[Bug middle-end/43340] New: miscompiled code at -O2

["jv244 at cam dot ac dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

I find that CP2K compiled with gfortran 4.3 and 4.4 is miscompiled and produces
incorrect results when compiled with '-O2' whereas '-O1' gives correct results.
4.5 is OK. At this point, I have been able to narrow it down to a single
subroutine (se_fock_matrix_integrals.F):

  SUBROUTINE fock2C(sepi, sepj, rij, switch, pi_tot, fi_mat, pj_tot, fj_mat, &
       factor, anag, se_int_control, se_taper, store_int_env, error)
    TYPE(semi_empirical_type), POINTER       :: sepi, sepj
    REAL(KIND=dp), DIMENSION(3), INTENT(IN)  :: rij
    LOGICAL, INTENT(IN)                      :: switch
    REAL(KIND=dp), DIMENSION(45, 45), &
      INTENT(IN)                             :: pi_tot
    REAL(KIND=dp), &
      DIMENSION(sepi%natorb, sepi%natorb), &
      INTENT(INOUT)                          :: fi_mat
    REAL(KIND=dp), DIMENSION(45, 45), &
      INTENT(IN)                             :: pj_tot
    REAL(KIND=dp), &
      DIMENSION(sepj%natorb, sepj%natorb), &
      INTENT(INOUT)                          :: fj_mat
    REAL(KIND=dp), INTENT(IN)                :: factor
    LOGICAL, INTENT(IN)                      :: anag
    TYPE(se_int_control_type), INTENT(IN)    :: se_int_control
    TYPE(se_taper_type), POINTER             :: se_taper
    TYPE(semi_empirical_si_type), POINTER    :: store_int_env
    TYPE(cp_error_type), INTENT(inout)       :: error

    CHARACTER(len=*), PARAMETER :: routineN = 'fock2C', &
      routineP = moduleN//':'//routineN

    INTEGER                                  :: i, iL, j, jL, k, kL, kr, l, &
                                                lL, natorb(2)
    LOGICAL                                  :: failure
    REAL(KIND=dp)                            :: a, aa, bb, irij(3)
    REAL(KIND=dp), DIMENSION(2025)           :: w

    failure = .FALSE.
    ! Evaluate integrals
    IF (.NOT.switch) THEN
       CALL rotint (sepi,sepj, rij,w,anag=anag,se_int_control=se_int_control,&
            se_taper=se_taper,store_int_env=store_int_env, error=error)
    ELSE
       irij = -rij
       CALL rotint (sepj,sepi,irij,w,anag=anag,se_int_control=se_int_control,&
            se_taper=se_taper,store_int_env=store_int_env, error=error)
    END IF
    kr = 0
    natorb(1) = sepi%natorb
    natorb(2) = sepj%natorb
    IF (switch) THEN
       natorb(1) = sepj%natorb
       natorb(2) = sepi%natorb
    END IF
    DO iL = 1, natorb(1)
       i = se_orbital_pointer(iL)
       aa = 2.0_dp
       DO jL = 1, iL
          j = se_orbital_pointer(jL)
          IF (i == j) THEN
             aa = 1.0_dp
          END IF
          DO kL = 1, natorb(2)
             k = se_orbital_pointer(kL)
             bb = 2.0_dp
             DO lL = 1, kL
                l = se_orbital_pointer(lL)
                IF (k == l) THEN
                   bb = 1.0_dp
                END IF
                kr = kr + 1
                a = w(kr)*factor
                ! Coulomb
                IF (.NOT.switch) THEN
                   fi_mat(i,j) = fi_mat(i,j) + bb * a * pj_tot(k,l)
                   fj_mat(k,l) = fj_mat(k,l) + aa * a * pi_tot(i,j)
                   fi_mat(j,i) = fi_mat(i,j)
                   fj_mat(l,k) = fj_mat(k,l)
                ELSE
                   fj_mat(i,j) = fj_mat(i,j) + bb * a * pi_tot(k,l)
                   fi_mat(k,l) = fi_mat(k,l) + aa * a * pj_tot(i,j)
                   fj_mat(j,i) = fj_mat(i,j)
                   fi_mat(l,k) = fi_mat(k,l)
                END IF
             END DO
          END DO
       END DO
    END DO

  END SUBROUTINE

unfortunately, due to the dependencies, getting a self-contained testcase that
produces wrong results is very difficult. The only reasonable thing I have
right now is build CP2K and run the test cp2k/tests/SE/regtest-3/O2.inp, and
see vastly wrong total energies. I'll attach the results of -fdump-tree-all to
the bug report for both -O1 and -O2, I hope that is helpful. I can easily try
to see the effect of various compile options.


-- 
           Summary: miscompiled code at -O2
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jv244 at cam dot ac dot uk


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43340