Implemented control flow graph loop analysis.

src/dk/camelot64/kickc/Compiler.java

@@ -110,8 +110,8 @@ public class Compiler {
       log.append(program.getGraph().toString(program.getScope()));
       pass2AssertSSA(program, log);
 
-      Pass3IdentifyLiveRanges pass3IdentifyLiveRanges = new Pass3IdentifyLiveRanges(program, log);
-      pass3IdentifyLiveRanges.findLiveRanges();
+      Pass3LiveRangesAnalysis pass3LiveRangesAnalysis = new Pass3LiveRangesAnalysis(program, log);
+      pass3LiveRangesAnalysis.findLiveRanges();
       log.append("CONTROL FLOW GRAPH - LIVE RANGES");
       log.append(program.getGraph().toString(program.getScope()));
       pass2AssertSSA(program, log);
@@ -121,13 +121,20 @@ public class Compiler {
       Pass2CullEmptyBlocks cullEmptyBlocks = new Pass2CullEmptyBlocks(program, log);
       cullEmptyBlocks.optimize();
       pass3BlockSequencePlanner.plan();
-      pass3IdentifyLiveRanges.findLiveRanges();
+      pass3LiveRangesAnalysis.findLiveRanges();
       log.append("CONTROL FLOW GRAPH - PHI MEM COALESCED");
       log.append(program.getGraph().toString(program.getScope()));
       pass2AssertSSA(program, log);
 
+      Pass3DominatorsAnalysis pass3DominatorsAnalysis = new Pass3DominatorsAnalysis(program, log);
+      pass3DominatorsAnalysis.findDominators();
+      log.append("DOMINATORS");
+      log.append(program.getGraph().getDominators().toString());
+
       Pass3LoopAnalysis pass3LoopAnalysis = new Pass3LoopAnalysis(program, log);
-      pass3LoopAnalysis.detectLoops();
+      pass3LoopAnalysis.findLoops();
+      log.append("NATURAL LOOPS");
+      log.append(program.getGraph().getLoopSet().toString());
 
    }
 

src/dk/camelot64/kickc/icl/ControlFlowBlock.java

@@ -5,6 +5,7 @@ import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
 /** A named/labelled sequence of SSA statements connected to other basic blocks.
@@ -158,4 +159,22 @@ public class ControlFlowBlock {
    }
 
 
+   /** Get all successors of the block
+    *
+    * @return All successors
+    */
+   @JsonIgnore
+   public Collection<LabelRef> getSuccessors() {
+      List<LabelRef> successors = new ArrayList<>();
+      if(defaultSuccessor!=null) {
+         successors.add(defaultSuccessor);
+      }
+      if(conditionalSuccessor!=null) {
+         successors.add(conditionalSuccessor);
+      }
+      if(callSuccessor!=null) {
+         successors.add(callSuccessor);
+      }
+      return successors;
+   }
 }

src/dk/camelot64/kickc/icl/ControlFlowGraph.java

@@ -13,6 +13,8 @@ public class ControlFlowGraph {
    private Map<LabelRef, ControlFlowBlock> blocks;
    private LabelRef firstBlockRef;
    private List<LabelRef> sequence;
+   private DominatorsGraph dominators;
+   private NaturalLoopSet loopSet;
 
    public ControlFlowGraph(Map<LabelRef, ControlFlowBlock> blocks, LabelRef firstBlockRef) {
       this.blocks = blocks;
@@ -175,4 +177,20 @@ public class ControlFlowGraph {
       return result;
    }
 
+   public void setDominators(DominatorsGraph dominators) {
+      this.dominators = dominators;
+   }
+
+   public DominatorsGraph getDominators() {
+      return dominators;
+   }
+
+   public void setLoops(NaturalLoopSet loopSet) {
+      this.loopSet = loopSet;
+   }
+
+   public NaturalLoopSet getLoopSet() {
+      return loopSet;
+   }
+
 }

src/dk/camelot64/kickc/icl/DominatorsBlock.java

@@ -0,0 +1,100 @@
+package dk.camelot64.kickc.icl;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+/** The Dominators for a specific block.
+ * <p>
+ * Definition: Block d dominates block i if all paths from entry to block i includes block d
+ * <p>
+ * See http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
+ * */
+public class DominatorsBlock {
+
+   /**
+    * Set containing the labels of all blocks that are dominators of the block.
+    */
+   Set<LabelRef> dominators;
+
+   public DominatorsBlock() {
+      this.dominators = new HashSet<>();
+   }
+
+   /**
+    * Add a single dominator
+    *
+    * @param dominator The dominator to add
+    */
+   public void add(LabelRef dominator) {
+      dominators.add(dominator);
+   }
+
+   /**
+    * Adds a bunch of dominators
+    *
+    * @param dominators The dominators to add
+    */
+   public void addAll(Collection<LabelRef> dominators) {
+      for (LabelRef dominator : dominators) {
+         add(dominator);
+      }
+
+   }
+
+   /**
+    * Modifies this set of dominators to be the intersection between this set and the passed set.
+    * Effectively removes all labels from this set that is not also present in the passed set.
+    *
+    * @param other The dominator set to intersect with
+    */
+   public void intersect(DominatorsBlock other) {
+      Iterator<LabelRef> iterator = dominators.iterator();
+      while (iterator.hasNext()) {
+         LabelRef dominator = iterator.next();
+         if (!other.contains(dominator)) {
+            iterator.remove();
+         }
+      }
+   }
+
+   /**
+    * Determines if the dominator set contains a specific block
+    *
+    * @param block The block to look for
+    * @return true if the dominator set contains the block
+    */
+   public boolean contains(LabelRef block) {
+      return dominators.contains(block);
+   }
+
+   public Set<LabelRef> getDominators() {
+      return dominators;
+   }
+
+   @Override
+   public boolean equals(Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+
+      DominatorsBlock that = (DominatorsBlock) o;
+
+      return dominators != null ? dominators.equals(that.dominators) : that.dominators == null;
+   }
+
+   @Override
+   public int hashCode() {
+      return dominators != null ? dominators.hashCode() : 0;
+   }
+
+   @Override
+   public String toString() {
+      StringBuilder out = new StringBuilder();
+      for (LabelRef dominator : dominators) {
+         out.append(dominator);
+         out.append(" ");
+      }
+      return out.toString();
+   }
+}

