Fix missing up/down phi peep.

Slight shuffling of sys.smp triggers different worklist order, triggers missing peep.
The pull-down phi op needs a reverse peep when more constants appear.
CodeGen driver can be called repeatedly.
Rename LogicalNode to ArithNode; use it on Add,Sub,MulDiv also.
Bugfix jump in loop that both exits on one path and enters a deeper loop on other.

23 files changed, 227 insertions, 283 deletions

diff --git a/chapter22/README.md b/chapter22/README.md
index 4cae3ee7..c7ff50f6 100644
--- a/chapter22/README.md
+++ b/chapter22/README.md
@@ -84,9 +84,10 @@ struct sys {
 };
 ```
 
-The `sys` import itself is Just Another `struct` like any other; it has fields
-and types declared internall.  Note that these assignments are all final and in
-the struct declaration, hence these are all *static* fields.
+The `sys` import itself is Just Another `struct` like any other struct; it has
+fields and assignments and types declared internally.  Note that these
+assignments are all final and in the struct declaration, hence these are all
+*static* fields.
 
 
 ## Casting a Pointer to an `i64`
@@ -102,9 +103,10 @@ struct base.
 ## Arrays of Constants and Constant Arrays
 
 The Simple type system now supports the notion of a "constant array" - an array
-of fixed constants, stored in the ELF file in the RODATA section.  We only
-support strings at the parser level: "Hello, World!" makes a `u8[13]` array
-containing ASCII bytes.
+of fixed constants, stored in the ELF file in the RODATA section.  Currently we
+only support strings at the parser level: "Hello, World!" makes a `u8[13]`
+array containing 13 ASCII bytes; like all arrays it has a length and will be
+range-checked in the future.
 
 A constant version of a non-constant array can be assigned using the `u8[~]`
 syntax.
@@ -126,5 +128,5 @@ val sum = { i32[~] is ->
 return sum(is);
 ```
 
-Note that this affects the deep contents of the array, and not the array
+Note that this affects the deep contents of the array and not the array
 variable itself.
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java b/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
index 8a28dacc..c3e211ea 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
@@ -21,7 +21,7 @@ public class CodeGen {
         Opto,                   // Run ideal optimizations
         TypeCheck,              // Last check for bad programs
         LoopTree,               // Build a loop tree; break infinite loops
-        InstSelect,             // Convert to target hardware nodes
+        Select,                 // Convert to target hardware nodes
         Schedule,               // Global schedule (code motion) nodes
         LocalSched,             // Local schedule
         RegAlloc,               // Register allocation
@@ -55,14 +55,15 @@ public class CodeGen {
     public CodeGen driver( Phase phase ) { return driver(phase,null,null); }
     public CodeGen driver( Phase phase, String cpu, String callingConv ) {
         if( _phase==null )                       parse();
-        if( _phase.ordinal() < phase.ordinal() ) opto();
-        if( _phase.ordinal() < phase.ordinal() ) typeCheck();
-        if( _phase.ordinal() < phase.ordinal() ) loopTree();
-        if( _phase.ordinal() < phase.ordinal() && cpu != null ) instSelect(cpu,callingConv);
-        if( _phase.ordinal() < phase.ordinal() ) GCM();
-        if( _phase.ordinal() < phase.ordinal() ) localSched();
-        if( _phase.ordinal() < phase.ordinal() ) regAlloc();
-        if( _phase.ordinal() < phase.ordinal() ) encode();
+        int p1 = phase.ordinal();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.Opto      .ordinal() ) opto();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.TypeCheck .ordinal() ) typeCheck();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.LoopTree  .ordinal() ) loopTree();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.Select    .ordinal() && cpu != null ) instSelect(cpu,callingConv);
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.Schedule  .ordinal() ) GCM();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.LocalSched.ordinal() ) localSched();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.RegAlloc  .ordinal() ) regAlloc();
+        if( _phase.ordinal() < p1 && _phase.ordinal() < Phase.Encoding  .ordinal() ) encode();
         return this;
     }
 
