[terrymah]

You can't just look at the codegen of the function itself, you also have to consider the metadata, and the overhead of processing any metadata

Specifically here (as I said in other comments) where it goes from complicated/quality of implementation issue to "shit this is complicated" is when you consider inlining. If noexcept inhibits inlining in any conceivable circumstances then it's having a dramatic (slightly indirect) impact on performance