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Unified Diff: bench/ScalarBench.cpp

Issue 305033002: TSAN caught us racing in ScalarBench.cpp (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: fix windows? Created 6 years, 7 months ago
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Index: bench/ScalarBench.cpp
diff --git a/bench/ScalarBench.cpp b/bench/ScalarBench.cpp
index 54ee0fcd195967a73bd532b2bf9b08872fc9b76d..77849c6444df2f0823e2b589499ff9ef40d4ca6f 100644
--- a/bench/ScalarBench.cpp
+++ b/bench/ScalarBench.cpp
@@ -41,18 +41,6 @@ private:
typedef SkBenchmark INHERITED;
};
-// we want to stop the compiler from eliminating code that it thinks is a no-op
-// so we have a non-static global we increment, hoping that will convince the
-// compiler to execute everything
-int gScalarBench_NonStaticGlobal;
-
-#define always_do(pred) \
- do { \
- if (pred) { \
- ++gScalarBench_NonStaticGlobal; \
- } \
- } while (0)
-
// having unknown values in our arrays can throw off the timing a lot, perhaps
// handling NaN values is a lot slower. Anyway, this guy is just meant to put
// reasonable values in our arrays.
@@ -71,8 +59,10 @@ public:
protected:
virtual int mulLoopCount() const { return 4; }
virtual void performTest() {
- always_do(fArray[6] != 0.0f || fArray[7] != 0.0f || fArray[8] != 1.0f);
- always_do(fArray[2] != 0.0f || fArray[5] != 0.0f);
+ // xoring into a volatile prevents the compiler from optimizing these checks away.
+ volatile bool junk = false;
+ junk ^= (fArray[6] != 0.0f || fArray[7] != 0.0f || fArray[8] != 1.0f);
+ junk ^= (fArray[2] != 0.0f || fArray[5] != 0.0f);
}
private:
float fArray[9];
@@ -88,11 +78,13 @@ public:
protected:
virtual int mulLoopCount() const { return 4; }
virtual void performTest() {
- always_do(SkScalarAs2sCompliment(fArray[6]) |
- SkScalarAs2sCompliment(fArray[7]) |
- (SkScalarAs2sCompliment(fArray[8]) - kPersp1Int));
- always_do(SkScalarAs2sCompliment(fArray[2]) |
- SkScalarAs2sCompliment(fArray[5]));
+ // xoring into a volatile prevents the compiler from optimizing these checks away.
+ volatile int32_t junk = 0;
+ junk ^= (SkScalarAs2sCompliment(fArray[6]) |
+ SkScalarAs2sCompliment(fArray[7]) |
+ (SkScalarAs2sCompliment(fArray[8]) - kPersp1Int));
+ junk ^= (SkScalarAs2sCompliment(fArray[2]) |
+ SkScalarAs2sCompliment(fArray[5]));
}
private:
static const int32_t kPersp1Int = 0x3f800000;
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