[RFC] add --enable-zstd-compressed-debug-sections configure option

diff --git a/configure b/configure
index f14e0efd675..03c26c455c7 100755
--- a/configure
+++ b/configure
@@ -792,6 +792,7 @@  enable_gold
 enable_ld
 enable_gprofng
 enable_compressed_debug_sections
+enable_zstd_compressed_debug_sections
 enable_year2038
 enable_libquadmath
 enable_libquadmath_support
@@ -1523,6 +1524,9 @@  Optional Features:
   --enable-compressed-debug-sections={all,gas,gold,ld,none}
                           Enable compressed debug sections for gas, gold or ld
                           by default
+  --enable-zstd-compressed-debug-sections
+                          Use zstd for debug info sections compression by
+                          default.
   --enable-year2038       enable support for timestamps past the year 2038
   --disable-libquadmath   do not build libquadmath directory
   --disable-libquadmath-support
@@ -3119,6 +3123,19 @@  else
 fi
 
 
+
+# Check whether --enable-zstd_compressed_debug_sections was given.
+if test "${enable_zstd_compressed_debug_sections+set}" = set; then :
+  enableval=$enable_zstd_compressed_debug_sections;
+  if test x"$enable_compressed_debug_sections" = xyes; then
+    as_fn_error $? "no program with compressed debug sections specified" "$LINENO" 5
+  fi
+
+else
+  zstd_compressed_debug_sections=
+fi
+
+
 # Configure extra directories which are host specific
 
 case "${host}" in
diff --git a/configure.ac b/configure.ac
index 0152c69292e..1728991ab8a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -422,6 +422,12 @@  AC_ARG_ENABLE(compressed_debug_sections,
   fi
 ], [enable_compressed_debug_sections=])
 
+
+AC_ARG_ENABLE(zstd_compressed_debug_sections,
+[AS_HELP_STRING([--enable-zstd-compressed-debug-sections],
+		[Use zstd for debug info sections compression by default.])],
+[], [zstd_compressed_debug_sections=])
+
 # Configure extra directories which are host specific
 
 case "${host}" in
diff --git a/gas/NEWS b/gas/NEWS
index 9a8b726b942..8f509f3aebf 100644
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -2,6 +2,9 @@ 
 
 * gas now supports --compress-debug-sections=zstd to compress
   debug sections with zstd.
+* Add a configure option --enable-zstd-compressed-debug-sections
+  in order to use zstd as a default compression algorithm when
+  --compress-debug-sections is used (or enabled by default).
 
 Changes in 2.39:
 
diff --git a/gas/as.c b/gas/as.c
index 9ce3d622f95..8c9c1d7abfd 100644
--- a/gas/as.c
+++ b/gas/as.c
@@ -226,8 +226,12 @@  print_version_id (void)
 
 #ifdef DEFAULT_FLAG_COMPRESS_DEBUG
 enum compressed_debug_section_type flag_compress_debug
+#if FLAG_ZSTD_COMPRESS_DEBUG
+  = COMPRESS_DEBUG_ZSTD;
+#else
   = COMPRESS_DEBUG_GABI_ZLIB;
 #endif
+#endif
 
 static void
 show_usage (FILE * stream)
@@ -250,21 +254,25 @@  Options:\n\
 
   fprintf (stream, _("\
   --alternate             initially turn on alternate macro syntax\n"));
-#ifdef DEFAULT_FLAG_COMPRESS_DEBUG
   fprintf (stream, _("\
   --compress-debug-sections[={none|zlib|zlib-gnu|zlib-gabi|zstd}]\n\
-                          compress DWARF debug sections using zlib [default]\n"));
+                          compress DWARF debug sections\n"));
+#ifdef DEFAULT_FLAG_COMPRESS_DEBUG
+#if FLAG_ZSTD_COMPRESS_DEBUG
   fprintf (stream, _("\
-  --nocompress-debug-sections\n\
-                          don't compress DWARF debug sections\n"));
+                            Default: zstd\n"));
 #else
   fprintf (stream, _("\
-  --compress-debug-sections[={none|zlib|zlib-gnu|zlib-gabi|zstd}]\n\
-                          compress DWARF debug sections using zlib\n"));
+                            Default: zlib-gabi\n"));
+#endif
+#else
   fprintf (stream, _("\
-  --nocompress-debug-sections\n\
-                          don't compress DWARF debug sections [default]\n"));
+                            Default: none\n"));
 #endif
+
+  fprintf (stream, _("\
+  --nocompress-debug-sections\n\
+                          don't compress DWARF debug sections\n"));
   fprintf (stream, _("\
   -D                      produce assembler debugging messages\n"));
   fprintf (stream, _("\
diff --git a/gas/config.in b/gas/config.in
index 0d1668a3eac..35b8c0cc26a 100644
--- a/gas/config.in
+++ b/gas/config.in
@@ -71,6 +71,9 @@ 
    language is requested. */
 #undef ENABLE_NLS
 
