[OE-core] [PATCH 3/3] Add basic PowerPC core tune config

[Kumar Gala]

On Jul 26, 2011, at 11:18 AM, Richard Purdie wrote:

> On Tue, 2011-07-26 at 10:22 -0500, Kumar Gala wrote:
>> On Jul 26, 2011, at 8:59 AM, Richard Purdie wrote:
>> 
>>> On Tue, 2011-07-26 at 08:47 -0500, Kumar Gala wrote:
>>>> On Jul 26, 2011, at 7:44 AM, Richard Purdie wrote:
>>>> 
>>>>> Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
>>>>> ---
>>>>> meta/conf/machine/include/powerpc/arch-powerpc.inc |   45 +++++++++++++++++++-
>>>>> meta/conf/machine/include/tune-ppc603e.inc         |   12 ++++-
>>>>> meta/conf/machine/include/tune-ppce300c2.inc       |   12 ++++-
>>>>> meta/conf/machine/include/tune-ppce500.inc         |   13 ++++--
>>>>> meta/conf/machine/include/tune-ppce500mc.inc       |   12 ++++-
>>>>> meta/conf/machine/include/tune-ppce500v2.inc       |   12 ++++-
>>>>> 6 files changed, 88 insertions(+), 18 deletions(-)
>>>> 
>>>> One thing I'm wondering about as we do this is the ability to pass
>>>> --with-cpu to gcc & [e]glibc configure to pickup proper optimized cfgs
>>>> & libs for a given target.
>>> 
>>> As far as I can tell, gcc 4.x has no --with-cpu option. We pass the
>>> correct march and mtune options to the compiler at runtime through
>>> CFLAGS and friends.
>> 
>> Hmm, gcc still supports this:
>> 
>> http://gcc.gnu.org/install/configure.html
>> 
>> --with-cpu=cpu
>> --with-cpu-32=cpu
>> --with-cpu-64=cpu
>> Specify which cpu variant the compiler should generate code for by default. cpu will be used as the default value of the -mcpu= switch. This option is only supported on some targets, including ARM, i386, M68k, PowerPC, and SPARC. The --with-cpu-32 and --with-cpu-64 options specify separate default CPUs for 32-bit and 64-bit modes; these options are only supported for i386, x86-64 and PowerPC. 
>> 
>> http://gcc.gnu.org/install/specific.html
>> 
>> powerpc-*-*
>> You can specify a default version for the -mcpu=cpu_type switch by using the configure option --with-cpu-cpu_type.
> 
> I couldn't find that looking at the configure script :/.
> 
> Anyhow, according to that page, its to "Specify which cpu variant the
> compiler should generate code for by default. cpu will be used as the
> default value of the -mcpu= switch". Since we always specify -mcpu when
> needed, I don't believe this is an issue for us as far as the build
> system goes.
> 
> If you're talking about the gcc we build for the target, we should
> really encode all the cpu/tune options in there, not just part of the
> config so again, I don't think its appropriate to the way we use gcc.

What about tool chains produced as part of a ADT, wouldn't it be useful for such as case?

Seems like having ability to pass '--with-cpu' ends up being useful to set default for things like 32 vs 64-bit on multiple.

- k