[Objective-C, NeXT ABI] Identify V2 IVAR refs by metadata.

For the NeXT 64b ABI, IVAR refs are supposed to be indirected for
Mach-O PIC.  Identify them so that we can act as needed.

gcc/objc/ChangeLog:

2019-10-10  Iain Sandoe  <iain@sandoe.co.uk>

	* objc-next-metadata-tags.h (OCTI_RT_META_IVAR_REF): New.
	(meta_ivar_ref): New.
	* objc-next-runtime-abi-02.c
	(next_runtime_abi_02_init_metadata_attributes): Create the
	IVAR ref metadata identifier.
	(ivar_offset_ref): Tag IVAR refs with specific metadata.

From-SVN: r276847

gcc/objc/ChangeLog

+2019-10-10  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* objc-next-metadata-tags.h (OCTI_RT_META_IVAR_REF): New.
+	(meta_ivar_ref): New.
+	* objc-next-runtime-abi-02.c
+	(next_runtime_abi_02_init_metadata_attributes): Create the
+	IVAR ref metadata identifier.
+	(ivar_offset_ref): Tag IVAR refs with specific metadata.
+
 2019-06-05  Martin Sebor  <msebor@redhat.com>
 
 	* objc-act.c (objc_build_setter_call): Adjust quoting and hyphenation.

gcc/objc/objc-next-metadata-tags.h

@@ -74,6 +74,8 @@ enum objc_runtime_tree_index
 
   OCTI_RT_META_CONST_STR,
 
+  OCTI_RT_META_IVAR_REF,
+
   OCTI_RT_META_MAX
 };
 
@@ -167,6 +169,8 @@ enum objc_runtime_tree_index
 
 #define meta_const_str	objc_rt_trees[OCTI_RT_META_CONST_STR]
 
+#define meta_ivar_ref	objc_rt_trees[OCTI_RT_META_IVAR_REF]
+
 #define OBJCMETA(DECL,VERS,KIND)					\
   if (VERS)								\
     DECL_ATTRIBUTES (DECL) = build_tree_list ((VERS), (KIND));

gcc/objc/objc-next-runtime-abi-02.c

@@ -345,6 +345,8 @@ next_runtime_abi_02_init_metadata_attributes (void)
   meta_ehtype = get_identifier ("V2_EHTY");
 
   meta_const_str = get_identifier ("V2_CSTR");
+
+  meta_ivar_ref = get_identifier ("V2_IVRF");
 }
 
 static void next_runtime_02_initialize (void)
@@ -2795,8 +2797,8 @@ ivar_offset_ref (tree class_name, tree field_decl)
   else
     decl = create_hidden_decl (TREE_TYPE (size_zero_node), buf);
 
-  /* Make sure it ends up in an ObjC section.  */
-  OBJCMETA (decl, objc_meta, meta_base);
+  /* Identify so that we can indirect these where the ABI requires.  */
+  OBJCMETA (decl, objc_meta, meta_ivar_ref);
 
   e.decl = decl;
   e.offset = byte_position (field_decl);