Add MIPS SIMD Arch (MSA) optimized MirrorRow function

source/row_msa.cc

+/*
+ *  Copyright 2016 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.
+ */
+
+#include "libyuv/row.h"
+
+#if !defined(LIBYUV_DISABLE_MSA) && defined(__mips_msa)
+#include "libyuv/macros_msa.h"
+#endif
+
+#ifdef __cplusplus
+namespace libyuv {
+extern "C" {
+#endif
+
+#if !defined(LIBYUV_DISABLE_MSA) && defined(__mips_msa)

[fbarchard1, 2016/09/17 01:01:30]

note this is fine for the entire file.

if theres a need to be selective, functions would sometimes have an ifdef as
well or instead.
leave this as is for now, til you have more functions and determine if you need
function level ifdefs.

[manojkumar.bhosale, 2016/09/19 08:07:21]

Acknowledged.

+void MirrorRow_MSA(const uint8* src, uint8* dst, int width) {
+    int count;

[fbarchard1, 2016/09/17 01:01:31]

indent should be 2 spaces
https://google.github.io/styleguide/cppguide.html#Spaces_vs._Tabs

[manojkumar.bhosale, 2016/09/19 08:07:21]

Done.

+    v16u8 src0, src1, src2, src3;
+    v16u8 dst0, dst1, dst2, dst3;
+    v16i8 mask = { 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 };
+
+    src += width;
+
+    for (count = 0; count < (width >> 6); count++) {

[fbarchard1, 2016/09/17 01:01:31]

I've usually done counting by pixels

for (x = 0; x < width; x += 64) {

where the 64 would match the src -= 64 and dst += 64, making it less error prone
compared to >> 6 which is / 64.

[manojkumar.bhosale, 2016/09/19 08:07:21]

Done.

+        src -= 64;
+        LD_UB4(src, 16, src3, src2, src1, src0);
+
+        VSHF_B2_UB(src3, src3, src2, src2, mask, mask, dst3, dst2);
+        VSHF_B2_UB(src1, src1, src0, src0, mask, mask, dst1, dst0);
+
+        ST_UB4(dst0, dst1, dst2, dst3, dst, 16);
+        dst += 64;
+    }
+}
+#endif  // !defined(LIBYUV_DISABLE_MSA) && defined(__mips_msa)
+
+#ifdef __cplusplus
+}  // extern "C"
+}  // namespace libyuv
+#endif