[PATCH v2 39/42] Pass existing_cu object to cutu_reader

Simon Marchi
2020-05-12T21:17:53Z

It is possible, seemingly for a special case described in
find_partial_die, for cutu_reader to re-use an existing dwarf2_cu
instead of creating a new one. This happens
---
gdb/dwarf2/read.c | 53 +++++++++++++++++++++++++++--------------------
1 file changed, 30 insertions(+), 23 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index dc72b6320a8..acc148a87d5 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -912,7 +912,7 @@ class cutu_reader : public die_reader_specs
cutu_reader (dwarf2_per_cu_data *this_cu,
dwarf2_per_objfile *per_objfile,
struct abbrev_table *abbrev_table,
- int use_existing_cu,
+ dwarf2_cu *existing_cu,
bool skip_partial);

explicit cutu_reader (struct dwarf2_per_cu_data *this_cu,
@@ -933,7 +933,7 @@ class cutu_reader : public die_reader_specs
private:
void init_tu_and_read_dwo_dies (dwarf2_per_cu_data *this_cu,
dwarf2_per_objfile *per_objfile,
- int use_existing_cu);
+ dwarf2_cu *existing_cu);

struct dwarf2_per_cu_data *m_this_cu;
std::unique_ptr<dwarf2_cu> m_new_cu;
@@ -6864,7 +6864,7 @@ lookup_dwo_unit (dwarf2_cu *cu, die_info *comp_unit_die, const char *dwo_name)
void
cutu_reader::init_tu_and_read_dwo_dies (dwarf2_per_cu_data *this_cu,
dwarf2_per_objfile *per_objfile,
- int use_existing_cu)
+ dwarf2_cu *existing_cu)
{
struct signatured_type *sig_type;

@@ -6874,24 +6874,28 @@ cutu_reader::init_tu_and_read_dwo_dies (dwarf2_per_cu_data *this_cu,
sig_type = (struct signatured_type *) this_cu;
gdb_assert (sig_type->dwo_unit != NULL);

- if (use_existing_cu && this_cu->cu != NULL)
+ dwarf2_cu *cu;
+
+ if (existing_cu != nullptr)
{
- gdb_assert (this_cu->cu->dwo_unit == sig_type->dwo_unit);
+ cu = existing_cu;
+ gdb_assert (cu->dwo_unit == sig_type->dwo_unit);
/* There's no need to do the rereading_dwo_cu handling that
cutu_reader does since we don't read the stub. */
}
else
{
- /* If !use_existing_cu, this_cu->cu must be NULL. */
+ /* If and existing_cu is provided, this_cu->cu must be NULL. */
gdb_assert (this_cu->cu == NULL);
m_new_cu.reset (new dwarf2_cu (this_cu, per_objfile));
+ cu = m_new_cu.get ();
}

/* A future optimization, if needed, would be to use an existing
abbrev table. When reading DWOs with skeletonless TUs, all the TUs
could share abbrev tables. */

- if (read_cutu_die_from_dwo (this_cu->cu, sig_type->dwo_unit,
+ if (read_cutu_die_from_dwo (cu, sig_type->dwo_unit,
NULL /* stub_comp_unit_die */,
sig_type->dwo_unit->dwo_file->comp_dir,
this, &info_ptr,
@@ -6916,7 +6920,7 @@ cutu_reader::init_tu_and_read_dwo_dies (dwarf2_per_cu_data *this_cu,
cutu_reader::cutu_reader (dwarf2_per_cu_data *this_cu,
dwarf2_per_objfile *dwarf2_per_objfile,
struct abbrev_table *abbrev_table,
- int use_existing_cu,
+ dwarf2_cu *existing_cu,
bool skip_partial)
: die_reader_specs {},
m_this_cu (this_cu)
@@ -6924,7 +6928,6 @@ cutu_reader::cutu_reader (dwarf2_per_cu_data *this_cu,
struct objfile *objfile = dwarf2_per_objfile->objfile;
struct dwarf2_section_info *section = this_cu->section;
bfd *abfd = section->get_bfd_owner ();
- struct dwarf2_cu *cu;
const gdb_byte *begin_info_ptr;
struct signatured_type *sig_type = NULL;
struct dwarf2_section_info *abbrev_section;
@@ -6945,7 +6948,7 @@ cutu_reader::cutu_reader (dwarf2_per_cu_data *this_cu,
/* Narrow down the scope of possibilities to have to understand. */
gdb_assert (this_cu->is_debug_types);
gdb_assert (abbrev_table == NULL);
- init_tu_and_read_dwo_dies (this_cu, dwarf2_per_objfile, use_existing_cu);
+ init_tu_and_read_dwo_dies (this_cu, dwarf2_per_objfile, existing_cu);
return;
}

@@ -6956,9 +6959,11 @@ cutu_reader::cutu_reader (dwarf2_per_cu_data *this_cu,

abbrev_section = get_abbrev_section_for_cu (this_cu);

