Start to vectorize SkTileGrid.

src/core/Sk4x_gcc.h

Index: src/core/Sk4x_gcc.h
diff --git a/src/core/Sk4x_gcc.h b/src/core/Sk4x_gcc.h
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index 0000000000000000000000000000000000000000..35bc39553359551707c9414ccd70b30f21689a6b
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+++ b/src/core/Sk4x_gcc.h
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+// It is important _not_ to put header guards here.
+// This file will be intentionally included three times.
+
+// Useful reading:
+//   https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
+
+#if defined(SK4X_PREAMBLE)
+
+#elif defined(SK4X_PRIVATE)
+    typedef T Vector __attribute__((vector_size(16)));
+
+    /*implicit*/ Sk4x(Vector vec) : fVec(vec) {}
+    static inline Vector ShuffleImpl(Vector a, Vector b, int __attribute__((vector_size(16))) mask);
+    template <int m, int a, int s, int k>
+    static Sk4x Shuffle(const Sk4x&, const Sk4x&);
+
+    Vector fVec;
+
+#else  // defined(SK4X_PRIVATE)
+
+template <typename T>
+Sk4x<T>::Sk4x() { }
+
+template <typename T>
+Sk4x<T>::Sk4x(T a, T b, T c, T d) { this->set(a,b,c,d); }
+
+template <typename T>
+Sk4x<T>::Sk4x(const T vals[4]) {
+    fVec = *reinterpret_cast<const Vector*>(vals);  // Should compile to moveaps or moveups.
+}
+
+template <typename T>
+Sk4x<T>::Sk4x(const Sk4x<T>& other) { *this = other; }
+
+template <typename T>
+Sk4x<T>& Sk4x<T>::operator=(const Sk4x<T>& other) { fVec = other.fVec; return *this; }
+
+template <typename T>
+void Sk4x<T>::set(T a, T b, T c, T d) {
+    Vector v = { a, b, c, d };
+    fVec = v;
+}
+
+template <typename T>
+void Sk4x<T>::store(T vals[4]) const {
+    *reinterpret_cast<Vector*>(vals) = fVec;
+}
+
+template <typename T>
+template <typename Dst> Dst Sk4x<T>::reinterpret() const {
+    return Dst((typename Dst::Vector)fVec);
+}
+
+template <typename T>
+template <typename Dst> Dst Sk4x<T>::cast() const {
+    return Dst(fVec[0], fVec[1], fVec[2], fVec[3]);
+}
+
+template <typename T>
+bool Sk4x<T>::allTrue() const { return fVec[0] & fVec[1] & fVec[2] & fVec[3]; }
+template <typename T>
+bool Sk4x<T>::anyTrue() const { return fVec[0] | fVec[1] | fVec[2] | fVec[3]; }
+
+template <typename T> Sk4x<T> Sk4x<T>::bitNot() const { return Sk4i(~fVec); }
+
+template <typename T> Sk4x<T> Sk4x<T>::bitAnd(const Sk4x& other) const { return fVec & other.fVec; }
+template <typename T> Sk4x<T> Sk4x<T>::bitOr (const Sk4x& other) const { return fVec | other.fVec; }
+
+template <typename T>
+Sk4i Sk4x<T>::           equal(const Sk4x<T>& other) const { return fVec == other.fVec; }
+template <typename T>
+Sk4i Sk4x<T>::        notEqual(const Sk4x<T>& other) const { return fVec != other.fVec; }
+template <typename T>
+Sk4i Sk4x<T>::        lessThan(const Sk4x<T>& other) const { return fVec  < other.fVec; }
+template <typename T>
+Sk4i Sk4x<T>::     greaterThan(const Sk4x<T>& other) const { return fVec  > other.fVec; }
+template <typename T>
+Sk4i Sk4x<T>::   lessThanEqual(const Sk4x<T>& other) const { return fVec <= other.fVec; }
+template <typename T>
+Sk4i Sk4x<T>::greaterThanEqual(const Sk4x<T>& other) const { return fVec >= other.fVec; }
+
+template <typename T>
+Sk4x<T> Sk4x<T>::     add(const Sk4x<T>& other) const { return fVec + other.fVec; }
+template <typename T>
+Sk4x<T> Sk4x<T>::subtract(const Sk4x<T>& other) const { return fVec - other.fVec; }
+template <typename T>
+Sk4x<T> Sk4x<T>::multiply(const Sk4x<T>& other) const { return fVec * other.fVec; }
+template <typename T>
+Sk4x<T> Sk4x<T>::  divide(const Sk4x<T>& other) const { return fVec / other.fVec; }
+
+template <typename T>
+Sk4x<T> Sk4x<T>::Min(const Sk4x<T>& a, const Sk4x<T>& b) {
+    return a.fVec < b.fVec ? a.fVec : b.fVec;  // This makes great SSE code (1 minps op)...
+}
+
+template <typename T>
+Sk4x<T> Sk4x<T>::Max(const Sk4x<T>& a, const Sk4x<T>& b) {
+    return a.fVec < b.fVec ? b.fVec : a.fVec;  // ...but this doesn't look so good (7 ops?).
+}
+
+// GCC 4.8 has a bug that leads it to segfault when presented with the obvious code for Shuffle:
+//   Sk4i::Vector mask = { m,a,s,k };
+//   return __builtin_shuffle(x.fVec, y.fVec, mask);
+//
+// This roundabout implementation via ShuffleImpl works around that bug,
+//   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57509
+
+template <>
+inline Sk4i::Vector Sk4i::ShuffleImpl(Sk4i::Vector x, Sk4i::Vector y, Sk4i::Vector mask) {
+    return __builtin_shuffle(x,y, mask);
+}
+
+template <>
+inline Sk4f::Vector Sk4f::ShuffleImpl(Sk4f::Vector x, Sk4f::Vector y, Sk4i::Vector mask) {
+    return __builtin_shuffle(x,y, mask);
+}
+
+template <typename T>
+template <int m, int a, int s, int k>
+Sk4x<T> Sk4x<T>::Shuffle(const Sk4x<T>& x, const Sk4x<T>& y) {
+    Sk4i::Vector mask = { m,a,s,k };
+    return ShuffleImpl(x.fVec, y.fVec, mask);
+}
+
+template <typename T>
+Sk4x<T> Sk4x<T>::zwxy() const { return Shuffle<2,3,0,1>(*this, *this); }
+
+template <typename T>
+Sk4x<T> Sk4x<T>::XYAB(const Sk4x& xyzw, const Sk4x& abcd) { return Shuffle<0,1,4,5>(xyzw, abcd); }
+
+template <typename T>
+Sk4x<T> Sk4x<T>::ZWCD(const Sk4x& xyzw, const Sk4x& abcd) { return Shuffle<2,3,6,7>(xyzw, abcd); }
+
+#endif // defined(SK4X_PRIVATE)