> The claim that the code is inefficient is really not substantiated well in this blog post.

I didn't run benchmarks, but in the case of clang writing zeros to memory (which are never used thereafter), there's no way that particular code is optimal.

For the gcc output, it seems unlikely that the three versions are all optimal, given the inconsistent strategies used. In particular, the code that sets the output value to 0 or 1 in the size = 3 version is highly unlikely to be optimal in my opinion. I'd be amazed if it is!

Your point that unintuitive code is sometimes actually optimal is well taken though :)