> I doubt that the fact that it's JS matters all that much given that either loop is absolutely tiny once it's compiled down to optimized assembly. It might ma

> I doubt that the fact that it's JS matters all that much given that either loop is absolutely tiny once it's compiled down to optimized assembly. It might matter. At least when run in the browser, JS needs to be interruptible (so pages don't hang on infinite loops), which is often done by checking a flag at the target of any backwards branch. So that's another (predictable) branch. And sometimes when you get enough branches, they have an effect even if they're near 100% predictable. I don't know if it's from branch aliasing, or using up general branch prediction resources, or prefetching / some other optimization giving up after too many branches, or what.