http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57927
Bug ID: 57927 Summary: -march=core-avx2 different than -march=native on INTEL Haswell (i7-4700K) Product: gcc Version: 4.9.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: vincenzo.innocente at cern dot ch for instance mkdir scimark2TMP cd scimark2TMP wget http://math.nist.gov/scimark2/scimark2_1c.zip . unzip scimark2_1c.zip c++ -S LU.c -O3 -march=native -o LU.native -v c++ -S LU.c -O3 -march=core-avx2 -o LU.avx2 -v diff LU.native LU.avx2 if you run the benchmark gcc -O3 -march=core-avx2 *.c -lm; ./a.out 5 gcc -O3 -march=native *.c -lm; ./a.out 5 "core-avx2" is better than "native"