https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110167
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- It's hard to bisect where it got slower between 10 and 11, and between 11 and 12, because for --enable-checking builds the extra assertions slow everything down and the difference between "fast with slow assertions" and "slow with slow assertions" is much less significant than "fast" and "slow".