set d19 alpha on inner loop

source/row_neon.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 247 matching lines @@
 }
 
 void I422ToRGBARow_NEON(const uint8* src_y,
                         const uint8* src_u,
                         const uint8* src_v,
                         uint8* dst_rgba,
                         const struct YuvConstants* yuvconstants,
                         int width) {
   asm volatile (
     YUVTORGB_SETUP
-    "vmov.u8    d19, #255                      \n"
   "1:                                          \n"
     READYUV422
     YUVTORGB
     "subs       %4, %4, #8                     \n"
+    "vmov.u8    d19, #255                      \n"  // d19 modified by YUVTORGB
     MEMACCESS(3)
     "vst4.8     {d19, d20, d21, d22}, [%3]!    \n"
     "bgt        1b                             \n"
     : "+r"(src_y),     // %0
       "+r"(src_u),     // %1
       "+r"(src_v),     // %2
       "+r"(dst_rgba),  // %3
       "+r"(width)      // %4
     : [kUVToRB]"r"(&yuvconstants->kUVToRB),
       [kUVToG]"r"(&yuvconstants->kUVToG),
@@ skipping 2627 matching lines @@
     "r"(6)             // %5
   : "cc", "memory", "q0", "q1"  // Clobber List
   );
 }
 #endif  // defined(__ARM_NEON__) && !defined(__aarch64__)
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif