I made an abortive attempt at doing this; see bug 1507322 comment 10. But it should really be done separately.

Note that this would free up one tag value in the MarkStack's TaggedPtr. And delete some code.

Hi sfink, Can you assign a priority? Thanks.

I'm going to put it at P3, but only because tcampbell is running into the TaggedPtr limit in his work to unify JSScript and LazyScript in bug 1529456, which is P2. I'm not making this P2 or a blocker for that bug because I'm not sure this is a hard blocker; I think Ted may be working around this in some other way? But I'm not sure.

I should clarify, the TaggedPtr limit was more about the convenience of implementation Bug 1529456 in stages. The end-state of that bug would unify LazyScript and JSScript, but currently they use different marking approaches.

If there is an performance concern around removing eager marking from LazyScripts (when they merge into JSScript), then this should be considered a blocker. I've not hit a deciding point on that bug yet, so we can leave this at P3. If this does become a blocker, I am also will to resolve it myself at that point.

Hey Steve, can you take a look at if this bug still makes any sense? After Bug 1615143, the LazyScript and JSScript are now sharing a TraceKind. There is no more eager marking of LazyScripts, so I think they all use the mark stack now. I don't really understand the original ephemeron marking concerns so I'm not sure what the ideal tracing of BaseScript should be..

(tcampbell and I talked) There's no longer code duplication, and the TaggedPtr value is no longer necessary, so closing. In theory, it might be a minor perf win, but then again it could be a perf loss for all I know.