Find cubic KLM functionals directly

- Updates GrPathUtils to computes the KLM functionals directly instead
  of deriving them from their explicit values at the control points.
- Updates the utility to return these functionals as a matrix
  rather than an array of scalar values.
- Adds a benchmark for chopCubicAtLoopIntersection.

BUG=skia:

Change-Id: I97a9b5cf610d33e15c9af96b9d9a8eb4a94b1ca7
Reviewed-on: https://skia-review.googlesource.com/9951
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/bench/CubicKLMBench.cpp b/bench/CubicKLMBench.cpp
new file mode 100644
index 0000000000..3c8f740bc7
--- /dev/null
+++ b/bench/CubicKLMBench.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Benchmark.h"
+
+#if SK_SUPPORT_GPU
+
+#include "GrPathUtils.h"
+#include "SkGeometry.h"
+
+class CubicKLMBench : public Benchmark {
+public:
+    CubicKLMBench(SkScalar x0, SkScalar y0, SkScalar x1, SkScalar y1,
+                  SkScalar x2, SkScalar y2, SkScalar x3, SkScalar y3)  {
+        fPoints[0].set(x0, y0);
+        fPoints[1].set(x1, y1);
+        fPoints[2].set(x2, y2);
+        fPoints[3].set(x3, y3);
+
+        fName = "cubic_klm_";
+        SkScalar d[3];
+        switch (SkClassifyCubic(fPoints, d)) {
+            case kSerpentine_SkCubicType:
+                fName.append("serp");
+                break;
+            case kLoop_SkCubicType:
+                fName.append("loop");
+                break;
+            default:
+                SkFAIL("Unexpected cubic type");
+                break;
+        }
+    }
+
+    bool isSuitableFor(Backend backend) override {
+        return backend == kNonRendering_Backend;
+    }
+
+    const char* onGetName() override {
+        return fName.c_str();
+    }
+
+    void onDraw(int loops, SkCanvas*) override {
+        SkPoint dst[10];
+        SkMatrix klm;
+        int loopIdx;
+        for (int i = 0; i < loops * 50000; ++i) {
+            GrPathUtils::chopCubicAtLoopIntersection(fPoints, dst, &klm, &loopIdx);
+        }
+    }
+
+private:
+    SkPoint     fPoints[4];
+    SkString    fName;
+
+    typedef Benchmark INHERITED;
+};
+
+DEF_BENCH( return new CubicKLMBench(285.625f, 499.687f, 411.625f, 808.188f,
+                                    1064.62f, 135.688f, 1042.63f, 585.187f); )
+DEF_BENCH( return new CubicKLMBench(635.625f, 614.687f, 171.625f, 236.188f,
+                                    1064.62f, 135.688f, 516.625f, 570.187f); )
+
+#endif