Re: [PATCH] [RFC] arm64: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
From: Arnd Bergmann
Date: Fri Feb 26 2021 - 04:53:07 EST
On Fri, Feb 26, 2021 at 10:05 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
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On Fri, Feb 26, 2021 at 9:14 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
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> > BTW, is CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y setable for x86 (64bit)?
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> > ( Did not look or check for it. )
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> No, in mainline, HAVE_LD_DEAD_CODE_DATA_ELIMINATION is currently
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> only selected on MIPS and PowerPC. I only sent experimental patches to
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> enable it on arm64 and m68k, but have not tried booting them. If you
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> select the symbol on x86, you should see similar results.
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OK, i see:
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$ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/mips/
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arch/mips/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
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$ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/powerpc/
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arch/powerpc/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
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So, I need to add this to arch/x86/Kconfig.
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You happen to know if changes to arch/x86/kernel/vmlinux.lds.S
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(sections) are needed?
No idea. I'm still debugging a possible regression on arm64, but both
issues I found for arm64 are specific to that architecture and won't
happen on x86. It's likely that something else breaks though.
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Last question:
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The last days I see a lot of fixes touching inlining with LLVM/Clang v13-git.
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What git tag are you using?
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What are your experiences?
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Pending patches (kernel-side)?
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I use:
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$ /opt/llvm-toolchain/bin/clang --version
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dileks clang version 13.0.0 (https://github.com/llvm/llvm-project.git
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c465429f286f50e52a8d2b3b39f38344f3381cce)
This is what I have on the build box:
Ubuntu clang version
13.0.0-++20210223104451+ebca13c66504-1~exp1~20210223095200.234
Arnd