In this profile, they’re showing pretty much the exact same performance, so that doesn’t tell us much. I believe the performance degradation is something that happens over time, and these are fresh runs of emacs. I’ll have to try and get from 25 next time it slows down on me.
One curious thing is that the emacs 24 profile shows all of the builtins (let/if/save-excusion) and the emacs 25 profile does not. Is there something I’m doing wrong that is causing that? I’m using the same `profiler-start` function.