https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89502
--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to H.J. Lu from comment #1) > Ever better, we can use UNSPEC_TP to handle it: > > movl %fs:24, %ecx > > to save a register. We do, with -O2, but -O1 CSEs the constant into the register for some reason.