Add ARGBExtractAlpha function

source/row_neon64.cc

 /*
  *  Copyright 2014 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 1381 matching lines @@
     "b.gt       1b                             \n"
   : "+r"(src_argb),  // %0
     "+r"(dst_y),     // %1
     "+r"(width)        // %2
   :
   : "cc", "memory", "v0", "v1", "v2", "v3", "v4", "v5", "v6", "v7"
   );
 }
 #endif  // HAS_ARGBTOYROW_NEON
 
+#ifdef HAS_ARGBEXTRACTALPHAROW_NEON
+void ARGBExtractAlphaRow_NEON(const uint8* src_argb, uint8* dst_a, int width) {
+  asm volatile (
+  "1:                                          \n"
+    MEMACCESS(0)
+    "ld4        {v0.8b,v1.8b,v2.8b,v3.8b}, [%0], #32 \n"  // load row 8 pixels
+    "subs       %w2, %w2, #8                   \n"  // 8 processed per loop
+    MEMACCESS(1)
+    "st1        {v3.8b}, [%1], #8              \n"  // store 8 A's.
+    "b.gt       1b                             \n"
+  : "+r"(src_argb),   // %0
+    "+r"(dst_a),      // %1
+    "+r"(width)       // %2
+  :
+  : "cc", "memory", "v0", "v1", "v2", "v3"  // Clobber List
+  );
+}
+#endif  // HAS_ARGBEXTRACTALPHAROW_NEON
+
 #ifdef HAS_ARGBTOYJROW_NEON
 void ARGBToYJRow_NEON(const uint8* src_argb, uint8* dst_y, int width) {
   asm volatile (
     "movi       v4.8b, #15                     \n"  // B * 0.11400 coefficient
     "movi       v5.8b, #75                     \n"  // G * 0.58700 coefficient
     "movi       v6.8b, #38                     \n"  // R * 0.29900 coefficient
   "1:                                          \n"
     MEMACCESS(0)
     "ld4        {v0.8b,v1.8b,v2.8b,v3.8b}, [%0], #32 \n"  // load 8 ARGB pixels.
     "subs       %w2, %w2, #8                   \n"  // 8 processed per loop.
@@ skipping 1540 matching lines @@
   : "cc", "memory", "v0", "v1", "v2", "v3"  // Clobber List
   );
 }
 #endif  // HAS_SOBELYROW_NEON
 #endif  // !defined(LIBYUV_DISABLE_NEON) && defined(__aarch64__)
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif