Clean up another silly race in benches when run concurrently.

bench/MatrixBench.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkBenchmark.h"
 #include "SkMatrix.h"
 #include "SkMatrixUtils.h"
@@ skipping 23 matching lines @@
     virtual void onDraw(const int loops, SkCanvas*) {
         for (int i = 0; i < loops; i++) {
             this->performTest();
         }
     }
 
 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 gMatrixBench_NonStaticGlobal;
-
-#define always_do(pred)                     \
-    do {                                    \
-        if (pred) {                         \
-            ++gMatrixBench_NonStaticGlobal; \
-        }                                   \
-    } while (0)
 
 class EqualsMatrixBench : public MatrixBench {
 public:
     EqualsMatrixBench() : INHERITED("equals") {}
 protected:
     virtual void performTest() {
         SkMatrix m0, m1, m2;
 
         m0.reset();
         m1.reset();
         m2.reset();
-        always_do(m0 == m1);
-        always_do(m1 == m2);
-        always_do(m2 == m0);
+
+        // xor into a volatile prevents these comparisons from being optimized away.
+        volatile bool junk = false;
+        junk ^= (m0 == m1);
+        junk ^= (m1 == m2);
+        junk ^= (m2 == m0);
     }
 private:
     typedef MatrixBench INHERITED;
 };
 
 class ScaleMatrixBench : public MatrixBench {
 public:
     ScaleMatrixBench() : INHERITED("scale") {
         fSX = fSY = 1.5f;
         fM0.reset();
@@ skipping 157 matching lines @@
         fArray[8] = (float) fRnd.nextS();
     }
 protected:
     // Putting random generation of the matrix inside performTest()
     // would help us avoid anomalous runs, but takes up 25% or
     // more of the function time.
     virtual void performTest() {
         fMatrix.setAll(fArray[0], fArray[1], fArray[2],
                        fArray[3], fArray[4], fArray[5],
                        fArray[6], fArray[7], fArray[8]);
-        always_do(fMatrix.getType());
+        // xoring into a volatile prevents the compiler from optimizing these away
+        volatile int junk = 0;
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
-        always_do(fMatrix.getType());
+        junk ^= (fMatrix.getType());
     }
 private:
     SkMatrix fMatrix;
     float fArray[9];
     SkRandom fRnd;
     typedef MatrixBench INHERITED;
 };
 
 class ScaleTransMixedMatrixBench : public MatrixBench {
  public:
@@ skipping 198 matching lines @@
 
 DEF_BENCH( return new InvertMapRectMatrixBench(
                            "invert_maprect_typemask_nonpersp",
                            InvertMapRectMatrixBench::kUncachedTypeMask_Flag |
                            InvertMapRectMatrixBench::kScale_Flag |
                            InvertMapRectMatrixBench::kRotate_Flag |
                            InvertMapRectMatrixBench::kTranslate_Flag); )
 
 DEF_BENCH( return new ScaleTransMixedMatrixBench(); )
 DEF_BENCH( return new ScaleTransDoubleMatrixBench(); )