port NV12ToRGB565Row_AVX2 to gcc

source/row_common.cc

 /*
  *  Copyright 2011 The LibYuv 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.
  */
 
@@ skipping 2577 matching lines @@
 void NV12ToRGB565Row_AVX2(const uint8* src_y,
                           const uint8* src_uv,
                           uint8* dst_rgb565,
                           const struct YuvConstants* yuvconstants,
                           int width) {
   // Row buffer for intermediate ARGB pixels.
   SIMD_ALIGNED32(uint8 row[MAXTWIDTH * 4]);
   while (width > 0) {
     int twidth = width > MAXTWIDTH ? MAXTWIDTH : width;
     NV12ToARGBRow_AVX2(src_y, src_uv, row, yuvconstants, twidth);
+#if defined(HAS_ARGBTORGB565ROW_AVX2)
     ARGBToRGB565Row_AVX2(row, dst_rgb565, twidth);
+#else
+    ARGBToRGB565Row_SSE2(row, dst_rgb565, twidth);
+#endif
     src_y += twidth;
     src_uv += twidth;
     dst_rgb565 += twidth * 2;
     width -= twidth;
   }
 }
 #endif
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif