[Bug tree-optimization/38723] New: default definitions not in avail_out

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

FRE does not optimize

int i;
int foo (void)
{
  int j;
  i = j;
  return i;
}

because j_1(D) is never in AVAIL_OUT, so we do not find a leader for it.

We can fix this by either pretending used default definitions are defined
in the entry block or by treating default definitions the same as constants
during elimination.

Danny?


-- 
           Summary: default definitions not in avail_out
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38723