[PATCH] New lang hook

https://gcc.gnu.org/ml/gcc-patches/2017-11/msg01340.html
	PR c++/82836
	PR c++/82737
	* tree.h (COPY_DECL_RTL): Rename parms for clarity.
	(SET_DECL_ASSEMBLER_NAME): Forward to
	overwrite_decl_assembler_name.
	(COPY_DECL_ASSEMBLER_NAME): Rename parms for clarity.
	(overwrite_decl_assembler_name): Declare.
	* tree.c (overwrite_decl_assembler_name): New.
	* langhooks-def.h (lhd_overwrite_decl_assembler_name): Declare.
	(LANG_HOOKS_OVERWRITE_DECL_ASSEMBLER_NAME): Provide default.
	(LANG_HOOKS_INITIALIZER): Add it.
	* langhooks.h (struct lang_hooks): Add overwrite_decl_assembler_name.
	* langhooks.c (lhd_set_decl_assembler_name): Use
	SET_DECL_ASSEMBLER_NAME.
	(lhd_overwrite_decl_assembler_name): Default implementation.

	PR c++/82836
	PR c++/82737
	* cp-objcp-common.h (LANG_HOOKS_OVERWRITE_DECL_ASSEMBLER_NAME):
	Override.
	* cp-tree.h (overwrite_mangling): Declare.
	* decl2.c (struct mangled_decl_hash): Entries are deletable.
	(overwrite_mangling): New.

	PR c++/82836
	PR c++/82737
	* g++.dg/pr82836.C: New.

From-SVN: r254823

4 files changed, 46 insertions, 3 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 31de2a6..9ceff2f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,13 @@
 2017-11-16  Nathan Sidwell  <nathan@acm.org>
 
+	PR c++/82836
+	PR c++/82737
+	* cp-objcp-common.h (LANG_HOOKS_OVERWRITE_DECL_ASSEMBLER_NAME):
+	Override.
+	* cp-tree.h (overwrite_mangling): Declare.
+	* decl2.c (struct mangled_decl_hash): Entries are deletable.
+	(overwrite_mangling): New.
+
 	PR c++/81060
 	* decl.c (xref_tag_1): Push lambda into current scope.
 	* name-lookup.c (do_pushtag): Don't deal with ts_lambda here.
diff --git a/gcc/cp/cp-objcp-common.h b/gcc/cp/cp-objcp-common.h
index 3e4cc9c..a1b1fcd 100644
--- a/gcc/cp/cp-objcp-common.h
+++ b/gcc/cp/cp-objcp-common.h
@@ -73,6 +73,8 @@ extern void cp_register_dumps (gcc::dump_manager *);
 #define LANG_HOOKS_DUP_LANG_SPECIFIC_DECL cxx_dup_lang_specific_decl
 #undef LANG_HOOKS_SET_DECL_ASSEMBLER_NAME
 #define LANG_HOOKS_SET_DECL_ASSEMBLER_NAME mangle_decl
+#undef LANG_HOOKS_OVERWRITE_DECL_ASSEMBLER_NAME
+#define LANG_HOOKS_OVERWRITE_DECL_ASSEMBLER_NAME overwrite_mangling
 #undef LANG_HOOKS_PRINT_STATISTICS
 #define LANG_HOOKS_PRINT_STATISTICS cxx_print_statistics
 #undef LANG_HOOKS_PRINT_XNODE
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 6051348..c655416 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6187,6 +6187,7 @@ extern tree cxx_maybe_build_cleanup		(tree, tsubst_flags_t);
 
 /* in decl2.c */
 extern void record_mangling			(tree, bool);
+extern void overwrite_mangling			(tree, tree);
 extern void note_mangling_alias			(tree, tree);
 extern void generate_mangling_aliases		(void);
 extern tree build_memfn_type			(tree, tree, cp_cv_quals, cp_ref_qualifier);
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 0b18308..bc0db00 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -123,9 +123,14 @@ struct mangled_decl_hash : ggc_remove <tree>
   static inline void mark_empty (value_type &p) {p = NULL_TREE;}
   static inline bool is_empty (value_type p) {return !p;}
 
-  /* Nothing is deletable.  Everything is insertable.  */
-  static bool is_deleted (value_type) { return false; }
-  static void mark_deleted (value_type) { gcc_unreachable (); }
+  static bool is_deleted (value_type e)
+  {
+    return e == reinterpret_cast <value_type> (1);
+  }
+  static void mark_deleted (value_type &e)
+  {
+    e = reinterpret_cast <value_type> (1);
+  }
 };
 
 /* A hash table of decls keyed by mangled name.  Used to figure out if
@@ -4439,6 +4444,33 @@ record_mangling (tree decl, bool need_warning)
     }
 }
 
+/* The mangled name of DECL is being forcibly changed to NAME.  Remove
+   any existing knowledge of DECL's mangled name meaning DECL.  */
+
+void
+overwrite_mangling (tree decl, tree name)
+{
+  if (tree id = DECL_ASSEMBLER_NAME_RAW (decl))
+    if ((TREE_CODE (decl) == VAR_DECL
+	 || TREE_CODE (decl) == FUNCTION_DECL)
+	&& mangled_decls)
+      if (tree *slot
+	  = mangled_decls->find_slot_with_hash (id, IDENTIFIER_HASH_VALUE (id),
+						NO_INSERT))
+	if (*slot == decl)
+	  {
+	    mangled_decls->clear_slot (slot);
+
+	    /* If this is an alias, remove it from the symbol table.  */
+	    if (DECL_ARTIFICIAL (decl) && DECL_IGNORED_P (decl))
+	      if (symtab_node *n = symtab_node::get (decl))
+		if (n->cpp_implicit_alias)
+		  n->remove ();
+	  }
+
+  DECL_ASSEMBLER_NAME_RAW (decl) = name;
+}
+
 /* The entire file is now complete.  If requested, dump everything
    to a file.  */