[Bug fortran/89920] do loop fails to complete

[mark.eggleston at codethink dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89920

--- Comment #2 from MarkEggleston <mark.eggleston at codethink dot com> ---
Affects 7, 8 and trunk branches.

A do loop from 1 to the maximum value of an integer does not exit. The example
below has a check that forces the loop to exit.

program test
  implicit none
  integer(4) :: i
  integer(4), parameter :: maximum = huge(i)
  integer(4) :: count
  logical :: wrap
  count = 0
  do i = 1,maximum
    if (i.gt.0) then
      count = count + 1
    else
      wrap = .true.
      exit
    endif
  enddo
  write(*,*) "count ", count
  write(*,*) "wrap", wrap
end

When compiled with 6.3 the result is:

 count   2147483647
 wrap F

When compiled with compiler built using 7, 8 and trunk code on x86_64 the
result is:

 count   2147483647
 wrap T

Also occurs with integer(1) and integer(2) expect the same is true of
integer(8) and integer(16).