lto-plugin: support LDPT_GET_SYMBOLS_V3

That supports skipping of an object file (LDPS_NO_SYMS).

lto-plugin/ChangeLog:

	* lto-plugin.c (struct plugin_file_info): Add skip_file flag.
	(write_resolution): Write resolution only if get_symbols != LDPS_NO_SYMS.
	(all_symbols_read_handler): Ignore file if skip_file is true.
	(onload): Handle LDPT_GET_SYMBOLS_V3.

lto-plugin/lto-plugin.c

@@ -136,6 +136,7 @@ struct plugin_file_info
   void *handle;
   struct plugin_symtab symtab;
   struct plugin_symtab conflicts;
+  bool skip_file;
 };
 
 /* List item with name of the file with offloading.  */
@@ -159,7 +160,7 @@ enum symbol_style
 static char *arguments_file_name;
 static ld_plugin_register_claim_file register_claim_file;
 static ld_plugin_register_all_symbols_read register_all_symbols_read;
-static ld_plugin_get_symbols get_symbols, get_symbols_v2;
+static ld_plugin_get_symbols get_symbols, get_symbols_v2, get_symbols_v3;
 static ld_plugin_register_cleanup register_cleanup;
 static ld_plugin_add_input_file add_input_file;
 static ld_plugin_add_input_library add_input_library;
@@ -547,15 +548,13 @@ free_symtab (struct plugin_symtab *symtab)
 static void
 write_resolution (void)
 {
-  unsigned int i;
+  unsigned int i, included_files = 0;
   FILE *f;
 
   check (resolution_file, LDPL_FATAL, "resolution file not specified");
   f = fopen (resolution_file, "w");
   check (f, LDPL_FATAL, "could not open file");
 
-  fprintf (f, "%d\n", num_claimed_files);
-
   for (i = 0; i < num_claimed_files; i++)
     {
       struct plugin_file_info *info = &claimed_files[i];
@@ -563,13 +562,38 @@ write_resolution (void)
       struct ld_plugin_symbol *syms = symtab->syms;
 
       /* Version 2 of API supports IRONLY_EXP resolution that is
-         accepted by GCC-4.7 and newer.  */
+	 accepted by GCC-4.7 and newer.
-      if (get_symbols_v2)
+	 Version 3 can return LDPS_NO_SYMS that means the object
+	 will not be used at all.  */
+      if (get_symbols_v3)
+	{
+	  enum ld_plugin_status status
+	    = get_symbols_v3 (info->handle, symtab->nsyms, syms);
+	  if (status == LDPS_NO_SYMS)
+	    {
+	      info->skip_file = true;
+	      continue;
+	    }
+	}
+      else if (get_symbols_v2)
         get_symbols_v2 (info->handle, symtab->nsyms, syms);
       else
         get_symbols (info->handle, symtab->nsyms, syms);
 
+      ++included_files;
+
       finish_conflict_resolution (symtab, &info->conflicts);
+    }
+
+  fprintf (f, "%d\n", included_files);
+
+  for (i = 0; i < num_claimed_files; i++)
+    {
+      struct plugin_file_info *info = &claimed_files[i];
+      struct plugin_symtab *symtab = &info->symtab;
+
+      if (info->skip_file)
+	continue;
 
       fprintf (f, "%s %d\n", info->name, symtab->nsyms + info->conflicts.nsyms);
       dump_symtab (f, symtab);
@@ -833,6 +857,7 @@ all_symbols_read_handler (void)
     {
       struct plugin_file_info *info = &claimed_files[i];
 
+      if (!info->skip_file)
 	*lto_arg_ptr++ = info->name;
     }
 
@@ -1410,6 +1435,9 @@ onload (struct ld_plugin_tv *tv)
 	case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
 	  register_all_symbols_read = p->tv_u.tv_register_all_symbols_read;
 	  break;
+	case LDPT_GET_SYMBOLS_V3:
+	  get_symbols_v3 = p->tv_u.tv_get_symbols;
+	  break;
 	case LDPT_GET_SYMBOLS_V2:
 	  get_symbols_v2 = p->tv_u.tv_get_symbols;
 	  break;