[Wasm GC] Enable GlobalTypeOptimization (#4305)

Now that all known issues with that pass are fixed, enable it by
default. This adds it in a place that seems to make sense on j2wasm,
but in general multiple cycles of optimization will be needed.

This adds a test showing that we run this pass and that it helps
ConstantFieldPropagation by running before it.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index fd31dada8..3b0faa6c3 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -524,7 +524,12 @@ void PassRunner::addDefaultGlobalOptimizationPrePasses() {
   }
   if (wasm->features.hasGC() && getTypeSystem() == TypeSystem::Nominal &&
       options.optimizeLevel >= 2) {
-    // TODO: investigate enabling --gto and --remove-module-elements before cfp
+    // Global type optimization can remove fields that are not needed, which can
+    // remove ref.funcs that were once assigned to vtables but are no longer
+    // needed, which can allow more code to be removed globally. After those,
+    // constant field propagation can be more effective.
+    addIfNoDWARFIssues("gto");
+    addIfNoDWARFIssues("remove-unused-module-elements");
     addIfNoDWARFIssues("cfp");
   }
 }