From c2cec7cb7fef6df603dd10180de4d0bb715ad47e Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Sat, 28 Dec 2024 16:39:00 -0800
Subject: New evaluator, more Compiler Driver cleanup

More compiler driver cleanup: Stop only has Return inputs, never an expr.  Drop extra lexical scope.  Linker table moves to CodeGen.
Replace evaluator with a simpler design; I was unable to get the current design to work with the other changes.
Updates to old eval; proper idoms; forced type checks; extensions for Fun, Return, Call, CallEnd.
Accessor find next control to execute.  Accessor for deciding when its ok to optimize a Function/Return, Call/CallEnd, Stop, ScopeMin (merge)
Add local scheduling pass.
IRPrinter uses SB instead of StringBuilder
Spelling SubF comment
---
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   2 +-
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   2 +-
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   4 +-
 .../java/com/seaofnodes/simple/node/SubNode.java   |   2 +-
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   2 +-
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   2 +-
 .../main/java/com/seaofnodes/simple/CodeGen.java   |  35 ++-
 .../com/seaofnodes/simple/GlobalCodeMotion.java    |   4 +-
 .../main/java/com/seaofnodes/simple/IRPrinter.java |  62 +++---
 .../main/java/com/seaofnodes/simple/IterPeeps.java |   1 +
 .../java/com/seaofnodes/simple/ListScheduler.java  | 110 ++++++++++
 .../main/java/com/seaofnodes/simple/Parser.java    | 104 +++++----
 .../java/com/seaofnodes/simple/node/CFGNode.java   |  14 +-
 .../java/com/seaofnodes/simple/node/CallNode.java  |   6 +-
 .../com/seaofnodes/simple/node/ConstantNode.java   |   9 +-
 .../java/com/seaofnodes/simple/node/CtrlNode.java  |  14 ++
 .../java/com/seaofnodes/simple/node/FunNode.java   |  36 ++-
 .../java/com/seaofnodes/simple/node/IfNode.java    |   3 +
 .../java/com/seaofnodes/simple/node/LoopNode.java  |  18 +-
 .../main/java/com/seaofnodes/simple/node/Node.java |   5 +-
 .../java/com/seaofnodes/simple/node/ParmNode.java  |   4 +-
 .../java/com/seaofnodes/simple/node/PhiNode.java   |  10 +-
 .../com/seaofnodes/simple/node/ReturnNode.java     |  12 +-
 .../com/seaofnodes/simple/node/ScopeMinNode.java   |  42 ++--
 .../java/com/seaofnodes/simple/node/ScopeNode.java |   8 +-
 .../java/com/seaofnodes/simple/node/StartNode.java |  14 +-
 .../java/com/seaofnodes/simple/node/StopNode.java  |  14 +-
 .../java/com/seaofnodes/simple/node/SubFNode.java  |   2 +-
 .../java/com/seaofnodes/simple/node/XCtrlNode.java |   4 +-
 .../java/com/seaofnodes/simple/BrainFuckTest.java  |   6 +-
 .../java/com/seaofnodes/simple/Chapter01Test.java  |   8 +-
 .../java/com/seaofnodes/simple/Chapter02Test.java  |  26 +--
 .../java/com/seaofnodes/simple/Chapter03Test.java  |  20 +-
 .../java/com/seaofnodes/simple/Chapter04Test.java  |  66 +++---
 .../java/com/seaofnodes/simple/Chapter05Test.java  |  18 +-
 .../java/com/seaofnodes/simple/Chapter06Test.java  |  47 ++--
 .../java/com/seaofnodes/simple/Chapter07Test.java  |  48 ++--
 .../java/com/seaofnodes/simple/Chapter08Test.java  |  43 ++--
 .../java/com/seaofnodes/simple/Chapter09Test.java  |  58 +++--
 .../java/com/seaofnodes/simple/Chapter10Test.java  |  36 ++-
 .../java/com/seaofnodes/simple/Chapter11Test.java  |  47 ++--
 .../java/com/seaofnodes/simple/Chapter12Test.java  |  18 +-
 .../java/com/seaofnodes/simple/Chapter13Test.java  |  21 +-
 .../java/com/seaofnodes/simple/Chapter14Test.java  |  57 +++--
 .../java/com/seaofnodes/simple/Chapter15Test.java  |  75 +++----
 .../java/com/seaofnodes/simple/Chapter16Test.java  |  60 ++---
 .../java/com/seaofnodes/simple/Chapter17Test.java  | 169 +++++++-------
 .../java/com/seaofnodes/simple/Chapter18Test.java  |  16 +-
 .../src/test/java/com/seaofnodes/simple/Eval2.java | 244 +++++++++++++++++++++
 .../com/seaofnodes/simple/evaluator/Evaluator.java |  11 +-
 .../com/seaofnodes/simple/evaluator/Scheduler.java |  47 ++--
 .../com/seaofnodes/simple/fuzzer/FuzzerUtils.java  |   6 +-
 52 files changed, 1073 insertions(+), 619 deletions(-)
 create mode 100644 chapter18/src/main/java/com/seaofnodes/simple/ListScheduler.java
 create mode 100644 chapter18/src/main/java/com/seaofnodes/simple/node/CtrlNode.java
 create mode 100644 chapter18/src/test/java/com/seaofnodes/simple/Eval2.java

diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..b591718d 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter14/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter14/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..b591718d 100644
--- a/chapter14/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter14/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter15/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..335b5f10 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -1,4 +1,4 @@
-package com.seaofnodes.simple.node;
+epackage com.seaofnodes.simple.node;
 
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/node/SubNode.java b/chapter15/src/main/java/com/seaofnodes/simple/node/SubNode.java
index 009fb30e..8ecdf13e 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/node/SubNode.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/node/SubNode.java
@@ -1,4 +1,4 @@
-package com.seaofnodes.simple.node;
+y!package com.seaofnodes.simple.node;
 
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
diff --git a/chapter16/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter16/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..b591718d 100644
--- a/chapter16/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter16/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter17/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter17/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..b591718d 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/CodeGen.java b/chapter18/src/main/java/com/seaofnodes/simple/CodeGen.java
index 184b6f9c..79d817f8 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/CodeGen.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/CodeGen.java
@@ -1,14 +1,13 @@
  package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.type.*;
-import java.util.*;
+import java.util.HashMap;
 
 public class CodeGen {
 
     public enum Phase {
-        Parse, Opto, TypeCheck, Schedule, RegAlloc;
+        Parse, Opto, TypeCheck, Schedule, LocalSched, RegAlloc;
     }
     public Phase _phase;
 
@@ -20,6 +19,11 @@ public class CodeGen {
     public StartNode _start;
     public  StopNode _stop ;
 
+
+    // "Linker" mapping from constant TypeFunPtrs to heads of function
+    public final HashMap<TypeFunPtr,FunNode> _linker = new HashMap<>();
+
+
     // Last created CodeGen as a global, for easier debugging prints
     public static CodeGen CODE;
 
@@ -30,6 +34,8 @@ public class CodeGen {
     public CodeGen parse(boolean disable) {
         assert _phase == null;
         _phase = Phase.Parse;
+        _linker.clear();
+
         P = new Parser(_src,_arg);
         Node._disablePeephole = disable;
         _stop = P.parse();
@@ -51,7 +57,7 @@ public class CodeGen {
     }
 
     public CodeGen typeCheck() {
-        assert _phase == Phase.Opto;
+        assert _phase == Phase.Opto || _phase == Phase.Parse;
         _phase = Phase.TypeCheck;
 
         // Type check
@@ -62,8 +68,8 @@ public class CodeGen {
     }
 
 
-    public CodeGen codegen() { return codegen(false); }
-    public CodeGen codegen(boolean show) {
+    public CodeGen GCM() { return GCM(false); }
+    public CodeGen GCM( boolean show) {
         assert _phase == Phase.TypeCheck;
         _phase = Phase.Schedule;
 
@@ -74,14 +80,23 @@ public class CodeGen {
 
         // TODO:
         // loop unroll, peel, RCE, etc
-
         GlobalCodeMotion.buildCFG(_start,_stop);
-
-        _phase = Phase.RegAlloc;
-
         return this;
     }
 
+     public CodeGen localSched() {
+        assert _phase == Phase.Schedule;
+        _phase = Phase.LocalSched;
+        ListScheduler.sched(this);
+        return this;
+     }
+
+
+    // Testing shortcuts
+    Node ctrl() { return _stop.ret().ctrl(); }
+    Node expr() { return _stop.ret().expr(); }
+    String print() { return _stop.print(); }
+
     // Debugging helper
     @Override public String toString() {
         return _stop.p(9999);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/GlobalCodeMotion.java b/chapter18/src/main/java/com/seaofnodes/simple/GlobalCodeMotion.java
index 7ce12091..6b0956ca 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/GlobalCodeMotion.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/GlobalCodeMotion.java
@@ -54,7 +54,7 @@ public abstract class GlobalCodeMotion {
         visit.set(n._nid);
         // Schedule not-pinned not-CFG inputs before self.  Since skipping
         // Pinned, this never walks the backedge of Phis (and thus spins around
-        // a data-only loop, eventually attempting relying on some pre-visited-
+        // a data-only loop), eventually attempting relying on some pre-visited-
         // not-post-visited data op with no scheduled control.
         for( Node def : n._inputs )
             if( def!=null && !(def instanceof PhiNode) )
@@ -65,7 +65,7 @@ public abstract class GlobalCodeMotion {
             CFGNode early = Parser.START; // Maximally early, lowest idepth
             if( n.in(0) instanceof CFGNode cfg ) early = cfg;
             for( int i=1; i<n.nIns(); i++ )
-                if( n.in(i).cfg0().idepth() > early.idepth() )
+                if( n.in(i)!=null && n.in(i).cfg0().idepth() > early.idepth() )
                     early = n.in(i).cfg0(); // Latest/deepest input
             n.setDef(0,early);              // First place this can go
         }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java b/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
index 4f422a25..adf67d8b 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
@@ -1,7 +1,6 @@
 package com.seaofnodes.simple;
 
 import com.seaofnodes.simple.node.*;
-import java.lang.StringBuilder;
 import java.util.ArrayList;
 import java.util.BitSet;
 import java.util.HashMap;
@@ -11,33 +10,31 @@ public class IRPrinter {
     // Print a node on 1 line, columnar aligned, as:
     // NNID NNAME DDEF DDEF  [[  UUSE UUSE  ]]  TYPE
     // 1234 sssss 1234 1234 1234 1234 1234 1234 tttttt
-    public static void printLine( Node n, StringBuilder sb ) {
-        sb.append("%4d %-7.7s ".formatted(n._nid,n.label()));
-        if( n._inputs==null ) {
-            sb.append("DEAD\n");
-            return;
-        }
+    public static SB printLine( Node n, SB sb ) {
+        sb.p("%4d %-7.7s ".formatted(n._nid,n.label()));
+        if( n._inputs==null )
+            return sb.p("DEAD\n");
         for( Node def : n._inputs )
-            sb.append(def==null ? "____" : "%4d".formatted(def._nid))
+            sb.p(def==null ? "____" : "%4d".formatted(def._nid))
                 // Lazy Phi indicator
-                .append(n instanceof ScopeMinNode && def instanceof ScopeMinNode ? "^" : " ");
+                .p(n instanceof ScopeMinNode && def instanceof ScopeMinNode ? "^" : " ");
         for( int i = n._inputs.size(); i<4; i++ )
-            sb.append("     ");
-        sb.append(" [[  ");
+            sb.p("     ");
+        sb.p(" [[  ");
         for( Node use : n._outputs )
-            sb.append(use==null ? "____ " : "%4d ".formatted(use._nid));
+            sb.p(use==null ? "____ " : "%4d ".formatted(use._nid));
         int lim = 6 - Math.max(n._inputs.size(),4);
         for( int i = n._outputs.size(); i<lim; i++ )
-            sb.append("     ");
-        sb.append(" ]]  ");
-        if( n._type!= null ) sb.append(n._type.str());
-        sb.append("\n");
+            sb.p("     ");
+        sb.p(" ]]  ");
+        if( n._type!= null ) sb.p(n._type.str());
+        return sb.p("\n");
     }
 
-    private static StringBuilder nodeId(StringBuilder sb, Node n) {
-        sb.append("%%%d".formatted(n._nid));
+    private static SB nodeId(SB sb, Node n) {
+        sb.p("%%%d".formatted(n._nid));
         if (n instanceof ProjNode proj) {
-            sb.append(".").append(proj._idx);
+            sb.p(".").p(proj._idx);
         }
         return sb;
     }
@@ -58,19 +55,19 @@ public class IRPrinter {
         for( int i=bfs._lim; i< bfs._bfs.size(); i++ )
             postOrd( bfs._bfs.get(i), null, rpos, visit, bfs._bs);
         // Reverse the post-order walk
-        StringBuilder sb = new StringBuilder();
+        SB sb = new SB();
         boolean gap=false;
         for( int i=rpos.size()-1; i>=0; i-- ) {
             Node n = rpos.get(i);
             if( n instanceof CFGNode || n.isMultiHead() ) {
-                if( !gap ) sb.append("\n"); // Blank before multihead
+                if( !gap ) sb.p("\n"); // Blank before multihead
                 printLine( n, sb );         // Print head
                 while( --i >= 0 ) {
                     Node t = rpos.get(i);
                     if( !t.isMultiTail() ) { i++; break; }
                     printLine( t, sb );
                 }
-                sb.append("\n"); // Blank after multitail
+                sb.p("\n"); // Blank after multitail
                 gap = true;
             } else {
                 printLine( n, sb );
@@ -180,7 +177,7 @@ public class IRPrinter {
             }
         }
         // Print by block with least idepth
-        StringBuilder sb = new StringBuilder();
+        SB sb = new SB();
         Ary<Node> bns = new Ary<>(Node.class);
         while( !ds.isEmpty() ) {
             CFGNode blk = null;
@@ -193,16 +190,15 @@ public class IRPrinter {
             ns.remove(blk);
 
             // Print block header
-            sb.append("%-13.13s".formatted(label(blk)+":"));
-            sb.append( "     ".repeat(4) ).append(" [[  ");
+            sb.p("%-13.13s".formatted(label(blk)+":"));
+            sb.p( "     ".repeat(4) ).p(" [[  ");
             if( blk instanceof StartNode ) ;
             else if( blk instanceof RegionNode || blk instanceof StopNode )
                 for( int i=(blk instanceof StopNode ? 3 : 1); i<blk.nIns(); i++ )
                     label(sb,blk.cfg(i));
             else
                 label(sb,blk.cfg(0));
-            sb.append(" ]]  \n");
-            sb.append(d);
+            sb.p(" ]]  \n");
             printLine(blk,sb);
 
             // Collect block contents that are in the depth limit
@@ -234,20 +230,21 @@ public class IRPrinter {
                         }
                     }
                 }
-            sb.append("\n");
+            sb.p("\n");
         }
         return sb.toString();
     }
 
     private static void _walk( HashMap<Integer,Integer> ds, ArrayList<Node> ns, Node node, int d ) {
         Integer nd = ds.get(node._nid);
-        if( nd!=null && d >= nd ) return; // Been there, done that
+        if( nd!=null && d <= nd ) return; // Been there, done that
         Integer old = ds.put(node._nid,d) ;
         if( old == null )
           ns.add(node);
         if( d == 0 ) return;    // Depth cutoff
         for( Node def : node._inputs )
             if( def != null &&
+                !(node instanceof LoopNode loop && loop.back()==def) &&
                 // Don't walk into or out of functions
                 !(node instanceof CallEndNode && def instanceof ReturnNode) &&
                 !(node instanceof FunNode && def instanceof CallNode) )
@@ -258,12 +255,11 @@ public class IRPrinter {
         if( blk instanceof StartNode ) return "START";
         return (blk instanceof LoopNode ? "LOOP" : "L")+blk._nid;
     }
-    static void label( StringBuilder sb, CFGNode blk ) {
+    static void label( SB sb, CFGNode blk ) {
         if( !blk.blockHead() ) blk = blk.cfg(0);
-        sb.append( "%-9.9s ".formatted( label( blk ) ) );
+        sb.p( "%-9.9s ".formatted( label( blk ) ) );
     }
-    static void printLine( Node n, StringBuilder sb, Ary<Node> bns, int i, HashMap<Integer,Integer> ds, ArrayList<Node> ns ) {
-        sb.append(ds.get(n._nid));
+    static void printLine( Node n, SB sb, Ary<Node> bns, int i, HashMap<Integer,Integer> ds, ArrayList<Node> ns ) {
         printLine( n, sb );
         if( i != -1 ) bns.del(i);
         ds.remove(n._nid);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java b/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
index a321b13e..998bd4f0 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
@@ -182,6 +182,7 @@ public abstract class IterPeeps {
          * True if Node is on the WorkList
          */
         boolean on( E x ) { return _on.get(x._nid); }
+        boolean isEmpty() { return _len==0; }
 
