PR c++/70462 - unnecessary base ctor variant with final.

As pointed out in the PR, we don't need base 'tor variants for a final
class, since it can never be a base.  I tried also dropping complete
variants for abstract classes, but that runs into ABI compatibility problems
with older releases that refer to those symbols.

	* optimize.c (populate_clone_array): Skip base variant if
	CLASSTYPE_FINAL.
	(maybe_clone_body): We don't need an alias if we are only defining
	one clone.

From-SVN: r272669

gcc/cp/ChangeLog

 2019-06-25  Jason Merrill  <jason@redhat.com>
 
+	PR c++/70462 - unnecessary base ctor variant with final.
+	* optimize.c (populate_clone_array): Skip base variant if
+	CLASSTYPE_FINAL.
+	(maybe_clone_body): We don't need an alias if we are only defining
+	one clone.
+
 	* class.c (resolves_to_fixed_type_p): Check CLASSTYPE_FINAL.
 
 2019-06-25  Jakub Jelinek  <jakub@redhat.com>

gcc/cp/optimize.c

@@ -247,15 +247,19 @@ populate_clone_array (tree fn, tree *fns)
   fns[1] = NULL_TREE;
   fns[2] = NULL_TREE;
 
-  /* Look for the complete destructor which may be used to build the
-     delete destructor.  */
+  tree ctx = DECL_CONTEXT (fn);
+
   FOR_EACH_CLONE (clone, fn)
     if (DECL_NAME (clone) == complete_dtor_identifier
 	|| DECL_NAME (clone) == complete_ctor_identifier)
       fns[1] = clone;
     else if (DECL_NAME (clone) == base_dtor_identifier
 	     || DECL_NAME (clone) == base_ctor_identifier)
+      {
+	/* We don't need to define the base variants for a final class.  */
+	if (!CLASSTYPE_FINAL (ctx))
 	  fns[0] = clone;
+      }
     else if (DECL_NAME (clone) == deleting_dtor_identifier)
       fns[2] = clone;
     else
@@ -480,7 +484,7 @@ maybe_clone_body (tree fn)
 
   /* Remember if we can't have multiple clones for some reason.  We need to
      check this before we remap local static initializers in clone_body.  */
-  if (!tree_versionable_function_p (fn))
+  if (!tree_versionable_function_p (fn) && fns[0] && fns[1])
     need_alias = true;
 
   /* We know that any clones immediately follow FN in the TYPE_FIELDS

gcc/testsuite/g++.dg/other/final8.C

+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler-not "_ZN1BC2Ev" } }
+// { dg-final { scan-assembler-not "_ZN1BD2Ev" } }
+
+struct A { int i; A(); virtual ~A() = 0; };
+struct B final: public virtual A { int j; B(); ~B(); };
+
+B::B() {}
+B::~B() {}