[Bug c++/36965] New: Unnecessary unrolling+regular call instead of tail call

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

The following code, compiled with "g++ -O2", unrolls a number of the recursive
calls of "is_frozen", then ends up with a "call" followed by a "leave" (non
tail-call). It could use tail-recursion instead, which would be more space and
cache efficient.

Using g++ (GCC) 4.4.0 20080727 (experimental).

struct Tag {
  bool is_frozen() const
  {
    return frozen || (parent && parent->is_frozen());
  };
  Tag* parent;
  bool frozen;
};

bool f(Tag& t)
{
  return t.is_frozen();
}


-- 
           Summary: Unnecessary unrolling+regular call instead of tail call
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sam at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36965