Add SHF_COMPRESSED support to gas and objcopy

This patch adds --compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}
options to gas and objcopy for ELF files. They control how DWARF debug
sections are compressed.  --compress-debug-sections=none is equivalent to
--nocompress-debug-sections.  --compress-debug-sections=zlib and
--compress-debug-sections=zlib-gnu are equivalent to
--compress-debug-sections.  --compress-debug-sections=zlib-gabi compresses
DWARF debug sections with SHF_COMPRESSED from the ELF ABI.  No linker
changes are required to support SHF_COMPRESSED.

bfd/

	* archive.c (_bfd_get_elt_at_filepos): Also copy BFD_COMPRESS_GABI
	bit.
	* bfd.c (bfd::flags): Increase size to 18 bits.
	(BFD_COMPRESS_GABI): New.
	(BFD_FLAGS_SAVED): Add BFD_COMPRESS_GABI.
	(BFD_FLAGS_FOR_BFD_USE_MASK): Likewise.
	(bfd_update_compression_header): New fuction.
	(bfd_check_compression_header): Likewise.
	(bfd_get_compression_header_size): Likewise.
	(bfd_is_section_compressed_with_header): Likewise.
	* compress.c (MAX_COMPRESSION_HEADER_SIZE): New.
	(bfd_compress_section_contents): Return the uncompressed size if
	the full section contents is compressed successfully.  Support
	converting from/to .zdebug* sections.
	(bfd_get_full_section_contents): Call
	bfd_get_compression_header_size to get compression header size.
	(bfd_is_section_compressed): Renamed to ...
	(bfd_is_section_compressed_with_header): This.  Add a pointer
	argument to return compression header size.
	(bfd_is_section_compressed): Use it.
	(bfd_init_section_decompress_status): Call
	bfd_get_compression_header_size to get compression header size.
	Return FALSE if uncompressed section size is 0.
	* elf.c (_bfd_elf_make_section_from_shdr): Support converting
	from/to .zdebug* sections.
	* bfd-in2.h: Regenerated.

binutils/

	* objcopy.c (do_debug_sections): Add compress_zlib,
	compress_gnu_zlib and compress_gabi_zlib.
	(copy_options): Use optional_argument on compress-debug-sections.
	(copy_usage): Update --compress-debug-sections.
	(copy_file): Handle compress_zlib, compress_gnu_zlib and
	compress_gabi_zlib.
	(copy_main): Handle
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* doc/binutils.texi: Document
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.

binutils/testsuite/

	* compress.exp: Add tests for
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* binutils-all/dw2-3.rS: New file.
	* binutils-all/dw2-3.rt: Likewise.
	* binutils-all/libdw2-compressedgabi.out: Likewise.

gas/

	* as.c (show_usage): Update --compress-debug-sections.
	(std_longopts): Use optional_argument on compress-debug-sections.
	(parse_args): Handle
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* as.h (compressed_debug_section_type): New.
	(flag_compress_debug): Change type to compressed_debug_section_type.
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* write.c (compress_debug): Set BFD_COMPRESS_GABI for
	--compress-debug-sections=zlib-gabi.  Call
	bfd_get_compression_header_size to get compression header size.
	Don't rename section name for --compress-debug-sections=zlib-gabi.
	* config/tc-i386.c (compressed_debug_section_type): Set to
	COMPRESS_DEBUG_ZLIB.
	* doc/as.texinfo: Document
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.

gas/testsuite/

	* gas/i386/dw2-compressed-1.d: New file.
	* gas/i386/dw2-compressed-2.d: Likewise.
	* gas/i386/dw2-compressed-3.d: Likewise.
	* gas/i386/x86-64-dw2-compressed-2.d: Likewise.
	* gas/i386/i386.exp: Run dw2-compressed-2, dw2-compressed-1,
	dw2-compressed-3 and x86-64-dw2-compressed-2.

