Personally, I would expect the opposite - the optimizer doing a lot of work on optimization passes that have minimal effect on one particular architecture. Rem

Personally, I would expect the opposite - the optimizer doing a lot of work on optimization passes that have minimal effect on one particular architecture. Remember that the optimizer is working on a generic intermediate form - as long as that form is a reasonable analogue of the target architecture (e.g. you're not targeting a registerless stack machine), then any "optimization" applicable to the target architecture is also (in theory) capable of being applied to the intermediate representation. This is, of course, assuming a well-implemented backend that efficiently transforms the IR to the target machine code, that can use optimal instructions even when there's no direct IR analogue to them.