1 files changed, 9 insertions, 0 deletions
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
index ecda014b..18271929 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
@@ -167,4 +167,13 @@ public class StoreNode extends MemOpNode {
             return Parser.error("Cannot modify final field '"+_name+"'",_loc);
         return null;
     }
+
+    // Do not GVN Stores. Two equal Stores on two of three paths are the easy
+    // failure: sharing them makes GCM place the Store on all three paths.
+    // Sharing is safe only if every exit path goes through an original Store,
+    // or GCM splits the shared Store to keep it on those paths. Stores must
+    // sink, not run on extra paths. GVN does not check this; GCM does not split.
+    // Identity also disables generic Phi factoring of Stores.
+    // The closed-loop Store sink is a separate peep and still applies.
+    @Override public boolean eq(Node n) { return this == n; }
 }