[Bug tree-optimization/47462] New: g++.dg/opt/devirt1.C no longer devirtualized

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47462

           Summary: g++.dg/opt/devirt1.C no longer devirtualized
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jamborm@gcc.gnu.org


Since the fix for PR 47382:

http://gcc.gnu.org/ml/gcc-patches/2011-01/msg01753.html

the test case g++.dg/opt/devirt1.C had to be XFAILed for reasons
explained in the email with the patch.

Basically, whenever we want to fold OBJ_TYPE_REF to a direct call
according to the type of its 1st argument, we need to check for
dynamic type changes.  

Patches http://gcc.gnu.org/ml/gcc-patches/2010-12/msg01218.html and
http://gcc.gnu.org/ml/gcc-patches/2010-12/msg01214.html do this but
suffer from another problem because currently we also must make sure
we do not create a call to a thunk which cannot be represented in the
call graph (or compensate for in the caller).  The patches do detect
thunks by looking at call graph nodes but we do not have a call graph
node for the destination and so the code bails out.