Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -6543,6 +6543,16 @@
         .Default(false);
   }
 
+  CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
+    switch (CC) {
+    case CC_C:
+    case CC_Swift:
+      return CCCR_OK;
+    default:
+      return CCCR_Warning;
+    }
+  }
+
   StringRef getABI() const override {
     if (HasVector)
       return "vector";
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -5702,12 +5702,12 @@
 
 namespace {
 
-class SystemZABIInfo : public ABIInfo {
+class SystemZABIInfo : public SwiftABIInfo {
   bool HasVector;
 
 public:
   SystemZABIInfo(CodeGenTypes &CGT, bool HV)
-    : ABIInfo(CGT), HasVector(HV) {}
+    : SwiftABIInfo(CGT), HasVector(HV) {}
 
   bool isPromotableIntegerType(QualType Ty) const;
   bool isCompoundType(QualType Ty) const;
@@ -5727,6 +5727,12 @@
 
   Address EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
                     QualType Ty) const override;
+
+  bool shouldPassIndirectlyForSwift(CharUnits totalSize,
+                                    ArrayRef<llvm::Type*> scalars,
+                                    bool asReturnValue) const override {
+    return occupiesMoreThan(CGT, scalars, /*total*/ 4);
+  }
 };
 
 class SystemZTargetCodeGenInfo : public TargetCodeGenInfo {