linux-kernel - Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

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Message-ID: <20181112030134.GA39035@gmail.com>
Date:   Mon, 12 Nov 2018 04:01:34 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        Richard Weinberger <richard@...ma-star.at>,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler
 option entirely


* Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:

> GCC 4.6 manual says:
> 
> -funit-at-a-time
>   This option is left for compatibility reasons. -funit-at-a-time has
>   no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
>   and -fno-section-anchors.
>   Enabled by default.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  arch/powerpc/Makefile | 4 ----
>  arch/x86/Makefile     | 4 ----
>  arch/x86/Makefile.um  | 5 -----
>  3 files changed, 13 deletions(-)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 88398fd..3508049 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -130,10 +130,6 @@ else
>  
>          KBUILD_CFLAGS += -mno-red-zone
>          KBUILD_CFLAGS += -mcmodel=kernel
> -
> -        # -funit-at-a-time shrinks the kernel .text considerably
> -        # unfortunately it makes reading oopses harder.
> -        KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
>  endif
>  
>  ifdef CONFIG_X86_X32
> diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> index 577976b..1db7913 100644
> --- a/arch/x86/Makefile.um
> +++ b/arch/x86/Makefile.um
> @@ -26,9 +26,6 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
>  # an unresolved reference.
>  cflags-y += -ffreestanding
>  
> -# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> -
>  KBUILD_CFLAGS += $(cflags-y)
>  
>  else
> @@ -50,6 +47,4 @@ ELF_FORMAT := elf64-x86-64
>  LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
>  LINK-y += -m64
>  
> -# Do unit-at-a-time unconditionally on x86_64, following the host
> -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
>  endif

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo