This discussion very much feels like theory vs practice. Can you beat C compilers with unlimited time, money and "ideal" programmer using inline assembly only ? Yes.
Is this a useful consideration when trying to actually produce something ? No. Software development is about producing a result with limited resources. The rest is just theoretical conjecture. How much resources would actually be necessary to create a compiler as robust, optimized and portable as gcc (keep in mind that gcc usually gets outclassed by proprietary C compiled such as IAR and ICC) from Nim AST ? In practice, C compilers will generate better, faster assembly than what 99.99% of C programmer are ever going to write - and even then it would be un-maintainable over time as you'd need to re-implement every C library out there. Yes, there are some case where writing inline assembly can be useful (reverse engineering, patching buggy start-up code given by a manufacturer, optimizing a specific operation on a critical function etc...) but it's still very limited in scope.
