Something broken in JS test case generation

[backes]

I am trying to get the newest spec tests to pass in V8. I am stuck at a problem which seems to be on the spec side.

Take this example (reduced from table_fill.wast):

(module
  (table $t 10 externref)
  (table $t64 i64 10 externref)

  (func (export "get") (param $i i32) (result externref)
    (table.get $t (local.get $i))
  )

  (func (export "get64") (param $i i64) (result externref)
    (table.get $t64 (local.get $i))
  )
)

(assert_return (invoke "get" (i32.const 1)) (ref.null extern))
(assert_return (invoke "get64" (i64.const 1)) (ref.null extern))

I run this through test/core/run.py --out /tmp test.wast.
The resulting test.js contains:

// test.wast:1
let $$1 = module("\x00\x61\x73\x6d\x01\x00\x00\x00\x01\x8b\x80\x80\x80\x00\x02\x60\x01\x7f\x01\x6f\x60\x01\x7e\x01\x6f\x03\x83\x80\x80\x80\x00\x02\x00\x01\x04\x87\x80\x80\x80\x00\x02\x6f\x00\x0a\x6f\x04\x0a\x07\x8f\x80\x80\x80\x00\x02\x03\x67\x65\x74\x00\x00\x05\x67\x65\x74\x36\x34\x00\x01\x0a\x97\x80\x80\x80\x00\x02\x86\x80\x80\x80\x00\x00\x20\x00\x25\x00\x0b\x86\x80\x80\x80\x00\x00\x20\x00\x25\x01\x0b");

// test.wast:1
let $1 = instance($$1);

// test.wast:14
assert_return(() => call($1, "get", [1]), null);

This looks like a reasonable straight-forward translation.

The second assertion translates to:

// test.wast:15
run(() => call(instance(module("\x00\x61\x73\x6d\x01\x00\x00\x00\x01\x94\x80\x80\x80\x00\x04\x60\x00\x00\x60\x01\x7f\x01\x6e\x60\x02\x6d\x6d\x01\x7f\x60\x01\x7e\x01\x6f\x02\xb5\x80\x80\x80\x00\x03\x06\x6d\x6f\x64\x75\x6c\x65\x05\x67\x65\x74\x36\x34\x00\x03\x08\x73\x70\x65\x63\x74\x65\x73\x74\x07\x68\x6f\x73\x74\x72\x65\x66\x00\x01\x08\x73\x70\x65\x63\x74\x65\x73\x74\x06\x65\x71\x5f\x72\x65\x66\x00\x02\x03\x82\x80\x80\x80\x00\x01\x00\x07\x87\x80\x80\x80\x00\x01\x03\x72\x75\x6e\x00\x03\x0a\x93\x80\x80\x80\x00\x01\x8d\x80\x80\x80\x00\x00\x02\x40\x42\x01\x10\x00\x0c\x00\x0f\x0b\x00\x0b"), exports($1)),  "run", []));  // assert_return(() => call($1, "get64", [int64("1")]), null)

The run function exported by the module is this:

  (func $run (;3;) (export "run")
    block $label0
      i64.const 1
      call $module.get64
      br $label0
      return
    end $label0
    unreachable
  )

This obviously results in unreachable being executed.

Does anyone spot what is broken here?
@bvisness @sbc100 @rossberg

Note: If the br would be a br_on_non_null, the test would test what it's supposed to test. No idea though if generating this was the intention.

[bvisness]

The wast itself seems fine; it's clear that there is no difference except the i64 index, and indeed it should return ref.null extern. So I guess this problem must lie in the testing machinery itself. I am not familiar with how that works, only with our own implementation in SpiderMonkey. (We consume the wast directly, and don't use the Python script in this repo.)

[rossberg]

This looks like a bug in the JS conversion backend. WebAssembly/spec#1836 should fix it, PTAL.