Use switch operator[](int) to kth<int>() so we can use vget_lane.

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
 
@@ skipping 20 matching lines @@
         : fColors(r,g,b,a) {}
     #else
         : fColors(b,g,r,a) {}
     #endif
 
 
     // Freely autoconvert between SkPMFloat and Sk4f.
     /*implicit*/ SkPMFloat(const Sk4f& fs) { fColors = fs; }
     /*implicit*/ operator Sk4f() const { return fColors; }
 
-    float a() const { return fColors[SK_A32_SHIFT / 8]; }
-    float r() const { return fColors[SK_R32_SHIFT / 8]; }
-    float g() const { return fColors[SK_G32_SHIFT / 8]; }
-    float b() const { return fColors[SK_B32_SHIFT / 8]; }
+    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>(); }
 
     // N.B. All methods returning an SkPMColor call SkPMColorAssert on that result before returning.
 
     // get() and clamped() round component values to the nearest integer.
     SkPMColor     get() const;  // Assumes all values in [0, 255].  Some implementations may clamp.
     SkPMColor clamped() const;  // Will clamp all values to [0, 255].
 
     // Like get(), 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;
@@ skipping 24 matching lines @@
     #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