[PATCH v2] lto: Don't include unused LTO archive members in output

[PATCH v2] lto: Don't include unused LTO archive members in output

[H.J. Lu]

When plugin_object_p is called by elf_link_is_defined_archive_symbol to
check if a symbol in archive is a real definition, set archive member
plugin_format to bfd_plugin_yes_unused to avoid including the unused LTO
archive members in linker output.  When plugin_object_p is called as
known used, call plugin claim_file if plugin_format is bfd_plugin_unknown
or bfd_plugin_yes_unused.

To get the proper support for archives with LTO common symbols with GCC,
the GCC fix for

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116361

is needed.

bfd/

	PR ld/32083
	* archures.c (bfd_arch_get_compatible): Treat bfd_plugin_yes_unused
	the same as bfd_plugin_yes.
	* elflink.c (elf_link_is_defined_archive_symbol): Likewise.
	* bfd.c (bfd_plugin_format): Add bfd_plugin_yes_unused.
	* plugin.c (try_claim): Try claim_file_v2 first.
	* bfd-in2.h: Regenerated.

ld/

	PR ld/32083
	* plugin.c (plugin_call_claim_file): Add an argument to return
	if LDPT_REGISTER_CLAIM_FILE_HOOK_V2 is used.
	(plugin_object_p): When KNOWN_USED is false, we call plugin
	claim_file if plugin_format is bfd_plugin_unknown and set
	plugin_format to bfd_plugin_yes_unused on LTO object.  When
	KNOWN_USED is true, we call plugin claim_file if plugin_format
	is bfd_plugin_unknown or bfd_plugin_yes_unused.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
---
 bfd/archures.c |  1 +
 bfd/bfd-in2.h  |  3 ++-
 bfd/bfd.c      |  3 ++-
 bfd/elflink.c  |  1 +
 bfd/plugin.c   | 22 ++++++++++++++++------
 ld/plugin.c    | 35 ++++++++++++++++++++++++++---------
 6 files changed, 48 insertions(+), 17 deletions(-)

diff --git a/bfd/archures.c b/bfd/archures.c
index 94118b8d2cf..c4decc59e4a 100644
--- a/bfd/archures.c
+++ b/bfd/archures.c
@@ -947,6 +947,7 @@ bfd_arch_get_compatible (const bfd *abfd,
      to assume that they know what they are doing.  */
   if (accept_unknowns
       || ubfd->plugin_format == bfd_plugin_yes
+      || ubfd->plugin_format == bfd_plugin_yes_unused
       || strcmp (bfd_get_target (ubfd), "binary") == 0)
     return kbfd->arch_info;
   return NULL;
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index e3b5a8b8522..40ec416dded 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -1947,7 +1947,8 @@ enum bfd_plugin_format
   {
     bfd_plugin_unknown = 0,
     bfd_plugin_yes = 1,
-    bfd_plugin_no = 2
+    bfd_plugin_yes_unused = 2,
+    bfd_plugin_no = 3
   };
 
 struct bfd_build_id
diff --git a/bfd/bfd.c b/bfd/bfd.c
index ae79c6490b5..a93be109f11 100644
--- a/bfd/bfd.c
+++ b/bfd/bfd.c
@@ -65,7 +65,8 @@ EXTERNAL
 .  {
 .    bfd_plugin_unknown = 0,
 .    bfd_plugin_yes = 1,
-.    bfd_plugin_no = 2
+.    bfd_plugin_yes_unused = 2,
+.    bfd_plugin_no = 3
 .  };
 .
 .struct bfd_build_id
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ed0bd71859b..9eb1122d513 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -3653,6 +3653,7 @@ elf_link_is_defined_archive_symbol (bfd * abfd, carsym * symdef)
      object file is an IR object, give linker LTO plugin a chance to
      get the correct symbol table.  */
   if (abfd->plugin_format == bfd_plugin_yes
+      || abfd->plugin_format == bfd_plugin_yes_unused
 #if BFD_SUPPORTS_PLUGINS
       || (abfd->plugin_format == bfd_plugin_unknown
 	  && bfd_link_plugin_object_p (abfd))
diff --git a/bfd/plugin.c b/bfd/plugin.c
index 026654fd9d3..f6c6fdbee69 100644
--- a/bfd/plugin.c
+++ b/bfd/plugin.c
@@ -329,13 +329,23 @@ try_claim (bfd *abfd)
   struct ld_plugin_input_file file;
 
