Bug 1615082 - Fix IsMarked assertions to allow use by off-thread mark…

…ing during sweeping and make wasm::Instance use IsMarked rather than IsAboutToBeFinalized r=sfink

I unintentionally changed the assertions in CheckIsMarkedThing to ignore marking (but left the comment intact!).

Also, IsAboutToBeFinalized always returns true during marking so this assertion will always pass. Fixed this by changing to IsMarked, but I had to add back a previouly removed version of IsMarked.

Differential Revision: https://phabricator.services.mozilla.com/D62938

js/src/gc/Marking.cpp

@@ -3544,7 +3544,8 @@ static inline void CheckIsMarkedThing(T* thingp) {
   // try to check the zone. Some threads have access to all zones when sweeping.
   JSContext* cx = TlsContext.get();
   MOZ_ASSERT(cx->gcUse != JSContext::GCUse::Finalizing);
-  if (cx->gcUse == JSContext::GCUse::Sweeping) {
+  if (cx->gcUse == JSContext::GCUse::Sweeping ||
+      cx->gcUse == JSContext::GCUse::Marking) {
     Zone* zone = thing->zoneFromAnyThread();
     MOZ_ASSERT_IF(cx->gcSweepZone,
                   cx->gcSweepZone == zone || zone->isAtomsZone());

js/src/gc/Marking.h

@@ -69,6 +69,15 @@ inline bool IsMarkedUnbarriered(JSRuntime* rt, T* thingp) {
   return IsMarkedInternal(rt, ConvertToBase(thingp));
 }
 
+// Report whether a GC thing has been marked with any color. Things which are in
+// zones that are not currently being collected or are owned by another runtime
+// are always reported as being marked.
+template <typename T>
+inline bool IsMarked(JSRuntime* rt, BarrieredBase<T>* thingp) {
+  return IsMarkedInternal(rt,
+                          ConvertToBase(thingp->unsafeUnbarrieredForTracing()));
+}
+
 template <typename T>
 inline bool IsAboutToBeFinalizedUnbarriered(T* thingp) {
   return IsAboutToBeFinalizedInternal(ConvertToBase(thingp));

js/src/wasm/WasmInstance.cpp

@@ -1436,7 +1436,7 @@ void Instance::tracePrivate(JSTracer* trc) {
   // This method is only called from WasmInstanceObject so the only reason why
   // TraceEdge is called is so that the pointer can be updated during a moving
   // GC.
-  MOZ_ASSERT(!gc::IsAboutToBeFinalized(&object_));
+  MOZ_ASSERT_IF(trc->isMarkingTracer(), gc::IsMarked(trc->runtime(), &object_));
   TraceEdge(trc, &object_, "wasm instance object");
 
   // OK to just do one tier here; though the tiers have different funcImports