[WebRTC] Add ScreenCapturerDifferWrapper to share Differ across ScreenCapturers

webrtc/modules/desktop_capture/differ_vector_sse2.cc

Index: webrtc/modules/desktop_capture/differ_vector_sse2.cc
diff --git a/webrtc/modules/desktop_capture/differ_vector_sse2.cc b/webrtc/modules/desktop_capture/differ_vector_sse2.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ce6cc297c6ea97f74932d1991b50bda2cabad98b
--- /dev/null
+++ b/webrtc/modules/desktop_capture/differ_vector_sse2.cc
@@ -0,0 +1,102 @@
+/*
+ *  Copyright (c) 2016 The WebRTC 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 "webrtc/modules/desktop_capture/differ_vector_sse2.h"
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#else
+#include <mmintrin.h>
+#include <emmintrin.h>
+#endif
+
+namespace webrtc {
+
+extern bool VectorDifference_SSE2_W16(const uint8_t* image1,
+                                      const uint8_t* image2) {
+  __m128i acc = _mm_setzero_si128();
+  __m128i v0;
+  __m128i v1;
+  __m128i sad;
+  const __m128i* i1 = reinterpret_cast<const __m128i*>(image1);
+  const __m128i* i2 = reinterpret_cast<const __m128i*>(image2);
+  v0 = _mm_loadu_si128(i1);
+  v1 = _mm_loadu_si128(i2);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 1);
+  v1 = _mm_loadu_si128(i2 + 1);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 2);
+  v1 = _mm_loadu_si128(i2 + 2);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 3);
+  v1 = _mm_loadu_si128(i2 + 3);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+
+  // This essential means sad = acc >> 64. We only care about the lower 16
+  // bits.
+  sad = _mm_shuffle_epi32(acc, 0xEE);
+  sad = _mm_adds_epu16(sad, acc);
+  return _mm_cvtsi128_si32(sad) != 0;
+}
+
+extern bool VectorDifference_SSE2_W32(const uint8_t* image1,
+                                      const uint8_t* image2) {
+  __m128i acc = _mm_setzero_si128();
+  __m128i v0;
+  __m128i v1;
+  __m128i sad;
+  const __m128i* i1 = reinterpret_cast<const __m128i*>(image1);
+  const __m128i* i2 = reinterpret_cast<const __m128i*>(image2);
+  v0 = _mm_loadu_si128(i1);
+  v1 = _mm_loadu_si128(i2);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 1);
+  v1 = _mm_loadu_si128(i2 + 1);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 2);
+  v1 = _mm_loadu_si128(i2 + 2);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 3);
+  v1 = _mm_loadu_si128(i2 + 3);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 4);
+  v1 = _mm_loadu_si128(i2 + 4);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 5);
+  v1 = _mm_loadu_si128(i2 + 5);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 6);
+  v1 = _mm_loadu_si128(i2 + 6);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+  v0 = _mm_loadu_si128(i1 + 7);
+  v1 = _mm_loadu_si128(i2 + 7);
+  sad = _mm_sad_epu8(v0, v1);
+  acc = _mm_adds_epu16(acc, sad);
+
+  // This essential means sad = acc >> 64. We only care about the lower 16
+  // bits.
+  sad = _mm_shuffle_epi32(acc, 0xEE);
+  sad = _mm_adds_epu16(sad, acc);
+  return _mm_cvtsi128_si32(sad) != 0;
+}
+
+}  // namespace webrtc