@@ -247,7 +248,7 @@ public class CodeGen {
     public CodeGen instSelect( String cpu, String callingConv ) { return instSelect(cpu,callingConv,PORTS); }
     public CodeGen instSelect( String cpu, String callingConv, String base ) {
         assert _phase.ordinal() == Phase.LoopTree.ordinal();
-        _phase = Phase.InstSelect;
+        _phase = Phase.Select;
 
         _callingConv = callingConv;
 
@@ -339,7 +340,7 @@ public class CodeGen {
     // Global schedule (code motion) nodes
     public CodeGen GCM() { return GCM(false); }
     public CodeGen GCM( boolean show) {
-        assert _phase.ordinal() <= Phase.InstSelect.ordinal();
+        assert _phase.ordinal() <= Phase.Select.ordinal();
         _phase = Phase.Schedule;
         long t0 = System.currentTimeMillis();
 
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java b/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
index 6efb84dd..f4b2ab69 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
@@ -299,7 +299,7 @@ public class Encoding {
     private static boolean forwardsEmptyScan( CFGNode c, int bld ) {
         if( c.nOuts()!=1 || c.loopDepth()!=bld ) return false;
         return c.uctrl() instanceof RegionNode cfg &&
-            (cfg instanceof LoopNode || forwardsEmptyScan(cfg,bld));
+            ((cfg instanceof LoopNode && cfg._ltree==c._ltree) || forwardsEmptyScan(cfg,bld));
     }
 
     // Is the CFG from "next" to the end empty?  This means jumping to "next"
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/AddNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/AddNode.java
index dd128e76..0f472829 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/AddNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/AddNode.java
@@ -7,42 +7,21 @@ import java.util.BitSet;
 
 import static com.seaofnodes.simple.Parser.con;
 
-public class AddNode extends Node {
+public class AddNode extends ArithNode {
     public AddNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Add"; }
-
-    @Override public String glabel() { return "+"; }
-
-    @Override
-    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("+"), visited);
-        return sb.append(")");
-    }
-
-
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i1 &&
-            t2 instanceof TypeInteger i2 ) {
-            if (i1.isConstant() && i2.isConstant())
-                return TypeInteger.constant(i1.value()+i2.value());
-            // Fold ranges like {0-1} + {2-3} into {2-4}.
-            if( !overflow(i1._min,i2._min) &&
-                !overflow(i1._max,i2._max) )
-                return TypeInteger.make(i1._min+i2._min,i1._max+i2._max);
-        }
+    @Override public String op() { return "+"; }
+
+    @Override long doOp( long x, long y ) { return x + y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
+        // Fold ranges like {0-1} + {2-3} into {2-4}.
+        if( !overflow(x._min,y._min) &&
+            !overflow(x._max,y._max) )
+            return TypeInteger.make(x._min+y._min,x._max+y._max);
         return TypeInteger.BOT;
     }
 
-    static boolean overflow( long x, long y ) {
-        if( (x ^    y ) < 0 ) return false; // unequal signs, never overflow
-        return (x ^ (x + y)) < 0; // sum has unequal signs, so overflow
-    }
     @Override
     public Node idealize () {
         Node lhs = in(1);
@@ -113,7 +92,7 @@ public class AddNode extends Node {
         if( spine_cmp(lhs.in(2),rhs,this) )
             return new AddNode(new AddNode(lhs.in(1),rhs).peephole(),lhs.in(2));
 
