From c8ac2a8b982ffb31a6998c2e32b054a572d61dc4 Mon Sep 17 00:00:00 2001
From: konsoletyper <konsoletyper@gmail.com>
Date: Fri, 10 Jan 2014 17:10:58 +0400
Subject: [PATCH] Adds liveness analyzer (incomplete)

---
 .../teavm/model/util/LivenessAnalyzer.java    | 91 +++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 teavm-core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java

diff --git a/teavm-core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java b/teavm-core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java
new file mode 100644
index 000000000..2f8525a82
--- /dev/null
+++ b/teavm-core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java
@@ -0,0 +1,91 @@
+/*
+ *  Copyright 2014 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.DominatorTree;
+import org.teavm.common.Graph;
+import org.teavm.common.GraphUtils;
+import org.teavm.model.Program;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class LivenessAnalyzer {
+    private BackNode[] backNodeGraph;
+    private int[] domLeft;
+    private int[] domRight;
+
+    public void analyze(Program program) {
+        Graph cfg = ProgramUtils.buildControlFlowGraph(program);
+        DominatorTree domTree = GraphUtils.buildDominatorTree(cfg);
+        Graph domGraph = GraphUtils.buildDominatorGraph(domTree, cfg.size());
+        computeDomLeftRight(domGraph);
+        prepareBackGraph(domTree, cfg);
+    }
+
+    private void computeDomLeftRight(Graph domGraph) {
+        domLeft = new int[domGraph.size()];
+        domRight = new int[domGraph.size()];
+        int index = 1;
+        int[] stack = new int[domGraph.size() * 2];
+        int top = 0;
+        for (int i = domGraph.size(); i >= 0; --i) {
+            if (domGraph.incomingEdgesCount(i) == 0) {
+                stack[top++] = i;
+            }
+        }
+        while (top > 0) {
+            int v = stack[top--];
+            if (domLeft[v] == 0) {
+                domLeft[v] = index++;
+                for (int succ : domGraph.outgoingEdges(v)) {
+                    stack[top++] = succ;
+                }
+            } else if (domRight[v] == 0) {
+                domRight[v] = index++;
+                if (domGraph.incomingEdgesCount(0) > 0) {
+                    stack[top++] = domGraph.incomingEdges(v)[0];
+                }
+            }
+        }
+    }
+
+    private void prepareBackGraph(DominatorTree domTree, Graph cfg) {
+        backNodeGraph = new BackNode[cfg.size() * 2];
+        int[] stack = new int[cfg.size() * 2];
+        int top = 0;
+        for (int i = 0; i < cfg.size(); ++i) {
+            if (cfg.outgoingEdgesCount(i) == 0) {
+                stack[top++] = i;
+            }
+        }
+        while (top > 0) {
+
+        }
+    }
+
+    private boolean dominates(int a, int b) {
+        return domLeft[a] <= domLeft[b] && domRight[a] >= domRight[b];
+    }
+
+    private static class BackNode {
+        final List<BackNode> successors = new ArrayList<>();
+        int blockIndex;
+    }
+}