On Wed, Aug 14, 2024 at 3:15 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> 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 including the unused LTO archive
> members in linker output. To get the proper support for archives with
> LTO common symbols, the linker fix for
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=32083
>
> is required.
>
> PR lto/116361
> * lto-plugin.c (claim_file_handler_v2): Include the LTO object
> only if it is known to be used for link output.
>
> Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
> ---
> lto-plugin/lto-plugin.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c
> index 152648338b9..2d2bfa60d42 100644
> --- a/lto-plugin/lto-plugin.c
> +++ b/lto-plugin/lto-plugin.c
> @@ -1286,13 +1286,17 @@ claim_file_handler_v2 (const struct
> ld_plugin_input_file *file, int *claimed,
> lto_file.symtab.syms);
> check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
We are still doing add_symbols, shouldn't what we do depend on what
that does? The
function comment says
If KNOWN_USED, the object is known by the linker
to be used, or an older API version is in use that does not provide that
information; otherwise, the linker is only determining whether this is
a plugin object and it should not be registered as having offload data if
not claimed by the plugin.
where do you check "if not claimed by the plugin"? I think this at least needs
clarification with the change.
> - LOCK_SECTION;
> - num_claimed_files++;
> - claimed_files =
> - xrealloc (claimed_files,
> - num_claimed_files * sizeof (struct plugin_file_info));
> - claimed_files[num_claimed_files - 1] = lto_file;
> - UNLOCK_SECTION;
> + /* Include it only if it is known to be used for link output. */
> + if (known_used)
> + {
> + LOCK_SECTION;
> + num_claimed_files++;
> + claimed_files =
> + xrealloc (claimed_files,
> + num_claimed_files * sizeof (struct plugin_file_info));
> + claimed_files[num_claimed_files - 1] = lto_file;
> + UNLOCK_SECTION;
> + }
>
> *claimed = 1;
> }
> @@ -1313,7 +1317,7 @@ claim_file_handler_v2 (const struct
> ld_plugin_input_file *file, int *claimed,
> if (*claimed && !obj.offload && offload_files_last_lto == NULL)
> offload_files_last_lto = offload_files_last;
>
> - if (obj.offload && (known_used || obj.found > 0))
> + if (obj.offload && known_used && obj.found > 0)
> {
> /* Add file to the list. The order must be exactly the same as the
> final
> order after recompilation and linking, otherwise host and target
> tables
> --
> 2.46.0
>
