commit to xfermode objects being immutable

bench/XfermodeBench.cpp

Index: bench/XfermodeBench.cpp
diff --git a/bench/XfermodeBench.cpp b/bench/XfermodeBench.cpp
index e9b3b95021ed5f1ed8ea9f4d4719d31938042651..da11b29e6a76bdd1471c9dfd4bbaa471b60ba431 100644
--- a/bench/XfermodeBench.cpp
+++ b/bench/XfermodeBench.cpp
@@ -62,6 +62,29 @@ private:
     typedef SkBenchmark INHERITED;
 };
 
+class XferCreateBench : public SkBenchmark {
+    enum {
+        N = 1000
+    };
+public:
+    XferCreateBench() {}
+    
+protected:
+    virtual const char* onGetName() SK_OVERRIDE { return "xfermode_create"; }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        for (int outer = 0; outer < N; ++outer) {

[mtklein, 2013/10/04 14:26:40]

Instead of N, use this->getLoops().  (Or N * this->getLoops() if you like, but
I'd drop the N.)

Here's how I diagnosed:
$ out/Release/bench --match xfermode_create --verbose

xfermode_create 8888: 2.76 1.36 0.679 0.342 0.17 0.0852 0.0425 0.0132 0.00439
0.0022 0.0011 0.000549 0.000275 0.000137 6.91e-05 3.43e-05 1.73e-05 8.58e-06
4.32e-06 2.16e-06 1.08e-06 5.4e-07 2.68e-07 1.34e-07 6.73e-08 3.35e-08 1.68e-08
8.38e-09 4.19e-09 2.09e-09 1.05e-09 Can't get xfermode_create 8888 to converge
in 4000ms.

... (other configs elided)

Notice how the times displayed are halving each time?  That's because it's
ramping up this->getLoops() by two each time, but the bench is ignoring it and
running a constant number of times.

+            for (int i = 0; i <= SkXfermode::kLastMode; ++i) {
+                SkXfermode* xfer = SkXfermode::Create(SkXfermode::Mode(i));
+                SkSafeUnref(xfer);
+            }
+        }
+    }
+    
+private:
+    typedef SkBenchmark INHERITED;
+};
+
 //////////////////////////////////////////////////////////////////////////////
 
 #define CONCAT_I(x, y) x ## y
@@ -106,3 +129,5 @@ BENCH(SkXfermode::kLuminosity_Mode)
 BENCH(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode), "SrcInLuma")
 BENCH(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode), "DstInLuma")
 BENCH(SkLumaMaskXfermode::Create(SkXfermode::kSrcOver_Mode), "SrcOverLuma")
+
+DEF_BENCH(return new XferCreateBench;)