[FFmpeg-cvslog] avcodec/hevc_refs: Optimize 16bit generate_missing_ref()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Aug  6 18:05:02 2019 +0200| [da8936969fe695a042282d5686e12227745d299a] | committer: Michael Niedermayer

avcodec/hevc_refs: Optimize 16bit generate_missing_ref()

Fixes: Timeout (86sec -> 8sec) [these numbers assume also "[FFmpeg-devel] [PATCH 2/5] [RFC] avcodec/hevcdec: Check for overread in hls_decode_entry()"]
Fixes: 15702/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5657764929470464

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=da8936969fe695a042282d5686e12227745d299a
---

 libavcodec/hevc_refs.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libavcodec/hevc_refs.c b/libavcodec/hevc_refs.c
index 7cf3a55725..7870a72fd6 100644
--- a/libavcodec/hevc_refs.c
+++ b/libavcodec/hevc_refs.c
@@ -394,7 +394,7 @@ static void mark_ref(HEVCFrame *frame, int flag)
 static HEVCFrame *generate_missing_ref(HEVCContext *s, int poc)
 {
     HEVCFrame *frame;
-    int i, x, y;
+    int i, y;
 
     frame = alloc_frame(s);
     if (!frame)
@@ -407,11 +407,11 @@ static HEVCFrame *generate_missing_ref(HEVCContext *s, int poc)
                        frame->frame->buf[i]->size);
         } else {
             for (i = 0; frame->frame->data[i]; i++)
-                for (y = 0; y < (s->ps.sps->height >> s->ps.sps->vshift[i]); y++)
-                    for (x = 0; x < (s->ps.sps->width >> s->ps.sps->hshift[i]); x++) {
-                        AV_WN16(frame->frame->data[i] + y * frame->frame->linesize[i] + 2 * x,
-                                1 << (s->ps.sps->bit_depth - 1));
-                    }
+                for (y = 0; y < (s->ps.sps->height >> s->ps.sps->vshift[i]); y++) {
+                    uint8_t *dst = frame->frame->data[i] + y * frame->frame->linesize[i];
+                    AV_WN16(dst, 1 << (s->ps.sps->bit_depth - 1));
+                    av_memcpy_backptr(dst + 2, 2, 2*(s->ps.sps->width >> s->ps.sps->hshift[i]) - 2);
+                }
         }
     }