From e7eb2db06d1b9c529f94f2da3a087c83c0498e05 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 19 Oct 2026 10:40:35 -0700
Subject: Turn off Store GVN with explaination

---
 .../java/com/seaofnodes/simple/Chapter10Test.java  | 23 ++++++++++++++++++--
 .../java/com/seaofnodes/simple/Chapter17bTest.java | 25 ++++++++++++++++++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

(limited to 'chapter18/src/test/java')

diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
index 2681e878..cf877cb8 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
@@ -7,6 +7,24 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
 public class Chapter10Test {
+    @Test public void testConditionalStoreSharing() {
+        // Sharing the writes on two of three paths must not write on the third.
+        // Return the object so Load forwarding cannot hide the physical Store.
+        String src = """
+            struct S { int x; };
+            !S !a = new S;
+            a.x = 10;
+            if (arg == 1) a.x = 9;
+            else if (arg == 2) a.x = 9;
+            return a;
+            """;
+        var code = new CodeGen(src).driver(CodeGen.Phase.LocalSched);
+        for( int arg : new int[]{0,1,2,3} ) {
+            long expected = (arg==1 || arg==2) ? 9 : 10;
+            assertEquals("S{x="+expected+"}",Eval2.eval(code,arg));
+        }
+    }
+
     @Test public void testDeadReferenceReturn() {
         for( String body : new String[] {
             "return new S; return 0;",
@@ -529,7 +547,7 @@ return 0;
         assertEquals("3",Eval2.eval(code,3));
     }
 
-    @Test public void testDropStores() {
+    @Test public void testKeepBranchStores() {
         var code = new CodeGen("""
             struct S { int x; };
             !S !s = new S;
@@ -537,7 +555,8 @@ return 0;
             return s;
             """).parse().iter();
         StopNode stop = code._stop;
-        assertEquals(1,countMemoryNodes(stop,StoreNode.class,new BitSet()));
+        // Keep each Store on its own branch.
+        assertEquals(2,countMemoryNodes(stop,StoreNode.class,new BitSet()));
         assertEquals("S{x=2}",Eval2.eval(code,0));
         assertEquals("S{x=4}",Eval2.eval(code,3));
     }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter17bTest.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter17bTest.java
index a5ce8f49..3c40f684 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter17bTest.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter17bTest.java
@@ -7,6 +7,31 @@ import static org.junit.Assert.fail;
 
 public class Chapter17bTest {
 
+    @Test public void testSinkLoopStores() {
+        var code = new CodeGen("""
+            struct S { int x; };
+            !S !a = new S;
+            a.x = 10;
+            int i = 0;
+            while (i < arg) { a.x = i + 1; i++; }
+            return a;
+            """).driver(CodeGen.Phase.LocalSched);
+        int[] stores = {0};
+        code._stop.walk(n -> {
+            if( n instanceof com.seaofnodes.simple.node.StoreNode st && st._name.equals("x") ) {
+                assertEquals(0,st.cfg0().loopDepth()); // One final Store outside the loop.
+                stores[0]++;
+            }
+            return null;
+        });
+        assertEquals(1,stores[0]);
+        for( int arg : new int[]{-1,0,1,4} ) {
+            long expected = arg<=0 ? 10 : arg;
+            assertEquals("S{x="+expected+"}",Eval2.eval(code,arg));
+        }
+    }
+
+
     @Ignore
     @Test
     public void testJig() {
-- 
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