   file.handle = abfd;
-  if (bfd_plugin_open_input (abfd, &file)
-      && current_plugin->claim_file)
+  if (bfd_plugin_open_input (abfd, &file))
     {
-      current_plugin->claim_file (&file, &claimed);
-      bfd_plugin_close_file_descriptor ((abfd->my_archive != NULL
-					 ? abfd : NULL),
-					file.fd);
+      bool claim_file_called = false;
+      if (current_plugin->claim_file_v2)
+	{
+	  current_plugin->claim_file_v2 (&file, &claimed, false);
+	  claim_file_called = true;
+	}
+      else if (current_plugin->claim_file)
+	{
+	  current_plugin->claim_file (&file, &claimed);
+	  claim_file_called = true;
+	}
+      if (claim_file_called)
+	bfd_plugin_close_file_descriptor ((abfd->my_archive != NULL
+					   ? abfd : NULL),
+					  file.fd);
     }
 
   return claimed;
diff --git a/ld/plugin.c b/ld/plugin.c
index 51c4765cc5b..34ae3a0e0d8 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -1174,10 +1174,11 @@ plugin_load_plugins (void)
 /* Call 'claim file' hook for all plugins.  */
 static int
 plugin_call_claim_file (const struct ld_plugin_input_file *file, int *claimed,
-			bool known_used)
+			int *claim_file_handler_v2, bool known_used)
 {
   plugin_t *curplug = plugins_list;
   *claimed = false;
+  *claim_file_handler_v2 = false;
   while (curplug && !*claimed)
     {
       if (curplug->claim_file_handler)
@@ -1186,7 +1187,11 @@ plugin_call_claim_file (const struct ld_plugin_input_file *file, int *claimed,
 
 	  called_plugin = curplug;
 	  if (curplug->claim_file_handler_v2)
-	    rv = (*curplug->claim_file_handler_v2) (file, claimed, known_used);
+	    {
+	      rv = (*curplug->claim_file_handler_v2) (file, claimed,
+						      known_used);
+	      *claim_file_handler_v2 = true;
+	    }
 	  else
 	    rv = (*curplug->claim_file_handler) (file, claimed);
 	  called_plugin = NULL;
@@ -1222,7 +1227,7 @@ plugin_cleanup (bfd *abfd ATTRIBUTE_UNUSED)
 static bfd_cleanup
 plugin_object_p (bfd *ibfd, bool known_used)
 {
-  int claimed;
+  int claimed, claim_file_handler_v2;
   plugin_input_file_t *input;
   struct ld_plugin_input_file file;
   bfd *abfd;
@@ -1231,12 +1236,17 @@ plugin_object_p (bfd *ibfd, bool known_used)
   if ((ibfd->flags & BFD_PLUGIN) != 0)
     return NULL;
 
-  if (ibfd->plugin_format != bfd_plugin_unknown)
+  /* When KNOWN_USED is false, we call plugin claim_file if plugin_format
+     is bfd_plugin_unknown and set plugin_format to bfd_plugin_yes_unused
+     on LTO object.  When KNOWN_USED is true, we call plugin claim_file
+     if plugin_format is bfd_plugin_unknown or bfd_plugin_yes_unused.  */
+  if (ibfd->plugin_format != bfd_plugin_unknown
+      && (!known_used || ibfd->plugin_format != bfd_plugin_yes_unused))
     {
-      if (ibfd->plugin_format == bfd_plugin_yes)
-	return plugin_cleanup;
-      else
+      if (ibfd->plugin_format == bfd_plugin_no)
 	return NULL;
+      else
+	return plugin_cleanup;
     }
 
   /* We create a dummy BFD, initially empty, to house whatever symbols
@@ -1272,7 +1282,8 @@ plugin_object_p (bfd *ibfd, bool known_used)
 
   claimed = 0;
 
-  if (plugin_call_claim_file (&file, &claimed, known_used))
+  if (plugin_call_claim_file (&file, &claimed, &claim_file_handler_v2,
+			      known_used))
     einfo (_("%F%P: %s: plugin reported error claiming file\n"),
 	   plugin_error_plugin ());
 
@@ -1292,7 +1303,13 @@ plugin_object_p (bfd *ibfd, bool known_used)
 
   if (claimed)
     {
-      ibfd->plugin_format = bfd_plugin_yes;
+      /* Set plugin_format to bfd_plugin_yes_unused if KNOWN_USED is
+	 false for plugin claim_file_v2 to avoid including the unused
+	 LTO archive members in linker output.  */
+      if (known_used || !claim_file_handler_v2)
+	ibfd->plugin_format = bfd_plugin_yes;
+      else
+	ibfd->plugin_format = bfd_plugin_yes_unused;
       ibfd->plugin_dummy_bfd = abfd;
       bfd_make_readable (abfd);
       abfd->no_export = ibfd->no_export;
-- 
2.46.0

Re: [PATCH v2] lto: Don't include unused LTO archive members in output

[Alan Modra]

That looks better, thanks.

-- 
Alan Modra