Add a sys.io.p

Remove dead sys calls
Saves many test cases tracking count of returned functions.
Move call unlinking even early.
Print extern calls better.
Fix call anti-dep register bug.
Fix TFP hash punning.
Fix ParmNode hash punning.
Sys calls get a sane name.
Stop filters sys calls.

21 files changed, 109 insertions, 53 deletions

diff --git a/chapter22/src/main/java/com/seaofnodes/simple/Parser.java b/chapter22/src/main/java/com/seaofnodes/simple/Parser.java
index ab2c775c..eae823eb 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/Parser.java
@@ -196,7 +196,7 @@ public class Parser {
         ScopeNode breakScope = _breakScope; _breakScope = null;
         ScopeNode continueScope = _continueScope; _continueScope = null;
 
-        FunNode fun = _fun = (FunNode)peep(new FunNode(loc(),sig,null,_code._start));
+        FunNode fun = _fun = (FunNode)peep(new FunNode(loc(),sig,_nestedType,null,_code._start));
         // Once the function header is available, install in linker table -
         // allowing recursive functions.  Linker matches on declared args and
         // exact fidx, and ignores the return (because the fidx will only match
@@ -731,7 +731,7 @@ public class Parser {
             // expr is a constant function
             if( t instanceof TypeFunPtr && expr._type instanceof TypeFunPtr tfp && tfp.isConstant() ) {
                 if( expr instanceof ExternNode ) t = expr._type; // Upgrade declared type to exact function
-                else _code.link(tfp)._name = name; // Assign debug name to Simple function
+                else _code.link(tfp).setName(name); // Assign debug name to Simple function
             }
 
         } else {
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 26f2e522..8a28dacc 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
@@ -166,6 +166,22 @@ public class CodeGen {
 
         // Pessimistic peephole optimization on a worklist
         _iter.iterate(this);
+
+        // Not really a true optimistic pass, but look for unlinked functions.
+        // This can be removed, which may trigger another round of pessimistic.
+        // This is the point where we flip from a virtual Call Graph (any call
+        // can call any function) to having a correct (but conservative) CG.
+
+        FunNode main = link(_main);
+        for( Node use : _start._outputs )
+            if( use instanceof FunNode fun &&
+                fun.nIns()==2 && fun.in(1)==_start && fun != main &&
+                    (fun._name==null || fun._name.startsWith("sys.")) ) {
+                add(fun).setDef(1,Parser.XCTRL);
+                addAll(fun._outputs);
+            }
+        _iter.iterate(this);
+
         _tOpto = (int)(System.currentTimeMillis() - t0);
 
         // TODO:
@@ -203,7 +219,7 @@ public class CodeGen {
         _phase = Phase.LoopTree;
         long t0 = System.currentTimeMillis();
         // Build the loop tree, fix never-exit loops
-        _start.buildLoopTree(_stop);
+        _start.buildLoopTree(_start,_stop);
         _tLoopTree = (int)(System.currentTimeMillis() - t0);
         return this;
     }
@@ -262,7 +278,6 @@ public class CodeGen {
         _rpcMask = new RegMask(_mach.rpc());
         _retMasks[3] = _rpcMask;
 
-
         // Convert to machine ops
         long t0 = System.currentTimeMillis();
         _uid = 1;               // All new machine nodes reset numbering
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java b/chapter22/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
index c05cfe2e..78e2f75f 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
@@ -13,19 +13,6 @@ public abstract class GlobalCodeMotion {
     // Node.use(0) is always a block tail (either IfNode or head of the
     // following block).  There are no unreachable infinite loops.
     public static void buildCFG( CodeGen code ) {
-        // Unlink all linked calls.  This can remove RPC constants which
-        // shuffled the StartNode outputs so requires a while loop.
-        boolean done=false;
-        while(!done) {
-            done = true;
-            for( Node use : code._start._outputs )
-                if( use instanceof FunNode fun )
-                    for( Node c : fun._inputs )
-                        if( c instanceof CallNode call )
-                            { call.unlink_all(); done=false; }
-        }
-
-
         Ary<CFGNode> rpo = new Ary<>(CFGNode.class);
         _rpo_cfg(null, code._start, code.visit(), rpo);
         // Reverse in-place
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/CFGNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/CFGNode.java
index 56a33a26..96597648 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/CFGNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/CFGNode.java
@@ -123,7 +123,19 @@ public abstract class CFGNode extends Node {
     // Tag all CFG Nodes with their containing LoopNode; LoopNodes themselves
     // also refer to *their* containing LoopNode, as well as have their depth.
     // Start is a LoopNode which contains all at depth 1.
-    public void buildLoopTree(StopNode stop) {
+    public void buildLoopTree(StartNode start, StopNode stop) {
+        // Unlink all linked calls.  This can remove RPC constants which
+        // shuffled the StartNode outputs so requires a while loop.
+        boolean done=false;
+        while(!done) {
+            done = true;
+            for( Node use : start._outputs )
+                if( use instanceof FunNode fun )
+                    for( Node c : fun._inputs )
+                        if( c instanceof CallNode call )
+                            { call.unlink_all(); done=false; }
+        }
+
         _ltree = stop._ltree = Parser.XCTRL._ltree = new LoopTree((StartNode)this);
         _bltWalk(2,null,stop, new BitSet());
     }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/CallNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/CallNode.java
index 773716f7..8b243e87 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/CallNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/CallNode.java
@@ -32,8 +32,11 @@ public class CallNode extends CFGNode {
         return sb.append(")");
     }
     public String name() {
-        if( fptr()._type instanceof TypeFunPtr tfp && tfp.isConstant() )
-            return CodeGen.CODE.link(tfp)._name;
+        if( fptr()._type instanceof TypeFunPtr tfp && tfp.isConstant() ) {
+            FunNode fun = CodeGen.CODE.link(tfp);
+            if( fun !=null ) return fun._name;
+            if( fptr() instanceof ExternNode ex )  return ex._extern;
+        }
         return null;
     }
 
@@ -139,7 +142,7 @@ public class CallNode extends CFGNode {
                 assert linked(fun);
                 int idx = fun._inputs.find(this);
                 for( Node use : fun._outputs )
-                    if( use instanceof ParmNode parm )
+                    if( use instanceof ParmNode )
                         use.delDef(idx);
                 fun.delDef(idx);
                 cend().delDef(cend()._inputs.find(fun.ret()));
@@ -162,6 +165,9 @@ public class CallNode extends CFGNode {
             if( !arg(i+2)._type.isa(tfp.arg(i)) )
                 return Parser.error( "Argument #"+i+" isa "+arg(i+2)._type+", but must be a "+tfp.arg(i), _loc);
 
+        if( tfp.fidxs() < 0 )
+            throw Utils.TODO(); // Infinite unknown TFPs?  Should be fairly precise CG
+
         return null;
     }
 
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/FunNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/FunNode.java
index 5a356185..c469fc96 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/FunNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/FunNode.java
@@ -21,7 +21,7 @@ public class FunNode extends RegionNode {
 
     public String _name;        // Debug name
 
-    public FunNode( Parser.Lexer loc, TypeFunPtr sig, Node... nodes ) { super(loc,nodes); _sig = sig; }
+    public FunNode( Parser.Lexer loc, TypeFunPtr sig, String name, Node... nodes ) { super(loc,nodes); _name=name; _sig = sig; }
     public FunNode( FunNode fun ) {
         super( fun, fun==null ? null : fun._loc );
         if( fun!=null ) {
@@ -69,6 +69,11 @@ public class FunNode extends RegionNode {
         }
     }
 
+    public void setName( String name ) {
+        if( _name==null ) _name=name;
+        else _name += "."+name;
+    }
+
     @Override
     public Type compute() {
         // Only dead if no callers after SCCP
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/ParmNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/ParmNode.java
index 9e11a129..32e41f54 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/ParmNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/ParmNode.java
@@ -45,4 +45,8 @@ public class ParmNode extends PhiNode {
 
     // Always in-progress until we run out of unknown callers
     @Override public boolean inProgress() { return fun().inProgress(); }
+
+    @Override public boolean eq( Node n ) {
+        return ((ParmNode)n)._idx==_idx && super.eq(n);
+    }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/StopNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/StopNode.java
index 9be08ad9..b65535f1 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/StopNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/StopNode.java
@@ -23,11 +23,15 @@ public class StopNode extends CFGNode {
     @Override
     public StringBuilder _print1(StringBuilder sb, BitSet visited) {
         // For the sake of many old tests, and single value prints as "return val"
-        if( ret()!=null ) return ret()._print0(sb,visited);
+        ReturnNode ret1 = ret();
+        if( ret1!=null ) return ret1._print0(sb,visited);
         sb.append("Stop[ ");
         for( Node ret : _inputs )
-            if( ret!=null )
-                ret._print0(sb, visited).append(" ");
+            if( ret!=null ) {
+                String name = ((ReturnNode)ret).fun()._name;
+                if( name== null || !name.startsWith("sys.") )
+                    ret._print0(sb, visited).append(" ");
+            }
         return sb.append("]");
     }
 
