https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85364
Bug ID: 85364 Summary: -fopenmp should not put array in program on the stack Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: tkoenig at gcc dot gnu.org Target Milestone: --- Currently, gfortran sometimes puts array in the main program on the stack with -fopenmp. This is not needed and makes no sense, because the main program in Fortran can never be called by anything else. It can also cause considerable confusion, as in PR85346. Test case: $ cat a.f90 ! { dg-do run } ! PR 83064 - this used to give wrong results. ! { dg-additional-options "-O1 -ftree-parallelize-loops=2" } ! Original test case by Christian Felter program main use, intrinsic :: iso_fortran_env implicit none integer, parameter :: nsplit = 4 integer(int64), parameter :: ne = 2**20 integer(int64) :: stride, low(nsplit), high(nsplit), i integer(int64), dimension(ne) :: edof real(real64), dimension(nsplit) :: pi edof(1::4) = 1 edof(2::4) = 2 edof(3::4) = 3 edof(4::4) = 4 stride = ceiling(real(ne)/nsplit) do i = 1, nsplit high(i) = stride*i end do do i = 2, nsplit low(i) = high(i-1) + 1 end do low(1) = 1 high(nsplit) = ne pi = 0 do concurrent (i = 1:nsplit) pi(i) = sum(compute( low(i), high(i) )) end do if (abs (sum(pi) - atan(1.0d0)) > 1e-5) STOP 1 contains pure function compute( low, high ) result( ttt ) integer(int64), intent(in) :: low, high real(real64), dimension(nsplit) :: ttt integer(int64) :: j, k ttt = 0 ! Unrolled loop ! do j = low, high, 4 ! k = 1 ! ttt(k) = ttt(k) + (-1)**(j+1) / real( 2*j-1 ) ! k = 2 ! ttt(k) = ttt(k) + (-1)**(j+2) / real( 2*j+1 ) ! k = 3 ! ttt(k) = ttt(k) + (-1)**(j+3) / real( 2*j+3 ) ! k = 4 ! ttt(k) = ttt(k) + (-1)**(j+4) / real( 2*j+5 ) ! end do ! Loop with modulo operation ! do j = low, high ! k = mod( j, nsplit ) + 1 ! ttt(k) = ttt(k) + (-1)**(j+1) / real( 2*j-1 ) ! end do ! Loop with subscripting via host association do j = low, high k = edof(j) ttt(k) = ttt(k) + (-1.0_real64)**(j+1) / real( 2*j-1 ) end do end function end program main $ gfortran -fopenmp a.f90 $ ./a.out Speicherzugriffsfehler (Speicherabzug geschrieben)