Some minor fixes found via fuzzing (#60)

4 files changed, 19 insertions, 10 deletions

diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/IfNode.java b/chapter08/src/main/java/com/seaofnodes/simple/node/IfNode.java
index e573010d..1d1da4fa 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/IfNode.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/IfNode.java
@@ -46,7 +46,7 @@ public class IfNode extends MultiNode {
             return prior instanceof ProjNode proj
               // Repeated test, dominated on one side.  Test result is the same.
               ? (proj._idx==0 ? TypeTuple.IF_TRUE : TypeTuple.IF_FALSE)
-              : null;           // Repeated test not dominated on one side
+              : dom._type;      // Repeated test not dominated on one side
         
         return TypeTuple.IF_BOTH;
     }
diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java
index 22b6f264..fd312c3d 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -140,10 +140,8 @@ public abstract class Node {
         sb.append("\n");
     }
 
-    public final String p(int depth) {
-        return IRPrinter.prettyPrint(this,depth);
-    }
-
+    public String p(int depth) { return IRPrinter.prettyPrint(this,depth); }
+    
     public boolean isMultiHead() { return false; }
     public boolean isMultiTail() { return false; }
     
diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/PhiNode.java b/chapter08/src/main/java/com/seaofnodes/simple/node/PhiNode.java
index e6cf338b..975630d0 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/PhiNode.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/PhiNode.java
@@ -85,10 +85,13 @@ public class PhiNode extends Node {
      */
     private Node singleUniqueInput() {
         Node live = null;
-        for( int i=1; i<nIns(); i++ ) 
+        for( int i=1; i<nIns(); i++ ) {
+            if( region() instanceof LoopNode loop && loop.entry()._type == Type.XCONTROL )
+                return null;    // Dead entry loops just ignore and let the loop collapse
             if( region().in(i)._type != Type.XCONTROL && in(i) != this )
                 if( live == null || live == in(i) ) live = in(i);
                 else return null;
+        }
         return live;
     }
 
diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/ScopeNode.java b/chapter08/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
index 3c4a2088..a6a7f536 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
@@ -202,14 +202,22 @@ public class ScopeNode extends Node {
                 PhiNode phi = (PhiNode)in(i);
                 assert phi.region()==ctrl && phi.in(2)==null;
                 phi.setDef(2,back.in(i));
-                // Do an eager useless-phi removal
-                Node in = phi.peephole();
-                if( in != phi )
-                    phi.subsume(in);
             }
             if( exit.in(i) == this ) // Replace a lazy-phi on the exit path also
                 exit.setDef(i,in(i));
         }
         back.kill();            // Loop backedge is dead
+        // Now one-time do a useless-phi removal
+        for( int i=1; i<nIns(); i++ ) {
+            if( in(i) instanceof PhiNode phi ) {
+                // Do an eager useless-phi removal
+                Node in = phi.peephole();
+                if( in != phi ) {
+                    phi.subsume(in);
+                    setDef(i,in); // Set the update back into Scope
+                }
+            }
+        }
+
     }
 }