[gcc r16-6175] analyzer: fix state dumps for return_event [PR122003]

[David Malcolm]

https://gcc.gnu.org/g:1823d42676a98804d8b05ee5ea59ed69da427b91

commit r16-6175-g1823d42676a98804d8b05ee5ea59ed69da427b91
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Dec 16 12:10:26 2025 -0500

    analyzer: fix state dumps for return_event [PR122003]
    
    In the reimplementation of supergraph (r16-6063-g0b786d961d4426) the
    class return_event moved from being a subclass of superedge_event to
    a subclass of checker_event, thus using checker_event::get_program_state
    which returns null.
    
    This stopped e.g. HTML state-graph output showing state at return events
    in e.g. event (8) of
    https://dmalcolm.fedorapeople.org/gcc/2025-12-15/state-diagram-1.c.html
    
    Fixed by implementing return_event::get_program_state.
    
    gcc/analyzer/ChangeLog:
            PR analyzer/122003
            * checker-event.cc (return_event::get_program_state): New.
            * checker-event.h (return_event::get_program_state): New decl.
    
    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

Diff:
---
 gcc/analyzer/checker-event.cc | 6 ++++++
 gcc/analyzer/checker-event.h  | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/gcc/analyzer/checker-event.cc b/gcc/analyzer/checker-event.cc
index bd62e3887a6e..67d5360e4e05 100644
--- a/gcc/analyzer/checker-event.cc
+++ b/gcc/analyzer/checker-event.cc
@@ -847,6 +847,12 @@ return_event::is_return_p () const
   return true;
 }
 
+const program_state *
+return_event::get_program_state () const
+{
+  return &m_eedge.m_dest->get_state ();
+}
+
 /* class start_consolidated_cfg_edges_event : public checker_event.  */
 
 void
diff --git a/gcc/analyzer/checker-event.h b/gcc/analyzer/checker-event.h
index f79130ffb382..64f625ee545a 100644
--- a/gcc/analyzer/checker-event.h
+++ b/gcc/analyzer/checker-event.h
@@ -603,6 +603,9 @@ public:
     return m_call_and_return_op;
   }
 
+  const program_state *
+  get_program_state () const override;
+
   /* Mark this edge event as being either an interprocedural call or
      return in which VAR is in STATE, and that this is critical to the
      diagnostic (so that print_desc can attempt to get a better description