diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index dcfb597f954..ed7da0f8c8f 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -25,6 +25,7 @@
 #include "PhysRegTracker.h"
 #include "VirtRegMap.h"
 #include <algorithm>
+#include <cmath>
 #include <iostream>
 
 using namespace llvm;