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Shrink size of dwarf2_per_cu_data

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I noticed some holes in struct dwarf2_per_cu_data.  This patch
rearranges the type slightly, and shrinks the size of some fields.
This reduces it from 136 bytes to 112 bytes (on x86-64).

I also reduced the size of the DWARF "version" fields in a couple of
spots.  It seemed needless to use a short to hold a value that ranges
from 2 to 5, and this also helped the goal of shrinking
dwarf2_per_cu_data.

2021-04-21  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.h (struct dwarf2_per_cu_data) <dwarf_version>: Now
	unsigned char.
	(struct dwarf2_per_cu_data): Rearrange.
	* dwarf2/comp-unit.h (struct comp_unit_head) <version>: Now
	unsigned char.
	(struct comp_unit_head): Rearrange.
	* dwarf2/comp-unit.c (read_comp_unit_head): Update.
This commit is contained in:
Tom Tromey 2021-04-21 16:10:44 -06:00
parent 6d5702a5eb
commit 7e7a35fbca
4 changed files with 34 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@ -1,3 +1,13 @@
2021-04-21 Tom Tromey <tom@tromey.com>
* dwarf2/read.h (struct dwarf2_per_cu_data) <dwarf_version>: Now
unsigned char.
(struct dwarf2_per_cu_data): Rearrange.
* dwarf2/comp-unit.h (struct comp_unit_head) <version>: Now
unsigned char.
(struct comp_unit_head): Rearrange.
* dwarf2/comp-unit.c (read_comp_unit_head): Update.
2021-04-21 Tom de Vries <tdevries@suse.de>
PR build/27681

7
gdb/dwarf2/comp-unit.c
View File

@ -48,11 +48,12 @@ read_comp_unit_head (struct comp_unit_head *cu_header,
cu_header->initial_length_size = bytes_read;
cu_header->offset_size = (bytes_read == 4) ? 4 : 8;
info_ptr += bytes_read;
cu_header->version = read_2_bytes (abfd, info_ptr);
if (cu_header->version < 2 || cu_header->version > 5)
unsigned version = read_2_bytes (abfd, info_ptr);
if (version < 2 || version > 5)
error (_("Dwarf Error: wrong version in compilation unit header "
"(is %d, should be 2, 3, 4 or 5) [in module %s]"),
cu_header->version, filename);
version, filename);
cu_header->version = version;
info_ptr += 2;
if (cu_header->version < 5)
switch (section_kind)

15
gdb/dwarf2/comp-unit.h
View File

@ -35,7 +35,7 @@
struct comp_unit_head
{
unsigned int length;
short version;
unsigned char version;
unsigned char addr_size;
unsigned char signed_addr_p;
sect_offset abbrev_sect_off;
@ -48,14 +48,16 @@ struct comp_unit_head
enum dwarf_unit_type unit_type;
/* Offset to the first byte of this compilation unit header in the
.debug_info section, for resolving relative reference dies. */
sect_offset sect_off;
/* Offset to first die in this cu from the start of the cu.
This will be the first byte following the compilation unit header. */
cu_offset first_die_cu_offset;
/* Offset to the first byte of this compilation unit header in the
.debug_info section, for resolving relative reference dies. */
sect_offset sect_off;
/* For types, offset in the type's DIE of the type defined by this TU. */
cu_offset type_cu_offset_in_tu;
/* 64-bit signature of this unit. For type units, it denotes the signature of
the type (DW_UT_type in DWARF 4, additionally DW_UT_split_type in DWARF 5).
@ -63,9 +65,6 @@ struct comp_unit_head
DW_UT_skeleton or DW_UT_split_compile. */
ULONGEST signature;
/* For types, offset in the type's DIE of the type defined by this TU. */
cu_offset type_cu_offset_in_tu;
/* Return the total length of the CU described by this header. */
unsigned int get_length () const
{

26
gdb/dwarf2/read.h
View File

@ -438,7 +438,7 @@ struct dwarf2_per_cu_data
unsigned int length;
/* DWARF standard version this data has been read from (such as 4 or 5). */
short dwarf_version;
unsigned char dwarf_version;
/* Flag indicating this compilation unit will be read in before
any of the current compilation units are processed. */
@ -474,6 +474,18 @@ struct dwarf2_per_cu_data
This flag is only valid if is_debug_types is true. */
unsigned int tu_read : 1;
/* 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 : 1;
/* The unit type of this CU. */
ENUM_BITFIELD (dwarf_unit_type) unit_type : 8;
/* The language of this CU. */
ENUM_BITFIELD (language) lang : LANGUAGE_BITS;
/* Our index in the unshared "symtabs" vector. */
unsigned index;
@ -482,12 +494,6 @@ struct dwarf2_per_cu_data
not the DWO file. */
struct dwarf2_section_info *section;
/* The unit type of this CU. */
enum dwarf_unit_type unit_type;
/* The language of this CU. */
enum language lang;
/* Backlink to the owner of this. */
dwarf2_per_bfd *per_bfd;
@ -500,12 +506,6 @@ struct dwarf2_per_cu_data
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