Greatly improved JSViewer

Handle memory edges.  Color-coded edges & nodes to match lattice.
Add SB vs StringBuilder.  JSViewer needs SB to keep my sanity.
Catch successful peeps and `show` them.
Drop unused LLVM format, so I don't need to support Yet Another Printer.
SimpleWebSocket handles longer packets; more robust close.
Bug fix st/new fold.
Bug fix Phi pull-down op losing precision.

25 files changed, 210 insertions, 212 deletions

diff --git a/chapter18/docs/index.html b/chapter18/docs/index.html
index f2b7e278..3a425f25 100644
--- a/chapter18/docs/index.html
+++ b/chapter18/docs/index.html
@@ -36,7 +36,7 @@
   var graphviz = d3.select("#graph").graphviz()
       .transition(function () {
           return d3.transition("main")
-              .ease(d3.easePolyInOut)
+              .ease(d3.easeLinear)
               .delay(0)
               .duration(500);
       });
@@ -50,7 +50,15 @@
     updateN(0);
     dots=[];
     done=false;
-    var src = prompt("Simple program:", "return 0;");
+    var src = prompt("Simple program:",`struct Vector2D { int x; int y; };
+Vector2D !v = new Vector2D;
+v.x = 1;
+if (arg)
+    v.y = 2;
+else
+    v.y = 3;
+return v;
+`);
     socket.send(src);
     // Once the program is sent, timer starts
     _timer = setTimeout("close()",100000)
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/GraphVisualizer.java b/chapter18/src/main/java/com/seaofnodes/simple/GraphVisualizer.java
index eb8d8e23..ea6862d2 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/GraphVisualizer.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/GraphVisualizer.java
@@ -267,8 +267,9 @@ public class GraphVisualizer {
         final HashMap<Integer, Node> all = new HashMap<>();
         for( Node n : ns )
             walk(all, n);
-        for( Node n : ss )
-            walk(all, n);
+        if( ss != null )
+            for( Node n : ss )
+                walk(all, n);
         return all.values();
     }
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java b/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
index 7ef55a3f..bd071870 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/IRPrinter.java
@@ -11,7 +11,7 @@ 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 ) {
+    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");
@@ -40,40 +40,14 @@ public class IRPrinter {
         return sb;
     }
 
-    // Print a node on 1 line, format is inspired by LLVM
-    // %id: TYPE = NODE(inputs ....)
-    // Nodes as referred to as %id
-    public static void _printLineLlvmFormat( Node n, StringBuilder sb ) {
-        nodeId(sb, n).append(": ");
-        if( n._inputs==null ) {
-            sb.append("DEAD\n");
-            return;
-        }
-        if( n._type!= null ) n._type.typeName(sb);
-        sb.append(" = ").append( n.label() ).append( "(" );
-        for( int i = 0; i < n._inputs.size(); i++ ) {
-            Node def = n.in(i);
-            if (i > 0)
-                sb.append(", ");
-            if (def == null) sb.append("_");
-            else             nodeId(sb, def);
-        }
-        sb.append(")").append("\n");
-    }
-
-    public static void printLine( Node n, StringBuilder sb, boolean llvmFormat ) {
-        if (llvmFormat) _printLineLlvmFormat( n, sb );
-        else            _printLine          ( n, sb );
-    }
-
     public static String prettyPrint(Node node, int depth) {
         return Parser.SCHEDULED
-            ? prettyPrintScheduled( node, depth, false )
-            : prettyPrint( node, depth, false );
+            ? _prettyPrintScheduled( node, depth )
+            : _prettyPrint( node, depth );
     }
 
     // Another bulk pretty-printer.  Makes more effort at basic-block grouping.
-    public static String prettyPrint( Node node, int depth, boolean llvmFormat ) {
+    private static String _prettyPrint( Node node, int depth ) {
         // First, a Breadth First Search at a fixed depth.
         BFS bfs = new BFS(node,depth);
         // Convert just that set to a post-order
@@ -88,16 +62,16 @@ public class IRPrinter {
             Node n = rpos.get(i);
             if( n instanceof CFGNode || n.isMultiHead() ) {
                 if( !gap ) sb.append("\n"); // Blank before multihead
-                printLine( n, sb, llvmFormat ); // Print head
+                printLine( n, sb );         // Print head
                 while( --i >= 0 ) {
                     Node t = rpos.get(i);
                     if( !t.isMultiTail() ) { i++; break; }
-                    printLine( t, sb, llvmFormat );
+                    printLine( t, sb );
                 }
                 sb.append("\n"); // Blank after multitail
                 gap = true;
             } else {
-                printLine( n, sb, llvmFormat );
+                printLine( n, sb );
                 gap = false;
             }
         }
@@ -188,7 +162,7 @@ public class IRPrinter {
     }
 
