[PATCH v2 03/42] Add dwarf2_per_cu_data::index

Simon Marchi
2020-05-12T21:09:17Z

From: Tom Tromey <tom@tromey.com>

Currently, a dwarf2_per_cu_data can hold a link to the corresponding
expanded compunit_symtab. However, the dwarf2_per_cu_data objects are
shared across objfiles, a simple pointer won't work: each objfile
sharing the dwarf2_per_cu_data instance will have a corresponding
compunit_symtab.

Instead, this link will be stored in the dwarf2_per_objfile object
(which will contain the objfile-specific data). To enable this, we add
an index to each dwarf2_per_cu_data and signatured_type. The data
structure in the dwarf2_per_objfile will use this new index to map a
dwarf2_per_cu_data to its corresponding compunit_symtab, for this
objfile.

2020-02-21 Tom Tromey <tom@tromey.com>

* dwarf2/read.h (struct dwarf2_per_objfile) <allocate_per_cu,
allocate_signatured_type>: Declare new methods.
<m_num_psymtabs>: New member.
(struct dwarf2_per_cu_data) <index>: 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/dwarf2/read.c | 46 +++++++++++++++++++++++++++-------------------
gdb/dwarf2/read.h | 19 +++++++++++++++++++
2 files changed, 46 insertions(+), 19 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 664520fbb4c..9217f784b38 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2408,6 +2408,26 @@ 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 = m_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 = m_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. */

@@ -2417,9 +2437,7 @@ create_cu_from_index_list (struct dwarf2_per_objfile *dwarf2_per_objfile,
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;
@@ -2508,8 +2526,7 @@ 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;
@@ -2565,8 +2582,7 @@ 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;
@@ -6206,8 +6222,7 @@ 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;
@@ -6322,8 +6337,7 @@ 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;
@@ -7928,16 +7942,10 @@ 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 8dbda90aa59..bbc4f96b7cf 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -111,6 +111,16 @@ struct dwarf2_per_objfile
/* Free all cached compilation units. */
void free_cached_comp_units ();

+ /* A convenience function to allocate a dwarf2_per_cu_data. The
+ returned object has its "index" field set properly. The object
+ is allocated on the dwarf2_per_objfile obstack. */
+ dwarf2_per_cu_data *allocate_per_cu ();
+
+ /* A convenience function to allocate a signatured_type. The
+ returned object has its "index" field set properly. The object
+ is allocated on the dwarf2_per_objfile obstack. */
+ signatured_type *allocate_signatured_type ();
+
/* Return pointer to string at .debug_line_str offset as read from BUF.
BUF is assumed to be in a compilation unit described by CU_HEADER.
Return *BYTES_READ_PTR count of bytes read from BUF. */
@@ -249,6 +259,12 @@ struct dwarf2_per_objfile

/* CUs that are queued to be read. */
std::queue<dwarf2_queue_item> queue;
+
+private:
+
+ /* The total number of per_cu and signatured_type objects that have
+ been created so far for this reader. */
+ size_t m_num_psymtabs = 0;
};

/* Get the dwarf2_per_objfile associated to OBJFILE. */
@@ -322,6 +338,9 @@ 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 "symtabs" 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. */
--
2.26.2