Although namespacing them keeps them out from under a programmer's feet, which is a significant benefit, it does seem like this would make it harder to find stuff. @cmpxchgStrong, @wasmMemorySize and @embedFile are completely unrelated, but since they're all builtins they're neighbours.

This is sort of an issue we already deal with in other languages, and imo it's not a huge deal in those. Personally I find @ more reasonable than __builtin_