src/dk/camelot64/kickc/icl/DominatorsGraph.java

@@ -0,0 +1,69 @@
+package dk.camelot64.kickc.icl;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/** Dominators for a control flow graph.
+ * <p>
+ * Definition: Block d dominates block i if all paths from entry to block i includes block d
+ * <p>
+ * See http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
+ *
+ * */
+public class DominatorsGraph {
+
+   /**
+    * Maps block label to the dominators of the block.
+    */
+   Map<LabelRef, DominatorsBlock> blockDominators;
+
+   public DominatorsGraph() {
+      this.blockDominators = new LinkedHashMap<>();
+   }
+
+   /**
+    * Get the dominators for a specific block.
+    *
+    * @param block Label of the block
+    * @return The block dominators
+    */
+   public DominatorsBlock getDominators(LabelRef block) {
+      return blockDominators.get(block);
+   }
+
+   /**
+    * Creates dominators for a specific block
+    *
+    * @param block Label of the block
+    * @return The newly created block dominators
+    */
+   public DominatorsBlock addDominators(LabelRef block) {
+      DominatorsBlock dominatorsBlock = new DominatorsBlock();
+      this.blockDominators.put(block, dominatorsBlock);
+      return dominatorsBlock;
+   }
+
+
+   /**
+    * Set the dominators for a specific block
+    *
+    * @param block      The block
+    * @param dominators The new dominators
+    */
+   public void setDominators(LabelRef block, DominatorsBlock dominators) {
+      blockDominators.put(block, dominators);
+   }
+
+   @Override
+   public String toString() {
+      StringBuilder out = new StringBuilder();
+      for (LabelRef block : blockDominators.keySet()) {
+         DominatorsBlock dominators = getDominators(block);
+         out.append(block);
+         out.append(" dominated by  ");
+         out.append(dominators.toString());
+         out.append("\n");
+      }
+      return out.toString();
+   }
+}

src/dk/camelot64/kickc/icl/LiveRange.java

@@ -66,7 +66,7 @@ public class LiveRange {
    private Integer getIndex(Statement statement) {
       Integer index = statement.getIndex();
       if (index == null) {
-         throw new RuntimeException("Statement index not defined! Live Ranges only work after defining statement indexes (Pass3IdentifyLiveRanges.generateStatementIndexes).");
+         throw new RuntimeException("Statement index not defined! Live Ranges only work after defining statement indexes (Pass3LiveRangesAnalysis.generateStatementIndexes).");
       }
       return index;
    }

src/dk/camelot64/kickc/icl/NaturalLoop.java

@@ -0,0 +1,129 @@
+package dk.camelot64.kickc.icl;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+/**
+ * A single natural loop in a control flow graph.
+ */
+public class NaturalLoop {
+
+   /**
+    * The head of the natural loop. The block where control enters the loop and the block where the back edge returns to. Dominates all nodes in the loop.
+    */
+   private LabelRef head;
+
+   /**
+    * The tail(s) of the natural loop. The source(s) of the back edge.
+    * Normally there is only one tail in a loop - but loops with multiple tails occur when the loop body is split. An example
+    * <code>while(i!=0) { if(i<5) { tail1; } else { tail2; }}</code>
+    */
+   private Set<LabelRef> tails;
+
+   /**
+    * The blocks of the natural loop (including head and tail)
+    */
+   private Set<LabelRef> blocks;
+
+   /**
+    * Create a new natural loop.
+    * The loop is not filled with all blocks from the start, but only holds the head & tail.
+    *
+    * @param head The head block, start of the loop.
+    * @param tail The tail block, source of the back edge
+    */
+   public NaturalLoop(LabelRef head, LabelRef tail) {
+      this.head = head;
+      this.tails = new LinkedHashSet<>();
+      tails.add(tail);
+      this.blocks = null;
+   }
+
+   public LabelRef getHead() {
+      return head;
+   }
+
+   public Set<LabelRef> getTails() {
+      return tails;
+   }
+
+   public Set<LabelRef> getBlocks() {
+      return blocks;
+   }
+
+   public void setBlocks(Set<LabelRef> blocks) {
+      this.blocks = blocks;
+   }
+
+   @Override
+   public String toString() {
+      StringBuilder out = new StringBuilder();
+      out.append("Loop head: ")
+            .append(head)
+            .append(" tails: ");
+      for (LabelRef tail : tails) {
+         out.append(tail).append(" ");
+      }
+      out.append("blocks: ");
+      if (blocks != null) {
+         for (LabelRef block : blocks) {
+            out.append(block.toString()).append(" ");
+         }
+      } else {
+         out.append("null");
+      }
+      return out.toString();
+   }
+
+   /**
+    * Determines if this loop contains another loop - ie. if the other loops blocks are all contained in this loops blocks.
+    *
+    * @param other The other loop
+    * @return true if this loop contains the other loop
+    */
+   public boolean nests(NaturalLoop other) {
+      for (LabelRef otherBlock : other.getBlocks()) {
+         if (!blocks.contains(otherBlock)) {
+            return false;
+         }
+      }
+      return true;
+   }
+
+   /**
+    * Add more tails to the loop
+    * @param tails The tails to add
+    */
+   public void addTails(Set<LabelRef> tails) {
+      this.tails.addAll(tails);
+   }
+
+   /**
+    * Add more blocks to the loop
+    * @param blocks The blocks to add
+    */
+   public void addBlocks(Set<LabelRef> blocks) {
+      this.blocks.addAll(blocks);
+   }
+
+   @Override
+   public boolean equals(Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+
+      NaturalLoop that = (NaturalLoop) o;
+
+      if (head != null ? !head.equals(that.head) : that.head != null) return false;
+      if (tails != null ? !tails.equals(that.tails) : that.tails != null) return false;
+      return blocks != null ? blocks.equals(that.blocks) : that.blocks == null;
+   }
+
+   @Override
+   public int hashCode() {
+      int result = head != null ? head.hashCode() : 0;
+      result = 31 * result + (tails != null ? tails.hashCode() : 0);
+      result = 31 * result + (blocks != null ? blocks.hashCode() : 0);
+      return result;
+   }
+
+}

src/dk/camelot64/kickc/icl/NaturalLoopSet.java

@@ -0,0 +1,80 @@
+package dk.camelot64.kickc.icl;
+
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+/** A set of natural loops in a control flow graph.
+ * <p>For definitions and more see http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
+ * */
+public class NaturalLoopSet {
+
+   private List<NaturalLoop> loops;
+
+   public NaturalLoopSet() {
+      this.loops = new ArrayList<>();
+   }
+
+   /**
+    * Add a loop to the set
+    *
+    * @param loop The loop to add
+    */
+   public void addLoop(NaturalLoop loop) {
+      loops.add(loop);
+   }
+
+   /**
+    * Get all the loops
+    * @return The loops
+    */
+   public List<NaturalLoop> getLoops() {
+      return loops;
+   }
+
+   @Override
+   public String toString() {
+      StringBuilder out = new StringBuilder();
+      for (NaturalLoop loop : loops) {
+         out.append(loop.toString());
+         out.append("\n");
+      }
+      return out.toString();
+   }
+
+   /**
+    * Get all blocks that are heads of a loop
+    * @return The labels for all blocks that are head of a loop.
+    */
+   public Set<LabelRef> getLoopHeads() {
+      LinkedHashSet<LabelRef> heads = new LinkedHashSet<>();
+      for (NaturalLoop loop : loops) {
+         heads.add(loop.getHead());
+      }
+      return heads;
+   }
+
+   /**
+    * Get all loops with a given loop head
+    * @param loopHead The loop head
+    * @return Set with all loops that have the given head
+    */
+   public Set<NaturalLoop> getLoopsFromHead(LabelRef loopHead) {
+      LinkedHashSet<NaturalLoop> result = new LinkedHashSet<>();
+      for (NaturalLoop loop : loops) {
+         if(loopHead.equals(loop.getHead())) {
+            result.add(loop);
+         }
+      }
+      return result;
+   }
+
+   /**
+    * Remove a loop from the set
+    * @param loop The loop to remove
+    */
+   public void remove(NaturalLoop loop) {
+      this.loops.remove(loop);
+   }
+}

