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add splay tree for info_ptr -> CU mapping

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While using perf top for MozillaThunderbird I noticed quite some slow
dissably call with source code involved. E.g.

time ./objdump --start-address=0x0000000004e0dcd0 --stop-address=0x0000000004e0df8b -l -d --no-show-raw-insn -S -C /usr/lib64/thunderbird/libxul.so

took 2.071s and I noticed quite some time is spent in
find_abstract_instance:

    33.46%  objdump  objdump               [.] find_abstract_instance
    18.22%  objdump  objdump               [.] arange_add
    13.77%  objdump  objdump               [.] read_attribute_value
     4.82%  objdump  objdump               [.] comp_unit_maybe_decode_line_info
     3.10%  objdump  libc.so.6             [.] __memset_avx2_unaligned_erms

where linked list of CU is iterated when searing for where info_ptr
belongs to:

         : 3452   for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
    0.00 :   4c61f7: mov    0x10(%rbx),%rax
    0.00 :   4c61fb: test   %rax,%rax
    0.00 :   4c61fe: je     4c6215 <find_abstract_instance+0x365>
         : 3453   if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
    0.00 :   4c6200: cmp    0x60(%rax),%rdx
   83.20 :   4c6204: jb     4c620c <find_abstract_instance+0x35c>
    0.00 :   4c6206: cmp    0x78(%rax),%rdx
    6.89 :   4c620a: jb     4c6270 <find_abstract_instance+0x3c0>
         : 3452   for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
    0.00 :   4c620c: mov    0x10(%rax),%rax
    7.90 :   4c6210: test   %rax,%rax
    0.00 :   4c6213: jne    4c6200 <find_abstract_instance+0x350>

The following scan can be replaced with search in a splay tree and with
that I can get to 1.5s and there are other symbols where the difference
is even bigger.

bfd/ChangeLog:

	PR 29081
	* dwarf2.c (struct addr_range): New.
	(addr_range_intersects): Likewise.
	(splay_tree_compare_addr_range): Likewise.
	(splay_tree_free_addr_range): Likewise.
	(struct dwarf2_debug_file): Add comp_unit_tree.
	(find_abstract_instance): Use the splay tree when searching
	for a info_ptr.
	(stash_comp_unit): Insert to the splay tree.
	(_bfd_dwarf2_cleanup_debug_info): Clean up the splay tree.
This commit is contained in:
Martin Liska 2022-08-03 11:28:10 +02:00
parent 06ce017c7d
commit e441b55e94
1 changed files with 67 additions and 10 deletions
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77
bfd/dwarf2.c
View File

@ -36,6 +36,7 @@
#include "elf-bfd.h"
#include "dwarf2.h"
#include "hashtab.h"
#include "splay-tree.h"
/* The data in the .debug_line statement prologue looks like this. */
@ -152,6 +153,45 @@ static struct trie_node *alloc_trie_leaf (bfd *abfd)
return &leaf->head;
}
struct addr_range
{
bfd_byte *start;
bfd_byte *end;
};
/* Return true if address range do intersect. */
static bool
addr_range_intersects (struct addr_range *r1, struct addr_range *r2)
{
return (r1->start <= r2->start && r2->start < r1->end)
|| (r1->start <= (r2->end - 1) && (r2->end - 1) < r1->end);
}
/* Compare function for splay tree of addr_ranges. */
static int
splay_tree_compare_addr_range (splay_tree_key xa, splay_tree_key xb)
{
struct addr_range *r1 = (struct addr_range *) xa;
struct addr_range *r2 = (struct addr_range *) xb;
if (addr_range_intersects (r1, r2) || addr_range_intersects (r2, r1))
return 0;
else if (r1->end <= r2->start)
return -1;
else
return 1;
}
/* Splay tree release function for keys (addr_range). */
static void
splay_tree_free_addr_range (splay_tree_key key)
{
free ((struct addr_range *)key);
}
struct dwarf2_debug_file
{
/* The actual bfd from which debug info was loaded. Might be
@ -235,6 +275,9 @@ struct dwarf2_debug_file
/* Root of a trie to map addresses to compilation units. */
struct trie_node *trie_root;
/* Splay tree to map info_ptr address to compilation units. */
splay_tree comp_unit_tree;
};
struct dwarf2_debug
@ -3447,16 +3490,12 @@ find_abstract_instance (struct comp_unit *unit,
else
{
/* Check other CUs to see if they contain the abbrev. */
struct comp_unit *u;
for (u = unit->prev_unit; u != NULL; u = u->prev_unit)
if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
break;
if (u == NULL)
for (u = unit->next_unit; u != NULL; u = u->next_unit)
if (info_ptr >= u->info_ptr_unit && info_ptr < u->end_ptr)
break;
struct comp_unit *u = NULL;
struct addr_range range = { info_ptr, info_ptr };
splay_tree_node v = splay_tree_lookup (unit->file->comp_unit_tree,
(splay_tree_key)&range);
if (v != NULL)
u = (struct comp_unit *)v->value;
if (attr_ptr->form == DW_FORM_ref_addr)
while (u == NULL)
@ -5509,6 +5548,22 @@ stash_comp_unit (struct dwarf2_debug *stash, struct dwarf2_debug_file *file)
info_ptr_unit, offset_size);
if (each)
{
if (file->comp_unit_tree == NULL)
file->comp_unit_tree
= splay_tree_new (splay_tree_compare_addr_range,
splay_tree_free_addr_range, NULL);
struct addr_range *r
= (struct addr_range *)bfd_malloc (sizeof (struct addr_range));
r->start = each->info_ptr_unit;
r->end = each->end_ptr;
splay_tree_node v = splay_tree_lookup (file->comp_unit_tree,
(splay_tree_key)r);
if (v != NULL || r->end <= r->start)
abort ();
splay_tree_insert (file->comp_unit_tree, (splay_tree_key)r,
(splay_tree_value)each);
if (file->all_comp_units)
file->all_comp_units->prev_unit = each;
else
@ -5982,6 +6037,8 @@ _bfd_dwarf2_cleanup_debug_info (bfd *abfd, void **pinfo)
free (file->line_table->dirs);
}
htab_delete (file->abbrev_offsets);
if (file->comp_unit_tree != NULL)
splay_tree_delete (file->comp_unit_tree);
free (file->dwarf_line_str_buffer);
free (file->dwarf_str_buffer);