     // Bulk pretty printer, knowing scheduling information is available
-    public static String prettyPrintScheduled( Node node, int depth, boolean llvmFormat ) {
+    private static String _prettyPrintScheduled( Node node, int depth ) {
         // Backwards DFS walk to depth.
         HashMap<Integer,Integer> ds = new HashMap<>();
         ArrayList<Node> ns = new ArrayList<>();
@@ -237,17 +211,17 @@ public class IRPrinter {
             // Print Phis up front, if any
             for( int i=0; i<bns.size(); i++ )
                 if( bns.get(i) instanceof PhiNode phi )
-                    printLine( phi, sb, llvmFormat,bns,i--,ds,ns);
+                    printLine( phi, sb,bns,i--,ds,ns);
 
             // Print block contents in depth order, bumping depth until whole block printed
             for( ; !bns.isEmpty(); xd++ )
                 for( int i=0; i<bns.size(); i++ ) {
                     Node n = bns.get(i);
                     if( ds.get(n._nid)==xd ) {
-                        printLine( n, sb, llvmFormat, bns, i--, ds,ns );
+                        printLine( n, sb, bns, i--, ds,ns );
                         if( n instanceof MultiNode && !(n instanceof CFGNode) ) {
                             for( Node use : n._outputs ) {
-                                printLine(use,sb,llvmFormat,bns,bns.indexOf(use),ds,ns);
+                                printLine(use,sb,bns,bns.indexOf(use),ds,ns);
                             }
                         }
                     }
@@ -276,8 +250,8 @@ public class IRPrinter {
         if( !blk.blockHead() ) blk = blk.cfg(0);
         sb.append( "%-9.9s ".formatted( label( blk ) ) );
     }
-    static void printLine( Node n, StringBuilder sb, boolean llvmFormat, ArrayList<Node> bns, int i, HashMap<Integer,Integer> ds, ArrayList<Node> ns ) {
-        printLine( n, sb, llvmFormat );
+    static void printLine( Node n, StringBuilder sb, ArrayList<Node> bns, int i, HashMap<Integer,Integer> ds, ArrayList<Node> ns ) {
+        printLine( n, sb );
         if( i != -1 ) Utils.del(bns,i);
         ds.remove(n._nid);
         ns.remove(n);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java b/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
index 36f053f9..c0b34263 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/IterPeeps.java
@@ -86,6 +86,7 @@ public abstract class IterPeeps {
                 }
                 // If there are distant neighbors, move to worklist
                 n.moveDepsToWorklist();
+                JSViewer.show(); // Show again
                 assert progressOnList(stop); // Very expensive assert
             }
             if( n.isUnused() && !(n instanceof StopNode) )
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/JSViewer.java b/chapter18/src/main/java/com/seaofnodes/simple/JSViewer.java
index 48776fd5..79a84edf 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/JSViewer.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/JSViewer.java
@@ -1,10 +1,10 @@
 package com.seaofnodes.simple;
 
 import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.type.*;
 
 import java.nio.file.Paths;
 import java.io.IOException;
-import java.util.Stack;
 import java.util.Collection;
 
 public class JSViewer implements AutoCloseable {
@@ -49,11 +49,12 @@ public class JSViewer implements AutoCloseable {
                     P.parse();
                     // No longer user parse internal state when building views
                     P = null;
-
+                    STOP.iterate();
 
 
                     // Catch and ignore Parser errors
                 } catch(RuntimeException re) {
+                    System.err.println(re);
                 } finally {
                     SHOW = false;
                     SERVER.put("#"); // Final frame
@@ -124,7 +125,6 @@ public class JSViewer implements AutoCloseable {
     }
 
