[binutils-gdb] compress .gnu.debuglto_.debug_* sections if requested

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=7afbac7ddd7299491a88341149bc72b38173447a

commit 7afbac7ddd7299491a88341149bc72b38173447a
Author: Martin Liska <mliska@suse.cz>
Date:   Thu Sep 29 14:10:30 2022 +0200

    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:
---
 bfd/elf.c   | 7 +++----
 gas/write.c | 4 +++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/bfd/elf.c b/bfd/elf.c
index d496c1b2983..8cd257fc65c 100644
--- 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 0e49df7c03f..b8d5253006c 100644
--- 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;