Many compilers will iterate the so called classical optimizations until they produce no effect (an iteration where no optimization took place) or some artificia

Many compilers will iterate the so called classical optimizations until they produce no effect (an iteration where no optimization took place) or some artificial limit (say 4 or 8 iterations through a basic block or a function). At some point, you risk several accidental de-optimizations such as inducing cache thrashing, cache spilling, architectural limitation, or, even optimization clashing where one optimization de-optimizes a previous optimization on one iteration that then gets re-optimized in the following iteration (A->Opt B->"De-"Opt A->Opt B->...). Another poster suggested profile directed optimization and that usually is even more effective naively iterating through optimization steps.