[Wasm GC] Allow extern.externalize in globals (#5585)

This fixes wasm-ctor-eval on evalling a GC data structure that contains a
field initialized with an externalized value.

Per the spec this is a constant instruction and I verified that V8 allows this.

Also add missing validation in wasm-ctor-eval of the output (which makes
debugging this kind of thing a little easier).

2 files changed, 8 insertions, 1 deletions

diff --git a/src/ir/properties.h b/src/ir/properties.h
index 0fee67ad2..13eea6ba2 100644
--- a/src/ir/properties.h
+++ b/src/ir/properties.h
@@ -83,7 +83,9 @@ inline bool isNamedControlFlow(Expression* curr) {
 // isValidInConstantExpression or find better names(#4845)
 inline bool isSingleConstantExpression(const Expression* curr) {
   return curr->is<Const>() || curr->is<RefNull>() || curr->is<RefFunc>() ||
-         curr->is<StringConst>();
+         curr->is<StringConst>() ||
+         (curr->is<RefAs>() && (curr->cast<RefAs>()->op == ExternExternalize ||
+                                curr->cast<RefAs>()->op == ExternInternalize));
 }
 
 inline bool isConstantExpression(const Expression* curr) {
diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 195a5350f..5e1bf6b22 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -1064,6 +1064,11 @@ int main(int argc, const char* argv[]) {
   if (canEval(wasm)) {
     evalCtors(wasm, ctors, keptExports);
 
+    if (!WasmValidator().validate(wasm)) {
+      std::cout << wasm << '\n';
+      Fatal() << "error in validating output";
+    }
+
     // Do some useful optimizations after the evalling
     {
       PassRunner passRunner(&wasm);