linux-kernel - Re: [RFC] [PATCH] arch: x86: change GCC optimisation target from atom to bonnell

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Date:   Mon, 10 Oct 2016 17:11:00 -0700
From:   hpa@...or.com
To:     Rui Salvaterra <rsalvaterra@...il.com>, tglx@...utronix.de,
        mingo@...hat.com
CC:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [PATCH] arch: x86: change GCC optimisation target from atom to bonnell

On October 10, 2016 2:45:38 PM PDT, Rui Salvaterra <rsalvaterra@...il.com> wrote:
>Hi, Thomas, Ingo, Peter,
>
>(Sending as RFC, since I don't know if this patch is acceptable.)
>
>The GCC team has deprecated atom as a march/mtune target since almost
>three
>years ago, according to this mailing list thread [1], in favour of
>specific
>microarchitecture names (bonnell, silvermont). This patch changes the
>Atom
>optimisation target in the kernel to bonnell, as it was originally
>intended.
>
>Tested on an x86-64 Atom 330 machine. No functional changes.
>
>[1] https://gcc.gnu.org/ml/gcc-patches/2013-12/msg01805.html
>
>Signed-off-by: Rui Salvaterra <rsalvaterra@...il.com>
>---
> arch/x86/Makefile        | 4 ++--
> arch/x86/Makefile_32.cpu | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>index 2d44933..b7d615f 100644
>--- a/arch/x86/Makefile
>+++ b/arch/x86/Makefile
>@@ -109,8 +109,8 @@ else
> 
>         cflags-$(CONFIG_MCORE2) += \
>        $(call cc-option,-march=core2,$(call cc-option,-mtune=generic))
>-	cflags-$(CONFIG_MATOM) += $(call cc-option,-march=atom) \
>-		$(call cc-option,-mtune=atom,$(call cc-option,-mtune=generic))
>+	cflags-$(CONFIG_MATOM) += $(call cc-option,-march=bonnell) \
>+		$(call cc-option,-mtune=bonnell,$(call cc-option,-mtune=generic))
>       cflags-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=generic)
>         KBUILD_CFLAGS += $(cflags-y)
> 
>diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu
>index 6647ed4..d66e5e3 100644
>--- a/arch/x86/Makefile_32.cpu
>+++ b/arch/x86/Makefile_32.cpu
>@@ -32,8 +32,8 @@ cflags-$(CONFIG_MCYRIXIII)	+= $(call
>cc-option,-march=c3,-march=i486) $(align)-f
> cflags-$(CONFIG_MVIAC3_2)	+= $(call cc-option,-march=c3-2,-march=i686)
> cflags-$(CONFIG_MVIAC7)		+= -march=i686
> cflags-$(CONFIG_MCORE2)		+= -march=i686 $(call tune,core2)
>-cflags-$(CONFIG_MATOM)		+= $(call cc-option,-march=atom,$(call
>cc-option,-march=core2,-march=i686)) \
>-	$(call cc-option,-mtune=atom,$(call cc-option,-mtune=generic))
>+cflags-$(CONFIG_MATOM)		+= $(call cc-option,-march=bonnell,$(call
>cc-option,-march=core2,-march=i686)) \
>+	$(call cc-option,-mtune=bonnell,$(call cc-option,-mtune=generic))
> 
> # AMD Elan support
> cflags-$(CONFIG_MELAN)		+= -march=i486

This just breaks backwards compatibility with older gcc.  If you want to add a comment that's fine, though.

Nacked-by: hpa
-- 
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