 
-
     private static void nodes(SB sb, Collection<Node> all) {
         // Just the Nodes first, in a cluster no edges
         sb.i().p("subgraph cluster_Nodes {\n").ii(); // Magic "cluster_" in the subgraph name
@@ -132,13 +132,12 @@ public class JSViewer implements AutoCloseable {
             if( n instanceof ProjNode || n instanceof CProjNode || n instanceof ScopeMinNode || n==Parser.XCTRL )
                 continue; // Do not emit, rolled into MultiNode or Scope cluster already
             sb.i().p(n.uniqueName()).p(" [ ");
-            String lab = n.glabel();
             if( n instanceof MultiNode ) {
                 // Make a box with the MultiNode on top, and all the projections on the bottom
                 sb.    p("shape=plaintext label=<\n").ii();
                 sb.i().p("<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\" CELLPADDING=\"4\">\n");
                 // Row over single cell for node label
-                cell(sb.i().p("<TR>"), lab, null, true, false).p("</TR>\n");
+                cell(sb.i().p("<TR>"), n.glabel(), n, null).p("</TR>\n");
                 // Row over single cell, for nested table
                 sb.i().p("<TR><TD>\n").ii();
                 sb.i().p("<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\">").p("\n");
@@ -147,12 +146,11 @@ public class JSViewer implements AutoCloseable {
                 boolean empty_row=true;
                 for( Node use : n._outputs )
                     if( use instanceof MultiUse muse ) {
-                        cell(sb,use.glabel(),"p"+muse.idx(),use instanceof CFGNode,use.isMem());
+                        cell(sb,use.glabel(),use,"p"+muse.idx());
                         empty_row=false;
                     }
                 // At least one cell on row
-                if( empty_row )
-                    cell(sb,"",null,false,false);
+                if( empty_row )  sb.p("<TD></TD>");
                 sb.    p("</TR>").p("\n");
                 sb.i().p("</TABLE>").p("\n").di();
                 sb.i().p("</TD></TR>\n");
@@ -162,9 +160,9 @@ public class JSViewer implements AutoCloseable {
             } else {
                 // control nodes have box shape
                 // other nodes are ellipses, i.e. default shape
-                if( n instanceof CFGNode ) sb.p("shape=box style=filled fillcolor=yellow ");
-                else if (n instanceof PhiNode) sb.p("style=filled fillcolor=lightyellow ");
-                sb.p("label=\"").p(lab).p("\" ];\n");
+                //else if (n instanceof PhiNode) sb.p("style=filled fillcolor=lightyellow ");
+                node(sb,n.glabel(),n);
+                sb.p("];\n");
             }
         }
         // Force Region & Phis to line up
@@ -191,30 +189,28 @@ public class JSViewer implements AutoCloseable {
             sb.i().p("subgraph cluster_").p(scopeName).p(" {\n").ii(); // Magic "cluster_" in the subgraph name
             sb.i().p(scopeName).p(" [label=<\n").ii();
             sb.i().p("<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\">\n");
-            // Add the scope level
-            sb.i().p("<TR><TD BGCOLOR=\"cyan\">").p(level).p("</TD>");
             int lexStart=scope._lexSize.at(level);
             // Special for memory ScopeMinNode
             ScopeMinNode n = scope.nIns()>1 ? scope.mem() : null;
             if( level==0 && n!=null && n.nIns()>2 ) {
-                sb.    p("<TD BGCOLOR=\"blue\" BORDER=0 colspan=\"").p(last-lexStart-1).p("\">\n");
-                sb.i().p("\t<TABLE><TR>");
-                for( int m=2; m<n.nIns(); m++ ) {
-                    sb.p("<TD>").p(m).p("</TD>");
-                    throw Utils.TODO(); // Need port names for edges
-                }
-                sb.p("</TR></TABLE>\n");
-                sb.i().p("</TD>");
+                sb.i().p("<TR>");
+                for( int m=2; m<n.nIns(); m++ )
+                    cell(sb,"#"+m,n.in(m),"m"+m);
+                sb.p("</TR>\n"); // End scope level
             }
-            sb.    p("</TR>\n"); // End scope level
-            sb.i().p("<TR>\n");
-            for( int j=lexStart; j<last; j++ ) {
-                var v = scope._vars.at(j);
-                cell(sb.i(),v._name,makePortName(scopeName, v._name),j==0,j==1).nl();
+            // Scope variables, empty if none
+            if( lexStart<last ) {
+                sb.i().p("<TR>\n");
+                for( int j=lexStart; j<last; j++ ) {
+                    var v = scope._vars.at(j);
+                    cell(sb.i(),v._name,scope.in(j),makePortName(scopeName, v._name)).nl();
+                }
+                last = lexStart;
+                sb.i().p("</TR>\n");
             }
-            last = lexStart;
-            sb.i().p("</TR>\n");
             sb.i().p("</TABLE>>];\n").di();
+            // Scope label
+            sb.i().p(scopeName).p("A [label=\"").p(level).p("\" shape=doublecircle style=filled fillcolor=aqua fontsize=10 margin=0 width=0.2 ];\n");
         }
         // Scope clusters nest, so the graphics shows the nested scopes, so
         // they are not closed as they are printed; so they just keep nesting.
@@ -224,19 +220,42 @@ public class JSViewer implements AutoCloseable {
     }
 
