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

[Paul Cercueil <paul@crapouillou.net>]

Hi,

On 04/04/2014 00:12, Yann E. MORIN wrote:
> 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.

I confirm it works. Why is it a bug?

Paul
>
>> 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
>>>>
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