Port SkUtils opts to SkOpts.

src/opts/SkOpts_neon.cpp

Index: src/opts/SkOpts_neon.cpp
diff --git a/src/opts/SkOpts_neon.cpp b/src/opts/SkOpts_neon.cpp
index ef667dc065306f405044e04cc961af4d4cddf7c1..cbb247efe5667ae5d7db033aa6ec59933b750f18 100644
--- a/src/opts/SkOpts_neon.cpp
+++ b/src/opts/SkOpts_neon.cpp
@@ -8,9 +8,66 @@
 #include "SkOpts.h"
 #include "SkFloatingPoint.h"
 
+namespace neon {  // This helps identify methods from this file when debugging / profiling.
+
+static float rsqrt(float x) {
+    return sk_float_rsqrt(x);  // This sk_float_rsqrt copy will take the NEON compile-time path.
+}
+
+static void memset16(uint16_t* dst, uint16_t value, int n) {
+    uint16x8_t   v8  = vdupq_n_u16(value);
+    uint16x8x4_t v32 = {{ v8, v8, v8, v8 }};
+
+    while (n >= 32) {
+        vst4q_u16(dst, v32);  // This swizzles, but we don't care: all lanes are the same, value.
+        dst += 32;
+        n   -= 32;
+    }
+    switch (n / 8) {
+        case 3: vst1q_u16(dst, v8); dst += 8;
+        case 2: vst1q_u16(dst, v8); dst += 8;
+        case 1: vst1q_u16(dst, v8); dst += 8;
+    }
+    if (n & 4) {
+        vst1_u16(dst, vget_low_u16(v8));
+        dst += 4;
+    }
+    switch (n & 3) {
+        case 3: *dst++ = value;
+        case 2: *dst++ = value;
+        case 1: *dst   = value;
+    }
+}
+
+static void memset32(uint32_t* dst, uint32_t value, int n) {
+    uint32x4_t   v4  = vdupq_n_u32(value);
+    uint32x4x4_t v16 = {{ v4, v4, v4, v4 }};
+
+    while (n >= 16) {
+        vst4q_u32(dst, v16);  // This swizzles, but we don't care: all lanes are the same, value.
+        dst += 16;
+        n   -= 16;
+    }
+    switch (n / 4) {
+        case 3: vst1q_u32(dst, v4); dst += 4;
+        case 2: vst1q_u32(dst, v4); dst += 4;
+        case 1: vst1q_u32(dst, v4); dst += 4;
+    }
+    if (n & 2) {
+        vst1_u32(dst, vget_low_u32(v4));
+        dst += 2;
+    }
+    if (n & 1) {
+        *dst = value;
+    }
+}
+
+}  // namespace neon
+
 namespace SkOpts {
     void Init_neon() {
-        rsqrt = sk_float_rsqrt;  // This copy of sk_float_rsqrt will take the NEON path.
-
+        rsqrt    = neon::rsqrt;
+        memset16 = neon::memset16;
+        memset32 = neon::memset32;
     }
 }