Re: [Qemu-devel] [RFC][PATCH 4/9] buffer_is_zero: use vector optimizations if possible

[Eric Blake <eblake@redhat.com>]

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On 03/12/2013 10:03 AM, Peter Lieven wrote:

>>> +    if (((uintptr_t) buf) % sizeof(VECTYPE) == 0
>>> +          && len % 8*sizeof(VECTYPE) == 0) {
>>
>> Space around binary operators.  Use CHAR_BITS instead of a magic number
>> 8.

> the 8 is not BITS_PER_BYTE or CHAR_BITS its the number of
> vectors in one loop in buffer_find_nonzero_offset(). I will add
> a constant for this to make it clearer.

Indeed, now I see it - 8 is the unroll factor.  Well, all the more
evidence that a named constant makes the code easier to read, compared
to me mis-interpreting the magic number.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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