I'm not. GCC started out as a work of idealistic licensing purists and was deliberately "obfuscated" to make it hard to extend and embed. That stance has since been softened considerably, but the code generator is still far more complex than it needs to be, and I think that has made it harder to modify for efficiency. Clang is far less ideology-focused and its structure makes implementing optimisations easier.

On the other hand, I find MSVC and especially ICC output to be quite decent, although I have never seen their source code.

Having inspected the output of compilers for several decades, it's rather easy to tell them apart.