libavcodec/vp9dsp.c:1601: error: Uninitialized Value
  The value read from p4 was never initialized.

libavcodec/vp9dsp.c:1601:13: 
1599. 
1600.         if (wd >= 16 && flat8out && flat8in) {
1601.             dst[strideb * -7] = (p7 + p7 + p7 + p7 + p7 + p7 + p7 + p6 * 2 +
                  ^
1602.                                  p5 + p4 + p3 + p2 + p1 + p0 + q0 + 8) >> 4;
1603.             dst[strideb * -6] = (p7 + p7 + p7 + p7 + p7 + p7 + p6 + p5 * 2 +