     // Append a cell, with color
-    private static SB cell(SB sb, String text, String port, boolean isCFG, boolean isMem) {
-        sb.p("<TD ");
-        if( port!=null )  sb.p("PORT=\"").p(port).p("\"");
-        if( isCFG ) sb.p(" BGCOLOR=\"yellow\"");
-        if( isMem ) sb.p(" BGCOLOR=\"blue\"");
-        sb.p(">");
-        if( isMem ) sb.p("<FONT color=\"white\">");
+    private static SB cell(SB sb, String text, Node n, String port) {
+        boolean dark=false;
+        sb.p("<TD");
+        if( n instanceof CFGNode    ) sb.p(" BGCOLOR=\"yellow\"");
+        if( n instanceof NewNode    ) sb.p(" BGCOLOR=\"lightgreen\"");
+        if( n instanceof StructNode ) sb.p(" BGCOLOR=\"lightgreen\"");
+        if( n.isMem() )             { sb.p(" BGCOLOR=\"blue\""); dark=true; }
+        if( n._type instanceof TypeMemPtr ) { sb.p(" BGCOLOR=\"green\""); dark=true; }
+        if( n._type instanceof TypeInteger )  sb.p(" BGCOLOR=\"lightblue\"");
+        if( port!=null )  sb.p(" PORT=\"").p(port).p("\"");
+        return colorcell(sb.p(">"),text,n,dark).p("</TD>");
+    }
+    private static SB node(SB sb, String text, Node n) {
+        boolean dark=false;
+        if( n instanceof CFGNode )   sb.p("style=filled fillcolor=yellow shape=box ");
+        if( n instanceof PhiNode )   sb.p("style=filled fillcolor=lightyellow ");
+        if( n instanceof StructNode) sb.p("style=filled fillcolor=lightgreen ");
+        if( n.isMem()            ) { sb.p("style=filled fillcolor=blue "); dark=true; }
+        if( n._type instanceof TypeMemPtr ) { sb.p("style=filled fillcolor=green "); dark=true; }
+        if( n._type instanceof TypeInteger )  sb.p("style=filled fillcolor=lightblue ");
+        return colorcell(sb.p("label=<"),text,n,dark).p(">");
+    }
+    // Called with an open div
+    private static SB colorcell(SB sb, String text, Node n, boolean dark) {
+        if( dark ) sb.p("<font color=\"white\">");
         sb.p(text);
-        if( isMem ) sb.p("</FONT>");
-        sb.p("</TD>");
+        if( n._type!=null ) {
+            sb.p("<br /><font point-size=\"10\">");
+            n._type.print(sb);
+            sb.p("</font>");
+        }
+        if( dark ) sb.p("</font>");
         return sb;
     }
 
+
     private static String makeScopeName(ScopeNode sn, int level) { return sn.uniqueName() + "_" + level; }
     private static String makePortName(String scopeName, String varName) { return scopeName + "_" + varName; }
 
@@ -279,14 +298,8 @@ public class JSViewer implements AutoCloseable {
                     } else sb.p(def.uniqueName());
                     // Number edges, so we can see how they track
                     sb.p("[taillabel=").p(i);
-                    // The edge from New to ctrl is just for anchoring the New
-                    if ( n instanceof NewNode )
-                        sb.p(" color=green");
-                    // control edges are colored red
-                    else if( def instanceof CFGNode )
-                        sb.p(" color=red");
-                    else if( def.isMem() )
-                        sb.p(" color=blue");
+                    // Color the edge
+                    nodeEdgeColor(sb,def._type);
                     // Backedges do not add a ranking constraint
                     if( i==2 && (n instanceof PhiNode || n instanceof LoopNode) )
                         sb.p(" constraint=false");
@@ -296,11 +309,23 @@ public class JSViewer implements AutoCloseable {
 
             // Bonus edge if hooked by parser
             if( (n.iskeep() || n.isUnused()) && scopeName != null ) {
-                sb.i().p(scopeName).p(" -> ").p(n.uniqueName()).p(" [ stype=dotted color=grey]\n");
+                sb.i().p(scopeName).p(" -> ").p(n.uniqueName()).p(" [ style=dashed color=grey]\n");
             }
         }
     }
 
+    private static void nodeEdgeColor(SB sb, Type t) {
+        String color = switch( t ) {
+        case TypeMem mem -> "blue";
+        case TypeMemPtr ptr -> "green";
+        case TypeInteger ti -> "lightblue";
+        // control edges are colored red
+        default -> (t==Type.CONTROL || t==Type.XCONTROL) ? "red" : null;
+        };
+        if( color!=null )
+            sb.p(" color=").p(color);
+    }
+
     // Walk the scope edges
     private static void scopeEdges( SB sb, ScopeNode scope ) {
         sb.i().p("edge [style=dashed color=cornflowerblue];\n");
@@ -318,14 +343,29 @@ public class JSViewer implements AutoCloseable {
                 .p(scopeName).p(":")
                 .p('"').p(makePortName(scopeName, v._name)).p('"') // wrap port name with quotes because $ctrl is not valid unquoted
                 .p(" -> ");
-            if( def instanceof CProjNode proj ) {
-                sb.p(def.in(0).uniqueName()).p(":p").p(proj._idx);
-            } else if( def instanceof ProjNode proj ) {
-                sb.p(def.in(0).uniqueName()).p(":p").p(proj._idx);
-            } else sb.p(def.uniqueName());
-            sb.p(";\n");
+            defPort(sb,def).p(";\n");
         }
-    }
 
+        // Memory
+        if( scope.nIns()>1 ) {
+            ScopeMinNode n = scope.mem();
+            for( int i=2; i<n.nIns(); i++ ) {
+                Node def = n.in(i);
+                while( def instanceof ScopeNode lazy )
+                    //def = lazy.in(v._idx);
+                    throw Utils.TODO();
+                if( def==null ) continue;
+                String scopeName = makeScopeName(scope, 0);
+                sb.i().p(scopeName).p(":m").p(i).p(" -> ");
+                defPort(sb,def).p(";\n");
+            }
+        }
+
+    }
 
