Re: [PATCH v2 0/4] riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

Palmer Dabbelt
2023-06-14T14:49:28Z

On Tue, 23 May 2023 09:54:58 PDT (-0700), jszhang@kernel.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.