[PATCH 07/14] Add dwarf2_per_cu_data::index

Tom Tromey
2020-02-15T16:54:53Z

Currently a dwarf2_per_cu_data can hold a link to the corresponding
compunit_symtab. However, once these objects are shared across
objfiles, a simple pointer won't work.

Instead, this link will be stored in the dwarf2_unshareable object.
To enable this, we add an index to each dwarf2_per_cu_data and
signatured_type.

2020-02-15 Tom Tromey <tom@tromey.com>

* dwarf2/read.h (struct dwarf2_per_objfile) <allocate_per_cu,
allocate_signatured_type>: Declare new methods.
(struct dwarf2_per_cu_data) <index>: New member.
(struct dwarf2_per_objfile) <num_psymtabs>: New member.
* dwarf2/read.c (dwarf2_per_objfile::allocate_per_cu)
(dwarf2_per_objfile::allocate_signatured_type): New methods.
(create_cu_from_index_list): Use allocate_per_cu.
(create_signatured_type_table_from_index)
(create_signatured_type_table_from_debug_names)
(create_debug_type_hash_table, add_type_unit)
(read_comp_units_from_section): Use allocate_signatured_type.
---
gdb/ChangeLog | 14 +++++++++++++
gdb/dwarf2/read.c | 52 +++++++++++++++++++++++++++--------------------
gdb/dwarf2/read.h | 18 ++++++++++++++++
3 files changed, 62 insertions(+), 22 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index cb04eb19beb..281d39ad271 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2415,18 +2415,36 @@ dwarf2_per_objfile::get_tu (int index)
return this->all_type_units[index];
}

+/* See read.h. */
+
+dwarf2_per_cu_data *
+dwarf2_per_objfile::allocate_per_cu ()
+{
+ dwarf2_per_cu_data *result = OBSTACK_ZALLOC (&obstack, dwarf2_per_cu_data);
+ result->index = num_psymtabs++;
+ return result;
+}
+
+/* See read.h. */
+
+signatured_type *
+dwarf2_per_objfile::allocate_signatured_type ()
+{
+ signatured_type *result = OBSTACK_ZALLOC (&obstack, signatured_type);
+ result->per_cu.index = num_psymtabs++;
+ return result;
+}
+
/* Return a new dwarf2_per_cu_data allocated on the dwarf2_per_objfile
obstack, and constructed with the specified field values. */

static dwarf2_per_cu_data *
create_cu_from_index_list (struct dwarf2_per_objfile *dwarf2_per_objfile,
- struct dwarf2_section_info *section,
- int is_dwz,
- sect_offset sect_off, ULONGEST length)
+ struct dwarf2_section_info *section,
+ int is_dwz,
+ sect_offset sect_off, ULONGEST length)
{
- dwarf2_per_cu_data *the_cu
- = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
- struct dwarf2_per_cu_data);
+ dwarf2_per_cu_data *the_cu = dwarf2_per_objfile->allocate_per_cu ();
the_cu->sect_off = sect_off;
the_cu->length = length;
the_cu->dwarf2_per_objfile = dwarf2_per_objfile;
@@ -2517,8 +2535,7 @@ create_signatured_type_table_from_index
signature = extract_unsigned_integer (bytes + 16, 8, BFD_ENDIAN_LITTLE);
bytes += 3 * 8;

- sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
- struct signatured_type);
+ sig_type = dwarf2_per_objfile->allocate_signatured_type ();
sig_type->signature = signature;
sig_type->type_offset_in_tu = type_offset_in_tu;
sig_type->per_cu.is_debug_types = 1;
@@ -2574,8 +2591,7 @@ create_signatured_type_table_from_debug_names
section->buffer + to_underlying (sect_off),
rcuh_kind::TYPE);

- sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
- struct signatured_type);
+ sig_type = dwarf2_per_objfile->allocate_signatured_type ();
sig_type->signature = cu_header.signature;
sig_type->type_offset_in_tu = cu_header.type_cu_offset_in_tu;
sig_type->per_cu.is_debug_types = 1;
@@ -6091,8 +6107,7 @@ create_debug_type_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
/* N.B.: type_offset is not usable if this type uses a DWO file.
The real type_offset is in the DWO file. */
dwo_tu = NULL;
- sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
- struct signatured_type);
+ sig_type = dwarf2_per_objfile->allocate_signatured_type ();
sig_type->signature = header.signature;
sig_type->type_offset_in_tu = header.type_cu_offset_in_tu;
sig_type->per_cu.dwarf2_per_objfile = dwarf2_per_objfile;
@@ -6207,8 +6222,7 @@ add_type_unit (struct dwarf2_per_objfile *dwarf2_per_objfile, ULONGEST sig,
== dwarf2_per_objfile->all_type_units.capacity ())
++dwarf2_per_objfile->tu_stats.nr_all_type_units_reallocs;

- signatured_type *sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
- struct signatured_type);
+ signatured_type *sig_type = dwarf2_per_objfile->allocate_signatured_type ();

dwarf2_per_objfile->all_type_units.push_back (sig_type);
sig_type->signature = sig;
@@ -7835,16 +7849,10 @@ read_comp_units_from_section (struct dwarf2_per_objfile *dwarf2_per_objfile,

/* Save the compilation unit for later lookup. */
if (cu_header.unit_type != DW_UT_type)
- {
- this_cu = XOBNEW (&dwarf2_per_objfile->obstack,
- struct dwarf2_per_cu_data);
- memset (this_cu, 0, sizeof (*this_cu));
- }
+ this_cu = dwarf2_per_objfile->allocate_per_cu ();
else
{
- auto sig_type = XOBNEW (&dwarf2_per_objfile->obstack,
- struct signatured_type);
- memset (sig_type, 0, sizeof (*sig_type));
+ auto sig_type = dwarf2_per_objfile->allocate_signatured_type ();
sig_type->signature = cu_header.signature;
sig_type->type_offset_in_tu = cu_header.type_cu_offset_in_tu;
this_cu = &sig_type->per_cu;
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 06a0fa3a19a..5fc7f7f72e5 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -128,6 +128,17 @@ struct dwarf2_per_objfile

/* Free all cached compilation units. */
void free_cached_comp_units ();
+
+ /* A convenience function to allocate a dwarf2_per_cu_data (or
+ object holding one, using C-style derivation). The returned
+ object has its "index" field set properly. The object is
+ allocated on the dwarf2_per_objfile obstack. FIXME the index
+ here is weird since it may not (!?!?) be the same as the other
+ index */
+ dwarf2_per_cu_data *allocate_per_cu ();
+
+ signatured_type *allocate_signatured_type ();
+
private:
/* This function is mapped across the sections and remembers the
offset and size of each of the debugging sections we are
@@ -255,6 +266,10 @@ public:
/* CUs that are queued to be read. */
std::queue<dwarf2_queue_item> queue;

+ /* The total number of per_cu and signatured_type objects that have
+ been created for this reader. */
+ size_t num_psymtabs = 0;
+
/* State that cannot be shared across objfiles. This is normally
nullptr and is temporarily set to the correct value at the entry
points of the reader. */
@@ -336,6 +351,9 @@ struct dwarf2_per_cu_data
This flag is only valid if is_debug_types is true. */
unsigned int tu_read : 1;

+ /* Our index in the unshared "all_cutus" vector. */
+ unsigned index;
+
/* The section this CU/TU lives in.
If the DIE refers to a DWO file, this is always the original die,
not the DWO file. */
--
2.17.2