Implement LDPT_REGISTER_CLAIM_FILE_HOOK_V2 linker plugin hook [PR109128]

This is one part of the fix for PR109128, along with a corresponding
binutils's linker change.  Without this patch, what happens in the
linker, when an unused object in a .a file has offload data, is that
elf_link_is_defined_archive_symbol calls bfd_link_plugin_object_p,
which ends up calling the plugin's claim_file_handler, which then
records the object as one with offload data. That is, the linker never
decides to use the object in the first place, but use of this _p
interface (called as part of trying to decide whether to use the
object) results in the plugin deciding to use its offload data (and a
consequent mismatch in the offload data present at runtime).

The new hook allows the linker plugin to distinguish calls to
claim_file_handler that know the object is being used by the linker
(from ldmain.c:add_archive_element), from calls that don't know it's
being used by the linker (from elf_link_is_defined_archive_symbol); in
the latter case, the plugin should avoid recording the object as one
with offload data.

	PR middle-end/109128

	include/
	* plugin-api.h (ld_plugin_claim_file_handler_v2)
	(ld_plugin_register_claim_file_v2)
	(LDPT_REGISTER_CLAIM_FILE_HOOK_V2): New.
	(struct ld_plugin_tv): Add tv_register_claim_file_v2.

	lto-plugin/
	* lto-plugin.c (register_claim_file_v2): New.
	(claim_file_handler_v2): New.
	(claim_file_handler): Wrap claim_file_handler_v2.
	(onload): Handle LDPT_REGISTER_CLAIM_FILE_HOOK_V2.

1 files changed, 16 insertions, 0 deletions

diff --git a/include/plugin-api.h b/include/plugin-api.h
index 379828ba854..395d5bcc598 100644
--- a/include/plugin-api.h
+++ b/include/plugin-api.h
@@ -260,6 +260,13 @@ enum ld_plugin_status
 (*ld_plugin_claim_file_handler) (
   const struct ld_plugin_input_file *file, int *claimed);
 
+/* The plugin library's "claim file" handler, version 2.  */
+
+typedef
+enum ld_plugin_status
+(*ld_plugin_claim_file_handler_v2) (
+  const struct ld_plugin_input_file *file, int *claimed, int known_used);
+
 /* The plugin library's "all symbols read" handler.  */
 
 typedef
@@ -278,6 +285,13 @@ typedef
 enum ld_plugin_status
 (*ld_plugin_register_claim_file) (ld_plugin_claim_file_handler handler);
 
+/* The linker's interface for registering the "claim file" handler,
+   version 2.  */
+
+typedef
+enum ld_plugin_status
+(*ld_plugin_register_claim_file_v2) (ld_plugin_claim_file_handler_v2 handler);
+
 /* The linker's interface for registering the "all symbols read" handler.  */
 
 typedef
@@ -553,6 +567,7 @@ enum ld_plugin_tag
   LDPT_GET_WRAP_SYMBOLS,
   LDPT_ADD_SYMBOLS_V2,
   LDPT_GET_API_VERSION,
+  LDPT_REGISTER_CLAIM_FILE_HOOK_V2
 };
 
 /* The plugin transfer vector.  */
@@ -565,6 +580,7 @@ struct ld_plugin_tv
     int tv_val;
     const char *tv_string;
     ld_plugin_register_claim_file tv_register_claim_file;
+    ld_plugin_register_claim_file_v2 tv_register_claim_file_v2;
     ld_plugin_register_all_symbols_read tv_register_all_symbols_read;
     ld_plugin_register_cleanup tv_register_cleanup;
     ld_plugin_add_symbols tv_add_symbols;