-        return null;
+        return super.idealize();
     }
 
     // Rotation is only valid for associative ops, e.g. Add, Mul, And, Or, Xor.
@@ -190,10 +169,4 @@ public class AddNode extends Node {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
-    @Override public Parser.ParseException err() {
-        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
-        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(1)._type,null);
-        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(2)._type,null);
-        return null;
-    }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/AndNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/AndNode.java
index 3cfcbda3..70b57d6d 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/AndNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/AndNode.java
@@ -4,30 +4,18 @@ import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
-
-public class AndNode extends LogicalNode {
+public class AndNode extends ArithNode {
     public AndNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "And"; }
     @Override public String op() { return "&"; }
-
     @Override public String glabel() { return "&"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1 ) {
-            if( i0.isConstant() && i1.isConstant() )
-                return TypeInteger.constant(i0.value()&i1.value());
-            // Sharpen allowed bits if either value is narrowed
-            long mask = i0.mask() & i1.mask();
-            return mask < 0 ? TypeInteger.BOT : TypeInteger.make(0,mask);
-        }
-        return TypeInteger.BOT;
+    @Override long doOp( long x, long y ) { return x & y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
+        // Sharpen allowed bits if either value is narrowed
+        long mask = x.mask() & y.mask();
+        return mask < 0 ? TypeInteger.BOT : TypeInteger.make(0,mask);
     }
 
     @Override
@@ -53,9 +41,10 @@ public class AndNode extends LogicalNode {
         // Do we have ((x & (phi cons)) & (phi cons)) ?
         // Push constant up through the phi: x & (phi con0&con0 con1&con1...)
         Node phicon = AddNode.phiCon(this,true);
-        if( phicon!=null ) return phicon;
+        if( phicon!=null )
+            return phicon;
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new AndNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/ArithNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/ArithNode.java
new file mode 100644
index 00000000..3e376418
--- /dev/null
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/ArithNode.java
@@ -0,0 +1,98 @@
+package com.seaofnodes.simple.node;
+
+import com.seaofnodes.simple.Parser;
+import com.seaofnodes.simple.Utils;
+import com.seaofnodes.simple.type.Type;
+import com.seaofnodes.simple.type.TypeInteger;
+import java.util.BitSet;
+
+public abstract class ArithNode extends Node {
+    // Source location for late reported errors
+    Parser.Lexer _loc;
+
+    public ArithNode( Parser.Lexer loc, Node lhs, Node rhs) { super(null, lhs, rhs); _loc = loc; }
+    @Override public String glabel() { return op(); }
+    abstract String op();
+
+    @Override
+    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
+        in(1)._print0(sb.append("("), visited);
+        in(2)._print0(sb.append(op()), visited);
+        return sb.append(")");
+    }
+
+    abstract long doOp(long x, long y);
+    abstract TypeInteger doOp(TypeInteger x, TypeInteger y);
+
+    // Generic airthmetic op math: high returns high; low returns low; 2
+    // constants fold; only 2 non-constants call specialized math.
+    @Override
+    public final TypeInteger compute() {
+        Type t1 = in(1)._type, t2 = in(2)._type;
+        if( t1.isHigh() || t2.isHigh() )
+            return TypeInteger.TOP;
+        if( t1 instanceof TypeInteger x &&
+            t2 instanceof TypeInteger y )
+            return x.isConstant() && y.isConstant()
+                ? con(x,y)
+                : doOp(x,y);
+        return TypeInteger.BOT;
+    }
+
+    private TypeInteger con( Type t1, Type t2 ) {
+        return TypeInteger.constant( doOp( ((TypeInteger)t1).value(), ((TypeInteger)t2).value()) );
+    }
+
+    // Check for "op(Phi(con,x),Phi(con,y))" and push-up through the Phi.
+    // Note that this is the exact reverse of Phi pulling a common op down
+    // to reduce total op-count.  We don't get in an endless push-up
+    // push-down peephole cycle because the constants all fold first.
+    // Returns "Phi(op(con,con),op(x,y))".
+
+    // This check is slightly different from the
+
+    // Expected to be called after other ideal checks are done.
+    @Override public Node idealize() {
+        if( in(1) instanceof PhiNode lhs &&
+            in(2) instanceof PhiNode rhs &&
+            lhs.nIns() >= 2 && !lhs.inProgress() &&
+            lhs.region()==rhs.region() ) {
+            // Profit check: only 1 instance of `this` will remain, all the
+            // others will fold to constants.
+            int cnt=0;
+            for( int i=1; i<lhs.nIns(); i++ )
+                if( isCon(lhs,rhs,i) )
+                    cnt++;
+            if( lhs.nIns()-1 - cnt <= 1 ) {
+                // Profit!  Push up-phi and fold
+                Node[] ns = new Node[lhs.nIns()];
+                ns[0] = lhs.in(0);
+                for( int i=1; i<lhs.nIns(); i++ ) {
+                    ns[i] = isCon(lhs,rhs,i)
+                        ? new ConstantNode(con(lhs.in(i)._type, rhs.in(i)._type)).peephole()
+                        : copy(lhs.in(i), rhs.in(i)).peephole();
+                }
+                String label = lhs._label==rhs._label ? lhs._label : lhs._label + rhs._label;
+                return new PhiNode(label,lhs._declaredType,ns).peephole();
+            }
+        }
+        return null;
+    }
+
+    static boolean isCon( PhiNode lhs, PhiNode rhs, int i ) {
+        return lhs.in(i)._type.isConstant() && rhs.in(i)._type.isConstant();
+    }
+
+
+    static boolean overflow( long x, long y ) {
+        if( (x ^    y ) < 0 ) return false; // unequal signs, never overflow
+        return (x ^ (x + y)) < 0; // sum has unequal signs, so overflow
+    }
+
+    @Override public Parser.ParseException err() {
+        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
+        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+op()+"' " + in(1)._type,_loc);
+        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+op()+"' " + in(2)._type,_loc);
+        return null;
+    }
+}
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/DivNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/DivNode.java
index 41518311..0de1c946 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/DivNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/DivNode.java
@@ -4,32 +4,14 @@ import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 import java.util.BitSet;
 