         /**
          * Removes a random Node from the WorkList; null if WorkList is empty
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/ListScheduler.java b/chapter18/src/main/java/com/seaofnodes/simple/ListScheduler.java
new file mode 100644
index 00000000..252a8f8e
--- /dev/null
+++ b/chapter18/src/main/java/com/seaofnodes/simple/ListScheduler.java
@@ -0,0 +1,110 @@
+ package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.IterPeeps.WorkList;
+import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.type.*;
+import java.util.*;
+
+public abstract class ListScheduler {
+
+    private static final BitSet VISIT = new BitSet();
+    private static int[] BCNTS;
+    public static void sched( CodeGen code ) {
+        assert VISIT.isEmpty();
+        BCNTS = new int[Node.UID()];
+        walk(code._start,VISIT);
+        VISIT.clear();
+    }
+
+    // Visit all CFG nodes
+    static void walk( CFGNode cfg, BitSet visit ) {
+        if( visit.get(cfg._nid) ) return;
+        visit.set(cfg._nid);
+        local(cfg);
+        for( Node n : cfg._outputs )
+            if( n instanceof CFGNode c )
+                walk(c,visit);
+    }
+
+    // Local schedule this one CFG
+    static void local( CFGNode bb ) {
+        if( !bb.blockHead() || bb instanceof StopNode ) return;
+        Node[] uses = bb._outputs._es;
+        int ulen = bb._outputs._len;
+
+        // Count block-locals
+        for( int i=0; i<ulen; i++ ) {
+            Node use = uses[i];
+            if( use.in(0)==bb && !(use instanceof PhiNode) ) {
+                // Normal basic block member: in(0)==bb and not a Phi
+                for( Node def : use._inputs )
+                    // Has defs from same block?  Then block-local inputs
+                    if( def != null && def.cfg0()==bb ) // Same block?
+                        BCNTS[use._nid]++;     // Raise block-local input count
+            }
+        }
+
+        // Nodes are ready if they are not used by other nodes in this block.
+        // Move ready up front. We will never look at remaining nodes, later
+        // nodes are found by looking at users of ready nodes.
+        int ready = 0;
+        for( int i=0; i<ulen; i++ )
+            if( BCNTS[uses[i]._nid]==0 )   // No block-local inputs?
+                uses[ready++] = uses[i];   // Move into ready set
+        assert ready > 0;
+
+        // Classic list scheduler.  Behind sched is scheduled.  Between sched
+        // and ready have zero counts and are ready to schedule.  Ahead of
+        // ready is undefined.
+        //
+        // As nodes are scheduled, the nodes they use decrement their _bcnt. Once
+        // that gets to 0, all the nodes using it are scheduled, so it's ready.
+        int sched = 0;
+        while( sched < ulen ) {
+            assert sched < ready : "Scheduling nodes that are not ready. Probably due to duplicate nodes in the user list.";
+            int pick = best(uses, sched,ready); // Pick best
+            Node best = uses[pick];       // Swap best to head of ready
+            uses[pick] = uses[sched];
+            uses[sched++] = best; // And move it into the scheduled set
+            // Lower ready count of users
+            for( Node use : best._outputs )
+                if( use instanceof ProjNode ) {
+                    for( Node useuse : use._outputs )
+                        ready = ready(bb,useuse,ready);
+                } else
+                    ready = ready(bb, use,ready);
+        }
+    }
+
+    private static int ready(CFGNode bb, Node use, int ready) {
+        if( use != null && use.in(0)==bb && !(use instanceof PhiNode) ) {
+            assert BCNTS[use._nid] >= 1;
+            if( --BCNTS[use._nid] == 0 )
+                bb._outputs._es[ready++] = use; // Became ready, move into ready set
+        }
+        return ready;
+    }
+
+
+    // Pick best between sched and ready.
+    private static int best( Node[] uses, int sched, int ready ) {
+        int pick = sched;
+        int score = score(uses[pick]);
+        for( int i=sched+1; i<ready; i++ ) {
+            int nscore = score(uses[i]);
+            if( nscore > score )
+                { score = nscore; pick = i; }
+        }
+        return pick;
+    }
+
+    // Highest score wins.  Max at 1000, min at 10, except specials.
+    private static int score( Node n ) {
+        if( n.isMultiTail()  ) return 1001; // Pinned just behind the multi-head
+        if( n instanceof CFGNode ) return n instanceof ReturnNode ? 2 : 1; // Pinned at block exit
+
+        // Nothing special
+        return 500;
+    }
+
+}
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
index f6bf71a9..ac497fe8 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
@@ -98,16 +98,12 @@ public class Parser {
     // Mapping from a type name to the constructor for a Type.
     public final HashMap<String, StructNode> INITS;
 
-    // "Linker" mapping from constant TypeFunPtrs to heads of function
-    public static final HashMap<TypeFunPtr,FunNode> LINKER = new HashMap<>();
-
 
     public Parser(String source) { this(source, TypeInteger.BOT); }
 
     public Parser(String source, TypeInteger arg) {
         Node.reset();
         IterPeeps.reset();
-        LINKER.clear();
         _lexer = new Lexer(source);
         _scope = new ScopeNode();
         _continueScope = _breakScope = null;
@@ -154,38 +150,38 @@ public class Parser {
     public StopNode parse() { return parse(false); }
     public StopNode parse(boolean show) {
         _xScopes.push(_scope);
-        // Enter a new scope for the initial control and arguments
-        _scope.push();
-        Node ctrl = new CProjNode(START, 0, ScopeNode.CTRL).peephole();
-        Node pmem = new  ProjNode(START, 1, ScopeNode.MEM0).peephole();
-        Node arg  = new  ProjNode(START, 2, ScopeNode.ARG0).peephole();
-        ScopeMinNode mem = new ScopeMinNode();
-        mem.addDef(null);
-        mem.addDef(pmem);
-        _scope.define(ScopeNode.CTRL, Type.CONTROL   , false, ctrl);
-        _scope.define(ScopeNode.MEM0, TypeMem.BOT    , false, mem );
-        _scope.define(ScopeNode.ARG0, TypeInteger.BOT, false, arg );
-
-        // Call main
-        CallNode main = (CallNode)new CallNode(ctrl,pmem,arg,con(TypeFunPtr.MAIN)).peephole();
-        // Call End
-        CallEndNode cend = (CallEndNode)new CallEndNode(main).peephole();
-        STOP.addDef(new CProjNode(cend,0,ScopeNode.CTRL).peephole());
-        STOP.addDef(new  ProjNode(cend,1,ScopeNode.MEM0).peephole());
-        STOP.addDef(new  ProjNode(cend,2,ScopeNode.ARG0).peephole());
+        //// Enter a new scope for the initial control and arguments
+        //_scope.push();
+        //Node ctrl = new CProjNode(START, 0, ScopeNode.CTRL).peephole();
+        //Node pmem = new  ProjNode(START, 1, ScopeNode.MEM0).peephole();
+        //Node arg  = new  ProjNode(START, 2, ScopeNode.ARG0).peephole();
+        //ScopeMinNode mem = new ScopeMinNode();
+        //mem.addDef(null);
+        //mem.addDef(pmem);
+        _scope.define(ScopeNode.CTRL, Type.CONTROL   , false, null);
+        _scope.define(ScopeNode.MEM0, TypeMem.BOT    , false, null);
+        _scope.define(ScopeNode.ARG0, TypeInteger.BOT, false, null);
+        //
+        //// Call main
+        //CallNode main = (CallNode)new CallNode(ctrl,pmem,arg,con(TypeFunPtr.MAIN)).peephole();
+        //// Call End
+        //CallEndNode cend = (CallEndNode)new CallEndNode(main).peephole();
+        //STOP.addDef(new CProjNode(cend,0,ScopeNode.CTRL).peephole());
+        //STOP.addDef(new  ProjNode(cend,1,ScopeNode.MEM0).peephole());
+        //STOP.addDef(new  ProjNode(cend,2,ScopeNode.ARG0).peephole());
 
         // Parse whole program, as-if function header "{ int arg -> body }"
         ReturnNode ret = parseFunctionBody("main",TypeFunPtr.MAIN,"arg");
-        LINKER.put(TypeFunPtr.MAIN,ret.fun());
-        main.peephole();
-        if( cend.peephole() != null )
-            IterPeeps.addAll(cend._outputs);
+        CodeGen.CODE._linker.put(TypeFunPtr.MAIN,ret.fun());
+        //main.peephole();
+        //if( cend.peephole() != null )
+        //    IterPeeps.addAll(cend._outputs);
 
         if( !_lexer.isEOF() ) throw _errorSyntax("unexpected");
 
         // Clean up and reset
-        _scope.kill();
         _xScopes.pop();
+        _scope.kill();
         for( StructNode init : INITS.values() )
             init.unkeep().kill();
         INITS.clear();
@@ -208,6 +204,7 @@ public class Parser {
         PhiNode rmem = new PhiNode(ScopeNode.MEM0,TypeMem.BOT,r,null);
         PhiNode rrez = new PhiNode(ScopeNode.ARG0,Type.BOTTOM,r,null);
         ReturnNode ret = new ReturnNode(r, rmem, rrez, fun);
+        fun.setRet(ret);
         assert ret.inProgress();
         STOP.addDef(ret);
 
@@ -217,10 +214,9 @@ public class Parser {
         _scope.push();
         ctrl(fun);              // Scope control from function
         // Private mem alias tracking per function
-        ScopeMinNode startMem = _scope.mem();
-        ScopeMinNode mem = new ScopeMinNode();
+        ScopeMinNode mem = new ScopeMinNode(true);
         mem.addDef(null);       // Alias#0
-        mem.addDef(new ParmNode(ScopeNode.MEM0,1,TypeMem.BOT,fun,startMem).peephole()); // All aliases
+        mem.addDef(new ParmNode(ScopeNode.MEM0,1,TypeMem.BOT,fun,con(TypeMem.BOT)).peephole()); // All aliases
         _scope.mem(mem);
         // All args, "as-if" called externally
         for( int i=0; i<ids.length; i++ ) {
@@ -236,7 +232,7 @@ public class Parser {
 
         // Last expression is the return
         if( ctrl()._type==Type.CONTROL )
-            STOP.addReturn(ctrl(), _scope.mem(), last, fun);
+            STOP.addReturn(ctrl(), _scope.mem().merge(), last, fun);
 
         // Function scope ends
         _scope.pop();
@@ -581,7 +577,9 @@ public class Parser {
      */
     private Node parseReturn() {
         var expr = require(parseAsgn(), ";");
-        STOP.addReturn(ctrl(), _scope.mem(), expr, _fun);
+        // Need default memory, since it can be lazy, need to force
+        // a non-lazy Phi
+        STOP.addReturn(ctrl(), _scope.mem().merge(), expr, _fun);
         ctrl(XCTRL);            // Kill control
         return expr;
     }
@@ -1043,26 +1041,36 @@ public class Parser {
         // Check for assign-update, x += e0;
         char ch = _lexer.matchOperAssign();
         if( ch==0  ) return rvalue;
+
+        // the rvalue is an l-value now; it will be updated
+        Node lhs = rvalue.keep();
         if( n._final )
             throw error("Cannot reassign final '"+n._name+"'");
+        // RHS of the update
+        Node rhs =
+            (byte)ch ==  1 ? con( 1) : // var++
+            (byte)ch == -1 ? con(-1) : // var--
+            parseAsgn();         // var op= rhs
+        // Widen RHS int to a RHS float
+        rhs = widenInt(rhs,n.type());
+        // Complain a RHS float into a LHS int
+        if( !rhs._type.isa(n.type()) )
+            throw error("Type " + rhs._type.str() + " is not of declared type " + n.type().str());
+
         Node op = switch(ch) {
-        case '+'      -> new AddNode(rvalue,null);
-        case '-'      -> new SubNode(rvalue,null);
-        case '*'      -> new MulNode(rvalue,null);
-        case '/'      -> new DivNode(rvalue,null);
-        case        1 -> new AddNode(rvalue,con( 1));
-        case (char)-1 -> new AddNode(rvalue,con(-1));
-        default -> throw Utils.TODO();
+        case 1, (char)-1,
+             '+' -> new AddNode(lhs,rhs);
+        case '-' -> new SubNode(lhs,rhs);
+        case '*' -> new MulNode(lhs,rhs);
+        case '/' -> new DivNode(lhs,rhs);
+        default  -> throw Utils.TODO();
         };
-        // Return pre-value (x+=1) or post-value (x++)
-        boolean pre = op.in(2)==null;
-        // Parse RHS argument as needed
-        if( pre )
-            { op.keep().setDef(2,parseAsgn());  op.unkeep(); }
-        else rvalue.keep();     // Keep post-value across peeps
-        op = zsMask(peep(op),n.type());
+
+        op = zsMask(peep(op.widen()),n.type());
         _scope.update(n,op);
-        return pre ? op : rvalue.unkeep();
+        // Return pre-value (x+=1) or post-value (x++)
+        lhs.unkeep();
+        return (byte)ch== 1 || (byte)ch== -1 ? lhs : op;
     }
 
     ScopeMinNode.Var requireLookupId(String msg) {
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/CFGNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/CFGNode.java
index bed4eb17..bacc1935 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/CFGNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/CFGNode.java
@@ -28,6 +28,17 @@ public abstract class CFGNode extends Node {
     // Block head is Start, Region, CProj, but not e.g. If, Return, Stop
     public boolean blockHead() { return false; }
 
+    // Get the one control following; error to call with more than one e.g. an
+    // IfNode or other multi-way branch.
+    public CFGNode uctrl() {
+        CFGNode c = null;
+        for( Node n : _outputs )
+            if( n instanceof CFGNode cfg )
+                {  assert c==null;  c = cfg; }
+        return c;
+    }
+
+
     // ------------------------------------------------------------------------
     /**
      * Immediate dominator tree depth, used to approximate a real IDOM during
@@ -90,13 +101,14 @@ public abstract class CFGNode extends Node {
         _pre = pre++;
         // Pre-walk
         for( Node use : _outputs )
-            if( use instanceof CFGNode usecfg )
+            if( use instanceof CFGNode usecfg && !(usecfg instanceof XCtrlNode) )
                 pre = usecfg._bltWalk(pre,use instanceof FunNode fuse ? fuse : fun,stop,post);
 
         // Post-order work: find innermost loop
         LoopTree inner = null, ltree;
         for( Node use : _outputs ) {
             if( !(use instanceof CFGNode usecfg) ) continue;
+            if( usecfg instanceof XCtrlNode ) continue;
             // Child visited but not post-visited?
             if( !post.get(usecfg._nid) ) {
                 // Must be a backedge to a LoopNode then
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/CallNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/CallNode.java
index 0839ad2c..3ec1cd0c 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/CallNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/CallNode.java
@@ -1,6 +1,6 @@
 package com.seaofnodes.simple.node;
 
-import com.seaofnodes.simple.Parser;
+import com.seaofnodes.simple.CodeGen;
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFunPtr;
@@ -21,7 +21,7 @@ public class CallNode extends CFGNode {
         String fname = null;
         Node fptr = fptr();
         if( fptr._type instanceof TypeFunPtr tfp && tfp.isConstant() )
-            fname = Parser.LINKER.get(tfp)._name;
+            fname = CodeGen.CODE._linker.get(tfp)._name;
         if( fname==null ) fptr._print0(sb,visited);
         else sb.append(fname);
         sb.append("( ");
@@ -62,7 +62,7 @@ public class CallNode extends CFGNode {
                 for( ; fidxs!=0; fidxs = TypeFunPtr.nextFIDX(fidxs) ) {
                     int fidx = Long.numberOfTrailingZeros(fidxs);
                     TypeFunPtr tfp0 = tfp.makeFrom(fidx);
-                    FunNode fun = Parser.LINKER.get(tfp0);
+                    FunNode fun = CodeGen.CODE._linker.get(tfp0);
                     if( fun!=null && !fun._folding && !linked(fun) )
                         link(fun);
                 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
index 406b20ca..e54797a5 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
@@ -19,12 +19,18 @@ import java.util.BitSet;
  * The Constant's value is the value stored in it.
  */
 public class ConstantNode extends Node {
-    Type _con;
+    public final Type _con;
     public ConstantNode( Type type ) {
         super(Parser.START);
         _con = type;
     }
 
+    public static Node make( Type type ) {
+        if( type==Type. CONTROL ) return new CtrlNode();
+        if( type==Type.XCONTROL ) return new XCtrlNode();
+        return new ConstantNode(type);
+    }
+
     @Override
     public String label() { return "#"+_con; }
 
@@ -37,6 +43,7 @@ public class ConstantNode extends Node {
     }
 
     @Override public boolean isMultiTail() { return true; }
+    @Override public boolean isConst() { return true; }
 
     @Override
     public Type compute() { return _con; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/CtrlNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/CtrlNode.java
new file mode 100644
index 00000000..162417bb
--- /dev/null
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/CtrlNode.java
@@ -0,0 +1,14 @@
+package com.seaofnodes.simple.node;
+
+import com.seaofnodes.simple.Parser;
+import com.seaofnodes.simple.type.Type;
+import java.util.BitSet;
+
+public class CtrlNode extends CFGNode {
+    public CtrlNode() { super(Parser.START); }
+    @Override public String label() { return "Ctrl"; }
+    @Override StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append("Cctrl"); }
+    @Override public boolean isConst() { return true; }
+    @Override  public Type compute() { return Type.CONTROL; }
+    @Override public Node idealize() { return null; }
+}
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/FunNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/FunNode.java
index 9087926e..94d7eff7 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/FunNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/FunNode.java
@@ -9,24 +9,27 @@ public class FunNode extends RegionNode {
     // When set true, this Call/CallEnd/Fun/Return is being trivially inlined
     boolean _folding;
 