src/dk/camelot64/kickc/icl/Program.java

@@ -5,6 +5,7 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 
 /** A KickC Intermediate Compiler Language (ICL) Program */
 public class Program {
+
    /** The main scope. */
    private ProgramScope scope;
    /** The control flow graph. */

src/dk/camelot64/kickc/passes/Pass3DominatorsAnalysis.java

@@ -0,0 +1,84 @@
+package dk.camelot64.kickc.passes;
+
+import dk.camelot64.kickc.CompileLog;
+import dk.camelot64.kickc.icl.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Finds the dominators for the control flow graph. */
+public class Pass3DominatorsAnalysis {
+
+   private Program program;
+   private CompileLog log;
+
+   public Pass3DominatorsAnalysis(Program program, CompileLog log) {
+      this.program = program;
+      this.log = log;
+   }
+
+   public Program getProgram() {
+      return program;
+   }
+
+   public CompileLog getLog() {
+      return log;
+   }
+
+   /**
+    * Analyse the control flow graph to find dominators for all blocks.
+    * <p>
+    * Definition: d dom i if all paths from entry to node i include d
+    * <p>
+    * See http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
+    *
+    * @return The graph dominators
+    */
+   public void findDominators() {
+      DominatorsGraph dominatorsGraph = new DominatorsGraph();
+
+      // Initialize dominators: Dom[first]={first}, Dom[block]={all}
+      LabelRef firstBlock = program.getGraph().getFirstBlock().getLabel();
+      DominatorsBlock firstDominators = dominatorsGraph.addDominators(firstBlock);
+      firstDominators.add(firstBlock);
+      List<LabelRef> allBlocks = new ArrayList<>();
+      for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
+         allBlocks.add(block.getLabel());
+      }
+      for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
+         if (!block.getLabel().equals(firstBlock)) {
+            DominatorsBlock dominatorsBlock = dominatorsGraph.addDominators(block.getLabel());
+            dominatorsBlock.addAll(allBlocks);
+         }
+      }
+
+      // Iteratively refine dominators until they do not change
+      // For all nodes:
+      // Dom[n] = {n} UNION ( INTERSECT Dom[p] for all p that are predecessors of n)
+      boolean change = false;
+      do {
+         change = false;
+         for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
+            if (!block.getLabel().equals(firstBlock)) {
+               List<ControlFlowBlock> predecessors = program.getGraph().getPredecessors(block);
+               DominatorsBlock newDominators = new DominatorsBlock();
+               newDominators.addAll(allBlocks);
+               for (ControlFlowBlock predecessor : predecessors) {
+                  DominatorsBlock predecessorDominators = dominatorsGraph.getDominators(predecessor.getLabel());
+                  newDominators.intersect(predecessorDominators);
+               }
+               newDominators.add(block.getLabel());
+               DominatorsBlock currentDominators = dominatorsGraph.getDominators(block.getLabel());
+               if (!currentDominators.equals(newDominators)) {
+                  change = true;
+                  dominatorsGraph.setDominators(block.getLabel(), newDominators);
+               }
+            }
+         }
+
+      } while (change);
+      program.getGraph().setDominators(dominatorsGraph);
+   }
+
+
+}

src/dk/camelot64/kickc/passes/Pass3LiveRangesAnalysis.java

@@ -11,12 +11,12 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-public class Pass3IdentifyLiveRanges {
+public class Pass3LiveRangesAnalysis {
 
    private final Program program;
    private final CompileLog log;
 
-   public Pass3IdentifyLiveRanges(Program program, CompileLog log) {
+   public Pass3LiveRangesAnalysis(Program program, CompileLog log) {
       this.program = program;
       this.log = log;
    }

src/dk/camelot64/kickc/passes/Pass3LoopAnalysis.java

@@ -1,14 +1,15 @@
 package dk.camelot64.kickc.passes;
 
 import dk.camelot64.kickc.CompileLog;
-import dk.camelot64.kickc.icl.ControlFlowBlock;
-import dk.camelot64.kickc.icl.LabelRef;
-import dk.camelot64.kickc.icl.Program;
+import dk.camelot64.kickc.icl.*;
 
 import java.util.*;
 
 /**
- * Finds loops and nested loops in the control flow graph
+ * Finds loops and nested loops in the control flow graph.
+ * Uses the dominators of the graph to find loops.
+ * <p>
+ * See http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
  */
 public class Pass3LoopAnalysis {
 
@@ -28,194 +29,73 @@ public class Pass3LoopAnalysis {
       return log;
    }
 
-   public void detectLoops() {
-
-      GraphDominators graphDominators = analyseDominators();
-
-
-   }
-
    /**
-    * Analyse the control flow graph to find dominators for all blocks.
-    * <p>
-    * Definition: d dom i if all paths from entry to node i include d
+    * Finds loops and nested loops in the control flow graph.
+    * Uses the dominators of the graph to find loops.
     * <p>
     * See http://www.cs.colostate.edu/~cs553/ClassNotes/lecture09-control-dominators.ppt.pdf
-    *
-    * @return The graph dominators
     */
-   private GraphDominators analyseDominators() {
-      GraphDominators graphDominators = new GraphDominators();
+   public void findLoops() {
+      DominatorsGraph dominators = program.getGraph().getDominators();
+      Collection<ControlFlowBlock> blocks = program.getGraph().getAllBlocks();
 
