[Flang] Pointer assignments for array pointers are slower than GFortran

[yus3710-fj]

The execution of the following codes is slower than GFortran.

• test.f90

subroutine piannn117(lhs,rhs)
  integer, target :: rhs(:)
  integer, pointer :: lhs(:)
  lhs => rhs
end subroutine

• main.f90

implicit none

integer, parameter :: count = 10000
integer, target :: i,j,k,a1(100)
integer, pointer :: pj(:)
real :: start_t, end_t
interface
  subroutine piannn117(lhs,rhs)
    integer, target :: rhs(:)
    integer, pointer :: lhs(:)
  end subroutine
end interface

call cpu_time(start_t)
do i=1,count
  do j=1,count
    call piannn117(pj,a1)
  end do
end do
call cpu_time(end_t)

print *, end_t - start_t
end

• commands

$ flang -Ofast -mcpu=native test.f90 main.f90 && ./a.out # for A64FX/Grace
$ flang -Ofast -march=native test.f90 main.f90 && ./a.out # for Xeon

	Flang [s]	GFortran [s]
A64FX	2.3188815	1.77965200
Grace	0.494064	0.256214023
Xeon	0.8129115	0.250275999