Refined redundant null check optimization

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/BoxingInterpreter.java

@@ -55,7 +55,7 @@ public class BoxingInterpreter extends OptimizationBasicInterpreter {
     }
 
     @NotNull
-    private BoxedBasicValue createNewBoxing(
+    protected BasicValue createNewBoxing(
             @NotNull AbstractInsnNode insn, @NotNull Type type,
             @Nullable ProgressionIteratorBasicValue progressionIterator
     ) {
@@ -201,7 +201,7 @@ public class BoxingInterpreter extends OptimizationBasicInterpreter {
         return super.unaryOperation(insn, value);
     }
 
-    private static boolean isExactValue(@NotNull BasicValue value) {
+    protected boolean isExactValue(@NotNull BasicValue value) {
         return value instanceof ProgressionIteratorBasicValue ||
                value instanceof BoxedBasicValue ||
                (value.getType() != null && isProgressionClass(value.getType().getInternalName()));

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/NullabilityInterpreter.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * 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.jetbrains.kotlin.codegen.optimization.boxing
+
+import org.jetbrains.org.objectweb.asm.tree.InsnList
+import org.jetbrains.org.objectweb.asm.tree.analysis.BasicValue
+import org.jetbrains.kotlin.codegen.optimization.common.BasicValueWrapper
+import org.jetbrains.org.objectweb.asm.Type
+import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode
+import org.jetbrains.org.objectweb.asm.Opcodes
+
+public class NullabilityInterpreter(insns: InsnList) : BoxingInterpreter(insns) {
+    override fun unaryOperation(insn: AbstractInsnNode, value: BasicValue) = makeNotNullIfNeeded(insn, super.unaryOperation(insn, value))
+
+    override fun newOperation(insn: AbstractInsnNode) = makeNotNullIfNeeded(insn, super.newOperation(insn))
+
+    override fun isExactValue(value: BasicValue) = super.isExactValue(value) || value is NotNullBasicValue
+
+    override fun createNewBoxing(insn: AbstractInsnNode, type: Type, progressionIterator: ProgressionIteratorBasicValue?) = 
+            NotNullBasicValue(BasicValue(type))
+}
+
+private fun makeNotNullIfNeeded(insn: AbstractInsnNode, value: BasicValue?): BasicValue? =
+    when (insn.getOpcode()) {
+        Opcodes.ANEWARRAY, Opcodes.NEWARRAY, Opcodes.LDC, Opcodes.NEW -> NotNullBasicValue(value)
+        else -> value
+    }
+
+class NotNullBasicValue(wrappedValue: BasicValue?) : BasicValueWrapper(wrappedValue) {
+    override fun equals(other: Any?): Boolean = other is NotNullBasicValue
+}

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/RedundantNullCheckMethodTransformer.java

@@ -39,7 +39,7 @@ public class RedundantNullCheckMethodTransformer extends MethodTransformer {
         InsnList insnList = methodNode.instructions;
         Frame<BasicValue>[] frames = analyze(
                 internalClassName, methodNode,
-                new BoxingInterpreter(insnList)
+                new NullabilityInterpreter(insnList)
         );
 
         List<AbstractInsnNode> insnsToOptimize = new ArrayList<AbstractInsnNode>();
@@ -49,8 +49,7 @@ public class RedundantNullCheckMethodTransformer extends MethodTransformer {
             AbstractInsnNode insn = insnList.get(i);
 
             if ((insn.getOpcode() == Opcodes.IFNULL || insn.getOpcode() == Opcodes.IFNONNULL) &&
-                frame != null && frame.getStack(frame.getStackSize() - 1) instanceof BoxedBasicValue) {
+                frame != null && frame.getStack(frame.getStackSize() - 1) instanceof NotNullBasicValue) {
-
                 insnsToOptimize.add(insn);
             }
         }

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/common/Util.kt

@@ -69,3 +69,11 @@ fun MethodNode.prepareForEmitting() {
         current = prev
     }
 }
+
+abstract class BasicValueWrapper(val wrappedValue: BasicValue?) : BasicValue(wrappedValue?.getType()) {
+    val basicValue: BasicValue? get() = (wrappedValue as? BasicValueWrapper)?.basicValue ?: wrappedValue
+
+    override fun equals(other: Any?): Boolean {
+        return super.equals(other) && this.javaClass == other?.javaClass
+    }
+}

compiler/testData/codegen/bytecodeText/deadCodeElimination/arrayConstructor.kt

@@ -0,0 +1,8 @@
+fun box() {
+    val x = Array(1) { "" }
+}
+
+// 0 IFNULL
+// 0 IFNONNULL
+// 0 ATHROW
+// 0 throwNpe

compiler/testData/codegen/bytecodeText/deadCodeElimination/boxing.kt

@@ -1,3 +1,5 @@
+class A
+
 fun foo(x: Any?) {}
 
 fun box() {
@@ -8,6 +10,9 @@ fun box() {
     z!!
 
     foo(1 as java.lang.Integer)
+    
+    val y: Any? = if (1 == 1) x else A()
+    y!!
 }
 
 // 0 IFNULL

compiler/testData/codegen/bytecodeText/deadCodeElimination/literal.kt

@@ -0,0 +1,12 @@
+fun box() {
+    val x: Any? = "abc"
+    val y: Any? = if (1 == 1) x else "cde"
+    
+    x!!
+    y!!
+}
+
+// 0 IFNULL
+// 0 IFNONNULL
+// 0 throwNpe
+// 0 ATHROW

compiler/testData/codegen/bytecodeText/deadCodeElimination/simpleConstructor.kt

@@ -0,0 +1,15 @@
+class A
+fun box() {
+    val x: A? = A()
+    val z: A? = A()
+    val z1: A? = if (1 == 1) z else x
+    
+    x!!
+    z!!
+    z1!!
+}
+
+// 0 IFNULL
+// 0 IFNONNULL
+// 0 throwNpe
+// 0 ATHROW

compiler/testData/codegen/bytecodeText/deadCodeElimination/simpleConstructorNotRedundant.kt

@@ -0,0 +1,18 @@
+class A
+fun box() {
+    val x: A? = A()
+    val y: A?
+    if (1 == 0) {
+        y = x
+    }
+    else {
+        y = null
+    }
+    
+    y!!
+}
+
+// 0 IFNULL
+// 1 IFNONNULL
+// 1 throwNpe
+// 0 ATHROW

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -309,6 +309,12 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/bytecodeText/deadCodeElimination"), Pattern.compile("^(.+)\\.kt$"), true);
         }
 
+        @TestMetadata("arrayConstructor.kt")
+        public void testArrayConstructor() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/arrayConstructor.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("boxing.kt")
         public void testBoxing() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/boxing.kt");
@@ -326,6 +332,24 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/lastReturn.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("literal.kt")
+        public void testLiteral() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/literal.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("simpleConstructor.kt")
+        public void testSimpleConstructor() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/simpleConstructor.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("simpleConstructorNotRedundant.kt")
+        public void testSimpleConstructorNotRedundant() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/deadCodeElimination/simpleConstructorNotRedundant.kt");
+            doTest(fileName);
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeText/directInvoke")