gdb: pass frames as `const frame_info_ptr &`

We currently pass frames to function by value, as `frame_info_ptr`.
This is somewhat expensive:

 - the size of `frame_info_ptr` is 64 bytes, which is a bit big to pass
   by value
 - the constructors and destructor link/unlink the object in the global
   `frame_info_ptr::frame_list` list.  This is an `intrusive_list`, so
   it's not so bad: it's just assigning a few points, there's no memory
   allocation as if it was `std::list`, but still it's useless to do
   that over and over.

As suggested by Tom Tromey, change many function signatures to accept
`const frame_info_ptr &` instead of `frame_info_ptr`.

Some functions reassign their `frame_info_ptr` parameter, like:

  void
  the_func (frame_info_ptr frame)
  {
    for (; frame != nullptr; frame = get_prev_frame (frame))
      {
        ...
      }
  }

I wondered what to do about them, do I leave them as-is or change them
(and need to introduce a separate local variable that can be
re-assigned).  I opted for the later for consistency.  It might not be
clear why some functions take `const frame_info_ptr &` while others take
`frame_info_ptr`.  Also, if a function took a `frame_info_ptr` because
it did re-assign its parameter, I doubt that we would think to change it
to `const frame_info_ptr &` should the implementation change such that
it doesn't need to take `frame_info_ptr` anymore.  It seems better to
have a simple rule and apply it everywhere.

Change-Id: I59d10addef687d157f82ccf4d54f5dde9a963fd0
Approved-By: Andrew Burgess <aburgess@redhat.com>

10 files changed, 12 insertions, 12 deletions

diff --git a/gdb/tui/tui-disasm.c b/gdb/tui/tui-disasm.c
index 45c60db..5dc27c3 100644
--- a/gdb/tui/tui-disasm.c
+++ b/gdb/tui/tui-disasm.c
@@ -490,7 +490,7 @@ tui_disasm_window::addr_is_displayed (CORE_ADDR addr) const
 }
 
 void
-tui_disasm_window::maybe_update (frame_info_ptr fi, symtab_and_line sal)
+tui_disasm_window::maybe_update (const frame_info_ptr &fi, symtab_and_line sal)
 {
   CORE_ADDR low;
 
diff --git a/gdb/tui/tui-disasm.h b/gdb/tui/tui-disasm.h
index 9c4eabb..0aef091 100644
--- a/gdb/tui/tui-disasm.h
+++ b/gdb/tui/tui-disasm.h
@@ -41,7 +41,7 @@ struct tui_disasm_window : public tui_source_window_base
 
   bool location_matches_p (struct bp_location *loc, int line_no) override;
 
-  void maybe_update (frame_info_ptr fi, symtab_and_line sal) override;
+  void maybe_update (const frame_info_ptr &fi, symtab_and_line sal) override;
 
   void erase_source_content () override
   {
diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index 28d0b74..289a259 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -66,7 +66,7 @@ tui_all_objfiles_removed (program_space *pspace)
 /* Observer for the register_changed notification.  */
 
 static void
-tui_register_changed (frame_info_ptr frame, int regno)
+tui_register_changed (const frame_info_ptr &frame, int regno)
 {
   frame_info_ptr fi;
 
diff --git a/gdb/tui/tui-regs.c b/gdb/tui/tui-regs.c
index 504aed4..e7c1839 100644
--- a/gdb/tui/tui-regs.c
+++ b/gdb/tui/tui-regs.c
@@ -85,7 +85,7 @@ tab_expansion_file::write (const char *buf, long length_buf)
    representation of it.  */
 
 static std::string
-tui_register_format (frame_info_ptr frame, int regnum)
+tui_register_format (const frame_info_ptr &frame, int regnum)
 {
   struct gdbarch *gdbarch = get_frame_arch (frame);
 
@@ -406,7 +406,7 @@ tui_data_window::do_scroll_vertical (int num_to_scroll)
    given a particular frame.  If the values have changed, they are
    updated with the new value and highlighted.  */
 void
-tui_data_window::check_register_values (frame_info_ptr frame)
+tui_data_window::check_register_values (const frame_info_ptr &frame)
 {
   if (frame == nullptr)
     set_register_group (nullptr);
diff --git a/gdb/tui/tui-regs.h b/gdb/tui/tui-regs.h
index 9d9cae4..07b9513 100644
--- a/gdb/tui/tui-regs.h
+++ b/gdb/tui/tui-regs.h
@@ -74,7 +74,7 @@ struct tui_data_window : public tui_win_info
     return DATA_NAME;
   }
 
-  void check_register_values (frame_info_ptr frame);
+  void check_register_values (const frame_info_ptr &frame);
 
   void set_register_group (const reggroup *group);
 
diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c
index 635cb2f..fa956b2 100644
--- a/gdb/tui/tui-source.c
+++ b/gdb/tui/tui-source.c
@@ -199,7 +199,7 @@ tui_source_window::line_is_displayed (int line) const
 }
 
 void
-tui_source_window::maybe_update (frame_info_ptr fi, symtab_and_line sal)
+tui_source_window::maybe_update (const frame_info_ptr &fi, symtab_and_line sal)
 {
   int start_line = (sal.line - ((height - box_size ()) / 2)) + 1;
   if (start_line <= 0)
diff --git a/gdb/tui/tui-source.h b/gdb/tui/tui-source.h
index 0bf43b6..6d4ad4e 100644
--- a/gdb/tui/tui-source.h
+++ b/gdb/tui/tui-source.h
@@ -46,7 +46,7 @@ struct tui_source_window : public tui_source_window_base
 
   bool showing_source_p (const char *filename) const;
 
-  void maybe_update (frame_info_ptr fi, symtab_and_line sal) override;
+  void maybe_update (const frame_info_ptr &fi, symtab_and_line sal) override;
 
   void erase_source_content () override
   {
diff --git a/gdb/tui/tui-status.c b/gdb/tui/tui-status.c
index df4675f..aac391d 100644
--- a/gdb/tui/tui-status.c
+++ b/gdb/tui/tui-status.c
@@ -213,7 +213,7 @@ tui_status_window::make_status_line () const
    name is demangled if demangling is turned on.  Returns a pointer to
    a static area holding the result.  */
 static char*
-tui_get_function_from_frame (frame_info_ptr fi)
+tui_get_function_from_frame (const frame_info_ptr &fi)
 {
   static char name[256];
   string_file stream;
@@ -267,7 +267,7 @@ tui_status_window::rerender ()
    refresh.  */
 
 void
-tui_show_frame_info (frame_info_ptr fi)
+tui_show_frame_info (const frame_info_ptr &fi)
 {
   bool status_changed_p;
 
diff --git a/gdb/tui/tui-status.h b/gdb/tui/tui-status.h
index efef537..0af4466 100644
--- a/gdb/tui/tui-status.h
+++ b/gdb/tui/tui-status.h
@@ -51,6 +51,6 @@ private:
 };
 
 extern void tui_show_status_content (void);
-extern void tui_show_frame_info (frame_info_ptr);
+extern void tui_show_frame_info (const frame_info_ptr &);
 
 #endif /* TUI_TUI_STATUS_H */
diff --git a/gdb/tui/tui-winsource.h b/gdb/tui/tui-winsource.h
index 628fc22..6465973 100644
--- a/gdb/tui/tui-winsource.h
+++ b/gdb/tui/tui-winsource.h
@@ -159,7 +159,7 @@ public:
 
   /* Update the window to display the given location.  Does nothing if
      the location is already displayed.  */
-  virtual void maybe_update (frame_info_ptr fi, symtab_and_line sal) = 0;
+  virtual void maybe_update (const frame_info_ptr &fi, symtab_and_line sal) = 0;
 
   void update_source_window_as_is  (struct gdbarch *gdbarch,
 				    const struct symtab_and_line &sal);