SkNx_shuffle

src/core/SkNx.h

Index: src/core/SkNx.h
diff --git a/src/core/SkNx.h b/src/core/SkNx.h
index ff94e0545870fa51bf9559b587fb615a3ca1e5bd..f8b27fc1ed0572c862839d80c707d2a3f25280f2 100644
--- a/src/core/SkNx.h
+++ b/src/core/SkNx.h
@@ -266,8 +266,27 @@ protected:
     T fVal;
 };
 
+// This default implementation can be specialized by ../opts/SkNx_foo.h
+// if there's a better platform-specific shuffle strategy.
+template <typename SkNx, int... Ix>
+inline SkNx SkNx_shuffle_impl(const SkNx& src) { return SkNx( src.template kth<Ix>()... ); }
+
+// This generic shuffle can be called on either SkNi or SkNf with 1 or N indices:
+//     Sk4f f(a,b,c,d);
+//     SkNx_shuffle<3>(f);        // ~~~> Sk4f(d,d,d,d)
+//     SkNx_shuffle<2,1,0,3>(f);  // ~~~> Sk4f(c,b,a,d)
+template <int... Ix, typename SkNx>
+inline SkNx SkNx_shuffle(const SkNx& src) { return SkNx_shuffle_impl<SkNx, Ix...>(src); }
+
+// A reminder alias that shuffles can be used to duplicate a single index across a vector.
+template <int Ix, typename SkNx>
+inline SkNx SkNx_dup(const SkNx& src) { return SkNx_shuffle<Ix>(src); }
+
 }  // namespace
 
+
+
+
 // Include platform specific specializations if available.
 #ifndef SKNX_NO_SIMD
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2