At work, I have a large C++ codebase in which I can observe slowdowns of one order of magnitude or more with -O0 compared to -O3. And for many bugs it still tak

At work, I have a large C++ codebase in which I can observe slowdowns of one order of magnitude or more with -O0 compared to -O3. And for many bugs it still takes 10 minutes of runtime to hit them, so not using optimizations just isn't tenable. As far as I can tell, this is worse than for the average C++ codebase. I have some ideas for why the optimizer is able to achieve such large improvements with this particular code and some of that could surely be done with better source, but it's a huge code base and a refactoring on that scale just isn't going to happen.