From a2b6c2be588a5d68c37c3663b78ea2012d48bb59 Mon Sep 17 00:00:00 2001
From: Alexey Andreev <konsoletyper@gmail.com>
Date: Wed, 26 Jun 2019 13:41:21 +0300
Subject: [PATCH] Fix bug in liveness analysis

---
 .../teavm/model/util/LivenessAnalyzer.java    | 42 ++++++++-----------
 1 file changed, 18 insertions(+), 24 deletions(-)

diff --git a/core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java b/core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java
index 541c149e6..ec86ceaea 100644
--- a/core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java
+++ b/core/src/main/java/org/teavm/model/util/LivenessAnalyzer.java
@@ -17,10 +17,11 @@ package org.teavm.model.util;
 
 import com.carrotsearch.hppc.IntHashSet;
 import com.carrotsearch.hppc.IntSet;
-import java.util.ArrayDeque;
+import com.carrotsearch.hppc.IntStack;
 import java.util.BitSet;
-import java.util.Deque;
+import org.teavm.common.DominatorTree;
 import org.teavm.common.Graph;
+import org.teavm.common.GraphUtils;
 import org.teavm.model.BasicBlock;
 import org.teavm.model.Incoming;
 import org.teavm.model.Instruction;
@@ -46,6 +47,7 @@ public class LivenessAnalyzer {
 
     public void analyze(Program program) {
         Graph cfg = ProgramUtils.buildControlFlowGraph(program);
+        DominatorTree dominatorTree = GraphUtils.buildDominatorTree(cfg);
         liveVars = new BitSet[cfg.size()];
         liveOutVars = new BitSet[cfg.size()];
         for (int i = 0; i < liveVars.length; ++i) {
@@ -55,7 +57,7 @@ public class LivenessAnalyzer {
 
         UsageExtractor usageExtractor = new UsageExtractor();
         DefinitionExtractor defExtractor = new DefinitionExtractor();
-        Deque<Task> stack = new ArrayDeque<>();
+        IntStack stack = new IntStack();
         int[] definitions = new int[program.variableCount()];
         for (int i = 0; i < program.basicBlockCount(); ++i) {
             BasicBlock block = program.basicBlockAt(i);
@@ -68,10 +70,8 @@ public class LivenessAnalyzer {
                 insn.acceptVisitor(usageExtractor);
                 IntSet usedVars = new IntHashSet();
                 for (Variable var : usageExtractor.getUsedVariables()) {
-                    Task task = new Task();
-                    task.block = i;
-                    task.var = var.getIndex();
-                    stack.push(task);
+                    stack.push(i);
+                    stack.push(var.getIndex());
                     usedVars.add(var.getIndex());
                 }
                 insn.acceptVisitor(defExtractor);
@@ -85,25 +85,24 @@ public class LivenessAnalyzer {
             for (Phi phi : block.getPhis()) {
                 definitions[phi.getReceiver().getIndex()] = i;
                 for (Incoming incoming : phi.getIncomings()) {
-                    Task task = new Task();
-                    task.block = incoming.getSource().getIndex();
-                    task.var = incoming.getValue().getIndex();
-                    stack.push(task);
+                    stack.push(incoming.getSource().getIndex());
+                    stack.push(incoming.getValue().getIndex());
                 }
             }
         }
 
         while (!stack.isEmpty()) {
-            Task task = stack.pop();
-            if (liveVars[task.block].get(task.var) || definitions[task.var] == task.block) {
+            int variable = stack.pop();
+            int block = stack.pop();
+            BitSet blockLiveVars = liveVars[block];
+            if (blockLiveVars.get(variable) || definitions[variable] == block
+                    || !dominatorTree.dominates(definitions[variable], block)) {
                 continue;
             }
-            liveVars[task.block].set(task.var, true);
-            for (int pred : cfg.incomingEdges(task.block)) {
-                Task nextTask = new Task();
-                nextTask.block = pred;
-                nextTask.var = task.var;
-                stack.push(nextTask);
+            liveVars[block].set(variable, true);
+            for (int pred : cfg.incomingEdges(block)) {
+                stack.push(pred);
+                stack.push(variable);
             }
         }
 
@@ -119,9 +118,4 @@ public class LivenessAnalyzer {
             }
         }
     }
-
-    private static class Task {
-        int block;
-        int var;
-    }
 }