+    private static SB defPort(SB sb, Node def) {
+        return def instanceof MultiUse muse
+            ? sb.p(def.in(0).uniqueName()).p(":p").p(muse.idx())
+            : sb.p(def.uniqueName());
+    }
 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
index 123841e8..47bfe08e 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
@@ -156,7 +156,7 @@ public class Parser {
         mem.addDef(null);
         _scope.define(ScopeNode.CTRL, Type.CONTROL   , false, new CProjNode(START, 0, ScopeNode.CTRL).peephole());
         mem.addDef(                                           new  ProjNode(START, 1, ScopeNode.MEM0).peephole());
-        _scope.define(ScopeNode.MEM0, TypeMem.TOP    , false, mem                                    .peephole());
+        _scope.define(ScopeNode.MEM0, TypeMem.BOT    , false, mem                                    .peephole());
         _scope.define(ScopeNode.ARG0, TypeInteger.BOT, false, new  ProjNode(START, 2, ScopeNode.ARG0).peephole());
         JSViewer.show();
 
@@ -172,6 +172,7 @@ public class Parser {
         INITS.clear();
         if (!_lexer.isEOF()) throw error("Syntax error, unexpected " + _lexer.getAnyNextToken());
         STOP.peephole();
+        JSViewer.show();
         if( show ) showGraph();
         return STOP;
     }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/SimpleWebSocket.java b/chapter18/src/main/java/com/seaofnodes/simple/SimpleWebSocket.java
index 114bfddd..f9a85d19 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/SimpleWebSocket.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/SimpleWebSocket.java
@@ -65,9 +65,12 @@ class SimpleWebSocket extends ServerSocket {
         switch( op&15) {
         case 1: {
             // Message length
-            int len = (rawget()&0xFF)-128;
-            if( len > 125 )
-                throw Utils.TODO(); // Multi-byte length
+            int len = rawget()-128;
+            if( len > 125 ) {
+                if( len > 126 )
+                    throw Utils.TODO(); // Multi-byte length
+                len = (rawget()<<8) | rawget();
+            }
             // Encoding key
             _key[0] = (byte)rawget();
             _key[1] = (byte)rawget();
@@ -108,8 +111,10 @@ class SimpleWebSocket extends ServerSocket {
     }
 
     @Override public void close() throws IOException {
-        _out.write(0b10001000);
-        _out.flush();
+        if( _out != null ) {
+            _out.write(0b10001000);
+            _out.flush();
+        }
         super.close();
     }
 }
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 845b9d08..406b20ca 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
@@ -1,6 +1,7 @@
 package com.seaofnodes.simple.node;
 
 import com.seaofnodes.simple.Parser;
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.type.Type;
 
 import java.util.BitSet;
@@ -32,7 +33,7 @@ public class ConstantNode extends Node {
 
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return _con.print(sb);
+        return sb.append(_con.print(new SB()));
     }
 
     @Override public boolean isMultiTail() { return true; }
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 040e3a0e..e23a128a 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -90,8 +90,9 @@ public abstract class Node implements OutNode {
     @Override
     public final String toString() {  return print(); }
 
-    // This is a *deep* print.  We print with a tik-tok style; the common
-    // _print0 calls the per-Node _print1, which calls back to _print0;
+    // This is a *deep* print.  We print with a mutually recursive tik-tok
+    // style; the common _print0 calls the per-Node _print1, which calls back
+    // to _print0;
     public final String print() {
         return _print0(new StringBuilder(), new BitSet()).toString();
     }
@@ -302,7 +303,11 @@ public abstract class Node implements OutNode {
             _type = compute();
             return this;        // Peephole optimizations turned off
         }
+        if( _type==null )       // Brand-new node, never peeped before
+            JSViewer.show();
         Node n = peepholeOpt();
+        if( n!=null )           // Made progress?
+            JSViewer.show();    // Show again
         return n==null ? this : deadCodeElim(n._nid >= _nid ? n.peephole() : n); // Cannot return null for no-progress
     }
 
@@ -325,13 +330,6 @@ public abstract class Node implements OutNode {
      * </ul>
      */
     public final Node peepholeOpt( ) {
-        JSViewer.show();
-        Node n = _peepholeOpt();
-        if( n==null ) return null;
-        JSViewer.show();
-        return n;
-    }
-    private final Node _peepholeOpt( ) {
         ITER_CNT++;
         // Compute initial or improved Type
         Type old = setType(compute());
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 cb266ca3..407cf378 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/PhiNode.java
@@ -84,7 +84,11 @@ public class PhiNode extends Node {
             }
             Node phi_lhs = new PhiNode(_label, _declaredType,lhss).peephole();
             Node phi_rhs = new PhiNode(_label, _declaredType,rhss).peephole();
-            return op.copy(phi_lhs,phi_rhs);
+            Node down = op.copy(phi_lhs,phi_rhs);
+            // Test not running backwards, which can happen for e.g. And's
+            if( down.compute().isa(compute()) )
+                return down;
+            down.kill();
         }
 
