2024.04.20 15:40:40 (Mastodon 112304301065128573, Twitter 1781709589605675182) from Daniel J. Bernstein:
Tracking down some TIMECOP alerts led to a 2021 gcc patch from ARM (https://gcc.gnu.org/git/?p=gcc.git;a=commit;f=gcc/match.pd;h=d70720c2382e687e192a9d666e80acb41bfda856) turning (-x)>>31 into a bool, often breaking constant-time code. Can often work around with (-x)>>30, and asm is safer anyway, but for portable fallbacks we need security-aware compilers.