-public class DivNode extends Node {
+public class DivNode extends ArithNode {
     public DivNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Div"; }
+    @Override public String op() { return "//"; }
 
-    @Override public String glabel() { return "//"; }
-
-    @Override
-    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("/"), visited);
-        return sb.append(")");
-    }
-
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i1 &&
-            t2 instanceof TypeInteger i2 ) {
-            if (i1.isConstant() && i2.isConstant())
-                return i2.value() == 0
-                    ? TypeInteger.ZERO
-                    : TypeInteger.constant(i1.value()/i2.value());
-        }
+    @Override long doOp( long x, long y ) { return y==0 ? 0 : x / y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
         return TypeInteger.BOT;
     }
 
@@ -38,7 +20,7 @@ public class DivNode extends Node {
         // Div of 1.
         if( in(2)._type == TypeInteger.TRUE )
             return in(1);
-        return null;
+        return super.idealize();
     }
 
     @Override Node copy(Node lhs, Node rhs) { return new DivNode(lhs,rhs); }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/LogicalNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/LogicalNode.java
deleted file mode 100644
index e8552789..00000000
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/LogicalNode.java
+++ /dev/null
@@ -1,29 +0,0 @@
-package com.seaofnodes.simple.node;
-
-import com.seaofnodes.simple.Parser;
-import com.seaofnodes.simple.type.Type;
-import com.seaofnodes.simple.type.TypeInteger;
-import java.util.BitSet;
-
-public abstract class LogicalNode extends Node {
-    // Source location for late reported errors
-    Parser.Lexer _loc;
-
-    public LogicalNode(Parser.Lexer loc, Node lhs, Node rhs) { super(null, lhs, rhs); _loc = loc; }
-    abstract String op();
-
-    @Override
-    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append(op()), visited);
-        return sb.append(")");
-    }
-
-
-    @Override public Parser.ParseException err() {
-        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
-        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+op()+"' " + in(1)._type,_loc);
-        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+op()+"' " + in(2)._type,_loc);
-        return null;
-    }
-}
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/MinusNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/MinusNode.java
index e06e0c69..059d0d00 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/MinusNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/MinusNode.java
@@ -23,7 +23,7 @@ public class MinusNode extends Node {
     public Type compute() {
         if( in(1)._type.isHigh() ) return TypeInteger.TOP;
         if( in(1)._type instanceof TypeInteger i0 &&
-            !(i0==TypeInteger.BOT || i0._min == Long.MIN_VALUE || i0._max == Long.MIN_VALUE) )
+            i0._min != Long.MIN_VALUE && i0._max != Long.MIN_VALUE )
             return TypeInteger.make(-i0._max,-i0._min);
         return TypeInteger.BOT;
     }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/MulNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/MulNode.java
index c1a5a524..debc2c56 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/MulNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/MulNode.java
@@ -5,32 +5,14 @@ import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 import java.util.BitSet;
 