@@ -37,7 +41,13 @@ public class StopNode extends CFGNode {
     // If a single Return, return it.
     // Otherwise, null because ambiguous.
     public ReturnNode ret() {
-        return nIns()==1 && in(0) instanceof ReturnNode ret ? ret : null;
+        Node ret1 = this;
+        for( Node ret : _inputs ) {
+            String name = ((ReturnNode)ret).fun()._name;
+            if( name==null || !name.startsWith("sys.") )
+                ret1 = ret1==this ? ((ReturnNode)ret) : null;
+        }
+        return ret1==this ? null : (ReturnNode)ret1;
     }
 
     @Override
@@ -49,7 +59,7 @@ public class StopNode extends CFGNode {
     public Node idealize() {
         int len = nIns();
         for( int i=0; i<nIns(); i++ )
-            if( ((ReturnNode)in(i)).fun().isDead() )
+            if( addDep(((ReturnNode)in(i)).fun()).isDead() )
                 delDef(i--);
         if( len != nIns() ) return this;
         return null;
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/arm/TFPARM.java b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/arm/TFPARM.java
index 16b56553..76e23c30 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/arm/TFPARM.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/arm/TFPARM.java
@@ -4,6 +4,7 @@ import com.seaofnodes.simple.*;
 import com.seaofnodes.simple.codegen.*;
 import com.seaofnodes.simple.node.ConstantNode;
 import com.seaofnodes.simple.node.MachNode;
+import com.seaofnodes.simple.node.Node;
 import com.seaofnodes.simple.node.cpus.riscv.riscv;
 import com.seaofnodes.simple.type.TypeFunPtr;
 
@@ -50,4 +51,5 @@ public class TFPARM extends ConstantNode implements MachNode, RIPRelSize {
         String reg = code.reg(this);
         _con.print(sb.p(reg).p(" #"));
     }
+    @Override public boolean eq(Node n) { return this==n; }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/riscv/TFPRISC.java b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/riscv/TFPRISC.java
index 17613009..a69cfbe8 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/riscv/TFPRISC.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/riscv/TFPRISC.java
@@ -4,6 +4,7 @@ import com.seaofnodes.simple.*;
 import com.seaofnodes.simple.codegen.*;
 import com.seaofnodes.simple.node.ConstantNode;
 import com.seaofnodes.simple.node.MachNode;
+import com.seaofnodes.simple.node.Node;
 import com.seaofnodes.simple.type.TypeFunPtr;
 
 public class TFPRISC extends ConstantNode implements MachNode, RIPRelSize {
@@ -51,5 +52,5 @@ public class TFPRISC extends ConstantNode implements MachNode, RIPRelSize {
     @Override public void asm(CodeGen code, SB sb) {
         _con.print(sb.p(code.reg(this)).p(" #"));
     }
-
+    @Override public boolean eq(Node n) { return this==n; }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TFPX86.java b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TFPX86.java
index be4d1a83..d7566f9e 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TFPX86.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TFPX86.java
@@ -63,4 +63,5 @@ public class TFPX86 extends ConstantNode implements MachNode, RIPRelSize {
         else
             _con.print(sb.p(reg).p(" = #"));
     }
+    @Override public boolean eq(Node n) { return this==n; }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TMPX86.java b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TMPX86.java
index 70b9dbb0..c44cf2f9 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TMPX86.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/TMPX86.java
@@ -31,4 +31,5 @@ public class TMPX86 extends ConstantNode implements MachNode, RIPRelSize{
     @Override public void asm(CodeGen code, SB sb) {
         _con.print(sb.p(code.reg(this)).p(" = #"));
     }
+    @Override public boolean eq(Node n) { return this==n; }
 }
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/x86_64_v2.java b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/x86_64_v2.java
index 0751a612..bf51f2cb 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/x86_64_v2.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/x86_64_v2.java
@@ -189,6 +189,7 @@ public class x86_64_v2 extends Machine {
     static RegMask callInMask( TypeFunPtr tfp, int idx ) {
         if( idx==0 ) return RPC_MASK;
         if( idx==1 ) return null;
+        if( idx-2 >= tfp.nargs() ) return null; // Anti-dependence
         return switch( CodeGen.CODE._callingConv ) {
         case "SystemV" -> callSys5 (tfp,idx);
         case "Win64"   -> callWin64(tfp,idx);
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 67de77ef..50d9166e 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp
+++ b/chapter22/src/main/java/com/seaofnodes/simple/sys/sys.smp
@@ -5,7 +5,7 @@ struct sys {
     // libc bindings
     /** https://www.man7.org/linux/man-pages/man2/<libc call>.2.html */
     struct libc {
-        // fd  buf   len -> len
+        // fd  buf len -> len
         {  i32 i64 i32 -> i32 } write = "C";
         // addr len prot flags fd  off -> void*
         {  i64  i64 i32  i32   i32 i32 -> i64 } mmap = "C";
@@ -17,4 +17,11 @@ struct sys {
         i32 MAP_PRIVATE = 2;
         i32 MAP_ANON = 32;
     };
+    struct io {
+        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);
+        };
+    };
 };
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter01Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter01Test.java
index cddbdfcf..ac9adacc 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter01Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter01Test.java
@@ -25,9 +25,9 @@ public class Chapter01Test {
     public void testZero() {
         CodeGen code = new CodeGen("return 0;");
         code.parse();
-        for( Node use : code._start._outputs )
-            if( use instanceof ConstantNode con && con._type instanceof TypeInteger )
-                assertEquals(TypeInteger.constant(0),con._type);
+        Node use = code.expr();
+        if( use instanceof ConstantNode con && con._type instanceof TypeInteger )
+            assertEquals(TypeInteger.constant(0),con._type);
     }
 
