[gold][patch] Avoid looking up Input_merge_map multiple times

[Rafael EspÃndola <rafael dot espindola at gmail dot com>]

The attached patch (which applies on top of my previous one) avoid
looking up Input_merge_map multiple times when we know were are
processing items from the same input section.

Cheers,
Rafael

diff --git a/gold/merge.cc b/gold/merge.cc
index 3cce843..7a532cc 100644
--- a/gold/merge.cc
+++ b/gold/merge.cc
@@ -33,6 +33,45 @@ namespace gold
 
 // Class Object_merge_map.
 
+void
+Object_merge_map::Input_merge_map::add_mapping(
+    section_offset_type input_offset, section_size_type length,
+    section_offset_type output_offset) {
+  // Try to merge the new entry in the last one we saw.
+  if (!this->entries.empty())
+    {
+      Input_merge_entry& entry(this->entries.back());
+
+      // Use section_size_type to avoid signed/unsigned warnings.
+      section_size_type input_offset_u = input_offset;
+      section_size_type output_offset_u = output_offset;
+
+      // If this entry is not in order, we need to sort the vector
+      // before looking anything up.
+      if (input_offset_u < entry.input_offset + entry.length)
+	{
+	  gold_assert(input_offset < entry.input_offset);
+	  gold_assert(input_offset_u + length
+		      <= static_cast<section_size_type>(entry.input_offset));
+	  this->sorted = false;
+	}
+      else if (entry.input_offset + entry.length == input_offset_u
+	       && (output_offset == -1
+		   ? entry.output_offset == -1
+		   : entry.output_offset + entry.length == output_offset_u))
+	{
+	  entry.length += length;
+	  return;
+	}
+    }
+
+  Input_merge_entry entry;
+  entry.input_offset = input_offset;
+  entry.length = length;
+  entry.output_offset = output_offset;
+  this->entries.push_back(entry);
+}
+
 // Destructor.
 
 Object_merge_map::~Object_merge_map()
@@ -94,39 +133,7 @@ Object_merge_map::add_mapping(unsigned int shndx,
 {
   Input_merge_map* map = this->get_or_make_input_merge_map(shndx);
 
-  // Try to merge the new entry in the last one we saw.
-  if (!map->entries.empty())
-    {
-      Input_merge_entry& entry(map->entries.back());
-
-      // Use section_size_type to avoid signed/unsigned warnings.
-      section_size_type input_offset_u = input_offset;
-      section_size_type output_offset_u = output_offset;
-
-      // If this entry is not in order, we need to sort the vector
-      // before looking anything up.
-      if (input_offset_u < entry.input_offset + entry.length)
-	{
-	  gold_assert(input_offset < entry.input_offset);
-	  gold_assert(input_offset_u + length
-		      <= static_cast<section_size_type>(entry.input_offset));
-	  map->sorted = false;
-	}
-      else if (entry.input_offset + entry.length == input_offset_u
-	       && (output_offset == -1
-		   ? entry.output_offset == -1
-		   : entry.output_offset + entry.length == output_offset_u))
-	{
-	  entry.length += length;
-	  return;
-	}
-    }
-
-  Input_merge_entry entry;
-  entry.input_offset = input_offset;
-  entry.length = length;
-  entry.output_offset = output_offset;
-  map->entries.push_back(entry);
+  map->add_mapping(input_offset, length, output_offset);
 }
 
 // Get the output offset for an input address.
@@ -339,6 +346,10 @@ Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 
   this->input_count_ += len / entsize;
 
+  Object_merge_map* merge_map = object->get_or_create_merge_map();
+  Object_merge_map::Input_merge_map* input_merge_map =
+    merge_map->get_or_make_input_merge_map(shndx);
+
   for (section_size_type i = 0; i < len; i += entsize, p += entsize)
     {
       // Add the constant to the section contents.  If we find that it
@@ -357,7 +368,7 @@ Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 	}
 
       // Record the offset of this constant in the output section.
-      object->add_merge_mapping(shndx, i, entsize, k);
+      input_merge_map->add_mapping(i, entsize, k);
     }
 
