wasm2c: restore older versions of some spec tests

[keithw]

Test wasm2c against versions of the "missing" spec tests (tracked at #1737) from before the bulk-memory and reference-types proposals were merged (as of commit WebAssembly/testsuite@a8bcbaf). It seems helpful to make sure these tests don't break through various refactors (including our #1814 which doesn't currently pass all of these). These can be replaced with the current versions of the tests once wasm2c supports bulk-memory and reference-types.

I had to make two changes to get these tests to pass today:

1. https://github.com/WebAssembly/testsuite/blob/a8bcbafe6d2fb191ce0188de0e18fdc107fa2598/elem.wast#L15-L18 (removed duplicate $t ids or else wast2json errors)
2. https://github.com/WebAssembly/testsuite/blob/a8bcbafe6d2fb191ce0188de0e18fdc107fa2598/exports.wast#L119-L137 (removed table export section or else wasm2c triggers an assertion failure)

[sbc100]

In general I like the idea of have more test coverage.

The fact that you have to modify these tests makes me a little sad. Could we perhaps fix the code to support the old tests without modifying them? Or would that end up moving the code backwards in some way?

How far are we from supporting bulk-memory and reference-types and thus not needing this PR? Could you make it clear in the README.txt that these files should be delete as soon as we do support support bulk-memory and reference-types. Perhaps with a link to https://github.com/WebAssembly/wabt/issues/1737?

[keithw]

The fact that you have to modify these tests makes me a little sad. Could we perhaps fix the code to support the old tests without modifying them? Or would that end up moving the code backwards in some way?

I'm guessing it would be pretty doable since wast2json and wasm2c passed these tests in the pass. Let me take a look.

How far are we from supporting bulk-memory and reference-types and thus not needing this PR?

We've started working on this because of our own needs (you can see WIP at https://github.com/fixpointOS/wabt/tree/bulk-memory), but if possible I'd rather not have to implement these features once for the un-instanced code and then rebase/reimplement for instanced modules (or vice versa). So if it were up to us and based on your comment in #1833, the sequence would go:

• Get this PR merged (after changes necessary to include the un-modified old tests)
• Get our module_instancing branch passing these newly added (but old) tests
• Finish implementing bulk-memory on top of our module_instancing branch
• Start and finish implementing reference-types on top of our module_instancing branch
• Confirm that all the current versions of the spec tests pass, restore them to the spec directory, and remove old-spec
• If rlbox passes the testsuite by this point, rebase it on top of module_instancing; otherwise, worry about it later.
• Merge module_instancing

Thoughts?

Could you make it clear in the README.txt that these files should be delete as soon as we do support support bulk-memory and reference-types. Perhaps with a link to https://github.com/WebAssembly/wabt/issues/1737?

Sure.

[sbc100]

That order of work sounds right to me! Thanks again for working on this.

[keithw]

Here you go -- the changes necessary to get the old tests passing unmodified were pretty small.

I was a little nervous removing the short-circuit here (https://github.com/WebAssembly/wabt/blob/main/src/c-writer.cc#L1029-L1033) that was recently added in 1c8efb3, but, it doesn't seem to add a warning or other breakage when I take this out. Re: the comment there, even if a module has no types, the table can still be exported (which is what the failing test seemed to hit).

[sbc100]

Thanks! LGTM. Can you explain why you needed those changes under src?