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Use unordered_set for frame_stash

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This changes the frame_stash global to be an unordered_set rather than
a htab_t.

Approved-By: Simon Marchi <simon.marchi@efficios.com>
This commit is contained in:
Tom Tromey
2025-07-06 08:38:55 -06:00
parent 18612e79c1
commit 05134ca32b
1 changed files with 116 additions and 84 deletions
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200
gdb/frame.c
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@@ -213,56 +213,6 @@ get_frame_pc_masked (const frame_info_ptr &frame)
return frame->next->prev_pc.masked;
}
/* A frame stash used to speed up frame lookups. Create a hash table
to stash frames previously accessed from the frame cache for
quicker subsequent retrieval. The hash table is emptied whenever
the frame cache is invalidated. */
static htab_t frame_stash;
/* Internal function to calculate a hash from the frame_id addresses,
using as many valid addresses as possible. Frames below level 0
are not stored in the hash table. */
static hashval_t
frame_addr_hash (const void *ap)
{
const frame_info *frame = (const frame_info *) ap;
const struct frame_id f_id = frame->this_id.value;
hashval_t hash = 0;
gdb_assert (f_id.stack_status != FID_STACK_INVALID
|| f_id.code_addr_p
|| f_id.special_addr_p);
if (f_id.stack_status == FID_STACK_VALID)
hash = iterative_hash (&f_id.stack_addr,
sizeof (f_id.stack_addr), hash);
if (f_id.code_addr_p)
hash = iterative_hash (&f_id.code_addr,
sizeof (f_id.code_addr), hash);
if (f_id.special_addr_p)
hash = iterative_hash (&f_id.special_addr,
sizeof (f_id.special_addr), hash);
char user_created_p = f_id.user_created_p;
hash = iterative_hash (&user_created_p, sizeof (user_created_p), hash);
return hash;
}
/* Internal equality function for the hash table. This function
defers equality operations to frame_id::operator==. */
static int
frame_addr_hash_eq (const void *a, const void *b)
{
const frame_info *f_entry = (const frame_info *) a;
const frame_info *f_element = (const frame_info *) b;
return f_entry->this_id.value == f_element->this_id.value;
}
/* Deletion function for the frame cache hash table. */
static void
@@ -275,20 +225,117 @@ frame_info_del (frame_info *frame)
frame->base->unwind->dealloc_cache (frame, frame->base_cache);
}
/* Internal function to create the frame_stash hash table. 100 seems
to be a good compromise to start the hash table at. */
/* A wrapper for frame_info that calls the 'frame_info_del' when
destroyed. */
static void
frame_stash_create (void)
struct frame_info_stash_entry
{
frame_stash = htab_create
(100, frame_addr_hash, frame_addr_hash_eq,
[] (void *p)
{
auto frame = static_cast<frame_info *> (p);
frame_info_del (frame);
});
}
explicit frame_info_stash_entry (frame_info *info)
: frame (info)
{
}
~frame_info_stash_entry ()
{
destroy ();
}
DISABLE_COPY_AND_ASSIGN (frame_info_stash_entry);
frame_info_stash_entry (frame_info_stash_entry &&other)
: frame (other.frame)
{
other.frame = nullptr;
}
frame_info_stash_entry &operator= (frame_info_stash_entry &&other)
{
destroy ();
frame = other.frame;
other.frame = nullptr;
return *this;
}
void destroy ()
{
if (frame != nullptr)
frame_info_del (frame);
}
frame_info *frame;
};
struct frame_info_stash_hash
{
using is_transparent = void;
using is_avalanching = void;
uint64_t operator() (const frame_id &f_id) const noexcept
{
hashval_t hash = 0;
gdb_assert (f_id.stack_status != FID_STACK_INVALID
|| f_id.code_addr_p
|| f_id.special_addr_p);
if (f_id.stack_status == FID_STACK_VALID)
hash = iterative_hash (&f_id.stack_addr,
sizeof (f_id.stack_addr), hash);
if (f_id.code_addr_p)
hash = iterative_hash (&f_id.code_addr,
sizeof (f_id.code_addr), hash);
if (f_id.special_addr_p)
hash = iterative_hash (&f_id.special_addr,
sizeof (f_id.special_addr), hash);
char user_created_p = f_id.user_created_p;
hash = iterative_hash (&user_created_p, sizeof (user_created_p), hash);
return hash;
}
uint64_t operator() (const frame_info_stash_entry &info) const noexcept
{
return (*this) (info.frame->this_id.value);
}
uint64_t operator() (const frame_info *frame) const noexcept
{
return (*this) (frame->this_id.value);
}
};
struct frame_info_stash_eq
{
using is_transparent = void;
bool operator() (const frame_id &lhs, const frame_info_stash_entry &rhs)
const noexcept
{
return lhs == rhs.frame->this_id.value;
}
bool operator() (const frame_info *lhs, const frame_info_stash_entry &rhs)
const noexcept
{
return (*this) (lhs->this_id.value, rhs);
}
bool operator() (const frame_info_stash_entry &lhs,
const frame_info_stash_entry &rhs)
const noexcept
{
return (*this) (lhs.frame->this_id.value, rhs);
}
};
/* A frame stash used to speed up frame lookups. Create a hash table
to stash frames previously accessed from the frame cache for
quicker subsequent retrieval. The hash table is emptied whenever
the frame cache is invalidated. */
static gdb::unordered_set<frame_info_stash_entry, frame_info_stash_hash,
frame_info_stash_eq> frame_stash;
/* Internal function to add a frame to the frame_stash hash table.
Returns false if a frame with the same ID was already stashed, true
@@ -300,18 +347,7 @@ frame_stash_add (frame_info *frame)
/* Valid frame levels are -1 (sentinel frames) and above. */
gdb_assert (frame->level >= -1);
frame_info **slot = (frame_info **) htab_find_slot (frame_stash,
frame, INSERT);
/* If we already have a frame in the stack with the same id, we
either have a stack cycle (corrupted stack?), or some bug
elsewhere in GDB. In any case, ignore the duplicate and return
an indication to the caller. */
if (*slot != nullptr)
return false;
*slot = frame;
return true;
return frame_stash.emplace (frame).second;
}
/* Internal function to search the frame stash for an entry with the
@@ -321,12 +357,10 @@ frame_stash_add (frame_info *frame)
static frame_info_ptr
frame_stash_find (struct frame_id id)
{
struct frame_info dummy;
frame_info *frame;
dummy.this_id.value = id;
frame = (frame_info *) htab_find (frame_stash, &dummy);
return frame_info_ptr (frame);
auto iter = frame_stash.find (id);
if (iter == frame_stash.end ())
return nullptr;
return frame_info_ptr (iter->frame);
}
/* Internal function to invalidate the frame stash by removing all
@@ -336,7 +370,7 @@ frame_stash_find (struct frame_id id)
static void
frame_stash_invalidate (void)
{
htab_empty (frame_stash);
frame_stash.clear ();
}
/* See frame.h */
@@ -2111,7 +2145,7 @@ reinit_frame_cache (void)
{
++frame_cache_generation;
if (htab_elements (frame_stash) > 0)
if (!frame_stash.empty ())
annotate_frames_invalid ();
invalidate_selected_frame ();
@@ -3426,8 +3460,6 @@ INIT_GDB_FILE (frame)
{
obstack_init (&frame_cache_obstack);
frame_stash_create ();
gdb::observers::target_changed.attach (frame_observer_target_changed,
"frame");