On 2024-07-16 22:01, Paul Eggert wrote:
> We could add an AC_RUN_IFELSE test for SSE2, though I doubt whether it 
> would affect builds significantly in practice.

On second thought the rare Arch or Gentoo user could still be building 
Emacs for the Pentium III, and for such a user a run-time test on the 
build host would be a win. This can be done via the attached revised 
patch. It uses AC_LINK_IFELSE to compile and run a single program, 
instead of AC_RUN_IFELSE which (when combined with AC_COMPILE_IFELSE) 
would mean compiling two test programs and running one.