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8480a37e14
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>
94 lines
2.5 KiB
C
94 lines
2.5 KiB
C
/* Code dealing with register stack frames, for GDB, the GNU debugger.
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Copyright (C) 1986-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "regcache.h"
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#include "sentinel-frame.h"
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#include "inferior.h"
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#include "frame-unwind.h"
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struct frame_unwind_cache
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{
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struct regcache *regcache;
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};
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void *
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sentinel_frame_cache (struct regcache *regcache)
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{
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struct frame_unwind_cache *cache =
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FRAME_OBSTACK_ZALLOC (struct frame_unwind_cache);
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cache->regcache = regcache;
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return cache;
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}
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/* Here the register value is taken direct from the register cache. */
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static struct value *
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sentinel_frame_prev_register (const frame_info_ptr &this_frame,
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void **this_prologue_cache,
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int regnum)
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{
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struct frame_unwind_cache *cache
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= (struct frame_unwind_cache *) *this_prologue_cache;
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struct value *value;
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frame_id this_frame_id = get_frame_id (this_frame);
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gdb_assert (is_sentinel_frame_id (this_frame_id));
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value = cache->regcache->cooked_read_value (regnum);
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return value;
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}
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static void
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sentinel_frame_this_id (const frame_info_ptr &this_frame,
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void **this_prologue_cache,
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struct frame_id *this_id)
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{
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/* The sentinel frame is used as a starting point for creating the
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previous (inner most) frame. That frame's THIS_ID method will be
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called to determine the inner most frame's ID. Not this one. */
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internal_error (_("sentinel_frame_this_id called"));
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}
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static struct gdbarch *
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sentinel_frame_prev_arch (const frame_info_ptr &this_frame,
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void **this_prologue_cache)
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{
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struct frame_unwind_cache *cache
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= (struct frame_unwind_cache *) *this_prologue_cache;
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return cache->regcache->arch ();
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}
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const struct frame_unwind sentinel_frame_unwind =
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{
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"sentinel",
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SENTINEL_FRAME,
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default_frame_unwind_stop_reason,
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sentinel_frame_this_id,
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sentinel_frame_prev_register,
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NULL,
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NULL,
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NULL,
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sentinel_frame_prev_arch,
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};
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