[Bug c++/50189] New: Wrong code error in -O2 compile, target independent

[pkoning at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50189

             Bug #: 50189
           Summary: Wrong code error in -O2 compile, target independent
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: pkon...@gcc.gnu.org


Created attachment 25105
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25105
Test program

The attached test program compiles to wrong code with GCC 4.5.3 (and 4.5.1)
when compiled -O2.  GCC 4.6.1 gets it right.

I did some digging and determined that the problem shows up in the
-fdump-tree-all output in the .068t.vrp1 dump file; the preceding file
(.067.mergephi2) is correct.  In the generated code that corresponds to the
check_pos method, the second compare "if (m_timestamp != a_timestamp)" is
transformed into "if (3 == a_timestamp)".  If m_timestamp were of time
position_t (an enum of range 0..3) that would be correct, but m_timestamp is an
unsigned int so it can, and in our application does, have values larger than 3.