[binutils-gdb] Move non-dependent gdb::observers::observable::visit_state outside template

[binutils-gdb] Move non-dependent gdb::observers::observable::visit_state outside template

[Pedro Alves]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=62b33fde9c7ffd498af0236a50e200210807374a

commit 62b33fde9c7ffd498af0236a50e200210807374a
Author: Pedro Alves <pedro@palves.net>
Date:   Fri May 6 16:28:37 2022 +0100

    Move non-dependent gdb::observers::observable::visit_state outside template
    
    The other day, while looking at the symbols that end up in a GDB
    index, I noticed that the gdb::observers::observable::visit_state enum
    class appears a number of times:
    
     $ grep VISIT gdb-index-symbol-names.txt
     gdb::observers::observable<bpstat*, int>::visit_state::NOT_VISITED
     gdb::observers::observable<bpstat*, int>::visit_state::VISITED
     gdb::observers::observable<bpstat*, int>::visit_state::VISITING
     gdb::observers::observable<breakpoint*>::visit_state::NOT_VISITED
     gdb::observers::observable<breakpoint*>::visit_state::VISITED
     gdb::observers::observable<breakpoint*>::visit_state::VISITING
     gdb::observers::observable<char const*, char const*>::visit_state::NOT_VISITED
     gdb::observers::observable<char const*, char const*>::visit_state::VISITED
     gdb::observers::observable<char const*, char const*>::visit_state::VISITING
     gdb::observers::observable<char const*>::visit_state::NOT_VISITED
     gdb::observers::observable<char const*>::visit_state::VISITED
     gdb::observers::observable<char const*>::visit_state::VISITING
     gdb::observers::observable<enum_flags<user_selected_what_flag> >::visit_state::NOT_VISITED
     gdb::observers::observable<enum_flags<user_selected_what_flag> >::visit_state::VISITED
     gdb::observers::observable<enum_flags<user_selected_what_flag> >::visit_state::VISITING
     gdb::observers::observable<frame_info*, int>::visit_state::NOT_VISITED
     gdb::observers::observable<frame_info*, int>::visit_state::VISITED
     gdb::observers::observable<frame_info*, int>::visit_state::VISITING
     gdb::observers::observable<gdbarch*>::visit_state::NOT_VISITED
     gdb::observers::observable<gdbarch*>::visit_state::VISITED
     gdb::observers::observable<gdbarch*>::visit_state::VISITING
     gdb::observers::observable<gdb_signal>::visit_state::NOT_VISITED
     gdb::observers::observable<gdb_signal>::visit_state::VISITED
     gdb::observers::observable<gdb_signal>::visit_state::VISITING
     [... snip ...]
    
     $ grep VISIT gdb-index-symbol-names.txt | wc -l
     72
    
    enum class visit_state is defined inside the class template
    observable, but it doesn't have to be, as it does not depend on the
    template parameters.  This commit moves it out, so that only one such
    type exists.  This reduces the size of a -O0 -g3 build for me by
    around 0.6%, like so:
    
     $ du -b gdb.before gdb.after
     164685280       gdb.before
     163707424       gdb.fixed
    
    and codesize by some 0.5%.
    
    Change-Id: I405f4ef27b8358fdd22158245b145d849b45658e

Diff:
---
 gdbsupport/observable.h | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/gdbsupport/observable.h b/gdbsupport/observable.h
index a58e23dbcff..c7475e523ef 100644
--- a/gdbsupport/observable.h
+++ b/gdbsupport/observable.h
@@ -62,6 +62,22 @@ struct token
   DISABLE_COPY_AND_ASSIGN (token);
 };
 
+namespace detail
+{
+  /* Types that don't depend on any template parameter.  This saves a
+     bit of code and debug info size, compared to putting them inside
+     class observable.  */
+
+  /* Use for sorting algorithm, to indicate which observer we have
+     visited.  */
+  enum class visit_state
+  {
+    NOT_VISITED,
+    VISITING,
+    VISITED,
+  };
+}
+
 template<typename... T>
 class observable
 {
@@ -156,14 +172,6 @@ private:
   std::vector<observer> m_observers;
   const char *m_name;
 
-  /* Use for sorting algorithm, to indicate which observer we have visited.  */
-  enum class visit_state
-  {
-    NOT_VISITED,
-    VISITING,
-    VISITED,
-  };
-
   /* Helper method for topological sort using depth-first search algorithm.
 
      Visit all dependencies of observer at INDEX in M_OBSERVERS (later referred
@@ -171,15 +179,16 @@ private:
 
      If the observer is already visited, do nothing.  */
   void visit_for_sorting (std::vector<observer> &sorted_observers,
-                          std::vector<visit_state> &visit_states, int index)
+			  std::vector<detail::visit_state> &visit_states,
+			  int index)
   {
-    if (visit_states[index] == visit_state::VISITED)
+    if (visit_states[index] == detail::visit_state::VISITED)
       return;
 
     /* If we are already visiting this observer, it means there's a cycle.  */
-    gdb_assert (visit_states[index] != visit_state::VISITING);
+    gdb_assert (visit_states[index] != detail::visit_state::VISITING);
 
-    visit_states[index] = visit_state::VISITING;
+    visit_states[index] = detail::visit_state::VISITING;
 
     /* For each dependency of this observer...  */
     for (const token *dep : m_observers[index].dependencies)
@@ -195,7 +204,7 @@ private:
           }
       }
 
-    visit_states[index] = visit_state::VISITED;
+    visit_states[index] = detail::visit_state::VISITED;
     sorted_observers.push_back (m_observers[index]);
   }
 
@@ -207,8 +216,8 @@ private:
   void sort_observers ()
   {
     std::vector<observer> sorted_observers;
-    std::vector<visit_state> visit_states (m_observers.size (),
-					   visit_state::NOT_VISITED);
+    std::vector<detail::visit_state> visit_states
+      (m_observers.size (), detail::visit_state::NOT_VISITED);
 
     for (size_t i = 0; i < m_observers.size (); i++)
       visit_for_sorting (sorted_observers, visit_states, i);