[PATCH] arm: Fix memchr() for Armv8-R

[Sebastian Huber]

On 09/12/2020 13:27, Richard Earnshaw wrote:

> On 09/12/2020 12:11, Sebastian Huber wrote:
>> On 04/12/2020 08:42, Sebastian Huber wrote:
>>
>>> The Cortex-R52 processor is an Armv8-R processor with a NEON unit.  This
>>> fix prevents conflicting architecture profiles A/R errors issued by the
>>> linker.
>>>
>>> Signed-off-by: Sebastian Huber<sebastian.huber@embedded-brains.de>
>>> ---
>>>    newlib/libc/machine/arm/memchr.S | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/newlib/libc/machine/arm/memchr.S
>>> b/newlib/libc/machine/arm/memchr.S
>>> index 7c22b117e..1a4c6512c 100644
>>> --- a/newlib/libc/machine/arm/memchr.S
>>> +++ b/newlib/libc/machine/arm/memchr.S
>>> @@ -79,7 +79,11 @@
>>>      @ NOTE: This ifdef MUST match the one in memchr-stub.c
>>>    #if defined (__ARM_NEON__) || defined (__ARM_NEON)
>>> +#if __ARM_ARCH >= 8 && __ARM_ARCH_PROFILE == 'R'
>>> +    .arch    armv8-r
>>> +#else
>>>        .arch    armv7-a
>>> +#endif
>>>        .fpu    neon
>>>      
>> The memchr.S from the ARM optimized routines package has little in
>> common with the file in Newlib:
>>
>> https://github.com/ARM-software/optimized-routines/blob/master/string/arm/memchr.S
>>
>>
>> The Newlib variant uses VFP instructions for example.
>>
>> I think this change should be checked in as is.
>>
> That probably means the newlib one is out of date and needs to be resynced.

I lack the background information to decide this. I have for example no 
idea why the VFP variant was removed or not included in 
ARM-software/optimized-routines. Was it intentional or an oversight? Was 
it based on benchmarks?

Without the patch above Newlib is currently unusable for Armv8-R targets 
with an VFP unit.

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