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

[Michael Niedermayer]

On Wed, Dec 26, 2018 at 10:02:15PM +0100, Paul B Mahol wrote:
> On 12/26/18, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > 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 ?
> 
> No, don't do that.
> 
> > All the code is already in a "special" memset though, this is
> > memset_bytes()
> >
> 
> I guess function is less useful if its static. So any duplicate should
> be avoided in codebase.

i can make it non static and export it if you want ?

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

If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
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