(C++) patch to debug info optimization

[Jason Merrill <jason at cygnus dot com>]

We were failing to emit debugging information for a class with
virtual functions, all inline or pure, that was used only as a base
class in the presence of optimization, because the reference to the
vtable was optimized away.

2000-03-03  Jason Merrill  <jason@casey.cygnus.com>

	* search.c (note_debug_info_needed, dfs_debug_mark, 
	dfs_debug_unmarkedp): Uncomment.  Adjust for new scheme.
	* decl2.c (finish_vtable_vardecl): Call note_debug_info_needed.

Index: decl2.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cp/decl2.c,v
retrieving revision 1.314
diff -c -p -r1.314 decl2.c
*** decl2.c	2000/03/03 02:27:14	1.314
--- decl2.c	2000/03/04 00:30:14
*************** finish_vtable_vardecl (t, data)
*** 2607,2623 ****
  
        /* Since we're writing out the vtable here, also write the debug 
  	 info.  */
!       if (TYPE_DECL_SUPPRESS_DEBUG (TYPE_MAIN_DECL (ctype)))
! 	{
! 	  TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (ctype)) = 0;
! 	  rest_of_type_compilation (ctype, toplevel_bindings_p ());
! 	}
  
        return 1;
      }
!   else if (!DECL_NEEDED_P (vars))
!     /* We don't know what to do with this one yet.  */
!     return 0;
  
    return 0;
  }
--- 2608,2623 ----
  
        /* Since we're writing out the vtable here, also write the debug 
  	 info.  */
!       note_debug_info_needed (ctype);
  
        return 1;
      }
! 
!   /* If the references to this class' vtables were optimized away, still
!      emit the appropriate debugging information.  See dfs_debug_mark.  */
!   if (DECL_COMDAT (vars)
!       && CLASSTYPE_DEBUG_REQUESTED (ctype))
!     note_debug_info_needed (ctype);
  
    return 0;
  }
Index: search.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cp/search.c,v
retrieving revision 1.161
diff -c -p -r1.161 search.c
*** search.c	2000/03/03 02:27:15	1.161
--- search.c	2000/03/04 00:30:18
*************** unmarked_pushdecls_p (binfo, data) 
*** 2571,2585 ****
  #if 0
  static int dfs_search_slot_nonempty_p (binfo) tree binfo;
  { return CLASSTYPE_SEARCH_SLOT (BINFO_TYPE (binfo)) != 0; }
- 
- static tree 
- dfs_debug_unmarkedp (binfo, data) 
-      tree binfo;
-      void *data ATTRIBUTE_UNUSED;
- { 
-   return (!CLASSTYPE_DEBUG_REQUESTED (BINFO_TYPE (binfo)) 
- 	  ? binfo : NULL_TREE);
- }
  #endif
  
  /* The worker functions for `dfs_walk'.  These do not need to
--- 2571,2576 ----
*************** dfs_unmark_new_vtable (binfo) tree binfo
*** 2639,2674 ****
  static void
  dfs_clear_search_slot (binfo) tree binfo;
  { CLASSTYPE_SEARCH_SLOT (BINFO_TYPE (binfo)) = 0; }
- 
- /* Keep this code around in case we later want to control debug info
-    based on whether a type is "used".  Currently, we only suppress debug
-    info if we can emit it with the vtable.  jason 1999-11-11) */
- static tree
- dfs_debug_mark (binfo, data)
-      tree binfo;
-      void *data ATTRIBUTE_UNUSED;
- {
-   tree t = BINFO_TYPE (binfo);
- 
-   CLASSTYPE_DEBUG_REQUESTED (t) = 1;
- 
-   /* If interface info is known, either we've already emitted the debug
-      info or we don't need to.  */
-   if (CLASSTYPE_INTERFACE_KNOWN (t))
-     return NULL_TREE;
- 
-   /* If the class has virtual functions, we'll emit the debug info
-      with the vtable.  */
-   if (TYPE_POLYMORPHIC_P (t))
-     return NULL_TREE;
- 
-   /* We cannot rely on some alien method to solve our problems,
-      so we must write out the debug info ourselves.  */
-   TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (t)) = 0;
-   rest_of_type_compilation (t, toplevel_bindings_p ());
- 
-   return NULL_TREE;
- }
  #endif
  
  struct vbase_info 
--- 2630,2635 ----
*************** maybe_suppress_debug_info (t)
*** 3254,3297 ****
    /* Otherwise, just emit the debug info normally.  */
  }
  
