re PR lto/61886 (LTO breaks fread with _FORTIFY_SOURCE=2)

	PR ipa/61886
	* lto-streamer.h (lto_symtab_merge_decls, lto_symtab_merge_symbols,
	lto_symtab_prevailing_decl): MOve to lto-symtab.h.
	* lto-streamer-out.c (DFS::DFS_write_tree_body): Check that
	DECL_ABSTRACT_ORIGIN is not error_mark_node.

	* lto-symtab.c: Include lto-symtab.h.
	(lto_cgraph_replace_node): Do not merge profiles here.
	(lto_symtab_merge_p): New function.
	(lto_symtab_merge_decls_2): Honor lto_symtab_merge_p.
	(lto_symtab_merge_symbols_1): Turn unmerged decls into transparent
	aliases.
	(lto_symtab_merge_symbols): Do not clear node->aux; we no longer use it.
	(lto_symtab_prevailing_decl): Move to lto-symtab.h; rewrite.
	* lto.c: Include lto-symtab.h
	* lto-symtab.h: New.

From-SVN: r231438

1 files changed, 47 insertions, 0 deletions

diff --git a/gcc/lto/lto-symtab.h b/gcc/lto/lto-symtab.h
new file mode 100644
index 0000000..c6b68b6
--- /dev/null
+++ b/gcc/lto/lto-symtab.h
@@ -0,0 +1,47 @@
+/* LTO symbol table merging.
+   Copyright (C) 2009-2015 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/>.  */
+
+extern void lto_symtab_merge_decls (void);
+extern void lto_symtab_merge_symbols (void);
+extern tree lto_symtab_prevailing_decl (tree decl);
+
+/* Mark DECL to be previailed by PREVAILING.
+   Use DECL_ABSTRACT_ORIGIN and DECL_CHAIN as special markers; those do not
+   disturb debug_tree and diagnostics.
+   We are safe to modify them as we wish, becuase the declarations disappear
+   from the IL after the merging.  */
+
+inline void
+lto_symtab_prevail_decl (tree prevailing, tree decl)
+{
+  gcc_checking_assert (DECL_ABSTRACT_ORIGIN (decl) != error_mark_node);
+  DECL_CHAIN (decl) = prevailing;
+  DECL_ABSTRACT_ORIGIN (decl) = error_mark_node;
+}
+
+/* Given the decl DECL, return the prevailing decl with the same name. */
+
+inline tree
+lto_symtab_prevailing_decl (tree decl)
+{
+  if (DECL_ABSTRACT_ORIGIN (decl) == error_mark_node)
+    return DECL_CHAIN (decl);
+  else
+    return decl;
+}