- if (use_existing_cu && this_cu->cu != NULL)
+ dwarf2_cu *cu;
+
+ if (existing_cu != nullptr)
{
- cu = this_cu->cu;
+ cu = existing_cu;
/* If this CU is from a DWO file we need to start over, we need to
refetch the attributes from the skeleton CU.
This could be optimized by retrieving those attributes from when we
@@ -6970,7 +6975,7 @@ cutu_reader::cutu_reader (dwarf2_per_cu_data *this_cu,
}
else
{
- /* If !use_existing_cu, this_cu->cu must be NULL. */
+ /* If an existing_cu is provided, this_cu->cu must be NULL. */
gdb_assert (this_cu->cu == NULL);
m_new_cu.reset (new dwarf2_cu (this_cu, dwarf2_per_objfile));
cu = m_new_cu.get ();
@@ -7523,7 +7528,7 @@ process_psymtab_comp_unit (dwarf2_per_cu_data *this_cu,
if (this_cu->cu != NULL)
free_one_cached_comp_unit (this_cu, per_objfile);

- cutu_reader reader (this_cu, per_objfile, NULL, 0, false);
+ cutu_reader reader (this_cu, per_objfile, nullptr, nullptr, false);

switch (reader.comp_unit_die->tag)
{
@@ -7705,7 +7710,7 @@ build_type_psymtabs_1 (struct dwarf2_per_objfile *dwarf2_per_objfile)
}

cutu_reader reader (&tu.sig_type->per_cu, dwarf2_per_objfile,
- abbrev_table.get (), 0, false);
+ abbrev_table.get (), nullptr, false);
if (!reader.dummy_p)
build_type_psymtabs_reader (&reader, reader.info_ptr,
reader.comp_unit_die);
@@ -7810,7 +7815,8 @@ process_skeletonless_type_unit (void **slot, void *info)
*slot = entry;

/* This does the job that build_type_psymtabs_1 would have done. */
- cutu_reader reader (&entry->per_cu, dwarf2_per_objfile, NULL, 0, false);
+ cutu_reader reader (&entry->per_cu, dwarf2_per_objfile, nullptr, nullptr,
+ false);
if (!reader.dummy_p)
build_type_psymtabs_reader (&reader, reader.info_ptr,
reader.comp_unit_die);
@@ -7946,9 +7952,10 @@ dwarf2_build_psymtabs_hard (struct dwarf2_per_objfile *dwarf2_per_objfile)

static void
load_partial_comp_unit (dwarf2_per_cu_data *this_cu,
- dwarf2_per_objfile *per_objfile)
+ dwarf2_per_objfile *per_objfile,
+ dwarf2_cu *existing_cu)
{
- cutu_reader reader (this_cu, per_objfile, NULL, 1, false);
+ cutu_reader reader (this_cu, per_objfile, nullptr, existing_cu, false);

if (!reader.dummy_p)
{
@@ -9067,7 +9074,7 @@ load_full_comp_unit (dwarf2_per_cu_data *this_cu,
{
gdb_assert (! this_cu->is_debug_types);

- cutu_reader reader (this_cu, per_objfile, NULL, 1, skip_partial);
+ cutu_reader reader (this_cu, per_objfile, NULL, this_cu->cu, skip_partial);
if (reader.dummy_p)
return;

@@ -18673,7 +18680,7 @@ find_partial_die (sect_offset sect_off, int offset_in_dwz, struct dwarf2_cu *cu)
dwarf2_per_objfile);

if (per_cu->cu == NULL || per_cu->cu->partial_dies == NULL)
- load_partial_comp_unit (per_cu, cu->per_objfile);
+ load_partial_comp_unit (per_cu, cu->per_objfile, nullptr);

per_cu->cu->last_used = 0;
pd = per_cu->cu->find_partial_die (sect_off);
@@ -18692,7 +18699,7 @@ find_partial_die (sect_offset sect_off, int offset_in_dwz, struct dwarf2_cu *cu)
DIEs alone (which can still be in use, e.g. in scan_partial_symbols),
and clobber THIS_CU->cu->partial_dies with the hash table for the new
set. */
- load_partial_comp_unit (per_cu, cu->per_objfile);
+ load_partial_comp_unit (per_cu, cu->per_objfile, cu);

pd = per_cu->cu->find_partial_die (sect_off);
}
@@ -19409,7 +19416,7 @@ dwarf2_read_addr_index (dwarf2_per_cu_data *per_cu,
}
else
{
- cutu_reader reader (per_cu, dwarf2_per_objfile, NULL, 0, false);
+ cutu_reader reader (per_cu, dwarf2_per_objfile, nullptr, nullptr, false);
addr_base = reader.cu->addr_base;
addr_size = reader.cu->header.addr_size;
}
@@ -22791,7 +22798,7 @@ read_signatured_type (signatured_type *sig_type,
gdb_assert (per_cu->is_debug_types);
gdb_assert (per_cu->cu == NULL);

- cutu_reader reader (per_cu, per_objfile, NULL, 0, false);
+ cutu_reader reader (per_cu, per_objfile, nullptr, nullptr, false);

if (!reader.dummy_p)
{
--
2.26.2