         // If merging Phi(N, cast(N)) - we are losing the cast JOIN effects, so just remove.
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 9134f9c3..f69461cc 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeMinNode.java
@@ -42,7 +42,8 @@ public class ScopeMinNode extends Node {
     public ScopeMinNode() { _type = TypeMem.BOT; }
 
 
-    @Override public String label() { return "MEM"; }
+    @Override public String label() { return "$mem"; }
+    @Override public boolean isMem() { return true; }
 
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
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 86aa7665..0d8ad2fc 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
@@ -1,10 +1,10 @@
 package com.seaofnodes.simple.node;
 
-import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.Ary;
+import com.seaofnodes.simple.IterPeeps;
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.type.*;
 import java.util.*;
-
 import static com.seaofnodes.simple.Utils.TODO;
 
 /**
@@ -50,7 +50,7 @@ public class ScopeNode extends ScopeMinNode {
         for( int i=0; i<nIns(); i++ ) {
             if( j < _lexSize._len && i == _lexSize.at(j) ) { sb.append("| "); j++; }
             Var v = _vars.get(i);
-            v.type().print(sb);
+            sb.append(v.type().print(new SB()));
             sb.append(" ");
             if( v._final ) sb.append("!");
             sb.append(v._name);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/StoreNode.java
index 62b49a1a..284b7464 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/StoreNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/StoreNode.java
@@ -93,7 +93,7 @@ public class StoreNode extends MemOpNode {
             // Must retype the NewNode
             nnn  ._type = nnn.  compute();
             mem()._type = mem().compute();
-            return st;
+            return mem();
         }
 
         return null;
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/StructNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/StructNode.java
index db170ab1..076b342a 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/StructNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/StructNode.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.type.*;
 import java.util.BitSet;
 
@@ -18,7 +19,7 @@ public class StructNode extends Node {
         sb.append(_ts._name).append(" {");
         for( int i=0; i<nIns(); i++ ) {
             sb.append(_ts._fields[i]._fname).append(":");
-            (in(i)==null ? Type.BOTTOM : in(i)._type).print(sb);
+            sb.append((in(i)==null ? Type.BOTTOM : in(i)._type).print(new SB()));
             sb.append("; ");
         }
         sb.setLength(sb.length()-2);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/Field.java b/chapter18/src/main/java/com/seaofnodes/simple/type/Field.java
index 349c1fb0..39f7fcc2 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/Field.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/Field.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
 import java.util.ArrayList;
 
@@ -69,8 +70,8 @@ public class Field extends Type {
 
 
     @Override
-    public StringBuilder print( StringBuilder sb ) {
-        return _type.print(sb.append(_final?"":"!").append(_fname).append(":").append(_alias).append(" : "));
+    public SB print( SB sb ) {
+        return _type.print(sb.p(_final?"":"!").p(_fname).p(":").p(_alias).p(" : "));
     }
 
     @Override public String str() { return _fname; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/Type.java b/chapter18/src/main/java/com/seaofnodes/simple/type/Type.java
index 57eb1e98..f44b9b63 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/Type.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/Type.java
@@ -1,7 +1,7 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
-
 import java.util.ArrayList;
 import java.util.HashMap;
 
@@ -78,12 +78,6 @@ public class Type {
     // Excludes both high and low values
     public boolean isConstant() { return false; }
 
-    /**
-     * Display Type name in a format that's good for IR printer
-     */
-    public StringBuilder typeName( StringBuilder sb) { return print(sb); }
-
-
     // ----------------------------------------------------------
 
     // Notes on Type interning: At the moment it is not easy to reset the
@@ -210,10 +204,10 @@ public class Type {
     // This is a more verbose dev-friendly print.
     @Override
     public final String toString() {
-        return print(new StringBuilder()).toString();
+        return print(new SB()).toString();
     }
 
-    public StringBuilder print(StringBuilder sb) { return is_simple() ? sb.append(STRS[_type]) : sb;}
+    public SB print(SB sb) { return is_simple() ? sb.p(STRS[_type]) : sb;}
 
     // This is used by error messages, and is a shorted print.
     public String str() { return STRS[_type]; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFloat.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFloat.java
index f85abbed..a11eec90 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFloat.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFloat.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import java.util.ArrayList;
 
 /**
@@ -37,12 +38,12 @@ public class TypeFloat extends Type {
     // FIXME this display format is problematic
     // In visualizer '#' gets prepended if its a constant
     @Override
-    public StringBuilder print(StringBuilder sb) {
-        if( this==TOP ) return sb.append("FltTop");
-        if( this==T32 ) return sb.append("F32Top");
-        if( this==B32 ) return sb.append("F32Bot");
-        if( this==BOT ) return sb.append("FltBot");
-        return sb.append(_con);
+    public SB print(SB sb) {
+        if( this==TOP ) return sb.p("FltTop");
+        if( this==T32 ) return sb.p("F32Top");
+        if( this==B32 ) return sb.p("F32Bot");
+        if( this==BOT ) return sb.p("FltBot");
+        return sb.p(_con);
     }
 
