WIP: possible fix

packages/swingset-liveslots/src/liveslots.js

@@ -284,19 +284,31 @@ function build(
 
       for (const vref of possiblyRetiredSet) {
         // eslint-disable-next-line no-use-before-define
-        if (!getValForSlot(vref) && !deadSet.has(vref)) {
-          // Don't retire things that haven't yet made the transition to dead,
-          // i.e., always drop before retiring
-          // eslint-disable-next-line no-use-before-define
-          if (!vrm.isVrefRecognizable(vref)) {
-            importsToRetire.add(vref);
+        if (getValForSlot(vref)) {
+          continue; // reachable by RAM pillar inhibits retirement
+        }
+        const { virtual, durable, allocatedByVat, type } = parseVatSlot(vref);
+        if (type !== 'object') {
+          continue; // we only retire objects
+        }
+        if (!virtual && !durable && !allocatedByVat) {
+          if (vrm.isPresenceReachable(vref)) {
+            continue; // reachable by vdata pillar inhibits retirement
           }
         }
+        // TODO: what was the deadSet check for? it wasn't sufficient.
+        // if (deadSet.has(vref)) {
+        //     continue;
+        // }
+        if (!vrm.isVrefRecognizable(vref)) {
+          importsToRetire.add(vref);
+        }
       }
       possiblyRetiredSet.clear();
 
       const deadBaseRefs = Array.from(deadSet);
       deadBaseRefs.sort();
+      console.log(`== sFDO scanning deadBaseRefs`, deadBaseRefs);
       for (const baseRef of deadBaseRefs) {
         const { virtual, durable, allocatedByVat, type } =
           parseVatSlot(baseRef);