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Avoid quadratic behavior when computing the value of a register. 

* frame.c (frame_stash): New static constant.
        (frame_stash_add, frame_stash_find, frame_stash_invalidate):
        New functions.
        (get_frame_id): Minor reformatting. Add the frame to the frame stash.
        (frame_find_by_id): Search the frame stash first before walking all
        frames starting from te current_frame.
        (reinit_frame_stash): Add call to frame_stash_invalidate ();
This commit is contained in:
Joel Brobecker 2009-09-09 17:39:21 +00:00
parent 9daa0d29f5
commit b83e9eb71c
2 changed files with 63 additions and 3 deletions
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11
gdb/ChangeLog
View File

@ -1,3 +1,14 @@
2009-09-08 Joel Brobecker <brobecker@adacore.com>
Avoid quadratic behavior when computing the value of a register.
* frame.c (frame_stash): New static constant.
(frame_stash_add, frame_stash_find, frame_stash_invalidate):
New functions.
(get_frame_id): Minor reformatting. Add the frame to the frame stash.
(frame_find_by_id): Search the frame stash first before walking all
frames starting from te current_frame.
(reinit_frame_stash): Add call to frame_stash_invalidate ();
2009-09-08 Joel Brobecker <brobecker@adacore.com>
* block.c (contained_in): Return zero for nested functions.

55
gdb/frame.c
View File

@ -122,6 +122,40 @@ struct frame_info
enum unwind_stop_reason stop_reason;
};
/* A frame stash used to speed up frame lookups. */
/* We currently only stash one frame at a time, as this seems to be
sufficient for now. */
static struct frame_info *frame_stash = NULL;
/* Add the following FRAME to the frame stash. */
static void
frame_stash_add (struct frame_info *frame)
{
frame_stash = frame;
}
/* Search the frame stash for an entry with the given frame ID.
If found, return that frame. Otherwise return NULL. */
static struct frame_info *
frame_stash_find (struct frame_id id)
{
if (frame_stash && frame_id_eq (frame_stash->this_id.value, id))
return frame_stash;
return NULL;
}
/* Invalidate the frame stash by removing all entries in it. */
static void
frame_stash_invalidate (void)
{
frame_stash = NULL;
}
/* Flag to control debugging. */
int frame_debug;
@ -279,9 +313,8 @@ struct frame_id
get_frame_id (struct frame_info *fi)
{
if (fi == NULL)
{
return null_frame_id;
}
return null_frame_id;
if (!fi->this_id.p)
{
if (frame_debug)
@ -300,6 +333,9 @@ get_frame_id (struct frame_info *fi)
fprintf_unfiltered (gdb_stdlog, " }\n");
}
}
frame_stash_add (fi);
return fi->this_id.value;
}
@ -514,6 +550,18 @@ frame_find_by_id (struct frame_id id)
if (!frame_id_p (id))
return NULL;
/* Try using the frame stash first. Finding it there removes the need
to perform the search by looping over all frames, which can be very
CPU-intensive if the number of frames is very high (the loop is O(n)
and get_prev_frame performs a series of checks that are relatively
expensive). This optimization is particularly useful when this function
is called from another function (such as value_fetch_lazy, case
VALUE_LVAL (val) == lval_register) which already loops over all frames,
making the overall behavior O(n^2). */
frame = frame_stash_find (id);
if (frame)
return frame;
for (frame = get_current_frame (); ; frame = prev_frame)
{
struct frame_id this = get_frame_id (frame);
@ -1285,6 +1333,7 @@ reinit_frame_cache (void)
current_frame = NULL; /* Invalidate cache */
select_frame (NULL);
frame_stash_invalidate ();
if (frame_debug)
fprintf_unfiltered (gdb_stdlog, "{ reinit_frame_cache () }\n");
}