[C++ PATCH] simplify clone predicate

[Nathan Sidwell <nathan@acm.org>]

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This patch replaces the decl_cloned_function_p function call with simpler macro 
uses.  As only cdtors are cloned, we can use IDENTIFIER_CDTOR_P to check.

In the process I discovered the documentation had bitrotted -- we were giving 
non-function_decls to the predicate, sometimes intentionally (template_decls), 
and sometimes unintentionally (record_types).  The new semantics are we can give 
  any _decl to the predicate and only function_decls to the accessor.  The 
change in pt.d is because at namespace scope, we chain record_types (&enums & 
unions) on the chain list.  Previously that was harmless but now causes the 
predicate to assert.

Applying to trunk.

nathan
-- 
Nathan Sidwell

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2019-09-15  Nathan Sidwell  <nathan@acm.org>

	* cp-tree.h (DECL_CLONED_FUNCTION_P): Reimplement using
	IDENTIFIER_CDTOR_P, correct documentation.
	(DECL_CLONED_FUNCTION): Directly access field.
	(decl_cloned_function_p): Delete.
	* class.c (decl_cloned_function_p): Delete.
	* pt.c (instantiate_template_1): Check DECL_CHAIN is a decl.

Index: gcc/cp/class.c
===================================================================
--- gcc/cp/class.c	(revision 275726)
+++ gcc/cp/class.c	(working copy)
@@ -4701,43 +4701,6 @@ build_clone (tree fn, tree name)
   return clone;
 }
 
-/* Implementation of DECL_CLONED_FUNCTION and DECL_CLONED_FUNCTION_P, do
-   not invoke this function directly.
-
-   For a non-thunk function, returns the address of the slot for storing
-   the function it is a clone of.  Otherwise returns NULL_TREE.
-
-   If JUST_TESTING, looks through TEMPLATE_DECL and returns NULL if
-   cloned_function is unset.  This is to support the separate
-   DECL_CLONED_FUNCTION and DECL_CLONED_FUNCTION_P modes; using the latter
-   on a template makes sense, but not the former.  */
-
-tree *
-decl_cloned_function_p (const_tree decl, bool just_testing)
-{
-  tree *ptr;
-  if (just_testing)
-    decl = STRIP_TEMPLATE (decl);
-
-  if (TREE_CODE (decl) != FUNCTION_DECL
-      || !DECL_LANG_SPECIFIC (decl)
-      || DECL_LANG_SPECIFIC (decl)->u.fn.thunk_p)
-    {
-#if defined ENABLE_TREE_CHECKING && (GCC_VERSION >= 2007)
-      if (!just_testing)
-	lang_check_failed (__FILE__, __LINE__, __FUNCTION__);
-      else
-#endif
-	return NULL;
-    }
-
-  ptr = &DECL_LANG_SPECIFIC (decl)->u.fn.u5.cloned_function;
-  if (just_testing && *ptr == NULL_TREE)
-    return NULL;
-  else
-    return ptr;
-}
-
 /* Produce declarations for all appropriate clones of FN.  If
    UPDATE_METHODS is true, the clones are added to the
    CLASSTYPE_MEMBER_VEC.  */
Index: gcc/cp/cp-tree.h
===================================================================
--- gcc/cp/cp-tree.h	(revision 275726)
+++ gcc/cp/cp-tree.h	(working copy)
@@ -2874,13 +2874,17 @@ struct GTY(()) lang_decl {
   (DECL_MAYBE_IN_CHARGE_CONSTRUCTOR_P (NODE)            \
    || DECL_MAYBE_IN_CHARGE_DESTRUCTOR_P (NODE))
 
-/* Nonzero if NODE (a FUNCTION_DECL) is a cloned constructor or
+/* Nonzero if NODE (a _DECL) is a cloned constructor or
    destructor.  */
-#define DECL_CLONED_FUNCTION_P(NODE) (!!decl_cloned_function_p (NODE, true))
+#define DECL_CLONED_FUNCTION_P(NODE)		\
+  (DECL_NAME (NODE)				\
+   && IDENTIFIER_CDTOR_P (DECL_NAME (NODE))	\
+   && !DECL_MAYBE_IN_CHARGE_CDTOR_P (NODE))
 
 /* If DECL_CLONED_FUNCTION_P holds, this is the function that was
    cloned.  */
-#define DECL_CLONED_FUNCTION(NODE) (*decl_cloned_function_p (NODE, false))
+#define DECL_CLONED_FUNCTION(NODE)		\
+  (DECL_LANG_SPECIFIC (FUNCTION_DECL_CHECK (NODE))->u.fn.u5.cloned_function)
 
 /* Perform an action for each clone of FN, if FN is a function with
    clones.  This macro should be used like:
@@ -6333,7 +6337,6 @@ extern void check_abi_tags			(tree);
 extern tree missing_abi_tags			(tree);
 extern void fixup_type_variants			(tree);
 extern void fixup_attribute_variants		(tree);
-extern tree* decl_cloned_function_p		(const_tree, bool);
 extern void clone_function_decl			(tree, bool);
 extern void adjust_clone_args			(tree);
 extern void deduce_noexcept_on_destructor       (tree);
Index: gcc/cp/pt.c
===================================================================
--- gcc/cp/pt.c	(revision 275726)
+++ gcc/cp/pt.c	(working copy)
@@ -19905,8 +19905,9 @@ instantiate_template_1 (tree tmpl, tree
      instantiate all the alternate entry points as well.  We do this
      by cloning the instantiation of the main entry point, not by
      instantiating the template clones.  */
-  if (DECL_CHAIN (gen_tmpl) && DECL_CLONED_FUNCTION_P (DECL_CHAIN (gen_tmpl)))
-    clone_function_decl (fndecl, /*update_methods=*/false);
+  if (tree chain = DECL_CHAIN (gen_tmpl))
+    if (DECL_P (chain) && DECL_CLONED_FUNCTION_P (chain))
+      clone_function_decl (fndecl, /*update_methods=*/false);
 
   if (!access_ok)
     {