From a882a4c95615d34388cda30c17a54c245a4c84b8 Mon Sep 17 00:00:00 2001
From: konsoletyper <konsoletyper@gmail.com>
Date: Sat, 21 Feb 2015 21:51:04 +0400
Subject: [PATCH] Begin implementing irreducible cfg node splitting. Implement
 DJ graph.

---
 .../main/java/org/teavm/common/DJGraph.java   | 89 +++++++++++++++++++
 .../model/util/IrreducibleGraphConverter.java | 47 ++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 teavm-core/src/main/java/org/teavm/common/DJGraph.java
 create mode 100644 teavm-core/src/main/java/org/teavm/model/util/IrreducibleGraphConverter.java

diff --git a/teavm-core/src/main/java/org/teavm/common/DJGraph.java b/teavm-core/src/main/java/org/teavm/common/DJGraph.java
new file mode 100644
index 000000000..0ece52948
--- /dev/null
+++ b/teavm-core/src/main/java/org/teavm/common/DJGraph.java
@@ -0,0 +1,89 @@
+/*
+ *  Copyright 2015 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.common;
+
+/**
+ *
+ * @author Alexey Andreev <konsoletyper@gmail.com>
+ */
+public class DJGraph {
+    private DominatorTree domTree;
+    private Graph graph;
+    private Graph backEdges;
+
+    public DJGraph(Graph src) {
+        domTree = GraphUtils.buildDominatorTree(src);
+        buildGraph(src);
+        dfs();
+    }
+
+    private void buildGraph(Graph graph) {
+        GraphBuilder builder = new GraphBuilder(graph.size());
+        for (int i = 0; i < graph.size(); ++i) {
+            for (int j : graph.outgoingEdges(i)) {
+                builder.addEdge(i, j);
+            }
+        }
+        for (int i = 1; i < graph.size(); ++i) {
+            int j = domTree.immediateDominatorOf(i);
+            boolean needsDomEdge = true;
+            for (int k : graph.incomingEdges(i)) {
+                if (k == j) {
+                    needsDomEdge = false;
+                    break;
+                }
+            }
+            if (needsDomEdge) {
+                builder.addEdge(j, i);
+            }
+        }
+        graph = builder.build();
+    }
+
+    private void dfs() {
+        GraphBuilder builder = new GraphBuilder();
+        boolean[] visited = new boolean[graph.size()];
+        IntegerStack stack = new IntegerStack(graph.size() * 2);
+        stack.push(0);
+        stack.push(-1);
+        while (!stack.isEmpty()) {
+            int node = stack.pop();
+            int source = stack.pop();
+            if (visited[node]) {
+                builder.addEdge(node, source);
+                continue;
+            }
+            visited[node] = true;
+            for (int succ : graph.outgoingEdges(node)) {
+                stack.push(node);
+                stack.push(succ);
+            }
+        }
+        backEdges = builder.build();
+    }
+
+    public DominatorTree getDomTree() {
+        return domTree;
+    }
+
+    public Graph getGraph() {
+        return graph;
+    }
+
+    public int[] getSpanningTreeBackEdges(int node) {
+        return backEdges.outgoingEdges(node);
+    }
+}
diff --git a/teavm-core/src/main/java/org/teavm/model/util/IrreducibleGraphConverter.java b/teavm-core/src/main/java/org/teavm/model/util/IrreducibleGraphConverter.java
new file mode 100644
index 000000000..8f9190aa9
--- /dev/null
+++ b/teavm-core/src/main/java/org/teavm/model/util/IrreducibleGraphConverter.java
@@ -0,0 +1,47 @@
+/*
+ *  Copyright 2015 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.model.util;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.teavm.common.DisjointSet;
+import org.teavm.common.Graph;
+import org.teavm.common.MutableGraphNode;
+
+/**
+ *
+ * @author Alexey Andreev <konsoletyper@gmail.com>
+ */
+public class IrreducibleGraphConverter {
+    List<MutableGraphNode> nodes = new ArrayList<>();
+    DisjointSet nodeClasses = new DisjointSet();
+
+    public void convertToReducible(Graph graph) {
+        buildMutableCFG(graph);
+    }
+
+    private void buildMutableCFG(Graph graph) {
+        nodes.clear();
+        for (int i = 0; i < graph.size(); ++i) {
+            nodes.add(new MutableGraphNode(i));
+        }
+        for (int i = 0; i < graph.size(); ++i) {
+            for (int j : graph.outgoingEdges(i)) {
+                nodes.get(i).connect(nodes.get(j));
+            }
+        }
+    }
+}