Am 22.03.2013 20:37, schrieb Eric Blake:
> On 03/22/2013 06:46 AM, Peter Lieven wrote:
>> this adds buffer_find_nonzero_offset() which is a SSE2/Altivec
>> optimized function that searches for non-zero content in a
>> buffer.
>>
>> due to the optimizations used in the function there are restrictions
>> on buffer address and search length. the function
>> can_use_buffer_find_nonzero_content() can be used to check if
>> the function can be used safely.
>>
>> Signed-off-by: Peter Lieven <p...@kamp.de>
>> ---
>> include/qemu-common.h | 13 +++++++++++++
>> util/cutils.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 58 insertions(+)
>> +#define BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR 8
>> +static inline bool
>> +can_use_buffer_find_nonzero_offset(const void *buf, size_t len)
>> +{
>> + if (len % (BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR
>> + * sizeof(VECTYPE)) == 0
>> + && ((uintptr_t) buf) % sizeof(VECTYPE) == 0) {
> I know that emacs tends to indent the second line to the column after
> the ( that it is associated with, as in:
>
> + if (len % (BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR
> + * sizeof(VECTYPE)) == 0
> + && ((uintptr_t) buf) % sizeof(VECTYPE) == 0) {
>
> But since checkpatch.pl didn't complain, and since I'm not sure if there
> is a codified qemu indentation style, and since I _am_ sure that not
> everyone uses emacs [hi, vi guys], it's not worth respinning. A
> maintainer can touch it up if desired.
Actually, I was totally unsure how to indent this. Maybe just give
a hint what you would like to see. As I will replace patch 4 with
an earlier version that is not vector optimized, but uses loop unrolling,
I will have to do a v5 and so I can fix this.
>
>> +
>> +size_t buffer_find_nonzero_offset(const void *buf, size_t len)
>> +{
>> + VECTYPE *p = (VECTYPE *)buf;
>> + VECTYPE zero = ZERO_SPLAT;
>> + size_t i;
>> +
>> + assert(len % (BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR
>> + * sizeof(VECTYPE)) == 0);
>> + assert(((uintptr_t) buf) % sizeof(VECTYPE) == 0);
> I would have written this:
>
> assert(can_use_buffer_find_nonzero_offset(buf, len));
Good point. Will be changed in v5.
> But that's cosmetic, and compiles to the same code, so it's not worth a
> respin.
>
> You've addressed my concerns on v3.
>
> Reviewed-by: Eric Blake <ebl...@redhat.com>
>
Peter
