Add DoNotOptimize and use it in tests.

Bug: http://b/148307629
Test: treehugger
Change-Id: I3b1726ae55116f6553ea38fe163abdde179c21f0

1 files changed, 6 insertions, 5 deletions

diff --git a/tests/fenv_test.cpp b/tests/fenv_test.cpp
index e983a1c08..89c7fd5c9 100644
--- a/tests/fenv_test.cpp
+++ b/tests/fenv_test.cpp
@@ -22,19 +22,20 @@
 #include <stdint.h>
 
 static void TestRounding(float expectation1, float expectation2) {
-  // volatile to prevent compiler optimizations.
+  // Volatile to prevent compile-time evaluation.
   volatile float f = 1.968750f;
   volatile float m = 0x1.0p23f;
-  volatile float x = f + m;
+  float x;
+  DoNotOptimize(x = f + m);
   ASSERT_FLOAT_EQ(expectation1, x);
-  x = x - m;
+  DoNotOptimize(x = x - m);
   ASSERT_EQ(expectation2, x);
 }
 
 static void DivideByZero() {
-  // volatile to prevent compiler optimizations.
+  // Volatile to prevent compile-time evaluation.
   volatile float zero = 0.0f;
-  volatile float result __attribute__((unused)) = 123.0f / zero;
+  DoNotOptimize(123.0f / zero);
 }
 
 TEST(fenv, fesetround_fegetround_FE_TONEAREST) {