[Bug debug/41447] New: Wrong debug with VTA on temporaries initialized from memory variable

[jakub at gcc dot gnu dot org]

As reported by Richard in
int a;

int foo()
{
  int tmp = a;
  int tmp2 = a;
  int tmp3;
  int res;
  a = 0;
  tmp3 = tmp2;
  res = tmp - tmp2 + 1;
  return res;
}
results in wrong-debug with -O2 -g.  Having # DEBUG tmp3 => a
after a = 0 is wrong certainly already at gimple levels, while # DEBUG tmp1 =>
a
and # DEBUG tmp2 => a could be in theory handled only at the var-tracking
level, but even there var-tracking fails to notice that the a = 0 store can
clobber the memory (i.e. that the VALUE should be clobbered, and in theory e.g.
most calls should be considered to clobber non-stack MEMs etc., as usually) and
add notes that tmp1/tmp2 don't have known values anymore.


-- 
           Summary: Wrong debug with VTA on temporaries initialized from
                    memory variable
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41447