diff --git a/Utilities/GNU.cpp b/Utilities/GNU.cpp
index bb0a784fe7..9fa46ebc9f 100644
--- a/Utilities/GNU.cpp
+++ b/Utilities/GNU.cpp
@@ -18,3 +18,31 @@ int clock_gettime(int foo, struct timespec *ts) {
   return(0);
 }
 #endif /* !__APPLE__ */
+
+#if defined(__GNUG__)
+int64_t InterlockedOr64(volatile int64_t *dest, int64_t val)
+{
+	int64_t olderval;
+	int64_t oldval = *dest;
+	do
+	{
+		olderval = oldval;
+		oldval = InterlockedCompareExchange64(dest, olderval | val, olderval);
+	} while (olderval != oldval);
+	return oldval;
+}
+
+uint64_t __umulh(uint64_t a, uint64_t b)
+{
+	uint64_t result;
+	__asm__("mulq %[b]" : "=d" (result) : [a] "a" (a), [b] "rm" (b));
+	return result;
+}
+
+int64_t  __mulh(int64_t a, int64_t b)
+{
+	int64_t result;
+	__asm__("imulq %[b]" : "=d" (result) : [a] "a" (a), [b] "rm" (b));
+	return result;
+}
+#endif
\ No newline at end of file
diff --git a/Utilities/GNU.h b/Utilities/GNU.h
index 2aa2362ce5..7b1b0b9482 100644
--- a/Utilities/GNU.h
+++ b/Utilities/GNU.h
@@ -3,6 +3,7 @@
 #if defined(__GNUG__)
 #include <cmath>
 #include <stdlib.h>
+#include <cstdint>
 
 #ifndef __APPLE__
 #include <malloc.h>
@@ -20,24 +21,11 @@
 #define InterlockedCompareExchange(ptr,new_val,old_val)  __sync_val_compare_and_swap(ptr,old_val,new_val)
 #define InterlockedCompareExchange64(ptr,new_val,old_val)  __sync_val_compare_and_swap(ptr,old_val,new_val)
 
-int64_t InterlockedOr64(volatile int64_t *dest, int64_t val)
-{
-	int64_t olderval;
-	int64_t oldval = *dest;
-	do
-	{
-		olderval = oldval;
-		oldval = InterlockedCompareExchange64(dest, olderval | val, olderval);
-	} while (olderval != oldval);
-	return oldval;
-}
+inline int64_t InterlockedOr64(volatile int64_t *dest, int64_t val);
 
-uint64_t __umulh(uint64_t a, uint64_t b)
-{
-	uint64_t result;
-	__asm__("mulq %[b]" : "=d" (result) : [a] "a" (a), [b] "rm" (b));
-	return result;
-}
+inline uint64_t __umulh(uint64_t a, uint64_t b);
+
+inline int64_t  __mulh(int64_t a, int64_t b);
 
 #ifndef __APPLE__
 #define _aligned_malloc(size,alignment) memalign(alignment,size)