1 files changed, 9 insertions, 0 deletions
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index efaf36a..509d88e 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -5349,6 +5349,15 @@ Sema::SemaBuiltinAtomicOverloaded(ExprResult TheCallResult) {
   // gracefully.
   TheCall->setType(ResultType);
 
+  // Prohibit use of _ExtInt with atomic builtins.
+  // The arguments would have already been converted to the first argument's
+  // type, so only need to check the first argument.
+  const auto *ExtIntValType = ValType->getAs<ExtIntType>();
+  if (ExtIntValType && !llvm::isPowerOf2_64(ExtIntValType->getNumBits())) {
+    Diag(FirstArg->getExprLoc(), diag::err_atomic_builtin_ext_int_size);
+    return ExprError();
+  }
+
   return TheCallResult;
 }