[Wasm GC] Fix CoalesceLocals ineffective tee removal with type changes (#5621)

When we remove a tee there, we must not change the type at all.

1 files changed, 10 insertions, 1 deletions

diff --git a/src/cfg/liveness-traversal.h b/src/cfg/liveness-traversal.h
index d9b310d6f..650ee4f47 100644
--- a/src/cfg/liveness-traversal.h
+++ b/src/cfg/liveness-traversal.h
@@ -152,7 +152,16 @@ struct LivenessWalker : public CFGWalker<SubType, VisitorType, Liveness> {
     // if it has side effects)
     if (!self->currBasicBlock) {
       if (curr->isTee()) {
-        *currp = curr->value;
+        // We can remove the tee, but must leave something of the exact same
+        // type.
+        auto originalType = curr->type;
+        if (originalType != curr->value->type) {
+          *currp =
+            Builder(*self->getModule()).makeBlock({curr->value}, originalType);
+        } else {
+          // No special handling, just use the value.
+          *currp = curr->value;
+        }
       } else {
         *currp = Builder(*self->getModule()).makeDrop(curr->value);
       }