https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83064
Dominique d'Humieres <dominiq at lps dot ens.fr> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2017-11-21 Ever confirmed|0 |1 --- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> --- > GCC revision r254890 Are you sure of the revision? I more or less confirm your results with r254966, but not with r254940 (the Unrolled do-loop is parallelized with -Ofast only and gives the correct result). Also -ftree-parallelize-loops=4 gives the same results as r254940.