[Buildroot] [PATCH 02/11] arch: MIPS: Add config option BR2_GCC_TARGET_TUNE

From: Yann E. MORIN <yann.morin.1998@free.fr>
To: buildroot@busybox.net
Subject: [Buildroot] [PATCH 02/11] arch: MIPS: Add config option BR2_GCC_TARGET_TUNE
Date: Fri, 4 Apr 2014 00:12:15 +0200	[thread overview]
Message-ID: <20140403221215.GA25471@free.fr> (raw)
In-Reply-To: <533DD7B6.8080009@crapouillou.net>

Paul, All,

On 2014-04-03 23:50 +0200, Paul Cercueil spake thusly:
> This patch would pass the same value to --with-arch and --with-tune, unless
> you define a different value for BR2_GCC_TARGET_TUNE in your defconfig.

I see what you expect, but since BR2_GCC_TARGET_TUNE is a prompt-less
option, setting it in a defconfig will be overriden when you use that
defconfig.

For example:

    $ cat defconfig
    BR2_MIPS=y
    BR2_GCC_TARGET_ARCH="FOO-YEM"
    $ make BR2_DEFCONFIG=$(pwd)/defconfig defconfig
    [...]
    $ grep FOO .config
    [empty, nada, zilch]

So, even if you set it in your defconfig, BR2_GCC_TARGET_ARCH is lost.

Ditto for BR2_GCC_TARGET_TUNE.

> We
> use that for the Ingenic jz4740 processor, which is a mips32 processor but
> running better the code tuned for mips32r2.

Oh, I see. But that's not gonna happen with this code, I'm afraid.

Can you double-check that it is indeed working for you? Because if it
does, we have a really big bug in Kconfig (Oh, no, not one more...)

Regards,
Yann E. MORIN.

> On 03/04/2014 23:19, Yann E. MORIN wrote:
> >Paul, All,
> >
> >On 2014-04-03 23:01 +0200, Paul Cercueil spake thusly:
> >>This option is actually already used in GCC's package.
> >>
> >>This allows to optimize the toolchain for a specific MIPS processor
> >>while supporting more than one family of processors.
> >Is that really needed? man gcc says:
> >
> >     When this option is not used, GCC optimizes for the processor
> >     specified by -march.
> >
> >Since this patch would pass the same value to --with-arch and
> >--with-tune, and since this is the default of gcc, is it really
> >needed?
> >
> >Neither ACKing nor NAKing this patch. Can you explain a bit more why we
> >would want that, given the above explanations?
> >
> >Regards,
> >Yann E. MORIN.
> >
> >>Signed-Off-By: Paul Cercueil <paul@crapouillou.net>
> >>---
> >>  arch/Config.in.mips | 10 ++++++++++
> >>  1 file changed, 10 insertions(+)
> >>
> >>diff --git a/arch/Config.in.mips b/arch/Config.in.mips
> >>index 20951e0..e4160a2 100644
> >>--- a/arch/Config.in.mips
> >>+++ b/arch/Config.in.mips
> >>@@ -83,6 +83,16 @@ config BR2_GCC_TARGET_ARCH
> >>  	default "mips64"	if BR2_mips_64
> >>  	default "mips64r2"	if BR2_mips_64r2
> >>+config BR2_GCC_TARGET_TUNE
> >>+	default "mips1"		if BR2_mips_1
> >>+	default "mips2"		if BR2_mips_2
> >>+	default "mips3"		if BR2_mips_3
> >>+	default "mips4"		if BR2_mips_4
> >>+	default "mips32"	if BR2_mips_32
> >>+	default "mips32r2"	if BR2_mips_32r2
> >>+	default "mips64"	if BR2_mips_64
> >>+	default "mips64r2"	if BR2_mips_64r2
> >>+
> >>  config BR2_MIPS_OABI32
> >>  	bool
> >>  	default y		if BR2_mips || BR2_mipsel
> >>-- 
> >>1.9.0
> >>
> >>_______________________________________________
> >>buildroot mailing list
> >>buildroot at busybox.net
> >>http://lists.busybox.net/mailman/listinfo/buildroot
> 

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