[Bug fortran/52473] CSHIFT slow - inline it?

["juergen.reuter at desy dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52473

--- Comment #18 from Jürgen Reuter <juergen.reuter at desy dot de> ---
The example by posted on May 20, 2017 on c.l.f. improved by Stefano Zaghi below
shows a factor of 10-20 improvement now in gfortran 9.0.0 including the work by
Thomas Koenig.
$ ./a.out
 Elapsed CPU time =   0.33764499999999997     
 Elapsed CPU time =   0.29224100000000003     
 Elapsed CPU time =   0.26565400000000006

Here is the code:

program testme

  use, intrinsic :: iso_fortran_env

  implicit none

  integer(int32), parameter :: n = 200
  real(real32) :: a(n,n,n), b(n,n,n)
  integer(int32) :: j, k
  real(real64) :: t1, t2

  call random_number(a)

  do k = 1, 3
     call cpu_time ( t1 )
     do j = 1, 100
        b = cshift(a, shift=1, DIM=k)
     end do
     call cpu_time ( t2 )
     write ( *, * ) 'Elapsed CPU time = ', t2-t1
  end do
end program testme