article I spotted this: > There’s only one case where an optimized call from JavaScript » WebAssembly

Thanks for the insight and the links! Scrolling down the article I spotted this: > There’s only one case where an optimized call from JavaScript » WebAssembly is not faster than JavaScript » JavaScript. That is when JavaScript has in-lined a function. Combined with your remark that 64 bit arithmetic is fast, I'd say this pretty much confirms the suspicion that a lack of inlining is what makes this particular WASM function execute slower