Maybe if the machine running the code is the machine that compiles it, or if you have a good way to send processor-specific binaries to the right places. More

Maybe if the machine running the code is the machine that compiles it, or if you have a good way to send processor-specific binaries to the right places. More useful, I think, would be a runtime check far enough up the stack (i.e., away from tight loops) that it doesn't affect performance. Probably doesn't even need to be that high, it'll branch-predict correctly every time but the first iteration, and the binary bloat probably won't hurt your icache because the number of instructions you ever actually execute stays more or less the same.