* incremental-dump.cc (dump_incremental_inputs): Print COMDAT groups.

* incremental.cc (Incremental_inputs::report_input_section): Fix
	comment, indentation.
	(Incremental_inputs::report_comdat_group): New function.
	(Output_section_incremental_inputs::set_final_data_size): Adjust size
	of data for incremental input file entry.
	(Output_section_incremental_inputs::write_info_blocks): Write COMDAT
	group count, COMDAT group signatures.
	(Sized_incr_relobj::do_layout): Record kept COMDAT group info from
	an unchanged input file.
	* incremental.h (Incremental_object_entry::Incremental_object_entry):
	Initialize new data member.
	(Incremental_object_entry::add_comdat_group): New function.
	(Incremental_object_entry::get_comdat_group_count): New function.
	(Incremental_object_entry::get_comdat_signature_key): New function.
	(Incremental_object_entry::groups_): New data member.
	(Incremental_inputs::report_comdat_group): New function.
	(Incremental_input_entry_reader::get_symbol_offset): Adjust size of
	data for incremental input file entry.
	(Incremental_input_entry_reader::get_comdat_group_count): New function.
	(Incremental_input_entry_reader::get_input_section): Adjust size of
	data for incremental input file entry.
	(Incremental_input_entry_reader::get_global_symbol_reader): Likewise.
	(Incremental_input_entry_reader::get_comdat_group_signature): New
	function.
	* object.cc (Sized_relobj::include_section_group): Report kept
	COMDAT groups for incremental links.

gold/incremental.h

@@ -325,7 +325,7 @@ class Incremental_object_entry : public Incremental_input_entry
   Incremental_object_entry(Stringpool::Key filename_key, Object* obj,
 			   unsigned int arg_serial, Timespec mtime)
     : Incremental_input_entry(filename_key, arg_serial, mtime), obj_(obj),
-      is_member_(false), sections_()
+      is_member_(false), sections_(), groups_()
   { this->sections_.reserve(obj->shnum()); }
 
   // Get the object.
@@ -368,6 +368,21 @@ class Incremental_object_entry : public Incremental_input_entry
   get_input_section_size(unsigned int n) const
   { return this->sections_[n].sh_size_; }
 
+  // Add a kept COMDAT group.
+  void
+  add_comdat_group(Stringpool::Key signature_key)
+  { this->groups_.push_back(signature_key); }
+
+  // Return the number of COMDAT groups.
+  unsigned int
+  get_comdat_group_count() const
+  { return this->groups_.size(); }
+
+  // Return the stringpool key for the signature of the Nth comdat group.
+  Stringpool::Key
+  get_comdat_signature_key(unsigned int n) const
+  { return this->groups_[n]; }
+
  protected:
   virtual Incremental_input_type
   do_type() const
@@ -400,6 +415,9 @@ class Incremental_object_entry : public Incremental_input_entry
     off_t sh_size_;
   };
   std::vector<Input_section> sections_;
+
+  // COMDAT groups.
+  std::vector<Stringpool::Key> groups_;
 };
 
 // Class for recording shared library input files.
@@ -546,6 +564,10 @@ class Incremental_inputs
   report_input_section(Object* obj, unsigned int shndx, const char* name,
 		       off_t sh_size);
 
+  // Record a kept COMDAT group belonging to object file OBJ.
+  void
+  report_comdat_group(Object* obj, const char* name);
+
   // Record the info for input script SCRIPT.
   void
   report_script(Script_info* script, unsigned int arg_serial,
@@ -814,7 +836,7 @@ class Incremental_inputs_reader
 		  || this->type() == INCREMENTAL_INPUT_ARCHIVE_MEMBER);
 
       unsigned int section_count = this->get_input_section_count();
-      return (this->info_offset_ + 24
+      return (this->info_offset_ + 28
 	      + section_count * input_section_entry_size
 	      + symndx * 20);
     }
@@ -869,6 +891,16 @@ class Incremental_inputs_reader
       return Swap32::readval(this->inputs_->p_ + this->info_offset_ + 20);
     }
 
+    // Return the COMDAT group count -- for objects only.
+    unsigned int
+    get_comdat_group_count() const
+    {
+      gold_assert(this->type() == INCREMENTAL_INPUT_OBJECT
+		  || this->type() == INCREMENTAL_INPUT_ARCHIVE_MEMBER);
+
+      return Swap32::readval(this->inputs_->p_ + this->info_offset_ + 24);
+    }
+
     // Return the object count -- for scripts only.
     unsigned int
     get_object_count() const
@@ -939,7 +971,7 @@ class Incremental_inputs_reader
     {
       Input_section_info info;
       const unsigned char* p = (this->inputs_->p_
-				+ this->info_offset_ + 24
+				+ this->info_offset_ + 28
 				+ n * input_section_entry_size);
       unsigned int name_offset = Swap32::readval(p);
       info.name = this->inputs_->get_string(name_offset);
@@ -957,12 +989,27 @@ class Incremental_inputs_reader
 		  || this->type() == INCREMENTAL_INPUT_ARCHIVE_MEMBER);
       unsigned int section_count = this->get_input_section_count();
       const unsigned char* p = (this->inputs_->p_
-				+ this->info_offset_ + 24
+				+ this->info_offset_ + 28
 				+ section_count * input_section_entry_size
 				+ n * 20);
       return Incremental_global_symbol_reader<big_endian>(p);
     }
 
+    // Return the signature of the Nth comdat group -- for objects only.
+    const char*
+    get_comdat_group_signature(unsigned int n) const
+    {
+      unsigned int section_count = this->get_input_section_count();
+      unsigned int symbol_count = this->get_global_symbol_count();
+      const unsigned char* p = (this->inputs_->p_
+				+ this->info_offset_ + 28
+				+ section_count * input_section_entry_size
+				+ symbol_count * 20
+				+ n * 4);
+      unsigned int name_offset = Swap32::readval(p);
+      return this->inputs_->get_string(name_offset);
+    }
+
     // Return the output symbol index for the Nth global symbol -- for shared
     // libraries only.  Sets *IS_DEF to TRUE if the symbol is defined in this
     // input file.