MathExtras UnitTest: Assert that isPowerOf2(0) is false. NFC.

Summary:
This is a follow-up on D34077. Elena observed that the
correctness of the code relies on isPowerOf2(0) returning false.
Adding a test to cover this corner-case.

Reviewers: delena, davide, craig.topper

Reviewed By: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34939

llvm-svn: 307046
diff --git a/llvm/unittests/Support/MathExtrasTest.cpp b/llvm/unittests/Support/MathExtrasTest.cpp
index e26653b..694a1f2 100644
--- a/llvm/unittests/Support/MathExtrasTest.cpp
+++ b/llvm/unittests/Support/MathExtrasTest.cpp
@@ -177,6 +177,7 @@
 }
 
 TEST(MathExtras, isPowerOf2_32) {
+  EXPECT_FALSE(isPowerOf2_32(0));
   EXPECT_TRUE(isPowerOf2_32(1 << 6));
   EXPECT_TRUE(isPowerOf2_32(1 << 12));
   EXPECT_FALSE(isPowerOf2_32((1 << 19) + 3));
@@ -184,6 +185,7 @@
 }
 
 TEST(MathExtras, isPowerOf2_64) {
+  EXPECT_FALSE(isPowerOf2_64(0));
   EXPECT_TRUE(isPowerOf2_64(1LL << 46));
   EXPECT_TRUE(isPowerOf2_64(1LL << 12));
   EXPECT_FALSE(isPowerOf2_64((1LL << 53) + 3));