Could not the main compilers get involved and add builtins so an ifdef makes the common path on the main compilers like gcc use builtins and the slowdown only hurts those using the less mainstream compilers? If it takes off the other compilers would quickly add the feature.
What you're suggesting is basically a worse version of adding built-in min() and max() to the C spec. Which, to be fair, would be quite nice, but I guess the working group didn't want it in the standard.
