TSAN caught us racing in ScalarBench.cpp
http://108.170.220.102:10117/builders/Test-Ubuntu13-ShuttleA-HD2000-x86_64-Debug-TSAN/builds/914/steps/RunDM/logs/stdio
BUG=skia:
Committed: http://code.google.com/p/skia/source/detail?r=14992
R=reed@google.com, mtklein@google.com
Author: mtklein@chromium.org
Review URL: https://codereview.chromium.org/305033002
diff --git a/bench/ScalarBench.cpp b/bench/ScalarBench.cpp
index 54ee0fc..77849c6 100644
--- a/bench/ScalarBench.cpp
+++ b/bench/ScalarBench.cpp
@@ -41,18 +41,6 @@
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 @@
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 @@
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;