[PATCH 3/4] Inline abbrev lookup

Tom Tromey
2020-05-20T17:40:35Z

Profiling showed that calls to abbrev_table::lookup_abbrev were "too
visible". As these are just forwarding calls to the hash table, this
patch inlines the lookup. Also, htab_find_with_hash is used, avoiding
another call.

The run previous to this had times of (see the first patch in the
series for an explanation):

gdb 1.69
libxul 2.02
Ada 2.52

This patch improves the times to:

gdb 1.64
libxul 1.99
Ada 2.47

gdb/ChangeLog
2020-05-20 Tom Tromey <tromey@adacore.com>

* dwarf2/abbrev.h (struct abbrev_table) <lookup_abbrev>: Inline.
Use htab_find_with_hash.
<add_abbrev>: Remove "abbrev_number" parameter.
* dwarf2/abbrev.c (abbrev_table::add_abbrev): Remove
"abbrev_number" parameter. Use htab_find_slot_with_hash.
(hash_abbrev): Add comment.
(abbrev_table::lookup_abbrev): Move to header file.
(abbrev_table::read): Update.
---
gdb/ChangeLog | 11 +++++++++++
gdb/dwarf2/abbrev.c | 22 ++++++----------------
gdb/dwarf2/abbrev.h | 13 +++++++++++--
3 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/gdb/dwarf2/abbrev.c b/gdb/dwarf2/abbrev.c
index b85018060fa..1552594efb5 100644
--- a/gdb/dwarf2/abbrev.c
+++ b/gdb/dwarf2/abbrev.c
@@ -36,6 +36,8 @@ static hashval_t
hash_abbrev (const void *item)
{
const struct abbrev_info *info = (const struct abbrev_info *) item;
+ /* Warning: if you change this next line, you must also update the
+ other code in this class using the _with_hash functions. */
return info->number;
}

@@ -79,25 +81,13 @@ abbrev_table::alloc_abbrev ()
/* Add an abbreviation to the table. */

void
-abbrev_table::add_abbrev (unsigned int abbrev_number,
- struct abbrev_info *abbrev)
+abbrev_table::add_abbrev (struct abbrev_info *abbrev)
{
- void **slot = htab_find_slot (m_abbrevs.get (), abbrev, INSERT);
+ void **slot = htab_find_slot_with_hash (m_abbrevs.get (), abbrev,
+ abbrev->number, INSERT);
*slot = abbrev;
}

-/* Look up an abbrev in the table.
- Returns NULL if the abbrev is not found. */
-
-struct abbrev_info *
-abbrev_table::lookup_abbrev (unsigned int abbrev_number)
-{
- struct abbrev_info search;
- search.number = abbrev_number;
-
- return (struct abbrev_info *) htab_find (m_abbrevs.get (), &search);
-}
-
/* Read in an abbrev table. */

abbrev_table_up
@@ -172,7 +162,7 @@ abbrev_table::read (struct objfile *objfile,
memcpy (cur_abbrev->attrs, cur_attrs.data (),
cur_abbrev->num_attrs * sizeof (struct attr_abbrev));

- abbrev_table->add_abbrev (abbrev_number, cur_abbrev);
+ abbrev_table->add_abbrev (cur_abbrev);

/* Get next abbreviation.
Under Irix6 the abbreviations for a compilation unit are not
diff --git a/gdb/dwarf2/abbrev.h b/gdb/dwarf2/abbrev.h
index b9ace64b448..888f04ebebb 100644
--- a/gdb/dwarf2/abbrev.h
+++ b/gdb/dwarf2/abbrev.h
@@ -27,6 +27,8 @@
#ifndef GDB_DWARF2_ABBREV_H
#define GDB_DWARF2_ABBREV_H

+#include "hashtab.h"
+
/* This data structure holds the information of an abbrev. */
struct abbrev_info
{
@@ -60,8 +62,15 @@ struct abbrev_table
/* Look up an abbrev in the table.
Returns NULL if the abbrev is not found. */

- struct abbrev_info *lookup_abbrev (unsigned int abbrev_number);
+ struct abbrev_info *lookup_abbrev (unsigned int abbrev_number)
+ {
+ struct abbrev_info search;
+ search.number = abbrev_number;

+ return (struct abbrev_info *) htab_find_with_hash (m_abbrevs.get (),
+ &search,
+ abbrev_number);
+ }

/* Where the abbrev table came from.
This is used as a sanity check when the table is used. */
@@ -78,7 +87,7 @@ struct abbrev_table
struct abbrev_info *alloc_abbrev ();

/* Add an abbreviation to the table. */
- void add_abbrev (unsigned int abbrev_number, struct abbrev_info *abbrev);
+ void add_abbrev (struct abbrev_info *abbrev);

/* Hash table of abbrevs. */
htab_up m_abbrevs;
--
2.21.3