Go patch committed: refactor Exports to encapsulate type refs map

Go patch committed: refactor Exports to encapsulate type refs map

[Ian Lance Taylor]

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This Go frontend patch by Than McIntosh refactors the Export class to
encapsulate the type refs map.  This convert the Export::type_refs map
from a static object to a field contained (indirectly, via an impl
class) in Export itself, for better encapsulation and to be able to
reclaim its memory when exporting is done.  No change in compiler
functionality.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

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Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE	(revision 272666)
+++ gcc/go/gofrontend/MERGE	(working copy)
@@ -1,4 +1,4 @@
-d3d0f3c5bbe9d272178d55bdb907b07c188800e1
+1e042a49d6f2e95d371301aa7b911522dc5877f4
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/export.cc
===================================================================
--- gcc/go/gofrontend/export.cc	(revision 272608)
+++ gcc/go/gofrontend/export.cc	(working copy)
@@ -41,14 +41,6 @@ const char Export::v2_magic[Export::magi
 
 const int Export::checksum_len;
 
-// Constructor.
-
-Export::Export(Stream* stream)
-  : stream_(stream), type_index_(1), packages_()
-{
-  go_assert(Export::checksum_len == Go_sha1_helper::checksum_len);
-}
-
 // Type hash table operations, treating aliases as distinct.
 
 class Type_hash_alias_identical
@@ -80,14 +72,31 @@ class Type_alias_identical
   }
 };
 
-// Mapping from Type objects to a constant index.  This would be nicer
-// as a field in Export, but then export.h would have to #include
-// types.h.
-
+// Mapping from Type objects to a constant index.
 typedef Unordered_map_hash(const Type*, int, Type_hash_alias_identical,
-			   Type_alias_identical) Type_refs;
+                           Type_alias_identical) Type_refs;
+
+// Implementation object for class Export.  Hidden implementation avoids
+// having to #include types.h in export.h, or use a static map.
+
+struct Export_impl {
+  Type_refs type_refs;
+};
 
-static Type_refs type_refs;
+// Constructor.
+
+Export::Export(Stream* stream)
+    : stream_(stream), type_index_(1), packages_(), impl_(new Export_impl)
+{
+  go_assert(Export::checksum_len == Go_sha1_helper::checksum_len);
+}
+
+// Destructor.
+
+Export::~Export()
+{
+  delete this->impl_;
+}
 
 // A traversal class to collect functions and global variables
 // referenced by inlined functions.
@@ -635,7 +644,7 @@ Export::set_type_index(Type* type)
   type = type->forwarded();
 
   std::pair<Type_refs::iterator, bool> ins =
-    type_refs.insert(std::make_pair(type, 0));
+    this->impl_->type_refs.insert(std::make_pair(type, 0));
   if (!ins.second)
     {
       // We've already seen this type.
@@ -1011,8 +1020,8 @@ Export::write_types(int unexported_type_
 {
   // Map from type index to type.
   std::vector<const Type*> types(static_cast<size_t>(this->type_index_));
-  for (Type_refs::const_iterator p = type_refs.begin();
-       p != type_refs.end();
+  for (Type_refs::const_iterator p = this->impl_->type_refs.begin();
+       p != this->impl_->type_refs.end();
        ++p)
     {
       if (p->second >= 0)
@@ -1152,8 +1161,8 @@ int
 Export::type_index(const Type* type)
 {
   type = type->forwarded();
-  Type_refs::const_iterator p = type_refs.find(type);
-  go_assert(p != type_refs.end());
+  Type_refs::const_iterator p = this->impl_->type_refs.find(type);
+  go_assert(p != this->impl_->type_refs.end());
   int index = p->second;
   go_assert(index != 0);
   return index;
@@ -1231,7 +1240,7 @@ Export::register_builtin_type(Gogo* gogo
   Named_object* named_object = gogo->lookup_global(name);
   go_assert(named_object != NULL && named_object->is_type());
   std::pair<Type_refs::iterator, bool> ins =
-    type_refs.insert(std::make_pair(named_object->type_value(), code));
+    this->impl_->type_refs.insert(std::make_pair(named_object->type_value(), code));
   go_assert(ins.second);
 
   // We also insert the underlying type.  We can see the underlying
@@ -1239,7 +1248,7 @@ Export::register_builtin_type(Gogo* gogo
   // fails--we expect duplications here, and it doesn't matter when
   // they occur.
   Type* real_type = named_object->type_value()->real_type();
-  type_refs.insert(std::make_pair(real_type, code));
+  this->impl_->type_refs.insert(std::make_pair(real_type, code));
 }
 
 // Class Export::Stream.
Index: gcc/go/gofrontend/export.h
===================================================================
--- gcc/go/gofrontend/export.h	(revision 272608)
+++ gcc/go/gofrontend/export.h	(working copy)
@@ -22,6 +22,7 @@ class Import_init_set;
 class Backend;
 class Temporary_statement;
 class Unnamed_label;
+struct Export_impl;
 
 // Codes used for the builtin types.  These are all negative to make
 // them easily distinct from the codes assigned by Export::write_type.
@@ -121,6 +122,7 @@ class Export : public String_dump
   };
 
   Export(Stream*);
+  ~Export();
 
   // Size of export data magic string (which includes version number).
   static const int magic_len = 4;
@@ -262,6 +264,8 @@ class Export : public String_dump
   int type_index_;
   // Packages we have written out.
   Unordered_map(const Package*, int) packages_;
+  // Hidden implementation-specific state.
+  Export_impl* impl_;
 };
 
 // An export streamer that puts the export stream in a named section.