-public class MulNode extends Node {
+public class MulNode extends ArithNode {
     public MulNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Mul"; }
+    @Override public String op() { return "*"; }
 
-    @Override public String glabel() { return "*"; }
-
-    @Override
-    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("*"), visited);
-        return sb.append(")");
-    }
-
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i1 &&
-            t2 instanceof TypeInteger i2 ) {
-            if( i1==TypeInteger.ZERO || i2==TypeInteger.ZERO)
-                return TypeInteger.ZERO;
-            if (i1.isConstant() && i2.isConstant())
-                return TypeInteger.constant(i1.value()*i2.value());
-        }
+    @Override long doOp( long x, long y ) { return x * y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
         return TypeInteger.BOT;
     }
 
@@ -74,14 +56,8 @@ public class MulNode extends Node {
         Node phicon = AddNode.phiCon(this,true);
         if( phicon!=null ) return phicon;
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
-    @Override public Parser.ParseException err() {
-        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
-        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(1)._type.glb(false),null);
-        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(2)._type.glb(false),null);
-        return null;
-    }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter22/src/main/java/com/seaofnodes/simple/node/Node.java
index 39010f3d..eadb984a 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -66,7 +66,7 @@ public abstract class Node implements Cloneable {
     // Make a Node using the existing arrays of nodes.
     // Used by any pass rewriting all Node classes but not the edges.
     Node( Node n ) {
-        assert CodeGen.CODE._phase.ordinal() >= CodeGen.Phase.InstSelect.ordinal();
+        assert CodeGen.CODE._phase.ordinal() >= CodeGen.Phase.Select.ordinal();
         _nid = CODE.getUID(); // allocate unique dense ID
         _inputs  = new Ary<>(n==null ? new Node[0] : n._inputs.asAry());
         _outputs = new Ary<>(Node.class);
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/OrNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/OrNode.java
index 9b03dc5d..ac0d8454 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/OrNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/OrNode.java
@@ -4,26 +4,16 @@ import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
-
-public class OrNode extends LogicalNode {
+public class OrNode extends ArithNode {
     public OrNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "Or"; }
     @Override public String op() { return "|"; }
-
     @Override public String glabel() { return "|"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1 ) {
-            if( i0.isConstant() && i1.isConstant() )
-                return TypeInteger.constant(i0.value()|i1.value());
-        }
+
+    @Override long doOp( long x, long y ) { return x | y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
         return TypeInteger.BOT;
     }
 
@@ -49,7 +39,7 @@ public class OrNode extends LogicalNode {
         Node phicon = AddNode.phiCon(this,true);
         if( phicon!=null ) return phicon;
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new OrNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/SarNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/SarNode.java
index 4a71ec06..ee15fa65 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/SarNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/SarNode.java
@@ -3,31 +3,19 @@ package com.seaofnodes.simple.node;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
-import java.util.BitSet;
 
-public class SarNode extends LogicalNode {
+public class SarNode extends ArithNode {
     public SarNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "Sar"; }
     @Override public String op() { return ">>"; }
-
     @Override public String glabel() { return "&gt;&gt;"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if (t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1) {
-            if( i0 == TypeInteger.ZERO )
-                return TypeInteger.ZERO;
-            if( i0.isConstant() && i1.isConstant() )
-                return TypeInteger.constant(i0.value()>>i1.value());
-            if( i1.isConstant() ) {
-                int log = (int)i1.value();
-                return TypeInteger.make(-1L<<(63-log),(1L<<(63-log))-1);
-            }
+    @Override long doOp( long x, long y ) { return x >> y; }
+    @Override TypeInteger doOp( TypeInteger x, TypeInteger y ) {
+        if( y.isConstant() ) {
+            int log = (int)y.value();
+            return TypeInteger.make(-1L<<(63-log),(1L<<(63-log))-1);
         }
         return TypeInteger.BOT;
     }
@@ -44,7 +32,7 @@ public class SarNode extends LogicalNode {
 
