https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85891
--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> --- On Thu, 24 May 2018, jason.vas.dias at gmail dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85891 > > --- Comment #7 from Jason Vas Dias <jason.vas.dias at gmail dot com> --- > Aha! > Yes, I was experimenting with the new '-march=haswell' and > '-mtune=intel' options > ( which seem to me to be the wrong way round - shouldn't 'haswell' be an > '-mtune' option and 'intel' be an '-march' option ? but this is not > the case, > according to documentation. > ) . > GCC 6.4.1 was configured with : > > ./configure \ > --prefix=/usr/local --libdir=/usr/local/lib64 --enable-languages=all \ > --enable-targets=all --enable-multilib --enable-threads=posix --enable-lto \ > --with-cpu-64=intel --with-cpu-32=generic \ > --with-arch-64=haswell --with-tune-64=intel --with-arch-32=i686 \ > --with-fp=sse+387 --with-tune-32=generic --enable-shared \ > --with-pic --with-gmp=/usr/local --with-isl=/usr/local \ > --with-cloog=/usr/local --with-mpc=/usr/local --with-isl=/usr/local \ > --with-system-zlib --with-gnu-ld --with-gnu-as --enable-serial-configure \ > --host=x86_64-linux-gnu --build=x86_64-linux-gnu --target=x86_64-linux-gnu > ' > > What I am trying to achieve is that the DEFAULT 64-bit platform for the > compiler > (the target the compiler builds for without any '-mxxxx=yyy' options) > should > be '-march=haswell -mtune=intel', which I think should be the equivalent > to the older options '-march=x86-64 -mtune=haswell' , and to > '-mtune=native' on this platform - please let me know if this is not the > case . > > The 5.5.0 & 7.3.1 compilers were built with > '--with-arch64=x86-64 --with-cpu64=haswell' , > but re-reading the updated 6.4.1 '-mtune'/'-march' documentation led > me to believe > that the new '--with-arch-64=haswell --with-tune-64=intel' options were > more appropriate . I guess not ? > (The 5.5.0 and 7.3.1 builds are 6months & 2months old, before the > '-march=haswell' support. > ). > > I will try rebuilding 6.3.1 with '--with-arch64=x86-64 > --with-cpu64=haswell' and > retest. Thanks! The testsuite is mostly "tuned" to the defaults, that is -march=x86-64 and -mtune=generic. So you likely won't have luck with the above choice either. The testcase could be improved to handle the situation more gracefully but really there's no point on the old GCC 6 branch.
