Protect a block of code from optimization?

[chamric . spammable]

I've got a bit of code in a multithreaded program that implements a
non-blocking concurrent queue.  I want to optimize my code as much as
possible because it must work in a high-performance environment, but
I'm afraid of the optimization routines messing up the ordering of my
queue code.

Is there some kind of preprocessor line or something to instruct the
optimizer to not optimize a certain section of code, but still be able
to optimize the rest?