Add support for non-nullable tables and init expressions

[pufferfish101007]

Resolves #5628

Adds support for non-nullable tables with init expressions. I'm not totally sure how I should go about adding new tests, but manual test cases are below. I have also unignored previously ignored spec tests instance.wast, ref_is_null.wast, table.wast, i31.wast, global.wast which now all pass. I have also changed the reason for ignoring array.wast as it does not (and has not in the past, AFAICT) rely on non-nullable table types.

This introduces a breaking change in the C api, as it adds an extra argument to addTable. Is this ok? Should a new method be added instead? (e.g. addTableWithInit?)

Manual tests

click to expand

The validation ones might overlap with the spec tests. Unchecked boxes indicate tests that currently fail.

• Nullable tables should continue to round-trip correctly:

(module
 (type $0 (func (param i32)))
 (table $0 0 funcref)
 (elem $0 (i32.const 0))
 (func $0 (param $0 i32)
 )
)

• Non-nullable tables with init expr should round-trip correctly:

(module
 (type $0 (func (param i32)))
 (table $0 0 (ref $0) (ref.func $0))
 (func $0 (param $0 i32)
 )
)

• Non-nullable table without an init expr should fail validation:

(module
 (type $0 (func (param i32)))
 (table $0 0 (ref $0))
 (func $0 (param $0 i32)
 )
)

Correctly fails with [wasm-validator error in module] unexpected false: tables with non-nullable types require an initializer expression, on table

• Nullable table with init expr should rountrip correctly:

(module
 (type $0 (func (param i32)))
 (table $0 0 funcref (ref.func $0))
 (func $0 (type $0) (param $0 i32)
 )
)

• Non-nullable table init expr should be validated to be a subtype of the table type

(module
 (type $0 (func (param i32)))
 (table $0 0 (ref $0) (i32.const 0))
 (func $0 (param $0 i32)
 )
)

Correctly fails with [wasm-validator error in module] init expression must be a subtype of the table type, on (i32.const 0)

• Nullable table init expr (if present) should be validated to be a subtype of the table type

(module
 (type $0 (func (param i32)))
 (table $0 0 funcref (i32.const 0))
 (func $0 (param $0 i32)
 )
)

Correctly fails with [wasm-validator error in module] init expression must be a subtype of the table type, on (i32.const 0)

• wasm-opt doesn't remove init expr as dead code

(module
 (type $0 (func (param i32)))
 (table $0 0 funcref (ref.func $0))
 (export "table" (table $0))
 (func $0 (type $0) (param $0 i32)
 )
)

TODO:

• Add test that imported globals can be referenced in the init expr
• add remove unused module elements pass test
• add unsubtyping pass test
• validate that imported tables do not have init exprs, add test for this
• add fuzzing support

---

dummy PR for CI tests to run automatically: pufferfish101007#2

[stevenfontanella]

I have also unignored previously ignored spec tests instance.wast, ref_is_null.wast, table.wast, i31.wast, which now all pass. I have also changed the reason for ignoring array.wast as it does not (and has not in the past, AFAICT) rely on non-nullable table types.

I don't see these changes in shared.py, can we add them?

[stevenfontanella]

Looks good from my side. I'll let @tlively have the final review. Thanks for the contribution!

[pufferfish101007]

@stevenfontanella thank you for such a thorough review!

[pufferfish101007]

Fuzzer support has been added (with room for improvements still, but it's already thrown up a bug). That's caused a test to fail though, with test/passes/translate-to-fuzz_all-features_metrics_noprint.txt failing to match - is this expected, and should it be updated to match what the test now produces?

[tlively]

is this expected, and should it be updated to match what the test now produces?

Yes and yes 👍

[pufferfish101007]

I've run the fuzzer 10159 times with no problems, so hopefully everything that needs to be updated has been.

[stevenfontanella]

LGTM, will let Thomas have the last look!

[tlively]

LGTM % a few last nits. Thanks again for working on this!