https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102294
--- Comment #3 from Bart Van Assche <bart.vanassche at gmail dot com> --- Thanks for the quick feedback. I have modified the test program and added target("no-sse") to the bio_init[123]() functions. With that change applied the results are as follows: $ gcc -O2 -o bio_init bio_init.c && ./bio_init Elapsed time: 0.965606 s Elapsed time: 0.529943 s Elapsed time: 0.734645 s $ clang -O2 -o bio_init-clang bio_init.c && ./bio_init-clang Elapsed time: 0.633179 s Elapsed time: 0.605532 s Elapsed time: 0.504315 s It seems like clang still generates significantly better code for bio_init3() than gcc?