diff --git a/clang/lib/Headers/prfchwintrin.h b/clang/lib/Headers/prfchwintrin.h
--- a/clang/lib/Headers/prfchwintrin.h
+++ b/clang/lib/Headers/prfchwintrin.h
@@ -47,9 +47,12 @@
 /// \param __P
 ///    A pointer specifying the memory address to be prefetched.
 static __inline__ void __attribute__((__always_inline__, __nodebug__))
-_m_prefetchw(void *__P)
+_m_prefetchw(volatile const void *__P)
 {
-  __builtin_prefetch (__P, 1, 3 /* _MM_HINT_T0 */);
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wcast-qual"
+  __builtin_prefetch ((const void*)__P, 1, 3 /* _MM_HINT_T0 */);
+#pragma clang diagnostic pop
 }
 
 #endif /* __PRFCHWINTRIN_H */