         // TODO: x >> 3 >> (y ? 1 : 2) ==> x >> (y ? 4 : 5)
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new SarNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/ShlNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/ShlNode.java
index 39a2698a..2557bf6b 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/ShlNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/ShlNode.java
@@ -3,34 +3,24 @@ package com.seaofnodes.simple.node;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
-import java.util.BitSet;
 
-public class ShlNode extends LogicalNode {
+public class ShlNode extends ArithNode {
     public ShlNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "Shl"; }
     @Override public String op() { return "<<"; }
-
     @Override public String glabel() { return "&lt;&lt;"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if (t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1 ) {
-            if( i0 == TypeInteger.ZERO )
-                return TypeInteger.ZERO;
-            if( i1.isConstant() ) {
-                int shf = (int)i1.value();
-                if( i0.isConstant() )
-                    return TypeInteger.constant(i0.value()<<shf);
-                // If no overflow, shift endpoints
-                if( !(((i0._min<<shf)>>shf) != i0._min ||
-                      ((i0._max<<shf)>>shf) != i0._max ) )
-                    return TypeInteger.make(i0._min<<shf,i0._max<<shf);
-            }
+    @Override long doOp( long x, long y ) { return x << y; }
+    @Override TypeInteger doOp( TypeInteger x, TypeInteger y ) {
+        if( x == TypeInteger.ZERO )
+            return TypeInteger.ZERO;
+        if( y.isConstant() ) {
+            int shf = (int)y.value();
+            // If no overflow, shift endpoints
+            if( !(((x._min<<shf)>>shf) != x._min ||
+                  ((x._max<<shf)>>shf) != x._max ) )
+                    return TypeInteger.make(x._min<<shf,x._max<<shf);
         }
         return TypeInteger.BOT;
     }
@@ -54,7 +44,7 @@ public class ShlNode extends LogicalNode {
 
         // TODO: x << 3 << (y ? 1 : 2) ==> x << (y ? 4 : 5)
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new ShlNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/ShrNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/ShrNode.java
index 789fb8a8..269f6b7f 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/ShrNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/ShrNode.java
@@ -3,29 +3,17 @@ package com.seaofnodes.simple.node;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
-import java.util.BitSet;
 
-public class ShrNode extends LogicalNode {
+public class ShrNode extends ArithNode {
     public ShrNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "Shr"; }
     @Override public String op() { return ">>>"; }
-
     @Override public String glabel() { return "&gt;&gt;&gt;"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if (t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1 ) {
-            if( i0 == TypeInteger.ZERO )
-                return TypeInteger.ZERO;
-            if( i0.isConstant() && i1.isConstant() )
-                return TypeInteger.constant(i0.value()>>>i1.value());
-        }
-        return TypeInteger.BOT;
+    @Override long doOp( long x, long y ) { return x >>> y; }
+    @Override TypeInteger doOp( TypeInteger x, TypeInteger y ) {
+        return x == TypeInteger.ZERO ? x : TypeInteger.BOT;
     }
 
     @Override
@@ -40,7 +28,7 @@ public class ShrNode extends LogicalNode {
 
         // TODO: x >>> 3 >>> (y ? 1 : 2) ==> x >>> (y ? 4 : 5)
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new ShrNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/SubNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/SubNode.java
index 4290ff9b..8e4f6f79 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/SubNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/SubNode.java
@@ -5,38 +5,22 @@ import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 import java.util.BitSet;
 
-public class SubNode extends Node {
+public class SubNode extends ArithNode {
     public SubNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Sub"; }
+    @Override public String op() { return "-"; }
 
