Again, reverse engineering is a valid use case of clean room implementation as I posted above, so you don't have a point there.
> “clean room implementation” is a term of art with a specific meaning.
What is the specific meaning you are talking about? If I set out to do a clean room implementation of some software, what do I need to do specifically so that I will prevail any copyright infringement claims? The answer is that there is no such a surefire guarantee.
Re: Sony v. Connectix, clean room is to protect against copyright infringement, and since Connectix was ruled not infringing on Sony's copyrights, their implementation is practically clean room under the law, despite all the pushbacks. If Connectix prevailed, I'm sure the C compiler in question would have prevailed as well if they got sued.
Finally, take Phoenix vs. IBM re: the former's BIOS implementation of the latter's PC:
Whenever Phoenix found parts of this new BIOS that didn't work like IBM's, the isolated programmer would be given written descriptions of the problems, but not any coded solutions that might have hinted at IBM's original version of the software - [0]
That very much sounds like using GCC as an online known-good compiler oracle to compare against in this case.
[0] - https://books.google.com/books?id=Bwng8NJ5fesC&pg=PA56#v=one...