[OE-core] libm accuracy, eglibc compared to glibc -- solved

[Khem Raj]

On Fri, Mar 21, 2014 at 9:45 AM, Mark Hatle <mark.hatle at windriver.com> wrote:
> On 3/21/14, 7:10 AM, Mats Kärrman wrote:
>>
>> Hi,
>>
>> On: Thursday, March 13, 2014 11:36 AM, Mats Kärrman wrote:
>>>
>>> My "home made" hard float tune for PowerPC looks like this:
>>>
>>> ------------------------------------------------------------------
>>> # Tune for the e300c3 core
>>> require conf/machine/include/tune-ppce300c3.inc
>>>
>>> # Use hardware floating point
>>> AVAILTUNES += "ppce300c3hf"
>>> TUNE_FEATURES_tune-ppce300c3hf = "m32 fpu-hard ppce300c3"
>>> TUNE_PKGARCH_tune-ppce300c3hf = "ppce300c3hf"
>>> PACKAGE_EXTRA_ARCHS_tune-ppce300c3hf =
>>> "${PACKAGE_EXTRA_ARCHS_tune-powerpc} ppce300c3hf"
>>> DEFAULTTUNE = "ppce300c3hf"
>>> ------------------------------------------------------------------
>>>
>>
>> I found the reason for the error (deviance) in the sqrt function. glibc
>> has
>> special code for PowerPC 603e core (e300 is an optimized variant of 603e).
>> By adding the following line to the tuning I now get the same result as
>> for all other environments that I've tried:
>>
>> GLIBC_EXTRA_OECONF += "${@bb.utils.contains("TUNE_FEATURES", "ppce300c3",
>> "-with-cpu=603e", "", d)}"
>>
>> Does anyone know about the reason for having soft-float as the default and
>> only available alternative for e300c2/3 tunings?
>
>
> My guess is because e300 e300c2 were both soft-float designs.  And e300c3 is
> the first hard float design.
>
> The e300c3 should inherit and use the 603e directly.  This includes
> definiting the TUNE_FEATURES that the 603e does.  If it doesn't do that, I'd
> suggest it's a mistake.
>
> The default 603e tune should include:
>
> GLIBC_EXTRA_OECONF += "${@bb.utils.contains("TUNE_FEATURES", "ppc603e",
> "-with-cpu=603e", "", d)}"
>
> or similar already -- and should already be hard float enabled.  (ppc603e
> soft-float should be the alternative -- as it is significantly rarer and the
> deviation.)


alternatively we should define fpu Iplies in glibc for e300c3,

>
>
>> Would it be worthwhile to send a patch to add the hf tuning to OE-core?
>
>
> As the e300c3 should be hard float, we shouldn't have the 'hf' designation.
> Otherwise, we should ensure the e300c3 tune is correctly configured.

may be for now controlling it in tune file is a quicker fix.

>
>
>> In that case what tests should be performed before that and what (related)
>> tests are performed by the OE auto-builder?
>>
>> BR // Mats
>>
>
> --
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