Start to vectorize SkTileGrid.

src/core/Sk4x.h

+#ifndef Sk4x_DEFINED
+#define Sk4x_DEFINED
+
+// Sk4x.h brings the fun of GCC vector extensions* to platforms without them (MSVC).
+// We also paper over some of the differences between GCC and Clang's flavors.
+//
+// * https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
+//   http://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-vectors
+
+// First code common to both Clang and GCC.
+#if defined(__GNUC__)
+    typedef float Sk4f __attribute__((vector_size(16)));
+    typedef int   Sk4i __attribute__((vector_size(16)));
+#endif
+
+// Now code specialized for Clang xor GCC.
+#if defined(__clang__)
+    #define Sk4Shuffle(x,y, m,a,s,k) __builtin_shufflevector(x,y, m,a,s,k)
+
+    #if __has_builtin(__builtin_convertvector)
+        template<typename D, typename S>
+        D Sk4Convert(S src) { return __builtin_convertvector(src, D); }
+    #else
+        template<typename D, typename S>
+        D Sk4Convert(S src) {
+            D dst = { (D)src[0], (D)src[1], (D)src[2], (D)src[3] };
+            return dst;
+        }
+    #endif
+
+#elif defined(__GNUC__)
+    template <typename V>
+    V Sk4Shuffle(V x, V y, int m, int a, int s, int k) {
+        Sk4i mask = { m, a, s, k };
+        return __builtin_shuffle(x, y, mask);
+    }
+
+    template<typename D, typename S>
+    D Sk4Convert(S src) {
+        D dst = { (D)src[0], (D)src[1], (D)src[2], (D)src[3] };
+        return dst;
+    }
+
+#endif
+
+#if !defined(__GNUC__)
+    #error "Need to implement scalar versions."
+#endif
+
+
+// Finally code that will work no matter the implementation.
+inline Sk4f SkLoad4f(float a, float b, float c, float d) {
+    Sk4f v = { a, b, c, d };
+    return v;
+}
+
+inline Sk4i SkLoad4i(int a, int b, int c, int d) {
+    Sk4i v = { a, b, c, d };
+    return v;
+}
+
+inline Sk4f SkLoad4f(const float fs[4]) {
+    Sk4f v = { fs[0], fs[1], fs[2], fs[3] };
+    return v;
+}
+
+inline Sk4i SkLoad4i(const int is[4]) {
+    Sk4i v = { is[0], is[1], is[2], is[3] };
+    return v;
+}
+
+inline void SkStore4(Sk4f v, float fs[4]) {
+    *reinterpret_cast<Sk4f*>(fs) = v;
+}
+
+inline void SkStore4(Sk4i v, int is[4]) {
+    *reinterpret_cast<Sk4i*>(is) = v;
+}
+
+inline bool Sk4All(Sk4i v) {

[reed1, 2014/10/10 16:06:11]

as we start to actually use these, we might discuss the best patterns for naming
some of these (for clarity). e.g. this name wasn't obvious to me. perhaps some
convention for all predicate helpers? (dunno) Sk4_AND Sk4_OR etc. ? No real
suggestion at this time.

[mtklein, 2014/10/10 21:26:07]

See what you think of the API at PS 20?

+    return v[0] & v[1] & v[2] & v[3];
+}
+
+template <typename V>
+V Sk4Min(V a, V b) {
+    Sk4i less = a < b;
+    return ((Sk4i)a & less) | ((Sk4i)b & ~less);
+}
+
+template <typename V>
+V Sk4Max(V a, V b) {
+    Sk4i less = a < b;
+    return ((Sk4i)b & less) | ((Sk4i)a & ~less);
+}
+
+#endif//Sk4x_DEFINED