Cherry pick vp8 halfpix variance fix

source/libvpx/vpx_dsp/x86/halfpix_variance_sse2.c

Index: source/libvpx/vpx_dsp/x86/halfpix_variance_sse2.c
diff --git a/source/libvpx/vpx_dsp/x86/halfpix_variance_sse2.c b/source/libvpx/vpx_dsp/x86/halfpix_variance_sse2.c
new file mode 100644
index 0000000000000000000000000000000000000000..5782155bf8a6bd698844d6997317dffa048b72f6
--- /dev/null
+++ b/source/libvpx/vpx_dsp/x86/halfpix_variance_sse2.c
@@ -0,0 +1,74 @@
+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "./vpx_config.h"
+#include "./vpx_dsp_rtcd.h"
+#include "vpx/vpx_integer.h"
+
+void vpx_half_horiz_vert_variance16x_h_sse2(const unsigned char *ref,
+                                            int ref_stride,
+                                            const unsigned char *src,
+                                            int src_stride,
+                                            unsigned int height,
+                                            int *sum,
+                                            unsigned int *sumsquared);
+void vpx_half_horiz_variance16x_h_sse2(const unsigned char *ref, int ref_stride,
+                                       const unsigned char *src, int src_stride,
+                                       unsigned int height, int *sum,
+                                       unsigned int *sumsquared);
+void vpx_half_vert_variance16x_h_sse2(const unsigned char *ref, int ref_stride,
+                                      const unsigned char *src, int src_stride,
+                                      unsigned int height, int *sum,
+                                      unsigned int *sumsquared);
+
+uint32_t vpx_variance_halfpixvar16x16_h_sse2(const unsigned char *src,
+                                             int src_stride,
+                                             const unsigned char *dst,
+                                             int dst_stride,
+                                             uint32_t *sse) {
+  int xsum0;
+  unsigned int xxsum0;
+
+  vpx_half_horiz_variance16x_h_sse2(src, src_stride, dst, dst_stride, 16,
+                                    &xsum0, &xxsum0);
+
+  *sse = xxsum0;
+  return (xxsum0 - (((uint32_t)xsum0 * xsum0) >> 8));
+}
+
+uint32_t vpx_variance_halfpixvar16x16_v_sse2(const unsigned char *src,
+                                             int src_stride,
+                                             const unsigned char *dst,
+                                             int dst_stride,
+                                             uint32_t *sse) {
+  int xsum0;
+  unsigned int xxsum0;
+  vpx_half_vert_variance16x_h_sse2(src, src_stride, dst, dst_stride, 16,
+                                   &xsum0, &xxsum0);
+
+  *sse = xxsum0;
+  return (xxsum0 - (((uint32_t)xsum0 * xsum0) >> 8));
+}
+
+
+uint32_t vpx_variance_halfpixvar16x16_hv_sse2(const unsigned char *src,
+                                              int src_stride,
+                                              const unsigned char *dst,
+                                              int dst_stride,
+                                              uint32_t *sse) {
+  int xsum0;
+  unsigned int xxsum0;
+
+  vpx_half_horiz_vert_variance16x_h_sse2(src, src_stride, dst, dst_stride, 16,
+                                         &xsum0, &xxsum0);
+
+  *sse = xxsum0;
+  return (xxsum0 - (((uint32_t)xsum0 * xsum0) >> 8));
+}