1 files changed, 59 insertions, 0 deletions
diff --git a/js/src/gc/TraceKind.h b/js/src/gc/TraceKind.h
new file mode 100644
index 0000000000..fdcb162239
--- /dev/null
+++ b/js/src/gc/TraceKind.h
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef gc_TraceKind_h
+#define gc_TraceKind_h
+
+#include "js/TraceKind.h"
+
+namespace js {
+namespace gc {
+
+// Map from all trace kinds to the base GC type.
+template <JS::TraceKind kind>
+struct MapTraceKindToType {};
+
+#define DEFINE_TRACE_KIND_MAP(name, type, _, _1)   \
+  template <>                                      \
+  struct MapTraceKindToType<JS::TraceKind::name> { \
+    using Type = type;                             \
+  };
+JS_FOR_EACH_TRACEKIND(DEFINE_TRACE_KIND_MAP);
+#undef DEFINE_TRACE_KIND_MAP
+
+// Map from a possibly-derived type to the base GC type.
+template <typename T>
+struct BaseGCType {
+  using type =
+      typename MapTraceKindToType<JS::MapTypeToTraceKind<T>::kind>::Type;
+  static_assert(std::is_base_of_v<type, T>, "Failed to find base type");
+};
+
+template <typename T>
+struct TraceKindCanBeGray {};
+#define EXPAND_TRACEKIND_DEF(_, type, canBeGray, _1) \
+  template <>                                        \
+  struct TraceKindCanBeGray<type> {                  \
+    static constexpr bool value = canBeGray;         \
+  };
+JS_FOR_EACH_TRACEKIND(EXPAND_TRACEKIND_DEF)
+#undef EXPAND_TRACEKIND_DEF
+
+struct TraceKindCanBeGrayFunctor {
+  template <typename T>
+  bool operator()() {
+    return TraceKindCanBeGray<T>::value;
+  }
+};
+
+static inline bool TraceKindCanBeMarkedGray(JS::TraceKind kind) {
+  return DispatchTraceKindTyped(TraceKindCanBeGrayFunctor(), kind);
+}
+
+} /* namespace gc */
+} /* namespace js */
+
+#endif /* gc_TraceKind_h */