linux-kernel - Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

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Date:   Tue, 13 Nov 2018 10:47:27 +0100
From:   Richard Weinberger <richard@....at>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

Am Montag, 12. November 2018, 03:35:19 CET schrieb Masahiro Yamada:
> Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
> bumped the minimum GCC version to 4.6 for all architectures.
> 
> '$(call cc-option,-fno-unit-at-a-time)' is now dead code since
> '$(cc-version) -lt 0400' is always false.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  arch/x86/Makefile.um | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> index 91085a0..577976b 100644
> --- a/arch/x86/Makefile.um
> +++ b/arch/x86/Makefile.um
> @@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
>  # an unresolved reference.
>  cflags-y += -ffreestanding
>  
> -# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
> -# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
> -# 4.3.0 needs -funit-at-a-time for extern inline functions.
> -KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
> -			echo $(call cc-option,-fno-unit-at-a-time); \
> -			else echo $(call cc-option,-funit-at-a-time); fi ;)
> +# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)

Acked-by: Richard Weinberger <richard@....at>

Thanks,
//richard