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>

1 files changed, 6 insertions, 6 deletions

diff --git a/gdb/xstormy16-tdep.c b/gdb/xstormy16-tdep.c
index b19c949..12b16c2 100644
--- a/gdb/xstormy16-tdep.c
+++ b/gdb/xstormy16-tdep.c
@@ -306,7 +306,7 @@ static CORE_ADDR
 xstormy16_analyze_prologue (struct gdbarch *gdbarch,
 			    CORE_ADDR start_addr, CORE_ADDR end_addr,
 			    struct xstormy16_frame_cache *cache,
-			    frame_info_ptr this_frame)
+			    const frame_info_ptr &this_frame)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   CORE_ADDR next_addr;
@@ -581,7 +581,7 @@ xstormy16_find_jmp_table_entry (struct gdbarch *gdbarch, CORE_ADDR faddr)
 }
 
 static CORE_ADDR
-xstormy16_skip_trampoline_code (frame_info_ptr frame, CORE_ADDR pc)
+xstormy16_skip_trampoline_code (const frame_info_ptr &frame, CORE_ADDR pc)
 {
   struct gdbarch *gdbarch = get_frame_arch (frame);
   CORE_ADDR tmp = xstormy16_resolve_jmp_table_entry (gdbarch, pc);
@@ -653,7 +653,7 @@ xstormy16_alloc_frame_cache (void)
 }
 
 static struct xstormy16_frame_cache *
-xstormy16_frame_cache (frame_info_ptr this_frame, void **this_cache)
+xstormy16_frame_cache (const frame_info_ptr &this_frame, void **this_cache)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   struct xstormy16_frame_cache *cache;
@@ -689,7 +689,7 @@ xstormy16_frame_cache (frame_info_ptr this_frame, void **this_cache)
 }
 
 static struct value *
-xstormy16_frame_prev_register (frame_info_ptr this_frame, 
+xstormy16_frame_prev_register (const frame_info_ptr &this_frame,
 			       void **this_cache, int regnum)
 {
   struct xstormy16_frame_cache *cache = xstormy16_frame_cache (this_frame,
@@ -707,7 +707,7 @@ xstormy16_frame_prev_register (frame_info_ptr this_frame,
 }
 
 static void
-xstormy16_frame_this_id (frame_info_ptr this_frame, void **this_cache,
+xstormy16_frame_this_id (const frame_info_ptr &this_frame, void **this_cache,
 			 struct frame_id *this_id)
 {
   struct xstormy16_frame_cache *cache = xstormy16_frame_cache (this_frame,
@@ -721,7 +721,7 @@ xstormy16_frame_this_id (frame_info_ptr this_frame, void **this_cache,
 }
 
 static CORE_ADDR
-xstormy16_frame_base_address (frame_info_ptr this_frame, void **this_cache)
+xstormy16_frame_base_address (const frame_info_ptr &this_frame, void **this_cache)
 {
   struct xstormy16_frame_cache *cache = xstormy16_frame_cache (this_frame,
 							       this_cache);