-    TypeFunPtr _sig;            // Initial signature may be missing return
-    String _name;               // Debug label, optional
+    public final TypeFunPtr _sig; // Initial signature
+    public String _name;        // Debug label, optional
+    private ReturnNode _ret;     // Return pointer
 
     public FunNode( StartNode start, TypeFunPtr sig, String name ) { super(null,start); _sig=sig; _name=name; }
 
     @Override
     public String label() { return _name; }
 
-    ReturnNode ret() {
-        ReturnNode ret=null;
+    // Find the one CFG user from Fun.  It's not always the Return, but always
+    // the Return *is* a CFG user of Fun.
+    @Override public CFGNode uctrl() {
         for( Node n : _outputs )
-            if( n instanceof ReturnNode ret0 ) {
-                assert ret==null || ret==ret0; // Found more than one return
-                ret=ret0;
-            }
-        return ret;
+            if( n instanceof CFGNode cfg &&
+                (cfg instanceof RegionNode || cfg.cfg0()==this) )
+                return cfg;
+        return null;
     }
 
+    public void setRet(ReturnNode ret) { _ret=ret; }
+    ReturnNode ret() { assert _ret!=null; return _ret; }
 
     @Override
     public Type compute() {
@@ -36,12 +39,23 @@ public class FunNode extends RegionNode {
 
     @Override
     public Node idealize() {
+        // When can we assume no callers?  Or no other callers (except main)?
+        // In a partial compilation, we assume Start gets access to any/all
+        // top-level public structures and recursively what they point to.
+        // This in turn is valid arguments to every callable function.
+        //
+        // In a total compilation, we can start from Start and keep things
+        // more contained.
+
+
         // If no default/unknown caller, use the normal RegionNode ideal rules
         // to collapse
-        if( inProgress() ) return null;
+        if( unknownCallers() ) return null;
         return super.idealize();
     }
 
     // Always in-progress until we run out of unknown callers
-    @Override public boolean inProgress() { return in(1) instanceof StartNode; }
+    public boolean unknownCallers() { return in(1) instanceof StartNode; }
+
+    @Override public boolean inProgress() { return unknownCallers(); }
 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
index dcd2d4c7..1e6b2878 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
@@ -26,6 +26,9 @@ public class IfNode extends CFGNode implements MultiNode {
     public Node ctrl() { return in(0); }
     public Node pred() { return in(1); }
 
+    // No one unique control follows
+    @Override public CFGNode uctrl() { return null; }
+
     @Override
     public Type compute() {
         // If the If node is not reachable then neither is any following Proj
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
index 33420eb9..3f2ae149 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
@@ -58,17 +58,13 @@ public class LoopNode extends RegionNode {
         setDef(2,f);
 
         // Now fold control into the exit
-        if( fun!=null )
-            throw Utils.TODO();
-
-        // If not in a function, look for a last-level merge point;
-        // make if not there.
-        RegionNode ctrl = stop.ctrl() instanceof RegionNode r ? r : new RegionNode(null,stop.ctrl());
-        PhiNode    mem  = stop.mem () instanceof PhiNode phi && phi.in(0)==ctrl ? phi : new PhiNode("",stop.mem ()._type,ctrl,stop.mem ());
-        PhiNode    expr = stop.expr() instanceof PhiNode phi && phi.in(0)==ctrl ? phi : new PhiNode("",stop.expr()._type,ctrl,stop.expr());
-        if( stop.ctrl()!=ctrl ) stop.setDef(0,ctrl);
-        if( stop.mem ()!=mem  ) stop.setDef(1,mem );
-        if( stop.expr()!=expr ) stop.setDef(2,expr);
+        ReturnNode ret = fun.ret();
+        RegionNode ctrl = ret.ctrl() instanceof RegionNode r ? r : new RegionNode(null,ret.ctrl());
+        PhiNode    mem  = ret.mem () instanceof PhiNode phi && phi.in(0)==ctrl ? phi : new PhiNode(ctrl,ret.mem ());
+        PhiNode    expr = ret.expr() instanceof PhiNode phi && phi.in(0)==ctrl ? phi : new PhiNode(ctrl,ret.expr());
+        if( ret.ctrl()!=ctrl ) ret.setDef(0,ctrl);
+        if( ret.mem ()!=mem  ) ret.setDef(1,mem );
+        if( ret.expr()!=expr ) ret.setDef(2,expr);
         Node top = new ConstantNode(Type.TOP).peephole();
         ctrl.addDef(t  );
         mem .addDef(top);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java
index 6369fb01..cc7a1d13 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -114,6 +114,7 @@ public abstract class Node {
 
     public boolean isMultiHead() { return false; }
     public boolean isMultiTail() { return false; }
+    public boolean isConst    () { return false; }
 
     // ------------------------------------------------------------------------
     // Graph Node & Edge manipulation
@@ -337,8 +338,8 @@ public abstract class Node {
         Type old = setType(compute());
 
         // Replace constant computations from non-constants with a constant node
-        if( !(this instanceof ConstantNode) && !(this instanceof XCtrlNode) && _type.isHighOrConst() )
-            return (_type==Type.XCONTROL ? new XCtrlNode() : new ConstantNode(_type)).peepholeOpt();
+        if( _type.isHighOrConst() && !isConst() )
+            return ConstantNode.make(_type).peepholeOpt();
 
         // Global Value Numbering
         if( _hash==0 ) {
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ParmNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ParmNode.java
index 136494b5..f139e4ca 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ParmNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ParmNode.java
@@ -7,7 +7,7 @@ import java.util.BitSet;
 public class ParmNode extends PhiNode {
 
     // Argument indices are mapped one-to-one on CallNode inputs
-    final int _idx;             // Argument index
+    public final int _idx;             // Argument index
 
     public ParmNode(String label, int idx, Type declaredType, Node... inputs) {
         super(label,declaredType,inputs);
@@ -18,7 +18,7 @@ public class ParmNode extends PhiNode {
 
     @Override public String glabel() { return _label; }
 
-    FunNode fun() { return (FunNode)in(0); }
+    public FunNode fun() { return (FunNode)in(0); }
 
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java
index 6dd4f57d..91334b6c 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java
@@ -8,7 +8,7 @@ import java.util.BitSet;
 
 public class PhiNode extends Node {
 
-    final String _label;
+    public final String _label;
 
     // The Phi type we compute must stay within the domain of the Phi.
     // Example Int stays Int, Ptr stays Ptr, Control stays Control, Mem stays Mem.
@@ -16,6 +16,14 @@ public class PhiNode extends Node {
 
     public PhiNode(String label, Type declaredType, Node... inputs) { super(inputs); _label = label;  assert declaredType!=null; _declaredType = declaredType; }
 
+    public PhiNode(RegionNode r, Node sample) {
+        super(r);
+        _label = "";
+        _declaredType = sample._type;
+        while( nIns() < r.nIns() )
+            addDef(sample);
+    }
+
     @Override public String label() { return "Phi_"+MemOpNode.mlabel(_label); }
 
     @Override public String glabel() { return "&phi;_"+_label; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index b305a96e..35563d6e 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -1,8 +1,7 @@
 package com.seaofnodes.simple.node;
 
-import com.seaofnodes.simple.Parser;
+import com.seaofnodes.simple.CodeGen;
 import com.seaofnodes.simple.type.*;
-
 import java.util.BitSet;
 
 /**
@@ -16,14 +15,16 @@ import java.util.BitSet;
  */
 public class ReturnNode extends CFGNode {
 
+    public final FunNode _fun;
     public ReturnNode(Node ctrl, Node mem, Node data, FunNode fun) {
-        super(ctrl, mem, data, fun);
+        super(ctrl, mem, data);
+        _fun = fun;
     }
 
     public Node ctrl() { return in(0); }
     public Node mem () { return in(1); }
     public Node expr() { return in(2); }
-    public FunNode fun() { return (FunNode)in(3); }
+    public FunNode fun() { return _fun; }
 
     @Override
     public String label() { return "Return"; }
@@ -31,7 +32,6 @@ public class ReturnNode extends CFGNode {
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
         sb.append("return ");
-        if( expr()==null ) return sb.append("INPROGRESS");
         expr()._print0(sb, visited);
         return sb.append(";");
     }
@@ -45,7 +45,7 @@ public class ReturnNode extends CFGNode {
     @Override public Node idealize() { return null; }
 
     public boolean inProgress() {
-        return ctrl() instanceof RegionNode r && r.inProgress();
+        return ctrl().getClass() == RegionNode.class && ((RegionNode)ctrl()).inProgress();
     }
 
     // Add a return exit to the current parsing function
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java
index f5a33890..f29ed20b 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java
@@ -11,6 +11,8 @@ import static com.seaofnodes.simple.Utils.TODO;
 /* */
 public class ScopeMinNode extends Node {
 
+    public final boolean _inProgress;
+
     /** The tracked fields are now complex enough to deserve a array-of-structs layout
      */
     public static class Var {
@@ -39,8 +41,12 @@ public class ScopeMinNode extends Node {
         }
     }
 
-    public ScopeMinNode() { _type = TypeMem.BOT; }
+    public ScopeMinNode(boolean inProgress) { _type = TypeMem.BOT; _inProgress = inProgress; }
+
 
+    // If being used by a Scope, this is "in progress" from the Parser.
+    // Otherwise its a memory merge
+    boolean inProgress() { return _inProgress; }
 
     @Override public String label() { return "ALLMEM"; }
     @Override public boolean isMem() { return true; }
@@ -63,6 +69,17 @@ public class ScopeMinNode extends Node {
         return sb.append("]");
     }
 
+    // Make a memory merge: no longer a Scope really, tracking memory state but
+    // not related to the parser in any way.
+    public Node merge() {
+        // Force default memory to not be lazy
+        ScopeMinNode merge = new ScopeMinNode(false);
+        for( Node n : _inputs )
+            merge.addDef(n);
+        merge._mem(1,null);
+        return merge.peephole();
+    }
+
 
     @Override public Type compute() { return TypeMem.BOT; }
 
@@ -127,13 +144,13 @@ public class ScopeMinNode extends Node {
 
     // Fill in the backedge of any inserted Phis
     void _endLoopMem( ScopeNode scope, ScopeMinNode back, ScopeMinNode exit ) {
-        for( int i=2; i<back.nIns(); i++ ) {
-            if( back.in(i) != scope ) {
-                PhiNode phi = (PhiNode)in(i);
-                assert phi.region()==scope.ctrl() && phi.in(2)==null;
-                phi.setDef(2,back.in(i)); // Fill backedge
+        Node exit_def = exit.alias(1);
+        for( int i=1; i<back.nIns(); i++ ) {
+            if( in(i) instanceof PhiNode phi && phi.region()==scope.ctrl() ) {
+                assert phi.in(2)==null;
+                phi.setDef(2,back.in(i)==scope ? phi : back.in(i)); // Fill backedge
             }
-            if( exit.alias(i) == scope ) // Replace a lazy-phi on the exit path also
+            if( exit_def == scope ) // Replace a lazy-phi on the exit path also
                 exit.alias(i,in(i));
         }
     }
@@ -155,16 +172,7 @@ public class ScopeMinNode extends Node {
         }
     }
 
-    // If being used by a Scope, this is "in progress" from the Parser.
-    // Once no more scope users, this is just a memory-merge.
-    boolean inProgress() {
-        for( Node n : _outputs )
-            if( n instanceof ScopeNode scope )
-                return true;
-        return false;
-    }
-
     @Override boolean eq( Node n ) {
-        return this==n || !inProgress();
+        return this==n || !_inProgress;
     }
 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
index 8685e66b..e4a4ddc0 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
@@ -3,7 +3,6 @@ package com.seaofnodes.simple.node;
 import com.seaofnodes.simple.*;
 import com.seaofnodes.simple.type.*;
 import java.util.*;
-import static com.seaofnodes.simple.Utils.TODO;
 
 /**
  * The Scope node is purely a parser helper - it tracks names to nodes with a
@@ -33,6 +32,7 @@ public class ScopeNode extends ScopeMinNode {
 
     // A new ScopeNode
     public ScopeNode() {
+        super(true);
         _vars   = new Ary<>(Var    .class);
         _lexSize= new Ary<>(Integer.class);
         _inCons = new Ary<>(Boolean.class);
@@ -113,8 +113,8 @@ public class ScopeNode extends ScopeMinNode {
      * Create a new variable name in the current scope
      */
     public boolean define( String name, Type declaredType, boolean xfinal, Node init ) {
-        assert name.charAt(0)!='$' || _lexSize.size()==1; // Later scopes do not define memory
-        if( _lexSize._len > 1 )
+        assert _lexSize.isEmpty() || name.charAt(0)!='$' ; // Later scopes do not define memory
+        if( _lexSize._len > 0 )
             for( int i=_vars.size()-1; i>=_lexSize.last(); i-- )
                 if( _vars.get(i)._name.equals(name) )
                     return false;   // Double define
@@ -203,7 +203,7 @@ public class ScopeNode extends ScopeMinNode {
         dup.addDef(ctrl());     // Control input is just copied
 
         // Memory input is a shallow copy
-        ScopeMinNode memdup = new ScopeMinNode(), mem = mem();
+        ScopeMinNode memdup = new ScopeMinNode(true), mem = mem();
         memdup.addDef(null);
         memdup.addDef(loop ? this : mem.in(1));
         for( int i=2; i<mem.nIns(); i++ )
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/StartNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/StartNode.java
index ab6e4931..008a910f 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/StartNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/StartNode.java
@@ -29,7 +29,19 @@ public class StartNode extends LoopNode implements MultiNode {
 
     @Override public boolean isMultiHead() { return true; }
     @Override public boolean blockHead() { return true; }
-    @Override public CFGNode cfg0() { return this; }
+    @Override public CFGNode cfg0() { return null; }
+
+    // Get the one control following; error to call with more than one e.g. an
+    // IfNode or other multi-way branch.  For Start, its "main"
+    @Override public CFGNode uctrl() {
+        // Find "main", its the start.
+        CFGNode C = null;
+        for( Node use : _outputs )
+            if( use instanceof FunNode fun && fun._sig==TypeFunPtr.MAIN )
+                { assert C==null; C = fun; }
+        return C;
+    }
+
 
     @Override public TypeTuple compute() {
         return TypeTuple.make(Type.CONTROL,TypeMem.TOP,_arg);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/StopNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/StopNode.java
index 4b91f1eb..fb78f720 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/StopNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/StopNode.java
@@ -22,7 +22,6 @@ public class StopNode extends CFGNode {
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
         // For the sake of many old tests, and single value prints as "return val"
-        if( nIns() == 3 ) return expr()._print0(sb.append("return "),visited).append(";");
         if( ret()!=null ) return ret()._print0(sb,visited);
         sb.append("Stop[ ");
         for( Node ret : _inputs )
@@ -33,14 +32,10 @@ public class StopNode extends CFGNode {
     @Override public boolean blockHead() { return true; }
 
 
-    public CFGNode ctrl() { return (CFGNode)in(0); }
-    public Node mem () { return in(1); }
-    public Node expr() { return in(2); }
-
     // If a single Return, return it.
     // Otherwise, null because ambiguous.
     public ReturnNode ret() {
-        return nIns()==4 && in(3) instanceof ReturnNode ret ? ret : null;
+        return nIns()==1 && in(0) instanceof ReturnNode ret ? ret : null;
     }
 
     @Override
@@ -51,7 +46,7 @@ public class StopNode extends CFGNode {
     @Override
     public Node idealize() {
         int len = nIns();
-        for( int i=3; i<nIns(); i++ )
+        for( int i=0; i<nIns(); i++ )
             if( ((ReturnNode)in(i)).fun()==null )
                 delDef(i--);
         if( len != nIns() ) return this;
@@ -61,9 +56,8 @@ public class StopNode extends CFGNode {
     @Override public int idepth() {
         if( _idepth!=0 ) return _idepth;
         int d=0;
-        for( Node n : _inputs )
-            if( n instanceof CFGNode cfg )
-                d = Math.max(d,cfg.idepth()+1);
+        for( Node ret : _inputs )
+            d = Math.max(d,((ReturnNode)ret).idepth()+1);
         return _idepth=d;
     }
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 682930e0..b591718d 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -34,7 +34,7 @@ public class SubFNode extends Node {
         Node lhs = in(1);
         Type t2 = in(2)._type;
 
-        // Sub of 1.
+        // Sub of 0.
         if ( t2.isConstant() && t2 instanceof TypeFloat i && i.value()==0 )
             return lhs;
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
index 83779dd2..3c6a5df3 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
@@ -5,9 +5,11 @@ import com.seaofnodes.simple.type.Type;
 import java.util.BitSet;
 
 public class XCtrlNode extends CFGNode {
-    public XCtrlNode( ) { super(Parser.START); }
+    public XCtrlNode() { super(Parser.START); }
     @Override public String label() { return "Xctrl"; }
     @Override StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append("Xctrl"); }
+    @Override public boolean isConst() { return true; }
+    @Override public boolean isMultiTail() { return true; }
     @Override  public Type compute() { return Type.XCONTROL; }
     @Override public Node idealize() { return null; }
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/BrainFuckTest.java b/chapter18/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
index f21b9afa..2995e89c 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
@@ -1,9 +1,7 @@
 package com.seaofnodes.simple;
 
 import com.seaofnodes.simple.evaluator.Evaluator;
-import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
-import org.junit.Ignore;
 
 import java.nio.charset.StandardCharsets;
 