+/* Define to 1 if you want compressed debug sections with zstd by default. */
+#undef FLAG_ZSTD_COMPRESS_DEBUG
+
 /* Define to 1 if you have the declaration of `asprintf', and to 0 if you
    don't. */
 #undef HAVE_DECL_ASPRINTF
diff --git a/gas/configure b/gas/configure
index 02cded59b6a..10a095f89c7 100755
--- a/gas/configure
+++ b/gas/configure
@@ -810,6 +810,7 @@  enable_largefile
 enable_targets
 enable_checking
 enable_compressed_debug_sections
+enable_zstd_compressed_debug_sections
 enable_x86_relax_relocations
 enable_elf_stt_common
 enable_generate_build_notes
@@ -1476,6 +1477,9 @@  Optional Features:
   --enable-checking       enable run-time checks
   --enable-compressed-debug-sections={all,gas,none}
                           compress debug sections by default
+  --enable-zstd-compressed-debug-sections
+                          Use zstd for debug info sections compression by
+                          default
   --enable-x86-relax-relocations
                           generate x86 relax relocations by default
   --enable-elf-stt-common generate ELF common symbols with STT_COMMON type by
@@ -10722,7 +10726,7 @@  else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10725 "configure"
+#line 10729 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -10828,7 +10832,7 @@  else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10831 "configure"
+#line 10835 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11502,6 +11506,12 @@  if test "${enable_compressed_debug_sections+set}" = set; then :
 esac
 fi
 
+# Use zstd compression algorithm by default.
+# Check whether --enable-zstd_compressed_debug_sections was given.
+if test "${enable_zstd_compressed_debug_sections+set}" = set; then :
+  enableval=$enable_zstd_compressed_debug_sections; ac_zstd_compressed_debug_sections=$enableval
+fi
+
 # PR gas/19520
 # Decide if x86 assembler should generate relax relocations.
 ac_default_x86_relax_relocations=unset
@@ -12671,6 +12681,12 @@  $as_echo "#define DEFAULT_FLAG_COMPRESS_DEBUG 1" >>confdefs.h
 
 fi
 
+if test x$ac_zstd_compressed_debug_sections = xyes ; then
+
+$as_echo "#define FLAG_ZSTD_COMPRESS_DEBUG 1" >>confdefs.h
+
+fi
+
 # Turn on all targets if possible
 if test ${all_targets} = "yes"; then
   case ${target_cpu_type} in
diff --git a/gas/configure.ac b/gas/configure.ac
index e6f3298cb3e..b46acfe9033 100644
--- a/gas/configure.ac
+++ b/gas/configure.ac
@@ -76,6 +76,12 @@  AC_ARG_ENABLE(compressed_debug_sections,
   *)   ac_default_compressed_debug_sections=unset ;;
 esac])dnl
 
+# Use zstd compression algorithm by default.
+AC_ARG_ENABLE(zstd_compressed_debug_sections,
+	      AS_HELP_STRING([--enable-zstd-compressed-debug-sections],
+	      [Use zstd for debug info sections compression by default]),
+[ac_zstd_compressed_debug_sections=$enableval])dnl
+
 # PR gas/19520
 # Decide if x86 assembler should generate relax relocations.
 ac_default_x86_relax_relocations=unset
@@ -755,6 +761,10 @@  if test x$ac_default_compressed_debug_sections = xyes ; then
   AC_DEFINE(DEFAULT_FLAG_COMPRESS_DEBUG, 1, [Define if you want compressed debug sections by default.])
 fi
 
+if test x$ac_zstd_compressed_debug_sections = xyes ; then
+  AC_DEFINE(FLAG_ZSTD_COMPRESS_DEBUG, 1, [Define to 1 if you want compressed debug sections with zstd by default.])
+fi
+
 # Turn on all targets if possible
 if test ${all_targets} = "yes"; then
   case ${target_cpu_type} in
diff --git a/ld/NEWS b/ld/NEWS
index dfe2690d9f2..82619b3625e 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -2,6 +2,9 @@ 
 
 * ld now supports zstd compressed debug sections.  The new option
   --compress-debug-sections=zstd compresses debug sections with zstd.
+* Add a configure option --enable-zstd-compressed-debug-sections
+  in order to use zstd as a default compression algorithm when
+  --compress-debug-sections is used (or enabled by default).
 