   // For script processing, we keep the input sections.
@@ -539,6 +550,11 @@ Output_merge_string<Char_type>::finalize_merged_data()
     {
       section_offset_type last_input_offset = 0;
       section_offset_type last_output_offset = 0;
+      Relobj *object = (*l)->object;
+      Object_merge_map* merge_map = object->get_or_create_merge_map();
+      Object_merge_map::Input_merge_map* input_merge_map =
+        merge_map->get_or_make_input_merge_map((*l)->shndx);
+
       for (typename Merged_strings::const_iterator p =
 	     (*l)->merged_strings.begin();
 	   p != (*l)->merged_strings.end();
@@ -546,9 +562,9 @@ Output_merge_string<Char_type>::finalize_merged_data()
 	{
 	  section_size_type length = p->offset - last_input_offset;
 	  if (length > 0)
-	    (*l)->object->add_merge_mapping((*l)->shndx, last_input_offset,
-					    length, last_output_offset);
-	  last_input_offset = p->offset;
+            input_merge_map->add_mapping(last_input_offset, length,
+                                         last_output_offset);
+          last_input_offset = p->offset;
 	  if (p->stringpool_key != 0)
 	    last_output_offset =
 	        this->stringpool_.get_offset_from_key(p->stringpool_key);
diff --git a/gold/merge.h b/gold/merge.h
index d07c4bd..56c084a 100644
--- a/gold/merge.h
+++ b/gold/merge.h
@@ -81,7 +81,6 @@ class Object_merge_map
       Unordered_map<section_offset_type,
 		    typename elfcpp::Elf_types<size>::Elf_Addr>*);
 
- private:
   // Map input section offsets to a length and an output section
   // offset.  An output section offset of -1 means that this part of
   // the input section is being discarded.
@@ -95,17 +94,12 @@ class Object_merge_map
     section_offset_type output_offset;
   };
 
-  // A less-than comparison routine for Input_merge_entry.
-  struct Input_merge_compare
-  {
-    bool
-    operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const
-    { return i1.input_offset < i2.input_offset; }
-  };
-
   // A list of entries for a particular input section.
   struct Input_merge_map
   {
+    void add_mapping(section_offset_type input_offset, section_size_type length,
+                     section_offset_type output_offset);
+
     typedef std::vector<Input_merge_entry> Entries;
 
     // The list of mappings.
@@ -118,6 +112,20 @@ class Object_merge_map
     { }
   };
 
+  // Get or make the Input_merge_map to use for the section SHNDX
+  // with MERGE_MAP.
+  Input_merge_map*
+  get_or_make_input_merge_map(unsigned int shndx);
+
+  private:
+  // A less-than comparison routine for Input_merge_entry.
+  struct Input_merge_compare
+  {
+    bool
+    operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const
+    { return i1.input_offset < i2.input_offset; }
+  };
+
   // Map input section indices to merge maps.
   typedef std::map<unsigned int, Input_merge_map*> Section_merge_maps;
 
@@ -126,11 +134,6 @@ class Object_merge_map
   Input_merge_map*
   get_input_merge_map(unsigned int shndx);
 
-  // Get or make the Input_merge_map to use for the section SHNDX
-  // with MERGE_MAP.
-  Input_merge_map*
-  get_or_make_input_merge_map(unsigned int shndx);
-
   // Any given object file will normally only have a couple of input
   // sections with mergeable contents.  So we keep the first two input
   // section numbers inline, and push any further ones into a map.  A
diff --git a/gold/object.cc b/gold/object.cc
index 51ad561..c3eaf77 100644
--- a/gold/object.cc
+++ b/gold/object.cc
@@ -273,13 +273,7 @@ void
 Relobj::add_merge_mapping(unsigned int shndx, section_offset_type offset,
                           section_size_type length,
                           section_offset_type output_offset) {
-  Object_merge_map* object_merge_map = this->merge_map();
-  if (object_merge_map == NULL)
-    {
-      object_merge_map = new Object_merge_map();
-      this->set_merge_map(object_merge_map);
-    }
-
+  Object_merge_map* object_merge_map = this->get_or_create_merge_map();
   object_merge_map->add_mapping(shndx, offset, length, output_offset);
 }
 
@@ -392,6 +386,14 @@ Relobj::finalize_incremental_relocs(Layout* layout, bool clear_counts)
   layout->incremental_inputs()->set_reloc_count(rindex);
 }
 
+Object_merge_map*
+Relobj::get_or_create_merge_map()
+{
+  if (!this->object_merge_map_)
+    this->object_merge_map_ = new Object_merge_map();
+  return this->object_merge_map_;
+}
+
 // Class Sized_relobj.
 
 // Iterate over local symbols, calling a visitor class V for each GOT offset
diff --git a/gold/object.h b/gold/object.h
index f3394d3..167513b 100644
--- a/gold/object.h
+++ b/gold/object.h
@@ -1206,13 +1206,8 @@ class Relobj : public Object
   merge_map() const
   { return this->object_merge_map_; }
 
-  // Set the object merge map.
-  void
-  set_merge_map(Object_merge_map* object_merge_map)
-  {
-    gold_assert(this->object_merge_map_ == NULL);
-    this->object_merge_map_ = object_merge_map;
-  }
+  Object_merge_map*
+  get_or_create_merge_map();
 
   void
   add_merge_mapping(unsigned int shndx, section_offset_type offset,