Conceivably, different ISAs could have the code compiled with different size/performance tradeoffs. One assumes that the Ubuntu and Fedora etc people would make sensible choices, consistent across ISAs. I don't know any reason why they would both make the same bad choices (which by "bad" here I am talking about small code at the expense of speed).

Gcc certainly supports unrolling, alignment of labels / loops / functions on all targets I'm aware of.