Add divide to Sk2x, use native vdiv and vsqrt on ARM 64.

src/opts/Sk2x_neon.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // It is important _not_ to put header guards here.
 // This file will be intentionally included three times.
 
@@ skipping 26 matching lines @@
     fVec = vset_lane_f32(b, fVec, 1);
 }
 M(Sk2f&) operator=(const Sk2f& o) { fVec = o.fVec; return *this; }
 
 M(Sk2f) Load(const float vals[2]) { return vld1_f32(vals); }
 M(void) store(float vals[2]) const { vst1_f32(vals, fVec); }
 
 M(Sk2f)      add(const Sk2f& o) const { return vadd_f32(fVec, o.fVec); }
 M(Sk2f) subtract(const Sk2f& o) const { return vsub_f32(fVec, o.fVec); }
 M(Sk2f) multiply(const Sk2f& o) const { return vmul_f32(fVec, o.fVec); }
+M(Sk2f)   divide(const Sk2f& o) const {
+#if defined(SK_CPU_ARM64)
+    return vdiv_f32(fVec, o.fVec);
+#else
+    float32x2_t est0 = vrecpe_f32(o.fVec),
+                est1 = vmul_f32(vrecps_f32(est0, o.fVec), est0),
+                est2 = vmul_f32(vrecps_f32(est1, o.fVec), est1);
+    return vmul_f32(est2, fVec);
+#endif
+}
 
 M(Sk2f) Min(const Sk2f& a, const Sk2f& b) { return vmin_f32(a.fVec, b.fVec); }
 M(Sk2f) Max(const Sk2f& a, const Sk2f& b) { return vmax_f32(a.fVec, b.fVec); }
 
 M(Sk2f) rsqrt() const {
     float32x2_t est0 = vrsqrte_f32(fVec),
                 est1 = vmul_f32(vrsqrts_f32(fVec, vmul_f32(est0, est0)), est0);
     return est1;
 }
 M(Sk2f)  sqrt() const {
+#if defined(SK_CPU_ARM64)
+    return vsqrt_f32(fVec);
+#else
     float32x2_t est1 = this->rsqrt().fVec,
     // An extra step of Newton's method to refine the estimate of 1/sqrt(this).
                 est2 = vmul_f32(vrsqrts_f32(fVec, vmul_f32(est1, est1)), est1);
     return vmul_f32(fVec, est2);
+#endif
 }
 
 #undef M
 
 #define M(...) template <> inline __VA_ARGS__ Sk2x<double>::
 
 #if defined(SK_CPU_ARM64)
     M() Sk2x() {}
     M() Sk2x(double val)        { fVec = vdupq_n_f64(val);    }
     M() Sk2x(double a, double b) {
         fVec = vsetq_lane_f64(a, fVec, 0);
         fVec = vsetq_lane_f64(b, fVec, 1);
     }
     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)   divide(const Sk2d& o) const { return vdivq_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);
-    }
+    M(Sk2d)  sqrt() const { return vsqrtq_f64(fVec); }
 
 #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)   divide(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
 
 #endif