binutils-gdb/gdb/ia64-libunwind-tdep.h
Simon Marchi 8480a37e14 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>
2024-02-20 10:42:25 -05:00

80 lines
2.6 KiB
C++

/* Frame unwinder for ia64 frames with libunwind frame information.
Copyright (C) 2003-2024 Free Software Foundation, Inc.
Contributed by Jeff Johnston.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef IA64_LIBUNWIND_TDEP_H
#define IA64_LIBUNWIND_TDEP_H 1
class frame_info_ptr;
struct frame_id;
struct regcache;
struct gdbarch;
struct frame_unwind;
/* IA-64 is the only target that currently uses libunwind. If some
other target wants to use it, we will need to do some abstracting
in order to make it possible to have more than one
ia64-libunwind-tdep instance. Including "libunwind.h" is wrong as
that ends up including the libunwind-$(arch).h for the host gdb is
running on. */
#include "libunwind-ia64.h"
#include "gdbarch.h"
struct libunwind_descr
{
int (*gdb2uw) (int) = nullptr;
int (*uw2gdb) (int) = nullptr;
int (*is_fpreg) (int) = nullptr;
void *accessors = nullptr;
void *special_accessors = nullptr;
};
int libunwind_frame_sniffer (const struct frame_unwind *self,
const frame_info_ptr &this_frame,
void **this_cache);
int libunwind_sigtramp_frame_sniffer (const struct frame_unwind *self,
const frame_info_ptr &this_frame,
void **this_cache);
void libunwind_frame_set_descr (struct gdbarch *arch,
struct libunwind_descr *descr);
void libunwind_frame_this_id (const frame_info_ptr &this_frame, void **this_cache,
struct frame_id *this_id);
struct value *libunwind_frame_prev_register (const frame_info_ptr &this_frame,
void **this_cache, int regnum);
void libunwind_frame_dealloc_cache (frame_info_ptr self, void *cache);
int libunwind_is_initialized (void);
int libunwind_search_unwind_table (void *as, long ip, void *di,
void *pi, int need_unwind_info, void *args);
unw_word_t libunwind_find_dyn_list (unw_addr_space_t, unw_dyn_info_t *,
void *);
int libunwind_get_reg_special (struct gdbarch *gdbarch,
readable_regcache *regcache,
int regnum, void *buf);
#endif /* IA64_LIBUNWIND_TDEP_H */