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Add comp_unit_head to dwarf2_per_cu_data 

The per_cu_header_read_in function allows obtaining a filled
comp_unit_head object for a given dwarf2_per_cu_data object.  If a
dwarf2_cu object exists for this dwarf2_per_cu_data, then it just
returns a pointer to the comp_unit_head from that dwarf2_cu.  Otherwise,
it reads the header into a temporary buffer provided by the caller, and
returns a pointer to that.

Since the dwarf2_per_cu_data::cu link is going to be removed
(dwarf2_per_cu_data will become objfile-independent while dwarf2_cu
stays objfile-dependent), we cannot rely anymore on returning the header
from the dwarf2_cu object.

The not too complex solution implemented by this patch is to keep a copy
of the header in the dwarf2_per_cu_data object, independent from the
copy in dwarf2_cu.  The new copy is only used in the addr_size,
offset_size and ref_addr_size methods of dwarf2_per_cu_data.

There's nothing intrinsic to the comp_unit_head object that prevents it
to be shared between two dwarf2_cu objects (belonging to different
objfiles) representing the same CU.  In other words, I think we could
eventually get rid of the copy in dwarf2_cu to only keep the one in
dwarf2_per_cu_data.  It is not trivial, however, so I have decided not
to do it for the moment.

gdb/ChangeLog:

	* dwarf2/read.h (struct dwarf2_per_cu_data) <m_header,
	m_header_read_in>: New fields.
	<get_header>: New method.
	* dwarf2/read.c (per_cu_header_read_in): Remove.
	(dwarf2_per_cu_data::get_header): New.
	(dwarf2_per_cu_data::addr_size): Update.
	(dwarf2_per_cu_data::offset_size): Update.
	(dwarf2_per_cu_data::ref_addr_size): Update.

Change-Id: Id7541fca7562843eba110ece21c4df38d45fca23
This commit is contained in:
Simon Marchi 2020-05-27 11:14:10 -04:00 committed by Simon Marchi
parent 1b555f1747
commit 2e6a9f7959
3 changed files with 48 additions and 34 deletions
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11
gdb/ChangeLog
View File

@ -1,3 +1,14 @@
2020-05-27 Simon Marchi <simon.marchi@polymtl.ca>
* dwarf2/read.h (struct dwarf2_per_cu_data) <m_header,
m_header_read_in>: New fields.
<get_header>: New method.
* dwarf2/read.c (per_cu_header_read_in): Remove.
(dwarf2_per_cu_data::get_header): New.
(dwarf2_per_cu_data::addr_size): Update.
(dwarf2_per_cu_data::offset_size): Update.
(dwarf2_per_cu_data::ref_addr_size): Update.
2020-05-27 Simon Marchi <simon.marchi@polymtl.ca>
* dwarf2/read.c (load_cu): Return dwarf2_cu.

52
gdb/dwarf2/read.c
View File

@ -23335,26 +23335,23 @@ dwarf2_symbol_mark_computed (const struct attribute *attr, struct symbol *sym,
}
}
/* Return comp_unit_head for PER_CU, either already available in PER_CU->CU
(CU_HEADERP is unused in such case) or prepare a temporary copy at
CU_HEADERP first. */
/* See read.h. */
static const struct comp_unit_head *
per_cu_header_read_in (struct comp_unit_head *cu_headerp,
const struct dwarf2_per_cu_data *per_cu)
const comp_unit_head *
dwarf2_per_cu_data::get_header () const
{
const gdb_byte *info_ptr;
if (!m_header_read_in)
{
const gdb_byte *info_ptr
= this->section->buffer + to_underlying (this->sect_off);
if (per_cu->cu)
return &per_cu->cu->header;
memset (&m_header, 0, sizeof (m_header));
info_ptr = per_cu->section->buffer + to_underlying (per_cu->sect_off);
read_comp_unit_head (&m_header, info_ptr, this->section,
rcuh_kind::COMPILE);
}
memset (cu_headerp, 0, sizeof (*cu_headerp));
read_comp_unit_head (cu_headerp, info_ptr, per_cu->section,
rcuh_kind::COMPILE);
return cu_headerp;
return &m_header;
}
/* See read.h. */
@ -23362,12 +23359,7 @@ per_cu_header_read_in (struct comp_unit_head *cu_headerp,
int
dwarf2_per_cu_data::addr_size () const
{
struct comp_unit_head cu_header_local;
const struct comp_unit_head *cu_headerp;
cu_headerp = per_cu_header_read_in (&cu_header_local, this);
return cu_headerp->addr_size;
return this->get_header ()->addr_size;
}
/* See read.h. */
@ -23375,12 +23367,7 @@ dwarf2_per_cu_data::addr_size () const
int
dwarf2_per_cu_data::offset_size () const
{
struct comp_unit_head cu_header_local;
const struct comp_unit_head *cu_headerp;
cu_headerp = per_cu_header_read_in (&cu_header_local, this);
return cu_headerp->offset_size;
return this->get_header ()->offset_size;
}
/* See read.h. */
@ -23388,15 +23375,12 @@ dwarf2_per_cu_data::offset_size () const
int
dwarf2_per_cu_data::ref_addr_size () const
{
struct comp_unit_head cu_header_local;
const struct comp_unit_head *cu_headerp;
const comp_unit_head *header = this->get_header ();
cu_headerp = per_cu_header_read_in (&cu_header_local, this);
if (cu_headerp->version == 2)
return cu_headerp->addr_size;
if (header->version == 2)
return header->addr_size;
else
return cu_headerp->offset_size;
return header->offset_size;
}
/* See read.h. */

19
gdb/dwarf2/read.h
View File

@ -22,6 +22,7 @@
#include <queue>
#include <unordered_map>
#include "dwarf2/comp-unit.h"
#include "dwarf2/index-cache.h"
#include "dwarf2/section.h"
#include "filename-seen-cache.h"
@ -468,6 +469,21 @@ struct dwarf2_per_cu_data
/* Backlink to the owner of this. */
dwarf2_per_bfd *per_bfd;
/* DWARF header of this CU. Note that dwarf2_cu reads its own version of the
header, which may differ from this one, since it may pass rcuh_kind::TYPE
to read_comp_unit_head, whereas for dwarf2_per_cu_data we always pass
rcuh_kind::COMPILE.
Don't access this field directly, use the get_header method instead. It
should be private, but we can't make it private at the moment. */
mutable comp_unit_head m_header;
/* True if HEADER has been read in.
Don't access this field directly. It should be private, but we can't make
it private at the moment. */
mutable bool m_header_read_in;
/* When dwarf2_per_bfd::using_index is true, the 'quick' field
is active. Otherwise, the 'psymtab' field is active. */
union
@ -537,6 +553,9 @@ struct dwarf2_per_cu_data
imported_symtabs = nullptr;
}
/* Get the header of this per_cu, reading it if necessary. */
const comp_unit_head *get_header () const;
/* Return the address size given in the compilation unit header for
this CU. */
int addr_size () const;