Moving to stage 4

[alexcrichton]

The entry requirements for Phase 4 are:

Two or more Web VMs have implemented the feature and pass the test suite (where applicable).

This is SpiderMonkey and JSC now

At least one toolchain has implemented the feature (where applicable).

This is LLVM/Rust

The spec document has been fully updated in the forked repo.

That's done in this repo

The reference interpreter has been fully updated in the forked repo and passes the test suite.

Also done in this repo

The Community Group has reached consensus in support of the feature and consensus that its specification is complete.

This is TBD

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I'd like to start collating data/thoughts on moving to Phase 4 for this proposal. I'm collecting updated numbers here and it's a work-in-progress since I think JSC might be buggy for now. I don't want to actually schedule anything until that's resolved, but I suspect the bug is relatively minor.

@jakobkummerow I wanted to specifically cc you on this though since you've had many thoughts on this proposal in the past. I also don't want to blindside V8 nor really lawyer around the two engine requirement, so I'd want to make sure you and V8 are on-board with eventually implementing this even if there's not resources now. To that end, I'm curious for your thoughts on moving to stage for now that all the letter-of-the-law requirements are met.

I'll probably cc other folks once this gets closer to double-check, but I don't want to spam too much for now.

[jakobkummerow]

Thanks for the ping. We have started implementing this in V8, but it's not complete yet.

I do think that the i1 question deserves more consideration before this design is set in stone; the primary motivation being to move the pattern matching that's required for optimal codegen from engines to toolchains, as is usually Wasm's preferred strategy. I've been meaning to raise that in a CG meeting, but I've been swamped lately.

[alexcrichton]

Would you be able to say when you'll be able to prepare such a presentation to the CG? I'm not in a particular rush to get this proposal to stage 4, but I would also like to not let it linger indefinitely.