-    @Override public String glabel() { return "-"; }
-
-    @Override
-    public StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("-"), visited);
-        return sb.append(")");
-    }
-
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
+    @Override long doOp( long x, long y ) { return x - y; }
+    @Override TypeInteger doOp(TypeInteger x, TypeInteger y) {
         // Sub of same is 0
         if( in(1)==in(2) )
             return TypeInteger.ZERO;
-        if( t1 instanceof TypeInteger i1 &&
-            t2 instanceof TypeInteger i2 ) {
-            if (i1.isConstant() && i2.isConstant())
-                return TypeInteger.constant(i1.value()-i2.value());
-            // Fold ranges like {2-3} - {0-1} into {1-3}.
-            if( !AddNode.overflow(i1._min,-i2._max) &&
-                !AddNode.overflow(i1._max,-i2._min) &&
-                i2._min != Long.MIN_VALUE  )
-                return TypeInteger.make(i1._min-i2._max,i1._max-i2._min);
-        }
+        // Fold ranges like {2-3} - {0-1} into {1-3}.
+        if( !AddNode.overflow(x._min,-y._max) &&
+            !AddNode.overflow(x._max,-y._min) &&
+            y._min != Long.MIN_VALUE  )
+            return TypeInteger.make(x._min-y._max,x._max-y._min);
 
         return TypeInteger.BOT;
     }
@@ -51,7 +35,7 @@ public class SubNode extends Node {
         if( in(1) instanceof MinusNode minus )
             return new MinusNode(new AddNode(minus.in(1),in(2)).peephole());
 
-        return null;
+        return super.idealize();
     }
 
     @Override Node copy(Node lhs, Node rhs) { return new SubNode(lhs,rhs); }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/XorNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/XorNode.java
index 37d7147d..fdb4863e 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/XorNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/XorNode.java
@@ -3,26 +3,16 @@ package com.seaofnodes.simple.node;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
-import java.util.BitSet;
 
-public class XorNode extends LogicalNode {
+public class XorNode extends ArithNode {
     public XorNode(Parser.Lexer loc, Node lhs, Node rhs) { super(loc, lhs, rhs); }
 
     @Override public String label() { return "Xor"; }
     @Override public String op() { return "^"; }
-
     @Override public String glabel() { return "^"; }
 
-    @Override
-    public Type compute() {
-        Type t1 = in(1)._type, t2 = in(2)._type;
-        if( t1.isHigh() || t2.isHigh() )
-            return TypeInteger.TOP;
-        if( t1 instanceof TypeInteger i0 &&
-            t2 instanceof TypeInteger i1 ) {
-            if( i0.isConstant() && i1.isConstant() )
-                return TypeInteger.constant(i0.value()^i1.value());
-        }
+    @Override long doOp( long x, long y ) { return x ^ y; }
+    @Override TypeInteger doOp( TypeInteger x, TypeInteger y ) {
         return TypeInteger.BOT;
     }
 
@@ -48,7 +38,7 @@ public class XorNode extends LogicalNode {
         Node phicon = AddNode.phiCon(this,true);
         if( phicon!=null ) return phicon;
 
-        return null;
+        return super.idealize();
     }
     @Override Node copy(Node lhs, Node rhs) { return new XorNode(_loc,lhs,rhs); }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java b/chapter22/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
index 3b946cb5..45f71e40 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
@@ -198,7 +198,7 @@ public abstract class ASMPrinter {
 
         // Encoding
         int fatEncoding = 0;
-        if( code._encoding != null ) {
+        if( code._encoding != null && code._encoding._opLen!=null ) {
             int size = code._encoding._opLen[n._nid];
             if( code._asmLittle )
                 for( int i=0; i<Math.min(size,dopz); i++ )
@@ -247,7 +247,7 @@ public abstract class ASMPrinter {
         sb.nl();
 
