[08/22] kbuild: lto: remove duplicate dependencies from .mod files
diff mbox series

Message ID 20200624203200.78870-9-samitolvanen@google.com
State New
Headers show
Series
  • add support for Clang LTO
Related show

Commit Message

Sami Tolvanen June 24, 2020, 8:31 p.m. UTC
With LTO, llvm-nm prints out symbols for each archive member
separately, which results in a lot of duplicate dependencies in the
.mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
consists of several compilation units, the output can exceed the
default xargs command size limit and split the dependency list to
multiple lines, which results in used symbols getting trimmed.

This change removes duplicate dependencies, which will reduce the
probability of this happening and makes .mod files smaller and
easier to read.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 scripts/Makefile.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Nick Desaulniers June 24, 2020, 9:13 p.m. UTC | #1
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> With LTO, llvm-nm prints out symbols for each archive member
> separately, which results in a lot of duplicate dependencies in the
> .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
> consists of several compilation units, the output can exceed the
> default xargs command size limit and split the dependency list to
> multiple lines, which results in used symbols getting trimmed.
>
> This change removes duplicate dependencies, which will reduce the
> probability of this happening and makes .mod files smaller and
> easier to read.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  scripts/Makefile.build | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 82977350f5a6..82b465ce3ca0 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -291,7 +291,7 @@ endef
>
>  # List module undefined symbols (or empty line if not enabled)
>  ifdef CONFIG_TRIM_UNUSED_KSYMS
> -cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
> +cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | sort -u | xargs echo
>  else
>  cmd_undef_syms = echo
>  endif
> --
> 2.27.0.212.ge8ba1cc988-goog
>

Patch
diff mbox series

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 82977350f5a6..82b465ce3ca0 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -291,7 +291,7 @@  endef
 
 # List module undefined symbols (or empty line if not enabled)
 ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | sort -u | xargs echo
 else
 cmd_undef_syms = echo
 endif