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, 67 insertions, 1 deletions

diff --git a/gold/object.h b/gold/object.h
index 6c8c7a3183..614a02ec57 100644
--- a/gold/object.h
+++ b/gold/object.h
@@ -1,6 +1,6 @@
 // object.h -- support for an object file for linking in gold  -*- C++ -*-
 
-// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
+// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
 // Written by Ian Lance Taylor <iant@google.com>.
 
 // This file is part of gold.
@@ -46,6 +46,7 @@ class Pluginobj;
 class Dynobj;
 class Object_merge_map;
 class Relocatable_relocs;
+class Symbols_data;
 
 template<typename Stringpool_char>
 class Stringpool_template;
@@ -598,11 +599,52 @@ class Relobj : public Object
       relocs_must_follow_section_writes_(false)
   { }
 
+  // During garbage collection, the Read_symbols_data pass for 
+  // each object is stored as layout needs to be done after 
+  // reloc processing.
+  Symbols_data* 
+  get_symbols_data()
+  { return this->sd_; }
+
+  // Decides which section names have to be included in the worklist
+  // as roots.
+  bool
+  is_section_name_included(const char *name);
+ 
+  void
+  copy_symbols_data(Symbols_data* gc_sd, Read_symbols_data* sd,
+                    unsigned int section_header_size);
+
+  void
+  set_symbols_data(Symbols_data* sd)
+  { this->sd_ = sd; }
+
+  // During garbage collection, the Read_relocs pass for all objects 
+  // is done before scanning the relocs.  In that case, this->rd_ is
+  // used to store the information from Read_relocs for each object.
+  // This data is also used to compute the list of relevant sections.
+  Read_relocs_data*
+  get_relocs_data()
+  { return this->rd_; }
+
+  void
+  set_relocs_data(Read_relocs_data* rd)
+  { this->rd_ = rd; }
+
+  virtual bool
+  is_output_section_offset_invalid(unsigned int shndx) const = 0;
+
   // Read the relocs.
   void
   read_relocs(Read_relocs_data* rd)
   { return this->do_read_relocs(rd); }
 
+  // Process the relocs, during garbage collection only.
+  void
+  gc_process_relocs(const General_options& options, Symbol_table* symtab,
+	            Layout* layout, Read_relocs_data* rd)
+  { return this->do_gc_process_relocs(options, symtab, layout, rd); }
+
   // Scan the relocs and adjust the symbol table.
   void
   scan_relocs(const General_options& options, Symbol_table* symtab,
@@ -728,6 +770,11 @@ class Relobj : public Object
   virtual void
   do_read_relocs(Read_relocs_data*) = 0;
 
+  // Process the relocs--implemented by child class.
+  virtual void
+  do_gc_process_relocs(const General_options&, Symbol_table*, Layout*,
+		 Read_relocs_data*) = 0;
+
   // Scan the relocs--implemented by child class.
   virtual void
   do_scan_relocs(const General_options&, Symbol_table*, Layout*,
@@ -810,6 +857,13 @@ class Relobj : public Object
   // Whether we need to wait for output sections to be written before
   // we can apply relocations.
   bool relocs_must_follow_section_writes_;
+  // Used to store the relocs data computed by the Read_relocs pass. 
+  // Used during garbage collection of unused sections.
+  Read_relocs_data* rd_;
+  // Used to store the symbols data computed by the Read_symbols pass.
+  // Again used during garbage collection when laying out referenced
+  // sections.
+  gold::Symbols_data *sd_;
 };
 
 // This class is used to handle relocations against a section symbol
@@ -1220,6 +1274,12 @@ class Sized_relobj : public Relobj
 
   ~Sized_relobj();
 
+  // Checks if the offset of input section SHNDX within its output
+  // section is invalid. 
+  bool
+  is_output_section_offset_invalid(unsigned int shndx) const
+  { return this->get_output_section_offset(shndx) == invalid_address; }
+
   // Set up the object file based on the ELF header.
   void
   setup(const typename elfcpp::Ehdr<size, big_endian>&);
@@ -1392,6 +1452,12 @@ class Sized_relobj : public Relobj
   void
   do_read_relocs(Read_relocs_data*);
 
+  // Process the relocs to find list of referenced sections. Used only
+  // during garbage collection.
+  void
+  do_gc_process_relocs(const General_options&, Symbol_table*, Layout*,
+		       Read_relocs_data*);
+
   // Scan the relocs and adjust the symbol table.
   void
   do_scan_relocs(const General_options&, Symbol_table*, Layout*,