__m128i span_0; /* 0,dcdx,2dcdx,3dcdx for plane 0 */
__m128i span_1; /* 0,dcdx,2dcdx,3dcdx for plane 1 */
__m128i span_2; /* 0,dcdx,2dcdx,3dcdx for plane 2 */
__m128i unused;
transpose4_epi32(&p0, &p1, &p2, &zero,
__m128i span_0; /* 0,dcdx,2dcdx,3dcdx for plane 0 */
__m128i span_1; /* 0,dcdx,2dcdx,3dcdx for plane 1 */
__m128i span_2; /* 0,dcdx,2dcdx,3dcdx for plane 2 */
__m128i unused;
transpose4_epi32(&p0, &p1, &p2, &zero,