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libdrgn: dwarf_index: store DIE indices as uint32_t

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It's very unlikely that we'll ever index more than 4 billion DIEs in a
single shard, so we can shrink the index a bit by using uint32_t
indices (and uint8_t tag).

Signed-off-by: Omar Sandoval <osandov@osandov.com>
This commit is contained in:
Omar Sandoval 2020-06-30 16:46:01 -07:00
parent 9ce9094ee0
commit 0b4ab1772b
2 changed files with 19 additions and 18 deletions
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33
libdrgn/dwarf_index.c
View File

@ -264,13 +264,13 @@ static inline const char *section_end(Elf_Data *data)
* name and tag.
*/
struct drgn_dwarf_index_die {
uint64_t tag;
uint64_t file_name_hash;
/*
* The next DIE with the same name (as an index into
* drgn_dwarf_index_shard::dies), or SIZE_MAX if this is the last DIE.
* drgn_dwarf_index_shard::dies), or UINT32_MAX if this is the last DIE.
*/
size_t next;
uint32_t next;
uint8_t tag;
uint64_t file_name_hash;
Dwfl_Module *module;
size_t offset;
};
@ -1780,25 +1780,26 @@ out:
return err;
}
static bool append_die_entry(struct drgn_dwarf_index_shard *shard, uint64_t tag,
static bool append_die_entry(struct drgn_dwarf_index_shard *shard, uint8_t tag,
uint64_t file_name_hash, Dwfl_Module *module,
size_t offset)
{
struct drgn_dwarf_index_die *die;
die = drgn_dwarf_index_die_vector_append_entry(&shard->dies);
if (shard->dies.size == UINT32_MAX)
return false;
struct drgn_dwarf_index_die *die =
drgn_dwarf_index_die_vector_append_entry(&shard->dies);
if (!die)
return false;
die->next = UINT32_MAX;
die->tag = tag;
die->file_name_hash = file_name_hash;
die->module = module;
die->offset = offset;
die->next = SIZE_MAX;
return true;
}
static struct drgn_error *index_die(struct drgn_dwarf_index *dindex,
const char *name, uint64_t tag,
const char *name, uint8_t tag,
uint64_t file_name_hash,
Dwfl_Module *module, size_t offset)
{
@ -1844,7 +1845,7 @@ static struct drgn_error *index_die(struct drgn_dwarf_index *dindex,
goto out;
}
if (die->next == SIZE_MAX)
if (die->next == UINT32_MAX)
break;
die = &shard->dies.data[die->next];
}
@ -2076,7 +2077,7 @@ static struct drgn_error *index_cu(struct drgn_dwarf_index *dindex,
.stmt_list = SIZE_MAX,
};
size_t die_offset = ptr - debug_info_buffer;
uint64_t tag;
uint8_t tag;
err = read_die(cu, &abbrev, &ptr, end, debug_str_buffer,
debug_str_end, &die);
@ -2203,9 +2204,9 @@ static void rollback_dwarf_index(struct drgn_dwarf_index *dindex)
*/
for (index = 0; index < shard->dies.size; i++) {
die = &shard->dies.data[index];
if (die->next != SIZE_MAX &&
if (die->next != UINT32_MAX &&
die->next >= shard->dies.size)
die->next = SIZE_MAX;
die->next = UINT32_MAX;
}
/* Finally, delete the new entries in the map. */
@ -2357,7 +2358,7 @@ void drgn_dwarf_index_iterator_init(struct drgn_dwarf_index_iterator *it,
shard = &dindex->shards[it->shard];
map_it = drgn_dwarf_index_die_map_search_hashed(&shard->map,
&key, hp);
it->index = map_it.entry ? map_it.entry->value : SIZE_MAX;
it->index = map_it.entry ? map_it.entry->value : UINT32_MAX;
it->any_name = false;
} else {
it->index = 0;
@ -2421,7 +2422,7 @@ drgn_dwarf_index_iterator_next(struct drgn_dwarf_index_iterator *it,
for (;;) {
struct drgn_dwarf_index_shard *shard;
if (it->index == SIZE_MAX)
if (it->index == UINT32_MAX)
return &drgn_stop;
shard = &dindex->shards[it->shard];

4
libdrgn/dwarf_index.h
View File

@ -63,7 +63,7 @@ extern const Dwfl_Callbacks drgn_linux_proc_dwfl_callbacks;
extern const Dwfl_Callbacks drgn_userspace_core_dump_dwfl_callbacks;
struct drgn_dwarf_index_die;
DEFINE_HASH_MAP_TYPE(drgn_dwarf_index_die_map, struct string, size_t)
DEFINE_HASH_MAP_TYPE(drgn_dwarf_index_die_map, struct string, uint32_t)
DEFINE_VECTOR_TYPE(drgn_dwarf_index_die_vector, struct drgn_dwarf_index_die)
struct drgn_dwarf_index_shard {
@ -347,7 +347,7 @@ struct drgn_dwarf_index_iterator {
const uint64_t *tags;
size_t num_tags;
size_t shard;
size_t index;
uint32_t index;
bool any_name;
};