[Wasm GC] Properly represent nulls in i31 (#4819)

The encoding here is simple: we store i31 values in the literal.i32
field. The top bit says if a value exists, which means literal.i32 == 0 is the
same as null.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index eb5dcd5a7..399910e7a 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -1419,6 +1419,9 @@ public:
     }
     const auto& value = flow.getSingleValue();
     NOTE_EVAL1(value);
+    if (value.isNull()) {
+      trap("null ref");
+    }
     return Literal(value.geti31(curr->signed_));
   }