     @Test
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index 9c8ad66c..16634580 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -78,7 +78,7 @@ var sq = { int x ->
 return sq(arg)+sq(3);
 """);
         code.driver(Phase.LocalSched);
-        assertEquals("Stop[ return (#2+#2); return (Parm_x(sq,int)*x); ]", code._stop.toString());
+        assertEquals("Stop[ return (Parm_x(sq,int)*x); return (#2+#2); ]", code._stop.toString());
         assertEquals("13", Eval2.eval(code, 2));
     }
 
@@ -116,7 +116,7 @@ var fcn = arg ? { int x -> x*x; } : { int x -> x+x; };
 return fcn(3);
 """);
         code.parse().opto();
-        assertEquals("Stop[ return #2; return (Parm_x($fun1,int,3)*x); return (Parm_x($fun2,int,3)<<1); ]", code._stop.toString());
+        assertEquals("Stop[ return (Parm_x($fun2,int,3)<<1); return #2; return (Parm_x($fun1,int,3)*x); ]", code._stop.toString());
         assertEquals("6", Eval2.eval(code, 0));
         assertEquals("9", Eval2.eval(code, 1));
     }
@@ -126,7 +126,7 @@ return fcn(3);
     public void testFcn5() {
         CodeGen code = new CodeGen("val fact = { int x -> x <= 1 ? 1 : x*fact(x-1); }; return fact(arg);");
         code.parse().opto().typeCheck();
-        assertEquals("Stop[ return #2; return Phi(Region,1,(Parm_x(fact,int,arg,(x-1))*#2)); ]", code._stop.toString());
+        assertEquals("Stop[ return Phi(Region,1,(Parm_x(fact,int,arg,(x-1))*#2)); return #2; ]", code._stop.toString());
         assertEquals( "1", Eval2.eval(code, 0));
         assertEquals( "1", Eval2.eval(code, 1));
         assertEquals( "2", Eval2.eval(code, 2));
@@ -158,7 +158,7 @@ val g = {->2;};
 return 2;
 """);
         code.parse().opto().typeCheck().GCM();
-        assertEquals("Stop[ return 1; return 1; return 2; ]", code._stop.toString());
+        assertEquals("Stop[ return 2; return 1; return 1; ]", code._stop.toString());
         assertEquals("1", Eval2.eval(code,  0));
     }
 
@@ -176,7 +176,7 @@ for(;;) {
 }
 """);
         code.driver(Phase.LocalSched);
-        assertEquals("Stop[ return #2; return Parm_i(x,int); ]", code._stop.toString());
+        assertEquals("Stop[ return Parm_i(x,int); return #2; ]", code._stop.toString());
         assertEquals("3", Eval2.eval(code,  0));
     }
 
@@ -348,7 +348,7 @@ if (i2i) return i2i(arg);
 return f2f(o)(1);
 """);
         code.driver(Phase.LocalSched);
-        assertEquals("Stop[ return Phi(Region,#2,#2); return Parm_i(o,int); ]", code._stop.toString());
+        assertEquals("Stop[ return Parm_i(i2i.o,int); return Phi(Region,#2,#2); ]", code._stop.toString());
         assertEquals("1", Eval2.eval(code,  2));
     }
 
