Specialize Sk2d for ARM64

src/opts/Sk2x_neon.h

Index: src/opts/Sk2x_neon.h
diff --git a/src/opts/Sk2x_neon.h b/src/opts/Sk2x_neon.h
index cc4e799490927c2fd4562df7bdd3336d26cfcf48..00ab00aeaa6ddd5a3db3eb58f161e6ef78eddef9 100644
--- a/src/opts/Sk2x_neon.h
+++ b/src/opts/Sk2x_neon.h
@@ -15,7 +15,11 @@
     #include <math.h>
     template <typename T> struct SkScalarToSIMD;
     template <> struct SkScalarToSIMD< float> { typedef float32x2_t Type; };
-    template <> struct SkScalarToSIMD<double> { typedef double Type[2];   };
+    #if defined(SK_CPU_ARM64)
+        template <> struct SkScalarToSIMD<double> { typedef float64x2_t Type; };
+    #else
+        template <> struct SkScalarToSIMD<double> { typedef double Type[2];   };
+    #endif
 
 
 #elif defined(SK2X_PRIVATE)
@@ -28,10 +32,7 @@
 
 M() Sk2x() {}
 M() Sk2x(float val)        { fVec = vdup_n_f32(val);    }
-M() Sk2x(float a, float b) {
-    fVec = vset_lane_f32(a, fVec, 0);
-    fVec = vset_lane_f32(b, fVec, 1);
-}
+M() Sk2x(float a, float b) { fVec = (float32x2_t) { a, b }; }
 M(Sk2f&) operator=(const Sk2f& o) { fVec = o.fVec; return *this; }
 
 M(Sk2f) Load(const float vals[2]) { return vld1_f32(vals); }
@@ -60,33 +61,62 @@ M(Sk2f)  sqrt() const {
 
 #define M(...) template <> inline __VA_ARGS__ Sk2x<double>::
 
