1 files changed, 9 insertions, 0 deletions
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index 10a688313..d21464c2b 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -171,6 +171,9 @@ void PassRegistry::registerPasses() {
   registerPass("local-cse",
                "common subexpression elimination inside basic blocks",
                createLocalCSEPass);
+  registerPass("local-subtyping",
+               "apply more specific subtypes to locals where possible",
+               createLocalSubtypingPass);
   registerPass("log-execution",
                "instrument the build with logging of where execution goes",
                createLogExecutionPass);
@@ -454,6 +457,12 @@ void PassRunner::addDefaultFunctionOptimizationPasses() {
   if (options.optimizeLevel >= 3 || options.shrinkLevel >= 2) {
     addIfNoDWARFIssues("merge-locals"); // very slow on e.g. sqlite
   }
+  if (options.optimizeLevel > 1 && wasm->features.hasGC()) {
+    // Coalescing may prevent subtyping (as a coalesced local must have the
+    // supertype of all those combined into it), so subtype first.
+    // TODO: when optimizing for size, maybe the order should reverse?
+    addIfNoDWARFIssues("local-subtyping");
+  }
   addIfNoDWARFIssues("coalesce-locals");
   addIfNoDWARFIssues("simplify-locals");
   addIfNoDWARFIssues("vacuum");