Some projects need to prevent reordering of specific top level
declarations with LTO, in particular declarations defining init calls.

The only way to do that with LTO was to use -fno-toplevel-reorder,
which stops reordering for all declarations and makes LTO partitioning
less efficient.

This patch adds a new no_reorder attribute that stops reordering only
for the marked declaration. The program can then only mark e.g. the
initcalls and leave all the other declarations alone.

The patch does:

- Adds the new no_reorder attribute for the C family.
- Initializes a new no_reorder flag in the symtab_nodes in the
function visibility flag.
- Maintains the no_reorder flag when creating new nodes.
- Changes the partition code to always keep a separate
sorted queue of ordered nodes and flush them in order with the other
nodes. This is used by all nodes with -fno-toplevel-reorder,
and only the marked ones without it.
Parts of the old -fno-toplevel-reorder code paths are reused.
- Adds various checks throughout the tree to make no_reorder
marked functions behave the same as with -fno-toplevel-reorder
- Changes the LTO streamer to serialize the no_reorder attribute.

gcc/c-family/:

2014-09-23  Andi Kleen  <ak@linux.intel.com>

	* c-common.c (handle_no_reorder_attribute): New function.
	(c_common_attribute_table): Add no_reorder attribute.

gcc/:

2014-09-23  Andi Kleen  <ak@linux.intel.com>

	* cgraph.h (symtab_node): Add no_reorder attribute.
	(symbol_table::output_asm_statements): Remove.
	* cgraphclones.c (cgraph_node::create_clone): Copy no_reorder.
	(cgraph_node::create_version_clone): Dito.
	(symbol_table::output_asm_statements): Remove.
	* trans-mem.c (ipa_tm_create_version_alias): Dito.
	* cgraphunit.c (varpool_node::finalize_decl): Check no_reorder.
	(output_in_order): Add no_reorder flag. Only handle no_reorder
	nodes when set.
	(symbol_table::compile): Add separate pass for no_reorder nodes.
	(process_common_attributes): Set no_reorder flag in symtab node.
	Add node argument.
	(process_function_and_variable_attributes): Pass symtab nodes to
	process_common_attributes.
	* doc/extend.texi (no_reorder): Document no_reorder attribute.
	* lto-cgraph.c (lto_output_node): Serialize no_reorder.
	(lto_output_varpool_node): Dito.
	(input_overwrite_node): Dito.
	(input_varpool_node): Dito.
	* varpool.c (varpool_node::add): Set no_reorder attribute.
	(symbol_table::remove_unreferenced_decls): Handle no_reorder.
	(symbol_table::output_variables): Dito.
	* symtab.c (symtab_node::dump_base): Print no_reorder.

gcc/lto/:

2014-09-23  Andi Kleen  <ak@linux.intel.com>

	* lto-partition.c (node_cmp): Update comment.
	(varpool_node_cmp): Use symtab_node for comparison.
	(add_sorted_nodes): New function.
	(lto_balanced_map): Change to keep ordered queue
	of ordered node. Handle no_reorder attribute.

From-SVN: r215537