shithub: libvpx

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neon variance: special case 4x

The sub pixel variance uses a temp buffer which guarantees width ==
stride. Take advantage of this with the 4x and avoid the very costly
lane loads.

Change-Id: Ia0c97eb8c29dc8dfa6e51a29dff9b75b3c6726f1

--- a/vpx_dsp/arm/mem_neon.h

+++ b/vpx_dsp/arm/mem_neon.h

@@ -83,6 +83,7 @@

 static INLINE uint8x16_t load_unaligned_u8q(const uint8_t *buf, int stride) {

   uint32_t a;

   uint32x4_t a_u32 = vdupq_n_u32(0);

+  if (stride == 4) return vld1q_u8(buf);

   memcpy(&a, buf, 4);

   buf += stride;

   a_u32 = vld1q_lane_u32(&a, a_u32, 0);

@@ -102,6 +103,10 @@

 static INLINE void store_unaligned_u8q(uint8_t *buf, int stride,

                                        const uint8x16_t a) {

   const uint32x4_t a_u32 = vreinterpretq_u32_u8(a);

+  if (stride == 4) {

+    vst1q_u8(buf, a);

+    return;

+  }

   uint32_to_mem(buf, vgetq_lane_u32(a_u32, 0));

   buf += stride;

   uint32_to_mem(buf, vgetq_lane_u32(a_u32, 1));