[PATCH] powerpc: strcasecmp/strncasecmp optmization for power8 [BZ 20327]

[Rajalakshmi Srinivasaraghavan]

On 07/05/2016 07:31 PM, Tulio Magno Quites Machado Filho wrote:
> Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com> writes:
>
>> On 07/04/2016 07:46 PM, Florian Weimer wrote:
>>> On 06/14/2016 11:45 AM, Rajalakshmi Srinivasaraghavan wrote:
>> Subject: [PATCH] POWER8: Fix return code of strcasecmp for unaligned inputs
> Could you replace POWER8 by powerpc, please?
>
>> If the input values are unaligned and if there are null characters in the
>> memory before the starting address of the input values, strcasecmp
>> gives incorrect return code. Fixed it by adding mask the bits that
>> are not part of the string.
>>
>> Tested on ppc64 and ppc64le.
> Despite this being a bug fix, I believe we need the approval from Adhemerval
> before integrating it during the freeze window.
>
>> 	[BZ #20327]
>> 	* sysdeps/powerpc/powerpc64/power8/strcasecmp.S: Mask bits that
>> 	are not part of the string.
> This is a very important case.  Can we improve the current testcase to
> validate this scenario too?
>
>> ---
>>   sysdeps/powerpc/powerpc64/power8/strcasecmp.S | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/sysdeps/powerpc/powerpc64/power8/strcasecmp.S b/sysdeps/powerpc/powerpc64/power8/strcasecmp.S
>> index 63f6217..d6a4df2 100644
>> --- a/sysdeps/powerpc/powerpc64/power8/strcasecmp.S
>> +++ b/sysdeps/powerpc/powerpc64/power8/strcasecmp.S
>> @@ -44,7 +44,9 @@
>>   #ifdef __LITTLE_ENDIAN__
>>   #define GET16BYTES(reg1, reg2, reg3) \
>>   	lvx	reg1, 0, reg2; \
>> -	vcmpequb.	v8, v0, reg1; \
>> +	vspltisb	v8, -1; \
>> +	vperm	v8, v8, reg1, reg3; \
>> +	vcmpequb.	v8, v0, v8; \
>>   	beq	cr6, 1f; \
>>   	vspltisb	v9, 0; \
>>   	b	2f; \
>> @@ -57,7 +59,9 @@
>>   #else
>>   #define GET16BYTES(reg1, reg2, reg3) \
>>   	lvx	reg1, 0, reg2; \
>> -	vcmpequb.	v8, v0, reg1; \
>> +	vspltisb	 v8, -1; \
>> +	vperm	v8, reg1, v8,  reg3; \
>> +	vcmpequb.	v8, v0, v8; \
>>   	beq	cr6, 1f; \
>>   	vspltisb	v9, 0; \
>>   	b	2f; \
> Although this code is simple, I believe this macro is missing more comments.
>
> I suggest to explain the following:
>   - How does this macro use reg1, reg2, reg3 and v8?
>   - Why is it setting v9 to 0?
>
Added comments and Committed it as
30e4cc5413f72c2c728a544389da0c48500d9904

-- 
Thanks
Rajalakshmi S