linux-kernel - Re: [PATCH 3/3] MIPS: Add support for LTO

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Message-ID: <CAKwvOd=GRFJd63CN43RsCTg3_sJ3j2Ak4JNve-N+rtuksz-wMg@mail.gmail.com>
Date:   Tue, 14 Dec 2021 11:45:54 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Nathan Chancellor <nathan@...nel.org>, list@...ndingux.net,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 3/3] MIPS: Add support for LTO

On Mon, Dec 13, 2021 at 2:49 PM Paul Cercueil <paul@...pouillou.net> wrote:
>
> Allow CONFIG_LTO_CLANG to be enabled. The ThinLTO variant is not yet
> supported.
>
> While this option allows to build a LTO'd kernel, the result kernel file
> ends up being *bigger* than the non-LTO variant (about 3.6 MiB with LTO
> vs. 3.1 MiB without with a ZSTD-compressed kernel).

LGTM but I think there's more work to be done first based on my
comments on the earlier patches.

In particular, we should be able to boot the result and not have to
modify any Makefiles outside of the series to get it to link.

Good to know we're close though!  Don't give up!

>
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  arch/mips/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 0215dc1529e9..6987db8d5f64 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -22,6 +22,7 @@ config MIPS
>         select ARCH_USE_QUEUED_RWLOCKS
>         select ARCH_USE_QUEUED_SPINLOCKS
>         select ARCH_SUPPORTS_HUGETLBFS if CPU_SUPPORTS_HUGEPAGES
> +       select ARCH_SUPPORTS_LTO_CLANG if CPU_LITTLE_ENDIAN
>         select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>         select ARCH_WANT_IPC_PARSE_VERSION
>         select ARCH_WANT_LD_ORPHAN_WARN
> --
> 2.33.0
>


-- 
Thanks,
~Nick Desaulniers