1572562 - [jsdbg2] DebuggerWeakMap instances cost more in code size than they should.

Status: NEW

(Core :: JavaScript Engine, defect, P2)

Description

[Jim Blandy :jimb]

In Bug 1567245 patch D38539, I added a type parameter to DebuggerWeakMap for the value type. Unfortunately, this resulted in a ~60kiB increase in code size.

I think we could recover much of this by allowing the underlying WeakMap to always use JSObject* as its value type, as it did before the patch, and then having DebuggerWeakMap methods downcast as necessary.

Unfortunately, the patch won't be small in terms of lines changed: WeakMap uses a lot of member types in its API (Ptr, AddPtr, Enum) that will now need custom counterparts in DebuggerWeakMap. But I expect all these methods could be simple inline wrappers for calls to the more weakly typed methods on the WeakMap's types.

Comment 1

[Jim Blandy :jimb]

Bug 1567245 patch D38543 also needs to be evaluated in this light.