starter procs for blending with pm4f

bench/Xfer4fBench.cpp

Index: bench/Xfer4fBench.cpp
diff --git a/bench/Xfer4fBench.cpp b/bench/Xfer4fBench.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2c281695ef02a8090834e476944135f47f8646db
--- /dev/null
+++ b/bench/Xfer4fBench.cpp
@@ -0,0 +1,73 @@
+
+/*
+ * Copyright 2016 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"
+#include "SkString.h"
+#include "SkXfer4f.h"
+
+#define INNER_LOOPS 100
+
+// Benchmark that draws non-AA rects or AA text with an SkXfermode::Mode.
+class Xfer4fBench : public Benchmark {
+public:
+    Xfer4fBench(SkXfermode::Mode mode, const char name[], bool doN, uint32_t flags) : fDoN(doN) {
+        fProc1 = SkPM4fXfer1ProcFactory(mode, flags);
+        fProcN = SkPM4fXferNProcFactory(mode, flags);
+        fName.printf("xfer4f_%s_%c_%s_%s", name, fDoN ? 'N' : '1',
+                     (flags & kSrcIsOpaque_SkXfer4fFlag) ? "opaque" : "alpha",
+                     (flags & kDstIsSRGB_SkXfer4fFlag) ? "srgb" : "linear");
+
+        SkPM4f c;
+        c.fVec[0] = 1; c.fVec[1] = 1; c.fVec[2] = 1; c.fVec[3] = 1;

[mtklein, 2016/01/29 15:23:00]

This can also be
   SkPM4f c = {{ 1,1,1,1 }};

[reed1, 2016/01/29 22:35:27]

Done.

+        for (int i = 0; i < N; ++i) {
+            fSrc[i] = c;
+            fDst[i] = 0;
+        }
+    }
+
+protected:
+    bool isSuitableFor(Backend backend) override { return backend == kNonRendering_Backend; }
+
+    const char* onGetName() override { return fName.c_str(); }
+
+    void onDraw(int loops, SkCanvas*) override {
+        for (int i = 0; i < loops; ++i) {

[mtklein, 2016/01/29 15:23:00]

Generally, you can also write 
  for (int i = 0; i < INNER_LOOPS*loops; ++i) {
     ...
  }

[reed1, 2016/01/29 22:35:27]

Ah, so you never pass 0 for loops?

[mtklein, 2016/01/30 01:18:19]

Um, it's true that nanobench happens to never pass 0 for loops, but I can't help
but ask... what do you think goes wrong if loops is 0?

That's still just

for (int i = 0; i < 0; ++i) {
    ...
}

+            for (int j = 0; j < INNER_LOOPS; ++j) {
+                if (fDoN) {
+                    fProcN(fDst, fSrc, N);
+                } else {
+                    fProc1(fDst, fSrc[0], N);
+                }
+            }
+        }
+    }
+
+private:
+    SkString        fName;
+    SkPM4fXfer1Proc fProc1;
+    SkPM4fXferNProc fProcN;
+    bool            fDoN;
+
+    enum {
+        N = 1000,
+    };
+    SkPM4f      fSrc[N];
+    SkPMColor   fDst[N];
+
+    typedef Benchmark INHERITED;
+};
+
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", false, kDstIsSRGB_SkXfer4fFlag); )

[mtklein, 2016/01/29 15:23:00]

Wanna throw in equal-pixel-count 8888 benchmarks here as a reference?

+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", false, 0); )
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", false, kDstIsSRGB_SkXfer4fFlag | kSrcIsOpaque_SkXfer4fFlag); )
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", false, kSrcIsOpaque_SkXfer4fFlag); )
+
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", true,  kDstIsSRGB_SkXfer4fFlag); )
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", true,  0); )
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", true,  kDstIsSRGB_SkXfer4fFlag | kSrcIsOpaque_SkXfer4fFlag); )
+DEF_BENCH( return new Xfer4fBench(SkXfermode::kSrcOver_Mode, "srcover", true,  kSrcIsOpaque_SkXfer4fFlag); )