Color dodge and burn with SkPMFloat.

src/opts/SkPMFloat_neon.h

Index: src/opts/SkPMFloat_neon.h
diff --git a/src/opts/SkPMFloat_neon.h b/src/opts/SkPMFloat_neon.h
index c8976860b1805ed29ad3b0592c3c123c916ee6a2..8bee5b551aebb708c09b7557ae74ea6a8618f083 100644
--- a/src/opts/SkPMFloat_neon.h
+++ b/src/opts/SkPMFloat_neon.h
@@ -27,4 +27,9 @@ inline SkPMColor SkPMFloat::round() const {
     return c;
 }
 
+inline Sk4f SkPMFloat::alphas() const {
+    static_assert(SK_A32_SHIFT == 24, "Assuming little-endian.");
+    return vdupq_lane_f32(vget_high_f32(fVec), 1);  // Duplicate high lane of high half i.e. lane 3.
+}
+
 }  // namespace