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gdb: pass frames as const frame_info_ptr &

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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>
This commit is contained in:
Simon Marchi
2024-02-19 13:07:47 -05:00
parent 1b2c120daf
commit 8480a37e14
224 changed files with 1351 additions and 1339 deletions
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8
gdb/dummy-frame.c
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@@ -288,7 +288,7 @@ struct dummy_frame_cache
static int
dummy_frame_sniffer (const struct frame_unwind *self,
frame_info_ptr this_frame,
const frame_info_ptr &this_frame,
void **this_prologue_cache)
{
/* When unwinding a normal frame, the stack structure is determined
@@ -334,7 +334,7 @@ dummy_frame_sniffer (const struct frame_unwind *self,
register value is taken from the local copy of the register buffer. */
static struct value *
dummy_frame_prev_register (frame_info_ptr this_frame,
dummy_frame_prev_register (const frame_info_ptr &this_frame,
void **this_prologue_cache,
int regnum)
{
@@ -364,7 +364,7 @@ dummy_frame_prev_register (frame_info_ptr this_frame,
dummy cache is located and saved in THIS_PROLOGUE_CACHE. */
static void
dummy_frame_this_id (frame_info_ptr this_frame,
dummy_frame_this_id (const frame_info_ptr &this_frame,
void **this_prologue_cache,
struct frame_id *this_id)
{
@@ -390,7 +390,7 @@ const struct frame_unwind dummy_frame_unwind =
/* See dummy-frame.h. */
struct frame_id
default_dummy_id (struct gdbarch *gdbarch, frame_info_ptr this_frame)
default_dummy_id (struct gdbarch *gdbarch, const frame_info_ptr &this_frame)
{
CORE_ADDR sp, pc;