-      // Initialize dominators: Dom[first]={first}, Dom[block]={all}
-      LabelRef firstBlock = program.getGraph().getFirstBlock().getLabel();
-      BlockDominators firstDominators = graphDominators.addDominators(firstBlock);
-      firstDominators.add(firstBlock);
-      List<LabelRef> allBlocks = new ArrayList<>();
-      for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
-         allBlocks.add(block.getLabel());
-      }
-      for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
-         if (!block.getLabel().equals(firstBlock)) {
-            BlockDominators blockDominators = graphDominators.addDominators(block.getLabel());
-            blockDominators.addAll(allBlocks);
-         }
-      }
-
-      // Iteratively refine dominators until they do not change
-      // For all nodes:
-      // Dom[n] = {n} UNION ( INTERSECT Dom[p] for all p that are predecessors of n)
-      boolean change = false;
-      do {
-         change = false;
-         for (ControlFlowBlock block : program.getGraph().getAllBlocks()) {
-            if (!block.getLabel().equals(firstBlock)) {
-               List<ControlFlowBlock> predecessors = program.getGraph().getPredecessors(block);
-               BlockDominators newDominators = new BlockDominators();
-               newDominators.addAll(allBlocks);
-               for (ControlFlowBlock predecessor : predecessors) {
-                  BlockDominators predecessorDominators = graphDominators.getDominators(predecessor.getLabel());
-                  newDominators.intersect(predecessorDominators);
-               }
-               newDominators.add(block.getLabel());
-               BlockDominators currentDominators = graphDominators.getDominators(block.getLabel());
-               if (!currentDominators.equals(newDominators)) {
-                  change = true;
-                  graphDominators.setDominators(block.getLabel(), newDominators);
-               }
-            }
-         }
-
-      } while (change);
-
-      return graphDominators;
-   }
-
-
-   public static class GraphDominators {
-
-      /**
-       * Maps block label to the dominators of the block.
-       */
-      Map<LabelRef, BlockDominators> blockDominators;
-
-      public GraphDominators() {
-         this.blockDominators = new LinkedHashMap<>();
-      }
-
-      /**
-       * Get the dominators for a specific block.
-       *
-       * @param block Label of the block
-       * @return The block dominators
-       */
-      public BlockDominators getDominators(LabelRef block) {
-         return blockDominators.get(block);
-      }
-
-      /**
-       * Creates dominators for a specific block
-       *
-       * @param block Label of the block
-       * @return The newly created block dominators
-       */
-      public BlockDominators addDominators(LabelRef block) {
-         BlockDominators blockDominators = new BlockDominators();
-         this.blockDominators.put(block, blockDominators);
-         return blockDominators;
-      }
-
-
-      /**
-       * Set the dominators for a specific block
-       *
-       * @param block      The block
-       * @param dominators The new dominators
-       */
-      public void setDominators(LabelRef block, BlockDominators dominators) {
-         blockDominators.put(block, dominators);
-      }
-   }
-
-   /**
-    * The Dominators for a specific block.
-    */
-   public static class BlockDominators {
-
-      /**
-       * Set containing the labels of all blocks that are dominators of the block.
-       */
-      Set<LabelRef> dominators;
-
-      public BlockDominators() {
-         this.dominators = new HashSet<>();
-      }
-
-      /**
-       * Add a single dominator
-       *
-       * @param dominator The dominator to add
-       */
-      public void add(LabelRef dominator) {
-         dominators.add(dominator);
-      }
-
-      /**
-       * Adds a bunch of dominators
-       *
-       * @param dominators The dominators to add
-       */
-      public void addAll(Collection<LabelRef> dominators) {
-         for (LabelRef dominator : dominators) {
-            add(dominator);
-         }
-
-      }
-
-      /**
-       * Modifies this set of dominators to be the intersection between this set and the passed set.
-       * Effectively removes all labels from this set that is not also present in the passed set.
-       *
-       * @param other The dominator set to intersect with
-       */
-      public void intersect(BlockDominators other) {
-         Iterator<LabelRef> iterator = dominators.iterator();
-         while (iterator.hasNext()) {
-            LabelRef dominator = iterator.next();
-            if (!other.contains(dominator)) {
-               iterator.remove();
+      // Look through graph for natural loop back edges
+      NaturalLoopSet loopSet = new NaturalLoopSet();
+      for (ControlFlowBlock block : blocks) {
+         DominatorsBlock blockDominators = dominators.getDominators(block.getLabel());
+         for (LabelRef successor : block.getSuccessors()) {
+            if (blockDominators.contains(successor)) {
+               // Found a loop back edge!
+               NaturalLoop loop = new NaturalLoop(successor, block.getLabel());
+               log.append("Found back edge: "+loop.toString());
+               loopSet.addLoop(loop);
             }
          }
       }
 
-      /**
-       * Determines if the dominator set contains a specific block
-       *
-       * @param block The block to look for
-       * @return true if the dominator set contains the block
-       */
-      private boolean contains(LabelRef block) {
-         return dominators.contains(block);
+      // Find all blocks for each loop
+      for (NaturalLoop loop : loopSet.getLoops()) {
+         Deque<LabelRef> todo = new ArrayDeque<>();
+         Set<LabelRef> loopBlocks = new LinkedHashSet<>();
+         todo.addAll(loop.getTails());
+         while(!todo.isEmpty()) {
+            LabelRef block = todo.pop();
+            loopBlocks.add(block);
+            if(block.equals(loop.getHead())) {
+               continue;
+            }
+            ControlFlowBlock controlFlowBlock = program.getGraph().getBlock(block);
+            List<ControlFlowBlock> predecessors = program.getGraph().getPredecessors(controlFlowBlock);
+            for (ControlFlowBlock predecessor : predecessors) {
+               if(!loopBlocks.contains(predecessor.getLabel()) && !todo.contains(predecessor.getLabel())) {
+                  todo.add(predecessor.getLabel());
+               }
+            }
+         }
+         loop.setBlocks(loopBlocks);
+         log.append("Populated: "+loop.toString());
       }
 
-      public Set<LabelRef> getDominators() {
-         return dominators;
-      }
-
-      @Override
-      public boolean equals(Object o) {
-         if (this == o) return true;
-         if (o == null || getClass() != o.getClass()) return false;
-
-         BlockDominators that = (BlockDominators) o;
-
-         return dominators != null ? dominators.equals(that.dominators) : that.dominators == null;
-      }
-
-      @Override
-      public int hashCode() {
-         return dominators != null ? dominators.hashCode() : 0;
+      // Coalesce loops that are neither nested, nor disjoint
+      for (NaturalLoop loop : loopSet.getLoops()) {
+         Set<NaturalLoop> headLoops = loopSet.getLoopsFromHead(loop.getHead());
+         for (NaturalLoop other : headLoops) {
+            if(other.equals(loop)) {
+               // Same loop - do not process
+               continue;
+            } else if(loop.nests(other) || other.nests(loop)) {
+               // One of the loops nest the other loop
+               continue;
+            } else {
+               // Two non-nested loops with a shared head - collect them to one loop
+               loop.addTails(other.getTails());
+               loop.addBlocks(other.getBlocks());
+               loopSet.remove(other);
+               log.append("Coalesced: "+loop.toString()) ;
+            }
+         }
       }
+      program.getGraph().setLoops(loopSet);
    }
 
 

src/dk/camelot64/kickc/test/TestCompilationOutput.java

@@ -48,6 +48,11 @@ public class TestCompilationOutput extends TestCase {
       tester.testFile("summin");
    }
 
+   public void testLoopSplit() throws IOException, URISyntaxException {
+      TestCompilationOutput tester = new TestCompilationOutput();
+      tester.testFile("loopsplit");
+   }
+
    private void testFile(String fileName) throws IOException, URISyntaxException {
       String inputPath = testPath + fileName + ".kc";
       System.out.println("Testing output for " + inputPath);

src/dk/camelot64/kickc/test/loopsplit.kc

@@ -0,0 +1,9 @@
+byte i=100;
+byte s=0;
+while(--i>0) {
+    if(i>50) {
+       s++;
+    } else {
+       s--;
+    }
+}

src/dk/camelot64/kickc/test/ref/bresenham.log

@@ -985,6 +985,18 @@ CONTROL FLOW GRAPH - PHI MEM COALESCED
   [10] (byte) e#2 ← (byte) e#1 - (byte) 39 [ x#1 cursor#2 e#2 y#1 ]
   to:@3
 
