Merge Cliff's fixes (#59)

* #52 Update chapter8 to align with chapter7

* #52 Update chapter8 to align with chapter7

* #52 Fix spacing

* #51 get started on break and continue

* #51 get started on break and continue

* #51 more on break and continue

* #51 more on break and continue

* #51 more on break and continue

* #51 more on break and continue

* #51 more on break and continue

* #51 more on break and continue

* break & continue scopes are made lazily, and merged into as discovered

Drop ContBreak.
Drop ScopeNode.addScope.
Add a simple mergeScopes.
Simplify Region.inProgress; drop from child classes, use in Region.
Add a ConstantNode.XCONTROL shortcut.

* Fix some regressions

* Error on dead code after break/continue

* A more robust dead-def check

* Fix for dead loop-back path

* Fix scope shadowing bug with continue/break

Turn on LAZY phis by default; fix minor golden test results

* Fix a case with both break & continue

* #51 more on break and continue

* #51 more on break and continue

* #51 more on break and continue

* #51 fix erroneous push of scope

* #51 fix import

* #51 update test expected results

* #51 Start Chapter8 writeup

* #51 Start Chapter8 writeup

* #51 _scope needs killing after continue

* Add graph evaluator (#56)

* #51 wip writeup

* #51 wip writeup

* #51 wip writeup

* #51 wip writeup

* #51 wip writeup

* #51 update code comments / add assertion

* #51 revert assertion

* #51 evaluate graph to verify test outcome

* #51 add code snippets

* #51 add examples

* Cleanup README

Comment for usefullness of true Loops.
Try to distiguish `PhiNode` as the programming construct from `phi` as the mathematically SSA notation.
Flow long lines.
Remove LAZY flag, set as `true`.  Fold up true tests.

* minor comment

* #51 Check _breakScope is not null when parsing break or continue to detect use outside of loop

* #51 in parseComparison we need to move the op= version above the op version, since at this time using <= and >= does not work since they are parsed as > and < with a preceeding = which causes an error

* #51 Update main README to link to chapter 8

* Remove useless test

* Fix regression for dead infinite loop

Add shortcut to fancy IRPrettyPrint

---------

Co-authored-by: Cliff Click <cliffc@acm.org>
Co-authored-by: XmiliaH <45106915+XmiliaH@users.noreply.github.com>

4 files changed, 28 insertions, 1 deletions

diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/AddNode.java b/chapter08/src/main/java/com/seaofnodes/simple/node/AddNode.java
index d23fa7c5..5878f340 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/AddNode.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/AddNode.java
@@ -69,6 +69,11 @@ public class AddNode extends Node {
             return spline_cmp(lhs,rhs) ? swap12() : phiCon(this,true);
 
         // Now we only see (add add non)
+
+        // Dead data cycle; comes about from dead infinite loops.  Do nothing,
+        // the loop will peep as dead after a bit.
+        if( lhs.in(1) == lhs )
+            return null;
         
         // Do we have (x + con1) + con2?
         // Replace with (x + (con1+con2) which then fold the constants
diff --git a/chapter08/src/main/java/com/seaofnodes/simple/node/LoopNode.java b/chapter08/src/main/java/com/seaofnodes/simple/node/LoopNode.java
index 0ed32464..0b84f897 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/LoopNode.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/LoopNode.java
@@ -15,6 +15,12 @@ public class LoopNode extends RegionNode {
     public String label() { return "Loop"; }
 
     @Override
+    public Type compute() {
+        if( inProgress() ) return Type.CONTROL;
+        return entry()._type;
+    }
+
+    @Override
     public Node idealize() {
         return inProgress() ? null : super.idealize();
     }
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 bc772fb5..22b6f264 100644
--- a/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter08/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.simple.IRPrinter;
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.type.Type;
 
@@ -100,6 +101,7 @@ public abstract class Node {
     public final String print() {
         return _print0(new StringBuilder(), new BitSet()).toString();
     }
+    
     // This is the common print: check for repeats, check for DEAD and print
     // "DEAD" else call the per-Node print1.
     final StringBuilder _print0(StringBuilder sb, BitSet visited) {
@@ -138,6 +140,10 @@ public abstract class Node {
         sb.append("\n");
     }
 
+    public final String p(int depth) {
+        return IRPrinter.prettyPrint(this,depth);
+    }
+
     public boolean isMultiHead() { return false; }
     public boolean isMultiTail() { return false; }
     
@@ -441,7 +447,10 @@ public abstract class Node {
      * Used to allow repeating tests in the same JVM.  This just resets the
      * Node unique id generator, and is done as part of making a new Parser.
      */
-    public static void reset() { UNIQUE_ID = 1; _disablePeephole=false; }
+    public static void reset() {
+        UNIQUE_ID = 1;
+        _disablePeephole=false;
+    }
 
     /**
      * Debugging utility to find a Node by index
diff --git a/chapter08/src/test/java/com/seaofnodes/simple/Chapter08Test.java b/chapter08/src/test/java/com/seaofnodes/simple/Chapter08Test.java
index 16f7e324..057742c5 100644
--- a/chapter08/src/test/java/com/seaofnodes/simple/Chapter08Test.java
+++ b/chapter08/src/test/java/com/seaofnodes/simple/Chapter08Test.java
@@ -139,6 +139,13 @@ return arg;
     }
 
     @Test
+    public void testChapter8Regress2() {
+        Parser parser = new Parser("if(1) return 0;  else while(arg>--arg) arg=arg+1; return 0;");
+        StopNode stop = parser.parse(true);
+        assertEquals("Stop[ return 0; return 0; ]", stop.toString());
+    }
+    
+    @Test
     public void testChapter8BreakOutsideLoop() {
         try { 
             new Parser("""