[Bug fortran/48864] New: -Ofast should imply -fno-protect-parens

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48864

           Summary: -Ofast should imply -fno-protect-parens
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org


-Ofast implies -O3 -ffast-math and possibly some more performance options; it
should also imply -fno-protect-parens

For -Ofast, cf. http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

For -fno-protect-parens,
cf. http://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html


That -Ofast implies -fno-protect-parens should also be documented for -Ofast.


An example how drastic the performance depends on -fno-protect-parens is the
following program; it additionally requires -funroll-loops:

http://openmp.org/forum/viewtopic.php?f=3&t=1134#p4565

gfortran timings can be found at
  http://openmp.org/forum/viewtopic.php?f=3&t=1134&start=11
  http://openmp.org/forum/viewtopic.php?f=3&t=1134&start=11#p4673