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@1 dominated by  @1 @BEGIN 
+@3 dominated by  @1 @BEGIN @3 
+@END dominated by  @1 @BEGIN @3 @END 
+@2 dominated by  @1 @BEGIN @2 
+
+Found back edge: Loop head: @1 tails: @3 blocks: null
+Populated: Loop head: @1 tails: @3 blocks: @3 @1 @2 
+NATURAL LOOPS
+Loop head: @1 tails: @3 blocks: @3 @1 @2 
+
 Initial phi equivalence classes
 [ cursor#3 cursor#5 cursor#1 cursor#2 ]
 [ x#2 x#1 ]

src/dk/camelot64/kickc/test/ref/flipper-rex2.log

@@ -3733,6 +3733,64 @@ prepare::@return: from prepare::@1
   [45] return  [ ]
   to:@RETURN
 
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@END dominated by  @BEGIN @END 
+main dominated by  @BEGIN main 
+main::@3 dominated by  @BEGIN main::@3 main 
+main::@4 dominated by  @BEGIN main::@4 main::@3 main 
+main::@6 dominated by  @BEGIN main::@4 main::@3 main::@6 main 
+main::@7 dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 
+main::@10 dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 main::@10 
+main::@11 dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 main::@10 main::@11 
+main::@return dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 main::@return main::@10 main::@11 
+plot dominated by  @BEGIN main::@4 main::@3 main::@6 plot main main::@7 main::@10 
+plot::@1 dominated by  @BEGIN main::@4 main::@3 main::@6 main plot main::@7 plot::@1 main::@10 
+plot::@2 dominated by  @BEGIN main::@4 main::@3 main::@6 main plot main::@7 plot::@2 plot::@1 main::@10 
+plot::@3 dominated by  @BEGIN main::@4 main::@3 main::@6 main plot main::@7 plot::@2 plot::@1 main::@10 plot::@3 
+plot::@return dominated by  @BEGIN main::@4 main::@3 plot::@return main::@6 main plot main::@7 plot::@2 plot::@1 main::@10 plot::@3 
+flip dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 flip 
+flip::@1 dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 flip::@1 flip 
+flip::@2 dominated by  @BEGIN main::@4 main::@3 main::@6 main main::@7 flip::@1 flip::@2 flip 
+flip::@4 dominated by  flip::@4 @BEGIN main::@4 main::@3 main::@6 main main::@7 flip::@1 flip::@2 flip 
+flip::@3 dominated by  flip::@4 flip::@3 @BEGIN main::@4 main::@3 main::@6 main main::@7 flip::@1 flip::@2 flip 
+flip::@return dominated by  flip::@4 flip::@3 @BEGIN main::@4 main::@3 main::@6 main main::@7 flip::@return flip::@1 flip::@2 flip 
+prepare dominated by  @BEGIN prepare main 
+prepare::@1 dominated by  @BEGIN prepare main prepare::@1 
+prepare::@return dominated by  @BEGIN prepare::@return prepare main prepare::@1 
+
+Found back edge: Loop head: main::@3 tails: main::@3 blocks: null
+Found back edge: Loop head: main::@4 tails: main::@4 blocks: null
+Found back edge: Loop head: main::@3 tails: main::@6 blocks: null
+Found back edge: Loop head: main::@3 tails: main::@11 blocks: null
+Found back edge: Loop head: plot::@2 tails: plot::@2 blocks: null
+Found back edge: Loop head: plot::@1 tails: plot::@3 blocks: null
+Found back edge: Loop head: flip::@2 tails: flip::@2 blocks: null
+Found back edge: Loop head: flip::@1 tails: flip::@4 blocks: null
+Found back edge: Loop head: flip::@3 tails: flip::@3 blocks: null
+Found back edge: Loop head: prepare::@1 tails: prepare::@1 blocks: null
+Populated: Loop head: main::@3 tails: main::@3 blocks: main::@3 
+Populated: Loop head: main::@4 tails: main::@4 blocks: main::@4 
+Populated: Loop head: main::@3 tails: main::@6 blocks: main::@6 main::@4 main::@3 
+Populated: Loop head: main::@3 tails: main::@11 blocks: main::@11 main::@10 main::@7 main::@6 main::@4 main::@3 
+Populated: Loop head: plot::@2 tails: plot::@2 blocks: plot::@2 
+Populated: Loop head: plot::@1 tails: plot::@3 blocks: plot::@3 plot::@2 plot::@1 
+Populated: Loop head: flip::@2 tails: flip::@2 blocks: flip::@2 
+Populated: Loop head: flip::@1 tails: flip::@4 blocks: flip::@4 flip::@2 flip::@1 
+Populated: Loop head: flip::@3 tails: flip::@3 blocks: flip::@3 
+Populated: Loop head: prepare::@1 tails: prepare::@1 blocks: prepare::@1 
+NATURAL LOOPS
+Loop head: main::@3 tails: main::@3 blocks: main::@3 
+Loop head: main::@4 tails: main::@4 blocks: main::@4 
+Loop head: main::@3 tails: main::@6 blocks: main::@6 main::@4 main::@3 
+Loop head: main::@3 tails: main::@11 blocks: main::@11 main::@10 main::@7 main::@6 main::@4 main::@3 
+Loop head: plot::@2 tails: plot::@2 blocks: plot::@2 
+Loop head: plot::@1 tails: plot::@3 blocks: plot::@3 plot::@2 plot::@1 
+Loop head: flip::@2 tails: flip::@2 blocks: flip::@2 
+Loop head: flip::@1 tails: flip::@4 blocks: flip::@4 flip::@2 flip::@1 
+Loop head: flip::@3 tails: flip::@3 blocks: flip::@3 
+Loop head: prepare::@1 tails: prepare::@1 blocks: prepare::@1 
+
 Initial phi equivalence classes
 [ main::c#2 main::c#1 ]
 [ plot::line#2 plot::line#1 ]

src/dk/camelot64/kickc/test/ref/loopmin.log

@@ -341,6 +341,18 @@ CONTROL FLOW GRAPH - PHI MEM COALESCED
   [5] (byte) s#1 ← (byte) s#2 + (byte) i#2 [ i#2 s#1 ]
   to:@3
 
