GCC 4.4: Avoid range check on switch/case statement in gcc?

Question

This is only an issue on GCC versions prior to 4.4, this was fixed in GCC 4.5.

Is it possible to tell the compiler the variable used in a switch fits within the provided

Answer 1

This question is certainly interesting from the standpoint of a missed compiler optimization that is seemingly obvious to us, and I did spend considerable time trying to come up with a straightforward solution, largely out of personal curiousity.

That said, I have to admit I am highly skeptical that this additional instruction will ever result in a measurable performance difference in practice, especially on a new mac. If you have any significant amount of data, you'll be I/O bound, and a single instruction will never be your bottleneck. If you have a tiny amount of data, then you'll need to perform a lot lot lot of calculations repeatedly before a single instruction will become a bottleneck.

Would you post some code to show that there really is a performance difference? Or describe the code and data your working with?