linux-kernel - Re: [PATCH v2 0/4] riscv: enable HAVE_LD_DEAD_CODE_DATA

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Message-ID: <mhng-4483745f-f356-454c-8c2a-5f0e5b6c9739@palmer-ri-x1c9>
Date:   Wed, 14 Jun 2023 07:49:17 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     jszhang@...nel.org
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        Arnd Bergmann <arnd@...db.de>, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject:     Re: [PATCH v2 0/4] riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

On Tue, 23 May 2023 09:54:58 PDT (-0700), jszhang@...nel.org wrote:
> When trying to run linux with various opensource riscv core on
> resource limited FPGA platforms, for example, those FPGAs with less
> than 16MB SDRAM, I want to save mem as much as possible. One of the
> major technologies is kernel size optimizations, I found that riscv
> does not currently support HAVE_LD_DEAD_CODE_DATA_ELIMINATION, which
> passes -fdata-sections, -ffunction-sections to CFLAGS and passes the
> --gc-sections flag to the linker.
>
> This not only benefits my case on FPGA but also benefits defconfigs.
> Here are some notable improvements from enabling this with defconfigs:
>
> nommu_k210_defconfig:
>    text    data     bss     dec     hex
> 1112009  410288   59837 1582134  182436     before
>  962838  376656   51285 1390779  1538bb     after
>
> rv32_defconfig:
>    text    data     bss     dec     hex
> 8804455 2816544  290577 11911576 b5c198     before
> 8692295 2779872  288977 11761144 b375f8     after
>
> defconfig:
>    text    data     bss     dec     hex
> 9438267 3391332  485333 13314932 cb2b74     before
> 9285914 3350052  483349 13119315 c82f53     after
>
> patch1 and patch2 are clean ups.
> patch3 fixes a typo.
> patch4 finally enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION for riscv.
>
> NOTE: Zhangjin Wu firstly sent out a patch to enable dead code
> elimination for riscv several months ago, I didn't notice it until
> yesterday. Although it missed some preparations and some sections's
> keeping, he is the first person to enable this feature for riscv. To
> ease merging, this series take his patch into my entire series and
> makes patch4 authored by him after getting his ack to reflect
> the above fact.
>
> Since v1:
>   - collect Reviewed-by, Tested-by tag
>   - Make patch4 authored by Zhangjin Wu, add my co-developed-by tag
>
> Jisheng Zhang (3):
>   riscv: move options to keep entries sorted
>   riscv: vmlinux-xip.lds.S: remove .alternative section
>   vmlinux.lds.h: use correct .init.data.* section name
>
> Zhangjin Wu (1):
>   riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
>
>  arch/riscv/Kconfig                  |  13 +-
>  arch/riscv/kernel/vmlinux-xip.lds.S |   6 -
>  arch/riscv/kernel/vmlinux.lds.S     |   6 +-
>  include/asm-generic/vmlinux.lds.h   |   2 +-
>  4 files changed, 11 insertions(+), 16 deletions(-)

Do you have a base commit for this?  It's not applying to 6.4-rc1 and 
the patchwork bot couldn't find one either.