I will admit up front to not having yet checked out your site, I'm at work just now. But if your test is "both compilers produce the same object code", then even both compilers *not* being subverted will not guarantee that.
If I use compilers A and B to build G(cc), the A-G and B-G objects will not necessarily be byte-identical, and it doesn't *matter* what object they each in turn produce, because that would have to be am exhaustive search, which is impossible.
Or are you suggesting that A-G and B-G then be used to again compile Gcc, and *those* binaries be compared? That would tell you that either A and B were not subverted, or were subverted in exactly the same way...
but how are you authenticating your GCC sources?
(If the answer is "read the damn paper, idiot", BTW, just say that. :-)