[Wasm GC] Do not refine types of exported globals in closed world (#5380)

Doing so can cause us to switch from a private type to a public type and error.

Also refactor export-utils to make this easy.

4 files changed, 64 insertions, 10 deletions

diff --git a/src/ir/CMakeLists.txt b/src/ir/CMakeLists.txt
index 2dadb743f..15aa74053 100644
--- a/src/ir/CMakeLists.txt
+++ b/src/ir/CMakeLists.txt
@@ -4,6 +4,7 @@ set(ir_SOURCES
   ExpressionManipulator.cpp
   drop.cpp
   eh-utils.cpp
+  export-utils.cpp
   intrinsics.cpp
   lubs.cpp
   memory-utils.cpp
diff --git a/src/ir/export-utils.cpp b/src/ir/export-utils.cpp
new file mode 100644
index 000000000..0b19b7204
--- /dev/null
+++ b/src/ir/export-utils.cpp
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2023 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ir/export-utils.h"
+#include "wasm.h"
+
+namespace wasm::ExportUtils {
+
+namespace {
+
+// Returns a vector of all the things that are exported of a particular kind,
+// given that kind and a way to look them up on the module.
+template<typename T, ExternalKind K, typename G>
+std::vector<T*> getExportedByKind(Module& wasm, G getModuleItem) {
+  std::vector<T*> ret;
+  for (auto& ex : wasm.exports) {
+    if (ex->kind == K) {
+      ret.push_back(getModuleItem(ex->value));
+    }
+  }
+  return ret;
+}
+
+} // anonymous namespace
+
+std::vector<Function*> getExportedFunctions(Module& wasm) {
+  return getExportedByKind<Function, ExternalKind::Function>(
+    wasm, [&](Name name) { return wasm.getFunction(name); });
+}
+
+std::vector<Global*> getExportedGlobals(Module& wasm) {
+  return getExportedByKind<Global, ExternalKind::Global>(
+    wasm, [&](Name name) { return wasm.getGlobal(name); });
+}
+
+} // namespace wasm::ExportUtils
diff --git a/src/ir/export-utils.h b/src/ir/export-utils.h
index 245365fbc..f50c0afa5 100644
--- a/src/ir/export-utils.h
+++ b/src/ir/export-utils.h
@@ -21,15 +21,8 @@
 
 namespace wasm::ExportUtils {
 
-inline std::vector<Function*> getExportedFunctions(Module& wasm) {
-  std::vector<Function*> ret;
-  for (auto& ex : wasm.exports) {
-    if (ex->kind == ExternalKind::Function) {
-      ret.push_back(wasm.getFunction(ex->value));
-    }
-  }
-  return ret;
-}
+std::vector<Function*> getExportedFunctions(Module& wasm);
+std::vector<Global*> getExportedGlobals(Module& wasm);
 
 } // namespace wasm::ExportUtils
 
diff --git a/src/passes/GlobalRefining.cpp b/src/passes/GlobalRefining.cpp
index 67a186f92..129f34283 100644
--- a/src/passes/GlobalRefining.cpp
+++ b/src/passes/GlobalRefining.cpp
@@ -18,6 +18,7 @@
 // Apply more specific subtypes to global variables where possible.
 //
 
+#include "ir/export-utils.h"
 #include "ir/find_all.h"
 #include "ir/lubs.h"
 #include "ir/module-utils.h"
@@ -63,10 +64,20 @@ struct GlobalRefining : public Pass {
       }
     }
 
+    // In closed world we cannot change the types of exports, as we might change
+    // from a public type to a private that would cause a validation error.
+    // TODO We could refine to a type that is still public, however.
+    std::unordered_set<Name> unoptimizable;
+    if (getPassOptions().closedWorld) {
+      for (auto* global : ExportUtils::getExportedGlobals(*module)) {
+        unoptimizable.insert(global->name);
+      }
+    }
+
     bool optimized = false;
 
     for (auto& global : module->globals) {
-      if (global->imported()) {
+      if (global->imported() || unoptimizable.count(global->name)) {
         continue;
       }