[PATCH v2 06/42] Remove symtab links from dwarf2_psymtab and dwarf2_per_cu_quick_data

Simon Marchi
2020-05-12T21:09:19Z

From: Simon Marchi <simon.marchi@polymtl.ca>

The dwarf2_psymtab and dwarf2_per_cu_quick_data types contain a pointer
to a compunit_symtab, which is a pointer to the corresponding full
symtab. The dwarf2_psymtab and dwarf2_per_cu_quick_data objects are
going to become objfile-independent, and possibly shared by multiple
objfiles, whereas compunit_symtab will stay objfile-dependent. This
backlink to the compunit_symtab must therefore be removed.

This patch replaces them with a vector in the dwarf2_per_objfile type,
that serves as a mapping from dwarf2_per_cu_data objects to
compunit_symtab objects, for this particular objfile. The vector is
indexed using the index assigned to the dwarf2_per_cu_data at its
creation.

I removed the get_compunit_symtab, as it appears to bring not much value
over calling dwarf2_per_objfile::get_symtab directly.

YYYY-MM-DD Tom Tromey <tom@tromey.com>
YYYY-MM-DD Simon Marchi <simon.marchi@efficios.com>

* dwarf2/read.h (struct dwarf2_per_bfd) <num_psymtabs>: New
method.
(struct dwarf2_per_objfile) <resize_symtabs, symtab_set_p,
get_symtab, set_symtab>: New methods.
<m_symtabs>: New field.
(struct dwarf2_psymtab): Derive from partial_symtab.
<readin_p, get_compunit_symtab>: Declare methods.
* dwarf2/read.c (dwarf2_per_objfile::symtab_set_p,
dwarf2_per_objfile::get_symtab, dwarf2_per_objfile::set_symtab):
New methods.
(struct dwarf2_per_cu_quick_data) <compunit_symtab>: Remove.
(dw2_do_instantiate_symtab, dw2_instantiate_symtab)
(dw2_map_expand_apply, dw2_map_symtabs_matching_filename)
(dw2_symtab_iter_next, dw2_print_stats)
(dw2_expand_symtabs_with_fullname)
(dw2_expand_symtabs_matching_one)
(dw_expand_symtabs_matching_file_matcher)
(dw2_find_pc_sect_compunit_symtab, dw2_map_symbol_filenames)
(dw2_debug_names_iterator::next)
(dw2_debug_names_map_matching_symbols)
(fill_in_sig_entry_from_dwo_entry, dwarf2_psymtab::read_symtab)
(process_queue, dwarf2_psymtab::expand_psymtab): Update.
(dwarf2_psymtab::readin_p, dwarf2_psymtab::get_compunit_symtab):
New methods.
(get_compunit_symtab, process_full_comp_unit)
(process_full_type_unit): Update.
(dwarf2_build_psymtabs, dwarf2_initialize_objfile, add_type_unit): Call
---
gdb/dwarf2/read.c | 162 +++++++++++++++++++++++++++-------------------
gdb/dwarf2/read.h | 37 ++++++++++-
2 files changed, 129 insertions(+), 70 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 0b16ec127f5..4dfa85ff0c7 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1811,6 +1811,38 @@ class free_cached_comp_units
dwarf2_per_objfile *m_per_objfile;
};

+/* See read.h. */
+
+bool
+dwarf2_per_objfile::symtab_set_p (const dwarf2_per_cu_data *per_cu) const
+{
+ gdb_assert (per_cu->index < this->m_symtabs.size ());
+
+ return this->m_symtabs[per_cu->index] != nullptr;
+}
+
+/* See read.h. */
+
+compunit_symtab *
+dwarf2_per_objfile::get_symtab (const dwarf2_per_cu_data *per_cu) const
+{
+ gdb_assert (per_cu->index < this->m_symtabs.size ());
+
+ return this->m_symtabs[per_cu->index];
+}
+
+/* See read.h. */
+
+void
+dwarf2_per_objfile::set_symtab (const dwarf2_per_cu_data *per_cu,
+ compunit_symtab *symtab)
+{
+ gdb_assert (per_cu->index < this->m_symtabs.size ());
+ gdb_assert (this->m_symtabs[per_cu->index] == nullptr);
+
+ this->m_symtabs[per_cu->index] = symtab;
+}
+
/* Try to locate the sections we need for DWARF 2 debugging
information and return true if we have enough to do something.
NAMES points to the dwarf2 section names, or is NULL if the standard
@@ -2198,10 +2230,6 @@ struct dwarf2_per_cu_quick_data
NOTE: This points into dwarf2_per_objfile->per_bfd->quick_file_names_table. */
struct quick_file_names *file_names;

