[Bug tree-optimization/21568] New: [3.4 regression] Casts in folding *& omitted

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

For the testcase

int x;
int foo(void)
{
        x = 0;
        return *(volatile int *)&x;
}

the tree-optimizers omit the volatile cast and cprop 0 to the
return statement which is invalid.  This is a regression from
3.4 where we produced (with -O)

foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    $0, x
        movl    x, %eax
        popl    %ebp
        ret

and now

foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    $0, x
        movl    $0, %eax
        popl    %ebp
        ret

-- 
           Summary: [3.4 regression] Casts in folding *& omitted
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21568