https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78611
--- Comment #11 from Jan Lachnitt <pepalogik at seznam dot cz> --- Thank you all for a rapid investigation of the problem. Here is a confirmation with the large test case: jenda@VivoBook ~/Bug reports/gfortran/6/PhSh1 $ gfortran-6 phsh1.f -std=legacy -I. -march=core-avx-i -o core-avx-i/phsh1 jenda@VivoBook ~/Bug reports/gfortran/6/PhSh1 $ cd core-avx-i/ jenda@VivoBook ~/Bug reports/gfortran/6/PhSh1/core-avx-i $ time ./phsh1 < ../bmtz Slab or Bulk calculation? input 1 for Slab or 0 for Bulk Input the MTZ value from the substrate calculation real 221m0.225s user 220m52.488s sys 0m4.488s jenda@VivoBook ~/Bug reports/gfortran/6/PhSh1/core-avx-i $ rm check.o mufftin.d jenda@VivoBook ~/Bug reports/gfortran/6/PhSh1/core-avx-i $ LD_BIND_NOW=1 time ./phsh1 < ../bmtz Slab or Bulk calculation? input 1 for Slab or 0 for Bulk Input the MTZ value from the substrate calculation 4512.06user 1.50system 1:15:16elapsed 99%CPU (0avgtext+0avgdata 7296maxresident)k 23408inputs+34424outputs (7major+1219minor)pagefaults 0swaps Really, LD_BIND_NOW=1 does wonders :-) . https://sourceware.org/bugzilla/show_bug.cgi?id=20495#c8 suggests building with "-Wl,-z,now" (I suppose this does the same as LD_BIND_NOW=1). Can it be used as a general workaround, before glibc 2.25 is available?