- /* The corresponding symbol table. This is NULL if symbols for this
- CU have not yet been read. */
- struct compunit_symtab *compunit_symtab;
-
/* A temporary mark bit used when iterating over all CUs in
expand_symtabs_matching. */
unsigned int mark : 1;
@@ -2325,9 +2353,7 @@ dw2_do_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
with the dwarf queue empty. */
dwarf2_queue_guard q_guard (dwarf2_per_objfile);

- if (dwarf2_per_objfile->per_bfd->using_index
- ? per_cu->v.quick->compunit_symtab == NULL
- : (per_cu->v.psymtab == NULL || !per_cu->v.psymtab->readin))
+ if (!dwarf2_per_objfile->symtab_set_p (per_cu))
{
queue_comp_unit (per_cu, language_minimal);
load_cu (per_cu, skip_partial);
@@ -2362,7 +2388,8 @@ dw2_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
struct dwarf2_per_objfile *dwarf2_per_objfile = per_cu->dwarf2_per_objfile;

gdb_assert (dwarf2_per_objfile->per_bfd->using_index);
- if (!per_cu->v.quick->compunit_symtab)
+
+ if (!dwarf2_per_objfile->symtab_set_p (per_cu))
{
free_cached_comp_units freer (dwarf2_per_objfile);
scoped_restore decrementer = increment_reading_symtab ();
@@ -2370,7 +2397,7 @@ dw2_instantiate_symtab (struct dwarf2_per_cu_data *per_cu, bool skip_partial)
process_cu_includes (dwarf2_per_objfile);
}

- return per_cu->v.quick->compunit_symtab;
+ return dwarf2_per_objfile->get_symtab (per_cu);
}

/* See declaration. */
@@ -3274,7 +3301,8 @@ dw2_map_expand_apply (struct objfile *objfile,
struct compunit_symtab *last_made = objfile->compunit_symtabs;

/* Don't visit already-expanded CUs. */
- if (per_cu->v.quick->compunit_symtab)
+ dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+ if (per_objfile->symtab_set_p (per_cu))
return 0;

/* This may expand more than one symtab, and we want to iterate over
@@ -3302,7 +3330,7 @@ dw2_map_symtabs_matching_filename
for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->per_bfd->all_comp_units)
{
/* We only need to look at symtabs not already expanded. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
continue;

quick_file_names *file_data = dw2_get_file_names (per_cu);
@@ -3444,7 +3472,7 @@ dw2_symtab_iter_next (struct dw2_symtab_iterator *iter)
dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->per_bfd->get_cutu (cu_index);

/* Skip if already read in. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
continue;

/* Check static vs global. */
@@ -3559,7 +3587,7 @@ dw2_print_stats (struct objfile *objfile)
{
dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->per_bfd->get_cutu (i);

- if (!per_cu->v.quick->compunit_symtab)
+ if (!dwarf2_per_objfile->symtab_set_p (per_cu))
++count;
}
printf_filtered (_(" Number of read CUs: %d\n"), total - count);
@@ -3642,7 +3670,7 @@ dw2_expand_symtabs_with_fullname (struct objfile *objfile,
for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->per_bfd->all_comp_units)
{
/* We only need to look at symtabs not already expanded. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
continue;

quick_file_names *file_data = dw2_get_file_names (per_cu);
@@ -4467,15 +4495,14 @@ dw2_expand_symtabs_matching_one
{
if (file_matcher == NULL || per_cu->v.quick->mark)
{
- bool symtab_was_null
- = (per_cu->v.quick->compunit_symtab == NULL);
+ dwarf2_per_objfile *per_objfile = per_cu->dwarf2_per_objfile;
+ bool symtab_was_null = !per_objfile->symtab_set_p (per_cu);

- dw2_instantiate_symtab (per_cu, false);
+ compunit_symtab *symtab = dw2_instantiate_symtab (per_cu, false);
+ gdb_assert (symtab != nullptr);

- if (expansion_notify != NULL
- && symtab_was_null
- && per_cu->v.quick->compunit_symtab != NULL)
- expansion_notify (per_cu->v.quick->compunit_symtab);
+ if (expansion_notify != NULL && symtab_was_null)
+ expansion_notify (symtab);
}
}

