diff --git a/llvm/include/Support/MathExtras.h b/llvm/include/Support/MathExtras.h
index bd5692b..d907658 100644
--- a/llvm/include/Support/MathExtras.h
+++ b/llvm/include/Support/MathExtras.h
@@ -19,7 +19,7 @@
 inline bool isPowerOf2(int64_t C, unsigned &getPow) {
   if (C < 0) C = -C;
   if (C > 0 && C == (C & ~(C - 1))) {
-    getPow = log2(C);
+    getPow = log2((uint64_t)C);
     return true;
   }