ctf: add support to pass through BTF tags

BTF generation currently relies on the internal CTF representation to
convert debug info from DWARF dies. This patch adds a new internal
header, "ctf-int.h", which defines CTF kinds to be used internally to
represent BTF tags which must pass through the CTF container. It also
adds a new type for representing information specific to those tags, and
a member for that type in struct ctf_dtdef.

This patch also updates ctf_add_reftype to accept a const char * name,
and add it for the newly added type.

gcc/

	* ctf-int.h: New file.
	* ctfc.h: Include ctf-int.h.
	(struct ctf_btf_annotation): New.
	(struct ctf_dtdef): Add dtu_btfnote member to dtd_u union.
	(enum ctf_dtu_d_union_enum): Add CTF_DTU_D_BTFNOTE.
	(ctf_add_reftype): Add name argument.
	* ctfc.cc (ctf_dtu_d_union_selector): Handle CTFC_INT_K_DECL_TAG.
	(ctf_add_reftype): Add name argument. Pass it to ctf_add_generic.
	(ctf_add_pointer): Update ctf_add_reftype call.
	* btfout.cc (btf_init_postprocess): Update ctf_add_reftype call.
	* dwarf2ctf.cc (gen_ctf_modifier_type): Update ctf_add_reftype call.

gcc/btfout.cc

@@ -1156,7 +1156,7 @@ btf_init_postprocess (void)
 
 	  /* Create the 'const' modifier type for void.  */
 	  if (constvoid_id == CTF_NULL_TYPEID)
-	    constvoid_id = ctf_add_reftype (tu_ctfc, CTF_ADD_ROOT,
+	    constvoid_id = ctf_add_reftype (tu_ctfc, CTF_ADD_ROOT, NULL,
 					    dvd->dvd_type, CTF_K_CONST, NULL);
 	  dvd->dvd_type = constvoid_id;
 	}

gcc/ctf-int.h

@@ -0,0 +1,28 @@
+/* ctf-int.h - GCC internal definitions used for CTF debug info.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, 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 GCC_CTF_INT_H
+#define GCC_CTF_INT_H 1
+
+/* This CTF kind exists only as a bridge to generating BTF types for
+   BTF_KIND_DECL_TAG.  It does not correspond to any representable type
+   kind in CTF.  */
+#define CTFC_INT_K_DECL_TAG  63
+
+#endif  /* GCC_CTF_INT_H */

gcc/ctfc.cc

@@ -107,6 +107,8 @@ ctf_dtu_d_union_selector (ctf_dtdef_ref ctftype)
       return CTF_DTU_D_ARGUMENTS;
     case CTF_K_SLICE:
       return CTF_DTU_D_SLICE;
+    case CTFC_INT_K_DECL_TAG:
+      return CTF_DTU_D_BTFNOTE;
     default:
       /* The largest member as default.  */
       return CTF_DTU_D_ARRAY;
@@ -428,15 +430,15 @@ ctf_add_encoded (ctf_container_ref ctfc, uint32_t flag, const char * name,
 }
 
 ctf_id_t
-ctf_add_reftype (ctf_container_ref ctfc, uint32_t flag, ctf_id_t ref,
-		 uint32_t kind, dw_die_ref die)
+ctf_add_reftype (ctf_container_ref ctfc, uint32_t flag, const char * name,
+		 ctf_id_t ref, uint32_t kind, dw_die_ref die)
 {
   ctf_dtdef_ref dtd;
   ctf_id_t type;
 
   gcc_assert (ref <= CTF_MAX_TYPE);
 
-  type = ctf_add_generic (ctfc, flag, NULL, &dtd, die);
+  type = ctf_add_generic (ctfc, flag, name, &dtd, die);
   dtd->dtd_data.ctti_info = CTF_TYPE_INFO (kind, flag, 0);
   /* Caller of this API must guarantee that a CTF type with id = ref already
      exists.  This will also be validated for us at link-time.  */
@@ -548,7 +550,7 @@ ctf_id_t
 ctf_add_pointer (ctf_container_ref ctfc, uint32_t flag, ctf_id_t ref,
 		 dw_die_ref die)
 {
-  return (ctf_add_reftype (ctfc, flag, ref, CTF_K_POINTER, die));
+  return (ctf_add_reftype (ctfc, flag, NULL, ref, CTF_K_POINTER, die));
 }
 
 ctf_id_t

gcc/ctfc.h

@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "dwarf2ctf.h"
 #include "ctf.h"
 #include "btf.h"
+#include "ctf-int.h"
 
 /* Invalid CTF type ID definition.  */
 
@@ -151,6 +152,13 @@ typedef struct GTY (()) ctf_func_arg
 
 #define ctf_farg_list_next(elem) ((ctf_func_arg_t *)((elem)->farg_next))
 
+/* BTF support: a BTF type tag or decl tag.  */
+
+typedef struct GTY (()) ctf_btf_annotation
+{
+  uint32_t component_idx;
+} ctf_btf_annotation_t;
+
 /* Type definition for CTF generation.  */
 
 struct GTY ((for_user)) ctf_dtdef
@@ -175,6 +183,8 @@ struct GTY ((for_user)) ctf_dtdef
     ctf_func_arg_t * GTY ((tag ("CTF_DTU_D_ARGUMENTS"))) dtu_argv;
     /* slice.  */
     ctf_sliceinfo_t GTY ((tag ("CTF_DTU_D_SLICE"))) dtu_slice;
+    /* btf annotation.  */
+    ctf_btf_annotation_t GTY ((tag ("CTF_DTU_D_BTFNOTE"))) dtu_btfnote;
   } dtd_u;
 };
 
@@ -214,7 +224,8 @@ enum ctf_dtu_d_union_enum {
   CTF_DTU_D_ARRAY,
   CTF_DTU_D_ENCODING,
   CTF_DTU_D_ARGUMENTS,
-  CTF_DTU_D_SLICE
+  CTF_DTU_D_SLICE,
+  CTF_DTU_D_BTFNOTE
 };
 
 enum ctf_dtu_d_union_enum
@@ -404,8 +415,8 @@ extern bool ctf_dvd_ignore_lookup (const ctf_container_ref ctfc,
 extern const char * ctf_add_string (ctf_container_ref, const char *,
 				    uint32_t *, int);
 
-extern ctf_id_t ctf_add_reftype (ctf_container_ref, uint32_t, ctf_id_t,
-				 uint32_t, dw_die_ref);
+extern ctf_id_t ctf_add_reftype (ctf_container_ref, uint32_t, const char *,
+				 ctf_id_t, uint32_t, dw_die_ref);
 extern ctf_id_t ctf_add_enum (ctf_container_ref, uint32_t, const char *,
 			      HOST_WIDE_INT, bool, dw_die_ref);
 extern ctf_id_t ctf_add_slice (ctf_container_ref, uint32_t, ctf_id_t,

gcc/dwarf2ctf.cc

@@ -511,7 +511,7 @@ gen_ctf_modifier_type (ctf_container_ref ctfc, dw_die_ref modifier)
   gcc_assert (kind != CTF_K_MAX);
   /* Now register the modifier itself.  */
   if (!ctf_type_exists (ctfc, modifier, &modifier_type_id))
-    modifier_type_id = ctf_add_reftype (ctfc, CTF_ADD_ROOT,
+    modifier_type_id = ctf_add_reftype (ctfc, CTF_ADD_ROOT, NULL,
 					qual_type_id, kind,
 					modifier);