New optimized string routines for Intel and alignment of stack.

[Florian Weimer]

On 06/07/2016 02:25 PM, Zack Weinberg wrote:
> On Tue, Jun 7, 2016 at 8:23 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 06/07/2016 01:51 PM, Adhemerval Zanella wrote:
>>
>>> Also, is there any performance issue with current unaligned version
>>
>> I think there is a performance penalty from not using vectorized copies for
>> small structs.  Even unaligned SSE loads/stores would be a win for the
>> example I posted, I assume.
>
> Is the gain from using vectorized copies large enough that manually
> aligning the stack in functions that want to use those instructions
> would be worth it?

Probably not, using unaligned loads/stores would likely be cheaper than 
stack alignment (unless the function already has a frame pointer for 
another reason).

Florian