Optimizing functions with try runs into assertions

[dcodeIO]

Found another assertion while testing try and throw instructions with the following module

(module
  (event $exception (attr 0) (param i32))
  (func $test
    (local $0 exnref)
    (try
      (throw $exception
        (i32.const 1)
      )
      (catch
        (local.set $0
          (exnref.pop)
        )
        (drop
          (block $catch|0 (result i32)
            (rethrow
              (br_on_exn $catch|0 $exception
                (local.get $0)
              )
            )
          )
        )
      )
    )
  )
  (export $test $test)
)

representing a try { throw 1; } catch { }, which yields

Fatal: IR must be flat: run --flatten beforehand (instructions must only have const, local.get, or unreachable as children, in $test)

if optimizeLevel == 4 (prepending flatten before default passes doesn't help) respectively

abort(Assertion failed: values.size() > 0, at: ./src/passes/StackIR.cpp,146,local2Stack).

if optimizeLevel > 2.

Again, I'm not sure how important it is at this point, so just putting it here :)

[aheejin]

Optimization support for exception handling is patchy for now, so there might be remaining bugs for unhandled passes. But looking at the error message, that looks like its not directly related to EH itself but more about the reference type thing (because EH uses exnref). So I guess this also will be solved by the reference type support patch, which is coming (hopefully in a few days).