Speeup hairline curves (quads and cubics)

/skia/trunk> cat ../old.txt
maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
   9M	1	4.28ms	4.32ms	4.36ms	4.67ms	3%	▄▁▁▃▂▂▁▁▂█	8888	path_hairline_small_AA_cubic
   9M	1	743µs	767µs	770µs	825µs	4%	▃▃▇▃▁▁▅▁█▁	8888	path_hairline_small_AA_conic
   9M	1	533µs	606µs	598µs	680µs	9%	▁▂▂█▆▇▇▄▂▂	8888	path_hairline_small_AA_quad
   9M	1	451µs	452µs	456µs	495µs	3%	▁▁▁▁█▁▁▁▁▁	8888	path_hairline_small_AA_line

/skia/trunk> cat ../new.txt
maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
   9M	1	827µs	827µs	831µs	869µs	2%	▁▁▁▁▁▁▁█▁▁	8888	path_hairline_small_AA_cubic
   9M	1	515µs	517µs	517µs	518µs	0%	▇█▆▅▃▃▁▁▁▅	8888	path_hairline_small_AA_conic
   9M	1	310µs	311µs	315µs	332µs	2%	▂▁█▆▁▁▁▁▁▁	8888	path_hairline_small_AA_quad
   9M	1	254µs	254µs	258µs	276µs	3%	▁▁▁▁▁▁▁█▇▂	8888	path_hairline_small_AA_line

Edited revert of https://codereview.chromium.org/1085013003

TBR=

Review URL: https://codereview.chromium.org/1078413003

1 files changed, 34 insertions, 0 deletions

diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp
index 50af22de37..5979615425 100644
--- a/src/core/SkGeometry.cpp
+++ b/src/core/SkGeometry.cpp
@@ -9,6 +9,7 @@
 #include "SkMatrix.h"
 #include "SkNx.h"
 
+#if 0
 static Sk2s from_point(const SkPoint& point) {
     return Sk2s::Load(&point.fX);
 }
@@ -18,6 +19,7 @@ static SkPoint to_point(const Sk2s& x) {
     x.store(&point.fX);
     return point;
 }
+#endif
 
 static SkVector to_vector(const Sk2s& x) {
     SkVector vector;
@@ -135,6 +137,18 @@ static SkScalar eval_quad_derivative(const SkScalar src[], SkScalar t) {
     return 2 * SkScalarMulAdd(A, t, B);
 }
 
+void SkQuadToCoeff(const SkPoint pts[3], SkPoint coeff[3]) {
+    Sk2s p0 = from_point(pts[0]);
+    Sk2s p1 = from_point(pts[1]);
+    Sk2s p2 = from_point(pts[2]);
+
+    Sk2s p1minus2 = p1 - p0;
+
+    coeff[0] = to_point(p2 - p1 - p1 + p0);     // A * t^2
+    coeff[1] = to_point(p1minus2 + p1minus2);   // B * t
+    coeff[2] = pts[0];                          // C
+}
+
 void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt, SkVector* tangent) {
     SkASSERT(src);
     SkASSERT(t >= 0 && t <= SK_Scalar1);
@@ -452,6 +466,26 @@ void SkChopCubicAt(const SkPoint src[4], SkPoint dst[7], SkScalar t) {
     dst[6] = src[3];
 }
 
+void SkCubicToCoeff(const SkPoint pts[4], SkPoint coeff[4]) {
+    Sk2s p0 = from_point(pts[0]);
+    Sk2s p1 = from_point(pts[1]);
+    Sk2s p2 = from_point(pts[2]);
+    Sk2s p3 = from_point(pts[3]);
+
+    const Sk2s three(3);
+    Sk2s p1minusp2 = p1 - p2;
+
+    Sk2s D = p0;
+    Sk2s A = p3 + three * p1minusp2 - D;
+    Sk2s B = three * (D - p1minusp2 - p1);
+    Sk2s C = three * (p1 - D);
+
+    coeff[0] = to_point(A);
+    coeff[1] = to_point(B);
+    coeff[2] = to_point(C);
+    coeff[3] = to_point(D);
+}
+
 /*  http://code.google.com/p/skia/issues/detail?id=32
 
     This test code would fail when we didn't check the return result of