@@ -67,7 +65,7 @@ for( int pc = 0; pc < program#; pc++ ) {
 }
 return output;
                 """);
-        code.parse().opto().typeCheck().codegen();
-        assertEquals("Hello World!\n", Evaluator.evaluate(code._stop, 0, 10000).toString());
+        code.parse().opto().typeCheck().GCM();
+        assertEquals("Hello World!\n", Eval2.eval(code, 0, 10000));
     }
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter01Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter01Test.java
index 7f111039..224a5f01 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter01Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter01Test.java
@@ -10,8 +10,8 @@ public class Chapter01Test {
 
     @Test
     public void testSimpleProgram() {
-        CodeGen code = new CodeGen("return 1;").parse().opto();
-        Node expr = code._stop.expr();
+        CodeGen code = new CodeGen("return 1;").parse();
+        Node expr = code.expr();
         if( expr instanceof ConstantNode con ) {
             assertEquals(code._start,con.in(0));
             assertEquals(TypeInteger.constant(1), con._type);
@@ -52,7 +52,7 @@ public class Chapter01Test {
     @Test
     public void testNotBad3() {
         // this test used to fail in chapter 1
-        assertEquals("return 12;", new CodeGen("return - -12;").parse().opto()._stop.print());
+        assertEquals("return 12;", new CodeGen("return - -12;").parse()._stop.print());
     }
 
     @Test
@@ -68,7 +68,7 @@ public class Chapter01Test {
     @Test
     public void testNotBad5() {
         // this test used to fail in chapter 1
-        assertEquals("return -100;", new CodeGen("return -100;").parse().opto()._stop.print());
+        assertEquals("return -100;", new CodeGen("return -100;").parse()._stop.print());
     }
 
     @Test
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter02Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter02Test.java
index c85bec6f..4254f0a6 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter02Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter02Test.java
@@ -12,49 +12,49 @@ public class Chapter02Test {
     public void testParseGrammar() {
         CodeGen code = new CodeGen("return 1+2*3+-5;");
         code.parse(true); // Disable peepholes
-        assertEquals("return Phi(Region,((1+(2*3))+(-5)));", code._stop.ret().print());
+        assertEquals("return Phi(Region,((1+(2*3))+(-5)));", code.print());
     }
 
     @Test
     public void testAddPeephole() {
         CodeGen code = new CodeGen("return 1+2;");
-        code.parse().opto();
-        assertEquals("return 3;", code._stop.print());
+        code.parse();
+        assertEquals("return 3;", code.print());
     }
 
     @Test
     public void testSubPeephole() {
         CodeGen code = new CodeGen("return 1-2;");
-        code.parse().opto();
-        assertEquals("return -1;", code._stop.print());
+        code.parse();
+        assertEquals("return -1;", code.print());
     }
 
     @Test
     public void testMulPeephole() {
         CodeGen code = new CodeGen("return 2*3;");
-        code.parse().opto();
-        assertEquals("return 6;", code._stop.print());
+        code.parse();
+        assertEquals("return 6;", code.print());
     }
 
     @Test
     public void testDivPeephole() {
         CodeGen code = new CodeGen("return 6/3;");
-        code.parse().opto();
-        assertEquals("return 2;", code._stop.print());
+        code.parse();
+        assertEquals("return 2;", code.print());
     }
 
     @Test
     public void testMinusPeephole() {
         CodeGen code = new CodeGen("return 6/-3;");
-        code.parse().opto();
-        assertEquals("return -2;", code._stop.print());
+        code.parse();
+        assertEquals("return -2;", code.print());
     }
 
     @Test
     public void testExample() {
         CodeGen code = new CodeGen("return 1+2*3+-5;");
-        code.parse().opto();
-        assertEquals("return 2;", code._stop.print());
+        code.parse();
+        assertEquals("return 2;", code.print());
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter03Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter03Test.java
index 9a97d5b8..2e45ee2a 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter03Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter03Test.java
@@ -9,41 +9,41 @@ public class Chapter03Test {
     @Test
     public void testVarDecl() {
         CodeGen code = new CodeGen("int a=1; return a;");
-        code.parse().opto(); assertEquals("return 1;", code._stop.print());
+        code.parse(); assertEquals("return 1;", code.print());
     }
 
     @Test
     public void testVarAdd() {
         CodeGen code = new CodeGen("int a=1; int b=2; return a+b;");
-        code.parse().opto();
-        assertEquals("return 3;", code._stop.print());
+        code.parse();
+        assertEquals("return 3;", code.print());
     }
 
     @Test
     public void testVarScope() {
         CodeGen code = new CodeGen("int a=1; int b=2; int c=0; { int b=3; c=a+b; } return c;");
-        code.parse().opto();
-        assertEquals("return 4;", code._stop.print());
+        code.parse();
+        assertEquals("return 4;", code.print());
     }
 
     @Test
     public void testVarScopeNoPeephole() {
         CodeGen code = new CodeGen("int a=1; int b=2; int !c=0; { int b=3; c=a+b;  } return c; ");
         code.parse(true);
-        assertEquals("return Phi(Region,(1+3));", code._stop.print());
+        assertEquals("return Phi(Region,(1+3));", code.print());
     }
 
     @Test
     public void testVarDist() {
         CodeGen code = new CodeGen("int x0=1; int y0=2; int x1=3; int y1=4; return (x0-x1)*(x0-x1) + (y0-y1)*(y0-y1); ");
-        code.parse().opto();
-        assertEquals("return 8;", code._stop.print());
+        code.parse();
+        assertEquals("return 8;", code.print());
     }
 
     @Test
     public void testSelfAssign() {
         try {
-            new CodeGen("int a=a; return a;").parse().opto();
+            new CodeGen("int a=a; return a;").parse();
             fail();
         } catch( RuntimeException e ) {
             assertEquals("Undefined name 'a'",e.getMessage());
@@ -53,7 +53,7 @@ public class Chapter03Test {
     @Test
     public void testBad1() {
         try {
-            new CodeGen("int a=1; int b=2; int !c=0; { int b=3; c=a+b;").parse().opto();
+            new CodeGen("int a=1; int b=2; int !c=0; { int b=3; c=a+b;").parse();
             fail();
         } catch( RuntimeException e ) {
             assertEquals("Syntax error, expected }: ",e.getMessage());
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter04Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter04Test.java
index c4073fef..27d42c43 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter04Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter04Test.java
@@ -3,6 +3,7 @@ package com.seaofnodes.simple;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.type.TypeInteger;
 import org.junit.Test;
+import org.junit.Ignore;
 
 import static org.junit.Assert.*;
 
@@ -11,100 +12,101 @@ public class Chapter04Test {
     @Test
     public void testPeephole() {
         CodeGen code = new CodeGen("return 1+arg+2; ");
-        code.parse().opto();
-        assertEquals("return (arg+3);", code._stop.print());
+        code.parse();
+        assertEquals("return (arg+3);", code.print());
     }
 
     @Test
     public void testPeephole2() {
         CodeGen code = new CodeGen("return (1+arg)+2;");
-        code.parse().opto();
-        assertEquals("return (arg+3);", code._stop.print());
+        code.parse();
+        assertEquals("return (arg+3);", code.print());
     }
 
     @Test
     public void testAdd0() {
         CodeGen code = new CodeGen("return 0+arg;");
-        code.parse().opto();
-        assertEquals("return arg;", code._stop.print());
+        code.parse();
+        assertEquals("return arg;", code.print());
     }
 
     @Test
     public void testAddAddMul() {
         CodeGen code = new CodeGen("return arg+0+arg;");
-        code.parse().opto();
-        assertEquals("return (arg*2);", code._stop.print());
+        code.parse();
+        assertEquals("return (arg*2);", code.print());
     }
 
     @Test
     public void testPeephole3() {
         CodeGen code = new CodeGen("return 1+arg+2+arg+3; ");
-        code.parse().opto();
-        assertEquals("return ((arg*2)+6);", code._stop.print());
+        code.parse();
+        assertEquals("return ((arg*2)+6);", code.print());
     }
 
     @Test
     public void testMul1() {
         CodeGen code = new CodeGen("return 1*arg;");
-        code.parse().opto();
-        assertEquals("return arg;", code._stop.print());
+        code.parse();
+        assertEquals("return arg;", code.print());
     }
 
     @Test
     public void testVarArg() {
         CodeGen code = new CodeGen("return arg; ");
-        code.parse().opto();
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
-        assertTrue(code._stop.expr() instanceof ProjNode);
+        code.parse();
+        assertTrue(code.ctrl() instanceof  FunNode);
+        assertTrue(code.expr() instanceof ParmNode);
     }
 
-    @Test
+    // Adding functions means `main` does not constant fold the incoming arg value
+    @Ignore @Test
     public void testConstantArg() {
         CodeGen code = new CodeGen("return arg; ", TypeInteger.constant(2));
-        code.parse().opto();
-        assertEquals("return 2;", code._stop.print());
+        code.parse();
+        assertEquals("return 2;", code.expr().in(1).toString());
     }
 
     @Test
     public void testCompEq() {
         CodeGen code = new CodeGen("return 3==3; ");
-        code.parse().opto();
-        assertEquals("return 1;", code._stop.print());
+        code.parse();
+        assertEquals("return 1;", code.print());
     }
 
     @Test
     public void testCompEq2() {
         CodeGen code = new CodeGen("return 3==4; ");
-        code.parse().opto();
-        assertEquals("return 0;", code._stop.print());
+        code.parse();
+        assertEquals("return 0;", code.print());
     }
 
     @Test
     public void testCompNEq() {
         CodeGen code = new CodeGen("return 3!=3; ");
-        code.parse().opto();
-        assertEquals("return 0;", code._stop.print());
+        code.parse();
+        assertEquals("return 0;", code.print());
     }
 
     @Test
     public void testCompNEq2() {
         CodeGen code = new CodeGen("return 3!=4; ");
-        code.parse().opto();
-        assertEquals("return 1;", code._stop.print());
+        code.parse();
+        assertEquals("return 1;", code.print());
     }
 
     @Test
     public void testBug1() {
         CodeGen code = new CodeGen("int a=arg+1; int !b=a; b=1; return a+2; ");
-        code.parse().opto();
-        assertEquals("return (arg+3);", code._stop.print());
+        code.parse();
+        assertEquals("return (arg+3);", code.print());
     }
 
     @Test
     public void testBug2() {
         CodeGen code = new CodeGen("int !a=arg+1; a=a; return a; ");
-        code.parse().opto();
-        assertEquals("return (arg+1);", code._stop.print());
+        code.parse();
+        assertEquals("return (arg+1);", code.print());
     }
 
     @Test
@@ -120,8 +122,8 @@ public class Chapter04Test {
     @Test
     public void testBug4() {
         CodeGen code = new CodeGen("return -arg;");
-        code.parse().opto();
-        assertEquals("return (-arg);", code._stop.print());
+        code.parse();
+        assertEquals("return (-arg);", code.print());
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter05Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter05Test.java
index bf074d0a..3bea9b9a 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter05Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter05Test.java
@@ -20,7 +20,7 @@ else {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,(arg+2),(arg-3));", code._stop.toString());
+        assertEquals("return Phi(Region,(arg+2),(arg-3));", code.print());
     }
 
     @Test
@@ -36,7 +36,7 @@ if (arg == 1) {
 return c;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,4,3);", code._stop.toString());
+        assertEquals("return Phi(Region,4,3);", code.print());
     }
 
     @Test
@@ -49,7 +49,7 @@ else
     return 4;
 """);
         code.parse();
-        assertEquals("return Phi(Region,3,4);", code._stop.expr().in(0).in(1).toString());
+        assertEquals("return Phi(Region,3,4);", code.print());
     }
 
     @Test
@@ -64,7 +64,7 @@ else
     b=a+1;
 return a+b;""");
         code.parse().opto();
-        assertEquals("return ((arg*2)+Phi(Region,2,3));", code._stop.toString());
+        assertEquals("return ((arg*2)+Phi(Region,2,3));", code.print());
     }
 
     @Test
@@ -79,7 +79,7 @@ else
     a=b+1;
 return a+b;""");
         code.parse().opto();
-        assertEquals("return ((Phi(Region,(arg*2),arg)+arg)+Phi(Region,4,5));", code._stop.toString());
+        assertEquals("return ((Phi(Region,(arg*2),arg)+arg)+Phi(Region,4,5));", code.print());
     }
 
     @Test
@@ -99,7 +99,7 @@ else
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Region,2,3),Phi(Region,4,5));", code._stop.toString());
+        assertEquals("return Phi(Region,Phi(Region,2,3),Phi(Region,4,5));", code.print());
     }
 
     @Test
@@ -115,7 +115,7 @@ if( arg==0 )
 return arg+a+b;
 """);
         code.parse().opto();
-        assertEquals("return ((arg+Phi(Region,1,0))+Phi(Region,2,0));", code._stop.toString());
+        assertEquals("return ((arg+Phi(Region,1,0))+Phi(Region,2,0));", code.print());
     }
 
     @Test
@@ -130,13 +130,13 @@ if( arg==1 )
 return a;
 """);
         code.parse().opto();
-        assertEquals("return (arg==Phi(Region,3,2));", code._stop.toString());
+        assertEquals("return (arg==Phi(Region,3,2));", code.print());
     }
 
     @Test
     public void testTrue() {
       StopNode stop = new Parser("return true;").parse();
-      assertEquals("return 1;",stop.expr().in(0).in(1).toString());
+      assertEquals("return 1;",stop.ret().print());
     }
 
     @Test
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter06Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter06Test.java
index 02814501..2107cdb0 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter06Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter06Test.java
@@ -10,14 +10,13 @@ public class Chapter06Test {
 
     @Test
     public void testPeepholeReturn() {
-        CodeGen code = new CodeGen(
-"""
+        CodeGen code = new CodeGen("""
 if( true ) return 2;
 return 1;
 """);
         code.parse().opto();
-        assertEquals("return 2;", code._stop.toString());
-        assertTrue(code._stop.in(0) instanceof CProjNode);
+        assertEquals("return 2;", code.print());
+        assertTrue(code.ctrl() instanceof FunNode);
     }
 
     @Test
@@ -30,7 +29,7 @@ if (arg)
 return (arg < a) < 3; // Because (arg < a) is a bool/uint1/[0-1], its always less than 3
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
+        assertEquals("return 1;", code.print());
     }
 
     @Test
@@ -45,8 +44,8 @@ else
 return a;
 """);
         code.parse().opto();
-        assertEquals("return 2;", code._stop.toString());
-        assertTrue(code._stop.in(0) instanceof CProjNode);
+        assertEquals("return 2;", code.print());
+        assertTrue(code.ctrl() instanceof FunNode);
     }
 
     @Test
@@ -66,7 +65,7 @@ else
 return b;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,42,5);", code._stop.toString());
+        assertEquals("return Phi(Region,42,5);", code.print());
     }
 
     @Test
@@ -85,13 +84,14 @@ else
     b=5;
 return b;""");
         code.parse().opto();
-        assertEquals("return Phi(Region,2,5);", code._stop.toString());
+        assertEquals("return Phi(Region,2,5);", code.print());
     }
 
     @Test
     public void testMerge3With2() {
         CodeGen code = new CodeGen(
 """
+arg=2;
 int a=1;
 if( arg==1 )
     if( arg==2 )
@@ -105,13 +105,14 @@ else
 return a;
 """, TypeInteger.constant(2));
         code.parse().opto();
-        assertEquals("return 5;", code._stop.toString());
+        assertEquals("return 5;", code.print());
     }
 
     @Test
     public void testMerge3With1() {
         CodeGen code = new CodeGen(
 """
+arg=1;
 int a=1;
 if( arg==1 )
     if( arg==2 )
@@ -125,7 +126,7 @@ else
 return a;
 """, TypeInteger.constant(1));
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
+        assertEquals("return 3;", code.print());
     }
 
     @Test
@@ -145,13 +146,14 @@ else
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,3,Phi(Region,4,5));", code._stop.toString());
+        assertEquals("return Phi(Region,3,Phi(Region,4,5));", code.print());
     }
 
     @Test
     public void testMerge3Peephole1() {
         CodeGen code = new CodeGen(
 """
+arg=1;
 int a=1;
 if( arg==1 )
     if( 1==2 )
@@ -165,13 +167,14 @@ else
 return a;
 """, TypeInteger.constant(1));
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
+        assertEquals("return 3;", code.print());
     }
 
     @Test
     public void testMerge3Peephole3() {
         CodeGen code = new CodeGen(
 """
+arg=3;
 int a=1;
 if( arg==1 )
     if( 1==2 )
@@ -185,7 +188,7 @@ else
 return a;
 """, TypeInteger.constant(3));
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
+        assertEquals("return 4;", code.print());
     }
 
     @Test
@@ -201,13 +204,14 @@ if( arg ) {
 return a+b;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,4,1);", code._stop.toString());
+        assertEquals("return Phi(Region,4,1);", code.print());
     }
 
 
     @Test
     public void testDemo1True() {
         CodeGen code = new CodeGen("""
+arg=1;
 int a = 0;
 int b = 1;
 if( arg ) {
@@ -218,12 +222,13 @@ if( arg ) {
 return a+b;
 """, TypeInteger.constant(1));
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
+        assertEquals("return 4;", code.print());
     }
 
     @Test
     public void testDemo1False() {
         CodeGen code = new CodeGen("""
+arg=0;
 int a = 0;
 int b = 1;
 if( arg ) {
@@ -234,7 +239,7 @@ if( arg ) {
 return a+b;
 """, TypeInteger.constant(0));
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
+        assertEquals("return 1;", code.print());
     }
 
     @Test
@@ -252,13 +257,14 @@ if( arg ) {
 return a+b+c;
 """);
         code.parse().opto();
-        assertEquals("return (Phi(Region,Phi(Region,2,3),0)+Phi(Region,3,1));", code._stop.toString());
+        assertEquals("return (Phi(Region,Phi(Region,2,3),0)+Phi(Region,3,1));", code.print());
     }
 
 
     @Test
     public void testDemo2True() {
         CodeGen code = new CodeGen("""
+arg=1;
 int a = 0;
 int b = 1;
 int c = 0;
@@ -271,12 +277,13 @@ if( arg ) {
 return a+b+c;
 """, TypeInteger.constant(1));
         code.parse().opto();
-        assertEquals("return 6;", code._stop.toString());
+        assertEquals("return 6;", code.print());
     }
 
     @Test
     public void testDemo2arg2() {
         CodeGen code = new CodeGen("""
+arg=2;
 int a = 0;
 int b = 1;
 int c = 0;
@@ -289,7 +296,7 @@ if( arg ) {
 return a+b+c;
 """, TypeInteger.constant(2));
         code.parse().opto();
-        assertEquals("return 5;", code._stop.toString());
+        assertEquals("return 5;", code.print());
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter07Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter07Test.java
index aad6a765..7cef0d9c 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter07Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter07Test.java
@@ -18,8 +18,8 @@ return arg;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -36,7 +36,7 @@ if(arg){}else{
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1,Phi(Loop,1,(Phi_a+1)));", code._stop.toString());
+        assertEquals("return Phi(Region,1,Phi(Loop,1,(Phi_a+1)));", code.print());
     }
 
     @Test
@@ -56,7 +56,7 @@ while(i < arg) {
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,Phi(Loop,Phi_sum,(Phi_sum+Phi(Loop,0,(Phi_j+1)))));", code._stop.toString());
+        assertEquals("return Phi(Loop,0,Phi(Loop,Phi_sum,(Phi_sum+Phi(Loop,0,(Phi_j+1)))));", code.print());
     }
 
     @Test
@@ -73,8 +73,8 @@ return b;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,2,Phi(Region,Phi_b,4));", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,2,Phi(Region,Phi_b,4));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -93,8 +93,8 @@ while(a < 10) {
 return b;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,2,(Phi(Region,Phi_b,4)+1));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,2,(Phi(Region,Phi_b,4)+1));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
 
@@ -111,8 +111,8 @@ return a;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -128,8 +128,8 @@ while(a < 10) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
     @Test
@@ -142,8 +142,8 @@ return a;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,1,2);", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,2);", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -156,8 +156,8 @@ while(arg) a = 2;
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,1,2);", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,2);", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
     @Test
@@ -173,8 +173,8 @@ return a;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -190,8 +190,8 @@ while(a < 10) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
     @Test
@@ -208,8 +208,8 @@ return a;
 """);
         Node._disablePeephole = true;
         code.parse();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.expr().in(0).in(1).toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
         Node._disablePeephole = false;
     }
 
@@ -226,8 +226,8 @@ while(a < 10) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,1,(Phi_a+3));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,(Phi_a+3));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter08Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter08Test.java
index 831a3272..03a2c50a 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter08Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter08Test.java
@@ -2,6 +2,7 @@ package com.seaofnodes.simple;
 
 import com.seaofnodes.simple.evaluator.Evaluator;
 import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.type.TypeInteger;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -23,10 +24,10 @@ while(arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add),Add);", code._stop.toString());
-        assertTrue(code._stop.in(0) instanceof RegionNode);
-        Assert.assertEquals(5L, Evaluator.evaluate(code._stop, 1));
-        Assert.assertEquals(10L, Evaluator.evaluate(code._stop, 6));
+        assertEquals("return Phi(Region,Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add),Add);", code.print());
+        assertTrue(code.ctrl() instanceof RegionNode);
+        Assert.assertEquals( "5", Eval2.eval(code, 1));
+        Assert.assertEquals("10", Eval2.eval(code, 6));
     }
 
 
@@ -46,8 +47,8 @@ while(arg < 10) {
 return a;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,1,Phi(Region,Phi_a,(Phi_a+1)));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,1,Phi(Region,Phi_a,(Phi_a+1)));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
 
@@ -65,8 +66,8 @@ while(arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add);", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof RegionNode);
+        assertEquals("return Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add);", code.print());
+        assertTrue(code.ctrl() instanceof RegionNode);
     }
 
     @Test
@@ -81,8 +82,8 @@ while(arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add);", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof RegionNode);
+        assertEquals("return Phi(Region,Phi(Loop,arg,(Phi_arg+1)),Add);", code.print());
+        assertTrue(code.ctrl() instanceof RegionNode);
     }
 
 
@@ -100,8 +101,8 @@ while(arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
 
@@ -117,8 +118,8 @@ while(arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode);
+        assertEquals("return Phi(Loop,arg,(Phi_arg+1));", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode);
     }
 
     @Test
@@ -133,14 +134,14 @@ while( arg < 10 ) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return arg;", code._stop.toString());
+        assertEquals("return arg;", code.print());
     }
 
     @Test
     public void testRegress2() {
         CodeGen code = new CodeGen("if(1) return 0;  else while(arg>- -arg) arg=arg+1; return 0;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -168,7 +169,7 @@ while(arg < 10) {
 return arg;
 """);
         code.parse().opto();
-        assertEquals("return arg;", code._stop.toString());
+        assertEquals("return arg;", code.print());
     }
 
     @Test
@@ -185,8 +186,8 @@ while(arg < 10) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Loop,1,(Phi_a+1)),Add);", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof RegionNode);
+        assertEquals("return Phi(Region,Phi(Loop,1,(Phi_a+1)),Add);", code.print());
+        assertTrue(code.ctrl() instanceof RegionNode);
     }
 
     @Test
@@ -201,8 +202,8 @@ while(1) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return (Phi(Loop,1,Add)+1);", code._stop.toString());
-        assertTrue(code._stop.ctrl() instanceof CProjNode prj && prj._idx==1 );
+        assertEquals("return (Phi(Loop,1,Add)+1);", code.print());
+        assertTrue(code.ctrl() instanceof CProjNode prj && prj._idx==1 );
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter09Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter09Test.java
index 27cd2be7..5b764013 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter09Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter09Test.java
@@ -41,35 +41,31 @@ else {
 return x;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,(arg*2),(Mul+1));", code._stop.toString());
-        Assert.assertEquals(2L, Evaluator.evaluate(code._stop, 1));
-        Assert.assertEquals(23L, Evaluator.evaluate(code._stop, 11));
+        assertEquals("return Phi(Region,(arg*2),(Mul+1));", code.print());
+        Assert.assertEquals( "2", Eval2.eval(code,  1));
+        Assert.assertEquals("23", Eval2.eval(code, 11));
     }
 
     @Test
     public void testGVN2() {
-        CodeGen code = new CodeGen(
-                """
-return arg*arg-arg*arg;
-                """);
+        CodeGen code = new CodeGen("return arg*arg-arg*arg;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        Assert.assertEquals(0L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return 0;", code.print());
+        Assert.assertEquals("0", Eval2.eval(code,  1, 1));
     }
 
     @Test
     public void testWorklist1() {
-        CodeGen code = new CodeGen(
-                """
+        CodeGen code = new CodeGen("""
 int step = 1;
 while (arg < 10) {
     arg = arg + step + 1;
 }
 return arg;
-                """);
+""");
         code.parse().opto();
-        assertEquals("return Phi(Loop,arg,(Phi_arg+2));", code._stop.toString());
-        Assert.assertEquals(11L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Loop,arg,(Phi_arg+2));", code.print());
+        Assert.assertEquals("11", Eval2.eval(code,  1));
     }
 
     @Test
@@ -85,8 +81,8 @@ while (arg < 10) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,arg,(Phi_arg+4));", code._stop.toString());
-        Assert.assertEquals(13L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Loop,arg,(Phi_arg+4));", code.print());
+        Assert.assertEquals("13", Eval2.eval(code,  1));
     }
 
     @Test
@@ -114,7 +110,7 @@ while (arg) {
 return arg;
                 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -132,14 +128,14 @@ while(v1+arg) {
 }
                 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
     public void testWhile0() {
         CodeGen code = new CodeGen("while(0) continue; if(0) arg=0;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -151,7 +147,7 @@ if(0) while(0) {
 }
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
 
@@ -159,14 +155,14 @@ if(0) while(0) {
     public void testPrecedence() {
         CodeGen code = new CodeGen("return 3-1+2;");
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
+        assertEquals("return 4;", code.print());
     }
 
     @Test
     public void testSwap2() {
         CodeGen code = new CodeGen("return 1+(1+1);");
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
+        assertEquals("return 3;", code.print());
     }
 
 
@@ -184,7 +180,7 @@ while(arg) {
 return a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(-(Phi_a+3)));", code._stop.toString());
+        assertEquals("return Phi(Loop,0,(-(Phi_a+3)));", code.print());
     }
 
     @Test
@@ -198,7 +194,7 @@ int v0=0!=0<-0;
 return -0+0+0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
 
@@ -206,14 +202,14 @@ return -0+0+0;
     public void testFuzz2() {
         CodeGen code = new CodeGen("return 0+-0;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
     public void testFuzz3() {
         CodeGen code = new CodeGen("int v0=0; while(0==69) while(v0) return 0;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -225,7 +221,7 @@ while(1) {
 }
 """);
         code.parse().opto();
-        assertEquals("return Top;", code._stop.toString());
+        assertEquals("return Top;", code.print());
     }
 
     @Test
@@ -247,7 +243,7 @@ while(1) {
 return 0!=0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -259,7 +255,7 @@ while(0==1) while(v0)
         v0=1+v0;
 """);
         code.parse().opto();
-        assertEquals("return ~int;", code._stop.toString());
+        assertEquals("return ~int;", code.print());
     }
 
     @Test
@@ -275,14 +271,14 @@ while(1)
 return v1+v0;
                                    """);
         code.parse().opto();
-        assertEquals("return Top;", code._stop.toString());
+        assertEquals("return Top;", code.print());
     }
 
     @Test
     public void testFuzz8() {
         CodeGen code = new CodeGen("while(arg) arg = arg - 1;  return arg;");
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
index 461c8ed8..1f6df190 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter10Test.java
@@ -1,7 +1,5 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
-import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
@@ -30,7 +28,7 @@ int r = g+h;
 return p-r;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -50,7 +48,7 @@ bar.a = 2;
 return bar.a;
 """);
         code.parse().opto();
-        assertEquals("return 2;", code._stop.toString());
+        assertEquals("return 2;", code.print());
     }
 
     @Test
@@ -66,7 +64,7 @@ else
 return v;
 """);
         code.parse().opto();
-        assertEquals("return Vector2D;", code._stop.toString());
+        assertEquals("return Vector2D;", code.print());
     }
 
     @Test
@@ -104,7 +102,7 @@ while (arg) {
 return bar.a;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_a+2));", code._stop.toString());
+        assertEquals("return Phi(Loop,0,(Phi_a+2));", code.print());
     }
 
     @Test
@@ -156,7 +154,7 @@ if( bar ) bar.a = 1;
 return bar;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,null,Bar);", code._stop.toString());
+        assertEquals("return Phi(Region,null,Bar);", code.print());
     }
 
     @Test
@@ -172,7 +170,7 @@ else bar.a = 1;
 return rez;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,4,3);", code._stop.toString());
+        assertEquals("return Phi(Region,4,3);", code.print());
     }
 
     @Test
@@ -226,7 +224,7 @@ while( i.x < i.len ) {
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi(Loop,0,(Phi_x+1))+Phi_sum));", code._stop.toString());
+        assertEquals("return Phi(Loop,0,(Phi(Loop,0,(Phi_x+1))+Phi_sum));", code.print());
     }
 
 
@@ -245,7 +243,7 @@ while(arg) {
 return ret;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code._stop.toString());
+        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code.print());
     }
 
     @Test
@@ -263,7 +261,7 @@ while(arg) {
 return ret;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code._stop.toString());
+        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code.print());
     }
 
 
@@ -280,7 +278,7 @@ while(arg < 10) {
 return ret;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code._stop.toString());
+        assertEquals("return Phi(Loop,s0,Phi(Region,s0,Phi_ret));", code.print());
     }
 
     @Test
@@ -291,8 +289,8 @@ return new s0;
 int v0=null.f0;
 """);
         code.parse().opto();
-        assertEquals("return s0;", code._stop.toString());
-        assertEquals("Obj<s0>{f0=0}", Evaluator.evaluate(code._stop, 0).toString());
+        assertEquals("return s0;", code.print());
+        assertEquals("s0{f0=0}", Eval2.eval(code, 0));
     }
 
     @Test
@@ -308,7 +306,7 @@ if(0) {
 }
    """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -322,7 +320,7 @@ else return new s0;
 if(new s0.f0) return 0;
     """);
         code.parse().opto();
-        assertEquals("return s0;", code._stop.toString());
+        assertEquals("return s0;", code.print());
     }
 
     @Test
@@ -350,7 +348,7 @@ s0 v1 = v0;
 return v1;
     """);
         code.parse().opto();
-        assertEquals("return (const)s0;", code._stop.toString());
+        assertEquals("return (const)s0;", code.print());
     }
 
 
@@ -382,7 +380,7 @@ while(0) {}
 }
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -393,7 +391,7 @@ while(v0) continue;
 return 0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter11Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter11Test.java
index 2854941f..0b24bd5d 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter11Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter11Test.java
@@ -1,6 +1,5 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
 import org.junit.Test;
 
 
@@ -290,8 +289,8 @@ else {
         }
 }
 """);
-        code.parse().opto().typeCheck().codegen();
-        assertEquals("return Phi(Region,9,Top,Top,Top,Top);", code._stop.toString());
+        code.parse().opto().typeCheck().GCM();
+        assertEquals("return Phi(Region,9,Top,Top,Top,Top);", code.print());
     }
 
 
@@ -323,13 +322,13 @@ while( prime <= arg ) {
 return primeCount;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,0,Phi(Loop,1,Phi(Region,Phi_primeCount,Phi(Region,(Phi_primeCount+1),Phi_primeCount))));", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  1)); // No primes 1 or below
-        assertEquals(1L, Evaluator.evaluate(code._stop,  2)); // 2
-        assertEquals(2L, Evaluator.evaluate(code._stop,  3)); // 2, 3
-        assertEquals(2L, Evaluator.evaluate(code._stop,  4)); // 2, 3
-        assertEquals(3L, Evaluator.evaluate(code._stop,  5)); // 2, 3, 5
-        assertEquals(4L, Evaluator.evaluate(code._stop, 10)); // 2, 3, 5, 7
+        assertEquals("return Phi(Region,0,Phi(Loop,1,Phi(Region,Phi_primeCount,Phi(Region,(Phi_primeCount+1),Phi_primeCount))));", code.print());
+        assertEquals("0", Eval2.eval(code,  1)); // No primes 1 or below
+        assertEquals("1", Eval2.eval(code,  2)); // 2
+        assertEquals("2", Eval2.eval(code,  3)); // 2, 3
+        assertEquals("2", Eval2.eval(code,  4)); // 2, 3
+        assertEquals("3", Eval2.eval(code,  5)); // 2, 3, 5
+        assertEquals("4", Eval2.eval(code, 10)); // 2, 3, 5, 7
     }
 
     @Test
@@ -345,9 +344,9 @@ if (arg) v.f=1;
 return i;
 """);
         code.parse().opto();
-        assertEquals("return 2;", code._stop.toString());
-        assertEquals(2L, Evaluator.evaluate(code._stop, 0));
-        assertEquals(2L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return 2;", code.print());
+        assertEquals("2", Eval2.eval(code, 0));
+        assertEquals("2", Eval2.eval(code, 1));
     }
 
     @Test
@@ -368,7 +367,7 @@ if (arg) {
 return i;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,.f,0);", code._stop.toString());
+        assertEquals("return Phi(Region,.f,0);", code.print());
     }
 
     @Test
@@ -387,7 +386,7 @@ if (v1) {
 return v0;
 """);
         code.parse().opto();
-        assertEquals("return S;", code._stop.toString());
+        assertEquals("return S;", code.print());
     }
 
 
@@ -405,7 +404,7 @@ while (arg) v.f = 2;
 return i;
 """);
         code.parse().opto();
-        assertEquals("return arg;", code._stop.toString());
+        assertEquals("return arg;", code.print());
     }
 
     @Test
@@ -422,7 +421,7 @@ while(1) {
 return v;
 """);
         code.parse().opto();
-        assertEquals("return S;", code._stop.toString());
+        assertEquals("return S;", code.print());
     }
 
     @Test
@@ -437,7 +436,7 @@ while(1)
   arg = arg+ptr.v;
 """);
         code.parse().opto();
-        assertEquals("return Top;", code._stop.toString());
+        assertEquals("return Top;", code.print());
     }
 
     @Test
@@ -455,7 +454,7 @@ while (arg) {
 return i;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -475,7 +474,7 @@ while(arg) {
 return arg;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -493,7 +492,7 @@ if (arg) {
 return v;
 """);
         code.parse().opto();
-        assertEquals("return S;", code._stop.toString());
+        assertEquals("return S;", code.print());
     }
 
     @Test
@@ -512,7 +511,7 @@ while (arg > 0) {
 return v;
                 """);
         code.parse().opto();
-        //assertEquals("return new S;", code._stop.toString());
+        //assertEquals("return new S;", code.print());
     }
 
     @Test
@@ -529,7 +528,7 @@ while(0>=0) {
 return 0;
 """);
         code.parse().opto();
-        assertEquals("return Top;", code._stop.toString());
+        assertEquals("return Top;", code.print());
     }
 
     @Test
@@ -547,7 +546,7 @@ u32 v0=0;
 }
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter12Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter12Test.java
index b5b6405c..21df8205 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter12Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter12Test.java
@@ -15,8 +15,8 @@ public class Chapter12Test {
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
     @Test
@@ -26,8 +26,8 @@ return 3.14;
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
     @Test
@@ -43,9 +43,9 @@ while( 1 ) {
 return guess;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,(flt)arg,(((ToFloat/Phi_guess)+Phi_guess)/2.0f));", code._stop.toString());
-        assertEquals(3.0, Evaluator.evaluate(code._stop,  9));
-        assertEquals(1.414213562373095, Evaluator.evaluate(code._stop,  2));
+        assertEquals("return Phi(Loop,(flt)arg,(((ToFloat/Phi_guess)+Phi_guess)/2.0f));", code.print());
+        assertEquals("3.0", Eval2.eval(code,  9));
+        assertEquals("1.414213562373095", Eval2.eval(code,  2));
     }
 
     @Test
@@ -56,7 +56,7 @@ flt x = arg;
 return x+1==x;
 """);
         code.parse().opto();
-        assertEquals("return ((flt)arg==(ToFloat+1.0f));", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return ((flt)arg==(ToFloat+1.0f));", code.print());
+        assertEquals("0", Eval2.eval(code, 1));
     }
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter13Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter13Test.java
index ca811a2a..645c066a 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter13Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter13Test.java
@@ -1,6 +1,5 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
 import org.junit.Test;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
@@ -13,8 +12,8 @@ public class Chapter13Test {
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
     @Test
@@ -55,8 +54,8 @@ if( next==null ) return 1;
 return next.i;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,0,1,.i);", code._stop.toString());
-        assertEquals(2L, Evaluator.evaluate(code._stop,  3));
+        assertEquals("return Phi(Region,0,1,.i);", code.print());
+        assertEquals("2", Eval2.eval(code,  3));
     }
 
     @Test
@@ -74,7 +73,7 @@ f0.i = i0;
 return f0.i.f.i.i;
 """);
         code.parse().opto();
-        assertEquals("return 17;", code._stop.toString());
+        assertEquals("return 17;", code.print());
     }
 
     @Test
@@ -86,7 +85,7 @@ N n = new N;
 return n.next;
 """);
         code.parse().opto();
-        assertEquals("return null;", code._stop.toString());
+        assertEquals("return null;", code.print());
     }
 
     @Test
@@ -99,7 +98,7 @@ N n = new N { next = new M; };
 return n.next;
 """);
         code.parse().opto();
-        assertEquals("return (const)M;", code._stop.toString());
+        assertEquals("return (const)M;", code.print());
     }
 
     @Test
@@ -135,8 +134,8 @@ return n.i;
 struct S{};
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
     @Test
@@ -159,7 +158,7 @@ struct S2 { int x; };
 return new S1.s=new S2;
 """);
         code.parse().opto();
-        assertEquals("return S2;", code._stop.toString());
+        assertEquals("return S2;", code.print());
     }
 
     @Test
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter14Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter14Test.java
index 41fb546d..a3025001 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter14Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter14Test.java
@@ -1,6 +1,5 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
 import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
 
@@ -16,8 +15,8 @@ public class Chapter14Test {
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
     @Test
@@ -32,8 +31,8 @@ if( b > 2 ) c =  1;
 return c;
 """);
         code.parse().opto();
-        assertEquals("return 99;", code._stop.toString());
-        assertEquals(99L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 99;", code.print());
+        assertEquals("99", Eval2.eval(code,  0));
     }
 
     @Test
@@ -45,8 +44,8 @@ b = b + 456;// Truncate
 return b;
 """);
         code.parse().opto();
-        assertEquals("return 67;", code._stop.toString());
-        assertEquals(67L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 67;", code.print());
+        assertEquals("67", Eval2.eval(code,  0));
     }
 
 
@@ -59,7 +58,7 @@ while( b ) b = b + 456;// Truncate
 return b;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -72,8 +71,8 @@ u1 c = b;   // No more truncate needed
 return c;
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code,  0));
     }
 
     @Test
@@ -85,8 +84,8 @@ b = b+456 & 31;                 // Precedence
 return b;
 """);
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3;", code.print());
+        assertEquals("3", Eval2.eval(code,  0));
     }
 
     @Test
@@ -99,8 +98,8 @@ f.b = 123;
 return f.b;
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code,  0));
     }
 
     @Test
@@ -111,8 +110,8 @@ i8 b = 255;                     // Chopped
 return b;                       // Sign extend
 """);
         code.parse().opto();
-        assertEquals("return -1;", code._stop.toString());
-        assertEquals(-1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return -1;", code.print());
+        assertEquals("-1", Eval2.eval(code,  0));
     }
 
     @Test
@@ -124,9 +123,9 @@ b = b + 1;// Truncate
 return b;
 """);
         code.parse().opto();
-        assertEquals("return (((((arg<<56)>>56)+1)<<56)>>56);", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
-        assertEquals(-128L, Evaluator.evaluate(code._stop, 127));
+        assertEquals("return (((((arg<<56)>>56)+1)<<56)>>56);", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
+        assertEquals("-128", Eval2.eval(code, 127));
     }
 
     @Test
@@ -138,8 +137,8 @@ int c = 123456789 & mask;
 return c;                       //
 """);
         code.parse().opto();
-        assertEquals("return 52501;", code._stop.toString());
-        assertEquals(52501L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 52501;", code.print());
+        assertEquals("52501", Eval2.eval(code,  0));
     }
 
     @Test
@@ -149,8 +148,8 @@ return c;                       //
 return (arg | 123 ^ 456) >>> 1;
 """);
         code.parse().opto();
-        assertEquals("return (((arg|123)^456)>>>1);", code._stop.toString());
-        assertEquals(217L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return (((arg|123)^456)>>>1);", code.print());
+        assertEquals("217", Eval2.eval(code,  0));
     }
 
     @Test
@@ -175,8 +174,8 @@ while(v1) break;
 return v1;
 """);
         code.parse().opto();
-        assertEquals("return (Phi(Loop,((1<<arg)&1),0)&Phi(Loop,Shl,4294967295));", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return (Phi(Loop,((1<<arg)&1),0)&Phi(Loop,Shl,4294967295));", code.print());
+        assertEquals("1", Eval2.eval(code,  0));
     }
 
     @Test
@@ -194,8 +193,8 @@ if(0&0>>>0) {
 return v0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
     @Test
@@ -220,8 +219,8 @@ f32 ff32 = 3.141592653589793;  if( ff32 != 3.1415927410125732) return 5;
 return 0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter15Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter15Test.java
index fc9624d8..86f5007d 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter15Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter15Test.java
@@ -1,7 +1,5 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
-import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
 import static org.junit.Assert.*;
 
@@ -14,8 +12,8 @@ public class Chapter15Test {
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
     @Test
@@ -28,8 +26,8 @@ c.l = c;
 return c;
 """);
         code.parse().opto();
-        assertEquals("return C;", code._stop.toString());
-        assertEquals("Obj<C>@1{l=obj@1}", Evaluator.evaluate(code._stop,  0).toString());
+        assertEquals("return C;", code.print());
+        assertEquals("C{l=$cyclic}", Eval2.eval(code,  0));
     }
 
     @Test
@@ -47,8 +45,8 @@ output[i] = 1;
 return output;
 """);
         code.parse().opto();
-        assertEquals("return [u8];", code._stop.toString());
-        assertEquals("\u0001", Evaluator.evaluate(code._stop,  0).toString());
+        assertEquals("return [u8];", code.print());
+        assertEquals("\u0001", Eval2.eval(code,  0));
     }
 
     @Test
@@ -59,8 +57,8 @@ int[] is = new int[2];
 return is[1];
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
     @Test
@@ -72,8 +70,8 @@ int[] is2 = new int[2];
 return is[1];
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
     @Test
@@ -86,8 +84,8 @@ a[1] = 2;
 return a[0];
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code,  0));
     }
 
     @Test
@@ -99,8 +97,8 @@ A?[] !a = new A?[2];
 return a;
 """);
         code.parse().opto();
-        assertEquals("return [*A?];", code._stop.toString());
-        assertEquals("Obj<[*A?]>{#=2,[]=[null,null]}", Evaluator.evaluate(code._stop, 0).toString());
+        assertEquals("return [*A?];", code.print());
+        assertEquals("*A {int !i; }?[ null,null]", Eval2.eval(code, 0));
     }
 
     @Test
@@ -128,9 +126,9 @@ else {
 return rez;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1.2,Phi(Region,2.3,3.14));", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop, 0));
-        assertEquals(1.2 , Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Region,1.2,Phi(Region,2.3,.y));", code.print());
+        assertEquals("3.14", Eval2.eval(code, 0));
+        assertEquals("1.2", Eval2.eval(code, 1));
     }
 
     @Test
@@ -169,8 +167,8 @@ root._kids[0] = new Tree;
 return root;
 """);
         code.parse().opto();
-        assertEquals("return Tree;", code._stop.toString());
-        assertEquals("Obj<Tree>{_kids=Obj<[*Tree?]>{#=2,[]=[Obj<Tree>{_kids=null},null]}}", Evaluator.evaluate(code._stop,  0).toString());
+        assertEquals("return Tree;", code.print());
+        assertEquals("Tree{_kids=*Tree?[ Tree{_kids=null},null]}", Eval2.eval(code,  0));
     }
 
     @Test
@@ -181,7 +179,7 @@ struct S { int a; int[] b; };
 return 0;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
     @Test
@@ -204,8 +202,8 @@ while( i < ary# - 1 ) {
 return ary[1] * 1000 + ary[3]; // 1 * 1000 + 6
 """);
         code.parse().opto();
-        assertEquals("return (.[]+(.[]*1000));", code._stop.toString());
-        assertEquals(1006L, Evaluator.evaluate(code._stop,  4));
+        assertEquals("return (.[]+(.[]*1000));", code.print());
+        assertEquals("1006", Eval2.eval(code,  4));
     }
 
     @Test
@@ -245,13 +243,8 @@ while( j < nprimes ) {
 return rez;
 """);
         code.parse().opto();
-        assertEquals("return [int];", code._stop.toString());
-        Evaluator.Obj obj = (Evaluator.Obj)Evaluator.evaluate(code._stop, 20);
-        assertEquals("[int] {int #; int ![]; }",obj.struct().toString());
-        long nprimes = (Long)obj.fields()[0];
-        long[] primes = new long[]{2,3,5,7,11,13,17,19};
-        for( int i=0; i<nprimes; i++ )
-            assertEquals(primes[i],(long)(Long)obj.fields()[i+1]);
+        assertEquals("return [int];", code.print());
+        assertEquals("int[ 2,3,5,7,11,13,17,19]",Eval2.eval(code, 20));
     }
 
     @Test
@@ -267,8 +260,8 @@ if (arg) s1 = new S;
 return s1.i + s1.f;
 """);
         code.parse().opto();
-        assertEquals("return ((flt).i+.f);", code._stop.toString());
-        assertEquals(0.0, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return ((flt).i+.f);", code.print());
+        assertEquals("0.0", Eval2.eval(code,  0));
     }
 
 
@@ -311,11 +304,11 @@ int[] is = new int[arg];
 return is[1];
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  4));
-        try { Evaluator.evaluate(code._stop,0); }
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  4));
+        try { Eval2.eval(code,0); }
         catch( ArrayIndexOutOfBoundsException e ) { assertEquals("Array index 1 out of bounds for array length 0",e.getMessage()); }
-        try { Evaluator.evaluate(code._stop,-1); }
+        try { Eval2.eval(code,-1); }
         catch( NegativeArraySizeException e ) { assertEquals("-1",e.getMessage()); }
     }
 
@@ -341,8 +334,8 @@ while(v5+(0&0)) {
 return v1;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
     @Test
@@ -356,7 +349,7 @@ int v8=0;
 while(0<--1>>>---(v7*0==v8)) {}
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 
 
@@ -380,6 +373,6 @@ else {
 }
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
+        assertEquals("return 0;", code.print());
     }
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter16Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter16Test.java
index 255a721a..ad3dc690 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter16Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter16Test.java
@@ -15,8 +15,8 @@ public class Chapter16Test {
 return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 3.14;", code._stop.toString());
-        assertEquals(3.14, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3.14;", code.print());
+        assertEquals("3.14", Eval2.eval(code,  0));
     }
 
 
@@ -28,8 +28,8 @@ int x, y;
 return x+y;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
     }
     @Test
     public void testMulti1() {
@@ -39,8 +39,8 @@ int x=2, y=x+1;
 return x+y;
 """);
         code.parse().opto();
-        assertEquals("return 5;", code._stop.toString());
-        assertEquals(5L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 5;", code.print());
+        assertEquals("5", Eval2.eval(code,  0));
     }
 
 //    @Test
@@ -64,9 +64,9 @@ if( arg ) { int x = y; x = x*x; y=x; } // Shadow final x
 return y;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,9,3);", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop, 0));
-        assertEquals(9L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Region,9,3);", code.print());
+        assertEquals("3", Eval2.eval(code, 0));
+        assertEquals("9", Eval2.eval(code, 1));
     }
 
     @Test
@@ -77,8 +77,8 @@ X z = new X;
 return z.x;
 """);
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3;", code.print());
+        assertEquals("3", Eval2.eval(code,  0));
     }
 
     @Test
@@ -89,8 +89,8 @@ X z = new X { x=3; };
 return z.x;
 """);
         code.parse().opto();
-        assertEquals("return 3;", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 3;", code.print());
+        assertEquals("3", Eval2.eval(code,  0));
     }
 
     @Test
@@ -101,8 +101,8 @@ X z = new X { x = 4; };
 return z.x;
 """);
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
-        assertEquals(4L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 4;", code.print());
+        assertEquals("4", Eval2.eval(code,  0));
     }
 
 
@@ -114,8 +114,8 @@ Point p = new Point { x=3; y=4; };
 return p;
 """);
         code.parse().opto();
-        assertEquals("return (const)Point;", code._stop.toString());
-        assertEquals("Obj<Point>{x=3,y=4}", Evaluator.evaluate(code._stop,  0).toString());
+        assertEquals("return (const)Point;", code.print());
+        assertEquals("Point{x=3,y=4}", Eval2.eval(code,  0));
     }
 
     @Test
@@ -175,8 +175,8 @@ p.x++;
 return p;
 """);
         code.parse().opto();
-        assertEquals("return Point;", code._stop.toString());
-        assertEquals("Obj<Point>{x=4,y=4}", Evaluator.evaluate(code._stop,  0).toString());
+        assertEquals("return Point;", code.print());
+        assertEquals("Point{x=4,y=4}", Eval2.eval(code,  0));
     }
 
     // Same as the Chapter13 test with the same name, but using the new
@@ -197,10 +197,10 @@ if( !next ) return 1;
 return next.i;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,0,1,.i);", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
-        assertEquals(1L, Evaluator.evaluate(code._stop,  1));
-        assertEquals(2L, Evaluator.evaluate(code._stop,  3));
+        assertEquals("return Phi(Region,0,1,.i);", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
+        assertEquals("1", Eval2.eval(code,  1));
+        assertEquals("2", Eval2.eval(code,  3));
     }
 
     @Test
@@ -228,10 +228,10 @@ if( !next ) return 1;
 return next.i;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,0,1,.i);", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
-        assertEquals(1L, Evaluator.evaluate(code._stop,  1));
-        assertEquals(2L, Evaluator.evaluate(code._stop, 11));
+        assertEquals("return Phi(Region,0,1,.i);", code.print());
+        assertEquals("0", Eval2.eval(code,  0));
+        assertEquals("1", Eval2.eval(code,  1));
+        assertEquals("2", Eval2.eval(code, 11));
     }
 
