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diff --git a/gcc/attr-callback.h b/gcc/attr-callback.h
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+/* Callback attribute handling
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   Contributed by Josef Melcr <jmelcr@gcc.gnu.org>
+
+   This file is part of GCC.
+
+   GCC is free software; you can redistribute it and/or modify
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   GCC is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef ATTR_CALLBACK_H
+#define ATTR_CALLBACK_H
+
+enum callback_position
+{
+  /* Value used when an argument of a callback function
+     is unknown or when multiple values may be used. */
+  CB_UNKNOWN_POS = 0
+};
+
+#define CALLBACK_ATTR_IDENT " callback"
+
+/* Returns a callback attribute with callback index FN_IDX, and ARG_COUNT
+   arguments specified by VA_ARGS.  */
+tree callback_build_attr (unsigned fn_idx, unsigned arg_count...);
+
+/* Returns TRUE if a function should be treated as if it had a callback
+   attribute despite the DECL not having it.  STMT can be passed NULL
+   if the call statement is not available at the time, for example WPA, but it
+   should be called with the statement itself whenever possible.  */
+bool callback_is_special_cased (tree decl, gcall *stmt);
+
+/* Returns an attribute for a special cased function.  */
+tree callback_special_case_attr (tree decl);
+
+/* Given an instance of callback attribute, return the 0-based
+   index of the called function in question.  */
+int callback_get_fn_index (tree cb_attr);
+
+/* For a given callback pair, retrieves the callback attribute used
+   to create E from the callee of CARRYING.  */
+tree callback_fetch_attr_by_edge (cgraph_edge *e, cgraph_edge *carrying);
+
+/* Given an instance of callback attribute, return the 0-base indices
+   of arguments passed to the callback.  For a callback function taking
+   n parameters, returns a vector of n indices of their values in the parameter
+   list of it's caller.  Indices with unknown positions contain -1.  */
+auto_vec<int> callback_get_arg_mapping (cgraph_edge *e, cgraph_edge *carrying);
+
+/* For a callback pair, returns the 0-based index of the address of
+   E's callee in the argument list of CARRYING's callee decl.  */
+int callback_fetch_fn_position (cgraph_edge *e, cgraph_edge *carrying);
+
+/* Handle a "callback" attribute; arguments as in
+   struct attribute_spec.handler.  */
+tree handle_callback_attribute (tree *node, tree name, tree args, int flags,
+				bool *no_add_attrs);
+
+/* Returns TRUE if E is considered useful in the callgraph, FALSE otherwise.  If
+   this predicate returns FALSE, then E wasn't used to optimize its callee and
+   can be safely removed from the callgraph.  */
+bool callback_edge_useful_p (cgraph_edge *e);
+
+/* Returns the number of arguments the callback function described by ATTR
+   takes.  */
+size_t callback_num_args (tree attr);
+
+#endif /* ATTR_CALLBACK_H  */