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@1 dominated by  @1 @BEGIN 
+@3 dominated by  @1 @BEGIN @3 
+@END dominated by  @1 @BEGIN @3 @END 
+@2 dominated by  @1 @BEGIN @2 
+
+Found back edge: Loop head: @1 tails: @3 blocks: null
+Populated: Loop head: @1 tails: @3 blocks: @3 @1 @2 
+NATURAL LOOPS
+Loop head: @1 tails: @3 blocks: @3 @1 @2 
+
 Initial phi equivalence classes
 [ i#2 i#1 ]
 [ s#2 s#4 s#1 ]

src/dk/camelot64/kickc/test/ref/loopsplit.asm

@@ -0,0 +1,24 @@
+BBEGIN:
+B1_from_BBEGIN:
+  lda #0
+  sta 3
+  lda #100
+  sta 2
+B1:
+  dec 2
+  lda 2
+BEND:
+B2:
+  lda 2
+  cmp #50
+  beq !+
+  bcs B4
+!:
+B5:
+  dec 3
+B1_from_B5:
+  jmp B1
+B4:
+  inc 3
+B1_from_B4:
+  jmp B1

src/dk/camelot64/kickc/test/ref/loopsplit.cfg

@@ -0,0 +1,18 @@
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  [0] (byte) s#3 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) 0 ) [ i#2 s#3 ]
+  [0] (byte) i#2 ← phi( @4/(byte) i#1 @5/(byte) i#1 @BEGIN/(byte) 100 ) [ i#2 s#3 ]
+  [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]
+  [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]
+  to:@END
+@END: from @1
+@2: from @1
+  [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]
+  to:@5
+@5: from @2
+  [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]
+  to:@1
+@4: from @2
+  [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]
+  to:@1

