diff --git a/clang/lib/CodeGen/SwiftCallingConv.cpp b/clang/lib/CodeGen/SwiftCallingConv.cpp
--- a/clang/lib/CodeGen/SwiftCallingConv.cpp
+++ b/clang/lib/CodeGen/SwiftCallingConv.cpp
@@ -99,6 +99,15 @@
     auto atomicSize = CGM.getContext().getTypeSizeInChars(atomicType);
     auto valueSize = CGM.getContext().getTypeSizeInChars(valueType);
 
+    auto valueTy = atomicType->getValueType();
+    // _Atomic(_Bool) does not correspond to i1.
+    if (valueTy == CGM.getContext().BoolTy) {
+      addTypedData(llvm::Type::getIntNTy(CGM.getLLVMContext(),
+                                         CGM.getContext().toBits(valueSize)),
+                   begin);
+    } else {
+      addTypedData(atomicType->getValueType(), begin);
+    }
     addTypedData(atomicType->getValueType(), begin);
 
     // Add atomic padding.