     @Test
@@ -253,8 +253,8 @@ struct Square {
 return new Square;
 """);
         code.parse().opto();
-        assertEquals("return Square;", code._stop.toString());
-        assertEquals("Obj<Square>{side=3.0,diag=1.7320508075688772}", Evaluator.evaluate(code._stop,  3).toString());
-        assertEquals("Obj<Square>{side=4.0,diag=2.0}", Evaluator.evaluate(code._stop, 4).toString());
+        assertEquals("return Square;", code.print());
+        assertEquals("Square{side=3.0,diag=1.7320508075688772}", Eval2.eval(code,  3));
+        assertEquals("Square{side=4.0,diag=2.0}", Eval2.eval(code, 4));
     }
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter17Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter17Test.java
index 06eb150d..4bcb9daa 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter17Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter17Test.java
@@ -1,9 +1,6 @@
 package com.seaofnodes.simple;
 
-import com.seaofnodes.simple.evaluator.Evaluator;
-import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
-import org.junit.Ignore;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
@@ -18,8 +15,8 @@ return i;
                                    //return 3.14;
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code,  0));
     }
 
 
@@ -30,8 +27,8 @@ return i;
 return arg++;
 """);
         code.parse().opto();
-        assertEquals("return arg;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return arg;", code.print());
+        assertEquals("0", Eval2.eval(code, 0));
     }
 
     @Test
@@ -40,8 +37,8 @@ return arg++;
 return arg+++arg++;
 """);
         code.parse().opto();
-        assertEquals("return ((arg*2)+1);", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return ((arg*2)+1);", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
     @Test
@@ -51,8 +48,8 @@ return arg+++arg++;
 return -arg---arg--;
 """);
         code.parse().opto();
-        assertEquals("return (-((arg*2)+-1));", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return (-((arg*2)+-1));", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
     @Test
@@ -64,8 +61,8 @@ xs[1]++;
 return xs[0];
 """);
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 2));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code, 2));
     }
 
     @Test
@@ -76,8 +73,8 @@ xs[0]--;
 return xs[0];
 """);
         code.parse().opto();
-        assertEquals("return 255;", code._stop.toString());
-        assertEquals(255L, Evaluator.evaluate(code._stop, 2));
+        assertEquals("return 255;", code.print());
+        assertEquals("255", Eval2.eval(code, 2));
     }
 
     @Test
@@ -89,34 +86,49 @@ s.x--;
 return s.x;
 """);
         code.parse().opto();
-        assertEquals("return 65535;", code._stop.toString());
-        assertEquals(65535L, Evaluator.evaluate(code._stop, 2));
+        assertEquals("return 65535;", code.print());
+        assertEquals("65535", Eval2.eval(code, 2));
     }
 
     @Test
     public void testInc6() {
         CodeGen code = new CodeGen("return --arg;");
         code.parse().opto();
-        assertEquals("return (arg+-1);", code._stop.toString());
-        assertEquals(-1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return (arg+-1);", code.print());
+        assertEquals("-1", Eval2.eval(code, 0));
     }
 
     @Test
     public void testInc7() {
         CodeGen code = new CodeGen("u8 x=0; return --x;");
         code.parse().opto();
-        assertEquals("return 255;", code._stop.toString());
-        assertEquals(255L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 255;", code.print());
+        assertEquals("255", Eval2.eval(code, 0));
     }
 
     @Test
     public void testInc8() {
         CodeGen code = new CodeGen("int x; x+=2; return x+=3;");
         code.parse().opto();
-        assertEquals("return 5;", code._stop.toString());
-        assertEquals(5L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 5;", code.print());
+        assertEquals("5", Eval2.eval(code, 0));
     }
 
+    @Test
+    public void testInc9() {
+        CodeGen code = new CodeGen("flt x = 1.5; x++; return x;");
+        code.parse().opto();
+        assertEquals("return 2.5f;", code.print());
+        assertEquals("2.5", Eval2.eval(code, 0));
+    }
+
+    @Test public void testInt10() {
+        CodeGen code = new CodeGen("flt x = 1.5; x++; int i = x; return i;");
+        try { code.parse().opto(); fail(); }
+        catch( Exception e ) { assertEquals("Type 2.5f is not of declared type int",e.getMessage()); }
+    }
+
+
     // ---------------------------------------------------------------
     @Test public void testVar0() {
         CodeGen code = new CodeGen("var d; return d;");
@@ -133,29 +145,29 @@ return s.x;
     @Test public void testVar2() {
         CodeGen code = new CodeGen("int x; x=3; x++; return x; // Ok, no initializer so x is mutable ");
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
-        assertEquals(4L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 4;", code.print());
+        assertEquals("4", Eval2.eval(code, 0));
     }
 
     @Test public void testVar3() {
         CodeGen code = new CodeGen("int x=3; x++; return x; // Ok, primitive so x is mutable despite initializer ");
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
-        assertEquals(4L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 4;", code.print());
+        assertEquals("4", Eval2.eval(code, 0));
     }
 
     @Test public void testVar4() {
         CodeGen code = new CodeGen("struct S{int x;}; S s; s=new S; s.x++; return s.x; // Ok, no initializer so x is mutable ");
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
     @Test public void testVar5() {
         CodeGen code = new CodeGen("struct S{int x;}; S s; s=new S{x=3;}; s.x++; return s.x; // Ok, no initializer so x is mutable ");
         code.parse().opto();
-        assertEquals("return 4;", code._stop.toString());
-        assertEquals(4L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 4;", code.print());
+        assertEquals("4", Eval2.eval(code, 0));
     }
 
     @Test public void testVar6() {
@@ -173,15 +185,15 @@ return s.x;
     @Test public void testVar8() {
         CodeGen code = new CodeGen("struct S{int x;}; S !s=new S; s.x++; return s.x; // Ok, has '!' so s.x is mutable ");
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
     @Test public void testVar9() {
         CodeGen code = new CodeGen("struct S{int x;}; var s=new S; s.x++; return s.x; // Ok, has var so s.x is mutable ");
         code.parse().opto();
-        assertEquals("return 1;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 1;", code.print());
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
     @Test public void testVar10() {
@@ -226,8 +238,8 @@ int x5 = xfoo.bar.x;   // Ok to read through xfoo, gets 5
 return x4*10+x5;
 """);
         code.parse().opto();
-        assertEquals("return 45;", code._stop.toString());
-        assertEquals(45L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 45;", code.print());
+        assertEquals("45", Eval2.eval(code, 0));
     }
 
     @Test
@@ -235,7 +247,7 @@ return x4*10+x5;
         CodeGen code = new CodeGen("""
 int i,i++;
 """);
-        try { code.parse().opto(); fail(); }
+        try { code.parse().opto().typeCheck(); fail(); }
         catch( Exception e ) { assertEquals("Redefining name 'i'",e.getMessage()); }
     }
 
@@ -274,9 +286,9 @@ return new A {
 return arg ? 1 : 2;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1,2);", code._stop.toString());
-        assertEquals(2L, Evaluator.evaluate(code._stop, 0));
-        assertEquals(1L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Region,1,2);", code.print());
+        assertEquals("2", Eval2.eval(code, 0));
+        assertEquals("1", Eval2.eval(code, 1));
     }
 
     @Test
@@ -285,8 +297,8 @@ return arg ? 1 : 2;
 return arg ? 0 : arg;
 """);
         code.parse().opto();
-        assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("return 0;", code.print());
+        assertEquals("0", Eval2.eval(code, 0));
     }
 
     @Test
@@ -297,9 +309,9 @@ var b = arg ? new Bar : null;
 return b ? b.x++ + b.x++ : -1;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1,-1);", code._stop.toString());
-        assertEquals(-1L, Evaluator.evaluate(code._stop, 0));
-        assertEquals( 1L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Region,((.x*2)+1),-1);", code.print());
+        assertEquals("-1", Eval2.eval(code, 0));
+        assertEquals("1", Eval2.eval(code, 1));
     }
 
     @Test
@@ -310,9 +322,9 @@ var b = arg ? new Bar;
 return b ? b.x++ + b.x++ : -1;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1,-1);", code._stop.toString());
-        assertEquals(-1L, Evaluator.evaluate(code._stop, 0));
-        assertEquals( 1L, Evaluator.evaluate(code._stop, 1));
+        assertEquals("return Phi(Region,((.x*2)+1),-1);", code.print());
+        assertEquals("-1", Eval2.eval(code, 0));
+        assertEquals("1", Eval2.eval(code, 1));
     }
 
     @Test
@@ -324,10 +336,10 @@ var b = arg ? new Bar { next = (arg==2) ? new Bar{x=2;}; x=1; };
 return b ? b.next ? b.next.x : b.x; // parses "b ? (b.next ? b.next.x : b.x) : 0"
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,Phi(Region,.x,.x),0);", code._stop.toString());
-        assertEquals( 0L, Evaluator.evaluate(code._stop, 0));
-        assertEquals( 1L, Evaluator.evaluate(code._stop, 1));
-        assertEquals( 2L, Evaluator.evaluate(code._stop, 2));
+        assertEquals("return Phi(Region,Phi(Region,.x,.x),0);", code.print());
+        assertEquals("0", Eval2.eval(code, 0));
+        assertEquals("1", Eval2.eval(code, 1));
+        assertEquals("2", Eval2.eval(code, 2));
     }
 
     @Test
@@ -337,8 +349,8 @@ flt f=arg?1:1.2;
 return f;   // missing widening
 """);
         code.parse().opto();
-        assertEquals("return Phi(Region,1.0f,1.2);", code._stop.toString());
-        assertEquals(1.2, Evaluator.evaluate(code._stop,  0));
+        assertEquals("return Phi(Region,1.0f,1.2);", code.print());
+        assertEquals("1.2", Eval2.eval(code,  0));
     }
 
     // ---------------------------------------------------------------
@@ -351,9 +363,9 @@ for( int i=0; i<arg; i++ )
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop, 3));
-        assertEquals(45L, Evaluator.evaluate(code._stop, 10));
+        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code.print());
+        assertEquals("3", Eval2.eval(code, 3));
+        assertEquals("45", Eval2.eval(code, 10));
     }
     @Test
     public void testFor1() {
@@ -364,9 +376,9 @@ for( ; i<arg; i++ )
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop, 3));
-        assertEquals(45L, Evaluator.evaluate(code._stop, 10));
+        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code.print());
+        assertEquals("3", Eval2.eval(code, 3));
+        assertEquals("45", Eval2.eval(code, 10));
     }
     @Test
     public void testFor2() {
@@ -379,9 +391,9 @@ for( int i=0; ; i++ ) {
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop, 3));
-        assertEquals(45L, Evaluator.evaluate(code._stop, 10));
+        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code.print());
+        assertEquals("3", Eval2.eval(code, 3));
+        assertEquals("45", Eval2.eval(code, 10));
     }
     @Test
     public void testFor3() {
@@ -392,9 +404,9 @@ for( int i=0; i<arg; )
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code._stop.toString());
-        assertEquals(3L, Evaluator.evaluate(code._stop, 3));
-        assertEquals(45L, Evaluator.evaluate(code._stop, 10));
+        assertEquals("return Phi(Loop,0,(Phi_sum+Phi(Loop,0,(Phi_i+1))));", code.print());
+        assertEquals("3", Eval2.eval(code, 3));
+        assertEquals("45", Eval2.eval(code, 10));
     }
     @Test
     public void testFor4() {
@@ -429,8 +441,8 @@ struct A{
 return new A;
 """);
         code.parse().opto();
-        assertEquals("return A;", code._stop.toString());
-        assertEquals("Obj<A>{f1=null,f2=null}", Evaluator.evaluate(code._stop).toString());
+        assertEquals("return A;", code.print());
+        assertEquals("A{f1=null,f2=null}", Eval2.eval(code,0));
     }
 
     @Test
@@ -443,8 +455,8 @@ struct A{
 return new A.not_array_of_b;
 """);
         code.parse().opto();
-        assertEquals("return (const)[*B?];", code._stop.toString());
-        assertEquals("Obj<[*B?]>{#=0,[]=[]}", Evaluator.evaluate(code._stop).toString());
+        assertEquals("return (const)[*B?];", code.print());
+        assertEquals("*B?[]", Eval2.eval(code,0));
     }
 
     // ---------------------------------------------------------------
@@ -462,8 +474,8 @@ for( ; ptr; ptr = ptr.next )
 return sum;
 """);
         code.parse().opto();
-        assertEquals("return Phi(Loop,0,(Phi_sum+.i));", code._stop.toString());
-        assertEquals(45L, Evaluator.evaluate(code._stop, 10));
+        assertEquals("return Phi(Loop,0,(Phi_sum+.i));", code.print());
+        assertEquals("45", Eval2.eval(code, 10));
     }
 
     @Test
@@ -492,14 +504,9 @@ for( int j=0; j<nprimes; j++ )
     rez[j] = primes[j];
 return rez;
 """);
-        code.parse().opto();
-        assertEquals("return [int];", code._stop.toString());
-        Evaluator.Obj obj = (Evaluator.Obj)Evaluator.evaluate(code._stop, 20);
-        assertEquals("[int] {int #; int ![]; }",obj.struct().toString());
-        long nprimes = (Long)obj.fields()[0];
-        long[] primes = new long[]{2,3,5,7,11,13,17,19};
-        for( int i=0; i<nprimes; i++ )
-            assertEquals(primes[i],(long)(Long)obj.fields()[i+1]);
+        code.parse().opto().typeCheck().GCM();
+        assertEquals("return [int];", code.print());
+        assertEquals("int[ 2,3,5,7,11,13,17,19]",Eval2.eval(code, 20));
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index 938feab0..15baccf7 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -1,7 +1,6 @@
 package com.seaofnodes.simple;
 
 import com.seaofnodes.simple.evaluator.Evaluator;
-import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
 import org.junit.Ignore;
 
@@ -11,17 +10,14 @@ public class Chapter18Test {
 
     @Test
     public void testJig() {
-        CodeGen code = new CodeGen(
-"""
-0 ;
+        CodeGen code = new CodeGen("""
+return 0;
 """);
-        code.parse().opto();
+        code.parse().opto().typeCheck().GCM();
         assertEquals("return 0;", code._stop.toString());
-        assertEquals(0L, Evaluator.evaluate(code._stop,  0));
+        assertEquals("0", Eval2.eval(code,  0));
     }
 
-        /*
-        */
 
     // ---------------------------------------------------------------
     @Test
@@ -32,7 +28,7 @@ return x2;
 """);
         code.parse().opto();
         assertEquals("return null;", code._stop.toString());
-        assertNull( Evaluator.evaluate( code._stop, 0 ) );
+        assertEquals("null", Eval2.eval(code, 0 ) );
     }
 
     @Ignore @Test
@@ -45,7 +41,7 @@ return sq;
 """);
         code.parse().opto();
         assertEquals("return fcn;", code._stop.toString());
-        assertEquals(1L, Evaluator.evaluate(code._stop, 0));
+        assertEquals("1", Eval2.eval(code, 0));
     }
 
