Remove unused definition only for synthetic variables

Bug: 18911912

Change-Id: I2530afc929431ccc4229daac5cbd218fc1b499b0
(cherry picked from commit d4f6789ff777d219c3411aec1104df17dba85eba)

4 files changed, 103 insertions, 1 deletions

diff --git a/jack-tests/tests/com/android/jack/AllTests.java b/jack-tests/tests/com/android/jack/AllTests.java
index 47b7a08..f1e39bd 100644
--- a/jack-tests/tests/com/android/jack/AllTests.java
+++ b/jack-tests/tests/com/android/jack/AllTests.java
@@ -47,6 +47,7 @@ import com.android.jack.nopackage.NoPackageTests;
 import com.android.jack.opcodes.OpcodesTests;
 import com.android.jack.optimizations.exprsimplifier.ExprsimplifierTests;
 import com.android.jack.optimizations.notsimplifier.NotsimplifierTests;
+import com.android.jack.optimizations.unuseddef.UnusedDefTest;
 import com.android.jack.optimizations.uselesscopy.UselessVariableCopyTest;
 import com.android.jack.order.OrderTests;
 import com.android.jack.preprocessor.PreProcessorTests;
@@ -134,6 +135,7 @@ import org.junit.runners.Suite.SuiteClasses;
     TryfinallyTests.class,
     TypeTests.class,
     UnaryTests.class,
+    UnusedDefTest.class,
     UselessVariableCopyTest.class,
     VerifyTests.class,
     WithPhantomTests.class,
diff --git a/jack-tests/tests/com/android/jack/optimizations/unuseddef/UnusedDefTest.java b/jack-tests/tests/com/android/jack/optimizations/unuseddef/UnusedDefTest.java
new file mode 100644
index 0000000..3fda172
--- /dev/null
+++ b/jack-tests/tests/com/android/jack/optimizations/unuseddef/UnusedDefTest.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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 com.android.jack.optimizations.unuseddef;
+
+import com.android.jack.TestTools;
+import com.android.jack.test.junit.KnownIssue;
+import com.android.jack.test.toolchain.AbstractTestTools;
+import com.android.jack.test.toolchain.JackBasedToolchain;
+
+import junit.framework.Assert;
+
+import org.jf.dexlib.CodeItem;
+import org.jf.dexlib.DexFile;
+import org.jf.dexlib.Code.Instruction;
+import org.jf.dexlib.Code.Opcode;
+import org.junit.Test;
+
+import java.io.File;
+
+import javax.annotation.Nonnull;
+
+public class UnusedDefTest {
+
+  /**
+   * Verify that generated dex contains a 'const_4' instruction corresponding to 'o = null'
+   * instruction.
+   */
+  @Test
+  @KnownIssue
+  public void test001() throws Exception {
+    File out = AbstractTestTools.createTempDir();
+    File outDex = new File(out, "classes.dex");
+    JackBasedToolchain toolchain = AbstractTestTools.getCandidateToolchain(JackBasedToolchain.class);
+    toolchain.disableDxOptimizations();
+    toolchain.addToClasspath(toolchain.getDefaultBootClasspath())
+    .srcToExe(out, /* zipFile = */ false,
+        AbstractTestTools.getTestRootDir("com.android.jack.optimizations.unuseddef.test001.jack"));
+
+    DexFile dexFile = new DexFile(outDex);
+    CodeItem ci =
+        TestTools.getEncodedMethod(dexFile,
+            "Lcom/android/jack/optimizations/unuseddef/test001/jack/Test001;", "test",
+            "()V").codeItem;
+
+    Assert.assertTrue(hasOpcode(ci, Opcode.CONST_4));
+  }
+
+  private boolean hasOpcode(@Nonnull CodeItem codeItem, @Nonnull Opcode opcode) {
+    for (Instruction inst : codeItem.getInstructions()) {
+      if (inst.opcode == opcode) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+}
diff --git a/jack-tests/tests/com/android/jack/optimizations/unuseddef/test001/jack/Test001.java b/jack-tests/tests/com/android/jack/optimizations/unuseddef/test001/jack/Test001.java
new file mode 100644
index 0000000..ce53880
--- /dev/null
+++ b/jack-tests/tests/com/android/jack/optimizations/unuseddef/test001/jack/Test001.java
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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 com.android.jack.optimizations.unuseddef.test001.jack;
+
+public class Test001 {
+
+  /**
+   * Check that 'o = null' always exists in generated code.
+   */
+  public void test() {
+    Object o = new Object();
+    o = null;
+  }
+
+}
diff --git a/jack/src/com/android/jack/optimizations/UnusedDefinitionRemover.java b/jack/src/com/android/jack/optimizations/UnusedDefinitionRemover.java
index cfc65d2..9706c0f 100644
--- a/jack/src/com/android/jack/optimizations/UnusedDefinitionRemover.java
+++ b/jack/src/com/android/jack/optimizations/UnusedDefinitionRemover.java
@@ -79,7 +79,7 @@ public class UnusedDefinitionRemover implements RunnableSchedulable<JMethod> {
           && !rhs.canThrow()) {
 
         DefinitionMarker dm = binary.getMarker(DefinitionMarker.class);
-        if (dm != null && dm.isUnused()) {
+        if (dm != null && dm.isUnused() && dm.getDefinedVariable().isSynthetic()) {
           assert !(binary.getLhs() instanceof JFieldRef || binary.getLhs() instanceof JArrayRef);
           removeUnusedDefinition((JAsgOperation) binary);
         }