2009-01-20 Sriraman Tallam <tmsriram@google.com>

	* Makefile.am (CCFILES): Add gc.cc.
	(HFILES): Add gc.h.
	* Makefile.in: Regenerate.
	* gold.cc (Gc_runner): New class.
	(queue_initial_tasks): Call garbage collection related tasks
	when corresponding options are invoked.
	(queue_middle_gc_tasks): New function.
	(queue_middle_tasks): Reorder tasks to allow relocs to be read and
	processed early before laying out sections during garbage collection.
	* gold.h (queue_middle_gc_tasks): New function.
	(is_prefix_of): Move from "layout.cc".
	* i386.cc (Target_i386::gc_process_relocs): New function.
	* layout.cc (is_prefix_of): Remove. Move to "gold.h"
	* main.cc (main): Create object of class "Garbage_collection".
	* object.cc (Relobj::copy_symbols_data): New function.
	(Relobj::is_section_name_included): New function.
	(Sized_relobj::do_layout): Allow this function to be called twice
	during garbage collection and defer layout of section during the
	first call.
	* object.h (Relobj::get_symbols_data): New function.
	(Relobj::is_section_name_included): New function.
	(Relobj::copy_symbols_data): New function.
	(Relobj::set_symbols_data): New function.
	(Relobj::get_relocs_data): New function.
	(Relobj::set_relocs_data): New function.
	(Relobj::is_output_section_offset_invalid): New pure virtual function.
	(Relobj::gc_process_relocs): New function.
	(Relobj::do_gc_process_relocs): New pure virtual function.
	(Relobj::sd_): New data member.
	(Sized_relobj::is_output_section_offset_invalid): New function.
	(Sized_relobj::do_gc_process_relocs): New function.
	* options.h (General_options::gc_sections): Modify to not be a no-op.
	(General_options::print_gc_sections): New option.
	* plugin.cc (Plugin_finish::run): Remove function call to
	Plugin_manager::layout_deferred_objects.  Move it to "gold.cc".
	* powerpc.cc (Target_powerpc::gc_process_relocs): New function.
	* reloc.cc (Read_relocs::run): Add task to process relocs and
	determine unreferenced sections when doing garbage collection.
	(Gc_process_relocs): New class.
	(Sized_relobj::do_gc_process_relocs): New function.
	(Sized_relobj::do_scan_relocs): Don't try to scan the relocs for
	sections that are garbage collected.
	* reloc.h (Gc_process_relocs): New class.
	* sparc.cc (Target_sparc::gc_process_relocs): New function.
	* symtab.cc (Symbol::should_add_dynsym_entry): Do not add entries for
	symbols whose corresponding sections are garbage collected.
	(Symbol_table::Symbol_table): Add new parameter for the garbage
	collection object.
	(Symbol_table::gc_mark_undef_symbols): New function.
	(Symbol_table::gc_mark_symbol_for_shlib): New function.
	(Symbol_table::gc_mark_dyn_syms): New function.
	(Symbol_table::resolve): Do not treat symbols seen in dynamic objects
	as garbage.
	(Symbol_table::add_from_object): Likewise.
	(Symbol_table::add_from_relobj): When building shared objects, do not
	treat externally visible symbols as garbage.
	(Symbol_table::sized_finalize_symbol): Do not check dynamic symbol
	table information for static and relocatable links.
	* symtab.h (Symbol_table::set_gc): New function.
	(Symbol_table::gc): New function.
	(Symbol_table::gc_mark_undef_symbols): New function.
	(Symbol_table::gc_mark_symbol_for_shlib): New function.
	(Symbol_table::gc_mark_dyn_syms): New function.
	(Symbol_table::gc_): New data member.
	* target.h (Sized_target::gc_process_relocs): New pure virtual
	function.
	* x86_64.cc (Target_x86_64::gc_process_relocs): New function.
	* testsuite/testfile.cc (Target_test::gc_process_relocs): New function.

1 files changed, 74 insertions, 0 deletions

diff --git a/gold/gc.cc b/gold/gc.cc
new file mode 100644
index 0000000..7a594a5
--- /dev/null
+++ b/gold/gc.cc
@@ -0,0 +1,74 @@
+// gc.cc -- garbage collection of unused sections
+
+// Copyright 2009 Free Software Foundation, Inc.
+// Written by Sriraman Tallam <tmsriram@google.com>.
+
+// This file is part of gold.
+
+// This program 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 of the License, or
+// (at your option) any later version.
+
+// This program 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 this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+// MA 02110-1301, USA.
+
+
+#include "gold.h"
+#include "object.h"
+#include "gc.h"
+#include "symtab.h"
+
+namespace gold
+{
+
+// Garbage collection uses a worklist style algorithm to determine the 
+// transitive closure of all referenced sections.
+void 
+Garbage_collection::do_transitive_closure()
+{
+  while (!this->worklist().empty())
+    {
+      // Add elements from the work list to the referenced list
+      // one by one.
+      Section_id entry = this->worklist().front();
+      this->worklist().pop();
+      if (this->referenced_list().find(entry)
+          == this->referenced_list().end()) 
+        {
+          this->referenced_list().insert(entry);
+        }
+      else
+        {
+          continue;
+        }
+      Garbage_collection::Section_ref::iterator find_it = 
+                this->section_reloc_map().find(entry);
+      if (find_it == this->section_reloc_map().end()) 
+          continue;
+      Garbage_collection::Sections_reachable v = find_it->second;
+      // Scan the vector of references for each work_list entry. 
+      for (Garbage_collection::Sections_reachable::iterator it_v = v.begin();
+           it_v != v.end();
+           ++it_v)
+        {
+          // Do not add already processed sections to the work_list. 
+          if (this->referenced_list().find(*it_v)
+              == this->referenced_list().end())
+            {
+              this->worklist().push(*it_v);   
+            }
+        }
+    }
+  this->worklist_ready();
+}
+
+} // End namespace gold.
+