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

[Iain Sandoe]

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.  A follow-up
patch implements the indirection.

tested on x86_64-darwin16 and powerpc-darwin9
committed to mainline,
thanks
Iain

gcc/objc/ChangeLog:

2019-10-10  Iain Sandoe  <i...@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.

diff --git a/gcc/objc/objc-next-metadata-tags.h 
b/gcc/objc/objc-next-metadata-tags.h
index 1822aa7d61..933f08c3ab 100644
--- a/gcc/objc/objc-next-metadata-tags.h
+++ b/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));
diff --git a/gcc/objc/objc-next-runtime-abi-02.c 
b/gcc/objc/objc-next-runtime-abi-02.c
index aa1cbde501..3e38b7dc11 100644
--- a/gcc/objc/objc-next-runtime-abi-02.c
+++ b/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);