[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.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 4a90dd698..b7ffcd8d7 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2879,6 +2879,9 @@ BinaryConsts::ASTNodes WasmBinaryBuilder::readExpression(Expression*& curr) {
     case BinaryConsts::RefAsNonNull:
       visitRefAs((curr = allocator.alloc<RefAs>())->cast<RefAs>(), code);
       break;
+    case BinaryConsts::BrOnNull:
+      maybeVisitBrOn(curr, code);
+      break;
     case BinaryConsts::Try:
       visitTryOrTryInBlock(curr);
       break;
@@ -5831,6 +5834,9 @@ bool WasmBinaryBuilder::maybeVisitRefCast(Expression*& out, uint32_t code) {
 bool WasmBinaryBuilder::maybeVisitBrOn(Expression*& out, uint32_t code) {
   BrOnOp op;
   switch (code) {
+    case BinaryConsts::BrOnNull:
+      op = BrOnNull;
+      break;
     case BinaryConsts::BrOnCast:
       op = BrOnCast;
       break;