You even have a problem with the same compiler as one compiler may generate poor code for some processors. I would even go so far as to state that you should generate code for generic targets as processor-specific software is still pretty hard to find.
Microsoft Office doesn't come packaged for MMX, SSE and SSE2. It runs x86 at the lowest level that they support.
You could put the branching stuff into your code but you incur an expense for those running without the new processor features and those are the processors that you don't want to use up additional cycles on.
Re: While I am not saying your take is without merits, why loose any breath talking about Spec-scores if you don't accept the rules of producing the benchmarks?
And what rules would those be? I am advocating the rules, not arguing against them.