src/dk/camelot64/kickc/test/ref/loopsplit.log

@@ -0,0 +1,564 @@
+byte i=100;
+byte s=0;
+while(--i>0) {
+    if(i>50) {
+       s++;
+    } else {
+       s--;
+    }
+}
+
+Adding pre/post-modifier (byte) i ← -- (byte) i
+Adding pre/post-modifier (byte) s ← ++ (byte) s
+Adding pre/post-modifier (byte) s ← -- (byte) s
+PROGRAM
+  (byte) i ← (byte) 100
+  (byte) s ← (byte) 0
+@1:
+  (byte) i ← -- (byte) i
+  (boolean~) $0 ← (byte) i > (byte) 0
+  if((boolean~) $0) goto @2
+  goto @3
+@2:
+  (boolean~) $1 ← (byte) i > (byte) 50
+  if((boolean~) $1) goto @4
+  goto @5
+@4:
+  (byte) s ← ++ (byte) s
+  goto @6
+@5:
+  (byte) s ← -- (byte) s
+@6:
+  goto @1
+@3:
+
+SYMBOLS
+(boolean~) $0
+(boolean~) $1
+(label) @1
+(label) @2
+(label) @3
+(label) @4
+(label) @5
+(label) @6
+(byte) i
+(byte) s
+
+INITIAL CONTROL FLOW GRAPH
+@BEGIN: from
+  (byte) i ← (byte) 100
+  (byte) s ← (byte) 0
+  to:@1
+@1: from @6 @BEGIN
+  (byte) i ← -- (byte) i
+  (boolean~) $0 ← (byte) i > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@7
+@2: from @1 @8
+  (boolean~) $1 ← (byte) i > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@9
+@7: from @1
+  to:@3
+@3: from @12 @7
+  to:@END
+@8: from
+  to:@2
+@4: from @10 @2
+  (byte) s ← ++ (byte) s
+  to:@6
+@9: from @2
+  to:@5
+@5: from @11 @9
+  (byte) s ← -- (byte) s
+  to:@6
+@10: from
+  to:@4
+@6: from @4 @5
+  to:@1
+@11: from
+  to:@5
+@12: from
+  to:@3
+@END: from @3
+
+Removing empty block @7
+Removing empty block @3
+Removing empty block @8
+Removing empty block @9
+Removing empty block @10
+Removing empty block @6
+Removing empty block @11
+Removing empty block @12
+CONTROL FLOW GRAPH
+@BEGIN: from
+  (byte) i ← (byte) 100
+  (byte) s ← (byte) 0
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) i ← -- (byte) i
+  (boolean~) $0 ← (byte) i > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (boolean~) $1 ← (byte) i > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) s ← ++ (byte) s
+  to:@1
+@5: from @2
+  (byte) s ← -- (byte) s
+  to:@1
+@END: from @1
+
+CONTROL FLOW GRAPH WITH ASSIGNMENT CALL
+@BEGIN: from
+  (byte) i ← (byte) 100
+  (byte) s ← (byte) 0
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) i ← -- (byte) i
+  (boolean~) $0 ← (byte) i > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (boolean~) $1 ← (byte) i > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) s ← ++ (byte) s
+  to:@1
+@5: from @2
+  (byte) s ← -- (byte) s
+  to:@1
+@END: from @1
+
+Completing Phi functions...
+Completing Phi functions...
+Completing Phi functions...
+CONTROL FLOW GRAPH SSA
+@BEGIN: from
+  (byte) i#0 ← (byte) 100
+  (byte) s#0 ← (byte) 0
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#6 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) s#0 )
+  (byte) i#2 ← phi( @4/(byte) i#4 @5/(byte) i#5 @BEGIN/(byte) i#0 )
+  (byte) i#1 ← -- (byte) i#2
+  (boolean~) $0 ← (byte) i#1 > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (byte) s#5 ← phi( @1/(byte) s#6 )
+  (byte) i#3 ← phi( @1/(byte) i#1 )
+  (boolean~) $1 ← (byte) i#3 > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) i#4 ← phi( @2/(byte) i#3 )
+  (byte) s#3 ← phi( @2/(byte) s#5 )
+  (byte) s#1 ← ++ (byte) s#3
+  to:@1
+@5: from @2
+  (byte) i#5 ← phi( @2/(byte) i#3 )
+  (byte) s#4 ← phi( @2/(byte) s#5 )
+  (byte) s#2 ← -- (byte) s#4
+  to:@1
+@END: from @1
+
+CONTROL FLOW GRAPH WITH ASSIGNMENT CALL & RETURN
+@BEGIN: from
+  (byte) i#0 ← (byte) 100
+  (byte) s#0 ← (byte) 0
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#6 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) s#0 )
+  (byte) i#2 ← phi( @4/(byte) i#4 @5/(byte) i#5 @BEGIN/(byte) i#0 )
+  (byte) i#1 ← -- (byte) i#2
+  (boolean~) $0 ← (byte) i#1 > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (byte) s#5 ← phi( @1/(byte) s#6 )
+  (byte) i#3 ← phi( @1/(byte) i#1 )
+  (boolean~) $1 ← (byte) i#3 > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) i#4 ← phi( @2/(byte) i#3 )
+  (byte) s#3 ← phi( @2/(byte) s#5 )
+  (byte) s#1 ← ++ (byte) s#3
+  to:@1
+@5: from @2
+  (byte) i#5 ← phi( @2/(byte) i#3 )
+  (byte) s#4 ← phi( @2/(byte) s#5 )
+  (byte) s#2 ← -- (byte) s#4
+  to:@1
+@END: from @1
+
+Constant (byte) i#0 (byte) 100
+Constant (byte) s#0 (byte) 0
+Succesful SSA optimization Pass2ConstantPropagation
+CONTROL FLOW GRAPH
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#6 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) 0 )
+  (byte) i#2 ← phi( @4/(byte) i#4 @5/(byte) i#5 @BEGIN/(byte) 100 )
+  (byte) i#1 ← -- (byte) i#2
+  (boolean~) $0 ← (byte) i#1 > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (byte) s#5 ← phi( @1/(byte) s#6 )
+  (byte) i#3 ← phi( @1/(byte) i#1 )
+  (boolean~) $1 ← (byte) i#3 > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) i#4 ← phi( @2/(byte) i#3 )
+  (byte) s#3 ← phi( @2/(byte) s#5 )
+  (byte) s#1 ← ++ (byte) s#3
+  to:@1
+@5: from @2
+  (byte) i#5 ← phi( @2/(byte) i#3 )
+  (byte) s#4 ← phi( @2/(byte) s#5 )
+  (byte) s#2 ← -- (byte) s#4
+  to:@1
+@END: from @1
+
+Alias (byte) i#1 = (byte) i#3 (byte) i#4 (byte) i#5 
+Alias (byte) s#3 = (byte) s#5 (byte) s#6 (byte) s#4 
+Succesful SSA optimization Pass2AliasElimination
+CONTROL FLOW GRAPH
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#3 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) 0 )
+  (byte) i#2 ← phi( @4/(byte) i#1 @5/(byte) i#1 @BEGIN/(byte) 100 )
+  (byte) i#1 ← -- (byte) i#2
+  (boolean~) $0 ← (byte) i#1 > (byte) 0
+  if((boolean~) $0) goto @2
+  to:@END
+@2: from @1
+  (boolean~) $1 ← (byte) i#1 > (byte) 50
+  if((boolean~) $1) goto @4
+  to:@5
+@4: from @2
+  (byte) s#1 ← ++ (byte) s#3
+  to:@1
+@5: from @2
+  (byte) s#2 ← -- (byte) s#3
+  to:@1
+@END: from @1
+
+Simple Condition (boolean~) $0 if((byte) i#1>(byte) 0) goto @2
+Simple Condition (boolean~) $1 if((byte) i#1>(byte) 50) goto @4
+Succesful SSA optimization Pass2ConditionalJumpSimplification
+CONTROL FLOW GRAPH
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#3 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) 0 )
+  (byte) i#2 ← phi( @4/(byte) i#1 @5/(byte) i#1 @BEGIN/(byte) 100 )
+  (byte) i#1 ← -- (byte) i#2
+  if((byte) i#1>(byte) 0) goto @2
+  to:@END
+@2: from @1
+  if((byte) i#1>(byte) 50) goto @4
+  to:@5
+@4: from @2
+  (byte) s#1 ← ++ (byte) s#3
+  to:@1
+@5: from @2
+  (byte) s#2 ← -- (byte) s#3
+  to:@1
+@END: from @1
+
+Block Sequence Planned @BEGIN @1 @END @2 @5 @4 
+Block Sequence Planned @BEGIN @1 @END @2 @5 @4 
+CONTROL FLOW GRAPH - PHI LIFTED
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  (byte) s#3 ← phi( @4/(byte~) s#7 @5/(byte~) s#8 @BEGIN/(byte) 0 )
+  (byte) i#2 ← phi( @4/(byte~) i#6 @5/(byte~) i#7 @BEGIN/(byte) 100 )
+  (byte) i#1 ← -- (byte) i#2
+  if((byte) i#1>(byte) 0) goto @2
+  to:@END
+@END: from @1
+@2: from @1
+  if((byte) i#1>(byte) 50) goto @4
+  to:@5
+@5: from @2
+  (byte) s#2 ← -- (byte) s#3
+  (byte~) i#7 ← (byte) i#1
+  (byte~) s#8 ← (byte) s#2
+  to:@1
+@4: from @2
+  (byte) s#1 ← ++ (byte) s#3
+  (byte~) i#6 ← (byte) i#1
+  (byte~) s#7 ← (byte) s#1
+  to:@1
+
+Propagating live ranges...
+Propagating live ranges...
+Propagating live ranges...
+Propagating live ranges...
+CONTROL FLOW GRAPH - LIVE RANGES
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  [0] (byte) s#3 ← phi( @4/(byte~) s#7 @5/(byte~) s#8 @BEGIN/(byte) 0 ) [ i#2 s#3 ]
+  [0] (byte) i#2 ← phi( @4/(byte~) i#6 @5/(byte~) i#7 @BEGIN/(byte) 100 ) [ i#2 s#3 ]
+  [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]
+  [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]
+  to:@END
+@END: from @1
+@2: from @1
+  [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]
+  to:@5
+@5: from @2
+  [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]
+  [5] (byte~) i#7 ← (byte) i#1 [ i#7 s#2 ]
+  [6] (byte~) s#8 ← (byte) s#2 [ i#7 s#8 ]
+  to:@1
+@4: from @2
+  [7] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]
+  [8] (byte~) i#6 ← (byte) i#1 [ i#6 s#1 ]
+  [9] (byte~) s#7 ← (byte) s#1 [ i#6 s#7 ]
+  to:@1
+
+Created 2 initial phi equivalence classes
+Coalesced [5] i#7 ← i#1
+Coalesced [6] s#8 ← s#2
+Coalesced (already) [8] i#6 ← i#1
+Coalesced [9] s#7 ← s#1
+Coalesced down to 2 phi equivalence classes
+Block Sequence Planned @BEGIN @1 @END @2 @5 @4 
+Propagating live ranges...
+Propagating live ranges...
+Propagating live ranges...
+Propagating live ranges...
+CONTROL FLOW GRAPH - PHI MEM COALESCED
+@BEGIN: from
+  to:@1
+@1: from @4 @5 @BEGIN
+  [0] (byte) s#3 ← phi( @4/(byte) s#1 @5/(byte) s#2 @BEGIN/(byte) 0 ) [ i#2 s#3 ]
+  [0] (byte) i#2 ← phi( @4/(byte) i#1 @5/(byte) i#1 @BEGIN/(byte) 100 ) [ i#2 s#3 ]
+  [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]
+  [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]
+  to:@END
+@END: from @1
+@2: from @1
+  [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]
+  to:@5
+@5: from @2
+  [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]
+  to:@1
+@4: from @2
+  [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]
+  to:@1
+
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@1 dominated by  @1 @BEGIN 
+@END dominated by  @1 @BEGIN @END 
+@2 dominated by  @1 @BEGIN @2 
+@5 dominated by  @1 @BEGIN @2 @5 
+@4 dominated by  @1 @BEGIN @2 @4 
+
+Found back edge: Loop head: @1 tails: @5 blocks: null
+Found back edge: Loop head: @1 tails: @4 blocks: null
+Populated: Loop head: @1 tails: @5 blocks: @5 @2 @1 
+Populated: Loop head: @1 tails: @4 blocks: @4 @2 @1 
+Coalesced: Loop head: @1 tails: @5 @4 blocks: @5 @2 @1 @4 
+NATURAL LOOPS
+Loop head: @1 tails: @5 @4 blocks: @5 @2 @1 @4 
+
+Initial phi equivalence classes
+[ i#2 i#1 ]
+[ s#3 s#1 s#2 ]
+Copy Coalesced equivalence classes
+[ i#2 i#1 ]
+[ s#3 s#1 s#2 ]
+Complete equivalence classes
+[ i#2 i#1 ]
+[ s#3 s#1 s#2 ]
+Allocated zp byte:2 to [ i#2 i#1 ]
+Allocated zp byte:3 to [ s#3 s#1 s#2 ]
+INITIAL ASM
+BBEGIN:
+B1_from_BBEGIN:
+  // (byte) s#3 = (byte) 0  // zpby1=coby1
+  lda #0
+  sta 3
+  // (byte) i#2 = (byte) 100  // zpby1=coby1
+  lda #100
+  sta 2
+  jmp B1
+B1:
+  // [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]  //  zpby1=_dec_zpby1
+  dec 2
+  // [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]  //  zpby1_gt_0_then_la1
+  lda 2
+  bne B2
+  jmp BEND
+BEND:
+B2:
+  // [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]  //  zpby1_gt_coby1_then_la1
+  lda 2
+  cmp #50
+  beq !+
+  bcs B4
+!:
+  jmp B5
+B5:
+  // [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]  //  zpby1=_dec_zpby1
+  dec 3
+B1_from_B5:
+  // (byte) s#3 = (byte) s#2  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+B4:
+  // [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]  //  zpby1=_inc_zpby1
+  inc 3
+B1_from_B4:
+  // (byte) s#3 = (byte) s#1  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+
+Removing instruction jmp B1
+Removing instruction jmp BEND
+Removing instruction jmp B5
+Succesful ASM optimization Pass5NextJumpElimination
+ASSEMBLER
+BBEGIN:
+B1_from_BBEGIN:
+  // (byte) s#3 = (byte) 0  // zpby1=coby1
+  lda #0
+  sta 3
+  // (byte) i#2 = (byte) 100  // zpby1=coby1
+  lda #100
+  sta 2
+B1:
+  // [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]  //  zpby1=_dec_zpby1
+  dec 2
+  // [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]  //  zpby1_gt_0_then_la1
+  lda 2
+  bne B2
+BEND:
+B2:
+  // [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]  //  zpby1_gt_coby1_then_la1
+  lda 2
+  cmp #50
+  beq !+
+  bcs B4
+!:
+B5:
+  // [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]  //  zpby1=_dec_zpby1
+  dec 3
+B1_from_B5:
+  // (byte) s#3 = (byte) s#2  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+B4:
+  // [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]  //  zpby1=_inc_zpby1
+  inc 3
+B1_from_B4:
+  // (byte) s#3 = (byte) s#1  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+
+Removing instruction bne B2
+Succesful ASM optimization Pass5NextJumpElimination
+ASSEMBLER
+BBEGIN:
+B1_from_BBEGIN:
+  // (byte) s#3 = (byte) 0  // zpby1=coby1
+  lda #0
+  sta 3
+  // (byte) i#2 = (byte) 100  // zpby1=coby1
+  lda #100
+  sta 2
+B1:
+  // [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]  //  zpby1=_dec_zpby1
+  dec 2
+  // [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]  //  zpby1_gt_0_then_la1
+  lda 2
+BEND:
+B2:
+  // [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]  //  zpby1_gt_coby1_then_la1
+  lda 2
+  cmp #50
+  beq !+
+  bcs B4
+!:
+B5:
+  // [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]  //  zpby1=_dec_zpby1
+  dec 3
+B1_from_B5:
+  // (byte) s#3 = (byte) s#2  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+B4:
+  // [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]  //  zpby1=_inc_zpby1
+  inc 3
+B1_from_B4:
+  // (byte) s#3 = (byte) s#1  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+
+FINAL SYMBOL TABLE
+(label) @1
+(label) @2
+(label) @4
+(label) @5
+(label) @BEGIN
+(label) @END
+(byte) i
+(byte) i#1 zp byte:2
+(byte) i#2 zp byte:2
+(byte) s
+(byte) s#1 zp byte:3
+(byte) s#2 zp byte:3
+(byte) s#3 zp byte:3
+
+FINAL CODE
+BBEGIN:
+B1_from_BBEGIN:
+  // (byte) s#3 = (byte) 0  // zpby1=coby1
+  lda #0
+  sta 3
+  // (byte) i#2 = (byte) 100  // zpby1=coby1
+  lda #100
+  sta 2
+B1:
+  // [1] (byte) i#1 ← -- (byte) i#2 [ i#1 s#3 ]  //  zpby1=_dec_zpby1
+  dec 2
+  // [2] if((byte) i#1>(byte) 0) goto @2 [ i#1 s#3 ]  //  zpby1_gt_0_then_la1
+  lda 2
+BEND:
+B2:
+  // [3] if((byte) i#1>(byte) 50) goto @4 [ i#1 s#3 ]  //  zpby1_gt_coby1_then_la1
+  lda 2
+  cmp #50
+  beq !+
+  bcs B4
+!:
+B5:
+  // [4] (byte) s#2 ← -- (byte) s#3 [ i#1 s#2 ]  //  zpby1=_dec_zpby1
+  dec 3
+B1_from_B5:
+  // (byte) s#3 = (byte) s#2  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+B4:
+  // [5] (byte) s#1 ← ++ (byte) s#3 [ i#1 s#1 ]  //  zpby1=_inc_zpby1
+  inc 3
+B1_from_B4:
+  // (byte) s#3 = (byte) s#1  // register copy 
+  // (byte) i#2 = (byte) i#1  // register copy 
+  jmp B1
+

