https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68123
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2015-10-28 Ever confirmed|0 |1 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- There is no loop ... what happens is that GCC lowers large vectors to a series of small vector (or scalar) operations. It does not lower to a loop (probably because nobody thought people would "abuse" the feature with such large vectors). The lowering process is very stupid as well, relying on following optimizations to clean up after it. You can look at the result with -fdump-tree-veclower which will generate a file like $source.114t.veclower2