diff --git a/clang/lib/Basic/Targets/Mips.h b/clang/lib/Basic/Targets/Mips.h
--- a/clang/lib/Basic/Targets/Mips.h
+++ b/clang/lib/Basic/Targets/Mips.h
@@ -407,6 +407,17 @@
 
   bool validateTarget(DiagnosticsEngine &Diags) const override;
   bool hasBitIntType() const override { return true; }
+
+  CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
+    switch (CC) {
+    case CC_Swift:
+      return CCCR_OK;
+    case CC_SwiftAsync:
+      return CCCR_Error;
+    default:
+      return CCCR_Warning;
+    }
+  }
 };
 } // namespace targets
 } // namespace clang
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -7864,7 +7864,7 @@
 //===----------------------------------------------------------------------===//
 
 namespace {
-class MipsABIInfo : public ABIInfo {
+class MipsABIInfo : public SwiftABIInfo {
   bool IsO32;
   const unsigned MinABIStackAlignInBytes, StackAlignInBytes;
   void CoerceToIntArgs(uint64_t TySize,
@@ -7873,9 +7873,10 @@
   llvm::Type* returnAggregateInRegs(QualType RetTy, uint64_t Size) const;
   llvm::Type* getPaddingType(uint64_t Align, uint64_t Offset) const;
 public:
-  MipsABIInfo(CodeGenTypes &CGT, bool _IsO32) :
-    ABIInfo(CGT), IsO32(_IsO32), MinABIStackAlignInBytes(IsO32 ? 4 : 8),
-    StackAlignInBytes(IsO32 ? 8 : 16) {}
+  MipsABIInfo(CodeGenTypes &CGT, bool _IsO32)
+      : SwiftABIInfo(CGT), IsO32(_IsO32),
+        MinABIStackAlignInBytes(IsO32 ? 4 : 8),
+        StackAlignInBytes(IsO32 ? 8 : 16) {}
 
   ABIArgInfo classifyReturnType(QualType RetTy) const;
   ABIArgInfo classifyArgumentType(QualType RetTy, uint64_t &Offset) const;
@@ -7883,6 +7884,14 @@
   Address EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
                     QualType Ty) const override;
   ABIArgInfo extendType(QualType Ty) const;
+
+private:
+  bool shouldPassIndirectlyForSwift(ArrayRef<llvm::Type *> scalars,
+                                    bool asReturnValue) const override {
+    return occupiesMoreThan(CGT, scalars, /*total*/ 4);
+  }
+
+  bool isSwiftErrorInRegister() const override { return false; }
 };
 
 class MIPSTargetCodeGenInfo : public TargetCodeGenInfo {