Sk4px: Difference and Exclusion

src/opts/Sk4px_NEON.h

Index: src/opts/Sk4px_NEON.h
diff --git a/src/opts/Sk4px_NEON.h b/src/opts/Sk4px_NEON.h
index 368551949cbc466b023c76ad57e989c53893c92a..f0d9b56c71194f3ec0050eeb0fdb793e5064d549 100644
--- a/src/opts/Sk4px_NEON.h
+++ b/src/opts/Sk4px_NEON.h
@@ -78,3 +78,13 @@ inline Sk4px Sk4px::Load2Alphas(const SkAlpha a[2]) {
     a32 = vorrq_u32(a32, vshlq_n_u32(a32, 16));           // ____ ____ 1111 0000
     return Sk16b((uint8x16_t)a32);
 }
+
+inline Sk4px Sk4px::zeroColors() const {
+    return Sk16b(vandq_u8(this->fVec, (uint8x16_t)vdupq_n_u32(0xFF << SK_A32_SHIFT)));
+}
+
+inline Sk4px Sk4px::zeroAlphas() const {
+    // vbic(a,b) == a & ~b
+    return Sk16b(vbicq_u8(this->fVec, (uint8x16_t)vdupq_n_u32(0xFF << SK_A32_SHIFT)));
+}
+