https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91936
--- Comment #3 from Weiqiang Wu <waikng at hotmail dot com> --- Thanks, Jonathan. The problem seems universal. I can replicate it with gcc 9.2.0 and glibc 2.27 through the following online compiler. ( https://gcc.godbolt.org/z/QXU8Wm ) When I switch to icc 19.0.1 there, the calculation time for both arrays are similar. Can you point me to the right place to report the problem if it is indeed in glibc? I feel like it is not vendor specific. Thanks.