[AArch64] Add SVE2 implementation of I212ToAR30Row

Observed reduction in runtime compared to the existing Neon code:

Cortex-A510: -15.4%
Cortex-A520:  -3.8%
Cortex-A715: -15.7%
Cortex-A720: -15.6%
  Cortex-X2:  -7.9%
  Cortex-X3:  -5.7%
  Cortex-X4:  -5.3%
Cortex-X925:  -4.8%

Bug: b/42280942
Change-Id: I99846820682687c8e0f52d05f5aa3d50369fe0a2
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/6025829
Reviewed-by: Justin Green <greenjustin@google.com>
Reviewed-by: Frank Barchard <fbarchard@chromium.org>

include/libyuv/row.h

@@ -554,6 +554,7 @@ extern "C" {
 #define HAS_DIVIDEROW_16_SVE2
 #define HAS_HALFFLOATROW_SVE2
 #define HAS_I210TOARGBROW_SVE2
+#define HAS_I212TOAR30ROW_SVE2
 #define HAS_I212TOARGBROW_SVE2
 #define HAS_I400TOARGBROW_SVE2
 #define HAS_I422ALPHATOARGBROW_SVE2
@@ -1144,6 +1145,12 @@ void I212ToAR30Row_NEON(const uint16_t* src_y,
                         uint8_t* rgb_buf,
                         const struct YuvConstants* yuvconstants,
                         int width);
+void I212ToAR30Row_SVE2(const uint16_t* src_y,
+                        const uint16_t* src_u,
+                        const uint16_t* src_v,
+                        uint8_t* rgb_buf,
+                        const struct YuvConstants* yuvconstants,
+                        int width);
 void I422ToARGBRow_NEON(const uint8_t* src_y,
                         const uint8_t* src_u,
                         const uint8_t* src_v,

source/convert_argb.cc

@@ -1160,6 +1160,11 @@ int I012ToAR30Matrix(const uint16_t* src_y,
       I212ToAR30Row = I212ToAR30Row_NEON;
     }
   }
+#endif
+#if defined(HAS_I212TOAR30ROW_SVE2)
+  if (TestCpuFlag(kCpuHasSVE2)) {
+    I212ToAR30Row = I212ToAR30Row_SVE2;
+  }
 #endif
   for (y = 0; y < height; ++y) {
     I212ToAR30Row(src_y, src_u, src_v, dst_ar30, yuvconstants, width);

source/row_sve.cc

@@ -2117,6 +2117,53 @@ void P410ToAR30Row_SVE2(const uint16_t* src_y,
       : "cc", "memory", YUVTORGB_SVE_REGS);
 }
 
+void I212ToAR30Row_SVE2(const uint16_t* src_y,
+                        const uint16_t* src_u,
+                        const uint16_t* src_v,
+                        uint8_t* dst_ar30,
+                        const struct YuvConstants* yuvconstants,
+                        int width) {
+  uint64_t vl;
+  asm("cnth %0" : "=r"(vl));
+  int width_last_y = width & (vl - 1);
+  width_last_y = width_last_y == 0 ? vl : width_last_y;
+  uint16_t limit = 0x3ff0;
+  asm volatile(
+      "ptrue    p0.b                                    \n" YUVTORGB_SVE_SETUP
+      "dup      z23.h, %w[limit]                        \n"
+      "subs     %w[width], %w[width], %w[vl]            \n"
+      "b.lt     2f                                      \n"
+
+      // Run bulk of computation with an all-true predicate to avoid predicate
+      // generation overhead.
+      "ptrue    p1.h                                    \n"
+      "1:                                               \n"  //
+      READI212_SVE I4XXTORGB_SVE STOREAR30_SVE
+      "subs     %w[width], %w[width], %w[vl]            \n"
+      "b.ge     1b                                      \n"
+
+      "2:                                               \n"
+      "adds     %w[width], %w[width], %w[vl]            \n"
+      "b.eq     99f                                     \n"
+
+      // Calculate a predicate for the final iteration to deal with the tail.
+      "whilelt  p1.h, wzr, %w[width_last_y]             \n"  //
+      READI212_SVE I4XXTORGB_SVE STOREAR30_SVE
+
+      "99:                                              \n"
+      : [src_y] "+r"(src_y),                                // %[src_y]
+        [src_u] "+r"(src_u),                                // %[src_u]
+        [src_v] "+r"(src_v),                                // %[src_v]
+        [dst_ar30] "+r"(dst_ar30),                          // %[dst_ar30]
+        [width] "+r"(width)                                 // %[width]
+      : [vl] "r"(vl),                                       // %[vl]
+        [kUVCoeff] "r"(&yuvconstants->kUVCoeff),            // %[kUVCoeff]
+        [kRGBCoeffBias] "r"(&yuvconstants->kRGBCoeffBias),  // %[kRGBCoeffBias]
+        [width_last_y] "r"(width_last_y),                   // %[width_last_y]
+        [limit] "r"(limit)                                  // %[limit]
+      : "cc", "memory", YUVTORGB_SVE_REGS);
+}
+
 void I212ToARGBRow_SVE2(const uint16_t* src_y,
                         const uint16_t* src_u,
                         const uint16_t* src_v,