@@ -4593,7 +4620,7 @@ dw_expand_symtabs_matching_file_matcher
per_cu->v.quick->mark = 0;

/* We only need to look at symtabs not already expanded. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
continue;

quick_file_names *file_data = dw2_get_file_names (per_cu);
@@ -4731,7 +4758,8 @@ dw2_find_pc_sect_compunit_symtab (struct objfile *objfile,
if (!data)
return NULL;

- if (warn_if_readin && data->v.quick->compunit_symtab)
+ dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+ if (warn_if_readin && per_objfile->symtab_set_p (data))
warning (_("(Internal error: pc %s in read in CU, but not in symtab.)"),
paddress (objfile->arch (), pc));

@@ -4764,7 +4792,7 @@ dw2_map_symbol_filenames (struct objfile *objfile, symbol_filename_ftype *fun,

for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->per_bfd->all_comp_units)
{
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
{
void **slot = htab_find_slot (visited.get (),
per_cu->v.quick->file_names,
@@ -4777,7 +4805,7 @@ dw2_map_symbol_filenames (struct objfile *objfile, symbol_filename_ftype *fun,
for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->per_bfd->all_comp_units)
{
/* We only need to look at symtabs not already expanded. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
continue;

quick_file_names *file_data = dw2_get_file_names (per_cu);
@@ -5448,7 +5476,7 @@ dw2_debug_names_iterator::next ()
}

/* Skip if already read in. */
- if (per_cu->v.quick->compunit_symtab)
+ if (dwarf2_per_objfile->symtab_set_p (per_cu))
goto again;

/* Check static vs global. */
@@ -5689,11 +5717,11 @@ dw2_debug_names_map_matching_symbols
the psymtab code does. */
for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->per_bfd->all_comp_units)
{
- struct compunit_symtab *cust = per_cu->v.quick->compunit_symtab;
- if (cust != nullptr)
+ compunit_symtab *symtab = dwarf2_per_objfile->get_symtab (per_cu);
+ if (symtab != nullptr)
{
const struct block *block
- = BLOCKVECTOR_BLOCK (COMPUNIT_BLOCKVECTOR (cust), block_kind);
+ = BLOCKVECTOR_BLOCK (COMPUNIT_BLOCKVECTOR (symtab), block_kind);
if (!iterate_over_symbols_terminated (block, name,
domain, callback))
break;
@@ -5843,6 +5871,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
dwarf2_per_objfile->per_bfd->quick_file_names_table
= create_quick_file_names_table
(dwarf2_per_objfile->per_bfd->all_comp_units.size ());
+ dwarf2_per_objfile->resize_symtabs ();

for (int i = 0; i < (dwarf2_per_objfile->per_bfd->all_comp_units.size ()
+ dwarf2_per_objfile->per_bfd->all_type_units.size ()); ++i)
@@ -5863,6 +5892,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
if (dwarf2_read_debug_names (dwarf2_per_objfile))
{
*index_kind = dw_index_kind::DEBUG_NAMES;
+ dwarf2_per_objfile->resize_symtabs ();
return true;
}

@@ -5871,6 +5901,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
get_gdb_index_contents_from_section<dwz_file>))
{
*index_kind = dw_index_kind::GDB_INDEX;
+ dwarf2_per_objfile->resize_symtabs ();
return true;
}

@@ -5881,6 +5912,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
{
global_index_cache.hit ();
*index_kind = dw_index_kind::GDB_INDEX;
+ dwarf2_per_objfile->resize_symtabs ();
return true;
}

@@ -5909,6 +5941,8 @@ dwarf2_build_psymtabs (struct objfile *objfile)
dwarf2_build_psymtabs_hard (dwarf2_per_objfile);
psymtabs.keep ();

+ dwarf2_per_objfile->resize_symtabs ();
+
/* (maybe) store an index in the cache. */
global_index_cache.store (dwarf2_per_objfile);
}
@@ -6339,6 +6373,8 @@ add_type_unit (struct dwarf2_per_objfile *dwarf2_per_objfile, ULONGEST sig,

signatured_type *sig_type = dwarf2_per_objfile->per_bfd->allocate_signatured_type ();

