Make try body start with 'do' (#2846)

In WebAssembly/exception-handling#52, We decided to put `try` bodies in
a `do` clause to be more consistent with `catch`.

- Before
```wast
(try
  ...
  (catch
    ...
  )
)
```

- After
```wast
(try
  (do
    ...
  )
  (catch
    ...
  )
)
```

Another upside of this change is when there are multiple instructions
within a `try` body, we no longer need to wrap them in a `block`.

3 files changed, 15 insertions, 7 deletions

diff --git a/test/binaryen.js/exception-handling.js b/test/binaryen.js/exception-handling.js
index b3c9974e7..3f5f6de74 100644
--- a/test/binaryen.js/exception-handling.js
+++ b/test/binaryen.js/exception-handling.js
@@ -19,7 +19,9 @@ module.setFeatures(binaryen.Features.ReferenceTypes |
 var event_ = module.addEvent("e", 0, binaryen.i32, binaryen.none);
 
 // (try
-//   (throw $e (i32.const 0))
+//   (do
+//     (throw $e (i32.const 0))
+//   )
 //   (catch
 //     ;; We don't support multi-value yet. Use locals instead.
 //     (local.set 0 (exnref.pop))
diff --git a/test/binaryen.js/exception-handling.js.txt b/test/binaryen.js/exception-handling.js.txt
index 99f8501a9..a2b10d37f 100644
--- a/test/binaryen.js/exception-handling.js.txt
+++ b/test/binaryen.js/exception-handling.js.txt
@@ -5,8 +5,10 @@
  (func $test
   (local $0 exnref)
   (try
-   (throw $e
-    (i32.const 0)
+   (do
+    (throw $e
+     (i32.const 0)
+    )
    )
    (catch
     (local.set $0
diff --git a/test/binaryen.js/kitchen-sink.js.txt b/test/binaryen.js/kitchen-sink.js.txt
index 9fae467bd..976e72453 100644
--- a/test/binaryen.js/kitchen-sink.js.txt
+++ b/test/binaryen.js/kitchen-sink.js.txt
@@ -1758,8 +1758,10 @@ getExpressionInfo(tuple[3])={"id":14,"type":5,"value":3.7}
        )
       )
       (try
-       (throw $a-event
-        (i32.const 0)
+       (do
+        (throw $a-event
+         (i32.const 0)
+        )
        )
        (catch
         (local.set $5
@@ -3524,8 +3526,10 @@ getExpressionInfo(tuple[3])={"id":14,"type":5,"value":3.7}
        )
       )
       (try
-       (throw $a-event
-        (i32.const 0)
+       (do
+        (throw $a-event
+         (i32.const 0)
+        )
        )
        (catch
         (local.set $5