[WASM] Sync calling convention between C++ and Swift

Author: kateinoigakukun

include/swift/Runtime/HeapObject.h

@@ -148,6 +148,7 @@ void swift_slowDealloc(void *ptr, size_t bytes, size_t alignMask);
 /// It may also prove worthwhile to have this use a custom CC
 /// which preserves a larger set of registers.
 SWIFT_RUNTIME_EXPORT
+SWIFT_CC(swift)
 HeapObject *swift_retain(HeapObject *object);
 
 SWIFT_RUNTIME_EXPORT

include/swift/Runtime/RuntimeFunctions.def

@@ -155,7 +155,7 @@ FUNCTION(CopyPOD, swift_copyPOD, C_CC, AlwaysAvailable,
          ATTRS(NoUnwind))
 
 // void *swift_retain(void *ptr);
-FUNCTION(NativeStrongRetain, swift_retain, C_CC, AlwaysAvailable,
+FUNCTION(NativeStrongRetain, swift_retain, SwiftCC, AlwaysAvailable,
          RETURNS(RefCountedPtrTy),
          ARGS(RefCountedPtrTy),
          ATTRS(NoUnwind, FirstParamReturned))

stdlib/public/runtime/HeapObject.cpp

@@ -341,6 +341,7 @@ static HeapObject *_swift_retain_(HeapObject *object) {
   return object;
 }
 
+SWIFT_CC(swift)
 HeapObject *swift::swift_retain(HeapObject *object) {
 #ifdef SWIFT_STDLIB_SINGLE_THREADED_RUNTIME
   return swift_nonatomic_retain(object);