 Changes in 2.39:
 
diff --git a/ld/config.in b/ld/config.in
index 3916740eee4..93ec9cee232 100644
--- a/ld/config.in
+++ b/ld/config.in
@@ -58,6 +58,9 @@ 
 /* Additional extension a shared object might have. */
 #undef EXTRA_SHLIB_EXTENSION
 
+/* Define to 1 if you want compressed debug sections with zstd by default. */
+#undef FLAG_ZSTD_COMPRESS_DEBUG
+
 /* Define to choose default GOT handling scheme */
 #undef GOT_HANDLING_DEFAULT
 
diff --git a/ld/configure b/ld/configure
index 9dd3ed5f1e7..fa21b5de04e 100755
--- a/ld/configure
+++ b/ld/configure
@@ -841,6 +841,7 @@  with_sysroot
 enable_gold
 enable_got
 enable_compressed_debug_sections
+enable_zstd_compressed_debug_sections
 enable_new_dtags
 enable_relro
 enable_textrel_check
@@ -1524,6 +1525,9 @@  Optional Features:
                           multigot)
   --enable-compressed-debug-sections={all,ld,none}
                           compress debug sections by default]
+  --enable-zstd-compressed-debug-sections
+                          Use zstd for debug info sections compression by
+                          default
   --enable-new-dtags      set DT_RUNPATH instead of DT_RPATH by default]
   --enable-relro          enable -z relro in ELF linker by default
   --enable-textrel-check=[yes|no|warning|error]
@@ -11620,7 +11624,7 @@  else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11623 "configure"
+#line 11627 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11726,7 +11730,7 @@  else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11729 "configure"
+#line 11733 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15544,6 +15548,12 @@  if test "${enable_compressed_debug_sections+set}" = set; then :
 esac
 fi
 
+# Use zstd compression algorithm by default.
+# Check whether --enable-zstd_compressed_debug_sections was given.
+if test "${enable_zstd_compressed_debug_sections+set}" = set; then :
+  enableval=$enable_zstd_compressed_debug_sections; ac_zstd_compressed_debug_sections=$enableval
+fi
+
 # Decide setting DT_RUNPATH instead of DT_RPATH by default
 ac_default_new_dtags=unset
 # Provide a configure time option to override our default.
@@ -17340,6 +17350,12 @@  $as_echo "#define DEFAULT_FLAG_COMPRESS_DEBUG 1" >>confdefs.h
 
 fi
 
+if test x$ac_zstd_compressed_debug_sections = xyes ; then
+
+$as_echo "#define FLAG_ZSTD_COMPRESS_DEBUG 1" >>confdefs.h
+
+fi
+
 if test "${ac_default_new_dtags}" = unset; then
   ac_default_new_dtags=0
 fi
diff --git a/ld/configure.ac b/ld/configure.ac
index f1b2f9897f8..729f07343aa 100644
--- a/ld/configure.ac
+++ b/ld/configure.ac
@@ -163,6 +163,12 @@  AC_ARG_ENABLE(compressed_debug_sections,
   ,no, | ,none,)  ac_default_compressed_debug_sections=no ;;
 esac])dnl
 
+# Use zstd compression algorithm by default.
+AC_ARG_ENABLE(zstd_compressed_debug_sections,
+	      AS_HELP_STRING([--enable-zstd-compressed-debug-sections],
+	      [Use zstd for debug info sections compression by default]),
+[ac_zstd_compressed_debug_sections=$enableval])dnl
+
 # Decide setting DT_RUNPATH instead of DT_RPATH by default
 ac_default_new_dtags=unset
 # Provide a configure time option to override our default.
@@ -510,6 +516,10 @@  if test x$ac_default_compressed_debug_sections = xyes ; then
   AC_DEFINE(DEFAULT_FLAG_COMPRESS_DEBUG, 1, [Define if you want compressed debug sections by default.])
 fi
 
+if test x$ac_zstd_compressed_debug_sections = xyes ; then
+  AC_DEFINE(FLAG_ZSTD_COMPRESS_DEBUG, 1, [Define to 1 if you want compressed debug sections with zstd by default.])
+fi
+
 if test "${ac_default_new_dtags}" = unset; then
   ac_default_new_dtags=0
 fi
diff --git a/ld/ldmain.c b/ld/ldmain.c
index d63002c994a..d0ad5f3d797 100644
--- a/ld/ldmain.c
+++ b/ld/ldmain.c
@@ -352,8 +352,12 @@  main (int argc, char **argv)
   link_info.spare_dynamic_tags = 5;
   link_info.path_separator = ':';
 #ifdef DEFAULT_FLAG_COMPRESS_DEBUG
+#if FLAG_ZSTD_COMPRESS_DEBUG
+  link_info.compress_debug = COMPRESS_DEBUG_ZSTD;
+#else
   link_info.compress_debug = COMPRESS_DEBUG_GABI_ZLIB;
 #endif
+#endif
 #ifdef DEFAULT_NEW_DTAGS
   link_info.new_dtags = DEFAULT_NEW_DTAGS;
 #endif
diff --git a/ld/lexsup.c b/ld/lexsup.c
index 299371fb775..c46f1f822a8 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -2149,8 +2149,13 @@  elf_static_list_options (FILE *file)
   --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi|zstd]\n\
 			      Compress DWARF debug sections\n"));
 #ifdef DEFAULT_FLAG_COMPRESS_DEBUG
+#if FLAG_ZSTD_COMPRESS_DEBUG
+  fprintf (file, _("\
+                                Default: zstd\n"));
+#else
   fprintf (file, _("\
                                 Default: zlib-gabi\n"));
+#endif
 #else
   fprintf (file, _("\
                                 Default: none\n"));