diff --git a/clang/lib/Basic/Targets/WebAssembly.h b/clang/lib/Basic/Targets/WebAssembly.h
--- a/clang/lib/Basic/Targets/WebAssembly.h
+++ b/clang/lib/Basic/Targets/WebAssembly.h
@@ -114,6 +114,16 @@
                ? (IsSigned ? SignedLongLong : UnsignedLongLong)
                : TargetInfo::getLeastIntTypeByWidth(BitWidth, IsSigned);
   }
+
+  CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
+    switch (CC) {
+    case CC_C:
+    case CC_Swift:
+      return CCCR_OK;
+    default:
+      return CCCR_Warning;
+    }
+  }
 };
 class LLVM_LIBRARY_VISIBILITY WebAssembly32TargetInfo
     : public WebAssemblyTargetInfo {
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -672,7 +672,8 @@
          CallConv == CallingConv::PreserveMost ||
          CallConv == CallingConv::PreserveAll ||
          CallConv == CallingConv::CXX_FAST_TLS ||
-         CallConv == CallingConv::WASM_EmscriptenInvoke;
+         CallConv == CallingConv::WASM_EmscriptenInvoke ||
+         CallConv == CallingConv::Swift;
 }
 
 SDValue