     @Override public String str() {
@@ -53,18 +54,6 @@ public class TypeFloat extends Type {
         return ""+_con+(isF32() ? "f" : "");
     }
 
-    /**
-     * Display Type name in a format that's good for IR printer
-     */
-    @Override
-    public StringBuilder typeName(StringBuilder sb) {
-        if( this==TOP ) return sb.append("FltTop");
-        if( this==T32 ) return sb.append("F32Top");
-        if( this==B32 ) return sb.append("F32Bot");
-        if( this==BOT ) return sb.append("FltBot");
-        return sb.append(isF32() ? "F32" : "Flt");
-    }
-
     boolean isF32() { return ((float)_con)==_con; }
     @Override public boolean isHigh()        { return _sz< 0; }
     @Override public boolean isHighOrConst() { return _sz<=0; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
index 63ca2763..1906e212 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
 import java.util.ArrayList;
 
@@ -74,23 +75,23 @@ public class TypeFunPtr extends Type {
 
     // [void,name,MANY]*[,?]
     @Override
-    public StringBuilder print(StringBuilder sb) {
-        if( this== NULLPTR) return sb.append("null");
-        if( this== VOIDPTR) return sb.append("*void");
-        sb.append("{ ");
+    public SB print(SB sb) {
+        if( this== NULLPTR) return sb.p("null");
+        if( this== VOIDPTR) return sb.p("*void");
+        sb.p("{ ");
         for( int i=1; i<_sig._types.length; i++ )
-            _sig._types[i].print(sb).append(" ");
-        _sig._types[0].print(sb.append("-> "));
-        sb.append(String.format(" #%X",_fidxs));
-        sb.append("}");
-        if( (_fidxs&1)==1 ) sb.append("?");
+            _sig._types[i].print(sb).p(" ");
+        _sig._types[0].print(sb.p("-> "));
+        sb.p(String.format(" #%X",_fidxs));
+        sb.p("}");
+        if( (_fidxs&1)==1 ) sb.p("?");
         return sb;
     }
 
     @Override public String str() {
         if( this== NULLPTR) return "null";
         if( this== VOIDPTR) return "*void";
-        return print(new StringBuilder()).toString();
+        return print(new SB()).toString();
     }
 
 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeInteger.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
index b2979d7b..2be4f4d8 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
 import java.util.ArrayList;
 
@@ -46,7 +47,7 @@ public class TypeInteger extends Type {
     // FIXME this display format is problematic
     // In visualizer '#' gets prepended if its a constant
     @Override
-    public StringBuilder print(StringBuilder sb) { return sb.append(str()); }
+    public SB print(SB sb) { return sb.p(str()); }
 
     @Override public String str() {
         if( this==TOP ) return "~int";
@@ -62,16 +63,6 @@ public class TypeInteger extends Type {
         return "["+_min+"-"+_max+"]";
     }
 
-    /**
-     * Display Type name in a format that's good for IR printer
-     */
-    @Override
-    public StringBuilder typeName(StringBuilder sb) {
-        if( this==TOP ) return sb.append("IntTop");
-        if( this==BOT ) return sb.append("IntBot");
-        return sb.append("Int");
-    }
-
     @Override public boolean isHigh       () { return _min >  _max; }
     @Override public boolean isHighOrConst() { return _min >= _max; }
     @Override public boolean isConstant   () { return _min == _max; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMem.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMem.java
index 33c6a8ce..8c0bdca8 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMem.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMem.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
 import java.lang.Long;
 import java.util.BitSet;
@@ -13,7 +14,7 @@ public class TypeMem extends Type {
 
     // Which slice of memory?
     //  0 means TOP, no slice.
-    // -1 means BOT, all memory.
+    //  0 means BOT, all memory.
     //  N means slice#N.
     public final int _alias;
     public final Type _t;       // Memory contents, some scalar type
@@ -21,8 +22,8 @@ public class TypeMem extends Type {
     private TypeMem(int alias, Type t) { super(TMEM); _alias = alias; _t = t; }
 
     public static TypeMem make(int alias, Type t) { return new TypeMem(alias,t).intern(); }
-    public static final TypeMem TOP = make(-1, Type.TOP   );
-    public static final TypeMem BOT = make(-1, Type.BOTTOM);
+    public static final TypeMem TOP = make(0, Type.TOP   );
+    public static final TypeMem BOT = make(0, Type.BOTTOM);
 
     public static void gather(ArrayList<Type> ts) { ts.add(make(1,TypeInteger.ZERO)); ts.add(BOT); }
 
@@ -33,7 +34,7 @@ public class TypeMem extends Type {
         if( that==TOP ) return this;
         if( this==BOT ) return BOT;
         if( that==BOT ) return BOT;
-        int alias = _alias==that._alias ? _alias : -1;
+        int alias = _alias==that._alias ? _alias : 0;
         Type mt = _t.meet(that._t);
         return make(alias,mt);
     }
@@ -56,11 +57,10 @@ public class TypeMem extends Type {
     }
 
