Code's more readable when SkPMFloat is an Sk4f.

src/core/SkPMFloat.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPM_DEFINED
 #define SkPM_DEFINED
 
 #include "SkTypes.h"
 #include "SkColor.h"
 #include "SkColorPriv.h"
 #include "SkNx.h"
 
 // A pre-multiplied color storing each component in the same order as SkPMColor,
 // but as a float in the range [0, 255].
-class SK_STRUCT_ALIGN(16) SkPMFloat {
+class SkPMFloat : public Sk4f {
 public:
     static SkPMFloat FromPMColor(SkPMColor c) { return SkPMFloat(c); }
     static SkPMFloat FromARGB(float a, float r, float g, float b) { return SkPMFloat(a,r,g,b); }
 
     // May be more efficient than one at a time.  No special alignment assumed for SkPMColors.
     static void From4PMColors(const SkPMColor[4], SkPMFloat*, SkPMFloat*, SkPMFloat*, SkPMFloat*);
 
     // Uninitialized.
     SkPMFloat() {}
     explicit SkPMFloat(SkPMColor);
     SkPMFloat(float a, float r, float g, float b)
     #ifdef SK_PMCOLOR_IS_RGBA
-        : fColors(r,g,b,a) {}
+        : INHERITED(r,g,b,a) {}
     #else
-        : fColors(b,g,r,a) {}
+        : INHERITED(b,g,r,a) {}
     #endif
 
+    SkPMFloat(const Sk4f& fs) : INHERITED(fs) {}
 
-    // Freely autoconvert between SkPMFloat and Sk4f.
-    /*implicit*/ SkPMFloat(const Sk4f& fs) { fColors = fs; }
-    /*implicit*/ operator Sk4f() const { return fColors; }
-
-    float a() const { return fColors.kth<SK_A32_SHIFT / 8>(); }
-    float r() const { return fColors.kth<SK_R32_SHIFT / 8>(); }
-    float g() const { return fColors.kth<SK_G32_SHIFT / 8>(); }
-    float b() const { return fColors.kth<SK_B32_SHIFT / 8>(); }
+    float a() const { return this->kth<SK_A32_SHIFT / 8>(); }
+    float r() const { return this->kth<SK_R32_SHIFT / 8>(); }
+    float g() const { return this->kth<SK_G32_SHIFT / 8>(); }
+    float b() const { return this->kth<SK_B32_SHIFT / 8>(); }
 
     // N.B. All methods returning an SkPMColor call SkPMColorAssert on that result before returning.
 
     // round() and roundClamp() round component values to the nearest integer.
     SkPMColor round() const;  // Assumes all values in [0, 255].  Some implementations may clamp.
     SkPMColor roundClamp() const;  // Will clamp all values to [0, 255].
 
     // Like round(), but truncates instead of rounding.
     // The domain of this function is (-1.0f, 256.0f).  Values in (-1.0f, 0.0f] trunc to a zero.
     SkPMColor trunc() const;
 
     // 4-at-a-time versions of round() and roundClamp(). Like From4PMColors(), no alignment assumed.
     static void RoundTo4PMColors(
             const SkPMFloat&, const SkPMFloat&, const SkPMFloat&, const SkPMFloat&, SkPMColor[4]);
     static void RoundClampTo4PMColors(
             const SkPMFloat&, const SkPMFloat&, const SkPMFloat&, const SkPMFloat&, SkPMColor[4]);
 
     bool isValid() const {
         return this->a() >= 0 && this->a() <= 255
             && this->r() >= 0 && this->r() <= this->a()
             && this->g() >= 0 && this->g() <= this->a()
             && this->b() >= 0 && this->b() <= this->a();
     }
 
 private:
-    Sk4f fColors;
+    typedef Sk4f INHERITED;
 };
 
 #ifdef SKNX_NO_SIMD
     // Platform implementations of SkPMFloat assume Sk4f uses SSE or NEON.  _none is generic.
     #include "../opts/SkPMFloat_none.h"
 #else
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
         #include "../opts/SkPMFloat_SSSE3.h"
     #elif SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/SkPMFloat_SSE2.h"
     #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/SkPMFloat_neon.h"
     #else
         #include "../opts/SkPMFloat_none.h"
     #endif
 #endif
 
 #endif//SkPM_DEFINED