! #if 0
! /* Keep this code around in case we later want to control debug info
!    based on whether a type is "used".  Currently, we only suppress debug
!    info if we can emit it with the vtable.  jason 1999-11-11) */
! 
! /* If we want debug info for a type TYPE, make sure all its base types
!    are also marked as being potentially interesting.  This avoids
!    the problem of not writing any debug info for intermediate basetypes
!    that have abstract virtual functions.  Also mark member types.  */
  
  void
  note_debug_info_needed (type)
       tree type;
  {
!   tree field;
! 
!   if (current_template_parms)
!     return;
!     
!   if (TYPE_BEING_DEFINED (type))
!     /* We can't go looking for the base types and fields just yet.  */
      return;
  
!   /* See the comment in maybe_suppress_debug_info.  */
!   if (write_symbols == DWARF_DEBUG || write_symbols == NO_DEBUG)
!     return;
  
    dfs_walk (TYPE_BINFO (type), dfs_debug_mark, dfs_debug_unmarkedp, 0);
-   for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
-     {
-       tree ttype;
-       if (TREE_CODE (field) == FIELD_DECL
- 	  && IS_AGGR_TYPE (ttype = target_type (TREE_TYPE (field)))
- 	  && dfs_debug_unmarkedp (TYPE_BINFO (ttype), 0))
- 	note_debug_info_needed (ttype);
-     }
  }
- #endif
  
  /* Subroutines of push_class_decls ().  */
  
--- 3215,3272 ----
    /* Otherwise, just emit the debug info normally.  */
  }
  
! /* Note that we want debugging information for a base class of a class
!    whose vtable is being emitted.  Normally, this would happen because
!    calling the constructor for a derived class implies calling the
!    constructors for all bases, which involve initializing the
!    appropriate vptr with the vtable for the base class; but in the
!    presence of optimization, this initialization may be optimized
!    away, so we tell finish_vtable_vardecl that we want the debugging
!    information anyway.  */
  
+ static tree
+ dfs_debug_mark (binfo, data)
+      tree binfo;
+      void *data ATTRIBUTE_UNUSED;
+ {
+   tree t = BINFO_TYPE (binfo);
+ 
+   CLASSTYPE_DEBUG_REQUESTED (t) = 1;
+ 
+   return NULL_TREE;
+ }
+ 
+ /* Returns BINFO if we haven't already noted that we want debugging
+    info for this base class.  */
+ 
+ static tree 
+ dfs_debug_unmarkedp (binfo, data) 
+      tree binfo;
+      void *data ATTRIBUTE_UNUSED;
+ { 
+   return (!CLASSTYPE_DEBUG_REQUESTED (BINFO_TYPE (binfo)) 
+ 	  ? binfo : NULL_TREE);
+ }
+ 
+ /* Write out the debugging information for TYPE, whose vtable is being
+    emitted.  Also walk through our bases and note that we want to
+    write out information for them.  This avoids the problem of not
+    writing any debug info for intermediate basetypes whose
+    constructors, and thus the references to their vtables, and thus
+    the vtables themselves, were optimized away.  */
+ 
  void
  note_debug_info_needed (type)
       tree type;
  {
!   if (! TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (type)))
      return;
  
!   TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (type)) = 0;
!   rest_of_type_compilation (type, toplevel_bindings_p ());
  
    dfs_walk (TYPE_BINFO (type), dfs_debug_mark, dfs_debug_unmarkedp, 0);
  }
  
  /* Subroutines of push_class_decls ().  */