From d32f97238c903765dec4e9a9f3cbfa5fd12cded6 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 10 Aug 2026 11:11:18 -0700
Subject: Chapter 25: Modules, Separate Compilation, and SSA Construction

Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: Symious <14933944+symious@users.noreply.github.com>
Co-authored-by: Jun Kawasaki <jun784@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
---
 .../java/com/seaofnodes/simple/node/StopNode.java  | 79 ++++++++++++++--------
 1 file changed, 52 insertions(+), 27 deletions(-)

(limited to 'src/main/java/com/seaofnodes/simple/node/StopNode.java')

diff --git a/src/main/java/com/seaofnodes/simple/node/StopNode.java b/src/main/java/com/seaofnodes/simple/node/StopNode.java
index 9f7a925b..e52a49a2 100644
--- a/src/main/java/com/seaofnodes/simple/node/StopNode.java
+++ b/src/main/java/com/seaofnodes/simple/node/StopNode.java
@@ -2,34 +2,45 @@ package com.seaofnodes.simple.node;
 
 import com.seaofnodes.print.ExprPrinter;
 
-import com.seaofnodes.simple.type.Type;
-import com.seaofnodes.simple.util.Utils;
+import com.seaofnodes.simple.codegen.CodeGen;
+import com.seaofnodes.simple.type.*;
+import com.seaofnodes.simple.util.BAOS;
 
-public class StopNode extends CFGNode {
+import java.util.HashMap;
+import java.util.IdentityHashMap;
 
-    public final String _src;
+// A collection of function ReturnNodes for a compilation unit.
+public class StopNode extends CFGNode {
 
-    public StopNode(String src) {
+    public StopNode() {
         super();
-        _src = src;
         _type = compute();
     }
-    public StopNode(StopNode stop) { super(stop);  _src = stop==null ? null : stop._src; }
-
-    @Override
-    public String label() {
-        return "Stop";
+    public StopNode(StopNode stop) { super(stop); }
+    @Override public Tag serialTag() { return Tag.Stop; }
+    @Override public void packed( BAOS baos, HashMap<String,Integer> strs, HashMap<Type,Integer> types, IdentityHashMap<Node, Integer> anodes ) { baos.packed1(nIns()); }
+    static Node make( BAOS bais ) {
+        StopNode stop = new StopNode();
+        stop.setDefX(bais.packed1()-1,null);
+        return stop;
     }
 
     @Override
     protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
         // For the sake of many old tests, and single value prints as "return val"
-        ReturnNode ret1 = ret();
+        ReturnNode ret1 = null;
+        for( Node n : _inputs ) {
+            if( n instanceof ReturnNode ret ) {
+                if( ret1 != null ) { ret1=null; break; }
+                ret1 = ret;
+            }
+        }
         if( ret1!=null ) return p.n(ret1);
+
         p.p("Stop[ ");
-        for( Node ret : _inputs )
-            if( ret!=null ) {
-                String name = ((ReturnNode)ret).fun()._name;
+        for( Node n : _inputs )
+            if( n instanceof ReturnNode ret ) {
+                String name = ret.fun()._name;
                 if( name== null || !name.startsWith("sys.") )
                     p.n(ret).p(" ");
             }
@@ -42,25 +53,36 @@ public class StopNode extends CFGNode {
     // If a single Return, return it.
     // Otherwise, null because ambiguous.
     public ReturnNode ret() {
-        Node ret1 = this;
-        for( Node ret : _inputs ) {
-            String name = ((ReturnNode)ret).fun()._name;
-            if( name==null || !name.startsWith("sys.") )
-                ret1 = ret1==this ? ((ReturnNode)ret) : null;
+        ReturnNode ret1 = null;
+        for( Node n : _inputs ) {
+            // TODO: remove isPublic
+            if( n instanceof ReturnNode ret && ret.fun().isPublic() ) {
+                if( ret1 != null ) return null; // Ambiguous
+                ret1 = ret;
+            }
         }
-        return ret1==this ? null : (ReturnNode)ret1;
+        return ret1;
     }
 
     @Override
-    public Type compute() {
-        return Type.BOTTOM;
+    public TypeTuple compute() {
+        // During Parsing, new Stops and Returns are being added.  This Stop
+        // cannot know if more are coming, so must assume the worst.
+        if( CodeGen.CODE._phase ==null || CodeGen.CODE._phase == CodeGen.Phase.Parse )
+            return TypeTuple.STATE;
+
+        // Just meet-over-inputs.
+        TypeTuple tt = TypeTuple.STOP_HIGH;
+        for( Node def : _inputs )
+            tt = (TypeTuple)tt.meet(def._type);
+        assert tt.mem()._alias==1 && !tt.mem()._one;
+        return tt;
     }
 
-    @Override
-    public Node idealize() {
+    @Override public Node idealize() {
         int len = nIns();
         for( int i=0; i<nIns(); i++ )
-            if( addDep(((ReturnNode)in(i)).fun()).isDead() )
+            if( in(i).nIns()==0 )
                 delDef(i--);
         if( len != nIns() ) return this;
         return null;
@@ -70,7 +92,10 @@ public class StopNode extends CFGNode {
         if( validIDepth() ) return _idepth;
         int d=0;
         for( Node ret : _inputs )
-            d = Math.max(d,((ReturnNode)ret).idepth()+1);
+            // All public results are hooked on the Stop, including data
+            // values, so must check CFG
+            if( ret instanceof CFGNode cfg )
+                d = Math.max(d,cfg.idepth()+1);
         return cacheIDepth(d);
     }
 }
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