compress .gnu.debuglto_.debug_* sections if requested

Right now, when using LTO, the intermediate object files do contain
debug info in sections starting with .gnu.debuglto_ prefix and are
not compressed when --compress-debug-sections is used.

It's a mistake and we can save quite some disk space. The following
example comes from tramp3d when the corresponding LTO sections
are compressed with zlib:

$ bloaty tramp3d-v4-v2.o -- tramp3d-v4.o
    FILE SIZE        VM SIZE
 --------------  --------------
   +83%     +10  [ = ]       0    [Unmapped]
 -68.0%    -441  [ = ]       0    .gnu.debuglto_.debug_line
 -52.3%    -759  [ = ]       0    .gnu.debuglto_.debug_line_str
 -62.4% -3.24Ki  [ = ]       0    .gnu.debuglto_.debug_abbrev
 -64.8% -1.12Mi  [ = ]       0    .gnu.debuglto_.debug_info
 -88.8% -4.58Mi  [ = ]       0    .gnu.debuglto_.debug_str
 -27.7% -5.70Mi  [ = ]       0    TOTAL

bfd/ChangeLog:

	* elf.c (_bfd_elf_make_section_from_shdr): Compress all debug
	  info sections.

gas/ChangeLog:

	* write.c (compress_debug): Compress also ".gnu.debuglto_.debug_"
	if the compression algorithm is different from zlib-gnu.

diff --git a/bfd/elf.c b/bfd/elf.c
index d496c1b2983b0ebaf9c8a6082ce42ec2a6a869d4..8cd257fc65cc0708fb9cc95449378198b10c8895 100644 (file)
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -1199,12 +1199,11 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
        }
     }
 
-  /* Compress/decompress DWARF debug sections with names: .debug_* and
-     .zdebug_*, after the section flags is set.  */
+  /* Compress/decompress DWARF debug sections with names: .debug_*,
+     .zdebug_*, .gnu.debuglto_.debug_, after the section flags is set.  */
   if ((newsect->flags & SEC_DEBUGGING) != 0
       && (newsect->flags & SEC_HAS_CONTENTS) != 0
-      && ((name[1] == 'd' && name[6] == '_')
-         || (name[1] == 'z' && name[7] == '_')))
+      && (newsect->flags & SEC_ELF_OCTETS) != 0)
     {
       enum { nothing, compress, decompress } action = nothing;
       int compression_header_size;

diff --git a/gas/write.c b/gas/write.c
index 0e49df7c03f110abf75e6f3357c5d336b74ef995..b8d5253006c98fec56e0c657723a1432d1b8fc21 100644 (file)
--- a/gas/write.c
+++ b/gas/write.c
@@ -1481,7 +1481,9 @@ compress_debug (bfd *abfd, asection *sec, void *xxx ATTRIBUTE_UNUSED)
     return;
 
   section_name = bfd_section_name (sec);
-  if (!startswith (section_name, ".debug_"))
+  if (!startswith (section_name, ".debug_")
+      && (!startswith (section_name, ".gnu.debuglto_.debug_")
+         || flag_compress_debug == COMPRESS_DEBUG_GNU_ZLIB))
     return;
 
   bool use_zstd = abfd->flags & BFD_COMPRESS_ZSTD;