-// TODO: #ifdef SK_CPU_ARM64 use float64x2_t for Sk2d.
-
-M() Sk2x() {}
-M() Sk2x(double val)         { fVec[0] = fVec[1] = val; }
-M() Sk2x(double a, double b) { fVec[0] = a; fVec[1] = b; }
-M(Sk2d&) operator=(const Sk2d& o) {
-    fVec[0] = o.fVec[0];
-    fVec[1] = o.fVec[1];
-    return *this;
-}
-
-M(Sk2d) Load(const double vals[2]) { return Sk2d(vals[0], vals[1]); }
-M(void) store(double vals[2]) const { vals[0] = fVec[0]; vals[1] = fVec[1]; }
-
-M(Sk2d)      add(const Sk2d& o) const { return Sk2d(fVec[0] + o.fVec[0], fVec[1] + o.fVec[1]); }
-M(Sk2d) subtract(const Sk2d& o) const { return Sk2d(fVec[0] - o.fVec[0], fVec[1] - o.fVec[1]); }
-M(Sk2d) multiply(const Sk2d& o) const { return Sk2d(fVec[0] * o.fVec[0], fVec[1] * o.fVec[1]); }
-
-M(Sk2d) Min(const Sk2d& a, const Sk2d& b) {
-    return Sk2d(SkTMin(a.fVec[0], b.fVec[0]), SkTMin(a.fVec[1], b.fVec[1]));
-}
-M(Sk2d) Max(const Sk2d& a, const Sk2d& b) {
-    return Sk2d(SkTMax(a.fVec[0], b.fVec[0]), SkTMax(a.fVec[1], b.fVec[1]));
-}
-
-M(Sk2d) rsqrt() const { return Sk2d(1.0/::sqrt(fVec[0]), 1.0/::sqrt(fVec[1])); }
-M(Sk2d)  sqrt() const { return Sk2d(    ::sqrt(fVec[0]),     ::sqrt(fVec[1])); }
+#if defined(SK_CPU_ARM64)
+    M() Sk2x() {}
+    M() Sk2x(double val)         { fVec = vdupq_n_f64(val);    }
+    M() Sk2x(double a, double b) { fVec = (float64x2_t) { a, b }; }
+    M(Sk2d&) operator=(const Sk2d& o) { fVec = o.fVec; return *this; }
+
+    M(Sk2d) Load(const double vals[2]) { return vld1q_f64(vals); }
+    M(void) store(double vals[2]) const { vst1q_f64(vals, fVec); }
+
+    M(Sk2d)      add(const Sk2d& o) const { return vaddq_f64(fVec, o.fVec); }
+    M(Sk2d) subtract(const Sk2d& o) const { return vsubq_f64(fVec, o.fVec); }
+    M(Sk2d) multiply(const Sk2d& o) const { return vmulq_f64(fVec, o.fVec); }
+
+    M(Sk2d) Min(const Sk2d& a, const Sk2d& b) { return vminq_f64(a.fVec, b.fVec); }
+    M(Sk2d) Max(const Sk2d& a, const Sk2d& b) { return vmaxq_f64(a.fVec, b.fVec); }
+
+    M(Sk2d) rsqrt() const {
+        float64x2_t est0 = vrsqrteq_f64(fVec),
+                    est1 = vmulq_f64(vrsqrtsq_f64(fVec, vmulq_f64(est0, est0)), est0);
+        return est1;
+    }
+    M(Sk2d)  sqrt() const {
+        float64x2_t est1 = this->rsqrt().fVec,
+        // Two extra steps of Newton's method to refine the estimate of 1/sqrt(this).
+                    est2 = vmulq_f64(vrsqrtsq_f64(fVec, vmulq_f64(est1, est1)), est1),
+                    est3 = vmulq_f64(vrsqrtsq_f64(fVec, vmulq_f64(est2, est2)), est2);
+        return vmulq_f64(fVec, est3);
+    }
+
+#else  // Scalar implementation for 32-bit chips, which don't have float64x2_t.
+    M() Sk2x() {}
+    M() Sk2x(double val)         { fVec[0] = fVec[1] = val; }
+    M() Sk2x(double a, double b) { fVec[0] = a; fVec[1] = b; }
+    M(Sk2d&) operator=(const Sk2d& o) {
+        fVec[0] = o.fVec[0];
+        fVec[1] = o.fVec[1];
+        return *this;
+    }
+
+    M(Sk2d) Load(const double vals[2]) { return Sk2d(vals[0], vals[1]); }
+    M(void) store(double vals[2]) const { vals[0] = fVec[0]; vals[1] = fVec[1]; }
+
+    M(Sk2d)      add(const Sk2d& o) const { return Sk2d(fVec[0] + o.fVec[0], fVec[1] + o.fVec[1]); }
+    M(Sk2d) subtract(const Sk2d& o) const { return Sk2d(fVec[0] - o.fVec[0], fVec[1] - o.fVec[1]); }
+    M(Sk2d) multiply(const Sk2d& o) const { return Sk2d(fVec[0] * o.fVec[0], fVec[1] * o.fVec[1]); }
+
+    M(Sk2d) Min(const Sk2d& a, const Sk2d& b) {
+        return Sk2d(SkTMin(a.fVec[0], b.fVec[0]), SkTMin(a.fVec[1], b.fVec[1]));
+    }
+    M(Sk2d) Max(const Sk2d& a, const Sk2d& b) {
+        return Sk2d(SkTMax(a.fVec[0], b.fVec[0]), SkTMax(a.fVec[1], b.fVec[1]));
+    }
+
+    M(Sk2d) rsqrt() const { return Sk2d(1.0/::sqrt(fVec[0]), 1.0/::sqrt(fVec[1])); }
+    M(Sk2d)  sqrt() const { return Sk2d(    ::sqrt(fVec[0]),     ::sqrt(fVec[1])); }
+#endif
 
 #undef M