Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -1305,9 +1305,10 @@
   //   M is C if C is an integer, and ptrdiff_t if C is a pointer, and
   //   the int parameters are for orderings.
 
-  assert(AtomicExpr::AO__c11_atomic_init == 0 &&
-         AtomicExpr::AO__c11_atomic_fetch_xor + 1 == AtomicExpr::AO__atomic_load
-         && "need to update code for modified C11 atomics");
+  static_assert(AtomicExpr::AO__c11_atomic_init == 0 &&
+                    AtomicExpr::AO__c11_atomic_fetch_xor + 1 ==
+                        AtomicExpr::AO__atomic_load,
+                "need to update code for modified C11 atomics");
   bool IsC11 = Op >= AtomicExpr::AO__c11_atomic_init &&
                Op <= AtomicExpr::AO__c11_atomic_fetch_xor;
   bool IsN = Op == AtomicExpr::AO__atomic_load_n ||