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter19Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter19Test.java
index f06d8a6a..c6a701a4 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter19Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter19Test.java
@@ -25,7 +25,7 @@ return 0;
     public void testString() throws IOException {
         String src = Files.readString(Path.of("src/test/java/com/seaofnodes/simple/progs/stringHash.smp"));
         CodeGen code = new CodeGen(src).parse().opto().typeCheck().GCM().localSched();
-        assertEquals("Stop[ return Phi(Region,._hashCode,Phi(Region,123456789,Phi(Loop,0,(.[]+((Phi_hash<<5)-Phi_hash))))); return Phi(Region,1,0,0,1); ]", code._stop.toString());
+        assertEquals("Stop[ return Phi(Region,1,0,0,1); return Phi(Region,._hashCode,Phi(Region,123456789,Phi(Loop,0,(.[]+((Phi_hash<<5)-Phi_hash))))); ]", code._stop.toString());
         //assertEquals("-4898613127354160978", Eval2.eval(code,  2));
     }
 
@@ -316,7 +316,7 @@ val fcn = arg ? { int x -> x*x; } : { int x -> x+x; };
 return fcn(2)*10 + fcn(3);
 """);
         code.driver(Phase.LocalSched,"x86_64_v2", "SystemV");
-        assertEquals("Stop[ return (add,#2,(muli,#2)); return (mul,Parm_x($fun1,int),x); return (shli,Parm_x($fun2,int)); ]", code.print());
+        assertEquals("Stop[ return (shli,Parm_x($fun2,int)); return (add,#2,(muli,#2)); return (mul,Parm_x($fun1,int),x); ]", code.print());
     }
 
     @Test
@@ -327,6 +327,6 @@ val sq = { int x -> x*x; };
 return sq(arg) + sq(3);
 """);
         code.driver(Phase.LocalSched,"x86_64_v2", "SystemV");
-        assertEquals("Stop[ return (add,#2,#2); return (mul,Parm_x(sq,int),x); ]", code.print());
+        assertEquals("Stop[ return (mul,Parm_x(sq,int),x); return (add,#2,#2); ]", code.print());
     }
 }
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter20Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter20Test.java
index f0b31065..4c4ac4e4 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter20Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter20Test.java
@@ -104,7 +104,7 @@ return sqrt(arg) + sqrt(cast_int);
         String src = Files.readString(Path.of("src/test/java/com/seaofnodes/simple/progs/stringHash.smp"));
         testCPU(src,"x86_64_v2", "SystemV", 9,null);
         testCPU(src,"riscv"    , "SystemV", 5,null);
-        testCPU(src,"arm"      , "SystemV", 6,null);
+        testCPU(src,"arm"      , "SystemV", 3,null);
     }
 
     @Test
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter21Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter21Test.java
index 96e6c5ff..c6e0a3bd 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter21Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter21Test.java
@@ -65,7 +65,7 @@ public class Chapter21Test {
         String src = Files.readString(Path.of("src/test/java/com/seaofnodes/simple/progs/stringHash.smp"));
         testCPU(src,"x86_64_v2", "SystemV", 9,null);
         testCPU(src,"riscv"    , "SystemV", 5,null);
-        testCPU(src,"arm"      , "SystemV", 6,null);
+        testCPU(src,"arm"      , "SystemV", 3,null);
     }
 
     @Test public void testStringExport() throws IOException {
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/progs/helloWorld.smp b/chapter22/src/test/java/com/seaofnodes/simple/progs/helloWorld.smp
index b83a055c..07ff935f 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/progs/helloWorld.smp
+++ b/chapter22/src/test/java/com/seaofnodes/simple/progs/helloWorld.smp
@@ -1,4 +1,3 @@
 // -*- mode: java;  -*-
-i64 buf = "Hello, World!";
-sys.libc.write(1,buf,13);
+sys.io.p("Hello, World!");
 return 0;
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/progs/jig.smp b/chapter22/src/test/java/com/seaofnodes/simple/progs/jig.smp
index b3bbf722..2d8d375b 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/progs/jig.smp
+++ b/chapter22/src/test/java/com/seaofnodes/simple/progs/jig.smp
@@ -1,10 +1,15 @@
 // -*- mode: java;  -*-
-struct s0 {
-    u16 v0;
-    i16 v3;
-    u32 v5;
+// theory: conservative approx to a CG will link all target fcsn.
+// unlinked *local* fcns with *no* TFP constants can be declared unreachable and removed.
+
+// Newtons approximation to the square root
+val sqrt = { int x ->
+    int guess = x;
+    while( 1 ) {
+        int next = (x/guess + guess)/2;
+        if( next == guess ) return guess;
+        guess = next;
+    }
 };
-return new s0.v3;
-if(0)
-    while(new s0.v5+new s0.v5) return 0;
-return new s0.v0;
+int cast_int = arg+2;
+return sqrt(arg) + sqrt(cast_int);