+ dwarf2_per_objfile->resize_symtabs ();
+
dwarf2_per_objfile->per_bfd->all_type_units.push_back (sig_type);
sig_type->signature = sig;
sig_type->per_cu.is_debug_types = 1;
@@ -6374,7 +6410,7 @@ fill_in_sig_entry_from_dwo_entry (struct dwarf2_per_objfile *dwarf2_per_objfile,
if (dwarf2_per_objfile->per_bfd->using_index)
{
gdb_assert (sig_entry->per_cu.v.quick != NULL);
- gdb_assert (sig_entry->per_cu.v.quick->compunit_symtab == NULL);
+ gdb_assert (!dwarf2_per_objfile->symtab_set_p (&sig_entry->per_cu));
}
else
gdb_assert (sig_entry->per_cu.v.psymtab == NULL);
@@ -8801,7 +8837,8 @@ dwarf2_psymtab::read_symtab (struct objfile *objfile)
struct dwarf2_per_objfile *dwarf2_per_objfile
= get_dwarf2_per_objfile (objfile);

- gdb_assert (!readin);
+ gdb_assert (!dwarf2_per_objfile->symtab_set_p (per_cu_data));
+
/* If this psymtab is constructed from a debug-only objfile, the
has_section_at_zero flag will not necessarily be correct. We
can get the correct value for this flag by looking at the data
@@ -8897,9 +8934,7 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
{
dwarf2_queue_item &item = dwarf2_per_objfile->per_bfd->queue.front ();

- if ((dwarf2_per_objfile->per_bfd->using_index
- ? !item.per_cu->v.quick->compunit_symtab
- : (item.per_cu->v.psymtab && !item.per_cu->v.psymtab->readin))
+ if (!dwarf2_per_objfile->symtab_set_p (item.per_cu)
/* Skip dummy CUs. */
&& item.per_cu->cu != NULL)
{
@@ -8954,7 +8989,7 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
void
dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
{
- gdb_assert (!readin);
+ gdb_assert (!readin_p (objfile));

expand_dependencies (objfile);

@@ -8962,6 +8997,24 @@ dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
gdb_assert (get_compunit_symtab (objfile) != nullptr);
}

+/* See psympriv.h. */
+
+bool
+dwarf2_psymtab::readin_p (struct objfile *objfile) const
+{
+ dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+ return per_objfile->symtab_set_p (per_cu_data);
+}
+
+/* See psympriv.h. */
+
+compunit_symtab *
+dwarf2_psymtab::get_compunit_symtab (struct objfile *objfile) const
+{
+ dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+ return per_objfile->get_symtab (per_cu_data);
+}
+
/* Trivial hash function for die_info: the hash value of a DIE
is its offset in .debug_info for this objfile. */

@@ -9499,17 +9552,6 @@ rust_union_quirks (struct dwarf2_cu *cu)
cu->rust_unions.clear ();
}

-/* Return the symtab for PER_CU. This works properly regardless of
- whether we're using the index or psymtabs. */
-
-static struct compunit_symtab *
-get_compunit_symtab (struct dwarf2_per_cu_data *per_cu)
-{
- return (per_cu->dwarf2_per_objfile->per_bfd->using_index
- ? per_cu->v.quick->compunit_symtab
- : per_cu->v.psymtab->compunit_symtab);
-}
-
/* A helper function for computing the list of all symbol tables
included by PER_CU. */

@@ -9519,10 +9561,7 @@ recursively_compute_inclusions (std::vector<compunit_symtab *> *result,
struct dwarf2_per_cu_data *per_cu,
struct compunit_symtab *immediate_parent)
{
- void **slot;
- struct compunit_symtab *cust;
-
- slot = htab_find_slot (all_children, per_cu, INSERT);
+ void **slot = htab_find_slot (all_children, per_cu, INSERT);
if (*slot != NULL)
{
/* This inclusion and its children have been processed. */
@@ -9530,8 +9569,9 @@ recursively_compute_inclusions (std::vector<compunit_symtab *> *result,
}

*slot = per_cu;
+
/* Only add a CU if it has a symbol table. */
- cust = get_compunit_symtab (per_cu);
+ compunit_symtab *cust = per_cu->dwarf2_per_objfile->get_symtab (per_cu);
if (cust != NULL)
{
/* If this is a type unit only add its symbol table if we haven't
@@ -9576,7 +9616,7 @@ compute_compunit_symtab_includes (struct dwarf2_per_cu_data *per_cu)
int len;
std::vector<compunit_symtab *> result_symtabs;
htab_t all_children, all_type_symtabs;
- struct compunit_symtab *cust = get_compunit_symtab (per_cu);
+ compunit_symtab *cust = per_cu->dwarf2_per_objfile->get_symtab (per_cu);