         // Printing more op bits than fit
-        if( isMultiOp != null && code._encoding != null ) {
+        if( isMultiOp != null && code._encoding != null && code._encoding._opLen!=null ) {
             // Multiple ops, template style, no RA, no scheduling.  Print out
             // one-line-per-newline, with encoding bits up front.
             int size = code._encoding._opLen[n._nid];
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp b/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp
index 50d9166e..bc0492e8 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp
+++ b/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp
@@ -5,8 +5,13 @@ struct sys {
     // libc bindings
     /** https://www.man7.org/linux/man-pages/man2/<libc call>.2.html */
     struct libc {
+        i32 errno = "C";
         // fd  buf len -> len
-        {  i32 i64 i32 -> i32 } write = "C";
+        {  i32 i64 u32 -> u32 } write = "C";
+        // fd  buf len -> len
+        {  i32 i64 u32 -> u32 } read = "C";
+        //// status
+        //{  i32 -> i32 } _exit = "C";
         // addr len prot flags fd  off -> void*
         {  i64  i64 i32  i32   i32 i32 -> i64 } mmap = "C";
         // mmap flags
@@ -18,10 +23,28 @@ struct sys {
         i32 MAP_ANON = 32;
     };
     struct io {
+        // Print string to stdout
         val p = { u8[~] str ->
             i64 ptr = str;  // cast array base to i64
-            i32 len = str#; // cast length to signed
-            return sys.libc.write(1,ptr,len);
+            return sys.libc.write(1,ptr,str#);
         };
+
+        //// Return stdin as a u8[]
+        //val stdin = { ->
+        //    var buf = new u8[8*1024];
+        //    i64 ptr = buf;
+        //    int len = 0;
+        //    while( true ) {
+        //        int rez = sys.libc.read(0,ptr,buf#);
+        //        if( rez < 0 ) sys.libc._exit(sys.libc.errno);
+        //        if( rez < buf# )
+        //            break;
+        //        sys.libc._exit(-2); // Need to implement
+        //    }
+        //    // Compress
+        //    var rez = new u8[len];
+        //    sys.ary.copy(buf,0,rez,0,len);
+        //    return rez;
+        //};
     };
 };
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
index b7d65b95..712704db 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
@@ -379,6 +379,7 @@ while(0) {}
             }
         }    }
 }
+return 0;
 """);
         code.parse().opto();
         assertEquals("return 0;", code.print());
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter13Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter13Test.java
index a4644917..a19f85e3 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter13Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter13Test.java
@@ -132,13 +132,13 @@ return n.i;
     public void testNullRef4() {
         CodeGen code = new CodeGen("return -null-5/null-5;");
         try { code.parse().opto().typeCheck(); fail(); }
-        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+        catch( Exception e ) { assertEquals("Cannot '+' null",e.getMessage()); }
     }
 
     @Test public void testNullRef5() {
         CodeGen code = new CodeGen("return null+42;");
         try { code.parse().opto().typeCheck(); fail(); }
-        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+        catch( Exception e ) { assertEquals("Cannot '+' null",e.getMessage()); }
     }
 
     @Test
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index 16634580..cd02fbca 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -33,7 +33,7 @@ while(arg--) {
 }
 return a;
 """);
-        code.parse().opto().typeCheck().GCM();
+        code.parse().opto().typeCheck();
         assertEquals("return Phi(Loop,1,Phi(Loop,2,Phi_a));", code._stop.toString());
         assertEquals("1", Eval2.eval(code,  0));
         assertEquals("2", Eval2.eval(code,  1));
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Eval2.java b/chapter22/src/test/java/com/seaofnodes/simple/Eval2.java
index 03221325..8ad72eaa 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Eval2.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Eval2.java
@@ -117,9 +117,7 @@ public abstract class Eval2 {
         if( code._start.uctrl()==null ) return ""; // The empty program
         SB trace = null; // new SB(); // TRACE, set to null for off, new SB() for on
         // Force local scheduling phase
-        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();
+        code.driver(CodeGen.Phase.LocalSched);
         // Set global, so don't have to pass everywhere
         CODE = code;