[FFmpeg-devel] cavs.c DECLARE_ALIGNED in ff_cavs_filter

Måns Rullgård mans
Mon May 25 21:02:41 CEST 2009

Loren Merritt <lorenm at u.washington.edu> writes:

> On Mon, 25 May 2009, M?ns Rullg?rd wrote:
>> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>>> currently there is this code in cavs.c:
>>>     DECLARE_ALIGNED_8(uint8_t, bs[8]);
>>> The reason for it is that kind of code:
>>>> *((uint64_t *)bs) = 0x0202020202020202ULL;
>>>> if( *((uint64_t *)bs) ) {
>>> I thought of "solving" this via a union, but is this code really this
>>> speed critical that we need such a mess?
>>> Can't we just use memset for the writes and e.g. AV_RN64 for the read?
> Are you complaining about the aliasing, or trying to simplify the code?
>> Such huge literals are fairly inefficient anyway on most CPUs.
> As opposed to what?

memset() or repeated stores of a smaller value.

> The compiler should emit the same code for memset as for
> *(uint64_t*),

I thought we'd already established that compilers suck.

> and gcc on x86 does.

Impressive.  What about other targets?

M?ns Rullg?rd
mans at mansr.com

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