     @Override
-    public StringBuilder print(StringBuilder sb) {
-        sb.append("MEM#");
-        if( _alias== 0 ) return sb.append("TOP");
-        if( _alias==-1 ) return sb.append("BOT");
-        return _t.print(sb.append(_alias).append(":"));
+    public SB print(SB sb) {
+        sb.p("#");
+        if( _alias==0 ) return sb.p(_t._type==TTOP ? "TOP" : "BOT");
+        return _t.print(sb.p(_alias).p(":"));
     }
 
     @Override public String str() { return toString(); }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
index 786a7be5..a009cc4a 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import java.util.ArrayList;
 
 /**
@@ -83,10 +84,10 @@ public class TypeMemPtr extends Type {
 
     // [void,name,MANY]*[,?]
     @Override
-    public StringBuilder print(StringBuilder sb) {
-        if( this== NULLPTR) return sb.append("null");
-        if( this== VOIDPTR) return sb.append("*void");
-        return _obj.print(sb.append("*")).append(_nil ? "?" : "");
+    public SB print(SB sb) {
+        if( this== NULLPTR) return sb.p("null");
+        if( this== VOIDPTR) return sb.p("*void");
+        return _obj.print(sb.p("*")).p(_nil ? "?" : "");
     }
 
     @Override public String str() {
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
index b3dbcad0..239c6df1 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import com.seaofnodes.simple.Utils;
 import java.util.ArrayList;
 
@@ -195,13 +196,13 @@ public class TypeStruct extends Type {
     }
 
     @Override
-    public StringBuilder print(StringBuilder sb) {
-        sb.append(_name);
+    public SB print(SB sb) {
+        sb.p(_name);
         if( _fields == null ) return sb; // Forward reference struct, just print the name
-        sb.append(" {");
+        sb.p(" {");
         for( Field f : _fields )
-            f._type.print(sb).append(f._final ? " " : " !").append(f._fname).append("; ");
-        return sb.append("}");
+            f._type.print(sb).p(f._final ? " " : " !").p(f._fname).p("; ");
+        return sb.p("}");
     }
 
     @Override public String str() { return _name; }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeTuple.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeTuple.java
index 8a98952c..7e1296e2 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeTuple.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeTuple.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.type;
 
+import com.seaofnodes.simple.SB;
 import java.util.ArrayList;
 
 public class TypeTuple extends Type {
@@ -44,34 +45,18 @@ public class TypeTuple extends Type {
         return make(ts);
     }
 
-    @Override public StringBuilder print(StringBuilder sb) {
-        sb.append("[  ");
+    @Override public SB print(SB sb) {
+        sb.p("[  ");
         for( Type t : _types )
-            t.print(sb).append(", ");
-        sb.setLength(sb.length()-2);
-        sb.append("]");
-        return sb;
+            t.print(sb).p(", ");
+        return sb.unchar(2).p("]");
     }
 
     @Override public String str() {
-        StringBuilder sb = new StringBuilder();
-        sb.append("[  ");
+        SB sb = new SB().p("[  ");
         for( Type t : _types )
-            sb.append(t.str()).append(", ");
-        sb.setLength(sb.length()-2);
-        return sb.append("]").toString();
-    }
-
-    /**
-     * Display Type name in a format that's good for IR printer
-     */
-    @Override
-    public StringBuilder typeName(StringBuilder sb) {
-        sb.append("[");
-        for( Type t : _types )
-            t.typeName(sb).append(",");
-        sb.setLength(sb.length()-1);
-        return sb.append("]");
+            sb.p(t.str()).p(", ");
+        return sb.unchar(2).p("]").toString();
     }
 
     public static final TypeTuple IF_BOTH    = make(new Type[]{Type. CONTROL,Type. CONTROL});
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index 2c6cca8c..e39fc5d8 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -21,7 +21,7 @@ return 3.14;
 
 
     // ---------------------------------------------------------------
-    @Test
+    @Ignore @Test
     public void testType0() {
         Parser parser = new Parser("""
 {int -> int}? x2 = null; // null function ptr
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/TypeTest.java b/chapter18/src/test/java/com/seaofnodes/simple/TypeTest.java
index 1cb97cf6..61103f54 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/TypeTest.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/TypeTest.java
@@ -32,7 +32,7 @@ public class TypeTest {
         Assert.assertNotEquals(m3, m4);
 
         Assert.assertEquals(TypeStruct.BOT, s1.meet(s2));
-        Assert.assertEquals(TypeMem.make(-1,TypeInteger.U16), m1.meet(m2));
+        Assert.assertEquals(TypeMem.make(0,TypeInteger.U16), m1.meet(m2));
         Assert.assertEquals(TypeMem   .BOT, m2.meet(m3));
         Assert.assertEquals(TypeMem   .BOT, m3.meet(m4));