 }
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Eval2.java b/chapter18/src/test/java/com/seaofnodes/simple/Eval2.java
new file mode 100644
index 00000000..50b26464
--- /dev/null
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Eval2.java
@@ -0,0 +1,244 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.type.*;
+import com.seaofnodes.simple.node.*;
+
+import java.util.Arrays;
+import java.util.IdentityHashMap;
+import java.util.Objects;
+
+public abstract class Eval2 {
+
+    private static Object[] DATA;
+    public static String eval( CodeGen code, long arg ) { return eval(code,arg,1000); }
+    public static String eval( CodeGen code, long arg, int timeout ) {
+        if( code._phase.ordinal() < CodeGen.Phase.TypeCheck .ordinal() )  code.typeCheck();
+        if( code._phase.ordinal() < CodeGen.Phase.Schedule  .ordinal() )  code.GCM();
+        if( code._phase.ordinal() < CodeGen.Phase.LocalSched.ordinal() )  code.localSched();
+
+
+        // Timer for when we run too long.  Ticks once per backedge or function call
+        int loopCnt = 0;
+
+        // Current value for each Node; boxed Long or Double; or an Object[] of
+        // fields, which themselves are just more Objects.
+        DATA = new Object[Node.UID()];
+
+        // Start at the START
+        CFGNode C = code._start, prior = null;
+
+        // Evaluate until we return or timeout.  Each outer loop step computes
+        // all data nodes under some new Control.
+        SB sb = null; //new SB(); // TRACE
+        IdentityHashMap visit = new IdentityHashMap();
+        while( true ) {
+            // Compute input path on Phis for this Region,
+            // or path is invalid for non-Region
+            int path = C instanceof RegionNode r ? r._inputs.find( prior ) : -1;
+
+            // Run the worklist dry, computing data nodes under control of C
+            if( sb!=null ) { IRPrinter.printLine(C,sb.p("--- ")); System.out.print(sb); sb.clear();  }
+            for( Node use : C._outputs )
+                step(use, path, arg, sb, visit);
+
+            // Find the next control target
+            prior = C;
+            C = C.uctrl();      // Next unique control target
+            switch( prior ) {
+            case  FunNode fun :    if( loopCnt++ > timeout ) return null;  break; // Timeout
+            case LoopNode loop:    if( loopCnt++ > timeout ) return null;  break; // Timeout
+            case IfNode iff:       C = iff.cproj( val(iff.pred())==null || (val(iff.pred()) instanceof Long x && x==0L)  ? 1 : 0);  break;
+            case RegionNode r:     break;
+            case CProjNode cproj:  break;
+                // TODO: Need a Call-stack here
+            case ReturnNode ret:   return prettyPrint(ret.expr()._type,val(ret.expr()));
+            default:               throw Utils.TODO();
+            }
+        }
+
+    }
+
+    private static Object con( Type t ) {
+        if( t instanceof TypeInteger i )
+            return i.isConstant() ? (Long)i.value() : "INT";
+        if( t instanceof TypeFloat f )
+            return f.isConstant() ? (Double)f.value() : "FLT";
+        //
+        return null;
+    }
+
+    // Use type to print x as a string
+    static String prettyPrint( Type t, Object x ) { return _print(t,x,new SB(), new IdentityHashMap()).toString(); }
+    static SB _print( Type t, Object x, SB sb, IdentityHashMap visit ) {
+        if( x instanceof String s ) return sb.p(s);
+        if( x == null ) return sb.p("null");
+        return switch( t ) {
+        case TypeInteger i -> sb.p(  (Long)x);
+        case TypeFloat   f -> sb.p((Double)x);
+        case TypeMemPtr tmp -> {
+            if( visit.containsKey(x) ) yield sb.p("$cyclic");
+            visit.put(x,x);
+            // Since never can close the type cycle, without cyclic types, have
+            // to handle FRefs even here
+            if( tmp.isFRef() )
+                tmp = tmp.makeFrom(((TypeMemPtr)Parser.TYPES.get(tmp._obj._name))._obj);
+
+            Object[] xs = (Object[])x; // Array of fields
+            if( tmp._obj.isAry() ) {
+                Type elem = tmp._obj._fields[1]._type;
+                if( elem == TypeInteger.U8 ) {
+                    // Shortcut u8[] as a String
+                    for( Object o : xs )
+                        sb.p((char)(long)(Long)o);
+                } else {
+                    // Array of elements
+                    elem.print(sb).p("[ ");
+                    for( Object o : xs )
+                        _print( elem, o, sb, visit ).p( "," );
+                    sb.unchar().p("]");
+                }
+            } else {
+                sb.p(tmp._obj._name).p("{");
+                Field[] flds = tmp._obj._fields;
+                for( int i=0; i<flds.length; i++ )
+                    _print( flds[i]._type,xs[i], sb.p(flds[i]._fname).p("="), visit ).p(",");
+                sb.unchar().p("}");
+            }
+            yield sb;
+        }
+        case TypeMem mem -> sb.p("$mem");
+        case TypeTuple tt -> {
+            if( tt._types.length>1 && tt._types[1] instanceof TypeMemPtr )
+                // Assume a NewNode
+                yield _print( tt._types[1], x, sb, visit );
+            throw Utils.TODO();
+        }
+        case Type tt -> {
+            if( tt == Type.NIL ) yield sb.p("null");
+            throw Utils.TODO();
+        }
+        };
+    }
+
+    // Take a worklist step: one data op from the current Control is updated.
+    private static void step(Node n, int path, long arg, SB sb, IdentityHashMap visit) {
+        // Only data nodes
+        if( n instanceof CFGNode )  return;
+        // Compute new value
+        DATA[n._nid] = compute(n,path,arg);
+        // Trace
+        if( sb!=null ) {
+            IRPrinter.printLine(n,sb).unchar();
+            _print( n._type, DATA[n._nid], sb.p('\t'), visit );
+            System.out.println(sb);
+            sb.clear();
+            visit.clear();
+        }
+        // Also do any following projections, which are not in the local schedule otherwise
+        if( n instanceof MultiNode )
+            for( Node use : n._outputs )
+                step(use,-1,arg,sb,visit);
+    }
+
+    // From here down shamelessly copied from Evaluator, written by @Xmilia
+    private static Object compute( Node n, int path, long arg ) {
+        return switch( n ) {
+        case AddFNode    adf   -> d(adf.in(1)) +  d(adf.in(2));
+        case AddNode     add   -> x(add.in(1)) +  x(add.in(2));
+        case AndNode     and   -> x(and.in(1)) &  x(and.in(2));
+        case BoolNode.EQ eq    -> Objects.equals(val(eq.in(1)), val(eq.in(2))) ? 1L : 0L; // Bool EQ supports pointers, nil, and integers
+        case BoolNode.LE le    -> x( le.in(1)) <= x(le .in(2)) ? 1L : 0L;
+        case BoolNode.LT lt    -> x( lt.in(1)) <  x(lt .in(2)) ? 1L : 0L;
+        case CastNode    cast  -> val(cast.in(1));
+        case ConstantNode con  -> con(con._con);
+        case DivFNode    dvf   -> d(dvf.in(2))==0 ? 0D : d(dvf.in(1)) /  d(dvf.in(2));
+        case DivNode     div   -> x(div.in(2))==0 ? 0L : x(div.in(1)) /  x(div.in(2));
+        case LoadNode    ld    -> load(ld);
+        case MinusNode   sub   -> - x(sub.in(1));
+        case MulNode     mul   -> x(mul.in(1)) *  x(mul.in(2));
+        case NewNode     alloc -> alloc(alloc);
+        case OrNode      or    -> x(or .in(1)) |  x(or .in(2));
+        case PhiNode     phi   -> phi instanceof ParmNode parm && parm.fun()._sig==TypeFunPtr.MAIN && parm._idx==2 ? arg : val(phi.in(path));
+        case ProjNode    proj  -> proj._type instanceof TypeMem ? "$mem" : val(proj.in(0));
+        case ReadOnlyNode read -> val(read.in(1));
+        case SarNode     sar   -> x(sar.in(1)) >> x(sar.in(2));
+        case ScopeMinNode merge-> "$mem";
+        case ShlNode     shl   -> x(shl.in(1)) << x(shl.in(2));
+        case ShrNode     shr   -> x(shr.in(1)) >>>x(shr.in(2));
+        case StoreNode   st    -> store(st);
+        case SubNode     sub   -> x(sub.in(1)) -  x(sub.in(2));
+        case ToFloatNode toflt -> (double)x(toflt.in(1));
+        case XorNode     xor   -> x(xor.in(1)) ^  x(xor.in(2));
+        default -> throw Utils.TODO();
+        };
+    }
+
+    // Fetch without unboxing
+    static Object val( Node n ) { return DATA[n._nid]; }
+    // Fetch and unbox as primitive long
+    static long   x( Node n ) { return DATA[n._nid]==null ? 0 : (Long)  DATA[n._nid];  }
+    // Fetch and unbox as primitive double
+    static double d( Node n ) { return DATA[n._nid]==null ? 0 : (Double)DATA[n._nid];  }
+
+    // Convert array size to array element count
+    private static int offToIdx( long off, TypeStruct t) {
+        off -= t.aryBase();
+        int scale = t.aryScale();
+        long mask = (1L << scale)-1;
+        assert (off & mask) == 0;
+        return (int)(off>>scale);
+    }
+
+    // Builds and returns a pointer Object
+    private static Object alloc(NewNode alloc) {
+        TypeStruct type = alloc._ptr._obj;
+        if( type.isAry() ) {
+            long sz = (Long)val(alloc.in(1));
+            long x = offToIdx(sz, type);
+            int n = (int)x;
+            if( n!=x || n<0 )
+                throw new NegativeArraySizeException(""+n);
+            Object[] ary = new Object[n]; // Array body
+            var elem = type._fields[1]._type;
+            if (elem instanceof TypeInteger) {
+                Arrays.fill( ary, 0L );
+            } else if (elem instanceof TypeFloat) {
+                Arrays.fill( ary, 0D );
+            } else {
+                assert elem instanceof TypeMemPtr;
+            }
+            // Length value
+            //body[0] = vall(alloc.in(2+2));
+            return ary;
+        }
+
+        int num = type._fields.length;
+        Object[] ptr = new Object[num];
+        for( int i=0; i<num; i++ )
+            ptr[i] = val(alloc.in(2+i+num));
+        return ptr;
+    }
+
+    private static Object load( LoadNode ld ) {
+        TypeMemPtr tmp = (TypeMemPtr)ld.ptr()._type;
+        Object[] fs = (Object[])val(ld.ptr());
+        if( ld._name.equals("#") )
+            return (long)fs.length;
+        int idx = tmp._obj.isAry()
+            ? offToIdx(x(ld.off()),tmp._obj)
+            : tmp._obj.find(ld._name);
+        return fs[idx];
+    }
+
+    private static Object store( StoreNode st ) {
+        TypeMemPtr tmp = (TypeMemPtr)st.ptr()._type;
+        Object[] fs = (Object[])val(st.ptr());
+        int idx = tmp._obj.isAry()
+            ? offToIdx(x(st.off()),tmp._obj)
+            : tmp._obj.find(st._name);
+        Object val = val(st.val());
+        fs[idx] = val;
+        return "$mem";
+    }
+
+}
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Evaluator.java b/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Evaluator.java
index ab413ed2..ff9eb1b1 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Evaluator.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Evaluator.java
@@ -269,9 +269,8 @@ public class Evaluator {
 
     private Object cons(ConstantNode cons) {
         var type = cons.compute();
-        if (type instanceof TypeInteger i) return i.value();
+        if (type instanceof TypeInteger i) return i.isConstant() ? i.value() : Integer.MAX_VALUE;
         if (type instanceof TypeFloat i) return i.value();
-        assert type == Type.NIL;
         return null;
     }
 
@@ -333,7 +332,6 @@ public class Evaluator {
             case null:
                 return Status.FALLTHROUGH;
             case ReturnNode ret :  return val(ret .expr());
-            case   StopNode stop:  return val(stop.expr());
             case IfNode ifn:
                 block = block.next()[isTrue(val(ifn.in(1))) ? 0 : 1];
                 if (block == null) return Status.FALLTHROUGH;
@@ -345,8 +343,11 @@ public class Evaluator {
                 block = block.next()[0];
                 assert block != null;
                 for (; i < block.nodes().length; i++) {
-                    if (!(block.nodes()[i] instanceof PhiNode)) break;
-                    phiCache.add(val(block.nodes()[i].in(exit)));
+                    if (!(block.nodes()[i] instanceof PhiNode phi)) break;
+                    var val = region instanceof FunNode fun && fun._name.equals("main") && ((ParmNode)phi)._idx==2 && exit==1
+                            ? parameter
+                            : val(phi.in(exit));
+                    phiCache.add(val);
                 }
                 for (i=0; i<phiCache.size(); i++) {
                     values[block.nodes()[i]._nid] = phiCache.get(i);
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Scheduler.java b/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Scheduler.java
index 8b13f12f..3cf63e0f 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Scheduler.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/evaluator/Scheduler.java
@@ -87,6 +87,9 @@ public class Scheduler {
             this.entry = entry;
             this.prev = prev;
         }
+        BasicBlock(Node entry, BasicBlock prev) {
+            this(entry,prev.depth+1,prev);
+        }
 
     }
 
@@ -358,25 +361,28 @@ public class Scheduler {
         var queue = new Stack<NodeData>();
         var phiQueue = new Stack<NodeData>();
         queue.push(d(start));
-        int depth = 0;
         while (!queue.isEmpty()) {
             var data = queue.pop();
             var node = data.node;
             assert node instanceof CFGNode;
             BasicBlock block = switch (node) {
-            case StartNode s -> new BasicBlock(s, depth++);
-            case LoopNode l -> new BasicBlock(l, depth++, d(l.in(1)).block);
+            case StartNode s -> new BasicBlock(s, 0);
+            case LoopNode l -> new BasicBlock(l, d(l.in(1)).block);
             case RegionNode r -> {
                     var prev = new ArrayList<BasicBlock>();
+                    int depth = 0;
                     for(int i=1; i<r.nIns(); i++) {
-                        od(r.in(i)).ifPresent(d->prev.add(d.block));
+                        if( !od(r.in(i)).isPresent() ) continue;
+                        BasicBlock bb = d(r.in(i)).block;
+                        prev.add(bb);
+                        depth = Math.max(depth,bb.depth);
                     }
-                    yield new BasicBlock(r, depth++, prev.toArray(BasicBlock[]::new));
+                    yield new BasicBlock(r, depth+1, prev.toArray(BasicBlock[]::new));
             }
             case IfNode i -> d(i.in(0)).block;
             case ReturnNode ret -> d(ret .in(0)).block;
-            case StopNode stop  -> d(stop.in(0)).block;
-            default -> new BasicBlock(node, depth++, d(node.in(0)).block);
+            case CallNode call -> throw Utils.TODO();
+            default -> new BasicBlock(node, d(node.in(0)).block);
             };
             data.block = block;
             if (node instanceof RegionNode r) {
@@ -392,10 +398,17 @@ public class Scheduler {
                     }
                 }
             }
-            if( !(node instanceof ReturnNode) && !(node instanceof StopNode) )
+            if( node instanceof FunNode fun ) {
+                // Cannot find CFG user from fun via a naive search, because always find
+                // Return but Return is not always the one CFG user.
+                CFGNode n = fun.uctrl();
+                assert isCFGNodeReady(n) && d(n).block==null;
+                queue.push(d(n));
+            } else if( !(node instanceof ReturnNode) ) {
                 for (Node n : node._outputs)
                     if(n instanceof CFGNode && isCFGNodeReady(n) && d(n).block == null)
                         queue.push(d(n));
+            }
             var b = block;
             for(var in:data.node._inputs) od(in).ifPresent(d->update(d, b));
         }
@@ -440,7 +453,7 @@ public class Scheduler {
             var data = cfgQueue.pop();
             node = data.node;
             assert node instanceof CFGNode;
-            if (!(node instanceof ReturnNode) && !(node instanceof StopNode) ) {
+            if (!(node instanceof ReturnNode) ) {
                 for (var out : node._outputs) if (out!=null && out instanceof CFGNode && isNotXCtrl(out)) markAlive(cfgQueue, out, true);
             }
             for (var in : node._inputs) if(in!=null && !(in instanceof CFGNode) && isNotXCtrl(in)) markAlive(dataQueue, in, false);
@@ -492,16 +505,16 @@ public class Scheduler {
      * @param node The node
      * @return THe CFG output of the node.
      */
-    private static Node findSingleCFGOut(Node node) {
+    private static CFGNode findSingleCFGOut(Node node) {
         if (node instanceof StartNode) {
-            for(var n:node._outputs) if (n instanceof CProjNode p && p._idx==0) return p;
+            for(var n:node._outputs)
+                if (n instanceof FunNode fun && fun._name.equals("main"))
+                   return fun;
             return null;
         }
-        // From start, a Call, or one of many functions
-        if( node instanceof CProjNode c && c.in(0) instanceof StartNode )
-            return c.out(0);
+        if( node instanceof FunNode fun ) return fun.uctrl();
         assert node._outputs.stream().filter(x -> x instanceof CFGNode).limit(2).count()<=1;
-        for(var n:node._outputs) if(n instanceof CFGNode) return n;
+        for(var n:node._outputs) if(n instanceof CFGNode cfg) return cfg;
         return null;
     }
 
@@ -544,7 +557,6 @@ public class Scheduler {
                     break;
                 }
                 if (last instanceof ReturnNode) break;
-                if( last instanceof StopNode ) break;
                 if (last instanceof IfNode if_) {
                     for(var out:if_._outputs) if (out instanceof CFGNode && blocks.get(out) == null) queue.push(d(out));
                     break;
@@ -557,7 +569,6 @@ public class Scheduler {
                 case IfNode i -> new Block(arr, i, -1, new Block[2]);
                 case RegionNode r -> new Block(arr, r, r._inputs.find(prev), new Block[1]);
                 case ReturnNode r -> new Block(arr, r   , -1, new Block[0]);
-                case StopNode stop-> new Block(arr, stop, -1, new Block[0]);
                 default -> throw new AssertionError("Unexpected block exit node");
             });
         }
@@ -572,7 +583,7 @@ public class Scheduler {
                     block.next[0] = blocks.get(r);
                     break;
                 default:
-                    assert block.exit instanceof ReturnNode || block.exit instanceof StopNode;
+                    assert block.exit instanceof ReturnNode;
             }
         }
         // And return the block for the start node.
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/fuzzer/FuzzerUtils.java b/chapter18/src/test/java/com/seaofnodes/simple/fuzzer/FuzzerUtils.java
index 1efe270c..81977522 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/fuzzer/FuzzerUtils.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/fuzzer/FuzzerUtils.java
@@ -2,7 +2,6 @@ package com.seaofnodes.simple.fuzzer;
 
 import com.seaofnodes.simple.CodeGen;
 import com.seaofnodes.simple.IterPeeps;
-import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.node.Node;
 import com.seaofnodes.simple.node.StopNode;
 import java.io.OutputStream;
@@ -129,7 +128,10 @@ class FuzzerUtils {
             var code = new CodeGen(script);
             Node._disablePeephole = !runPeeps;
             code.parse();
-            return runPeeps ? code.opto().typeCheck().codegen()._stop : code._stop;
+            if( runPeeps ) code.opto();
+            code.typeCheck();
+            if( runPeeps ) code.GCM(); // Fixup infinite loops
+            return code._stop;
         } finally {
             NodeWalkVisit.clear();
             System.setErr(err);
-- 
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