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SubjectRe: [PATCH 4/4] Makefile: lld: set -O2 linker flag when linking with LLD
On Thu, Feb 07, 2019 at 02:01:52PM -0800, ndesaulniers@google.com wrote:
> -O2 enables tail merging of string table strings.
>
> For arm64:
> 0.34% size improvement with lld -O2 over lld for vmlinux.
> 3.30% size improvement with lld -O2 over lld for Image.lz4-dtb.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/343
> Suggested-by: Rui Ueyama <ruiu@google.com>
> Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> Makefile | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 6307c17259ea..c07208ec49d4 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -718,6 +718,10 @@ else
> KBUILD_CFLAGS += -Wno-unused-but-set-variable
> endif
>
> +ifdef CONFIG_LD_IS_LLD
> +KBUILD_LDFLAGS += -O2
> +endif
> +
> KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
> ifdef CONFIG_FRAME_POINTER
> KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
> --
> 2.20.1.791.gb4d0f1c61a-goog
>

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