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, 12 insertions, 12 deletions

diff --git a/gdb/frame-unwind.c b/gdb/frame-unwind.c
index 27aa9e1..e9983a9 100644
--- a/gdb/frame-unwind.c
+++ b/gdb/frame-unwind.c
@@ -123,7 +123,7 @@ frame_unwind_append_unwinder (struct gdbarch *gdbarch,
    unchanged and returns 0.  */
 
 static int
-frame_unwind_try_unwinder (frame_info_ptr this_frame, void **this_cache,
+frame_unwind_try_unwinder (const frame_info_ptr &this_frame, void **this_cache,
 			  const struct frame_unwind *unwinder)
 {
   int res = 0;
@@ -183,7 +183,7 @@ frame_unwind_try_unwinder (frame_info_ptr this_frame, void **this_cache,
    by this function.  Possibly initialize THIS_CACHE.  */
 
 void
-frame_unwind_find_by_frame (frame_info_ptr this_frame, void **this_cache)
+frame_unwind_find_by_frame (const frame_info_ptr &this_frame, void **this_cache)
 {
   FRAME_SCOPED_DEBUG_ENTER_EXIT;
   frame_debug_printf ("this_frame=%d", frame_relative_level (this_frame));
@@ -217,7 +217,7 @@ frame_unwind_find_by_frame (frame_info_ptr this_frame, void **this_cache)
 
 int
 default_frame_sniffer (const struct frame_unwind *self,
-		       frame_info_ptr this_frame,
+		       const frame_info_ptr &this_frame,
 		       void **this_prologue_cache)
 {
   return 1;
@@ -226,7 +226,7 @@ default_frame_sniffer (const struct frame_unwind *self,
 /* The default frame unwinder stop_reason callback.  */
 
 enum unwind_stop_reason
-default_frame_unwind_stop_reason (frame_info_ptr this_frame,
+default_frame_unwind_stop_reason (const frame_info_ptr &this_frame,
 				  void **this_cache)
 {
   struct frame_id this_id = get_frame_id (this_frame);
@@ -240,7 +240,7 @@ default_frame_unwind_stop_reason (frame_info_ptr this_frame,
 /* See frame-unwind.h.  */
 
 CORE_ADDR
-default_unwind_pc (struct gdbarch *gdbarch, frame_info_ptr next_frame)
+default_unwind_pc (struct gdbarch *gdbarch, const frame_info_ptr &next_frame)
 {
   int pc_regnum = gdbarch_pc_regnum (gdbarch);
   CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum);
@@ -251,7 +251,7 @@ default_unwind_pc (struct gdbarch *gdbarch, frame_info_ptr next_frame)
 /* See frame-unwind.h.  */
 
 CORE_ADDR
-default_unwind_sp (struct gdbarch *gdbarch, frame_info_ptr next_frame)
+default_unwind_sp (struct gdbarch *gdbarch, const frame_info_ptr &next_frame)
 {
   int sp_regnum = gdbarch_sp_regnum (gdbarch);
   return frame_unwind_register_unsigned (next_frame, sp_regnum);
@@ -263,7 +263,7 @@ default_unwind_sp (struct gdbarch *gdbarch, frame_info_ptr next_frame)
 /* Return a value which indicates that FRAME did not save REGNUM.  */
 
 struct value *
-frame_unwind_got_optimized (frame_info_ptr frame, int regnum)
+frame_unwind_got_optimized (const frame_info_ptr &frame, int regnum)
 {
   struct gdbarch *gdbarch = frame_unwind_arch (frame);
   struct type *type = register_type (gdbarch, regnum);
@@ -275,7 +275,7 @@ frame_unwind_got_optimized (frame_info_ptr frame, int regnum)
    register NEW_REGNUM.  */
 
 struct value *
-frame_unwind_got_register (frame_info_ptr frame,
+frame_unwind_got_register (const frame_info_ptr &frame,
 			   int regnum, int new_regnum)
 {
   return value_of_register_lazy (get_next_frame_sentinel_okay (frame),
@@ -286,7 +286,7 @@ frame_unwind_got_register (frame_info_ptr frame,
    ADDR.  */
 
 struct value *
-frame_unwind_got_memory (frame_info_ptr frame, int regnum, CORE_ADDR addr)
+frame_unwind_got_memory (const frame_info_ptr &frame, int regnum, CORE_ADDR addr)
 {
   struct gdbarch *gdbarch = frame_unwind_arch (frame);
   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
@@ -299,7 +299,7 @@ frame_unwind_got_memory (frame_info_ptr frame, int regnum, CORE_ADDR addr)
    REGNUM has a known constant (computed) value of VAL.  */
 
 struct value *
-frame_unwind_got_constant (frame_info_ptr frame, int regnum,
+frame_unwind_got_constant (const frame_info_ptr &frame, int regnum,
 			   ULONGEST val)
 {
   struct gdbarch *gdbarch = frame_unwind_arch (frame);
@@ -313,7 +313,7 @@ frame_unwind_got_constant (frame_info_ptr frame, int regnum,
 }
 
 struct value *
-frame_unwind_got_bytes (frame_info_ptr frame, int regnum, const gdb_byte *buf)
+frame_unwind_got_bytes (const frame_info_ptr &frame, int regnum, const gdb_byte *buf)
 {
   struct gdbarch *gdbarch = frame_unwind_arch (frame);
   struct value *reg_val;
@@ -329,7 +329,7 @@ frame_unwind_got_bytes (frame_info_ptr frame, int regnum, const gdb_byte *buf)
    CORE_ADDR to a target address if necessary.  */
 
 struct value *
-frame_unwind_got_address (frame_info_ptr frame, int regnum,
+frame_unwind_got_address (const frame_info_ptr &frame, int regnum,
 			  CORE_ADDR addr)
 {
   struct gdbarch *gdbarch = frame_unwind_arch (frame);