Unbreak VC++ build.

llvm-svn: 32113
diff --git a/llvm/lib/ExecutionEngine/Interpreter/Execution.cpp b/llvm/lib/ExecutionEngine/Interpreter/Execution.cpp
index 5b287b2..fd5fb6f 100644
--- a/llvm/lib/ExecutionEngine/Interpreter/Execution.cpp
+++ b/llvm/lib/ExecutionEngine/Interpreter/Execution.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Support/GetElementPtrTypeIterator.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Support/Debug.h"
+#include <cmath>
 using namespace llvm;
 
 namespace {