[Bug fortran/30752] New: SECNDS() or DATE_AND_TIME() intrinsic optimized incorrectly.

["brooks at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Consider the following piece of code, derived from the secnds-1.f test case
(with some changes I'd added to avoid the 20ms arbitrary tolerance):

C {dg-do run}
      character*20 dum1, dum2, dum3
      real t1, t1a, t2, t2a
      real dat1, dat2
      integer i, j, values(8)
      t1 = secnds (0.0)
      call date_and_time (dum1, dum2, dum3, values)
      t1a = secnds (0.0)
      dat1 = 0.001*real (values(8)) + real (values(7)) +
     &        60.0*real (values(6)) + 3600.0* real (values(5))
C The following line is critical here.
C     write (*,*) (((dat1 - t1) < 0.) .or. ((dat1 - t1) > (t1a - t1)))
      if (((dat1 - t1) < 0.) .or. ((dat1 - t1) > (t1a - t1))) then
        write (*,*) (((dat1 - t1) < 0.) .or. ((dat1 - t1) > (t1a - t1)))
        write (*,*) dat1, t1, t1a, dat1-t1, t1a-t1
        call abort ()
      end if
      end

If I run this through the usual testsuite apparatus, it will fail on about 30%
(on average) of the optimized runs, but never (so far as I've seen) with -O0. 
The output, though, usually looks like this:

 F
   16806.37       16806.37       16806.37       0.000000       0.000000

Note the "F", for the exact check that just evaluated as true in the IF
statement.

If I uncomment the WRITE statement prior to the IF, the failures go away.


-- 
           Summary: SECNDS() or DATE_AND_TIME() intrinsic optimized
                    incorrectly.
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: brooks at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30752