alt Hacker NewsAllegedly the pre and post conditions, in varying degrees of certainty according to the evaluation semantics selected, are propagated to the optimization passes of gcc and llvm. However, I haven’t seen any detailed blog posts or summaries of the effectiveness or reliability of this feature. Sorry it’s not a lot of info, but it was what I knew off hand based on previous reading.
But for the most use you'd specifcially want them used for optimizations when they are NOT being evaluated as that's the build where perf matters.