Prevent pops from sinking in SimplifyLocals (#2885)

This prevents `exnref.pop`s from being sinked and separated from
`catch`. For example,
```wast
(try
  (do)
  (catch
    (local.set $0 (exnref.pop))
    (call $foo
      (i32.const 3)
      (local.get $0)
    )
  )
)
```
Here, if we sink `exnref.pop` to remove `local.set $0` and
`local.get $0`, it becomes this:
```wast
(try
  (do)
  (catch
    (nop)
    (call $foo
      (i32.const 3)
      (exnref.pop)
    )
  )
)
```
This move was possible because `i32.const 3` does not have any side
effects. But this is incorrect because now `exnref.pop` does not follow
right after `catch`.

To prevent this, this patch checks this case in `canSink` in
SimplifyLocals. When we encountered a similar case in CodeFolding, we
prevented every expression that contains `Pop` anywhere in it from being
moved, which was too conservative. This adds `danglingPop` property in
`EffectAnalyzer`, so that only pops that are not enclosed within a
`catch` count as 'dangling pops` and we only prevent those pops from
being moved or sinked.

0 files changed, 0 insertions, 0 deletions