diff --git a/clang/include/clang/Basic/Features.def b/clang/include/clang/Basic/Features.def
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -92,6 +92,7 @@
 FEATURE(thread_sanitizer, LangOpts.Sanitize.has(SanitizerKind::Thread))
 FEATURE(dataflow_sanitizer, LangOpts.Sanitize.has(SanitizerKind::DataFlow))
 FEATURE(scudo, LangOpts.Sanitize.hasOneOf(SanitizerKind::Scudo))
+FEATURE(swiftasynccc, PP.getTargetInfo().isSwiftAsyncCCSupported())
 // Objective-C features
 FEATURE(objc_arr, LangOpts.ObjCAutoRefCount) // FIXME: REMOVE?
 FEATURE(objc_arc, LangOpts.ObjCAutoRefCount)
diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -1415,6 +1415,17 @@
 
   virtual CallingConvKind getCallingConvKind(bool ClangABICompat4) const;
 
+  /// \brief Is the Swift async calling convention supported for this target.
+  bool isSwiftAsyncCCSupported() const {
+    auto &triple = getTriple();
+    return triple.getArch() == llvm::Triple::x86_64 || triple.isARM() ||
+           triple.isAArch64();
+  }
+
+  CallingConvCheckResult checkSwiftAsyncCCSupported() const {
+    return isSwiftAsyncCCSupported() ? CCCR_OK : CCCR_Error;
+  }
+
   /// Controls if __builtin_longjmp / __builtin_setjmp can be lowered to
   /// llvm.eh.sjlj.longjmp / llvm.eh.sjlj.setjmp.
   virtual bool hasSjLjLowering() const {
diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -537,13 +537,14 @@
   switch (CC) {
   case CC_C:
   case CC_Swift:
-  case CC_SwiftAsync:
   case CC_PreserveMost:
   case CC_PreserveAll:
   case CC_OpenCLKernel:
   case CC_AArch64VectorCall:
   case CC_Win64:
     return CCCR_OK;
+  case CC_SwiftAsync:
+    return checkSwiftAsyncCCSupported();
   default:
     return CCCR_Warning;
   }
@@ -811,9 +812,10 @@
   case CC_PreserveMost:
   case CC_PreserveAll:
   case CC_Swift:
-  case CC_SwiftAsync:
   case CC_Win64:
     return CCCR_OK;
+  case CC_SwiftAsync:
+    return checkSwiftAsyncCCSupported();
   default:
     return CCCR_Warning;
   }
diff --git a/clang/lib/Basic/Targets/ARM.cpp b/clang/lib/Basic/Targets/ARM.cpp
--- a/clang/lib/Basic/Targets/ARM.cpp
+++ b/clang/lib/Basic/Targets/ARM.cpp
@@ -1120,9 +1120,10 @@
   case CC_AAPCS:
   case CC_AAPCS_VFP:
   case CC_Swift:
-  case CC_SwiftAsync:
   case CC_OpenCLKernel:
     return CCCR_OK;
+  case CC_SwiftAsync:
+    return checkSwiftAsyncCCSupported();
   default:
     return CCCR_Warning;
   }
@@ -1200,8 +1201,9 @@
   case CC_PreserveMost:
   case CC_PreserveAll:
   case CC_Swift:
-  case CC_SwiftAsync:
     return CCCR_OK;
+  case CC_SwiftAsync:
+    return checkSwiftAsyncCCSupported();
   default:
     return CCCR_Warning;
   }
diff --git a/clang/lib/Basic/Targets/PPC.h b/clang/lib/Basic/Targets/PPC.h
--- a/clang/lib/Basic/Targets/PPC.h
+++ b/clang/lib/Basic/Targets/PPC.h
@@ -450,8 +450,9 @@
   CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
     switch (CC) {
     case CC_Swift:
-    case CC_SwiftAsync:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }
diff --git a/clang/lib/Basic/Targets/SystemZ.h b/clang/lib/Basic/Targets/SystemZ.h
--- a/clang/lib/Basic/Targets/SystemZ.h
+++ b/clang/lib/Basic/Targets/SystemZ.h
@@ -141,9 +141,10 @@
     switch (CC) {
     case CC_C:
     case CC_Swift:
-    case CC_SwiftAsync:
     case CC_OpenCLKernel:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }
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
@@ -129,8 +129,9 @@
     switch (CC) {
     case CC_C:
     case CC_Swift:
-    case CC_SwiftAsync:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }
diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -344,11 +344,12 @@
     case CC_C:
     case CC_PreserveMost:
     case CC_Swift:
-    case CC_SwiftAsync:
     case CC_X86Pascal:
     case CC_IntelOclBicc:
     case CC_OpenCLKernel:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }
@@ -703,7 +704,6 @@
     switch (CC) {
     case CC_C:
     case CC_Swift:
-    case CC_SwiftAsync:
     case CC_X86VectorCall:
     case CC_IntelOclBicc:
     case CC_Win64:
@@ -712,6 +712,8 @@
     case CC_X86RegCall:
     case CC_OpenCLKernel:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }
@@ -785,10 +787,11 @@
     case CC_PreserveAll:
     case CC_X86_64SysV:
     case CC_Swift:
-    case CC_SwiftAsync:
     case CC_X86RegCall:
     case CC_OpenCLKernel:
       return CCCR_OK;
+    case CC_SwiftAsync:
+      return checkSwiftAsyncCCSupported();
     default:
       return CCCR_Warning;
     }