/* If we don't have a symtab, we can just skip this case. */
if (cust == NULL)
@@ -9713,14 +9753,7 @@ process_full_comp_unit (struct dwarf2_per_cu_data *per_cu,
cust->call_site_htab = cu->call_site_htab;
}

- if (dwarf2_per_objfile->per_bfd->using_index)
- per_cu->v.quick->compunit_symtab = cust;
- else
- {
- dwarf2_psymtab *pst = per_cu->v.psymtab;
- pst->compunit_symtab = cust;
- pst->readin = true;
- }
+ dwarf2_per_objfile->set_symtab (per_cu, cust);

/* Push it for inclusion processing later. */
dwarf2_per_objfile->per_bfd->just_read_cus.push_back (per_cu);
@@ -9793,14 +9826,7 @@ process_full_type_unit (struct dwarf2_per_cu_data *per_cu,
cust = sig_type->type_unit_group->compunit_symtab;
}

- if (dwarf2_per_objfile->per_bfd->using_index)
- per_cu->v.quick->compunit_symtab = cust;
- else
- {
- dwarf2_psymtab *pst = per_cu->v.psymtab;
- pst->compunit_symtab = cust;
- pst->readin = true;
- }
+ dwarf2_per_objfile->set_symtab (per_cu, cust);

/* Not needed any more. */
cu->reset_builder ();
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 4dc9496046f..7631938edb0 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -123,6 +123,11 @@ struct dwarf2_per_bfd
is allocated on the dwarf2_per_bfd obstack. */
signatured_type *allocate_signatured_type ();

+ /* Return the number of partial symtabs allocated with allocate_per_cu
+ and allocate_signatured_type so far. */
+ int num_psymtabs () const
+ { return m_num_psymtabs; }
+
private:
/* This function is mapped across the sections and remembers the
offset and size of each of the debugging sections we are
@@ -278,12 +283,38 @@ struct dwarf2_per_objfile
const struct comp_unit_head *cu_header,
unsigned int *bytes_read_ptr);

+ /* Resize the M_SYMTABS vector to the needed size (the number of partial
+ symtabs allocated by the per-bfd). */
+ void resize_symtabs ()
+ {
+ /* The symtabs vector should only grow, not shrink. */
+ gdb_assert (per_bfd->num_psymtabs () >= m_symtabs.size ());
+
+ m_symtabs.resize (per_bfd->num_psymtabs ());
+ }
+
+ /* Return true if the symtab corresponding to PER_CU has been set,
+ false otherwise. */
+ bool symtab_set_p (const dwarf2_per_cu_data *per_cu) const;
+
+ /* Return the compunit_symtab associated to PER_CU, if it has been created. */
+ compunit_symtab *get_symtab (const dwarf2_per_cu_data *per_cu) const;
+
+ /* Set the compunit_symtab associated to PER_CU. */
+ void set_symtab (const dwarf2_per_cu_data *per_cu, compunit_symtab *symtab);
+
/* Back link. */
struct objfile *objfile;

/* Pointer to the data that is (possibly) shared between this objfile and
other objfiles backed by the same BFD. */
struct dwarf2_per_bfd *per_bfd;
+
+private:
+ /* Hold the corresponding compunit_symtab for each CU or TU. This
+ is indexed by dwarf2_per_cu_data::index. A NULL value means
+ that the CU/TU has not been expanded yet. */
+ std::vector<compunit_symtab *> m_symtabs;
};

/* Get the dwarf2_per_objfile associated to OBJFILE. */
@@ -291,17 +322,19 @@ struct dwarf2_per_objfile
dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);

/* A partial symtab specialized for DWARF. */
-struct dwarf2_psymtab : public standard_psymtab
+struct dwarf2_psymtab : public partial_symtab
{
dwarf2_psymtab (const char *filename, struct objfile *objfile,
dwarf2_per_cu_data *per_cu)
- : standard_psymtab (filename, objfile, 0),
+ : partial_symtab (filename, objfile, 0),
per_cu_data (per_cu)
{
}

void read_symtab (struct objfile *) override;
void expand_psymtab (struct objfile *) override;
+ bool readin_p (struct objfile *) const override;
+ compunit_symtab *get_compunit_symtab (struct objfile *) const override;

struct dwarf2_per_cu_data *per_cu_data;
};
--
2.26.2