Start to vectorize SkTileGrid.

src/core/Sk4x.h

+#ifndef Sk4x_DEFINED
+#define Sk4x_DEFINED
+
+#include "SkTypes.h"
+
+// First we'll let Clang or GCC try their best with whatever instructions are available.
+// Otherwise fall back on portable code.  This really should be a last resort.
+
+#define SK4X_PREAMBLE 1
+    #if defined(__clang__)
+        #include "Sk4x_clang.h"
+    #elif defined(__GNUC__)
+        #include "Sk4x_gcc.h"
+    #else
+        #include "Sk4x_portable.h"
+    #endif
+#undef SK4X_PREAMBLE
+
+template <typename T> class Sk4x;
+typedef Sk4x<int>   Sk4i;
+typedef Sk4x<float> Sk4f;
+
+template <typename T> class Sk4x {
+public:
+    Sk4x();  // Uninitialized; use Sk4x(0,0,0,0) for zero.
+    Sk4x(T, T, T, T);
+    explicit Sk4x(const T[4]);
+
+    Sk4x(const Sk4x&);
+    Sk4x& operator=(const Sk4x&);
+
+    void set(T, T, T, T);
+
+    void store(T[4]) const;
+
+    template <typename Dst> Dst reinterpret() const;
+    template <typename Dst> Dst cast() const;
+
+    bool allTrue() const;
+    bool anyTrue() const;
+
+    Sk4x bitNot() const;
+    Sk4x bitAnd(const Sk4x&) const;
+    Sk4x bitOr (const Sk4x&) const;
+
+    Sk4i            equal(const Sk4x&) const;
+    Sk4i         notEqual(const Sk4x&) const;
+    Sk4i         lessThan(const Sk4x&) const;
+    Sk4i      greaterThan(const Sk4x&) const;
+    Sk4i    lessThanEqual(const Sk4x&) const;
+    Sk4i greaterThanEqual(const Sk4x&) const;
+
+    Sk4x      add(const Sk4x&) const;
+    Sk4x subtract(const Sk4x&) const;
+    Sk4x multiply(const Sk4x&) const;
+    Sk4x   divide(const Sk4x&) const;
+
+    static Sk4x Min(const Sk4x& a, const Sk4x& b);
+    static Sk4x Max(const Sk4x& a, const Sk4x& b);
+
+    // Swizzles follow OpenCL xyzw convention.
+    Sk4x zwxy() const;
+
+    // When there's a second argument, it's abcd.
+    static Sk4x XYAB(const Sk4x& xyzw, const Sk4x& abcd);
+    static Sk4x ZWCD(const Sk4x& xyzw, const Sk4x& abcd);
+
+private:
+    // It's handy to have Sk4f and Sk4i be mutual friends.
+    template <typename S> friend class Sk4x;
+
+#define SK4X_PRIVATE 1
+    #if defined(__clang__)
+        #include "Sk4x_clang.h"
+    #elif defined(__GNUC__)
+        #include "Sk4x_gcc.h"
+    #else
+        #include "Sk4x_portable.h"
+    #endif
+#undef SK4X_PRIVATE
+};
+
+#if defined(__clang__)
+    #include "Sk4x_clang.h"
+#elif defined(__GNUC__)
+    #include "Sk4x_gcc.h"
+#else
+    #include "Sk4x_portable.h"
+#endif
+
+// TODO ideas for enterprising coders:
+//   1) Code generated for Max() isn't as good in Sk4x_gcc.h as it is in _clang.  Why?
+//   2) Sk4x_sse.h would be good for Windows, and could possibly beat _clang / _gcc.
+//   3) Sk4x_neon.h might be a good idea if _clang / _gcc aren't good enough on ARM.
+
+
+#endif//Sk4x_DEFINED