Stronger inf loop assert

Handle returning value after inf loop.
Loop nesting check does not use depth until after loop tree is built.
ASMPrint can be called no machine.

7 files changed, 17 insertions, 7 deletions

diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/Encoding.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
index 335715c6..8c894f8a 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/Encoding.java
@@ -250,6 +250,7 @@ public class Encoding {
                 _rpo_cfg(f,visit,rpo);
             }
         }
+        assert rpo._len>0 || bb instanceof ReturnNode;
         rpo.add(bb);
     }
 
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
index 40bb626d..c81eb9b5 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
@@ -56,7 +56,7 @@ public abstract class GlobalCodeMotion {
                     FunNode fun = null;
                     boolean done=true;
                     for( Node use : con.outs() ) {
-                        FunNode fun2 = use.cfg0().fun();
+                        FunNode fun2 = use instanceof ReturnNode ret ? ret.fun() : use.cfg0().fun();
                         if( fun==null || fun==fun2 ) fun=fun2;
                         else { done=false; break; }
                     }
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/node/CFGNode.java b/chapter21/src/main/java/com/seaofnodes/simple/node/CFGNode.java
index f198e65c..0b97c574 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/node/CFGNode.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/node/CFGNode.java
@@ -108,7 +108,7 @@ public abstract class CFGNode extends Node {
 
     LoopTree _ltree;
     public int _pre;            // Pre-order numbers for loop tree finding
-    private static class LoopTree {
+    static class LoopTree {
         LoopTree _par;
         final LoopNode _head;
         int _depth;
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/node/LoopNode.java b/chapter21/src/main/java/com/seaofnodes/simple/node/LoopNode.java
index 787b43d2..3a57fde7 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/node/LoopNode.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/node/LoopNode.java
@@ -40,7 +40,7 @@ public class LoopNode extends RegionNode {
         while( x != this ) {
             if( x instanceof CProjNode exit && exit.in(0) instanceof IfNode iff ) {
                 CFGNode other = iff.cproj(1-exit._idx);
-                if( other!=null && other.loopDepth() < loopDepth() )
+                if( other!=null && other._ltree != _ltree && nested(_ltree,other._ltree) )
                     return stop; // Found an exit, not an infinite loop
             }
             x = x.idom();
@@ -86,4 +86,12 @@ public class LoopNode extends RegionNode {
 
         return stop;
     }
+
+    private static boolean nested(LoopTree inner, LoopTree outer) {
+        for( ; inner!=null; inner = inner._par )
+            if( inner == outer )
+                return true;
+        return false;
+    }
+
 }
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter21/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index f0b7d49e..6fa76ef8 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -29,7 +29,7 @@ public class ReturnNode extends CFGNode {
     public Node mem () { return in(1); }
     public Node expr() { return in(2); }
     public Node rpc () { return in(3); }
-    public FunNode fun() { return _fun; }
+    @Override public FunNode fun() { return _fun; }
 
     @Override
     public String label() { return "Return"; }
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java b/chapter21/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
index d9b0ec36..b39e2705 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/print/ASMPrinter.java
@@ -71,7 +71,7 @@ public abstract class ASMPrinter {
     static private final int opWidth = 5;
     static private final int argWidth = 30;
     static int doBlock(int iadr, SB sb, CodeGen code, FunNode fun, int cfgidx) {
-        final int encWidth = code._mach.defaultOpSize()*2;
+        final int encWidth = code._mach==null ? 2 : code._mach.defaultOpSize()*2;
         CFGNode bb = code._cfg.at(cfgidx);
         if( bb != fun && !(bb instanceof IfNode) && !(bb instanceof CallEndNode) && !(bb instanceof CallNode)  && !(bb instanceof CProjNode && bb.in(0) instanceof CallEndNode ))
             sb.p(label(bb)).p(":").nl();
@@ -110,12 +110,12 @@ public abstract class ASMPrinter {
     }
 
     static int doInst( int iadr, SB sb, CodeGen code, int cfgidx, Node n, boolean postAlloc, boolean postEncode ) {
-        if( n instanceof CProjNode ) return iadr;
+        if( n==null || n instanceof CProjNode ) return iadr;
         if( postAlloc && n instanceof CalleeSaveNode ) return iadr;
         if( postEncode && n instanceof ProjNode ) return iadr;
         if( n instanceof MemMergeNode ) return iadr;
         if( n.getClass() == ConstantNode.class ) return iadr; // Default placeholders
-        final int dopz = code._mach.defaultOpSize();
+        final int dopz = code._mach==null ? 2 : code._mach.defaultOpSize();
         final int encWidth = dopz*2;
 
         // All blocks ending in a Region will need to either fall into or jump
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/print/IRPrinter.java b/chapter21/src/main/java/com/seaofnodes/simple/print/IRPrinter.java
index c91f844b..b171e9f7 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/print/IRPrinter.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/print/IRPrinter.java
@@ -16,6 +16,7 @@ public abstract class IRPrinter {
     // NNID NNAME DDEF DDEF  [[  UUSE UUSE  ]]  TYPE
     // 1234 sssss 1234 1234 1234 1234 1234 1234 tttttt
     public static SB printLine( Node n, SB sb ) {
+        if( n==null ) return sb;
         sb.p("%4d %-7.7s ".formatted(n._nid,n.label()));
         if( n._inputs==null )
             return sb.p("DEAD\n");