[Bug c/18784] New: Floating point calculation inconsistent within program with -O2

[Graham dot Murphy at jhuapl dot edu]

Attached (hopefully) is a C program that performs a simple
floating point calculation that produces a number very close
to an integer. When this calculation is done twice within 
the same program, two different answers are produced if
there is an intervening print statement and -O2 or greater
optimization.

Problem appears with gcc 2.9 through 3.4.2 and Pentiums 1 - 4.
Not seen on AMD or Sparcs.

I have examined the FPU IEEE rounding control bits but see no
difference between the two sections.

-- 
           Summary: Floating point calculation inconsistent within program
                    with -O2
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Graham dot Murphy at jhuapl dot edu
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux
  GCC host triplet: i686-pc-linux
GCC target triplet: i686-pc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18784