From 7e7a35fbca94c5bfe45781067c75671ba508a0c8 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Wed, 21 Apr 2021 16:10:44 -0600 Subject: [PATCH] Shrink size of dwarf2_per_cu_data 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 * dwarf2/read.h (struct dwarf2_per_cu_data) : Now unsigned char. (struct dwarf2_per_cu_data): Rearrange. * dwarf2/comp-unit.h (struct comp_unit_head) : Now unsigned char. (struct comp_unit_head): Rearrange. * dwarf2/comp-unit.c (read_comp_unit_head): Update. --- gdb/ChangeLog | 10 ++++++++++ gdb/dwarf2/comp-unit.c | 7 ++++--- gdb/dwarf2/comp-unit.h | 15 +++++++-------- gdb/dwarf2/read.h | 26 +++++++++++++------------- 4 files changed, 34 insertions(+), 24 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 5e7971211db..20558b5a764 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2021-04-21 Tom Tromey + + * dwarf2/read.h (struct dwarf2_per_cu_data) : Now + unsigned char. + (struct dwarf2_per_cu_data): Rearrange. + * dwarf2/comp-unit.h (struct comp_unit_head) : Now + unsigned char. + (struct comp_unit_head): Rearrange. + * dwarf2/comp-unit.c (read_comp_unit_head): Update. + 2021-04-21 Tom de Vries PR build/27681 diff --git a/gdb/dwarf2/comp-unit.c b/gdb/dwarf2/comp-unit.c index ce3b55778f4..e22f2e9a91c 100644 --- a/gdb/dwarf2/comp-unit.c +++ b/gdb/dwarf2/comp-unit.c @@ -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) diff --git a/gdb/dwarf2/comp-unit.h b/gdb/dwarf2/comp-unit.h index 9568c6420df..2d3ff4d054b 100644 --- a/gdb/dwarf2/comp-unit.h +++ b/gdb/dwarf2/comp-unit.h @@ -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 { diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h index 416d8eae959..4dea86f841d 100644 --- a/gdb/dwarf2/read.h +++ b/gdb/dwarf2/read.h @@ -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 -- 2.30.2