[Bug libfortran/77278] Use LTO for libgfortran

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77278

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-08-20
     Ever confirmed|0                           |1

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
It is not easy to find a simple test case where an advantage
can be found.  With my hand-hacked LTO libgfortran, I get

ig25@linux-fd1f:~/Krempel/LTO> cat write.f90
program main
  implicit none
  integer :: i
  real(kind=8) :: a
  do i=1,10**7
    call random_number(a)
    write (10,'(E17.8," ")',advance="NO") a
  end do
end program main

With -static-libgfortran -lto I get for three consecutive runs

real    0m16.463s
user    0m15.979s
sys     0m0.449s

real    0m17.839s
user    0m17.440s
sys     0m0.388s

real    0m16.824s
user    0m16.378s
sys     0m0.436s

and with the normal shared library

real    0m19.508s
user    0m19.086s
sys     0m0.410s

real    0m19.850s
user    0m19.395s
sys     0m0.444s

real    0m18.213s
user    0m17.802s
sys     0m0.400s