mmx for linux yuv convert function....

media/base/yuv_convert.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This webpage shows layout of YV12 and other YUV formats
 // http://www.fourcc.org/yuv.php
 // The actual conversion is best described here
 // http://en.wikipedia.org/wiki/YUV
 // An article on optimizing YUV conversion using tables instead of multiplies
 // http://lestourtereaux.free.fr/papers/data/yuvrgb.pdf
@@ skipping 113 matching lines @@
     }
   }
 
   for (int y = 0; y < scaled_height; ++y) {
     uint8* dest_pixel = rgb_buf + y * rgb_pitch;
     int scaled_y = (y * height / scaled_height);
     const uint8* y_ptr = y_buf + scaled_y * y_pitch;
     const uint8* u_ptr = u_buf + (scaled_y >> y_shift) * uv_pitch;
     const uint8* v_ptr = v_buf + (scaled_y >> y_shift) * uv_pitch;
 
-#if USE_MMX
+#if USE_MMX && defined(_MSC_VER)
     if (scaled_width == (width * 2)) {
       DoubleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
                           dest_pixel, scaled_width);
     } else if ((scaled_dx & 15) == 0) {  // Scaling by integer scale factor.
       if (scaled_dx_uv == scaled_dx) {   // Not rotated.
         if (scaled_dx == 16) {           // Not scaled
           FastConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
                                    dest_pixel, scaled_width);
         } else {  // Simple scale down. ie half
           ConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
@@ skipping 13 matching lines @@
       ScaleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
                          dest_pixel, scaled_width, scaled_dx);
     }
   }
 
   // MMX used for FastConvertYUVToRGB32Row requires emms instruction.
   EMMS();
 }
 
 }  // namespace media