[FFmpeg-devel] [PATCH 1/3] avutil/imgutils: Optimize writing 4 bytes in memset_bytes()

[Michael Niedermayer]

On Wed, Dec 26, 2018 at 04:32:17PM +0100, Paul B Mahol wrote:
> On 12/25/18, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > Fixes: Timeout
> > Fixes:
> > 11502/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WCMV_fuzzer-5664893810769920
> > Before: Executed
> > clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WCMV_fuzzer-5664893810769920
> > in 11294 ms
> > After : Executed
> > clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WCMV_fuzzer-5664893810769920
> > in 4249 ms
> >
> > Found-by: continuous fuzzing process
> > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavutil/imgutils.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/libavutil/imgutils.c b/libavutil/imgutils.c
> > index 4938a7ef67..cc38f1e878 100644
> > --- a/libavutil/imgutils.c
> > +++ b/libavutil/imgutils.c
> > @@ -529,6 +529,12 @@ static void memset_bytes(uint8_t *dst, size_t dst_size,
> > uint8_t *clear,
> >          }
> >      } else if (clear_size == 4) {
> >          uint32_t val = AV_RN32(clear);
> > +        uint64_t val8 = val * 0x100000001ULL;
> > +        for (; dst_size >= 32; dst_size -= 32) {
> > +            AV_WN64(dst   , val8); AV_WN64(dst+ 8, val8);
> > +            AV_WN64(dst+16, val8); AV_WN64(dst+24, val8);
> > +            dst += 32;
> > +        }
> >          for (; dst_size >= 4; dst_size -= 4) {
> >              AV_WN32(dst, val);
> >              dst += 4;
> > --
> > 2.20.1
> >
> 
> NAK, implement special memset function instead.

I can move the added loop into a seperate function, if thats what you
suggest ?
All the code is already in a "special" memset though, this is
memset_bytes()

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

"I am not trying to be anyone's saviour, I'm trying to think about the
 future and not be sad" - Elon Musk

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20181226/29aaf7a9/attachment.sig>