[GC] br_on_null (#3528)

This is only partial support, as br_on_null also has an extra optional
value in the spec. Implementing that is cumbersome in binaryen, and
there is ongoing spec discussions about it (see
https://github.com/WebAssembly/function-references/issues/45 ), so
for now we only support the simple case without the default value.

Also fix prefixed opcodes to be LEBs in RefAs, which was noticed here
as the change here made it noticeable whether the values were int8 or
LEBs.

4 files changed, 42 insertions, 12 deletions

diff --git a/test/heap-types.wast b/test/heap-types.wast
index e06d1dff6..7558e1676 100644
--- a/test/heap-types.wast
+++ b/test/heap-types.wast
@@ -195,6 +195,12 @@
   )
   (func $br_on_X (param $x anyref)
     (local $y anyref)
+    (local $z (ref any))
+    (block $null
+      (local.set $z
+        (br_on_null $null (local.get $x))
+      )
+    )
     (drop
       (block $func (result funcref)
         (local.set $y
diff --git a/test/heap-types.wast.from-wast b/test/heap-types.wast.from-wast
index f3e8d5ce6..a93bd0d90 100644
--- a/test/heap-types.wast.from-wast
+++ b/test/heap-types.wast.from-wast
@@ -243,6 +243,14 @@
  )
  (func $br_on_X (param $x anyref)
   (local $y anyref)
+  (local $z anyref)
+  (block $null
+   (local.set $z
+    (br_on_null $null
+     (local.get $x)
+    )
+   )
+  )
   (drop
    (block $func (result funcref)
     (local.set $y
diff --git a/test/heap-types.wast.fromBinary b/test/heap-types.wast.fromBinary
index 80c91d2fe..d8ddb48ed 100644
--- a/test/heap-types.wast.fromBinary
+++ b/test/heap-types.wast.fromBinary
@@ -242,10 +242,18 @@
  )
  (func $br_on_X (param $x anyref)
   (local $y anyref)
+  (local $z anyref)
+  (block $label$1
+   (local.set $z
+    (br_on_null $label$1
+     (local.get $x)
+    )
+   )
+  )
   (drop
-   (block $label$1 (result funcref)
+   (block $label$2 (result funcref)
     (local.set $y
-     (br_on_func $label$1
+     (br_on_func $label$2
       (local.get $x)
      )
     )
@@ -253,9 +261,9 @@
    )
   )
   (drop
-   (block $label$2 (result (ref null data))
+   (block $label$3 (result (ref null data))
     (local.set $y
-     (br_on_data $label$2
+     (br_on_data $label$3
       (local.get $x)
      )
     )
@@ -263,9 +271,9 @@
    )
   )
   (drop
-   (block $label$3 (result (ref null i31))
+   (block $label$4 (result (ref null i31))
     (local.set $y
-     (br_on_i31 $label$3
+     (br_on_i31 $label$4
       (local.get $x)
      )
     )
diff --git a/test/heap-types.wast.fromBinary.noDebugInfo b/test/heap-types.wast.fromBinary.noDebugInfo
index 2852b8bea..63f7e132e 100644
--- a/test/heap-types.wast.fromBinary.noDebugInfo
+++ b/test/heap-types.wast.fromBinary.noDebugInfo
@@ -242,10 +242,18 @@
  )
  (func $7 (param $0 anyref)
   (local $1 anyref)
+  (local $2 anyref)
+  (block $label$1
+   (local.set $2
+    (br_on_null $label$1
+     (local.get $0)
+    )
+   )
+  )
   (drop
-   (block $label$1 (result funcref)
+   (block $label$2 (result funcref)
     (local.set $1
-     (br_on_func $label$1
+     (br_on_func $label$2
       (local.get $0)
      )
     )
@@ -253,9 +261,9 @@
    )
   )
   (drop
-   (block $label$2 (result (ref null data))
+   (block $label$3 (result (ref null data))
     (local.set $1
-     (br_on_data $label$2
+     (br_on_data $label$3
       (local.get $0)
      )
     )
@@ -263,9 +271,9 @@
    )
   )
   (drop
-   (block $label$3 (result (ref null i31))
+   (block $label$4 (result (ref null i31))
     (local.set $1
-     (br_on_i31 $label$3
+     (br_on_i31 $label$4
       (local.get $0)
      )
     )