Remove accidental hack in ipa_polymorphic_call_context::set_by_invariant

[Jan Hubicka]

Hi,
I managed to commit a hack setting offset to 0 in
ipa_polymorphic_call_context::set_by_invariant.  This makes it to give up on 
multiple
inheritance, but most likely won't give bad code since the ohter base will be of
different type.  

Bootstrapped/regtested x86_64-linux, comitted.

gcc/ChangeLog:

        * ipa-polymorphic-call.cc 
(ipa_polymorphic_call_context::set_by_invariant): Remove
        accidental hack reseting offset.

diff --git a/gcc/ipa-polymorphic-call.cc b/gcc/ipa-polymorphic-call.cc
index 8667059abee..81de6d7fc33 100644
--- a/gcc/ipa-polymorphic-call.cc
+++ b/gcc/ipa-polymorphic-call.cc
@@ -766,7 +766,6 @@ ipa_polymorphic_call_context::set_by_invariant (tree cst,
   tree base;
 
   invalid = false;
-  off = 0;
   clear_outer_type (otr_type);
 
   if (TREE_CODE (cst) != ADDR_EXPR)