src/dk/camelot64/kickc/test/ref/loopsplit.sym

@@ -0,0 +1,13 @@
+(label) @1
+(label) @2
+(label) @4
+(label) @5
+(label) @BEGIN
+(label) @END
+(byte) i
+(byte) i#1 zp byte:2
+(byte) i#2 zp byte:2
+(byte) s
+(byte) s#1 zp byte:3
+(byte) s#2 zp byte:3
+(byte) s#3 zp byte:3

src/dk/camelot64/kickc/test/ref/minus.log

@@ -263,6 +263,16 @@ CONTROL FLOW GRAPH - PHI MEM COALESCED
   to:@END
 @END: from @1
 
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@1 dominated by  @1 @BEGIN 
+@END dominated by  @1 @BEGIN @END 
+
+Found back edge: Loop head: @1 tails: @1 blocks: null
+Populated: Loop head: @1 tails: @1 blocks: @1 
+NATURAL LOOPS
+Loop head: @1 tails: @1 blocks: @1 
+
 Initial phi equivalence classes
 [ i#2 i#1 ]
 Copy Coalesced equivalence classes

src/dk/camelot64/kickc/test/ref/summin.log

@@ -298,6 +298,15 @@ sum::@return: from sum
   [4] return (byte) s1#0 [ ]
   to:@RETURN
 
+DOMINATORS
+@BEGIN dominated by  @BEGIN 
+@2 dominated by  @BEGIN @2 
+@END dominated by  @BEGIN @2 @END 
+sum dominated by  @BEGIN sum 
+sum::@return dominated by  @BEGIN sum::@return sum 
+
+NATURAL LOOPS
+
 Initial phi equivalence classes
 [ sum::a#2 ]
 [ sum::b#2 ]