ld/testsuite/

	* ld-elf/compress.exp: Add a test for
	--compress-debug-sections=zlib-gabi.
	(build_tests): Add 2 tests for --compress-debug-sections=zlib-gabi.
	(run_tests): Likewise.
	Verify linker output with zlib-gabi compressed debug input.
	* ld-elf/compressed1a.d: New file.
	* ld-elf/compressed1b.d: Likewise.
	* ld-elf/compressed1c.d: Likewise.

bfd/elf.c

@@ -1042,26 +1042,35 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
     {
       enum { nothing, compress, decompress } action = nothing;
       char *new_name;
+      int compression_header_size;
+      bfd_boolean compressed
+	= bfd_is_section_compressed_with_header (abfd, newsect,
+						 &compression_header_size);
 
-      if (bfd_is_section_compressed (abfd, newsect))
+      if (compressed)
 	{
 	  /* Compressed section.  Check if we should decompress.  */
 	  if ((abfd->flags & BFD_DECOMPRESS))
 	    action = decompress;
 	}
-      else
+
+      /* Compress the uncompressed section or convert from/to .zdebug*
+	 section.  Check if we should compress.  */
+      if (action == nothing)
 	{
-	  /* Normal section.  Check if we should compress.  */
-	  if ((abfd->flags & BFD_COMPRESS) && newsect->size != 0)
+	  if (newsect->size != 0
+	      && (abfd->flags & BFD_COMPRESS)
+	      && compression_header_size >= 0
+	      && (!compressed
+		  || ((compression_header_size > 0)
+		      != ((abfd->flags & BFD_COMPRESS_GABI) != 0))))
 	    action = compress;
+	  else
+	    return TRUE;
 	}
 
-      new_name = NULL;
-      switch (action)
+      if (action == compress)
 	{
-	case nothing:
-	  break;
-	case compress:
 	  if (!bfd_init_section_compress_status (abfd, newsect))
 	    {
 	      (*_bfd_error_handler)
@@ -1069,25 +1078,9 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 		 abfd, name);
 	      return FALSE;
 	    }
-	  /* PR binutils/18087: Compression does not always make a section
-	     smaller.  So only rename the section when compression has
-	     actually taken place.  */
-	  if (newsect->compress_status == COMPRESS_SECTION_DONE)
-	    {
-	      if (name[1] != 'z')
-		{
-		  unsigned int len = strlen (name);
-
-		  new_name = bfd_alloc (abfd, len + 2);
-		  if (new_name == NULL)
-		    return FALSE;
-		  new_name[0] = '.';
-		  new_name[1] = 'z';
-		  memcpy (new_name + 2, name + 1, len);
-		}
-	    }
-	  break;
-	case decompress:
+	}
+      else
+	{
 	  if (!bfd_init_section_decompress_status (abfd, newsect))
 	    {
 	      (*_bfd_error_handler)
@@ -1095,6 +1088,13 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 		 abfd, name);
 	      return FALSE;
 	    }
+	}
+
+      new_name = NULL;
+      if (action == decompress
+	   || (action == compress
+	       && (abfd->flags & BFD_COMPRESS_GABI) != 0))
+	{
 	  if (name[1] == 'z')
 	    {
 	      unsigned int len = strlen (name);
@@ -1105,7 +1105,24 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 	      new_name[0] = '.';
 	      memcpy (new_name + 1, name + 2, len - 1);
 	    }
-	  break;
+	}
+      else if (action == compress
+	       && newsect->compress_status == COMPRESS_SECTION_DONE)
+	{
+	  /* PR binutils/18087: Compression does not always make a section
+	     smaller.  So only rename the section when compression has
+	     actually taken place.  */
+	  if (name[1] != 'z')
+	    {
+	      unsigned int len = strlen (name);
+
+	      new_name = bfd_alloc (abfd, len + 2);
+	      if (new_name == NULL)
+		return FALSE;
+	      new_name[0] = '.';
+	      new_name[1] = 'z';
+	      memcpy (new_name + 2, name + 1, len);
+	    }
 	}
       if (new_name != NULL)
 	bfd_rename_section (abfd, newsect, new_name);