[Bug fortran/54932] Invalid loop code generated by Fortran FE for loops with bounds in HIGH(type)

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54932

--- Comment #14 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-02-12 18:21:53 UTC ---
(In reply to comment #13)
> Please also split the testcase - it contains
> several tests and only one has invalid overflow.

Actually there are three of them
(a)

program do_1
  implicit none
  integer i, j

  ! limit=HUGE(i), step 1
  j = 0
  do i = HUGE(i) - 10, HUGE(i), 1
    j = j + 1
  end do
!  print *, i
  if (j .ne. 11) call abort
end program

(b)

program do_1
  implicit none
  integer i, j

  ! limit=HUGE(i), step > 1
  j = 0
  do i = HUGE(i) - 10, HUGE(i), 2
    j = j + 1
  end do
  if (j .ne. 6) call abort
!  print *, i
end program

(c)

program do_1
  implicit none
  integer i, j

  ! limit=HUGE(i), step > 1
  j = 0
  do i = HUGE(i) - 9, HUGE(i), 2
    j = j + 1
  end do
!  print *, i
  if (j .ne. 5) call abort

end program

Only (a) aborts and only if the PRINT is commented. (b) and (c) don't abort
even in the PRINT is uncommented.

Finally I have tested

program do_1
  implicit none
  integer i, j, i1, i2, i3, j1, j2, j3

  ! limit=HUGE(i), step 1
  j = 0
  do i = HUGE(i) - 10, HUGE(i), 1
    j = j + 1
  end do
  i1 = i
  j1 = j
!  if (j .ne. 11) call abort
  ! limit=HUGE(i), step > 1
  j = 0
  do i = HUGE(i) - 10, HUGE(i), 2
    j = j + 1
  end do
  i2 = i
  j2 = j
!  if (j .ne. 6) call abort
  j = 0
  do i = HUGE(i) - 9, HUGE(i), 2
    j = j + 1
  end do
  i3 = i
  j3 = j
!  if (j .ne. 5) call abort

  ! Same again, but unknown loop step
  if (test1(10, 1) .ne. 11) call abort
  if (test1(10, 2) .ne. 6) call abort
  if (test1(9, 2) .ne. 5) call abort

  print *, i3, j3
  if (j3 .ne. 5) call abort
  print *, i2, j2
  if (j2 .ne. 6) call abort
  print *, i1, j1
  if (j1 .ne. 11) call abort
contains
! Returns the number of iterations performed.
function test1(r, step)
  implicit none
  integer test1, r, step
  integer k, n
  k = 0
  do n = HUGE(n) - r, HUGE(n), step
    k = k + 1
  end do
  print *, n, k
  test1 = k
end function

end program

which shows that a contained function is enough to hide the invalid behavior,
which detected for the three loops when put together.