From 80f709a0d7f2f1d0d35a292c0c3189d3a50b4993 Mon Sep 17 00:00:00 2001 From: mtklein Date: Mon, 2 Jun 2014 12:41:07 -0700 Subject: 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 --- bench/ScalarBench.cpp | 30 +++++++++++------------------- 1 file changed, 11 insertions(+), 19 deletions(-) (limited to 'bench/ScalarBench.cpp') diff --git a/bench/ScalarBench.cpp b/bench/ScalarBench.cpp index 54ee0fcd19..77849c6444 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; -- cgit v1.2.3